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+The Project Gutenberg EBook of Speciation and Evolution of the Pygmy Mice,
+Genus Baiomys, by Robert L. Packard
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Speciation and Evolution of the Pygmy Mice, Genus Baiomys
+
+Author: Robert L. Packard
+
+Release Date: December 13, 2011 [EBook #38290]
+
+Language: English
+
+Character set encoding: ISO-8859-1
+
+*** START OF THIS PROJECT GUTENBERG EBOOK SPECIATION AND EVOLUTION OF ***
+
+
+
+
+Produced by Chris Curnow, Tom Cosmas, Joseph Cooper and
+the Online Distributed Proofreading Team at
+http://www.pgdp.net
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+
+
+  UNIVERSITY OF KANSAS PUBLICATIONS
+
+  MUSEUM OF NATURAL HISTORY
+
+
+  Volume 9, No. 23, pp. 579-670, 4 pls., 12 figs. in text
+
+  June 16, 1960
+
+
+  Speciation and Evolution of the
+  Pygmy Mice, Genus Baiomys
+
+  BY
+
+  ROBERT L. PACKARD
+
+  UNIVERSITY OF KANSAS
+  LAWRENCE
+  1960
+
+
+
+
+  UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY
+
+  Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
+
+  Robert W. Wilson
+
+  Volume 9, No. 23, pp. 579-670, 4 pls., 12 figs. in text
+  Published June 16, 1960
+
+
+  UNIVERSITY OF KANSAS
+  Lawrence, Kansas
+
+
+  PRINTED IN
+  THE STATE PRINTING PLANT
+  TOPEKA, KANSAS
+
+  1960
+
+  [Illustration: Look for the Union Label]
+  28-3030
+
+
+
+
+Speciation and Evolution of the Pygmy Mice, Genus Baiomys
+
+BY
+
+ROBERT L. PACKARD
+
+
+
+
+CONTENTS
+
+
+                                                                      PAGE
+  Introduction                                                         583
+  Materials, Methods and Acknowledgments                               584
+  Paleontology of the Genus                                            587
+     _Baiomys sawrockensis_                                            588
+     _Baiomys rexroadi_                                                589
+     _Baiomys kolbi_                                                   590
+     _Baiomys brachygnathus_                                           590
+     _Baiomys minimus_                                                 591
+  Phyletic trends                                                      592
+  Non-Geographic Variation                                             595
+     Variation with age                                                595
+     Secondary sexual variation                                        597
+     Individual variation                                              597
+     Pelage and molts                                                  598
+  Taxonomic Characters and Relationships                               600
+     External parts                                                    600
+     Pelage                                                            600
+     Skull                                                             600
+     Teeth                                                             601
+     Hyoid apparatus                                                   601
+     Baculum                                                           603
+     Auditory ossicles                                                 605
+  Genus Baiomys                                                        607
+  Systematic Accounts of Species and Subspecies                        608
+     _Baiomys musculus_                                                608
+     _Baiomys musculus brunneus_                                       612
+     _Baiomys musculus grisescens_                                     614
+     _Baiomys musculus handleyi_                                       617
+     _Baiomys musculus infernatis_                                     618
+     _Baiomys musculus musculus_                                       620
+     _Baiomys musculus nigrescens_                                     623
+     _Baiomys musculus pallidus_                                       625
+     _Baiomys musculus pullus_                                         628
+     _Baiomys taylori_                                                 630
+     _Baiomys taylori allex_                                           633
+     _Baiomys taylori analogous_                                       637
+     _Baiomys taylori ater_                                            640
+     _Baiomys taylori canutus_                                         643
+     _Baiomys taylori fuliginatus_                                     645
+     _Baiomys taylori paulus_                                          647
+     _Baiomys taylori subater_                                         650
+     _Baiomys taylori taylori_                                         651
+  Evolution and Speciation                                             655
+     Formation of the Recent Species                                   658
+     Areas of present differentiation                                  661
+     Zoogeographic position                                            661
+  Conclusions                                                          664
+  Literature Cited                                                     665
+
+
+
+
+INTRODUCTION
+
+
+Pygmy mice (_Genus Baiomys_) are the smallest cricetine rodents in North
+America. They occur from Nicaragua in Central America into the
+southwestern United States. The principal part of the geographic range
+of the pygmy mice lies in the Republic of México. They are notably
+common in central México, but are only locally common to the north and
+to the south, and then only in certain seasons.
+
+Pygmy mice were first brought to the attention of biologists in 1887
+when Oldfield Thomas described a diminutive species of cricetine rodent,
+_Hesperomys_ (_Vesperimus_) _taylori_. The description was based on a
+specimen obtained by William Taylor from San Diego, Duval County, Texas.
+C. Hart Merriam (1892:70) described _Sitomys musculus_ on the basis of
+specimens from Colima [City of], Colima, México. Merriam (_loc. cit._)
+mentioned that the two kinds of mice, _Hesperomys taylori_ and _Sitomys
+musculus_, "in general appearance look almost precisely like the common
+house mouse (_Mus musculus_) but are still smaller and have shorter
+tails." He placed the two species in the genus _Sitomys_. Frederick W.
+True in 1894 regarded them as composing a distinct subgenus of _Sitomys,
+Baiomys_. According to True (1894:758), _S. taylori_ and _S. musculus_
+possessed a different combination of characters (ascending ramus of
+mandible short and erect, condyle terminal, coronoid process
+well-developed, uncinate, and near the condyle, size small, tail short,
+plantar tubercles six, soles hairy) than either _Vesperimus_, or
+_Onychomys_ (which had been considered as a subgenus of _Hesperomys_
+until 1889). In 1907, E. A. Mearns accorded _Baiomys_ generic rank.
+Osgood (1909:252) treated _Baiomys_ us a subgenus of _Peromyscus_,
+whereas, Miller, in 1912, regarded _Baiomys_ as a distinct genus. Most
+recent students of North American mammals have followed Miller, but
+usually with reservations. Ellerman (1941:402) emphasized that the
+taxonomic position of the genus was uncertain, and wrote that _Baiomys_
+"... seems to be considerably distinct from _Peromyscus_, and may
+perhaps be a northern representative of _Hesperomys_ or one of the small
+South American genera."
+
+Only two comprehensive analyses of geographic variation and
+interspecific taxonomic relationships have been made; the first was by
+Osgood (1909) who had fewer than a fourth of the specimens of _Baiomys_
+available to me; the second was by Hooper (1952a:90-97) who contributed
+importantly to understanding the relationships of the two living species
+in central México. No attempts heretofore have been made to correlate
+and understand the relationships of the five fossil species to one
+another and to the living species assigned to the genus.
+
+Six objectives of the following report are to: (1) list characters
+taxonomically useful in recognizing species and subspecies; (2) record
+amount of variation within and between populations; (3) correlate
+observed variations with known biological principles; (4) show
+geographic ranges of the two living species; (5) indicate relationships
+between fossil and living species of the genus; and (6) clarify the
+systematic position of the genus.
+
+
+
+
+MATERIALS, METHODS AND ACKNOWLEDGMENTS
+
+
+This report is based on the study of approximately 3,520 museum study
+skins, skulls, complete skeletons, and entire animals preserved in
+liquid. Most specimens examined were accompanied by an attached label
+bearing data on locality and date of capture, name of collector,
+external measurements, and sex. In addition, 49 fossil specimens
+referable to _Baiomys_ were studied. Nearly two-thirds of the specimens
+were assembled at the University of Kansas Museum of Natural History;
+the remainder were examined in other institutions.
+
+Specimens studied were grouped by geographic origin, sex, age, and
+season of capture. Individual variation was then measured in several of
+the larger samples of each living species and in measurable fossil
+material. External measurements used were those recorded by the
+collectors on the labels attached to the skins. Twenty cranial
+measurements employed in the past in the study of _Baiomys_ and closely
+related cricetine rodents were statistically analyzed. The coefficient
+of variation was calculated for each of the 20 measurements in order to
+determine which varied least. In general, measurements having the least
+coefficient of variation were used in comparing samples from different
+geographic areas. Figure 1 shows the points between which measurements
+were taken.
+
+_Occipitonasal length._--From anteriormost projection of nasal bones to
+posteriormost projection of supraoccipital bone. _A_ to _A'_
+
+_Zygomatic breadth._--Greatest distance across zygomatic arches of
+cranium at right angles to long axis of skull. _B_ to _B'_
+
+_Postpalatal length._--From posterior margin of hard palate to anterior
+margin of foramen magnum. _C_ to _C'_
+
+_Least interorbital breadth._--Least distance across top of skull
+between orbits. _D_ to _D'_
+
+_Length of incisive foramina._--From anteriormost point to posteriormost
+point of incisive foramina. _E_ to _E'_
+
+_Length of rostrum._--The distance in a straight line from the notch
+that lies lateral to the lacrimal to the tip of the nasal on the same
+side. _F_ to _F'_
+
+_Breadth of braincase._--Greatest distance across braincase, taken at
+right angles to long axis of skull. _G_ to _G'_
+
+_Depth of cranium._--The distance from the dorsalmost part of the
+braincase to a flat plane touching tips of incisors and ventral border
+of each auditory bulla. A glass slide one millimeter thick was placed on
+the ventral side of the skull. One jaw of the caliper was on the lower
+surface of the slide and the other jaw on the dorsalmost part of the
+braincase. The depth of the slide was subtracted from the total reading.
+_H_ to _H'_
+
+_Alveolar length of maxillary tooth-row._--From anterior border of
+alveolus of M1 to posterior alveolus of M3. _I_ to _I'_
+
+    [Illustration: FIG. 1. Three views of the skull to show points
+       between which measurements were taken. Based on _B. m. pullus_,
+       adult, female, No. 71611 KU, 8 mi. S Condega, Estelí, Nicaragua.
+       × 1-1/3.]
+
+Capitalized color-terms refer to Ridgway (1912). Color terms without
+initial letters capitalized do not refer to any one standard.
+
+The names of the cusps and ridges of the teeth (see Figure 2) are those
+suggested by Wood and Wilson (1936:389-390). Terminology of the enamel
+grooves and folds is that of Hershkovitz (1944:17) and Hooper
+(1952b:20-21).
+
+Because secondary sexual variation was not significant (see page 597),
+both males and females of like age and pelage were used in comparisons
+of samples designed to reveal geographic variation.
+
+The species are arranged from less to more progressive; the subspecies
+are arranged alphabetically.
+
+In the synonymy of each subspecies, the plan has been to cite: (1) the
+name first proposed; (2) the first usage of the name combination
+employed by me; (3) all other name combinations in chronological order
+that have been applied to the subspecies concerned.
+
+The localities of specimens examined are listed by country from north to
+south. Within a country, the listing is by state, beginning with the
+northwesternmost state and proceeding by tiers (west to east) to the
+southeasternmost state. Within a state of the United States, the listing
+is by counties in the same geographic order as described for states.
+Within any county in the United States, within any state in México, and
+within any country in Central America, the listing of localities is from
+north to south. When more than one locality is on the same line of
+latitude, the westernmost locality is listed first. Marginal localities
+for each subspecies are listed in a paragraph at the end of each
+account. Each marginal locality is mapped by means of a circle. The
+circles are listed in clockwise order, beginning with the northernmost.
+When more than one of these localities lies on the same line of
+latitude, the westernmost is cited first. Localities not represented on
+the distribution maps, so as to avoid undue crowding of symbols, are
+italicized in the lists of specimens examined.
+
+    [Illustration: FIG. 2. Occlusal views of molars. × 13.
+
+    A.  _B. taylori analogous_, subadult, female, No. 28102 KU, 4 km.
+        ENE Tlalmanalco, 2290 meters, Estado de México. Right, upper
+        molars.
+
+    B.  _B. musculus musculus_, subadult, male, No. 45456 USNM, Colima,
+        Colima, México. Left, upper molars.
+
+    A'. _B. taylori analogous_, subadult, female, No. 28102 KU 4 km.
+        ENE Tlalmanalco, 2290 meters, Estado de México. Left, lower
+        molars.
+
+    B'. _B. musculus musculus_, subadult, male, No. 45456 USNM, Colima,
+        Colima, México. Right, lower molars.]
+
+The largest single collection of pygmy mice is in the University of
+Kansas Museum of Natural History, and, unless otherwise indicated,
+specimens cited in the taxonomic accounts beyond are there.
+
+I am indebted to the following named institutions and persons for making
+specimens available for study:
+
+  American Museum of Natural History, G. G. Goodwin and R. G. VanGelder.
+
+  Carnegie Museum, J. K. Doutt.
+
+  California Academy of Sciences, Robert T. Orr.
+
+  Chicago Natural History Museum, Phillip H. Hershkovitz.
+
+  Cleveland Museum of Natural History (Collection now a part of Museum of
+     Zoology, University of Michigan, W. H. Burt, E. T. Hooper).
+
+  Louisiana State University, Museum of Natural History, George H. Lowery,
+     Jr.
+
+  Los Angeles County Museum, Charles A. McLaughlin.
+
+  United States National Museum (Biological Survey Collections), David A.
+     Johnson, and Viola S. Schantz.
+
+  United States National Museum, Division of Vertebrate Paleontology,
+     C. Lewis Gazin.
+
+  University of Arizona, E. L. Cockrum, and G. VR. Bradshaw.
+
+  University of California, Museum of Vertebrate Zoology, Seth B. Benson,
+     and W. Z. Lidicker.
+
+  University of Illinois, Museum of Natural History, Donald F.
+     Hoffmeister.
+
+  University of Michigan, Museum of Zoology, W. H. Burt, E. T. Hooper, and
+     Claude W. Hibbard.
+
+  University of New Mexico, James S. Findley.
+
+  University of Texas, Frank W. Blair.
+
+  Texas A & M, Cooperative Wildlife Research Collection, W. B. Davis.
+
+  The Museum, Michigan State University, Rollin H. Baker.
+
+  University of Florida Collections, James N. Layne.
+
+I am especially grateful to Professor E. Raymond Hall who guided me in
+my study and gave critical assistance with the manuscript. Additional
+appreciated suggestions were made by Professors A. Byron Leonard, Robert
+W. Wilson, Henry S. Fitch, Ronald L. McGregor, and fellow graduate
+students. For the illustrations, I am indebted to Mrs. Lorna Cordonnier,
+Miss Lucy Remple and Mrs. Connie Spitz. Mr. B. J. Wilks of the
+University of Texas, Department of Zoology, provided a number of living
+pygmy mice for study in captivity. Mr. J. Raymond Alcorn and his son,
+Albert, collected a large share of specimens of pygmy mice now in the
+University of Kansas, Museum of Natural History. My wife, Patricia,
+aided me in secretarial work and typing of the manuscript.
+
+For financial assistance, I am indebted to the National Science
+Foundation when I was a Research Assistant, to the Sigma Xi-RESA
+Research Fund for a Grant-in-Aid, and to the Kansas University Endowment
+Association through its A. Henley Aid Fund, and the Watkins Fund for
+out-of-state field work by the Museum of Natural History.
+
+
+
+
+PALEONTOLOGY OF THE GENUS
+
+
+Five fossil species, all extinct, have been assigned to the genus and
+range in time from early late Pliocene (Saw Rock Canyon fauna of
+Hibbard, 1953:408) to Mid-Pleistocene (see Hibbard, 1958:25, who
+assigns the Curtis Ranch fauna to late Kansan or early Yarmouth).
+
+I examined all known fossil material and compared it with Recent
+material. When the antiquity of the genus is considered, the degree of
+difference between the oldest fossil species and the two living species
+is much less than might be expected.
+
+
+=Baiomys sawrockensis= Hibbard
+
+    _Baiomys sawrockensis_ Hibbard, Papers Mich. Acad. Sci., Arts and
+       Letters, 38:402, April 27, 1953.
+
+_Type._--No. 27506, Univ. Michigan; left mandibular ramus bearing m1-m3
+and incisor; Saw Rock Canyon, early late Pliocene, XI member of the
+Rexroad formation, sec. 36, T. 34 S, R. 31 W, Seward County, Kansas
+(University of Kansas, Locality 6).
+
+_Referred material._--Univ. Michigan, Nos. 25781, 27503-27505,
+28159-28165, 29708-29715, 31015.
+
+_Diagnosis._--Ramus of medium size to small for the genus; lower incisor
+broad, moderately recurved; diastemal region broad; anterior median fold
+between anterior labial conulid and anterior lingual conulid of m1 deep;
+primary first fold between anteroconulid and protoconid of m2 deep;
+cingular ridge (ectolophid) at entrance to posteroexternal reëntrant
+valley (major fold, see Figure 2) between protoconid and hypoconid of m1
+and m2; average and extreme measurements of lower molar row of eight
+specimens are, 2.65 (2.5-2.7).
+
+_Comparisons._--For comparisons with _B. brachygnathus_, see account of
+that species. From _B. rexroadi_, _B. sawrockensis_ differs in: anterior
+median fold of m1 deeper; incisor narrower; diastemal region broader;
+coronoid process broader and better developed; cingular ridges
+(ectolophids and mesolophids) more pronounced in their development;
+incisors less proödont, more retrodont.
+
+From _B. kolbi_, _B. sawrockensis_ differs in: crowns of molars
+narrower; incisors less proödont; cingular ridges (ectolophids and
+mesolophids) of m1 and m2 more pronounced in their development.
+
+From _B. minimus_, _B. sawrockensis_ differs in: incisor less
+procumbent; masseteric ridge extending farther anteriorly; anterior
+cingulum of m2 slightly larger.
+
+From _B. musculus_, _B. sawrockensis_ differs in: over-all size of jaw
+and molar row less; diastema more acutely curved; incisors shorter;
+anterior median fold of m1 slightly deeper.
+
+From _B. taylori_, _B. sawrockensis_ differs in: m1 and m2 smaller;
+cingular ridges in m1 and m2 more pronounced; anterolingual conulid
+farther forward; incisors shorter, more proödont; molar teeth depressed,
+less hypsodont; diastemal region broader, more acutely curved;
+masseteric ridge not extending so far anteriorly.
+
+_Remarks._--_B. sawrockensis_ is the oldest known pygmy mouse. The
+extreme development of the anterior median fold between the
+anterolingual conulid and the anterolabial conulid is regarded as a
+primitive feature in the pygmy mice. In this character, the Recent
+species can be traced back in time through _B. minimus_ to _B.
+sawrockensis_. _B. sawrockensis_ resembles _Calomys laucha_ of South
+America in general conformation of jaw and tooth structure. The molars
+of _sawrockensis_ are smaller than those of _C. laucha_, and the
+anterolingual conulid of _sawrockensis_ is farther forward.
+
+
+=Baiomys rexroadi= Hibbard
+
+    _Baiomys rexroadi_ Hibbard, Amer. Midland Nat., 26:351, September,
+       1941; Hibbard, Contrib. Mus. Paleo., Univ. Michigan, 8(2):145,
+       June 29, 1950 (part); Hibbard, Papers Mich. Acad. Sci., Arts
+       and Letters, 38:403, April 27, 1953.
+
+_Type._--No. 4670, Univ. Kansas; left mandibular ramus bearing m1-m3,
+and incisor; Rexroad fauna, Locality no. 2, Upper Pliocene, Meade
+County, Kansas.
+
+_Referred material._--Univ. of Michigan Nos. 24840, 24851, 27493, 27496,
+27501, 28862-28867.
+
+_Diagnosis._--Ramus medium in size for the genus; incisors small,
+proödont; anterior median fold of m1 slight; cingulum of all molars
+poorly developed; average and external measurements of lower molar row
+of seven specimens are, 2.7 (2.6-3.0).
+
+_Comparisons._--For comparisons with _B. sawrockensis_ and _B. minimus_,
+see accounts of those species. From _B. kolbi_, _B. rexroadi_ differs
+in: over-all size of mandibular ramus, incisors, and molars smaller;
+anterior median fold of m1 present, though poorly developed.
+
+From _B. brachygnathus_, _B. rexroadi_ differs in: over-all size of
+mandibular ramus smaller; m3 larger; posterior cusps (hypoconid and
+entoconid) elongated; diastema shorter, less acutely recurved; incisors
+less proödont; cingular ridges of m1 and m2 less well-developed.
+
+From _B. musculus_, _B. rexroadi_ differs in: over-all size of
+mandibular ramus less; cingular ridges of m1 and m2 less well-developed;
+incisors smaller, more proödont; molars less depressed.
+
+From _B. taylori_, _B. rexroadi_ differs in: m3 more triangular,
+posterior part narrower; mental foramen closer to anterior root of m1;
+masseteric ridge closer to alveolus of m1; incisor shorter, more
+proödont; molars more depressed.
+
+_Remarks._--Two maxillary tooth-rows and associated parts were studied.
+On one of these specimens, the M2 has a well-developed mesostyle; the
+anterior median fold of M1 is also well-developed. The other specimen
+possesses a low cingular ridge (enteroloph) between the protocone and
+the hypocone, a reduced cingular ridge (mesoloph) between the paracone
+and metacone of M1. On the second molar, M2, a mesostyle joins with the
+mesoloph somewhat in the fashion indicated by Hooper (1957:9, encircled
+number 2).
+
+
+=Baiomys kolbi= Hibbard
+
+    _Baiomys kolbi_ Hibbard, Trans. Kansas Acad. Sci., 55:201, June 18,
+       1952; Hibbard, Papers Mich. Acad. Sci., Arts and Letters, 38:403,
+       April 27, 1953.
+
+_Type._--No. 24846, Univ. Michigan; right mandibular ramus bearing m1-m3
+and incisor; Fox Canyon, upper Pliocene, Rexroad formation, Rexroad
+fauna, Univ. Michigan Locality K1-47, sec. 35, T. 34 S, R. 30 W, XI
+Ranch, Meade County, Kansas.
+
+_Referred material._--Univ. Michigan Nos. 24845-24848, 27494, 27497,
+27499, 28566, 28861, 28878, 28880-28882, 28884, 28886.
+
+_Diagnosis._--Ramus of medium size to large for the genus; lower incisor
+short, narrow transversely, proödont; anterior median fold of m1 reduced
+or absent; cingular ridges of m1 and m2 moderately well-developed; m3
+large relative to m1 and m2; average and extreme measurements of lower
+molars of seven specimens are, 3.0 (3.0-3.1).
+
+_Comparisons._--For comparisons with _B. sawrockensis_ and _B.
+rexroadi_, see accounts of those species. From _B. brachygnathus_, _B.
+kolbi_ differs in: molar row longer; m3 and jaw larger; diastema longer;
+masseteric ridge not so far forward; molars more depressed.
+
+From _B. minimus_, _B. kolbi_ differs in: molar row longer; m3 larger;
+jaw larger; diastema not so acutely curved; incisor shorter, narrower
+transversely, more proödont.
+
+From _B. musculus_, _B. kolbi_ differs in: anterior median fold of m1
+slightly developed or absent, instead of well-developed; m3 larger (not
+reduced), external reëntrant valley broad and extending farther across
+crown of tooth; incisor smaller, and more proödont; cingular ridges of
+m1 and m2 less well-developed.
+
+From _B. taylori_, _B. kolbi_ differs in: molars larger, more depressed;
+incisor shorter, more proödont; m3 smaller relative to m1 and m2;
+external reëntrant valley of m3 broad, extending farther across crown of
+tooth.
+
+_Remarks._--The slight development or absence of the anterior median
+fold in _kolbi_ suggests that it was specialized. The anterior median
+fold is well-developed in all species of _Baiomys_ save _B.
+brachygnathus_ and _B. taylori_, in which the fold is only slightly
+developed or absent. _B. kolbi_ may have paralleled _B. taylori_ in
+specialization for a diet of grasses and for a life in open country.
+
+
+=Baiomys brachygnathus= (Gidley)
+
+    _Peromyscus brachygnathus_ Gidley, U. S. Geol. Surv. Prof. Papers,
+       131:124, March 15, 1922.
+
+    _Baiomys brachygnathus_, Hibbard, Amer. Midland Nat., 26:352,
+       September, 1941.
+
+    _P. [eromyscus] brachygnathus_, Wilson, Carnegie Inst. Washington
+       Publ., 473:33, May 21, 1936.
+
+_Type._--No. 10501, U. S. Nat. Mus.; right mandibular ramus bearing
+m1-m3, and incisor; 2 mi. NE Curtis Ranch house, near a line between
+sec. 28 and 29, T. 18 S, R. 21 E, Mid-Pleistocene (Hibbard, 1958:25),
+Cochise County, Arizona.
+
+_Referred material._--None.
+
+_Diagnosis._--Ramus small for the genus; m3 reduced; jaw reduced
+anteroposteriorly; incisor short, slender, proödont; cingular ridges
+well-developed, posterior ectolophid continuous from protoconid to
+hypoconid in m1 and m2; diastema short; length of molar row 2.8 mm.
+
+_Comparisons._--For comparisons with _B. rexroadi_ and _B. kolbi_, see
+accounts of those species. From _B. minimus_, _B. brachygnathus_ differs
+in: jaw not so slender anteriorly; masseteric ridge not so far anterior;
+cheek-teeth slightly broader, less depressed, therefore, more hypsodont;
+incisor shorter, more proödont.
+
+From _B. sawrockensis_, _B. brachygnathus_ differs in: molar row
+slightly longer; teeth slightly less depressed; masseteric ridge extends
+farther anteriorly; incisors more proödont.
+
+From _B. musculus_, _B. brachygnathus_ differs in: jaw smaller; molar
+row slightly shorter; molars less depressed; incisors slender, shorter,
+narrower, and more proödont.
+
+From _B. taylori_, _B. brachygnathus_ differs in: incisor more slender,
+shorter, more proödont; diastema shorter.
+
+_Remarks._--The molar teeth of _B. brachygnathus_, although worn,
+resemble those of _B. taylori_ more than those of any known fossil
+species. Gidley (1922:124) stated that the absence of the divided
+anterior lobe of the first molar (anterior median fold) in
+_brachygnathus_ was one of the chief characters separating
+_brachygnathus_ from _taylori_. In _taylori_, the anterior median fold
+characteristically is only slightly developed, and in some specimens is
+absent. _B. brachygnathus_ differs from _taylori_ chiefly in proödont
+incisors, which feature seems to preclude _brachygnathus_ being
+ancestral to _taylori_. _B. brachygnathus_ may have been a specialized
+divergence from _B. minimus_.
+
+
+=Baiomys minimus= (Gidley)
+
+    _Peromyscus minimus_ Gidley, U. S. Geol. Surv. Prof. Papers,
+       131:124, March 15, 1922.
+
+    _Baiomys minimus_, Hibbard, Amer. Midland Nat., 26:352, September,
+       1941; Gazin, Prof. U. S. Nat. Mus., 92(3155):488, 1942.
+
+    _P. [eromyscus] minimus_, Wilson, Carnegie Inst. Washington Publ.,
+       473:33, May 21, 1936.
+
+_Type._--No. 10500, U. S. Nat. Mus.; left mandibular ramus bearing m1-m3
+and incisor; 2 mi. S Benson, sec. 22, T. 17 S, R. 20 E, Late Pliocene
+(Blancan, Gazin, 1942:482), Cochise County, Arizona.
+
+_Referred material._--None.
+
+_Diagnosis._--Ramus small for the genus; molar teeth depressed; cingular
+ridges (ectolophids) of m1 and m2 well-developed; anterior median fold
+present (appearing larger owing to chip of enamel missing); external
+reëntrant fold of m3 progresses half way across crown of tooth; diastema
+short; incisor moderately large, recurved; length of molar row, 2.6 mm.
+
+_Comparisons._--For comparisons with _B. brachygnathus_, _B. kolbi_, and
+_B. sawrockensis_, see accounts of those species. From _B. rexroadi_,
+_B. minimus_ differs in: anterior median fold deeper; incisor longer,
+more recurved, less proödont; molars slightly more depressed (though
+worn).
+
+From _B. musculus_, _B. minimus_ differs in: over-all size of jaw and
+molars smaller; incisors shorter; masseteric ridge more depressed.
+
+From _B. taylori_, _B. minimus_ differs in: anterior median fold
+slightly deeper; molar teeth more depressed; cingular ridges on m1 and
+m2 better developed; masseteric ridge more depressed.
+
+_Remarks._--Gidley (1922:124) stated that _B. minimus_ differed
+considerably from _B. taylori_ in that the coronoid portion of the
+ascending ramus diverges at a wider angle from the alveolar part of the
+jaw. Study of large samples of lower jaws of _B. taylori_ reveals
+considerable individual variation in the angle formed between the
+coronoid part of the jaw and the alveolar part.
+
+_B. minimus_, except for its small size, is like _B. musculus_ and is
+considered to be ancestral to that species.
+
+
+
+
+PHYLETIC TRENDS
+
+
+It seems that the important trends in phyletic development in the pygmy
+mice have been from an ancestral stock (see Figure 3) that possessed
+relatively brachydont teeth having raised cingular ridges (ectolophids
+and mesolophids) and relatively short orthodont to proödont incisors, to
+species having teeth more hypsodont on which cingular ridges were
+reduced, stylids were isolated or completely absent, and incisors were
+longer and more recurved or retrodont. _Baiomys sawrockensis_, or an
+unknown stock resembling it, might have been ancestral to the other
+known species. Of the four remaining fossil species, _B. kolbi_ seems
+least likely to have been ancestral to the two living species, owing to
+its proödont incisors, reduction of cingular ridges, loss of an anterior
+median fold in m1, and long mandibular tooth-row. _B. kolbi_ may have
+been an early, specialized derivation from the ancestral stock. From his
+knowledge of the habitats of _B. musculus_, the larger species, and _B.
+taylori_, the smaller species, Hibbard (1952:203) suggests that _B.
+kolbi_, a large species, might have inhabited lowlands, and _B.
+rexroadi_, a small species, highlands. I have no evidence to dispute
+this suggestion except that _B. musculus_ has more prominent cingular
+ridges (or at least vestiges of this lophid condition) than either _B.
+kolbi_ or _B. rexroadi_. _B. musculus_ (see page 610) is less of an open
+grassland inhabitant than is _B. taylori_. Therefore, both _B. kolbi_
+and _B. rexroadi_, because of their poorly developed cingular ridges,
+might be expected to have lived in a relatively open grassland habitat.
+
+The relationship of _B. rexroadi_ to fossil species other than _B.
+kolbi_ is not clear. Superficially, the former resembles _B. taylori_,
+but, owing to the specialized development of the molars of _rexroadi_,
+it could hardly have been ancestral to either of the living species. The
+resemblance of _B. rexroadi_ to _B. taylori_ may result from each having
+occupied the same ecological niche in different periods. The incisors of
+_B. rexroadi_, however, are much shorter than those of _B. taylori_ and
+suggest somewhat different food habits.
+
+_B. minimus_ seemingly is more closely related to _B. sawrockensis_ and
+_B. musculus_ than to the other described species. The development of
+the cingular ridges leads one to suspect that _B. minimus_ was the
+ancestor of _B. musculus_. _B. minimus_ may have been derived from a
+_sawrockensis_-like stock and probably gave rise to _B. musculus_.
+
+Hershkovitz (1955:643-644) suggests that "... primitive brachydont,
+buno-mesolophodont cricetines have survived ... in forested parts of the
+range," whereas "... the progressive branch of cricetines with mesoloph
+absent or vestigal, has become increasingly specialized for life in open
+country and a diet of grasses." Species of the genus _Baiomys_ can be
+divided into two morphological groups. One group, composed of _B.
+sawrockensis_, _B. minimus_, and _B. musculus_, includes those species,
+the teeth of which were relatively brachydont and had prominently
+developed cingular ridges (ectolophids or mesolophids) or, at least,
+showed some development of these ridges. _B. sawrockensis_ probably
+lived in semi-wooded to shrubby habitats. According to Hibbard
+(1953:409), "The Saw Rock Canyon fauna lived in that area at a time when
+conditions were comparable to the conditions at the time the Rexroad
+fauna lived." The conditions in which the Rexroad fauna lived are
+discussed by Hibbard (1941:95). Presumably, there were at least some
+well-wooded situations, and the climate was warm. _B. sawrockensis_
+probably inhabited denser vegetation than did _B. minimus_ or than does
+_B. musculus_. The teeth of the second group (_B. kolbi_, _B. rexroadi_,
+_B. brachygnathus_, and _B. taylori_) lack cingular ridges or have them
+much reduced and have more hypsodont molars. The three fossil species
+probably inhabited relatively open grassland. This assumption is based
+largely on the known habitat of _B. taylori_ (see page 632).
+
+The suggested grouping, based on supposed similarities in niches
+inhabited by the extinct species, does not necessarily indicate degree
+of relationship. _B. taylori_ probably was not derived from an ancestor
+like _B. rexroadi_ or _B. kolbi_, although, in certain characters, the
+three species resemble one another. _B. kolbi_ and _B. rexroadi_ were
+already specialized in Blancan times, probably for living on grassland.
+_B. taylori_ shows only a slight advance in specialization of molar
+structures compared to either of the aforementioned species but is
+slightly smaller and does have longer and more recurved incisors. If
+only morphological criteria of lower jaws were considered, without
+recourse to other data derived from the study of many samples of
+populations of the living species, time alone might account for the
+differences among _B. taylori_, _B. rexroadi_, and _B. kolbi_. The
+available evidence (see page 658) suggests, however, that _B. taylori_
+was derived from the _B. sawrockensis_-_B. minimus_-_B. musculus_ line.
+
+    [Illustration: FIG. 3. Diagram indicating probable relationships
+       of living and extinct species of pygmy mice.]
+
+_Baiomys_ seems to have undergone little basic evolutionary and
+morphological change since Late Pliocene time. According to Simpson
+(1945:207), hesperomine rodents as a group have undergone little basic
+evolution, and "The rapid evolution of new genera was more a matter of
+segregation of characters in a group with a great variation than of the
+origin of significantly new characters." Perhaps, the living southern
+pygmy mouse retains many basic characteristics of one of the early North
+American cricetine-like stocks that emigrated to South America near the
+end of the Pliocene epoch. There is much to suggest close relationship
+of the pygmy mice to certain species of South American hesperomine
+rodents of the genus _Calomys_.
+
+
+
+
+NON-GEOGRAPHIC VARIATION
+
+
+Non-geographic variation in pygmy mice (variation in a single population
+resulting from age, individual, seasonal, and secondary sexual
+differences) has been but little studied in the past. Mearns (1907:381)
+figured progressive stages of wear on the teeth of _B. taylori_; Osgood
+(1909:252) and Blair (1941:380) referred to changes in dentition,
+weights, and pelages.
+
+The largest samples available for this study were 47 _B. taylori_ from
+the vicinity of Altamira (6 mi. N, 6 mi. W; 5 mi. N, 5 mi. W; 1 mi. S),
+Tamaulipas, and 44 _B. musculus_ from El Salvador (1 mi. S Los Planes,
+and 1 mi. NW San Salvador--two localities 3 miles apart).
+
+
+VARIATION WITH AGE
+
+Specimens of both species were segregated into five categories:
+Juveniles, young, subadults, adults, and old adults. Juvenal and young
+pygmy mice are readily separable from the other three categories;
+subadults are less easily distinguished from adults. In order to obtain
+an accurate understanding of geographic variation in these mice, only
+adults should be used in making taxonomic comparisons.
+
+_Juveniles._--Nestling mice yet unweaned; sutures in cranium
+incompletely closed; bony parts of skull fragile; M3 and m3 not erupted
+or only partly erupted and not protruding above margins of alveoli.
+
+At birth, juveniles are pink, without pelage except for the mystacial
+vibrissae and a few hairs about the eye. Blair (_op. cit._:381) recorded
+changes with age in color of the skin of new-born and suckling pygmy
+mice. Data obtained by me from three litters born in captivity agree
+with his findings. Pygmy mice are weaned when 17 to 24 days old. At that
+time, the mice possess a fine, but not dense, dusky-gray fur.
+
+_Young._--Weaned mice; cranium fragile; sutures between frontals and
+parietals, interparietal and parietals, basioccipital and basisphenoid,
+basisphenoid and presphenoid, premaxillaries and maxillaries widely
+open; M3 and m3 erupted beyond margins of their alveoli (molars erupt
+from anterior to posterior; M3 and m3, therefore, are last to erupt); in
+some specimens, molars slightly worn; pelage still dusky and relatively
+fine and sparse.
+
+_Subadults._--Sutures between bones of skull less widely open than in
+young; epiphyses of long bones incompletely coalesced to shaft; relative
+to length of skull, braincase higher and rostrum shorter than in adults;
+all cusps worn, but dentine not occlusally confluent; primary first and
+second folds of third upper molars present; primary first fold and major
+fold of lower molars visible; pelage a subtle mixture of colors of young
+and adult, but resembling most that of adult; molts into postjuvenal
+pelage between 46 and 50 days.
+
+_Adults._--Sutures of skull, and those between epiphyses and shaft of
+long bones obliterated except that, in some mice, sutures of skull
+persist between frontoparietal, and interparietal; cusps of molars so
+worn that dentine occlusally confluent; small island of enamel in third
+upper and lower molars of some specimens; relative to length of skull,
+cranium lower, rostrum longer, and interorbital region narrower than in
+subadult; cranium appears to be more flattened dorsoventrally; between
+subadult and adult stages, principal growth occurs in basioccipital,
+basisphenoid, frontals, and parietals; nasals grow less.
+
+Although all bones of the skull grow in the subadult and early adult
+stages (see table 1), the above-named bones grow faster than others and
+thus cause the general flattening of the skull, typical of adults
+(similar to that reported by Hoffmeister, 1951:7). The body continues to
+lengthen, accounting for the increase in total length of the adult (see
+table 1). Hind foot, tail and ear, reach their maximum lengths by
+subadult stage. Adult pelage has been acquired, and the color is
+brighter than in either subadults or old adults.
+
+_Old Adults._--Characterized principally by well-worn molars; only thin
+peripheral band of enamel along with slight evidence of any primary or
+secondary folds on any teeth remain; all bones of skull coalesced;
+epiphyses and shafts of long bones ankylosed; small bony protuberances
+on many skulls; pelage usually ragged, tips of the hairs being worn
+away; white flecking and spotting not common, but occurs in some adults.
+
+    TABLE 1.--Average and Extreme Measurements (in Millimeters) of
+       Skulls of Five Age-groups of Baiomys taylori from vic.
+       (see p. 595) Altamira, Tamaulipas, Mexico.
+
+  =============+===========+===========+===========+===========+===========
+  Age groups   | Juvenile  |   Young   | Subadult  |   Adult   | Old adult
+  -------------+-----------+-----------+-----------+-----------+-----------
+  Number       |           |           |           |           |
+  examined     |     3     |     3     |     14    |    19     |    8
+               |           |           |           |           |
+               |           |           |           |           |
+  Total length |   77.0    |   92.6    |    97.6   |   99.9    |  101.6
+               |  (74-79)  |  (89-96)  |   (91-103)| (93-105)  | (98-107)
+               |           |           |           |           |
+               |           |           |           |           |
+  Length       |   27.3    |   39.3    |   40.4    |   39.8    |   40.9
+  of tail      |  (24-29)  |  (37-41)  |  (36-43)  |  (35-45)  |  (38-45)
+               |           |           |           |           |
+               |           |           |           |           |
+  Length       |   49.6    |   53.3    |   57.0    |   60.0    |   60.7
+  of body      |  (49-50)  |  (52-55)  |  (51-61)  |  (56-67)  |  (57-67)
+               |           |           |           |           |
+               |           |           |           |           |
+  Length of    |    11.0   |     13.6  |   14.3    |   14.5    |   14.2
+  hind foot    |    (11)   |  (13-14)  |(13.5-15.0)|  (14-15)  |  (13-15)
+               |           |           |           |           |
+               |           |           |           |           |
+  Occipitonasal|   14.2    |    16.3   |   17.1    |   17.7    |   17.8
+  length       |(13.6-15.2)|(15.8-16.9)|(16.7-17.6)|(17.2-18.3)|(17.6-18.1)
+               |           |           |           |           |
+               |           |           |           |           |
+  Zygomatic    |    8.1    |    8.7    |    8.9    |    9.3    |    9.4
+  breadth      | (7.8-8.6) | (8.6-8.8) | (8.6-9.3) | (9.0-9.6) | (9.1-9.6)
+               |           |           |           |           |
+               |           |           |           |           |
+  Interorbital |    3.4    |    3.4    |    3.4    |    3.6    |    3.5
+  breadth      | (3.3-3.5) | (3.3-3.6) | (3.3-3.6) | (3.4-3.8) | (3.3-3.6)
+               |           |           |           |           |
+               |           |           |           |           |
+  Incisive     |           |           |           |           |
+  foramina     |     2.9   |    3.5    |    3.7    |    3.9    |    3.9
+  (length)     | (2.8-2.9) | (3.4-3.6) | (3.6-3.9) | (3.6-4.1) | (3.5-4.0)
+               |           |           |           |           |
+               |           |           |           |           |
+  Depth        |    5.9    |    6.5    |    6.5    |    6.7    |    6.8
+  of cranium   | (5.6-6.2) | (6.3-6.8) | (6.2-6.8) | (6.4-7.0) | (6.5-7.1)
+               |           |           |           |           |
+               |           |           |           |           |
+  Alveolar     |           |           |           |           |
+  length,      |    2.7    |    2.9    |    2.9    |    3.0    |    3.0
+  upper molars | (2.5-2.8) | (2.9-3.0) | (2.8-3.1) | (2.9-3.2) | (3.0-3.1)
+               |           |           |           |           |
+               |           |           |           |           |
+  Postpalatal  |    4.8    |    5.9    |    6.2    |    6.5    |    6.5
+  length       | (4.5-5.3) | (5.8-6.0) | (5.8-6.6) | (6.2-7.2) | (6.3-6.7)
+               |           |           |           |           |
+               |           |           |           |           |
+  Breadth      |    8.1    |    8.5    |    8.4    |    8.6    |   8.6
+  of braincase | (7.8-8.7) |   (8.5)   | (8.0-8.7) | (8.3-8.9) |(8.4-8.8)
+  -------------+-----------+-----------+-----------+-----------+-----------
+
+
+SECONDARY SEXUAL VARIATION
+
+The method employed by Dice and Leraas (1936:2) was used to measure the
+secondary sexual differences, if there were any, in each of several age
+classes. As pointed out by Hooper (1952b:11), individual variation in
+small samples can obscure secondary sexual differences. The samples of
+_B. taylori_ from the vicinity (see page 595) of Altamira, Tamaulipas,
+and the samples of _B. musculus_ from El Salvador (table 2) were large
+enough to prevent individual variation from obscuring sexual
+differences. Nevertheless, no significant secondary sexual differences
+were found in either _B. taylori_ or _B. musculus_ (see table 2).
+Therefore, the sexes have been considered together for purposes of
+geographic studies.
+
+    TABLE 2.--Analysis of Secondary Sexual Variation in Adult B. taylori
+       Vicinity of (see p. 595) Altamira, Tamaulipas, and Adult B.
+       musculus from El Salvador (see p. 595). (One Standard Deviation
+       on Either Side of the Mean is Given.)
+
+  ==============+==========================+============================
+                | Baiomys taylori          | Baiomys musculus
+   Character    +------------+-------------+-------------+--------------
+                |  21 Males  | 18 Females  |  17 Males   |  13 Females
+  --------------+------------+-------------+-------------+--------------
+                |            |             |             |
+  Total length  |98.4 ± 2.95 |100.5 ± 4.72 |112.04 ± 5.49|113.12 ± 4.23
+                |            |             |             |
+  Length of tail|40.1 ± 2.31 | 40.3 ± 2.39 | 47.12 ± 2.95| 45.70 ± 2.92
+                |            |             |             |
+  Length of body|57.83 ± 1.65| 60.10 ± 4.13| 66.67 ± 3.97| 67.75 ± 2.38
+                |            |             |             |
+  Length of     |            |             |             |
+  hind foot     |14.21 ± .53 | 14.44 ± .51 | 15.60 ± .49 | 15.38 ± .64
+                |            |             |             |
+  Length of ear |10.00 ± .00 | 10.00 ± .00 | 11.80 ± .65 | 12.00 ± .41
+                |            |             |             |
+  Occipitonasal |            |             |             |
+  length        |17.48 ± .40 | 17.47 ± .47 | 19.32 ± .35 | 19.04 ± .44
+                |            |             |             |
+  Zygomatic     |            |             |             |
+  breadth       | 9.17 ± .33 |  9.15 ± .30 |  9.84 ± .21 |  9.91 ± .28
+                |            |             |             |
+  Least         |            |             |             |
+  interorbital  |            |             |             |
+  breadth       | 3.53 ± .11 |  3.48 ± .11 |  3.88 ± .08 |  3.88 ± .12
+                |            |             |             |
+  Postpalatal   |            |             |             |
+  length        | 6.35 ± .19 |  6.38 ± .30 |  7.11 ± .15 |  6.95 ± .20
+                |            |             |             |
+  Depth         |            |             |             |
+  of cranium    | 6.65 ± .24 |  6.61 ± .17 |  7.10 ± .18 |  7.08 ± .18
+                |            |             |             |
+  Incisive      |            |             |             |
+  foramina      |            |             |             |
+  (length)      | 3.82 ± .15 |  3.81 ± .18 |  4.43 ± .11 |  4.35 ± .14
+                |            |             |             |
+  Length        |            |             |             |
+  of rostrum    | 5.87 ± .20 |  5.88 ± .21 |  6.81 ± .16 |  6.66 ± .31
+                |            |             |             |
+  Breadth       |            |             |             |
+  of braincase  | 8.54 ± .23 |  8.52 ± .12 |  9.84 ± .38 |  9.52 ± .20
+                |            |             |             |
+  Alveolar      |            |             |             |
+  length,       |            |             |             |
+  upper molars  | 2.98 ± .08 |  3.01 ± .08 |  3.20 ± .09 |  3.24 ± .10
+  --------------+------------+-------------+-------------+--------------
+
+
+INDIVIDUAL VARIATION
+
+Length of tail varied more than any other measurement used by
+me in taxonomic comparisons. Clark (1941:298), Hoffmeister
+(1951:16), and Van Gelder (1959:239) point out that external
+measurements generally are more variable than measurements of
+the cranium, probably because different techniques of measuring
+are employed by different collectors. As can be noted in table 3,
+females varied more than males.
+
+In the 3520 specimens examined, an extra tooth was observed in
+only one (see Hooper, 1955:298). The left mandibular tooth-row
+of an adult male (USNM 71539) from Omentepec, Guerrero, is
+worn more than the right one. Irregularities in number of teeth
+and abnormalities in individual teeth seem to be rare in pygmy
+mice.
+
+    TABLE 3.--Individual Variation: Coefficients of Variation for
+       Dimensions of External and Cranial Parts in a Population of
+       B. Musculus and B. Taylori.
+
+  =====================+=========================+=========================
+                       | Baiomys taylori         | Baiomys musculus
+                       +-------------------------+-------------------------
+                       |   Vic. (see page 595)   |  Vic. (see  page 595)
+    Measurement        |   Altamira, Tamaulipas  |      El Salvador
+                       +-----------+-------------+------------+------------
+                       | 21 Males  | 18 Females  | 17 Males   | 13 Females
+                       |   C. V.   |    C. V.    |   C. V.    |    C. V.
+  ---------------------+-----------+-------------+------------+------------
+                       |           |             |            |
+  Total length         |    3.0    |     4.7     |   4.9      |    3.7
+  Length of tail       |    5.7    |     5.9     |   6.2      |    6.4
+  Length of body       |    2.8    |     5.0     |   5.9      |    3.5
+  Length of hind foot  |    3.7    |     3.4     |   3.0      |    4.1
+  Length of ear        |    0.0    |     0.0     |   5.5      |    3.3
+                       |           |             |            |
+  Occipitonasal length |    2.2    |     2.7     |   1.8      |    2.3
+  Zygomatic breadth    |    3.6    |     3.3     |   2.2      |    2.7
+  Interorbital breadth |    3.2    |     3.3     |   2.2      |    2.9
+  Incisive foramina    |           |             |            |
+    (length)           |    3.8    |     4.6     |   2.5      |    3.2
+  Depth of cranium     |    3.6    |     2.5     |   2.5      |    2.5
+  Alveolar length,     |           |             |            |
+    upper molars       |    2.7    |     2.5     |   2.8      |    3.2
+  Postpalatal length   |    3.1    |     4.7     |   2.1      |    2.9
+  Length of rostrum    |    3.3    |     3.6     |   2.4      |    4.7
+  Breadth of braincase |    2.7    |     1.4     |   4.0      |    4.9
+  ---------------------+-----------+-------------+------------+------------
+
+The posterior margin of the bony palate varies from semicircular to
+nearly V-shaped. The suture between the nasals and frontals varies from
+V-shaped to truncate to W-shaped. The maxillary part of the zygoma
+varies from broad to slender in dorsoventral width in both species.
+
+
+PELAGE AND MOLTS
+
+There are three distinct pelages, juvenal, postjuvenal, and adult. The
+sequences of molt and change of pelage from the juvenal, to the
+postjuvenal, and from it to adult, are essentially as reported for
+_Peromyscus_ by Collins (1918:78-81; 1924:58-60) and Hoffmeister
+(1951:5). The juvenal pelage is uniformly dusky gray throughout except
+for the paler gray on the venter. In most juvenal mice, the yellow to
+ochraceous pigments of the subterminal bands are reduced or absent.
+Unlike _Peromyscus_, _Baiomys_ has bright brownish hairs on the head as
+the first evidence of the postjuvenal molt (see Figure 4, part a). Blair
+(1941:381) reports adult pelage in pygmy mice being evident first at an
+age of 46 days. Two of my juveniles born in captivity began the
+postjuvenal molt on the 38th and 40th days. The area of new hairs on the
+head spreads most rapidly posteriorly. New hair appears ventrally and
+laterally at the end of 46 days (see Figure 4, part b). Hair replacement
+proceeds more slowly after the "saddle back" stage (described in
+_Peromyscus_ by Collins, 1918:80) has been reached. That stage was
+reached in two pygmy mice at 52 days (see Figure 4, part c). Areas
+immediately posterior to the ears, in the scapular region, molt last.
+The postjuvenal pelage was seemingly complete in one captive pygmy mouse
+at the end of 60 days. Another captive failed to complete its growth of
+new pelage until two additional weeks had elapsed. Length of time
+required to molt in pygmy mice is about the same as that reported by
+Layne (1959:72) in _Reithrodontomys_.
+
+    [Illustration: FIG. 4. Diagrams showing progress of the postjuvenal
+       molt in pygmy mice. For explanation of a, b, and c, see text.
+       All approximately 2/3 natural size.]
+
+If, after the postjuvenal molt, a distinct adult pelage is acquired it
+is difficult to separate it from the annual replacement of pelage in
+adults at the beginning of the rainy season. Adults of both species have
+been found in molt in all months of the year. To the north, in Texas,
+the pelage of winter-taken specimens is denser and slightly more reddish
+than that of specimens taken in spring and summer. In the two last
+mentioned seasons, the pelage is more uniformly gray. To the south, in
+México, the pelage is heavy and long in most specimens taken in the
+rainy season. The percentage of specimens in molt immediately before the
+rainy season and immediately before the dry season is slightly higher
+than in specimens taken at other times of the year. The adult or
+seasonal molt (both loss of old pelage and growth of new) resembles that
+in _Peromyscus truei gilberti_, described by Hoffmeister (1951:6) as
+proceeding "posteriorly as a wave over the entire back." The new hair is
+slightly brighter than the old. Old adults are usually in ragged pelage
+regardless of season; possibly only one regular annual change of pelage
+occurs in most animals before they die. Only one case of melanism was
+observed among all the specimens of both species examined. It was a
+young male _B. t. taylori_, KU 35943, from 6 mi. SW San Gerónimo,
+Coahuila, possessing black hairs throughout. Its hairs are longer and
+finer than those on specimens of comparable age and sex. No albino was
+found, although Stickel and Stickel (1949:145) record one--an adult male
+of _B. taylori_.
+
+
+
+
+TAXONOMIC CHARACTERS AND RELATIONSHIPS
+
+
+_External parts._--Length of body, foot, ear, and tail are useful when
+considered together in distinguishing species and subspecies. I found as
+Hooper (1952a:91) did that length of ear in combination with length of
+hind foot suffices to identify nearly all specimens to species,
+especially where the two species occur together.
+
+_Pelage._--Color in adults is of especial value in subspecific
+determination; the manner in which it varies geographically is described
+on pages 609, 630.
+
+_Skull._--Difference in occipitonasal length and zygomatic breadth, both
+having low coefficients of variation, are useful in separating species,
+especially where they are sympatric. Shape of presphenoid, nasals,
+interparietal, frontoparietal sutures, and length and degree of the
+openings of the incisive foramina are useful in delimiting subspecies.
+The rostrum of _B. taylori_, in front of the frontonasal suture, is
+deflected three to five degrees ventrally in 85 per cent of the adults
+examined, and in _B. musculus_ is less, or not at all, deflected.
+
+_Teeth._--Alveolar length of the upper and lower molar tooth-rows aids
+in distinguishing fossil and Recent species, and to a lesser degree in
+delimiting subspecies. Occlusal pattern is useful in estimating the
+relationship of fossil and living species. Degree of development of the
+mesostyle, mesostylid, mesoloph, and mesolophid have been useful in
+determining relationship between fossil and living species as well as
+useful in separating the living species. Rinker (1954:119) and Hooper
+(1957:48) have shown the degree of variation in dental patterns in
+_Peromyscus_, _Sigmodon_, and _Oryzomys_, mice thought to be closely
+related to _Baiomys_. In pygmy mice, however, the dental patterns are
+relatively constant. The lophs and styles are subject to some geographic
+variation but, nevertheless, are useful in estimating relationships.
+
+    [Illustration: FIG. 5. Ventral view of hyoid bones. × 18.
+
+    A. _Baiomys musculus brunneus_, adult, female, No. 30182 KU,
+       Potrero Viejo, 1700 feet, Veracruz.
+
+    B. _Baiomys taylori analogous_, adult, female, No. 36761 KU,
+       2 mi. N Ciudad Guzmán, 5000 feet, Jalisco.]
+
+_Hyoid apparatus._--Shape and, to a lesser extent, size of the hyoid
+apparatus differentiate nearly all specimens of _B. taylori_ from all
+those of _B. musculus_. The hyoid of _B. taylori_ differs from that of
+_B. musculus_ principally in the shape of the basihyal. It possesses an
+anteriorly pointed entoglossal process in _B. musculus_, and is not
+rounded to completely absent as in _B. taylori_ (see Figure 5). The
+shoulders of the basihyal protrude anteriorly in _B. musculus_, and are
+not flattened as in _B. taylori_. The total length was measured in a
+sample of 55 basihyals of _B. musculus_, and was compared to the total
+length of a sample of 80 basihyals of _B. taylori_. The means of the two
+samples differ significantly at the 95 per cent level; the mean plus two
+standard errors of _B. musculus_ and _B. taylori_, are, respectively,
+2.43 ± .02; 2.18 ± .03. There is sufficient overlap of the samples
+(mean plus one standard deviation of _B. musculus_ and _B. taylori_,
+respectively: 2.43 ± .15; 2.18 ± .15) to make the total length of the
+basihyal of only secondary importance in distinguishing species, but
+shape and total length of the basihyal, when considered together, serve
+to identify all specimens to species. When length of the basihyal is
+plotted against occipitonasal length (see Figure 6), all specimens
+studied, regardless of age or geographical origin, were separated at the
+level of species. The hypohyals of _B. taylori_ seemingly remain
+distinct throughout life; those of _B. musculus_ completely fuse in some
+adults. The ceratohyals are highly variable in shape and of little
+taxonomic use.
+
+    [Illustration: FIG. 6. Relationship of length of basihyal to
+       occipitonasal length of skull. Black symbols, all below the curved
+       line, represent measurements of _B. taylori_; open symbols, all
+       above the curved line, represent measurements of _B. musculus_.]
+
+The degree of geographic variation in shape of basihyal is not great.
+Specimens of _B. musculus pallidus_ from 1 km. NW Chapa, Guerrero, have
+a small indentation on the anteriormost part of the entoglossal process.
+The shoulder of the basihyal is directed less forward in specimens of
+_B. taylori taylori_ from 6 mi. N, 6 mi. W Altamira, Tamaulipas, than in
+other specimens of the species. The variations observed seemed not to be
+clinal.
+
+According to White (1953:548) the hyoid, like the baculum (Burt,
+1936:146), is little influenced by changes in external environment and
+may serve to clarify intergeneric relationships. Hyoids of both species
+of _Baiomys_ are smaller than hyoids of all subgenera of _Peromyscus_.
+In shape, the hyoids of _Baiomys_ resemble those of _Ochrotomys
+nuttalli_ (as explained on page 605, _Ochrotomys_ is here accorded
+generic, instead of subgeneric, rank). In size, the hyoid of both
+species of _Baiomys_ resembles that in _Reithrodontomys_. Sprague
+(1941:304) reports a resemblance in shape between the ceratohyals of
+_Baiomys_ and _Reithrodontomys_. The thyrohyals differ from those of
+_Reithrodontomys_, being less boot-shaped, and having a slight terminal
+expansion as in _Ochrotomys_ (see Sprague, _loc. cit._). In shape, the
+large basihyal of _Onychomys_ resembles the smaller one of _B.
+musculus_. The basihyal of _Oryzomys_ lacks the entoglossal process
+present in _Baiomys_. On the basis of shape of hyoid, _Baiomys_ seems to
+be most closely related to _Ochrotomys_.
+
+    [Illustration: FIG. 7. Dorsal view of bacula. × 16.
+
+    A. _B. musculus brunneus_, adult, No. 24336 KU, 3 kms.
+       W Boca del Río, 10 feet, Veracruz.
+
+    B. _B. taylori taylori_, adult, No. 35937 KU, 6 mi.
+       SW San Gerónimo, Coahuila.]
+
+_Baculum._--Of _Baiomys_, 166 bacula were processed, using the method of
+White (1951:125), and studied. They provide characters of taxonomic
+worth at the level of species and aid in evaluating generic
+relationships.
+
+The baculum of _B. taylori_ differs from that of _B. musculus_ in: shaft
+narrow; wings anterior to base projecting dorsolaterally instead of
+anteriorly; anterior part knob-shaped having indentation at tip, instead
+of anterior part spatulate-shaped (in some) to knob-shaped (see Figure
+7), without indentation; significantly shorter (see Table 4).
+
+    TABLE 4.--Length of Bacula
+
+  ==============+===========+=========+==========+===========+==========
+                | Number of | Average |   3 ×    |    1      |
+     Species    | specimens | length  | standard | standard  | Range
+                |           |         |  error   | deviation |
+  --------------+-----------+---------+----------+-----------+----------
+  _B. taylori_  |      108  |  2.535  |   .078   |    .274   | 2.00-3.12
+                |           |         |          |           |
+  _B. musculus_ |       58  |  3.324  |   .090   |    .233   | 2.80-3.88
+  --------------+-----------+---------+----------+-----------+----------
+
+In each of the two species, individual and geographic variation in the
+baculum is slight; its length varies insignificantly according to age.
+Excluding juveniles contained in Table 4, but including young and
+subadults, only three bacula of _B. taylori_ were longer than 3 mm., and
+only one baculum of _B. musculus_ (a young) was shorter than 3 mm. The
+total length of the baculum, considered together with its shape, serves
+to identify to species all specimens examined by me.
+
+The bacula of both species of _Baiomys_ were compared with bacula of
+_Akodon_, _Scotinomys_, _Holochilus_, _Oryzomys_, _Zygodontomys_,
+_Reithrodontomys_, _Thaptomys_, and _Calomys_ and illustrations of
+bacula by Blair (1942:197, 200) of _Peromyscus_ (subgenera _Peromyscus_,
+_Haplomylomys_, _Podomys_), _Ochrotomys_, and material at the University
+of Kansas Museum of Natural History of _Megadontomys_. Shape of baculum
+most resembled that of _Ochrotomys_ and _Calomys_. The bacula of
+_Baiomys_, as pointed out by Blair (_op cit._:203), differ as much from
+those of the genus _Peromyscus_ as do the bacula of _Reithrodontomys_
+and _Onychomys_. In size of baculum, _Baiomys_ resembles _Ochrotomys_.
+Blair (_op. cit._:202) pointed out that the length of the baculum of _B.
+taylori subater_ was contained in the length of the animal's body 20.3
+times, and 24.2 times in the length of that of _Ochrotomys nuttalli_.
+The length of the baculum of _B. musculus_ (average of 58 specimens
+without regard to subspecies) is contained in the length of the body (of
+specimens from which the bacula were removed) 22.7 times, a figure
+approaching that in _Ochrotomys_. When bacula of both species of
+_Baiomys_ were compared to those of _O. nuttalli_, bacula of _B.
+musculus_ were found to most closely resemble those of _O. nuttalli_.
+The baculum of a single specimen of _Calomys_ (_C. laucha_) was
+contained in the length of the body 15.5 times. In general shape, as
+well as in possession of an anterior knob and the position of the
+expanded posterior wings, the baculum of _C. laucha_ resembles the
+baculum of _Ochrotomys_ and _Baiomys musculus_.
+
+Blair (_op. cit._:201) considers generic _versus_ subgeneric rank for
+_Ochrotomys_, and on the basis of studies of the phallus Hooper
+(1958:23) stated that "it is clear that _nuttalli_ should be removed
+from _Peromyscus_ and should be listed as _Ochrotomys nuttalli_
+(Harlan)." I agree with Hooper (_loc. cit._) and point out that on the
+basis of the baculum, there is less of a hiatus between _Baiomys_ on the
+one hand, and _Ochrotomys_ and _Calomys_ on the other hand, than there
+is between any one of those three genera and _Peromyscus_.
+
+White (1953:631) reported that the baculum of chipmunks might indicate
+relationships more clearly than do skulls and skins. He thought that
+skulls might more quickly than bacula reflect the habitus of the animal.
+The resemblance in cranial morphology between _Peromyscus_ and _Baiomys_
+is judged to be the result of such a convergence of habitus and the
+baculum in _Baiomys_ is thought to reflect relationships more accurately
+than does the skull.
+
+_Auditory ossicles._--Examination of a number of auditory ossicles of
+_Baiomys_ reveals constant interspecific differences in the malleus and
+incus. There is only slight individual variation, slight variation with
+age, and no secondary sexual variation. In _Baiomys taylori_ the
+orbicular apophysis of the malleus (see Figure 8, A) is rounded to
+nearly ovoid; the anterior process is pointed, and the neck is short,
+being slightly recurved. The body of the incus is round and the short
+process is elongate. The sides of the long limb of the incus are nearly
+parallel. The lenticular process is relatively large. The posterior and
+anterior crus of the stapes are bowed, and the muscular process is
+either absent or much reduced.
+
+In _Baiomys musculus_, the orbicular apophysis of the malleus (see
+Figure 8, B) is round to oblong, and less ovoid than in _B. taylori_;
+the anterior process is less acutely pointed than in _B. taylori_, and
+the neck is long, less recurved than in _B. taylori_. The body of the
+incus, though tending to be round, is more flattened, and the short
+process is knob-shaped, not elongated. The sides of the long limb of the
+incus are not parallel. The lenticular process is, relative to the size
+of the incus, small. The posterior and anterior crus of the stapes are
+more nearly straight than in _taylori_. A prominent muscular process
+occurs on the posterior crus.
+
+The auditory ossicles of representative species of all the subgenera of
+_Peromyscus_ were studied as were the ossicles of _Onychomys_,
+_Ochrotomys_, _Oryzomys_, _Akodon_, _Thaptomys_, _Zygodontomys_,
+_Calomys_, _Reithrodontomys_, and _Holochilus_.
+
+    [Illustration: FIG. 8. Lateral views of auditory ossicles. × 20.
+
+    A. _B. taylori analogous_, adult, female, No. 28104 KU, 4 kms.
+       ENE Tlalmanalco, 2290 meters, Estado de México.
+
+    B. _B. musculus pallidus_, adult, male, No. 28346 KU, Cahuilotal,
+       Sacacoyuca, 960 meters, Guerrero.]
+
+The general plan of structure of the auditory ossicles in _Baiomys_
+resembles that in _Calomys_, _Akodon_, and _Thaptomys_. The ossicles of
+_Calomys_ and _Thaptomys_, in particular, closely resemble the auditory
+ossicles of _Baiomys musculus_. The short process of the incus is
+knoblike in _Calomys_ and _Thaptomys_, and the general conformation of
+malleus and stapes in those two genera is nearly identical to that in
+_B. musculus_. In _Akodon_, the anterior and posterior crus of the
+stapes is more rounded than in _B. musculus_, resembling that in _B.
+taylori_.
+
+_Reithrodontomys_ differ from _Baiomys_ in having a more elongate
+orbicular apophysis on the body of the malleus, an elongated short limb
+on the incus, and a stapes having anterior and posterior crura bowed as
+in mice of the genus _Peromyscus_.
+
+In _Ochrotomys_, the orbicular apophysis of the malleus resembles the
+orbicular apophysis of _B. musculus_, but the short process of the incus
+is longer, resembling the short process of _B. taylori_. In general
+conformation of the malleus, incus, and stapes, _Ochrotomys_ shows
+closer resemblance to _B. taylori_ than to _B. musculus_.
+
+In _Holochilus_ the anterior crus and posterior crus of the stapes are
+similar to those in _B. musculus_, but in shape and size of malleus and
+incus, _Holochilus_ differs considerably from _B. musculus_ and _B.
+taylori_.
+
+In _Zygodontomys_, size and shape of the ossicles differ greatly from
+those of _Baiomys_.
+
+In the genus _Peromyscus_, only _Peromyscus floridanus_ (subgenus
+_Podomys_) possesses a knoblike short process on the incus similar to
+that in _B. musculus_; representatives of the other subgenera examined
+possess an elongated short limb on the incus. The conformation of the
+ossicles of both _Onychomys_ and _Oryzomys_ appears to be more nearly
+like that in _Peromyscus_ than that of _Baiomys_.
+
+On the basis of shape and size of auditory ossicles, _Baiomys_ resembles
+South American hesperomines (_Calomys_ and _Thaptomys_) rather than
+North American hesperomines.
+
+
+
+
+Genus =Baiomys= True
+
+
+    1894. _Baiomys_ True, Proc. U. S. Nat. Mus., 16:758, February 7.
+       Type, _Hesperomys (Vesperimus) taylori_ Thomas.
+
+_Diagnosis._--Size small (total length in adults, 93-135); tail shorter
+than head and body; hind foot in adults 12-17; ears small (8-12) and
+rounded; upper parts blackish sepia to ochraceous-buff; underparts slaty
+gray to white or pale buffy; eyes small; hind feet having six plantar
+pads, soles nearly naked except for some hairs on anterior parts of
+soles and anteriorly to base of toes and between toes; occipitonasal
+length of skull in adults, 17.0-21.5; zygomatic breadth, 9.0-11.5;
+coronoid process of mandible well developed, strongly recurved;
+ascending ramus of mandible short and erect; anterior palatine foramina
+(incisive foramina) long, usually terminating posterior to plane of the
+front of first molars; posterior palatine foramina nearly opposite
+middle of M2; interorbital space wide relative to widest part of
+frontals; nasals projecting only slightly over incisors; condyle
+terminal; upper incisors relatively heavy; primary first fold of M3
+obliterated at an early stage of wear; major cusps of upper and lower
+anteriormost two molars alternating, more so in m1-m2 than in M1-M2,
+dental formula I/i, 1/1; C/c, 0/0; P/p, M/m, 3/3 = 16.
+
+For distribution of the genus, see Figure 9.
+
+    [Illustration: FIG. 9. Geographic distribution of the genus
+       _Baiomys_. Black area shows where the two species occur together.
+       Black dot (Acultzingo, Veracruz) shows locality where _Baiomys
+       taylori_ occurs within the range of _B. musculus_, but _B. musculus_
+       is not known to occur at that locality.]
+
+
+
+
+SYSTEMATIC ACCOUNT OF SPECIES AND SUBSPECIES
+
+
+=Baiomys musculus=
+
+Southern Pygmy Mouse
+
+(Synonymy under subspecies)
+
+    _Type._--_Sitomys musculus_ Merriam, Proc. Biol. Soc. Washington,
+       7:170, September 29, 1892.
+
+_Range._--Southern Nayarit, Michoacán, México, Morelos, Puebla, and
+central Veracruz, southeastward to western Nicaragua, but unknown from
+southern Veracruz, Tabasco, and the Yucatán Peninsula (see Figure 10);
+occurs principally in the arid upper and lower divisions of the Tropical
+Life-zone.
+
+_Characters for ready recognition._--Unless otherwise noted, characters
+are usable only for the two age-categories of adult and old adult.
+Differs from _B. taylori_ in: hind foot 16 millimeters or more;
+occipitonasal length, 19 millimeters or more; zygomatic breadth, 10
+millimeters or more; rostrum not deflected ventrally at frontoparietal
+suture but, instead, curving gradually toward anteriormost point of
+nasals; cingular ridges and secondary cusps on teeth more pronounced;
+basihyal having anterior pointed entoglossal process, shoulders of
+basihyal protruding anteriorly (characteristic of all age categories);
+baculum having broader shaft, spatulate to knob-shaped tip, wings at
+base projecting anteriorly; baculum more than 3 millimeters long; short
+process of incus knob-shaped rather than attenuate; muscular process of
+posterior crus of stapes prominent.
+
+_Characters of the species._--Size large (extremes in external
+measurements of adults; total length, 100-135; length of tail vertebrae,
+33-56; length of hind foot, 14.1-17; length of ear, 9-12); upper parts
+dark reddish brown, or ochraceous-buff to nearly black; underparts pale
+pinkish buff to white or pale buffy.
+
+_Geographic variation._--Eight subspecies are here recognized (see
+Figure 10). Features that vary geographically are external size, color
+of pelage, certain cranial dimensions (occipitonasal length, zygomatic
+breadth, least interorbital breadth, length of rostrum, length of
+incisive foramina, depth and breadth of cranium, and alveolar length of
+upper molar tooth-row).
+
+External and cranial size (except for _B. m. handleyi_) is less in the
+southernmost subspecies, _B. m. pullus_, _B. m. grisescens_, _B. m.
+nigrescens_, and more in the northernmost subspecies, _B. m. musculus_,
+_B. m. brunneus_, and _B. m. infernatis_. Increase in size from south to
+north is in keeping with Bergman's Rule that within a species, smaller
+individuals occur in warmer parts of its geographic range. Southern
+pygmy mice at high altitudes average larger than those from low
+elevations, except where the two species are sympatric. There the
+Southern Pygmy Mouse is uniformly larger, regardless of altitude.
+
+Osgood (1909:257, 259) suggested that degree of relative humidity might
+in some way control color of pelage in both _B. taylori_ and _B.
+musculus_. In _B. musculus_, the darker subspecies, _B. m. brunneus_,
+_B. m. nigrescens_, and _B. m. pullus_, occur in zones of rather
+constant high relative humidity, whereas the paler subspecies
+_infernatis_, _musculus_, _handleyi_, and to a less extent _grisescens_
+and _pallidus_, occur in zones of lower relative humidity. This is in
+keeping with Gloger's Rule, which states that melanins increase in the
+warm and humid parts of the range of a species, and reddish or
+yellowish-brown phaeomelanins prevail in arid climates. _B. m. musculus_
+ranges into areas where relative humidity is such that darker pelages
+might be expected, but this is in the area where the two species are
+sympatric, and color of pelage may be an important character of
+recognition.
+
+    [Illustration: FIG. 10. Distribution of _Baiomys musculus_. Known
+       localities of occurrence are represented by circles and black dots;
+       the former denote localities that are peripheral (marginal) for the
+       subspecies concerned.
+
+    1. _B. m. brunneus_
+    2. _B. m. grisescens_
+    3. _B. m. handleyi_
+    4. _B. m. infernatis_
+    5. _B. m. musculus_
+    6. _B. m. nigrescens_
+    7. _B. m. pallidus_
+    8. _B. m. pullus_]
+
+_Natural History_
+
+_Habitat and numbers._--In Veracruz, Dalquest obtained the southern
+pygmy mouse in stands of tall grass (_Spartina?_) in sandy loam soil
+bordering, and in, dense vegetation; Davis (1944:394) found the species
+living in dense stands of grasses and seemingly utilizing underground
+burrows. Near Chilpancingo, Guerrero, rocky situations seemed to be the
+preferred habitat. Davis (_loc. cit._) believed that the species has a
+wide tolerance to kinds of habitats. In Morelos, Davis and Russell
+(1954:75) found these mice to be abundant along rock fences separating
+cultivated fields, and in arid lowlands. In Colima, Hooper (1955b:13)
+obtained specimens from an open thorn forest in sparse grass and rocky
+hillside bounding a stream and in litter below shrubs on the floor of a
+nut-palm forest; in Michoacán, these mice were taken in cane grass,
+shrubs, and mesquite near an irrigation ditch. From Guatemala, Goodwin
+(1934:39, 40) records specimens from Sacapulas, a hot, dry, sandy area
+where cactus and sparse grasses are present, and from La Primavera, on
+the edges of pine-oak-alder forests. Felten (1958:137) has taken
+_musculus_ from bushy areas in El Salvadore. In 1955, I obtained the
+southern pygmy mouse 6 mi. SW Izucár de Matemores, Puebla, along a
+stream in heavy grass bordered by cypress, willow, fig, bamboo, and in
+rocky grazed area near sugar cane fields.
+
+The southern pygmy mouse seems to be locally abundant in certain parts
+of its geographic range, and in other parts, scarce. For example,
+Dalquest (_in. litt._) recorded the pygmy mouse as common at a place 2
+km. N Paraje Nuevo, 1700 feet, Veracruz, where, by means of 50 traps, he
+took 14 of these mice in one night. The species was scarcer, although
+the habitat seemed suitable, 3 km. N Presidio, 1500 feet, Veracruz,
+where he caught only two pygmy mice in several days of trapping. Six
+miles southwest of Izucár de Matemores, the pygmy mouse was the most
+common rodent. I have trapped for it in Oaxaca and Veracruz in habitats
+that seemed almost identical to those mentioned by Dalquest, and also
+that at Izucár de Matemores, Puebla, with almost no success. The reason
+for the seeming disparity in numbers at different localities having
+nearly the same kind of habitat is unknown to me and bears further
+investigation.
+
+_Behavior._--Little is recorded concerning the behavior of this species.
+David and Russell (_op. cit._:76) found that of small mammals _B.
+musculus_ was the first to appear at night. I caught mice of this
+species by hand in the afternoon in Puebla. They seemed to be active
+from noon until dark. Albert Alcorn wrote in his field notes that
+specimens were taken near noon at a place 9 mi. NNW Estelí, Nicaragua.
+My impression is that _musculus_ is diurnal to crepuscular.
+
+_Enemies and food._--Owl pellets (thought to be those of a barn owl,
+_Tyto alba_) from within the geographic range of _B. musculus_, from 6
+mi. SW Izucár de Matemores, yielded mandibular tooth-rows belonging to
+_musculus_. Presumably, most of the carnivorous mammals and raptorial
+birds within the range of the southern pygmy mouse could be listed as
+enemies. Diurnal to crepuscular habits of this mouse may protect it from
+some of the nocturnal carnivorous mammals and raptorial birds.
+
+Food of the southern pygmy mouse includes nuts, bark, grass seeds, and
+leaves. Dalquest (MS) writes that bits of banana proved to be useful
+bait in trapping these mice in Veracruz.
+
+_Reproduction._--Notations concerning lactation and embryos on specimen
+labels of females suggest that the southern pygmy mouse breeds in all
+months. I have records of pregnant or lactating females in every month,
+save January, April, May, and June. The average of 26 counts of embryos
+or young per litter is 2.92 (1-4).
+
+
+=Baiomys musculus brunneus= (J. A. Allen and Chapman)
+
+    _Peromyscus musculus brunneus_ J. A. Allen and Chapman, Bull. Amer.
+       Mus. Nat. Hist., 9:203, June 16, 1897; Elliott, Field Columb. Mus.
+       Publ., 105(4):136, July 1, 1905; Elliott, Field Columb. Mus. Publ.,
+       115(8):203, 1907; Osgood, N. Amer. Fauna, 28:259, April 17, 1909.
+
+    _Baiomys musculus brunneus_, Miller, Bull. U. S. Nat. Mus., 79:137,
+       December 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:318, April 29,
+       1924; Ellerman, The Families and Genera of Living Rodents, 2:402,
+       March 21, 1941; Goldman, Smith. Miscl. Coll., 115:437, July 31,
+       1951; Goodwin, Bull. Amer. Mus. Nat. Hist., 102:318, August 31,
+       1953; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:512, March 3,
+       1955; Booth, Walla Walla Publs., Dept. Biol. Sci., 20:15, July 10,
+       1957; Hall and Kelson, The Mammals of North America, 2:661, March
+       31, 1959 (part).
+
+    [_Peromyscus musculus_] _brunneus_, Elliott, Field Columb. Mus.
+       Publ., 95(4): 176, 1904.
+
+    _Peromyscus musculus_ [_musculus_], Osgood, N. Amer. Fauna, 28:258,
+       April 17, 1909 (part).
+
+    _Baiomys musculus musculus_, Davis, Jour. Mamm., 25:394, December
+       12, 1944 (part); Goldman, Smith Miscl. Coll., 115:437, July 31,
+       1951; Hooper, Jour. Mamm., 33:97, February 18, 1952 (part); Hall and
+       Kelson, The Mammals of North America, 2:661, March 31, 1959 (part).
+
+    _B._ [_aiomys_] _m._ [_usculus_] _brunneus_, Hooper, Jour. Mamm.,
+       33:96, February 18, 1952.
+
+    _Baiomys taylori_, Hooper, Jour. Mamm., 33:97, February 18, 1952
+       (part).
+
+_Type._--Adult female, skin and skull; No. 12535/10845 American Museum
+of Natural History; Jalapa, Veracruz, Republic of México; obtained on
+April 13, 1897, by F. M. Chapman, original number 1203.
+
+_Range._--Central Veracruz, coastal plains and eastern slopes of the
+plateau of Central México, see Figure 10. Zonal range: Upper Tropical
+Life-zone (Lowery and Dalquest, 1951:537), parts of the Veracruz and
+eastern Transverse Volcanic biotic provinces of Goldman and Moore
+(1945:349). Occurs from near sea level at Boca del Río, Veracruz, up to
+5500 feet 3 km. SE Orizaba.
+
+_Diagnosis._--Size medium to large for the species; ground color of
+dorsum of paratypes near Olive Brown; darkest of specimens of this
+subspecies examined (from Potrero Viejo, Veracruz) between Prouts Brown
+and Mummy Brown; distal two-thirds of guard hairs of dorsum black,
+proximal third dark gray to sooty; hairs of dorsum black-tipped having
+subterminal band of Ochraceous-Tawny; sides paler (less of dark brown)
+than dorsum; venter Deep Olive Buff to clay color, individual hairs pale
+olive buff at tips, dark gray basally; region of throat and chin sooty
+gray; ventralmost vibrissae white to base, other vibrissae black to
+base; ears dark brown, sparsely haired; forefeet and hind feet
+flesh-colored in palest specimens, sooty in darkest; tail pale brown,
+slightly paler below than above; presphenoid only slightly constricted
+towards midline; average and extreme external and cranial measurements
+of 10 adults from Cerro Gordo, Veracruz, are as follows: total length,
+118.9 (112-127); length of tail vertebrae, 45.1 (42-50); length of body,
+74.0 (69-78); length of hind foot, 16.0 (16); length of ear from notch,
+12.8 (12-13); occipitonasal length, 19.5 (19.0-20.0); zygomatic breadth,
+10.3 (10.0-10.8); postpalatal length, 7.1 (6.7-7.5); least interorbital
+breadth, 3.9 (3.7-4.0); length of incisive foramina, 4.4 (4.1-4.6);
+length of rostrum, 6.9 (6.5-7.2); breadth of braincase, 9.5 (9.2-9.7);
+depth of cranium, 7.1 (7.1-7.4); alveolar length of maxillary tooth-row,
+3.3 (3.2-3.3); for photographs of skull, see Plate 1_a_, and Plate 3_a_.
+
+_Comparisons._--For comparisons with _B. m. nigrescens_, see account of
+that subspecies. From _B. m. pallidus_, _B. m. brunneus_ differs in:
+dorsal, lateral, and facial coloration deeper reddish brown, more
+melanins present; venter darker; buff gray rather than whitish buff to
+gray as in paratypical series; vibrissae black rather than brownish to
+white; tail sooty, less flesh-colored; forefeet and hind feet averaging
+slightly grayer; most external and cranial dimensions averaging slightly
+larger; nasals less attenuated; presphenoid less hour-glass shaped,
+sides more nearly straight.
+
+From _B. m. infernatis_, _B. m. brunneus_ differs in: side of face and
+neck deep reddish-brown rather than yellowish-gray (the differences in
+dorsal colorations are greater between _brunneus_ and _infernatis_ than
+between _brunneus_ and _pallidus_); venter darker buff-gray; tail
+brownish rather than flesh-colored; forefeet and hind feet average
+slightly grayer; most external dimensions averaging slightly larger;
+cranial dimensions nearly the same except length of incisive foramina,
+which is smaller; presphenoid differs in much the same way as from
+pallidus.
+
+_Remarks_.--Specimens from Chichicaxtle, Puente Nacional, 3 km. W Boca
+del Río, 1 km. E. Mecayucan, and Río Blanco (20 km. WNW Piedras Negras),
+are all paler than the paratypical series and other specimens from
+within the assigned range of _B. m. brunneus_. All these specimens from
+the coastal plain average considerably paler than those from the front
+range and slopes of the mountains. Specimens from Puente Nacional are
+intermediate in color between paler, grayish brown, specimens from the
+coastal plains and the darker, brown, specimens from the mountains. When
+Allen and Chapman (1897:203) described _brunneus_, they did so on the
+basis of the darker brown mice from the higher altitudes. The name,
+_brunneus_, _sensu stricto_, could be restricted to those mice from the
+higher altitudes of central Veracruz. However, when the mice of
+intermediate color from Puente Nacional are considered, it seems best to
+include the material from the coastal plain with _brunneus_. Crania from
+the higher altitudes are slightly larger than, but not significantly
+different from, crania of specimens from the coastal plains. Specimens
+examined from the coastal plains resemble the darker series of _B. m.
+pallidus_ to the west in central México. But there is no evidence of
+gene flow between the paler coastal specimens and _B. m. pallidus_ to
+the west. In fact, these paler brown mice on the coastal plain grade in
+color into the darker brown mice from the mountains. The paler mice from
+the coast may be an incipient subspecies.
+
+The type and paratypes seem to have faded somewhat since they were
+described by Allen and Chapman (_loc. cit._) and by Osgood (1909:259).
+However, the color of the paratypes and other specimens herein assigned
+is the feature most useful for distinguishing _brunneus_ from all other
+subspecies of _B. musculus_.
+
+_Specimens examined._--Total 187 all from VERACRUZ, Republic of México,
+and distributed as follows: type locality, 4400 ft., 16[1] (including
+the type), 6[2], 1[3]; _Cerro Gordo_, 1500 ft., 19; _Teocelo_
+[= _Texolo_], 4500 ft., 1; _2 mi. NW Plan del Río_, 1000 ft., 14[4];
+_Plan del Río_, 1000 ft., 2[5]; _Carrizal_, 4[2]; Chichicaxtle, 3[2];
+_Puente Nacional_, 500 ft., 1[5], 2; _Santa Maria, near Mirador_, 1800 ft.,
+10[2]; Boca del Río, 10 ft., 1[5], 8; _Córdoba_ [= _Córdova_], 14[1];
+_4 km. WNW Fortín_, 4; _Río Atoyac, 8 km. NW Potrero_, 1; _2 km. N.
+Paraje Nuevo_, 1700 ft., 9; _El Xuchil_, _1 mi. W. Paraje Nuevo_, 6[6];
+Potrero Viejo, 1700 ft. 15; _Cautlapán_ [= _Ixtaczequitlán_], 4000 ft.,
+16; _Micayucan_, 1; 3 km. SE Orizaba, 5500 ft., 3; Río Blanco, 20 km.
+WNW Piedras Negras, 400 ft, 7; _29 km. SE Córdoba, Presidio_, 15[4];
+_3 km. N Presidio_, 1500 ft., 2; Presidio, 600 meters, 6[3].
+
+_Marginal records._--VERACRUZ: type locality; Chichicaxtle; Boca del
+Río, 10 ft.; Río Blanco, 20 km. WNW Piedras Negras, 400 ft; Presidio; 3
+km. SE Orizaba, 5500 ft.
+
+[1] American Museum of Natural History.
+
+[2] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[3] Chicago Natural History Museum.
+
+[4] Univ. Michigan, Museum of Zoology.
+
+[5] Texas A & M, Coop. Wildlife Res. Coll.
+
+[6] Univ. Illinois, Mus. Nat. History.
+
+
+=Baiomys musculus grisescens= Goldman
+
+    _Baiomys musculus griesescens_ Goldman, Proc. Biol. Soc. Washington,
+       45:121, July 30, 1932; Ellerman, The Families and Genera of Living
+       Rodents, 2:402, March 21, 1941; Poole and Schantz, Bull. U. S. Nat.
+       Mus., 178:259, March 6, 1942; Goodwin, Bull. Amer. Mus. Nat. Hist.,
+       79(2):160-161, May 29, 1942 (part); Miller and Kellogg, Bull. U. S.
+       Nat. Mus., 205:513, March 3, 1955 (part); Felten, Senck. Biol.,
+       39:136, August 30, 1958; Packard, Univ. Kansas Publs., Mus. Nat.
+       Hist., 9:401, December 19, 1958; Hall and Kelson, The Mammals of
+       North America, 2:661, March 31, 1959 (part).
+
+_Type._--Adult female, skin and skull; No. 257083 U. S. Nat. Mus. (Biol.
+Surv. Coll.); Comayabuela [= Comayaguela] just south of Tegucigalpa,
+3100 feet, Honduras; obtained on March 6, 1932, by C. F. Underwood,
+original number 838.
+
+_Range._--Central to south-central Guatemala, east to south-central
+Honduras. Zonal range: Lower parts of the Merendon Biotic Province of
+Smith (1949:235). Occurs from 3200 feet at a place 1/2 mi. N and 1 mi. W
+Salama, Guatemala, up to approximately 4500 feet at Monte Redondo,
+Guatemala.
+
+_Diagnosis._--Size medium to small for the species; general ground color
+of dorsum between Olive Brown and Buffy Brown; distal fourth of
+individual guard hairs of dorsum black-tipped, proximal three-fourths
+gray, underfur black-tipped with subterminal band of Vinaceous-Buff,
+gray basally; facial region below eye Olive-Buff to Deep Olive-Buff;
+regions of flanks without black-tipped guard hairs, therefore, appearing
+paler brownish-buff than dorsum; venter Pale Olive-Buff to whitish in
+midline, hairs there white to base, laterally grayish basally; hairs in
+region of throat and chin resemble those of underparts; forefeet and
+hind feet flesh-colored with grayish suffusion; ears dusky brown; tail
+almost unicolored, slightly darker brown above than below; coronoid
+process less acutely falcate than in other subspecies; zygoma bowed.
+Average and extreme external and cranial measurements of 14 adults from
+La Piedra de Jesús Sabana Grande, Honduras, are as follows: Total
+length, 110.7 (100-123); length of tail vertebrae, 44.0 (32-55); length
+of body, 66.7 (60-70); length of hind foot, 14.1 (12-15); length of ear
+from notch, 11.8 (10-13); occipitonasal length, 19.3 (18.9-19.8);
+zygomatic breadth, 10.1 (9.8-10.4); postpalatal length, 6.8 (6.2-7.3);
+least interorbital breadth, 3.9 (3.8-4.1); length of incisive foramina,
+4.3 (4.0-4.5); length of rostrum, 6.9 (6.6-7.2); breadth of braincase,
+9.6 (9.2-10.1); depth of cranium, 7.0 (6.8-7.3); alveolar length of
+maxillary tooth-row, 3.2 (3.0-3.4); for photographs of skull, see Plate
+1_b_, and Plate 3_b_.
+
+_Comparisons._--For comparisons with _B. m. pullus_ and _B. m.
+handleyi_, see accounts of those subspecies. From _B. m. nigrescens_,
+_B. m. grisescens_ differs in: dorsum less blackish (dark brown to
+buffy); face buffy below eye rather than brownish-black; venter buffy to
+whitish in midline, not sooty gray; forefeet and hind feet flesh-colored
+with gray overtones, not dusky to sooty; zygoma bowed, sides less
+parallel; braincase and bony palate slightly broader.
+
+_Remarks._--Goodwin (1942:160) mentioned that a specimen from the type
+locality of _grisescens_ was as dark as specimens of _B. m. nigrescens_
+from Guatemala. However, all specimens from Guatemala, other than those
+from Sacapulas, were referred by Goodwin (1934:40) to _B. m.
+nigrescens_. My studies reveal a grayish-brown population in central
+Honduras near to and including the type locality. This population
+appears to grade into a slightly paler, particularly as concerns color
+of hind foot and tail, group of Guatemalan mice from 1 mi. S Rabinal,
+from 1/2 mi. N, 1 mi. E Salama, and from Lake Atescatempa. Specimens
+from western Guatemala at Nentón and Jacaltenango, on the other hand,
+are darker brownish-black, more nearly like the paratypical series of
+_nigrescens_ from the Valley of Comitán, Chiapas, Republic of México.
+This darker brownish-black color of the back persists in specimens from
+southern Guatemala and El Salvador (see specimens examined of _B. m.
+nigrescens_ for localities), and they are best referred to _nigrescens_.
+_B. m. grisescens_, in color and certain cranial characters, therefore,
+seems to grade into two different subspecies: (1) _B. m. handleyi_, pale
+mice in the Río Negro valley in central Guatemala, and (2) _B. m.
+nigrescens_, dark mice from southern Guatemala, and parts of El
+Salvador.
+
+Felten (1958:136) referred all _B. musculus_ from El Salvador to _B. m.
+grisescens_. Although I have not examined the specimens reported on by
+Felten (_loc. cit._), I have examined specimens from Lake Atescatempa,
+Guatemala (which I refer to _grisescens_), not too distant from Cerro
+Blanco, and Finca Las Canarias, Department of Ahuachapan, and Laguna de
+Guija, Department of Santa Ana (localities listed by Felten). It would
+seem that specimens from these localities might indeed be _grisescens_.
+However, specimens that I examined from 1 mi. S Los Planes, and 1 mi. NW
+San Salvador were considerably darker than paratypes of _grisescens_ and
+were nearly intermediate in color between _nigrescens_ and _pullus_. I
+refer the specimens from 1 mi. NW San Salvador, and 1 mi. S Los Planes
+to _nigrescens_ rather than to _grisescens_.
+
+There is no positive evidence that _B. m. grisescens_ intergrades with
+_B. m. pullus_ to the south in Nicaragua. But, there is a suggestion
+that intergradation occurs between these subspecies in a series of 76
+skins from La Piedra de Jesús Sabana Grande, Honduras, referable to
+_grisescens_. A total of 16 of 76 skins from this locality (21 per cent)
+possess the mid-ventral white stripe found in 18 of 20 skins (90 per
+cent), from the type locality of _pullus_ in Nicaragua. Further
+collection in areas between central Honduras and western Nicaragua may
+yield specimens of _B. musculus_ that are intermediate in characters
+between _grisescens_ and _pullus_.
+
+_Specimens examined._--Total 149, distributed as follows: GUATEMALA: 1
+mi. S Rabinal, 3450 ft., 14; 1/2 mi. N, 1 mi. E Salama, 3200 ft., 10;
+Lake Atescatempa, 10[7]. HONDURAS: Cementario, Gracias, 1[8]; Monte
+Redondo, 1[8]; El Caliche, Cedros, 1[8]; _La Flor Archaga_, 2[8], 1[9];
+Hatillo, 1[8]; _type locality_, 7[8], 6[7] (including the type), 3[9];
+_El Zapote_, _Sabana Grande_, 4[8]; La Piedra de Jesús Sabana Grande,
+76[8]; _Cerro de las Cuches Sabana Grande_, 5.
+
+_Marginal records._--GUATEMALA: 1/2 mi. N, 1 mi. E Salama, 3200 ft.
+HONDURAS: El Caliche, Cedros; Hatillo; La Piedra de Jesús Sabana Grande;
+Cementario. GUATEMALA: Lake Atescatempa; 1 mi. S Rabinal, 3450 ft.
+
+[7] United States National Museum (Biol. Surv. Collections).
+
+[8] American Museum of Natural History.
+
+[9] Univ. Michigan, Museum of Zoology.
+
+
+=Baiomys musculus handleyi= Packard
+
+    _Baiomys musculus handleyi_ Packard, Univ. Kansas Publs., Mus. Nat.
+       Hist., 9:399, December 19, 1958.
+
+    _Baiomys musculus musculus_, Goodwin, Bull. Amer. Mus. Nat. Hist.,
+       68(1):39-40, December 12, 1934 (part); Miller and Kellogg, Bull.
+       U. S. Nat. Mus., 205:512, March 3, 1955 (part).
+
+    _Baiomys musculus nigrescens_, Hall and Kelson, The Mammals of North
+       America, 2:661, March 31, 1959 (part).
+
+_Type._--Adult female, skin and skull; No. 275604 U. S. Nat. Mus. (Biol.
+Surv. Coll.); Sacapulas, El Quiche, Guatemala; obtained on April 24,
+1947, by Charles O. Handley, Jr., original number 991.
+
+_Range._--Known only from the type locality in the valley of the Río
+Negro. Zonal range: Part of the Chimaltenangan Province of Smith
+(1949:235).
+
+_Diagnosis._--Size medium to large for the species; dorsum Wood Brown in
+some series to Buffy Brown; guard hairs of dorsum black-tipped, color of
+underhairs Avellaneous; hairs white to base in region of chin, throat,
+and median venter; in lateral region, hairs Neutral Gray at base; dorsal
+surfaces of forefeet and hind feet and ankles white; tail white below,
+brownish above; nasals truncate anteriorly; frontoparietal suture
+forming an obtuse angle with the suture separating the parietals;
+alveolar length of upper molar tooth-row and tail long. Average and
+extreme external and cranial measurements for nine adults from the type
+locality are as follows: Total length, 121.4 (115-128); length of tail
+vertebrae, 50.7 (49-54); length of body, 70.8 (66-77); length of hind
+foot, 15.3 (15-16); occipitonasal length, 19.6 (18.8-20.7); zygomatic
+breadth, 10.5 (10.2-11.0); postpalatal length, 6.9 (6.4-7.4); least
+interorbital breadth, 4.0 (3.9-4.0); length of incisive foramina, 4.2
+(4.0-4.5); length of rostrum, 7.2 (7.0-7.7); breadth of braincase, 9.8
+(9.7-10.2); depth of cranium, 7.1 (6.8-7.2); alveolar length of
+maxillary tooth-row, 3.5 (3.4-3.6); for photographs of skull, see Plate
+1_c_, and Plate 3_c_.
+
+_Comparisons._--From _B. m. nigrescens_, _B. m. handleyi_ differs as
+follows: everywhere paler; forefeet and hind feet whitish instead of
+dusky to sooty; hairs of anterior part of face white instead of brown;
+tail bicolored instead of unicolored; anterior tips of nasals truncate
+rather than rounded; frontoparietal suture forming obtuse angle with
+suture separating parietals instead of forming right angle; tail and
+upper molar tooth-row longer.
+
+From _B. m. grisescens_, _B. m. handleyi_ differs in: slightly paler
+above and below, primarily as a result of lacking buff-colored hairs;
+forefeet and hind feet white, not flesh-colored with gray overtones;
+tail bicolored, not unicolored; anterior tips of nasals truncate rather
+than flaring; tail and upper molar tooth-row longer.
+
+_Remarks._--_B. m. handleyi_ seems to be restricted to the valley of the
+Río Negro, in the region of Sacapulas, Guatemala. Stuart (1954:7) points
+out that the Río Negro drops down into a gorge at a place near Sacapulas
+and flows northward through a deep canyon for approximately 60
+kilometers. The Río Negro, then, flows onto the lowlands of the Yucatán
+Peninsula. The habitat is xerophytic in the valley of the Río Negro near
+Sacapulas. Stuart (_op. cit._:10) suggests that this xerophytic habitat
+may be continuous to a place to the north of Chixoy, Chiapas, where the
+vegetation then becomes more mesic. The mesic conditions to the north in
+Tabasco and Yucatán probably have restricted the movement of pygmy mice
+to the north. No specimens of this mouse are known from the Yucatán
+Peninsula or from the State of Tabasco, México. _B. m. handleyi_
+intergrades with _B. m. grisescens_ to the south. Specimens from 1 mi. S
+Rabinal, and those from a second locality 1/2 mi. N and 1 mi. E Salama,
+Guatemala, are intermediate in color of pelage between _handleyi_ and
+_grisescens_. Stuart (_op. cit._:5) mentions the continuity of habitat
+and tributaries from the Salama Basin into the valley of the Río Negro.
+Absence of physiographic and biotic barriers in the corridor between
+these two basins probably allows for some gene flow between _handleyi_
+and _grisescens_, and results in populations intermediate in color. To
+the north and northwest of Sacapulas, the Sierra de los Cuchumatanes
+rises abruptly and separates the known geographic range of _handleyi_
+from that of _nigrescens_ to the north, while to the west the
+cactus-mesquite habitat of _handleyi_ gives way to the oak-pine timber
+that, so far as known, does not support _Baiomys_. The difference in
+elevation and flora seems to restrict gene flow between _handleyi_ and
+the more northern _nigrescens_. The only evidence of integration between
+these two subspecies is provided by one specimen from Chanquejelve,
+Guatemala. That specimen is intermediate in color between the pale
+_handleyi_ and blackish-brown _nigrescens_.
+
+The subspecies closest, geographically, to _B. m. handleyi_ is _B. m.
+nigrescens_, from which _B. m. handleyi_ differs more in color than from
+any of the other named subspecies, except _B. m. pullus_. There is a
+close correlation of pallor of mice and the xeric Río Negro Valley, and
+the darkness (melanistic color) of mice and the mesic mountains and
+valleys to the north.
+
+_Specimens examined._--Total 49, from GUATEMALA: type locality,
+including the type: 12 (U. S. Nat. Mus., Biol. Surv. Coll.), 37 (Amer.
+Mus. Nat. Hist.).
+
+
+=Baiomys musculus infernatis= Hooper
+
+    _Baiomys musculus infernatis_ Hooper, Jour. Mamm., 33:96, February
+       18, 1952; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:512,
+       March 3, 1955; Hall and Kelson, The Mammals of North America,
+       2:661, March 31, 1959.
+
+    _Baiomys musculus musculus_, Hooper, Jour. Mamm., 28:50, February
+       15, 1947 (part).
+
+_Type._--Adult male, skin and skull; No. 91497 Univ. of Michigan, Museum
+of Zoology; Teotitlán, Oaxaca, Republic of México, obtained on February
+24, 1947, by Helmuth O. Wagner, original number 2702.
+
+_Range._--Southeastern Puebla, in the basin drained by the Río Salado
+and Río Quiotepec, into northern Oaxaca. Zonal range: Arid Tropical in a
+part of the Orizaba-Zempoaltepec Faunal District of the Transverse
+Volcanic Biotic Province of Moore (1945:218). Occurs from 3100 feet in
+Oaxaca up to 6000 feet in Puebla.
+
+_Diagnosis._--Size medium for the species; dorsum Drab, terminal parts
+of individual guard hairs black, Neutral Gray basally, distal parts of
+underfur Pinkish Buff, proximally Neutral Gray; sides same color as
+dorsum; hairs in region of throat and chin white to base; venter whitish
+to Neutral Gray with tinges of Pinkish Buff; dorsal parts of forefeet
+and hind feet whitish with flesh-colored undertones, ventral parts
+whitish to dusky-gray; tail bicolored, grayish-brown above, white below;
+tip of tail not bicolored, instead grayish-brown throughout; ears pale
+brown, sparsely haired; incisive foramina long, not constricted
+posteriorly. Average and extreme external measurements for 9 adults from
+the type locality are as follows: total length, 113.9 (106-122); length
+of tail vertebrae, 44.1 (41-48); length of body, 71.0 (65-79); length of
+hind foot, 14.8 (13-16); length of ear, 11.9 (11-12). Average and
+extreme cranial measurements of 7 adults from the type locality are as
+follows: Occipitonasal length, 20.1 (19.7-20.4); zygomatic breadth, 10.4
+(10.2-10.6); postpalatal length, 7.3 (7.0-7.7); least interorbital
+breadth, 4.2 (4.0-4.4); length of incisive foramina, 4.8 (4.4-5.6);
+length of rostrum, 7.2 (6.6-7.5); breadth of braincase, 9.6 (9.5-9.8);
+depth of cranium, 7.4 (7.1-7.6); alveolar length of maxillary tooth-row,
+3.3 (3.1-3.4); for photographs of skull, see Plate 1_d_, and Plate 3_d_.
+
+_Comparisons._--For comparisons with _B. m. nigrescens_ and _B. m.
+brunneus_, see accounts of those subspecies. From _B. m. pallidus_, _B.
+m. infernatis_ differs in: sides, ears, and dorsum paler (less of dark
+brown); venter whitish gray rather than gray with tinge of buff and
+brown; forefeet and hind feet paler; tail bicolored, not unicolored;
+incisive foramina longer and not constricted posteriorly; mastoid
+process turning dorsally and sickle-shaped at posteriormost point rather
+than capitate.
+
+_Remarks._--_B. m. infernatis_ resembles _B. m. handleyi_ more than any
+other subspecies in color of pelage and in external and cranial
+dimensions. The resemblance in color between _B. m. pallidus_, in
+certain parts of its range, and _B. m. handleyi_ may have resulted from
+nearly parallel selective forces that gave rise to two subspecies,
+widely separated geographically. The same relation obtains between _B.
+m. infernatis_ and _B. m. handleyi_. Both inhabit arid river basins. In
+them, pale soil and low relative humidity are important passive factors
+of selection that give adaptive value to the pale colors of pelage of
+both _infernatis_ and _handleyi_.
+
+Specimens from 6-1/2 mi. SW Izucár de Matemores, and 1 mi. SSW Tilapa,
+Puebla, are intergrades between _B. m. infernatis_ and _B. m.
+pallidus_. These specimens are intermediate in color and cranial
+characters between the aforementioned subspecies but possess more of the
+pale brown overtones seen in paratypes of _pallidus_, and are best
+referred to that subspecies.
+
+_Specimens examined_ (All in Univ. Michigan, Mus. Zool.).--Total 18, all
+from the Republic of México and distributed as follows: PUEBLA,
+Tepanaco, 6000 ft., 3, Tehuacán, 5400 ft., 3. OAXACA: Type locality,
+3100 ft., 12 (including the type).
+
+_Marginal records._--See specimens examined.
+
+
+=Baiomys musculus musculus= (Merriam)
+
+    _Sitomys musculus_ Merriam, Proc. Biol. Soc. Washington, 7:170,
+       September 29, 1892; Lyon and Osgood, Bull. U. S. Nat. Mus.,
+       62:135, January 15, 1909.
+
+    _Baiomys musculus_ [= _musculus_], Mearns, Bull. U. S. Nat. Mus.,
+       56:381, April 13, 1907; Hooper, Jour. Mamm., 36:29, May 26, 1955.
+
+    _Peromyscus musculus_ [_musculus_], J. A. Allen and Chapman, Bull.
+       Amer. Mus. Nat. Hist., 9:203, June 16, 1897; Elliot, Field Columb.
+       Mus. Publ., 105(4):135, July 1, 1905; Osgood, N. Amer. Fauna,
+       28:257, April 17, 1909 (part).
+
+    [_Peromyscus_] _musculus_, Trouessart, Cat. Mamm., 1:518, 1898.
+
+    [_Peromyscus_] _musculus_ [_musculus_], Elliot, Field Columb. Mus.
+       Publ., 95(4):175, July 15, 1904.
+
+    _Baiomys musculus musculus_, Miller, Bull. U. S. Nat. Mus., 79:137,
+       December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:318,
+       April 29, 1924 (part); Ellerman, The Families and Genera of Living
+       Rodents, 2:402, March 21, 1941; Poole and Schantz, Bull. U. S. Nat.
+       Mus., 178:258, March 6, 1942; Davis, Jour. Mamm., 25:394, December
+       12, 1944 (part); Hooper, Jour. Mamm., 28:50, February 15, 1947
+       (part); Hall and Villa-R., Univ. Kansas Publs., Mus. Nat. Hist.,
+       1:460, December 27, 1949 (part); Hall and Villa-R., Anal. del Inst.
+       Biol., 21:196, September 28, 1950 (part); Goldman, Smith. Miscl.
+       Coll., 115:336, July 31, 1951 (part); Miller and Kellogg, Bull.
+       U. S. Nat. Mus., 205:512, March 3, 1955 (part); Hooper, Occas.
+       Papers Mus. Zool. Univ. Michigan, 565:13, March 31, 1955; Hall and
+       Kelson, The Mammals of North America, 2:661, March 31, 1959 (part).
+
+    _B._ [_aiomys_] _m._ [_usculus_] _musculus_, Hooper, Jour. Mamm.,
+       33:97, February 18, 1952 (part); Packard, Univ. Kansas Publs.,
+       Mus. Nat. Hist., 9:400; December 19, 1958.
+
+    _Baiomys taylori allex_, Hall and Kelson, The Mammals of North
+       America, 2:659, March 31, 1959 (part).
+
+_Type._--Adult female, skin and skull; No. 33437/45460 U. S. Nat. Mus.
+(Biol. Surv. Coll.); Colima (City), Colima, Republic of México, obtained
+on March 9, 1892, by E. W. Nelson, original number 2055.
+
+_Range._--Southwestern Nayarit and northwestern Jalisco, south into
+Colima, thence eastward into Michoacán. Zonal range: part of arid Lower
+Tropical Subzone of Goldman (1951:330); approximates part of the
+Nayarit-Guerrero Biotic Province of Goldman and Moore (1945:349). Occurs
+from near sea level in Colima up to 5800 feet in Jalisco.
+
+_Diagnosis._--Size large for the species; dorsum Olive-Brown in darkest
+series to Buffy Brown with tones of Fawn Color in the palest series;
+guard hairs of dorsum black-tipped, gray basally (in some specimens,
+guard hairs gray-tipped with subterminal black band, and gray base);
+underfur of dorsum black-tipped with subterminal band of fawn to buff,
+Neutral Gray basally; face and head paler than back because of greater
+number of fawn-colored and buff-colored hairs; hairs on throat and chin
+white to base; venter and flanks Pale Olive-Buff in palest series to
+Gray (Pale Gull Gray) in darkest series; individual hairs of venter
+tipped with white to buff, basally Gray (Dark Gull Gray); forefeet and
+hind feet white to gray with flesh-colored undertones; tail faintly
+bicolored, individual hairs above black, below white; nasals flared
+anteriorly; zygoma and zygomatic plate thick. Average and extreme
+external and cranial measurements for 8 adults from Armeria, Colima, are
+as follows: total length, 125.5 (115-135); length of tail vertebrae,
+47.5 (42-54); length of body, 75.6 (68-81); length of hind foot, 16.5
+(16-17); occipitonasal length, 20.3 (19.8-20.7); zygomatic breadth, 10.7
+(10.3-11.1); postpalatal length, 7.4 (7.1-7.7); least interorbital
+breadth, 4.0 (3.9-4.1); length of incisive foramina, 4.3 (4.1-4.5);
+length of rostrum, 7.3 (6.9-7.6); breadth of braincase, 9.8 (9.4-10.0);
+depth of cranium, 7.1 (6.7-7.2); alveolar length of maxillary tooth-row,
+3.4 (3.3-3.6); for photographs of skull, see Plate 1_e_, and Plate 3_e_.
+
+_Comparisons._--For comparisons with _B. m. brunneus_, _B. m.
+infernatis_, and _B. m. pallidus_, see accounts of those subspecies.
+From _B. m. nigrescens_, _B. m. musculus_ differs in: dorsum paler
+throughout (less of blackish brown); region of face and ears paler, more
+buff and fawn-colored hairs rather than blackish-brown to grayish hairs;
+vibrissae paler; venter paler, less dark gray and less of sooty-colored
+undertones, tips of hairs whitish to pale Olive-Buff rather than light
+gray at tips becoming darker basally; forefeet and hind feet paler,
+whitish to pale buff-color with flesh-colored undertones, not
+sooty-colored to dark brown; tail paler below; nasals flaring outward,
+not tapering toward midline at anteriormost point; zygoma more massive;
+larger in external and cranial dimensions.
+
+_Remarks._--Merriam (1892:170) described _Sitomys_ [= _Baiomys_]
+_musculus_ on the basis of 23 specimens (from Colima City, Colima;
+Armeria, Colima; Plantinar, and Zapotlán, Jalisco). According to the
+original description, _B. musculus_ resembled a small house mouse and
+was smaller than any known species of _Sitomys_ except _S. taylori_ [=
+_Baiomys taylori_]. From _taylori_, _musculus_ differed in being larger
+[in size of body], and in having longer ears and tail, and larger hind
+feet. When Allen and Chapman (1897:203) described _Peromyscus_ [=
+_Baiomys_] _musculus brunneus_ from Jalapa, Veracruz, the specimens
+described by Merriam from Colima and Jalisco became representative of
+the nominal subspecies _B. m. musculus_. Osgood (1909:258) assigned
+specimens from Colima, Guerrero, Jalisco, Michoacán, Morelos, Oaxaca,
+Puebla, Sinaloa, Veracruz, and Zacatecas to the subspecies _musculus_.
+Subsequently, Russell (1952:21) named the subspecies _pallidus_ from the
+arid lowlands of Morelos; Hooper (1952:96) described the subspecies
+_infernatis_ from northern Oaxaca and southeastern Puebla; and Goodwin
+(1959:1) described a new subspecies _nebulosus_ from the Oaxaca
+highlands. Each of the subspecies mentioned immediately above was
+described from within the geographic range assigned to _B. m. musculus_
+by Osgood (_loc. cit._). Hall and Kelson (1959:661) mapped the range of
+_B. m. musculus_ so as to include Colima, parts of Jalisco, Michoacán,
+Guerrero, Oaxaca, and Veracruz. Lukens (1955:159), in a study of the
+mammals of Guerrero, has shown that the characters attributed to _B. m.
+pallidus_ are not significantly different from those of pygmy mice
+studied from Guerrero. He (_loc. cit._) concluded that: (1) if the
+specimens of pygmy mice from central Guerrero were typical of the
+subspecies _musculus_, then _pallidus_ did not deserve subspecific
+recognition, or; (2) the name _B. m. musculus_ should be restricted to
+the larger pygmy mice inhabiting the lowlands immediately adjacent to
+the Pacific Coast and the area to the north. My data (see Figure 12)
+show pygmy mice from southwestern Nayarit, northwestern and central
+Jalisco, Colima, and parts of Michoacán to be significantly larger in
+certain cranial and external measurements than pygmy mice from Guerrero,
+Oaxaca, Morelos, and parts of Puebla. This finding essentially
+corroborates Hooper's (1952a:96) findings. It seems advisable,
+therefore, to restrict the range of _B. musculus musculus_ to the large
+mice inhabiting west-central México and the coastal lowlands of Colima
+and Michoacán. The name _pallidus_ is applicable to the smaller mice
+occupying Morelos, southwestern Puebla, Guerrero, Oaxaca, and
+southwestern Chiapas.
+
+_B. m. musculus_ intergrades with _B. m. pallidus_ in eastern Michoacán
+and central and western Guerrero. Specimens from San José Prura and 12
+mi. S Tzitzio, Michoacán, though referable to _B. m. musculus_ because
+of slightly larger size of crania are intermediate in size and color
+between the smaller and slightly darker _pallidus_ to the south and east
+and the larger, slightly paler _musculus_ to the northwest.
+
+_Specimens examined._--Total 156 all from the Republic of México, and
+distributed as follows: NAYARIT: 3 mi. NNW Las Varas, 150 ft., 1.
+JALISCO: 7 mi. W Ameca, 4000 ft., 2[10]; _6 mi. W Ameca_, 4300 ft., 3[10];
+_10 mi. S Ameca_, 5800 ft., 1[10]; _13 mi. S, 15 mi. W Guadalajara_, 3;
+_13 mi. S, 9-1/2 mi. W Guadalajara_, 1; _3 mi. ENE Santa Cruz de las
+Flores_, 1; 27 mi. S, 12 mi. W Guadalajara, 1; _4 mi. NE Autlán_, 3000
+ft., 5[10]; _Sierra de Autlán_, 5000 ft., 2[10]; _2-1/2 mi. NNE Autlán_,
+3000 ft., 8; 2 mi. SSE Autlán, 1; _5 mi. S Purificación_, 2; Chamela
+Bay, 1[10]; _2 mi. N La Resolana_, 1500 ft., 6[10]; _1 mi. N San Gabriel_,
+4000 ft., 32[10]; 2 mi. N Cuidad Guzmán, 5000 ft., 1; 3 mi. E Navidad,
+4300 ft., 10[10]. COLIMA: _type locality_, 10[11] (including the type); _3
+mi. SE Colima_ (_City_), 5[10]; _4 mi. SW Colima City_, 1; Armeria, 200
+ft., 8[11]; _Paso del Río_, 20[10].
+
+MICHOACÁN: 12 mi. S Tzitzio, 6[10]; San José Prura, 4[12]; 1 mi. E, 6 mi.
+S Tacámbaro, 4000 ft., 3[13]; La Salada, 3[11]; 1/2 mi. SE Coalcomán,
+15[10].
+
+_Marginal records._--NAYARIT: 3 mi. NNW Las Varas, 150 ft. JALISCO: 3
+mi. E Navidad, 4300 ft.; 27 mi. S, 12 mi. W Guadalajara. MICHOACÁN: 12
+mi. S Tzitzio; San José Prura; 1/2 mi. SE Coalcomán. COLIMA: Armeria,
+200 ft. JALISCO: Chamela Bay.
+
+[10] Univ. Michigan, Museum of Zoology.
+
+[11] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[12] Chicago Natural History Museum.
+
+[13] Univ. California, Mus. Vert. Zoology.
+
+
+=Baiomys musculus nigrescens= (Osgood)
+
+    _Peromyscus musculus nigrescens_ Osgood, Proc. Biol. Soc.
+       Washington, 17:76, March 21, 1904; Elliot, Field Columb. Mus. Publ.,
+       105(4):136, July 1, 1905; Lyon and Osgood, Bull. U. S. Nat. Mus.,
+       62:135, January 15, 1909; Osgood, N. Amer. Fauna, 28:259, April 17,
+       1909.
+
+    _Baiomys musculus nigrescens_, Miller, Bull. U. S. Nat. Mus.,
+       79:137, March 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:318,
+       April 29, 1924; Goodwin, Bull. Amer. Mus. Nat. Hist., 68(1):40,
+       December 12, 1934; Ellerman, The Families and Genera of Living
+       Rodents, 2:402, March 21, 1941; Poole and Schantz, Bull. U. S. Nat.
+       Mus., 178:259, March 6, 1942; Hooper, Jour. Mamm., 28:50, February
+       15, 1947; Goldman, Smith. Miscl. Coll., 115:357, July 31, 1951;
+       Miller and Kellogg, Bull. U. S. Nat. Mus., 205:513, March 3, 1955;
+       Booth, Walla Walla Publs., Dept. Biol. Sci., 20:15, July 10, 1957;
+       Hall and Kelson, The Mammals of North America, 2:661, March 31, 1959
+       (part).
+
+    [_Peromyscus musculus_] _nigrescens_, Elliot, Field Columb. Mus.
+       Publ., 95(4):176, 1904.
+
+    _B._ [_aiomys_] _m._ [_usculus_] _nigrescens_, Goodwin, Bull. Amer.
+       Mus. Nat. Hist., 79(2):160, May 29, 1942; Hooper, Jour. Mamm.,
+       33:97, February 18, 1952 (part); Packard, Univ. Kansas Publs.,
+       Mus. Nat. Hist., 9:399, December 19, 1958.
+
+    _B._ [_aiomys_] _m._ [_usculus_] _musculus_, Booth, Walla Walla
+       Publs., Dept. Biol. Sci., 20:15, July 10, 1957 (part).
+
+_Type._--Adult female, skin and skull; No. 76827 U. S. Nat. Mus. (Biol.
+Surv. Coll.); Valley of Comitán, Chiapas, Republic of México, obtained
+on December 9, 1895, by E. W. Nelson and E. A. Goldman, original number
+8719.
+
+_Range._--Southern coastal region and eastern parts of Chiapas,
+southeastward into central and southern Guatemala, thence south into El
+Salvador (see Figure 10). Zonal range: parts of Lower Austral; also
+occurs in parts of the arid division of the Upper Tropical Life-zone,
+and in parts of the arid division of the Lower Tropical Life-zone;
+approximates a part of the Chiapas Highlands Biotic Province of Goldman
+and Moore (1945:349), and parts of the Guatemalan Subregion of Smith
+(1949:235).
+
+_Diagnosis._--Size medium to small for the species; dorsum Vandyke Brown
+mixed with blackish, individual hairs black-tipped with a subterminal
+band of Warm Buff, Neutral Gray at base; guard hairs of dorsum black
+distally, Neutral Gray basally; hairs on sides grayish-brown, facial
+region like dorsum; chin buffy-brown; vibrissae brown, ventrally some
+white; venter creamy-buff to grayish, individual hairs creamy-buff at
+tips, gray basally; in region of throat and chin, hairs tipped with
+Ochraceous-Buff; dorsal surface of forefeet and hind feet dull whitish
+gray to brownish-black; tail indistinctly bicolored, dusky above,
+grayish to brownish below; incisive foramina short, wide medially;
+average and extreme external and cranial measurements of 15 adults from
+6 mi. NW Tonalá, Chiapas, are as follows: total length, 107.5 (100-116);
+length of tail vertebrae, 41.1 (33-48); length of body, 66.1 (62-73);
+length of hind foot, 15.0 (14-16); length of ear, 10.9 (10-12);
+occipitonasal length, 18.9 (18.4-19.7); zygomatic breadth, 9.8
+(9.4-10.2); postpalatal length, 6.9 (6.6-7.4); least interorbital
+breadth, 3.7 (3.5-3.8); length of incisive foramina, 4.4 (4.1-4.8);
+length of rostrum, 6.7 (6.1-7.1); breadth of braincase, 9.2 (9.0-9.4);
+depth of cranium, 6.9 (6.5-7.3); alveolar length of maxillary tooth-row,
+3.1 (2.9-3.2); for photographs of skull, see Plate 1_f_, and Plate 3_f_.
+
+_Comparisons._--For comparisons with _B. m. handleyi_, _B. m.
+grisescens_, _B. m. musculus_, _B. m. pallidus_, and _B. m. pullus_, see
+accounts of those subspecies.
+
+From _B. m. brunneus_, _B. m. nigrescens_ differs in: dorsum
+blackish-brown rather than reddish to ochraceous brown; face and ears
+brownish-black rather than brownish with tinges of ochraceous; vibrissae
+darker; forefeet and hind feet darker; venter with more grayish tones;
+dorsalmost part of zygomatic plate projects farther anteriorly;
+interparietal oval to diamond-shaped and narrower anteroposteriorly;
+zygomata narrower at anteriormost part; slightly smaller in most cranial
+and external measurements.
+
+From _B. m. infernatis_, _B. m. nigrescens_ differs in: dorsum darker;
+region of face and ears darker; venter buffy to gray rather than
+whitish-buff; vibrissae darker; forefeet and hind feet darker; tail
+darker above and below; incisive foramina shorter, more constricted
+laterally; cranium slightly smaller in most dimensions.
+
+_Remarks._--Hooper (1952a:93-94) reported specimens from the coastal
+strip of southern Chiapas as the most intensely pigmented, whereas,
+specimens from central and western Chiapas were distinctly paler. Crania
+of specimens from the coastal region of southern Chiapas were smaller
+than crania from the central highlands and mountains of Chiapas. My
+studies essentially corroborate the findings of Hooper. The gradation of
+color between the pale brown _pallidus_ to the north in Oaxaca, and the
+brownish-black _nigrescens_ to the south in Chiapas is extremely
+gradual. Specimens from the central and western parts of Chiapas (see
+Figure 10 for localities) are difficult to assign to either _pallidus_
+or _nigrescens_. Equal justification exists for assignment to either
+subspecies. I have assigned the specimens to _nigrescens_ because they
+are geographically closer to the type locality of _nigrescens_.
+Specimens from Reforma, Oaxaca (assigned by Hooper, 1952a:93-94, to
+_nigrescens_), are nearly identical in size and color to paratypes of
+_pallidus_. I assign the Reforma specimens to _pallidus_.
+
+The darkest of all the specimens examined and assigned to _nigrescens_
+are from 1 mi. NW San Salvador and 1 mi. S Los Planes, El Salvador. The
+variations in color in this subspecies closely correspond to degree of
+relative humidity; the palest samples are from areas of low relative
+humidity and the darkest are from areas of high relative humidity. In
+view of the present state of differentiation of specimens from the
+southern coastal areas of Chiapas and mountainous areas of El Salvador,
+it would seem that populations there might be incipient subspecies.
+
+_Specimens examined._--Total 319. CHIAPAS: _17 mi. W Bochil_, 1[14]; _15
+mi. W Bochil_, 1[14]; _14 mi. W Bochil_, 1[14]; Bochil, 6[15]; Ocuilapa,
+3500 ft., 5[16]; _5 mi. NNW Tuxtla Gutiérrez_, 9; _11 km. W Tuxtla
+Gutiérrez_, 800 m., 2[15]; _10 km. W Tuxtla Gutiérrez_, 800 m., 2[15];
+_Tuxtla Gutiérrez_, 2600 ft., 8[16], 11; _Ocozocoautla_, 10[15], 2[16]; 25
+mi. E Comitán, Las Margaritas, 1250 m., 5[17], 24[15]; Cintalpa, 555 m.,
+1[14], 18[15], 3[17]; _Jiquilpilas_, 2000 ft., 1[16]; San Bartolome, 3[16];
+_type locality_, 5700 ft., 26[16] (including the type); 15 mi. SW Las
+Cruces, 1; Villa Flores, 600 m., 12[15]; _23 mi. S Comitán_, 1[14]; _15
+mi. S, 2 mi. E La Trinitaria_, 4; _30 mi. S Comitán_, 2[14]; 35 mi. S
+Comitán, 1[14]; _3 mi. E Arriga_, 1[14]; 6 mi. NW Tonalá, 19; _Tonalá_,
+8[16]; _Los Amates_, 1[14]; Pijijiapan, 10 m., 7[15]; Mapastepec, 45 m.,
+25[15], 4[17].
+
+GUATEMALA: Chanquejelve, 1[14]; _Nentón_, 3000 ft., 1[16]; Jacaltenango,
+5400 ft., 8[16]; La Primavera, 5[14]; 4 mi. S Guatemala City, 4700 ft., 3;
+_5 mi. S Guatemala City_, 4050 ft., 10; _6 mi. S Guatemala City_, 4680
+ft., 1; _Lake Amatitlán_, 4500 ft., 13[16]; El Progresso (Distrito Santa
+Rosa), 3[15]; _2 mi. N, 1 mi. W Cuilapa_, 2980 ft., 1[14]; _1 mi. WSW El
+Molino_ (_Distrito Santa Rosa_), 2; _2-1/2 mi. W, 2-1/4 mi. N San
+Cristobal_, 2900 ft., 1; El Zapote, 1[15].
+
+EL SALVADOR: 1 mi. NW San Salvador, 29; 1 mi. S Los Planes, 15.
+
+_Marginal Records._--CHIAPAS: Bochil; 25 mi. E Comitán, Las Margaritas,
+1250 ft. GUATEMALA: Chanquejelve; La Primavera; Jacaltenango, 5400 ft.;
+4 mi. S Guatemala City, 4700 ft.; El Progresso. _El Salvador_: 1 mi. NW
+San Salvador; 1 mi. S Los Planes. GUATEMALA: El Zapote. CHIAPAS:
+Mapastepec, 45 m.; Pijijiapan, 10 m.; 6 mi. NW Tonalá; 15 mi. SW Las
+Cruces; Cintalpa, 555 m.; Ocuilapa, 3500 ft.
+
+[14] American Museum of Natural History.
+
+[15] Univ. Michigan, Museum of Zoology.
+
+[16] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[17] University of Florida Collections.
+
+
+=Baiomys musculus pallidus= Russell
+
+    _Baiomys musculus pallidus_ Russell, Proc. Biol. Soc. Washington,
+       January 29, 1952; Davis and Russell, Jour. Mamm., 35:75, February
+       10, 1954; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:512; Hall
+       and Kelson, The Mammals of North America, 2:662, March 31, 1959.
+
+    _Peromyscus musculus brunneus_, Elliot, Field Columb. Mus. Publ.,
+       115(8):203, 1907 (part).
+
+    _Peromyscus musculus_ [_musculus_], Osgood, N. Amer. Fauna, 28:257,
+       April 17, 1909 (part).
+
+    _Baiomys musculus musculus_, Miller, Bull. U. S. Nat. Mus., 79:137,
+       December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:318,
+       April 29, 1924 (part); Davis, Jour. Mamm., 25:394, December 12, 1944
+       (part); Hooper, Jour. Mamm., 28:50, February 15, 1947 (part);
+       Goldman, Smith, Miscl. Coll., 115:336, July 31, 1951 (part); Miller
+       and Kellogg, Bull. U. S. Nat. Mus., 205:512, March 3, 1955 (part);
+       Booth, Walla Walla Publs., Dept. Biol. Sci., 20:15, July 10, 1957
+       (part); Hall and Kelson, The Mammals of North America, 2:661,
+       March 31, 1959 (part); Goodwin, Amer. Mus. Novitates, 1929:1,
+       March 5, 1959.
+
+    _B._ [_aiomys_] _m._ [_usculus_] _musculus_, Hooper, Jour. Mamm.,
+       33:97, February 18, 1952 (part).
+
+    _B._ [_aiomys_] _m._ [_usculus_] _nigrescens_, Hooper, Jour. Mamm.,
+       33:97, February 18, 1952 (part).
+
+    _Baiomys musculus nebulosus Goodwin_, Amer. Mus. Novitates, 1929,
+       March 5, 1959.
+
+_Type._--Adult female, skin and skull; No. 4501 Texas A&M Cooperative
+Wildlife Collection; 12 kms. NW Axochiapán, 3500 feet, Morelos, Republic
+of México, obtained on July 28, 1950, by W. B. Davis, original number
+5112.
+
+_Range._--Guerrero thence eastward into Morelos and west central Puebla
+along the southern edge of the Transverse Volcanic Biotic Province
+(Goldman and Moore, 1945:349), south into Oaxaca, see Figure 10. Zonal
+range: largely Arid Lower Tropical Subzone of Goldman (1951:330). Occurs
+from near sea level in Oaxaca and Guerrero up to 6550 feet in Oaxaca.
+
+_Diagnosis._--Size medium for the species; dorsum Buffy Brown in palest
+series to Olive-Brown in darkest series, individual hairs Warm Buff,
+Neutral Gray basally, some with black tips and a subterminal band of
+Warm Buff, guard hairs of dorsum black-tipped, gray basally; hairs on
+sides creamy-buff, gray basally; face same color as back fading to white
+on throat; vibrissae white-tipped, pale brown basally; venter, whitish
+with tinges of buff on lower throat, individual hairs having tips white
+to buffy-white, light gray basally; dorsal surface of forefeet and hind
+feet whitish to flesh-color; tail indistinctly bicolored, brownish
+above, grayish brown below; zygoma bowed as in _B. m. grisescens_; tail
+short; average and extreme external and cranial measurements for 17
+adults from Tehuantepec, Oaxaca, are: total length, 117.3 (110-126);
+length of tail vertebrae, 46.9 (41-51); length of body, 70.4 (65-76);
+length of hind foot, 15.8 (15-16); occipitonasal length, 18.9
+(18.2-20.1); zygomatic breadth, 10.1 (9.7-10.6); postpalatal length, 6.9
+(6.6-7.5); least interorbital breadth, 3.8 (3.6-3.9); length of incisive
+foramina, 4.4 (4.2-4.7); length of rostrum, 6.7 (6.3-7.2); breadth of
+braincase, 9.3 (8.7-9.7); depth of cranium, 6.6 (6.4-6.8); alveolar
+length of maxillary tooth-row, 3.2 (3.1-3.4); for photographs of skull,
+see Plate 1g, and Plate 3g.
+
+_Comparisons._--For comparisons with _B. m. brunneus_ and _B. m.
+infernatis_, see accounts of those subspecies.
+
+From _B. m. musculus_, _B. m. pallidus_ differs in: dorsum more
+olive-gray and brown, less ochraceous on either side of mid-dorsal
+region; face below eye grayish, not buffy; sides gray with buffy
+overtone, not creamy with light yellow overtones; venter grayish-white
+rather than an olive-buff; zygomata more tapering anteriorly; maxillary
+part of zygoma narrower when viewed from above; external and cranial
+dimensions smaller.
+
+From _B. m. nigrescens_, _B. m. pallidus_ differs in: dorsum paler,
+fewer black hairs medially; face paler, less sooty; vibrissae brownish
+with white tips rather than black with brownish tips; venter paler;
+dorsal surface of forefeet and hind feet whitish to flesh-colored rather
+than sooty to dusky-white; tail paler; nasals slightly more attenuated;
+averaging slightly larger in external and cranial measurements.
+
+_Remarks._--Russell (1952:21) described _pallidus_, on the basis of
+specimens from the arid Balsas Basin, of Morelos, as pale gray dorsally.
+After examining the original material from Morelos, I find the dorsal
+color of _pallidus_ to be much closer to a buffy brown than a pale
+grayish. Even so, smaller size differentiates _pallidus_ from
+_musculus_. _B. m. infernatis_, not _B. m. pallidus_, is the most pallid
+of all named subspecies of _B. musculus_.
+
+_B. m. pallidus_ intergrades to the northwest with _B. m. musculus_, to
+the northeast with _B. m. infernatis_, and to the southeast with _B. m.
+nigrescens_.
+
+According to Goodwin (1959:2), _B. m. nebulosus_ (named on the basis of
+one specimen) differs from _B. m. musculus_ [= _pallidus_] from southern
+Oaxaca in: darker and longer pelage; larger skull; interorbital region
+broader and less constricted posteriorly. From _B. m. nigrescens_ and
+_B. m. brunneus_, _B. m. nebulosus_ differs as follows: pelage longer
+and softer; skull larger.
+
+Study of specimens of _B. musculus_ from Oaxaca reveals considerable
+variation in external and cranial measurements as well as color,
+corresponding to that reported by Goodwin (_loc. cit._). Specimens from
+higher altitudes average somewhat darker and larger in external and
+cranial size than those at lower elevations. These differences seem to
+be microgeographic and not of subspecific rank. Among specimens that I
+have studied in Oaxaca are several from different localities (KU 63052,
+an adult male, from 3 mi. W Miahuatlán; KU 68964, an adult male from 3
+mi. W Mitla, 6000 ft.; KU 63055, an adult female from 3 mi. S
+Candelario, 1200 ft.) that, according to Goodwin (_in. litt._) match
+_nebulosus_ in reported color, size of body and skull (except for the
+region of the rostrum).
+
+Two of the three specimens (KU 63052 and 63055) are the darkest of a
+series in which the palest are inseparable from _B. m. pallidus_.
+Goodwin, who kindly compared the three specimens with the type of
+_nebulosus_, mentioned (_in. litt._) that the skull of the type has a
+slenderer rostrum. Included in the series of skulls of _B. m. pallidus_
+from 3 mi. W Mitla are several adults (not seen by Goodwin) with slender
+rostra. _B. m. nebulosus_ is judged to be a synonym of _B. m. pallidus_.
+
+Populations of pygmy mice occurring in partially isolated areas of
+highland in Oaxaca seem to me to be incipient subspecies.
+
+_Specimens examined._--Total 824 all from the Republic of México and
+distributed as follows: PUEBLA: 2 mi. S Atlixco, 5800 ft., 1; _1 mi. SSW
+Tilapa_, 5800 ft., 2; _6 mi. SW Izucár de Matemores_, 7; _Piaxtla_, 3900
+ft., 4[18]; Acatlán, 4100 ft., 1. MORELOS: 5 mi. W Tepoztlán, 6000 ft.,
+7[19]; _1 mi. W Tepoztlán_, 6000 ft., 9[19]; _2 mi. SW Tepoztlán_, 7000
+ft., 1[20]; _Cuernvaca_, 9[19]; _6 mi. W Yautepec_, 4500 ft., 1[20];
+_Yautepec_, 12[19]; _3 mi. N Alpuyeca_, 4000 ft., 2[20]; _Puente de
+Ixtla_, 2[19]; _Tetecala_, 4[21]; _2 km. S Jonacatepec_, 4500 ft., 6[20];
+_type locality_, 6 (including the type). GUERRERO: _Yerbabuena_, 1800
+m., 1; _Cueva de tia Juana_ [= _1.5 km. SSW Yerbabuena_], 1; _Laguna
+Honda_, 1840 m. [= _1.5 km. S Yerbabuena_], 3; 9 mi. SE Taxco, 3800 ft.,
+1[22]; _17 km. S Taxco_, 4000 ft., 2[20]; _Iguala_, 5[19]; _3.2 km. SSE
+Iguala_, 970 m., 1; 1 km. SSE Texcaizintla, 1600 m., 2; _Teloloapán_,
+20[19], 5[24]; _1 km. N Chapa_, 1470 m., 6; _Chapa_, 1470 m., 5; El Limón,
+3[18]; 2-1/2 mi. W Mexcala, 2100 ft., 1[20]; _Río Balsas_, 1[18]; Ayusinaha
+[= Ayotzinapa], 1[18]; _Tlapa_, 3900 ft, 1[18]; _2.5 mi. S Almolonga_,
+5600 ft., 13[20]; _1 km. N Zihuatanejo_, 1; Zihuatanejo Bay, 4[19]; _Las
+Gatas_ [= _2 km. S. Zihuatanejo_], 2; _2 km. SSE Zihuatanejo_, 9; _4 mi.
+W Chilpancingo_, 5800 ft., 3[20]; _Chilpancingo_, 4800 ft., 14[18], 21[19],
+45[21]; _2 mi. N Tixtla_, 4400 ft., 3[20]; _3.2 km. S Chilpancingo_, 4;
+_Cd. Chamilpa_ [= _12 km. ESE Chilpancingo_], 5; _Tlalixtaquilla_, 4200
+ft., 2[18]; _15 km. S. Chilpancingo_, 4300 ft., 10[20]; _1 mi. SW
+Colotlipa_, 2700 ft., 16[20]; _2 mi. SW Colotlipa_, 2700 ft., 1[20];
+_Achuitzotla_, 2800 ft., 7[20]; _8 mi. SW Colotlipa_, 1[20]; _5 mi. S
+Rincón_, 2600 ft., 2[20]; _8 mi. SW Tierra Colorado_, 600 ft., 1[20]; Río
+Aguacatillo, _30 km. N Acapulco_, 1000 ft., 3[20]; 5 mi. ESE Tecpán, 50
+ft., 9; _Ejido Viejo_, _12 km. NNW Acapulco_, 1; _2 mi. NNW Acapulco_,
+7; Acapulco, 3[18], 3[21]; Omentepec, 200 ft., 7[18]. OAXACA: _4 mi. E
+Huajuapám_, 5000 ft., 1; 2 mi. NW Tamazulapán, 6550 ft., 1; Yalalag,
+3000 ft., 5[18]; _11 mi. NW Oaxaca_ [_City_], 1; _Yaganiza_, 3900 ft.,
+1[18]; Oaxaca [City], 5000 ft., 15, 7[21], 7[19], 5[24]; _3 mi. ESE Oaxaca_
+[_City_], 30; _4 mi. ESE Oaxaca_ [_City_], 5050 ft., 1; _10 mi. SE
+Oaxaca_ [City], 1[22]; _Cerro Ocotepec_, 1[23]; Tepantepec, 9[23]; _1 mi. E
+Tlacolula_, 5500 ft., 53[19]; _3 mi. W Mitla_, 11; Jalapa, El Campanario,
+1[23]; _2 mi. SE Matalán_, 5950 ft., 14; _Lachiguiri_, 2[23]; _Tres
+Cruces_, 10[23]; _Agua Blanca_, 11[23]; _San José_, 1[23]; Reforma, 30[19],
+7[21], 10[23], 6[24] _Totolapa_, 1[18]; _Nejapa_, _85 km. WNW Tehuantepec_,
+500 m., 12[19], 6[24]; _Chicapa_, 2[18]; _Gueladu_ [= _Jalapa_], 6[23];
+_Juchitán_, _Laguna Superior_; Manteca, 8[23], 1[23]; San Bartolo, 3000
+ft., 1[18]; _Ejutla_, 1400 m., 21[19]; _El Bambita_, _Tequisitlán_ 4[23];
+_Mixtequilla_, 2[23]; _Guiencola_, 5[23]; _Tehuantepec_, 200 ft., 26[18],
+11[19]; _Sola de la Vega_, 26[19], 3[24]; Huilotepec, 13[18], 3[23]; _Santa
+Lucia_, 24[23]; _Cerro de Paste_, _Tenango_, 7[23]; _Sta. C. Quieri_,
+3[23]; _Santa Marie Ecatepec_, _Zarzamora_, 13[23]; _Rincón Bamba_, 11[23];
+_3 mi. W Miahuatlán_, 5300 ft., 1; _Miahuatlán_, 12[19], 1[23], 6[24]; _San
+Juan Acaltepec_, 5[23]; _Zapotitlán_, 1[23]; _Llano Grande_, 3[18];
+Pinotepa, 700 ft., 2[18]; Juquila, 8[18]; _Arroyo_, _San Juan_, _north of
+Cerro Otate_, 1[23]; Cerro Otate, 3[23]; 3 mi. S Candelaria, 1.
+
+_Marginal records._--MORELOS: 5 mi, W Tepoztlán, 6000 ft. PUEBLA: 2 mi.
+S Atlixco, 5800 ft.; Acatlán, 4100 ft. OAXACA: 2 mi. NW Tamazulapán,
+6550 ft; Tepantepec; Oaxaca [City], 5000 ft; Yalalag, 3000 ft; Jalapa,
+El Campanario; Reforma; Huilotepec; 3 mi. S Candelaria; Cerro Otate;
+Pinotepa, 700 ft. GUERRERO: Acapulco; Zihuatanejo Bay; El Limón; 9 mi.
+SE Taxco, 3800 ft.
+
+[18] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[19] Univ. Michigan, Museum of Zoology.
+
+[20] Texas A & M, Cooperative Wildlife Research Collection.
+
+[21] Chicago Natural History Museum.
+
+[22] California Academy of Sciences.
+
+[23] American Museum of Natural History.
+
+[24] University of Florida Collections.
+
+
+=Baiomys musculus pullus= Packard
+
+    _Baiomys musculus pullus_ Packard, Univ. Kansas Publs., Mus. Nat.
+       Hist., 9:401, December 19, 1958.
+
+    _Baiomys musculus grisescens_, Goodwin, Bull. Amer. Mus. Nat. Hist.,
+       79(2):161, May 29, 1942 (part); Miller and Kellogg, Bull. U. S. Nat.
+       Mus., 205:513, March 3, 1955 (part); Hall and Kelson, The Mammals of
+       North America, 2:661, March 31, 1959 (part).
+
+_Type._--Adult female, skin and skull; No. 71605 University of Kansas
+Museum of Natural History; 8 mi. S Condega, Estelí, Nicaragua, obtained
+on July 15, 1956, by A. A. Alcorn, original number 4218.
+
+_Range._--West-central Nicaragua, from Matagalpa northwest into the
+valley of the Río Estelí, east as far as Jinotega, see Figure 10. Zonal
+range: Upper Tropical Life-zone.
+
+_Diagnosis._--Size medium to small for the species; dorsum
+Fuscous-Black, individual hairs black-tipped with a subterminal band of
+Ochraceous-Buff, Neutral Gray at base; some hairs on dorsum all black to
+Neutral Gray at base; hair on sides Neutral Gray tinged with blackish;
+face blackish, becoming buffy on sides of head, and white on throat;
+vibrissae black; tail unicolored Chaetura Black; forefeet and hind feet
+sooty to dusky-white; mid-ventral region of venter white, hairs white to
+base; in region of anus and throat, hairs white-tipped, Neutral Gray at
+base; average and extreme external and cranial measurements of the type
+and 16 paratypes are as follows: total length, 117.3 (111-121); length
+of tail vertebrae, 47.2 (44-50); length of body, 70.4 (66-74); length of
+hind foot, 15.5 (14-17); length of ear from notch, 11.9 (10-13);
+occipitonasal length, 19.3 (18.9-19.8); zygomatic breadth, 10.2
+(9.7-10.6); postpalatal length, 7.0 (6.8-7.3); least interorbital
+breadth, 3.9 (3.8-4.1); length of incisive foramina, 4.3 (4.0-4.6);
+length of rostrum, 7.0 (6.5-7.4); breadth of braincase, 9.6 (9.3-10.0);
+depth of cranium, 7.0 (6.8-7.3); alveolar length of maxillary tooth-row,
+3.1 (3.0-3.2); for photographs of skull, see Plate 1_h_, and Plate 3_h_.
+
+_Comparisons._--From _B. m. grisescens_, _B. m. pullus_ differs in:
+dorsum and tail darker; sides and lateral parts of venter grayish
+instead of buffy-brown, thus forming distinct mid-ventral white stripe;
+average length of body and tail significantly longer, thus total length
+greater; maxillary tooth-row significantly shorter; slightly larger in
+other cranial and external dimensions.
+
+From _B. m. nigrescens_, _B. m. pullus_ differs in: dorsum slightly
+darker; face grayish, not sooty; mid-ventral white stripe (absent in
+most specimens of _nigrescens_) present and becoming grayish laterally;
+tail darker, less hairy, and averaging significantly longer; smaller in
+most external and cranial dimensions.
+
+_Remarks._--_B. m. pullus_ resembles _B. m. nigrescens_ in size and
+color but can readily be distinguished from _nigrescens_ by the shorter
+tail. _B. m. pullus_ intergrades with _nigrescens_ as shown by
+specimens, referable to _B. m. nigrescens_, from 1 mi. NW San Salvador
+and from 1 mi. S Los Planes, El Salvador. In color of the dorsum,
+specimens from these localities are intermediate between _nigrescens_
+and _pullus_.
+
+The mid-ventral white stripe characteristic of _pullus_ is present in
+three of 28 adults from El Salvador. Goodwin (1942:160) reported white
+hairs on the pectoral region of several topotypes of _B. m. grisescens_.
+The areas of white hairs on the venter of _grisescens_ occur in
+approximately 10 per cent of the specimens examined, whereas in
+_pullus_, the frequency of occurrence is 90 per cent. The areas of white
+hairs in _grisescens_ are in broad patches on the pectoral region, while
+in _pullus_, a white stripe passes from the pectoral region to the
+inguinal region in both males and females. I know of no selective
+advantage that the presence of this white stripe would confer on the
+mice.
+
+_Specimens examined._--Total 46, all from NICARAGUA, and distributed as
+follows: Type locality, 32 (including the type); _9 mi. NNW Estelí_, 8;
+_8 mi. NNW Estelí_, 3; San Rafael Del Norte, 1 (Amer. Mus. Nat. Hist.);
+_1 mi. NW Jinotega_, 1; Matagalpa, 1 (Amer. Mus. Nat. Hist.).
+
+_Marginal records._--NICARAGUA: San Rafael Del Norte; Matagalpa; type
+locality.
+
+
+=Baiomys taylori=
+
+Northern Pygmy Mouse
+
+(Synonymy under subspecies)
+
+_Type._--_Hesperomys_ (_Vesperimus_) _taylori_ Thomas, Ann. Mag. Nat.
+Hist., Ser. 5, 19:66, January, 1887.
+
+_Range._--Southeastern Arizona and southwestern New Mexico, south into
+Chihuahua and Durango, just east of the Sierra Madre Occidental, thence
+southeast through Zacatecas, Aquascalientes, Jalisco, Querétaro, and
+Guanajuato; two fingerlike projections extend northward, one on the west
+along the coast of Sinaloa into southern Sonora, and the other on the
+east covering eastern San Luis Potosí, Tamaulipas, eastern Coahuila,
+Nuevo León, into south, southeast, and north-central Texas. Southern
+margin of range in central México approximates the 19th degree of
+latitude (see Figure 11). Arid lower and arid upper subdivisions of the
+Tropical Life-zone in south; principally Lower Sonoran and Lower Austral
+life-zones in north.
+
+_Characters for ready recognition._--Unless otherwise noted, characters
+are usable for the age-categories of adult and old adult. Differs from
+_B. musculus_ in: hind foot less than 16 millimeters; occipitonasal
+length less than 19 millimeters; zygomatic breadth less than 10
+millimeters; rostrum deflected ventrally at frontoparietal suture rather
+than curving gradually toward anteriormost point of nasals; cingular
+ridges and secondary cusps on teeth reduced or absent; basihyal having
+entoglossal process much reduced or absent, shoulders of basihyal not
+protruding anteriorly, but more flattened (characteristic of all age
+categories); baculum having narrower shaft, knob-shaped tip, wings at
+base projecting laterally, baculum less than 3 millimeters long; short
+process of incus attenuate; muscular process of posterior crus of stapes
+reduced.
+
+_Characters of the species._--Size small (extremes in external
+measurements of adults: total length, 87-123; length of tail vertebrae,
+34-53; length of hind foot, 12-15; length of ear, 9-12). Upper parts
+pale drab or reddish-brown to almost black; underparts grayish to
+cream-buff.
+
+_Geographic variation._--Eight subspecies are here recognized (see
+Figure 11). Features that vary geographically are mostly the same as
+those that do so in _B. musculus_ (see page 609).
+
+External and cranial size is less in _B. t. allex_, the southernmost
+subspecies, and progressively more in _B. t. paulus_, _B. t. taylori_,
+_B. t. ater_, _B. t. subater_, _B. t. fuliginatus_, _B. t. canutus_, and
+_B. t. analogous_. Size is largest in subspecies that occur at higher
+altitudes. Those subspecies are _B. t. analogous_ and _B. t.
+fuliginatus_. The correlation with Bergman's Rule is less exact in _B.
+taylori_ than in _B. musculus_. It is noteworthy that the smallest
+subspecies, _B. t. allex_, occurs in the area where the two species are
+sympatric.
+
+There is close correlation in _B. taylori_, as also in _B. musculus_, of
+darker pelages with zones of high relative humidity. The subspecies
+having dark pelages are: _analogous_, _fuliginatus_, and _subater_. The
+two first-mentioned subspecies occur at high altitudes, and the other,
+_subater_, occurs in the humid coastal region of Texas. The paler
+subspecies, _taylori_, _canutus_, and _allex_, occur at lower altitudes.
+Two subspecies that occur at relatively high altitudes, _ater_ and
+_paulus_, are reddish-brown. The color of pelage in these subspecies
+resembles the color of soil upon which they live. Blair and Blossom
+(1948:5) demonstrated close correlation of color of soil with color of
+pelage in _B. t. ater_ by use of an Ives tint photometer.
+
+    [Illustration: FIG. 11. Distribution of _Baiomys taylori_. Known
+       localities of occurrence are represented by circles and black dots;
+       the former denote localities that are peripheral (marginal) for the
+       subspecies concerned.
+
+    1. _B. t. allex_
+    2. _B. t. analogous_
+    3. _B. t. ater_
+    4. _B. t. canutus_
+    5. _B. t. fuliginatus_
+    6. _B. t. paulus_
+    7. _B. t. subater_
+    8. _B. t. taylori_]
+
+_Natural History_
+
+_Habitat and numbers._--The habitat occupied by the northern pygmy mouse
+ranges from sparse grassy areas along rock walls in central México (see
+Davis, 1944:394), and mesquite-cactus associations in southern Texas
+(Blair, 1952:242) to heavy stands of grasses such as _Bouteloua_ sp.,
+_Andropogon_ sp., _Hilaria_ sp., and sacaton grass intermixed with
+_Yucca glauca_ in New Mexico, Arizona (see Hoffmeister 1956:281), and
+Chihuahua. Baker (1951:213) reports the species from 2 km. W El Carrizo,
+Tamaulipas, in dense grass and weeds at the edge of a cornfield. Hooper
+(1953:7) recorded the northern pygmy mouse in a cultivated field
+overgrown with herbaceous vegetation at Pano Ayuctle, Tamaulipas. In the
+State of Sinaloa, Hooper (1955b:13) obtained specimens in grass and
+among shrubs and vines bordering a fallow field. The northern pygmy
+mouse, in general, lives in situations more xerophytic and more grassy
+than does the southern pygmy mouse.
+
+The northern pygmy mouse, as the southern pygmy mouse, is locally
+abundant in its geographic range. Stickel and Stickel (_op. cit._: 145)
+pointed out that on the third night of live-trapping in Bexar County,
+Texas, there was a sudden increase in unmarked pygmy mice trapped. This
+increase in numbers, after the resident population was seemingly marked,
+followed a one-half inch rainfall. Collectors from the University of
+Kansas, myself included, have had similar experiences in trapping these
+mice. In the Mexican states of Guanajuato, Querétaro, and Jalisco, _B.
+taylori_ is one of the commonest small mammals. In New Mexico and
+Arizona and the Mexican states of Sonora and Sinaloa, nevertheless,
+these mice are rare.
+
+Stickel and Stickel (_loc. cit._) thought that the home range normal for
+_B. taylori_ in a grassy habitat was less than 100 square feet, but
+Blair (1953:10) thought that a complete home range had not been recorded
+by Stickel and Stickel.
+
+_Behavior._--The northern pygmy mouse is crepuscular to nocturnal and
+where I trapped in northern Mexico was one of the first small rodents to
+appear in my traps in the evening. Hall and Villa-R (1949:460) recorded
+this habit in Michoacán. Observations of wild-taken _B. taylori_ held in
+captivity, lend support to its being crepuscular. Captives were rarely
+active in bright lights, but in diffuse or dim lights the same mice were
+active.
+
+Blair (1941:381) pointed out that captive _B. t. subater_ were much more
+tolerant of one another than mice of the genus _Peromyscus_. He pointed
+out also that males aided in care of young. In one litter born in
+captivity in the course of my study, the female killed the male when the
+young were four days old. In another instance, the female and two
+eight-day-old young were killed by the male. Until that time, the male,
+female, and young had lived together peacefully. In other litters born
+in captivity, adult males did not harm the other mice.
+
+I have noted, as Blair (_loc. cit._) did, that _B. taylori_ utters
+high-pitched squeals in a "singing" posture resembling that of the
+coyote, yet remains silent when being handled.
+
+The northern pygmy mouse makes runways in the grass, in miniature
+resembling those of _Microtus_, and often uses runways constructed by
+_Sigmodon_. A small firm nest of finely shredded plant material (mostly
+grasses) is constructed in burrows or under logs, rocks, or fallen
+cactus plants. Thomas (1888:447) recorded nests of fine curly grass and
+cornsilk. Secondary refuge nests are not uncommon. Thomas (_loc. cit._)
+states, "If other mice live in the same place, the individuals of
+_Baiomys_ watch till others disappear, then suddenly steal part of the
+other nest and run to their own with it."
+
+_Enemies and food._--Little is recorded of the animals that prey upon
+the northern pygmy mouse. Twente and Baker (1951:120) found remains of
+_B. taylori_ in 16 per cent of barn owl pellets (_Tyto alba pratincola_)
+collected 21 mi. SW Guadalajara, Jalisco. Presumably most of the
+crepuscular and early nocturnal raptorial birds and carnivorous mammals
+feed on these mice.
+
+Food of _B. taylori_ consists in part of grass seeds and leaves, prickly
+pear (_Opuntia_ sp.) and the softer exposed parts of roots of vegetation
+among which the mice reside.
+
+_Reproduction._--The northern pygmy mouse breeds throughout the year.
+The only months in which I have not recorded pregnant females or females
+with young are June and October. Forty-one records of embryos or young
+per litter average 2.48 (less than in _B. musculus_), and range from as
+few as one to as many as four per litter.
+
+
+=Baiomys taylori allex= (Osgood)
+
+    _Peromyscus allex_ Osgood, Proc. Biol. Soc. Washington, 17:76-77,
+       March 21, 1904; Elliot, Field Columb. Mus. Publ., 105(6):135,
+       July 1, 1905; Lyon and Osgood, Bull. U. S. Nat. Mus., 62:124,
+       January 15, 1909.
+
+    _Baiomys taylori allex_, Packard, Proc. Biol. Soc. Washington,
+       71:17, April 11, 1958; Hall and Kelson, The Mammals of North
+       America, 2:659, March 31, 1959 (part).
+
+    [_Peromyscus_] _allex_, Elliot, Field Columb. Mus. Publ., 95(4):175,
+       July 15, 1904.
+
+    _Peromyscus taylori paulus_, Osgood, N. Amer. Fauna, 28:255, April
+       17, 1909 (part).
+
+    _Baiomys taylori paulus_, Miller, Bull. U. S. Nat. Mus., 79:137,
+       December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317,
+       April 29, 1924 (part); Ellerman, The Families and Genera of Living
+       Rodents, British Mus. Nat. Hist., 2:402, March 21, 1941 (part);
+       Poole and Schantz, Bull. U. S. Nat. Mus., 178:259, March 6, 1942;
+       Goldman, Smith. Miscl. Coll., 115:373, July 31, 1951 (part); Miller
+       and Kellogg, Bull. U. S. Nat. Mus., 205:512, March 3, 1955 (part);
+       Hall and Kelson, The Mammals of North America, 2:659, March 31, 1959
+       (part).
+
+    _Baiomys taylori analogous_, Hall and Kelson, Univ. Kansas Publs.,
+       Mus. Nat. Hist., 5:367, December 15, 1952 (part).
+
+_Type._--Adult male, skin and skull; No. 33429/45452 U. S. Nat. Mus.
+(Biol. Surv. Coll.); Colima (City), Colima, Republic of México, obtained
+on March 7, 1892, by E. W. Nelson, original number 2029.
+
+_Range._--Colima, western lowlands of Michoacán and Jalisco, thence
+north into southern half of Nayarit, see Figure 11. Zonal range: arid
+lower tropical, approximates northern half of the Nayarit-Guerrero
+Biotic Province of Goldman and Moore (1945:349). Occurs from near sea
+level in Nayarit, up to 4000 feet in Jalisco.
+
+_Diagnosis._--Size small for the species; dorsal ground color pale
+grayish-brown, near Isabella color; mid-dorsal region washed with
+blackish, individual guard hairs black to base, other hairs black-tipped
+with subterminal light olive bands, Neutral Gray at base; laterally,
+black-tipped hairs less abundant, hairs grayish-white to base; venter
+Pale Gull Gray to whitish, distal half of individual hairs white,
+proximal half Neutral Gray; hairs in regions of throat and chin white to
+base; facial region colored like dorsum, becoming paler below eye; in
+region of mouth, hairs white to base; dorsalmost vibrissae black to
+base, others white to base; ears flesh-colored, sparsely haired; tail
+unicolored, sparsely haired for the species; dark blotches on tail of
+some series (particularly the paratypical series); dorsal and ventral
+parts of forefeet and hind feet flesh-colored, whitish to gray in some
+series. Slightly smaller in most cranial dimensions. Maxillary part of
+zygoma forming almost a right angle with rostrum, rather than tapering
+at less than a right angle to rostrum; supraoccipital rounded
+posteriorly rather than indented on each side of foramen magnum;
+cranium, relative to length of rostrum, more nearly square;
+interparietal large relative to size of cranium. Average and extreme
+measurements of five adults from 2 mi. SSE Autlán are as follows: total
+length, 100.0 (93-107); length of tail vertebrae, 40.0 (37-44); length
+of body, 60.0 (56-63); length of hind foot, 14.0 (14); length of ear
+from notch, 10.5 (10-11); occipitonasal length, 17.3 (16.8-17.9);
+zygomatic breadth, 9.1 (8.7-9.4); postpalatal length, 6.3 (6.0-6.6);
+least interorbital breadth, 3.4 (3.3-3.5); length of incisive foramina,
+3.9 (3.8-4.0); length of rostrum, 5.5 (5.2-5.8); breadth of braincase,
+8.6 (8.0-8.9); depth of cranium, 6.4 (6.0-6.7); alveolar length of
+maxillary tooth-row, 3.0 (2.8-3.1); for photographs of skull, see Plate
+1_i_ and Plate 4_a_.
+
+_Comparisons._--For comparisons with _B. t. canutus_, see account of
+that subspecies. From _B. t. analogous_, _B. t. allex_ differs in:
+external and cranial dimensions less; dorsal coloration paler; tail and
+ears paler and less hairy; dorsum and belly paler; dorsal and ventral
+parts of forefeet and hind feet paler; median parts of incisive foramina
+less constricted on either side of midline and wider open laterally;
+interparietal larger in relation to skull; interorbital breadth greater
+relative to occipitonasal length.
+
+_B. t. allex_ differs from _B. t. paulus_ as follows: dorsum gray with
+yellowish-brown wash rather than fawn to buff; tail unicolored in most
+series, less hairy; hind feet flesh-colored to light sooty, rather than
+whitish; rostrum slightly longer relative to occipitonasal length;
+incisive foramina differ from those of _paulus_ in much the same way as
+from _analogous_.
+
+_Remarks._--Osgood (1909:255-256) dismissed as taxonomically unimportant
+the differences in color of pelage and size of cranium that he observed
+between the specimens from Colima (City), Colima, representative of
+_allex_ and those representing _paulus_ and chose to synonomize _allex_
+with _paulus_. The differences that Osgood (_loc. cit._) deemed "...
+scarcely worthy of recognition ...," are, in fact, not only worthy of
+recognition, but also important in an understanding of the evolution of
+_Baiomys taylori_ (see speciation p. 659). Recently, I (1958b:17-18)
+studied ten specimens from Colima (City), Colima, and chose to regard
+_Peromyscus [= Baiomys] allex_ as a subspecies. I suggested (_loc.
+cit._) that the geographic range of _B. t. allex_ might encompass the
+southern part of Nayarit, and western Jalisco. Subsequent study of
+specimens from these areas reveals that the populations there are
+referable to _allex_. Most of the specimens obtained from these areas,
+however, merit special comment.
+
+In color of pelage, those populations from south of the Río Grande de
+Santiago and northwest of Guadalajara (4 mi. SE Ahuacatlán; 1 mi. E
+Ixtlán; Etzatlán) show evidence of intergradation with _paulus_ to the
+east and south (Magdalena, Tequila, and Tala, Jalisco), and with
+populations more closely adjacent to the south bank of that river.
+Intergradation is indeed complex in this area. Specimens from some
+localities seem to be intergrades between _allex_ and _paulus_; from
+other localities, some specimens are referable to _allex_, and the
+others to _paulus_; from still other localities, all specimens are
+referable to _allex_.
+
+A series of 39 specimens from 1 mi. SSE Ameca, 4000 ft., Jalisco, are
+uniformly grayish-brown. This series averages grayer than paratypes of
+_allex_. There is little, if any, difference between the series from 1
+mi. SSE Ameca and paratypes of _allex_ in external size of body, hind
+foot, length of ear, and size and conformation of the cranium.
+Populations from Ameca and vicinity might be expected to average
+considerably larger inasmuch as they occur at higher altitudes (see
+Bergman's Rule, p. 609) then the material from the lower coastal plains
+to the south in Colima and Michoacán, and at lower elevations in the
+west in Jalisco and Nayarit. The means of external and cranial
+measurements are not significantly different between the specimens from
+the highlands and those from the lowlands. In the area of Ameca where
+the two species _B. musculus_ and _B. taylori_ occur together,
+interspecific competition seems to have limited, perhaps even reduced,
+size of external and cranial parts of _taylori_ (see p. 660).
+
+In color, specimens from the northern part of the valley of the Río
+Tepalcatepec (10 mi. S, 1 mi. W Apatzingán) in Michoacán resemble
+paratypes of _allex_. Intergradation probably occurs to the north with
+_analogous_.
+
+In the eight specimens from 13 mi. E and 1 mi. N Talpa de Allendé, the
+skull, as reflected in occipitonasal length and zygomatic breadth
+relative to length of body, is larger than in other specimens here
+assigned to _allex_. The median part of the belly of the eight specimens
+is buff-colored rather than whitish-gray as in typical _allex_; the
+mid-dorsal region also averages darker than in any other specimens
+referred to _allex_. Additional specimens are needed from this and
+closely adjacent areas, especially to the west on the coastal plain, in
+order to determine more accurately the taxonomic status of the mice
+there. At present, it seems best to refer them to _allex_. Possibly the
+population represented by the eight specimens is an incipient
+subspecies.
+
+There is no evidence of hybridization or intergradation of populations
+of _B. t. allex_ with any population of _B. musculus_ where the two
+species occur together.
+
+_Specimens examined._--Total 233, all from the Republic of México,
+distributed as follows: NAYARIT: 3 mi. SE Mirador, 7; _2 mi. S.
+Compostela_, 2900 ft., 5; _4 mi. N Santa Isabel_, 3800 ft., 2[25]; _2 mi.
+N Santa Isabel_, 3800 ft., 22[25]; _4 mi SE Ahuacatlán_, 5200 ft., 2[26];
+_1 mi. E Ixtlán_, 4000 ft., 13[25]; 1 mi. E Ixtlán del Río, 3700 ft., 1;
+2 mi. WNW Valle de Banderas, near sea level, 1. JALISCO: Arroyo de
+Gavalán, 16[28]; Etzatlán, 6[27]; _Mascota_, 3900 ft., 6[27]; _7 mi W
+Ameca_, 15[25]; _6 mi. W Ameca_, 15[25]; _3 mi. W Ameca_, 5[25]; Ameca,
+4000 ft., 11[27]; _1 mi. SSE Ameca_, 4000 ft., 38; 2 mi. N Resolana, 1500
+ft., 28[25]; 13 mi. E, 1 mi. N Talpa de Allendé, 8; 2 mi. SSE Autlán, 5;
+1 mi. N San Gabriel, 4000 ft., 1[25]; Las Canoas, l[28]. COLIMA: Type
+locality, 10[27] (including the type). MICHOACÁN: 9 mi. S Lombardia, 1500
+ft., 1; _3 mi. W Apatzingán_, 1000 ft, 1; Apatzingán, 3[25]; 10 mi. S, 1
+mi. W Apatzingán, 800 ft., 10.
+
+_Marginal records._--NAYARIT: 3 mi. SE Mirador; 1 mi. E Ixtlán del Río.
+JALISCO: Etzatlán; Ameca; 2 mi. N Resolana; Las Canoas. MICHOACÁN: 9 mi.
+S Lombardia; 10 mi. S, 1 mi. W Apatzingán. COLIMA: type locality.
+NAYARIT: Valle de Banderas.
+
+[25] Univ. Michigan, Museum of Zoology.
+
+[26] California Academy of Sciences.
+
+[27] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[28] American Museum of Natural History.
+
+
+=Baiomys taylori analogous= (Osgood)
+
+    _Peromyscus taylori analogous_ Osgood, N. Amer. Fauna, 28:256,
+       April 17, 1909 (part); Elliott, Check-List Mamm., N. Amer. Cont.,
+       West Indies and Neighboring Seas, Suppl., Amer. Mus. Nat. Hist.,
+       p. 44, January 8, 1917.
+
+    _Baiomys taylori analogous_, Miller, Bull. U. S. Nat. Mus., 79:137,
+       December 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:318, April 29,
+       1924; Ellerman, The Families and Genera of Living Rodents, British
+       Mus. Nat. Hist., 2:402, March 21, 1941; Poole and Schantz, Bull.
+       U. S. Nat. Mus., 178:259, March 6, 1942; Davis, Jour. Mamm., 25:394,
+       December 12, 1944; Hooper, Jour. Mamm., 28:50, February 15, 1947;
+       Hall and Villa-R., Univ. Kansas Publs., Mus. Nat. Hist., 1:460,
+       December 27, 1949; Hall and Villa-R., Anal. del Inst. Biol., 21:196,
+       September 28, 1950; Goldman, Smith. Miscl. Coll., 114:373, July 31,
+       1951 (part); Hall and Kelson, Univ. Kansas Publs., Mus. Nat. Hist.,
+       5:367, December 15, 1952 (part); Villa-R., Anal. del Inst. Biol.,
+       23:435, May 20, 1953; Miller and Kellogg, Bull. U. S. Nat. Mus.,
+       205:512, March 3, 1955; Hooper, Occas. Papers Mus. Zool. Univ.
+       Michigan, 565:13, March 31, 1955; Packard, Proc. Biol. Soc.
+       Washington, 71:17, April 11, 1958.
+
+    _Peromyscus musculus brunneus_, Elliot, Field Columb. Mus. Publ.,
+       115(8):203, 1907 (part).
+
+    _Peromyscus musculus_ [_musculus_], Osgood, N. Amer. Fauna, 28:258,
+       April 17, 1909 (part).
+
+    _Baiomys musculus musculus_, Hall and Villa-R., Univ. Kansas Publs.,
+       Mus. Nat. Hist., 1:460, December 27, 1949 (part); Hall and Villa-R.,
+       Anal. del Inst. Biol., 21:196, September 28, 1950 (part).
+
+    _Baiomys taylori taylori_, Dalquest, Louisiana State Univ. Studies
+       (Biol. Sci. Ser.), 1:155, December 28, 1953 (part); Hall and Kelson,
+       The Mammals of North America, 2:660, March 31, 1959 (part).
+
+    _Baiomys taylori allex_, Hall and Kelson, The Mammals of North
+       America, 2:659, March 31, 1959 (part).
+
+    _Baiomys musculus musculus_, Hall and Kelson, The Mammals of North
+       America, 2:661, March 31, 1959 (part).
+
+_Type._--Adult male, skin and skull; No. 120261 U. S. Nat. Mus. (Biol.
+Surv. Coll.); Zamora, Michoacán, Republic of México, obtained on January
+15, 1903, by E. W. Nelson, and E. A. Goldman, original number 15764.
+
+_Range._--Central and eastern Jalisco south into Michoacán, east through
+Guanajuato, Querétaro, thence into Estado México, and Distrito Federal,
+and west-central Veracruz, see Figure 11. Zonal range: approximately the
+Transverse Volcanic Biotic Province of Moore (1945:218) and of Goldman
+and Moore (1945:349). Occurs from 5000 feet, 7 mi. S Ocotlán, Jalisco,
+up to 8000 feet in Ixtapalapa, Distrito Federal.
+
+_Diagnosis._--Size large for the species; dorsum dark Sepia to near
+blackish medially in freshly taken specimens (Sepia fading to near
+Fuscous in prepared specimens); belly slaty-gray, hairs Deep Neutral
+Gray near tips and Dusky Neutral Gray at bases; hairs on back
+black-tipped with subterminal band of Ochraceous-Tawny (guard hairs
+blackish to base); hairs of throat and chin white-tipped, gray at bases;
+dorsal vibrissae black, ventral and anteriormost vibrissae white; hairs
+on face and sides black-tipped, and Ochraceous-Tawny at base; ears
+sparsely haired, individual hairs grayish, blackish, and ochraceous;
+tail sooty to blackish dorsally, lighter ventrally; forefeet and hind
+feet sooty brown on dorsal and ventral surface. Skull relatively broad
+interorbitally; zygoma broad and squared; cranium larger in all
+dimensions than in most other subspecies. Average and extreme
+measurements of 10 adults from 1 mi. S, 11 mi. W Zamora, 5400 ft.,
+Michoacán, are: total length, 109.4 (102-121); length of body, 64.3
+(58-72); length of tail, 44.9 (39-51); length of hind foot, 14.6
+(14-15); occipitonasal length, 18.0 (17.5-18.6); zygomatic breadth, 9.4
+(9.1-9.7); postpalatal length, 6.6 (6.2-7.2); least interorbital
+breadth, 3.5 (3.3-3.8); length of incisive foramina, 4.0 (3.8-4.2);
+length of rostrum, 6.2 (5.8-6.5); breadth of braincase, 8.7 (8.5-8.9);
+depth of cranium, 6.6 (6.3-6.9); alveolar length of maxillary tooth-row,
+3.1 (3.0-3.3); for photographs of skull, see Plate 2_a_ and Plate 4_b_.
+
+_Comparisons._--For comparisons with _B. t. allex_, _B. t. canutus_, _B.
+t. paulus_, and _B. t. fuliginatus_, see accounts of those subspecies.
+From _B. t. taylori_, _B. t. analogous_ differs as follows: sides and
+dorsum darker, differing most in freshly prepared specimens; dorsal
+surface of forefeet and hind feet darker; basal part of hairs on belly
+darker gray; frontal bones less constricted, causing less taper
+anteriorly in interorbital space; interparietal wider transversely;
+basioccipital more expanded laterally, narrowing more abruptly at suture
+between basioccipital and basisphenoid.
+
+_Remarks._--The pelage of _analogous_ becomes paler with wear as pointed
+out by Osgood (1909:257). A paratype, U. S. Nat. Mus. 120260, and
+several specimens from 1 mi. S, 11 mi. W Zamora, Michoacán, are grayish
+rather than brownish-black. All of these are old adults having the
+terminal black parts of the hairs on the dorsum nearly worn away.
+Excluding such grayish individuals, _B. t. analogous_, like _B. t.
+subater_ and _B. t. fuliginatus_, is uniformly brownish-black. Both
+_analogous_ and _fuliginatus_ occur in relatively high mountainous
+country on dark soils or pedregals, and all three of the aforementioned
+subspecies occur in zones of high relative humidity.
+
+_B. t. analogous_ intergrades with _B. t. paulus_ (see account of that
+subspecies) and _B. t. allex_ south and west of Lago de Chapala in
+Jalisco. Additional specimens are needed from Querétaro and San Luis
+Potosí in order to ascertain whether or not _B. t. analogous_
+intergrades with _B. t. fuliginatus_ or _B. t. taylori_. Specimens from
+western Jalisco, in the past referred to _B. t. analogous_, are
+referable to _B. t. allex_ (see account of that subspecies). Specimens
+obtained west of, and bordering, the Río del Naranjo in Jalisco show a
+mixture of characters of both _B. t. allex_ and _B. t. analogous_. For
+example, specimens from 2 mi. N Ciudad Guzmán resemble _analogous_ on
+the dorsum, whereas, on the belly, the individual hairs are
+white-tipped, pale gray at the base, and in over-all appearance are
+whitish-gray, unlike typical _analogous_ (being like _allex_ instead).
+The dorsal surface of the forefeet are sooty to light brownish (as in
+_analogous_), whereas, the hind feet are flesh-colored (as in _allex_).
+Another series of specimens from 4 mi. W León, Guanajuato, are
+intergrades between _B. t. analogous_ and _B. t. paulus_. These
+specimens are grayish to brownish on the dorsum, have sooty forefeet and
+hind feet (more nearly as in _analogous_ than in _paulus_), are
+grayish-white on the venter, and have a distinctly bicolored tail
+(resembling that of _paulus_ more than that of _analogous_). When the
+average of cranial characters is considered, both series are best
+referred to _analogous_.
+
+Hooper (1947:50) pointed out that specimens from the pedregal San
+Gerónimo, Distrito Federal, were more nearly black than topotypes and
+generally showed less brownish hues typical of _analogous_. I have
+examined this series and several others from this area (see Specimens
+examined, p. 640) and am convinced that these populations average
+darker. Actually, the dorsum is more nearly black and the venter is more
+buffy than in typical _analogous_. The hairs of these individuals
+average longer than in other populations of _analogous_. Skulls of the
+specimens from the pedregal are indistinguishable from those of
+paratypes of _analogous_. The populations from the Distrito Federal seem
+to be incipient subspecies.
+
+_Specimens examined._--Total 696, all from the Republic of México,
+distributed as follows: SAN LUIS POTOSÍ: Hacienda Capulín, 5[33]; _3.3
+mi. N Tamazunchale, by-road_, 2[34]; 1 mi. N Tamazunchale, 700 ft., 1[35].
+VERACRUZ: Acultzingo, 4[29], 1[31]. JALISCO: 1 mi. S Jalostotitlán, 5700
+ft., 5; 7 mi. NW Tepatitlán, 3[29]; _6 mi. N, 4 mi. E Tepatitlán_, 6400
+ft., 25; _2-1/2 mi. E Tepatitlán_, 6200 ft., 15; _2 mi. S, 1/2 mi. W
+Tepatitlán_, 9; _near Tepatitlán_, 2; _5 mi. SW Arrandas_, 6700 ft., 6;
+_2 mi. E Zapotlanejo_, 23; _2-1/2 mi. E Puente Grande_ (_5-1/2 mi. SW
+Zapotlanejo_), 3; _8 mi. S Guadalajara_, 10[29]; _3 mi. ENE Santa Cruz de
+las Flores_, 9; _4 mi. NE Ocotlán_, 5050 ft., 18; _13 mi. S, 9-1/2 mi. W
+Guadalajara_, 1; _2 mi. WNW Ocotlán_, 5000 ft., 15; 13 mi. S, 15 mi. W
+Guadalajara, 2; _Ocotlán_, 5000 ft., 8[30]; _1 mi. S Ocotlán_, 5000 ft.,
+12; 27 mi. S, 12 mi. W Guadalajara, 9; _1-1/2 mi. N Mazatmitla_, 6[29];
+_1/2 mi. NW Mazatmitla_, 4; _3 mi. WSW Mazatmitla_, 4; 2 mi. N Ciudad
+Guzmán, 5000 ft., 18. GUANAJUATO: 4 mi. N, 5 mi. W León, 7000 ft., 25; 5
+mi. S Salamanca, 2[29]; _5 mi. E Celaya_, 6000 ft., 6; _1 mi. E Yuriria_,
+5725 ft., 3; Salvatierra, 5775 ft., 8; _NE edge Acambaro_, 6050 ft., 10;
+_Acambaro_, 3[30]. QUERÉTARO: Tolimán, 7[30]; 6 mi. E Querétaro, 6550 ft.,
+37. HIDALGO: Tula, 2050 m., 1[31]. MICHOACÁN: _2 mi. E La Palma, SE side
+Lago de Chapala_, 7; type locality, 4000 ft., 10[30] (including the
+type); _9 mi. E Zamora_ (_Camenaro_), 2[29]; _1 mi. S, 11 mi. W Zamora_,
+5400 ft., 17; S Cuitzeo, 36[29]; _Jiquilpan_, 4800 ft., 15; _11 mi. W
+Jiquilpan_, 6700 ft., 2; _1 mi. E Jiquilpan_, 7; _1 mi. E Zinapecuaro_,
+6300 ft., 17; _4-1/2 mi. NE Tarequato_ (_Tarecuato_), 6600 ft, 1;
+_Tanganciguaro_ (_Tangancicuaro_), 5500 ft., 4; _2 mi. N Tarecuato_,
+7200 ft., 1; _2 mi. S Maravatio_, 6650 ft, 6; _2 mi. SE Zacapu_, 6600
+ft., 11; _1 mi. N Tinquindin_ (_Tinguindin_), 6300 ft., 2; _3 mi. E
+Morelia_, 6600 ft., 3; _11 mi. E, 2 mi. S Morelia_, 1; 2 mi. SE Hidalgo
+(Villa Hidalgo), 6; _1-1/2 mi. N Los Reyes_, 1; _E Los Reyes_, 18[29];
+_Los Reyes_, 8[30]; _3 mi. W, 1 mi. N Pátzucuaro_, 6600 ft., 2; _N
+Pátzucuaro_, 2[29]; _Pátzucuaro_ 9[31], 4[30], 4[29]; Uruapan, 1[29]; _E
+Uruapan_, 12; _2-1/2 mi. E Uruapan_ (_La Presca_), 2[29]; 2 mi. SW
+Zitacuaro, 1; 1 mi. E, 6 mi. S Tacámbaro, 4000 ft., 11[37]; _La Huacana_,
+1[30]. MEXICO: Templo del Sol, Pyramídes de San Juan, Teotihuacán, 8000
+ft., 1; _31 km. E México City_, 7500 ft., 11[36]; _17 km. E México City_,
+7500 ft, 1[36]; _Cerro La Caldera, 11 mi. ESE México_, 2350 m., 5; 4 km.
+ENE Tlalmanalco, 2290 m., 9; _Hacienda Córdoba_ (_Córdova_), 6. MEXICO,
+D. F.: _Cerro de la Estrella, Ixtapalapa_, 2450 m., 1; _3/4 mi. S, 1 mi.
+E Churubusco_, 2400 m., 2; _5 km. S México City, South of Cd.
+Universitaria_, l[32]; _Pedregal San Angel_, _2.6 mi. S Monumento a
+Obregón, 2_; _El Pedregal, 1 km. S San Angel_, 2260 m., 1; _Falda SW
+Cerro Zacatepec, 3.9 mi. SW Monumento a Obregón_, 1; _2 mi. N Tlalpan,
+Zacayuca_, 2380 m., 5; _Tlalpan_ (_Pedregal_), 2400 m., 21[31]; _San
+Gerónimo_, 37[29], 6[38]; _Santa Rosa_, 2700 m., 1[32]; _Tlalpan_, 8; _3/4
+mi. SW Las Fuentes, Tlalpan_, 2450 m., 25[30]; _Tepepán_, 6[29]; _Rancho
+La Noria, 1 mi. W Xochimilco_, 2270 m., 4; _500 meters N Xochitepec_,
+2250 m., 7; 200 m. N San Mateo Xalpa (Jalpa), 2390 m., 2.
+
+_Marginal records._--SAN LUIS POTOSÍ: Hacienda Capulín; 1 mi. N
+Tamazunchale. HIDALGO: Tula, 2050 m. MEXICO: Templo del Sol, Pyramídes
+de San Juan, Teotihuacán. VERACRUZ: Acultzingo. MEXICO: 4 km. ENE
+Tlalmanalco. MEXICO, D. F.: 200 m. N San Mateo Xalpa (Jalpa), 2390 m.
+MICHOACÁN: 2 mi. SW Zitacuaro; 1 mi. E, 6 mi. S Tacámbaro; Uruapan.
+JALISCO: 2 mi. N Ciudad Guzmán; 27 mi. S, 12 mi. W Guadalajara; 13 mi.
+S, 15 mi. W Guadalajara; 7 mi. NW Tepatitlán; 1 mi. S Jalostotitlán,
+5700 ft. GUANAJUATO: 4 mi. N, 5 mi. W León. QUERÉTARO: 6 mi. E
+Querétaro, 6550 ft.; Tolimán.
+
+[29] Univ. Michigan, Museum of Zoology.
+
+[30] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[31] Chicago Natural History Museum.
+
+[32] American Museum of Natural History.
+
+[33] Museum of Natural History, Louisiana State University.
+
+[34] Univ. Illinois, Mus. Nat. History.
+
+[35] The Museum, Michigan State Univ.
+
+[36] Texas A & M, Cooperative Wildlife Research Collection.
+
+[37] Univ. California, Mus. Vert. Zoology.
+
+[38] University of Florida Collections.
+
+
+=Baiomys taylori ater= (Blossom and Burt)
+
+    _Baiomys taylori ater_ Blossom and Burt, Occas. Papers Mus. Zool.,
+       Univ. Michigan, 465:2, October 8, 1942; Blair and Blossom, Contrib.
+       Lab. Vert. Biol., Univ. Michigan, 40:1, March, 1948; Hoffmeister and
+       Goodpaster, Ill. Biol. Monogr., 24(1):115, December 31, 1954; Miller
+       and Kellogg, Bull. U. S. Nat. Mus., 205:511, March 3, 1955;
+       Hoffmeister, Amer. Midland Nat., 55:281, April, 1956; Packard, Jour.
+       Mamm., 40:146, February 20, 1959; Hall and Kelson, The Mammals of
+       North America, 2:659, March 31, 1959 (part).
+
+    _Peromyscus taylori paulus_, Osgood, N. Amer. Fauna, 28:256, April
+       17, 1909 (part).
+
+    _Baiomys taylori_ [_ater_], Justice, Jour. Mamm., 38:520, November
+       20, 1957.
+
+_Type._--Adult male, skin and skull; No. 85425, University of Michigan,
+Museum of Zoology; 7 mi. W Hereford, Cochise County, Arizona, obtained
+on March 25, 1941, by Philip M. Blossom, original number 2195.
+
+_Range._--Southeastern Arizona, north to Graham County, thence east to
+the Animas Valley, Hidalgo County, New Mexico; south to northern
+Chihuahua and northwest to the southern border of Cochise County,
+Arizona, see Figure 11. Zonal range: largely lower Sonoran (Apachian
+Biotic Province of Dice, 1943:56). Occurs from 4300 feet in Chihuahua up
+to 6200 feet in New Mexico.
+
+_Diagnosis._--Size medium for the species; dorsum between Mummy Brown
+and Prouts Brown; individual tips of hairs intermixture of black and
+Ochraceous-Tawny, bases of all hairs slate-gray; sides of body and face,
+Buffy Brown to Cinnamon Brown; belly Cinnamon Buff, proximal half of
+individual hairs Deep Neutral Gray, distal half white; in region of
+throat, proximal fourth of individual hairs gray, distal three-fourths
+white; dorsal vibrissae black to base, ventral vibrissae white to base;
+tail brownish above, gray below; dorsal and ventral surface of forefeet
+and hind feet buffy to gray; interparietal somewhat compressed
+anteroposteriorly. Average and extreme cranial measurements of 15 adults
+from 9-1/2 mi. W New Mexico State Line, 5-1/2 mi. N Mexican border,
+Cochise County, Arizona, are as follows: occipitonasal length, 18.0
+(17.5-18.6); zygomatic breadth, 9.5 (9.2-9.9); postpalatal length, 6.6
+(6.0-7.1); least interorbital breadth, 3.6 (3.4-3.8); length of incisive
+foramina, 4.0 (3.8-4.2); length of rostrum, 6.1 (5.7-6.4); breadth of
+braincase, 8.6 (8.4-9.1); depth of cranium, 6.5 (6.3-6.9); alveolar
+length of maxillary tooth-row, 3.2 (3.1-3.4). Average and extreme
+external measurements for six adults from 9 mi. W Hereford, Cochise
+County, are as follows: total length, 106.3 (98-115); length of tail
+vertebrae, 42.3 (39-46); length of body, 64 (59-69); length of hind
+foot, 13.6 (13-14.2); length of ear from notch, 11.1 (10.5-11.5); for
+photographs of skull, see Plate 2_b_, and Plate 4_c_.
+
+_Comparisons._--For comparisons with _B. t. canutus_, see account of
+that subspecies. From _B. t. paulus_, the subspecies to the southeast,
+_B. t. ater_ differs in: dorsum darker brown; tail less strikingly
+bicolored; belly buffy rather than whitish to white-gray; forefeet and
+hind feet darker dorsally and ventrally; posterior margin of
+basioccipital bowed anteriorly in a broad U-shape with a secondary small
+median anteriorly directed U-shaped curve, rather than bowed anteriorly
+in a simple U-shape; interparietal more compressed anteroposteriorly;
+coronoid process of mandible so acutely recurved that tip of coronoid
+points posteroventrally and appears sickle-shaped.
+
+_Remarks._--Blossom and Burt (1942:1) described _B. t. ater_ as the
+darkest of the known subspecies. It is dark, but specimens from some
+parts of the ranges of _B. t. analogous_, _B. t. fuliginatus_, and _B.
+t. subater_ exceed in melanins the darkest individuals of _ater_. Blair
+and Blossom (1948:5) also concluded by the use of an Ives tint
+photometer that _B. t. subater_ was significantly darker than _B. t.
+ater_.
+
+When paratypes of _ater_ and specimens of _B. t. paulus_ are compared,
+the darkest individuals of _ater_ exceed but slightly the darkest of
+_paulus_. The darkest specimens of _paulus_ occur in southern Zacatecas,
+and northern Jalisco, and the palest of the series are in northern
+Durango and southern Chihuahua. When paratypes of _ater_ and _paulus_
+are compared, the difference in color is readily distinguishable.
+Specimens from 1-1/2 mi. N San Francisco, in northern Chihuahua, appear
+to be intermediate in color between _ater_ and _paulus_ except for a
+faint tinge of buff ventrally. In characters of the crania, these
+specimens resemble _ater_ and are referred to that subspecies. A
+slightly different pattern of color is present in pygmy mice from the
+Peloncillo Mountains and the Animas Valley of New Mexico; the upper
+parts resemble those of paratypes of _ater_, but the venter has only the
+faintest suggestion of the buffy wash. Crania of these specimens from
+New Mexico are inseparable from those of paratypes of _ater_, and the
+specimens are, therefore, referred to _ater_.
+
+When specimens are arranged by localities from Arizona east into
+southern New Mexico, thence south into Chihuahua and Durango, gradual
+intergradation in color is evident from dark in the north to pale browns
+in the south, whereas, size and shape of interparietal and size and
+shape of coronoid process of the lower jaw divide quite distinctly into
+two morphological types in central Chihuahua.
+
+Cranial variation in size and proportion among adults is slight
+throughout the range of _ater_ compared to variation detected in other
+subspecies of _Baiomys taylori_. Perhaps such a relatively stable
+pattern of characters of the crania reflects the homogeneity of the gene
+pool, with respect to these characters, of the populations sampled. The
+fact that the color of the pelage of this subspecies varies considerable
+throughout its known range and that the crania do not is perhaps a clue
+to the mode of inheritance of characters in these mice. Seemingly, color
+of pelage is inherited independently of characters of the cranium. The
+relative lack of variability in the crania of _ater_ may result from
+uniform environmental conditions, which have served to select for
+uniform characters in the populations. All of the other wide-ranging
+subspecies of _B. taylori_ occupy more diverse habitats than _ater_.
+Secondly, the rather abrupt change in the cline of measured characters
+of the crania between _ater_ and _paulus_ in central Chihuahua suggests
+a secondary zone of intergradation. The probable cessation of gene flow
+in the past between these two subspecies, allowing _ater_ to be isolated
+for a time, may also, in part, account for the relative lack of
+variability in the crania of _ater_.
+
+_Specimens examined._--Total 58, distributed as follows: ARIZONA:
+_Graham County_: 1-1/2 mi. SW Ft. Grant, Graham Mts., 1[39]; _Pima
+County_: 1-1/2 mi. ENE Greaterville, Thurber Ranch, 2[39]; _Santa Cruz
+County_: Patagonia, 3[39]; _Cochise County_: _9 mi. W Hereford_, 10[43];
+type locality, 2[43] (including the type); _5 mi. W Hereford_, 5[43];
+9-1/2 mi. W New Mexico State Line, 5-1/2 mi. N Mexican border, 20[42]; _3
+mi. E, 1 mi. N Chiricahua_, 1[42]. NEW MEXICO: _Hidalgo County_: 18 mi.
+S, 2 mi. W Animas, 2; _22 mi. S, 2 mi. W Rodeo_, 6000 ft., 1[40]; _22 mi.
+S, 2 mi. E Rodeo_, 6000 ft., 3[40]; 25-1/2 mi. S Animas, 6200 ft. (in Big
+Bill Canyon), 1[40]. CHIHUAHUA: _5-1/2 mi. N, 2 mi. W San Francisco_,
+5100 ft., 1; _2-1/2 mi. N, 3 mi. W San Francisco_, 5200 ft., 1; 1-1/2
+mi. N San Francisco, 5100 ft., 4; Casas Grandes, 4300 ft., 1[41].
+
+_Marginal records_--ARIZONA: 1-1/2 mi. SW Ft. Grant, Graham Mts. NEW
+MEXICO: 18 mi. S, 2 mi. W Animas; 25-1/2 mi. S Animas (in Big Bill
+Canyon). CHIHUAHUA: 1-1/2 mi. N San Francisco; Casas Grandes. ARIZONA:
+Patagonia; 1-1/2 mi. ENE Greaterville, Thurber Ranch.
+
+[39] University of Illinois, Museum of Natural History.
+
+[40] University of New Mexico.
+
+[41] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[42] University of Arizona.
+
+[43] Univ. Michigan, Museum of Zoology.
+
+
+=Baiomys taylori canutus=, new subspecies
+
+    _Peromyscus taylori paulus_, Osgood, N. Amer. Fauna, 28:255, April
+       17, 1909 (part).
+
+    _Peromyscus musculus_ [_musculus_], Osgood, N. Amer. Fauna, 28:256,
+       April 17, 1909 (part).
+
+    _Baiomys taylori paulus_, Miller, Bull. U. S. Nat. Mus., 79:137,
+       December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317,
+       April 29, 1924 (part); Burt, Miscl. Publ., Mus. Zool., Univ.
+       Michigan, 39:54, February 14, 1938; Goldman, Smith. Miscl. Coll.,
+       115:373, July 31, 1951 (part); Miller and Kellogg, Bull. U. S. Nat.
+       Mus., 205:512, March 3, 1955 (part); Hooper, Occas. Papers Mus.
+       Zool., Univ. Michigan, 565:13, March 31, 1955; Hall and Kelson, The
+       Mammals of North America, 2:659, March 31, 1959 (part).
+
+    _Baiomys musculus musculus_, Goldman, Smith. Miscl. Coll., 115:336,
+       July 31, 1951 (part).
+
+_Type._--Adult male, skin and skull; No. 62075, University of Kansas,
+Museum of Natural History; 1 mi. S Pericos, Sinaloa, Republic of México;
+obtained on June 14, 1954, by A. A. Alcorn, original number 1754.
+
+_Range._--Central Nayarit northward through western Sinaloa, to as far
+north as south-central Sonora, see Figure 11. Zonal range: Lower arid
+tropical, closely approximating the Sinaloan Biotic Province of Goldman
+and Moore (1945:349). Occurs from near sea level at Escuinapa (43 feet),
+Sinaloa, to 3200 feet at a place 2 mi. WNW Tepic, Nayarit.
+
+_Diagnosis._--Dorsal ground color Buffy Brown (some specimens near Olive
+Brown); proximal fourth of individual guard hairs of dorsum
+black-tipped, distal three-fourths dark grayish; dorsal underfur
+black-tipped having subterminal band of Buffy Brown; hair around eyes
+buffy to base; belly Pallid Neutral Gray with overtones of buff;
+individual hairs in region of chin whitish-gray to bases; vibrissae
+blackish to bases except ventralmost, those being white to base; tail
+Dark Olive above, slightly paler below. Average and extreme external
+measurements of 13 adults from 15 mi. N Rosario, Chelé, Sinaloa, 300
+ft., are as follows: Total length, 109.6 (99-120); length of tail, 43.4
+(38-49); length of body, 66.2 (58-75); length of hind foot, 11.2
+(10-12). Average and extreme cranial measurements of 19 adults from the
+same place are as follows: occipitonasal length, 18.2 (17.7-18.9);
+zygomatic breadth, 9.6 (9.2-10.1); postpalatal length, 6.9 (6.5-7.3);
+least interorbital breadth, 3.6 (3.4-3.8); length of incisive foramina,
+3.9 (3.5-4.2); length of rostrum, 5.9 (5.5-6.6); breadth of braincase,
+8.7 (8.3-8.9); depth of cranium, 6.5 (6.2-6.7); alveolar length of
+maxillary tooth-row, 3.1 (3.0-3.2); breadth of zygomatic plate, 1.8
+(1.6-2.0); for photographs of skull, see Plate 2_c_, and Plate 4_d_.
+
+_Comparisons._--From _B. t. ater_, _B. t. canutus_ differs in: dorsum
+slightly grayer; belly whitish to pale-gray with only faint tones of
+buff, rather than cinnamon-buff to buff-gray; forefeet and hind feet
+flesh-colored to grayish above instead of whitish to flesh-colored; tail
+paler above, less hairy, scales more evident; interparietal relatively
+larger from anteriormost to posteriormost points; incisive foramina
+tapering less abruptly posteriorly, not constricted towards midline;
+over-all size of body and cranium somewhat larger.
+
+From _B. t. paulus_, _B. t. canutus_ differs in: dorsum grayish-brown
+rather than fawn-colored (not differing appreciably from extremes of
+darker brown specimens of _paulus_); forefeet and hind feet
+flesh-colored to grayish above rather than white above; tail less
+hairy, unicolored to faintly bicolored rather than distinctly bicolored;
+braincase slightly larger; alveolar length of maxillary tooth-row
+slightly less.
+
+From _B. t. analogous_, _B. t. canutus_ differs in: dorsum paler, less
+of dark brown hues; belly paler; forefeet and hind feet slightly paler,
+less sooty above; tail less hairy, paler and having scales evident;
+jugal of zygoma extending ventrally to a point immediately above,
+instead of below, level of alveolus of upper molars; nasals more nearly
+truncate anteriorly; infraorbital foramina less deeply notched toward
+midline of skull; body and skull averaging smaller throughout.
+
+From _B. t. allex_, _B. t. canutus_ differs in: dorsal ground color
+grayish rather than fawn color having grayish overtones; underfur on
+dorsum darker gray; dorsal surface of forefeet and hind feet
+flesh-colored to grayish rather than flesh-colored; incisive foramina
+tapering to a point posteriorly rather than rounded posteriorly;
+interparietal relatively smaller; body and skull averaging larger
+throughout.
+
+_Remarks._--Burt (1938:54) reluctantly assigned specimens from Ciudad
+Obregón to _B. t. paulus_, probably being influenced by the resemblance
+in size. He suggested that, perhaps, a distinct subspecies occurs in the
+State of Sonora. Study of larger series of specimens than were available
+to Burt reveals that populations of pygmy mice inhabiting the northwest
+coastal plains of México are indeed distinct.
+
+The darkest of the material assigned to _canutus_ is from Nayarit (for
+specific localities see specimens examined). According to Tamayo
+(1949:Carta de Suelos), color of soil changes from chestnut in northern
+Sinaloa to black in southern Sinaloa and northern Nayarit. There seems,
+therefore, to be a close correlation between color of pelage and color
+of soil in this area. In Nayarit, particularly in the central and
+southern parts, the mice are intermediate in color between the paler,
+grayer population to the north and the more brownish samples,
+representative of _allex_ to the south. The coastal vegetation changes
+from the arid tropical thorn forests of the north and central parts of
+Sinaloa to a savannah in Nayarit, thence to a tropical deciduous forest
+farther south (see Leopold, 1950:508).
+
+In size and color, specimens from 3 mi. SE Tepic and 2 mi. SW Rosa
+Morada are intermediate between the larger, grayer _canutus_ and the
+smaller, light-brownish _allex_. In size of cranium, these specimens are
+more nearly like _canutus_, and are referred to that subspecies. Mice
+from the western coastal plain are relatively homogeneous as regards
+size of body and skull, except that those from 13.5 mi. S Acaponéta,
+Nayarit, average somewhat larger.
+
+_B. t. canutus_, like _B. t. subater_, is predominantly a lowland or
+coastal subspecies. The pallor of the former, that lives on generally
+paler soils, presumably is of adaptive value.
+
+Pygmy mice are seemingly rare in the northern part of the range of this
+subspecies. J. Raymond Alcorn and Albert Alcorn were successful in
+collecting only two specimens from the type locality after three
+successive nights of trapping with 100 traps set each night. Only six
+specimens are known from Sonora. These were obtained in the irrigated
+regions of Ciudad, Obregón, and Navajoa. Charles Sibley obtained one
+specimen 10.6 mi. SE Ciudad Obregón in a "maguey field." I obtained one
+specimen 1 mi. NNW Navajoa in a sparse grassway, 20 feet wide, bordering
+an open sewer, which coursed northward into the Río Mayo. Irrigated
+wheat fields bordered the grassway and ditch.
+
+_Specimens examined._--Total 70 all from the Republic of México and
+distributed as follows: SONORA: [Ciudad] Obregón, 4[44]; 10.6 mi. SE
+[Ciudad] Obregón, 1[45]; 1 mi. NNW Navajoa, 1. SINALOA: type locality, 2
+(including the type); Culiacán, 175 ft., 2[46]; Mazatlán, 1[48]; _15 mi. N
+Rosario, Chelé_, 300 ft., 35[47]; Rosario, 3[46]; Escuinapa, 5[48];
+_Railroad Station Escuinapa_, 43 ft., 2[45]. NAYARIT: Acaponéta, 4[46];
+_13.5 mi. S Acaponéta Junction_, 6[49]; 2 mi. SW Rosa Morada, 2; _2 mi.
+WNW Tepic_, 3200 ft., 1; 3 mi. SE Tepic, 1.
+
+_Marginal records._--SONORA [Ciudad] Obregón. SINALOA: type locality;
+Escuinapa. NAYARIT: Acaponéta; 3 mi. SE Tepic. SINALOA: Mazatlán.
+
+[44] Coll. Univ. California, Los Angeles.
+
+[45] Univ. California, Mus. Vert. Zoology.
+
+[46] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[47] Univ. Michigan, Museum of Zoology.
+
+[48] American Museum of Natural History.
+
+[49] Univ. Illinois, Mus. Nat. History.
+
+
+=Baiomys taylori fuliginatus=, new subspecies
+
+    _Baiomys taylori taylori_, Dalquest, Louisiana State Univ. Studies
+       (Biol. Sci. Ser.) 1:155, December 28, 1953 (part).
+
+    _Baiomys taylori taylori_, Booth, Walla Walla Publs. Dept. Biol.
+       Sci., 20:15, July 10, 1957 (part).
+
+_Type._--Adult male, skin and skull; No. 36765, University of Kansas,
+Museum of Natural History; 10 mi. E, 2 mi. N Ciudad del Maíz, 4000 ft.,
+San Luis Potosí, Republic of México; obtained on January 17, 1950, by J.
+R. Alcorn, original number 10400.
+
+_Range._--Occurs in the Sierra Madre Oriental of the northeastern third
+of San Luis Potosí. Zonal range: Upper Tropical (see Dalquest, 1953:10);
+approximates a part of the Sierra Madre Oriental Biotic Province of
+Goldman and Moore (1945:349, 356). Occurs from 2000 feet at El Salto up
+to 4000 feet at Ciudad del Maíz.
+
+_Diagnosis._--Size large for the species; ground color of dorsum
+Chaetura Drab; individual guard hairs of dorsum black to base, distal
+fourth of hairs of underfur in posterior half of dorsum tipped with
+grayish-brown, proximal three-fourths Dark Neutral Gray; in anterior
+region of dorsum, posterior to ears, distal third of hairs grayish-brown
+and proximal two-thirds Dark Neutral Gray to base; sides slightly paler
+than dorsum; ground color of belly Neutral Gray, individual hairs of
+belly and throat tipped with Pallid Neutral Gray, basally Deep Neutral
+Gray to Dark Neutral Gray; tips of individual hairs of face
+Ochraceous-Tawny; lateral vibrissae whitish, dorsal and ventral
+vibrissae black to base; forefeet and hind feet sooty above and below,
+thigh bearing some white-tipped hairs; tail near Chaetura Drab above,
+Pale Neutral Gray below; anterior part of jugal projecting slightly
+ventrally and forming small protuberance at point of articulation with
+maxillary part of zygoma; jugal extending anteriorly nearly to lacrimal.
+In most cranial measurements averaging as large as _B. t. analogous_.
+Average and extreme measurements of the type and three additional
+paratypes, all adults, are: total length, 105.5 (101-109); length of
+tail, 39.8 (35-42); length of body, 65.8 (63-68); length of hind foot,
+14.3 (14-15); length of ear from notch, 11 (11); occipitonasal length,
+18.1 (18.1-18.8); zygomatic breadth, 9.6 (9.3-9.8); postpalatal length,
+6.5 (6.0-6.7); least interorbital breadth, 3.4 (3.3-3.6); length of
+incisive foramina, 4.0 (3.8-4.2); length of rostrum, 6.3 (6.1-6.4);
+breadth of braincase, 8.8 (8.6-8.9); depth of cranium, 6.7 (6.5-6.8);
+alveolar length of maxillary tooth-row, 3.2 (3.1-3.3); for photograph of
+skull, see Plate 2_d_, and Plate 4_e_.
+
+_Comparisons._--From _B. t. taylori_, _B. t. fuliginatus_ differs in:
+dorsum slightly darker than in darkest _taylori_; tail densely haired,
+bicolored rather than unicolored; belly sooty to grayish rather than
+grayish to whitish; forefeet and hind feet sooty to grayish rather than
+flesh-colored; incisive foramina less bowed laterally, more nearly
+straight; interparietal compressed anteroposteriorly, less
+diamond-shaped.
+
+From _B. t. paulus_, _B. t. fuliginatus_ differs in: dorsum dusky to
+blackish rather than fawn color; belly sooty to grayish rather than
+buffy to whitish-gray; forefeet and hind feet sooty to grayish rather
+than whitish; zygoma more nearly forming a right angle with rostrum or
+skull, less tapered anteriorly; anterior part of jugal possessing
+ventral projection; jugal extending nearly to lacrimal on posterior
+surface of maxillary part of zygoma.
+
+From _B. t. analogous_, _B. t. fuliginatus_ differs in: mid-dorsal
+region blacker, less brownish; tail distinctly bicolored rather than
+unicolored to faintly bicolored; incisive foramina not constricted
+medially; presphenoid broader (at narrowest point); jugal differs much
+the same as it does from _paulus_; nasals anteriorly truncate instead of
+rounded.
+
+_Remarks._--Dalquest (1953:155-157) and Booth (1957:15) assigned all of
+the pygmy mice that they examined from the state of San Luis Potosí to
+_B. t. taylori_. Examination of all of the material that was available
+to Dalquest, plus additional specimens at the University of Kansas
+Museum of Natural History, reveals that there are three subspecies in
+San Luis Potosí. _B. t. taylori_ occurs in the eastern part of the State
+at lower altitudes; _B. t. analogous_ occurs to the southeast at higher
+altitudes; _B. t. fuliginatus_ occurs in the northeastern part of the
+State in the Sierra Madre Oriental.
+
+Specimens obtained from Ebano, Pujal, and Tamuín, representative of _B.
+t. taylori_, are much paler on the belly and on the ventral surface of
+the forefeet and hind feet than are specimens from Ciudad del Maíz,
+representative of _B. t. fuliginatus_. The tail in _B. t. taylori_ is
+nearly unicolored and less hairy than in the paratypical series of
+_fuliginatus_. Specimens from 4 km. NE Ciudad Valles are nearly
+intermediate in color of the belly, dorsum, forefeet and hind feet, and
+tail, between the palest mice from the coastal plain and the darker mice
+in the mountains of the northeastern part of the State (specimens from
+El Salto average paler, however, than the type and paratypes). These
+specimens seem to be intergrades between _B. t. taylori_ to the east on
+the coastal plain and _fuliginatus_ to the northwest in the mountains.
+It seems best to refer the mice from 4 km. N Ciudad Valles to _B. t.
+taylori_ on the basis of the average of external and cranial characters.
+Specimens from 6 mi. SW San Gerónimo, Coahuila, also referred to _B. t.
+taylori_, resemble in color the mice from 4 km. N Ciudad Valles. When
+more specimens are obtained from the front range of the Sierra Madre
+Oriental, at lower altitudes, the manner in which these two subspecies
+intergrade with one another will be better understood. At present,
+populations from higher altitudes in the mountains seem to represent a
+dark subspecies; populations from the coastal plain represent a pale
+subspecies, and those from the lower slopes and high valleys seemingly
+are intergrades. _B. t. fuliginatus_ occurs in a somewhat limited strip
+of chernozem soil (or suelos negros of Tamayo, 1949: Carta de Suelos).
+The populations occurring at lower altitudes on the coastal plain are on
+generally paler soils.
+
+_Specimens examined._--Total 39, all from the Republic of México, as
+follows: SAN LUIS POTOSÍ: El Salto, 24 Mus. Nat. Hist., Louisiana State
+Univ., 7 Amer. Mus. Nat. Hist.; type locality, 8 (including the type).
+
+_Marginal records._--See specimens examined.
+
+
+=Baiomys taylori paulus= (J. A. Allen)
+
+    _Peromyscus paulus_, J. A. Allen, Bull. Amer. Mus. Nat. Hist.,
+       19:598, November 12, 1903; Elliot, Field Columb. Mus. Publ.,
+       105(6): 136, July 1, 1905.
+
+    _Baiomys taylori paulus_, Miller, Bull. U. S. Nat. Mus., 79:137,
+       December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317,
+       April 29, 1924 (part); Ellerman, The Families and Genera of Living
+       Rodents, 2:402, March 21, 1941 (part); Goldman, Smith, Miscl. Coll.,
+       115:373, July 31, 1951 (part); Hall and Kelson, Univ. Kansas Publs.,
+       Mus. Nat. Hist., 26:367, December 15, 1952; Goodwin, Bull. Amer.
+       Mus. Nat. Hist., 102:318, August 31, 1953; Miller and Kellogg, Bull.
+       U. S. Nat. Mus., 205:511, March 3, 1955 (part); Packard, Proc. Biol.
+       Soc. Washington, 71:17, April 11, 1958; Packard, Jour. Mamm.,
+       40:146, February 20, 1959; Hall and Kelson, The Mammals of North
+       America, 2:659, March 31, 1959 (part).
+
+    [_Peromyscus_] _paulus_, Elliot, Field Columb, Mus. Publ.,
+       95(4):136, July 15, 1904.
+
+    _Peromyscus taylori paulus_, Osgood, N. Amer. Fauna, 28:255, April
+       17, 1909 (part).
+
+    _Peromyscus musculus_ [_musculus_], Osgood, N. Amer. Fauna, 28:256,
+       April 17, 1909 (part).
+
+    _Baiomys taylori_ [= _paulus_], Twente and Baker, Jour. Mamm.,
+       32:121, February 15, 1951.
+
+    _Baiomys musculus musculus_, Goldman, Smith. Miscl. Coll., 115:336,
+       July 31, 1951 (part).
+
+    _Baiomys taylori allex_, Hall and Kelson, The Mammals of North
+       America, 2:659, March 31, 1959 (part).
+
+_Type._--Adult male, skin and skull; No. 21165, American Museum of
+Natural History; Río Sestín, Durango, Republic of México; obtained on
+April 15, 1903, by J. H. Batty, original number 455.
+
+_Range._--Central Chihuahua south through Durango (west to eastern edge
+of Sierra Madre Occidental), to Zacatecas and Aguascalientes, thence
+west into northern and northwestern Jalisco, see Figure 11. Zonal range:
+Lower Sonoran, approximately the Chihuahua Desert Biotic Province of
+Goldman and Moore (1945:349). Occurs from 4000 feet 2 mi. ESE Tequila,
+Jalisco, up to 6700 feet 2 mi. W Miñaca, Chihuahua.
+
+_Diagnosis._--Size medium to small for the species; dorsum Buffy Brown
+to fawn color; dorsal ground color of unworn pelage of adults varying
+from Buffy Brown in darkest series (especially those from higher
+altitudes) to Avellaneous with grayish overtones in palest series; worn
+pelage in mid-dorsal region of adults fawn to grayish; terminal parts of
+individual hairs buffy, gray basally; guard hairs on dorsum
+black-tipped, grayish basally; belly Light Gull Gray, distal half of
+hairs white, proximal half Neutral Gray; hairs in region of throat and
+chin white to base (some specimens with faint buffy overtones); forefeet
+dusky below, whitish above; hind feet whitish above, ventral surface
+whitish to dusky; dorsal and lateral vibrissae black, other vibrissae
+white. Average and extreme measurements of six adults from the type
+locality are as follows: total length, 109 (106-117); length of tail,
+44.5 (43-48); length of body, 63 (57-69); length of hind foot, 13.1
+(12.7-14.0); occipitonasal length, 17.5 (17.4-18.0); zygomatic breadth,
+9.3 (9.1-9.5); postpalatal length, 6.6 (6.2-6.9); least interorbital
+breadth, 3.5 (3.4-3.6); length of incisive foramina, 3.8 (3.6-4.1);
+length of rostrum, 5.9 (5.7-6.0); breadth of braincase, 8.6 (8.5-8.8);
+depth of cranium, 6.6 (6.2-6.9); alveolar length of maxillary tooth-row,
+3.2 (3.1-3.4); for photographs of the skull, see Plate 2_e_ and Plate
+4_f_.
+
+_Comparisons._--For comparisons with _B. t. allex_, _B. t. canutus_, _B.
+t. ater_, and _B. t. taylori_, see accounts of those subspecies. From
+_B. t. analogous_, _B. t. paulus_ differs as follows: dorsal color paler
+having more reddish-brown than blackish-brown tones; venter whitish to
+buffy, instead of gray to light-gray; tail bicolored (not unicolored),
+usually having more hairs; hind feet white (not sooty) above. Cranially,
+_B. t. paulus_ differs from _B. t. analogous_ in: skull slightly smaller
+in all dimensions; maxillary part of zygoma narrowing and forming
+oblique angle rather than a near right angle with rostrum; anterior
+incisive foramina constricted posteriorly; tips of nasals truncate (less
+rounded).
+
+_Remarks._--J. A. Allen (1903:599) correctly pointed out that young
+specimens, in first pelage, were gray brown; young adults were darker
+and more varied with some blackish; adults and old adults were buffy to
+grayish. The change in color of pelage with increasing age is more
+pronounced in _paulus_ than in other subspecies of _B. taylori_. Of two
+males collected on April 12, 1949, one, an adult, is buffy brown, and
+the other, an old adult with worn pelage, is grayish-brown. In mice in
+the earlier stages of adulthood, underfur of the dorsum is buffy at the
+tips and gray basally. With increased wear, the buffy tip is lost.
+Consequently, mice in the later stages of adulthood are grayish.
+
+_B. t. paulus_ intergrades with _ater_ to the north in Chihuahua (see
+account of that subspecies), with _analogous_ to the south in Jalisco,
+and with _allex_ (see account of that subspecies) to the southwest in
+Nayarit and Jalisco. The zone of intergradation between _paulus_ and
+_analogous_ in Jalisco approximately borders the Río Grande de Santiago
+from the western part of the State to the northwest shore of Lago de
+Chapala. Nineteen specimens from 2 mi. WNW Lagos de Moreno in northwest
+Jalisco seem to be intermediate between _paulus_ and _analogous_ in
+color, averaging slightly grayer than typical _paulus_. The series of 19
+is referable to _paulus_ on the basis of cranial characters.
+
+A series of 34 specimens from 3 mi. W La Venta, Jalisco (referable to
+_paulus_), is indistinguishable in color of pelage from two series of
+_paulus_ from 5 mi. N Durango, and from 8 mi. NE of Durango, except that
+the antiplantar surfaces of the hind feet are sooty as in _analogous_.
+Seemingly, features of color mentioned above as diagnostic of the two
+subspecies are either present or absent and there is no tendency toward
+intermediacy in color in the population from 3 mi. W La Venta.
+
+The Río Grande de Santiago may have acted in the past as a physical
+barrier reducing gene flow between _allex_ and _paulus_ and in
+separating completely the two populations for limited periods.
+
+_Specimens examined._--Total 176, all from the Republic of México and
+distributed as follows: CHIHUAHUA: Rancho Sanignacio, 4 mi. S, 1 mi. W
+Santo Tomás, 1; El Rosario, 6700 ft., 1; 2 mi. W Miñaca, 6900 ft., 11;
+Balleza, 1[50]. DURANGO: Rosario, 1[51]; type locality, 14[51] (including
+the type); _San Gabriel_, 2[51]; _Rancho Santuario_, 2[51]; 1 mi. N
+Chorro, 6450 ft., 1; _8 mi. NE Durango_, 6200 ft., 2; 5 mi. N Durango,
+6400 ft., 2. ZACATECAS: Valparaíso, 6500 ft., 10[50]. AGUASCALIENTES: _18
+mi. W, 2 mi. S Aguascalientes_, 6000 ft., 1; 16 mi. S Aguascalientes,
+5[52]. JALISCO: 1 mi. NE Villa Hidalgo, 6500 ft., 1; 2 mi. WNW Lagos de
+Moreno, 6370 ft., 19; _2 mi. ESE Tequila_, 4000 ft., 11; _3 mi. W La
+Venta_, 33, 1[53]; _12 mi. W Guadalajara_, 3[54]; _Atemajac_, 12[50]; 4 mi.
+W Guadalajara, 5100 ft., 3; _2 mi. N, 1/2 mi. W Guadalajara_, 11; 2 mi.
+NW Magdalena, 4500 ft., 7[50]; _1 mi. N Tala_, 4400 ft., 3; 3 mi. W Tala,
+4300 ft., 18.
+
+_Marginal records._--CHIHUAHUA: Rancho Sanignacio, 4 mi. S, 1 mi. W
+Santo Tomás; El Rosario; Balleza. DURANGO: Rosario, 6700 ft.; 1 mi. E
+Zarca (Blossom and Burt, 1942:1); 1 mi. N Chorro, 6450 ft. ZACATECAS:
+Valparaíso, 6500 ft. AGUASCALIENTES: 1 mi. N Chicalote (Blossom and
+Burt, 1942:4). JALISCO: 2 mi. WNW Lagos de Moreno, 6370 ft.; 4 mi. W
+Guadalajara, 5100 ft.; 3 mi. W Tala, 4300 ft.; 2 mi. NW Magdalena, 4500
+ft. DURANGO: 5 mi. N Durango, 6400 ft.; type locality. CHIHUAHUA: 2 mi.
+W Miñaca, 6900 ft.
+
+[50] United States National Museum (Biol. Surv. Collections).
+
+[51] American Museum of Natural History.
+
+[52] Univ. Illinois, Mus. Nat. History.
+
+[53] The Museum, Michigan State Univ.
+
+[54] Univ. Michigan, Museum of Zoology.
+
+
+=Baiomys taylori subater= (V. Bailey)
+
+    _Peromyscus taylori subater_, V. Bailey, N. Amer. Fauna, 25:102,
+       October 24, 1905; Lyon and Osgood, Bull. U. S. Nat. Mus., 62:139,
+       January 15, 1909; Osgood, N. Amer. Fauna, 28:255, April 17, 1909;
+       Elliot, Check-List Mamm. N. Amer. Continent, West Indies and
+       Neighboring Seas, Suppl., Amer. Mus. Nat. Hist, p. 44, January 8,
+       1917.
+
+    _Baiomys taylori subater_, Miller, Bull. U. S. Nat. Mus., 79:136,
+       December 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:317, April 29,
+       1924; Anthony, Field Book of North American Mammals, p. 348, 1928;
+       Baker, Jour. Mamm., 21:223, May 14, 1940; Ellerman, The Families and
+       Genera of Living Rodents, 2:402, March 21, 1941; Blair, Jour. Mamm.,
+       22:378, November 14, 1941; Poole and Schantz, Bull. U. S. Nat. Mus.,
+       178:259, March 6, 1942; Blair, Jour. Mamm., 23:196, May 14, 1942;
+       Blair and Blossom, Contrib. Lab. Vert. Biol., Univ. Michigan, 40:1,
+       March, 1948; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:511,
+       March 3, 1955; Hall and Kelson, The Mammals of North America, 2:659,
+       March 31, 1959.
+
+    _Baiomys taylori_ [= _subater_], Taylor and Davis, Texas Game, Fish
+       and Oyster Comm. Bull., 27:56, August, 1947 (part).
+
+_Type._--Subadult female, skin and skull; No. 32616/44539 U. S. Nat.
+Mus. (Biol. Surv. Coll.); Bernard Creek, near Columbia, Brazoria County,
+Texas; obtained on February 25, 1892, by W. Lloyd, original number 1122.
+
+_Range._--Southeastern Texas, north of Matagorda Bay west to Lavaca
+County, north to Brazos and Walker counties thence east to Jefferson
+County, see Figure 11. Occurs from near sea level in Brazoria and
+Galveston counties, up to 500 feet in western part of range. Zonal
+range: Humid division of lower Austral (the western part of the
+Austroriparian Biotic Province of Dice, 1943:18-21).
+
+_Diagnosis._--Size medium to large for the species; mid-dorsal region
+Clove Brown (sooty in freshly captured specimens); some parts of
+mid-dorsal region all blackish; individual guard hairs of dorsum
+black-tipped, Deep Neutral Gray basally; underfur black-tipped with
+subterminal band of light buff, Neutral Gray at base; belly
+grayish-white, laterally Isabella Color; distal three-fourths of hairs
+in region of throat and chin white, proximal fourth light gray; in
+median region of belly distal half of individual hairs white, proximal
+half dark gray; vibrissae in most specimens black to base. Average and
+extreme cranial measurements of six adults from 7 mi. S La Belle are as
+follows: occipitonasal length, 18.9 (17.5-19.4); zygomatic breadth, 9.6
+(9.1-9.9); postpalatal length, 6.8 (6.2-7.2); least interorbital
+breadth, 3.7 (3.4-3.9); length of incisive foramina, 4.0 (3.6-4.2);
+length of rostrum, 6.5 (6.1-6.8); breadth of braincase, 8.7 (8.3-8.9);
+depth of cranium, 6.7 (6.6-6.8); alveolar length of maxillary tooth-row,
+3.1 (2.9-3.2). Average and extreme external measurements of four adults
+from Richmond are as follows: total length, 111.5 (108-118); length of
+tail vertebrae, 43.5 (41-47); length of body, 68 (67-71); length of hind
+foot, 14 (13-15); for photographs of the skull, see Plate 2_f_, and
+Plate 4_g_.
+
+_Comparisons._--Because _B. t. subater_ intergrades only with _B. t.
+taylori_ to the south and west, _subater_ is compared only with
+_taylori_. Young adults of both subspecies in unworn pelage show best
+the colors that differentiate the two subspecies. Old adults of
+_subater_ in worn pelage appear grayish, resembling _taylori_, and at
+that age, only certain cranial characters are of taxonomic use.
+Cranially, _subater_ differs from _taylori_ in: presphenoid not shaped
+like an hour-glass; parapterygoid processes thicker medially;
+interparietal diamond-shaped instead of elongated and compressed. Skull
+slightly larger in most measurements.
+
+
+    [Illustration: PLATE 1
+
+    Photographs of skulls in dorsal view of _Baiomys_. × 2.
+
+    _a._ _B. m. brunneus_, [F] ad., 10834, AMNH, Jalapa, Veracruz.
+    _b._ _B. m. grisescens_, [F] ad., 257080, USNM, Comayabuela, Honduras.
+    _c._ _B. m. handleyi_, [F] ad., 275597, USNM, Sacapulas, Guatemala.
+    _d._ _B. m. infernatis_, [F] ad., 91499, MZUM, Teotitlán, Oaxaca.
+    _e._ _B. m. musculus_, [F] ad., 45462, USNM, Colima, Colima.
+    _f._ _B. m. nigrescens_, [M] ad., 76834, USNM, Comitán, Chiapas.
+    _g._ _B. m. pallidus_, [F] ad., 4802, Texas A & M, Axochiapán, Morelos.
+    _h._ _B. m. pullus_, [F] ad., 71608, KU, 8 mi. S Condega, Nicaragua.
+    _i._ _B. t. allex_, [F] ad., 45453, USNM, Colima, Colima.]
+
+
+    [Illustration: PLATE 2
+
+    Photographs of skulls (_a-g_) in dorsal view of _Baiomys_. × 2.
+
+    _a._ _B. t. analogous_, [F] ad., 120265, USNM, Zamora, Michoacán.
+    _b._ _B. t. ater_, [F] ad., 15056, UI, 1-1/2 mi. ENE Greaterville,
+          Arizona.
+    _c._ _B. t. canutus_, [F] ad., 62076, KU, 1 mi. S Pericos, Sinaloa.
+    _d._ _B. t. fuliginatus_, [F] ad., 36771, KU, type locality.
+    _e._ _B. t. paulus_, [F] ad., 40032, KU, 18 mi. W, 2 mi. S
+          Aguascalientes.
+    _f._ _B. t. subater_, [F] ad., 44543, USNM, type locality.
+    _g._ _B. t. taylori_, [F] ad., 57944, KU, 5 mi. E San Antonio, Texas.
+    _h._ Photo. of captive [M] _B. t. taylori_, 25 mi. E Austin, Texas.
+    × 1.]
+
+
+    [Illustration: PLATE 3
+
+    Photographs of skulls in ventral view of _Baiomys_. × 2.
+
+    _a._ _B. m. brunneus_, [F] ad., 10834, AMNH, Jalapa, Veracruz.
+    _b._ _B. m. grisescens_, [F] ad., 257080, USNM, Comayabuela, Honduras.
+    _c._ _B. m. handleyi_, [F] ad., 275597, USNM, Sacapulas, Guatemala.
+    _d._ _B. m. infernatis_, [F] ad., 91499, MZUM, Teotitlán, Oaxaca.
+    _e._ _B. m. musculus_, [F] ad., 45462, USNM, Colima, Colima.
+    _f._ _B. m. nigrescens_, [M] ad., 76834, USNM, Comitán, Chiapas.
+    _g._ _B. m. pallidus_, [F] ad., 4802, Texas A & M, Axochiapán, Morelos.
+    _h._ _B. m. pullus_, [F] ad., 71608, KU, 8 mi. S Condega, Nicaragua.]
+
+
+    [Illustration: PLATE 4
+
+    Photographs of skulls in ventral view of _Baiomys_. × 2.
+
+    _a._ _B. t. allex_, [F] ad., 45453, USNM, Colima, Colima.
+    _b._ _B. t. analogous_, [F] ad., 120265, USNM, Zamora, Michoacán.
+    _c._ _B. t. ater_, [F] ad., 15056, UI, 1 mi. ENE Greaterville, Arizona.
+    _d._ _B. t. canutus_, [F] ad., 62076, KU, 1 mi. S Pericos, Sinaloa
+    _e._ _B. t. fuliginatus_, [F] ad., 36771, KU, type locality.
+    _f._ _B. t. paulus_, [F] ad., 40032, KU, 18 mi. W, 2 mi. S
+          Aguascalientes.
+    _g._ _B. t. subater_, [F] ad., 44543, USNM, type locality.
+    _h._ _B. t. taylori_, [F] ad., 57944, KU, 5 mi. E San Antonio, Texas.]
+
+_Remarks._--This subspecies retains its chief diagnostic character,
+blackish mid-dorsal region, throughout nearly all parts of its range.
+Specimens from the general area of Matagorda Bay and Lavaca County grade
+into _taylori_ in characters of color and crania. The Colorado and
+Brazos rivers seemingly serve as barriers reducing gene flow between
+_taylori_ and _subater_. These rivers may well have been important
+factors in the origin and the limitation of these two seemingly
+closely-related subspecies.
+
+_Baiomys taylori subater_ is not differentiated in color of pelage and
+characters of crania from _B. t. taylori_ to the same degree that _B. t.
+paulus_ is differentiated from _B. t. analogous_, or that _B. t.
+taylori_ is differentiated from several of the other subspecies of
+_Baiomys taylori_. _B. t. subater_ probably is a more recent occupant of
+the area in which it now lives than is the case with any other one of
+the subspecies of _taylori_. Sufficient time probably has not elapsed to
+allow for formation of more distinctive phenotypic patterns.
+
+_Specimens examined._--Total 65, all from TEXAS and distributed as
+follows: _Brazos County_: 1/2 mi. NW College Station, 1[55]; _3 mi. W
+College Station_, _1 mi. W Easterwood Airport_, 1[55]; _College Station_,
+1[55]. _Walker County_: Huntsville, 1[55]. _Hardin County_: Sour Lake,
+1[57]. _Jefferson County_: 7 mi. S Labelle, 10. _Harris County_: 6 mi. NE
+Crosby, 1[56]. _Colorado County_: _10 mi. N Eagle Lake_, 1[55]; _9 mi. N
+Eagle Lake_, 1[55]; 2 mi. W Eagle Lake, 1; _Eagle Lake_, 1[55], 5. _Fort
+Bend County_: Richmond, 4[57]. _Galveston County_: _Texas City_, 6[58];
+Virginia Point, 1[57]. _Brazoria County_: _Austin Bayou near Alvin_,
+2[57]; 14 mi. SSE Alvin, 2[59]; type locality, 7[57] (including the type).
+_Lavaca County_: 4 mi. W Hallettsville, 1[55]; _1 mi. SW Hallettsville_,
+3[55]; _13.7 mi. SW Hallettsville_, 2[55]; 4 mi. NE Yoakum, 11.
+
+_Marginal records._--TEXAS: Huntsville; Sour Lake; 7 mi. S La Belle;
+Virginia Point; 14 mi. SSE Alvin; type locality; 4 mi. NE Yoakum; 4 mi.
+W Hallettsville; 1/2 mi. NW College Station.
+
+[55] Texas A & M, Cooperative Wildlife Research Collection.
+
+[56] Carnegie Museum.
+
+[57] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[58] Los Angeles County Museum.
+
+[59] American Museum of Natural History.
+
+
+=Baiomys taylori taylori= (Thomas)
+
+    _Hesperomys_ (_Vesperimus_) _taylori_ Thomas, Ann. Mag. Nat. Hist.,
+       ser. 5, 19:66, January, 1887.
+
+    _Baiomys taylori_ [_taylori_], Mearns, Bull. U. S. Nat. Mus.,
+       56:381, April 13, 1907; Stickel and Stickel, Jour. Mamm., 30:141,
+       May 23, 1949.
+
+    Baiomys taylori taylori, Miller, Bull. U. S. Nat. Mus., 79:136,
+       December 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:317, April 29,
+       1924; Anthony, Field Book of North American Mammals, p. 327, 1928;
+       Ellerman, The Families and Genera of Living Rodents, 2:402, March
+       21, 1941; Taylor and Davis, Texas Game, Fish and Oyster Comm. Bull.,
+       27:56, August, 1947 (part); Blair, Texas Jour. Sci., 2:104, March
+       31, 1950; Goldman, Smith. Miscl. Coll., 115:373, 426, July 31,
+       1951; Baker, Univ. Kansas Publs., Mus. Nat. Hist., 5:212, December
+       15, 1951; Blair, Texas Jour. Sci., 4:242, June 30, 1952; Hooper,
+       Occas. Papers, Univ. Michigan, Mus. Zool., 544:7, March 25, 1953;
+       Dalquest, Louisiana State Univ. Studies (Biol. Sci. Ser.), 1:155,
+       December 28, 1953 (part); Blair, Adv. in Genetics, 5:10, January 27,
+       1954; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:511, March 3,
+       1955; Baker, Univ. Kansas Publs., Mus. Nat. Hist., 9:273, June 15,
+       1956; Packard, Proc. Biol. Soc. Washington, 71:17, April 11, 1958;
+       Hall and Kelson, The Mammals of North America, 2:659, March 31, 1959
+       (part).
+
+    _Cricetus_ (_Vesperimus_) _taylori_, Thomas, Proc. Zool. Soc.
+       London, 68:446, November 20, 1888.
+
+    _Sitomys taylori_, Merriam, Proc. Biol. Soc. Washington, 7:170,
+       September 29, 1892.
+
+    _Sitomys_ (_Baiomys_) _taylori_, True, Proc. U. S. Nat. Mus.,
+       16(972):758, February 7, 1894; J. A. Allen, Bull. Amer. Mus. Nat.
+       Hist., 6:181, May 31, 1894.
+
+    _S._ [_itomys_] _taylori_, Rhoads, Proc. Acad. Nat. Sci.
+       Philadelphia, 46:256, October, 1894.
+
+    _Peromyscus_ (_Baiomys_) _taylori_, J. A. Allen, Bull. Amer. Mus.
+       Nat. Hist., 8:65, April 22, 1896.
+
+    [_Peromyscus_] _taylori_, Trouessart, Cat. Mamm., 1:517, 1898.
+
+    _Peromyscus taylori_ [_taylori_], Elliot, Field Columb. Mus. Publ.,
+       105(4):135, July 1, 1905; V. Bailey, N. Amer. Fauna, 25:101, October
+       24, 1905; Elliot, Field Columb. Mus. Publ., 115(8):203, 1907;
+       Osgood, N. Amer. Fauna, 28:253, April 17, 1909.
+
+_Type._--Adult male, skin and skull; No. 87.11.24.1, British Museum,
+Natural History; San Diego, Duval County, Texas; obtained by William
+Taylor.
+
+_Range._--North-central to southeastern Texas, excluding the coastal
+plain north of the region of Matagorda Bay, thence south into the
+southern part of Tamaulipas and west into Coahuila and Nuevo León, see
+Figure 11. Occurs from near sea level in Texas up to 1500 feet in
+Coahuila. Zonal range: mostly Lower Austral (in México and southeastern
+half of Texas, the Tamaulipas Biotic Province of Goldman and Moore,
+1945:349, and Blair, 1952:230).
+
+_Diagnosis._--Size medium for the species; dorsum grayish in freshly
+taken specimens to Hair Brown in preserved specimens; individual guard
+hairs of dorsum black-tipped, grayish basally, underfur black-tipped
+with a subterminal band of olive-buff; sides of body pale-grayish near
+venter, individual hairs buffy proximally, grayish basally; belly pale
+grayish, individual hairs white-tipped, Pale Neutral Gray basally;
+throat and chin colored as is belly; forefeet and hind feet sooty-gray
+dorsally, sparsely-haired ventrally, thus appearing flesh-colored; tail
+unicolored gray to sooty-gray. Average and extreme cranial measurements
+of 22 adults from 6 mi. SW San Gerónimo, Coahuila, are as follows:
+occipitonasal length, 18.0 (17.4-19.0); zygomatic breadth, 9.6
+(9.2-10.2); postpalatal length, 6.5 (5.9-7.1); least interorbital
+breadth, 3.6 (3.3-3.8); length of incisive foramina, 4.0 (3.6-4.3);
+length of rostrum, 6.1 (5.7-6.7); breadth of brain case, 8.8 (8.5-9.1);
+depth of cranium, 6.5 (6.0-7.0); alveolar length of maxillary tooth-row,
+3.1 (3.0-3.3). Average and extreme external measurements of 19 adults
+from 6 mi. SW San Gerónimo are as follows: total length, 102.2 (95-115);
+length of tail vertebrae, 39.4 (21-46); length of body, 62.8 (53-76);
+length of hind foot, 14.0 (12-15); length of ear from notch, 10.7
+(10-12); for photographs of skull, see Plate 2_g_, and Plate 4_h_.
+
+_Comparisons._--For comparisons with _B. t. subater_, _B. t. analogous_,
+and _B. t. fuliginatus_, see accounts of those subspecies. From _B. t.
+paulus_, found to the southwest, _B. t. taylori_ differs as follows:
+dorsum grayish rather than fawn-colored; hairs on dorsal parts of
+forefeet and hind feet sooty-gray (not white to white-brown); venter
+gray to Light Drab-Gray, rather than whitish with gray overtones; tail
+unicolored instead of bicolored; skull averaging slightly larger
+over-all; maxillary part of zygoma forms right angle with rostrum rather
+than obtuse angle; incisive foramina extending posteriorly to anterior
+plane of first upper molars instead of to a transverse plane at middle
+of right and left first upper molars; bullae less inflated; interorbital
+region broader relative to length of skull; rostrum sloping gently from
+frontonasal suture to anterior tip of nasals rather than declining
+abruptly from frontonasal suture to anterior tip of nasals.
+
+_Remarks._--The geographic range of _taylori_ is relatively large, and
+the subspecies is locally variable. Nevertheless, none of the external
+and cranial measurements of specimens assigned to this subspecies
+differs significantly from the corresponding measurements of material
+from the type locality and adjacent areas in southeastern Texas. In
+southeastern Texas, south of the Guadalupe River, south to the coastal
+plain of Tamaulipas, this subspecies differs in color (being paler) from
+_B. t. subater_ with which _taylori_ might be confused. The foothills of
+the Sierra Madre Oriental in western Tamaulipas, north through Nuevo
+León and Coahuila, seem to mark the southwestern limit of the range
+assignable to _taylori_.
+
+On December 27, 1958, a specimen, KU 81552, was obtained 3 mi. N Bowie,
+Montague County, Texas. This record station extends the known range of
+_B. taylori_ 65 miles northward from the previous northernmost locality,
+listed by Hunsaker, Raun, and Swindells (1959:447). Two specimens, KU
+81553 and 81554, were collected by the author 2 mi. NE Cedar Hill,
+Dallas County, Texas, on October 31, 1958. These two specimens, plus the
+single specimen from Bowie County are all paler with more buffy bellies
+than either _B. t. taylori_ or _B. t. subater_. They may represent an
+incipient subspecies. I tentatively assign them to _B. t. taylori_
+because of the pale rather than dark (like _B. t. subater_) pelage.
+Additional specimens are needed from these areas and from the hiatus
+between the ranges of _B. t. taylori_ and _B. t. subater_ the better to
+understand the manner in which these two subspecies intergrade.
+
+Among named subspecies of _Baiomys taylori_, _B. t. taylori_ most
+closely resembles _B. t. subater_ to the north in Texas. Nine specimens
+examined from Yoakum are intergrades between _taylori_ and _subater_.
+These specimens have the sooty dorsal color of _subater_, but ventrally
+are inseparable from topotypes of _taylori_. In length of body and
+tail, specimens from Yoakum are like _subater_, but in length of hind
+foot, they are intermediate between the two subspecies. Cranially, they
+are like _subater_. When all characters are considered, the specimens
+are best referred to _subater_. Bailey (1905:103) suggested that
+specimens from the southern part of the range, which he ascribed to
+_subater_, tended to a more grayish color than topotypes of _subater_,
+therefore, grading into _taylori_. The zone of intergradation runs from
+Matagorda Bay northwest through Lavaca County, thence north to the
+Colorado River, and closely follows the boundary between the Lower
+Austral and Humid Division of Lower Austral Life-zone as plotted by
+Bailey (_loc. cit._). Findley (1955:44) pointed out that where two
+life-zones meet, the resulting populations of shrews are mostly
+intergrades. Such is the case between these two subspecies of _Baiomys
+taylori_ in an area where life-zones might seem less important than in
+the mountainous west.
+
+In the southern part of the range of _taylori_, intergradation occurs
+between _B. t. taylori_ in western Tamaulipas and _B. t. fuliginatus_ in
+the mountains of San Luis Potosí.
+
+Dalquest (1953:156) found no indication of intergradation between the
+two species, _B. taylori_ and _B. musculus_, in San Luis Potosí. After
+examination of specimens from San Luis Potosí, I am in agreement that
+they are all referable to the species _taylori_.
+
+_Specimens examined._--Total 435. TEXAS: _Montague County_: 3 mi. N
+Bowie, 1. _Dallas County_: 2 mi. NE Cedar Hill, 2. _Travis County_:
+8 mi. NW Austin, 2[60]; _Austin_, 2[60]; _4 mi. E Austin_, 4[60];
+_5 mi. E Austin_, 3[60]; _6 mi. E Austin_, 16[60], 1; _7 mi. E Austin_,
+1[60]; _15 mi. E Austin_, 1[60]; _4 mi. S Austin_, 1[60]. _Bastrop
+County_: 25 mi. E Austin, 2. _Kendall County_: Boerne, 1[61].
+_Bexar County_: _1 mi. N Randolph Field_, 3[64]; _5 mi. ENE_
+(_on U. S. Highway 81_) _San Antonio_, 1; _3 mi. NE San Antonio_, 1;
+San Antonio, 26[61], 11[62], 1[63]; _5 mi. E San Antonio_, 11;
+_4-1/2 mi. E Sayers_, 3. _Gonzales County_: 7 mi. S Luling, 2[60].
+_Wilson County: 4 mi. W LaVernia_, 3; 12 mi. W Floresville, 1.
+_Atascosa County_: 9 mi. SW Somerset, 1. _Goliad County_: 8 mi.
+NE Goliad, 1[60]. _Bee County_: Beeville, 1[61]. _Aransas County_:
+Aransas (Wildlife) Refuge, 1[65]; _5 mi. E Copana Bay_, 1[65];
+_4.6 mi. NE Rockport_, 5[60]; _4.5 mi. NW Rockport_, 2[60]; 3 mi. N,
+2 mi. E Rockport, 4; _Rockport_, 1[60], 1[61], 1[63]; _1-1/2 mi.
+SW Rockport_, 1[60]; _2 mi. SW Rockport_, 2[60]; _13.4 mi. SW Rockport_,
+1[60]; _14 mi. SW Rockport_, 1. _San Patricio County_: Welder Wildlife
+Refuge, 7. _Duval County_: type locality, 2[61], 1[66]. _Nueces County_:
+Corpus Christi (south Nueces Bay), 1[64] (Cleveland Mus. Coll.). _Kleberg
+County_: 2 mi. S Riviera, 3[65]. _Brooks County_: 3 mi. S Falfurrias,
+2[65]. _Hidalgo County_: 6 mi. S McAllen, 17[60]. _Willacy County_: 28 mi.
+E Raymondville, 10[65]. _Cameron County_: Brownsville, 31[61], 23[62],
+5[64]. COAHUILA: 6 mi. SW San Gerónimo, 32. NUEVO LEÓN: Santa Catarina,
+1[61]; 14 mi. N Monterrey, 1950 ft., 2[67]; Monterrey, 1[61]; 20 km. N
+General Terán, 3[64]. TAMAULIPAS: _Near Headwaters Río Sabinas, 8 km. W,
+10 km. N El Encino_, 400 ft., 1; Camargo, 5[61]; Charco Escondido, 20 mi.
+S Reynosa, 3[67]; Matomoras, 5[61]; _Ejido Santa Isabel, 2 km. W
+Inter-American Highway_, 2000 ft., 7; Hidaglo, 7[61]; _Hda. Station
+Engracia_, 4[63]; 4 mi. N La Pesca, 1; 29 mi. N Ciudad Victoria, 1[67];
+Ciudad Victoria, 6[61], 3; Jaumavé, 2400 ft., 6[64], 10; Sierra de
+Tamaulipas, 3[64]; _25 mi. N El Manté, 3 km. W Inter-American Highway_
+(_on Rancho Pano Ayuctle_), 300 ft., 4; _6 mi. N Gomez Farias_ (_on
+Rancho Pano Ayuctle_), 1; _5 mi. NE Gomez Farias_, 12[64], 1[62]; 70 km.
+(by highway) S Ciudad Victoria, 2 km. W El Carrizo, 5[62], 2; Antigua
+Morelos, 5[64]; _6 mi. N, 6 mi. W Altamira_, 31; _5 mi. N, 5 mi. W
+Altamira_, 4; _Alta Mira_ (_Altamira_), 2[61]; 1 mi. S Altamira, 6; _10
+mi. NW Tampico_, 1. SAN LUIS POTOSÍ: Ebano, 5[68]; _4 km. NE Ciudad
+Valles_, 1; Ciudad Valles, 1; _3 km. W Tamuín_, 1[68]; _Tamuín_, 6[68];
+_Pujal_, 300 m., 1[64]. VERACRUZ: Tampico Alto, 50 ft., 1; Potrero Llano,
+350 ft., 1; Ozulama, 2; Cerro Azul, 350 ft., 1.
+
+_Marginal Records._--TEXAS: 3 mi. N Bowie; 2 mi. NE Cedar Hill; 25 mi. E
+Austin; 7 mi. S Luling; 8 mi. NE Goliad; Aransas (Wildlife) Refuge; 3
+mi. N, 2 mi. E Rockport; Corpus Christi (South Nueces Bay); 2 mi. S
+Riviera; 28 mi. E Raymondville; Brownsville. TAMAULIPAS: Matomores; 4
+mi. N La Pesca; 1 mi. S Altamira. VERACRUZ: Tampico Alto; Ozulama; Cerro
+Azul; Potrero Llano. SAN LUIS POTOSÍ: Ciudad Valles. TAMAULIPAS: Antigua
+Morelos; 70 km. S Ciudad Victoria, 2 km. W El Carrizo; Jaumavé; Hidalgo.
+NUEVO LEÓN: 20 km. N General Terán; Santa Catarina. COAHUILA: 6 mi. SW
+San Gerónimo. TEXAS: 9 mi. SW Somerset; Boerne; 8 mi. NW Austin.
+
+[60] Coll. University of Texas.
+
+[61] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[62] American Museum of Natural History.
+
+[63] Chicago Natural History Museum.
+
+[64] Univ. Michigan, Museum of Zoology.
+
+[65] Texas A & M Coop. Wildlife Res. Coll.
+
+[66] Carnegie Museum.
+
+[67] Univ. California, Mus. Vert. Zool.
+
+[68] Museum of Natural History, Louisiana State University.
+
+
+
+
+EVOLUTION AND SPECIATION
+
+
+The history of the genus dates back to the early late Pliocene, but
+morphological change since then has been slight insofar as can be judged
+from lower jaws. _Baiomys_ seems to have been relatively conservative
+also in types of habitat occupied.
+
+According to Wilson (1937:59), the late Pliocene was a time of decided
+expansion of myomorph rodents, more particularly cricetines.
+Furthermore, at this time, the climate in the interior basin of
+southwestern North America presumably was becoming arid, if we can judge
+from the spread of elements of the Madro-Tertiary flora. Axelrod
+(1950:266) points out that the drier, continental climate initiated in
+the early Tertiary probably had its culmination in middle Pliocene time.
+Some floras of early late Pliocene of the southwestern United States
+reflect a climate slightly cooler and more moist than the climates of
+the middle Pliocene. However, late Pliocene times reflect an arid
+climate. The flora of the southwestern interior basin of North America
+in early late to late Pliocene was intermediate between the previous
+grassland floras of the middle Pliocene and the savannah flora of upper
+Pliocene. Axelrod (_loc. cit._) suggests that this intermediate flora of
+the interior basin of southwestern North America resulted from the
+folding of the Cascades and uplifting of the Sierra Nevada and
+Peninsular ranges to the south. The development of these mountains
+produced greater aridity to the lee of the mountains, thus accounting
+for the grassland-savannah flora. Pygmy mice probably originated in that
+time, I judge in México, and moved northward and southward in a
+grassland-savannah habitat that seemingly existed as far north as what
+is now Meade County, Kansas (where the Sawrock fauna lived). Further
+evidence for occupancy of a grassland-savannah habitat by ancestral
+pygmy mice stems from the distribution of the living species, _B.
+taylori_, that at present occupies territory adjacent to parts of the
+Sonoran and Chihuahuan deserts. _B. taylori_ seems to be morphologically
+more specialized for life in an arid grassland than was _B.
+sawrockensis_.
+
+The geographic range of ancestral pygmy mice possibly extended farther
+south in late Pliocene time than the range of _B. musculus_ does now.
+Anyhow, _B. sawrockensis_ of the early late Pliocene dwelt in a more
+mesic type of habitat than _B. musculus_ does, and such habitat may have
+existed from the Pacific lowlands of Central America to the Caribbean
+lowlands of northern South America (see Duellman, 1958:136, and Dunn,
+1940:156) during late Pliocene times. An ancestral stock of hesperomine
+mice, not greatly different from _Baiomys_, may have emigrated from the
+North American continent into South America across the continuous land
+connection, which Simpson (1950:395) suggests was formed in the
+Chapadmalalan age (= Blancan age of North American terminology). The
+length of time of interchange of genes between northern and southern
+populations of mice across the Central American land connection probably
+was brief. Duellman (_op. cit._:129) pointed out that once the
+Panamanian portal was closed, the warm counter equatorial current, El
+Niño, combined with the uplifting of the Andes, began to produce heavy
+rain forests in Central America and northern South America in late
+Pliocene or early Pleistocene times. These forests presumably isolated
+the stock in North America from that in South America where the latter
+probably evolved rapidly into kinds that differed from one another and
+from _Baiomys_ in shape of body, type of pelage, and shape of skull.
+Internal structures such as hyoid apparatus, auditory ossicles, and
+baculum remained almost unchanged, as for example in _Calomys_ now
+living in South America. The present resemblance in internal
+morphological features between it and _Baiomys_, I judge, reflects
+taxonomic relationships more accurately than do shape and conformation
+of body and skull that seem to respond more rapidly to external
+environmental changes. The cranial characters distinguishing _Baiomys
+musculus_ from _Calomys laucha_ are as follows: posterior lacerate
+foramina between second, rather than first, upper molars; parapterygoid
+fossa shallower; mesopterygoid fossa as wide or wider, instead of
+narrower, than parapterygoid processes; burr for attachment of
+superficial masseter muscle hypertrophied instead of well-developed. In
+other cranial characters studied, the two genera closely resemble each
+other. Such similarities of crania between _Calomys_ and _Baiomys_ may
+reflect convergence, but the total of internal and external
+morphological characters shared, I think reflects true relationships.
+
+_Peromyscus_ has a large number of living and extinct species and
+exhibits a wide range of morphological variation, whereas _Baiomys_ has
+a small number (7) of species and exhibits a narrow range of
+morphological variation. The small number of known species of pygmy mice
+suggests their conservatism in elaboration of morphological characters.
+Possibly this is because the habitat, or even the ecological niche,
+occupied in geological time by these mice was restricted, geographically
+and in kind. If the habitat of the pygmy mice oscillated between
+savannah and arid grassland, then an hypothesis can be made possibly
+accounting for the origin of species of these mice. My idea is that the
+geographical distribution of _Baiomys_ today reflects a predilection on
+the part of these mice for a relatively uniform warm climate. Therefore,
+in the past, in times of warmer continental climate, these mice moved
+toward favorable habitat northward from an area in central and northern
+México. In cooler periods, the mice moved southward as habitats to the
+north became unfavorable.
+
+Dr. W. B. Davis (_in. litt._) informs me that _B. taylori_ was uncommon
+in Brazos County, Texas, approximately 15 years ago, and suggests that
+the abundance there now of this mouse and my taking it in 1958 northward
+nearly to the southern border of Oklahoma reflects a definite movement
+northward. Movement in the same direction in late years has been
+suggested for the nine-banded armadillo and the hispid cotton rat (Hall,
+1959:373) that are associated with warm climates to the south. These
+movements possibly reflect only minor fluctuations of climate, but in a
+long period of warmth movements northward would be expected to be
+pronounced and extensive.
+
+Extinct species of _Baiomys_ may have originated as a result of
+extension northward of the geographical range and subsequent retreat
+southward of the northern populations, as follows: (1) the range of the
+genus moved northward in a warm period; (2) in cooler times, most of the
+mice in the north disappeared and only isolated colonies remained in
+small patches of remaining habitat still favorable to the mice; (3) the
+small populations of isolated pygmy mice after a time changed through
+mutations, recombinations and subsequent selection to a degree that
+prevented crossbreeding once populations from the south again moved
+northward and came in contact with previously isolated stocks; (4) then
+competition caused further divergence in morphological characters. Such
+an hypothesis would account for the morphological differences between
+the extinct _B. kolbi_ and _B. rexroadi_. The extinct _B.
+brachygnathus_, presumably a dweller of a xerophytic grassland, may have
+had its origin from a _B. minimus_-like stock in the manner outlined.
+
+
+FORMATION OF THE RECENT SPECIES
+
+The morphological difference between the extinct _B. minimus_ and the
+living _B. musculus_ is not great, and musculus seems to be the product
+of the _B. sawrockensis-B. minimus_ line of development. Morphological
+characters of the parental stock of the two living species, _musculus_
+and _taylori_, may have been intermediate between those of _B. minimus_
+and those of _B. musculus_. The principal part of the range of _Baiomys_
+today is in México, and probably was there through much of Pleistocene
+time. Extension northward of the species and retreat southward of those
+northern populations of pygmy mice would not only have left isolated
+populations in the north, but would have allowed the mice that retreated
+south to share a common gene pool. Therefore, populations of pygmy mice
+occurring to the south in central México might be expected to maintain a
+relatively high degree of heterozygosity in morphological and behavioral
+characters. The occurrence of any physical or biotic barrier that would
+have separated this homogeneous group would be conducive to speciation.
+There is evidence that a barrier occurred in the Pleistocene in central
+México sufficient to separate the supposed interbreeding, relatively
+homogeneous populations of pygmy mice. According to Sears (1955:529) and
+De Terra _et al_. (1949:51), parts of the higher regions in the Valley
+of México, and the transverse volcanic zone in central México were
+glaciated. On the mountain Ixtaccihuatl, De Terra (_op. cit._:52) found
+evidence of four marked advances of ice, from oldest to youngest, as
+follows: Salto, ice advanced to 3100 meters; Xopano, ice at 3200-3300
+meters; Trancas, ice to 3400 meters; Ayolotepito, ice to 4350 meters.
+The Salto advance is correlated by De Terra (_loc. cit._) with the Iowan
+glacial period. The advance of ice down the mountain sides in the
+transverse volcanic zone was accompanied by cool moist climates or
+pluvial periods. Such climates probably altered habitat formerly
+suitable for _Baiomys_. There is no record of _Baiomys_ known to me
+exceeding 8000 feet in elevation, although the lower edge of the ice on
+Ixtaccihuatl is at approximately 15,300 feet (4600 meters, Sears, _loc.
+cit._). Presumably, the advance of ice down the mountains forced the
+pygmy mice to move to lower altitudes. Pluvial conditions possibly
+rendered the habitat even at lower altitudes uninhabitable for the mice,
+with the result that none continued to live in the transverse volcanic
+zone, but only north and south thereof. Long-continued separation of
+these northern and southern segments allowed species formation to occur.
+As climatic and habitat conditions became more favorable in central
+México, the two species moved back toward each other, and eventually
+their geographic ranges overlapped.
+
+An analysis of external and cranial characters of pygmy mice (see Figure
+12) reveals that both species are essentially largest to the north and
+smallest to the south. There are exceptions to this cline in both
+species. For example, _B. taylori analogous_ is a large subspecies; it
+lives allopatrically in the southern part of the range of the species.
+_B. musculus pallidus_ is not the largest subspecies; it lives
+allopatrically in the northern part of the range of the species. In
+west-central México, where the two species are sympatric, _B. taylori_
+is smaller than elsewhere and _B. musculus_ is larger than elsewhere.
+_B. t. analogous_ lives in the mountains of the transverse volcanic zone
+in central México. Its large size may be a result of the cooler climate
+in the mountains. _B. t. allex_, the smallest subspecies, lives
+sympatrically with _B. musculus musculus_ at lower elevations in
+west-central México. The small size of _allex_ could be a result of the
+warmer climate of the lower elevations. _B. m. pallidus_, at lower
+elevations in southern Oaxaca, is smaller than other subspecies of
+_musculus_ to the south at higher elevations. _B. m. musculus_ lives at
+low elevations along the coast of west-central México. Unlike _B. m.
+pallidus_, _B. m. musculus_ is large at lower elevations. It occurs
+sympatrically with _B. t. allex_. It is my idea that during the period
+of separation, when the two species were evolving, larger subspecies
+evolved to the north or at higher altitudes where climates were cooler;
+smaller subspecies evolved to the south or at lower elevations; the two
+cognate species, _musculus_ and _taylori_, made contact at lower
+elevations where individuals of _taylori_ may have been smallest, but
+individuals of _musculus_ were not the largest of the species. The
+differences, therefore, between the two species in their initial contact
+probably were slight. Hybrids, if they occurred, were probably
+inviable, sterile, or ill-suited for occupancy of the habitat of either
+of the parental stocks. The occurrence of hybrids, therefore, would
+result in what geneticists call "gamete wastage," and any further
+divergence in the parental stock, either in external characters (size
+and shape of body and head), or behavior, useful in recognition of
+species, would be favored by natural selection (see Dobzhansky,
+1951:225; and Koopman, 1950:147). The two species seem to have diverged
+more in external characters where they occur together than in areas
+where they live separately (see Figure 12). The two species could be
+confused if a sample of adults of _taylori_ from 7 mi. S La Belle,
+Jefferson County, Texas, were compared to a sample of adults of
+_musculus_ from Tehuantepec, Oaxaca (see Figure 12). No confusion in
+species identity would arise, however, if a sample of adults was taken
+from the area where the two species live together (see Figure 12). Brown
+and Wilson (1956:49) pointed out that where two closely related species
+occur together, characters (morphological, ecological, physiological, or
+behavioral) of each species are easily distinguished. However, where the
+two species are allopatric, the two closely related species so resemble
+one another that the species are not easily distinguished. This
+phenomenon has been called "character displacement" by Brown and Wilson
+(_loc. cit._).
+
+In the area where the two species of pygmy mice occur together, there
+seems to be a disparity in numbers between them. Hooper (1952a:91) has
+recorded the collection of both _B. musculus_ and _B. taylori_ in a
+single trap line. A series of pygmy mice collected from San Gabriel,
+Jalisco, contained one _taylori_ and 33 _musculus_; another sample from
+La Resolana, Jalisco, had a ratio of 25 _taylori_ to 6 _musculus_. The
+disparity in numbers where the two species occur together has been
+further substantiated by collections of the University of Kansas.
+Possibly this disparity in numbers is a result of interspecific
+competition. Hooper (_op. cit._:90) pointed out that where the range of
+_B. musculus_ (typical of arid tropical lowlands) meets that of _B.
+taylori_ (typical of arid temperate highlands), the two geographic
+ranges interdigitate with parts of the range of _musculus_ extending
+into the highlands and parts of the range of _taylori_ extending into
+the lowlands. In the lowlands, _musculus_ may be better adapted to
+environmental conditions and, therefore, more successful in competition
+with _taylori_ for available habitat. The reverse situation may exist in
+the highlands. Also, the fact that _musculus_ is more of a diurnal
+animal than is _taylori_ may account for the difference in numbers of
+individuals of the two species taken in trap lines. Many collectors set
+their traps in late afternoon or evening and retrieve them in early
+morning. Such a schedule might not yield many _musculus_. If
+interspecific competition does occur in the area where the two species
+occur, any change in habits or microhabitat by either species that would
+reduce this competition would be favored by natural selection (see Mayr,
+1949:518; Lack, 1944:262-263; and Brown, 1958:154-155). Brown (_op.
+cit._:154), as I understand him, pointed out (taking account of Gause's
+principle) that when two species having similar ecological valences move
+into the same niche in the same locality, one of three things must
+eventually happen: (_a_) the two species occupy different geographic
+ranges; (_b_) they compete and one is eventually eliminated; (_c_) the
+two species, because of differentiation or specialization, exploit
+different aspects of the niche. In _Baiomys_, (_c_) seems to apply.
+Natural selection probably would favor a continuation of diurnal
+activity in _musculus_ and nocturnal activity in _taylori_, thereby
+preventing frequent meeting of the two species.
+
+
+AREAS OF PRESENT DIFFERENTIATION
+
+In both species of _Baiomys_, the most distinct subspecies, _B. t.
+allex_ and _B. m. musculus_, occur in the area where the two species are
+sympatric. Seven subspecies, or 44 per cent, occur either in or adjacent
+to the transverse volcanic zone. This area is the major area of active
+differentiation. Incipient subspecies are also evident in these areas. A
+secondary area of differentiation is indicated within the range of _B.
+musculus_ in Guatemala, El Salvador and Honduras. Three subspecies occur
+in this area (_grisescens, handleyi_ and _nigrescens_) and incipient
+subspeciation is in evidence there.
+
+
+ZOOGEOGRAPHIC POSITION
+
+Hooper (1949:25) regards _Baiomys_ as a member of the rodent fauna of
+the arid, western Sonoran region, whereas Hershkovitz (1958:609)
+suggests that _Baiomys_ is a nearctic-neotropical varicant (a kind that
+occurs in contiguous zoogeographic regions without our knowing in which
+region the taxon originated). The findings from my study do not
+contradict either of the above suggestions. Because of the close
+resemblance of _Baiomys_ to certain hesperomine mice of South America,
+it is postulated that _Baiomys_, in more primitive form than now,
+occurred farther south in past times than it does now. Fossils show that
+primitive stocks of the genus in late Pliocene or early Pleistocene
+times occurred also north of the present range of the genus. The belt in
+west-central México between nearctic and neotropical regions is the
+current center of distribution of the genus and probably has been for a
+considerable time.
+
+    [Illustration:
+
+    FIG. 12. Averages of the occipitonasal lengths of skulls of adults
+       at 19 localities of occurrence (solid symbols) of _Baiomys taylori_,
+       and at 17 localities of occurrence (open symbols) of _Baiomys
+       musculus_. Note that the occipitonasal length decreases from north
+       to south in each of the two species, and that in the region where
+       the two species occur together, west-central México, _B. taylori_
+       is smallest and _B. musculus_ is largest. Average, extremes, number
+       of specimens averaged (in italic type), and name of locality, from
+       north to south for each species, are as follows:
+
+    _Baiomys taylori_
+
+    18.0  (17.5-18.6)  _15_, 9-1/2 mi. W New Mexico state line, Ariz.
+    18.9  (18.2-19.4)   _6_, 7 mi. S. La Belle, Jefferson Co., Texas.
+    18.2  (17.8-18.5)  _10_, San Antonio, Bexar Co., Texas.
+    18.2  (18.0-18.5)   _5_, 2 mi. W Miñaca, Chihuahua.
+    18.0  (17.6-19.0)  _22_, 6 mi. SW San Gerónimo, Coahuila.
+    18.2  (18.1-18.3)   _3_, Ciudad Obregón, Sonora.
+    18.1  (17.4-18.5)   _5_, vic. (see p. 649) Durango, Durango.
+    18.1  (17.5-18.5)   _9_, Jaumavé, Tamaulipas.
+    18.2  (17.7-18.9)  _19_, 15 mi. N Rosario Chelé, Sinaloa.
+    17.9  (17.4-18.3)  _27_, vic. (see p. 655) Altamira, Tamaulipas.
+    18.3  (17.9-18.7)   _9_, Valparaíso, Zacatecas.
+    18.1  (18.1-18.2)   _4_, Ciudad del Maíz, San Luis Potosí.
+    18.6  (18.3-18.9)   _8_, Tepic, Nayarit.
+    18.0  (17.7-18.4)  _18_, 4 mi. N, 5 mi. W León, Guanajuato.
+    18.1  (17.5-18.9)  _28_, 6 mi. E Querétaro, Querétaro.
+    17.7  (17.1-18.1)  _17_, 1 mi. SSE Ameca, Jalisco.
+    17.3  (16.8-17.9)  _10_, 2 mi. SSE Autlán, Jalisco.
+    18.0  (17.5-18.6)  _10_, 1 mi. S, 11 mi. W Zamora, Michoacán.
+    17.6  (17.4-18.2)   _8_, Colima, Colima.
+
+
+    _Baiomys musculus_
+
+    20.2  (19.9-20.3)  _6_, vic. (see p. 622) Ameca, Jalisco.
+    20.2  (19.9-20.3)  _6_, 2 mi. SSE Autlán, Jalisco.
+    19.6  (19.2-20.1)  _6_, Jalapa, Veracruz.
+    20.3  (19.7-20.9)  _9_, Colima, Colima.
+    19.5  (19.0-20.0) _10_, Cerro Gordo, Veracruz.
+    19.8  (19.4-20.3)  _6_, 6 mi. S Izucár de Matemores, Puebla.
+    20.0  (18.8-20.5)  _7_, Teotitlán, Oaxaca.
+    20.1  (19.7-20.7)  _7_, 1 km. NW Chapa, Guerrero.
+    19.9  (19.4-20.4)  _8_, 5 mi. ESE Tecpán, Guerrero.
+    19.5  (19.1-20.1) _22_, 3 mi. ESE Oaxaca, Oaxaca.
+    19.5  (19.1-19.9) _11_, Valley of Comitán, Chiapas.
+    18.9  (18.2-20.1) _17_, Tehuantepec, Oaxaca.
+    18.9  (18.4-19.7) _15_, 6 mi. NW Tonalá, Chiapas.
+    19.1  (18.8-20.4) _10_, 1 mi. S Rabinal, Guatemala.
+    19.7  (18.8-20.4) _10_, Lake Amatitlán, Guatemala.
+    19.2  (18.4-19.8) _26_, vic. (see p. 625) San Salvador, El Salvador.
+    19.3  (18.9-19.9) _24_, 8 mi. S Condega, Estelí, Nicaragua.]
+
+
+
+
+CONCLUSIONS
+
+
+1. Two Recent species, each polytypic with eight subspecies, and five
+fossil species are recognized.
+
+2. The phyletic trends in the genus _Baiomys_ have been from an
+ancestral stock that possessed relatively brachydont teeth having raised
+cingular ridges and orthodont to proödont incisors, to species having
+hypsodont teeth with reduced cingular ridges and retrodont incisors.
+
+3. Reduction of cingular ridges in pygmy mice is associated with an
+existence in open grassland (more xeric than mesic), whereas, the
+presence of cingular ridges is associated with an existence in a
+savannah habitat (more mesic than xeric).
+
+4. Shifts of geographical range of populations of pygmy mice at and near
+the periphery of their geographic range may account for the
+differentiation of the extinct species.
+
+5. The two living species, _B. musculus_ and _B. taylori_, are seemingly
+derived from a common ancestor that in morphological structure was
+intermediate between _B. minimus_ and _B. musculus_.
+
+6. The living species of pygmy mice resulted from a geographic
+separation, perhaps occurring in the Iowan glacial period (See De Terra,
+1949:51) in the transverse volcanic zone of central México.
+
+7. The two species are now sympatric in west central México, where
+morphological characters (size and shape of body and length of skull)
+differ most. Where the two species are allopatric, these same
+morphological characters differ least.
+
+8. This is a documented instance of character displacement in mammals.
+
+9. On the basis of internal morphological characters studied (auditory
+ossicles, hyoid apparatus, and baculum), _Baiomys_ seems to be more
+closely related to a South American hesperomine, perhaps _Calomys_, than
+to any North American cricetine.
+
+10. Pygmy mice were more widely distributed in the past than they are at
+present. Part of the ancestral stock of the pygmy mice may have
+emigrated from North America into South America in a brief period in the
+Pliocene; if so, it is easy to understand why certain South American
+hesperomines resemble _Baiomys_.
+
+11. The combination of morphological and behavioral characters in the
+living pygmy mice warrants generic status for them. If _Baiomys_ were
+treated as a subgenus of the genus _Peromyscus_, there would be adequate
+justification for including in the genus _Peromyscus_ a number of other
+genera, some of them occurring in South America. Such lumping of genera
+would reduce our understanding of the natural relationships among this
+group of cricetine rodents.
+
+
+
+
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+  TRUE, F. W.
+
+  1894.  On the relationships of Taylor's Mouse, _Sitomys taylori_. Proc.
+         U. S. Nat. Mus., 16:757-758, February 7.
+
+
+  TWENTE, J. H., and BAKER, R. H.
+
+  1951.  New records of mammals from Jalisco, México, from barn owl
+         pellets. Jour. Mamm., 32:120-121, 1 table, February 15.
+
+
+  VAN GELDER, R. G.
+
+  1959.  A taxonomic revision of the spotted skunks (Genus _Spilogale_).
+         Bull. Amer. Mus. Nat. Hist., 117(5):229-392, 47 figs., 32 tables,
+         June 15.
+
+
+  WHITE, J. A.
+
+  1951.  A practical method for mounting the bacula of small mammals.
+         Jour. Mamm., 32:125, February 15.
+
+  1953.  The baculum in the chipmunks of western North America. Univ.
+         Kansas Publ., Mus. Nat. Hist., 5:611-631, 19 figs., December 1.
+
+
+  WILSON, R. W.
+
+  1937.  Pliocene rodents of western North America. Carnegie Inst.
+         Washington, Publ. 487:21-73, 2 figs., July 23.
+
+
+  WOOD, A. E., and WILSON, R. W.
+
+  1936.  A suggested nomenclature for the cusps of the cheek teeth of
+         rodents. Jour. Paleon., 10:388-391, 2 figs.
+
+
+_Transmitted March 4, 1960._
+
+
+[]
+28-3030
+
+
+
+
+UNIVERSITY OF KANSAS PUBLICATIONS
+
+MUSEUM OF NATURAL HISTORY
+
+
+Institutional libraries interested in publications exchange may obtain
+this series by addressing the Exchange Librarian, University of Kansas
+Library, Lawrence, Kansas. Copies for individuals, persons working in a
+particular field of study, may be obtained by addressing instead the
+Museum of Natural History, University of Kansas, Lawrence, Kansas. There
+is no provision for sale of this series by the University Library, which
+meets institutional requests, or by the Museum of Natural History, which
+meets the requests of individuals. However, when individuals request
+copies from the Museum, 25 cents should be included, for each separate
+number that is 100 pages or more in length, for the purpose of defraying
+the costs of wrapping and mailing.
+
+    * An asterisk designates those numbers of which the Museum's supply
+      (not the Library's supply) is exhausted. Numbers published to date,
+      in this series, are as follows:
+
+   Vol.  1. Nos. 1-26 and index. Pp. 1-638, 1946-1950.
+
+  *Vol.  2. (Complete) Mammals of Washington. By Walter W. Dalquest.
+                Pp. 1-444, 140 figures in text. April 9, 1948.
+
+   Vol.  3. *1. The avifauna of Micronesia, its origin, evolution, and
+                distribution. By Rollin H. Baker, Pp. 1-359, 16 figures in
+                text. June 12, 1951.
+
+            *2. A quantitative study of the nocturnal migration of birds.
+                By George H. Lowery, Jr. Pp. 361-472, 47 figures in text.
+                June 29, 1951.
+
+             3. Phylogeny of the waxwings and allied birds. By M. Dale
+                Arvey. Pp. 473-530, 49 figures in text, 13 tables.
+                October 10, 1951.
+
+             4. Birds from the state of Veracruz, Mexico. By George H.
+                Lowery, Jr., and Walter W. Dalquest. Pp. 531-649,
+                7 figures in text, 2 tables. October 10, 1951.
+
+            Index. Pp. 651-681.
+
+  *Vol.  4. (Complete) American weasels. By E. Raymond Hall. Pp. 1-466,
+                41 plates, 31 figures in text. December 27, 1951.
+
+   Vol.  5. Nos. 1-37 and index. Pp. 1-676,  1951-1953.
+
+  *Vol.  6. (Complete) Mammals of Utah, _taxonomy and distribution_.
+                By Stephen D. Durrant. Pp. 1-549, 91 figures in text,
+                30 tables. August 10, 1952.
+
+   Vol.  7. *1. Mammals of Kansas. By E. Lendell Cockrum. Pp. 1-303.
+                73 figures in text, 37 tables. August 25, 1952.
+
+             2. Ecology of the opossum on a natural area in northeastern
+                Kansas. By Henry S. Fitch and Lewis L. Sandidge.
+                Pp. 305-338, 5 figures in text. August 24, 1953.
+
+             3. The silky pocket mice (Perognathus flavus) of Mexico.
+                By Rollin H. Baker. Pp. 339-347, 1 figure in text.
+                February 15, 1954.
+
+             4. North American jumping mice (Genus Zapus). By Philip H.
+                Krutzch. Pp. 349-472, 47 figures in text, 4 tables.
+                April 21, 1954.
+
+             5. Mammals from Southeastern Alaska. By Rollin H. Baker and
+                James S. Findley. Pp. 473-477. April 21, 1954.
+
+             6. Distribution of Some Nebraskan Mammals. By J. Knox Jones,
+                Jr. Pp. 479-487. April 21, 1954.
+
+             7. Subspeciation in the montane meadow mouse. Microtus
+                montanus, in Wyoming and Colorado. By Sydney Anderson.
+                Pp. 489-506, 2 figures in text. July 23, 1954.
+
+             8. A new subspecies of bat (Myotis velifer) from southeastern
+                California and Arizona. By Terry A. Vaughan. Pp. 507-512.
+                July 23, 1954.
+
+             9. Mammals of the San Gabriel mountains of California.
+                By Terry A. Vaughan. Pp. 513-582. 1 figure in text,
+                12 tables. November 15, 1954.
+
+            10. A new bat (Genus Pipistrellus) from northeastern Mexico.
+                By Rollin H. Baker. Pp. 583-586. November 15, 1954.
+
+            11. A new subspecies of pocket mouse from Kansas. By E. Raymond
+                Hall. Pp. 587-590. November 15, 1954.
+
+            12. Geographic variation in the pocket gopher, Cratogeomys
+                castanops, in Coahuila, Mexico. By Robert J. Russell and
+                Rollin H. Baker. Pp. 591-608. March 15, 1955.
+
+            13. A new cottontail (Sylvilagus floridanus) from northeastern
+                Mexico. By Rollin H. Baker. Pp. 609-612. April 8, 1955.
+
+            14. Taxonomy and distribution of some American shrews.
+                By James S. Findley. Pp. 613-618. June 10, 1955.
+
+            15. The pigmy woodrat, Neotoma goldmani, its distribution and
+                systematic position. By Dennis G. Rainey and Rollin H.
+                Baker. Pp. 619-624, 2 figures in text. June 10, 1955.
+
+            Index. Pp. 625-651.
+
+   Vol.  8.  1. Life history and ecology of the five-lined skink, Eumeces
+                fasciatus. By Henry S. Fitch. Pp. 1-156, 26 figures in
+                text. September 1, 1954.
+
+             2. Myology end serology of the Avian Family Fringillidae,
+                a taxonomic study. By William B. Stallcup. Pp. 157-211,
+                23 figures in text, 4 tables. November 15, 1954.
+
+             3. An ecological study of the collared lizard (Crotaphytus
+                collaris). By Henry S. Fitch. Pp. 213-274, 10 figures in
+                text. February 10, 1956.
+
+             4. A field study of the Kansas ant-eating frog, Gastrophryne
+                olivacea. By Henry S. Fitch. Pp. 275-306, 9 figures in
+                text. February 10, 1956.
+
+             5. Check-list of the birds of Kansas. By Harrison E.
+                Tordoff. Pp. 307-359, 1 figure in text. March 10, 1956.
+
+             6. A population study of the prairie vole (Microtus
+                ochrogaster) in northeastern Kansas. By Edwin P. Martin.
+                Pp. 361-416, 19 figures in text.  April 2, 1956.
+
+             7. Temperature responses in free-living amphibians and
+                reptiles of northeastern Kansas. By Henry S. Fitch.
+                Pp. 417-476, 10 figures in text, 6 tables. June 1, 1956.
+
+             8. Food of the crow, Corvus brachyrhynchos Brehm, in
+                south-central Kansas. By Dwight Platt. Pp. 477-498.
+                4 tables. June 8, 1956.
+
+             9. Ecological observations on the woodrat, Neotoma floridana.
+                By Henry S. Fitch and Dennis G. Rainey. Pp. 499-533,
+                3 figures in text. June 12, 1956.
+
+            10. Eastern woodrat, Neotoma floridana: Life history and
+                ecology. By Dennis G. Rainey. Pp. 535-646, 12 plates,
+                13 figures in text. August 15, 1956.
+
+            Index. Pp. 647-675.
+
+   Vol.  9.  1. Speciation of the wandering shrew. By James S. Findley.
+                Pp. 1-68, 18 figures in text. December 10, 1955.
+
+             2. Additional records and extensions of ranges of mammals from
+                Utah. By Stephen D. Durrant, M. Raymond Lee, and Richard M.
+                Hansen. Pp. 69-80. December 10, 1955.
+
+             3. A new long-eared myotis (Myotis evotis) from northeastern
+                Mexico. By Rollin H. Baker and Howard J. Stains. Pp. 81-84.
+                December 10, 1955.
+
+             4. Subspeciation in the meadow mouse, Microtus
+                pennsylvanicus, in Wyoming. By Sydney Anderson.
+                Pp. 85-104, 2 figures in text. May 10, 1956.
+
+             5. The condylarth genus Ellipsodon. By Robert W. Wilson.
+                Pp. 105-116, 6 figures In text. May 19, 1956.
+
+             6. Additional remains of the multituberculate genus
+                Eucosmodon. By Robert W. Wilson. Pp. 117-123, 10 figures
+                in text. May 19, 1956.
+
+             7. Mammals of Coahuila, Mexico. By Rollin H. Baker.
+                Pp. 125-335, 75 figures in text. June 15, 1956.
+
+             8. Comments on the taxonomic status of Apodemus peninsulae,
+                with description of a new subspecies from North China.
+                By J. Knox Jones, Jr. Pp. 337-346, 1 figure in text,
+                1 table. August 15, 1956.
+
+             9. Extensions of known ranges of Mexican bats. By Sydney
+                Anderson. Pp. 347-351. August 15, 1956.
+
+            10. A new bat (Genus Leptonycteris) from Coahuila. By Howard J.
+                Stains. Pp. 353-356. January 21, 1957.
+
+            11. A new species of pocket gopher (Genus Pappogeomys) from
+                Jalisco, Mexico. By Robert J. Russell. Pp. 357-361.
+                January 21, 1957.
+
+            12. Geographic variation in the pocket gopher, Thomomys bottae,
+                in Colorado. By Phillip M. Youngman. Pp. 363-385, 7 figures
+                in text. February 21, 1958.
+
+            13. New bog lemming (genus Synaptomys) from Nebraska.
+                By J. Knox Jones, Jr. Pp. 385-388. May 12, 1958.
+
+            14. Pleistocene  bats from San Josecito Cave, Nuevo León,
+                México. By J. Knox Jones, Jr. Pp. 389-396.
+                December 19, 1958.
+
+            15. New Subspecies of the rodent Baiomys from Central America.
+                By Robert L. Packard. Pp. 397-404. December 19, 1958.
+
+            16. Mammals of the Grand Mesa, Colorado. By Sydney Anderson.
+                Pp, 405-414, 1 figure in text. May 20, 1959.
+
+            17. Distribution, variation, and relationships of the montane
+                vole, Microtus montanus. By Emil K. Urban. Pp. 415-511.
+                12 figures in text, 2 tables. August 1, 1959.
+
+            18. Conspecificity of two pocket mice, Perognathus goldmani and
+                P. artus. By E. Raymond Hall and Marilyn Bailey Ogilvie.
+                Pp. 513-518, 1 map. January 14, 1960.
+
+            19. Records of harvest mice, Reithrodontomys, from Central
+                America, with description of a new subspecies from
+                Nicaragua. By Sydney Anderson and J. Knox Jones, Jr.
+                Pp. 519-529. January 14, 1960.
+
+            20. Small carnivores from San Josecito Cave (Pleistocene),
+                Nuevo León, México. By E. Raymond Hall. Pp. 531-538,
+                1 figure in text. January 14, 1960.
+
+            21. Pleistocene pocket gophers from San Josecito Cave, Nuevo
+                León, México. By Robert J. Russell. Pp. 539-548, 1 figure
+                in text. January 14, 1960.
+
+            22. Review of the insectivores of Korea. By J. Knox Jones, Jr.,
+                and David H. Johnson. Pp. 549-578. February 23, 1960.
+
+            23. Speciation and evolution of the pygmy mice, genus Baiomys.
+                By Robert L. Packard. Pp. 579-670, 4 plates, 12 figures in
+                text. June 16, 1960.
+
+            Index will follow.
+
+   Vol. 10.  1. Studies of birds killed in nocturnal migration. By
+                Harrison B. Tordoff and Robert M. Mengel. Pp. 1-44,
+                6 figures in text, 2 tables. September 12, 1956.
+
+             2. Comparative breeding behavior of Ammospiza caudacuta and
+                A. maritime. By Glen E. Woolfenden. Pp. 45-75, 6 plates,
+                1 figure. December 20, 1956.
+
+             3. The forest habitat of the University of Kansas Natural
+                History Reservation. By Henry S. Fitch and Ronald R.
+                McGregor. Pp. 77-127, 2 plates, 7 figures in text,
+                4 tables. December 31, 1956.
+
+             4. Aspects of reproduction and development in the prairie vole
+                (Microtus ochrogaster). By Henry S. Fitch, Pp. 129-161,
+                8 figures in text, 4 tables. December 19, 1957.
+
+             5. Birds found on the Arctic slope of northern Alaska. By
+                James W. Bee. Pp. 163-211, pls. 9-10, 1 figure in text.
+                March 12, 1958.
+
+             6. The wood rats of Colorado; distribution and ecology.
+                By Robert B. Finley, Jr. Pp. 213-552, 34 plates,
+                8 figures in text, 35 tables. November 7, 1958.
+
+             7. Home ranges and movements of the eastern cottontail in
+                Kansas. By Donald  W. Janes. Pp. 553-572, 4 plates,
+                3 figures in text. May 4, 1959.
+
+             8. Natural history of the salamander, Aneides hardyi.
+                By Richard F. Johnston and Schad Gerhard. Pp. 573-585.
+                October 8, 1959.
+
+             9. A new subspecies of lizard, Cnemidophorus sacki, from
+                Michoacán, México. By William E. Duellman. Pp. 587-598,
+                2 figures in text. May 2, 1960.
+
+            10. A taxonomic study of the Middle American Snake, Pituophis
+                deppei. By William E. Duellman. Pp. 599-612, 1 plate,
+                1 figure in text. May 2, 1960.
+
+            Index will follow.
+
+   Vol. 11.  1. The systematic status of the colubrid snake, Leptodeira
+                discolor Günther. By William E. Duellman. Pp. 1-9,
+                4 figs. July 14, 1958.
+
+             2. Natural history of the six-lined racerunner, Cnemidophorus
+                sexlineatus. By Henry S. Fitch. Pp. 11-62, 9 figs.,
+                9 tables. September 19, 1958.
+
+             3. Home ranges, territories, and seasonal movements of
+                vertebrates of the Natural History Reservation. By Henry
+                S. Fitch, Pp. 68-326, 6 plates, 24 figures in text,
+                8 tables. December 12, 1958.
+
+             4. A new snake of the genus Geophis from Chihuahua, Mexico.
+                By John M. Legler. Pp. 327-334, 2 figures in text.
+                January 28, 1959.
+
+             5. A new tortoise, genus Gopherus, from north-central Mexico.
+                By John M. Legler. Pp. 335-343. April 24, 1959.
+
+             6. Fishes of Chautauqua, Cowley and Elk counties, Kansas.
+                By Artie L. Metcalf. Pp. 345-400, 2 plates, 2 figures in
+                text, 10 tables. May 6, 1959.
+
+             7. Fishes of the Big Blue River Basin, Kansas. By W. L.
+                Minckley. Pp. 401-442, 2 plates, 4 figures in text,
+                5 tables. May 8, 1959.
+
+             8. Birds from Coahuila, México. By Emll K. Urban. Pp. 443-516.
+                August 1, 1959.
+
+             9. Description of a new softshell turtle from the southeastern
+                United States. By Robert G. Webb. Pp. 517-525, 2 pls.,
+                1 figure in text, August 14, 1959.
+
+            10. Natural history of the ornate box turtle, Terrapene ornata
+                ornata Agassiz. By John M. Legler. Pp. 527-669, 16 pls.,
+                29 figures in text. March 7, 1960.
+
+            Index will follow.
+
+   Vol. 12.  1. Functional morphology of three bats: Eumops, Myotis,
+                Macrotus. By Terry A. Vaughan. Pp. 1-153, 4 plates,
+                24 figures in text. July 8, 1959.
+
+             2. The ancestry of modern Amphibia: a review of the evidence.
+                By Theodore H. Eaton, Jr. Pp. 155-180, 10 figures in text.
+                July 10, 1959.
+
+             3. The baculum in microtine rodents. By Sydney Anderson.
+                Pp. 181-216, 49 figures in text. February 19, 1960.
+
+             4. A new order of fishlike Amphibia from the Pennsylvanian of
+                Kansas. By Theodore H. Eaton, Jr., and Peggy Lou Stewart.
+                Pp. 217-240, 12 figures in text. May 2, 1960.
+
+            More numbers will appear In volume 12.
+
+
+
+
+Transcriber's Notes
+
+The text presented is that of the original printed version except for
+the revisions below and a few assumed typesetting errors. The subsection
+headers under "VARIATION WITH AGE" were converted to italic only to
+match the rest. All other section title formatting retained as printed.
+The words Miscellaneous and Monograph were abbreviated as Miscl. and
+Mongr. respectively. Except for the two variant spellings of one word
+(Mexico/México) which were retained, the most prevalent form of accented
+words was used.
+
+Both decimal and whole plus fractional part of numbers (i.e., 9-1/2)
+were retained as printed. The male and female symbols are represented by
+[M] and [F] respectively. Footnotes were all placed at the end of each
+species account. The list of KU Publications were compiled after the
+article's text.
+
+
+Typographical Corrections
+
+  Page Correction
+  ==== ====================
+  591 proödent => proödont
+  694 hesperomyines => hesperomines
+
+
+Text Emphasis
+
+  _Text_ - Italic
+
+  =Text= - Bold
+
+
+
+
+
+End of the Project Gutenberg EBook of Speciation and Evolution of the Pygmy
+Mice, Genus Baiomys, by Robert L. Packard
+
+*** END OF THIS PROJECT GUTENBERG EBOOK SPECIATION AND EVOLUTION OF ***
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+    <meta http-equiv="Content-Type" content="text/html;charset=ISO-8859-1" />
+    <meta http-equiv="Content-Style-Type" content="text/css" />
+    <title>
+      The Project Gutenberg eBook of Speciation And Evolution Of The Pygmy Mice, Genus Baiomys, by Robert L. Packard.
+    </title>
+    <style type="text/css">
+
+  p                {text-align: justify; text-indent: 1.5em;}
+  sub, sup         {font-size: 0.75em;}
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+<pre>
+
+The Project Gutenberg EBook of Speciation and Evolution of the Pygmy Mice,
+Genus Baiomys, by Robert L. Packard
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Speciation and Evolution of the Pygmy Mice, Genus Baiomys
+
+Author: Robert L. Packard
+
+Release Date: December 13, 2011 [EBook #38290]
+
+Language: English
+
+Character set encoding: ISO-8859-1
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+*** START OF THIS PROJECT GUTENBERG EBOOK SPECIATION AND EVOLUTION OF ***
+
+
+
+
+Produced by Chris Curnow, Tom Cosmas, Joseph Cooper and
+the Online Distributed Proofreading Team at
+http://www.pgdp.net
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+</pre>
+
+
+<div class="book"><!-- Begin Book -->
+
+<div class="fig_center" style="width: 313px;">
+<img src="images/cover.jpg" width="313" height="524" alt="cover" /><br />
+<div class="smaller">[Transcriber's Note: Cover compiled from scanned images.]</div>
+<br />
+</div>
+
+<p><span class="pagenum"><a name="Page_579" id="Page_579">[Pg 579]</a></span></p>
+<div class="center">
+<div class="fig_center">
+<img src="images/bar_double.png" width="100%" height="15" alt="" />
+</div>
+<span class="smcap">University of Kansas Publications</span><br />
+<br />
+<span class="smcap">Museum of Natural History</span><br />
+<br />
+<hr class="hr25" />
+<br />
+Volume 9, No. 23, pp. 579-670, 4 pls., 12 figs. in text<br />
+<br />
+<img src="images/bar_single.png" width="40%" height="15" alt="" />
+&nbsp;June 16, 1960&nbsp;
+<img src="images/bar_single.png" width="40%" height="15" alt="" /><br />
+<br />
+<br />
+<div class="caption1">Speciation and Evolution of the<br />
+Pygmy Mice, Genus Baiomys</div>
+<br />
+<div class="caption3"><b>BY</b></div>
+<br />
+<div class="caption2">ROBERT L. PACKARD</div>
+<br />
+<span class="smcap">University of Kansas</span><br />
+<span class="smcap">Lawrence</span><br />
+1960<br />
+<br />
+</div>
+
+<p><span class="pagenum"><a name="Page_580" id="Page_580">[Pg 580]</a></span></p>
+<div class="center">
+<span class="smcap">University of Kansas Publications, Museum of Natural History</span><br />
+<br />
+Editors: E. Raymond Hall, Chairman, Henry S. Fitch,<br />
+<br />
+Robert W. Wilson<br />
+<br />
+Volume 9, No. 23, pp. 579-670, 4 pls., 12 figs. in text<br />
+Published June 16, 1960<br />
+<br />
+<br />
+<span class="smcap">University of Kansas</span><br />
+Lawrence, Kansas<br />
+<br />
+<br />
+PRINTED IN<br />
+THE STATE PRINTING PLANT<br />
+TOPEKA, KANSAS<br />
+<br />
+1960<br />
+<br />
+<img src="images/union_label.png" width="74" height="27" alt="Look for the Union Label" /><br />
+28-3030<br />
+<br />
+<br />
+</div>
+
+<p><span class="pagenum"><a name="Page_581" id="Page_581">[Pg 581]</a></span></p>
+<div class="caption2"><a name="Speciation_and_Evolution_of_the" id="Speciation_and_Evolution_of_the"></a>Speciation and Evolution of the
+Pygmy Mice, Genus Baiomys</div>
+
+<div class="caption3"><b>BY</b></div>
+
+<div class="caption2">ROBERT L. PACKARD</div>
+<br />
+
+<div class="caption2"><a name="CONTENTS" id="CONTENTS"></a>CONTENTS</div>
+
+
+<table width="80%" summary="Contents">
+<tr>
+  <td>&nbsp;</td>
+  <td>PAGE</td>
+</tr>
+<tr>
+  <td><a href="#INTRODUCTION">Introduction</a></td>
+  <td class="text_rt">583</td>
+</tr>
+<tr>
+  <td class="text_lf"><a href="#MATERIALS_METHODS_AND_ACKNOWLEDGMENTS">Materials, Methods and Acknowledgments</a></td>
+  <td class="text_rt">584</td>
+</tr>
+<tr>
+  <td class="text_lf"><a href="#PALEONTOLOGY_OF_THE_GENUS">Paleontology of the Genus</a></td>
+  <td class="text_rt">587</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_sawrockensis"><i>Baiomys sawrockensis</i></a></td>
+  <td class="text_rt">588</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_rexroadi"><i>Baiomys rexroadi</i></a></td>
+  <td class="text_rt">589</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_kolbi"><i>Baiomys kolbi</i></a></td>
+  <td class="text_rt">590</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_brachygnathus"><i>Baiomys brachygnathus</i></a></td>
+  <td class="text_rt">590</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_minimus"><i>Baiomys minimus</i></a></td>
+  <td class="text_rt">591</td>
+</tr>
+<tr>
+  <td class="text_lf"><a href="#PHYLETIC_TRENDS">Phyletic trends</a></td>
+  <td class="text_rt">592</td>
+</tr>
+<tr>
+  <td class="text_lf"><a href="#NON-GEOGRAPHIC_VARIATION">Non-Geographic Variation</a></td>
+  <td class="text_rt">595</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#VARIATION_WITH_AGE">Variation with age</a></td>
+  <td class="text_rt">595</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#SECONDARY_SEXUAL_VARIATION">Secondary sexual variation</a></td>
+  <td class="text_rt">597</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#INDIVIDUAL_VARIATION">Individual variation</a></td>
+  <td class="text_rt">597</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#PELAGE_AND_MOLTS">Pelage and molts</a></td>
+  <td class="text_rt">598</td>
+</tr>
+<tr>
+  <td class="text_lf"><a href="#TAXONOMIC_CHARACTERS_AND_RELATIONSHIPS">Taxonomic Characters and Relationships</a></td>
+  <td class="text_rt">600</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#External_parts">External parts</a></td>
+  <td class="text_rt">600</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Pelage">Pelage</a></td>
+  <td class="text_rt">600</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Skull">Skull</a></td>
+  <td class="text_rt">600</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Teeth">Teeth</a></td>
+  <td class="text_rt">601</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Hyoid_apparatus">Hyoid apparatus</a></td>
+  <td class="text_rt">601</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baculum">Baculum</a></td>
+  <td class="text_rt">603</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Auditory_ossicles">Auditory ossicles</a></td>
+  <td class="text_rt">605</td>
+</tr>
+<tr>
+  <td class="text_lf"><a href="#Genus_Baiomys">Genus Baiomys</a></td>
+  <td class="text_rt">607</td>
+</tr>
+<tr>
+  <td class="text_lf"><a href="#SYSTEMATIC_ACCOUNTS">Systematic Accounts of Species and Subspecies</a></td>
+  <td class="text_rt">608</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_musculus"><i>Baiomys musculus</i></a></td>
+  <td class="text_rt">608</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_musculus_brunneus"><i>Baiomys musculus brunneus</i></a></td>
+  <td class="text_rt">612</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_musculus_grisescens"><i>Baiomys musculus grisescens</i></a></td>
+  <td class="text_rt">614</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_musculus_handleyi"><i>Baiomys musculus handleyi</i></a></td>
+  <td class="text_rt">617</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_musculus_infernatis"><i>Baiomys musculus infernatis</i></a></td>
+  <td class="text_rt">618</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_musculus_musculus"><i>Baiomys musculus musculus</i></a></td>
+  <td class="text_rt">620</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_musculus_nigrescens"><i>Baiomys musculus nigrescens</i></a></td>
+  <td class="text_rt">623</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_musculus_pallidus"><i>Baiomys musculus pallidus</i></a>
+     <span class="pagenum"><a name="Page_582" id="Page_582">[Pg 582]</a></span></td>
+  <td class="text_rt">625</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_musculus_pullus"><i>Baiomys musculus pullus</i></a></td>
+  <td class="text_rt">628</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_taylori"><i>Baiomys taylori</i></a></td>
+  <td class="text_rt">630</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_taylori_allex"><i>Baiomys taylori allex</i></a></td>
+  <td class="text_rt">633</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_taylori_analogous"><i>Baiomys taylori analogous</i></a></td>
+  <td class="text_rt">637</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_taylori_ater"><i>Baiomys taylori ater</i></a></td>
+  <td class="text_rt">640</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_taylori_canutus"><i>Baiomys taylori canutus</i></a></td>
+  <td class="text_rt">643</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_taylori_fuliginatus"><i>Baiomys taylori fuliginatus</i></a></td>
+  <td class="text_rt">645</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_taylori_paulus"><i>Baiomys taylori paulus</i></a></td>
+  <td class="text_rt">647</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_taylori_subater"><i>Baiomys taylori subater</i></a></td>
+  <td class="text_rt">650</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#Baiomys_taylori_taylori"><i>Baiomys taylori taylori</i></a></td>
+  <td class="text_rt">651</td>
+</tr>
+<tr>
+  <td class="text_lf"><a href="#EVOLUTION_AND_SPECIATION">Evolution and Speciation</a></td>
+  <td class="text_rt">655</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#FORMATION_OF_THE_RECENT_SPECIES">Formation of the Recent Species</a></td>
+  <td class="text_rt">658</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#AREAS_OF_PRESENT_DIFFERENTIATION">Areas of present differentiation</a></td>
+  <td class="text_rt">661</td>
+</tr>
+<tr>
+  <td class="text_lf">&nbsp;&nbsp;&nbsp;&nbsp;<a href="#ZOOGEOGRAPHIC_POSITION">Zoogeographic position</a></td>
+  <td class="text_rt">661</td>
+</tr>
+<tr>
+  <td class="text_lf"><a href="#CONCLUSIONS">Conclusions</a></td>
+  <td class="text_rt">664</td>
+</tr>
+<tr>
+  <td class="text_lf"><a href="#LITERATURE_CITED">Literature Cited</a></td>
+  <td class="text_rt">665</td>
+</tr>
+</table>
+<br />
+<br />
+
+<p><span class="pagenum"><a name="Page_583" id="Page_583">[Pg 583]</a></span></p>
+
+<div class="caption2"><a name="INTRODUCTION" id="INTRODUCTION"></a>INTRODUCTION</div>
+
+<p>Pygmy mice (<i>Genus Baiomys</i>) are the smallest cricetine rodents
+in North America. They occur from Nicaragua in Central America
+into the southwestern United States. The principal part of the
+geographic range of the pygmy mice lies in the Republic of México.
+They are notably common in central México, but are only locally
+common to the north and to the south, and then only in certain
+seasons.</p>
+
+<p>Pygmy mice were first brought to the attention of biologists in
+1887 when Oldfield Thomas described a diminutive species of
+cricetine rodent, <i>Hesperomys</i> (<i>Vesperimus</i>) <i>taylori</i>. The description
+was based on a specimen obtained by William Taylor from San
+Diego, Duval County, Texas. C. Hart Merriam (1892:70) described
+<i>Sitomys musculus</i> on the basis of specimens from Colima
+[City of], Colima, México. Merriam (<i>loc. cit.</i>) mentioned that the
+two kinds of mice, <i>Hesperomys taylori</i> and <i>Sitomys musculus</i>, "in
+general appearance look almost precisely like the common house
+mouse (<i>Mus musculus</i>) but are still smaller and have shorter tails."
+He placed the two species in the genus <i>Sitomys</i>. Frederick
+W. True in 1894 regarded them as composing a distinct subgenus
+of <i>Sitomys, Baiomys</i>. According to True (1894:758), <i>S.
+taylori</i> and <i>S. musculus</i> possessed a different combination of characters
+(ascending ramus of mandible short and erect, condyle terminal,
+coronoid process well-developed, uncinate, and near the condyle,
+size small, tail short, plantar tubercles six, soles hairy) than
+either <i>Vesperimus</i>, or <i>Onychomys</i> (which had been considered as a
+subgenus of <i>Hesperomys</i> until 1889). In 1907, E. A. Mearns accorded
+<i>Baiomys</i> generic rank. Osgood (1909:252) treated <i>Baiomys</i>
+us a subgenus of <i>Peromyscus</i>, whereas, Miller, in 1912, regarded
+<i>Baiomys</i> as a distinct genus. Most recent students of North American
+mammals have followed Miller, but usually with reservations.
+Ellerman (1941:402) emphasized that the taxonomic position of the
+genus was uncertain, and wrote that <i>Baiomys</i> "&#8230; seems to be
+considerably distinct from <i>Peromyscus</i>, and may perhaps be a
+northern representative of <i>Hesperomys</i> or one of the small South
+American genera."</p>
+
+<p>Only two comprehensive analyses of geographic variation and
+interspecific taxonomic relationships have been made; the first was
+by Osgood (1909) who had fewer than a fourth of the specimens of
+<i>Baiomys</i> available to me; the second was by Hooper (1952a:90-97)
+<span class="pagenum"><a name="Page_584" id="Page_584">[Pg 584]</a></span>
+who contributed importantly to understanding the relationships of
+the two living species in central México. No attempts heretofore
+have been made to correlate and understand the relationships of the
+five fossil species to one another and to the living species assigned
+to the genus.</p>
+
+<p>Six objectives of the following report are to: (1) list characters
+taxonomically useful in recognizing species and subspecies; (2)
+record amount of variation within and between populations; (3)
+correlate observed variations with known biological principles; (4)
+show geographic ranges of the two living species; (5) indicate relationships
+between fossil and living species of the genus; and (6)
+clarify the systematic position of the genus.</p>
+
+
+<div class="caption2"><a name="MATERIALS_METHODS_AND_ACKNOWLEDGMENTS" id="MATERIALS_METHODS_AND_ACKNOWLEDGMENTS"></a>MATERIALS, METHODS AND ACKNOWLEDGMENTS</div>
+
+
+<p>This report is based on the study of approximately 3,520 museum
+study skins, skulls, complete skeletons, and entire animals preserved
+in liquid. Most specimens examined were accompanied by an attached
+label bearing data on locality and date of capture, name of
+collector, external measurements, and sex. In addition, 49 fossil
+specimens referable to <i>Baiomys</i> were studied. Nearly two-thirds
+of the specimens were assembled at the University of Kansas Museum
+of Natural History; the remainder were examined in other
+institutions.</p>
+
+<p>Specimens studied were grouped by geographic origin, sex, age,
+and season of capture. Individual variation was then measured in
+several of the larger samples of each living species and in measurable
+fossil material. External measurements used were those recorded
+by the collectors on the labels attached to the skins. Twenty
+cranial measurements employed in the past in the study of <i>Baiomys</i>
+and closely related cricetine rodents were statistically analyzed.
+The coefficient of variation was calculated for each of the 20 measurements
+in order to determine which varied least. In general,
+measurements having the least coefficient of variation were used
+in comparing samples from different geographic areas. <a href="#fig1">Figure 1</a>
+shows the points between which measurements were taken.</p>
+
+<div class="smaller">
+<i>Occipitonasal length.</i>&mdash;From anteriormost projection of nasal bones to posteriormost
+projection of supraoccipital bone. <i>A</i> to <i>A'</i>
+
+<i>Zygomatic breadth.</i>&mdash;Greatest distance across zygomatic arches of cranium at
+right angles to long axis of skull. <i>B</i> to <i>B'</i>
+
+<i>Postpalatal length.</i>&mdash;From posterior margin of hard palate to anterior margin
+of foramen magnum. <i>C</i> to <i>C'</i>
+
+<i>Least interorbital breadth.</i>&mdash;Least distance across top of skull between orbits.
+<i>D</i> to <i>D'</i>
+<span class="pagenum2"><a name="Page_585" id="Page_585">[Pg 585]</a></span>
+<i>Length of incisive foramina.</i>&mdash;From anteriormost point to posteriormost point
+of incisive foramina. <i>E</i> to <i>E'</i>
+
+<i>Length of rostrum.</i>&mdash;The distance in a straight line from the notch that lies
+lateral to the lacrimal to the tip of the nasal on the same side. <i>F</i> to <i>F'</i>
+
+<i>Breadth of braincase.</i>&mdash;Greatest distance across braincase, taken at right angles
+to long axis of skull. <i>G</i> to <i>G'</i>
+
+<i>Depth of cranium.</i>&mdash;The distance from the dorsalmost part of the braincase to
+a flat plane touching tips of incisors and ventral border of each auditory
+bulla. A glass slide one millimeter thick was placed on the ventral side of
+the skull. One jaw of the caliper was on the lower surface of the slide and
+the other jaw on the dorsalmost part of the braincase. The depth of the
+slide was subtracted from the total reading. <i>H</i> to <i>H'</i>
+
+<i>Alveolar length of maxillary tooth-row.</i>&mdash;From anterior border of alveolus of
+M1 to posterior alveolus of M3. <i>I</i> to <i>I'</i>
+</div>
+
+<div class="fig_center">
+<a name="fig1" id="fig1"></a>
+<img src="images/fig_1.png" width="425" height="201" alt="" /><br />
+<span class="fig_caption"><span class="smcap">Fig. 1.</span> Three views of the skull to show points between which measurements
+were taken.<br />Based on <i>B. m. pullus</i>, adult, female, No. 71611 KU, 8 mi. S
+Condega, Estelí, Nicaragua. &#215; 1<sup>1</sup>/<sub>3</sub>.</span>
+</div>
+
+<p>Capitalized color-terms refer to Ridgway (1912). Color terms without
+initial letters capitalized do not refer to any one standard.</p>
+
+<p>The names of the cusps and ridges of the teeth (see <a href="#fig2">Figure 2</a>) are those
+suggested by Wood and Wilson (1936:389-390). Terminology of the enamel
+grooves and folds is that of Hershkovitz (1944:17) and Hooper (1952b:20-21).</p>
+
+<p>Because secondary sexual variation was not significant (see <a href="#Page_597">page 597</a>), both
+males and females of like age and pelage were used in comparisons of samples
+designed to reveal geographic variation.</p>
+
+<p>The species are arranged from less to more progressive; the subspecies are
+arranged alphabetically.</p>
+
+<p>In the synonymy of each subspecies, the plan has been to cite: (1) the
+name first proposed; (2) the first usage of the name combination employed
+by me; (3) all other name combinations in chronological order that have been
+applied to the subspecies concerned.</p>
+
+<p>The localities of specimens examined are listed by country from north to
+south. Within a country, the listing is by state, beginning with the northwesternmost
+state and proceeding by tiers (west to east) to the southeasternmost
+state. Within a state of the United States, the listing is by counties in the
+same geographic order as described for states. Within any county in the
+United States, within any state in México, and within any country in Central
+America, the listing of localities is from north to south. When more than
+one locality is on the same line of latitude, the westernmost locality is listed
+first. Marginal localities for each subspecies are listed in a paragraph at the
+end of each account. Each marginal locality is mapped by means of a circle.
+The circles are listed in clockwise order, beginning with the northernmost.
+When more than one of these localities lies on the same line of latitude, the
+westernmost is cited first. Localities not represented on the distribution maps,
+so as to avoid undue crowding of symbols, are italicized in the lists of specimens
+examined.</p>
+
+<p><span class="pagenum"><a name="Page_586" id="Page_586">[Pg 586]</a></span></p>
+<div class="fig_center">
+<a name="fig2" id="fig2"></a>
+<img src="images/fig_2.png" width="470" height="509" alt="" /><br />
+<div class="fig_caption"><span class="smcap">Fig. 2.</span> Occlusal views of molars. &#215; 13.<br />
+<br />
+<table style="text-align: left" summary="teeth">
+<tr>
+  <td class="vtop">A.</td>
+  <td><i>B. taylori analogous</i>, subadult, female, No. 28102 KU, 4 km. ENE Tlalmanalco,
+     2290 meters, Estado de México. Right, upper molars.</td>
+</tr>
+<tr>
+  <td class="vtop">B.</td>
+  <td><i>B. musculus musculus</i>, subadult, male, No. 45456 USNM, Colima, Colima,
+     México. Left, upper molars.</td>
+</tr>
+<tr>
+  <td class="vtop">A&#39;.</td>
+  <td><i>B. taylori analogous</i>, subadult, female, No. 28102 KU 4 km. ENE Tlalmanalco,
+     2290 meters, Estado de México. Left, lower molars.</td>
+</tr>
+<tr>
+  <td class="vtop">B&#39;.</td>
+  <td><i>B. musculus musculus</i>, subadult, male, No. 45456 USNM, Colima, Colima,
+     México. Right, lower molars.</td>
+</tr>
+</table>
+<br />
+</div>
+</div>
+
+<p><span class="pagenum"><a name="Page_587" id="Page_587">[Pg 587]</a></span></p>
+
+<p>The largest single collection of pygmy mice is in the University of Kansas
+Museum of Natural History, and, unless otherwise indicated, specimens cited in
+the taxonomic accounts beyond are there.</p>
+
+<p>I am indebted to the following named institutions and persons for making
+specimens available for study:</p>
+
+<div class="references">&nbsp;&nbsp;American Museum of Natural History, G. G. Goodwin and R. G. VanGelder.</div>
+
+<div class="references">&nbsp;&nbsp;Carnegie Museum, J. K. Doutt.</div>
+
+<div class="references">&nbsp;&nbsp;California Academy of Sciences, Robert T. Orr.</div>
+
+<div class="references">&nbsp;&nbsp;Chicago Natural History Museum, Phillip H. Hershkovitz.</div>
+
+<div class="references">&nbsp;&nbsp;Cleveland Museum of Natural History (Collection now a part of Museum of
+Zoology, University of Michigan, W. H. Burt, E. T. Hooper).</div>
+
+<div class="references">&nbsp;&nbsp;Louisiana State University, Museum of Natural History, George H.
+Lowery, Jr.</div>
+
+<div class="references">&nbsp;&nbsp;Los Angeles County Museum, Charles A. McLaughlin.</div>
+
+<div class="references">&nbsp;&nbsp;United States National Museum (Biological Survey Collections), David A.
+Johnson, and Viola S. Schantz.</div>
+
+<div class="references">&nbsp;&nbsp;United States National Museum, Division of Vertebrate Paleontology, C.
+Lewis Gazin.</div>
+
+<div class="references">&nbsp;&nbsp;University of Arizona, E. L. Cockrum, and G. VR. Bradshaw.</div>
+
+<div class="references">&nbsp;&nbsp;University of California, Museum of Vertebrate Zoology, Seth B. Benson,
+and W. Z. Lidicker.</div>
+
+<div class="references">&nbsp;&nbsp;University of Illinois, Museum of Natural History, Donald F. Hoffmeister.</div>
+
+<div class="references">&nbsp;&nbsp;University of Michigan, Museum of Zoology, W. H. Burt, E. T. Hooper, and
+Claude W. Hibbard.</div>
+
+<div class="references">&nbsp;&nbsp;University of New Mexico, James S. Findley.</div>
+
+<div class="references">&nbsp;&nbsp;University of Texas, Frank W. Blair.</div>
+
+<div class="references">&nbsp;&nbsp;Texas A &amp; M, Cooperative Wildlife Research Collection, W. B. Davis.</div>
+
+<div class="references">&nbsp;&nbsp;The Museum, Michigan State University, Rollin H. Baker.</div>
+
+<div class="references">&nbsp;&nbsp;University of Florida Collections, James N. Layne.</div>
+
+<p>I am especially grateful to Professor E. Raymond Hall who guided me in
+my study and gave critical assistance with the manuscript. Additional appreciated
+suggestions were made by Professors A. Byron Leonard, Robert W. Wilson,
+Henry S. Fitch, Ronald L. McGregor, and fellow graduate students. For the
+illustrations, I am indebted to Mrs. Lorna Cordonnier, Miss Lucy Remple and
+Mrs. Connie Spitz. Mr. B. J. Wilks of the University of Texas, Department
+of Zoology, provided a number of living pygmy mice for study in captivity.
+Mr. J. Raymond Alcorn and his son, Albert, collected a large share of specimens
+of pygmy mice now in the University of Kansas, Museum of Natural History.
+My wife, Patricia, aided me in secretarial work and typing of the manuscript.</p>
+
+<p>For financial assistance, I am indebted to the National Science Foundation
+when I was a Research Assistant, to the Sigma Xi-RESA Research Fund for a
+Grant-in-Aid, and to the Kansas University Endowment Association through
+its A. Henley Aid Fund, and the Watkins Fund for out-of-state field work by
+the Museum of Natural History.</p>
+
+
+<div class="caption2"><a name="PALEONTOLOGY_OF_THE_GENUS" id="PALEONTOLOGY_OF_THE_GENUS"></a>PALEONTOLOGY OF THE GENUS</div>
+
+<p>Five fossil species, all extinct, have been assigned to the genus
+and range in time from early late Pliocene (Saw Rock Canyon
+fauna of Hibbard, 1953:408) to Mid-Pleistocene (see Hibbard,
+<span class="pagenum"><a name="Page_588" id="Page_588">[Pg 588]</a></span>
+1958:25, who assigns the Curtis Ranch fauna to late Kansan or
+early Yarmouth).</p>
+
+<p>I examined all known fossil material and compared it with Recent
+material. When the antiquity of the genus is considered, the degree
+of difference between the oldest fossil species and the two living
+species is much less than might be expected.</p>
+
+
+<div class="caption3"><a name="Baiomys_sawrockensis" id="Baiomys_sawrockensis"></a>
+<b>Baiomys sawrockensis</b> Hibbard</div>
+
+<div class="species_ref"><i>Baiomys sawrockensis</i> Hibbard, Papers Mich. Acad. Sci., Arts and Letters,
+38:402, April 27, 1953.</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;No. 27506, Univ. Michigan; left mandibular ramus bearing m1-m3
+and incisor; Saw Rock Canyon, early late Pliocene, XI member of the Rexroad
+formation, sec. 36, T. 34 S, R. 31 W, Seward County, Kansas (University
+of Kansas, Locality 6).</p>
+
+<p><i>Referred material.</i>&mdash;Univ. Michigan, Nos. 25781, 27503-27505, 28159-28165,
+29708-29715, 31015.</p>
+
+<p><i>Diagnosis.</i>&mdash;Ramus of medium size to small for the genus; lower incisor
+broad, moderately recurved; diastemal region broad; anterior median fold
+between anterior labial conulid and anterior lingual conulid of m1 deep; primary
+first fold between anteroconulid and protoconid of m2 deep; cingular
+ridge (ectolophid) at entrance to posteroexternal reëntrant valley (major fold,
+see <a href="#fig2">Figure 2</a>) between protoconid and hypoconid of m1 and m2; average
+and extreme measurements of lower molar row of eight specimens are, 2.65
+(2.5-2.7).</p>
+
+<p><i>Comparisons.</i>&mdash;For comparisons with <i>B. brachygnathus</i>, see account of that
+species. From <i>B. rexroadi</i>, <i>B. sawrockensis</i> differs in: anterior median fold of
+m1 deeper; incisor narrower; diastemal region broader; coronoid process
+broader and better developed; cingular ridges (ectolophids and mesolophids)
+more pronounced in their development; incisors less proödont, more retrodont.</p>
+
+<p>From <i>B. kolbi</i>, <i>B. sawrockensis</i> differs in: crowns of molars narrower;
+incisors less proödont; cingular ridges (ectolophids and mesolophids) of m1
+and m2 more pronounced in their development.</p>
+
+<p>From <i>B. minimus</i>, <i>B. sawrockensis</i> differs in: incisor less procumbent;
+masseteric ridge extending farther anteriorly; anterior cingulum of m2 slightly
+larger.</p>
+
+<p>From <i>B. musculus</i>, <i>B. sawrockensis</i> differs in: over-all size of jaw and
+molar row less; diastema more acutely curved; incisors shorter; anterior
+median fold of m1 slightly deeper.</p>
+
+<p>From <i>B. taylori</i>, <i>B. sawrockensis</i> differs in: m1 and m2 smaller; cingular
+ridges in m1 and m2 more pronounced; anterolingual conulid farther forward;
+incisors shorter, more proödont; molar teeth depressed, less hypsodont; diastemal
+region broader, more acutely curved; masseteric ridge not extending so
+far anteriorly.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;<i>B. sawrockensis</i> is the oldest known pygmy mouse.
+The extreme development of the anterior median fold between the
+<span class="pagenum"><a name="Page_589" id="Page_589">[Pg 589]</a></span>
+anterolingual conulid and the anterolabial conulid is regarded as a
+primitive feature in the pygmy mice. In this character, the Recent
+species can be traced back in time through <i>B. minimus</i> to <i>B. sawrockensis</i>.
+<i>B. sawrockensis</i> resembles <i>Calomys laucha</i> of South
+America in general conformation of jaw and tooth structure. The
+molars of <i>sawrockensis</i> are smaller than those of <i>C. laucha</i>, and
+the anterolingual conulid of <i>sawrockensis</i> is farther forward.</p>
+
+
+<div class="caption3"><a name="Baiomys_rexroadi" id="Baiomys_rexroadi"></a>
+<b>Baiomys rexroadi</b> Hibbard</div>
+
+<div class="species_ref"><i>Baiomys rexroadi</i> Hibbard, Amer. Midland Nat., 26:351, September, 1941;
+Hibbard, Contrib. Mus. Paleo., Univ. Michigan, 8(2):145, June 29, 1950
+(part); Hibbard, Papers Mich. Acad. Sci., Arts and Letters, 38:403,
+April 27, 1953.</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;No. 4670, Univ. Kansas; left mandibular ramus bearing m1-m3, and
+incisor; Rexroad fauna, Locality no. 2, Upper Pliocene, Meade County, Kansas.</p>
+
+<p><i>Referred material.</i>&mdash;Univ. of Michigan Nos. 24840, 24851, 27493, 27496,
+27501, 28862-28867.</p>
+
+<p><i>Diagnosis.</i>&mdash;Ramus medium in size for the genus; incisors small, proödont;
+anterior median fold of m1 slight; cingulum of all molars poorly developed;
+average and external measurements of lower molar row of seven specimens
+are, 2.7 (2.6-3.0).</p>
+
+<p><i>Comparisons.</i>&mdash;For comparisons with <i>B. sawrockensis</i> and <i>B. minimus</i>, see
+accounts of those species. From <i>B. kolbi</i>, <i>B. rexroadi</i> differs in: over-all size
+of mandibular ramus, incisors, and molars smaller; anterior median fold of m1
+present, though poorly developed.</p>
+
+<p>From <i>B. brachygnathus</i>, <i>B. rexroadi</i> differs in: over-all size of mandibular
+ramus smaller; m3 larger; posterior cusps (hypoconid and entoconid) elongated;
+diastema shorter, less acutely recurved; incisors less proödont; cingular
+ridges of m1 and m2 less well-developed.</p>
+
+<p>From <i>B. musculus</i>, <i>B. rexroadi</i> differs in: over-all size of mandibular ramus
+less; cingular ridges of m1 and m2 less well-developed; incisors smaller, more
+proödont; molars less depressed.</p>
+
+<p>From <i>B. taylori</i>, <i>B. rexroadi</i> differs in: m3 more triangular, posterior part
+narrower; mental foramen closer to anterior root of m1; masseteric ridge closer
+to alveolus of m1; incisor shorter, more proödont; molars more depressed.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;Two maxillary tooth-rows and associated parts were
+studied. On one of these specimens, the M2 has a well-developed
+mesostyle; the anterior median fold of M1 is also well-developed.
+The other specimen possesses a low cingular ridge (enteroloph)
+between the protocone and the hypocone, a reduced cingular
+ridge (mesoloph) between the paracone and metacone of M1.
+On the second molar, M2, a mesostyle joins with the mesoloph
+somewhat in the fashion indicated by Hooper (1957:9, encircled
+number 2).</p>
+
+<p><span class="pagenum"><a name="Page_590" id="Page_590">[Pg 590]</a></span></p>
+
+<div class="caption3"><a name="Baiomys_kolbi" id="Baiomys_kolbi"></a>
+<b>Baiomys kolbi</b> Hibbard</div>
+
+<div class="species_ref"><i>Baiomys kolbi</i> Hibbard, Trans. Kansas Acad. Sci., 55:201, June 18, 1952;
+Hibbard, Papers Mich. Acad. Sci., Arts and Letters, 38:403, April 27,
+1953.</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;No. 24846, Univ. Michigan; right mandibular ramus bearing m1-m3
+and incisor; Fox Canyon, upper Pliocene, Rexroad formation, Rexroad fauna,
+Univ. Michigan Locality K1-47, sec. 35, T. 34 S, R. 30 W, XI Ranch, Meade
+County, Kansas.</p>
+
+<p><i>Referred material.</i>&mdash;Univ. Michigan Nos. 24845-24848, 27494, 27497,
+27499, 28566, 28861, 28878, 28880-28882, 28884, 28886.</p>
+
+<p><i>Diagnosis.</i>&mdash;Ramus of medium size to large for the genus; lower incisor
+short, narrow transversely, proödont; anterior median fold of m1 reduced or
+absent; cingular ridges of m1 and m2 moderately well-developed; m3 large
+relative to m1 and m2; average and extreme measurements of lower molars
+of seven specimens are, 3.0 (3.0-3.1).</p>
+
+<p><i>Comparisons.</i>&mdash;For comparisons with <i>B. sawrockensis</i> and <i>B. rexroadi</i>, see
+accounts of those species. From <i>B. brachygnathus</i>, <i>B. kolbi</i> differs in: molar
+row longer; m3 and jaw larger; diastema longer; masseteric ridge not so far
+forward; molars more depressed.</p>
+
+<p>From <i>B. minimus</i>, <i>B. kolbi</i> differs in: molar row longer; m3 larger; jaw
+larger; diastema not so acutely curved; incisor shorter, narrower transversely,
+more proödont.</p>
+
+<p>From <i>B. musculus</i>, <i>B. kolbi</i> differs in: anterior median fold of m1 slightly
+developed or absent, instead of well-developed; m3 larger (not reduced),
+external reëntrant valley broad and extending farther across crown of tooth;
+incisor smaller, and more proödont; cingular ridges of m1 and m2 less well-developed.</p>
+
+<p>From <i>B. taylori</i>, <i>B. kolbi</i> differs in: molars larger, more depressed; incisor
+shorter, more proödont; m3 smaller relative to m1 and m2; external reëntrant
+valley of m3 broad, extending farther across crown of tooth.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;The slight development or absence of the anterior
+median fold in <i>kolbi</i> suggests that it was specialized. The anterior
+median fold is well-developed in all species of <i>Baiomys</i> save <i>B.
+brachygnathus</i> and <i>B. taylori</i>, in which the fold is only slightly developed
+or absent. <i>B. kolbi</i> may have paralleled <i>B. taylori</i> in specialization
+for a diet of grasses and for a life in open country.</p>
+
+
+<div class="caption3"><a name="Baiomys_brachygnathus" id="Baiomys_brachygnathus"></a>
+<b>Baiomys brachygnathus</b> (Gidley)</div>
+
+<div class="species_ref"><i>Peromyscus brachygnathus</i> Gidley, U. S. Geol. Surv. Prof. Papers, 131:124,
+March 15, 1922.</div>
+
+<div class="species_ref"><i>Baiomys brachygnathus</i>, Hibbard, Amer. Midland Nat., 26:352, September,
+1941.</div>
+
+<div class="species_ref"><i>P. [eromyscus] brachygnathus</i>, Wilson, Carnegie Inst. Washington Publ.,
+473:33, May 21, 1936.</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;No. 10501, U. S. Nat. Mus.; right mandibular ramus bearing m1-m3,
+and incisor; 2 mi. NE Curtis Ranch house, near a line between sec. 28 and 29,
+T. 18 S, R. 21 E, Mid-Pleistocene (Hibbard, 1958:25), Cochise County,
+Arizona.</p>
+
+<p><span class="pagenum2"><a name="Page_591" id="Page_591">[Pg 591]</a></span></p>
+
+<p><i>Referred material.</i>&mdash;None.</p>
+
+<p><i>Diagnosis.</i>&mdash;Ramus small for the genus; m3 reduced; jaw reduced anteroposteriorly;
+incisor short, slender, proödont; cingular ridges well-developed,
+posterior ectolophid continuous from protoconid to hypoconid in m1 and m2;
+diastema short; length of molar row 2.8 mm.</p>
+
+<p><i>Comparisons.</i>&mdash;For comparisons with <i>B. rexroadi</i> and <i>B. kolbi</i>, see accounts
+of those species. From <i>B. minimus</i>, <i>B. brachygnathus</i> differs in: jaw not so
+slender anteriorly; masseteric ridge not so far anterior; cheek-teeth slightly
+broader, less depressed, therefore, more hypsodont; incisor shorter, more
+proödont.</p>
+
+<p>From <i>B. sawrockensis</i>, <i>B. brachygnathus</i> differs in: molar row slightly
+longer; teeth slightly less depressed; masseteric ridge extends farther anteriorly;
+incisors more proödont.</p>
+
+<p>From <i>B. musculus</i>, <i>B. brachygnathus</i> differs in: jaw smaller; molar row
+slightly shorter; molars less depressed; incisors slender, shorter, narrower, and
+more proödont.</p>
+
+<p>From <i>B. taylori</i>, <i>B. brachygnathus</i> differs in: incisor more slender, shorter,
+more proödont; diastema shorter.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;The molar teeth of <i>B. brachygnathus</i>, although worn,
+resemble those of <i>B. taylori</i> more than those of any known fossil
+species. Gidley (1922:124) stated that the absence of the divided
+anterior lobe of the first molar (anterior median fold) in <i>brachygnathus</i>
+was one of the chief characters separating <i>brachygnathus</i>
+from <i>taylori</i>. In <i>taylori</i>, the anterior median fold characteristically
+is only slightly developed, and in some specimens is absent. <i>B.
+brachygnathus</i> differs from <i>taylori</i> chiefly in proödont incisors, which
+feature seems to preclude <i>brachygnathus</i> being ancestral to <i>taylori</i>.
+<i>B. brachygnathus</i> may have been a specialized divergence from
+<i>B. minimus</i>.</p>
+
+
+<div class="caption3"><a name="Baiomys_minimus" id="Baiomys_minimus"></a>
+<b>Baiomys minimus</b> (Gidley)</div>
+
+<div class="species_ref"><i>Peromyscus minimus</i> Gidley, U. S. Geol. Surv. Prof. Papers, 131:124, March
+15, 1922.</div>
+
+<div class="species_ref"><i>Baiomys minimus</i>, Hibbard, Amer. Midland Nat., 26:352, September, 1941;
+Gazin, Prof. U. S. Nat. Mus., 92(3155):488, 1942.</div>
+
+<div class="species_ref"><i>P. [eromyscus] minimus</i>, Wilson, Carnegie Inst. Washington Publ., 473:33,
+May 21, 1936.</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;No. 10500, U. S. Nat. Mus.; left mandibular ramus bearing m1-m3
+and incisor; 2 mi. S Benson, sec. 22, T. 17 S, R. 20 E, Late Pliocene (Blancan,
+Gazin, 1942:482), Cochise County, Arizona.</p>
+
+<p><i>Referred material.</i>&mdash;None.</p>
+
+<p><i>Diagnosis.</i>&mdash;Ramus small for the genus; molar teeth depressed; cingular
+ridges (ectolophids) of m1 and m2 well-developed; anterior median fold present
+(appearing larger owing to chip of enamel missing); external reëntrant fold of
+m3 progresses half way across crown of tooth; diastema short; incisor moderately
+large, recurved; length of molar row, 2.6 mm.</p>
+
+<p><i>Comparisons.</i>&mdash;For comparisons with <i>B. brachygnathus</i>, <i>B. kolbi</i>, and <i>B.
+sawrockensis</i>, see accounts of those species. From <i>B. rexroadi</i>, <i>B. minimus</i>
+<span class="pagenum2"><a name="Page_592" id="Page_592">[Pg 592]</a></span>
+differs in: anterior median fold deeper; incisor longer, more recurved, less
+proödont; molars slightly more depressed (though worn).</p>
+
+<p>From <i>B. musculus</i>, <i>B. minimus</i> differs in: over-all size of jaw and molars
+smaller; incisors shorter; masseteric ridge more depressed.</p>
+
+<p>From <i>B. taylori</i>, <i>B. minimus</i> differs in: anterior median fold slightly deeper;
+molar teeth more depressed; cingular ridges on m1 and m2 better developed;
+masseteric ridge more depressed.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;Gidley (1922:124) stated that <i>B. minimus</i> differed
+considerably from <i>B. taylori</i> in that the coronoid portion of the
+ascending ramus diverges at a wider angle from the alveolar part of
+the jaw. Study of large samples of lower jaws of <i>B. taylori</i> reveals
+considerable individual variation in the angle formed between the
+coronoid part of the jaw and the alveolar part.</p>
+
+<p><i>B. minimus</i>, except for its small size, is like <i>B. musculus</i> and is
+considered to be ancestral to that species.</p>
+
+
+<div class="caption2"><a name="PHYLETIC_TRENDS" id="PHYLETIC_TRENDS"></a>
+PHYLETIC TRENDS</div>
+
+<p>It seems that the important trends in phyletic development in the
+pygmy mice have been from an ancestral stock (see <a href="#fig3">Figure 3</a>) that
+possessed relatively brachydont teeth having raised cingular ridges
+(ectolophids and mesolophids) and relatively short orthodont to
+proödont incisors, to species having teeth more hypsodont on which
+cingular ridges were reduced, stylids were isolated or completely
+absent, and incisors were longer and more recurved or retrodont.
+<i>Baiomys sawrockensis</i>, or an unknown stock resembling it, might
+have been ancestral to the other known species. Of the four remaining
+fossil species, <i>B. kolbi</i> seems least likely to have been ancestral
+to the two living species, owing to its proödont incisors,
+reduction of cingular ridges, loss of an anterior median fold in m1,
+and long mandibular tooth-row. <i>B. kolbi</i> may have been an early,
+specialized derivation from the ancestral stock. From his knowledge
+of the habitats of <i>B. musculus</i>, the larger species, and <i>B.
+taylori</i>, the smaller species, Hibbard (1952:203) suggests that <i>B.
+kolbi</i>, a large species, might have inhabited lowlands, and <i>B.
+rexroadi</i>, a small species, highlands. I have no evidence to dispute
+this suggestion except that <i>B. musculus</i> has more prominent cingular
+ridges (or at least vestiges of this lophid condition) than
+either <i>B. kolbi</i> or <i>B. rexroadi</i>. <i>B. musculus</i> (see <a href="#Page_610">page 610</a>) is less
+of an open grassland inhabitant than is <i>B. taylori</i>. Therefore, both
+<i>B. kolbi</i> and <i>B. rexroadi</i>, because of their poorly developed cingular
+ridges, might be expected to have lived in a relatively open
+grassland habitat.</p>
+
+<p><span class="pagenum"><a name="Page_593" id="Page_593">[Pg 593]</a></span></p>
+
+<p>The relationship of <i>B. rexroadi</i> to fossil species other than <i>B.
+kolbi</i> is not clear. Superficially, the former resembles <i>B. taylori</i>,
+but, owing to the specialized development of the molars of <i>rexroadi</i>,
+it could hardly have been ancestral to either of the living
+species. The resemblance of <i>B. rexroadi</i> to <i>B. taylori</i> may result
+from each having occupied the same ecological niche in different
+periods. The incisors of <i>B. rexroadi</i>, however, are much shorter
+than those of <i>B. taylori</i> and suggest somewhat different food habits.</p>
+
+<p><i>B. minimus</i> seemingly is more closely related to <i>B. sawrockensis</i>
+and <i>B. musculus</i> than to the other described species. The development
+of the cingular ridges leads one to suspect that <i>B. minimus</i>
+was the ancestor of <i>B. musculus</i>. <i>B. minimus</i> may have been derived
+from a <i>sawrockensis</i>-like stock and probably gave rise to <i>B.
+musculus</i>.</p>
+
+<p>Hershkovitz (1955:643-644) suggests that "&#8230; primitive
+brachydont, buno-mesolophodont cricetines have survived &#8230;
+in forested parts of the range," whereas "&#8230; the progressive
+branch of cricetines with mesoloph absent or vestigal, has become
+increasingly specialized for life in open country and a diet of
+grasses." Species of the genus <i>Baiomys</i> can be divided into two
+morphological groups. One group, composed of <i>B. sawrockensis</i>,
+<i>B. minimus</i>, and <i>B. musculus</i>, includes those species, the teeth of
+which were relatively brachydont and had prominently developed
+cingular ridges (ectolophids or mesolophids) or, at least, showed
+some development of these ridges. <i>B. sawrockensis</i> probably lived
+in semi-wooded to shrubby habitats. According to Hibbard (1953:409),
+"The Saw Rock Canyon fauna lived in that area at a time
+when conditions were comparable to the conditions at the time the
+Rexroad fauna lived." The conditions in which the Rexroad fauna
+lived are discussed by Hibbard (1941:95). Presumably, there were
+at least some well-wooded situations, and the climate was warm.
+<i>B. sawrockensis</i> probably inhabited denser vegetation than did <i>B.
+minimus</i> or than does <i>B. musculus</i>. The teeth of the second group
+(<i>B. kolbi</i>, <i>B. rexroadi</i>, <i>B. brachygnathus</i>, and <i>B. taylori</i>) lack cingular
+ridges or have them much reduced and have more hypsodont
+molars. The three fossil species probably inhabited relatively open
+grassland. This assumption is based largely on the known habitat
+of <i>B. taylori</i> (see <a href="#Page_632">page 632</a>).</p>
+
+<p>The suggested grouping, based on supposed similarities in niches
+inhabited by the extinct species, does not necessarily indicate degree
+of relationship. <i>B. taylori</i> probably was not derived from an
+<span class="pagenum"><a name="Page_594" id="Page_594">[Pg 594]</a></span>
+ancestor like <i>B. rexroadi</i> or <i>B. kolbi</i>, although, in certain characters,
+the three species resemble one another. <i>B. kolbi</i> and <i>B. rexroadi</i>
+were already specialized in Blancan times, probably for living on
+grassland. <i>B. taylori</i> shows only a slight advance in specialization
+of molar structures compared to either of the aforementioned species
+but is slightly smaller and does have longer and more recurved incisors.
+If only morphological criteria of lower jaws were considered,
+without recourse to other data derived from the study of many
+samples of populations of the living species, time alone might account
+for the differences among <i>B. taylori</i>, <i>B. rexroadi</i>, and <i>B. kolbi</i>.
+The available evidence (see <a href="#Page_658">page 658</a>) suggests, however, that <i>B.
+taylori</i> was derived from the <i>B. sawrockensis</i>-<i>B. minimus</i>-<i>B. musculus</i>
+line.</p>
+
+<div class="fig_center">
+<a name="fig3" id="fig3"></a>
+<img src="images/fig_3.png" width="578" height="361" alt="" />
+<div class="fig_caption"><span class="smcap">Fig. 3.</span> Diagram indicating probable relationships of living and extinct species
+of pygmy mice.</div>
+</div>
+
+<p><i>Baiomys</i> seems to have undergone little basic evolutionary and
+morphological change since Late Pliocene time. According to
+Simpson (1945:207), hesperomine rodents as a group have undergone
+little basic evolution, and "The rapid evolution of new genera
+was more a matter of segregation of characters in a group with a
+great variation than of the origin of significantly new characters."
+Perhaps, the living southern pygmy mouse retains many basic characteristics
+of one of the early North American cricetine-like stocks
+that emigrated to South America near the end of the Pliocene epoch.
+<span class="pagenum"><a name="Page_595" id="Page_595">[Pg 595]</a></span>
+There is much to suggest close relationship of the pygmy mice to
+certain species of South American hesperomine rodents of the
+genus <i>Calomys</i>.</p>
+
+
+
+
+<div class="caption2"><a name="NON-GEOGRAPHIC_VARIATION" id="NON-GEOGRAPHIC_VARIATION"></a>NON-GEOGRAPHIC VARIATION</div>
+
+
+<p>Non-geographic variation in pygmy mice (variation in a single
+population resulting from age, individual, seasonal, and secondary
+sexual differences) has been but little studied in the past. Mearns
+(1907:381) figured progressive stages of wear on the teeth of
+<i>B. taylori</i>; Osgood (1909:252) and Blair (1941:380) referred to
+changes in dentition, weights, and pelages.</p>
+
+<p>The largest samples available for this study were 47 <i>B. taylori</i> from
+the vicinity of Altamira (6 mi. N, 6 mi. W; 5 mi. N, 5 mi. W; 1 mi. S),
+Tamaulipas, and 44 <i>B. musculus</i> from El Salvador (1 mi. S Los
+Planes, and 1 mi. NW San Salvador&mdash;two localities 3 miles apart).</p>
+
+
+<div class="caption3"><a name="VARIATION_WITH_AGE" id="VARIATION_WITH_AGE"></a>
+VARIATION WITH AGE</div>
+
+<p>Specimens of both species were segregated into five categories:
+Juveniles, young, subadults, adults, and old adults. Juvenal and
+young pygmy mice are readily separable from the other three categories;
+subadults are less easily distinguished from adults. In order
+to obtain an accurate understanding of geographic variation in these
+mice, only adults should be used in making taxonomic comparisons.</p>
+
+<p><i>Juveniles.</i>&mdash;Nestling mice yet unweaned; sutures in cranium incompletely
+closed; bony parts of skull fragile; M3 and m3 not
+erupted or only partly erupted and not protruding above margins
+of alveoli.</p>
+
+<p>At birth, juveniles are pink, without pelage except for the mystacial
+vibrissae and a few hairs about the eye. Blair (<i>op. cit.</i>:381)
+recorded changes with age in color of the skin of new-born and
+suckling pygmy mice. Data obtained by me from three litters born
+in captivity agree with his findings. Pygmy mice are weaned when
+17 to 24 days old. At that time, the mice possess a fine, but not
+dense, dusky-gray fur.</p>
+
+<p><i>Young.</i>&mdash;Weaned mice; cranium fragile; sutures between frontals
+and parietals, interparietal and parietals, basioccipital and basisphenoid,
+basisphenoid and presphenoid, premaxillaries and maxillaries
+widely open; M3 and m3 erupted beyond margins of their
+alveoli (molars erupt from anterior to posterior; M3 and m3, therefore,
+are last to erupt); in some specimens, molars slightly worn;
+pelage still dusky and relatively fine and sparse.</p>
+
+<p><span class="pagenum"><a name="Page_596" id="Page_596">[Pg 596]</a></span></p>
+
+<p><i>Subadults.</i>&mdash;Sutures between bones of skull less widely open than
+in young; epiphyses of long bones incompletely coalesced to shaft;
+relative to length of skull, braincase higher and rostrum shorter than
+in adults; all cusps worn, but dentine not occlusally confluent; primary
+first and second folds of third upper molars present; primary
+first fold and major fold of lower molars visible; pelage a subtle
+mixture of colors of young and adult, but resembling most that of
+adult; molts into postjuvenal pelage between 46 and 50 days.</p>
+
+<p><i>Adults.</i>&mdash;Sutures of skull, and those between epiphyses and shaft
+of long bones obliterated except that, in some mice, sutures of skull
+persist between frontoparietal, and interparietal; cusps of molars so
+worn that dentine occlusally confluent; small island of enamel in
+third upper and lower molars of some specimens; relative to length
+of skull, cranium lower, rostrum longer, and interorbital region narrower
+than in subadult; cranium appears to be more flattened dorsoventrally;
+between subadult and adult stages, principal growth
+occurs in basioccipital, basisphenoid, frontals, and parietals; nasals
+grow less.</p>
+
+<p>Although all bones of the skull grow in the subadult and early
+adult stages (see <a href="#Table_1">table 1</a>), the above-named bones grow faster than
+others and thus cause the general flattening of the skull, typical of
+adults (similar to that reported by Hoffmeister, 1951:7). The body
+continues to lengthen, accounting for the increase in total length
+of the adult (see <a href="#Table_1">table 1</a>). Hind foot, tail and ear, reach their
+maximum lengths by subadult stage. Adult pelage has been acquired,
+and the color is brighter than in either subadults or old
+adults.</p>
+
+<p><i>Old Adults.</i>&mdash;Characterized principally by well-worn molars; only
+thin peripheral band of enamel along with slight evidence of any
+primary or secondary folds on any teeth remain; all bones of skull
+coalesced; epiphyses and shafts of long bones ankylosed; small bony
+protuberances on many skulls; pelage usually ragged, tips of the
+hairs being worn away; white flecking and spotting not common,
+but occurs in some adults.</p>
+
+<div class="center smcap"><a name="Table_1" id="Table_1"></a>
+Table 1.&mdash;Average and Extreme Measurements (in Millimeters) of Skulls of Five Age-groups<br />
+of Baiomys taylori from vic. (see <a href="#Page_595">p. 595</a>) Altamira, Tamaulipas, Mexico.</div>
+<br />
+<table width="80%" style="text-align: center" summary="Skull Dimensions">
+<tr>
+  <td class="brdtp2 brdbt">Age groups</td>
+  <td class="brdtp2 brdbt brdlf">Juvenile</td>
+  <td class="brdtp2 brdbt brdlf">Young</td>
+  <td class="brdtp2 brdbt brdlf">Subadult</td>
+  <td class="brdtp2 brdbt brdlf">Adult</td>
+  <td class="brdtp2 brdbt brdlf">Old adult</td>
+</tr>
+<tr>
+  <td class="text_lf">Number examined</td>
+  <td class="brdlf">3</td>
+  <td class="brdlf">3</td>
+  <td class="brdlf">14</td>
+  <td class="brdlf">19</td>
+  <td class="brdlf">8</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Total length</td>
+  <td class="brdlf">77.0<br />(74-79)</td>
+  <td class="brdlf">92.6<br />(89-96)</td>
+  <td class="brdlf">97.6<br />(91-103)</td>
+  <td class="brdlf">99.9<br />(93-105)</td>
+  <td class="brdlf">101.6<br />(98-107)</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Length of tail</td>
+  <td class="brdlf">27.3<br />(24-29)</td>
+  <td class="brdlf">39.3<br />(37-41)</td>
+  <td class="brdlf">40.4<br />(36-43)</td>
+  <td class="brdlf">39.8<br />(35-45)</td>
+  <td class="brdlf">40.9<br />(38-45)</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Length of body</td>
+  <td class="brdlf">49.6<br />(49-50)</td>
+  <td class="brdlf">53.3<br />(52-55)</td>
+  <td class="brdlf">57.0<br />(51-61)</td>
+  <td class="brdlf">60.0<br />(56-67)</td>
+  <td class="brdlf">60.7<br />(57-67)</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Length of hind foot</td>
+  <td class="brdlf">11.0<br />(11)</td>
+  <td class="brdlf">13.6<br />(13-14)</td>
+  <td class="brdlf">14.3<br />(13.5-15.0)</td>
+  <td class="brdlf">14.5<br />(14-15)</td>
+  <td class="brdlf">14.2<br />(13-15)</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Occipitonasal length</td>
+  <td class="brdlf">14.2<br />(13.6-15.2)</td>
+  <td class="brdlf">16.3<br />(15.8-16.9)</td>
+  <td class="brdlf">17.1<br />(16.7-17.6)</td>
+  <td class="brdlf">17.7<br />(17.2-18.3)</td>
+  <td class="brdlf">17.8<br />(17.6-18.1)</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Zygomatic breadth</td>
+  <td class="brdlf">8.1<br />(7.8- 8.6)</td>
+  <td class="brdlf">8.7<br />(8.6-8.8)</td>
+  <td class="brdlf">8.9<br />(8.6-9.3)</td>
+  <td class="brdlf">9.3<br />(9.0-9.6)</td>
+  <td class="brdlf">9.4<br />(9.1-9.6)</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Interorbital breadth</td>
+  <td class="brdlf">3.4<br />(3.3- 3.5)</td>
+  <td class="brdlf">3.4<br />(3.3-3.6)</td>
+  <td class="brdlf">3.4<br />(3.3-3.6)</td>
+  <td class="brdlf">3.6<br />(3.4-3.8)</td>
+  <td class="brdlf">3.5<br />(3.3-3.6)</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Incisive foramina (length)</td>
+  <td class="brdlf">2.9<br />(2.8- 2.9)</td>
+  <td class="brdlf">3.5<br />(3.4-3.6)</td>
+  <td class="brdlf">3.7<br />(3.6-3.9)</td>
+  <td class="brdlf">3.9<br />(3.6-4.1)</td>
+  <td class="brdlf">3.9<br />(3.5-4.0)</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Depth of cranium</td>
+  <td class="brdlf">5.9<br />(5.6- 6.2)</td>
+  <td class="brdlf">6.5<br />(6.3-6.8)</td>
+  <td class="brdlf">6.5<br />(6.2-6.8)</td>
+  <td class="brdlf">6.7<br />(6.4-7.0)</td>
+  <td class="brdlf">6.8<br />(6.5-7.1)</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Alveolar length, upper molars</td>
+  <td class="brdlf">2.7<br />(2.5- 2.8)</td>
+  <td class="brdlf">2.9<br />(2.9-3.0)</td>
+  <td class="brdlf">2.9<br />(2.8-3.1)</td>
+  <td class="brdlf">3.0<br />(2.9-3.2)</td>
+  <td class="brdlf">3.0<br />(3.0-3.1)</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Postpalatal length</td>
+  <td class="brdlf">4.8<br />(4.5- 5.3)</td>
+  <td class="brdlf">5.9<br />(5.8-6.0)</td>
+  <td class="brdlf">6.2<br />(5.8-6.6)</td>
+  <td class="brdlf">6.5<br />(6.2-7.2)</td>
+  <td class="brdlf">6.5<br />(6.3-6.7)</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf brdbt">Breadth of braincase</td>
+  <td class="brdbt brdlf">8.1<br />(7.8- 8.7)</td>
+  <td class="brdbt brdlf">8.5<br />(8.5)</td>
+  <td class="brdbt brdlf">8.4<br />(8.0-8.7)</td>
+  <td class="brdbt brdlf">8.6<br />(8.3-8.9)</td>
+  <td class="brdbt brdlf">8.6<br />(8.4-8.8)</td>
+</tr>
+</table>
+
+<p><span class="pagenum"><a name="Page_597" id="Page_597">[Pg 597]</a></span></p>
+
+
+<div class="caption3"><a name="SECONDARY_SEXUAL_VARIATION" id="SECONDARY_SEXUAL_VARIATION"></a>
+SECONDARY SEXUAL VARIATION</div>
+
+<p>The method employed by Dice and Leraas (1936:2) was used
+to measure the secondary sexual differences, if there were any, in
+each of several age classes. As pointed out by Hooper (1952b:11),
+individual variation in small samples can obscure secondary sexual
+differences. The samples of <i>B. taylori</i> from the vicinity (see page
+595) of Altamira, Tamaulipas, and the samples of <i>B. musculus</i> from
+El Salvador (<a href="#Table_2">table 2</a>) were large enough to prevent individual
+variation from obscuring sexual differences. Nevertheless, no significant
+secondary sexual differences were found in either <i>B. taylori</i>
+or <i>B. musculus</i> (see <a href="#Table_2">table 2</a>). Therefore, the sexes have been considered
+together for purposes of geographic studies.</p>
+
+<div class="center smcap"><a name="Table_2" id="Table_2"></a>
+Table 2.&mdash;Analysis of Secondary Sexual Variation in Adult B. taylori Vicinity of (see <a href="#Page_595">p. 595</a>)<br />
+Altamira, Tamaulipas, and Adult B. musculus from El Salvador (see <a href="#Page_595">p. 595</a>).<br />
+(One Standard Deviation on Either Side of the Mean is Given.)</div>
+<br />
+<table width="80%" style="text-align: center" summary="Sexual Variation">
+<tr>
+  <td rowspan="2" class="brdtp2 brdbt">Character</td>
+  <td colspan="2" class="brdtp2 brdbt brdlf">Baiomys taylori</td>
+  <td colspan="2" class="brdtp2 brdbt brdlf">Baiomys musculus</td>
+</tr>
+<tr>
+  <td class="brdbt brdlf">21 Males</td>
+  <td class="brdbt brdlf">18 Females</td>
+  <td class="brdbt brdlf">17 Males</td>
+  <td class="brdbt brdlf">13 Females</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Total length</td>
+  <td class="brdlf">98.4 &#177; 2.95</td>
+  <td class="brdlf">100.5 &#177; 4.72</td>
+  <td class="brdlf">112.04 &#177; 5.49</td>
+  <td class="brdlf">113.12 &#177; 4.23</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Length of tail</td>
+  <td class="brdlf">40.1 &#177; 2.31</td>
+  <td class="brdlf">40.3 &#177; 2.39</td>
+  <td class="brdlf">47.12 &#177; 2.95</td>
+  <td class="brdlf">45.70 &#177; 2.92</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Length of body</td>
+  <td class="brdlf">57.83 &#177; 1.65</td>
+  <td class="brdlf">60.10 &#177; 4.13</td>
+  <td class="brdlf">66.67 &#177; 3.97</td>
+  <td class="brdlf">67.75 &#177; 2.38</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Length of<br />hind foot</td>
+  <td class="brdlf">14.21 &#177; .53</td>
+  <td class="brdlf">14.44 &#177; .51</td>
+  <td class="brdlf">15.60 &#177; .49</td>
+  <td class="brdlf">15.38 &#177; .64</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Length of ear</td>
+  <td class="brdlf">10.00 &#177; .00</td>
+  <td class="brdlf">10.00 &#177; .00</td>
+  <td class="brdlf">11.80 &#177; .65</td>
+  <td class="brdlf">12.00 &#177; .41</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Occipitonasal<br />length</td>
+  <td class="brdlf">17.48 &#177; .40</td>
+  <td class="brdlf">17.47 &#177; .47</td>
+  <td class="brdlf">19.32 &#177; .35</td>
+  <td class="brdlf">19.04 &#177; .44</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Zygomatic<br />breadth</td>
+  <td class="brdlf">9.17 &#177; .33</td>
+  <td class="brdlf">9.15 &#177; .30</td>
+  <td class="brdlf">9.84 &#177; .21</td>
+  <td class="brdlf">9.91 &#177; .28</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Least<br />interorbital<br />breadth</td>
+  <td class="brdlf">3.53 &#177; .11</td>
+  <td class="brdlf">3.48 &#177; .11</td>
+  <td class="brdlf">3.88 &#177; .08</td>
+  <td class="brdlf">3.88 &#177; .12</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Postpalatal<br />length</td>
+  <td class="brdlf">6.35 &#177; .19</td>
+  <td class="brdlf">6.38 &#177; .30</td>
+  <td class="brdlf">7.11 &#177; .15</td>
+  <td class="brdlf">6.95 &#177; .20</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Depth<br />of cranium</td>
+  <td class="brdlf">6.65 &#177; .24</td>
+  <td class="brdlf">6.61 &#177; .17</td>
+  <td class="brdlf">7.10 &#177; .18</td>
+  <td class="brdlf">7.08 &#177; .18</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Incisive<br />foramina<br />(length)</td>
+  <td class="brdlf">3.82 &#177; .15</td>
+  <td class="brdlf">3.81 &#177; .18</td>
+  <td class="brdlf">4.43 &#177; .11</td>
+  <td class="brdlf">4.35 &#177; .14</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Length<br />of rostrum</td>
+  <td class="brdlf">5.87 &#177; .20</td>
+  <td class="brdlf">5.88 &#177; .21</td>
+  <td class="brdlf">6.81 &#177; .16</td>
+  <td class="brdlf">6.66 &#177; .31</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Breadth<br />of braincase</td>
+  <td class="brdlf">8.54 &#177; .23</td>
+  <td class="brdlf">8.52 &#177; .12</td>
+  <td class="brdlf">9.84 &#177; .38</td>
+  <td class="brdlf">9.52 &#177; .20</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="brdbt text_lf">Alveolar<br />length,<br />upper molars</td>
+  <td class="brdbt brdlf">2.98 &#177; .08</td>
+  <td class="brdbt brdlf">3.01 &#177; .08</td>
+  <td class="brdbt brdlf">3.20 &#177; .09</td>
+  <td class="brdbt brdlf">3.24 &#177; .10</td>
+</tr>
+</table>
+
+
+<div class="caption3"><a name="INDIVIDUAL_VARIATION" id="INDIVIDUAL_VARIATION"></a>
+INDIVIDUAL VARIATION</div>
+
+<p>Length of tail varied more than any other measurement used by
+me in taxonomic comparisons. Clark (1941:298), Hoffmeister
+(1951:16), and Van Gelder (1959:239) point out that external
+measurements generally are more variable than measurements of
+the cranium, probably because different techniques of measuring
+are employed by different collectors. As can be noted in <a href="#Table_3">table 3</a>,
+females varied more than males.</p>
+
+<p><span class="pagenum"><a name="Page_598" id="Page_598">[Pg 598]</a></span></p>
+
+<p>In the 3520 specimens examined, an extra tooth was observed in
+only one (see Hooper, 1955:298). The left mandibular tooth-row
+of an adult male (USNM 71539) from Omentepec, Guerrero, is
+worn more than the right one. Irregularities in number of teeth
+and abnormalities in individual teeth seem to be rare in pygmy
+mice.</p>
+
+<div class="center smcap"><a name="Table_3" id="Table_3"></a>
+Table 3.&mdash;Individual Variation: Coefficients of Variation for Dimensions of External<br />
+and Cranial Parts in a Population of B. Musculus and B. Taylori.</div>
+<br />
+<table width="80%" style="text-align: center" summary="physical variations">
+<tr>
+  <td class="brdtp2 brdbt" rowspan="3">Measurement</td>
+  <td class="brdtp2 brdbt brdlf" colspan="2">Baiomys taylori</td>
+  <td class="brdtp2 brdbt brdlf" colspan="2">Baiomys musculus</td>
+</tr>
+<tr>
+  <td class="brdlf" colspan="2">Vic. (see <a href="#Page_595">page 595</a>)<br />Altamira, Tamaulipas</td>
+  <td class="brdlf" colspan="2">Vic. (see <a href="#Page_595">page 595</a>)<br />El Salvador</td>
+</tr>
+<tr>
+  <td class="brdtp brdbt brdlf">21 Males<br />C. V.</td>
+  <td class="brdtp brdbt brdlf">18 Females<br />C. V.</td>
+  <td class="brdtp brdbt brdlf">17 Males<br />C. V.</td>
+  <td class="brdtp brdbt brdlf">13 Females<br />C. V.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Total length</td>
+  <td class="brdlf">3.0</td>
+  <td class="brdlf">4.7</td>
+  <td class="brdlf">4.9</td>
+  <td class="brdlf">3.7</td>
+</tr>
+<tr>
+  <td class="text_lf">Length of tail</td>
+  <td class="brdlf">5.7</td>
+  <td class="brdlf">5.9</td>
+  <td class="brdlf">6.2</td>
+  <td class="brdlf">6.4</td>
+</tr>
+<tr>
+  <td class="text_lf">Length of body</td>
+  <td class="brdlf">2.8</td>
+  <td class="brdlf">5.0</td>
+  <td class="brdlf">5.9</td>
+  <td class="brdlf">3.5</td>
+</tr>
+<tr>
+  <td class="text_lf">Length of hind foot</td>
+  <td class="brdlf">3.7</td>
+  <td class="brdlf">3.4</td>
+  <td class="brdlf">3.0</td>
+  <td class="brdlf">4.1</td>
+</tr>
+<tr>
+  <td class="text_lf">Length of ear</td>
+  <td class="brdlf">0.0</td>
+  <td class="brdlf">0.0</td>
+  <td class="brdlf">5.5</td>
+  <td class="brdlf">3.3</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="text_lf">Occipitonasal length</td>
+  <td class="brdlf">2.2</td>
+  <td class="brdlf">2.7</td>
+  <td class="brdlf">1.8</td>
+  <td class="brdlf">2.3</td>
+</tr>
+<tr>
+  <td class="text_lf">Zygomatic breadth</td>
+  <td class="brdlf">3.6</td>
+  <td class="brdlf">3.3</td>
+  <td class="brdlf">2.2</td>
+  <td class="brdlf">2.7</td>
+</tr>
+<tr>
+  <td class="text_lf">Interorbital breadth</td>
+  <td class="brdlf">3.2</td>
+  <td class="brdlf">3.3</td>
+  <td class="brdlf">2.2</td>
+  <td class="brdlf">2.9</td>
+</tr>
+<tr>
+  <td class="text_lf">Incisive foramina<br />(length)</td>
+  <td class="brdlf">3.8</td>
+  <td class="brdlf">4.6</td>
+  <td class="brdlf">2.5</td>
+  <td class="brdlf">3.2</td>
+</tr>
+<tr>
+  <td class="text_lf">Depth of cranium</td>
+  <td class="brdlf">3.6</td>
+  <td class="brdlf">2.5</td>
+  <td class="brdlf">2.5</td>
+  <td class="brdlf">2.5</td>
+</tr>
+<tr>
+  <td class="text_lf">Alveolar length,<br />upper molars</td>
+  <td class="brdlf">2.7</td>
+  <td class="brdlf">2.5</td>
+  <td class="brdlf">2.8</td>
+  <td class="brdlf">3.2</td>
+</tr>
+<tr>
+  <td class="text_lf">Postpalatal length</td>
+  <td class="brdlf">3.1</td>
+  <td class="brdlf">4.7</td>
+  <td class="brdlf">2.1</td>
+  <td class="brdlf">2.9</td>
+</tr>
+<tr>
+  <td class="text_lf">Length of rostrum</td>
+  <td class="brdlf">3.3</td>
+  <td class="brdlf">3.6</td>
+  <td class="brdlf">2.4</td>
+  <td class="brdlf">4.7</td>
+</tr>
+<tr>
+  <td class="text_lf brdbt">Breadth of braincase</td>
+  <td class="brdbt brdlf">2.7</td>
+  <td class="brdbt brdlf">1.4</td>
+  <td class="brdbt brdlf">4.0</td>
+  <td class="brdbt brdlf">4.9</td>
+</tr>
+</table>
+
+<p>The posterior margin of the bony palate varies from semicircular
+to nearly V-shaped. The suture between the nasals and frontals
+varies from V-shaped to truncate to W-shaped. The maxillary part
+of the zygoma varies from broad to slender in dorsoventral width
+in both species.</p>
+
+
+<div class="caption3"><a name="PELAGE_AND_MOLTS" id="PELAGE_AND_MOLTS"></a>
+PELAGE AND MOLTS</div>
+
+<p>There are three distinct pelages, juvenal, postjuvenal, and adult.
+The sequences of molt and change of pelage from the juvenal, to
+the postjuvenal, and from it to adult, are essentially as reported for
+<i>Peromyscus</i> by Collins (1918:78-81; 1924:58-60) and Hoffmeister
+(1951:5). The juvenal pelage is uniformly dusky gray throughout
+except for the paler gray on the venter. In most juvenal mice, the
+<span class="pagenum"><a name="Page_599" id="Page_599">[Pg 599]</a></span>
+yellow to ochraceous pigments of the subterminal bands are reduced
+or absent. Unlike <i>Peromyscus</i>, <i>Baiomys</i> has bright brownish hairs
+on the head as the first evidence of the postjuvenal molt (see
+<a href="#Table_4">Figure 4, part a</a>). Blair (1941:381) reports adult pelage in pygmy
+mice being evident first at an age of 46 days. Two of my juveniles
+born in captivity began the postjuvenal molt on the 38th and 40th
+days. The area of new hairs on the head spreads most rapidly
+posteriorly. New hair appears ventrally and laterally at the end
+of 46 days (see <a href="#fig4">Figure 4, part b</a>). Hair replacement proceeds more
+slowly after the "saddle back" stage (described in <i>Peromyscus</i> by
+Collins, 1918:80) has been reached. That stage was reached in
+two pygmy mice at 52 days (see <a href="#fig4">Figure 4, part c</a>). Areas immediately
+posterior to the ears, in the scapular region, molt last. The
+postjuvenal pelage was seemingly complete in one captive pygmy
+mouse at the end of 60 days. Another captive failed to complete
+its growth of new pelage until two additional weeks had elapsed.
+Length of time required to molt in pygmy mice is about the same
+as that reported by Layne (1959:72) in <i>Reithrodontomys</i>.</p>
+
+<div class="fig_center">
+<a name="fig4" id="fig4"></a>
+<img src="images/fig_4.png" width="472" height="454" alt="" />
+<div class="fig_caption"><span class="smcap">Fig. 4.</span>
+Diagrams showing progress of the postjuvenal molt in pygmy mice.<br />
+For explanation of a, b, and c, see text. All approximately <sup>2</sup>/<sub>3</sub> natural size.</div>
+</div>
+
+<p><span class="pagenum"><a name="Page_600" id="Page_600">[Pg 600]</a></span></p>
+
+<p>If, after the postjuvenal molt, a distinct adult pelage is acquired
+it is difficult to separate it from the annual replacement of pelage
+in adults at the beginning of the rainy season. Adults of both species
+have been found in molt in all months of the year. To the north, in
+Texas, the pelage of winter-taken specimens is denser and slightly
+more reddish than that of specimens taken in spring and summer.
+In the two last mentioned seasons, the pelage is more uniformly
+gray. To the south, in México, the pelage is heavy and long in
+most specimens taken in the rainy season. The percentage of specimens
+in molt immediately before the rainy season and immediately
+before the dry season is slightly higher than in specimens taken at
+other times of the year. The adult or seasonal molt (both loss of
+old pelage and growth of new) resembles that in <i>Peromyscus truei
+gilberti</i>, described by Hoffmeister (1951:6) as proceeding "posteriorly
+as a wave over the entire back." The new hair is slightly
+brighter than the old. Old adults are usually in ragged pelage
+regardless of season; possibly only one regular annual change of
+pelage occurs in most animals before they die. Only one case of
+melanism was observed among all the specimens of both species
+examined. It was a young male <i>B. t. taylori</i>, KU 35943, from 6 mi.
+SW San Gerónimo, Coahuila, possessing black hairs throughout.
+Its hairs are longer and finer than those on specimens of comparable
+age and sex. No albino was found, although Stickel and Stickel
+(1949:145) record one&mdash;an adult male of <i>B. taylori</i>.</p>
+
+
+<div class="caption2"><a name="TAXONOMIC_CHARACTERS_AND_RELATIONSHIPS" id="TAXONOMIC_CHARACTERS_AND_RELATIONSHIPS"></a>
+TAXONOMIC CHARACTERS AND RELATIONSHIPS</div>
+
+<p><a name="External_parts" id="External_parts"></a>
+<i>External parts.</i>&mdash;Length of body, foot, ear, and tail are useful
+when considered together in distinguishing species and subspecies.
+I found as Hooper (1952a:91) did that length of ear in combination
+with length of hind foot suffices to identify nearly all specimens
+to species, especially where the two species occur together.</p>
+
+<p><a name="Pelage" id="Pelage"></a>
+<i>Pelage.</i>&mdash;Color in adults is of especial value in subspecific determination;
+the manner in which it varies geographically is described
+on pages 609, 630.</p>
+
+<p><a name="Skull" id="Skull"></a>
+<i>Skull.</i>&mdash;Difference in occipitonasal length and zygomatic breadth,
+both having low coefficients of variation, are useful in separating
+species, especially where they are sympatric. Shape of presphenoid,
+nasals, interparietal, frontoparietal sutures, and length and degree
+of the openings of the incisive foramina are useful in delimiting
+subspecies. The rostrum of <i>B. taylori</i>, in front of the frontonasal
+suture, is deflected three to five degrees ventrally in 85 per cent of
+<span class="pagenum"><a name="Page_601" id="Page_601">[Pg 601]</a></span>
+the adults examined, and in <i>B. musculus</i> is less, or not at all, deflected.</p>
+
+<p><a name="Teeth" id="Teeth"></a>
+<i>Teeth.</i>&mdash;Alveolar length of the upper and lower molar tooth-rows
+aids in distinguishing fossil and Recent species, and to a lesser degree
+in delimiting subspecies. Occlusal pattern is useful in estimating
+the relationship of fossil and living species. Degree of
+development of the mesostyle, mesostylid, mesoloph, and mesolophid
+have been useful in determining relationship between fossil
+and living species as well as useful in separating the living species.
+Rinker (1954:119) and Hooper (1957:48) have shown the degree
+of variation in dental patterns in <i>Peromyscus</i>, <i>Sigmodon</i>, and <i>Oryzomys</i>,
+mice thought to be closely related to <i>Baiomys</i>. In pygmy
+mice, however, the dental patterns are relatively constant. The
+lophs and styles are subject to some geographic variation but, nevertheless,
+are useful in estimating relationships.</p>
+
+<div class="fig_center">
+<a name="fig5" id="fig5"></a>
+<img src="images/fig_5.png" width="479" height="342" alt="" />
+<div class="fig_caption">
+<span class="smcap">Fig. 5.</span> Ventral view of hyoid bones. &#215; 18.<br />
+<br />
+A. <i>Baiomys musculus brunneus</i>, adult, female, No. 30182 KU, Potrero Viejo,
+1700 feet, Veracruz.<br />
+<br />
+B. <i>Baiomys taylori analogous</i>, adult, female, No. 36761 KU, 2 mi. N Ciudad
+Guzmán, 5000 feet, Jalisco.<br />
+</div>
+</div>
+
+<p><a name="Hyoid_apparatus" id="Hyoid_apparatus"></a>
+<i>Hyoid apparatus.</i>&mdash;Shape and, to a lesser extent, size of the hyoid
+apparatus differentiate nearly all specimens of <i>B. taylori</i> from all
+those of <i>B. musculus</i>. The hyoid of <i>B. taylori</i> differs from that of
+<i>B. musculus</i> principally in the shape of the basihyal. It possesses
+<span class="pagenum"><a name="Page_602" id="Page_602">[Pg 602]</a></span>
+an anteriorly pointed entoglossal process in <i>B. musculus</i>, and is not
+rounded to completely absent as in <i>B. taylori</i> (see <a href="#fig5">Figure 5</a>). The
+shoulders of the basihyal protrude anteriorly in <i>B. musculus</i>, and are
+not flattened as in <i>B. taylori</i>. The total length was measured in a
+sample of 55 basihyals of <i>B. musculus</i>, and was compared to the total
+length of a sample of 80 basihyals of <i>B. taylori</i>. The means of the
+two samples differ significantly at the 95 per cent level; the mean
+plus two standard errors of <i>B. musculus</i> and <i>B. taylori</i>, are, respectively,
+2.43 &#177; .02; 2.18 &#177; .03. There is sufficient overlap of the
+samples (mean plus one standard deviation of <i>B. musculus</i> and <i>B.
+taylori</i>, respectively: 2.43 &#177; .15; 2.18 &#177; .15) to make the total
+length of the basihyal of only secondary importance in distinguishing
+species, but shape and total length of the basihyal, when considered
+together, serve to identify all specimens to species. When
+length of the basihyal is plotted against occipitonasal length (see
+<a href="#fig6">Figure 6</a>), all specimens studied, regardless of age or geographical
+origin, were separated at the level of species. The hypohyals of
+<i>B. taylori</i> seemingly remain distinct throughout life; those of <i>B.
+musculus</i> completely fuse in some adults. The ceratohyals are
+highly variable in shape and of little taxonomic use.</p>
+
+<div class="fig_center">
+<a name="fig6" id="fig6"></a>
+<img src="images/fig_6.png" width="580" height="373" alt="" />
+<div class="fig_caption">
+<span class="smcap">Fig. 6.</span> Relationship of length of basihyal to occipitonasal length of skull.
+Black symbols, all below the curved line, represent measurements of <i>B. taylori</i>;
+open symbols, all above the curved line, represent measurements of <i>B. musculus</i>.
+</div>
+</div>
+
+<p>The degree of geographic variation in shape of basihyal is not
+great. Specimens of <i>B. musculus pallidus</i> from 1 km. NW Chapa,
+<span class="pagenum"><a name="Page_603" id="Page_603">[Pg 603]</a></span>
+Guerrero, have a small indentation on the anteriormost part of the
+entoglossal process. The shoulder of the basihyal is directed less
+forward in specimens of <i>B. taylori taylori</i> from 6 mi. N, 6 mi. W
+Altamira, Tamaulipas, than in other specimens of the species. The
+variations observed seemed not to be clinal.</p>
+
+<p>According to White (1953:548) the hyoid, like the baculum (Burt,
+1936:146), is little influenced by changes in external environment
+and may serve to clarify intergeneric relationships. Hyoids of both
+species of <i>Baiomys</i> are smaller than hyoids of all subgenera of
+<i>Peromyscus</i>. In shape, the hyoids of <i>Baiomys</i> resemble those of
+<i>Ochrotomys nuttalli</i> (as explained on <a href="#Page_605">page 605</a>, <i>Ochrotomys</i> is here
+accorded generic, instead of subgeneric, rank). In size, the hyoid
+of both species of <i>Baiomys</i> resembles that in <i>Reithrodontomys</i>.
+Sprague (1941:304) reports a resemblance in shape between the
+ceratohyals of <i>Baiomys</i> and <i>Reithrodontomys</i>. The thyrohyals
+differ from those of <i>Reithrodontomys</i>, being less boot-shaped, and
+having a slight terminal expansion as in <i>Ochrotomys</i> (see Sprague,
+<i>loc. cit.</i>). In shape, the large basihyal of <i>Onychomys</i> resembles
+the smaller one of <i>B. musculus</i>. The basihyal of <i>Oryzomys</i> lacks
+the entoglossal process present in <i>Baiomys</i>. On the basis of shape
+of hyoid, <i>Baiomys</i> seems to be most closely related to <i>Ochrotomys</i>.</p>
+
+<div class="fig_center">
+<a name="fig7" id="fig7"></a>
+<img src="images/fig_7.png" width="212" height="271" alt="" />
+<div class="fig_caption">
+<span class="smcap">Fig. 7.</span> Dorsal view of bacula. &#215; 16.<br />
+<br />
+A. <i>B. musculus brunneus</i>, adult, No.
+24336 KU, 3 kms. W Boca del Río,
+10 feet, Veracruz.<br />
+<br />
+B. <i>B. taylori taylori</i>, adult, No. 35937
+KU, 6 mi. SW San Gerónimo, Coahuila.<br />
+</div>
+</div>
+
+<p><a name="Baculum" id="Baculum"></a>
+<i>Baculum.</i>&mdash;Of <i>Baiomys</i>, 166 bacula were processed, using the
+method of White (1951:125), and studied. They provide characters
+of taxonomic worth at the level of species and aid in evaluating
+generic relationships.</p>
+
+<p>The baculum of <i>B. taylori</i> differs from that of <i>B. musculus</i> in:
+shaft narrow; wings anterior to base projecting dorsolaterally instead
+<span class="pagenum"><a name="Page_604" id="Page_604">[Pg 604]</a></span>
+of anteriorly; anterior part knob-shaped having indentation at tip,
+instead of anterior part spatulate-shaped (in some) to knob-shaped
+(see <a href="#fig7">Figure 7</a>), without indentation; significantly shorter (see
+<a href="#Table_4">Table 4</a>).</p>
+
+<div class="center smcap"><a name="Table_4" id="Table_4"></a>
+Table 4.&mdash;Length of Bacula</div>
+<br />
+
+<table width="80%" style="text-align: center" summary="length data">
+<tr>
+  <td class="brdtp2 brdbt">&nbsp;</td>
+  <td class="brdtp2 brdbt brdlf">Number of <br />specimens</td>
+  <td class="brdtp2 brdbt brdlf">Average <br />length</td>
+  <td class="brdtp2 brdbt brdlf">3 &#215; <br />standard</td>
+  <td class="brdtp2 brdbt brdlf">1 <br />standard</td>
+  <td class="brdtp2 brdbt brdlf">Range</td>
+</tr>
+<tr>
+  <td><i>B. taylori</i></td>
+  <td class="brdlf">108</td>
+  <td class="brdlf">2.535</td>
+  <td class="brdlf">.078</td>
+  <td class="brdlf">.274</td>
+  <td class="brdlf">2.00-3.12</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+  <td class="brdlf">&nbsp;</td>
+</tr>
+<tr>
+  <td class="brdbt"><i>B. musculus</i></td>
+  <td class="brdbt brdlf">58</td>
+  <td class="brdbt brdlf">3.324</td>
+  <td class="brdbt brdlf">.090</td>
+  <td class="brdbt brdlf">.233</td>
+  <td class="brdbt brdlf">2.80-3.88</td>
+</tr>
+</table>
+
+<p>In each of the two species, individual and geographic variation
+in the baculum is slight; its length varies insignificantly according
+to age. Excluding juveniles contained in <a href="#Table_4">Table 4</a>, but including
+young and subadults, only three bacula of <i>B. taylori</i> were longer
+than 3 mm., and only one baculum of <i>B. musculus</i> (a young) was
+shorter than 3 mm. The total length of the baculum, considered
+together with its shape, serves to identify to species all specimens
+examined by me.</p>
+
+<p>The bacula of both species of <i>Baiomys</i> were compared with bacula
+of <i>Akodon</i>, <i>Scotinomys</i>, <i>Holochilus</i>, <i>Oryzomys</i>, <i>Zygodontomys</i>, <i>Reithrodontomys</i>,
+<i>Thaptomys</i>, and <i>Calomys</i> and illustrations of bacula
+by Blair (1942:197, 200) of <i>Peromyscus</i> (subgenera <i>Peromyscus</i>,
+<i>Haplomylomys</i>, <i>Podomys</i>), <i>Ochrotomys</i>, and material at the University
+of Kansas Museum of Natural History of <i>Megadontomys</i>.
+Shape of baculum most resembled that of <i>Ochrotomys</i> and <i>Calomys</i>.
+The bacula of <i>Baiomys</i>, as pointed out by Blair (<i>op cit.</i>:203), differ
+as much from those of the genus <i>Peromyscus</i> as do the bacula of
+<i>Reithrodontomys</i> and <i>Onychomys</i>. In size of baculum, <i>Baiomys</i>
+resembles <i>Ochrotomys</i>. Blair (<i>op. cit.</i>:202) pointed out that the
+length of the baculum of <i>B. taylori subater</i> was contained in the
+length of the animal's body 20.3 times, and 24.2 times in the length
+of that of <i>Ochrotomys nuttalli</i>. The length of the baculum of <i>B.
+musculus</i> (average of 58 specimens without regard to subspecies) is
+contained in the length of the body (of specimens from which the
+bacula were removed) 22.7 times, a figure approaching that in
+<i>Ochrotomys</i>. When bacula of both species of <i>Baiomys</i> were compared
+to those of <i>O. nuttalli</i>, bacula of <i>B. musculus</i> were found to
+most closely resemble those of <i>O. nuttalli</i>. The baculum of a single
+<span class="pagenum"><a name="Page_605" id="Page_605">[Pg 605]</a></span>
+specimen of <i>Calomys</i> (<i>C. laucha</i>) was contained in the length of the
+body 15.5 times. In general shape, as well as in possession of an
+anterior knob and the position of the expanded posterior wings, the
+baculum of <i>C. laucha</i> resembles the baculum of <i>Ochrotomys</i> and
+<i>Baiomys musculus</i>.</p>
+
+<p>Blair (<i>op. cit.</i>:201) considers generic <i>versus</i> subgeneric rank for
+<i>Ochrotomys</i>, and on the basis of studies of the phallus Hooper
+(1958:23) stated that "it is clear that <i>nuttalli</i> should be removed
+from <i>Peromyscus</i> and should be listed as <i>Ochrotomys nuttalli</i> (Harlan)."
+I agree with Hooper (<i>loc. cit.</i>) and point out that on the
+basis of the baculum, there is less of a hiatus between <i>Baiomys</i> on
+the one hand, and <i>Ochrotomys</i> and <i>Calomys</i> on the other hand,
+than there is between any one of those three genera and <i>Peromyscus</i>.</p>
+
+<p>White (1953:631) reported that the baculum of chipmunks might
+indicate relationships more clearly than do skulls and skins. He
+thought that skulls might more quickly than bacula reflect the
+habitus of the animal. The resemblance in cranial morphology
+between <i>Peromyscus</i> and <i>Baiomys</i> is judged to be the result of such
+a convergence of habitus and the baculum in <i>Baiomys</i> is thought to
+reflect relationships more accurately than does the skull.</p>
+
+<p><a name="Auditory_ossicles" id="Auditory_ossicles"></a>
+<i>Auditory ossicles.</i>&mdash;Examination of a number of auditory ossicles
+of <i>Baiomys</i> reveals constant interspecific differences in the malleus
+and incus. There is only slight individual variation, slight variation
+with age, and no secondary sexual variation. In <i>Baiomys taylori</i>
+the orbicular apophysis of the malleus (see <a href="#fig8">Figure 8, A</a>) is rounded
+to nearly ovoid; the anterior process is pointed, and the neck is
+short, being slightly recurved. The body of the incus is round and
+the short process is elongate. The sides of the long limb of the
+incus are nearly parallel. The lenticular process is relatively large.
+The posterior and anterior crus of the stapes are bowed, and the
+muscular process is either absent or much reduced.</p>
+
+<p>In <i>Baiomys musculus</i>, the orbicular apophysis of the malleus
+(see <a href="#fig8">Figure 8, B</a>) is round to oblong, and less ovoid than in <i>B.
+taylori</i>; the anterior process is less acutely pointed than in <i>B. taylori</i>,
+and the neck is long, less recurved than in <i>B. taylori</i>. The body of
+the incus, though tending to be round, is more flattened, and the
+short process is knob-shaped, not elongated. The sides of the long
+limb of the incus are not parallel. The lenticular process is, relative
+to the size of the incus, small. The posterior and anterior crus
+of the stapes are more nearly straight than in <i>taylori</i>. A prominent
+muscular process occurs on the posterior crus.</p>
+
+<p><span class="pagenum"><a name="Page_606" id="Page_606">[Pg 606]</a></span></p>
+
+<p>The auditory ossicles of representative species of all the subgenera
+of <i>Peromyscus</i> were studied as were the ossicles of <i>Onychomys</i>,
+<i>Ochrotomys</i>, <i>Oryzomys</i>, <i>Akodon</i>, <i>Thaptomys</i>, <i>Zygodontomys</i>,
+<i>Calomys</i>, <i>Reithrodontomys</i>, and <i>Holochilus</i>.</p>
+
+<div class="fig_center">
+<a name="fig8" id="fig8"></a>
+<img src="images/fig_8.png" width="539" height="505" alt="" />
+<div class="fig_caption">
+<span class="smcap">Fig. 8.</span> Lateral views of auditory ossicles. &#215; 20.<br />
+<br />
+A. <i>B. taylori analogous</i>, adult, female, No. 28104 KU, 4 kms. ENE Tlalmanalco,
+2290 meters, Estado de México.<br />
+<br />
+B. <i>B. musculus pallidus</i>, adult, male, No. 28346 KU, Cahuilotal, Sacacoyuca,
+960 meters, Guerrero.<br />
+</div>
+</div>
+
+<p>The general plan of structure of the auditory ossicles in <i>Baiomys</i>
+resembles that in <i>Calomys</i>, <i>Akodon</i>, and <i>Thaptomys</i>. The ossicles
+of <i>Calomys</i> and <i>Thaptomys</i>, in particular, closely resemble the auditory
+ossicles of <i>Baiomys musculus</i>. The short process of the incus
+is knoblike in <i>Calomys</i> and <i>Thaptomys</i>, and the general conformation
+of malleus and stapes in those two genera is nearly identical
+to that in <i>B. musculus</i>. In <i>Akodon</i>, the anterior and posterior crus
+of the stapes is more rounded than in <i>B. musculus</i>, resembling that
+in <i>B. taylori</i>.</p>
+
+<p><span class="pagenum"><a name="Page_607" id="Page_607">[Pg 607]</a></span></p>
+
+<p><i>Reithrodontomys</i> differ from <i>Baiomys</i> in having a more elongate
+orbicular apophysis on the body of the malleus, an elongated short
+limb on the incus, and a stapes having anterior and posterior crura
+bowed as in mice of the genus <i>Peromyscus</i>.</p>
+
+<p>In <i>Ochrotomys</i>, the orbicular apophysis of the malleus resembles
+the orbicular apophysis of <i>B. musculus</i>, but the short process of the
+incus is longer, resembling the short process of <i>B. taylori</i>. In general
+conformation of the malleus, incus, and stapes, <i>Ochrotomys</i>
+shows closer resemblance to <i>B. taylori</i> than to <i>B. musculus</i>.</p>
+
+<p>In <i>Holochilus</i> the anterior crus and posterior crus of the stapes
+are similar to those in <i>B. musculus</i>, but in shape and size of malleus
+and incus, <i>Holochilus</i> differs considerably from <i>B. musculus</i> and
+<i>B. taylori</i>.</p>
+
+<p>In <i>Zygodontomys</i>, size and shape of the ossicles differ greatly
+from those of <i>Baiomys</i>.</p>
+
+<p>In the genus <i>Peromyscus</i>, only <i>Peromyscus floridanus</i> (subgenus
+<i>Podomys</i>) possesses a knoblike short process on the incus similar
+to that in <i>B. musculus</i>; representatives of the other subgenera examined
+possess an elongated short limb on the incus. The conformation
+of the ossicles of both <i>Onychomys</i> and <i>Oryzomys</i> appears
+to be more nearly like that in <i>Peromyscus</i> than that of <i>Baiomys</i>.</p>
+
+<p>On the basis of shape and size of auditory ossicles, <i>Baiomys</i>
+resembles South American hesperomines (<i>Calomys</i> and <i>Thaptomys</i>)
+rather than North American hesperomines.</p>
+
+
+<div class="caption2"><a name="Genus_Baiomys" id="Genus_Baiomys"></a>
+Genus <b>Baiomys</b> True</div>
+
+<div class="species_ref">1894. <i>Baiomys</i> True, Proc. U. S. Nat. Mus., 16:758, February 7. Type,
+<i>Hesperomys (Vesperimus) taylori</i> Thomas.</div>
+
+<p><i>Diagnosis.</i>&mdash;Size small (total length in adults, 93-135); tail shorter than
+head and body; hind foot in adults 12-17; ears small (8-12) and rounded;
+upper parts blackish sepia to ochraceous-buff; underparts slaty gray to white
+or pale buffy; eyes small; hind feet having six plantar pads, soles nearly
+naked except for some hairs on anterior parts of soles and anteriorly to base
+of toes and between toes; occipitonasal length of skull in adults, 17.0-21.5;
+zygomatic breadth, 9.0-11.5; coronoid process of mandible well developed,
+strongly recurved; ascending ramus of mandible short and erect; anterior
+palatine foramina (incisive foramina) long, usually terminating posterior to
+plane of the front of first molars; posterior palatine foramina nearly opposite
+middle of M2; interorbital space wide relative to widest part of frontals;
+nasals projecting only slightly over incisors; condyle terminal; upper incisors
+relatively heavy; primary first fold of M3 obliterated at an early stage of wear;
+major cusps of upper and lower anteriormost two molars alternating, more so
+in m1-m2 than in M1-M2, dental formula I/i, 1/1; C/c, 0/0; P/p, M/m, 3/3 = 16.</p>
+
+<p>For distribution of the genus, see <a href="#fig9">Figure 9</a>.</p>
+
+<p><span class="pagenum"><a name="Page_608" id="Page_608">[Pg 608]</a></span></p>
+
+<div class="fig_center">
+<a name="fig9" id="fig9"></a>
+<img src="images/fig_9.png" width="530" height="522" alt="" />
+<div class="fig_caption">
+<span class="smcap">Fig. 9.</span> Geographic distribution of the genus <i>Baiomys</i>. Black area shows where
+the two species occur together. Black dot (Acultzingo, Veracruz) shows
+locality where <i>Baiomys taylori</i> occurs within the range of <i>B. musculus</i>, but
+<i>B. musculus</i> is not known to occur at that locality.
+</div>
+</div>
+<br />
+
+
+<div class="caption2"><a name="SYSTEMATIC_ACCOUNTS" id="SYSTEMATIC_ACCOUNTS"></a>
+SYSTEMATIC ACCOUNT OF SPECIES AND SUBSPECIES</div>
+
+<div class="caption3"><a name="Baiomys_musculus" id="Baiomys_musculus"></a>
+<b>Baiomys musculus</b></div>
+
+<div class="center">Southern Pygmy Mouse</div>
+
+<div class="center">(Synonymy under subspecies)</div>
+
+<div class="species_ref"><i>Type.</i>&mdash;<i>Sitomys musculus</i> Merriam, Proc. Biol. Soc. Washington, 7:170, September
+29, 1892.</div>
+
+<div class="smaller">
+<p><i>Range.</i>&mdash;Southern Nayarit, Michoacán, México, Morelos, Puebla, and central
+Veracruz, southeastward to western Nicaragua, but unknown from southern
+Veracruz, Tabasco, and the Yucatán Peninsula (see <a href="#fig10">Figure 10</a>); occurs principally
+in the arid upper and lower divisions of the Tropical Life-zone.</p>
+
+<p><i>Characters for ready recognition.</i>&mdash;Unless otherwise noted, characters are
+usable only for the two age-categories of adult and old adult. Differs from
+<i>B. taylori</i> in: hind foot 16 millimeters or more; occipitonasal length, 19 millimeters
+<span class="pagenum2"><a name="Page_609" id="Page_609">[Pg 609]</a></span>
+or more; zygomatic breadth, 10 millimeters or more; rostrum not deflected
+ventrally at frontoparietal suture but, instead, curving gradually toward
+anteriormost point of nasals; cingular ridges and secondary cusps on teeth more
+pronounced; basihyal having anterior pointed entoglossal process, shoulders of
+basihyal protruding anteriorly (characteristic of all age categories); baculum
+having broader shaft, spatulate to knob-shaped tip, wings at base projecting
+anteriorly; baculum more than 3 millimeters long; short process of incus knob-shaped
+rather than attenuate; muscular process of posterior crus of stapes
+prominent.</p>
+
+<p><i>Characters of the species.</i>&mdash;Size large (extremes in external measurements
+of adults; total length, 100-135; length of tail vertebrae, 33-56; length of hind
+foot, 14.1-17; length of ear, 9-12); upper parts dark reddish brown, or
+ochraceous-buff to nearly black; underparts pale pinkish buff to white or pale
+buffy.</p>
+</div>
+
+<p><i>Geographic variation.</i>&mdash;Eight subspecies are here recognized (see
+<a href="#fig10">Figure 10</a>). Features that vary geographically are external size,
+color of pelage, certain cranial dimensions (occipitonasal length,
+zygomatic breadth, least interorbital breadth, length of rostrum,
+length of incisive foramina, depth and breadth of cranium, and
+alveolar length of upper molar tooth-row).</p>
+
+<p>External and cranial size (except for <i>B. m. handleyi</i>) is less in
+the southernmost subspecies, <i>B. m. pullus</i>, <i>B. m. grisescens</i>, <i>B. m.
+nigrescens</i>, and more in the northernmost subspecies, <i>B. m. musculus</i>,
+<i>B. m. brunneus</i>, and <i>B. m. infernatis</i>. Increase in size from south
+to north is in keeping with Bergman's Rule that within a species,
+smaller individuals occur in warmer parts of its geographic range.
+Southern pygmy mice at high altitudes average larger than those
+from low elevations, except where the two species are sympatric.
+There the Southern Pygmy Mouse is uniformly larger, regardless of
+altitude.</p>
+
+<p>Osgood (1909:257, 259) suggested that degree of relative humidity
+might in some way control color of pelage in both <i>B. taylori</i>
+and <i>B. musculus</i>. In <i>B. musculus</i>, the darker subspecies, <i>B. m.
+brunneus</i>, <i>B. m. nigrescens</i>, and <i>B. m. pullus</i>, occur in zones of rather
+constant high relative humidity, whereas the paler subspecies
+<i>infernatis</i>, <i>musculus</i>, <i>handleyi</i>, and to a less extent <i>grisescens</i> and
+<i>pallidus</i>, occur in zones of lower relative humidity. This is in keeping
+with Gloger's Rule, which states that melanins increase in the
+warm and humid parts of the range of a species, and reddish or
+yellowish-brown phaeomelanins prevail in arid climates. <i>B. m.
+musculus</i> ranges into areas where relative humidity is such that
+darker pelages might be expected, but this is in the area where the
+two species are sympatric, and color of pelage may be an important
+character of recognition.</p>
+
+<p><span class="pagenum"><a name="Page_610" id="Page_610">[Pg 610]</a></span></p>
+
+<div class="center">
+<a name="fig10" id="fig10"></a>
+<img src="images/fig_10.png" width="524" height="596" alt="" />
+<div class="fig_caption center"><span class="smcap">Fig. 10.</span>
+Distribution of <i>Baiomys musculus</i>. Known localities of occurrence
+are represented by circles and black dots;
+the former denote localities that are peripheral (marginal) for the subspecies concerned.<br />
+</div>
+<br />
+<table style="text-align:left" summary="species">
+<tr>
+  <td>
+    1. <i>B. m. brunneus</i><br />
+    2. <i>B. m. grisescens</i><br />
+    3. <i>B. m. handleyi</i><br />
+    4. <i>B. m. infernatis</i><br />
+  </td>
+  <td>
+    &nbsp;&nbsp;&nbsp;&nbsp;
+  </td>
+  <td>
+    5. <i>B. m. musculus</i><br />
+    6. <i>B. m. nigrescens</i><br />
+    7. <i>B. m. pallidus</i><br />
+    8. <i>B. m. pullus</i><br />
+  </td>
+</tr>
+</table>
+</div>
+
+<div class="caption3"><i>Natural History</i></div>
+
+<p><i>Habitat and numbers.</i>&mdash;In Veracruz, Dalquest obtained the southern
+pygmy mouse in stands of tall grass (<i>Spartina?</i>) in sandy loam
+soil bordering, and in, dense vegetation; Davis (1944:394) found
+the species living in dense stands of grasses and seemingly utilizing
+underground burrows. Near Chilpancingo, Guerrero, rocky situations
+seemed to be the preferred habitat. Davis (<i>loc. cit.</i>) believed
+<span class="pagenum"><a name="Page_611" id="Page_611">[Pg 611]</a></span>
+that the species has a wide tolerance to kinds of habitats. In Morelos,
+Davis and Russell (1954:75) found these mice to be abundant along
+rock fences separating cultivated fields, and in arid lowlands. In
+Colima, Hooper (1955b:13) obtained specimens from an open thorn
+forest in sparse grass and rocky hillside bounding a stream and in
+litter below shrubs on the floor of a nut-palm forest; in Michoacán,
+these mice were taken in cane grass, shrubs, and mesquite near an
+irrigation ditch. From Guatemala, Goodwin (1934:39, 40) records
+specimens from Sacapulas, a hot, dry, sandy area where cactus and
+sparse grasses are present, and from La Primavera, on the edges of
+pine-oak-alder forests. Felten (1958:137) has taken <i>musculus</i> from
+bushy areas in El Salvadore. In 1955, I obtained the southern
+pygmy mouse 6 mi. SW Izucár de Matemores, Puebla, along a
+stream in heavy grass bordered by cypress, willow, fig, bamboo, and
+in rocky grazed area near sugar cane fields.</p>
+
+<p>The southern pygmy mouse seems to be locally abundant in certain
+parts of its geographic range, and in other parts, scarce. For
+example, Dalquest (<i>in. litt.</i>) recorded the pygmy mouse as common
+at a place 2 km. N Paraje Nuevo, 1700 feet, Veracruz, where, by
+means of 50 traps, he took 14 of these mice in one night. The species
+was scarcer, although the habitat seemed suitable, 3 km. N Presidio,
+1500 feet, Veracruz, where he caught only two pygmy mice in several
+days of trapping. Six miles southwest of Izucár de Matemores, the
+pygmy mouse was the most common rodent. I have trapped for it
+in Oaxaca and Veracruz in habitats that seemed almost identical to
+those mentioned by Dalquest, and also that at Izucár de Matemores,
+Puebla, with almost no success. The reason for the seeming disparity
+in numbers at different localities having nearly the same kind
+of habitat is unknown to me and bears further investigation.</p>
+
+<p><i>Behavior.</i>&mdash;Little is recorded concerning the behavior of this
+species. David and Russell (<i>op. cit.</i>:76) found that of small mammals
+<i>B. musculus</i> was the first to appear at night. I caught mice of
+this species by hand in the afternoon in Puebla. They seemed to be
+active from noon until dark. Albert Alcorn wrote in his field notes
+that specimens were taken near noon at a place 9 mi. NNW Estelí,
+Nicaragua. My impression is that <i>musculus</i> is diurnal to crepuscular.</p>
+
+<p><i>Enemies and food.</i>&mdash;Owl pellets (thought to be those of a barn
+owl, <i>Tyto alba</i>) from within the geographic range of <i>B. musculus</i>,
+from 6 mi. SW Izucár de Matemores, yielded mandibular tooth-rows
+belonging to <i>musculus</i>. Presumably, most of the carnivorous mammals
+<span class="pagenum"><a name="Page_612" id="Page_612">[Pg 612]</a></span>
+and raptorial birds within the range of the southern pygmy
+mouse could be listed as enemies. Diurnal to crepuscular habits of
+this mouse may protect it from some of the nocturnal carnivorous
+mammals and raptorial birds.</p>
+
+<p>Food of the southern pygmy mouse includes nuts, bark, grass
+seeds, and leaves. Dalquest (MS) writes that bits of banana proved
+to be useful bait in trapping these mice in Veracruz.</p>
+
+<p><i>Reproduction.</i>&mdash;Notations concerning lactation and embryos on
+specimen labels of females suggest that the southern pygmy mouse
+breeds in all months. I have records of pregnant or lactating females
+in every month, save January, April, May, and June. The average of
+26 counts of embryos or young per litter is 2.92 (1-4).</p>
+
+
+<div class="caption3"><a name="Baiomys_musculus_brunneus" id="Baiomys_musculus_brunneus"></a>
+<b>Baiomys musculus brunneus</b> (J. A. Allen and Chapman)</div>
+
+<div class="species_ref"><i>Peromyscus musculus brunneus</i> J. A. Allen and Chapman, Bull. Amer. Mus.
+Nat. Hist., 9:203, June 16, 1897; Elliott, Field Columb. Mus. Publ.,
+105(4):136, July 1, 1905; Elliott, Field Columb. Mus. Publ., 115(8):203,
+1907; Osgood, N. Amer. Fauna, 28:259, April 17, 1909.</div>
+
+<div class="species_ref"><i>Baiomys musculus brunneus</i>, Miller, Bull. U. S. Nat. Mus., 79:137, December
+31, 1912; Miller, Bull. U. S. Nat. Mus., 128:318, April 29, 1924; Ellerman,
+The Families and Genera of Living Rodents, 2:402, March 21, 1941;
+Goldman, Smith. Miscl. Coll., 115:437, July 31, 1951; Goodwin, Bull.
+Amer. Mus. Nat. Hist., 102:318, August 31, 1953; Miller and Kellogg,
+Bull. U. S. Nat. Mus., 205:512, March 3, 1955; Booth, Walla Walla
+Publs., Dept. Biol. Sci., 20:15, July 10, 1957; Hall and Kelson, The
+Mammals of North America, 2:661, March 31, 1959 (part).</div>
+
+<div class="species_ref">[<i>Peromyscus musculus</i>] <i>brunneus</i>, Elliott, Field Columb. Mus. Publ., 95(4):
+176, 1904.</div>
+
+<i>Peromyscus musculus</i> [<i>musculus</i>], Osgood, N. Amer. Fauna, 28:258, April
+17,  1909 (part).
+
+<div class="species_ref"><i>Baiomys musculus musculus</i>, Davis, Jour. Mamm., 25:394, December 12,
+1944 (part); Goldman, Smith Miscl. Coll., 115:437, July 31, 1951;
+Hooper, Jour. Mamm., 33:97, February 18, 1952 (part); Hall and Kelson,
+The Mammals of North America, 2:661, March 31, 1959 (part).</div>
+
+<div class="species_ref"><i>B.</i> [<i>aiomys</i>] <i>m.</i> [<i>usculus</i>] <i>brunneus</i>, Hooper, Jour. Mamm., 33:96, February
+18,  1952.</div>
+
+<div class="species_ref"><i>Baiomys taylori</i>, Hooper, Jour. Mamm., 33:97, February 18, 1952 (part).</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;Adult female, skin and skull; No. 12535/10845 American Museum
+of Natural History; Jalapa, Veracruz, Republic of México; obtained on April
+13, 1897, by F. M. Chapman, original number 1203.</p>
+
+<p><i>Range.</i>&mdash;Central Veracruz, coastal plains and eastern slopes of the plateau
+of Central México, see <a href="#fig10">Figure 10</a>. Zonal range: Upper Tropical Life-zone
+(Lowery and Dalquest, 1951:537), parts of the Veracruz and eastern Transverse
+Volcanic biotic provinces of Goldman and Moore (1945:349). Occurs
+from near sea level at Boca del Río, Veracruz, up to 5500 feet 3 km. SE
+Orizaba.</p>
+
+<p><i>Diagnosis.</i>&mdash;Size medium to large for the species; ground color of dorsum
+of paratypes near Olive Brown; darkest of specimens of this subspecies examined
+(from Potrero Viejo, Veracruz) between Prouts Brown and Mummy
+<span class="pagenum2"><a name="Page_613" id="Page_613">[Pg 613]</a></span>
+Brown; distal two-thirds of guard hairs of dorsum black, proximal third dark
+gray to sooty; hairs of dorsum black-tipped having subterminal band of
+Ochraceous-Tawny; sides paler (less of dark brown) than dorsum; venter Deep
+Olive Buff to clay color, individual hairs pale olive buff at tips, dark gray
+basally; region of throat and chin sooty gray; ventralmost vibrissae white to
+base, other vibrissae black to base; ears dark brown, sparsely haired; forefeet and
+hind feet flesh-colored in palest specimens, sooty in darkest; tail pale brown,
+slightly paler below than above; presphenoid only slightly constricted towards
+midline; average and extreme external and cranial measurements of 10 adults
+from Cerro Gordo, Veracruz, are as follows: total length, 118.9 (112-127);
+length of tail vertebrae, 45.1 (42-50); length of body, 74.0 (69-78); length
+of hind foot, 16.0 (16); length of ear from notch, 12.8 (12-13); occipitonasal
+length, 19.5 (19.0-20.0); zygomatic breadth, 10.3 (10.0-10.8); postpalatal
+length, 7.1 (6.7-7.5); least interorbital breadth, 3.9 (3.7-4.0); length of
+incisive foramina, 4.4 (4.1-4.6); length of rostrum, 6.9 (6.5-7.2); breadth of
+braincase, 9.5 (9.2-9.7); depth of cranium, 7.1 (7.1-7.4); alveolar length of
+maxillary tooth-row, 3.3 (3.2-3.3); for photographs of skull, see <a href="#plate1">Plate 1<i>a</i></a>, and
+<a href="#plate3">Plate 3<i>a</i></a>.</p>
+
+<p><i>Comparisons.</i>&mdash;For comparisons with <i>B. m. nigrescens</i>, see account of that
+subspecies. From <i>B. m. pallidus</i>, <i>B. m. brunneus</i> differs in: dorsal, lateral,
+and facial coloration deeper reddish brown, more melanins present; venter
+darker; buff gray rather than whitish buff to gray as in paratypical series;
+vibrissae black rather than brownish to white; tail sooty, less flesh-colored;
+forefeet and hind feet averaging slightly grayer; most external and cranial
+dimensions averaging slightly larger; nasals less attenuated; presphenoid less
+hour-glass shaped, sides more nearly straight.</p>
+
+<p>From <i>B. m. infernatis</i>, <i>B. m. brunneus</i> differs in: side of face and neck
+deep reddish-brown rather than yellowish-gray (the differences in dorsal
+colorations are greater between <i>brunneus</i> and <i>infernatis</i> than between <i>brunneus</i>
+and <i>pallidus</i>); venter darker buff-gray; tail brownish rather than flesh-colored;
+forefeet and hind feet average slightly grayer; most external dimensions averaging
+slightly larger; cranial dimensions nearly the same except length of
+incisive foramina, which is smaller; presphenoid differs in much the same way
+as from pallidus.</p>
+</div>
+
+<p><i>Remarks</i>.&mdash;Specimens from Chichicaxtle, Puente Nacional, 3 km.
+W Boca del Río, 1 km. E. Mecayucan, and Río Blanco (20 km.
+WNW Piedras Negras), are all paler than the paratypical series and
+other specimens from within the assigned range of <i>B. m. brunneus</i>.
+All these specimens from the coastal plain average considerably
+paler than those from the front range and slopes of the mountains.
+Specimens from Puente Nacional are intermediate in color between
+paler, grayish brown, specimens from the coastal plains and the
+darker, brown, specimens from the mountains. When Allen and
+Chapman (1897:203) described <i>brunneus</i>, they did so on the basis
+of the darker brown mice from the higher altitudes. The name,
+<i>brunneus</i>, <i>sensu stricto</i>, could be restricted to those mice from the
+<span class="pagenum"><a name="Page_614" id="Page_614">[Pg 614]</a></span>
+higher altitudes of central Veracruz. However, when the mice of
+intermediate color from Puente Nacional are considered, it seems
+best to include the material from the coastal plain with <i>brunneus</i>.
+Crania from the higher altitudes are slightly larger than, but not
+significantly different from, crania of specimens from the coastal
+plains. Specimens examined from the coastal plains resemble the
+darker series of <i>B. m. pallidus</i> to the west in central México. But
+there is no evidence of gene flow between the paler coastal specimens
+and <i>B. m. pallidus</i> to the west. In fact, these paler brown mice
+on the coastal plain grade in color into the darker brown mice from
+the mountains. The paler mice from the coast may be an incipient
+subspecies.</p>
+
+<p>The type and paratypes seem to have faded somewhat since they
+were described by Allen and Chapman (<i>loc. cit.</i>) and by Osgood
+(1909:259). However, the color of the paratypes and other specimens
+herein assigned is the feature most useful for distinguishing
+<i>brunneus</i> from all other subspecies of <i>B. musculus</i>.</p>
+
+<div class="smaller">
+<a name="FNanchor_1_1" id="FNanchor_1_1"></a>
+<a name="FNanchor_2_2" id="FNanchor_2_2"></a>
+<a name="FNanchor_3_3" id="FNanchor_3_3"></a>
+<a name="FNanchor_4_4" id="FNanchor_4_4"></a>
+<a name="FNanchor_5_5" id="FNanchor_5_5"></a>
+<a name="FNanchor_6_6" id="FNanchor_6_6"></a>
+<p><i>Specimens examined.</i>&mdash;Total 187 all from <span class="smcap">Veracruz</span>, Republic of México,
+and distributed as follows: type locality, 4400 ft., 16<a href="#Footnote_1_1" class="fnanchor">[1]</a>
+(including the type), 6<a href="#Footnote_2_2" class="fnanchor">[2]</a>,
+1<a href="#Footnote_3_3" class="fnanchor">[3]</a>; <i>Cerro Gordo</i>, 1500 ft., 19;
+<i>Teocelo</i> [= <i>Texolo</i>], 4500 ft., 1; <i>2 mi. NW Plan del Río</i>, 1000 ft., 14<a href="#Footnote_4_4" class="fnanchor">[4]</a>;
+<i>Plan del Río</i>, 1000 ft., 2<a href="#Footnote_5_5" class="fnanchor">[5]</a>;
+<i>Carrizal</i>, 4<a href="#Footnote_2_2" class="fnanchor">[2]</a>; Chichicaxtle, 3<a href="#Footnote_2_2" class="fnanchor">[2]</a>;
+<i>Puente Nacional</i>, 500 ft., 1<a href="#Footnote_5_5" class="fnanchor">[5]</a>, 2;
+<i>Santa Maria, near Mirador</i>, 1800 ft., 10<a href="#Footnote_2_2" class="fnanchor">[2]</a>;
+Boca del Río, 10 ft., 1<a href="#Footnote_5_5" class="fnanchor">[5]</a>, 8;
+<i>Córdoba</i> [= <i>Córdova</i>], 14<a href="#Footnote_1_1" class="fnanchor">[1]</a>; <i>4 km. WNW Fortín</i>, 4;
+<i>Río Atoyac, 8 km. NW Potrero</i>, 1; <i>2 km. N. Paraje Nuevo</i>, 1700 ft., 9;
+<i>El Xuchil</i>, <i>1 mi. W. Paraje Nuevo</i>, 6<a href="#Footnote_6_6" class="fnanchor">[6]</a>;
+Potrero Viejo, 1700 ft. 15; <i>Cautlapán</i> [= <i>Ixtaczequitlán</i>], 4000 ft., 16; <i>Micayucan</i>, 1;
+3 km. SE Orizaba, 5500 ft., 3; Río Blanco, 20 km. WNW Piedras Negras, 400 ft, 7;
+<i>29 km. SE Córdoba, Presidio</i>, 15<a href="#Footnote_4_4" class="fnanchor">[4]</a>; <i>3 km. N Presidio</i>, 1500 ft., 2;
+Presidio, 600 meters, 6<a href="#Footnote_3_3" class="fnanchor">[3]</a>.</p>
+
+<p><i>Marginal records.</i>&mdash;<span class="smcap">Veracruz</span>: type locality; Chichicaxtle; Boca del Río,
+10 ft.; Río Blanco, 20 km. WNW Piedras Negras, 400 ft; Presidio; 3 km. SE
+Orizaba, 5500 ft.</p>
+</div>
+
+<div class="footnote"><p><a name="Footnote_1_1" id="Footnote_1_1"></a>
+<a href="#FNanchor_1_1"><span class="label">[1]</span></a> American Museum of Natural History.</p></div>
+
+<div class="footnote"><p><a name="Footnote_2_2" id="Footnote_2_2"></a>
+<a href="#FNanchor_2_2"><span class="label">[2]</span></a> U. S. Nat. Museum (Biol. Surv. Coll.).</p></div>
+
+<div class="footnote"><p><a name="Footnote_3_3" id="Footnote_3_3"></a>
+<a href="#FNanchor_3_3"><span class="label">[3]</span></a> Chicago Natural History Museum.</p></div>
+
+<div class="footnote"><p><a name="Footnote_4_4" id="Footnote_4_4"></a>
+<a href="#FNanchor_4_4"><span class="label">[4]</span></a> Univ. Michigan, Museum of Zoology.</p></div>
+
+<div class="footnote"><p><a name="Footnote_5_5" id="Footnote_5_5"></a>
+<a href="#FNanchor_5_5"><span class="label">[5]</span></a> Texas A &amp; M, Coop. Wildlife Res. Coll.</p></div>
+
+<div class="footnote"><p><a name="Footnote_6_6" id="Footnote_6_6"></a>
+<a href="#FNanchor_6_6"><span class="label">[6]</span></a> Univ. Illinois, Mus. Nat. History.</p></div>
+
+
+<div class="caption3"><a name="Baiomys_musculus_grisescens" id="Baiomys_musculus_grisescens"></a>
+<b>Baiomys musculus grisescens</b> Goldman</div>
+
+<div class="species_ref"><i>Baiomys musculus griesescens</i> Goldman, Proc. Biol. Soc. Washington, 45:121,
+July 30, 1932; Ellerman, The Families and Genera of Living Rodents,
+2:402, March 21, 1941; Poole and Schantz, Bull. U. S. Nat. Mus., 178:259,
+March 6, 1942; Goodwin, Bull. Amer. Mus. Nat. Hist., 79(2):160-161,
+May 29, 1942 (part); Miller and Kellogg, Bull. U. S. Nat. Mus., 205:513,
+March 3, 1955 (part); Felten, Senck. Biol., 39:136, August 30, 1958;
+Packard, Univ. Kansas Publs., Mus. Nat. Hist., 9:401, December 19,
+1958; Hall and Kelson, The Mammals of North America, 2:661, March
+31, 1959 (part).</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;Adult female, skin and skull; No. 257083 U. S. Nat. Mus. (Biol.
+Surv. Coll.); Comayabuela [= Comayaguela] just south of Tegucigalpa, 3100
+feet, Honduras; obtained on March 6, 1932, by C. F. Underwood, original
+number 838.</p>
+
+<p><span class="pagenum2"><a name="Page_615" id="Page_615">[Pg 615]</a></span></p>
+
+<p><i>Range.</i>&mdash;Central to south-central Guatemala, east to south-central Honduras.
+Zonal range: Lower parts of the Merendon Biotic Province of Smith (1949:235).
+Occurs from 3200 feet at a place <sup>1</sup>/<sub>2</sub> mi. N and 1 mi. W Salama, Guatemala, up
+to approximately 4500 feet at Monte Redondo, Guatemala.</p>
+
+<p><i>Diagnosis.</i>&mdash;Size medium to small for the species; general ground color of
+dorsum between Olive Brown and Buffy Brown; distal fourth of individual
+guard hairs of dorsum black-tipped, proximal three-fourths gray, underfur
+black-tipped with subterminal band of Vinaceous-Buff, gray basally; facial
+region below eye Olive-Buff to Deep Olive-Buff; regions of flanks without
+black-tipped guard hairs, therefore, appearing paler brownish-buff than dorsum;
+venter Pale Olive-Buff to whitish in midline, hairs there white to base, laterally
+grayish basally; hairs in region of throat and chin resemble those of underparts;
+forefeet and hind feet flesh-colored with grayish suffusion; ears dusky
+brown; tail almost unicolored, slightly darker brown above than below; coronoid
+process less acutely falcate than in other subspecies; zygoma bowed. Average
+and extreme external and cranial measurements of 14 adults from La Piedra
+de Jesús Sabana Grande, Honduras, are as follows: Total length, 110.7
+(100-123); length of tail vertebrae, 44.0 (32-55); length of body, 66.7 (60-70);
+length of hind foot, 14.1 (12-15); length of ear from notch, 11.8 (10-13);
+occipitonasal length, 19.3 (18.9-19.8); zygomatic breadth, 10.1 (9.8-10.4);
+postpalatal length, 6.8 (6.2-7.3); least interorbital breadth, 3.9 (3.8-4.1);
+length of incisive foramina, 4.3 (4.0-4.5); length of rostrum, 6.9 (6.6-7.2);
+breadth of braincase, 9.6 (9.2-10.1); depth of cranium, 7.0 (6.8-7.3); alveolar
+length of maxillary tooth-row, 3.2 (3.0-3.4); for photographs of skull, see
+<a href="#plate1">Plate 1<i>b</i></a>, and <a href="#plate3">Plate 3<i>b</i></a>.</p>
+
+<p><i>Comparisons.</i>&mdash;For comparisons with <i>B. m. pullus</i> and <i>B. m. handleyi</i>, see
+accounts of those subspecies. From <i>B. m. nigrescens</i>, <i>B. m. grisescens</i> differs
+in: dorsum less blackish (dark brown to buffy); face buffy below eye rather
+than brownish-black; venter buffy to whitish in midline, not sooty gray; forefeet
+and hind feet flesh-colored with gray overtones, not dusky to sooty;
+zygoma bowed, sides less parallel; braincase and bony palate slightly broader.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;Goodwin (1942:160) mentioned that a specimen from
+the type locality of <i>grisescens</i> was as dark as specimens of <i>B. m.
+nigrescens</i> from Guatemala. However, all specimens from Guatemala,
+other than those from Sacapulas, were referred by Goodwin
+(1934:40) to <i>B. m. nigrescens</i>. My studies reveal a grayish-brown
+population in central Honduras near to and including the type
+locality. This population appears to grade into a slightly paler,
+particularly as concerns color of hind foot and tail, group of Guatemalan
+mice from 1 mi. S Rabinal, from <sup>1</sup>/<sub>2</sub> mi. N, 1 mi. E Salama, and
+from Lake Atescatempa. Specimens from western Guatemala at
+Nentón and Jacaltenango, on the other hand, are darker brownish-black,
+more nearly like the paratypical series of <i>nigrescens</i> from the
+Valley of Comitán, Chiapas, Republic of México. This darker
+brownish-black color of the back persists in specimens from southern
+<span class="pagenum"><a name="Page_616" id="Page_616">[Pg 616]</a></span>
+Guatemala and El Salvador (see specimens examined of <i>B. m.
+nigrescens</i> for localities), and they are best referred to <i>nigrescens</i>.
+<i>B. m. grisescens</i>, in color and certain cranial characters, therefore,
+seems to grade into two different subspecies: (1) <i>B. m. handleyi</i>,
+pale mice in the Río Negro valley in central Guatemala, and (2)
+<i>B. m. nigrescens</i>, dark mice from southern Guatemala, and parts of
+El Salvador.</p>
+
+<p>Felten (1958:136) referred all <i>B. musculus</i> from El Salvador to
+<i>B. m. grisescens</i>. Although I have not examined the specimens
+reported on by Felten (<i>loc. cit.</i>), I have examined specimens from
+Lake Atescatempa, Guatemala (which I refer to <i>grisescens</i>), not
+too distant from Cerro Blanco, and Finca Las Canarias, Department
+of Ahuachapan, and Laguna de Guija, Department of Santa Ana
+(localities listed by Felten). It would seem that specimens from
+these localities might indeed be <i>grisescens</i>. However, specimens
+that I examined from 1 mi. S Los Planes, and 1 mi. NW San
+Salvador were considerably darker than paratypes of <i>grisescens</i>
+and were nearly intermediate in color between <i>nigrescens</i> and
+<i>pullus</i>. I refer the specimens from 1 mi. NW San Salvador, and 1
+mi. S Los Planes to <i>nigrescens</i> rather than to <i>grisescens</i>.</p>
+
+<p>There is no positive evidence that <i>B. m. grisescens</i> intergrades
+with <i>B. m. pullus</i> to the south in Nicaragua. But, there is a suggestion
+that intergradation occurs between these subspecies in a
+series of 76 skins from La Piedra de Jesús Sabana Grande, Honduras,
+referable to <i>grisescens</i>. A total of 16 of 76 skins from this locality
+(21 per cent) possess the mid-ventral white stripe found in 18
+of 20 skins (90 per cent), from the type locality of <i>pullus</i> in
+Nicaragua. Further collection in areas between central Honduras
+and western Nicaragua may yield specimens of <i>B. musculus</i> that
+are intermediate in characters between <i>grisescens</i> and <i>pullus</i>.</p>
+
+<div class="smaller">
+<a name="FNanchor_1_7" id="FNanchor_1_7"></a>
+<a name="FNanchor_2_8" id="FNanchor_2_8"></a>
+<a name="FNanchor_3_9" id="FNanchor_3_9"></a>
+<p><i>Specimens examined</i>.&mdash;Total 149, distributed as follows:
+<span class="smcap">Guatemala</span>: 1 mi. S Rabinal, 3450 ft., 14; <sup>1</sup>/<sub>2</sub> mi. N, 1 mi. E Salama, 3200 ft., 10;
+Lake Atescatempa, 10<a href="#Footnote_1_7" class="fnanchor">[7]</a>.
+<span class="smcap">Honduras</span>: Cementario, Gracias, 1<a href="#Footnote_2_8" class="fnanchor">[8]</a>;
+Monte Redondo, 1<a href="#Footnote_2_8" class="fnanchor">[8]</a>;
+El Caliche, Cedros, 1<a href="#Footnote_2_8" class="fnanchor">[8]</a>;
+<i>La Flor Archaga</i>, 2<a href="#Footnote_2_8" class="fnanchor">[8]</a>, 1<a href="#Footnote_3_9" class="fnanchor">[9]</a>;
+Hatillo, 1<a href="#Footnote_2_8" class="fnanchor">[8]</a>;
+<i>type locality</i>, 7<a href="#Footnote_2_8" class="fnanchor">[8]</a>,
+6<a href="#Footnote_1_7" class="fnanchor">[7]</a> (including the type),
+3<a href="#Footnote_3_9" class="fnanchor">[9]</a>;
+<i>El Zapote</i>, <i>Sabana Grande</i>, 4<a href="#Footnote_2_8" class="fnanchor">[8]</a>;
+La Piedra de Jesús Sabana Grande, 76<a href="#Footnote_2_8" class="fnanchor">[8]</a>;
+<i>Cerro de las Cuches Sabana Grande</i>, 5.</p>
+
+<p><i>Marginal records.</i>&mdash;<span class="smcap">Guatemala</span>: <sup>1</sup>/<sub>2</sub> mi. N, 1 mi. E Salama, 3200 ft.
+<span class="smcap">Honduras</span>: El Caliche, Cedros; Hatillo; La Piedra de Jesús Sabana Grande; Cementario.
+<span class="smcap">Guatemala</span>: Lake Atescatempa; 1 mi. S Rabinal, 3450 ft.</p>
+</div>
+
+<div class="footnote"><p><a name="Footnote_1_7" id="Footnote_1_7"></a>
+<a href="#FNanchor_1_7"><span class="label">[7]</span></a> United States National Museum
+(Biol. Surv. Collections).</p></div>
+
+<div class="footnote"><p><a name="Footnote_2_8" id="Footnote_2_8"></a>
+<a href="#FNanchor_2_8"><span class="label">[8]</span></a> American Museum of Natural History.</p></div>
+
+<div class="footnote"><p><a name="Footnote_3_9" id="Footnote_3_9"></a>
+<a href="#FNanchor_3_9"><span class="label">[9]</span></a> Univ. Michigan, Museum of Zoology.</p>
+
+<p><span class="pagenum"><a name="Page_617" id="Page_617">[Pg 617]</a></span></p></div>
+
+
+<div class="caption3"><a name="Baiomys_musculus_handleyi" id="Baiomys_musculus_handleyi"></a>
+<b>Baiomys musculus handleyi</b> Packard</div>
+
+<div class="species_ref"><i>Baiomys musculus handleyi</i> Packard, Univ. Kansas Publs., Mus. Nat. Hist.,
+9:399, December 19, 1958.</div>
+
+<div class="species_ref"><i>Baiomys musculus musculus</i>, Goodwin, Bull. Amer. Mus. Nat. Hist., 68(1):39-40,
+December 12, 1934 (part); Miller and Kellogg, Bull. U. S.
+Nat. Mus., 205:512, March 3, 1955 (part).</div>
+
+<div class="species_ref"><i>Baiomys musculus nigrescens</i>, Hall and Kelson, The Mammals of North
+America, 2:661, March 31, 1959 (part).</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;Adult female, skin and skull; No. 275604 U. S. Nat. Mus. (Biol.
+Surv. Coll.); Sacapulas, El Quiche, Guatemala; obtained on April 24, 1947, by
+Charles O. Handley, Jr., original number 991.</p>
+
+<p><i>Range.</i>&mdash;Known only from the type locality in the valley of the Río Negro.
+Zonal range: Part of the Chimaltenangan Province of Smith (1949:235).</p>
+
+<p><i>Diagnosis.</i>&mdash;Size medium to large for the species; dorsum Wood Brown in
+some series to Buffy Brown; guard hairs of dorsum black-tipped, color of underhairs
+Avellaneous; hairs white to base in region of chin, throat, and median
+venter; in lateral region, hairs Neutral Gray at base; dorsal surfaces of forefeet
+and hind feet and ankles white; tail white below, brownish above; nasals
+truncate anteriorly; frontoparietal suture forming an obtuse angle with the
+suture separating the parietals; alveolar length of upper molar tooth-row and
+tail long. Average and extreme external and cranial measurements for nine
+adults from the type locality are as follows: Total length, 121.4 (115-128);
+length of tail vertebrae, 50.7 (49-54); length of body, 70.8 (66-77); length of
+hind foot, 15.3 (15-16); occipitonasal length, 19.6 (18.8-20.7); zygomatic
+breadth, 10.5 (10.2-11.0); postpalatal length, 6.9 (6.4-7.4); least interorbital
+breadth, 4.0 (3.9-4.0); length of incisive foramina, 4.2 (4.0-4.5); length of
+rostrum, 7.2 (7.0-7.7); breadth of braincase, 9.8 (9.7-10.2); depth of cranium,
+7.1 (6.8-7.2); alveolar length of maxillary tooth-row, 3.5 (3.4-3.6); for photographs
+of skull, see <a href="#plate1">Plate 1<i>c</i></a>, and <a href="#plate3">Plate 3<i>c</i></a>.</p>
+
+<p><i>Comparisons.</i>&mdash;From <i>B. m. nigrescens</i>, <i>B. m. handleyi</i> differs as follows:
+everywhere paler; forefeet and hind feet whitish instead of dusky to sooty;
+hairs of anterior part of face white instead of brown; tail bicolored instead of
+unicolored; anterior tips of nasals truncate rather than rounded; frontoparietal
+suture forming obtuse angle with suture separating parietals instead of forming
+right angle; tail and upper molar tooth-row longer.</p>
+
+<p>From <i>B. m. grisescens</i>, <i>B. m. handleyi</i> differs in: slightly paler above and
+below, primarily as a result of lacking buff-colored hairs; forefeet and hind feet
+white, not flesh-colored with gray overtones; tail bicolored, not unicolored;
+anterior tips of nasals truncate rather than flaring; tail and upper molar tooth-row
+longer.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;<i>B. m. handleyi</i> seems to be restricted to the valley of
+the Río Negro, in the region of Sacapulas, Guatemala. Stuart
+(1954:7) points out that the Río Negro drops down into a gorge at
+a place near Sacapulas and flows northward through a deep canyon
+<span class="pagenum"><a name="Page_618" id="Page_618">[Pg 618]</a></span>
+for approximately 60 kilometers. The Río Negro, then, flows onto
+the lowlands of the Yucatán Peninsula. The habitat is xerophytic
+in the valley of the Río Negro near Sacapulas. Stuart (<i>op. cit.</i>:10)
+suggests that this xerophytic habitat may be continuous to a place
+to the north of Chixoy, Chiapas, where the vegetation then becomes
+more mesic. The mesic conditions to the north in Tabasco
+and Yucatán probably have restricted the movement of pygmy mice
+to the north. No specimens of this mouse are known from the
+Yucatán Peninsula or from the State of Tabasco, México. <i>B. m.
+handleyi</i> intergrades with <i>B. m. grisescens</i> to the south. Specimens
+from 1 mi. S Rabinal, and those from a second locality <sup>1</sup>/<sub>2</sub> mi. N and
+1 mi. E Salama, Guatemala, are intermediate in color of pelage between
+<i>handleyi</i> and <i>grisescens</i>. Stuart (<i>op. cit.</i>:5) mentions the
+continuity of habitat and tributaries from the Salama Basin into the
+valley of the Río Negro. Absence of physiographic and biotic barriers
+in the corridor between these two basins probably allows for
+some gene flow between <i>handleyi</i> and <i>grisescens</i>, and results in
+populations intermediate in color. To the north and northwest of
+Sacapulas, the Sierra de los Cuchumatanes rises abruptly and separates
+the known geographic range of <i>handleyi</i> from that of <i>nigrescens</i>
+to the north, while to the west the cactus-mesquite habitat of
+<i>handleyi</i> gives way to the oak-pine timber that, so far as known,
+does not support <i>Baiomys</i>. The difference in elevation and flora
+seems to restrict gene flow between <i>handleyi</i> and the more northern
+<i>nigrescens</i>. The only evidence of integration between these two
+subspecies is provided by one specimen from Chanquejelve, Guatemala.
+That specimen is intermediate in color between the pale
+<i>handleyi</i> and blackish-brown <i>nigrescens</i>.</p>
+
+<p>The subspecies closest, geographically, to <i>B. m. handleyi</i> is <i>B. m.
+nigrescens</i>, from which <i>B. m. handleyi</i> differs more in color than
+from any of the other named subspecies, except <i>B. m. pullus</i>. There
+is a close correlation of pallor of mice and the xeric Río Negro Valley,
+and the darkness (melanistic color) of mice and the mesic
+mountains and valleys to the north.</p>
+
+<div class="smaller">
+<p><i>Specimens examined.</i>&mdash;Total 49, from <span class="smcap">Guatemala</span>: type locality, including
+the type: 12 (U. S. Nat. Mus., Biol. Surv. Coll.), 37 (Amer. Mus. Nat. Hist.).</p>
+</div>
+
+
+<div class="caption3"><a name="Baiomys_musculus_infernatis" id="Baiomys_musculus_infernatis"></a>
+<b>Baiomys musculus infernatis</b> Hooper</div>
+
+<div class="species_ref"><i>Baiomys musculus infernatis</i> Hooper, Jour. Mamm., 33:96, February 18,
+1952; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:512, March 3, 1955;
+Hall and Kelson, The Mammals of North America, 2:661, March 31,
+1959.</div>
+
+<div class="species_ref"><i>Baiomys musculus musculus</i>, Hooper, Jour. Mamm., 28:50, February 15,
+1947 (part).</div>
+
+<p><span class="pagenum"><a name="Page_619" id="Page_619">[Pg 619]</a></span></p>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;Adult male, skin and skull; No. 91497 Univ. of Michigan, Museum
+of Zoology; Teotitlán, Oaxaca, Republic of México, obtained on February 24,
+1947, by Helmuth O. Wagner, original number 2702.</p>
+
+<p><i>Range.</i>&mdash;Southeastern Puebla, in the basin drained by the Río Salado and
+Río Quiotepec, into northern Oaxaca. Zonal range: Arid Tropical in a part
+of the Orizaba-Zempoaltepec Faunal District of the Transverse Volcanic Biotic
+Province of Moore (1945:218). Occurs from 3100 feet in Oaxaca up to 6000
+feet in Puebla.</p>
+
+<p><i>Diagnosis.</i>&mdash;Size medium for the species; dorsum Drab, terminal parts of
+individual guard hairs black, Neutral Gray basally, distal parts of underfur
+Pinkish Buff, proximally Neutral Gray; sides same color as dorsum; hairs in
+region of throat and chin white to base; venter whitish to Neutral Gray with
+tinges of Pinkish Buff; dorsal parts of forefeet and hind feet whitish with
+flesh-colored undertones, ventral parts whitish to dusky-gray; tail bicolored,
+grayish-brown above, white below; tip of tail not bicolored, instead grayish-brown
+throughout; ears pale brown, sparsely haired; incisive foramina long,
+not constricted posteriorly. Average and extreme external measurements for
+9 adults from the type locality are as follows: total length, 113.9 (106-122);
+length of tail vertebrae, 44.1 (41-48); length of body, 71.0 (65-79); length
+of hind foot, 14.8 (13-16); length of ear, 11.9 (11-12). Average and extreme
+cranial measurements of 7 adults from the type locality are as follows: Occipitonasal
+length, 20.1 (19.7-20.4); zygomatic breadth, 10.4 (10.2-10.6); postpalatal
+length, 7.3 (7.0-7.7); least interorbital breadth, 4.2 (4.0-4.4); length
+of incisive foramina, 4.8 (4.4-5.6); length of rostrum, 7.2 (6.6-7.5); breadth
+of braincase, 9.6 (9.5-9.8); depth of cranium, 7.4 (7.1-7.6); alveolar length of
+maxillary tooth-row, 3.3 (3.1-3.4); for photographs of skull, see <a href="#plate1">Plate 1<i>d</i></a>, and
+<a href="#plate3">Plate 3<i>d</i></a>.</p>
+
+<p><i>Comparisons.</i>&mdash;For comparisons with <i>B. m. nigrescens</i> and <i>B. m. brunneus</i>,
+see accounts of those subspecies. From <i>B. m. pallidus</i>, <i>B. m. infernatis</i> differs
+in: sides, ears, and dorsum paler (less of dark brown); venter whitish gray
+rather than gray with tinge of buff and brown; forefeet and hind feet paler;
+tail bicolored, not unicolored; incisive foramina longer and not constricted
+posteriorly; mastoid process turning dorsally and sickle-shaped at posteriormost
+point rather than capitate.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;<i>B. m. infernatis</i> resembles <i>B. m. handleyi</i> more than
+any other subspecies in color of pelage and in external and cranial
+dimensions. The resemblance in color between <i>B. m. pallidus</i>, in
+certain parts of its range, and <i>B. m. handleyi</i> may have resulted
+from nearly parallel selective forces that gave rise to two subspecies,
+widely separated geographically. The same relation obtains between
+<i>B. m. infernatis</i> and <i>B. m. handleyi</i>. Both inhabit arid river
+basins. In them, pale soil and low relative humidity are important
+passive factors of selection that give adaptive value to the pale
+colors of pelage of both <i>infernatis</i> and <i>handleyi</i>.</p>
+
+<p>Specimens from 6<sup>1</sup>/<sub>2</sub> mi. SW Izucár de Matemores, and 1 mi. SSW
+Tilapa, Puebla, are intergrades between <i>B. m. infernatis</i> and <i>B. m.
+<span class="pagenum"><a name="Page_620" id="Page_620">[Pg 620]</a></span>
+pallidus</i>. These specimens are intermediate in color and cranial
+characters between the aforementioned subspecies but possess more
+of the pale brown overtones seen in paratypes of <i>pallidus</i>, and are
+best referred to that subspecies.</p>
+
+<div class="smaller">
+<p><i>Specimens examined</i> (All in Univ. Michigan, Mus. Zool.).&mdash;Total 18, all
+from the Republic of México and distributed as follows: <span class="smcap">Puebla</span>, Tepanaco,
+6000 ft., 3, Tehuacán, 5400 ft., 3. <span class="smcap">Oaxaca</span>: Type locality, 3100 ft., 12
+(including the type).</p>
+
+<p><i>Marginal records.</i>&mdash;See specimens examined.</p>
+</div>
+
+
+<div class="caption3"><a name="Baiomys_musculus_musculus" id="Baiomys_musculus_musculus"></a>
+<b>Baiomys musculus musculus</b> (Merriam)</div>
+
+<div class="species_ref"><i>Sitomys musculus</i> Merriam, Proc. Biol. Soc. Washington, 7:170, September
+29, 1892; Lyon and Osgood, Bull. U. S. Nat. Mus., 62:135, January 15,
+1909.</div>
+
+<div class="species_ref"><i>Baiomys musculus</i> [= <i>musculus</i>], Mearns, Bull. U. S. Nat. Mus., 56:381,
+April 13, 1907; Hooper, Jour. Mamm., 36:29, May 26, 1955.</div>
+
+<div class="species_ref"><i>Peromyscus musculus</i> [<i>musculus</i>], J. A. Allen and Chapman, Bull. Amer.
+Mus. Nat. Hist., 9:203, June 16, 1897; Elliot, Field Columb. Mus. Publ.,
+105(4):135, July 1, 1905; Osgood, N. Amer. Fauna, 28:257, April 17,
+1909 (part).</div>
+
+<div class="species_ref">[<i>Peromyscus</i>] <i>musculus</i>, Trouessart, Cat. Mamm., 1:518, 1898.</div>
+
+<div class="species_ref">[<i>Peromyscus</i>] <i>musculus</i> [<i>musculus</i>], Elliot, Field Columb. Mus. Publ.,
+95(4):175, July 15, 1904.</div>
+
+<div class="species_ref"><i>Baiomys musculus musculus</i>, Miller, Bull. U. S. Nat. Mus., 79:137, December
+31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:318, April
+29, 1924 (part); Ellerman, The Families and Genera of Living Rodents,
+2:402, March 21, 1941; Poole and Schantz, Bull. U. S. Nat. Mus., 178:258,
+March 6, 1942; Davis, Jour. Mamm., 25:394, December 12, 1944
+(part); Hooper, Jour. Mamm., 28:50, February 15, 1947 (part);
+Hall and Villa-R., Univ. Kansas Publs., Mus. Nat. Hist., 1:460, December
+27, 1949 (part); Hall and Villa-R., Anal. del Inst. Biol.,
+21:196, September 28, 1950 (part); Goldman, Smith. Miscl. Coll., 115:336,
+July 31, 1951 (part); Miller and Kellogg, Bull. U. S. Nat. Mus.,
+205:512, March 3, 1955 (part); Hooper, Occas. Papers Mus. Zool. Univ.
+Michigan, 565:13, March 31, 1955; Hall and Kelson, The Mammals of
+North America, 2:661, March 31, 1959 (part).</div>
+
+<div class="species_ref"><i>B.</i> [<i>aiomys</i>] <i>m.</i> [<i>usculus</i>] <i>musculus</i>, Hooper, Jour. Mamm., 33:97, February
+18, 1952 (part); Packard, Univ. Kansas Publs., Mus. Nat. Hist., 9:400;
+December 19, 1958.</div>
+
+<div class="species_ref"><i>Baiomys taylori allex</i>, Hall and Kelson, The Mammals of North America,
+2:659, March 31, 1959 (part).</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;Adult female, skin and skull; No. 33437/45460 U. S. Nat. Mus. (Biol. Surv.
+Coll.); Colima (City), Colima, Republic of México, obtained on March 9,
+1892, by E. W. Nelson, original number 2055.</p>
+
+<p><i>Range.</i>&mdash;Southwestern Nayarit and northwestern Jalisco, south into Colima,
+thence eastward into Michoacán. Zonal range: part of arid Lower Tropical
+Subzone of Goldman (1951:330); approximates part of the Nayarit-Guerrero
+Biotic Province of Goldman and Moore (1945:349). Occurs from near sea
+level in Colima up to 5800 feet in Jalisco.</p>
+
+<p><i>Diagnosis.</i>&mdash;Size large for the species; dorsum Olive-Brown in darkest
+series to Buffy Brown with tones of Fawn Color in the palest series; guard
+<span class="pagenum2"><a name="Page_621" id="Page_621">[Pg 621]</a></span>
+hairs of dorsum black-tipped, gray basally (in some specimens, guard hairs
+gray-tipped with subterminal black band, and gray base); underfur of dorsum
+black-tipped with subterminal band of fawn to buff, Neutral Gray basally; face
+and head paler than back because of greater number of fawn-colored and buff-colored
+hairs; hairs on throat and chin white to base; venter and flanks Pale
+Olive-Buff in palest series to Gray (Pale Gull Gray) in darkest series; individual
+hairs of venter tipped with white to buff, basally Gray (Dark Gull
+Gray); forefeet and hind feet white to gray with flesh-colored undertones; tail
+faintly bicolored, individual hairs above black, below white; nasals flared anteriorly;
+zygoma and zygomatic plate thick. Average and extreme external
+and cranial measurements for 8 adults from Armeria, Colima, are as follows:
+total length, 125.5 (115-135); length of tail vertebrae, 47.5 (42-54); length of
+body, 75.6 (68-81); length of hind foot, 16.5 (16-17); occipitonasal length,
+20.3 (19.8-20.7); zygomatic breadth, 10.7 (10.3-11.1); postpalatal length, 7.4
+(7.1-7.7); least interorbital breadth, 4.0 (3.9-4.1); length of incisive foramina,
+4.3 (4.1-4.5); length of rostrum, 7.3 (6.9-7.6); breadth of braincase, 9.8
+(9.4-10.0); depth of cranium, 7.1 (6.7-7.2); alveolar length of maxillary
+tooth-row, 3.4 (3.3-3.6); for photographs of skull, see
+<a href="#plate1">Plate 1<i>e</i></a>, and <a href="#plate3">Plate 3<i>e</i></a>.</p>
+
+<p><i>Comparisons.</i>&mdash;For comparisons with <i>B. m. brunneus</i>, <i>B. m. infernatis</i>, and
+<i>B. m. pallidus</i>, see accounts of those subspecies. From <i>B. m. nigrescens</i>, <i>B. m.
+musculus</i> differs in: dorsum paler throughout (less of blackish brown); region
+of face and ears paler, more buff and fawn-colored hairs rather than blackish-brown
+to grayish hairs; vibrissae paler; venter paler, less dark gray and less of
+sooty-colored undertones, tips of hairs whitish to pale Olive-Buff rather than
+light gray at tips becoming darker basally; forefeet and hind feet paler, whitish
+to pale buff-color with flesh-colored undertones, not sooty-colored to dark
+brown; tail paler below; nasals flaring outward, not tapering toward midline
+at anteriormost point; zygoma more massive; larger in external and cranial
+dimensions.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;Merriam (1892:170) described <i>Sitomys</i> [= <i>Baiomys</i>]
+<i>musculus</i> on the basis of 23 specimens (from Colima City, Colima;
+Armeria, Colima; Plantinar, and Zapotlán, Jalisco). According to
+the original description, <i>B. musculus</i> resembled a small house mouse
+and was smaller than any known species of <i>Sitomys</i> except <i>S. taylori</i>
+[= <i>Baiomys taylori</i>]. From <i>taylori</i>, <i>musculus</i> differed in being
+larger [in size of body], and in having longer ears and tail, and
+larger hind feet. When Allen and Chapman (1897:203) described
+<i>Peromyscus</i> [= <i>Baiomys</i>] <i>musculus brunneus</i> from Jalapa, Veracruz,
+the specimens described by Merriam from Colima and Jalisco became
+representative of the nominal subspecies <i>B. m. musculus</i>.
+Osgood (1909:258) assigned specimens from Colima, Guerrero,
+Jalisco, Michoacán, Morelos, Oaxaca, Puebla, Sinaloa, Veracruz,
+and Zacatecas to the subspecies <i>musculus</i>. Subsequently, Russell
+(1952:21) named the subspecies <i>pallidus</i> from the arid lowlands
+of Morelos; Hooper (1952:96) described the subspecies <i>infernatis</i>
+<span class="pagenum"><a name="Page_622" id="Page_622">[Pg 622]</a></span>
+from northern Oaxaca and southeastern Puebla; and Goodwin
+(1959:1) described a new subspecies <i>nebulosus</i> from the Oaxaca
+highlands. Each of the subspecies mentioned immediately above
+was described from within the geographic range assigned to <i>B. m.
+musculus</i> by Osgood (<i>loc. cit.</i>). Hall and Kelson (1959:661)
+mapped the range of <i>B. m. musculus</i> so as to include Colima, parts
+of Jalisco, Michoacán, Guerrero, Oaxaca, and Veracruz. Lukens
+(1955:159), in a study of the mammals of Guerrero, has shown that
+the characters attributed to <i>B. m. pallidus</i> are not significantly
+different from those of pygmy mice studied from Guerrero. He
+(<i>loc. cit.</i>) concluded that: (1) if the specimens of pygmy mice
+from central Guerrero were typical of the subspecies <i>musculus</i>,
+then <i>pallidus</i> did not deserve subspecific recognition, or; (2) the
+name <i>B. m. musculus</i> should be restricted to the larger pygmy mice
+inhabiting the lowlands immediately adjacent to the Pacific Coast
+and the area to the north. My data (see <a href="#fig12">Figure 12</a>) show pygmy
+mice from southwestern Nayarit, northwestern and central Jalisco,
+Colima, and parts of Michoacán to be significantly larger in certain
+cranial and external measurements than pygmy mice from Guerrero,
+Oaxaca, Morelos, and parts of Puebla. This finding essentially
+corroborates Hooper's (1952a:96) findings. It seems advisable,
+therefore, to restrict the range of <i>B. musculus musculus</i> to the large
+mice inhabiting west-central México and the coastal lowlands of
+Colima and Michoacán. The name <i>pallidus</i> is applicable to the
+smaller mice occupying Morelos, southwestern Puebla, Guerrero,
+Oaxaca, and southwestern Chiapas.</p>
+
+<p><i>B. m. musculus</i> intergrades with <i>B. m. pallidus</i> in eastern
+Michoacán and central and western Guerrero. Specimens from
+San José Prura and 12 mi. S Tzitzio, Michoacán, though referable
+to <i>B. m. musculus</i> because of slightly larger size of crania are
+intermediate in size and color between the smaller and slightly
+darker <i>pallidus</i> to the south and east and the larger, slightly paler
+<i>musculus</i> to the northwest.</p>
+
+<div class="smaller">
+<a name="FNanchor_1_10" id="FNanchor_1_10"></a>
+<a name="FNanchor_2_11" id="FNanchor_2_11"></a>
+<a name="FNanchor_3_12" id="FNanchor_3_12"></a>
+<a name="FNanchor_4_13" id="FNanchor_4_13"></a>
+<p><i>Specimens examined.</i>&mdash;Total 156 all from the Republic of México, and
+distributed as follows: <span class="smcap">Nayarit</span>: 3 mi. NNW Las Varas, 150 ft., 1.
+<span class="smcap">Jalisco</span>: 7 mi. W Ameca, 4000 ft.,
+2<a href="#Footnote_1_10" class="fnanchor">[10]</a>;
+<i>6 mi. W Ameca</i>, 4300 ft., 3<a href="#Footnote_1_10" class="fnanchor">[10]</a>;
+<i>10 mi. S Ameca</i>, 5800 ft., 1<a href="#Footnote_1_10" class="fnanchor">[10]</a>;
+<i>13 mi. S, 15 mi. W Guadalajara</i>, 3; <i>13 mi. S, 9<sup>1</sup>/<sub>2</sub> mi. W Guadalajara</i>, 1;
+<i>3 mi. ENE Santa Cruz de las Flores</i>, 1; 27 mi. S, 12 mi. W Guadalajara, 1;
+<i>4 mi. NE Autlán</i>, 3000 ft., 5<a href="#Footnote_1_10" class="fnanchor">[10]</a>;
+<i>Sierra de Autlán</i>, 5000 ft., 2<a href="#Footnote_1_10" class="fnanchor">[10]</a>;
+<i>2<sup>1</sup>/<sub>2</sub> mi. NNE Autlán</i>, 3000 ft., 8; 2 mi. SSE Autlán, 1;
+<i>5 mi. S Purificación</i>, 2; Chamela Bay, 1<a href="#Footnote_1_10" class="fnanchor">[10]</a>;
+<i>2 mi. N La Resolana</i>, 1500 ft., 6<a href="#Footnote_1_10" class="fnanchor">[10]</a>;
+<i>1 mi. N San Gabriel</i>, 4000 ft., 32<a href="#Footnote_1_10" class="fnanchor">[10]</a>;
+2 mi. N Cuidad Guzmán, 5000 ft., 1; 3 mi. E Navidad, 4300 ft., 10<a href="#Footnote_1_10" class="fnanchor">[10]</a>.
+<span class="smcap">Colima</span>: <i>type locality</i>, 10<a href="#Footnote_2_11" class="fnanchor">[11]</a>
+(including the type); <i>3 mi. SE Colima</i> (<i>City</i>), 5<a href="#Footnote_1_10" class="fnanchor">[10]</a>;
+<i>4 mi. SW Colima City</i>, 1; Armeria, 200 ft., 8<a href="#Footnote_2_11" class="fnanchor">[11]</a>;
+<i>Paso del Río</i>, 20<a href="#Footnote_1_10" class="fnanchor">[10]</a>.
+<span class="pagenum2"><a name="Page_623" id="Page_623">[Pg 623]</a></span>
+<span class="smcap">Michoacán</span>: 12 mi. S Tzitzio, 6<a href="#Footnote_1_10" class="fnanchor">[10]</a>;
+San José Prura, 4<a href="#Footnote_3_12" class="fnanchor">[12]</a>;
+1 mi. E, 6 mi. S Tacámbaro, 4000 ft., 3<a href="#Footnote_4_13" class="fnanchor">[13]</a>;
+La Salada, 3<a href="#Footnote_2_11" class="fnanchor">[11]</a>;
+<sup>1</sup>/<sub>2</sub> mi. SE Coalcomán, 15<a href="#Footnote_1_10" class="fnanchor">[10]</a>.</p>
+
+<p><i>Marginal records.</i>&mdash;<span class="smcap">Nayarit</span>: 3 mi. NNW Las Varas, 150 ft.
+<span class="smcap">Jalisco</span>: 3 mi. E Navidad, 4300 ft.; 27 mi. S, 12 mi. W Guadalajara.
+<span class="smcap">Michoacán</span>: 12 mi. S Tzitzio; San José Prura; <sup>1</sup>/<sub>2</sub> mi. SE Coalcomán.
+<span class="smcap">Colima</span>: Armeria, 200 ft. <span class="smcap">Jalisco</span>: Chamela Bay.</p>
+</div>
+
+<div class="footnote"><p><a name="Footnote_1_10" id="Footnote_1_10"></a>
+<a href="#FNanchor_1_10"><span class="label">[10]</span></a> Univ. Michigan, Museum of Zoology.</p></div>
+
+<div class="footnote"><p><a name="Footnote_2_11" id="Footnote_2_11"></a>
+<a href="#FNanchor_2_11"><span class="label">[11]</span></a> U. S. Nat. Museum (Biol. Surv. Coll.).</p></div>
+
+<div class="footnote"><p><a name="Footnote_3_12" id="Footnote_3_12"></a>
+<a href="#FNanchor_3_12"><span class="label">[12]</span></a> Chicago Natural History Museum.</p></div>
+
+<div class="footnote"><p><a name="Footnote_4_13" id="Footnote_4_13"></a>
+<a href="#FNanchor_4_13"><span class="label">[13]</span></a> Univ. California, Mus. Vert. Zoology.</p></div>
+
+
+<div class="caption3"><a name="Baiomys_musculus_nigrescens" id="Baiomys_musculus_nigrescens"></a>
+<b>Baiomys musculus nigrescens</b> (Osgood)</div>
+
+<div class="species_ref"><i>Peromyscus musculus nigrescens</i> Osgood, Proc. Biol. Soc. Washington,
+17:76, March 21, 1904; Elliot, Field Columb. Mus. Publ., 105(4):136,
+July 1, 1905; Lyon and Osgood, Bull. U. S. Nat. Mus., 62:135, January
+15, 1909; Osgood, N. Amer. Fauna, 28:259, April 17, 1909.</div>
+
+<div class="species_ref"><i>Baiomys musculus nigrescens</i>, Miller, Bull. U. S. Nat. Mus., 79:137, March
+31, 1912; Miller, Bull. U. S. Nat. Mus., 128:318, April 29, 1924; Goodwin,
+Bull. Amer. Mus. Nat. Hist., 68(1):40, December 12, 1934; Ellerman,
+The Families and Genera of Living Rodents, 2:402, March 21,
+1941; Poole and Schantz, Bull. U. S. Nat. Mus., 178:259, March 6, 1942;
+Hooper, Jour. Mamm., 28:50, February 15, 1947; Goldman, Smith. Miscl.
+Coll., 115:357, July 31, 1951; Miller and Kellogg, Bull. U. S. Nat. Mus.,
+205:513, March 3, 1955; Booth, Walla Walla Publs., Dept. Biol. Sci.,
+20:15, July 10, 1957; Hall and Kelson, The Mammals of North America,
+2:661, March 31, 1959 (part).</div>
+
+<div class="species_ref">[<i>Peromyscus musculus</i>] <i>nigrescens</i>, Elliot, Field Columb. Mus. Publ.,
+95(4):176, 1904.</div>
+
+<div class="species_ref"><i>B.</i> [<i>aiomys</i>] <i>m.</i> [<i>usculus</i>] <i>nigrescens</i>, Goodwin, Bull. Amer. Mus. Nat. Hist.,
+79(2):160, May 29, 1942; Hooper, Jour. Mamm., 33:97, February 18,
+1952 (part); Packard, Univ. Kansas Publs., Mus. Nat. Hist., 9:399,
+December 19, 1958.</div>
+
+<div class="species_ref"><i>B.</i> [<i>aiomys</i>] <i>m.</i> [<i>usculus</i>] <i>musculus</i>, Booth, Walla Walla Publs., Dept. Biol.
+Sci., 20:15, July 10, 1957 (part).</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;Adult female, skin and skull; No. 76827 U. S. Nat. Mus. (Biol.
+Surv. Coll.); Valley of Comitán, Chiapas, Republic of México, obtained on
+December 9, 1895, by E. W. Nelson and E. A. Goldman, original number 8719.</p>
+
+<p><i>Range.</i>&mdash;Southern coastal region and eastern parts of Chiapas, southeastward
+into central and southern Guatemala, thence south into El Salvador (see
+<a href="#fig10">Figure 10</a>). Zonal range: parts of Lower Austral; also occurs in parts of the
+arid division of the Upper Tropical Life-zone, and in parts of the arid division
+of the Lower Tropical Life-zone; approximates a part of the Chiapas Highlands
+Biotic Province of Goldman and Moore (1945:349), and parts of the
+Guatemalan Subregion of Smith (1949:235).</p>
+
+<p><i>Diagnosis.</i>&mdash;Size medium to small for the species; dorsum Vandyke Brown
+mixed with blackish, individual hairs black-tipped with a subterminal band of
+Warm Buff, Neutral Gray at base; guard hairs of dorsum black distally, Neutral
+Gray basally; hairs on sides grayish-brown, facial region like dorsum; chin
+buffy-brown; vibrissae brown, ventrally some white; venter creamy-buff to
+grayish, individual hairs creamy-buff at tips, gray basally; in region of throat
+and chin, hairs tipped with Ochraceous-Buff; dorsal surface of forefeet and
+hind feet dull whitish gray to brownish-black; tail indistinctly bicolored, dusky
+above, grayish to brownish below; incisive foramina short, wide medially;
+<span class="pagenum2"><a name="Page_624" id="Page_624">[Pg 624]</a></span>
+average and extreme external and cranial measurements of 15 adults from 6
+mi. NW Tonalá, Chiapas, are as follows: total length, 107.5 (100-116);
+length of tail vertebrae, 41.1 (33-48); length of body, 66.1 (62-73); length
+of hind foot, 15.0 (14-16); length of ear, 10.9 (10-12); occipitonasal length,
+18.9 (18.4-19.7); zygomatic breadth, 9.8 (9.4-10.2); postpalatal length, 6.9
+(6.6-7.4); least interorbital breadth, 3.7 (3.5-3.8); length of incisive foramina,
+4.4 (4.1-4.8); length of rostrum, 6.7 (6.1-7.1); breadth of braincase, 9.2
+(9.0-9.4); depth of cranium, 6.9 (6.5-7.3); alveolar length of maxillary tooth-row,
+3.1 (2.9-3.2); for photographs of skull, see <a href="#plate1">Plate 1<i>f</i></a>,
+and <a href="#plate3">Plate 3<i>f</i></a>.</p>
+
+<p><i>Comparisons.</i>&mdash;For comparisons with <i>B. m. handleyi</i>, <i>B. m. grisescens</i>, <i>B. m.
+musculus</i>, <i>B. m. pallidus</i>, and <i>B. m. pullus</i>, see accounts of those subspecies.</p>
+
+<p>From <i>B. m. brunneus</i>, <i>B. m. nigrescens</i> differs in: dorsum blackish-brown
+rather than reddish to ochraceous brown; face and ears brownish-black rather
+than brownish with tinges of ochraceous; vibrissae darker; forefeet and hind
+feet darker; venter with more grayish tones; dorsalmost part of zygomatic plate
+projects farther anteriorly; interparietal oval to diamond-shaped and narrower
+anteroposteriorly; zygomata narrower at anteriormost part; slightly smaller in
+most cranial and external measurements.</p>
+
+<p>From <i>B. m. infernatis</i>, <i>B. m. nigrescens</i> differs in: dorsum darker; region of
+face and ears darker; venter buffy to gray rather than whitish-buff; vibrissae
+darker; forefeet and hind feet darker; tail darker above and below; incisive
+foramina shorter, more constricted laterally; cranium slightly smaller in most
+dimensions.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;Hooper (1952a:93-94) reported specimens from the
+coastal strip of southern Chiapas as the most intensely pigmented,
+whereas, specimens from central and western Chiapas were
+distinctly paler. Crania of specimens from the coastal region of
+southern Chiapas were smaller than crania from the central highlands
+and mountains of Chiapas. My studies essentially corroborate
+the findings of Hooper. The gradation of color between the pale
+brown <i>pallidus</i> to the north in Oaxaca, and the brownish-black
+<i>nigrescens</i> to the south in Chiapas is extremely gradual. Specimens
+from the central and western parts of Chiapas (see <a href="#fig10">Figure 10</a> for
+localities) are difficult to assign to either <i>pallidus</i> or <i>nigrescens</i>.
+Equal justification exists for assignment to either subspecies. I
+have assigned the specimens to <i>nigrescens</i> because they are geographically
+closer to the type locality of <i>nigrescens</i>. Specimens
+from Reforma, Oaxaca (assigned by Hooper, 1952a:93-94, to
+<i>nigrescens</i>), are nearly identical in size and color to paratypes of
+<i>pallidus</i>. I assign the Reforma specimens to <i>pallidus</i>.</p>
+
+<p>The darkest of all the specimens examined and assigned to
+<i>nigrescens</i> are from 1 mi. NW San Salvador and 1 mi. S Los Planes,
+El Salvador. The variations in color in this subspecies closely
+correspond to degree of relative humidity; the palest samples are
+from areas of low relative humidity and the darkest are from areas
+<span class="pagenum"><a name="Page_625" id="Page_625">[Pg 625]</a></span>
+of high relative humidity. In view of the present state of differentiation
+of specimens from the southern coastal areas of Chiapas and
+mountainous areas of El Salvador, it would seem that populations
+there might be incipient subspecies.</p>
+
+<div class="smaller">
+<a name="FNanchor_1_14" id="FNanchor_1_14"></a>
+<a name="FNanchor_2_15" id="FNanchor_2_15"></a>
+<a name="FNanchor_3_16" id="FNanchor_3_16"></a>
+<a name="FNanchor_4_17" id="FNanchor_4_17"></a>
+<p><i>Specimens examined.</i>&mdash;Total 319. <span class="smcap">Chiapas</span>:
+<i>17 mi. W Bochil</i>, 1<a href="#Footnote_1_14" class="fnanchor">[14]</a>;
+<i>15 mi. W Bochil</i>, 1<a href="#Footnote_1_14" class="fnanchor">[14]</a>;
+<i>14 mi. W Bochil</i>, 1<a href="#Footnote_1_14" class="fnanchor">[14]</a>;
+Bochil, 6<a href="#Footnote_2_15" class="fnanchor">[15]</a>;
+Ocuilapa, 3500 ft., 5<a href="#Footnote_3_16" class="fnanchor">[16]</a>;
+<i>5 mi. NNW Tuxtla Gutiérrez</i>, 9; <i>11 km. W Tuxtla Gutiérrez</i>, 800 m.,
+2<a href="#Footnote_2_15" class="fnanchor">[15]</a>;
+<i>10 km. W Tuxtla Gutiérrez</i>, 800 m., 2<a href="#Footnote_2_15" class="fnanchor">[15]</a>;
+<i>Tuxtla Gutiérrez</i>, 2600 ft., 8<a href="#Footnote_3_16" class="fnanchor">[16]</a>, 11;
+<i>Ocozocoautla</i>, 10<a href="#Footnote_2_15" class="fnanchor">[15]</a>, 2<a href="#Footnote_3_16" class="fnanchor">[16]</a>;
+25 mi. E Comitán, Las Margaritas, 1250 m., 5<a href="#Footnote_4_17" class="fnanchor">[17]</a>,
+24<a href="#Footnote_2_15" class="fnanchor">[15]</a>; Cintalpa, 555 m., 1<a href="#Footnote_1_14" class="fnanchor">[14]</a>,
+18<a href="#Footnote_2_15" class="fnanchor">[15]</a>, 3<a href="#Footnote_4_17" class="fnanchor">[17]</a>;
+<i>Jiquilpilas</i>, 2000 ft., 1<a href="#Footnote_3_16" class="fnanchor">[16]</a>;
+San Bartolome, 3<a href="#Footnote_3_16" class="fnanchor">[16]</a>;
+<i>type locality</i>, 5700 ft., 26<a href="#Footnote_3_16" class="fnanchor">[16]</a> (including the type);
+15 mi. SW Las Cruces, 1; Villa Flores, 600 m., 12<a href="#Footnote_2_15" class="fnanchor">[15]</a>;
+<i>23 mi. S Comitán</i>, 1<a href="#Footnote_1_14" class="fnanchor">[14]</a>; <i>15 mi. S, 2 mi. E La Trinitaria</i>, 4;
+<i>30 mi. S Comitán</i>, 2<a href="#Footnote_1_14" class="fnanchor">[14]</a>;
+35 mi. S Comitán, 1<a href="#Footnote_1_14" class="fnanchor">[14]</a>;
+<i>3 mi. E Arriga</i>, 1<a href="#Footnote_1_14" class="fnanchor">[14]</a>;
+6 mi. NW Tonalá, 19; <i>Tonalá</i>, 8<a href="#Footnote_3_16" class="fnanchor">[16]</a>;
+<i>Los Amates</i>, 1<a href="#Footnote_1_14" class="fnanchor">[14]</a>;
+Pijijiapan, 10 m., 7<a href="#Footnote_2_15" class="fnanchor">[15]</a>;
+Mapastepec, 45 m., 25<a href="#Footnote_2_15" class="fnanchor">[15]</a>,
+4<a href="#Footnote_4_17" class="fnanchor">[17]</a>.</p>
+
+<p><span class="smcap">Guatemala</span>: Chanquejelve, 1<a href="#Footnote_1_14" class="fnanchor">[14]</a>;
+<i>Nentón</i>, 3000 ft., 1<a href="#Footnote_3_16" class="fnanchor">[16]</a>;
+Jacaltenango, 5400 ft., 8<a href="#Footnote_3_16" class="fnanchor">[16]</a>;
+La Primavera, 5<a href="#Footnote_1_14" class="fnanchor">[14]</a>; 4 mi. S Guatemala City, 4700 ft., 3;
+<i>5 mi. S Guatemala City</i>, 4050 ft., 10; <i>6 mi. S Guatemala City</i>, 4680 ft., 1;
+<i>Lake Amatitlán</i>, 4500 ft., 13<a href="#Footnote_3_16" class="fnanchor">[16]</a>;
+El Progresso (Distrito Santa Rosa), 3<a href="#Footnote_2_15" class="fnanchor">[15]</a>;
+<i>2 mi. N, 1 mi. W Cuilapa</i>, 2980 ft., 1<a href="#Footnote_1_14" class="fnanchor">[14]</a>;
+<i>1 mi. WSW El Molino</i> (<i>Distrito Santa Rosa</i>), 2;
+<i>2<sup>1</sup>/<sub>2</sub> mi. W, 2<sup>1</sup>/<sub>4</sub> mi. N San Cristobal</i>, 2900 ft., 1;
+El Zapote, 1<a href="#Footnote_2_15" class="fnanchor">[15]</a>.</p>
+
+<p><span class="smcap">El Salvador</span>: 1 mi. NW San Salvador, 29; 1 mi. S Los Planes, 15.</p>
+
+<p><i>Marginal Records.</i>&mdash;<span class="smcap">Chiapas</span>: Bochil; 25 mi. E Comitán, Las Margaritas,
+1250 ft. <span class="smcap">Guatemala</span>: Chanquejelve; La Primavera; Jacaltenango, 5400 ft.;
+4 mi. S Guatemala City, 4700 ft.; El Progresso. <i>El Salvador</i>: 1 mi. NW San Salvador;
+1 mi. S Los Planes. <span class="smcap">Guatemala</span>: El Zapote. <span class="smcap">Chiapas</span>: Mapastepec,
+45 m.; Pijijiapan, 10 m.; 6 mi. NW Tonalá; 15 mi. SW Las Cruces; Cintalpa, 555 m.; Ocuilapa, 3500 ft.</p>
+</div>
+
+<div class="footnote"><p><a name="Footnote_1_14" id="Footnote_1_14"></a>
+<a href="#FNanchor_1_14"><span class="label">[14]</span></a> American Museum of Natural History.</p></div>
+
+<div class="footnote"><p><a name="Footnote_2_15" id="Footnote_2_15"></a>
+<a href="#FNanchor_2_15"><span class="label">[15]</span></a> Univ. Michigan, Museum of Zoology.</p></div>
+
+<div class="footnote"><p><a name="Footnote_3_16" id="Footnote_3_16"></a>
+<a href="#FNanchor_3_16"><span class="label">[16]</span></a> U. S. Nat. Museum (Biol. Surv. Coll.).</p></div>
+
+<div class="footnote"><p><a name="Footnote_4_17" id="Footnote_4_17"></a>
+<a href="#FNanchor_4_17"><span class="label">[17]</span></a> University of Florida Collections.</p></div>
+
+
+<div class="caption3"><a name="Baiomys_musculus_pallidus" id="Baiomys_musculus_pallidus"></a>
+<b>Baiomys musculus pallidus</b> Russell</div>
+
+<div class="species_ref"><i>Baiomys musculus pallidus</i> Russell, Proc. Biol. Soc. Washington, January 29,
+1952; Davis and Russell, Jour. Mamm., 35:75, February 10, 1954; Miller
+and Kellogg, Bull. U. S. Nat. Mus., 205:512; Hall and Kelson, The Mammals
+of North America, 2:662, March 31, 1959.</div>
+
+<div class="species_ref"><i>Peromyscus musculus brunneus</i>, Elliot, Field Columb. Mus. Publ., 115(8):203,
+1907 (part).</div>
+
+<div class="species_ref"><i>Peromyscus musculus</i> [<i>musculus</i>], Osgood, N. Amer. Fauna, 28:257, April
+17, 1909 (part).</div>
+
+<div class="species_ref"><i>Baiomys musculus musculus</i>, Miller, Bull. U. S. Nat. Mus., 79:137, December
+31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:318, April 29, 1924
+(part); Davis, Jour. Mamm., 25:394, December 12, 1944 (part); Hooper,
+Jour. Mamm., 28:50, February 15, 1947 (part); Goldman, Smith, Miscl.
+Coll., 115:336, July 31, 1951 (part); Miller and Kellogg, Bull. U. S.
+Nat. Mus., 205:512, March 3, 1955 (part); Booth, Walla Walla Publs.,
+Dept. Biol. Sci., 20:15, July 10, 1957 (part); Hall and Kelson, The
+Mammals of North America, 2:661, March 31, 1959 (part); Goodwin,
+Amer. Mus. Novitates, 1929:1, March 5, 1959.</div>
+
+<div class="species_ref"><i>B.</i> [<i>aiomys</i>] <i>m.</i> [<i>usculus</i>] <i>musculus</i>, Hooper, Jour. Mamm., 33:97, February
+18, 1952 (part).</div>
+
+<div class="species_ref"><i>B.</i> [<i>aiomys</i>] <i>m.</i> [<i>usculus</i>] <i>nigrescens</i>, Hooper, Jour. Mamm., 33:97, February
+18, 1952 (part).</div>
+
+<div class="species_ref"><i>Baiomys musculus nebulosus Goodwin</i>, Amer. Mus. Novitates, 1929, March
+5, 1959.</div>
+
+<p><span class="pagenum"><a name="Page_626" id="Page_626">[Pg 626]</a></span></p>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;Adult female, skin and skull; No. 4501 Texas A&amp;M Cooperative
+Wildlife Collection; 12 kms. NW Axochiapán, 3500 feet, Morelos, Republic
+of México, obtained on July 28, 1950, by W. B. Davis, original number 5112.</p>
+
+<p><i>Range.</i>&mdash;Guerrero thence eastward into Morelos and west central Puebla
+along the southern edge of the Transverse Volcanic Biotic Province (Goldman
+and Moore, 1945:349), south into Oaxaca, see <a href="#fig10">Figure 10</a>. Zonal range: largely
+Arid Lower Tropical Subzone of Goldman (1951:330). Occurs from near sea
+level in Oaxaca and Guerrero up to 6550 feet in Oaxaca.</p>
+
+<p><i>Diagnosis.</i>&mdash;Size medium for the species; dorsum Buffy Brown in palest
+series to Olive-Brown in darkest series, individual hairs Warm Buff, Neutral
+Gray basally, some with black tips and a subterminal band of Warm Buff, guard
+hairs of dorsum black-tipped, gray basally; hairs on sides creamy-buff, gray
+basally; face same color as back fading to white on throat; vibrissae white-tipped,
+pale brown basally; venter, whitish with tinges of buff on lower throat,
+individual hairs having tips white to buffy-white, light gray basally; dorsal
+surface of forefeet and hind feet whitish to flesh-color; tail indistinctly bicolored,
+brownish above, grayish brown below; zygoma bowed as in <i>B. m.
+grisescens</i>; tail short; average and extreme external and cranial measurements
+for 17 adults from Tehuantepec, Oaxaca, are: total length, 117.3 (110-126);
+length of tail vertebrae, 46.9 (41-51); length of body, 70.4 (65-76);
+length of hind foot, 15.8 (15-16); occipitonasal length, 18.9 (18.2-20.1); zygomatic
+breadth, 10.1 (9.7-10.6); postpalatal length, 6.9 (6.6-7.5); least interorbital
+breadth, 3.8 (3.6-3.9); length of incisive foramina, 4.4 (4.2-4.7);
+length of rostrum, 6.7 (6.3-7.2); breadth of braincase, 9.3 (8.7-9.7); depth of
+cranium, 6.6 (6.4-6.8); alveolar length of maxillary tooth-row, 3.2 (3.1-3.4);
+for photographs of skull, see <a href="#plate1">Plate 1<i>g</i></a>, and <a href="#plate3">Plate 3<i>g</i></a>.</p>
+
+<p><i>Comparisons.</i>&mdash;For comparisons with <i>B. m. brunneus</i> and <i>B. m. infernatis</i>,
+see accounts of those subspecies.</p>
+
+<p>From <i>B. m. musculus</i>, <i>B. m. pallidus</i> differs in: dorsum more olive-gray and
+brown, less ochraceous on either side of mid-dorsal region; face below eye
+grayish, not buffy; sides gray with buffy overtone, not creamy with light yellow
+overtones; venter grayish-white rather than an olive-buff; zygomata more
+tapering anteriorly; maxillary part of zygoma narrower when viewed from
+above; external and cranial dimensions smaller.</p>
+
+<p>From <i>B. m. nigrescens</i>, <i>B. m. pallidus</i> differs in: dorsum paler, fewer black
+hairs medially; face paler, less sooty; vibrissae brownish with white tips rather
+than black with brownish tips; venter paler; dorsal surface of forefeet and
+hind feet whitish to flesh-colored rather than sooty to dusky-white; tail paler;
+nasals slightly more attenuated; averaging slightly larger in external and cranial
+measurements.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;Russell (1952:21) described <i>pallidus</i>, on the basis of
+specimens from the arid Balsas Basin, of Morelos, as pale gray
+dorsally. After examining the original material from Morelos, I
+find the dorsal color of <i>pallidus</i> to be much closer to a buffy brown
+than a pale grayish. Even so, smaller size differentiates <i>pallidus</i>
+from <i>musculus</i>. <i>B. m. infernatis</i>, not <i>B. m. pallidus</i>, is the most
+pallid of all named subspecies of <i>B. musculus</i>.</p>
+
+<p><span class="pagenum"><a name="Page_627" id="Page_627">[Pg 627]</a></span></p>
+
+<p><i>B. m. pallidus</i> intergrades to the northwest with <i>B. m. musculus</i>,
+to the northeast with <i>B. m. infernatis</i>, and to the southeast with
+<i>B. m. nigrescens</i>.</p>
+
+<p>According to Goodwin (1959:2), <i>B. m. nebulosus</i> (named on the
+basis of one specimen) differs from <i>B. m. musculus</i> [= <i>pallidus</i>]
+from southern Oaxaca in: darker and longer pelage; larger skull;
+interorbital region broader and less constricted posteriorly. From
+<i>B. m. nigrescens</i> and <i>B. m. brunneus</i>, <i>B. m. nebulosus</i> differs as
+follows: pelage longer and softer; skull larger.</p>
+
+<p>Study of specimens of <i>B. musculus</i> from Oaxaca reveals considerable
+variation in external and cranial measurements as well as
+color, corresponding to that reported by Goodwin (<i>loc. cit.</i>).
+Specimens from higher altitudes average somewhat darker and
+larger in external and cranial size than those at lower elevations.
+These differences seem to be microgeographic and not of subspecific
+rank. Among specimens that I have studied in Oaxaca are
+several from different localities (KU 63052, an adult male, from 3
+mi. W Miahuatlán; KU 68964, an adult male from 3 mi. W Mitla,
+6000 ft.; KU 63055, an adult female from 3 mi. S Candelario, 1200
+ft.) that, according to Goodwin (<i>in. litt.</i>) match <i>nebulosus</i> in reported
+color, size of body and skull (except for the region of the
+rostrum).</p>
+
+<p>Two of the three specimens (KU 63052 and 63055) are the
+darkest of a series in which the palest are inseparable from <i>B. m.
+pallidus</i>. Goodwin, who kindly compared the three specimens
+with the type of <i>nebulosus</i>, mentioned (<i>in. litt.</i>) that the skull of
+the type has a slenderer rostrum. Included in the series of skulls
+of <i>B. m. pallidus</i> from 3 mi. W Mitla are several adults (not seen
+by Goodwin) with slender rostra. <i>B. m. nebulosus</i> is judged to
+be a synonym of <i>B. m. pallidus</i>.</p>
+
+<p>Populations of pygmy mice occurring in partially isolated areas
+of highland in Oaxaca seem to me to be incipient subspecies.</p>
+
+<div class="smaller">
+<a name="FNanchor_1_18" id="FNanchor_1_18"></a>
+<a name="FNanchor_2_19" id="FNanchor_2_19"></a>
+<a name="FNanchor_3_20" id="FNanchor_3_20"></a>
+<a name="FNanchor_4_21" id="FNanchor_4_21"></a>
+<a name="FNanchor_5_22" id="FNanchor_5_22"></a>
+<a name="FNanchor_6_23" id="FNanchor_6_23"></a>
+<a name="FNanchor_7_24" id="FNanchor_7_24"></a>
+<p><i>Specimens examined.</i>&mdash;Total 824 all from the Republic of México and distributed
+as follows: <span class="smcap">Puebla</span>: 2 mi. S Atlixco, 5800 ft., 1;
+<i>1 mi. SSW Tilapa</i>, 5800 ft., 2; <i>6 mi. SW Izucár de Matemores</i>, 7;
+<i>Piaxtla</i>, 3900 ft., 4<a href="#Footnote_1_18" class="fnanchor">[18]</a>;
+Acatlán, 4100 ft., 1. <span class="smcap">Morelos</span>: 5 mi. W Tepoztlán, 6000 ft.,
+7<a href="#Footnote_2_19" class="fnanchor">[19]</a>; <i>1 mi. W Tepoztlán</i>,
+6000 ft., 9<a href="#Footnote_2_19" class="fnanchor">[19]</a>; <i>2 mi. SW Tepoztlán</i>,
+7000 ft., 1<a href="#Footnote_3_20" class="fnanchor">[20]</a>; <i>Cuernvaca</i>,
+9<a href="#Footnote_2_19" class="fnanchor">[19]</a>;
+<i>6 mi. W Yautepec</i>, 4500 ft., 1<a href="#Footnote_3_20" class="fnanchor">[20]</a>;
+<i>Yautepec</i>, 12<a href="#Footnote_2_19" class="fnanchor">[19]</a>;
+<i>3 mi. N Alpuyeca</i>, 4000 ft., 2<a href="#Footnote_3_20" class="fnanchor">[20]</a>;
+<i>Puente de Ixtla</i>, 2<a href="#Footnote_2_19" class="fnanchor">[19]</a>;
+<i>Tetecala</i>, 4<a href="#Footnote_4_21" class="fnanchor">[21]</a>;
+<i>2 km. S Jonacatepec</i>, 4500 ft., 6<a href="#Footnote_3_20" class="fnanchor">[20]</a>;
+<i>type locality</i>, 6 (including the type).
+<span class="smcap">Guerrero</span>: <i>Yerbabuena</i>, 1800 m., 1;
+<i>Cueva de tia Juana</i> [= <i>1.5 km. SSW Yerbabuena</i>], 1;
+<i>Laguna Honda</i>, 1840 m. [= <i>1.5 km. S Yerbabuena</i>], 3;
+9 mi. SE Taxco, 3800 ft., 1<a href="#Footnote_5_22" class="fnanchor">[22]</a>;
+<i>17 km. S Taxco</i>, 4000 ft., 2<a href="#Footnote_3_20" class="fnanchor">[20]</a>;
+<i>Iguala</i>, 5<a href="#Footnote_2_19" class="fnanchor">[19]</a>;
+<i>3.2 km. SSE Iguala</i>, 970 m., 1; 1 km. SSE Texcaizintla, 1600 m., 2;
+<i>Teloloapán</i>, 20<a href="#Footnote_2_19" class="fnanchor">[19]</a>,
+5<a href="#Footnote_7_24" class="fnanchor">[24]</a>; <i>1 km. N Chapa</i>, 1470 m., 6;
+<i>Chapa</i>, 1470 m., 5; El Limón, 3<a href="#Footnote_1_18" class="fnanchor">[18]</a>;
+2<sup>1</sup>/<sub>2</sub> mi. W Mexcala, 2100 ft., 1<a href="#Footnote_3_20" class="fnanchor">[20]</a>;
+<i>Río Balsas</i>, 1<a href="#Footnote_1_18" class="fnanchor">[18]</a>;
+Ayusinaha [= Ayotzinapa], 1<a href="#Footnote_1_18" class="fnanchor">[18]</a>;
+<i>Tlapa</i>, <span class="pagenum2"><a name="Page_628" id="Page_628">[Pg 628]</a></span>
+3900 ft, 1<a href="#Footnote_1_18" class="fnanchor">[18]</a>;
+<i>2.5 mi. S Almolonga</i>, 5600 ft., 13<a href="#Footnote_3_20" class="fnanchor">[20]</a>;
+<i>1 km. N Zihuatanejo</i>, 1; Zihuatanejo Bay, 4<a href="#Footnote_2_19" class="fnanchor">[19]</a>;
+<i>Las Gatas</i> [= <i>2 km. S. Zihuatanejo</i>], 2;
+<i>2 km. SSE Zihuatanejo</i>, 9; <i>4 mi. W Chilpancingo</i>, 5800 ft.,
+3<a href="#Footnote_3_20" class="fnanchor">[20]</a>; <i>Chilpancingo</i>, 4800 ft.,
+14<a href="#Footnote_1_18" class="fnanchor">[18]</a>, 21<a href="#Footnote_2_19" class="fnanchor">[19]</a>,
+45<a href="#Footnote_4_21" class="fnanchor">[21]</a>; <i>2 mi. N Tixtla</i>, 4400 ft.,
+3<a href="#Footnote_3_20" class="fnanchor">[20]</a>; <i>3.2 km. S Chilpancingo</i>, 4;
+<i>Cd. Chamilpa</i> [= <i>12 km. ESE Chilpancingo</i>], 5;
+<i>Tlalixtaquilla</i>, 4200 ft., 2<a href="#Footnote_1_18" class="fnanchor">[18]</a>;
+<i>15 km. S. Chilpancingo</i>, 4300 ft., 10<a href="#Footnote_3_20" class="fnanchor">[20]</a>;
+<i>1 mi. SW Colotlipa</i>, 2700 ft., 16<a href="#Footnote_3_20" class="fnanchor">[20]</a>;
+<i>2 mi. SW Colotlipa</i>, 2700 ft., 1<a href="#Footnote_3_20" class="fnanchor">[20]</a>;
+<i>Achuitzotla</i>, 2800 ft., 7<a href="#Footnote_3_20" class="fnanchor">[20]</a>;
+<i>8 mi. SW Colotlipa</i>, 1<a href="#Footnote_3_20" class="fnanchor">[20]</a>;
+<i>5 mi. S Rincón</i>, 2600 ft., 2<a href="#Footnote_3_20" class="fnanchor">[20]</a>;
+<i>8 mi. SW Tierra Colorado</i>, 600 ft., 1<a href="#Footnote_3_20" class="fnanchor">[20]</a>;
+Río Aguacatillo, <i>30 km. N Acapulco</i>, 1000 ft., 3<a href="#Footnote_3_20" class="fnanchor">[20]</a>;
+5 mi. ESE Tecpán, 50 ft., 9; <i>Ejido Viejo</i>, <i>12 km. NNW Acapulco</i>, 1;
+<i>2 mi. NNW Acapulco</i>, 7; Acapulco, 3<a href="#Footnote_1_18" class="fnanchor">[18]</a>,
+3<a href="#Footnote_4_21" class="fnanchor">[21]</a>;
+Omentepec, 200 ft., 7<a href="#Footnote_1_18" class="fnanchor">[18]</a>.
+<span class="smcap">Oaxaca</span>: <i>4 mi. E Huajuapám</i>, 5000 ft., 1; 2 mi.
+NW Tamazulapán, 6550 ft., 1; Yalalag, 3000 ft., 5<a href="#Footnote_1_18" class="fnanchor">[18]</a>;
+<i>11 mi. NW Oaxaca</i> [<i>City</i>], 1; <i>Yaganiza</i>, 3900 ft.,
+1<a href="#Footnote_1_18" class="fnanchor">[18]</a>; Oaxaca [City], 5000 ft.,
+15, 7<a href="#Footnote_4_21" class="fnanchor">[21]</a>, 7<a href="#Footnote_2_19" class="fnanchor">[19]</a>,
+5<a href="#Footnote_7_24" class="fnanchor">[24]</a>; <i>3 mi. ESE Oaxaca</i> [<i>City</i>], 30;
+<i>4 mi. ESE Oaxaca</i> [<i>City</i>], 5050 ft., 1; <i>10 mi. SE Oaxaca</i> [City],
+1<a href="#Footnote_5_22" class="fnanchor">[22]</a>; <i>Cerro Ocotepec</i>,
+1<a href="#Footnote_6_23" class="fnanchor">[23]</a>;
+Tepantepec, 9<a href="#Footnote_6_23" class="fnanchor">[23]</a>;
+<i>1 mi. E Tlacolula</i>, 5500 ft., 53<a href="#Footnote_2_19" class="fnanchor">[19]</a>;
+<i>3 mi. W Mitla</i>, 11; Jalapa, El Campanario, 1<a href="#Footnote_6_23" class="fnanchor">[23]</a>;
+<i>2 mi. SE Matalán</i>, 5950 ft., 14; <i>Lachiguiri</i>, 2<a href="#Footnote_6_23" class="fnanchor">[23]</a>;
+<i>Tres Cruces</i>, 10<a href="#Footnote_6_23" class="fnanchor">[23]</a>; <i>Agua Blanca</i>,
+11<a href="#Footnote_6_23" class="fnanchor">[23]</a>;
+<i>San José</i>, 1<a href="#Footnote_6_23" class="fnanchor">[23]</a>;
+Reforma, 30<a href="#Footnote_2_19" class="fnanchor">[19]</a>,
+7<a href="#Footnote_4_21" class="fnanchor">[21]</a>, 10<a href="#Footnote_6_23" class="fnanchor">[23]</a>,
+6<a href="#Footnote_7_24" class="fnanchor">[24]</a> <i>Totolapa</i>,
+1<a href="#Footnote_1_18" class="fnanchor">[18]</a>;
+<i>Nejapa</i>, <i>85 km. WNW Tehuantepec</i>, 500 m., 12<a href="#Footnote_2_19" class="fnanchor">[19]</a>,
+6<a href="#Footnote_7_24" class="fnanchor">[24]</a>; <i>Chicapa</i>,
+2<a href="#Footnote_1_18" class="fnanchor">[18]</a>; <i>Gueladu</i>
+[= <i>Jalapa</i>], 6<a href="#Footnote_6_23" class="fnanchor">[23]</a>;
+<i>Juchitán</i>, <i>Laguna Superior</i>; Manteca, 8<a href="#Footnote_6_23" class="fnanchor">[23]</a>,
+1<a href="#Footnote_6_23" class="fnanchor">[23]</a>; San Bartolo, 3000 ft.,
+1<a href="#Footnote_1_18" class="fnanchor">[18]</a>; <i>Ejutla</i>, 1400 m.,
+21<a href="#Footnote_2_19" class="fnanchor">[19]</a>; <i>El Bambita</i>, <i>Tequisitlán</i> 4<a href="#Footnote_6_23" class="fnanchor">[23]</a>; <i>Mixtequilla</i>,
+2<a href="#Footnote_6_23" class="fnanchor">[23]</a>; <i>Guiencola</i>,
+5<a href="#Footnote_6_23" class="fnanchor">[23]</a>; <i>Tehuantepec</i>, 200 ft.,
+26<a href="#Footnote_1_18" class="fnanchor">[18]</a>, 11<a href="#Footnote_2_19" class="fnanchor">[19]</a>;
+<i>Sola de la Vega</i>, 26<a href="#Footnote_2_19" class="fnanchor">[19]</a>,
+3<a href="#Footnote_7_24" class="fnanchor">[24]</a>;
+Huilotepec, 13<a href="#Footnote_1_18" class="fnanchor">[18]</a>,
+3<a href="#Footnote_6_23" class="fnanchor">[23]</a>;
+<i>Santa Lucia</i>, 24<a href="#Footnote_6_23" class="fnanchor">[23]</a>;
+<i>Cerro de Paste</i>, <i>Tenango</i>, 7<a href="#Footnote_6_23" class="fnanchor">[23]</a>;
+<i>Sta. C. Quieri</i>, 3<a href="#Footnote_6_23" class="fnanchor">[23]</a>;
+<i>Santa Marie Ecatepec</i>, <i>Zarzamora</i>,
+13<a href="#Footnote_6_23" class="fnanchor">[23]</a>;
+<i>Rincón Bamba</i>, 11<a href="#Footnote_6_23" class="fnanchor">[23]</a>;
+<i>3 mi. W Miahuatlán</i>, 5300 ft., 1; <i>Miahuatlán</i>,
+12<a href="#Footnote_2_19" class="fnanchor">[19]</a>, 1<a href="#Footnote_6_23" class="fnanchor">[23]</a>,
+6<a href="#Footnote_7_24" class="fnanchor">[24]</a>;
+<i>San Juan Acaltepec</i>, 5<a href="#Footnote_6_23" class="fnanchor">[23]</a>;
+<i>Zapotitlán</i>, 1<a href="#Footnote_6_23" class="fnanchor">[23]</a>;
+<i>Llano Grande</i>, 3<a href="#Footnote_1_18" class="fnanchor">[18]</a>;
+Pinotepa, 700 ft., 2<a href="#Footnote_1_18" class="fnanchor">[18]</a>;
+Juquila, 8<a href="#Footnote_1_18" class="fnanchor">[18]</a>;
+<i>Arroyo</i>, <i>San Juan</i>, <i>north of Cerro Otate</i>,
+1<a href="#Footnote_6_23" class="fnanchor">[23]</a>;
+Cerro Otate, 3<a href="#Footnote_6_23" class="fnanchor">[23]</a>; 3 mi. S Candelaria, 1.</p>
+
+<p><i>Marginal records.</i>&mdash;<span class="smcap">Morelos</span>: 5 mi, W Tepoztlán,
+6000 ft. <span class="smcap">Puebla</span>: 2 mi. S Atlixco, 5800 ft.;
+Acatlán, 4100 ft. <span class="smcap">Oaxaca</span>: 2 mi. NW Tamazulapán,
+6550 ft; Tepantepec; Oaxaca [City], 5000 ft; Yalalag, 3000 ft; Jalapa, El
+Campanario; Reforma; Huilotepec; 3 mi. S Candelaria; Cerro Otate; Pinotepa,
+700 ft. <span class="smcap">Guerrero</span>: Acapulco; Zihuatanejo Bay; El Limón;
+9 mi. SE Taxco, 3800 ft.</p>
+</div>
+
+<div class="footnote"><p><a name="Footnote_1_18" id="Footnote_1_18"></a>
+<a href="#FNanchor_1_18"><span class="label">[18]</span></a> U. S. Nat. Museum (Biol. Surv. Coll.).</p></div>
+
+<div class="footnote"><p><a name="Footnote_2_19" id="Footnote_2_19"></a>
+<a href="#FNanchor_2_19"><span class="label">[19]</span></a> Univ. Michigan, Museum of Zoology.</p></div>
+
+<div class="footnote"><p><a name="Footnote_3_20" id="Footnote_3_20"></a>
+<a href="#FNanchor_3_20"><span class="label">[20]</span></a> Texas A &amp; M, Cooperative Wildlife Research Collection.</p></div>
+
+<div class="footnote"><p><a name="Footnote_4_21" id="Footnote_4_21"></a>
+<a href="#FNanchor_4_21"><span class="label">[21]</span></a> Chicago Natural History Museum.</p></div>
+
+<div class="footnote"><p><a name="Footnote_5_22" id="Footnote_5_22"></a>
+<a href="#FNanchor_5_22"><span class="label">[22]</span></a> California Academy of Sciences.</p></div>
+
+<div class="footnote"><p><a name="Footnote_6_23" id="Footnote_6_23"></a>
+<a href="#FNanchor_6_23"><span class="label">[23]</span></a> American Museum of Natural History.</p></div>
+
+<div class="footnote"><p><a name="Footnote_7_24" id="Footnote_7_24"></a>
+<a href="#FNanchor_7_24"><span class="label">[24]</span></a> University of Florida Collections.</p></div>
+
+
+<div class="caption3"><a name="Baiomys_musculus_pullus" id="Baiomys_musculus_pullus"></a>
+<b>Baiomys musculus pullus</b> Packard</div>
+
+<div class="species_ref"><i>Baiomys musculus pullus</i> Packard, Univ. Kansas Publs., Mus. Nat. Hist.,
+9:401, December 19, 1958.</div>
+
+<div class="species_ref"><i>Baiomys musculus grisescens</i>, Goodwin, Bull. Amer. Mus. Nat. Hist., 79(2):161,
+May 29, 1942 (part); Miller and Kellogg, Bull. U. S. Nat. Mus.,
+205:513, March 3, 1955 (part); Hall and Kelson, The Mammals of
+North America, 2:661, March 31, 1959 (part).</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;Adult female, skin and skull; No. 71605 University of Kansas Museum
+of Natural History; 8 mi. S Condega, Estelí, Nicaragua, obtained on July
+15, 1956, by A. A. Alcorn, original number 4218.</p>
+
+<p><i>Range.</i>&mdash;West-central Nicaragua, from Matagalpa northwest into the valley
+of the Río Estelí, east as far as Jinotega, see <a href="#fig10">Figure 10</a>. Zonal range: Upper
+Tropical Life-zone.</p>
+
+<p><i>Diagnosis.</i>&mdash;Size medium to small for the species; dorsum Fuscous-Black, individual
+hairs black-tipped with a subterminal band of Ochraceous-Buff, Neutral
+Gray at base; some hairs on dorsum all black to Neutral Gray at base; hair on
+sides Neutral Gray tinged with blackish; face blackish, becoming buffy on sides
+<span class="pagenum2"><a name="Page_629" id="Page_629">[Pg 629]</a></span>
+of head, and white on throat; vibrissae black; tail unicolored Chaetura Black;
+forefeet and hind feet sooty to dusky-white; mid-ventral region of venter white,
+hairs white to base; in region of anus and throat, hairs white-tipped, Neutral
+Gray at base; average and extreme external and cranial measurements of the
+type and 16 paratypes are as follows: total length, 117.3 (111-121); length of
+tail vertebrae, 47.2 (44-50); length of body, 70.4 (66-74); length of hind
+foot, 15.5 (14-17); length of ear from notch, 11.9 (10-13); occipitonasal
+length, 19.3 (18.9-19.8); zygomatic breadth, 10.2 (9.7-10.6); postpalatal length,
+7.0 (6.8-7.3); least interorbital breadth, 3.9 (3.8-4.1); length of incisive foramina,
+4.3 (4.0-4.6); length of rostrum, 7.0 (6.5-7.4); breadth of braincase, 9.6
+(9.3-10.0); depth of cranium, 7.0 (6.8-7.3); alveolar length of maxillary tooth-row,
+3.1 (3.0-3.2); for photographs of skull, see <a href="#plate1">Plate 1<i>h</i></a>,
+and <a href="#plate3">Plate 3<i>h</i></a>.</p>
+
+<p><i>Comparisons.</i>&mdash;From <i>B. m. grisescens</i>, <i>B. m. pullus</i> differs in: dorsum and
+tail darker; sides and lateral parts of venter grayish instead of buffy-brown, thus
+forming distinct mid-ventral white stripe; average length of body and tail
+significantly longer, thus total length greater; maxillary tooth-row significantly
+shorter; slightly larger in other cranial and external dimensions.</p>
+
+<p>From <i>B. m. nigrescens</i>, <i>B. m. pullus</i> differs in: dorsum slightly darker; face
+grayish, not sooty; mid-ventral white stripe (absent in most specimens of
+<i>nigrescens</i>) present and becoming grayish laterally; tail darker, less hairy, and
+averaging significantly longer; smaller in most external and cranial dimensions.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;<i>B. m. pullus</i> resembles <i>B. m. nigrescens</i> in size and
+color but can readily be distinguished from <i>nigrescens</i> by the shorter
+tail. <i>B. m. pullus</i> intergrades with <i>nigrescens</i> as shown by specimens,
+referable to <i>B. m. nigrescens</i>, from 1 mi. NW San Salvador
+and from 1 mi. S Los Planes, El Salvador. In color of the dorsum,
+specimens from these localities are intermediate between <i>nigrescens</i>
+and <i>pullus</i>.</p>
+
+<p>The mid-ventral white stripe characteristic of <i>pullus</i> is present in
+three of 28 adults from El Salvador. Goodwin (1942:160) reported
+white hairs on the pectoral region of several topotypes of <i>B. m.
+grisescens</i>. The areas of white hairs on the venter of <i>grisescens</i> occur
+in approximately 10 per cent of the specimens examined, whereas
+in <i>pullus</i>, the frequency of occurrence is 90 per cent. The areas of
+white hairs in <i>grisescens</i> are in broad patches on the pectoral region,
+while in <i>pullus</i>, a white stripe passes from the pectoral region to the
+inguinal region in both males and females. I know of no selective
+advantage that the presence of this white stripe would confer on the
+mice.</p>
+
+<div class="smaller">
+<p><i>Specimens examined.</i>&mdash;Total 46, all from <span class="smcap">Nicaragua</span>, and distributed as
+follows: Type locality, 32 (including the type); <i>9 mi. NNW Estelí</i>, 8; <i>8 mi.
+NNW Estelí</i>, 3; San Rafael Del Norte, 1 (Amer. Mus. Nat. Hist.); <i>1 mi. NW
+Jinotega</i>, 1; Matagalpa, 1 (Amer. Mus. Nat. Hist.).</p>
+
+<p><i>Marginal records.</i>&mdash;<span class="smcap">Nicaragua</span>: San Rafael Del Norte; Matagalpa; type
+locality.</p>
+</div>
+
+<p><span class="pagenum"><a name="Page_630" id="Page_630">[Pg 630]</a></span></p>
+
+
+<div class="caption3"><a name="Baiomys_taylori" id="Baiomys_taylori"></a>
+<b>Baiomys taylori</b><br />
+<br />
+Northern Pygmy Mouse<br />
+<br />
+(Synonymy under subspecies)</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;<i>Hesperomys</i> (<i>Vesperimus</i>) <i>taylori</i> Thomas, Ann. Mag. Nat. Hist.,
+Ser. 5, 19:66, January, 1887.</p>
+
+<p><i>Range.</i>&mdash;Southeastern Arizona and southwestern New Mexico, south into
+Chihuahua and Durango, just east of the Sierra Madre Occidental, thence
+southeast through Zacatecas, Aquascalientes, Jalisco, Querétaro, and Guanajuato;
+two fingerlike projections extend northward, one on the west along the coast of
+Sinaloa into southern Sonora, and the other on the east covering eastern San
+Luis Potosí, Tamaulipas, eastern Coahuila, Nuevo León, into south, southeast,
+and north-central Texas. Southern margin of range in central México approximates
+the 19th degree of latitude (see <a href="#fig11">Figure 11</a>). Arid lower and arid
+upper subdivisions of the Tropical Life-zone in south; principally Lower
+Sonoran and Lower Austral life-zones in north.</p>
+
+<p><i>Characters for ready recognition.</i>&mdash;Unless otherwise noted, characters are
+usable for the age-categories of adult and old adult. Differs from <i>B. musculus</i>
+in: hind foot less than 16 millimeters; occipitonasal length less than 19 millimeters;
+zygomatic breadth less than 10 millimeters; rostrum deflected ventrally
+at frontoparietal suture rather than curving gradually toward anteriormost point
+of nasals; cingular ridges and secondary cusps on teeth reduced or absent;
+basihyal having entoglossal process much reduced or absent, shoulders of
+basihyal not protruding anteriorly, but more flattened (characteristic of all age
+categories); baculum having narrower shaft, knob-shaped tip, wings at base
+projecting laterally, baculum less than 3 millimeters long; short process of
+incus attenuate; muscular process of posterior crus of stapes reduced.</p>
+
+<p><i>Characters of the species.</i>&mdash;Size small (extremes in external measurements of
+adults: total length, 87-123; length of tail vertebrae, 34-53; length of hind
+foot, 12-15; length of ear, 9-12). Upper parts pale drab or reddish-brown to
+almost black; underparts grayish to cream-buff.</p>
+</div>
+
+<p><i>Geographic variation.</i>&mdash;Eight subspecies are here recognized (see
+<a href="#fig11">Figure 11</a>). Features that vary geographically are mostly the same
+as those that do so in <i>B. musculus</i> (see <a href="#Page_609">page 609</a>).</p>
+
+<p>External and cranial size is less in <i>B. t. allex</i>, the southernmost
+subspecies, and progressively more in <i>B. t. paulus</i>, <i>B. t. taylori</i>,
+<i>B. t. ater</i>, <i>B. t. subater</i>, <i>B. t. fuliginatus</i>, <i>B. t. canutus</i>, and <i>B. t.
+analogous</i>. Size is largest in subspecies that occur at higher altitudes.
+Those subspecies are <i>B. t. analogous</i> and <i>B. t. fuliginatus</i>.
+The correlation with Bergman's Rule is less exact in <i>B. taylori</i> than
+in <i>B. musculus</i>. It is noteworthy that the smallest subspecies, <i>B. t.
+allex</i>, occurs in the area where the two species are sympatric.</p>
+
+<p>There is close correlation in <i>B. taylori</i>, as also in <i>B. musculus</i>, of
+darker pelages with zones of high relative humidity. The subspecies
+having dark pelages are: <i>analogous</i>, <i>fuliginatus</i>, and <i>subater</i>.
+The two first-mentioned subspecies occur at high altitudes, and
+<span class="pagenum"><a name="Page_631" id="Page_631">[Pg 631]</a></span>
+the other, <i>subater</i>, occurs in the humid coastal region of Texas.
+The paler subspecies, <i>taylori</i>, <i>canutus</i>, and <i>allex</i>, occur at lower altitudes.
+Two subspecies that occur at relatively high altitudes, <i>ater</i>
+and <i>paulus</i>, are reddish-brown. The color of pelage in these subspecies
+resembles the color of soil upon which they live. Blair and
+Blossom (1948:5) demonstrated close correlation of color of soil
+with color of pelage in <i>B. t. ater</i> by use of an Ives tint photometer.</p>
+
+<div class="fig_center">
+<a name="fig11" id="fig11"></a>
+<img src="images/fig_11.png" width="531" height="597" alt="" />
+<div class="fig_caption"><span class="smcap">Fig. 11.</span> Distribution of <i>Baiomys taylori</i>. Known localities of occurrence are
+represented by circles and black dots; the former denote localities that are
+peripheral (marginal) for the subspecies concerned.<br />
+<br />
+<table style="text-align:left" summary="species">
+<tr>
+  <td>
+    1. <i>B. t. allex</i><br />
+    2. <i>B. t. analogous</i><br />
+    3. <i>B. t. ater</i><br />
+    4. <i>B. t. canutus</i><br />
+  </td>
+  <td>
+    &nbsp;&nbsp;&nbsp;&nbsp;
+  </td>
+  <td>
+    5. <i>B. t. fuliginatus</i><br />
+    6. <i>B. t. paulus</i><br />
+    7. <i>B. t. subater</i><br />
+    8. <i>B. t. taylori</i><br />
+  </td>
+</tr>
+</table>
+</div>
+</div>
+
+<p><span class="pagenum"><a name="Page_632" id="Page_632">[Pg 632]</a></span></p>
+
+<div class="caption3"><i>Natural History</i></div>
+
+<p><i>Habitat and numbers.</i>&mdash;The habitat occupied by the northern
+pygmy mouse ranges from sparse grassy areas along rock walls in
+central México (see Davis, 1944:394), and mesquite-cactus associations
+in southern Texas (Blair, 1952:242) to heavy stands of
+grasses such as <i>Bouteloua</i> sp., <i>Andropogon</i> sp., <i>Hilaria</i> sp., and
+sacaton grass intermixed with <i>Yucca glauca</i> in New Mexico, Arizona
+(see Hoffmeister 1956:281), and Chihuahua. Baker (1951:213)
+reports the species from 2 km. W El Carrizo, Tamaulipas, in dense
+grass and weeds at the edge of a cornfield. Hooper (1953:7) recorded
+the northern pygmy mouse in a cultivated field overgrown
+with herbaceous vegetation at Pano Ayuctle, Tamaulipas. In the
+State of Sinaloa, Hooper (1955b:13) obtained specimens in grass
+and among shrubs and vines bordering a fallow field. The northern
+pygmy mouse, in general, lives in situations more xerophytic and
+more grassy than does the southern pygmy mouse.</p>
+
+<p>The northern pygmy mouse, as the southern pygmy mouse, is
+locally abundant in its geographic range. Stickel and Stickel (<i>op.
+cit.</i>: 145) pointed out that on the third night of live-trapping in
+Bexar County, Texas, there was a sudden increase in unmarked
+pygmy mice trapped. This increase in numbers, after the resident
+population was seemingly marked, followed a one-half inch rainfall.
+Collectors from the University of Kansas, myself included, have had
+similar experiences in trapping these mice. In the Mexican states
+of Guanajuato, Querétaro, and Jalisco, <i>B. taylori</i> is one of the commonest
+small mammals. In New Mexico and Arizona and the Mexican
+states of Sonora and Sinaloa, nevertheless, these mice are rare.</p>
+
+<p>Stickel and Stickel (<i>loc. cit.</i>) thought that the home range normal
+for <i>B. taylori</i> in a grassy habitat was less than 100 square feet, but
+Blair (1953:10) thought that a complete home range had not been
+recorded by Stickel and Stickel.</p>
+
+<p><i>Behavior.</i>&mdash;The northern pygmy mouse is crepuscular to nocturnal
+and where I trapped in northern Mexico was one of the first
+small rodents to appear in my traps in the evening. Hall and
+Villa-R (1949:460) recorded this habit in Michoacán. Observations
+of wild-taken <i>B. taylori</i> held in captivity, lend support to its being
+crepuscular. Captives were rarely active in bright lights, but in
+diffuse or dim lights the same mice were active.</p>
+
+<p>Blair (1941:381) pointed out that captive <i>B. t. subater</i> were much
+more tolerant of one another than mice of the genus <i>Peromyscus</i>.
+He pointed out also that males aided in care of young. In one
+<span class="pagenum"><a name="Page_633" id="Page_633">[Pg 633]</a></span>
+litter born in captivity in the course of my study, the female killed
+the male when the young were four days old. In another instance,
+the female and two eight-day-old young were killed by the male.
+Until that time, the male, female, and young had lived together
+peacefully. In other litters born in captivity, adult males did not
+harm the other mice.</p>
+
+<p>I have noted, as Blair (<i>loc. cit.</i>) did, that <i>B. taylori</i> utters high-pitched
+squeals in a "singing" posture resembling that of the coyote,
+yet remains silent when being handled.</p>
+
+<p>The northern pygmy mouse makes runways in the grass, in miniature
+resembling those of <i>Microtus</i>, and often uses runways constructed
+by <i>Sigmodon</i>. A small firm nest of finely shredded plant
+material (mostly grasses) is constructed in burrows or under logs,
+rocks, or fallen cactus plants. Thomas (1888:447) recorded nests of
+fine curly grass and cornsilk. Secondary refuge nests are not uncommon.
+Thomas (<i>loc. cit.</i>) states, "If other mice live in the same
+place, the individuals of <i>Baiomys</i> watch till others disappear, then
+suddenly steal part of the other nest and run to their own with it."</p>
+
+<p><i>Enemies and food.</i>&mdash;Little is recorded of the animals that prey
+upon the northern pygmy mouse. Twente and Baker (1951:120)
+found remains of <i>B. taylori</i> in 16 per cent of barn owl pellets (<i>Tyto
+alba pratincola</i>) collected 21 mi. SW Guadalajara, Jalisco. Presumably
+most of the crepuscular and early nocturnal raptorial birds
+and carnivorous mammals feed on these mice.</p>
+
+<p>Food of <i>B. taylori</i> consists in part of grass seeds and leaves,
+prickly pear (<i>Opuntia</i> sp.) and the softer exposed parts of roots
+of vegetation among which the mice reside.</p>
+
+<p><i>Reproduction.</i>&mdash;The northern pygmy mouse breeds throughout
+the year. The only months in which I have not recorded pregnant
+females or females with young are June and October. Forty-one
+records of embryos or young per litter average 2.48 (less than in
+<i>B. musculus</i>), and range from as few as one to as many as four
+per litter.</p>
+
+
+<div class="caption3"><a name="Baiomys_taylori_allex" id="Baiomys_taylori_allex"></a>
+<b>Baiomys taylori allex</b> (Osgood)</div>
+
+<div class="species_ref"><i>Peromyscus allex</i> Osgood, Proc. Biol. Soc. Washington, 17:76-77, March
+21, 1904; Elliot, Field Columb. Mus. Publ., 105(6):135, July 1, 1905;
+Lyon and Osgood, Bull. U. S. Nat. Mus., 62:124, January 15, 1909.</div>
+
+<div class="species_ref"><i>Baiomys taylori allex</i>, Packard, Proc. Biol. Soc. Washington, 71:17, April
+11, 1958; Hall and Kelson, The Mammals of North America, 2:659,
+March 31, 1959 (part).</div>
+
+<div class="species_ref">[<i>Peromyscus</i>] <i>allex</i>, Elliot, Field Columb. Mus. Publ., 95(4):175, July 15,
+1904.</div>
+
+<div class="species_ref"><i>Peromyscus taylori paulus</i>, Osgood, N. Amer. Fauna, 28:255, April 17,
+1909 (part).</div>
+
+<p><span class="pagenum"><a name="Page_634" id="Page_634">[Pg 634]</a></span></p>
+
+<div class="species_ref"><i>Baiomys taylori paulus</i>, Miller, Bull. U. S. Nat. Mus., 79:137, December
+31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317, April 29, 1924
+(part); Ellerman, The Families and Genera of Living Rodents, British
+Mus. Nat. Hist., 2:402, March 21, 1941 (part); Poole and Schantz,
+Bull. U. S. Nat. Mus., 178:259, March 6, 1942; Goldman, Smith. Miscl.
+Coll., 115:373, July 31, 1951 (part); Miller and Kellogg, Bull. U. S.
+Nat. Mus., 205:512, March 3, 1955 (part); Hall and Kelson, The Mammals
+of North America, 2:659, March 31, 1959 (part).</div>
+
+<div class="species_ref"><i>Baiomys taylori analogous</i>, Hall and Kelson, Univ. Kansas Publs., Mus.
+Nat. Hist., 5:367, December 15, 1952 (part).</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;Adult male, skin and skull; No. 33429/45452 U. S. Nat. Mus.
+(Biol. Surv. Coll.); Colima (City), Colima, Republic of México, obtained on
+March 7, 1892, by E. W. Nelson, original number 2029.</p>
+
+<p><i>Range.</i>&mdash;Colima, western lowlands of Michoacán and Jalisco, thence north
+into southern half of Nayarit, see <a href="#fig11">Figure 11</a>. Zonal range: arid lower tropical,
+approximates northern half of the Nayarit-Guerrero Biotic Province of Goldman
+and Moore (1945:349). Occurs from near sea level in Nayarit, up to
+4000 feet in Jalisco.</p>
+
+<p><i>Diagnosis.</i>&mdash;Size small for the species; dorsal ground color pale grayish-brown,
+near Isabella color; mid-dorsal region washed with blackish, individual
+guard hairs black to base, other hairs black-tipped with subterminal light
+olive bands, Neutral Gray at base; laterally, black-tipped hairs less abundant,
+hairs grayish-white to base; venter Pale Gull Gray to whitish, distal half of
+individual hairs white, proximal half Neutral Gray; hairs in regions of throat
+and chin white to base; facial region colored like dorsum, becoming paler
+below eye; in region of mouth, hairs white to base; dorsalmost vibrissae black
+to base, others white to base; ears flesh-colored, sparsely haired; tail unicolored,
+sparsely haired for the species; dark blotches on tail of some series (particularly
+the paratypical series); dorsal and ventral parts of forefeet and hind feet
+flesh-colored, whitish to gray in some series. Slightly smaller in most cranial
+dimensions. Maxillary part of zygoma forming almost a right angle with
+rostrum, rather than tapering at less than a right angle to rostrum; supraoccipital
+rounded posteriorly rather than indented on each side of foramen magnum;
+cranium, relative to length of rostrum, more nearly square; interparietal large
+relative to size of cranium. Average and extreme measurements of five adults
+from 2 mi. SSE Autlán are as follows: total length, 100.0 (93-107); length
+of tail vertebrae, 40.0 (37-44); length of body, 60.0 (56-63); length of hind
+foot, 14.0 (14); length of ear from notch, 10.5 (10-11); occipitonasal length,
+17.3 (16.8-17.9); zygomatic breadth, 9.1 (8.7-9.4); postpalatal length, 6.3
+(6.0-6.6); least interorbital breadth, 3.4 (3.3-3.5); length of incisive foramina,
+3.9 (3.8-4.0); length of rostrum, 5.5 (5.2-5.8); breadth of braincase, 8.6 (8.0-8.9);
+depth of cranium, 6.4 (6.0-6.7); alveolar length of maxillary tooth-row,
+3.0 (2.8-3.1); for photographs of skull, see <a href="#plate1">Plate 1<i>i</i></a>
+and <a href="#plate4">Plate 4<i>a</i></a>.</p>
+
+<p><i>Comparisons.</i>&mdash;For comparisons with <i>B. t. canutus</i>, see account of that subspecies.
+From <i>B. t. analogous</i>, <i>B. t. allex</i> differs in: external and cranial dimensions
+less; dorsal coloration paler; tail and ears paler and less hairy; dorsum
+and belly paler; dorsal and ventral parts of forefeet and hind feet paler; median
+parts of incisive foramina less constricted on either side of midline and wider
+open laterally; interparietal larger in relation to skull; interorbital breadth greater
+relative to occipitonasal length.</p>
+
+<p><span class="pagenum2"><a name="Page_635" id="Page_635">[Pg 635]</a></span></p>
+
+<p><i>B. t. allex</i> differs from <i>B. t. paulus</i> as follows: dorsum gray with yellowish-brown
+wash rather than fawn to buff; tail unicolored in most series, less hairy;
+hind feet flesh-colored to light sooty, rather than whitish; rostrum slightly longer
+relative to occipitonasal length; incisive foramina differ from those of <i>paulus</i>
+in much the same way as from <i>analogous</i>.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;Osgood (1909:255-256) dismissed as taxonomically unimportant
+the differences in color of pelage and size of cranium that
+he observed between the specimens from Colima (City), Colima,
+representative of <i>allex</i> and those representing <i>paulus</i> and chose to
+synonomize <i>allex</i> with <i>paulus</i>. The differences that Osgood (<i>loc.
+cit.</i>) deemed "&#8230; scarcely worthy of recognition &#8230;," are,
+in fact, not only worthy of recognition, but also important in an
+understanding of the evolution of <i>Baiomys taylori</i> (see speciation
+<a href="#Page_659">p. 659</a>). Recently, I (1958b:17-18) studied ten specimens from Colima
+(City), Colima, and chose to regard <i>Peromyscus [= Baiomys]
+allex</i> as a subspecies. I suggested (<i>loc. cit.</i>) that the geographic
+range of <i>B. t. allex</i> might encompass the southern part of Nayarit,
+and western Jalisco. Subsequent study of specimens from these
+areas reveals that the populations there are referable to <i>allex</i>. Most
+of the specimens obtained from these areas, however, merit special
+comment.</p>
+
+<p>In color of pelage, those populations from south of the Río Grande
+de Santiago and northwest of Guadalajara (4 mi. SE Ahuacatlán; 1
+mi. E Ixtlán; Etzatlán) show evidence of intergradation with <i>paulus</i>
+to the east and south (Magdalena, Tequila, and Tala, Jalisco), and
+with populations more closely adjacent to the south bank of that
+river. Intergradation is indeed complex in this area. Specimens
+from some localities seem to be intergrades between <i>allex</i> and
+<i>paulus</i>; from other localities, some specimens are referable to <i>allex</i>,
+and the others to <i>paulus</i>; from still other localities, all specimens are
+referable to <i>allex</i>.</p>
+
+<p>A series of 39 specimens from 1 mi. SSE Ameca, 4000 ft., Jalisco,
+are uniformly grayish-brown. This series averages grayer than paratypes
+of <i>allex</i>. There is little, if any, difference between the series
+from 1 mi. SSE Ameca and paratypes of <i>allex</i> in external size of
+body, hind foot, length of ear, and size and conformation of the
+cranium. Populations from Ameca and vicinity might be expected to
+average considerably larger inasmuch as they occur at higher altitudes
+(see Bergman's Rule, <a href="#Page_609">p. 609</a>) then the material from the lower
+coastal plains to the south in Colima and Michoacán, and at lower
+elevations in the west in Jalisco and Nayarit. The means of external
+<span class="pagenum"><a name="Page_636" id="Page_636">[Pg 636]</a></span>
+and cranial measurements are not significantly different between
+the specimens from the highlands and those from the lowlands. In
+the area of Ameca where the two species <i>B. musculus</i> and <i>B. taylori</i>
+occur together, interspecific competition seems to have limited, perhaps
+even reduced, size of external and cranial parts of <i>taylori</i> (see
+<a href="#Page_660">p. 660</a>).</p>
+
+<p>In color, specimens from the northern part of the valley of the
+Río Tepalcatepec (10 mi. S, 1 mi. W Apatzingán) in Michoacán
+resemble paratypes of <i>allex</i>. Intergradation probably occurs to the
+north with <i>analogous</i>.</p>
+
+<p>In the eight specimens from 13 mi. E and 1 mi. N Talpa de
+Allendé, the skull, as reflected in occipitonasal length and zygomatic
+breadth relative to length of body, is larger than in other specimens
+here assigned to <i>allex</i>. The median part of the belly of the eight
+specimens is buff-colored rather than whitish-gray as in typical
+<i>allex</i>; the mid-dorsal region also averages darker than in any other
+specimens referred to <i>allex</i>. Additional specimens are needed from
+this and closely adjacent areas, especially to the west on the coastal
+plain, in order to determine more accurately the taxonomic status
+of the mice there. At present, it seems best to refer them to <i>allex</i>.
+Possibly the population represented by the eight specimens is an
+incipient subspecies.</p>
+
+<p>There is no evidence of hybridization or intergradation of populations
+of <i>B. t. allex</i> with any population of <i>B. musculus</i> where the
+two species occur together.</p>
+
+<div class="smaller">
+<a name="FNanchor_1_25" id="FNanchor_1_25"></a>
+<a name="FNanchor_2_26" id="FNanchor_2_26"></a>
+<a name="FNanchor_3_27" id="FNanchor_3_27"></a>
+<a name="FNanchor_4_28" id="FNanchor_4_28"></a>
+<p><i>Specimens examined.</i>&mdash;Total 233, all from the Republic of México, distributed
+as follows: <span class="smcap">Nayarit</span>: 3 mi. SE Mirador, 7;
+2 <i>mi. S. Compostela</i>, 2900 ft., 5; 4 <i>mi. N Santa Isabel</i>, 3800 ft.,
+2<a href="#Footnote_1_25" class="fnanchor">[25]</a>;
+<i>2 mi. N Santa Isabel</i>, 3800 ft., 22<a href="#Footnote_1_25" class="fnanchor">[25]</a>;
+<i>4 mi SE Ahuacatlán</i>, 5200 ft., 2<a href="#Footnote_2_26" class="fnanchor">[26]</a>;
+<i>1 mi. E Ixtlán</i>, 4000 ft., 13<a href="#Footnote_1_25" class="fnanchor">[25]</a>;
+1 mi. E Ixtlán del Río, 3700 ft., 1; 2 mi. WNW Valle de Banderas, near sea level, 1.
+<span class="smcap">Jalisco</span>: Arroyo de Gavalán, 16<a href="#Footnote_4_28" class="fnanchor">[28]</a>;
+Etzatlán, 6<a href="#Footnote_3_27" class="fnanchor">[27]</a>;
+<i>Mascota</i>, 3900 ft., 6<a href="#Footnote_3_27" class="fnanchor">[27]</a>;
+<i>7 mi W Ameca</i>, 15<a href="#Footnote_1_25" class="fnanchor">[25]</a>;
+<i>6 mi. W Ameca</i>, 15<a href="#Footnote_1_25" class="fnanchor">[25]</a>;
+<i>3 mi. W Ameca</i>, 5<a href="#Footnote_1_25" class="fnanchor">[25]</a>;
+Ameca, 4000 ft., 11<a href="#Footnote_3_27" class="fnanchor">[27]</a>;
+<i>1 mi. SSE Ameca</i>, 4000 ft., 38; 2 mi. N Resolana, 1500 ft.,
+28<a href="#Footnote_1_25" class="fnanchor">[25]</a>; 13 mi. E,
+1 mi. N Talpa de Allendé, 8; 2 mi. SSE Autlán, 5;
+1 mi. N San Gabriel, 4000 ft., 1<a href="#Footnote_1_25" class="fnanchor">[25]</a>;
+Las Canoas, l<a href="#Footnote_4_28" class="fnanchor">[28]</a>.
+<span class="smcap">Colima</span>: Type locality,
+10<a href="#Footnote_3_27" class="fnanchor">[27]</a> (including the type).
+<span class="smcap">Michoacán</span>: 9 mi. S Lombardia, 1500 ft., 1;
+<i>3 mi. W Apatzingán</i>, 1000 ft, 1;
+Apatzingán, 3<a href="#Footnote_1_25" class="fnanchor">[25]</a>;
+10 mi. S, 1 mi. W Apatzingán, 800 ft., 10.</p>
+
+<p><i>Marginal records.</i>&mdash;<span class="smcap">Nayarit</span>: 3 mi. SE Mirador;
+1 mi. E Ixtlán del Río. <span class="smcap">Jalisco</span>: Etzatlán; Ameca;
+2 mi. N Resolana; Las Canoas. <span class="smcap">Michoacán</span>: 9 mi.
+S Lombardia; 10 mi. S, 1 mi. W Apatzingán. <span class="smcap">Colima</span>:
+type locality. <span class="smcap">Nayarit</span>: Valle de Banderas.</p>
+</div>
+
+<div class="footnote"><p><a name="Footnote_1_25" id="Footnote_1_25"></a>
+<a href="#FNanchor_1_25"><span class="label">[25]</span></a> Univ. Michigan, Museum of Zoology.</p></div>
+
+<div class="footnote"><p><a name="Footnote_2_26" id="Footnote_2_26"></a>
+<a href="#FNanchor_2_26"><span class="label">[26]</span></a> California Academy of Sciences.</p></div>
+
+<div class="footnote"><p><a name="Footnote_3_27" id="Footnote_3_27"></a>
+<a href="#FNanchor_3_27"><span class="label">[27]</span></a> U. S. Nat. Museum (Biol. Surv. Coll.).</p></div>
+
+<div class="footnote"><p><a name="Footnote_4_28" id="Footnote_4_28"></a>
+<a href="#FNanchor_4_28"><span class="label">[28]</span></a> American Museum of Natural History.</p>
+
+<p><span class="pagenum"><a name="Page_637" id="Page_637">[Pg 637]</a></span></p></div>
+
+
+<div class="caption3"><a name="Baiomys_taylori_analogous" id="Baiomys_taylori_analogous"></a>
+<b>Baiomys taylori analogous</b> (Osgood)</div>
+
+<div class="species_ref"><i>Peromyscus taylori analogous</i> Osgood, N. Amer. Fauna, 28:256, April 17,
+1909 (part); Elliott, Check-List Mamm., N. Amer. Cont., West Indies
+and Neighboring Seas, Suppl., Amer. Mus. Nat. Hist., p. 44, January
+8, 1917.</div>
+
+<div class="species_ref"><i>Baiomys taylori analogous</i>, Miller, Bull. U. S. Nat. Mus., 79:137, December
+31, 1912; Miller, Bull. U. S. Nat. Mus., 128:318, April 29, 1924; Ellerman,
+The Families and Genera of Living Rodents, British Mus. Nat.
+Hist., 2:402, March 21, 1941; Poole and Schantz, Bull. U. S. Nat. Mus.,
+178:259, March 6, 1942; Davis, Jour. Mamm., 25:394, December 12,
+1944; Hooper, Jour. Mamm., 28:50, February 15, 1947; Hall and Villa-R.,
+Univ. Kansas Publs., Mus. Nat. Hist., 1:460, December 27, 1949; Hall
+and Villa-R., Anal. del Inst. Biol., 21:196, September 28, 1950; Goldman,
+Smith. Miscl. Coll., 114:373, July 31, 1951 (part); Hall and
+Kelson, Univ. Kansas Publs., Mus. Nat. Hist., 5:367, December 15,
+1952 (part); Villa-R., Anal. del Inst. Biol., 23:435, May 20, 1953; Miller
+and Kellogg, Bull. U. S. Nat. Mus., 205:512, March 3, 1955; Hooper,
+Occas. Papers Mus. Zool. Univ. Michigan, 565:13, March 31, 1955;
+Packard, Proc. Biol. Soc. Washington, 71:17, April 11, 1958.</div>
+
+<div class="species_ref"><i>Peromyscus musculus brunneus</i>, Elliot, Field Columb. Mus. Publ., 115(8):203,
+1907 (part).</div>
+
+<div class="species_ref"><i>Peromyscus musculus</i> [<i>musculus</i>], Osgood, N. Amer. Fauna, 28:258, April
+17, 1909 (part).</div>
+
+<div class="species_ref"><i>Baiomys musculus musculus</i>, Hall and Villa-R., Univ. Kansas Publs., Mus.
+Nat. Hist., 1:460, December 27, 1949 (part); Hall and Villa-R., Anal.
+del Inst. Biol., 21:196, September 28, 1950 (part).</div>
+
+<div class="species_ref"><i>Baiomys taylori taylori</i>, Dalquest, Louisiana State Univ. Studies (Biol. Sci.
+Ser.), 1:155, December 28, 1953 (part); Hall and Kelson, The Mammals
+of North America, 2:660, March 31, 1959 (part).</div>
+
+<div class="species_ref"><i>Baiomys taylori allex</i>, Hall and Kelson, The Mammals of North America,
+2:659, March 31, 1959 (part).</div>
+
+<div class="species_ref"><i>Baiomys musculus musculus</i>, Hall and Kelson, The Mammals of North
+America, 2:661, March 31, 1959 (part).</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;Adult male, skin and skull; No. 120261 U. S. Nat. Mus. (Biol. Surv.
+Coll.); Zamora, Michoacán, Republic of México, obtained on January 15, 1903,
+by E. W. Nelson, and E. A. Goldman, original number 15764.</p>
+
+<p><i>Range.</i>&mdash;Central and eastern Jalisco south into Michoacán, east through
+Guanajuato, Querétaro, thence into Estado México, and Distrito Federal, and
+west-central Veracruz, see <a href="#fig11">Figure 11</a>. Zonal range: approximately the Transverse
+Volcanic Biotic Province of Moore (1945:218) and of Goldman and
+Moore (1945:349). Occurs from 5000 feet, 7 mi. S Ocotlán, Jalisco, up to
+8000 feet in Ixtapalapa, Distrito Federal.</p>
+
+<p><i>Diagnosis.</i>&mdash;Size large for the species; dorsum dark Sepia to near blackish
+medially in freshly taken specimens (Sepia fading to near Fuscous in prepared
+specimens); belly slaty-gray, hairs Deep Neutral Gray near tips and Dusky
+Neutral Gray at bases; hairs on back black-tipped with subterminal band of
+Ochraceous-Tawny (guard hairs blackish to base); hairs of throat and chin
+white-tipped, gray at bases; dorsal vibrissae black, ventral and anteriormost
+vibrissae white; hairs on face and sides black-tipped, and Ochraceous-Tawny
+at base; ears sparsely haired, individual hairs grayish, blackish, and ochraceous;
+<span class="pagenum2"><a name="Page_638" id="Page_638">[Pg 638]</a></span>
+tail sooty to blackish dorsally, lighter ventrally; forefeet and hind feet sooty
+brown on dorsal and ventral surface. Skull relatively broad interorbitally;
+zygoma broad and squared; cranium larger in all dimensions than in most
+other subspecies. Average and extreme measurements of 10 adults from 1 mi.
+S, 11 mi. W Zamora, 5400 ft., Michoacán, are: total length, 109.4 (102-121);
+length of body, 64.3 (58-72); length of tail, 44.9 (39-51); length of hind foot,
+14.6 (14-15); occipitonasal length, 18.0 (17.5-18.6); zygomatic breadth, 9.4
+(9.1-9.7); postpalatal length, 6.6 (6.2-7.2); least interorbital breadth, 3.5
+(3.3-3.8); length of incisive foramina, 4.0 (3.8-4.2); length of rostrum, 6.2
+(5.8-6.5); breadth of braincase, 8.7 (8.5-8.9); depth of cranium, 6.6 (6.3-6.9);
+alveolar length of maxillary tooth-row, 3.1 (3.0-3.3); for photographs of skull,
+see <a href="#plate2">Plate 2<i>a</i></a> and <a href="#plate4">Plate 4<i>b</i></a>.</p>
+
+<p><i>Comparisons.</i>&mdash;For comparisons with <i>B. t. allex</i>, <i>B. t. canutus</i>, <i>B. t. paulus</i>,
+and <i>B. t. fuliginatus</i>, see accounts of those subspecies. From <i>B. t. taylori</i>, <i>B. t.
+analogous</i> differs as follows: sides and dorsum darker, differing most in freshly
+prepared specimens; dorsal surface of forefeet and hind feet darker; basal part
+of hairs on belly darker gray; frontal bones less constricted, causing less taper
+anteriorly in interorbital space; interparietal wider transversely; basioccipital
+more expanded laterally, narrowing more abruptly at suture between basioccipital
+and basisphenoid.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;The pelage of <i>analogous</i> becomes paler with wear as
+pointed out by Osgood (1909:257). A paratype, U. S. Nat. Mus.
+120260, and several specimens from 1 mi. S, 11 mi. W Zamora,
+Michoacán, are grayish rather than brownish-black. All of these are
+old adults having the terminal black parts of the hairs on the dorsum
+nearly worn away. Excluding such grayish individuals, <i>B. t. analogous</i>,
+like <i>B. t. subater</i> and <i>B. t. fuliginatus</i>, is uniformly brownish-black.
+Both <i>analogous</i> and <i>fuliginatus</i> occur in relatively high
+mountainous country on dark soils or pedregals, and all three of the
+aforementioned subspecies occur in zones of high relative humidity.</p>
+
+<p><i>B. t. analogous</i> intergrades with <i>B. t. paulus</i> (see account of that
+subspecies) and <i>B. t. allex</i> south and west of Lago de Chapala in
+Jalisco. Additional specimens are needed from Querétaro and San
+Luis Potosí in order to ascertain whether or not <i>B. t. analogous</i>
+intergrades with <i>B. t. fuliginatus</i> or <i>B. t. taylori</i>. Specimens from
+western Jalisco, in the past referred to <i>B. t. analogous</i>, are referable
+to <i>B. t. allex</i> (see account of that subspecies). Specimens obtained
+west of, and bordering, the Río del Naranjo in Jalisco show a mixture
+of characters of both <i>B. t. allex</i> and <i>B. t. analogous</i>. For example,
+specimens from 2 mi. N Ciudad Guzmán resemble <i>analogous</i>
+on the dorsum, whereas, on the belly, the individual hairs are white-tipped,
+pale gray at the base, and in over-all appearance are whitish-gray,
+unlike typical <i>analogous</i> (being like <i>allex</i> instead). The dorsal
+surface of the forefeet are sooty to light brownish (as in <i>analogous</i>),
+<span class="pagenum"><a name="Page_639" id="Page_639">[Pg 639]</a></span>
+whereas, the hind feet are flesh-colored (as in <i>allex</i>). Another
+series of specimens from 4 mi. W León, Guanajuato, are intergrades
+between <i>B. t. analogous</i> and <i>B. t. paulus</i>. These specimens are
+grayish to brownish on the dorsum, have sooty forefeet and hind
+feet (more nearly as in <i>analogous</i> than in <i>paulus</i>), are grayish-white
+on the venter, and have a distinctly bicolored tail (resembling that
+of <i>paulus</i> more than that of <i>analogous</i>). When the average of
+cranial characters is considered, both series are best referred to
+<i>analogous</i>.</p>
+
+<p>Hooper (1947:50) pointed out that specimens from the pedregal
+San Gerónimo, Distrito Federal, were more nearly black than
+topotypes and generally showed less brownish hues typical of
+<i>analogous</i>. I have examined this series and several others from this
+area (see Specimens examined, <a href="#Page_640">p. 640</a>) and am convinced that
+these populations average darker. Actually, the dorsum is more
+nearly black and the venter is more buffy than in typical <i>analogous</i>.
+The hairs of these individuals average longer than in other populations
+of <i>analogous</i>. Skulls of the specimens from the pedregal
+are indistinguishable from those of paratypes of <i>analogous</i>. The
+populations from the Distrito Federal seem to be incipient subspecies.</p>
+
+<div class="smaller">
+<a name="FNanchor_1_29" id="FNanchor_1_29"></a>
+<a name="FNanchor_2_30" id="FNanchor_2_30"></a>
+<a name="FNanchor_3_31" id="FNanchor_3_31"></a>
+<a name="FNanchor_4_32" id="FNanchor_4_32"></a>
+<a name="FNanchor_5_33" id="FNanchor_5_33"></a>
+<a name="FNanchor_6_34" id="FNanchor_6_34"></a>
+<a name="FNanchor_7_35" id="FNanchor_7_35"></a>
+<a name="FNanchor_8_36" id="FNanchor_8_36"></a>
+<a name="FNanchor_9_37" id="FNanchor_9_37"></a>
+<a name="FNanchor_10_38" id="FNanchor_10_38"></a>
+<p><i>Specimens examined.</i>&mdash;Total 696, all from the Republic of México,
+distributed as follows: <span class="smcap">San Luis Potosí</span>:
+Hacienda Capulín, 5<a href="#Footnote_5_33" class="fnanchor">[33]</a>;
+<i>3.3 mi. N Tamazunchale, by-road</i>, 2<a href="#Footnote_6_34" class="fnanchor">[34]</a>;
+1 mi. N Tamazunchale, 700 ft., 1<a href="#Footnote_7_35" class="fnanchor">[35]</a>.
+<span class="smcap">Veracruz</span>: Acultzingo, 4<a href="#Footnote_1_29" class="fnanchor">[29]</a>,
+1<a href="#Footnote_3_31" class="fnanchor">[31]</a>.
+<span class="smcap">Jalisco</span>: 1 mi. S Jalostotitlán, 5700 ft., 5;
+7 mi. NW Tepatitlán, 3<a href="#Footnote_1_29" class="fnanchor">[29]</a>;
+<i>6 mi. N, 4 mi. E Tepatitlán</i>, 6400 ft., 25; <i>2<sup>1</sup>/<sub>2</sub> mi. E Tepatitlán</i>, 6200 ft., 15;
+<i>2 mi. S, <sup>1</sup>/<sub>2</sub> mi. W Tepatitlán</i>, 9; <i>near Tepatitlán</i>, 2;
+<i>5 mi. SW Arrandas</i>, 6700 ft., 6; <i>2 mi. E Zapotlanejo</i>, 23;
+<i>2<sup>1</sup>/<sub>2</sub> mi. E Puente Grande</i> (<i>5<sup>1</sup>/<sub>2</sub> mi. SW Zapotlanejo</i>), 3;
+<i>8 mi. S Guadalajara</i>, 10<a href="#Footnote_1_29" class="fnanchor">[29]</a>;
+<i>3 mi. ENE Santa Cruz de las Flores</i>, 9; <i>4 mi. NE Ocotlán</i>, 5050 ft., 18;
+<i>13 mi. S, 9<sup>1</sup>/<sub>2</sub> mi. W Guadalajara</i>, 1; <i>2 mi. WNW Ocotlán</i>, 5000 ft., 15;
+13 mi. S, 15 mi. W Guadalajara, 2; <i>Ocotlán</i>, 5000 ft.,
+8<a href="#Footnote_2_30" class="fnanchor">[30]</a>; <i>1 mi. S Ocotlán</i>, 5000 ft., 12;
+27 mi. S, 12 mi. W Guadalajara, 9; <i>1<sup>1</sup>/<sub>2</sub> mi. N Mazatmitla</i>,
+6<a href="#Footnote_1_29" class="fnanchor">[29]</a>; <i><sup>1</sup>/<sub>2</sub> mi. NW Mazatmitla</i>, 4;
+<i>3 mi. WSW Mazatmitla</i>, 4; 2 mi. N Ciudad Guzmán, 5000 ft., 18.
+<span class="smcap">Guanajuato</span>: 4 mi. N, 5 mi. W León, 7000 ft., 25;
+5 mi. S Salamanca, 2<a href="#Footnote_1_29" class="fnanchor">[29]</a>; <i>5 mi. E Celaya</i>, 6000 ft., 6;
+<i>1 mi. E Yuriria</i>, 5725 ft., 3; Salvatierra, 5775 ft., 8; <i>NE edge Acambaro</i>, 6050 ft., 10;
+<i>Acambaro</i>, 3<a href="#Footnote_2_30" class="fnanchor">[30]</a>.
+<span class="smcap">Querétaro</span>: Tolimán, 7<a href="#Footnote_2_30" class="fnanchor">[30]</a>;
+6 mi. E Querétaro, 6550 ft., 37. <span class="smcap">Hidalgo</span>: Tula, 2050 m.,
+1<a href="#Footnote_3_31" class="fnanchor">[31]</a>. <span class="smcap">Michoacán</span>:
+<i>2 mi. E La Palma, SE side Lago de Chapala</i>, 7; type locality, 4000 ft.,
+10<a href="#Footnote_2_30" class="fnanchor">[30]</a> (including the type);
+<i>9 mi. E Zamora</i> (<i>Camenaro</i>), 2<a href="#Footnote_1_29" class="fnanchor">[29]</a>;
+<i>1 mi. S, 11 mi. W Zamora</i>, 5400 ft., 17; S Cuitzeo, 36<a href="#Footnote_1_29" class="fnanchor">[29]</a>;
+<i>Jiquilpan</i>, 4800 ft., 15; <i>11 mi. W Jiquilpan</i>, 6700 ft., 2; <i>1 mi. E Jiquilpan</i>, 7;
+<i>1 mi. E Zinapecuaro</i>, 6300 ft., 17; <i>4<sup>1</sup>/<sub>2</sub> mi. NE Tarequato</i> (<i>Tarecuato</i>), 6600 ft, 1;
+<i>Tanganciguaro</i> (<i>Tangancicuaro</i>), 5500 ft., 4; <i>2 mi. N Tarecuato</i>, 7200 ft., 1;
+<i>2 mi. S Maravatio</i>, 6650 ft, 6; <i>2 mi. SE Zacapu</i>, 6600 ft., 11;
+<i>1 mi. N Tinquindin</i> (<i>Tinguindin</i>), 6300 ft., 2; <i>3 mi. E Morelia</i>, 6600 ft., 3;
+<i>11 mi. E, 2 mi. S Morelia</i>, 1; 2 mi. SE Hidalgo (Villa Hidalgo), 6; <i>1<sup>1</sup>/<sub>2</sub> mi. N Los Reyes</i>, 1;
+<i>E Los Reyes</i>, 18<a href="#Footnote_1_29" class="fnanchor">[29]</a>;
+<i>Los Reyes</i>, 8<a href="#Footnote_2_30" class="fnanchor">[30]</a>;
+<i>3 mi. W, 1 mi. N Pátzucuaro</i>, 6600 ft., 2; <i>N Pátzucuaro</i>,
+2<a href="#Footnote_1_29" class="fnanchor">[29]</a>; <i>Pátzucuaro</i>
+9<a href="#Footnote_3_31" class="fnanchor">[31]</a>, 4<a href="#Footnote_2_30" class="fnanchor">[30]</a>,
+4<a href="#Footnote_1_29" class="fnanchor">[29]</a>;
+Uruapan, 1<a href="#Footnote_1_29" class="fnanchor">[29]</a>; <i>E Uruapan</i>, 12;
+<i>2<sup>1</sup>/<sub>2</sub> mi. E Uruapan</i> (<i>La Presca</i>), 2<a href="#Footnote_1_29" class="fnanchor">[29]</a>;
+2 mi. SW Zitacuaro, 1; 1 mi. E, 6 mi. S Tacámbaro, 4000 ft.,
+11<a href="#Footnote_9_37" class="fnanchor">[37]</a>; <i>La Huacana</i>,
+1<a href="#Footnote_2_30" class="fnanchor">[30]</a>. <span class="smcap">Mexico</span>:
+Templo del Sol, Pyramídes de San Juan,
+<span class="pagenum2"><a name="Page_640" id="Page_640">[Pg 640]</a></span>
+Teotihuacán, 8000 ft., 1; <i>31 km. E México City</i>, 7500 ft.,
+11<a href="#Footnote_8_36" class="fnanchor">[36]</a>; <i>17 km. E México City</i>, 7500 ft,
+1<a href="#Footnote_8_36" class="fnanchor">[36]</a>; <i>Cerro La Caldera, 11 mi. ESE México</i>, 2350 m., 5;
+4 km. ENE Tlalmanalco, 2290 m., 9; <i>Hacienda Córdoba</i> (<i>Córdova</i>), 6.
+<span class="smcap">Mexico</span>, D. F.: <i>Cerro de la Estrella, Ixtapalapa</i>, 2450 m., 1;
+<i><sup>3</sup>/<sub>4</sub> mi. S, 1 mi. E Churubusco</i>, 2400 m., 2; <i>5 km. S México City, South of Cd.
+Universitaria</i>, l<a href="#Footnote_4_32" class="fnanchor">[32]</a>;
+<i>Pedregal San Angel</i>, <i>2.6 mi. S Monumento a Obregón, 2</i>;
+<i>El Pedregal, 1 km. S San Angel</i>, 2260 m., 1; <i>Falda SW Cerro Zacatepec,
+3.9 mi. SW Monumento a Obregón</i>, 1; <i>2 mi. N Tlalpan, Zacayuca</i>, 2380 m., 5;
+<i>Tlalpan</i> (<i>Pedregal</i>), 2400 m., 21<a href="#Footnote_3_31" class="fnanchor">[31]</a>;
+<i>San Gerónimo</i>, 37<a href="#Footnote_1_29" class="fnanchor">[29]</a>,
+6<a href="#Footnote_10_38" class="fnanchor">[38]</a>; <i>Santa Rosa</i>, 2700 m.,
+1<a href="#Footnote_4_32" class="fnanchor">[32]</a>; <i>Tlalpan</i>, 8;
+<i><sup>3</sup>/<sub>4</sub> mi. SW Las Fuentes, Tlalpan</i>, 2450 m., 25<a href="#Footnote_2_30" class="fnanchor">[30]</a>;
+<i>Tepepán</i>, 6<a href="#Footnote_1_29" class="fnanchor">[29]</a>; <i>Rancho La Noria, 1 mi. W
+Xochimilco</i>, 2270 m., 4; <i>500 meters N Xochitepec</i>, 2250 m., 7;
+200 m. N San Mateo Xalpa (Jalpa), 2390 m., 2.</p>
+
+<p><i>Marginal records.</i>&mdash;<span class="smcap">San Luis Potosí</span>: Hacienda Capulín;
+1 mi. N Tamazunchale. <span class="smcap">Hidalgo</span>: Tula, 2050 m.
+<span class="smcap">Mexico</span>: Templo del Sol, Pyramídes de San Juan, Teotihuacán.
+<span class="smcap">Veracruz</span>: Acultzingo. <span class="smcap">Mexico</span>:
+4 km. ENE Tlalmanalco. <span class="smcap">Mexico, D. F.</span>: 200 m. N San Mateo Xalpa (Jalpa), 2390 m.
+<span class="smcap">Michoacán</span>: 2 mi. SW Zitacuaro; 1 mi. E, 6 mi. S Tacámbaro; Uruapan.
+<span class="smcap">Jalisco</span>: 2 mi. N Ciudad Guzmán; 27 mi. S, 12 mi. W Guadalajara; 13 mi.
+S, 15 mi. W Guadalajara; 7 mi. NW Tepatitlán; 1 mi. S Jalostotitlán, 5700 ft.
+<span class="smcap">Guanajuato</span>: 4 mi. N, 5 mi. W León. <span class="smcap">Querétaro</span>:
+6 mi. E Querétaro, 6550 ft.; Tolimán.</p>
+</div>
+
+<div class="footnote"><p><a name="Footnote_1_29" id="Footnote_1_29"></a>
+<a href="#FNanchor_1_29"><span class="label">[29]</span></a> Univ. Michigan, Museum of Zoology.</p></div>
+
+<div class="footnote"><p><a name="Footnote_2_30" id="Footnote_2_30"></a>
+<a href="#FNanchor_2_30"><span class="label">[30]</span></a> U. S. Nat. Museum (Biol. Surv. Coll.).</p></div>
+
+<div class="footnote"><p><a name="Footnote_3_31" id="Footnote_3_31"></a>
+<a href="#FNanchor_3_31"><span class="label">[31]</span></a> Chicago Natural History Museum.</p></div>
+
+<div class="footnote"><p><a name="Footnote_4_32" id="Footnote_4_32"></a>
+<a href="#FNanchor_4_32"><span class="label">[32]</span></a> American Museum of Natural History.</p></div>
+
+<div class="footnote"><p><a name="Footnote_5_33" id="Footnote_5_33"></a>
+<a href="#FNanchor_5_33"><span class="label">[33]</span></a> Museum of Natural History, Louisiana State University.</p></div>
+
+<div class="footnote"><p><a name="Footnote_6_34" id="Footnote_6_34"></a>
+<a href="#FNanchor_6_34"><span class="label">[34]</span></a> Univ. Illinois, Mus. Nat. History.</p></div>
+
+<div class="footnote"><p><a name="Footnote_7_35" id="Footnote_7_35"></a>
+<a href="#FNanchor_7_35"><span class="label">[35]</span></a> The Museum, Michigan State Univ.</p></div>
+
+<div class="footnote"><p><a name="Footnote_8_36" id="Footnote_8_36"></a>
+<a href="#FNanchor_8_36"><span class="label">[36]</span></a> Texas A &amp; M, Cooperative Wildlife Research Collection.</p></div>
+
+<div class="footnote"><p><a name="Footnote_9_37" id="Footnote_9_37"></a>
+<a href="#FNanchor_9_37"><span class="label">[37]</span></a>  Univ. California, Mus. Vert. Zoology.</p></div>
+
+<div class="footnote"><p><a name="Footnote_10_38" id="Footnote_10_38"></a>
+<a href="#FNanchor_10_38"><span class="label">[38]</span></a> University of Florida Collections.</p></div>
+
+
+<div class="caption3"><a name="Baiomys_taylori_ater" id="Baiomys_taylori_ater"></a>
+<b>Baiomys taylori ater</b> (Blossom and Burt)</div>
+
+<div class="species_ref"><i>Baiomys taylori ater</i> Blossom and Burt, Occas. Papers Mus. Zool., Univ.
+Michigan, 465:2, October 8, 1942; Blair and Blossom, Contrib. Lab.
+Vert. Biol., Univ. Michigan, 40:1, March, 1948; Hoffmeister and Goodpaster,
+Ill. Biol. Monogr., 24(1):115, December 31, 1954; Miller and
+Kellogg, Bull. U. S. Nat. Mus., 205:511, March 3, 1955; Hoffmeister,
+Amer. Midland Nat., 55:281, April, 1956; Packard, Jour. Mamm., 40:146,
+February 20, 1959; Hall and Kelson, The Mammals of North America,
+2:659, March 31, 1959 (part).</div>
+
+<div class="species_ref"><i>Peromyscus taylori paulus</i>, Osgood, N. Amer. Fauna, 28:256, April 17,
+1909 (part).</div>
+
+<div class="species_ref"><i>Baiomys taylori</i> [<i>ater</i>], Justice, Jour. Mamm., 38:520, November 20, 1957.</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;Adult male, skin and skull; No. 85425, University of Michigan,
+Museum of Zoology; 7 mi. W Hereford, Cochise County, Arizona, obtained
+on March 25, 1941, by Philip M. Blossom, original number 2195.</p>
+
+<p><i>Range.</i>&mdash;Southeastern Arizona, north to Graham County, thence east to
+the Animas Valley, Hidalgo County, New Mexico; south to northern Chihuahua
+and northwest to the southern border of Cochise County, Arizona,
+see <a href="#fig11">Figure 11</a>. Zonal range: largely lower Sonoran (Apachian Biotic Province
+of Dice, 1943:56). Occurs from 4300 feet in Chihuahua up to 6200 feet in
+New Mexico.</p>
+
+<p><i>Diagnosis.</i>&mdash;Size medium for the species; dorsum between Mummy Brown
+and Prouts Brown; individual tips of hairs intermixture of black and Ochraceous-Tawny,
+bases of all hairs slate-gray; sides of body and face, Buffy
+Brown to Cinnamon Brown; belly Cinnamon Buff, proximal half of individual
+hairs Deep Neutral Gray, distal half white; in region of throat, proximal
+<span class="pagenum2"><a name="Page_641" id="Page_641">[Pg 641]</a></span>
+fourth of individual hairs gray, distal three-fourths white; dorsal vibrissae
+black to base, ventral vibrissae white to base; tail brownish above, gray below;
+dorsal and ventral surface of forefeet and hind feet buffy to gray; interparietal
+somewhat compressed anteroposteriorly. Average and extreme cranial
+measurements of 15 adults from 9<sup>1</sup>/<sub>2</sub> mi. W New Mexico State Line, 5<sup>1</sup>/<sub>2</sub> mi. N
+Mexican border, Cochise County, Arizona, are as follows: occipitonasal
+length, 18.0 (17.5-18.6); zygomatic breadth, 9.5 (9.2-9.9); postpalatal length,
+6.6 (6.0-7.1); least interorbital breadth, 3.6 (3.4-3.8); length of incisive
+foramina, 4.0 (3.8-4.2); length of rostrum, 6.1 (5.7-6.4); breadth of braincase,
+8.6 (8.4-9.1); depth of cranium, 6.5 (6.3-6.9); alveolar length of maxillary
+tooth-row, 3.2 (3.1-3.4). Average and extreme external measurements for
+six adults from 9 mi. W Hereford, Cochise County, are as follows: total
+length, 106.3 (98-115); length of tail vertebrae, 42.3 (39-46); length of body,
+64 (59-69); length of hind foot, 13.6 (13-14.2); length of ear from notch,
+11.1 (10.5-11.5); for photographs of skull, see <a href="#plate2">Plate 2<i>b</i></a>,
+and <a href="#plate4">Plate 4<i>c</i></a>.</p>
+
+<p><i>Comparisons.</i>&mdash;For comparisons with <i>B. t. canutus</i>, see account of that
+subspecies. From <i>B. t. paulus</i>, the subspecies to the southeast, <i>B. t. ater</i>
+differs in: dorsum darker brown; tail less strikingly bicolored; belly buffy
+rather than whitish to white-gray; forefeet and hind feet darker dorsally and
+ventrally; posterior margin of basioccipital bowed anteriorly in a broad U-shape
+with a secondary small median anteriorly directed U-shaped curve, rather
+than bowed anteriorly in a simple U-shape; interparietal more compressed
+anteroposteriorly; coronoid process of mandible so acutely recurved that tip
+of coronoid points posteroventrally and appears sickle-shaped.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;Blossom and Burt (1942:1) described <i>B. t. ater</i> as the
+darkest of the known subspecies. It is dark, but specimens from
+some parts of the ranges of <i>B. t. analogous</i>, <i>B. t. fuliginatus</i>, and
+<i>B. t. subater</i> exceed in melanins the darkest individuals of <i>ater</i>.
+Blair and Blossom (1948:5) also concluded by the use of an Ives
+tint photometer that <i>B. t. subater</i> was significantly darker than <i>B. t.
+ater</i>.</p>
+
+<p>When paratypes of <i>ater</i> and specimens of <i>B. t. paulus</i> are compared,
+the darkest individuals of <i>ater</i> exceed but slightly the darkest
+of <i>paulus</i>. The darkest specimens of <i>paulus</i> occur in southern
+Zacatecas, and northern Jalisco, and the palest of the series are in
+northern Durango and southern Chihuahua. When paratypes of
+<i>ater</i> and <i>paulus</i> are compared, the difference in color is readily
+distinguishable. Specimens from 1<sup>1</sup>/<sub>2</sub> mi. N San Francisco, in northern
+Chihuahua, appear to be intermediate in color between <i>ater</i>
+and <i>paulus</i> except for a faint tinge of buff ventrally. In characters
+of the crania, these specimens resemble <i>ater</i> and are referred to
+that subspecies. A slightly different pattern of color is present
+in pygmy mice from the Peloncillo Mountains and the Animas
+Valley of New Mexico; the upper parts resemble those of paratypes
+of <i>ater</i>, but the venter has only the faintest suggestion of the
+<span class="pagenum"><a name="Page_642" id="Page_642">[Pg 642]</a></span>
+buffy wash. Crania of these specimens from New Mexico are
+inseparable from those of paratypes of <i>ater</i>, and the specimens
+are, therefore, referred to <i>ater</i>.</p>
+
+<p>When specimens are arranged by localities from Arizona east
+into southern New Mexico, thence south into Chihuahua and
+Durango, gradual intergradation in color is evident from dark
+in the north to pale browns in the south, whereas, size and shape
+of interparietal and size and shape of coronoid process of the lower
+jaw divide quite distinctly into two morphological types in central
+Chihuahua.</p>
+
+<p>Cranial variation in size and proportion among adults is slight
+throughout the range of <i>ater</i> compared to variation detected in
+other subspecies of <i>Baiomys taylori</i>. Perhaps such a relatively
+stable pattern of characters of the crania reflects the homogeneity
+of the gene pool, with respect to these characters, of the populations
+sampled. The fact that the color of the pelage of this subspecies
+varies considerable throughout its known range and that the
+crania do not is perhaps a clue to the mode of inheritance of
+characters in these mice. Seemingly, color of pelage is inherited
+independently of characters of the cranium. The relative lack of
+variability in the crania of <i>ater</i> may result from uniform environmental
+conditions, which have served to select for uniform characters
+in the populations. All of the other wide-ranging subspecies
+of <i>B. taylori</i> occupy more diverse habitats than <i>ater</i>. Secondly,
+the rather abrupt change in the cline of measured characters of
+the crania between <i>ater</i> and <i>paulus</i> in central Chihuahua suggests
+a secondary zone of intergradation. The probable cessation of
+gene flow in the past between these two subspecies, allowing <i>ater</i>
+to be isolated for a time, may also, in part, account for the relative
+lack of variability in the crania of <i>ater</i>.</p>
+
+<div class="smaller">
+<a name="FNanchor_1_39" id="FNanchor_1_39"></a>
+<a name="FNanchor_2_40" id="FNanchor_2_40"></a>
+<a name="FNanchor_3_41" id="FNanchor_3_41"></a>
+<a name="FNanchor_4_42" id="FNanchor_4_42"></a>
+<a name="FNanchor_5_43" id="FNanchor_5_43"></a>
+<p><i>Specimens examined.</i>&mdash;Total 58, distributed as follows:
+<span class="smcap">Arizona</span>: <i>Graham County</i>: 1<sup>1</sup>/<sub>2</sub> mi. SW Ft. Grant, Graham Mts.,
+1<a href="#Footnote_1_39" class="fnanchor">[39]</a>; <i>Pima County</i>: 1<sup>1</sup>/<sub>2</sub> mi. ENE
+Greaterville, Thurber Ranch, 2<a href="#Footnote_1_39" class="fnanchor">[39]</a>;
+<i>Santa Cruz County</i>: Patagonia, 3<a href="#Footnote_1_39" class="fnanchor">[39]</a>;
+<i>Cochise County</i>: <i>9 mi. W Hereford</i>, 10<a href="#Footnote_5_43" class="fnanchor">[43]</a>;
+type locality, 2<a href="#Footnote_5_43" class="fnanchor">[43]</a> (including the type);
+<i>5 mi. W Hereford</i>, 5<a href="#Footnote_5_43" class="fnanchor">[43]</a>;
+9<sup>1</sup>/<sub>2</sub> mi. W New Mexico State Line, 5<sup>1</sup>/<sub>2</sub> mi. N Mexican border,
+20<a href="#Footnote_4_42" class="fnanchor">[42]</a>; <i>3 mi. E, 1 mi. N Chiricahua</i>,
+1<a href="#Footnote_4_42" class="fnanchor">[42]</a>. <span class="smcap">New Mexico</span>:
+<i>Hidalgo County</i>: 18 mi. S, 2 mi. W Animas, 2; <i>22 mi. S, 2 mi. W Rodeo</i>, 6000 ft.,
+1<a href="#Footnote_2_40" class="fnanchor">[40]</a>; <i>22 mi. S, 2 mi. E Rodeo</i>, 6000 ft.,
+3<a href="#Footnote_2_40" class="fnanchor">[40]</a>; 25<sup>1</sup>/<sub>2</sub> mi. S Animas, 6200 ft. (in Big Bill Canyon),
+1<a href="#Footnote_2_40" class="fnanchor">[40]</a>. <span class="smcap">Chihuahua</span>:
+<i>5<sup>1</sup>/<sub>2</sub> mi. N, 2 mi. W San Francisco</i>, 5100 ft., 1; <i>2<sup>1</sup>/<sub>2</sub> mi. N, 3 mi. W San Francisco</i>,
+5200 ft., 1; 1<sup>1</sup>/<sub>2</sub> mi. N San Francisco, 5100 ft., 4; Casas Grandes, 4300 ft.,
+1<a href="#Footnote_3_41" class="fnanchor">[41]</a>.</p>
+
+<p><i>Marginal records></i>&mdash;<span class="smcap">Arizona</span>: 1<sup>1</sup>/<sub>2</sub> mi. SW Ft. Grant, Graham Mts.
+<span class="smcap">New Mexico</span>: 18 mi. S, 2 mi. W Animas; 25<sup>1</sup>/<sub>2</sub> mi. S Animas (in Big Bill Canyon).
+<span class="smcap">Chihuahua</span>: 1<sup>1</sup>/<sub>2</sub> mi. N San Francisco; Casas Grandes.
+<span class="smcap">Arizona</span>: Patagonia; 1<sup>1</sup>/<sub>2</sub> mi. ENE Greaterville, Thurber Ranch.</p>
+</div>
+
+<div class="footnote"><p><a name="Footnote_1_39" id="Footnote_1_39"></a>
+<a href="#FNanchor_1_39"><span class="label">[39]</span></a> University of Illinois, Museum of Natural History.</p></div>
+
+<div class="footnote"><p><a name="Footnote_2_40" id="Footnote_2_40"></a>
+<a href="#FNanchor_2_40"><span class="label">[40]</span></a> University of New Mexico.</p></div>
+
+<div class="footnote"><p><a name="Footnote_3_41" id="Footnote_3_41"></a>
+<a href="#FNanchor_3_41"><span class="label">[41]</span></a> U. S. Nat. Museum (Biol. Surv. Coll.).</p></div>
+
+<div class="footnote"><p><a name="Footnote_4_42" id="Footnote_4_42"></a>
+<a href="#FNanchor_4_42"><span class="label">[42]</span></a> University of Arizona.</p></div>
+
+<div class="footnote"><p><a name="Footnote_5_43" id="Footnote_5_43"></a>
+<a href="#FNanchor_5_43"><span class="label">[43]</span></a> Univ. Michigan, Museum of Zoology.</p>
+
+<p><span class="pagenum"><a name="Page_643" id="Page_643">[Pg 643]</a></span></p></div>
+
+
+<div class="caption3"><a name="Baiomys_taylori_canutus" id="Baiomys_taylori_canutus"></a>
+<b>Baiomys taylori canutus</b>, new subspecies</div>
+
+<div class="species_ref"><i>Peromyscus taylori paulus</i>, Osgood, N. Amer. Fauna, 28:255, April 17, 1909
+(part).</div>
+
+<div class="species_ref"><i>Peromyscus musculus</i> [<i>musculus</i>], Osgood, N. Amer. Fauna, 28:256, April
+17, 1909 (part).</div>
+
+<div class="species_ref"><i>Baiomys taylori paulus</i>, Miller, Bull. U. S. Nat. Mus., 79:137, December 31,
+1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317, April 29, 1924
+(part); Burt, Miscl. Publ., Mus. Zool., Univ. Michigan, 39:54, February
+14, 1938; Goldman, Smith. Miscl. Coll., 115:373, July 31, 1951 (part);
+Miller and Kellogg, Bull. U. S. Nat. Mus., 205:512, March 3, 1955 (part);
+Hooper, Occas. Papers Mus. Zool., Univ. Michigan, 565:13, March 31,
+1955; Hall and Kelson, The Mammals of North America, 2:659, March
+31, 1959 (part).</div>
+
+<div class="species_ref"><i>Baiomys musculus musculus</i>, Goldman, Smith. Miscl. Coll., 115:336, July
+31, 1951 (part).</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;Adult male, skin and skull; No. 62075, University of Kansas,
+Museum of Natural History; 1 mi. S Pericos, Sinaloa, Republic of México;
+obtained on June 14, 1954, by A. A. Alcorn, original number 1754.</p>
+
+<p><i>Range.</i>&mdash;Central Nayarit northward through western Sinaloa, to as far
+north as south-central Sonora, see <a href="#fig11">Figure 11</a>. Zonal range: Lower arid
+tropical, closely approximating the Sinaloan Biotic Province of Goldman and
+Moore (1945:349). Occurs from near sea level at Escuinapa (43 feet),
+Sinaloa, to 3200 feet at a place 2 mi. WNW Tepic, Nayarit.</p>
+
+<p><i>Diagnosis.</i>&mdash;Dorsal ground color Buffy Brown (some specimens near Olive
+Brown); proximal fourth of individual guard hairs of dorsum black-tipped,
+distal three-fourths dark grayish; dorsal underfur black-tipped having subterminal
+band of Buffy Brown; hair around eyes buffy to base; belly Pallid
+Neutral Gray with overtones of buff; individual hairs in region of chin whitish-gray
+to bases; vibrissae blackish to bases except ventralmost, those being
+white to base; tail Dark Olive above, slightly paler below. Average and
+extreme external measurements of 13 adults from 15 mi. N Rosario, Chelé,
+Sinaloa, 300 ft., are as follows: Total length, 109.6 (99-120); length of
+tail, 43.4 (38-49); length of body, 66.2 (58-75); length of hind foot, 11.2
+(10-12). Average and extreme cranial measurements of 19 adults from the
+same place are as follows: occipitonasal length, 18.2 (17.7-18.9); zygomatic
+breadth, 9.6 (9.2-10.1); postpalatal length, 6.9 (6.5-7.3); least interorbital
+breadth, 3.6 (3.4-3.8); length of incisive foramina, 3.9 (3.5-4.2); length of
+rostrum, 5.9 (5.5-6.6); breadth of braincase, 8.7 (8.3-8.9); depth of cranium,
+6.5 (6.2-6.7); alveolar length of maxillary tooth-row, 3.1 (3.0-3.2); breadth
+of zygomatic plate, 1.8 (1.6-2.0); for photographs of skull, see <a href="#plate2">Plate 2<i>c</i></a>, and
+<a href="#plate4">Plate 4<i>d</i></a>.</p>
+
+<p><i>Comparisons.</i>&mdash;From <i>B. t. ater</i>, <i>B. t. canutus</i> differs in: dorsum slightly
+grayer; belly whitish to pale-gray with only faint tones of buff, rather than
+cinnamon-buff to buff-gray; forefeet and hind feet flesh-colored to grayish
+above instead of whitish to flesh-colored; tail paler above, less hairy, scales
+more evident; interparietal relatively larger from anteriormost to posteriormost
+points; incisive foramina tapering less abruptly posteriorly, not constricted
+towards midline; over-all size of body and cranium somewhat larger.</p>
+
+<p>From <i>B. t. paulus</i>, <i>B. t. canutus</i> differs in: dorsum grayish-brown rather
+than fawn-colored (not differing appreciably from extremes of darker brown
+specimens of <i>paulus</i>); forefeet and hind feet flesh-colored to grayish above
+<span class="pagenum2"><a name="Page_644" id="Page_644">[Pg 644]</a></span>
+rather than white above; tail less hairy, unicolored to faintly bicolored rather
+than distinctly bicolored; braincase slightly larger; alveolar length of maxillary
+tooth-row slightly less.</p>
+
+<p>From <i>B. t. analogous</i>, <i>B. t. canutus</i> differs in: dorsum paler, less of dark
+brown hues; belly paler; forefeet and hind feet slightly paler, less sooty
+above; tail less hairy, paler and having scales evident; jugal of zygoma extending
+ventrally to a point immediately above, instead of below, level of alveolus
+of upper molars; nasals more nearly truncate anteriorly; infraorbital foramina
+less deeply notched toward midline of skull; body and skull averaging smaller
+throughout.</p>
+
+<p>From <i>B. t. allex</i>, <i>B. t. canutus</i> differs in: dorsal ground color grayish rather
+than fawn color having grayish overtones; underfur on dorsum darker gray;
+dorsal surface of forefeet and hind feet flesh-colored to grayish rather than
+flesh-colored; incisive foramina tapering to a point posteriorly rather than
+rounded posteriorly; interparietal relatively smaller; body and skull averaging
+larger throughout.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;Burt (1938:54) reluctantly assigned specimens from
+Ciudad Obregón to <i>B. t. paulus</i>, probably being influenced by the
+resemblance in size. He suggested that, perhaps, a distinct subspecies
+occurs in the State of Sonora. Study of larger series of
+specimens than were available to Burt reveals that populations of
+pygmy mice inhabiting the northwest coastal plains of México are
+indeed distinct.</p>
+
+<p>The darkest of the material assigned to <i>canutus</i> is from Nayarit
+(for specific localities see specimens examined). According to
+Tamayo (1949:Carta de Suelos), color of soil changes from chestnut
+in northern Sinaloa to black in southern Sinaloa and northern
+Nayarit. There seems, therefore, to be a close correlation between
+color of pelage and color of soil in this area. In Nayarit, particularly
+in the central and southern parts, the mice are intermediate in color
+between the paler, grayer population to the north and the more
+brownish samples, representative of <i>allex</i> to the south. The coastal
+vegetation changes from the arid tropical thorn forests of the north
+and central parts of Sinaloa to a savannah in Nayarit, thence to a
+tropical deciduous forest farther south (see Leopold, 1950:508).</p>
+
+<p>In size and color, specimens from 3 mi. SE Tepic and 2 mi. SW
+Rosa Morada are intermediate between the larger, grayer <i>canutus</i>
+and the smaller, light-brownish <i>allex</i>. In size of cranium, these
+specimens are more nearly like <i>canutus</i>, and are referred to that
+subspecies. Mice from the western coastal plain are relatively
+homogeneous as regards size of body and skull, except that those
+from 13.5 mi. S Acaponéta, Nayarit, average somewhat larger.</p>
+
+<p><i>B. t. canutus</i>, like <i>B. t. subater</i>, is predominantly a lowland or
+coastal subspecies. The pallor of the former, that lives on generally
+paler soils, presumably is of adaptive value.</p>
+
+<p><span class="pagenum"><a name="Page_645" id="Page_645">[Pg 645]</a></span></p>
+
+<p>Pygmy mice are seemingly rare in the northern part of the range
+of this subspecies. J. Raymond Alcorn and Albert Alcorn were
+successful in collecting only two specimens from the type locality
+after three successive nights of trapping with 100 traps set each
+night. Only six specimens are known from Sonora. These were
+obtained in the irrigated regions of Ciudad, Obregón, and Navajoa.
+Charles Sibley obtained one specimen 10.6 mi. SE Ciudad Obregón
+in a "maguey field." I obtained one specimen 1 mi. NNW Navajoa
+in a sparse grassway, 20 feet wide, bordering an open sewer, which
+coursed northward into the Río Mayo. Irrigated wheat fields bordered
+the grassway and ditch.</p>
+
+<div class="smaller">
+<a name="FNanchor_1_44" id="FNanchor_1_44"></a>
+<a name="FNanchor_2_45" id="FNanchor_2_45"></a>
+<a name="FNanchor_3_46" id="FNanchor_3_46"></a>
+<a name="FNanchor_4_47" id="FNanchor_4_47"></a>
+<a name="FNanchor_5_48" id="FNanchor_5_48"></a>
+<a name="FNanchor_6_49" id="FNanchor_6_49"></a>
+<p><i>Specimens examined.</i>&mdash;Total 70 all from the Republic of México and distributed
+as follows: <span class="smcap">Sonora</span>: [Ciudad] Obregón,
+4<a href="#Footnote_1_44" class="fnanchor">[44]</a>; 10.6 mi. SE [Ciudad]
+Obregón, 1<a href="#Footnote_2_45" class="fnanchor">[45]</a>; 1 mi. NNW Navajoa, 1.
+<span class="smcap">Sinaloa</span>: type locality, 2 (including the type);
+Culiacán, 175 ft., 2<a href="#Footnote_3_46" class="fnanchor">[46]</a>;
+Mazatlán, 1<a href="#Footnote_5_48" class="fnanchor">[48]</a>; <i>15 mi. N Rosario, Chelé</i>, 300 ft.,
+35<a href="#Footnote_4_47" class="fnanchor">[47]</a>;
+Rosario, 3<a href="#Footnote_3_46" class="fnanchor">[46]</a>;
+Escuinapa, 5<a href="#Footnote_5_48" class="fnanchor">[48]</a>;
+<i>Railroad Station Escuinapa</i>, 43 ft., 2<a href="#Footnote_2_45" class="fnanchor">[45]</a>.
+<span class="smcap">Nayarit</span>: Acaponéta, 4<a href="#Footnote_3_46" class="fnanchor">[46]</a>;
+<i>13.5 mi. S Acaponéta Junction</i>, 6<a href="#Footnote_6_49" class="fnanchor">[49]</a>;
+2 mi. SW Rosa Morada, 2; <i>2 mi. WNW Tepic</i>, 3200 ft., 1; 3 mi. SE Tepic, 1.</p>
+
+<p><i>Marginal records.</i>&mdash;<span class="smcap">Sonora</span> [Ciudad] Obregón. <span class="smcap">Sinaloa</span>: type locality;
+Escuinapa. <span class="smcap">Nayarit</span>: Acaponéta; 3 mi. SE Tepic. <span class="smcap">Sinaloa</span>: Mazatlán.</p>
+</div>
+
+<div class="footnote"><p><a name="Footnote_1_44" id="Footnote_1_44"></a>
+<a href="#FNanchor_1_44"><span class="label">[44]</span></a> Coll. Univ. California, Los Angeles.</p></div>
+
+<div class="footnote"><p><a name="Footnote_2_45" id="Footnote_2_45"></a>
+<a href="#FNanchor_2_45"><span class="label">[45]</span></a> Univ. California, Mus. Vert. Zoology.</p></div>
+
+<div class="footnote"><p><a name="Footnote_3_46" id="Footnote_3_46"></a>
+<a href="#FNanchor_3_46"><span class="label">[46]</span></a> U. S. Nat. Museum (Biol. Surv. Coll.).</p></div>
+
+<div class="footnote"><p><a name="Footnote_4_47" id="Footnote_4_47"></a>
+<a href="#FNanchor_4_47"><span class="label">[47]</span></a> Univ. Michigan, Museum of Zoology.</p></div>
+
+<div class="footnote"><p><a name="Footnote_5_48" id="Footnote_5_48"></a>
+<a href="#FNanchor_5_48"><span class="label">[48]</span></a> American Museum of Natural History.</p></div>
+
+<div class="footnote"><p><a name="Footnote_6_49" id="Footnote_6_49"></a>
+<a href="#FNanchor_6_49"><span class="label">[49]</span></a> Univ. Illinois, Mus. Nat. History.</p></div>
+
+
+<div class="caption3"><a name="Baiomys_taylori_fuliginatus" id="Baiomys_taylori_fuliginatus"></a>
+<b>Baiomys taylori fuliginatus</b>, new subspecies</div>
+
+<div class="species_ref"><i>Baiomys taylori taylori</i>, Dalquest, Louisiana State Univ. Studies (Biol.
+Sci. Ser.) 1:155, December 28, 1953 (part).</div>
+
+<div class="species_ref"><i>Baiomys taylori taylori</i>, Booth, Walla Walla Publs. Dept. Biol. Sci., 20:15,
+July 10, 1957 (part).</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;Adult male, skin and skull; No. 36765, University of Kansas,
+Museum of Natural History; 10 mi. E, 2 mi. N Ciudad del Maíz, 4000 ft., San
+Luis Potosí, Republic of México; obtained on January 17, 1950, by J. R.
+Alcorn, original number 10400.</p>
+
+<p><i>Range.</i>&mdash;Occurs in the Sierra Madre Oriental of the northeastern third of
+San Luis Potosí. Zonal range: Upper Tropical (see Dalquest, 1953:10);
+approximates a part of the Sierra Madre Oriental Biotic Province of Goldman
+and Moore (1945:349, 356). Occurs from 2000 feet at El Salto up to 4000
+feet at Ciudad del Maíz.</p>
+
+<p><i>Diagnosis.</i>&mdash;Size large for the species; ground color of dorsum Chaetura
+Drab; individual guard hairs of dorsum black to base, distal fourth of hairs
+of underfur in posterior half of dorsum tipped with grayish-brown, proximal
+three-fourths Dark Neutral Gray; in anterior region of dorsum, posterior to
+ears, distal third of hairs grayish-brown and proximal two-thirds Dark Neutral
+Gray to base; sides slightly paler than dorsum; ground color of belly Neutral
+Gray, individual hairs of belly and throat tipped with Pallid Neutral Gray,
+basally Deep Neutral Gray to Dark Neutral Gray; tips of individual hairs of
+face Ochraceous-Tawny; lateral vibrissae whitish, dorsal and ventral vibrissae
+black to base; forefeet and hind feet sooty above and below, thigh bearing
+<span class="pagenum2"><a name="Page_646" id="Page_646">[Pg 646]</a></span>
+some white-tipped hairs; tail near Chaetura Drab above, Pale Neutral Gray
+below; anterior part of jugal projecting slightly ventrally and forming small
+protuberance at point of articulation with maxillary part of zygoma; jugal
+extending anteriorly nearly to lacrimal. In most cranial measurements averaging
+as large as <i>B. t. analogous</i>. Average and extreme measurements of the type
+and three additional paratypes, all adults, are: total length, 105.5 (101-109);
+length of tail, 39.8 (35-42); length of body, 65.8 (63-68); length of hind
+foot, 14.3 (14-15); length of ear from notch, 11 (11); occipitonasal length,
+18.1 (18.1-18.8); zygomatic breadth, 9.6 (9.3-9.8); postpalatal length, 6.5
+(6.0-6.7); least interorbital breadth, 3.4 (3.3-3.6); length of incisive foramina,
+4.0 (3.8-4.2); length of rostrum, 6.3 (6.1-6.4); breadth of braincase, 8.8
+(8.6-8.9); depth of cranium, 6.7 (6.5-6.8); alveolar length of maxillary tooth-row,
+3.2 (3.1-3.3); for photograph of skull, see <a href="#plate2">Plate 2<i>d</i></a>,
+and <a href="#plate4">Plate 4<i>e</i></a>.</p>
+
+<p><i>Comparisons.</i>&mdash;From <i>B. t. taylori</i>, <i>B. t. fuliginatus</i> differs in: dorsum
+slightly darker than in darkest <i>taylori</i>; tail densely haired, bicolored rather
+than unicolored; belly sooty to grayish rather than grayish to whitish; forefeet
+and hind feet sooty to grayish rather than flesh-colored; incisive foramina
+less bowed laterally, more nearly straight; interparietal compressed anteroposteriorly,
+less diamond-shaped.</p>
+
+<p>From <i>B. t. paulus</i>, <i>B. t. fuliginatus</i> differs in: dorsum dusky to blackish
+rather than fawn color; belly sooty to grayish rather than buffy to whitish-gray;
+forefeet and hind feet sooty to grayish rather than whitish; zygoma
+more nearly forming a right angle with rostrum or skull, less tapered anteriorly;
+anterior part of jugal possessing ventral projection; jugal extending nearly to
+lacrimal on posterior surface of maxillary part of zygoma.</p>
+
+<p>From <i>B. t. analogous</i>, <i>B. t. fuliginatus</i> differs in: mid-dorsal region blacker,
+less brownish; tail distinctly bicolored rather than unicolored to faintly bicolored;
+incisive foramina not constricted medially; presphenoid broader (at
+narrowest point); jugal differs much the same as it does from <i>paulus</i>; nasals
+anteriorly truncate instead of rounded.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;Dalquest (1953:155-157) and Booth (1957:15) assigned
+all of the pygmy mice that they examined from the state of
+San Luis Potosí to <i>B. t. taylori</i>. Examination of all of the material
+that was available to Dalquest, plus additional specimens at the
+University of Kansas Museum of Natural History, reveals that
+there are three subspecies in San Luis Potosí. <i>B. t. taylori</i> occurs
+in the eastern part of the State at lower altitudes; <i>B. t. analogous</i>
+occurs to the southeast at higher altitudes; <i>B. t. fuliginatus</i> occurs
+in the northeastern part of the State in the Sierra Madre Oriental.</p>
+
+<p>Specimens obtained from Ebano, Pujal, and Tamuín, representative
+of <i>B. t. taylori</i>, are much paler on the belly and on the ventral
+surface of the forefeet and hind feet than are specimens from Ciudad
+del Maíz, representative of <i>B. t. fuliginatus</i>. The tail in <i>B. t.
+taylori</i> is nearly unicolored and less hairy than in the paratypical
+series of <i>fuliginatus</i>. Specimens from 4 km. NE Ciudad Valles are
+nearly intermediate in color of the belly, dorsum, forefeet and hind
+<span class="pagenum"><a name="Page_647" id="Page_647">[Pg 647]</a></span>
+feet, and tail, between the palest mice from the coastal plain and
+the darker mice in the mountains of the northeastern part of the
+State (specimens from El Salto average paler, however, than the
+type and paratypes). These specimens seem to be intergrades
+between <i>B. t. taylori</i> to the east on the coastal plain and <i>fuliginatus</i>
+to the northwest in the mountains. It seems best to refer the mice
+from 4 km. N Ciudad Valles to <i>B. t. taylori</i> on the basis of the
+average of external and cranial characters. Specimens from 6 mi.
+SW San Gerónimo, Coahuila, also referred to <i>B. t. taylori</i>, resemble
+in color the mice from 4 km. N Ciudad Valles. When more
+specimens are obtained from the front range of the Sierra Madre
+Oriental, at lower altitudes, the manner in which these two subspecies
+intergrade with one another will be better understood. At
+present, populations from higher altitudes in the mountains seem
+to represent a dark subspecies; populations from the coastal plain
+represent a pale subspecies, and those from the lower slopes and
+high valleys seemingly are intergrades. <i>B. t. fuliginatus</i> occurs in a
+somewhat limited strip of chernozem soil (or suelos negros of
+Tamayo, 1949: Carta de Suelos). The populations occurring at
+lower altitudes on the coastal plain are on generally paler soils.</p>
+
+<div class="smaller">
+<p><i>Specimens examined.</i>&mdash;Total 39, all from the Republic of México, as follows:
+<span class="smcap">San Luis Potosí</span>: El Salto, 24 Mus. Nat. Hist., Louisiana State Univ., 7 Amer.
+Mus. Nat. Hist.; type locality, 8 (including the type).</p>
+
+<p><i>Marginal records.</i>&mdash;See specimens examined.</p>
+</div>
+
+
+<div class="caption3"><a name="Baiomys_taylori_paulus" id="Baiomys_taylori_paulus"></a>
+<b>Baiomys taylori paulus</b> (J. A. Allen)</div>
+
+<div class="species_ref"><i>Peromyscus paulus</i>, J. A. Allen, Bull. Amer. Mus. Nat. Hist., 19:598,
+November 12, 1903; Elliot, Field Columb. Mus. Publ., 105(6): 136,
+July 1, 1905.</div>
+
+<div class="species_ref"><i>Baiomys taylori paulus</i>, Miller, Bull. U. S. Nat. Mus., 79:137, December 31,
+1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317, April 29, 1924
+(part); Ellerman, The Families and Genera of Living Rodents, 2:402,
+March 21, 1941 (part); Goldman, Smith, Miscl. Coll., 115:373, July 31,
+1951 (part); Hall and Kelson, Univ. Kansas Publs., Mus. Nat. Hist.,
+26:367, December 15, 1952; Goodwin, Bull. Amer. Mus. Nat. Hist.,
+102:318, August 31, 1953; Miller and Kellogg, Bull. U. S. Nat. Mus.,
+205:511, March 3, 1955 (part); Packard, Proc. Biol. Soc. Washington,
+71:17, April 11, 1958; Packard, Jour. Mamm., 40:146, February 20,
+1959; Hall and Kelson, The Mammals of North America, 2:659, March
+31, 1959 (part).</div>
+
+<div class="species_ref">[<i>Peromyscus</i>] <i>paulus</i>, Elliot, Field Columb, Mus. Publ., 95(4):136, July
+15, 1904.</div>
+
+<div class="species_ref"><i>Peromyscus taylori paulus</i>, Osgood, N. Amer. Fauna, 28:255, April 17,
+1909 (part).</div>
+
+<div class="species_ref"><i>Peromyscus musculus</i> [<i>musculus</i>], Osgood, N. Amer. Fauna, 28:256, April
+17, 1909 (part).</div>
+
+<div class="species_ref"><i>Baiomys taylori</i> [= <i>paulus</i>], Twente and Baker, Jour. Mamm., 32:121,
+February 15, 1951.</div>
+
+<p><span class="pagenum"><a name="Page_648" id="Page_648">[Pg 648]</a></span></p>
+
+<div class="species_ref"><i>Baiomys musculus musculus</i>, Goldman, Smith. Miscl. Coll., 115:336, July
+31, 1951 (part).</div>
+
+<div class="species_ref"><i>Baiomys taylori allex</i>, Hall and Kelson, The Mammals of North America,
+2:659, March 31, 1959 (part).</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;Adult male, skin and skull; No. 21165, American Museum of Natural
+History; Río Sestín, Durango, Republic of México; obtained on April 15, 1903,
+by J. H. Batty, original number 455.</p>
+
+<p><i>Range.</i>&mdash;Central Chihuahua south through Durango (west to eastern edge
+of Sierra Madre Occidental), to Zacatecas and Aguascalientes, thence west
+into northern and northwestern Jalisco, see <a href="#fig11">Figure 11</a>. Zonal range: Lower
+Sonoran, approximately the Chihuahua Desert Biotic Province of Goldman
+and Moore (1945:349). Occurs from 4000 feet 2 mi. ESE Tequila, Jalisco,
+up to 6700 feet 2 mi. W Miñaca, Chihuahua.</p>
+
+<p><i>Diagnosis.</i>&mdash;Size medium to small for the species; dorsum Buffy Brown to
+fawn color; dorsal ground color of unworn pelage of adults varying from
+Buffy Brown in darkest series (especially those from higher altitudes) to
+Avellaneous with grayish overtones in palest series; worn pelage in mid-dorsal
+region of adults fawn to grayish; terminal parts of individual hairs buffy, gray
+basally; guard hairs on dorsum black-tipped, grayish basally; belly Light Gull
+Gray, distal half of hairs white, proximal half Neutral Gray; hairs in region
+of throat and chin white to base (some specimens with faint buffy overtones);
+forefeet dusky below, whitish above; hind feet whitish above, ventral surface
+whitish to dusky; dorsal and lateral vibrissae black, other vibrissae white.
+Average and extreme measurements of six adults from the type locality are as
+follows: total length, 109 (106-117); length of tail, 44.5 (43-48); length of
+body, 63 (57-69); length of hind foot, 13.1 (12.7-14.0); occipitonasal length,
+17.5 (17.4-18.0); zygomatic breadth, 9.3 (9.1-9.5); postpalatal length, 6.6
+(6.2-6.9); least interorbital breadth, 3.5 (3.4-3.6); length of incisive foramina,
+3.8 (3.6-4.1); length of rostrum, 5.9 (5.7-6.0); breadth of braincase, 8.6
+(8.5-8.8); depth of cranium, 6.6 (6.2-6.9); alveolar length of maxillary tooth-row,
+3.2 (3.1-3.4); for photographs of the skull, see <a href="#plate2">Plate 2<i>e</i></a>
+and <a href="#plate4">Plate 4<i>f</i></a>.</p>
+
+<p><i>Comparisons.</i>&mdash;For comparisons with <i>B. t. allex</i>, <i>B. t. canutus</i>, <i>B. t. ater</i>, and
+<i>B. t. taylori</i>, see accounts of those subspecies. From <i>B. t. analogous</i>, <i>B. t. paulus</i>
+differs as follows: dorsal color paler having more reddish-brown than blackish-brown
+tones; venter whitish to buffy, instead of gray to light-gray; tail
+bicolored (not unicolored), usually having more hairs; hind feet white (not
+sooty) above. Cranially, <i>B. t. paulus</i> differs from <i>B. t. analogous</i> in: skull
+slightly smaller in all dimensions; maxillary part of zygoma narrowing and
+forming oblique angle rather than a near right angle with rostrum; anterior
+incisive foramina constricted posteriorly; tips of nasals truncate (less rounded).</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;J. A. Allen (1903:599) correctly pointed out that
+young specimens, in first pelage, were gray brown; young adults
+were darker and more varied with some blackish; adults and old
+adults were buffy to grayish. The change in color of pelage with
+increasing age is more pronounced in <i>paulus</i> than in other subspecies
+of <i>B. taylori</i>. Of two males collected on April 12, 1949, one,
+an adult, is buffy brown, and the other, an old adult with worn
+pelage, is grayish-brown. In mice in the earlier stages of adulthood,
+<span class="pagenum"><a name="Page_649" id="Page_649">[Pg 649]</a></span>
+underfur of the dorsum is buffy at the tips and gray basally. With
+increased wear, the buffy tip is lost. Consequently, mice in the
+later stages of adulthood are grayish.</p>
+
+<p><i>B. t. paulus</i> intergrades with <i>ater</i> to the north in Chihuahua (see
+account of that subspecies), with <i>analogous</i> to the south in Jalisco,
+and with <i>allex</i> (see account of that subspecies) to the southwest in
+Nayarit and Jalisco. The zone of intergradation between <i>paulus</i>
+and <i>analogous</i> in Jalisco approximately borders the Río Grande de
+Santiago from the western part of the State to the northwest shore
+of Lago de Chapala. Nineteen specimens from 2 mi. WNW Lagos
+de Moreno in northwest Jalisco seem to be intermediate between
+<i>paulus</i> and <i>analogous</i> in color, averaging slightly grayer than typical
+<i>paulus</i>. The series of 19 is referable to <i>paulus</i> on the basis of cranial
+characters.</p>
+
+<p>A series of 34 specimens from 3 mi. W La Venta, Jalisco (referable
+to <i>paulus</i>), is indistinguishable in color of pelage from two series
+of <i>paulus</i> from 5 mi. N Durango, and from 8 mi. NE of Durango,
+except that the antiplantar surfaces of the hind feet are sooty as in
+<i>analogous</i>. Seemingly, features of color mentioned above as diagnostic
+of the two subspecies are either present or absent and there
+is no tendency toward intermediacy in color in the population from
+3 mi. W La Venta.</p>
+
+<p>The Río Grande de Santiago may have acted in the past as a
+physical barrier reducing gene flow between <i>allex</i> and <i>paulus</i> and
+in separating completely the two populations for limited periods.</p>
+
+<div class="smaller">
+<a name="FNanchor_1_50" id="FNanchor_1_50"></a>
+<a name="FNanchor_2_51" id="FNanchor_2_51"></a>
+<a name="FNanchor_3_52" id="FNanchor_3_52"></a>
+<a name="FNanchor_4_53" id="FNanchor_4_53"></a>
+<a name="FNanchor_5_54" id="FNanchor_5_54"></a>
+<p><i>Specimens examined.</i>&mdash;Total 176, all from the Republic of México and distributed
+as follows: <span class="smcap">Chihuahua</span>: Rancho Sanignacio, 4 mi. S, 1 mi. W Santo
+Tomás, 1; El Rosario, 6700 ft., 1; 2 mi. W Miñaca, 6900 ft., 11;
+Balleza, 1<a href="#Footnote_1_50" class="fnanchor">[50]</a>.
+<span class="smcap">Durango</span>: Rosario, 1<a href="#Footnote_2_51" class="fnanchor">[51]</a>;
+type locality, 14<a href="#Footnote_2_51" class="fnanchor">[51]</a> (including the type);
+<i>San Gabriel</i>, 2<a href="#Footnote_2_51" class="fnanchor">[51]</a>;
+<i>Rancho Santuario</i>, 2<a href="#Footnote_2_51" class="fnanchor">[51]</a>;
+1 mi. N Chorro, 6450 ft., 1; <i>8 mi. NE Durango</i>, 6200 ft., 2; 5 mi. N Durango, 6400 ft., 2.
+<span class="smcap">Zacatecas</span>: Valparaíso, 6500 ft., 10<a href="#Footnote_1_50" class="fnanchor">[50]</a>.
+<span class="smcap">Aguascalientes</span>: <i>18 mi. W, 2 mi. S Aguascalientes</i>, 6000 ft., 1;
+16 mi. S Aguascalientes, 5<a href="#Footnote_3_52" class="fnanchor">[52]</a>.
+<span class="smcap">Jalisco</span>: 1 mi. NE Villa Hidalgo, 6500 ft., 1;
+2 mi. WNW Lagos de Moreno, 6370 ft., 19; <i>2 mi. ESE Tequila</i>, 4000 ft., 11;
+<i>3 mi. W La Venta</i>, 33, 1<a href="#Footnote_4_53" class="fnanchor">[53]</a>;
+<i>12 mi. W Guadalajara</i>, 3<a href="#Footnote_5_54" class="fnanchor">[54]</a>;
+<i>Atemajac</i>, 12<a href="#Footnote_1_50" class="fnanchor">[50]</a>;
+4 mi. W Guadalajara, 5100 ft., 3; <i>2 mi. N, <sup>1</sup>/<sub>2</sub> mi. W Guadalajara</i>, 11; 2 mi.
+NW Magdalena, 4500 ft., 7<a href="#Footnote_1_50" class="fnanchor">[50]</a>;
+<i>1 mi. N Tala</i>, 4400 ft., 3; 3 mi. W Tala, 4300 ft., 18.</p>
+
+<p><i>Marginal records.</i>&mdash;<span class="smcap">Chihuahua</span>: Rancho Sanignacio, 4 mi. S, 1 mi. W
+Santo Tomás; El Rosario; Balleza. <span class="smcap">Durango</span>: Rosario, 6700 ft.; 1 mi. E Zarca
+(Blossom and Burt, 1942:1); 1 mi. N Chorro, 6450 ft. <span class="smcap">Zacatecas</span>: Valparaíso,
+6500 ft. <span class="smcap">Aguascalientes</span>: 1 mi. N Chicalote (Blossom and Burt,
+1942:4). <span class="smcap">Jalisco</span>: 2 mi. WNW Lagos de Moreno, 6370 ft.; 4 mi. W Guadalajara,
+5100 ft.; 3 mi. W Tala, 4300 ft.; 2 mi. NW Magdalena, 4500 ft.
+<span class="smcap">Durango</span>: 5 mi. N Durango, 6400 ft.; type locality. <span class="smcap">Chihuahua</span>: 2 mi. W
+Miñaca, 6900 ft.</p>
+</div>
+
+<div class="footnote"><p><a name="Footnote_1_50" id="Footnote_1_50"></a>
+<a href="#FNanchor_1_50"><span class="label">[50]</span></a> United States National Museum (Biol. Surv. Collections).</p></div>
+
+<div class="footnote"><p><a name="Footnote_2_51" id="Footnote_2_51"></a>
+<a href="#FNanchor_2_51"><span class="label">[51]</span></a> American Museum of Natural History.</p></div>
+
+<div class="footnote"><p><a name="Footnote_3_52" id="Footnote_3_52"></a>
+<a href="#FNanchor_3_52"><span class="label">[52]</span></a> Univ. Illinois, Mus. Nat. History.</p></div>
+
+<div class="footnote"><p><a name="Footnote_4_53" id="Footnote_4_53"></a>
+<a href="#FNanchor_4_53"><span class="label">[53]</span></a> The Museum, Michigan State Univ.</p></div>
+
+<div class="footnote"><p><a name="Footnote_5_54" id="Footnote_5_54"></a>
+<a href="#FNanchor_5_54"><span class="label">[54]</span></a> Univ. Michigan, Museum of Zoology.</p>
+
+<p><span class="pagenum"><a name="Page_650" id="Page_650">[Pg 650]</a></span></p></div>
+
+
+<div class="caption3"><a name="Baiomys_taylori_subater" id="Baiomys_taylori_subater"></a>
+<b>Baiomys taylori subater</b> (V. Bailey)</div>
+
+<div class="species_ref"><i>Peromyscus taylori subater</i>, V. Bailey, N. Amer. Fauna, 25:102, October 24,
+1905; Lyon and Osgood, Bull. U. S. Nat. Mus., 62:139, January 15,
+1909; Osgood, N. Amer. Fauna, 28:255, April 17, 1909; Elliot, Check-List
+Mamm. N. Amer. Continent, West Indies and Neighboring Seas,
+Suppl., Amer. Mus. Nat. Hist, p. 44, January 8, 1917.</div>
+
+<div class="species_ref"><i>Baiomys taylori subater</i>, Miller, Bull. U. S. Nat. Mus., 79:136, December
+31, 1912; Miller, Bull. U. S. Nat. Mus., 128:317, April 29, 1924; Anthony,
+Field Book of North American Mammals, p. 348, 1928; Baker, Jour.
+Mamm., 21:223, May 14, 1940; Ellerman, The Families and Genera of
+Living Rodents, 2:402, March 21, 1941; Blair, Jour. Mamm., 22:378,
+November 14, 1941; Poole and Schantz, Bull. U. S. Nat. Mus., 178:259,
+March 6, 1942; Blair, Jour. Mamm., 23:196, May 14, 1942; Blair and
+Blossom, Contrib. Lab. Vert. Biol., Univ. Michigan, 40:1, March, 1948;
+Miller and Kellogg, Bull. U. S. Nat. Mus., 205:511, March 3, 1955; Hall
+and Kelson, The Mammals of North America, 2:659, March 31, 1959.</div>
+
+<div class="species_ref"><i>Baiomys taylori</i> [= <i>subater</i>], Taylor and Davis, Texas Game, Fish and
+Oyster Comm. Bull., 27:56, August, 1947 (part).</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;Subadult female, skin and skull; No. 32616/44539 U. S. Nat. Mus.
+(Biol. Surv. Coll.); Bernard Creek, near Columbia, Brazoria County, Texas;
+obtained on February 25, 1892, by W. Lloyd, original number 1122.</p>
+
+<p><i>Range.</i>&mdash;Southeastern Texas, north of Matagorda Bay west to Lavaca
+County, north to Brazos and Walker counties thence east to Jefferson County,
+see <a href="#fig11">Figure 11</a>. Occurs from near sea level in Brazoria and Galveston counties,
+up to 500 feet in western part of range. Zonal range: Humid division of
+lower Austral (the western part of the Austroriparian Biotic Province of Dice,
+1943:18-21).</p>
+
+<p><i>Diagnosis.</i>&mdash;Size medium to large for the species; mid-dorsal region Clove
+Brown (sooty in freshly captured specimens); some parts of mid-dorsal region
+all blackish; individual guard hairs of dorsum black-tipped, Deep Neutral
+Gray basally; underfur black-tipped with subterminal band of light buff,
+Neutral Gray at base; belly grayish-white, laterally Isabella Color; distal three-fourths
+of hairs in region of throat and chin white, proximal fourth light gray;
+in median region of belly distal half of individual hairs white, proximal half
+dark gray; vibrissae in most specimens black to base. Average and extreme
+cranial measurements of six adults from 7 mi. S La Belle are as follows:
+occipitonasal length, 18.9 (17.5-19.4); zygomatic breadth, 9.6 (9.1-9.9); postpalatal
+length, 6.8 (6.2-7.2); least interorbital breadth, 3.7 (3.4-3.9); length
+of incisive foramina, 4.0 (3.6-4.2); length of rostrum, 6.5 (6.1-6.8); breadth
+of braincase, 8.7 (8.3-8.9); depth of cranium, 6.7 (6.6-6.8); alveolar length
+of maxillary tooth-row, 3.1 (2.9-3.2). Average and extreme external measurements
+of four adults from Richmond are as follows: total length, 111.5
+(108-118); length of tail vertebrae, 43.5 (41-47); length of body, 68 (67-71);
+length of hind foot, 14 (13-15); for photographs of the skull,
+see <a href="#plate2">Plate 2<i>f</i></a>, and <a href="#plate4">Plate 4<i>g</i></a>.</p>
+
+<p><i>Comparisons.</i>&mdash;Because <i>B. t. subater</i> intergrades only with <i>B. t. taylori</i> to
+the south and west, <i>subater</i> is compared only with <i>taylori</i>. Young adults of
+both subspecies in unworn pelage show best the colors that differentiate the
+two subspecies. Old adults of <i>subater</i> in worn pelage appear grayish, resembling
+<i>taylori</i>, and at that age, only certain cranial characters are of
+taxonomic use. Cranially, <i>subater</i> differs from <i>taylori</i> in: presphenoid not
+shaped like an hour-glass; parapterygoid processes thicker medially; interparietal
+diamond-shaped instead of elongated and compressed. Skull slightly larger
+in most measurements.</p>
+</div>
+<br />
+<br />
+
+<div class="caption1">PLATE 1</div>
+<br />
+<div class="fig_center" style="width: 444px;">
+<a name="plate1" id="plate1"></a>
+<img src="images/plate_1.png" width="444" height="692" alt="" />
+</div>
+<br />
+Photographs of skulls in dorsal view of <i>Baiomys</i>. &#215; 2.<br />
+<br />
+<table summary="list">
+<tr><td class="text_lf"><i>a.</i> <i>B. m. brunneus</i>, &#9792; ad., 10834, AMNH, Jalapa, Veracruz.<br />
+<i>b.</i> <i>B. m. grisescens</i>, &#9792; ad., 257080, USNM, Comayabuela, Honduras.<br />
+<i>c.</i> <i>B. m. handleyi</i>, &#9792; ad., 275597, USNM, Sacapulas, Guatemala.<br />
+<i>d.</i> <i>B. m. infernatis</i>, &#9792; ad., 91499, MZUM, Teotitlán, Oaxaca.<br />
+<i>e.</i> <i>B. m. musculus</i>, &#9792; ad., 45462, USNM, Colima, Colima.<br />
+<i>f.</i> <i>B. m. nigrescens</i>, &#9794; ad., 76834, USNM, Comitán, Chiapas.<br />
+<i>g.</i> <i>B. m. pallidus</i>, &#9792; ad., 4802, Texas A &amp; M, Axochiapán, Morelos.<br />
+<i>h.</i> <i>B. m. pullus</i>, &#9792; ad., 71608, KU, 8 mi. S Condega, Nicaragua.<br />
+<i>i.</i> <i>B. t. allex</i>, &#9792; ad., 45453, USNM, Colima, Colima.<br />
+</td>
+</tr>
+</table>
+<br />
+<br />
+
+<div class="caption1">PLATE 2</div>
+<br />
+<div class="fig_center" style="width: 437px;">
+<a name="plate2" id="plate2"></a>
+<img src="images/plate_2.png" width="437" height="670" alt="" />
+</div>
+<br />
+Photographs of skulls (<i>a-g</i>) in dorsal view of <i>Baiomys</i>. &#215; 2.<br />
+<br />
+<table summary="list">
+<tr><td class="text_lf"><i>a.</i> <i>B. t. analogous</i>, &#9792; ad., 120265, USNM, Zamora, Michoacán.<br />
+<i>b.</i> <i>B. t. ater</i>, &#9792; ad., 15056, UI, 1<sup>1</sup>/<sub>2</sub> mi. ENE Greaterville, Arizona.<br />
+<i>c.</i> <i>B. t. canutus</i>, &#9792; ad., 62076, KU, 1 mi. S Pericos, Sinaloa.<br />
+<i>d.</i> <i>B. t. fuliginatus</i>, &#9792; ad., 36771, KU, type locality.<br />
+<i>e.</i> <i>B. t. paulus</i>, &#9792; ad., 40032, KU, 18 mi. W, 2 mi. S Aguascalientes.<br />
+<i>f.</i> <i>B. t. subater</i>, &#9792; ad., 44543, USNM, type locality.<br />
+<i>g.</i> <i>B. t. taylori</i>, &#9792; ad., 57944, KU, 5 mi. E San Antonio, Texas.<br />
+<i>h.</i> Photo. of captive &#9794; <i>B. t. taylori</i>, 25 mi. E Austin, Texas. &#215; 1.<br />
+</td>
+</tr>
+</table>
+<br />
+<br />
+
+<div class="caption1">PLATE 3</div>
+<br />
+<div class="fig_center" style="width: 433px;">
+<a name="plate3" id="plate3"></a>
+<img src="images/plate_3.png" width="433" height="673" alt="" />
+</div>
+<br />
+Photographs of skulls in ventral view of <i>Baiomys</i>. &#215; 2.<br />
+<br />
+<table summary="list">
+<tr><td class="text_lf"><i>a.</i> <i>B. m. brunneus</i>, &#9792; ad., 10834, AMNH, Jalapa, Veracruz.<br />
+<i>b.</i> <i>B. m. grisescens</i>, &#9792; ad., 257080, USNM, Comayabuela, Honduras.<br />
+<i>c.</i> <i>B. m. handleyi</i>, &#9792; ad., 275597, USNM, Sacapulas, Guatemala.<br />
+<i>d.</i> <i>B. m. infernatis</i>, &#9792; ad., 91499, MZUM, Teotitlán, Oaxaca.<br />
+<i>e.</i> <i>B. m. musculus</i>, &#9792; ad., 45462, USNM, Colima, Colima.<br />
+<i>f.</i> <i>B. m. nigrescens</i>, &#9794; ad., 76834, USNM, Comitán, Chiapas.<br />
+<i>g.</i> <i>B. m. pallidus</i>, &#9792; ad., 4802, Texas A &amp; M, Axochiapán, Morelos.<br />
+<i>h.</i> <i>B. m. pullus</i>, &#9792; ad., 71608, KU, 8 mi. S Condega, Nicaragua.<br />
+</td>
+</tr>
+</table>
+<br />
+<br />
+
+<div class="caption1">PLATE 4</div>
+<br />
+<div class="fig_center" style="width: 450px;">
+<a name="plate4" id="plate4"></a>
+<img src="images/plate_4.png" width="450" height="687" alt="" />
+</div>
+<br />
+Photographs of skulls in ventral view of <i>Baiomys</i>. &#215; 2.<br />
+<br />
+<table summary="list">
+<tr><td class="text_lf">
+<i>a.</i> <i>B. t. allex</i>, &#9792; ad., 45453, USNM, Colima, Colima.<br />
+<i>b.</i> <i>B. t. analogous</i>, &#9792; ad., 120265, USNM, Zamora, Michoacán.<br />
+<i>c.</i> <i>B. t. ater</i>, &#9792; ad., 15056, UI, 1 mi. ENE Greaterville, Arizona.<br />
+<i>d.</i> <i>B. t. canutus</i>, &#9792; ad., 62076, KU, 1 mi. S Pericos, Sinaloa<br />
+<i>e.</i> <i>B. t. fuliginatus</i>, &#9792; ad., 36771, KU, type locality.<br />
+<i>f.</i> <i>B. t. paulus</i>, &#9792; ad., 40032, KU, 18 mi. W, 2 mi. S Aguascalientes.<br />
+<i>g.</i> <i>B. t. subater</i>, &#9792; ad., 44543, USNM, type locality.<br />
+<i>h.</i> <i>B. t. taylori</i>, &#9792; ad., 57944, KU, 5 mi. E San Antonio, Texas.<br />
+</td>
+</tr>
+</table>
+<br />
+<br />
+
+<p><span class="pagenum"><a name="Page_651" id="Page_651">[Pg 651]</a></span></p>
+
+<p><i>Remarks.</i>&mdash;This subspecies retains its chief diagnostic character,
+blackish mid-dorsal region, throughout nearly all parts of its range.
+Specimens from the general area of Matagorda Bay and Lavaca
+County grade into <i>taylori</i> in characters of color and crania. The
+Colorado and Brazos rivers seemingly serve as barriers reducing
+gene flow between <i>taylori</i> and <i>subater</i>. These rivers may well have
+been important factors in the origin and the limitation of these two
+seemingly closely-related subspecies.</p>
+
+<p><i>Baiomys taylori subater</i> is not differentiated in color of pelage
+and characters of crania from <i>B. t. taylori</i> to the same degree that
+<i>B. t. paulus</i> is differentiated from <i>B. t. analogous</i>, or that <i>B. t. taylori</i>
+is differentiated from several of the other subspecies of <i>Baiomys
+taylori</i>. <i>B. t. subater</i> probably is a more recent occupant of the
+area in which it now lives than is the case with any other one of
+the subspecies of <i>taylori</i>. Sufficient time probably has not elapsed
+to allow for formation of more distinctive phenotypic patterns.</p>
+
+<div class="smaller">
+<a name="FNanchor_1_55" id="FNanchor_1_55"></a>
+<a name="FNanchor_2_56" id="FNanchor_2_56"></a>
+<a name="FNanchor_3_57" id="FNanchor_3_57"></a>
+<a name="FNanchor_4_58" id="FNanchor_4_58"></a>
+<a name="FNanchor_5_59" id="FNanchor_5_59"></a>
+<p><i>Specimens examined.</i>&mdash;Total 65, all from <span class="smcap">Texas</span>
+and distributed as follows: <i>Brazos County</i>: <sup>1</sup>/<sub>2</sub> mi. NW College Station,
+1<a href="#Footnote_1_55" class="fnanchor">[55]</a>; <i>3 mi. W College Station</i>,
+<i>1 mi. W Easterwood Airport</i>, 1<a href="#Footnote_1_55" class="fnanchor">[55]</a>;
+<i>College Station</i>, 1<a href="#Footnote_1_55" class="fnanchor">[55]</a>.
+<i>Walker County</i>: Huntsville, 1<a href="#Footnote_1_55" class="fnanchor">[55]</a>.
+<i>Hardin County</i>: Sour Lake, 1<a href="#Footnote_3_57" class="fnanchor">[57]</a>.
+<i>Jefferson County</i>: 7 mi. S Labelle, 10. <i>Harris County</i>: 6 mi. NE Crosby,
+1<a href="#Footnote_2_56" class="fnanchor">[56]</a>. <i>Colorado County</i>: <i>10 mi. N Eagle Lake</i>,
+1<a href="#Footnote_1_55" class="fnanchor">[55]</a>; <i>9 mi. N Eagle Lake</i>,
+1<a href="#Footnote_1_55" class="fnanchor">[55]</a>; 2 mi. W Eagle Lake, 1;
+<i>Eagle Lake</i>, 1<a href="#Footnote_1_55" class="fnanchor">[55]</a>, 5.
+<i>Fort Bend County</i>: Richmond, 4<a href="#Footnote_3_57" class="fnanchor">[57]</a>.
+<i>Galveston County</i>: <i>Texas City</i>, 6<a href="#Footnote_4_58" class="fnanchor">[58]</a>;
+Virginia Point, 1<a href="#Footnote_3_57" class="fnanchor">[57]</a>.
+<i>Brazoria County</i>: <i>Austin Bayou near Alvin</i>, 2<a href="#Footnote_3_57" class="fnanchor">[57]</a>;
+14 mi. SSE Alvin, 2<a href="#Footnote_5_59" class="fnanchor">[59]</a>;
+type locality, 7<a href="#Footnote_3_57" class="fnanchor">[57]</a> (including the type).
+<i>Lavaca County</i>: 4 mi. W Hallettsville, 1<a href="#Footnote_1_55" class="fnanchor">[55]</a>;
+<i>1 mi. SW Hallettsville</i>, 3<a href="#Footnote_1_55" class="fnanchor">[55]</a>;
+<i>13.7 mi. SW Hallettsville</i>, 2<a href="#Footnote_1_55" class="fnanchor">[55]</a>;
+4 mi. NE Yoakum, 11.</p>
+
+<p><i>Marginal records.</i>&mdash;<span class="smcap">Texas</span>: Huntsville; Sour Lake; 7 mi. S La Belle;
+Virginia Point; 14 mi. SSE Alvin; type locality; 4 mi. NE Yoakum; 4 mi. W
+Hallettsville; <sup>1</sup>/<sub>2</sub> mi. NW College Station.</p>
+</div>
+
+<div class="footnote"><p><a name="Footnote_1_55" id="Footnote_1_55"></a>
+<a href="#FNanchor_1_55"><span class="label">[55]</span></a> Texas A &amp; M, Cooperative Wildlife Research Collection.</p></div>
+
+<div class="footnote"><p><a name="Footnote_2_56" id="Footnote_2_56"></a>
+<a href="#FNanchor_2_56"><span class="label">[56]</span></a> Carnegie Museum.</p></div>
+
+<div class="footnote"><p><a name="Footnote_3_57" id="Footnote_3_57"></a>
+<a href="#FNanchor_3_57"><span class="label">[57]</span></a> U. S. Nat. Museum (Biol. Surv. Coll.).</p></div>
+
+<div class="footnote"><p><a name="Footnote_4_58" id="Footnote_4_58"></a>
+<a href="#FNanchor_4_58"><span class="label">[58]</span></a> Los Angeles County Museum.</p></div>
+
+<div class="footnote"><p><a name="Footnote_5_59" id="Footnote_5_59"></a>
+<a href="#FNanchor_5_59"><span class="label">[59]</span></a> American Museum of Natural History.</p></div>
+
+
+<div class="caption3"><a name="Baiomys_taylori_taylori" id="Baiomys_taylori_taylori"></a>
+<b>Baiomys taylori taylori</b> (Thomas)</div>
+
+<div class="species_ref"><i>Hesperomys</i> (<i>Vesperimus</i>) <i>taylori</i> Thomas, Ann. Mag. Nat. Hist., ser. 5,
+19:66, January, 1887.</div>
+
+<div class="species_ref"><i>Baiomys taylori</i> [<i>taylori</i>], Mearns, Bull. U. S. Nat. Mus., 56:381, April 13,
+1907; Stickel and Stickel, Jour. Mamm., 30:141, May 23, 1949.</div>
+
+<div class="species_ref">Baiomys taylori taylori, Miller, Bull. U. S. Nat. Mus., 79:136, December 31,
+1912; Miller, Bull. U. S. Nat. Mus., 128:317, April 29, 1924; Anthony,
+Field Book of North American Mammals, p. 327, 1928; Ellerman, The
+Families and Genera of Living Rodents, 2:402, March 21, 1941; Taylor
+and Davis, Texas Game, Fish and Oyster Comm. Bull., 27:56, August,
+1947 (part); Blair, Texas Jour. Sci., 2:104, March 31, 1950; Goldman,
+<span class="pagenum2"><a name="Page_652" id="Page_652">[Pg 652]</a></span>
+Smith. Miscl. Coll., 115:373, 426, July 31, 1951; Baker, Univ. Kansas
+Publs., Mus. Nat. Hist., 5:212, December 15, 1951; Blair, Texas Jour.
+Sci., 4:242, June 30, 1952; Hooper, Occas. Papers, Univ. Michigan, Mus.
+Zool., 544:7, March 25, 1953; Dalquest, Louisiana State Univ. Studies
+(Biol. Sci. Ser.), 1:155, December 28, 1953 (part); Blair, Adv. in
+Genetics, 5:10, January 27, 1954; Miller and Kellogg, Bull. U. S. Nat.
+Mus., 205:511, March 3, 1955; Baker, Univ. Kansas Publs., Mus. Nat.
+Hist., 9:273, June 15, 1956; Packard, Proc. Biol. Soc. Washington, 71:17,
+April 11, 1958; Hall and Kelson, The Mammals of North America, 2:659,
+March 31, 1959 (part).</div>
+
+<div class="species_ref"><i>Cricetus</i> (<i>Vesperimus</i>) <i>taylori</i>, Thomas, Proc. Zool. Soc. London, 68:446,
+November 20, 1888.</div>
+
+<div class="species_ref"><i>Sitomys taylori</i>, Merriam, Proc. Biol. Soc. Washington, 7:170, September
+29, 1892.</div>
+
+<div class="species_ref"><i>Sitomys</i> (<i>Baiomys</i>) <i>taylori</i>, True, Proc. U. S. Nat. Mus., 16(972):758,
+February 7, 1894; J. A. Allen, Bull. Amer. Mus. Nat. Hist., 6:181, May
+31, 1894.</div>
+
+<div class="species_ref"><i>S.</i> [<i>itomys</i>] <i>taylori</i>, Rhoads, Proc. Acad. Nat. Sci. Philadelphia, 46:256,
+October, 1894.</div>
+
+<div class="species_ref"><i>Peromyscus</i> (<i>Baiomys</i>) <i>taylori</i>, J. A. Allen, Bull. Amer. Mus. Nat. Hist.,
+8:65, April 22, 1896.</div>
+
+<div class="species_ref">[<i>Peromyscus</i>] <i>taylori</i>, Trouessart, Cat. Mamm., 1:517, 1898.</div>
+
+<div class="species_ref"><i>Peromyscus taylori</i> [<i>taylori</i>], Elliot, Field Columb. Mus. Publ., 105(4):135,
+July 1, 1905; V. Bailey, N. Amer. Fauna, 25:101, October 24, 1905; Elliot,
+Field Columb. Mus. Publ., 115(8):203, 1907; Osgood, N. Amer. Fauna,
+28:253, April 17, 1909.</div>
+
+<div class="smaller">
+<p><i>Type.</i>&mdash;Adult male, skin and skull; No. 87.11.24.1, British Museum, Natural
+History; San Diego, Duval County, Texas; obtained by William Taylor.</p>
+
+<p><i>Range.</i>&mdash;North-central to southeastern Texas, excluding the coastal plain
+north of the region of Matagorda Bay, thence south into the southern part of
+Tamaulipas and west into Coahuila and Nuevo León, see <a href="#fig11">Figure 11</a>. Occurs
+from near sea level in Texas up to 1500 feet in Coahuila. Zonal range: mostly
+Lower Austral (in México and southeastern half of Texas, the Tamaulipas
+Biotic Province of Goldman and Moore, 1945:349, and Blair, 1952:230).</p>
+
+<p><i>Diagnosis.</i>&mdash;Size medium for the species; dorsum grayish in freshly taken
+specimens to Hair Brown in preserved specimens; individual guard hairs of
+dorsum black-tipped, grayish basally, underfur black-tipped with a subterminal
+band of olive-buff; sides of body pale-grayish near venter, individual hairs
+buffy proximally, grayish basally; belly pale grayish, individual hairs white-tipped,
+Pale Neutral Gray basally; throat and chin colored as is belly; forefeet
+and hind feet sooty-gray dorsally, sparsely-haired ventrally, thus appearing
+flesh-colored; tail unicolored gray to sooty-gray. Average and extreme cranial
+measurements of 22 adults from 6 mi. SW San Gerónimo, Coahuila, are as
+follows: occipitonasal length, 18.0 (17.4-19.0); zygomatic breadth, 9.6
+(9.2-10.2); postpalatal length, 6.5 (5.9-7.1); least interorbital breadth, 3.6
+(3.3-3.8); length of incisive foramina, 4.0 (3.6-4.3); length of rostrum, 6.1
+(5.7-6.7); breadth of brain case, 8.8 (8.5-9.1); depth of cranium, 6.5 (6.0-7.0);
+alveolar length of maxillary tooth-row, 3.1 (3.0-3.3). Average and extreme
+external measurements of 19 adults from 6 mi. SW San Gerónimo are as follows:
+total length, 102.2 (95-115); length of tail vertebrae, 39.4 (21-46);
+length of body, 62.8 (53-76); length of hind foot, 14.0 (12-15); length of
+ear from notch, 10.7 (10-12); for photographs of skull,
+see <a href="#plate2">Plate 2<i>g</i></a>, and <a href="#plate4">Plate 4<i>h</i></a>.</p>
+
+<p><span class="pagenum2"><a name="Page_653" id="Page_653">[Pg 653]</a></span></p>
+
+<p><i>Comparisons.</i>&mdash;For comparisons with <i>B. t. subater</i>, <i>B. t. analogous</i>, and <i>B. t.
+fuliginatus</i>, see accounts of those subspecies. From <i>B. t. paulus</i>, found to the
+southwest, <i>B. t. taylori</i> differs as follows: dorsum grayish rather than fawn-colored;
+hairs on dorsal parts of forefeet and hind feet sooty-gray (not white
+to white-brown); venter gray to Light Drab-Gray, rather than whitish with
+gray overtones; tail unicolored instead of bicolored; skull averaging slightly
+larger over-all; maxillary part of zygoma forms right angle with rostrum
+rather than obtuse angle; incisive foramina extending posteriorly to anterior
+plane of first upper molars instead of to a transverse plane at middle of right
+and left first upper molars; bullae less inflated; interorbital region broader
+relative to length of skull; rostrum sloping gently from frontonasal suture to
+anterior tip of nasals rather than declining abruptly from frontonasal suture
+to anterior tip of nasals.</p>
+</div>
+
+<p><i>Remarks.</i>&mdash;The geographic range of <i>taylori</i> is relatively large,
+and the subspecies is locally variable. Nevertheless, none of the
+external and cranial measurements of specimens assigned to this
+subspecies differs significantly from the corresponding measurements
+of material from the type locality and adjacent areas in
+southeastern Texas. In southeastern Texas, south of the Guadalupe
+River, south to the coastal plain of Tamaulipas, this subspecies
+differs in color (being paler) from <i>B. t. subater</i> with which <i>taylori</i>
+might be confused. The foothills of the Sierra Madre Oriental in
+western Tamaulipas, north through Nuevo León and Coahuila,
+seem to mark the southwestern limit of the range assignable to
+<i>taylori</i>.</p>
+
+<p>On December 27, 1958, a specimen, KU 81552, was obtained 3 mi.
+N Bowie, Montague County, Texas. This record station extends
+the known range of <i>B. taylori</i> 65 miles northward from the previous
+northernmost locality, listed by Hunsaker, Raun, and Swindells
+(1959:447). Two specimens, KU 81553 and 81554, were collected
+by the author 2 mi. NE Cedar Hill, Dallas County, Texas, on October
+31, 1958. These two specimens, plus the single specimen from
+Bowie County are all paler with more buffy bellies than either
+<i>B. t. taylori</i> or <i>B. t. subater</i>. They may represent an incipient subspecies.
+I tentatively assign them to <i>B. t. taylori</i> because of the
+pale rather than dark (like <i>B. t. subater</i>) pelage. Additional specimens
+are needed from these areas and from the hiatus between the
+ranges of <i>B. t. taylori</i> and <i>B. t. subater</i> the better to understand
+the manner in which these two subspecies intergrade.</p>
+
+<p>Among named subspecies of <i>Baiomys taylori</i>, <i>B. t. taylori</i> most
+closely resembles <i>B. t. subater</i> to the north in Texas. Nine specimens
+examined from Yoakum are intergrades between <i>taylori</i> and <i>subater</i>.
+These specimens have the sooty dorsal color of <i>subater</i>, but ventrally
+are inseparable from topotypes of <i>taylori</i>. In length of body and
+<span class="pagenum"><a name="Page_654" id="Page_654">[Pg 654]</a></span>
+tail, specimens from Yoakum are like <i>subater</i>, but in length of hind
+foot, they are intermediate between the two subspecies. Cranially,
+they are like <i>subater</i>. When all characters are considered, the specimens
+are best referred to <i>subater</i>. Bailey (1905:103) suggested
+that specimens from the southern part of the range, which he ascribed
+to <i>subater</i>, tended to a more grayish color than topotypes of
+<i>subater</i>, therefore, grading into <i>taylori</i>. The zone of intergradation
+runs from Matagorda Bay northwest through Lavaca County, thence
+north to the Colorado River, and closely follows the boundary between
+the Lower Austral and Humid Division of Lower Austral
+Life-zone as plotted by Bailey (<i>loc. cit.</i>). Findley (1955:44) pointed
+out that where two life-zones meet, the resulting populations of
+shrews are mostly intergrades. Such is the case between these two
+subspecies of <i>Baiomys taylori</i> in an area where life-zones might seem
+less important than in the mountainous west.</p>
+
+<p>In the southern part of the range of <i>taylori</i>, intergradation occurs
+between <i>B. t. taylori</i> in western Tamaulipas and <i>B. t. fuliginatus</i> in
+the mountains of San Luis Potosí.</p>
+
+<p>Dalquest (1953:156) found no indication of intergradation between
+the two species, <i>B. taylori</i> and <i>B. musculus</i>, in San Luis Potosí.
+After examination of specimens from San Luis Potosí, I am in agreement
+that they are all referable to the species <i>taylori</i>.</p>
+
+<div class="smaller">
+<a name="FNanchor_1_60" id="FNanchor_1_60"></a>
+<a name="FNanchor_2_61" id="FNanchor_2_61"></a>
+<a name="FNanchor_3_62" id="FNanchor_3_62"></a>
+<a name="FNanchor_4_63" id="FNanchor_4_63"></a>
+<a name="FNanchor_5_64" id="FNanchor_5_64"></a>
+<a name="FNanchor_6_65" id="FNanchor_6_65"></a>
+<a name="FNanchor_7_66" id="FNanchor_7_66"></a>
+<a name="FNanchor_8_67" id="FNanchor_8_67"></a>
+<a name="FNanchor_9_68" id="FNanchor_9_68"></a>
+<p><i>Specimens examined.</i>&mdash;Total 435. <span class="smcap">Texas</span>:
+<i>Montague County</i>: 3 mi. N Bowie, 1. <i>Dallas County</i>: 2 mi. NE Cedar Hill, 2.
+<i>Travis County</i>: 8 mi. NW Austin, 2<a href="#Footnote_1_60" class="fnanchor">[60]</a>;
+<i>Austin</i>, 2<a href="#Footnote_1_60" class="fnanchor">[60]</a>;
+<i>4 mi. E Austin</i>, 4<a href="#Footnote_1_60" class="fnanchor">[60]</a>;
+<i>5 mi. E Austin</i>, 3<a href="#Footnote_1_60" class="fnanchor">[60]</a>;
+<i>6 mi. E Austin</i>, 16<a href="#Footnote_1_60" class="fnanchor">[60]</a>, 1;
+<i>7 mi. E Austin</i>, 1<a href="#Footnote_1_60" class="fnanchor">[60]</a>;
+<i>15 mi. E Austin</i>, 1<a href="#Footnote_1_60" class="fnanchor">[60]</a>;
+<i>4 mi. S Austin</i>, 1<a href="#Footnote_1_60" class="fnanchor">[60]</a>.
+<i>Bastrop County</i>: 25 mi. E Austin, 2. <i>Kendall County</i>:
+Boerne, 1<a href="#Footnote_2_61" class="fnanchor">[61]</a>.
+<i>Bexar County</i>: <i>1 mi. N Randolph Field</i>, 3<a href="#Footnote_5_64" class="fnanchor">[64]</a>;
+<i>5 mi. ENE</i> (<i>on U. S. Highway 81</i>) <i>San Antonio</i>, 1;
+<i>3 mi. NE San Antonio</i>, 1; San Antonio, 26<a href="#Footnote_2_61" class="fnanchor">[61]</a>,
+11<a href="#Footnote_3_62" class="fnanchor">[62]</a>, 1<a href="#Footnote_4_63" class="fnanchor">[63]</a>;
+<i>5 mi. E San Antonio</i>, 11; <i>4<sup>1</sup>/<sub>2</sub> mi. E Sayers</i>, 3.
+<i>Gonzales County</i>: 7 mi. S Luling, 2<a href="#Footnote_1_60" class="fnanchor">[60]</a>.
+<i>Wilson County: 4 mi. W LaVernia</i>, 3; 12 mi. W Floresville, 1.
+<i>Atascosa County</i>: 9 mi. SW Somerset, 1. <i>Goliad County</i>: 8 mi. NE Goliad,
+1<a href="#Footnote_1_60" class="fnanchor">[60]</a>.
+<i>Bee County</i>: Beeville, 1<a href="#Footnote_2_61" class="fnanchor">[61]</a>.
+<i>Aransas County</i>: Aransas (Wildlife) Refuge, 1<a href="#Footnote_6_65" class="fnanchor">[65]</a>;
+<i>5 mi. E Copana Bay</i>, 1<a href="#Footnote_6_65" class="fnanchor">[65]</a>;
+<i>4.6 mi. NE Rockport</i>, 5<a href="#Footnote_1_60" class="fnanchor">[60]</a>;
+<i>4.5 mi. NW Rockport</i>, 2<a href="#Footnote_1_60" class="fnanchor">[60]</a>;
+3 mi. N, 2 mi. E Rockport, 4; <i>Rockport</i>, 1<a href="#Footnote_1_60" class="fnanchor">[60]</a>,
+1<a href="#Footnote_2_61" class="fnanchor">[61]</a>, 1<a href="#Footnote_4_63" class="fnanchor">[63]</a>;
+<i>1<sup>1</sup>/<sub>2</sub> mi. SW Rockport</i>, 1<a href="#Footnote_1_60" class="fnanchor">[60]</a>;
+<i>2 mi. SW Rockport</i>, 2<a href="#Footnote_1_60" class="fnanchor">[60]</a>;
+<i>13.4 mi. SW Rockport</i>, 1<a href="#Footnote_1_60" class="fnanchor">[60]</a>;
+<i>14 mi. SW Rockport</i>, 1. <i>San Patricio County</i>: Welder Wildlife Refuge, 7.
+<i>Duval County</i>: type locality, 2<a href="#Footnote_2_61" class="fnanchor">[61]</a>,
+1<a href="#Footnote_7_66" class="fnanchor">[66]</a>.
+<i>Nueces County</i>: Corpus Christi (south Nueces Bay), 1<a href="#Footnote_5_64" class="fnanchor">[64]</a>
+(Cleveland Mus. Coll.). <i>Kleberg County:</i> 2 mi. S Riviera,
+3<a href="#Footnote_6_65" class="fnanchor">[65]</a>. <i>Brooks County</i>: 3 mi. S Falfurrias,
+2<a href="#Footnote_6_65" class="fnanchor">[65]</a>. <i>Hidalgo County</i>:
+6 mi. S McAllen, 17<a href="#Footnote_1_60" class="fnanchor">[60]</a>.
+<i>Willacy County</i>: 28 mi. E Raymondville, 10<a href="#Footnote_6_65" class="fnanchor">[65]</a>.
+<i>Cameron County</i>: Brownsville, 31<a href="#Footnote_2_61" class="fnanchor">[61]</a>,
+23<a href="#Footnote_3_62" class="fnanchor">[62]</a>, 5<a href="#Footnote_5_64" class="fnanchor">[64]</a>.
+<span class="smcap">Coahuila</span>: 6 mi. SW San Gerónimo, 32.
+<span class="smcap">Nuevo León</span>: Santa Catarina, 1<a href="#Footnote_2_61" class="fnanchor">[61]</a>;
+14 mi. N Monterrey, 1950 ft., 2<a href="#Footnote_8_67" class="fnanchor">[67]</a>;
+Monterrey, 1<a href="#Footnote_2_61" class="fnanchor">[61]</a>;
+20 km. N General Terán, 3<a href="#Footnote_5_64" class="fnanchor">[64]</a>.
+<span class="smcap">Tamaulipas</span>: <i>Near Headwaters Río Sabinas, 8 km. W, 10 km. N El Encino</i>,
+400 ft., 1; Camargo, 5<a href="#Footnote_2_61" class="fnanchor">[61]</a>;
+Charco Escondido, 20 mi. S Reynosa, 3<a href="#Footnote_8_67" class="fnanchor">[67]</a>;
+Matomoras, 5<a href="#Footnote_2_61" class="fnanchor">[61]</a>; <i>Ejido Santa Isabel,
+2 km. W Inter-American Highway</i>, 2000 ft., 7; Hidaglo, 7<a href="#Footnote_2_61" class="fnanchor">[61]</a>;
+<i>Hda. Station Engracia</i>, 4<a href="#Footnote_4_63" class="fnanchor">[63]</a>;
+4 mi. N La Pesca, 1; 29 mi. N Ciudad Victoria, 1<a href="#Footnote_8_67" class="fnanchor">[67]</a>;
+Ciudad Victoria, 6<a href="#Footnote_2_61" class="fnanchor">[61]</a>, 3;
+Jaumavé, 2400 ft., 6<a href="#Footnote_5_64" class="fnanchor">[64]</a>, 10;
+Sierra de Tamaulipas, 3<a href="#Footnote_5_64" class="fnanchor">[64]</a>; <i>25 mi. N El Manté,
+3 km. W Inter-American Highway</i> (<i>on Rancho Pano Ayuctle</i>), 300 ft., 4;
+<i>6 mi. N Gomez Farias</i> (<i>on Rancho Pano Ayuctle</i>), 1; <i>5 mi. NE Gomez Farias</i>,
+12<a href="#Footnote_5_64" class="fnanchor">[64]</a>,
+1<a href="#Footnote_3_62" class="fnanchor">[62]</a>; 70 km. (by highway)
+<span class="pagenum"><a name="Page_655" id="Page_655">[Pg 655]</a></span>
+S Ciudad Victoria, 2 km. W El Carrizo, 5<a href="#Footnote_3_62" class="fnanchor">[62]</a>, 2;
+Antigua Morelos, 5<a href="#Footnote_5_64" class="fnanchor">[64]</a>; <i>6 mi. N, 6 mi. W Altamira</i>, 31;
+<i>5 mi. N, 5 mi. W Altamira</i>, 4; <i>Alta Mira</i> (<i>Altamira</i>),
+2<a href="#Footnote_2_61" class="fnanchor">[61]</a>; 1 mi. S Altamira, 6; <i>10 mi. NW Tampico</i>, 1.
+<span class="smcap">San Luis Potosí</span>: Ebano, 5<a href="#Footnote_9_68" class="fnanchor">[68]</a>;
+<i>4 km. NE Ciudad Valles</i>, 1; Ciudad Valles, 1; <i>3 km. W Tamuín</i>,
+1<a href="#Footnote_9_68" class="fnanchor">[68]</a>; <i>Tamuín</i>,
+6<a href="#Footnote_9_68" class="fnanchor">[68]</a>;
+<i>Pujal</i>, 300 m., 1<a href="#Footnote_5_64" class="fnanchor">[64]</a>.
+<span class="smcap">Veracruz</span>: Tampico Alto, 50 ft., 1; Potrero Llano, 350 ft., 1;
+Ozulama, 2; Cerro Azul, 350 ft., 1.</p>
+
+<p><i>Marginal Records.</i>&mdash;<span class="smcap">Texas</span>: 3 mi. N Bowie; 2 mi. NE Cedar Hill;
+25 mi. E Austin; 7 mi. S Luling; 8 mi. NE Goliad; Aransas (Wildlife) Refuge;
+3 mi. N, 2 mi. E Rockport; Corpus Christi (South Nueces Bay); 2 mi. S Riviera;
+28 mi. E Raymondville; Brownsville. <span class="smcap">Tamaulipas</span>: Matomores;
+4 mi. N La Pesca; 1 mi. S Altamira. <span class="smcap">Veracruz</span>: Tampico Alto; Ozulama;
+Cerro Azul; Potrero Llano. <span class="smcap">San Luis Potosí</span>: Ciudad Valles.
+<span class="smcap">Tamaulipas</span>: Antigua Morelos; 70 km. S Ciudad Victoria, 2 km. W El Carrizo;
+Jaumavé; Hidalgo. <span class="smcap">Nuevo León</span>: 20 km. N General Terán; Santa Catarina.
+<span class="smcap">Coahuila</span>: 6 mi. SW San Gerónimo.
+<span class="smcap">Texas</span>: 9 mi. SW Somerset; Boerne; 8 mi. NW Austin.</p>
+</div>
+
+<div class="footnote"><p><a name="Footnote_1_60" id="Footnote_1_60"></a>
+<a href="#FNanchor_1_60"><span class="label">[60]</span></a> Coll. University of Texas.</p></div>
+
+<div class="footnote"><p><a name="Footnote_2_61" id="Footnote_2_61"></a>
+<a href="#FNanchor_2_61"><span class="label">[61]</span></a> U. S. Nat. Museum (Biol. Surv. Coll.).</p></div>
+
+<div class="footnote"><p><a name="Footnote_3_62" id="Footnote_3_62"></a>
+<a href="#FNanchor_3_62"><span class="label">[62]</span></a> American Museum of Natural History.</p></div>
+
+<div class="footnote"><p><a name="Footnote_4_63" id="Footnote_4_63"></a>
+<a href="#FNanchor_4_63"><span class="label">[63]</span></a> Chicago Natural History Museum.</p></div>
+
+<div class="footnote"><p><a name="Footnote_5_64" id="Footnote_5_64"></a>
+<a href="#FNanchor_5_64"><span class="label">[64]</span></a> Univ. Michigan, Museum of Zoology.</p></div>
+
+<div class="footnote"><p><a name="Footnote_6_65" id="Footnote_6_65"></a>
+<a href="#FNanchor_6_65"><span class="label">[65]</span></a> Texas A &amp; M Coop. Wildlife Res. Coll</p></div>.
+
+<div class="footnote"><p><a name="Footnote_7_66" id="Footnote_7_66"></a>
+<a href="#FNanchor_7_66"><span class="label">[66]</span></a> Carnegie Museum.</p></div>
+
+<div class="footnote"><p><a name="Footnote_8_67" id="Footnote_8_67"></a>
+<a href="#FNanchor_8_67"><span class="label">[67]</span></a> Univ. California, Mus. Vert. Zool.</p></div>
+
+<div class="footnote"><p><a name="Footnote_9_68" id="Footnote_9_68"></a>
+<a href="#FNanchor_9_68"><span class="label">[68]</span></a> Museum of Natural History, Louisiana State University.</p></div>
+
+
+<div class="caption2"><a name="EVOLUTION_AND_SPECIATION" id="EVOLUTION_AND_SPECIATION"></a>
+EVOLUTION AND SPECIATION</div>
+
+<p>The history of the genus dates back to the early late Pliocene,
+but morphological change since then has been slight insofar as can
+be judged from lower jaws. <i>Baiomys</i> seems to have been relatively
+conservative also in types of habitat occupied.</p>
+
+<p>According to Wilson (1937:59), the late Pliocene was a time of
+decided expansion of myomorph rodents, more particularly cricetines.
+Furthermore, at this time, the climate in the interior basin
+of southwestern North America presumably was becoming arid, if
+we can judge from the spread of elements of the Madro-Tertiary
+flora. Axelrod (1950:266) points out that the drier, continental
+climate initiated in the early Tertiary probably had its culmination
+in middle Pliocene time. Some floras of early late Pliocene of the
+southwestern United States reflect a climate slightly cooler and
+more moist than the climates of the middle Pliocene. However,
+late Pliocene times reflect an arid climate. The flora of the southwestern
+interior basin of North America in early late to late Pliocene
+was intermediate between the previous grassland floras of the
+middle Pliocene and the savannah flora of upper Pliocene. Axelrod
+(<i>loc. cit.</i>) suggests that this intermediate flora of the interior basin
+of southwestern North America resulted from the folding of the
+Cascades and uplifting of the Sierra Nevada and Peninsular ranges
+to the south. The development of these mountains produced
+greater aridity to the lee of the mountains, thus accounting for the
+grassland-savannah flora. Pygmy mice probably originated in that
+time, I judge in México, and moved northward and southward in
+<span class="pagenum"><a name="Page_656" id="Page_656">[Pg 656]</a></span>
+a grassland-savannah habitat that seemingly existed as far north
+as what is now Meade County, Kansas (where the Sawrock fauna
+lived). Further evidence for occupancy of a grassland-savannah
+habitat by ancestral pygmy mice stems from the distribution of
+the living species, <i>B. taylori</i>, that at present occupies territory
+adjacent to parts of the Sonoran and Chihuahuan deserts. <i>B.
+taylori</i> seems to be morphologically more specialized for life in an
+arid grassland than was <i>B. sawrockensis</i>.</p>
+
+<p>The geographic range of ancestral pygmy mice possibly extended
+farther south in late Pliocene time than the range of <i>B. musculus</i>
+does now. Anyhow, <i>B. sawrockensis</i> of the early late Pliocene
+dwelt in a more mesic type of habitat than <i>B. musculus</i> does, and
+such habitat may have existed from the Pacific lowlands of Central
+America to the Caribbean lowlands of northern South America (see
+Duellman, 1958:136, and Dunn, 1940:156) during late Pliocene
+times. An ancestral stock of hesperomine mice, not greatly different
+from <i>Baiomys</i>, may have emigrated from the North American
+continent into South America across the continuous land connection,
+which Simpson (1950:395) suggests was formed in the
+Chapadmalalan age (= Blancan age of North American terminology).
+The length of time of interchange of genes between northern
+and southern populations of mice across the Central American land
+connection probably was brief. Duellman (<i>op. cit.</i>:129) pointed
+out that once the Panamanian portal was closed, the warm counter
+equatorial current, El Niño, combined with the uplifting of the
+Andes, began to produce heavy rain forests in Central America and
+northern South America in late Pliocene or early Pleistocene times.
+These forests presumably isolated the stock in North America from
+that in South America where the latter probably evolved rapidly
+into kinds that differed from one another and from <i>Baiomys</i> in
+shape of body, type of pelage, and shape of skull. Internal structures
+such as hyoid apparatus, auditory ossicles, and baculum remained
+almost unchanged, as for example in <i>Calomys</i> now living in South
+America. The present resemblance in internal morphological
+features between it and <i>Baiomys</i>, I judge, reflects taxonomic relationships
+more accurately than do shape and conformation of
+body and skull that seem to respond more rapidly to external environmental
+changes. The cranial characters distinguishing <i>Baiomys
+musculus</i> from <i>Calomys laucha</i> are as follows: posterior
+lacerate foramina between second, rather than first, upper molars;
+parapterygoid fossa shallower; mesopterygoid fossa as wide or
+<span class="pagenum"><a name="Page_657" id="Page_657">[Pg 657]</a></span>
+wider, instead of narrower, than parapterygoid processes; burr for
+attachment of superficial masseter muscle hypertrophied instead
+of well-developed. In other cranial characters studied, the two
+genera closely resemble each other. Such similarities of crania
+between <i>Calomys</i> and <i>Baiomys</i> may reflect convergence, but the
+total of internal and external morphological characters shared, I
+think reflects true relationships.</p>
+
+<p><i>Peromyscus</i> has a large number of living and extinct species and
+exhibits a wide range of morphological variation, whereas <i>Baiomys</i>
+has a small number (7) of species and exhibits a narrow range of
+morphological variation. The small number of known species of
+pygmy mice suggests their conservatism in elaboration of morphological
+characters. Possibly this is because the habitat, or even
+the ecological niche, occupied in geological time by these mice
+was restricted, geographically and in kind. If the habitat of the
+pygmy mice oscillated between savannah and arid grassland, then
+an hypothesis can be made possibly accounting for the origin of
+species of these mice. My idea is that the geographical distribution
+of <i>Baiomys</i> today reflects a predilection on the part of these
+mice for a relatively uniform warm climate. Therefore, in the
+past, in times of warmer continental climate, these mice moved
+toward favorable habitat northward from an area in central and
+northern México. In cooler periods, the mice moved southward
+as habitats to the north became unfavorable.</p>
+
+<p>Dr. W. B. Davis (<i>in. litt.</i>) informs me that <i>B. taylori</i> was uncommon
+in Brazos County, Texas, approximately 15 years ago, and
+suggests that the abundance there now of this mouse and my taking
+it in 1958 northward nearly to the southern border of Oklahoma
+reflects a definite movement northward. Movement in the same
+direction in late years has been suggested for the nine-banded armadillo
+and the hispid cotton rat (Hall, 1959:373) that are associated
+with warm climates to the south. These movements possibly reflect
+only minor fluctuations of climate, but in a long period of
+warmth movements northward would be expected to be pronounced
+and extensive.</p>
+
+<p>Extinct species of <i>Baiomys</i> may have originated as a result of
+extension northward of the geographical range and subsequent
+retreat southward of the northern populations, as follows: (1) the
+range of the genus moved northward in a warm period; (2) in
+cooler times, most of the mice in the north disappeared and only
+isolated colonies remained in small patches of remaining habitat
+<span class="pagenum"><a name="Page_658" id="Page_658">[Pg 658]</a></span>
+still favorable to the mice; (3) the small populations of isolated
+pygmy mice after a time changed through mutations, recombinations
+and subsequent selection to a degree that prevented crossbreeding
+once populations from the south again moved northward
+and came in contact with previously isolated stocks; (4) then
+competition caused further divergence in morphological characters.
+Such an hypothesis would account for the morphological differences
+between the extinct <i>B. kolbi</i> and <i>B. rexroadi</i>. The extinct
+<i>B. brachygnathus</i>, presumably a dweller of a xerophytic grassland,
+may have had its origin from a <i>B. minimus</i>-like stock in the manner
+outlined.</p>
+
+
+<div class="caption3"><a name="FORMATION_OF_THE_RECENT_SPECIES" id="FORMATION_OF_THE_RECENT_SPECIES"></a>
+FORMATION OF THE RECENT SPECIES</div>
+
+<p>The morphological difference between the extinct <i>B. minimus</i>
+and the living <i>B. musculus</i> is not great, and musculus seems to be
+the product of the <i>B. sawrockensis-B. minimus</i> line of development.
+Morphological characters of the parental stock of the two living
+species, <i>musculus</i> and <i>taylori</i>, may have been intermediate between
+those of <i>B. minimus</i> and those of <i>B. musculus</i>. The principal part
+of the range of <i>Baiomys</i> today is in México, and probably was there
+through much of Pleistocene time. Extension northward of the species
+and retreat southward of those northern populations of pygmy
+mice would not only have left isolated populations in the north,
+but would have allowed the mice that retreated south to share a
+common gene pool. Therefore, populations of pygmy mice occurring
+to the south in central México might be expected to maintain
+a relatively high degree of heterozygosity in morphological and
+behavioral characters. The occurrence of any physical or biotic
+barrier that would have separated this homogeneous group would
+be conducive to speciation. There is evidence that a barrier occurred
+in the Pleistocene in central México sufficient to separate the
+supposed interbreeding, relatively homogeneous populations of
+pygmy mice. According to Sears (1955:529) and De Terra <i>et al</i>.
+(1949:51), parts of the higher regions in the Valley of México, and
+the transverse volcanic zone in central México were glaciated. On
+the mountain Ixtaccihuatl, De Terra (<i>op. cit.</i>:52) found evidence of
+four marked advances of ice, from oldest to youngest, as follows:
+Salto, ice advanced to 3100 meters; Xopano, ice at 3200-3300 meters;
+Trancas, ice to 3400 meters; Ayolotepito, ice to 4350 meters. The
+Salto advance is correlated by De Terra (<i>loc. cit.</i>) with the Iowan
+glacial period. The advance of ice down the mountain sides in
+the transverse volcanic zone was accompanied by cool moist climates
+<span class="pagenum"><a name="Page_659" id="Page_659">[Pg 659]</a></span>
+or pluvial periods. Such climates probably altered habitat
+formerly suitable for <i>Baiomys</i>. There is no record of <i>Baiomys</i>
+known to me exceeding 8000 feet in elevation, although the lower
+edge of the ice on Ixtaccihuatl is at approximately 15,300 feet (4600
+meters, Sears, <i>loc. cit.</i>). Presumably, the advance of ice down the
+mountains forced the pygmy mice to move to lower altitudes.
+Pluvial conditions possibly rendered the habitat even at lower
+altitudes uninhabitable for the mice, with the result that none continued
+to live in the transverse volcanic zone, but only north and
+south thereof. Long-continued separation of these northern and
+southern segments allowed species formation to occur. As climatic
+and habitat conditions became more favorable in central México,
+the two species moved back toward each other, and eventually their
+geographic ranges overlapped.</p>
+
+<p>An analysis of external and cranial characters of pygmy mice
+(see <a href="#fig12">Figure 12</a>) reveals that both species are essentially largest to
+the north and smallest to the south. There are exceptions to this
+cline in both species. For example, <i>B. taylori analogous</i> is a large
+subspecies; it lives allopatrically in the southern part of the range
+of the species. <i>B. musculus pallidus</i> is not the largest subspecies;
+it lives allopatrically in the northern part of the range of the species.
+In west-central México, where the two species are sympatric,
+<i>B. taylori</i> is smaller than elsewhere and <i>B. musculus</i> is larger than
+elsewhere. <i>B. t. analogous</i> lives in the mountains of the transverse
+volcanic zone in central México. Its large size may be a result of
+the cooler climate in the mountains. <i>B. t. allex</i>, the smallest subspecies,
+lives sympatrically with <i>B. musculus musculus</i> at lower
+elevations in west-central México. The small size of <i>allex</i> could be
+a result of the warmer climate of the lower elevations. <i>B. m. pallidus</i>,
+at lower elevations in southern Oaxaca, is smaller than other
+subspecies of <i>musculus</i> to the south at higher elevations. <i>B. m.
+musculus</i> lives at low elevations along the coast of west-central
+México. Unlike <i>B. m. pallidus</i>, <i>B. m. musculus</i> is large at lower
+elevations. It occurs sympatrically with <i>B. t. allex</i>. It is my idea
+that during the period of separation, when the two species were
+evolving, larger subspecies evolved to the north or at higher altitudes
+where climates were cooler; smaller subspecies evolved to
+the south or at lower elevations; the two cognate species, <i>musculus</i>
+and <i>taylori</i>, made contact at lower elevations where individuals of
+<i>taylori</i> may have been smallest, but individuals of <i>musculus</i> were
+not the largest of the species. The differences, therefore, between
+the two species in their initial contact probably were slight. Hybrids,
+<span class="pagenum"><a name="Page_660" id="Page_660">[Pg 660]</a></span>
+if they occurred, were probably inviable, sterile, or ill-suited
+for occupancy of the habitat of either of the parental stocks. The
+occurrence of hybrids, therefore, would result in what geneticists
+call "gamete wastage," and any further divergence in the parental
+stock, either in external characters (size and shape of body and
+head), or behavior, useful in recognition of species, would be favored
+by natural selection (see Dobzhansky, 1951:225; and Koopman,
+1950:147). The two species seem to have diverged more in
+external characters where they occur together than in areas where
+they live separately (see <a href="#fig12">Figure 12</a>). The two species could be
+confused if a sample of adults of <i>taylori</i> from 7 mi. S La Belle, Jefferson
+County, Texas, were compared to a sample of adults of
+<i>musculus</i> from Tehuantepec, Oaxaca (see <a href="#fig12">Figure 12</a>). No confusion
+in species identity would arise, however, if a sample of adults
+was taken from the area where the two species live together (see
+<a href="#fig12">Figure 12</a>). Brown and Wilson (1956:49) pointed out that where
+two closely related species occur together, characters (morphological,
+ecological, physiological, or behavioral) of each species
+are easily distinguished. However, where the two species are allopatric,
+the two closely related species so resemble one another
+that the species are not easily distinguished. This phenomenon has
+been called "character displacement" by Brown and Wilson (<i>loc.
+cit.</i>).</p>
+
+<p>In the area where the two species of pygmy mice occur together,
+there seems to be a disparity in numbers between them. Hooper
+(1952a:91) has recorded the collection of both <i>B. musculus</i> and
+<i>B. taylori</i> in a single trap line. A series of pygmy mice collected
+from San Gabriel, Jalisco, contained one <i>taylori</i> and 33 <i>musculus</i>;
+another sample from La Resolana, Jalisco, had a ratio of 25 <i>taylori</i>
+to 6 <i>musculus</i>. The disparity in numbers where the two species
+occur together has been further substantiated by collections of the
+University of Kansas. Possibly this disparity in numbers is a result
+of interspecific competition. Hooper (<i>op. cit.</i>:90) pointed out
+that where the range of <i>B. musculus</i> (typical of arid tropical lowlands)
+meets that of <i>B. taylori</i> (typical of arid temperate highlands),
+the two geographic ranges interdigitate with parts of
+the range of <i>musculus</i> extending into the highlands and parts of
+the range of <i>taylori</i> extending into the lowlands. In the lowlands,
+<i>musculus</i> may be better adapted to environmental conditions and,
+therefore, more successful in competition with <i>taylori</i> for available
+habitat. The reverse situation may exist in the highlands. Also,
+the fact that <i>musculus</i> is more of a diurnal animal than is <i>taylori</i>
+<span class="pagenum"><a name="Page_661" id="Page_661">[Pg 661]</a></span>
+may account for the difference in numbers of individuals of the
+two species taken in trap lines. Many collectors set their traps in
+late afternoon or evening and retrieve them in early morning.
+Such a schedule might not yield many <i>musculus</i>. If interspecific
+competition does occur in the area where the two species occur,
+any change in habits or microhabitat by either species that would
+reduce this competition would be favored by natural selection
+(see Mayr, 1949:518; Lack, 1944:262-263; and Brown, 1958:154-155).
+Brown (<i>op. cit.</i>:154), as I understand him, pointed out
+(taking account of Gause's principle) that when two species having
+similar ecological valences move into the same niche in the same
+locality, one of three things must eventually happen: (<i>a</i>) the
+two species occupy different geographic ranges; (<i>b</i>) they compete
+and one is eventually eliminated; (<i>c</i>) the two species, because
+of differentiation or specialization, exploit different aspects of the
+niche. In <i>Baiomys</i>, (<i>c</i>) seems to apply. Natural selection probably
+would favor a continuation of diurnal activity in <i>musculus</i> and
+nocturnal activity in <i>taylori</i>, thereby preventing frequent meeting of
+the two species.</p>
+
+
+<div class="caption3"><a name="AREAS_OF_PRESENT_DIFFERENTIATION" id="AREAS_OF_PRESENT_DIFFERENTIATION"></a>
+AREAS OF PRESENT DIFFERENTIATION</div>
+
+<p>In both species of <i>Baiomys</i>, the most distinct subspecies, <i>B. t.
+allex</i> and <i>B. m. musculus</i>, occur in the area where the two species
+are sympatric. Seven subspecies, or 44 per cent, occur either in
+or adjacent to the transverse volcanic zone. This area is the
+major area of active differentiation. Incipient subspecies are also
+evident in these areas. A secondary area of differentiation is indicated
+within the range of <i>B. musculus</i> in Guatemala, El Salvador
+and Honduras. Three subspecies occur in this area (<i>grisescens,
+handleyi</i> and <i>nigrescens</i>) and incipient subspeciation is in evidence
+there.</p>
+
+
+<div class="caption3"><a name="ZOOGEOGRAPHIC_POSITION" id="ZOOGEOGRAPHIC_POSITION"></a>
+ZOOGEOGRAPHIC POSITION</div>
+
+<p>Hooper (1949:25) regards <i>Baiomys</i> as a member of the rodent
+fauna of the arid, western Sonoran region, whereas Hershkovitz
+(1958:609) suggests that <i>Baiomys</i> is a nearctic-neotropical varicant
+(a kind that occurs in contiguous zoogeographic regions without
+our knowing in which region the taxon originated). The findings
+from my study do not contradict either of the above suggestions.
+Because of the close resemblance of <i>Baiomys</i> to certain hesperomine
+mice of South America, it is postulated that <i>Baiomys</i>, in more
+primitive form than now, occurred farther south in past times
+than it does now. Fossils show that primitive stocks of the genus
+<span class="pagenum"><a name="Page_662" id="Page_662">[Pg 662]</a></span>
+in late Pliocene or early Pleistocene times occurred also north
+of the present range of the genus. The belt in west-central México
+between nearctic and neotropical regions is the current center of
+distribution of the genus and probably has been for a considerable
+time.</p>
+
+<p><span class="pagenum"><a name="Page_663" id="Page_663">[Pg 663]</a></span></p>
+<div class="fig_center">
+<a name="fig12" id="fig12"></a>
+<img src="images/fig_12.png" width="718" height="502" alt="" />
+</div>
+
+<div class="fig_caption"><span class="smcap">Fig. 12.</span> Averages of the occipitonasal lengths of skulls of adults at 19 localities of occurrence (solid symbols) of
+<i>Baiomys taylori</i>, and at 17 localities of occurrence (open symbols) of <i>Baiomys musculus</i>. Note that the occipitonasal
+length decreases from north to south in each of the two species, and that in the region where the two
+species occur together, west-central México, <i>B. taylori</i> is smallest and <i>B. musculus</i> is largest. Average, extremes,
+number of specimens averaged (in italic type), and name of locality, from north to south for each species, are
+as follows:</div>
+
+<table summary="species">
+<tr>
+<td class="vtop">
+<div class="center">
+<i>Baiomys taylori</i><br />
+<br />
+<table summary="physical data">
+<tr><td align="left">18.0&nbsp;&nbsp;(17.5-18.6)&nbsp;&nbsp;<i>15</i>,&nbsp;&nbsp;9<sup>1</sup>/<sub>2</sub> mi. W New Mexico state line, Ariz.</td>
+</tr>
+<tr><td align="left">18.9&nbsp;&nbsp;(18.2-19.4)&nbsp;&nbsp;&nbsp;<i>6</i>,&nbsp;&nbsp;7 mi. S. La Belle, Jefferson Co., Texas.</td>
+</tr>
+<tr><td align="left">18.2&nbsp;&nbsp;(17.8-18.5)&nbsp;&nbsp;<i>10</i>,&nbsp;&nbsp;San Antonio, Bexar Co., Texas.</td>
+</tr>
+<tr><td align="left">18.2&nbsp;&nbsp;(18.0-18.5)&nbsp;&nbsp;&nbsp;<i>5</i>,&nbsp;&nbsp;2 mi. W Miñaca, Chihuahua.</td>
+</tr>
+<tr><td align="left">18.0&nbsp;&nbsp;(17.6-19.0)&nbsp;&nbsp;<i>22</i>,&nbsp;&nbsp;6 mi. SW San Gerónimo, Coahuila.</td>
+</tr>
+<tr><td align="left">18.2&nbsp;&nbsp;(18.1-18.3)&nbsp;&nbsp;&nbsp;<i>3</i>,&nbsp;&nbsp;Ciudad Obregón, Sonora.</td>
+</tr>
+<tr><td align="left">18.1&nbsp;&nbsp;(17.4-18.5)&nbsp;&nbsp;&nbsp;<i>5</i>,&nbsp;&nbsp;vic. (see <a href="#Page_649">p. 649</a>) Durango, Durango.</td>
+</tr>
+<tr><td align="left">18.1&nbsp;&nbsp;(17.5-18.5)&nbsp;&nbsp;&nbsp;<i>9</i>,&nbsp;&nbsp;Jaumavé, Tamaulipas.</td>
+</tr>
+<tr><td align="left">18.2&nbsp;&nbsp;(17.7-18.9)&nbsp;&nbsp;<i>19</i>,&nbsp;&nbsp;15 mi. N Rosario Chelé, Sinaloa.</td>
+</tr>
+<tr><td align="left">17.9&nbsp;&nbsp;(17.4-18.3)&nbsp;&nbsp;<i>27</i>,&nbsp;&nbsp;vic. (see <a href="#Page_655">p. 655</a>) Altamira, Tamaulipas.</td>
+</tr>
+<tr><td align="left">18.3&nbsp;&nbsp;(17.9-18.7)&nbsp;&nbsp;&nbsp;<i>9</i>,&nbsp;&nbsp;Valparaíso, Zacatecas.</td>
+</tr>
+<tr><td align="left">18.1&nbsp;&nbsp;(18.1-18.2)&nbsp;&nbsp;&nbsp;<i>4</i>,&nbsp;&nbsp;Ciudad del Maíz, San Luis Potosí.</td>
+</tr>
+<tr><td align="left">18.6&nbsp;&nbsp;(18.3-18.9)&nbsp;&nbsp;&nbsp;<i>8</i>,&nbsp;&nbsp;Tepic, Nayarit.</td>
+</tr>
+<tr><td align="left">18.0&nbsp;&nbsp;(17.7-18.4)&nbsp;&nbsp;<i>18</i>,&nbsp;&nbsp;4 mi. N, 5 mi. W León, Guanajuato.</td>
+</tr>
+<tr><td align="left">18.1&nbsp;&nbsp;(17.5-18.9)&nbsp;&nbsp;<i>28</i>,&nbsp;&nbsp;6 mi. E Querétaro, Querétaro.</td>
+</tr>
+<tr><td align="left">17.7&nbsp;&nbsp;(17.1-18.1)&nbsp;&nbsp;<i>17</i>,&nbsp;&nbsp;1 mi. SSE Ameca, Jalisco.</td>
+</tr>
+<tr><td align="left">17.3&nbsp;&nbsp;(16.8-17.9)&nbsp;&nbsp;<i>10</i>,&nbsp;&nbsp;2 mi. SSE Autlán, Jalisco.</td>
+</tr>
+<tr><td align="left">18.0&nbsp;&nbsp;(17.5-18.6)&nbsp;&nbsp;<i>10</i>,&nbsp;&nbsp;1 mi. S, 11 mi. W Zamora, Michoacán.</td>
+</tr>
+<tr><td align="left">17.6&nbsp;&nbsp;(17.4-18.2)&nbsp;&nbsp;&nbsp;<i>8</i>,&nbsp;&nbsp;Colima, Colima.</td>
+</tr>
+</table></div>
+</td>
+<td>&nbsp;&nbsp;&nbsp;&nbsp;</td>
+<td class="vtop">
+<div class="center">
+<i>Baiomys musculus</i><br />
+<br />
+<table summary="physical data">
+<tr><td align="left">20.2&nbsp;&nbsp;(19.9-20.3)&nbsp;&nbsp;&nbsp;<i>6</i>,&nbsp;&nbsp;vic. (see <a href="#Page_622">p. 622</a>) Ameca, Jalisco.</td>
+</tr>
+<tr><td align="left">20.2&nbsp;&nbsp;(19.9-20.3)&nbsp;&nbsp;&nbsp;<i>6</i>,&nbsp;&nbsp;2 mi. SSE Autlán, Jalisco.</td>
+</tr>
+<tr><td align="left">19.6&nbsp;&nbsp;(19.2-20.1)&nbsp;&nbsp;&nbsp;<i>6</i>,&nbsp;&nbsp;Jalapa, Veracruz.</td>
+</tr>
+<tr><td align="left">20.3&nbsp;&nbsp;(19.7-20.9)&nbsp;&nbsp;&nbsp;<i>9</i>,&nbsp;&nbsp;Colima, Colima.</td>
+</tr>
+<tr><td align="left">19.5&nbsp;&nbsp;(19.0-20.0)&nbsp;&nbsp;<i>10</i>,&nbsp;&nbsp;Cerro Gordo, Veracruz.</td>
+</tr>
+<tr><td align="left">19.8&nbsp;&nbsp;(19.4-20.3)&nbsp;&nbsp;&nbsp;<i>6</i>,&nbsp;&nbsp;6 mi. S Izucár de Matemores, Puebla.</td>
+</tr>
+<tr><td align="left">20.0&nbsp;&nbsp;(18.8-20.5)&nbsp;&nbsp;&nbsp;<i>7</i>,&nbsp;&nbsp;Teotitlán, Oaxaca.</td>
+</tr>
+<tr><td align="left">20.1&nbsp;&nbsp;(19.7-20.7)&nbsp;&nbsp;&nbsp;<i>7</i>,&nbsp;&nbsp;1 km. NW Chapa, Guerrero.</td>
+</tr>
+<tr><td align="left">19.9&nbsp;&nbsp;(19.4-20.4)&nbsp;&nbsp;&nbsp;<i>8</i>,&nbsp;&nbsp;5 mi. ESE Tecpán, Guerrero.</td>
+</tr>
+<tr><td align="left">19.5&nbsp;&nbsp;(19.1-20.1)&nbsp;&nbsp;<i>22</i>,&nbsp;&nbsp;3 mi. ESE Oaxaca, Oaxaca.</td>
+</tr>
+<tr><td align="left">19.5&nbsp;&nbsp;(19.1-19.9)&nbsp;&nbsp;<i>11</i>,&nbsp;&nbsp;Valley of Comitán, Chiapas.</td>
+</tr>
+<tr><td align="left">18.9&nbsp;&nbsp;(18.2-20.1)&nbsp;&nbsp;<i>17</i>,&nbsp;&nbsp;Tehuantepec, Oaxaca.</td>
+</tr>
+<tr><td align="left">18.9&nbsp;&nbsp;(18.4-19.7)&nbsp;&nbsp;<i>15</i>,&nbsp;&nbsp;6 mi. NW Tonalá, Chiapas.</td>
+</tr>
+<tr><td align="left">19.1&nbsp;&nbsp;(18.8-20.4)&nbsp;&nbsp;<i>10</i>,&nbsp;&nbsp;1 mi. S Rabinal, Guatemala.</td>
+</tr>
+<tr><td align="left">19.7&nbsp;&nbsp;(18.8-20.4)&nbsp;&nbsp;<i>10</i>,&nbsp;&nbsp;Lake Amatitlán, Guatemala.</td>
+</tr>
+<tr><td align="left">19.2&nbsp;&nbsp;(18.4-19.8)&nbsp;&nbsp;<i>26</i>,&nbsp;&nbsp;vic. (see <a href="#Page_625">p. 625</a>) San Salvador, El Salvador.</td>
+</tr>
+<tr><td align="left">19.3&nbsp;&nbsp;(18.9-19.9)&nbsp;&nbsp;<i>24</i>,&nbsp;&nbsp;8 mi. S Condega, Estelí, Nicaragua.</td>
+</tr>
+</table></div>
+</td>
+</tr>
+</table>
+
+
+<p><span class="pagenum"><a name="Page_664" id="Page_664">[Pg 664]</a></span></p>
+
+
+<div class="caption2"><a name="CONCLUSIONS" id="CONCLUSIONS"></a>CONCLUSIONS</div>
+
+
+<p>1. Two Recent species, each polytypic with eight subspecies, and
+five fossil species are recognized.</p>
+
+<p>2. The phyletic trends in the genus <i>Baiomys</i> have been from an
+ancestral stock that possessed relatively brachydont teeth having
+raised cingular ridges and orthodont to proödont incisors, to species
+having hypsodont teeth with reduced cingular ridges and retrodont
+incisors.</p>
+
+<p>3. Reduction of cingular ridges in pygmy mice is associated with
+an existence in open grassland (more xeric than mesic), whereas,
+the presence of cingular ridges is associated with an existence in a
+savannah habitat (more mesic than xeric).</p>
+
+<p>4. Shifts of geographical range of populations of pygmy mice
+at and near the periphery of their geographic range may account
+for the differentiation of the extinct species.</p>
+
+<p>5. The two living species, <i>B. musculus</i> and <i>B. taylori</i>, are seemingly
+derived from a common ancestor that in morphological structure
+was intermediate between <i>B. minimus</i> and <i>B. musculus</i>.</p>
+
+<p>6. The living species of pygmy mice resulted from a geographic
+separation, perhaps occurring in the Iowan glacial period (See De
+Terra, 1949:51) in the transverse volcanic zone of central México.</p>
+
+<p>7. The two species are now sympatric in west central México,
+where morphological characters (size and shape of body and length
+of skull) differ most. Where the two species are allopatric, these
+same morphological characters differ least.</p>
+
+<p>8. This is a documented instance of character displacement in
+mammals.</p>
+
+<p>9. On the basis of internal morphological characters studied
+(auditory ossicles, hyoid apparatus, and baculum), <i>Baiomys</i> seems
+to be more closely related to a South American hesperomine, perhaps
+<i>Calomys</i>, than to any North American cricetine.</p>
+
+<p>10. Pygmy mice were more widely distributed in the past than
+they are at present. Part of the ancestral stock of the pygmy mice
+may have emigrated from North America into South America in a
+brief period in the Pliocene; if so, it is easy to understand why
+certain South American hesperomines resemble <i>Baiomys</i>.</p>
+
+<p><span class="pagenum"><a name="Page_665" id="Page_665">[Pg 665]</a></span></p>
+
+<p>11. The combination of morphological and behavioral characters
+in the living pygmy mice warrants generic status for them. If
+<i>Baiomys</i> were treated as a subgenus of the genus <i>Peromyscus</i>, there
+would be adequate justification for including in the genus <i>Peromyscus</i>
+a number of other genera, some of them occurring in South
+America. Such lumping of genera would reduce our understanding
+of the natural relationships among this group of cricetine rodents.</p>
+<br />
+<br />
+
+
+<div class="caption2"><a name="LITERATURE_CITED" id="LITERATURE_CITED"></a>
+LITERATURE CITED</div>
+
+
+<div class="smcap">Allen, J. A.</div>
+
+<div class="references">1903.&nbsp; List of mammals collected by Mr. J. H. Batty in New Mexico and
+Durango, with descriptions of new species and subspecies. Bull.
+Amer. Mus. Nat. Hist., 19:587-612, November 12.</div>
+<br />
+
+<div><span class="smcap">Allen, J. A.</span>, and <span class="smcap">Chapman, F. M.</span></div>
+
+<div class="references">1897.&nbsp; On a collection of mammals from Jalapa and Las Vigas, state of
+Veracruz. Bull. Amer. Mus. Nat. Hist., 9:197-208, June 16.</div>
+<br />
+
+<div class="smcap">Axelrod, D. I.</div>
+
+<div class="references">1950.&nbsp; Evolution of the desert vegetation in western North America.
+Carnegie Inst. Washington (Contrib. Paleo.), Publ. 590(6):215-306,
+4 figs., 3 pls., 1 table, December 27.</div>
+<br />
+
+<div class="smcap">Bailey, V.</div>
+
+<div class="references">1905.&nbsp; Biological survey of Texas. N. Amer. Fauna, 25:1-222, 16 pls.,
+24 figs., October 24.</div>
+<br />
+
+<div class="smcap">Baker, R. H.</div>
+
+<div class="references">1951.&nbsp; Mammals from Tamaulipas México. Univ. Kansas Publ., Mus. Nat.
+Hist., 5:207-218, December 15.</div>
+<br />
+
+<div class="smcap">Blair, W. F.</div>
+
+<div class="references">1941.&nbsp; Observations on the life history of <i>Baiomys taylori subater</i>. Jour.
+Mamm., 22:378-383, 1 fig., November 14.</div>
+
+<div class="references">1942. Systematic relationships of <i>Peromyscus</i> and several related genera
+as shown by the baculum. Jour. Mamm., 23:196-204, 2 figs., 1
+table, May 14.</div>
+
+<div class="references">1952.&nbsp; Mammals of the Tamaulipan Biotic Province in Texas. Texas
+Jour. Sci., 4:230-250, 1 fig., 2 tables, June 30.</div>
+
+<div class="references">1953.&nbsp; Population dynamics of rodents and other small mammals. Advances
+in Genetics, 5:1-41, 1 table.</div>
+<br />
+
+<div><span class="smcap">Blair, W. F.</span>, and <span class="smcap">Blossom, P. M.</span></div>
+
+<div class="references">1948.&nbsp; Variation in the pygmy mouse (<i>Baiomys taylori</i>) from Texas and
+Arizona. Contrib. Lab. Vert. Biol., Univ. Michigan, 40:1-7, 3
+tables, March.</div>
+<br />
+
+<div><span class="smcap">Blossom, P. M.</span>, and <span class="smcap">Burt, W. H.</span></div>
+
+<div class="references">1942. A new race of pygmy mouse (<i>Baiomys</i>) from Arizona. Occas.
+Papers, Univ. Michigan, 465:1-4, October 8.</div>
+<br />
+
+<span class="smcap">Booth, E. S.</span>
+
+<div class="references">1957.&nbsp; Mammals collected in Mexico from 1951 to 1956 by the Walla
+Walla College Museum of Natural History. Walla Walla College
+Publs., Dept. Biol. Sci. and Biol. Station, 20:1-19, 4 unnumbered
+figures, July 10.</div>
+<br />
+
+<p><span class="pagenum"><a name="Page_666" id="Page_666">[Pg 666]</a></span></p>
+
+<span class="smcap">Brown, W. L.</span>
+
+<div class="references">1958.&nbsp; Some zoological concepts applied to problems in evolution of the
+hominid lineage. Amer. Scientist, 46:151-158, 1 fig., June.</div>
+<br />
+
+<div><span class="smcap">Brown, W. L., Jr.</span>, and <span class="smcap">Wilson, E. O.</span></div>
+
+<div class="references">1956. Character displacement. Soc. Syst. Zool., 5:49-64, 6 figs., June.</div>
+<br />
+
+<span class="smcap">Burt, W. H.</span>
+
+<div class="references">1936.&nbsp; A study of the baculum in the genera <i>Perognathus</i> and <i>Dipodomys</i>.
+Jour. Mamm., 17:145-156, 6 figs., 2 tables, May 14.</div>
+
+<div class="references">1938.&nbsp; Faunal relationships and geographic distribution of mammals in
+Sonora, México. Miscl. Publ. Mus. Zool., Univ. Michigan, 39:1-77,
+2 tables, 26 maps, February 15.</div>
+<br />
+
+<span class="smcap">Clark, F. H.</span>
+
+<div class="references">1941.&nbsp; Correlation and body proportions in mature mice of the genus
+<i>Peromyscus</i>. Jour. Genetics, 26:283-300, 8 tables, May.</div>
+<br />
+
+<span class="smcap">Collins, H. H.</span>
+
+<div class="references">1918.&nbsp; Studies of normal moult and of artificially induced regeneration
+of pelage in <i>Peromyscus</i>. Jour. Exper. Zool., 27:73-95, 3 figs., 2
+pls., October.</div>
+
+<div class="references">1924.&nbsp; Studies of the pelage phases and of the nature of color variations
+in mice of the genus <i>Peromyscus</i>. Jour. Exper. Zool., 38:45-107,
+57 figs.</div>
+<br />
+
+<span class="smcap">Dalquest, W. W.</span>
+
+<div class="references">1953.&nbsp; Mammals of the Mexican state of San Luis Potosí. Louisiana
+State Univ. Studies, Biol. Ser., 1:1-229, 1 fig., December 28.</div>
+<br />
+
+<span class="smcap">Davis, W. B.</span>
+
+<div class="references">1944.&nbsp; Notes on Mexican mammals. Jour. Mamm., 25:370-403, 1 fig.,
+3 tables, November 12.</div>
+<br />
+
+<div><span class="smcap">Davis, W. B.</span>, and <span class="smcap">Russell, J. R., Jr.</span></div>
+
+<div class="references">1954.&nbsp; Mammals of the Mexican state of Morelos. Jour. Mamm., 35:63-80,
+February 10.</div>
+<br />
+
+<div><span class="smcap">Deterra, H., Romero, J.,</span> and <span class="smcap">Steward, T. D.</span></div>
+
+<div class="references">1949.&nbsp; Tepexpan Man. Viking Fund Publ. in Anthropology, 11:1-160, 22
+figs., 37 pls., 10 tables.</div>
+<br />
+
+<span class="smcap">Dice, L. R.</span>
+
+<div class="references">1943.&nbsp; The biotic provinces of North America. Univ. Michigan Press,
+Ann Arbor, viii + 78 pp., 1 map.</div>
+<br />
+
+<div><span class="smcap">Dice, L. R.</span>, and <span class="smcap">Leraas, H. J.</span></div>
+
+<div class="references">1936.&nbsp; A graphic method for comparing several sets of measurements.
+Contrib. Lab. Vert. Genetics, Univ. Michigan, 3:1-3, 1 fig., July.</div>
+<br />
+
+<span class="smcap">Dobzhansky, T.</span>
+
+<div class="references">1951.&nbsp; Genetics and the origin of species. Columbia Univ. Press, x + 364
+pp., 23 figs., 15 tables.</div>
+<br />
+
+<span class="smcap">Duellman, W. E.</span>
+
+<div class="references">1958.&nbsp; A monographic study of the colubrid snake genus <i>Leptodeira</i>.
+Bull. Amer. Mus. Nat. Hist., 114(1):1-152, 25 figs., 31 pls., 25
+maps, 30 tables, February 24.</div>
+<br />
+
+<span class="smcap">Dunn, E. R.</span>
+
+<div class="references">1940.&nbsp; Some aspects of herpetology in lower Central America. Trans.
+New York Acad. Sci., 2:156-158, April.</div>
+<br />
+
+<p><span class="pagenum"><a name="Page_667" id="Page_667">[Pg 667]</a></span></p>
+
+<span class="smcap">Ellerman, J. R.</span>
+
+<div class="references">1941.&nbsp; The families and genera of living rodents with a list of named
+forms (1758-1936). British Museum (Nat. Hist.), London, 2:
+xii + 690, 50 figs., March 21.</div>
+<br />
+
+<span class="smcap">Felten, H.</span>
+
+<div class="references">1958.&nbsp; Nagetiere (Mammalia, Rodentia) aus El Salvador. Senckenbergiana
+Biologica, 39:133-144, August 30.</div>
+<br />
+
+<span class="smcap">Findley, J. S.</span>
+
+<div class="references">1955.&nbsp; Speciation of the wandering shrew. Univ. Kansas Publ., Mus.
+Nat. Hist., 9:1-68, 18 figs., 1 table, December 10.</div>
+<br />
+
+<span class="smcap">Gazin, C. Lewis</span>
+
+<div class="references">1942.&nbsp; The late Cenozoic vertebrate faunas from the San Pedro Valley,
+Ariz. Proc. U. S. Nat. Mus., 92(3155):475-518.</div>
+<br />
+
+<span class="smcap">Gidley, J. W.</span>
+
+<div class="references">1922.&nbsp; Preliminary report on fossil vertebrates of the San Pedro Valley,
+Arizona, with descriptions of new species of Rodentia and
+Lagomorpha. U. S. Geol. Surv. Prof. Paper, 131:119-131, 2 pls.,
+March 15.</div>
+<br />
+
+<span class="smcap">Goldman, E. A.</span>
+
+<div class="references">1951.&nbsp; Biological investigations in México. Smiths. Miscl. Coll., 115:
+xiii + 476, frontispiece, 71 pls., 1 map, July 31.</div>
+<br />
+
+<div><span class="smcap">Goldman, E. A.</span> and <span class="smcap">Moore, R. T.</span></div>
+
+<div class="references">1945.&nbsp; The biotic provinces of México. Jour. Mamm., 26:347-360, 1 fig.,
+November 14.</div>
+<br />
+
+<span class="smcap">Goodwin, G. G</span>.
+
+<div class="references">1934.&nbsp; Mammals collected by A. W. Anthony in Guatemala, 1924-1928.
+Bull. Amer. Mus. Nat. Hist., 68:1-60, pls. 1-5, December 12.</div>
+
+<div class="references">1942.&nbsp; Mammals of Honduras. Bull. Amer. Mus. Nat. Hist., 79:107-195,
+May 29.</div>
+
+<div class="references">1959.&nbsp; A new pygmy mouse of the genus <i>Baiomys</i> from Oaxaca, Mexico.
+Amer. Mus. Novit., 1929:1-2, March 5.</div>
+<br />
+
+<span class="smcap">Hall, E. R.</span>
+
+<div class="references">1959.&nbsp; Geographic distribution of contemporary organisms, pp. 371-373,
+<i>in</i> Zoogeography. Publ., Amer. Assoc. Adv. Sci., 55:x + 509 pp.
+January 19.</div>
+<br />
+
+<div><span class="smcap">Hall, E. R.</span>, and <span class="smcap">Kelson, K. R.</span></div>
+
+<div class="references">1959.&nbsp; The mammals of North America. 2 Vols., xxx + 1083 pp. (79 pp.
+index), 553 figs., 500 maps, March 31, 1959.</div>
+<br />
+
+<div><span class="smcap">Hall, E. R.</span>, and <span class="smcap">Villa-R., B.</span></div>
+
+<div class="references">1949.&nbsp; An annotated check list of the Mammals of Michoacán, México.
+Univ. Kansas Publ., Mus. Nat. Hist., 1:431-472, pls. 4-5, 1 fig.,
+December 27.</div>
+<br />
+
+<span class="smcap">Hershkovitz, P.</span>
+
+<div class="references">1944.&nbsp; A systematic review of the neotropical water rats of the genus
+<i>Nectomys</i> (Cricetinae). Miscl. Publ. Mus. Zool., Univ. Michigan,
+58:1-101, 4 pls., 5 figs., 2 maps, 19 tables, January 4.</div>
+
+<div class="references">1955.&nbsp; South American marsh rats Genus <i>Holochilus</i> with a summary of
+sigmodont rodents. Fieldiana-Zool., Chicago Nat. Hist. Mus.,
+37:639-673, 6 figs., 29 pls., 5 tables, June 19.</div>
+
+<p><span class="pagenum"><a name="Page_668" id="Page_668">[Pg 668]</a></span></p>
+
+<div class="references">1958.&nbsp; A geographical classification of neotropical mammals. Fieldiana-Zool.,
+Chicago Nat. Hist. Mus., 36:583-620, 2 figs., 13 tables,
+July 11.</div>
+<br />
+
+<span class="smcap">Hibbard, C. W.</span>
+
+<div class="references">1941.&nbsp; Paleoecology and correlation of the Rexroad Fauna from the upper
+Pliocene of southwestern Kansas, as indicated by the mammals.
+Univ. Kansas Sci. Bull., 27:79-104, 1 fig., December 15.</div>
+
+<div class="references">1952.&nbsp; A contribution to the Rexroad Fauna. Trans. Kansas Acad. Sci.,
+55:196-208, 2 figs., June 18.</div>
+
+<div class="references">1953.&nbsp; The saw rock canyon fauna and its stratigraphic significance.
+Papers, Michigan Acad. Sci., Arts and Letters, 38:387-411, 5 figs.,
+April 27.</div>
+
+<div class="references">1958.&nbsp; Summary of North American Pleistocene mammalian local faunas.
+Papers, Michigan Acad. Sci., Arts and Letters, 43:3-32, 1 table.</div>
+<br />
+
+<span class="smcap">Hoffmeister, D. F.</span>
+
+<div class="references">1951.&nbsp; A taxonomic and evolutionary study of the pinon mouse, <i>Peromyscus
+truei</i>. Ill. Biol. Monogr., 21:x + 104, 5 pls., 24 figs., 7 tables,
+November 12.</div>
+
+<div class="references">1956.&nbsp; Mammals of the Graham (Pinaleno) Mountains, Arizona. Amer.
+Midland Nat., 55:257-288, 7 figs., 1 table, April.</div>
+<br />
+
+<span class="smcap">Hooper, E. T.</span>
+
+<div class="references">1947.&nbsp; Notes on Mexican mammals. Jour. Mamm., 28:40-57, February 15.</div>
+
+<div class="references">1949.&nbsp; Faunal relationships of recent North American rodents. Miscl.
+Publ. Mus. Zool., Univ. Michigan, 72:1-28, 5 tables, May 20.</div>
+
+<div class="references">1952a. Notes on the pygmy mouse (<i>Baiomys</i>), with description of a
+new subspecies from México. Jour. Mamm., 33:90-97, 3 figs.,
+February 18.</div>
+
+<div class="references">1952b. A systematic review of the harvest mice (genus <i>Reithrodontomys</i>) of
+Latin America. Miscl. Publ. Mus. Zool., Univ. Michigan, 77:1-255,
+9 pls., 24 figs., 12 maps, 7 tables, January 16.</div>
+
+<div class="references">1953.&nbsp; Notes on the mammals of Tamaulipas, México. Occas. Papers
+Mus. Zool., Univ. Michigan, 544:1-12, March 25.</div>
+
+<div class="references">1955a. Extra teeth in the pygmy mouse, <i>Baiomys musculus</i>. Jour. Mamm.,
+36:298-299, May 26.</div>
+
+<div class="references">1955b. Notes on Mammals of western México. Occas. Papers Mus. Zool.,
+Univ. Michigan, 565:1-26, November 9.</div>
+
+<div class="references">1957.&nbsp; Dental patterns in mice of the Genus <i>Peromyscus</i>. Miscl. Publ.
+Mus. Zool., Univ. Michigan, 99:1-59, 24 figs., 3 tables, March 28.</div>
+
+<div class="references">1958.&nbsp; The male phallus in mice of the genus <i>Peromyscus</i>. Miscl. Publ.
+Mus. Zool., Univ. Michigan, 105:1-24, 1 fig., 24 pls., 1 table, December
+29.</div>
+<br />
+
+<div><span class="smcap">Hunsaker, D.</span>, <span class="smcap">Raun, G. G.</span>, and <span class="smcap">Swindells, J. E.</span></div>
+
+<div class="references">1959.&nbsp; Range expansion of <i>Baiomys taylori</i> in Texas. Jour. Mamm.,
+40:477-478, August 20.</div>
+<br />
+
+<span class="smcap">Koopman, K. F.</span>
+
+<div class="references">1950.&nbsp; Natural selection for reproductive isolation between <i>Drosophila
+pseudoobscura</i> and <i>Drosophila persimilis</i>. Evolution, 4:135-148,
+3 figs., 7 tables, June.</div>
+<br />
+
+<span class="smcap">Lack, D.</span>
+
+<div class="references">1944.&nbsp; Ecological aspects of species formation in passerine birds. Ibis,
+86:260-286, July.</div>
+<br />
+
+<p><span class="pagenum"><a name="Page_669" id="Page_669">[Pg 669]</a></span></p>
+
+<span class="smcap">Layne, James N.</span>
+
+<div class="references">1959.&nbsp; Growth and development of the eastern harvest mouse, <i>Reithrodontomys
+humulis</i>. Bull. Florida State Mus., 4:61-82, 5 figs.,
+April 27.</div>
+<br />
+
+<span class="smcap">Leopold, A. S.</span>
+
+<div class="references">1950.&nbsp; Vegetation zones of México. Ecol., 31:507-518, 1 fig., 1 table,
+October.</div>
+<br />
+
+<div><span class="smcap">Lowery, G. H.</span>, and <span class="smcap">Dalquest, W. W.</span></div>
+
+<div class="references">1951.&nbsp; Birds from the state of Veracruz, México. Univ. Kansas Publ.,
+Mus. Nat. Hist., 3:531-649, 7 figs., 2 tables, October 10.</div>
+<br />
+
+<span class="smcap">Lukens, P. W., Jr.</span>
+
+<div class="references">1955.&nbsp; The mammals of the Chilpancingo area of the Mexican state of
+Guerrero. Unpublished Master's dissertation, Texas Agricultural
+and Mechanical College of Texas. 209 pp.</div>
+<br />
+
+<span class="smcap">Mayr, E.</span>
+
+<div class="references">1949.&nbsp; Speciation and selection. Proc. Amer. Phil. Soc., 93:514-519,
+December.</div>
+<br />
+
+<span class="smcap">Mearns, E. A.</span>
+
+<div class="references">1907.&nbsp; Mammals of the Mexican boundary of the United States &#8230; Pt.
+1, Families Didelphidae to Muridae. Bull. U. S. Nat. Mus.,
+56:xv + 530, 13 pls., 126 figs., numerous tables, April 13.</div>
+<br />
+
+<span class="smcap">Merriam, C. Hart</span>
+
+<div class="references">1892.&nbsp; Descriptions of new mammals collected by E. W. Nelson in the
+states of Colima and Jalisco, México. Proc. Biol. Soc. Washington,
+7:164-174, September 29.</div>
+<br />
+
+<span class="smcap">Moore, R. T.</span>
+
+<div class="references">1945.&nbsp; The transverse volcanic biotic province of central México and its
+relationship to adjacent provinces. Trans. San Diego Soc. Nat.
+Hist., 10:217-236, 1 map, 4 tables, August 31.</div>
+<br />
+
+<span class="smcap">Osgood, W. H.</span>
+
+<div class="references">1909.&nbsp; Revision of the mice of the American Genus <i>Peromyscus</i>. N. Amer.
+Fauna, 28:1-285, 8 pls., 12 figs., several tables, April 17.</div>
+<br />
+
+<span class="smcap">Packard, R. L.</span>
+
+<div class="references">1958a. New subspecies of the rodent <i>Baiomys</i> from Central America.
+Univ. Kansas Publ., Mus. Nat. Hist., 9:397-404, 2 tables, December 19.</div>
+
+<div class="references">1958b. The taxonomic status of <i>Peromyscus allex</i> Osgood. Proc. Biol.
+Soc. Washington, 71:17-20, April 11.</div>
+<br />
+
+<span class="smcap">Ridgway, R.</span>
+
+<div class="references">1912.&nbsp; Color standards and color nomenclature. Published by the author,
+Washington, D. C., iii + 43 pp., 53 pls.</div>
+<br />
+
+<span class="smcap">Rinker, G. C.</span>
+
+<div class="references">1954.&nbsp; The comparative myology of the mammalian genera <i>Sigmodon</i>,
+<i>Oryzomys</i>, <i>Neotoma</i>, and <i>Peromyscus</i> (Cricetinae), with remarks
+on their intergeneric relationships. Miscl. Publ. Mus. Zool., Univ.
+Michigan, 83:1-124, 18 figs., 2 tables, June 4</div>.
+<br />
+
+<span class="smcap">Russell, R. J., Jr.</span>
+
+<div class="references">1952.&nbsp; A new subspecies of pygmy mouse, <i>Baiomys musculus</i>, from
+Morelos, México. Proc. Biol. Soc. Washington, 65:21-22, January 29.</div>
+<br />
+
+<p><span class="pagenum"><a name="Page_670" id="Page_670">[Pg 670]</a></span></p>
+
+<span class="smcap">Sears, P. B.</span>
+
+<div class="references">1955.&nbsp; Palynology in southern North America, Part 4: Pleistocene Climate
+in México. Bull. Geol. Soc. America, 66:521-530, 6 figs., 1 pl.,
+1 table, May.</div>
+<br />
+
+<span class="smcap">Simpson, G. G.</span>
+
+<div class="references">1945.&nbsp; The principles of classification and a classification of mammals.
+Bull. Amer. Mus. Nat. Hist., 85:xvi + 350, October 5.</div>
+
+<div class="references">1950.&nbsp; History of the fauna of Latin America.  Amer. Sci., 38(3):361-389,
+10 figs.</div>
+<br />
+
+<span class="smcap">Smith, H. M.</span>
+
+<div class="references">1949.&nbsp; Herpetogeny in México and Guatemala. Ann. Association Amer.
+Geogr., 39:219-238, 1 fig., 1 table, September.</div>
+<br />
+
+<span class="smcap">Sprague, J. M.</span>
+
+<div class="references">1941.&nbsp; A study of the hyoid apparatus of the cricetinae. Jour. Mamm.,
+22:296-310, 5 figs., August 14.</div>
+<br />
+
+<div><span class="smcap">Stickel, L. F.</span>, and <span class="smcap">Stickel, W. H.</span></div>
+
+<div class="references">1949.&nbsp; A <i>Sigmodon</i> and <i>Baiomys</i> population in ungrazed and unburned
+Texas prairie. Jour. Mamm., 30:141-150, 3 tables, May 23.</div>
+<br />
+
+<span class="smcap">Stuart, L. C.</span>
+
+<div class="references">1954.&nbsp; A description of a subhumid corridor across northern central
+America, with comments on its herpetofaunal indicators. Contrib.
+Lab. Vert. Biol., Univ. Michigan, 65:1-26, 6 maps, 6 pls., March.</div>
+<br />
+
+<span class="smcap">Tamayo, Jorge L.</span>
+
+<div class="references">1949.&nbsp; Atlas Geografico general de México, con cartas fisicas, biologicas,
+demograficas, sociales, economicas, y cartogramas, Mexico, 24
+maps, December 12.</div>
+<br />
+
+<span class="smcap">Thomas, O.</span>
+
+<div class="references">1888.&nbsp; On the small mammals of Duval County, Texas. Proc. Zool.
+Soc. London, pp. 443-450.</div>
+<br />
+
+<span class="smcap">True, F. W.</span>
+
+<div class="references">1894.&nbsp; On the relationships of Taylor's Mouse, <i>Sitomys taylori</i>. Proc.
+U. S. Nat. Mus., 16:757-758, February 7.</div>
+<br />
+
+<div><span class="smcap">Twente, J. H.</span>, and <span class="smcap">Baker, R. H.</span></div>
+
+<div class="references">1951.&nbsp; New records of mammals from Jalisco, México, from barn owl
+pellets. Jour. Mamm., 32:120-121, 1 table, February 15.</div>
+<br />
+
+<span class="smcap">Van Gelder, R. G.</span>
+
+<div class="references">1959.&nbsp; A taxonomic revision of the spotted skunks (Genus <i>Spilogale</i>).
+Bull. Amer. Mus. Nat. Hist., 117(5):229-392, 47 figs., 32 tables,
+June 15.</div>
+<br />
+
+<span class="smcap">White, J. A.</span>
+
+<div class="references">1951.&nbsp; A practical method for mounting the bacula of small mammals.
+Jour. Mamm., 32:125, February 15.</div>
+
+<div class="references">1953.&nbsp; The baculum in the chipmunks of western North America. Univ.
+Kansas Publ., Mus. Nat. Hist., 5:611-631, 19 figs., December 1.</div>
+<br />
+
+<span class="smcap">Wilson, R. W.</span>
+
+<div class="references">1937.&nbsp; Pliocene rodents of western North America. Carnegie Inst. Washington,
+Publ. 487:21-73, 2 figs., July 23.</div>
+<br />
+
+<div><span class="smcap">Wood, A. E.</span>, and <span class="smcap">Wilson, R. W.</span></div>
+
+<div class="references">1936.&nbsp; A suggested nomenclature for the cusps of the cheek teeth of
+rodents. Jour. Paleon., 10:388-391, 2 figs.</div>
+<br />
+<br />
+
+<p><i>Transmitted March 4, 1960.</i></p>
+<br />
+<br />
+
+<div class="fig_center">
+<img src="images/square.png" width="16" height="17" alt="" /><br />
+28-3030<br />
+<br />
+<br />
+</div>
+
+<p><span class="pagenum"><a name="Page_i" id="Page_i">[Pg i]</a></span></p>
+
+<div class="caption2"><a name="PUBLICATIONS" id="PUBLICATIONS"></a>
+UNIVERSITY OF KANSAS PUBLICATIONS</div>
+
+<div class="caption2">MUSEUM OF NATURAL HISTORY</div>
+
+
+<p>Institutional libraries interested in publications exchange may obtain this
+series by addressing the Exchange Librarian, University of Kansas Library,
+Lawrence, Kansas. Copies for individuals, persons working in a particular
+field of study, may be obtained by addressing instead the Museum of Natural
+History, University of Kansas, Lawrence, Kansas. There is no provision for
+sale of this series by the University Library, which meets institutional requests,
+or by the Museum of Natural History, which meets the requests of individuals.
+However, when individuals request copies from the Museum, 25 cents should
+be included, for each separate number that is 100 pages or more in length, for
+the purpose of defraying the costs of wrapping and mailing.</p>
+
+<p>* An asterisk designates those numbers of which the Museum's supply (not the Library's
+supply) is exhausted. Numbers published to date, in this series, are as follows:</p>
+
+<table summary="Publications">
+<tr><td class="vtop">&nbsp;Vol.&nbsp;&nbsp;1.</td>
+  <td class="text_lf" colspan="2">Nos. 1-26 and index. Pp. 1-638, 1946-1950.</td>
+</tr>
+
+<tr>
+  <td class="vtop">*Vol.&nbsp;&nbsp;2.</td>
+  <td colspan="2">(Complete) Mammals of Washington. By Walter W. Dalquest. Pp. 1-444, 140
+  figures in text. April 9, 1948.</td>
+</tr>
+<tr>
+  <td class="vtop">&nbsp;Vol. &nbsp;3.</td>
+  <td class="text_rt vtop">*1.</td>
+  <td>The avifauna of Micronesia, its origin, evolution, and distribution. By Rollin
+  H. Baker, Pp. 1-359, 16 figures in text. June 12, 1951.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">*2.</td>
+  <td>A quantitative study of the nocturnal migration of birds. By George H.
+  Lowery, Jr. Pp. 361-472, 47 figures in text. June 29, 1951.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">3.</td>
+  <td>Phylogeny of the waxwings and allied birds. By M. Dale Arvey. Pp. 473-530,
+  49 figures in text, 13 tables. October 10, 1951.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">4.</td>
+  <td>Birds from the state of Veracruz, Mexico. By George H. Lowery, Jr., and
+  Walter W. Dalquest. Pp. 531-649, 7 figures in text, 2 tables. October 10, 1951.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_lf" colspan="2">Index. Pp. 651-681.</td>
+</tr>
+<tr>
+  <td class="vtop">*Vol. 4.</td>
+  <td colspan="2">(Complete) American weasels. By E. Raymond Hall. Pp. 1-466, 41 plates, 31
+  figures in text. December 27, 1951.</td>
+</tr>
+<tr>
+  <td class="vtop">&nbsp;Vol. 5.</td>
+  <td colspan="2">Nos. 1-37 and index. Pp. 1-676,  1951-1953.</td>
+</tr>
+<tr>
+  <td class="vtop">*Vol. 6.</td>
+  <td colspan="2">(Complete) Mammals of Utah, <i>taxonomy and distribution</i>.  By Stephen D.
+  Durrant. Pp. 1-549, 91 figures in text, 30 tables. August 10, 1952.</td>
+</tr>
+<tr>
+  <td class="vtop">&nbsp;Vol. 7.</td>
+  <td class="text_rt vtop">*1.</td>
+  <td>Mammals of Kansas. By E. Lendell Cockrum. Pp. 1-303. 73 figures in
+  text, 37 tables. August 25, 1952.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">2.</td>
+  <td>Ecology of the opossum on a natural area in northeastern Kansas. By Henry
+  S. Fitch and Lewis L. Sandidge. Pp. 305-338, 5 figures in text. August
+  24, 1953.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">3.</td>
+  <td>The silky pocket mice (Perognathus flavus) of Mexico. By Rollin H. Baker.
+  Pp. 339-347, 1 figure in text, February 15, 1954.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">4.</td>
+  <td>North American jumping mice (Genus Zapus). By Philip H. Krutzch. Pp.
+  349-472, 47 figures in text, 4 tables. April 21, 1954.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">5.</td>
+  <td>Mammals from Southeastern Alaska. By Rollin H. Baker and James S.
+  Findley. Pp. 473-477. April 21, 1954.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">6.</td>
+  <td>Distribution of Some Nebraskan Mammals. By J. Knox Jones, Jr. Pp. 479-487.
+  April 21, 1954.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">7.</td>
+  <td>Subspeciation in the montane meadow mouse. Microtus montanus, in Wyoming
+  and Colorado. By Sydney Anderson. Pp. 489-506, 2 figures in text.
+  July 23, 1954.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">8.</td>
+  <td>A new subspecies of bat (Myotis velifer) from southeastern California and
+  Arizona. By Terry A. Vaughan. Pp. 507-512. July 23, 1954.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">9.</td>
+  <td>Mammals of the San Gabriel mountains of California. By Terry A. Vaughan.
+  Pp. 513-582. 1 figure in text, 12 tables. November 15, 1954.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">10.</td>
+  <td>A new bat (Genus Pipistrellus) from northeastern Mexico. By Rollin H.
+  Baker. Pp. 583-586. November 15, 1954.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">11.</td>
+  <td>A new subspecies of pocket mouse from Kansas. By E. Raymond Hall. Pp.
+  587-590. November 15, 1954.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">12.</td>
+  <td>Geographic variation in the pocket gopher, Cratogeomys castanops, in Coahuila,
+  Mexico. By Robert J. Russell and Rollin H. Baker. Pp. 591-608.
+  March 15, 1955.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">13.</td>
+  <td>A new cottontail (Sylvilagus floridanus) from northeastern Mexico. By Rollin
+  H. Baker. Pp. 609-612. April 8, 1955.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">14.</td>
+  <td>Taxonomy and distribution of some American shrews. By James S. Findley.
+  Pp. 613-618. June 10, 1955.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">15.</td>
+  <td>The pigmy woodrat, Neotoma goldmani, its distribution and systematic position.
+  By Dennis G. Rainey and Rollin H. Baker. Pp. 619-624, 2 figures in
+  text. June 10, 1955.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_lf" colspan="2">Index. Pp. 625-651.</td>
+</tr>
+<tr>
+  <td class="vtop">&nbsp;Vol. 8.</td>
+  <td class="text_rt vtop">1.</td>
+  <td>Life history and ecology of the five-lined skink, Eumeces fasciatus. By Henry
+  S. Fitch. Pp. 1-156, 26 figures in text. September 1, 1954.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">2.</td>
+  <td>Myology end serology of the Avian Family Fringillidae, a taxonomic study.
+  By William B. Stallcup. Pp. 157-211, 23 figures in text, 4 tables. November
+  15, 1954.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">3.</td>
+  <td>An ecological study of the collared lizard (Crotaphytus collaris). By Henry
+  S. Fitch. Pp. 213-274, 10 figures to text. February 10, 1956.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">4.</td>
+  <td>A field study of the Kansas ant-eating frog, Gastrophryne olivacea. By Henry
+  S. Fitch. Pp. 275-306, 9 figures in text. February 10, 1956.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">5.</td>
+  <td>Check-list of the birds of Kansas. By Harrison E. Tordoff. Pp. 307-359, 1
+  figure in text. March 10, 1956.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">6.</td>
+  <td>A population study of the prairie vole (Microtus ochrogaster) in northeastern
+  Kansas. By Edwin P. Martin. Pp. 361-416, 19 figures in text.  April 2, 1956.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">7.</td>
+  <td>Temperature responses in free-living amphibians and reptiles of northeastern
+  Kansas. By Henry S. Fitch. Pp. 417-476, 10 figures in text, 6 tables. June
+  1, 1956.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">8.</td>
+  <td>Food of the crow, Corvus brachyrhynchos Brehm, in south-central Kansas. By
+  Dwight Platt. Pp. 477-498. 4 tables. June 8, 1956.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">9.</td>
+  <td>Ecological observations on the woodrat, Neotoma floridana. By Henry S.
+  Fitch and Dennis G. Rainey. Pp. 499-533, 3 figures in text. June 12, 1956.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">10.</td>
+  <td>Eastern woodrat, Neotoma floridana: Life history and ecology. By Dennis
+  G. Rainey. Pp. 535-646, 12 plates, 13 figures in text. August 15, 1956.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_lf" colspan="2">Index. Pp. 647-675.</td>
+</tr>
+<tr>
+  <td class="vtop">&nbsp;Vol. &nbsp;9.</td>
+  <td class="text_rt vtop">1.</td>
+  <td>Speciation of the wandering shrew. By James S. Findley. Pp. 1-68, 18 figures
+  in text. December 10, 1955.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">2.</td>
+  <td>Additional records and extensions of ranges of mammals from Utah. By
+  Stephen D. Durrant, M. Raymond Lee, and Richard M. Hansen. Pp. 69-80.
+  December 10, 1955.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">3.</td>
+  <td>A new long-eared myotis (Myotis evotis) from northeastern Mexico. By Rollin
+  H. Baker and Howard J. Stains. Pp. 81-84. December 10, 1955.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">4.</td>
+  <td>Subspeciation in the meadow mouse, Microtus pennsylvanicus, in Wyoming.
+  By Sydney Anderson. Pp. 85-104, 2 figures in text. May 10, 1956.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">5.</td>
+  <td>The condylarth genus Ellipsodon. By Robert W. Wilson. Pp. 105-116, 6
+  figures In text. May 19, 1956.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">6.</td>
+  <td>Additional remains of the multituberculate genus Eucosmodon. By Robert
+  W. Wilson. Pp. 117-123, 10 figures in text. May 19, 1956.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">7.</td>
+  <td>Mammals of Coahuila, Mexico. By Rollin H. Baker. Pp. 125-335, 75 figures
+  in text. June 15, 1956.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">8.</td>
+  <td>Comments on the taxonomic status of Apodemus peninsulae, with description
+  of a new subspecies from North China. By J. Knox Jones, Jr. Pp. 337-346,
+  1 figure in text, 1 table. August 15, 1956.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">9.</td>
+  <td>Extensions of known ranges of Mexican bats. By Sydney Anderson. Pp.
+  347-351. August 15, 1956.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">10.</td>
+  <td>A new bat (Genus Leptonycteris) from Coahuila. By Howard J. Stains.
+  Pp. 353-356. January 21, 1957.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">11.</td>
+  <td>A new species of pocket gopher (Genus Pappogeomys) from Jalisco, Mexico.
+  By Robert J. Russell. Pp. 357-361. January 21, 1957.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">12.</td>
+  <td>Geographic variation in the pocket gopher, Thomomys bottae, in Colorado.
+  By Phillip M. Youngman. Pp. 363-385, 7, figures in text. February 21, 1958.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">13.</td>
+  <td>New bog lemming (genus Synaptomys) from Nebraska. By J. Knox Jones,
+  Jr. Pp. 385-388. May 12, 1958.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">14.</td>
+  <td>Pleistocene  bats from San Josecito Cave, Nuevo León, México. By J. Knox
+  Jones, Jr. Pp. 389-396. December 19, 1958.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">15.</td>
+  <td>New Subspecies of the rodent Baiomys from Central America. By Robert L.
+  Packard. Pp. 397-404. December 19, 1958.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">16.</td>
+  <td>Mammals of the Grand Mesa, Colorado. By Sydney Anderson. Pp, 405-414,
+  1 figure in text. May 20, 1959.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">17.</td>
+  <td>Distribution, variation, and relationships of the montane vole, Microtus montanus.
+  By Emil K. Urban. Pp. 415-511. 12 figures in text, 2 tables.
+  August 1, 1959.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">18.</td>
+  <td>Conspecificity of two pocket mice, Perognathus goldmani and P. artus. By
+  E. Raymond Hall and Marilyn Bailey Ogilvie. Pp. 513-518, 1 map.
+  January 14, 1960.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">19.</td>
+  <td>Records of harvest mice, Reithrodontomys, from Central America, with
+  description of a new subspecies from Nicaragua. By Sydney Anderson and
+  J. Knox Jones, Jr. Pp. 519-529. January 14, 1960.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">20.</td>
+  <td>Small carnivores from San Josecito Cave (Pleistocene), Nuevo León, México.
+  By E. Raymond Hall. Pp. 531-538, 1 figure in text. January 14, 1960.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">21.</td>
+  <td>Pleistocene pocket gophers from San Josecito Cave, Nuevo León, México.
+  By Robert J. Russell. Pp. 539-548, 1 figure in text. January 14, 1960.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">22.</td>
+  <td>Review of the insectivores of Korea. By J. Knox Jones, Jr., and David
+  H. Johnson. Pp. 549-578. February 23, 1960.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">23.</td>
+  <td>Speciation and evolution of the pygmy mice, genus Baiomys. By Robert
+  L. Packard. Pp. 579-670, 4 plates, 12 figures in text. June 16, 1960.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_lf" colspan="2">Index will follow.</td>
+</tr>
+<tr>
+  <td class="vtop">Vol. 10.</td>
+  <td class="text_rt vtop">1.</td>
+  <td>Studies of birds killed in nocturnal migration. By Harrison B. Tordoff and
+  Robert M. Mengel. Pp. 1-44, 6 figures in text, 2 tables. September 12, 1956.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">2.</td>
+  <td>Comparative breeding behavior of Ammospiza caudacuta and A. maritime.
+  By Glen E. Woolfenden. Pp. 45-75, 6 plates, 1 figure. December 20, 1956.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">3.</td>
+  <td>The forest habitat of the University of Kansas Natural History Reservation.
+  By Henry S. Fitch and Ronald R. McGregor. Pp. 77-127, 2 plates, 7 figures
+  in text, 4 tables. December 31, 1956.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">4.</td>
+  <td>Aspects of reproduction and development in the prairie vole (Microtus ochrogaster).
+  By Henry S. Fitch, Pp. 129-161, 8 figures in text, 4 tables. December 19, 1957.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">5.</td>
+  <td>Birds found on the Arctic slope of northern Alaska. By James W. Bee.
+  Pp. 163-211, pls. 9-10, 1 figure in text. March 12, 1958.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">6.</td>
+  <td>The wood rats of Colorado; distribution and ecology. By Robert B. Finley,
+  Jr. Pp. 213-552, 34 plates, 8 figures in text, 35 tables. November 7, 1958.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">7.</td>
+  <td>Home ranges and movements of the eastern cottontail in Kansas. By Donald
+  W. Janes. Pp. 553-572, 4 plates, 3 figures in text. May 4, 1959.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">8.</td>
+  <td>Natural history of the salamander, Aneides hardyi. By Richard F. Johnston
+  and Schad Gerhard. Pp. 573-585. October 8, 1959.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">9.</td>
+  <td>A new subspecies of lizard, Cnemidophorus sacki, from Michoacán, México.
+  By William E. Duellman. Pp. 587-598, 2 figures in text. May 2, 1960.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">10.</td>
+  <td>A taxonomic study of the Middle American Snake, Pituophis deppei. By
+  William E. Duellman. Pp. 599-612, 1 plate, 1 figure in text. May 2, 1960.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_lf" colspan="2">Index will follow.</td>
+</tr>
+<tr>
+  <td class="vtop">&nbsp;Vol. 11.</td>
+  <td class="text_rt vtop">1.</td>
+  <td>The systematic status of the colubrid snake, Leptodeira discolor Günther.
+  By William E. Duellman. Pp. 1-9, 4 figs. July 14, 1958.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">2.</td>
+  <td>Natural history of the six-lined racerunner, Cnemidophorus sexlineatus. By
+  Henry S. Fitch. Pp. 11-62, 9 figs., 9 tables. September 19, 1958.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">3.</td>
+  <td>Home ranges, territories, and seasonal movements of vertebrates of the
+  Natural History Reservation. By Henry S. Fitch, Pp. 68-326, 6 plates, 24
+  figures in text, 8 tables. December 12, 1958.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">4.</td>
+  <td>A new snake of the genus Geophis from Chihuahua, Mexico. By John M.
+  Legler. Pp. 327-334, 2 figures in text. January 28, 1959.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">5.</td>
+  <td>A new tortoise, genus Gopherus, from north-central Mexico. By John M.
+  Legler. Pp. 335-343. April 24, 1959.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">6.</td>
+  <td>Fishes of Chautauqua, Cowley and Elk counties, Kansas.  By Artie L.
+  Metcalf. Pp. 345-400, 2 plates, 2 figures in text, 10 tables. May 6, 1959.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">7.</td>
+  <td>Fishes of the Big Blue River Basin, Kansas. By W. L. Minckley. Pp. 401-442,
+  2 plates, 4 figures in text, 5 tables. May 8, 1959.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">8.</td>
+  <td>Birds from Coahuila, México. By Emll K. Urban. Pp. 443-516. August 1, 1959.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">9.</td>
+  <td>Description of a new softshell turtle from the southeastern United States.
+  By Robert G. Webb. Pp. 517-525, 2 pls., 1 figure in text, August 14, 1959.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">10.</td>
+  <td>Natural history of the ornate box turtle, Terrapene ornata ornata Agassiz. By
+  John M. Legler. Pp. 527-669, 16 pls., 29 figures in text. March 7, 1960.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_lf" colspan="2">Index will follow.</td>
+</tr>
+<tr>
+  <td class="vtop">&nbsp;Vol. 12.</td>
+  <td class="text_rt vtop">1.</td>
+  <td>Functional morphology of three bats: Eumops, Myotis, Macrotus. By Terry
+  A. Vaughan. Pp. 1-153, 4 plates, 24 figures in text. July 8, 1959.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">2.</td>
+  <td>The ancestry of modern Amphibia: a review of the evidence. By Theodore
+  H. Eaton, Jr. Pp. 155-180, 10 figures in text. July 10, 1959.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">3.</td>
+  <td>The baculum in microtine rodents. By Sydney Anderson. Pp. 181-216, 49
+  figures in text. February 19, 1960.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_rt vtop">4.</td>
+  <td>A new order of fishlike Amphibia from the Pennsylvanian of Kansas. By
+  Theodore H. Eaton, Jr., and Peggy Lou Stewart. Pp. 217-240, 12 figures inv
+  text. May 2, 1960.</td>
+</tr>
+<tr>
+  <td>&nbsp;</td>
+  <td class="text_lf" colspan="2">More numbers will appear In volume 12.</td>
+</tr>
+</table>
+<br />
+<br />
+
+<div class="trans_notes">
+<div class="caption2"><a name="Transcribers_Notes" id="Transcribers_Notes"></a>
+Transcriber's Notes</div>
+
+<p>The text presented is that of the original printed version except for
+the revisions below and a few assumed typesetting errors. The subsection
+headers under "<a href="#VARIATION_WITH_AGE">VARIATION WITH AGE</a>" were
+converted to italic only to match the rest. All other section title
+formatting retained as printed. The words Miscellaneous and Monograph
+were abbreviated as Miscl. and Mongr. respectively. Except for the two
+variant spellings of one word (Mexico/México) which were retained, the
+most prevalent form of accented words was used.</p>
+
+<p>Both decimal and whole and fractional part of numbers (i.e., 9<sup>1</sup>/<sub>2</sub>)
+were retained as printed. Where a relative size as
+indicated for illustrations (i.e., &#215; 3), they may not be correct for the
+displayed images as resolution of monitors vary. Each set of footnotes were
+placed at the end of each species account. The list of KU Publications were
+compiled after the article's text.</p>
+
+
+<div class="caption2">Typographical Corrections</div>
+
+<table summary="typos">
+<tr>
+  <td class="brdbt2">Page</td>
+  <td>&nbsp;&nbsp;&nbsp;&nbsp;</td>
+  <td class="brdbt2">Correction</td>
+</tr>
+<tr>
+  <td>591</td>
+  <td>&nbsp;</td>
+  <td>proödent &#8658; proödont</td>
+</tr>
+<tr>
+  <td>694</td>
+  <td>&nbsp;</td>
+  <td>hesperomyines &#8658; hesperomines</td>
+</tr>
+</table>
+<br />
+</div>
+<br />
+<br />
+</div><!-- End Book -->
+
+
+
+
+
+
+
+<pre>
+
+
+
+
+
+End of the Project Gutenberg EBook of Speciation and Evolution of the Pygmy
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+</body>
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@@ -0,0 +1,5739 @@
+The Project Gutenberg EBook of Speciation and Evolution of the Pygmy Mice,
+Genus Baiomys, by Robert L. Packard
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
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+
+
+Title: Speciation and Evolution of the Pygmy Mice, Genus Baiomys
+
+Author: Robert L. Packard
+
+Release Date: December 13, 2011 [EBook #38290]
+
+Language: English
+
+Character set encoding: ASCII
+
+*** START OF THIS PROJECT GUTENBERG EBOOK SPECIATION AND EVOLUTION OF ***
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+Produced by Chris Curnow, Tom Cosmas, Joseph Cooper and
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+  UNIVERSITY OF KANSAS PUBLICATIONS
+
+  MUSEUM OF NATURAL HISTORY
+
+
+  Volume 9, No. 23, pp. 579-670, 4 pls., 12 figs. in text
+
+  June 16, 1960
+
+
+  Speciation and Evolution of the
+  Pygmy Mice, Genus Baiomys
+
+  BY
+
+  ROBERT L. PACKARD
+
+  UNIVERSITY OF KANSAS
+  LAWRENCE
+  1960
+
+
+
+
+  UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY
+
+  Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
+
+  Robert W. Wilson
+
+  Volume 9, No. 23, pp. 579-670, 4 pls., 12 figs. in text
+  Published June 16, 1960
+
+
+  UNIVERSITY OF KANSAS
+  Lawrence, Kansas
+
+
+  PRINTED IN
+  THE STATE PRINTING PLANT
+  TOPEKA, KANSAS
+
+  1960
+
+  [Illustration: Look for the Union Label]
+  28-3030
+
+
+
+
+Speciation and Evolution of the Pygmy Mice, Genus Baiomys
+
+BY
+
+ROBERT L. PACKARD
+
+
+
+
+CONTENTS
+
+
+                                                                      PAGE
+  Introduction                                                         583
+  Materials, Methods and Acknowledgments                               584
+  Paleontology of the Genus                                            587
+     _Baiomys sawrockensis_                                            588
+     _Baiomys rexroadi_                                                589
+     _Baiomys kolbi_                                                   590
+     _Baiomys brachygnathus_                                           590
+     _Baiomys minimus_                                                 591
+  Phyletic trends                                                      592
+  Non-Geographic Variation                                             595
+     Variation with age                                                595
+     Secondary sexual variation                                        597
+     Individual variation                                              597
+     Pelage and molts                                                  598
+  Taxonomic Characters and Relationships                               600
+     External parts                                                    600
+     Pelage                                                            600
+     Skull                                                             600
+     Teeth                                                             601
+     Hyoid apparatus                                                   601
+     Baculum                                                           603
+     Auditory ossicles                                                 605
+  Genus Baiomys                                                        607
+  Systematic Accounts of Species and Subspecies                        608
+     _Baiomys musculus_                                                608
+     _Baiomys musculus brunneus_                                       612
+     _Baiomys musculus grisescens_                                     614
+     _Baiomys musculus handleyi_                                       617
+     _Baiomys musculus infernatis_                                     618
+     _Baiomys musculus musculus_                                       620
+     _Baiomys musculus nigrescens_                                     623
+     _Baiomys musculus pallidus_                                       625
+     _Baiomys musculus pullus_                                         628
+     _Baiomys taylori_                                                 630
+     _Baiomys taylori allex_                                           633
+     _Baiomys taylori analogous_                                       637
+     _Baiomys taylori ater_                                            640
+     _Baiomys taylori canutus_                                         643
+     _Baiomys taylori fuliginatus_                                     645
+     _Baiomys taylori paulus_                                          647
+     _Baiomys taylori subater_                                         650
+     _Baiomys taylori taylori_                                         651
+  Evolution and Speciation                                             655
+     Formation of the Recent Species                                   658
+     Areas of present differentiation                                  661
+     Zoogeographic position                                            661
+  Conclusions                                                          664
+  Literature Cited                                                     665
+
+
+
+
+INTRODUCTION
+
+
+Pygmy mice (_Genus Baiomys_) are the smallest cricetine rodents in North
+America. They occur from Nicaragua in Central America into the
+southwestern United States. The principal part of the geographic range
+of the pygmy mice lies in the Republic of Mexico. They are notably
+common in central Mexico, but are only locally common to the north and
+to the south, and then only in certain seasons.
+
+Pygmy mice were first brought to the attention of biologists in 1887
+when Oldfield Thomas described a diminutive species of cricetine rodent,
+_Hesperomys_ (_Vesperimus_) _taylori_. The description was based on a
+specimen obtained by William Taylor from San Diego, Duval County, Texas.
+C. Hart Merriam (1892:70) described _Sitomys musculus_ on the basis of
+specimens from Colima [City of], Colima, Mexico. Merriam (_loc. cit._)
+mentioned that the two kinds of mice, _Hesperomys taylori_ and _Sitomys
+musculus_, "in general appearance look almost precisely like the common
+house mouse (_Mus musculus_) but are still smaller and have shorter
+tails." He placed the two species in the genus _Sitomys_. Frederick W.
+True in 1894 regarded them as composing a distinct subgenus of _Sitomys,
+Baiomys_. According to True (1894:758), _S. taylori_ and _S. musculus_
+possessed a different combination of characters (ascending ramus of
+mandible short and erect, condyle terminal, coronoid process
+well-developed, uncinate, and near the condyle, size small, tail short,
+plantar tubercles six, soles hairy) than either _Vesperimus_, or
+_Onychomys_ (which had been considered as a subgenus of _Hesperomys_
+until 1889). In 1907, E. A. Mearns accorded _Baiomys_ generic rank.
+Osgood (1909:252) treated _Baiomys_ us a subgenus of _Peromyscus_,
+whereas, Miller, in 1912, regarded _Baiomys_ as a distinct genus. Most
+recent students of North American mammals have followed Miller, but
+usually with reservations. Ellerman (1941:402) emphasized that the
+taxonomic position of the genus was uncertain, and wrote that _Baiomys_
+"... seems to be considerably distinct from _Peromyscus_, and may
+perhaps be a northern representative of _Hesperomys_ or one of the small
+South American genera."
+
+Only two comprehensive analyses of geographic variation and
+interspecific taxonomic relationships have been made; the first was by
+Osgood (1909) who had fewer than a fourth of the specimens of _Baiomys_
+available to me; the second was by Hooper (1952a:90-97) who contributed
+importantly to understanding the relationships of the two living species
+in central Mexico. No attempts heretofore have been made to correlate
+and understand the relationships of the five fossil species to one
+another and to the living species assigned to the genus.
+
+Six objectives of the following report are to: (1) list characters
+taxonomically useful in recognizing species and subspecies; (2) record
+amount of variation within and between populations; (3) correlate
+observed variations with known biological principles; (4) show
+geographic ranges of the two living species; (5) indicate relationships
+between fossil and living species of the genus; and (6) clarify the
+systematic position of the genus.
+
+
+
+
+MATERIALS, METHODS AND ACKNOWLEDGMENTS
+
+
+This report is based on the study of approximately 3,520 museum study
+skins, skulls, complete skeletons, and entire animals preserved in
+liquid. Most specimens examined were accompanied by an attached label
+bearing data on locality and date of capture, name of collector,
+external measurements, and sex. In addition, 49 fossil specimens
+referable to _Baiomys_ were studied. Nearly two-thirds of the specimens
+were assembled at the University of Kansas Museum of Natural History;
+the remainder were examined in other institutions.
+
+Specimens studied were grouped by geographic origin, sex, age, and
+season of capture. Individual variation was then measured in several of
+the larger samples of each living species and in measurable fossil
+material. External measurements used were those recorded by the
+collectors on the labels attached to the skins. Twenty cranial
+measurements employed in the past in the study of _Baiomys_ and closely
+related cricetine rodents were statistically analyzed. The coefficient
+of variation was calculated for each of the 20 measurements in order to
+determine which varied least. In general, measurements having the least
+coefficient of variation were used in comparing samples from different
+geographic areas. Figure 1 shows the points between which measurements
+were taken.
+
+_Occipitonasal length._--From anteriormost projection of nasal bones to
+posteriormost projection of supraoccipital bone. _A_ to _A'_
+
+_Zygomatic breadth._--Greatest distance across zygomatic arches of
+cranium at right angles to long axis of skull. _B_ to _B'_
+
+_Postpalatal length._--From posterior margin of hard palate to anterior
+margin of foramen magnum. _C_ to _C'_
+
+_Least interorbital breadth._--Least distance across top of skull
+between orbits. _D_ to _D'_
+
+_Length of incisive foramina._--From anteriormost point to posteriormost
+point of incisive foramina. _E_ to _E'_
+
+_Length of rostrum._--The distance in a straight line from the notch
+that lies lateral to the lacrimal to the tip of the nasal on the same
+side. _F_ to _F'_
+
+_Breadth of braincase._--Greatest distance across braincase, taken at
+right angles to long axis of skull. _G_ to _G'_
+
+_Depth of cranium._--The distance from the dorsalmost part of the
+braincase to a flat plane touching tips of incisors and ventral border
+of each auditory bulla. A glass slide one millimeter thick was placed on
+the ventral side of the skull. One jaw of the caliper was on the lower
+surface of the slide and the other jaw on the dorsalmost part of the
+braincase. The depth of the slide was subtracted from the total reading.
+_H_ to _H'_
+
+_Alveolar length of maxillary tooth-row._--From anterior border of
+alveolus of M1 to posterior alveolus of M3. _I_ to _I'_
+
+    [Illustration: FIG. 1. Three views of the skull to show points
+       between which measurements were taken. Based on _B. m. pullus_,
+       adult, female, No. 71611 KU, 8 mi. S Condega, Esteli, Nicaragua.
+       x 1-1/3.]
+
+Capitalized color-terms refer to Ridgway (1912). Color terms without
+initial letters capitalized do not refer to any one standard.
+
+The names of the cusps and ridges of the teeth (see Figure 2) are those
+suggested by Wood and Wilson (1936:389-390). Terminology of the enamel
+grooves and folds is that of Hershkovitz (1944:17) and Hooper
+(1952b:20-21).
+
+Because secondary sexual variation was not significant (see page 597),
+both males and females of like age and pelage were used in comparisons
+of samples designed to reveal geographic variation.
+
+The species are arranged from less to more progressive; the subspecies
+are arranged alphabetically.
+
+In the synonymy of each subspecies, the plan has been to cite: (1) the
+name first proposed; (2) the first usage of the name combination
+employed by me; (3) all other name combinations in chronological order
+that have been applied to the subspecies concerned.
+
+The localities of specimens examined are listed by country from north to
+south. Within a country, the listing is by state, beginning with the
+northwesternmost state and proceeding by tiers (west to east) to the
+southeasternmost state. Within a state of the United States, the listing
+is by counties in the same geographic order as described for states.
+Within any county in the United States, within any state in Mexico, and
+within any country in Central America, the listing of localities is from
+north to south. When more than one locality is on the same line of
+latitude, the westernmost locality is listed first. Marginal localities
+for each subspecies are listed in a paragraph at the end of each
+account. Each marginal locality is mapped by means of a circle. The
+circles are listed in clockwise order, beginning with the northernmost.
+When more than one of these localities lies on the same line of
+latitude, the westernmost is cited first. Localities not represented on
+the distribution maps, so as to avoid undue crowding of symbols, are
+italicized in the lists of specimens examined.
+
+    [Illustration: FIG. 2. Occlusal views of molars. x 13.
+
+    A.  _B. taylori analogous_, subadult, female, No. 28102 KU, 4 km.
+        ENE Tlalmanalco, 2290 meters, Estado de Mexico. Right, upper
+        molars.
+
+    B.  _B. musculus musculus_, subadult, male, No. 45456 USNM, Colima,
+        Colima, Mexico. Left, upper molars.
+
+    A'. _B. taylori analogous_, subadult, female, No. 28102 KU 4 km.
+        ENE Tlalmanalco, 2290 meters, Estado de Mexico. Left, lower
+        molars.
+
+    B'. _B. musculus musculus_, subadult, male, No. 45456 USNM, Colima,
+        Colima, Mexico. Right, lower molars.]
+
+The largest single collection of pygmy mice is in the University of
+Kansas Museum of Natural History, and, unless otherwise indicated,
+specimens cited in the taxonomic accounts beyond are there.
+
+I am indebted to the following named institutions and persons for making
+specimens available for study:
+
+  American Museum of Natural History, G. G. Goodwin and R. G. VanGelder.
+
+  Carnegie Museum, J. K. Doutt.
+
+  California Academy of Sciences, Robert T. Orr.
+
+  Chicago Natural History Museum, Phillip H. Hershkovitz.
+
+  Cleveland Museum of Natural History (Collection now a part of Museum of
+     Zoology, University of Michigan, W. H. Burt, E. T. Hooper).
+
+  Louisiana State University, Museum of Natural History, George H. Lowery,
+     Jr.
+
+  Los Angeles County Museum, Charles A. McLaughlin.
+
+  United States National Museum (Biological Survey Collections), David A.
+     Johnson, and Viola S. Schantz.
+
+  United States National Museum, Division of Vertebrate Paleontology,
+     C. Lewis Gazin.
+
+  University of Arizona, E. L. Cockrum, and G. VR. Bradshaw.
+
+  University of California, Museum of Vertebrate Zoology, Seth B. Benson,
+     and W. Z. Lidicker.
+
+  University of Illinois, Museum of Natural History, Donald F.
+     Hoffmeister.
+
+  University of Michigan, Museum of Zoology, W. H. Burt, E. T. Hooper, and
+     Claude W. Hibbard.
+
+  University of New Mexico, James S. Findley.
+
+  University of Texas, Frank W. Blair.
+
+  Texas A & M, Cooperative Wildlife Research Collection, W. B. Davis.
+
+  The Museum, Michigan State University, Rollin H. Baker.
+
+  University of Florida Collections, James N. Layne.
+
+I am especially grateful to Professor E. Raymond Hall who guided me in
+my study and gave critical assistance with the manuscript. Additional
+appreciated suggestions were made by Professors A. Byron Leonard, Robert
+W. Wilson, Henry S. Fitch, Ronald L. McGregor, and fellow graduate
+students. For the illustrations, I am indebted to Mrs. Lorna Cordonnier,
+Miss Lucy Remple and Mrs. Connie Spitz. Mr. B. J. Wilks of the
+University of Texas, Department of Zoology, provided a number of living
+pygmy mice for study in captivity. Mr. J. Raymond Alcorn and his son,
+Albert, collected a large share of specimens of pygmy mice now in the
+University of Kansas, Museum of Natural History. My wife, Patricia,
+aided me in secretarial work and typing of the manuscript.
+
+For financial assistance, I am indebted to the National Science
+Foundation when I was a Research Assistant, to the Sigma Xi-RESA
+Research Fund for a Grant-in-Aid, and to the Kansas University Endowment
+Association through its A. Henley Aid Fund, and the Watkins Fund for
+out-of-state field work by the Museum of Natural History.
+
+
+
+
+PALEONTOLOGY OF THE GENUS
+
+
+Five fossil species, all extinct, have been assigned to the genus and
+range in time from early late Pliocene (Saw Rock Canyon fauna of
+Hibbard, 1953:408) to Mid-Pleistocene (see Hibbard, 1958:25, who
+assigns the Curtis Ranch fauna to late Kansan or early Yarmouth).
+
+I examined all known fossil material and compared it with Recent
+material. When the antiquity of the genus is considered, the degree of
+difference between the oldest fossil species and the two living species
+is much less than might be expected.
+
+
+=Baiomys sawrockensis= Hibbard
+
+    _Baiomys sawrockensis_ Hibbard, Papers Mich. Acad. Sci., Arts and
+       Letters, 38:402, April 27, 1953.
+
+_Type._--No. 27506, Univ. Michigan; left mandibular ramus bearing m1-m3
+and incisor; Saw Rock Canyon, early late Pliocene, XI member of the
+Rexroad formation, sec. 36, T. 34 S, R. 31 W, Seward County, Kansas
+(University of Kansas, Locality 6).
+
+_Referred material._--Univ. Michigan, Nos. 25781, 27503-27505,
+28159-28165, 29708-29715, 31015.
+
+_Diagnosis._--Ramus of medium size to small for the genus; lower incisor
+broad, moderately recurved; diastemal region broad; anterior median fold
+between anterior labial conulid and anterior lingual conulid of m1 deep;
+primary first fold between anteroconulid and protoconid of m2 deep;
+cingular ridge (ectolophid) at entrance to posteroexternal reentrant
+valley (major fold, see Figure 2) between protoconid and hypoconid of m1
+and m2; average and extreme measurements of lower molar row of eight
+specimens are, 2.65 (2.5-2.7).
+
+_Comparisons._--For comparisons with _B. brachygnathus_, see account of
+that species. From _B. rexroadi_, _B. sawrockensis_ differs in: anterior
+median fold of m1 deeper; incisor narrower; diastemal region broader;
+coronoid process broader and better developed; cingular ridges
+(ectolophids and mesolophids) more pronounced in their development;
+incisors less prooedont, more retrodont.
+
+From _B. kolbi_, _B. sawrockensis_ differs in: crowns of molars
+narrower; incisors less prooedont; cingular ridges (ectolophids and
+mesolophids) of m1 and m2 more pronounced in their development.
+
+From _B. minimus_, _B. sawrockensis_ differs in: incisor less
+procumbent; masseteric ridge extending farther anteriorly; anterior
+cingulum of m2 slightly larger.
+
+From _B. musculus_, _B. sawrockensis_ differs in: over-all size of jaw
+and molar row less; diastema more acutely curved; incisors shorter;
+anterior median fold of m1 slightly deeper.
+
+From _B. taylori_, _B. sawrockensis_ differs in: m1 and m2 smaller;
+cingular ridges in m1 and m2 more pronounced; anterolingual conulid
+farther forward; incisors shorter, more prooedont; molar teeth depressed,
+less hypsodont; diastemal region broader, more acutely curved;
+masseteric ridge not extending so far anteriorly.
+
+_Remarks._--_B. sawrockensis_ is the oldest known pygmy mouse. The
+extreme development of the anterior median fold between the
+anterolingual conulid and the anterolabial conulid is regarded as a
+primitive feature in the pygmy mice. In this character, the Recent
+species can be traced back in time through _B. minimus_ to _B.
+sawrockensis_. _B. sawrockensis_ resembles _Calomys laucha_ of South
+America in general conformation of jaw and tooth structure. The molars
+of _sawrockensis_ are smaller than those of _C. laucha_, and the
+anterolingual conulid of _sawrockensis_ is farther forward.
+
+
+=Baiomys rexroadi= Hibbard
+
+    _Baiomys rexroadi_ Hibbard, Amer. Midland Nat., 26:351, September,
+       1941; Hibbard, Contrib. Mus. Paleo., Univ. Michigan, 8(2):145,
+       June 29, 1950 (part); Hibbard, Papers Mich. Acad. Sci., Arts
+       and Letters, 38:403, April 27, 1953.
+
+_Type._--No. 4670, Univ. Kansas; left mandibular ramus bearing m1-m3,
+and incisor; Rexroad fauna, Locality no. 2, Upper Pliocene, Meade
+County, Kansas.
+
+_Referred material._--Univ. of Michigan Nos. 24840, 24851, 27493, 27496,
+27501, 28862-28867.
+
+_Diagnosis._--Ramus medium in size for the genus; incisors small,
+prooedont; anterior median fold of m1 slight; cingulum of all molars
+poorly developed; average and external measurements of lower molar row
+of seven specimens are, 2.7 (2.6-3.0).
+
+_Comparisons._--For comparisons with _B. sawrockensis_ and _B. minimus_,
+see accounts of those species. From _B. kolbi_, _B. rexroadi_ differs
+in: over-all size of mandibular ramus, incisors, and molars smaller;
+anterior median fold of m1 present, though poorly developed.
+
+From _B. brachygnathus_, _B. rexroadi_ differs in: over-all size of
+mandibular ramus smaller; m3 larger; posterior cusps (hypoconid and
+entoconid) elongated; diastema shorter, less acutely recurved; incisors
+less prooedont; cingular ridges of m1 and m2 less well-developed.
+
+From _B. musculus_, _B. rexroadi_ differs in: over-all size of
+mandibular ramus less; cingular ridges of m1 and m2 less well-developed;
+incisors smaller, more prooedont; molars less depressed.
+
+From _B. taylori_, _B. rexroadi_ differs in: m3 more triangular,
+posterior part narrower; mental foramen closer to anterior root of m1;
+masseteric ridge closer to alveolus of m1; incisor shorter, more
+prooedont; molars more depressed.
+
+_Remarks._--Two maxillary tooth-rows and associated parts were studied.
+On one of these specimens, the M2 has a well-developed mesostyle; the
+anterior median fold of M1 is also well-developed. The other specimen
+possesses a low cingular ridge (enteroloph) between the protocone and
+the hypocone, a reduced cingular ridge (mesoloph) between the paracone
+and metacone of M1. On the second molar, M2, a mesostyle joins with the
+mesoloph somewhat in the fashion indicated by Hooper (1957:9, encircled
+number 2).
+
+
+=Baiomys kolbi= Hibbard
+
+    _Baiomys kolbi_ Hibbard, Trans. Kansas Acad. Sci., 55:201, June 18,
+       1952; Hibbard, Papers Mich. Acad. Sci., Arts and Letters, 38:403,
+       April 27, 1953.
+
+_Type._--No. 24846, Univ. Michigan; right mandibular ramus bearing m1-m3
+and incisor; Fox Canyon, upper Pliocene, Rexroad formation, Rexroad
+fauna, Univ. Michigan Locality K1-47, sec. 35, T. 34 S, R. 30 W, XI
+Ranch, Meade County, Kansas.
+
+_Referred material._--Univ. Michigan Nos. 24845-24848, 27494, 27497,
+27499, 28566, 28861, 28878, 28880-28882, 28884, 28886.
+
+_Diagnosis._--Ramus of medium size to large for the genus; lower incisor
+short, narrow transversely, prooedont; anterior median fold of m1 reduced
+or absent; cingular ridges of m1 and m2 moderately well-developed; m3
+large relative to m1 and m2; average and extreme measurements of lower
+molars of seven specimens are, 3.0 (3.0-3.1).
+
+_Comparisons._--For comparisons with _B. sawrockensis_ and _B.
+rexroadi_, see accounts of those species. From _B. brachygnathus_, _B.
+kolbi_ differs in: molar row longer; m3 and jaw larger; diastema longer;
+masseteric ridge not so far forward; molars more depressed.
+
+From _B. minimus_, _B. kolbi_ differs in: molar row longer; m3 larger;
+jaw larger; diastema not so acutely curved; incisor shorter, narrower
+transversely, more prooedont.
+
+From _B. musculus_, _B. kolbi_ differs in: anterior median fold of m1
+slightly developed or absent, instead of well-developed; m3 larger (not
+reduced), external reentrant valley broad and extending farther across
+crown of tooth; incisor smaller, and more prooedont; cingular ridges of
+m1 and m2 less well-developed.
+
+From _B. taylori_, _B. kolbi_ differs in: molars larger, more depressed;
+incisor shorter, more prooedont; m3 smaller relative to m1 and m2;
+external reentrant valley of m3 broad, extending farther across crown of
+tooth.
+
+_Remarks._--The slight development or absence of the anterior median
+fold in _kolbi_ suggests that it was specialized. The anterior median
+fold is well-developed in all species of _Baiomys_ save _B.
+brachygnathus_ and _B. taylori_, in which the fold is only slightly
+developed or absent. _B. kolbi_ may have paralleled _B. taylori_ in
+specialization for a diet of grasses and for a life in open country.
+
+
+=Baiomys brachygnathus= (Gidley)
+
+    _Peromyscus brachygnathus_ Gidley, U. S. Geol. Surv. Prof. Papers,
+       131:124, March 15, 1922.
+
+    _Baiomys brachygnathus_, Hibbard, Amer. Midland Nat., 26:352,
+       September, 1941.
+
+    _P. [eromyscus] brachygnathus_, Wilson, Carnegie Inst. Washington
+       Publ., 473:33, May 21, 1936.
+
+_Type._--No. 10501, U. S. Nat. Mus.; right mandibular ramus bearing
+m1-m3, and incisor; 2 mi. NE Curtis Ranch house, near a line between
+sec. 28 and 29, T. 18 S, R. 21 E, Mid-Pleistocene (Hibbard, 1958:25),
+Cochise County, Arizona.
+
+_Referred material._--None.
+
+_Diagnosis._--Ramus small for the genus; m3 reduced; jaw reduced
+anteroposteriorly; incisor short, slender, prooedont; cingular ridges
+well-developed, posterior ectolophid continuous from protoconid to
+hypoconid in m1 and m2; diastema short; length of molar row 2.8 mm.
+
+_Comparisons._--For comparisons with _B. rexroadi_ and _B. kolbi_, see
+accounts of those species. From _B. minimus_, _B. brachygnathus_ differs
+in: jaw not so slender anteriorly; masseteric ridge not so far anterior;
+cheek-teeth slightly broader, less depressed, therefore, more hypsodont;
+incisor shorter, more prooedont.
+
+From _B. sawrockensis_, _B. brachygnathus_ differs in: molar row
+slightly longer; teeth slightly less depressed; masseteric ridge extends
+farther anteriorly; incisors more prooedont.
+
+From _B. musculus_, _B. brachygnathus_ differs in: jaw smaller; molar
+row slightly shorter; molars less depressed; incisors slender, shorter,
+narrower, and more prooedont.
+
+From _B. taylori_, _B. brachygnathus_ differs in: incisor more slender,
+shorter, more prooedont; diastema shorter.
+
+_Remarks._--The molar teeth of _B. brachygnathus_, although worn,
+resemble those of _B. taylori_ more than those of any known fossil
+species. Gidley (1922:124) stated that the absence of the divided
+anterior lobe of the first molar (anterior median fold) in
+_brachygnathus_ was one of the chief characters separating
+_brachygnathus_ from _taylori_. In _taylori_, the anterior median fold
+characteristically is only slightly developed, and in some specimens is
+absent. _B. brachygnathus_ differs from _taylori_ chiefly in prooedont
+incisors, which feature seems to preclude _brachygnathus_ being
+ancestral to _taylori_. _B. brachygnathus_ may have been a specialized
+divergence from _B. minimus_.
+
+
+=Baiomys minimus= (Gidley)
+
+    _Peromyscus minimus_ Gidley, U. S. Geol. Surv. Prof. Papers,
+       131:124, March 15, 1922.
+
+    _Baiomys minimus_, Hibbard, Amer. Midland Nat., 26:352, September,
+       1941; Gazin, Prof. U. S. Nat. Mus., 92(3155):488, 1942.
+
+    _P. [eromyscus] minimus_, Wilson, Carnegie Inst. Washington Publ.,
+       473:33, May 21, 1936.
+
+_Type._--No. 10500, U. S. Nat. Mus.; left mandibular ramus bearing m1-m3
+and incisor; 2 mi. S Benson, sec. 22, T. 17 S, R. 20 E, Late Pliocene
+(Blancan, Gazin, 1942:482), Cochise County, Arizona.
+
+_Referred material._--None.
+
+_Diagnosis._--Ramus small for the genus; molar teeth depressed; cingular
+ridges (ectolophids) of m1 and m2 well-developed; anterior median fold
+present (appearing larger owing to chip of enamel missing); external
+reentrant fold of m3 progresses half way across crown of tooth; diastema
+short; incisor moderately large, recurved; length of molar row, 2.6 mm.
+
+_Comparisons._--For comparisons with _B. brachygnathus_, _B. kolbi_, and
+_B. sawrockensis_, see accounts of those species. From _B. rexroadi_,
+_B. minimus_ differs in: anterior median fold deeper; incisor longer,
+more recurved, less prooedont; molars slightly more depressed (though
+worn).
+
+From _B. musculus_, _B. minimus_ differs in: over-all size of jaw and
+molars smaller; incisors shorter; masseteric ridge more depressed.
+
+From _B. taylori_, _B. minimus_ differs in: anterior median fold
+slightly deeper; molar teeth more depressed; cingular ridges on m1 and
+m2 better developed; masseteric ridge more depressed.
+
+_Remarks._--Gidley (1922:124) stated that _B. minimus_ differed
+considerably from _B. taylori_ in that the coronoid portion of the
+ascending ramus diverges at a wider angle from the alveolar part of the
+jaw. Study of large samples of lower jaws of _B. taylori_ reveals
+considerable individual variation in the angle formed between the
+coronoid part of the jaw and the alveolar part.
+
+_B. minimus_, except for its small size, is like _B. musculus_ and is
+considered to be ancestral to that species.
+
+
+
+
+PHYLETIC TRENDS
+
+
+It seems that the important trends in phyletic development in the pygmy
+mice have been from an ancestral stock (see Figure 3) that possessed
+relatively brachydont teeth having raised cingular ridges (ectolophids
+and mesolophids) and relatively short orthodont to prooedont incisors, to
+species having teeth more hypsodont on which cingular ridges were
+reduced, stylids were isolated or completely absent, and incisors were
+longer and more recurved or retrodont. _Baiomys sawrockensis_, or an
+unknown stock resembling it, might have been ancestral to the other
+known species. Of the four remaining fossil species, _B. kolbi_ seems
+least likely to have been ancestral to the two living species, owing to
+its prooedont incisors, reduction of cingular ridges, loss of an anterior
+median fold in m1, and long mandibular tooth-row. _B. kolbi_ may have
+been an early, specialized derivation from the ancestral stock. From his
+knowledge of the habitats of _B. musculus_, the larger species, and _B.
+taylori_, the smaller species, Hibbard (1952:203) suggests that _B.
+kolbi_, a large species, might have inhabited lowlands, and _B.
+rexroadi_, a small species, highlands. I have no evidence to dispute
+this suggestion except that _B. musculus_ has more prominent cingular
+ridges (or at least vestiges of this lophid condition) than either _B.
+kolbi_ or _B. rexroadi_. _B. musculus_ (see page 610) is less of an open
+grassland inhabitant than is _B. taylori_. Therefore, both _B. kolbi_
+and _B. rexroadi_, because of their poorly developed cingular ridges,
+might be expected to have lived in a relatively open grassland habitat.
+
+The relationship of _B. rexroadi_ to fossil species other than _B.
+kolbi_ is not clear. Superficially, the former resembles _B. taylori_,
+but, owing to the specialized development of the molars of _rexroadi_,
+it could hardly have been ancestral to either of the living species. The
+resemblance of _B. rexroadi_ to _B. taylori_ may result from each having
+occupied the same ecological niche in different periods. The incisors of
+_B. rexroadi_, however, are much shorter than those of _B. taylori_ and
+suggest somewhat different food habits.
+
+_B. minimus_ seemingly is more closely related to _B. sawrockensis_ and
+_B. musculus_ than to the other described species. The development of
+the cingular ridges leads one to suspect that _B. minimus_ was the
+ancestor of _B. musculus_. _B. minimus_ may have been derived from a
+_sawrockensis_-like stock and probably gave rise to _B. musculus_.
+
+Hershkovitz (1955:643-644) suggests that "... primitive brachydont,
+buno-mesolophodont cricetines have survived ... in forested parts of the
+range," whereas "... the progressive branch of cricetines with mesoloph
+absent or vestigal, has become increasingly specialized for life in open
+country and a diet of grasses." Species of the genus _Baiomys_ can be
+divided into two morphological groups. One group, composed of _B.
+sawrockensis_, _B. minimus_, and _B. musculus_, includes those species,
+the teeth of which were relatively brachydont and had prominently
+developed cingular ridges (ectolophids or mesolophids) or, at least,
+showed some development of these ridges. _B. sawrockensis_ probably
+lived in semi-wooded to shrubby habitats. According to Hibbard
+(1953:409), "The Saw Rock Canyon fauna lived in that area at a time when
+conditions were comparable to the conditions at the time the Rexroad
+fauna lived." The conditions in which the Rexroad fauna lived are
+discussed by Hibbard (1941:95). Presumably, there were at least some
+well-wooded situations, and the climate was warm. _B. sawrockensis_
+probably inhabited denser vegetation than did _B. minimus_ or than does
+_B. musculus_. The teeth of the second group (_B. kolbi_, _B. rexroadi_,
+_B. brachygnathus_, and _B. taylori_) lack cingular ridges or have them
+much reduced and have more hypsodont molars. The three fossil species
+probably inhabited relatively open grassland. This assumption is based
+largely on the known habitat of _B. taylori_ (see page 632).
+
+The suggested grouping, based on supposed similarities in niches
+inhabited by the extinct species, does not necessarily indicate degree
+of relationship. _B. taylori_ probably was not derived from an ancestor
+like _B. rexroadi_ or _B. kolbi_, although, in certain characters, the
+three species resemble one another. _B. kolbi_ and _B. rexroadi_ were
+already specialized in Blancan times, probably for living on grassland.
+_B. taylori_ shows only a slight advance in specialization of molar
+structures compared to either of the aforementioned species but is
+slightly smaller and does have longer and more recurved incisors. If
+only morphological criteria of lower jaws were considered, without
+recourse to other data derived from the study of many samples of
+populations of the living species, time alone might account for the
+differences among _B. taylori_, _B. rexroadi_, and _B. kolbi_. The
+available evidence (see page 658) suggests, however, that _B. taylori_
+was derived from the _B. sawrockensis_-_B. minimus_-_B. musculus_ line.
+
+    [Illustration: FIG. 3. Diagram indicating probable relationships
+       of living and extinct species of pygmy mice.]
+
+_Baiomys_ seems to have undergone little basic evolutionary and
+morphological change since Late Pliocene time. According to Simpson
+(1945:207), hesperomine rodents as a group have undergone little basic
+evolution, and "The rapid evolution of new genera was more a matter of
+segregation of characters in a group with a great variation than of the
+origin of significantly new characters." Perhaps, the living southern
+pygmy mouse retains many basic characteristics of one of the early North
+American cricetine-like stocks that emigrated to South America near the
+end of the Pliocene epoch. There is much to suggest close relationship
+of the pygmy mice to certain species of South American hesperomine
+rodents of the genus _Calomys_.
+
+
+
+
+NON-GEOGRAPHIC VARIATION
+
+
+Non-geographic variation in pygmy mice (variation in a single population
+resulting from age, individual, seasonal, and secondary sexual
+differences) has been but little studied in the past. Mearns (1907:381)
+figured progressive stages of wear on the teeth of _B. taylori_; Osgood
+(1909:252) and Blair (1941:380) referred to changes in dentition,
+weights, and pelages.
+
+The largest samples available for this study were 47 _B. taylori_ from
+the vicinity of Altamira (6 mi. N, 6 mi. W; 5 mi. N, 5 mi. W; 1 mi. S),
+Tamaulipas, and 44 _B. musculus_ from El Salvador (1 mi. S Los Planes,
+and 1 mi. NW San Salvador--two localities 3 miles apart).
+
+
+VARIATION WITH AGE
+
+Specimens of both species were segregated into five categories:
+Juveniles, young, subadults, adults, and old adults. Juvenal and young
+pygmy mice are readily separable from the other three categories;
+subadults are less easily distinguished from adults. In order to obtain
+an accurate understanding of geographic variation in these mice, only
+adults should be used in making taxonomic comparisons.
+
+_Juveniles._--Nestling mice yet unweaned; sutures in cranium
+incompletely closed; bony parts of skull fragile; M3 and m3 not erupted
+or only partly erupted and not protruding above margins of alveoli.
+
+At birth, juveniles are pink, without pelage except for the mystacial
+vibrissae and a few hairs about the eye. Blair (_op. cit._:381) recorded
+changes with age in color of the skin of new-born and suckling pygmy
+mice. Data obtained by me from three litters born in captivity agree
+with his findings. Pygmy mice are weaned when 17 to 24 days old. At that
+time, the mice possess a fine, but not dense, dusky-gray fur.
+
+_Young._--Weaned mice; cranium fragile; sutures between frontals and
+parietals, interparietal and parietals, basioccipital and basisphenoid,
+basisphenoid and presphenoid, premaxillaries and maxillaries widely
+open; M3 and m3 erupted beyond margins of their alveoli (molars erupt
+from anterior to posterior; M3 and m3, therefore, are last to erupt); in
+some specimens, molars slightly worn; pelage still dusky and relatively
+fine and sparse.
+
+_Subadults._--Sutures between bones of skull less widely open than in
+young; epiphyses of long bones incompletely coalesced to shaft; relative
+to length of skull, braincase higher and rostrum shorter than in adults;
+all cusps worn, but dentine not occlusally confluent; primary first and
+second folds of third upper molars present; primary first fold and major
+fold of lower molars visible; pelage a subtle mixture of colors of young
+and adult, but resembling most that of adult; molts into postjuvenal
+pelage between 46 and 50 days.
+
+_Adults._--Sutures of skull, and those between epiphyses and shaft of
+long bones obliterated except that, in some mice, sutures of skull
+persist between frontoparietal, and interparietal; cusps of molars so
+worn that dentine occlusally confluent; small island of enamel in third
+upper and lower molars of some specimens; relative to length of skull,
+cranium lower, rostrum longer, and interorbital region narrower than in
+subadult; cranium appears to be more flattened dorsoventrally; between
+subadult and adult stages, principal growth occurs in basioccipital,
+basisphenoid, frontals, and parietals; nasals grow less.
+
+Although all bones of the skull grow in the subadult and early adult
+stages (see table 1), the above-named bones grow faster than others and
+thus cause the general flattening of the skull, typical of adults
+(similar to that reported by Hoffmeister, 1951:7). The body continues to
+lengthen, accounting for the increase in total length of the adult (see
+table 1). Hind foot, tail and ear, reach their maximum lengths by
+subadult stage. Adult pelage has been acquired, and the color is
+brighter than in either subadults or old adults.
+
+_Old Adults._--Characterized principally by well-worn molars; only thin
+peripheral band of enamel along with slight evidence of any primary or
+secondary folds on any teeth remain; all bones of skull coalesced;
+epiphyses and shafts of long bones ankylosed; small bony protuberances
+on many skulls; pelage usually ragged, tips of the hairs being worn
+away; white flecking and spotting not common, but occurs in some adults.
+
+    TABLE 1.--Average and Extreme Measurements (in Millimeters) of
+       Skulls of Five Age-groups of Baiomys taylori from vic.
+       (see p. 595) Altamira, Tamaulipas, Mexico.
+
+  =============+===========+===========+===========+===========+===========
+  Age groups   | Juvenile  |   Young   | Subadult  |   Adult   | Old adult
+  -------------+-----------+-----------+-----------+-----------+-----------
+  Number       |           |           |           |           |
+  examined     |     3     |     3     |     14    |    19     |    8
+               |           |           |           |           |
+               |           |           |           |           |
+  Total length |   77.0    |   92.6    |    97.6   |   99.9    |  101.6
+               |  (74-79)  |  (89-96)  |   (91-103)| (93-105)  | (98-107)
+               |           |           |           |           |
+               |           |           |           |           |
+  Length       |   27.3    |   39.3    |   40.4    |   39.8    |   40.9
+  of tail      |  (24-29)  |  (37-41)  |  (36-43)  |  (35-45)  |  (38-45)
+               |           |           |           |           |
+               |           |           |           |           |
+  Length       |   49.6    |   53.3    |   57.0    |   60.0    |   60.7
+  of body      |  (49-50)  |  (52-55)  |  (51-61)  |  (56-67)  |  (57-67)
+               |           |           |           |           |
+               |           |           |           |           |
+  Length of    |    11.0   |     13.6  |   14.3    |   14.5    |   14.2
+  hind foot    |    (11)   |  (13-14)  |(13.5-15.0)|  (14-15)  |  (13-15)
+               |           |           |           |           |
+               |           |           |           |           |
+  Occipitonasal|   14.2    |    16.3   |   17.1    |   17.7    |   17.8
+  length       |(13.6-15.2)|(15.8-16.9)|(16.7-17.6)|(17.2-18.3)|(17.6-18.1)
+               |           |           |           |           |
+               |           |           |           |           |
+  Zygomatic    |    8.1    |    8.7    |    8.9    |    9.3    |    9.4
+  breadth      | (7.8-8.6) | (8.6-8.8) | (8.6-9.3) | (9.0-9.6) | (9.1-9.6)
+               |           |           |           |           |
+               |           |           |           |           |
+  Interorbital |    3.4    |    3.4    |    3.4    |    3.6    |    3.5
+  breadth      | (3.3-3.5) | (3.3-3.6) | (3.3-3.6) | (3.4-3.8) | (3.3-3.6)
+               |           |           |           |           |
+               |           |           |           |           |
+  Incisive     |           |           |           |           |
+  foramina     |     2.9   |    3.5    |    3.7    |    3.9    |    3.9
+  (length)     | (2.8-2.9) | (3.4-3.6) | (3.6-3.9) | (3.6-4.1) | (3.5-4.0)
+               |           |           |           |           |
+               |           |           |           |           |
+  Depth        |    5.9    |    6.5    |    6.5    |    6.7    |    6.8
+  of cranium   | (5.6-6.2) | (6.3-6.8) | (6.2-6.8) | (6.4-7.0) | (6.5-7.1)
+               |           |           |           |           |
+               |           |           |           |           |
+  Alveolar     |           |           |           |           |
+  length,      |    2.7    |    2.9    |    2.9    |    3.0    |    3.0
+  upper molars | (2.5-2.8) | (2.9-3.0) | (2.8-3.1) | (2.9-3.2) | (3.0-3.1)
+               |           |           |           |           |
+               |           |           |           |           |
+  Postpalatal  |    4.8    |    5.9    |    6.2    |    6.5    |    6.5
+  length       | (4.5-5.3) | (5.8-6.0) | (5.8-6.6) | (6.2-7.2) | (6.3-6.7)
+               |           |           |           |           |
+               |           |           |           |           |
+  Breadth      |    8.1    |    8.5    |    8.4    |    8.6    |   8.6
+  of braincase | (7.8-8.7) |   (8.5)   | (8.0-8.7) | (8.3-8.9) |(8.4-8.8)
+  -------------+-----------+-----------+-----------+-----------+-----------
+
+
+SECONDARY SEXUAL VARIATION
+
+The method employed by Dice and Leraas (1936:2) was used to measure the
+secondary sexual differences, if there were any, in each of several age
+classes. As pointed out by Hooper (1952b:11), individual variation in
+small samples can obscure secondary sexual differences. The samples of
+_B. taylori_ from the vicinity (see page 595) of Altamira, Tamaulipas,
+and the samples of _B. musculus_ from El Salvador (table 2) were large
+enough to prevent individual variation from obscuring sexual
+differences. Nevertheless, no significant secondary sexual differences
+were found in either _B. taylori_ or _B. musculus_ (see table 2).
+Therefore, the sexes have been considered together for purposes of
+geographic studies.
+
+    TABLE 2.--Analysis of Secondary Sexual Variation in Adult B. taylori
+       Vicinity of (see p. 595) Altamira, Tamaulipas, and Adult B.
+       musculus from El Salvador (see p. 595). (One Standard Deviation
+       on Either Side of the Mean is Given.)
+
+  ==============+==========================+============================
+                | Baiomys taylori          | Baiomys musculus
+   Character    +------------+-------------+-------------+--------------
+                |  21 Males  | 18 Females  |  17 Males   |  13 Females
+  --------------+------------+-------------+-------------+--------------
+                |            |             |             |
+  Total length  |98.4 +- 2.95 |100.5 +- 4.72 |112.04 +- 5.49|113.12 +- 4.23
+                |            |             |             |
+  Length of tail|40.1 +- 2.31 | 40.3 +- 2.39 | 47.12 +- 2.95| 45.70 +- 2.92
+                |            |             |             |
+  Length of body|57.83 +- 1.65| 60.10 +- 4.13| 66.67 +- 3.97| 67.75 +- 2.38
+                |            |             |             |
+  Length of     |            |             |             |
+  hind foot     |14.21 +- .53 | 14.44 +- .51 | 15.60 +- .49 | 15.38 +- .64
+                |            |             |             |
+  Length of ear |10.00 +- .00 | 10.00 +- .00 | 11.80 +- .65 | 12.00 +- .41
+                |            |             |             |
+  Occipitonasal |            |             |             |
+  length        |17.48 +- .40 | 17.47 +- .47 | 19.32 +- .35 | 19.04 +- .44
+                |            |             |             |
+  Zygomatic     |            |             |             |
+  breadth       | 9.17 +- .33 |  9.15 +- .30 |  9.84 +- .21 |  9.91 +- .28
+                |            |             |             |
+  Least         |            |             |             |
+  interorbital  |            |             |             |
+  breadth       | 3.53 +- .11 |  3.48 +- .11 |  3.88 +- .08 |  3.88 +- .12
+                |            |             |             |
+  Postpalatal   |            |             |             |
+  length        | 6.35 +- .19 |  6.38 +- .30 |  7.11 +- .15 |  6.95 +- .20
+                |            |             |             |
+  Depth         |            |             |             |
+  of cranium    | 6.65 +- .24 |  6.61 +- .17 |  7.10 +- .18 |  7.08 +- .18
+                |            |             |             |
+  Incisive      |            |             |             |
+  foramina      |            |             |             |
+  (length)      | 3.82 +- .15 |  3.81 +- .18 |  4.43 +- .11 |  4.35 +- .14
+                |            |             |             |
+  Length        |            |             |             |
+  of rostrum    | 5.87 +- .20 |  5.88 +- .21 |  6.81 +- .16 |  6.66 +- .31
+                |            |             |             |
+  Breadth       |            |             |             |
+  of braincase  | 8.54 +- .23 |  8.52 +- .12 |  9.84 +- .38 |  9.52 +- .20
+                |            |             |             |
+  Alveolar      |            |             |             |
+  length,       |            |             |             |
+  upper molars  | 2.98 +- .08 |  3.01 +- .08 |  3.20 +- .09 |  3.24 +- .10
+  --------------+------------+-------------+-------------+--------------
+
+
+INDIVIDUAL VARIATION
+
+Length of tail varied more than any other measurement used by
+me in taxonomic comparisons. Clark (1941:298), Hoffmeister
+(1951:16), and Van Gelder (1959:239) point out that external
+measurements generally are more variable than measurements of
+the cranium, probably because different techniques of measuring
+are employed by different collectors. As can be noted in table 3,
+females varied more than males.
+
+In the 3520 specimens examined, an extra tooth was observed in
+only one (see Hooper, 1955:298). The left mandibular tooth-row
+of an adult male (USNM 71539) from Omentepec, Guerrero, is
+worn more than the right one. Irregularities in number of teeth
+and abnormalities in individual teeth seem to be rare in pygmy
+mice.
+
+    TABLE 3.--Individual Variation: Coefficients of Variation for
+       Dimensions of External and Cranial Parts in a Population of
+       B. Musculus and B. Taylori.
+
+  =====================+=========================+=========================
+                       | Baiomys taylori         | Baiomys musculus
+                       +-------------------------+-------------------------
+                       |   Vic. (see page 595)   |  Vic. (see  page 595)
+    Measurement        |   Altamira, Tamaulipas  |      El Salvador
+                       +-----------+-------------+------------+------------
+                       | 21 Males  | 18 Females  | 17 Males   | 13 Females
+                       |   C. V.   |    C. V.    |   C. V.    |    C. V.
+  ---------------------+-----------+-------------+------------+------------
+                       |           |             |            |
+  Total length         |    3.0    |     4.7     |   4.9      |    3.7
+  Length of tail       |    5.7    |     5.9     |   6.2      |    6.4
+  Length of body       |    2.8    |     5.0     |   5.9      |    3.5
+  Length of hind foot  |    3.7    |     3.4     |   3.0      |    4.1
+  Length of ear        |    0.0    |     0.0     |   5.5      |    3.3
+                       |           |             |            |
+  Occipitonasal length |    2.2    |     2.7     |   1.8      |    2.3
+  Zygomatic breadth    |    3.6    |     3.3     |   2.2      |    2.7
+  Interorbital breadth |    3.2    |     3.3     |   2.2      |    2.9
+  Incisive foramina    |           |             |            |
+    (length)           |    3.8    |     4.6     |   2.5      |    3.2
+  Depth of cranium     |    3.6    |     2.5     |   2.5      |    2.5
+  Alveolar length,     |           |             |            |
+    upper molars       |    2.7    |     2.5     |   2.8      |    3.2
+  Postpalatal length   |    3.1    |     4.7     |   2.1      |    2.9
+  Length of rostrum    |    3.3    |     3.6     |   2.4      |    4.7
+  Breadth of braincase |    2.7    |     1.4     |   4.0      |    4.9
+  ---------------------+-----------+-------------+------------+------------
+
+The posterior margin of the bony palate varies from semicircular to
+nearly V-shaped. The suture between the nasals and frontals varies from
+V-shaped to truncate to W-shaped. The maxillary part of the zygoma
+varies from broad to slender in dorsoventral width in both species.
+
+
+PELAGE AND MOLTS
+
+There are three distinct pelages, juvenal, postjuvenal, and adult. The
+sequences of molt and change of pelage from the juvenal, to the
+postjuvenal, and from it to adult, are essentially as reported for
+_Peromyscus_ by Collins (1918:78-81; 1924:58-60) and Hoffmeister
+(1951:5). The juvenal pelage is uniformly dusky gray throughout except
+for the paler gray on the venter. In most juvenal mice, the yellow to
+ochraceous pigments of the subterminal bands are reduced or absent.
+Unlike _Peromyscus_, _Baiomys_ has bright brownish hairs on the head as
+the first evidence of the postjuvenal molt (see Figure 4, part a). Blair
+(1941:381) reports adult pelage in pygmy mice being evident first at an
+age of 46 days. Two of my juveniles born in captivity began the
+postjuvenal molt on the 38th and 40th days. The area of new hairs on the
+head spreads most rapidly posteriorly. New hair appears ventrally and
+laterally at the end of 46 days (see Figure 4, part b). Hair replacement
+proceeds more slowly after the "saddle back" stage (described in
+_Peromyscus_ by Collins, 1918:80) has been reached. That stage was
+reached in two pygmy mice at 52 days (see Figure 4, part c). Areas
+immediately posterior to the ears, in the scapular region, molt last.
+The postjuvenal pelage was seemingly complete in one captive pygmy mouse
+at the end of 60 days. Another captive failed to complete its growth of
+new pelage until two additional weeks had elapsed. Length of time
+required to molt in pygmy mice is about the same as that reported by
+Layne (1959:72) in _Reithrodontomys_.
+
+    [Illustration: FIG. 4. Diagrams showing progress of the postjuvenal
+       molt in pygmy mice. For explanation of a, b, and c, see text.
+       All approximately 2/3 natural size.]
+
+If, after the postjuvenal molt, a distinct adult pelage is acquired it
+is difficult to separate it from the annual replacement of pelage in
+adults at the beginning of the rainy season. Adults of both species have
+been found in molt in all months of the year. To the north, in Texas,
+the pelage of winter-taken specimens is denser and slightly more reddish
+than that of specimens taken in spring and summer. In the two last
+mentioned seasons, the pelage is more uniformly gray. To the south, in
+Mexico, the pelage is heavy and long in most specimens taken in the
+rainy season. The percentage of specimens in molt immediately before the
+rainy season and immediately before the dry season is slightly higher
+than in specimens taken at other times of the year. The adult or
+seasonal molt (both loss of old pelage and growth of new) resembles that
+in _Peromyscus truei gilberti_, described by Hoffmeister (1951:6) as
+proceeding "posteriorly as a wave over the entire back." The new hair is
+slightly brighter than the old. Old adults are usually in ragged pelage
+regardless of season; possibly only one regular annual change of pelage
+occurs in most animals before they die. Only one case of melanism was
+observed among all the specimens of both species examined. It was a
+young male _B. t. taylori_, KU 35943, from 6 mi. SW San Geronimo,
+Coahuila, possessing black hairs throughout. Its hairs are longer and
+finer than those on specimens of comparable age and sex. No albino was
+found, although Stickel and Stickel (1949:145) record one--an adult male
+of _B. taylori_.
+
+
+
+
+TAXONOMIC CHARACTERS AND RELATIONSHIPS
+
+
+_External parts._--Length of body, foot, ear, and tail are useful when
+considered together in distinguishing species and subspecies. I found as
+Hooper (1952a:91) did that length of ear in combination with length of
+hind foot suffices to identify nearly all specimens to species,
+especially where the two species occur together.
+
+_Pelage._--Color in adults is of especial value in subspecific
+determination; the manner in which it varies geographically is described
+on pages 609, 630.
+
+_Skull._--Difference in occipitonasal length and zygomatic breadth, both
+having low coefficients of variation, are useful in separating species,
+especially where they are sympatric. Shape of presphenoid, nasals,
+interparietal, frontoparietal sutures, and length and degree of the
+openings of the incisive foramina are useful in delimiting subspecies.
+The rostrum of _B. taylori_, in front of the frontonasal suture, is
+deflected three to five degrees ventrally in 85 per cent of the adults
+examined, and in _B. musculus_ is less, or not at all, deflected.
+
+_Teeth._--Alveolar length of the upper and lower molar tooth-rows aids
+in distinguishing fossil and Recent species, and to a lesser degree in
+delimiting subspecies. Occlusal pattern is useful in estimating the
+relationship of fossil and living species. Degree of development of the
+mesostyle, mesostylid, mesoloph, and mesolophid have been useful in
+determining relationship between fossil and living species as well as
+useful in separating the living species. Rinker (1954:119) and Hooper
+(1957:48) have shown the degree of variation in dental patterns in
+_Peromyscus_, _Sigmodon_, and _Oryzomys_, mice thought to be closely
+related to _Baiomys_. In pygmy mice, however, the dental patterns are
+relatively constant. The lophs and styles are subject to some geographic
+variation but, nevertheless, are useful in estimating relationships.
+
+    [Illustration: FIG. 5. Ventral view of hyoid bones. x 18.
+
+    A. _Baiomys musculus brunneus_, adult, female, No. 30182 KU,
+       Potrero Viejo, 1700 feet, Veracruz.
+
+    B. _Baiomys taylori analogous_, adult, female, No. 36761 KU,
+       2 mi. N Ciudad Guzman, 5000 feet, Jalisco.]
+
+_Hyoid apparatus._--Shape and, to a lesser extent, size of the hyoid
+apparatus differentiate nearly all specimens of _B. taylori_ from all
+those of _B. musculus_. The hyoid of _B. taylori_ differs from that of
+_B. musculus_ principally in the shape of the basihyal. It possesses an
+anteriorly pointed entoglossal process in _B. musculus_, and is not
+rounded to completely absent as in _B. taylori_ (see Figure 5). The
+shoulders of the basihyal protrude anteriorly in _B. musculus_, and are
+not flattened as in _B. taylori_. The total length was measured in a
+sample of 55 basihyals of _B. musculus_, and was compared to the total
+length of a sample of 80 basihyals of _B. taylori_. The means of the two
+samples differ significantly at the 95 per cent level; the mean plus two
+standard errors of _B. musculus_ and _B. taylori_, are, respectively,
+2.43 +- .02; 2.18 +- .03. There is sufficient overlap of the samples
+(mean plus one standard deviation of _B. musculus_ and _B. taylori_,
+respectively: 2.43 +- .15; 2.18 +- .15) to make the total length of the
+basihyal of only secondary importance in distinguishing species, but
+shape and total length of the basihyal, when considered together, serve
+to identify all specimens to species. When length of the basihyal is
+plotted against occipitonasal length (see Figure 6), all specimens
+studied, regardless of age or geographical origin, were separated at the
+level of species. The hypohyals of _B. taylori_ seemingly remain
+distinct throughout life; those of _B. musculus_ completely fuse in some
+adults. The ceratohyals are highly variable in shape and of little
+taxonomic use.
+
+    [Illustration: FIG. 6. Relationship of length of basihyal to
+       occipitonasal length of skull. Black symbols, all below the curved
+       line, represent measurements of _B. taylori_; open symbols, all
+       above the curved line, represent measurements of _B. musculus_.]
+
+The degree of geographic variation in shape of basihyal is not great.
+Specimens of _B. musculus pallidus_ from 1 km. NW Chapa, Guerrero, have
+a small indentation on the anteriormost part of the entoglossal process.
+The shoulder of the basihyal is directed less forward in specimens of
+_B. taylori taylori_ from 6 mi. N, 6 mi. W Altamira, Tamaulipas, than in
+other specimens of the species. The variations observed seemed not to be
+clinal.
+
+According to White (1953:548) the hyoid, like the baculum (Burt,
+1936:146), is little influenced by changes in external environment and
+may serve to clarify intergeneric relationships. Hyoids of both species
+of _Baiomys_ are smaller than hyoids of all subgenera of _Peromyscus_.
+In shape, the hyoids of _Baiomys_ resemble those of _Ochrotomys
+nuttalli_ (as explained on page 605, _Ochrotomys_ is here accorded
+generic, instead of subgeneric, rank). In size, the hyoid of both
+species of _Baiomys_ resembles that in _Reithrodontomys_. Sprague
+(1941:304) reports a resemblance in shape between the ceratohyals of
+_Baiomys_ and _Reithrodontomys_. The thyrohyals differ from those of
+_Reithrodontomys_, being less boot-shaped, and having a slight terminal
+expansion as in _Ochrotomys_ (see Sprague, _loc. cit._). In shape, the
+large basihyal of _Onychomys_ resembles the smaller one of _B.
+musculus_. The basihyal of _Oryzomys_ lacks the entoglossal process
+present in _Baiomys_. On the basis of shape of hyoid, _Baiomys_ seems to
+be most closely related to _Ochrotomys_.
+
+    [Illustration: FIG. 7. Dorsal view of bacula. x 16.
+
+    A. _B. musculus brunneus_, adult, No. 24336 KU, 3 kms.
+       W Boca del Rio, 10 feet, Veracruz.
+
+    B. _B. taylori taylori_, adult, No. 35937 KU, 6 mi.
+       SW San Geronimo, Coahuila.]
+
+_Baculum._--Of _Baiomys_, 166 bacula were processed, using the method of
+White (1951:125), and studied. They provide characters of taxonomic
+worth at the level of species and aid in evaluating generic
+relationships.
+
+The baculum of _B. taylori_ differs from that of _B. musculus_ in: shaft
+narrow; wings anterior to base projecting dorsolaterally instead of
+anteriorly; anterior part knob-shaped having indentation at tip, instead
+of anterior part spatulate-shaped (in some) to knob-shaped (see Figure
+7), without indentation; significantly shorter (see Table 4).
+
+    TABLE 4.--Length of Bacula
+
+  ==============+===========+=========+==========+===========+==========
+                | Number of | Average |   3 x    |    1      |
+     Species    | specimens | length  | standard | standard  | Range
+                |           |         |  error   | deviation |
+  --------------+-----------+---------+----------+-----------+----------
+  _B. taylori_  |      108  |  2.535  |   .078   |    .274   | 2.00-3.12
+                |           |         |          |           |
+  _B. musculus_ |       58  |  3.324  |   .090   |    .233   | 2.80-3.88
+  --------------+-----------+---------+----------+-----------+----------
+
+In each of the two species, individual and geographic variation in the
+baculum is slight; its length varies insignificantly according to age.
+Excluding juveniles contained in Table 4, but including young and
+subadults, only three bacula of _B. taylori_ were longer than 3 mm., and
+only one baculum of _B. musculus_ (a young) was shorter than 3 mm. The
+total length of the baculum, considered together with its shape, serves
+to identify to species all specimens examined by me.
+
+The bacula of both species of _Baiomys_ were compared with bacula of
+_Akodon_, _Scotinomys_, _Holochilus_, _Oryzomys_, _Zygodontomys_,
+_Reithrodontomys_, _Thaptomys_, and _Calomys_ and illustrations of
+bacula by Blair (1942:197, 200) of _Peromyscus_ (subgenera _Peromyscus_,
+_Haplomylomys_, _Podomys_), _Ochrotomys_, and material at the University
+of Kansas Museum of Natural History of _Megadontomys_. Shape of baculum
+most resembled that of _Ochrotomys_ and _Calomys_. The bacula of
+_Baiomys_, as pointed out by Blair (_op cit._:203), differ as much from
+those of the genus _Peromyscus_ as do the bacula of _Reithrodontomys_
+and _Onychomys_. In size of baculum, _Baiomys_ resembles _Ochrotomys_.
+Blair (_op. cit._:202) pointed out that the length of the baculum of _B.
+taylori subater_ was contained in the length of the animal's body 20.3
+times, and 24.2 times in the length of that of _Ochrotomys nuttalli_.
+The length of the baculum of _B. musculus_ (average of 58 specimens
+without regard to subspecies) is contained in the length of the body (of
+specimens from which the bacula were removed) 22.7 times, a figure
+approaching that in _Ochrotomys_. When bacula of both species of
+_Baiomys_ were compared to those of _O. nuttalli_, bacula of _B.
+musculus_ were found to most closely resemble those of _O. nuttalli_.
+The baculum of a single specimen of _Calomys_ (_C. laucha_) was
+contained in the length of the body 15.5 times. In general shape, as
+well as in possession of an anterior knob and the position of the
+expanded posterior wings, the baculum of _C. laucha_ resembles the
+baculum of _Ochrotomys_ and _Baiomys musculus_.
+
+Blair (_op. cit._:201) considers generic _versus_ subgeneric rank for
+_Ochrotomys_, and on the basis of studies of the phallus Hooper
+(1958:23) stated that "it is clear that _nuttalli_ should be removed
+from _Peromyscus_ and should be listed as _Ochrotomys nuttalli_
+(Harlan)." I agree with Hooper (_loc. cit._) and point out that on the
+basis of the baculum, there is less of a hiatus between _Baiomys_ on the
+one hand, and _Ochrotomys_ and _Calomys_ on the other hand, than there
+is between any one of those three genera and _Peromyscus_.
+
+White (1953:631) reported that the baculum of chipmunks might indicate
+relationships more clearly than do skulls and skins. He thought that
+skulls might more quickly than bacula reflect the habitus of the animal.
+The resemblance in cranial morphology between _Peromyscus_ and _Baiomys_
+is judged to be the result of such a convergence of habitus and the
+baculum in _Baiomys_ is thought to reflect relationships more accurately
+than does the skull.
+
+_Auditory ossicles._--Examination of a number of auditory ossicles of
+_Baiomys_ reveals constant interspecific differences in the malleus and
+incus. There is only slight individual variation, slight variation with
+age, and no secondary sexual variation. In _Baiomys taylori_ the
+orbicular apophysis of the malleus (see Figure 8, A) is rounded to
+nearly ovoid; the anterior process is pointed, and the neck is short,
+being slightly recurved. The body of the incus is round and the short
+process is elongate. The sides of the long limb of the incus are nearly
+parallel. The lenticular process is relatively large. The posterior and
+anterior crus of the stapes are bowed, and the muscular process is
+either absent or much reduced.
+
+In _Baiomys musculus_, the orbicular apophysis of the malleus (see
+Figure 8, B) is round to oblong, and less ovoid than in _B. taylori_;
+the anterior process is less acutely pointed than in _B. taylori_, and
+the neck is long, less recurved than in _B. taylori_. The body of the
+incus, though tending to be round, is more flattened, and the short
+process is knob-shaped, not elongated. The sides of the long limb of the
+incus are not parallel. The lenticular process is, relative to the size
+of the incus, small. The posterior and anterior crus of the stapes are
+more nearly straight than in _taylori_. A prominent muscular process
+occurs on the posterior crus.
+
+The auditory ossicles of representative species of all the subgenera of
+_Peromyscus_ were studied as were the ossicles of _Onychomys_,
+_Ochrotomys_, _Oryzomys_, _Akodon_, _Thaptomys_, _Zygodontomys_,
+_Calomys_, _Reithrodontomys_, and _Holochilus_.
+
+    [Illustration: FIG. 8. Lateral views of auditory ossicles. x 20.
+
+    A. _B. taylori analogous_, adult, female, No. 28104 KU, 4 kms.
+       ENE Tlalmanalco, 2290 meters, Estado de Mexico.
+
+    B. _B. musculus pallidus_, adult, male, No. 28346 KU, Cahuilotal,
+       Sacacoyuca, 960 meters, Guerrero.]
+
+The general plan of structure of the auditory ossicles in _Baiomys_
+resembles that in _Calomys_, _Akodon_, and _Thaptomys_. The ossicles of
+_Calomys_ and _Thaptomys_, in particular, closely resemble the auditory
+ossicles of _Baiomys musculus_. The short process of the incus is
+knoblike in _Calomys_ and _Thaptomys_, and the general conformation of
+malleus and stapes in those two genera is nearly identical to that in
+_B. musculus_. In _Akodon_, the anterior and posterior crus of the
+stapes is more rounded than in _B. musculus_, resembling that in _B.
+taylori_.
+
+_Reithrodontomys_ differ from _Baiomys_ in having a more elongate
+orbicular apophysis on the body of the malleus, an elongated short limb
+on the incus, and a stapes having anterior and posterior crura bowed as
+in mice of the genus _Peromyscus_.
+
+In _Ochrotomys_, the orbicular apophysis of the malleus resembles the
+orbicular apophysis of _B. musculus_, but the short process of the incus
+is longer, resembling the short process of _B. taylori_. In general
+conformation of the malleus, incus, and stapes, _Ochrotomys_ shows
+closer resemblance to _B. taylori_ than to _B. musculus_.
+
+In _Holochilus_ the anterior crus and posterior crus of the stapes are
+similar to those in _B. musculus_, but in shape and size of malleus and
+incus, _Holochilus_ differs considerably from _B. musculus_ and _B.
+taylori_.
+
+In _Zygodontomys_, size and shape of the ossicles differ greatly from
+those of _Baiomys_.
+
+In the genus _Peromyscus_, only _Peromyscus floridanus_ (subgenus
+_Podomys_) possesses a knoblike short process on the incus similar to
+that in _B. musculus_; representatives of the other subgenera examined
+possess an elongated short limb on the incus. The conformation of the
+ossicles of both _Onychomys_ and _Oryzomys_ appears to be more nearly
+like that in _Peromyscus_ than that of _Baiomys_.
+
+On the basis of shape and size of auditory ossicles, _Baiomys_ resembles
+South American hesperomines (_Calomys_ and _Thaptomys_) rather than
+North American hesperomines.
+
+
+
+
+Genus =Baiomys= True
+
+
+    1894. _Baiomys_ True, Proc. U. S. Nat. Mus., 16:758, February 7.
+       Type, _Hesperomys (Vesperimus) taylori_ Thomas.
+
+_Diagnosis._--Size small (total length in adults, 93-135); tail shorter
+than head and body; hind foot in adults 12-17; ears small (8-12) and
+rounded; upper parts blackish sepia to ochraceous-buff; underparts slaty
+gray to white or pale buffy; eyes small; hind feet having six plantar
+pads, soles nearly naked except for some hairs on anterior parts of
+soles and anteriorly to base of toes and between toes; occipitonasal
+length of skull in adults, 17.0-21.5; zygomatic breadth, 9.0-11.5;
+coronoid process of mandible well developed, strongly recurved;
+ascending ramus of mandible short and erect; anterior palatine foramina
+(incisive foramina) long, usually terminating posterior to plane of the
+front of first molars; posterior palatine foramina nearly opposite
+middle of M2; interorbital space wide relative to widest part of
+frontals; nasals projecting only slightly over incisors; condyle
+terminal; upper incisors relatively heavy; primary first fold of M3
+obliterated at an early stage of wear; major cusps of upper and lower
+anteriormost two molars alternating, more so in m1-m2 than in M1-M2,
+dental formula I/i, 1/1; C/c, 0/0; P/p, M/m, 3/3 = 16.
+
+For distribution of the genus, see Figure 9.
+
+    [Illustration: FIG. 9. Geographic distribution of the genus
+       _Baiomys_. Black area shows where the two species occur together.
+       Black dot (Acultzingo, Veracruz) shows locality where _Baiomys
+       taylori_ occurs within the range of _B. musculus_, but _B. musculus_
+       is not known to occur at that locality.]
+
+
+
+
+SYSTEMATIC ACCOUNT OF SPECIES AND SUBSPECIES
+
+
+=Baiomys musculus=
+
+Southern Pygmy Mouse
+
+(Synonymy under subspecies)
+
+    _Type._--_Sitomys musculus_ Merriam, Proc. Biol. Soc. Washington,
+       7:170, September 29, 1892.
+
+_Range._--Southern Nayarit, Michoacan, Mexico, Morelos, Puebla, and
+central Veracruz, southeastward to western Nicaragua, but unknown from
+southern Veracruz, Tabasco, and the Yucatan Peninsula (see Figure 10);
+occurs principally in the arid upper and lower divisions of the Tropical
+Life-zone.
+
+_Characters for ready recognition._--Unless otherwise noted, characters
+are usable only for the two age-categories of adult and old adult.
+Differs from _B. taylori_ in: hind foot 16 millimeters or more;
+occipitonasal length, 19 millimeters or more; zygomatic breadth, 10
+millimeters or more; rostrum not deflected ventrally at frontoparietal
+suture but, instead, curving gradually toward anteriormost point of
+nasals; cingular ridges and secondary cusps on teeth more pronounced;
+basihyal having anterior pointed entoglossal process, shoulders of
+basihyal protruding anteriorly (characteristic of all age categories);
+baculum having broader shaft, spatulate to knob-shaped tip, wings at
+base projecting anteriorly; baculum more than 3 millimeters long; short
+process of incus knob-shaped rather than attenuate; muscular process of
+posterior crus of stapes prominent.
+
+_Characters of the species._--Size large (extremes in external
+measurements of adults; total length, 100-135; length of tail vertebrae,
+33-56; length of hind foot, 14.1-17; length of ear, 9-12); upper parts
+dark reddish brown, or ochraceous-buff to nearly black; underparts pale
+pinkish buff to white or pale buffy.
+
+_Geographic variation._--Eight subspecies are here recognized (see
+Figure 10). Features that vary geographically are external size, color
+of pelage, certain cranial dimensions (occipitonasal length, zygomatic
+breadth, least interorbital breadth, length of rostrum, length of
+incisive foramina, depth and breadth of cranium, and alveolar length of
+upper molar tooth-row).
+
+External and cranial size (except for _B. m. handleyi_) is less in the
+southernmost subspecies, _B. m. pullus_, _B. m. grisescens_, _B. m.
+nigrescens_, and more in the northernmost subspecies, _B. m. musculus_,
+_B. m. brunneus_, and _B. m. infernatis_. Increase in size from south to
+north is in keeping with Bergman's Rule that within a species, smaller
+individuals occur in warmer parts of its geographic range. Southern
+pygmy mice at high altitudes average larger than those from low
+elevations, except where the two species are sympatric. There the
+Southern Pygmy Mouse is uniformly larger, regardless of altitude.
+
+Osgood (1909:257, 259) suggested that degree of relative humidity might
+in some way control color of pelage in both _B. taylori_ and _B.
+musculus_. In _B. musculus_, the darker subspecies, _B. m. brunneus_,
+_B. m. nigrescens_, and _B. m. pullus_, occur in zones of rather
+constant high relative humidity, whereas the paler subspecies
+_infernatis_, _musculus_, _handleyi_, and to a less extent _grisescens_
+and _pallidus_, occur in zones of lower relative humidity. This is in
+keeping with Gloger's Rule, which states that melanins increase in the
+warm and humid parts of the range of a species, and reddish or
+yellowish-brown phaeomelanins prevail in arid climates. _B. m. musculus_
+ranges into areas where relative humidity is such that darker pelages
+might be expected, but this is in the area where the two species are
+sympatric, and color of pelage may be an important character of
+recognition.
+
+    [Illustration: FIG. 10. Distribution of _Baiomys musculus_. Known
+       localities of occurrence are represented by circles and black dots;
+       the former denote localities that are peripheral (marginal) for the
+       subspecies concerned.
+
+    1. _B. m. brunneus_
+    2. _B. m. grisescens_
+    3. _B. m. handleyi_
+    4. _B. m. infernatis_
+    5. _B. m. musculus_
+    6. _B. m. nigrescens_
+    7. _B. m. pallidus_
+    8. _B. m. pullus_]
+
+_Natural History_
+
+_Habitat and numbers._--In Veracruz, Dalquest obtained the southern
+pygmy mouse in stands of tall grass (_Spartina?_) in sandy loam soil
+bordering, and in, dense vegetation; Davis (1944:394) found the species
+living in dense stands of grasses and seemingly utilizing underground
+burrows. Near Chilpancingo, Guerrero, rocky situations seemed to be the
+preferred habitat. Davis (_loc. cit._) believed that the species has a
+wide tolerance to kinds of habitats. In Morelos, Davis and Russell
+(1954:75) found these mice to be abundant along rock fences separating
+cultivated fields, and in arid lowlands. In Colima, Hooper (1955b:13)
+obtained specimens from an open thorn forest in sparse grass and rocky
+hillside bounding a stream and in litter below shrubs on the floor of a
+nut-palm forest; in Michoacan, these mice were taken in cane grass,
+shrubs, and mesquite near an irrigation ditch. From Guatemala, Goodwin
+(1934:39, 40) records specimens from Sacapulas, a hot, dry, sandy area
+where cactus and sparse grasses are present, and from La Primavera, on
+the edges of pine-oak-alder forests. Felten (1958:137) has taken
+_musculus_ from bushy areas in El Salvadore. In 1955, I obtained the
+southern pygmy mouse 6 mi. SW Izucar de Matemores, Puebla, along a
+stream in heavy grass bordered by cypress, willow, fig, bamboo, and in
+rocky grazed area near sugar cane fields.
+
+The southern pygmy mouse seems to be locally abundant in certain parts
+of its geographic range, and in other parts, scarce. For example,
+Dalquest (_in. litt._) recorded the pygmy mouse as common at a place 2
+km. N Paraje Nuevo, 1700 feet, Veracruz, where, by means of 50 traps, he
+took 14 of these mice in one night. The species was scarcer, although
+the habitat seemed suitable, 3 km. N Presidio, 1500 feet, Veracruz,
+where he caught only two pygmy mice in several days of trapping. Six
+miles southwest of Izucar de Matemores, the pygmy mouse was the most
+common rodent. I have trapped for it in Oaxaca and Veracruz in habitats
+that seemed almost identical to those mentioned by Dalquest, and also
+that at Izucar de Matemores, Puebla, with almost no success. The reason
+for the seeming disparity in numbers at different localities having
+nearly the same kind of habitat is unknown to me and bears further
+investigation.
+
+_Behavior._--Little is recorded concerning the behavior of this species.
+David and Russell (_op. cit._:76) found that of small mammals _B.
+musculus_ was the first to appear at night. I caught mice of this
+species by hand in the afternoon in Puebla. They seemed to be active
+from noon until dark. Albert Alcorn wrote in his field notes that
+specimens were taken near noon at a place 9 mi. NNW Esteli, Nicaragua.
+My impression is that _musculus_ is diurnal to crepuscular.
+
+_Enemies and food._--Owl pellets (thought to be those of a barn owl,
+_Tyto alba_) from within the geographic range of _B. musculus_, from 6
+mi. SW Izucar de Matemores, yielded mandibular tooth-rows belonging to
+_musculus_. Presumably, most of the carnivorous mammals and raptorial
+birds within the range of the southern pygmy mouse could be listed as
+enemies. Diurnal to crepuscular habits of this mouse may protect it from
+some of the nocturnal carnivorous mammals and raptorial birds.
+
+Food of the southern pygmy mouse includes nuts, bark, grass seeds, and
+leaves. Dalquest (MS) writes that bits of banana proved to be useful
+bait in trapping these mice in Veracruz.
+
+_Reproduction._--Notations concerning lactation and embryos on specimen
+labels of females suggest that the southern pygmy mouse breeds in all
+months. I have records of pregnant or lactating females in every month,
+save January, April, May, and June. The average of 26 counts of embryos
+or young per litter is 2.92 (1-4).
+
+
+=Baiomys musculus brunneus= (J. A. Allen and Chapman)
+
+    _Peromyscus musculus brunneus_ J. A. Allen and Chapman, Bull. Amer.
+       Mus. Nat. Hist., 9:203, June 16, 1897; Elliott, Field Columb. Mus.
+       Publ., 105(4):136, July 1, 1905; Elliott, Field Columb. Mus. Publ.,
+       115(8):203, 1907; Osgood, N. Amer. Fauna, 28:259, April 17, 1909.
+
+    _Baiomys musculus brunneus_, Miller, Bull. U. S. Nat. Mus., 79:137,
+       December 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:318, April 29,
+       1924; Ellerman, The Families and Genera of Living Rodents, 2:402,
+       March 21, 1941; Goldman, Smith. Miscl. Coll., 115:437, July 31,
+       1951; Goodwin, Bull. Amer. Mus. Nat. Hist., 102:318, August 31,
+       1953; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:512, March 3,
+       1955; Booth, Walla Walla Publs., Dept. Biol. Sci., 20:15, July 10,
+       1957; Hall and Kelson, The Mammals of North America, 2:661, March
+       31, 1959 (part).
+
+    [_Peromyscus musculus_] _brunneus_, Elliott, Field Columb. Mus.
+       Publ., 95(4): 176, 1904.
+
+    _Peromyscus musculus_ [_musculus_], Osgood, N. Amer. Fauna, 28:258,
+       April 17, 1909 (part).
+
+    _Baiomys musculus musculus_, Davis, Jour. Mamm., 25:394, December
+       12, 1944 (part); Goldman, Smith Miscl. Coll., 115:437, July 31,
+       1951; Hooper, Jour. Mamm., 33:97, February 18, 1952 (part); Hall and
+       Kelson, The Mammals of North America, 2:661, March 31, 1959 (part).
+
+    _B._ [_aiomys_] _m._ [_usculus_] _brunneus_, Hooper, Jour. Mamm.,
+       33:96, February 18, 1952.
+
+    _Baiomys taylori_, Hooper, Jour. Mamm., 33:97, February 18, 1952
+       (part).
+
+_Type._--Adult female, skin and skull; No. 12535/10845 American Museum
+of Natural History; Jalapa, Veracruz, Republic of Mexico; obtained on
+April 13, 1897, by F. M. Chapman, original number 1203.
+
+_Range._--Central Veracruz, coastal plains and eastern slopes of the
+plateau of Central Mexico, see Figure 10. Zonal range: Upper Tropical
+Life-zone (Lowery and Dalquest, 1951:537), parts of the Veracruz and
+eastern Transverse Volcanic biotic provinces of Goldman and Moore
+(1945:349). Occurs from near sea level at Boca del Rio, Veracruz, up to
+5500 feet 3 km. SE Orizaba.
+
+_Diagnosis._--Size medium to large for the species; ground color of
+dorsum of paratypes near Olive Brown; darkest of specimens of this
+subspecies examined (from Potrero Viejo, Veracruz) between Prouts Brown
+and Mummy Brown; distal two-thirds of guard hairs of dorsum black,
+proximal third dark gray to sooty; hairs of dorsum black-tipped having
+subterminal band of Ochraceous-Tawny; sides paler (less of dark brown)
+than dorsum; venter Deep Olive Buff to clay color, individual hairs pale
+olive buff at tips, dark gray basally; region of throat and chin sooty
+gray; ventralmost vibrissae white to base, other vibrissae black to
+base; ears dark brown, sparsely haired; forefeet and hind feet
+flesh-colored in palest specimens, sooty in darkest; tail pale brown,
+slightly paler below than above; presphenoid only slightly constricted
+towards midline; average and extreme external and cranial measurements
+of 10 adults from Cerro Gordo, Veracruz, are as follows: total length,
+118.9 (112-127); length of tail vertebrae, 45.1 (42-50); length of body,
+74.0 (69-78); length of hind foot, 16.0 (16); length of ear from notch,
+12.8 (12-13); occipitonasal length, 19.5 (19.0-20.0); zygomatic breadth,
+10.3 (10.0-10.8); postpalatal length, 7.1 (6.7-7.5); least interorbital
+breadth, 3.9 (3.7-4.0); length of incisive foramina, 4.4 (4.1-4.6);
+length of rostrum, 6.9 (6.5-7.2); breadth of braincase, 9.5 (9.2-9.7);
+depth of cranium, 7.1 (7.1-7.4); alveolar length of maxillary tooth-row,
+3.3 (3.2-3.3); for photographs of skull, see Plate 1_a_, and Plate 3_a_.
+
+_Comparisons._--For comparisons with _B. m. nigrescens_, see account of
+that subspecies. From _B. m. pallidus_, _B. m. brunneus_ differs in:
+dorsal, lateral, and facial coloration deeper reddish brown, more
+melanins present; venter darker; buff gray rather than whitish buff to
+gray as in paratypical series; vibrissae black rather than brownish to
+white; tail sooty, less flesh-colored; forefeet and hind feet averaging
+slightly grayer; most external and cranial dimensions averaging slightly
+larger; nasals less attenuated; presphenoid less hour-glass shaped,
+sides more nearly straight.
+
+From _B. m. infernatis_, _B. m. brunneus_ differs in: side of face and
+neck deep reddish-brown rather than yellowish-gray (the differences in
+dorsal colorations are greater between _brunneus_ and _infernatis_ than
+between _brunneus_ and _pallidus_); venter darker buff-gray; tail
+brownish rather than flesh-colored; forefeet and hind feet average
+slightly grayer; most external dimensions averaging slightly larger;
+cranial dimensions nearly the same except length of incisive foramina,
+which is smaller; presphenoid differs in much the same way as from
+pallidus.
+
+_Remarks_.--Specimens from Chichicaxtle, Puente Nacional, 3 km. W Boca
+del Rio, 1 km. E. Mecayucan, and Rio Blanco (20 km. WNW Piedras Negras),
+are all paler than the paratypical series and other specimens from
+within the assigned range of _B. m. brunneus_. All these specimens from
+the coastal plain average considerably paler than those from the front
+range and slopes of the mountains. Specimens from Puente Nacional are
+intermediate in color between paler, grayish brown, specimens from the
+coastal plains and the darker, brown, specimens from the mountains. When
+Allen and Chapman (1897:203) described _brunneus_, they did so on the
+basis of the darker brown mice from the higher altitudes. The name,
+_brunneus_, _sensu stricto_, could be restricted to those mice from the
+higher altitudes of central Veracruz. However, when the mice of
+intermediate color from Puente Nacional are considered, it seems best to
+include the material from the coastal plain with _brunneus_. Crania from
+the higher altitudes are slightly larger than, but not significantly
+different from, crania of specimens from the coastal plains. Specimens
+examined from the coastal plains resemble the darker series of _B. m.
+pallidus_ to the west in central Mexico. But there is no evidence of
+gene flow between the paler coastal specimens and _B. m. pallidus_ to
+the west. In fact, these paler brown mice on the coastal plain grade in
+color into the darker brown mice from the mountains. The paler mice from
+the coast may be an incipient subspecies.
+
+The type and paratypes seem to have faded somewhat since they were
+described by Allen and Chapman (_loc. cit._) and by Osgood (1909:259).
+However, the color of the paratypes and other specimens herein assigned
+is the feature most useful for distinguishing _brunneus_ from all other
+subspecies of _B. musculus_.
+
+_Specimens examined._--Total 187 all from VERACRUZ, Republic of Mexico,
+and distributed as follows: type locality, 4400 ft., 16[1] (including
+the type), 6[2], 1[3]; _Cerro Gordo_, 1500 ft., 19; _Teocelo_
+[= _Texolo_], 4500 ft., 1; _2 mi. NW Plan del Rio_, 1000 ft., 14[4];
+_Plan del Rio_, 1000 ft., 2[5]; _Carrizal_, 4[2]; Chichicaxtle, 3[2];
+_Puente Nacional_, 500 ft., 1[5], 2; _Santa Maria, near Mirador_, 1800 ft.,
+10[2]; Boca del Rio, 10 ft., 1[5], 8; _Cordoba_ [= _Cordova_], 14[1];
+_4 km. WNW Fortin_, 4; _Rio Atoyac, 8 km. NW Potrero_, 1; _2 km. N.
+Paraje Nuevo_, 1700 ft., 9; _El Xuchil_, _1 mi. W. Paraje Nuevo_, 6[6];
+Potrero Viejo, 1700 ft. 15; _Cautlapan_ [= _Ixtaczequitlan_], 4000 ft.,
+16; _Micayucan_, 1; 3 km. SE Orizaba, 5500 ft., 3; Rio Blanco, 20 km.
+WNW Piedras Negras, 400 ft, 7; _29 km. SE Cordoba, Presidio_, 15[4];
+_3 km. N Presidio_, 1500 ft., 2; Presidio, 600 meters, 6[3].
+
+_Marginal records._--VERACRUZ: type locality; Chichicaxtle; Boca del
+Rio, 10 ft.; Rio Blanco, 20 km. WNW Piedras Negras, 400 ft; Presidio; 3
+km. SE Orizaba, 5500 ft.
+
+[1] American Museum of Natural History.
+
+[2] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[3] Chicago Natural History Museum.
+
+[4] Univ. Michigan, Museum of Zoology.
+
+[5] Texas A & M, Coop. Wildlife Res. Coll.
+
+[6] Univ. Illinois, Mus. Nat. History.
+
+
+=Baiomys musculus grisescens= Goldman
+
+    _Baiomys musculus griesescens_ Goldman, Proc. Biol. Soc. Washington,
+       45:121, July 30, 1932; Ellerman, The Families and Genera of Living
+       Rodents, 2:402, March 21, 1941; Poole and Schantz, Bull. U. S. Nat.
+       Mus., 178:259, March 6, 1942; Goodwin, Bull. Amer. Mus. Nat. Hist.,
+       79(2):160-161, May 29, 1942 (part); Miller and Kellogg, Bull. U. S.
+       Nat. Mus., 205:513, March 3, 1955 (part); Felten, Senck. Biol.,
+       39:136, August 30, 1958; Packard, Univ. Kansas Publs., Mus. Nat.
+       Hist., 9:401, December 19, 1958; Hall and Kelson, The Mammals of
+       North America, 2:661, March 31, 1959 (part).
+
+_Type._--Adult female, skin and skull; No. 257083 U. S. Nat. Mus. (Biol.
+Surv. Coll.); Comayabuela [= Comayaguela] just south of Tegucigalpa,
+3100 feet, Honduras; obtained on March 6, 1932, by C. F. Underwood,
+original number 838.
+
+_Range._--Central to south-central Guatemala, east to south-central
+Honduras. Zonal range: Lower parts of the Merendon Biotic Province of
+Smith (1949:235). Occurs from 3200 feet at a place 1/2 mi. N and 1 mi. W
+Salama, Guatemala, up to approximately 4500 feet at Monte Redondo,
+Guatemala.
+
+_Diagnosis._--Size medium to small for the species; general ground color
+of dorsum between Olive Brown and Buffy Brown; distal fourth of
+individual guard hairs of dorsum black-tipped, proximal three-fourths
+gray, underfur black-tipped with subterminal band of Vinaceous-Buff,
+gray basally; facial region below eye Olive-Buff to Deep Olive-Buff;
+regions of flanks without black-tipped guard hairs, therefore, appearing
+paler brownish-buff than dorsum; venter Pale Olive-Buff to whitish in
+midline, hairs there white to base, laterally grayish basally; hairs in
+region of throat and chin resemble those of underparts; forefeet and
+hind feet flesh-colored with grayish suffusion; ears dusky brown; tail
+almost unicolored, slightly darker brown above than below; coronoid
+process less acutely falcate than in other subspecies; zygoma bowed.
+Average and extreme external and cranial measurements of 14 adults from
+La Piedra de Jesus Sabana Grande, Honduras, are as follows: Total
+length, 110.7 (100-123); length of tail vertebrae, 44.0 (32-55); length
+of body, 66.7 (60-70); length of hind foot, 14.1 (12-15); length of ear
+from notch, 11.8 (10-13); occipitonasal length, 19.3 (18.9-19.8);
+zygomatic breadth, 10.1 (9.8-10.4); postpalatal length, 6.8 (6.2-7.3);
+least interorbital breadth, 3.9 (3.8-4.1); length of incisive foramina,
+4.3 (4.0-4.5); length of rostrum, 6.9 (6.6-7.2); breadth of braincase,
+9.6 (9.2-10.1); depth of cranium, 7.0 (6.8-7.3); alveolar length of
+maxillary tooth-row, 3.2 (3.0-3.4); for photographs of skull, see Plate
+1_b_, and Plate 3_b_.
+
+_Comparisons._--For comparisons with _B. m. pullus_ and _B. m.
+handleyi_, see accounts of those subspecies. From _B. m. nigrescens_,
+_B. m. grisescens_ differs in: dorsum less blackish (dark brown to
+buffy); face buffy below eye rather than brownish-black; venter buffy to
+whitish in midline, not sooty gray; forefeet and hind feet flesh-colored
+with gray overtones, not dusky to sooty; zygoma bowed, sides less
+parallel; braincase and bony palate slightly broader.
+
+_Remarks._--Goodwin (1942:160) mentioned that a specimen from the type
+locality of _grisescens_ was as dark as specimens of _B. m. nigrescens_
+from Guatemala. However, all specimens from Guatemala, other than those
+from Sacapulas, were referred by Goodwin (1934:40) to _B. m.
+nigrescens_. My studies reveal a grayish-brown population in central
+Honduras near to and including the type locality. This population
+appears to grade into a slightly paler, particularly as concerns color
+of hind foot and tail, group of Guatemalan mice from 1 mi. S Rabinal,
+from 1/2 mi. N, 1 mi. E Salama, and from Lake Atescatempa. Specimens
+from western Guatemala at Nenton and Jacaltenango, on the other hand,
+are darker brownish-black, more nearly like the paratypical series of
+_nigrescens_ from the Valley of Comitan, Chiapas, Republic of Mexico.
+This darker brownish-black color of the back persists in specimens from
+southern Guatemala and El Salvador (see specimens examined of _B. m.
+nigrescens_ for localities), and they are best referred to _nigrescens_.
+_B. m. grisescens_, in color and certain cranial characters, therefore,
+seems to grade into two different subspecies: (1) _B. m. handleyi_, pale
+mice in the Rio Negro valley in central Guatemala, and (2) _B. m.
+nigrescens_, dark mice from southern Guatemala, and parts of El
+Salvador.
+
+Felten (1958:136) referred all _B. musculus_ from El Salvador to _B. m.
+grisescens_. Although I have not examined the specimens reported on by
+Felten (_loc. cit._), I have examined specimens from Lake Atescatempa,
+Guatemala (which I refer to _grisescens_), not too distant from Cerro
+Blanco, and Finca Las Canarias, Department of Ahuachapan, and Laguna de
+Guija, Department of Santa Ana (localities listed by Felten). It would
+seem that specimens from these localities might indeed be _grisescens_.
+However, specimens that I examined from 1 mi. S Los Planes, and 1 mi. NW
+San Salvador were considerably darker than paratypes of _grisescens_ and
+were nearly intermediate in color between _nigrescens_ and _pullus_. I
+refer the specimens from 1 mi. NW San Salvador, and 1 mi. S Los Planes
+to _nigrescens_ rather than to _grisescens_.
+
+There is no positive evidence that _B. m. grisescens_ intergrades with
+_B. m. pullus_ to the south in Nicaragua. But, there is a suggestion
+that intergradation occurs between these subspecies in a series of 76
+skins from La Piedra de Jesus Sabana Grande, Honduras, referable to
+_grisescens_. A total of 16 of 76 skins from this locality (21 per cent)
+possess the mid-ventral white stripe found in 18 of 20 skins (90 per
+cent), from the type locality of _pullus_ in Nicaragua. Further
+collection in areas between central Honduras and western Nicaragua may
+yield specimens of _B. musculus_ that are intermediate in characters
+between _grisescens_ and _pullus_.
+
+_Specimens examined._--Total 149, distributed as follows: GUATEMALA: 1
+mi. S Rabinal, 3450 ft., 14; 1/2 mi. N, 1 mi. E Salama, 3200 ft., 10;
+Lake Atescatempa, 10[7]. HONDURAS: Cementario, Gracias, 1[8]; Monte
+Redondo, 1[8]; El Caliche, Cedros, 1[8]; _La Flor Archaga_, 2[8], 1[9];
+Hatillo, 1[8]; _type locality_, 7[8], 6[7] (including the type), 3[9];
+_El Zapote_, _Sabana Grande_, 4[8]; La Piedra de Jesus Sabana Grande,
+76[8]; _Cerro de las Cuches Sabana Grande_, 5.
+
+_Marginal records._--GUATEMALA: 1/2 mi. N, 1 mi. E Salama, 3200 ft.
+HONDURAS: El Caliche, Cedros; Hatillo; La Piedra de Jesus Sabana Grande;
+Cementario. GUATEMALA: Lake Atescatempa; 1 mi. S Rabinal, 3450 ft.
+
+[7] United States National Museum (Biol. Surv. Collections).
+
+[8] American Museum of Natural History.
+
+[9] Univ. Michigan, Museum of Zoology.
+
+
+=Baiomys musculus handleyi= Packard
+
+    _Baiomys musculus handleyi_ Packard, Univ. Kansas Publs., Mus. Nat.
+       Hist., 9:399, December 19, 1958.
+
+    _Baiomys musculus musculus_, Goodwin, Bull. Amer. Mus. Nat. Hist.,
+       68(1):39-40, December 12, 1934 (part); Miller and Kellogg, Bull.
+       U. S. Nat. Mus., 205:512, March 3, 1955 (part).
+
+    _Baiomys musculus nigrescens_, Hall and Kelson, The Mammals of North
+       America, 2:661, March 31, 1959 (part).
+
+_Type._--Adult female, skin and skull; No. 275604 U. S. Nat. Mus. (Biol.
+Surv. Coll.); Sacapulas, El Quiche, Guatemala; obtained on April 24,
+1947, by Charles O. Handley, Jr., original number 991.
+
+_Range._--Known only from the type locality in the valley of the Rio
+Negro. Zonal range: Part of the Chimaltenangan Province of Smith
+(1949:235).
+
+_Diagnosis._--Size medium to large for the species; dorsum Wood Brown in
+some series to Buffy Brown; guard hairs of dorsum black-tipped, color of
+underhairs Avellaneous; hairs white to base in region of chin, throat,
+and median venter; in lateral region, hairs Neutral Gray at base; dorsal
+surfaces of forefeet and hind feet and ankles white; tail white below,
+brownish above; nasals truncate anteriorly; frontoparietal suture
+forming an obtuse angle with the suture separating the parietals;
+alveolar length of upper molar tooth-row and tail long. Average and
+extreme external and cranial measurements for nine adults from the type
+locality are as follows: Total length, 121.4 (115-128); length of tail
+vertebrae, 50.7 (49-54); length of body, 70.8 (66-77); length of hind
+foot, 15.3 (15-16); occipitonasal length, 19.6 (18.8-20.7); zygomatic
+breadth, 10.5 (10.2-11.0); postpalatal length, 6.9 (6.4-7.4); least
+interorbital breadth, 4.0 (3.9-4.0); length of incisive foramina, 4.2
+(4.0-4.5); length of rostrum, 7.2 (7.0-7.7); breadth of braincase, 9.8
+(9.7-10.2); depth of cranium, 7.1 (6.8-7.2); alveolar length of
+maxillary tooth-row, 3.5 (3.4-3.6); for photographs of skull, see Plate
+1_c_, and Plate 3_c_.
+
+_Comparisons._--From _B. m. nigrescens_, _B. m. handleyi_ differs as
+follows: everywhere paler; forefeet and hind feet whitish instead of
+dusky to sooty; hairs of anterior part of face white instead of brown;
+tail bicolored instead of unicolored; anterior tips of nasals truncate
+rather than rounded; frontoparietal suture forming obtuse angle with
+suture separating parietals instead of forming right angle; tail and
+upper molar tooth-row longer.
+
+From _B. m. grisescens_, _B. m. handleyi_ differs in: slightly paler
+above and below, primarily as a result of lacking buff-colored hairs;
+forefeet and hind feet white, not flesh-colored with gray overtones;
+tail bicolored, not unicolored; anterior tips of nasals truncate rather
+than flaring; tail and upper molar tooth-row longer.
+
+_Remarks._--_B. m. handleyi_ seems to be restricted to the valley of the
+Rio Negro, in the region of Sacapulas, Guatemala. Stuart (1954:7) points
+out that the Rio Negro drops down into a gorge at a place near Sacapulas
+and flows northward through a deep canyon for approximately 60
+kilometers. The Rio Negro, then, flows onto the lowlands of the Yucatan
+Peninsula. The habitat is xerophytic in the valley of the Rio Negro near
+Sacapulas. Stuart (_op. cit._:10) suggests that this xerophytic habitat
+may be continuous to a place to the north of Chixoy, Chiapas, where the
+vegetation then becomes more mesic. The mesic conditions to the north in
+Tabasco and Yucatan probably have restricted the movement of pygmy mice
+to the north. No specimens of this mouse are known from the Yucatan
+Peninsula or from the State of Tabasco, Mexico. _B. m. handleyi_
+intergrades with _B. m. grisescens_ to the south. Specimens from 1 mi. S
+Rabinal, and those from a second locality 1/2 mi. N and 1 mi. E Salama,
+Guatemala, are intermediate in color of pelage between _handleyi_ and
+_grisescens_. Stuart (_op. cit._:5) mentions the continuity of habitat
+and tributaries from the Salama Basin into the valley of the Rio Negro.
+Absence of physiographic and biotic barriers in the corridor between
+these two basins probably allows for some gene flow between _handleyi_
+and _grisescens_, and results in populations intermediate in color. To
+the north and northwest of Sacapulas, the Sierra de los Cuchumatanes
+rises abruptly and separates the known geographic range of _handleyi_
+from that of _nigrescens_ to the north, while to the west the
+cactus-mesquite habitat of _handleyi_ gives way to the oak-pine timber
+that, so far as known, does not support _Baiomys_. The difference in
+elevation and flora seems to restrict gene flow between _handleyi_ and
+the more northern _nigrescens_. The only evidence of integration between
+these two subspecies is provided by one specimen from Chanquejelve,
+Guatemala. That specimen is intermediate in color between the pale
+_handleyi_ and blackish-brown _nigrescens_.
+
+The subspecies closest, geographically, to _B. m. handleyi_ is _B. m.
+nigrescens_, from which _B. m. handleyi_ differs more in color than from
+any of the other named subspecies, except _B. m. pullus_. There is a
+close correlation of pallor of mice and the xeric Rio Negro Valley, and
+the darkness (melanistic color) of mice and the mesic mountains and
+valleys to the north.
+
+_Specimens examined._--Total 49, from GUATEMALA: type locality,
+including the type: 12 (U. S. Nat. Mus., Biol. Surv. Coll.), 37 (Amer.
+Mus. Nat. Hist.).
+
+
+=Baiomys musculus infernatis= Hooper
+
+    _Baiomys musculus infernatis_ Hooper, Jour. Mamm., 33:96, February
+       18, 1952; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:512,
+       March 3, 1955; Hall and Kelson, The Mammals of North America,
+       2:661, March 31, 1959.
+
+    _Baiomys musculus musculus_, Hooper, Jour. Mamm., 28:50, February
+       15, 1947 (part).
+
+_Type._--Adult male, skin and skull; No. 91497 Univ. of Michigan, Museum
+of Zoology; Teotitlan, Oaxaca, Republic of Mexico, obtained on February
+24, 1947, by Helmuth O. Wagner, original number 2702.
+
+_Range._--Southeastern Puebla, in the basin drained by the Rio Salado
+and Rio Quiotepec, into northern Oaxaca. Zonal range: Arid Tropical in a
+part of the Orizaba-Zempoaltepec Faunal District of the Transverse
+Volcanic Biotic Province of Moore (1945:218). Occurs from 3100 feet in
+Oaxaca up to 6000 feet in Puebla.
+
+_Diagnosis._--Size medium for the species; dorsum Drab, terminal parts
+of individual guard hairs black, Neutral Gray basally, distal parts of
+underfur Pinkish Buff, proximally Neutral Gray; sides same color as
+dorsum; hairs in region of throat and chin white to base; venter whitish
+to Neutral Gray with tinges of Pinkish Buff; dorsal parts of forefeet
+and hind feet whitish with flesh-colored undertones, ventral parts
+whitish to dusky-gray; tail bicolored, grayish-brown above, white below;
+tip of tail not bicolored, instead grayish-brown throughout; ears pale
+brown, sparsely haired; incisive foramina long, not constricted
+posteriorly. Average and extreme external measurements for 9 adults from
+the type locality are as follows: total length, 113.9 (106-122); length
+of tail vertebrae, 44.1 (41-48); length of body, 71.0 (65-79); length of
+hind foot, 14.8 (13-16); length of ear, 11.9 (11-12). Average and
+extreme cranial measurements of 7 adults from the type locality are as
+follows: Occipitonasal length, 20.1 (19.7-20.4); zygomatic breadth, 10.4
+(10.2-10.6); postpalatal length, 7.3 (7.0-7.7); least interorbital
+breadth, 4.2 (4.0-4.4); length of incisive foramina, 4.8 (4.4-5.6);
+length of rostrum, 7.2 (6.6-7.5); breadth of braincase, 9.6 (9.5-9.8);
+depth of cranium, 7.4 (7.1-7.6); alveolar length of maxillary tooth-row,
+3.3 (3.1-3.4); for photographs of skull, see Plate 1_d_, and Plate 3_d_.
+
+_Comparisons._--For comparisons with _B. m. nigrescens_ and _B. m.
+brunneus_, see accounts of those subspecies. From _B. m. pallidus_, _B.
+m. infernatis_ differs in: sides, ears, and dorsum paler (less of dark
+brown); venter whitish gray rather than gray with tinge of buff and
+brown; forefeet and hind feet paler; tail bicolored, not unicolored;
+incisive foramina longer and not constricted posteriorly; mastoid
+process turning dorsally and sickle-shaped at posteriormost point rather
+than capitate.
+
+_Remarks._--_B. m. infernatis_ resembles _B. m. handleyi_ more than any
+other subspecies in color of pelage and in external and cranial
+dimensions. The resemblance in color between _B. m. pallidus_, in
+certain parts of its range, and _B. m. handleyi_ may have resulted from
+nearly parallel selective forces that gave rise to two subspecies,
+widely separated geographically. The same relation obtains between _B.
+m. infernatis_ and _B. m. handleyi_. Both inhabit arid river basins. In
+them, pale soil and low relative humidity are important passive factors
+of selection that give adaptive value to the pale colors of pelage of
+both _infernatis_ and _handleyi_.
+
+Specimens from 6-1/2 mi. SW Izucar de Matemores, and 1 mi. SSW Tilapa,
+Puebla, are intergrades between _B. m. infernatis_ and _B. m.
+pallidus_. These specimens are intermediate in color and cranial
+characters between the aforementioned subspecies but possess more of the
+pale brown overtones seen in paratypes of _pallidus_, and are best
+referred to that subspecies.
+
+_Specimens examined_ (All in Univ. Michigan, Mus. Zool.).--Total 18, all
+from the Republic of Mexico and distributed as follows: PUEBLA,
+Tepanaco, 6000 ft., 3, Tehuacan, 5400 ft., 3. OAXACA: Type locality,
+3100 ft., 12 (including the type).
+
+_Marginal records._--See specimens examined.
+
+
+=Baiomys musculus musculus= (Merriam)
+
+    _Sitomys musculus_ Merriam, Proc. Biol. Soc. Washington, 7:170,
+       September 29, 1892; Lyon and Osgood, Bull. U. S. Nat. Mus.,
+       62:135, January 15, 1909.
+
+    _Baiomys musculus_ [= _musculus_], Mearns, Bull. U. S. Nat. Mus.,
+       56:381, April 13, 1907; Hooper, Jour. Mamm., 36:29, May 26, 1955.
+
+    _Peromyscus musculus_ [_musculus_], J. A. Allen and Chapman, Bull.
+       Amer. Mus. Nat. Hist., 9:203, June 16, 1897; Elliot, Field Columb.
+       Mus. Publ., 105(4):135, July 1, 1905; Osgood, N. Amer. Fauna,
+       28:257, April 17, 1909 (part).
+
+    [_Peromyscus_] _musculus_, Trouessart, Cat. Mamm., 1:518, 1898.
+
+    [_Peromyscus_] _musculus_ [_musculus_], Elliot, Field Columb. Mus.
+       Publ., 95(4):175, July 15, 1904.
+
+    _Baiomys musculus musculus_, Miller, Bull. U. S. Nat. Mus., 79:137,
+       December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:318,
+       April 29, 1924 (part); Ellerman, The Families and Genera of Living
+       Rodents, 2:402, March 21, 1941; Poole and Schantz, Bull. U. S. Nat.
+       Mus., 178:258, March 6, 1942; Davis, Jour. Mamm., 25:394, December
+       12, 1944 (part); Hooper, Jour. Mamm., 28:50, February 15, 1947
+       (part); Hall and Villa-R., Univ. Kansas Publs., Mus. Nat. Hist.,
+       1:460, December 27, 1949 (part); Hall and Villa-R., Anal. del Inst.
+       Biol., 21:196, September 28, 1950 (part); Goldman, Smith. Miscl.
+       Coll., 115:336, July 31, 1951 (part); Miller and Kellogg, Bull.
+       U. S. Nat. Mus., 205:512, March 3, 1955 (part); Hooper, Occas.
+       Papers Mus. Zool. Univ. Michigan, 565:13, March 31, 1955; Hall and
+       Kelson, The Mammals of North America, 2:661, March 31, 1959 (part).
+
+    _B._ [_aiomys_] _m._ [_usculus_] _musculus_, Hooper, Jour. Mamm.,
+       33:97, February 18, 1952 (part); Packard, Univ. Kansas Publs.,
+       Mus. Nat. Hist., 9:400; December 19, 1958.
+
+    _Baiomys taylori allex_, Hall and Kelson, The Mammals of North
+       America, 2:659, March 31, 1959 (part).
+
+_Type._--Adult female, skin and skull; No. 33437/45460 U. S. Nat. Mus.
+(Biol. Surv. Coll.); Colima (City), Colima, Republic of Mexico, obtained
+on March 9, 1892, by E. W. Nelson, original number 2055.
+
+_Range._--Southwestern Nayarit and northwestern Jalisco, south into
+Colima, thence eastward into Michoacan. Zonal range: part of arid Lower
+Tropical Subzone of Goldman (1951:330); approximates part of the
+Nayarit-Guerrero Biotic Province of Goldman and Moore (1945:349). Occurs
+from near sea level in Colima up to 5800 feet in Jalisco.
+
+_Diagnosis._--Size large for the species; dorsum Olive-Brown in darkest
+series to Buffy Brown with tones of Fawn Color in the palest series;
+guard hairs of dorsum black-tipped, gray basally (in some specimens,
+guard hairs gray-tipped with subterminal black band, and gray base);
+underfur of dorsum black-tipped with subterminal band of fawn to buff,
+Neutral Gray basally; face and head paler than back because of greater
+number of fawn-colored and buff-colored hairs; hairs on throat and chin
+white to base; venter and flanks Pale Olive-Buff in palest series to
+Gray (Pale Gull Gray) in darkest series; individual hairs of venter
+tipped with white to buff, basally Gray (Dark Gull Gray); forefeet and
+hind feet white to gray with flesh-colored undertones; tail faintly
+bicolored, individual hairs above black, below white; nasals flared
+anteriorly; zygoma and zygomatic plate thick. Average and extreme
+external and cranial measurements for 8 adults from Armeria, Colima, are
+as follows: total length, 125.5 (115-135); length of tail vertebrae,
+47.5 (42-54); length of body, 75.6 (68-81); length of hind foot, 16.5
+(16-17); occipitonasal length, 20.3 (19.8-20.7); zygomatic breadth, 10.7
+(10.3-11.1); postpalatal length, 7.4 (7.1-7.7); least interorbital
+breadth, 4.0 (3.9-4.1); length of incisive foramina, 4.3 (4.1-4.5);
+length of rostrum, 7.3 (6.9-7.6); breadth of braincase, 9.8 (9.4-10.0);
+depth of cranium, 7.1 (6.7-7.2); alveolar length of maxillary tooth-row,
+3.4 (3.3-3.6); for photographs of skull, see Plate 1_e_, and Plate 3_e_.
+
+_Comparisons._--For comparisons with _B. m. brunneus_, _B. m.
+infernatis_, and _B. m. pallidus_, see accounts of those subspecies.
+From _B. m. nigrescens_, _B. m. musculus_ differs in: dorsum paler
+throughout (less of blackish brown); region of face and ears paler, more
+buff and fawn-colored hairs rather than blackish-brown to grayish hairs;
+vibrissae paler; venter paler, less dark gray and less of sooty-colored
+undertones, tips of hairs whitish to pale Olive-Buff rather than light
+gray at tips becoming darker basally; forefeet and hind feet paler,
+whitish to pale buff-color with flesh-colored undertones, not
+sooty-colored to dark brown; tail paler below; nasals flaring outward,
+not tapering toward midline at anteriormost point; zygoma more massive;
+larger in external and cranial dimensions.
+
+_Remarks._--Merriam (1892:170) described _Sitomys_ [= _Baiomys_]
+_musculus_ on the basis of 23 specimens (from Colima City, Colima;
+Armeria, Colima; Plantinar, and Zapotlan, Jalisco). According to the
+original description, _B. musculus_ resembled a small house mouse and
+was smaller than any known species of _Sitomys_ except _S. taylori_ [=
+_Baiomys taylori_]. From _taylori_, _musculus_ differed in being larger
+[in size of body], and in having longer ears and tail, and larger hind
+feet. When Allen and Chapman (1897:203) described _Peromyscus_ [=
+_Baiomys_] _musculus brunneus_ from Jalapa, Veracruz, the specimens
+described by Merriam from Colima and Jalisco became representative of
+the nominal subspecies _B. m. musculus_. Osgood (1909:258) assigned
+specimens from Colima, Guerrero, Jalisco, Michoacan, Morelos, Oaxaca,
+Puebla, Sinaloa, Veracruz, and Zacatecas to the subspecies _musculus_.
+Subsequently, Russell (1952:21) named the subspecies _pallidus_ from the
+arid lowlands of Morelos; Hooper (1952:96) described the subspecies
+_infernatis_ from northern Oaxaca and southeastern Puebla; and Goodwin
+(1959:1) described a new subspecies _nebulosus_ from the Oaxaca
+highlands. Each of the subspecies mentioned immediately above was
+described from within the geographic range assigned to _B. m. musculus_
+by Osgood (_loc. cit._). Hall and Kelson (1959:661) mapped the range of
+_B. m. musculus_ so as to include Colima, parts of Jalisco, Michoacan,
+Guerrero, Oaxaca, and Veracruz. Lukens (1955:159), in a study of the
+mammals of Guerrero, has shown that the characters attributed to _B. m.
+pallidus_ are not significantly different from those of pygmy mice
+studied from Guerrero. He (_loc. cit._) concluded that: (1) if the
+specimens of pygmy mice from central Guerrero were typical of the
+subspecies _musculus_, then _pallidus_ did not deserve subspecific
+recognition, or; (2) the name _B. m. musculus_ should be restricted to
+the larger pygmy mice inhabiting the lowlands immediately adjacent to
+the Pacific Coast and the area to the north. My data (see Figure 12)
+show pygmy mice from southwestern Nayarit, northwestern and central
+Jalisco, Colima, and parts of Michoacan to be significantly larger in
+certain cranial and external measurements than pygmy mice from Guerrero,
+Oaxaca, Morelos, and parts of Puebla. This finding essentially
+corroborates Hooper's (1952a:96) findings. It seems advisable,
+therefore, to restrict the range of _B. musculus musculus_ to the large
+mice inhabiting west-central Mexico and the coastal lowlands of Colima
+and Michoacan. The name _pallidus_ is applicable to the smaller mice
+occupying Morelos, southwestern Puebla, Guerrero, Oaxaca, and
+southwestern Chiapas.
+
+_B. m. musculus_ intergrades with _B. m. pallidus_ in eastern Michoacan
+and central and western Guerrero. Specimens from San Jose Prura and 12
+mi. S Tzitzio, Michoacan, though referable to _B. m. musculus_ because
+of slightly larger size of crania are intermediate in size and color
+between the smaller and slightly darker _pallidus_ to the south and east
+and the larger, slightly paler _musculus_ to the northwest.
+
+_Specimens examined._--Total 156 all from the Republic of Mexico, and
+distributed as follows: NAYARIT: 3 mi. NNW Las Varas, 150 ft., 1.
+JALISCO: 7 mi. W Ameca, 4000 ft., 2[10]; _6 mi. W Ameca_, 4300 ft., 3[10];
+_10 mi. S Ameca_, 5800 ft., 1[10]; _13 mi. S, 15 mi. W Guadalajara_, 3;
+_13 mi. S, 9-1/2 mi. W Guadalajara_, 1; _3 mi. ENE Santa Cruz de las
+Flores_, 1; 27 mi. S, 12 mi. W Guadalajara, 1; _4 mi. NE Autlan_, 3000
+ft., 5[10]; _Sierra de Autlan_, 5000 ft., 2[10]; _2-1/2 mi. NNE Autlan_,
+3000 ft., 8; 2 mi. SSE Autlan, 1; _5 mi. S Purificacion_, 2; Chamela
+Bay, 1[10]; _2 mi. N La Resolana_, 1500 ft., 6[10]; _1 mi. N San Gabriel_,
+4000 ft., 32[10]; 2 mi. N Cuidad Guzman, 5000 ft., 1; 3 mi. E Navidad,
+4300 ft., 10[10]. COLIMA: _type locality_, 10[11] (including the type); _3
+mi. SE Colima_ (_City_), 5[10]; _4 mi. SW Colima City_, 1; Armeria, 200
+ft., 8[11]; _Paso del Rio_, 20[10].
+
+MICHOACAN: 12 mi. S Tzitzio, 6[10]; San Jose Prura, 4[12]; 1 mi. E, 6 mi.
+S Tacambaro, 4000 ft., 3[13]; La Salada, 3[11]; 1/2 mi. SE Coalcoman,
+15[10].
+
+_Marginal records._--NAYARIT: 3 mi. NNW Las Varas, 150 ft. JALISCO: 3
+mi. E Navidad, 4300 ft.; 27 mi. S, 12 mi. W Guadalajara. MICHOACAN: 12
+mi. S Tzitzio; San Jose Prura; 1/2 mi. SE Coalcoman. COLIMA: Armeria,
+200 ft. JALISCO: Chamela Bay.
+
+[10] Univ. Michigan, Museum of Zoology.
+
+[11] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[12] Chicago Natural History Museum.
+
+[13] Univ. California, Mus. Vert. Zoology.
+
+
+=Baiomys musculus nigrescens= (Osgood)
+
+    _Peromyscus musculus nigrescens_ Osgood, Proc. Biol. Soc.
+       Washington, 17:76, March 21, 1904; Elliot, Field Columb. Mus. Publ.,
+       105(4):136, July 1, 1905; Lyon and Osgood, Bull. U. S. Nat. Mus.,
+       62:135, January 15, 1909; Osgood, N. Amer. Fauna, 28:259, April 17,
+       1909.
+
+    _Baiomys musculus nigrescens_, Miller, Bull. U. S. Nat. Mus.,
+       79:137, March 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:318,
+       April 29, 1924; Goodwin, Bull. Amer. Mus. Nat. Hist., 68(1):40,
+       December 12, 1934; Ellerman, The Families and Genera of Living
+       Rodents, 2:402, March 21, 1941; Poole and Schantz, Bull. U. S. Nat.
+       Mus., 178:259, March 6, 1942; Hooper, Jour. Mamm., 28:50, February
+       15, 1947; Goldman, Smith. Miscl. Coll., 115:357, July 31, 1951;
+       Miller and Kellogg, Bull. U. S. Nat. Mus., 205:513, March 3, 1955;
+       Booth, Walla Walla Publs., Dept. Biol. Sci., 20:15, July 10, 1957;
+       Hall and Kelson, The Mammals of North America, 2:661, March 31, 1959
+       (part).
+
+    [_Peromyscus musculus_] _nigrescens_, Elliot, Field Columb. Mus.
+       Publ., 95(4):176, 1904.
+
+    _B._ [_aiomys_] _m._ [_usculus_] _nigrescens_, Goodwin, Bull. Amer.
+       Mus. Nat. Hist., 79(2):160, May 29, 1942; Hooper, Jour. Mamm.,
+       33:97, February 18, 1952 (part); Packard, Univ. Kansas Publs.,
+       Mus. Nat. Hist., 9:399, December 19, 1958.
+
+    _B._ [_aiomys_] _m._ [_usculus_] _musculus_, Booth, Walla Walla
+       Publs., Dept. Biol. Sci., 20:15, July 10, 1957 (part).
+
+_Type._--Adult female, skin and skull; No. 76827 U. S. Nat. Mus. (Biol.
+Surv. Coll.); Valley of Comitan, Chiapas, Republic of Mexico, obtained
+on December 9, 1895, by E. W. Nelson and E. A. Goldman, original number
+8719.
+
+_Range._--Southern coastal region and eastern parts of Chiapas,
+southeastward into central and southern Guatemala, thence south into El
+Salvador (see Figure 10). Zonal range: parts of Lower Austral; also
+occurs in parts of the arid division of the Upper Tropical Life-zone,
+and in parts of the arid division of the Lower Tropical Life-zone;
+approximates a part of the Chiapas Highlands Biotic Province of Goldman
+and Moore (1945:349), and parts of the Guatemalan Subregion of Smith
+(1949:235).
+
+_Diagnosis._--Size medium to small for the species; dorsum Vandyke Brown
+mixed with blackish, individual hairs black-tipped with a subterminal
+band of Warm Buff, Neutral Gray at base; guard hairs of dorsum black
+distally, Neutral Gray basally; hairs on sides grayish-brown, facial
+region like dorsum; chin buffy-brown; vibrissae brown, ventrally some
+white; venter creamy-buff to grayish, individual hairs creamy-buff at
+tips, gray basally; in region of throat and chin, hairs tipped with
+Ochraceous-Buff; dorsal surface of forefeet and hind feet dull whitish
+gray to brownish-black; tail indistinctly bicolored, dusky above,
+grayish to brownish below; incisive foramina short, wide medially;
+average and extreme external and cranial measurements of 15 adults from
+6 mi. NW Tonala, Chiapas, are as follows: total length, 107.5 (100-116);
+length of tail vertebrae, 41.1 (33-48); length of body, 66.1 (62-73);
+length of hind foot, 15.0 (14-16); length of ear, 10.9 (10-12);
+occipitonasal length, 18.9 (18.4-19.7); zygomatic breadth, 9.8
+(9.4-10.2); postpalatal length, 6.9 (6.6-7.4); least interorbital
+breadth, 3.7 (3.5-3.8); length of incisive foramina, 4.4 (4.1-4.8);
+length of rostrum, 6.7 (6.1-7.1); breadth of braincase, 9.2 (9.0-9.4);
+depth of cranium, 6.9 (6.5-7.3); alveolar length of maxillary tooth-row,
+3.1 (2.9-3.2); for photographs of skull, see Plate 1_f_, and Plate 3_f_.
+
+_Comparisons._--For comparisons with _B. m. handleyi_, _B. m.
+grisescens_, _B. m. musculus_, _B. m. pallidus_, and _B. m. pullus_, see
+accounts of those subspecies.
+
+From _B. m. brunneus_, _B. m. nigrescens_ differs in: dorsum
+blackish-brown rather than reddish to ochraceous brown; face and ears
+brownish-black rather than brownish with tinges of ochraceous; vibrissae
+darker; forefeet and hind feet darker; venter with more grayish tones;
+dorsalmost part of zygomatic plate projects farther anteriorly;
+interparietal oval to diamond-shaped and narrower anteroposteriorly;
+zygomata narrower at anteriormost part; slightly smaller in most cranial
+and external measurements.
+
+From _B. m. infernatis_, _B. m. nigrescens_ differs in: dorsum darker;
+region of face and ears darker; venter buffy to gray rather than
+whitish-buff; vibrissae darker; forefeet and hind feet darker; tail
+darker above and below; incisive foramina shorter, more constricted
+laterally; cranium slightly smaller in most dimensions.
+
+_Remarks._--Hooper (1952a:93-94) reported specimens from the coastal
+strip of southern Chiapas as the most intensely pigmented, whereas,
+specimens from central and western Chiapas were distinctly paler. Crania
+of specimens from the coastal region of southern Chiapas were smaller
+than crania from the central highlands and mountains of Chiapas. My
+studies essentially corroborate the findings of Hooper. The gradation of
+color between the pale brown _pallidus_ to the north in Oaxaca, and the
+brownish-black _nigrescens_ to the south in Chiapas is extremely
+gradual. Specimens from the central and western parts of Chiapas (see
+Figure 10 for localities) are difficult to assign to either _pallidus_
+or _nigrescens_. Equal justification exists for assignment to either
+subspecies. I have assigned the specimens to _nigrescens_ because they
+are geographically closer to the type locality of _nigrescens_.
+Specimens from Reforma, Oaxaca (assigned by Hooper, 1952a:93-94, to
+_nigrescens_), are nearly identical in size and color to paratypes of
+_pallidus_. I assign the Reforma specimens to _pallidus_.
+
+The darkest of all the specimens examined and assigned to _nigrescens_
+are from 1 mi. NW San Salvador and 1 mi. S Los Planes, El Salvador. The
+variations in color in this subspecies closely correspond to degree of
+relative humidity; the palest samples are from areas of low relative
+humidity and the darkest are from areas of high relative humidity. In
+view of the present state of differentiation of specimens from the
+southern coastal areas of Chiapas and mountainous areas of El Salvador,
+it would seem that populations there might be incipient subspecies.
+
+_Specimens examined._--Total 319. CHIAPAS: _17 mi. W Bochil_, 1[14]; _15
+mi. W Bochil_, 1[14]; _14 mi. W Bochil_, 1[14]; Bochil, 6[15]; Ocuilapa,
+3500 ft., 5[16]; _5 mi. NNW Tuxtla Gutierrez_, 9; _11 km. W Tuxtla
+Gutierrez_, 800 m., 2[15]; _10 km. W Tuxtla Gutierrez_, 800 m., 2[15];
+_Tuxtla Gutierrez_, 2600 ft., 8[16], 11; _Ocozocoautla_, 10[15], 2[16]; 25
+mi. E Comitan, Las Margaritas, 1250 m., 5[17], 24[15]; Cintalpa, 555 m.,
+1[14], 18[15], 3[17]; _Jiquilpilas_, 2000 ft., 1[16]; San Bartolome, 3[16];
+_type locality_, 5700 ft., 26[16] (including the type); 15 mi. SW Las
+Cruces, 1; Villa Flores, 600 m., 12[15]; _23 mi. S Comitan_, 1[14]; _15
+mi. S, 2 mi. E La Trinitaria_, 4; _30 mi. S Comitan_, 2[14]; 35 mi. S
+Comitan, 1[14]; _3 mi. E Arriga_, 1[14]; 6 mi. NW Tonala, 19; _Tonala_,
+8[16]; _Los Amates_, 1[14]; Pijijiapan, 10 m., 7[15]; Mapastepec, 45 m.,
+25[15], 4[17].
+
+GUATEMALA: Chanquejelve, 1[14]; _Nenton_, 3000 ft., 1[16]; Jacaltenango,
+5400 ft., 8[16]; La Primavera, 5[14]; 4 mi. S Guatemala City, 4700 ft., 3;
+_5 mi. S Guatemala City_, 4050 ft., 10; _6 mi. S Guatemala City_, 4680
+ft., 1; _Lake Amatitlan_, 4500 ft., 13[16]; El Progresso (Distrito Santa
+Rosa), 3[15]; _2 mi. N, 1 mi. W Cuilapa_, 2980 ft., 1[14]; _1 mi. WSW El
+Molino_ (_Distrito Santa Rosa_), 2; _2-1/2 mi. W, 2-1/4 mi. N San
+Cristobal_, 2900 ft., 1; El Zapote, 1[15].
+
+EL SALVADOR: 1 mi. NW San Salvador, 29; 1 mi. S Los Planes, 15.
+
+_Marginal Records._--CHIAPAS: Bochil; 25 mi. E Comitan, Las Margaritas,
+1250 ft. GUATEMALA: Chanquejelve; La Primavera; Jacaltenango, 5400 ft.;
+4 mi. S Guatemala City, 4700 ft.; El Progresso. _El Salvador_: 1 mi. NW
+San Salvador; 1 mi. S Los Planes. GUATEMALA: El Zapote. CHIAPAS:
+Mapastepec, 45 m.; Pijijiapan, 10 m.; 6 mi. NW Tonala; 15 mi. SW Las
+Cruces; Cintalpa, 555 m.; Ocuilapa, 3500 ft.
+
+[14] American Museum of Natural History.
+
+[15] Univ. Michigan, Museum of Zoology.
+
+[16] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[17] University of Florida Collections.
+
+
+=Baiomys musculus pallidus= Russell
+
+    _Baiomys musculus pallidus_ Russell, Proc. Biol. Soc. Washington,
+       January 29, 1952; Davis and Russell, Jour. Mamm., 35:75, February
+       10, 1954; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:512; Hall
+       and Kelson, The Mammals of North America, 2:662, March 31, 1959.
+
+    _Peromyscus musculus brunneus_, Elliot, Field Columb. Mus. Publ.,
+       115(8):203, 1907 (part).
+
+    _Peromyscus musculus_ [_musculus_], Osgood, N. Amer. Fauna, 28:257,
+       April 17, 1909 (part).
+
+    _Baiomys musculus musculus_, Miller, Bull. U. S. Nat. Mus., 79:137,
+       December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:318,
+       April 29, 1924 (part); Davis, Jour. Mamm., 25:394, December 12, 1944
+       (part); Hooper, Jour. Mamm., 28:50, February 15, 1947 (part);
+       Goldman, Smith, Miscl. Coll., 115:336, July 31, 1951 (part); Miller
+       and Kellogg, Bull. U. S. Nat. Mus., 205:512, March 3, 1955 (part);
+       Booth, Walla Walla Publs., Dept. Biol. Sci., 20:15, July 10, 1957
+       (part); Hall and Kelson, The Mammals of North America, 2:661,
+       March 31, 1959 (part); Goodwin, Amer. Mus. Novitates, 1929:1,
+       March 5, 1959.
+
+    _B._ [_aiomys_] _m._ [_usculus_] _musculus_, Hooper, Jour. Mamm.,
+       33:97, February 18, 1952 (part).
+
+    _B._ [_aiomys_] _m._ [_usculus_] _nigrescens_, Hooper, Jour. Mamm.,
+       33:97, February 18, 1952 (part).
+
+    _Baiomys musculus nebulosus Goodwin_, Amer. Mus. Novitates, 1929,
+       March 5, 1959.
+
+_Type._--Adult female, skin and skull; No. 4501 Texas A&M Cooperative
+Wildlife Collection; 12 kms. NW Axochiapan, 3500 feet, Morelos, Republic
+of Mexico, obtained on July 28, 1950, by W. B. Davis, original number
+5112.
+
+_Range._--Guerrero thence eastward into Morelos and west central Puebla
+along the southern edge of the Transverse Volcanic Biotic Province
+(Goldman and Moore, 1945:349), south into Oaxaca, see Figure 10. Zonal
+range: largely Arid Lower Tropical Subzone of Goldman (1951:330). Occurs
+from near sea level in Oaxaca and Guerrero up to 6550 feet in Oaxaca.
+
+_Diagnosis._--Size medium for the species; dorsum Buffy Brown in palest
+series to Olive-Brown in darkest series, individual hairs Warm Buff,
+Neutral Gray basally, some with black tips and a subterminal band of
+Warm Buff, guard hairs of dorsum black-tipped, gray basally; hairs on
+sides creamy-buff, gray basally; face same color as back fading to white
+on throat; vibrissae white-tipped, pale brown basally; venter, whitish
+with tinges of buff on lower throat, individual hairs having tips white
+to buffy-white, light gray basally; dorsal surface of forefeet and hind
+feet whitish to flesh-color; tail indistinctly bicolored, brownish
+above, grayish brown below; zygoma bowed as in _B. m. grisescens_; tail
+short; average and extreme external and cranial measurements for 17
+adults from Tehuantepec, Oaxaca, are: total length, 117.3 (110-126);
+length of tail vertebrae, 46.9 (41-51); length of body, 70.4 (65-76);
+length of hind foot, 15.8 (15-16); occipitonasal length, 18.9
+(18.2-20.1); zygomatic breadth, 10.1 (9.7-10.6); postpalatal length, 6.9
+(6.6-7.5); least interorbital breadth, 3.8 (3.6-3.9); length of incisive
+foramina, 4.4 (4.2-4.7); length of rostrum, 6.7 (6.3-7.2); breadth of
+braincase, 9.3 (8.7-9.7); depth of cranium, 6.6 (6.4-6.8); alveolar
+length of maxillary tooth-row, 3.2 (3.1-3.4); for photographs of skull,
+see Plate 1g, and Plate 3g.
+
+_Comparisons._--For comparisons with _B. m. brunneus_ and _B. m.
+infernatis_, see accounts of those subspecies.
+
+From _B. m. musculus_, _B. m. pallidus_ differs in: dorsum more
+olive-gray and brown, less ochraceous on either side of mid-dorsal
+region; face below eye grayish, not buffy; sides gray with buffy
+overtone, not creamy with light yellow overtones; venter grayish-white
+rather than an olive-buff; zygomata more tapering anteriorly; maxillary
+part of zygoma narrower when viewed from above; external and cranial
+dimensions smaller.
+
+From _B. m. nigrescens_, _B. m. pallidus_ differs in: dorsum paler,
+fewer black hairs medially; face paler, less sooty; vibrissae brownish
+with white tips rather than black with brownish tips; venter paler;
+dorsal surface of forefeet and hind feet whitish to flesh-colored rather
+than sooty to dusky-white; tail paler; nasals slightly more attenuated;
+averaging slightly larger in external and cranial measurements.
+
+_Remarks._--Russell (1952:21) described _pallidus_, on the basis of
+specimens from the arid Balsas Basin, of Morelos, as pale gray dorsally.
+After examining the original material from Morelos, I find the dorsal
+color of _pallidus_ to be much closer to a buffy brown than a pale
+grayish. Even so, smaller size differentiates _pallidus_ from
+_musculus_. _B. m. infernatis_, not _B. m. pallidus_, is the most pallid
+of all named subspecies of _B. musculus_.
+
+_B. m. pallidus_ intergrades to the northwest with _B. m. musculus_, to
+the northeast with _B. m. infernatis_, and to the southeast with _B. m.
+nigrescens_.
+
+According to Goodwin (1959:2), _B. m. nebulosus_ (named on the basis of
+one specimen) differs from _B. m. musculus_ [= _pallidus_] from southern
+Oaxaca in: darker and longer pelage; larger skull; interorbital region
+broader and less constricted posteriorly. From _B. m. nigrescens_ and
+_B. m. brunneus_, _B. m. nebulosus_ differs as follows: pelage longer
+and softer; skull larger.
+
+Study of specimens of _B. musculus_ from Oaxaca reveals considerable
+variation in external and cranial measurements as well as color,
+corresponding to that reported by Goodwin (_loc. cit._). Specimens from
+higher altitudes average somewhat darker and larger in external and
+cranial size than those at lower elevations. These differences seem to
+be microgeographic and not of subspecific rank. Among specimens that I
+have studied in Oaxaca are several from different localities (KU 63052,
+an adult male, from 3 mi. W Miahuatlan; KU 68964, an adult male from 3
+mi. W Mitla, 6000 ft.; KU 63055, an adult female from 3 mi. S
+Candelario, 1200 ft.) that, according to Goodwin (_in. litt._) match
+_nebulosus_ in reported color, size of body and skull (except for the
+region of the rostrum).
+
+Two of the three specimens (KU 63052 and 63055) are the darkest of a
+series in which the palest are inseparable from _B. m. pallidus_.
+Goodwin, who kindly compared the three specimens with the type of
+_nebulosus_, mentioned (_in. litt._) that the skull of the type has a
+slenderer rostrum. Included in the series of skulls of _B. m. pallidus_
+from 3 mi. W Mitla are several adults (not seen by Goodwin) with slender
+rostra. _B. m. nebulosus_ is judged to be a synonym of _B. m. pallidus_.
+
+Populations of pygmy mice occurring in partially isolated areas of
+highland in Oaxaca seem to me to be incipient subspecies.
+
+_Specimens examined._--Total 824 all from the Republic of Mexico and
+distributed as follows: PUEBLA: 2 mi. S Atlixco, 5800 ft., 1; _1 mi. SSW
+Tilapa_, 5800 ft., 2; _6 mi. SW Izucar de Matemores_, 7; _Piaxtla_, 3900
+ft., 4[18]; Acatlan, 4100 ft., 1. MORELOS: 5 mi. W Tepoztlan, 6000 ft.,
+7[19]; _1 mi. W Tepoztlan_, 6000 ft., 9[19]; _2 mi. SW Tepoztlan_, 7000
+ft., 1[20]; _Cuernvaca_, 9[19]; _6 mi. W Yautepec_, 4500 ft., 1[20];
+_Yautepec_, 12[19]; _3 mi. N Alpuyeca_, 4000 ft., 2[20]; _Puente de
+Ixtla_, 2[19]; _Tetecala_, 4[21]; _2 km. S Jonacatepec_, 4500 ft., 6[20];
+_type locality_, 6 (including the type). GUERRERO: _Yerbabuena_, 1800
+m., 1; _Cueva de tia Juana_ [= _1.5 km. SSW Yerbabuena_], 1; _Laguna
+Honda_, 1840 m. [= _1.5 km. S Yerbabuena_], 3; 9 mi. SE Taxco, 3800 ft.,
+1[22]; _17 km. S Taxco_, 4000 ft., 2[20]; _Iguala_, 5[19]; _3.2 km. SSE
+Iguala_, 970 m., 1; 1 km. SSE Texcaizintla, 1600 m., 2; _Teloloapan_,
+20[19], 5[24]; _1 km. N Chapa_, 1470 m., 6; _Chapa_, 1470 m., 5; El Limon,
+3[18]; 2-1/2 mi. W Mexcala, 2100 ft., 1[20]; _Rio Balsas_, 1[18]; Ayusinaha
+[= Ayotzinapa], 1[18]; _Tlapa_, 3900 ft, 1[18]; _2.5 mi. S Almolonga_,
+5600 ft., 13[20]; _1 km. N Zihuatanejo_, 1; Zihuatanejo Bay, 4[19]; _Las
+Gatas_ [= _2 km. S. Zihuatanejo_], 2; _2 km. SSE Zihuatanejo_, 9; _4 mi.
+W Chilpancingo_, 5800 ft., 3[20]; _Chilpancingo_, 4800 ft., 14[18], 21[19],
+45[21]; _2 mi. N Tixtla_, 4400 ft., 3[20]; _3.2 km. S Chilpancingo_, 4;
+_Cd. Chamilpa_ [= _12 km. ESE Chilpancingo_], 5; _Tlalixtaquilla_, 4200
+ft., 2[18]; _15 km. S. Chilpancingo_, 4300 ft., 10[20]; _1 mi. SW
+Colotlipa_, 2700 ft., 16[20]; _2 mi. SW Colotlipa_, 2700 ft., 1[20];
+_Achuitzotla_, 2800 ft., 7[20]; _8 mi. SW Colotlipa_, 1[20]; _5 mi. S
+Rincon_, 2600 ft., 2[20]; _8 mi. SW Tierra Colorado_, 600 ft., 1[20]; Rio
+Aguacatillo, _30 km. N Acapulco_, 1000 ft., 3[20]; 5 mi. ESE Tecpan, 50
+ft., 9; _Ejido Viejo_, _12 km. NNW Acapulco_, 1; _2 mi. NNW Acapulco_,
+7; Acapulco, 3[18], 3[21]; Omentepec, 200 ft., 7[18]. OAXACA: _4 mi. E
+Huajuapam_, 5000 ft., 1; 2 mi. NW Tamazulapan, 6550 ft., 1; Yalalag,
+3000 ft., 5[18]; _11 mi. NW Oaxaca_ [_City_], 1; _Yaganiza_, 3900 ft.,
+1[18]; Oaxaca [City], 5000 ft., 15, 7[21], 7[19], 5[24]; _3 mi. ESE Oaxaca_
+[_City_], 30; _4 mi. ESE Oaxaca_ [_City_], 5050 ft., 1; _10 mi. SE
+Oaxaca_ [City], 1[22]; _Cerro Ocotepec_, 1[23]; Tepantepec, 9[23]; _1 mi. E
+Tlacolula_, 5500 ft., 53[19]; _3 mi. W Mitla_, 11; Jalapa, El Campanario,
+1[23]; _2 mi. SE Matalan_, 5950 ft., 14; _Lachiguiri_, 2[23]; _Tres
+Cruces_, 10[23]; _Agua Blanca_, 11[23]; _San Jose_, 1[23]; Reforma, 30[19],
+7[21], 10[23], 6[24] _Totolapa_, 1[18]; _Nejapa_, _85 km. WNW Tehuantepec_,
+500 m., 12[19], 6[24]; _Chicapa_, 2[18]; _Gueladu_ [= _Jalapa_], 6[23];
+_Juchitan_, _Laguna Superior_; Manteca, 8[23], 1[23]; San Bartolo, 3000
+ft., 1[18]; _Ejutla_, 1400 m., 21[19]; _El Bambita_, _Tequisitlan_ 4[23];
+_Mixtequilla_, 2[23]; _Guiencola_, 5[23]; _Tehuantepec_, 200 ft., 26[18],
+11[19]; _Sola de la Vega_, 26[19], 3[24]; Huilotepec, 13[18], 3[23]; _Santa
+Lucia_, 24[23]; _Cerro de Paste_, _Tenango_, 7[23]; _Sta. C. Quieri_,
+3[23]; _Santa Marie Ecatepec_, _Zarzamora_, 13[23]; _Rincon Bamba_, 11[23];
+_3 mi. W Miahuatlan_, 5300 ft., 1; _Miahuatlan_, 12[19], 1[23], 6[24]; _San
+Juan Acaltepec_, 5[23]; _Zapotitlan_, 1[23]; _Llano Grande_, 3[18];
+Pinotepa, 700 ft., 2[18]; Juquila, 8[18]; _Arroyo_, _San Juan_, _north of
+Cerro Otate_, 1[23]; Cerro Otate, 3[23]; 3 mi. S Candelaria, 1.
+
+_Marginal records._--MORELOS: 5 mi, W Tepoztlan, 6000 ft. PUEBLA: 2 mi.
+S Atlixco, 5800 ft.; Acatlan, 4100 ft. OAXACA: 2 mi. NW Tamazulapan,
+6550 ft; Tepantepec; Oaxaca [City], 5000 ft; Yalalag, 3000 ft; Jalapa,
+El Campanario; Reforma; Huilotepec; 3 mi. S Candelaria; Cerro Otate;
+Pinotepa, 700 ft. GUERRERO: Acapulco; Zihuatanejo Bay; El Limon; 9 mi.
+SE Taxco, 3800 ft.
+
+[18] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[19] Univ. Michigan, Museum of Zoology.
+
+[20] Texas A & M, Cooperative Wildlife Research Collection.
+
+[21] Chicago Natural History Museum.
+
+[22] California Academy of Sciences.
+
+[23] American Museum of Natural History.
+
+[24] University of Florida Collections.
+
+
+=Baiomys musculus pullus= Packard
+
+    _Baiomys musculus pullus_ Packard, Univ. Kansas Publs., Mus. Nat.
+       Hist., 9:401, December 19, 1958.
+
+    _Baiomys musculus grisescens_, Goodwin, Bull. Amer. Mus. Nat. Hist.,
+       79(2):161, May 29, 1942 (part); Miller and Kellogg, Bull. U. S. Nat.
+       Mus., 205:513, March 3, 1955 (part); Hall and Kelson, The Mammals of
+       North America, 2:661, March 31, 1959 (part).
+
+_Type._--Adult female, skin and skull; No. 71605 University of Kansas
+Museum of Natural History; 8 mi. S Condega, Esteli, Nicaragua, obtained
+on July 15, 1956, by A. A. Alcorn, original number 4218.
+
+_Range._--West-central Nicaragua, from Matagalpa northwest into the
+valley of the Rio Esteli, east as far as Jinotega, see Figure 10. Zonal
+range: Upper Tropical Life-zone.
+
+_Diagnosis._--Size medium to small for the species; dorsum
+Fuscous-Black, individual hairs black-tipped with a subterminal band of
+Ochraceous-Buff, Neutral Gray at base; some hairs on dorsum all black to
+Neutral Gray at base; hair on sides Neutral Gray tinged with blackish;
+face blackish, becoming buffy on sides of head, and white on throat;
+vibrissae black; tail unicolored Chaetura Black; forefeet and hind feet
+sooty to dusky-white; mid-ventral region of venter white, hairs white to
+base; in region of anus and throat, hairs white-tipped, Neutral Gray at
+base; average and extreme external and cranial measurements of the type
+and 16 paratypes are as follows: total length, 117.3 (111-121); length
+of tail vertebrae, 47.2 (44-50); length of body, 70.4 (66-74); length of
+hind foot, 15.5 (14-17); length of ear from notch, 11.9 (10-13);
+occipitonasal length, 19.3 (18.9-19.8); zygomatic breadth, 10.2
+(9.7-10.6); postpalatal length, 7.0 (6.8-7.3); least interorbital
+breadth, 3.9 (3.8-4.1); length of incisive foramina, 4.3 (4.0-4.6);
+length of rostrum, 7.0 (6.5-7.4); breadth of braincase, 9.6 (9.3-10.0);
+depth of cranium, 7.0 (6.8-7.3); alveolar length of maxillary tooth-row,
+3.1 (3.0-3.2); for photographs of skull, see Plate 1_h_, and Plate 3_h_.
+
+_Comparisons._--From _B. m. grisescens_, _B. m. pullus_ differs in:
+dorsum and tail darker; sides and lateral parts of venter grayish
+instead of buffy-brown, thus forming distinct mid-ventral white stripe;
+average length of body and tail significantly longer, thus total length
+greater; maxillary tooth-row significantly shorter; slightly larger in
+other cranial and external dimensions.
+
+From _B. m. nigrescens_, _B. m. pullus_ differs in: dorsum slightly
+darker; face grayish, not sooty; mid-ventral white stripe (absent in
+most specimens of _nigrescens_) present and becoming grayish laterally;
+tail darker, less hairy, and averaging significantly longer; smaller in
+most external and cranial dimensions.
+
+_Remarks._--_B. m. pullus_ resembles _B. m. nigrescens_ in size and
+color but can readily be distinguished from _nigrescens_ by the shorter
+tail. _B. m. pullus_ intergrades with _nigrescens_ as shown by
+specimens, referable to _B. m. nigrescens_, from 1 mi. NW San Salvador
+and from 1 mi. S Los Planes, El Salvador. In color of the dorsum,
+specimens from these localities are intermediate between _nigrescens_
+and _pullus_.
+
+The mid-ventral white stripe characteristic of _pullus_ is present in
+three of 28 adults from El Salvador. Goodwin (1942:160) reported white
+hairs on the pectoral region of several topotypes of _B. m. grisescens_.
+The areas of white hairs on the venter of _grisescens_ occur in
+approximately 10 per cent of the specimens examined, whereas in
+_pullus_, the frequency of occurrence is 90 per cent. The areas of white
+hairs in _grisescens_ are in broad patches on the pectoral region, while
+in _pullus_, a white stripe passes from the pectoral region to the
+inguinal region in both males and females. I know of no selective
+advantage that the presence of this white stripe would confer on the
+mice.
+
+_Specimens examined._--Total 46, all from NICARAGUA, and distributed as
+follows: Type locality, 32 (including the type); _9 mi. NNW Esteli_, 8;
+_8 mi. NNW Esteli_, 3; San Rafael Del Norte, 1 (Amer. Mus. Nat. Hist.);
+_1 mi. NW Jinotega_, 1; Matagalpa, 1 (Amer. Mus. Nat. Hist.).
+
+_Marginal records._--NICARAGUA: San Rafael Del Norte; Matagalpa; type
+locality.
+
+
+=Baiomys taylori=
+
+Northern Pygmy Mouse
+
+(Synonymy under subspecies)
+
+_Type._--_Hesperomys_ (_Vesperimus_) _taylori_ Thomas, Ann. Mag. Nat.
+Hist., Ser. 5, 19:66, January, 1887.
+
+_Range._--Southeastern Arizona and southwestern New Mexico, south into
+Chihuahua and Durango, just east of the Sierra Madre Occidental, thence
+southeast through Zacatecas, Aquascalientes, Jalisco, Queretaro, and
+Guanajuato; two fingerlike projections extend northward, one on the west
+along the coast of Sinaloa into southern Sonora, and the other on the
+east covering eastern San Luis Potosi, Tamaulipas, eastern Coahuila,
+Nuevo Leon, into south, southeast, and north-central Texas. Southern
+margin of range in central Mexico approximates the 19th degree of
+latitude (see Figure 11). Arid lower and arid upper subdivisions of the
+Tropical Life-zone in south; principally Lower Sonoran and Lower Austral
+life-zones in north.
+
+_Characters for ready recognition._--Unless otherwise noted, characters
+are usable for the age-categories of adult and old adult. Differs from
+_B. musculus_ in: hind foot less than 16 millimeters; occipitonasal
+length less than 19 millimeters; zygomatic breadth less than 10
+millimeters; rostrum deflected ventrally at frontoparietal suture rather
+than curving gradually toward anteriormost point of nasals; cingular
+ridges and secondary cusps on teeth reduced or absent; basihyal having
+entoglossal process much reduced or absent, shoulders of basihyal not
+protruding anteriorly, but more flattened (characteristic of all age
+categories); baculum having narrower shaft, knob-shaped tip, wings at
+base projecting laterally, baculum less than 3 millimeters long; short
+process of incus attenuate; muscular process of posterior crus of stapes
+reduced.
+
+_Characters of the species._--Size small (extremes in external
+measurements of adults: total length, 87-123; length of tail vertebrae,
+34-53; length of hind foot, 12-15; length of ear, 9-12). Upper parts
+pale drab or reddish-brown to almost black; underparts grayish to
+cream-buff.
+
+_Geographic variation._--Eight subspecies are here recognized (see
+Figure 11). Features that vary geographically are mostly the same as
+those that do so in _B. musculus_ (see page 609).
+
+External and cranial size is less in _B. t. allex_, the southernmost
+subspecies, and progressively more in _B. t. paulus_, _B. t. taylori_,
+_B. t. ater_, _B. t. subater_, _B. t. fuliginatus_, _B. t. canutus_, and
+_B. t. analogous_. Size is largest in subspecies that occur at higher
+altitudes. Those subspecies are _B. t. analogous_ and _B. t.
+fuliginatus_. The correlation with Bergman's Rule is less exact in _B.
+taylori_ than in _B. musculus_. It is noteworthy that the smallest
+subspecies, _B. t. allex_, occurs in the area where the two species are
+sympatric.
+
+There is close correlation in _B. taylori_, as also in _B. musculus_, of
+darker pelages with zones of high relative humidity. The subspecies
+having dark pelages are: _analogous_, _fuliginatus_, and _subater_. The
+two first-mentioned subspecies occur at high altitudes, and the other,
+_subater_, occurs in the humid coastal region of Texas. The paler
+subspecies, _taylori_, _canutus_, and _allex_, occur at lower altitudes.
+Two subspecies that occur at relatively high altitudes, _ater_ and
+_paulus_, are reddish-brown. The color of pelage in these subspecies
+resembles the color of soil upon which they live. Blair and Blossom
+(1948:5) demonstrated close correlation of color of soil with color of
+pelage in _B. t. ater_ by use of an Ives tint photometer.
+
+    [Illustration: FIG. 11. Distribution of _Baiomys taylori_. Known
+       localities of occurrence are represented by circles and black dots;
+       the former denote localities that are peripheral (marginal) for the
+       subspecies concerned.
+
+    1. _B. t. allex_
+    2. _B. t. analogous_
+    3. _B. t. ater_
+    4. _B. t. canutus_
+    5. _B. t. fuliginatus_
+    6. _B. t. paulus_
+    7. _B. t. subater_
+    8. _B. t. taylori_]
+
+_Natural History_
+
+_Habitat and numbers._--The habitat occupied by the northern pygmy mouse
+ranges from sparse grassy areas along rock walls in central Mexico (see
+Davis, 1944:394), and mesquite-cactus associations in southern Texas
+(Blair, 1952:242) to heavy stands of grasses such as _Bouteloua_ sp.,
+_Andropogon_ sp., _Hilaria_ sp., and sacaton grass intermixed with
+_Yucca glauca_ in New Mexico, Arizona (see Hoffmeister 1956:281), and
+Chihuahua. Baker (1951:213) reports the species from 2 km. W El Carrizo,
+Tamaulipas, in dense grass and weeds at the edge of a cornfield. Hooper
+(1953:7) recorded the northern pygmy mouse in a cultivated field
+overgrown with herbaceous vegetation at Pano Ayuctle, Tamaulipas. In the
+State of Sinaloa, Hooper (1955b:13) obtained specimens in grass and
+among shrubs and vines bordering a fallow field. The northern pygmy
+mouse, in general, lives in situations more xerophytic and more grassy
+than does the southern pygmy mouse.
+
+The northern pygmy mouse, as the southern pygmy mouse, is locally
+abundant in its geographic range. Stickel and Stickel (_op. cit._: 145)
+pointed out that on the third night of live-trapping in Bexar County,
+Texas, there was a sudden increase in unmarked pygmy mice trapped. This
+increase in numbers, after the resident population was seemingly marked,
+followed a one-half inch rainfall. Collectors from the University of
+Kansas, myself included, have had similar experiences in trapping these
+mice. In the Mexican states of Guanajuato, Queretaro, and Jalisco, _B.
+taylori_ is one of the commonest small mammals. In New Mexico and
+Arizona and the Mexican states of Sonora and Sinaloa, nevertheless,
+these mice are rare.
+
+Stickel and Stickel (_loc. cit._) thought that the home range normal for
+_B. taylori_ in a grassy habitat was less than 100 square feet, but
+Blair (1953:10) thought that a complete home range had not been recorded
+by Stickel and Stickel.
+
+_Behavior._--The northern pygmy mouse is crepuscular to nocturnal and
+where I trapped in northern Mexico was one of the first small rodents to
+appear in my traps in the evening. Hall and Villa-R (1949:460) recorded
+this habit in Michoacan. Observations of wild-taken _B. taylori_ held in
+captivity, lend support to its being crepuscular. Captives were rarely
+active in bright lights, but in diffuse or dim lights the same mice were
+active.
+
+Blair (1941:381) pointed out that captive _B. t. subater_ were much more
+tolerant of one another than mice of the genus _Peromyscus_. He pointed
+out also that males aided in care of young. In one litter born in
+captivity in the course of my study, the female killed the male when the
+young were four days old. In another instance, the female and two
+eight-day-old young were killed by the male. Until that time, the male,
+female, and young had lived together peacefully. In other litters born
+in captivity, adult males did not harm the other mice.
+
+I have noted, as Blair (_loc. cit._) did, that _B. taylori_ utters
+high-pitched squeals in a "singing" posture resembling that of the
+coyote, yet remains silent when being handled.
+
+The northern pygmy mouse makes runways in the grass, in miniature
+resembling those of _Microtus_, and often uses runways constructed by
+_Sigmodon_. A small firm nest of finely shredded plant material (mostly
+grasses) is constructed in burrows or under logs, rocks, or fallen
+cactus plants. Thomas (1888:447) recorded nests of fine curly grass and
+cornsilk. Secondary refuge nests are not uncommon. Thomas (_loc. cit._)
+states, "If other mice live in the same place, the individuals of
+_Baiomys_ watch till others disappear, then suddenly steal part of the
+other nest and run to their own with it."
+
+_Enemies and food._--Little is recorded of the animals that prey upon
+the northern pygmy mouse. Twente and Baker (1951:120) found remains of
+_B. taylori_ in 16 per cent of barn owl pellets (_Tyto alba pratincola_)
+collected 21 mi. SW Guadalajara, Jalisco. Presumably most of the
+crepuscular and early nocturnal raptorial birds and carnivorous mammals
+feed on these mice.
+
+Food of _B. taylori_ consists in part of grass seeds and leaves, prickly
+pear (_Opuntia_ sp.) and the softer exposed parts of roots of vegetation
+among which the mice reside.
+
+_Reproduction._--The northern pygmy mouse breeds throughout the year.
+The only months in which I have not recorded pregnant females or females
+with young are June and October. Forty-one records of embryos or young
+per litter average 2.48 (less than in _B. musculus_), and range from as
+few as one to as many as four per litter.
+
+
+=Baiomys taylori allex= (Osgood)
+
+    _Peromyscus allex_ Osgood, Proc. Biol. Soc. Washington, 17:76-77,
+       March 21, 1904; Elliot, Field Columb. Mus. Publ., 105(6):135,
+       July 1, 1905; Lyon and Osgood, Bull. U. S. Nat. Mus., 62:124,
+       January 15, 1909.
+
+    _Baiomys taylori allex_, Packard, Proc. Biol. Soc. Washington,
+       71:17, April 11, 1958; Hall and Kelson, The Mammals of North
+       America, 2:659, March 31, 1959 (part).
+
+    [_Peromyscus_] _allex_, Elliot, Field Columb. Mus. Publ., 95(4):175,
+       July 15, 1904.
+
+    _Peromyscus taylori paulus_, Osgood, N. Amer. Fauna, 28:255, April
+       17, 1909 (part).
+
+    _Baiomys taylori paulus_, Miller, Bull. U. S. Nat. Mus., 79:137,
+       December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317,
+       April 29, 1924 (part); Ellerman, The Families and Genera of Living
+       Rodents, British Mus. Nat. Hist., 2:402, March 21, 1941 (part);
+       Poole and Schantz, Bull. U. S. Nat. Mus., 178:259, March 6, 1942;
+       Goldman, Smith. Miscl. Coll., 115:373, July 31, 1951 (part); Miller
+       and Kellogg, Bull. U. S. Nat. Mus., 205:512, March 3, 1955 (part);
+       Hall and Kelson, The Mammals of North America, 2:659, March 31, 1959
+       (part).
+
+    _Baiomys taylori analogous_, Hall and Kelson, Univ. Kansas Publs.,
+       Mus. Nat. Hist., 5:367, December 15, 1952 (part).
+
+_Type._--Adult male, skin and skull; No. 33429/45452 U. S. Nat. Mus.
+(Biol. Surv. Coll.); Colima (City), Colima, Republic of Mexico, obtained
+on March 7, 1892, by E. W. Nelson, original number 2029.
+
+_Range._--Colima, western lowlands of Michoacan and Jalisco, thence
+north into southern half of Nayarit, see Figure 11. Zonal range: arid
+lower tropical, approximates northern half of the Nayarit-Guerrero
+Biotic Province of Goldman and Moore (1945:349). Occurs from near sea
+level in Nayarit, up to 4000 feet in Jalisco.
+
+_Diagnosis._--Size small for the species; dorsal ground color pale
+grayish-brown, near Isabella color; mid-dorsal region washed with
+blackish, individual guard hairs black to base, other hairs black-tipped
+with subterminal light olive bands, Neutral Gray at base; laterally,
+black-tipped hairs less abundant, hairs grayish-white to base; venter
+Pale Gull Gray to whitish, distal half of individual hairs white,
+proximal half Neutral Gray; hairs in regions of throat and chin white to
+base; facial region colored like dorsum, becoming paler below eye; in
+region of mouth, hairs white to base; dorsalmost vibrissae black to
+base, others white to base; ears flesh-colored, sparsely haired; tail
+unicolored, sparsely haired for the species; dark blotches on tail of
+some series (particularly the paratypical series); dorsal and ventral
+parts of forefeet and hind feet flesh-colored, whitish to gray in some
+series. Slightly smaller in most cranial dimensions. Maxillary part of
+zygoma forming almost a right angle with rostrum, rather than tapering
+at less than a right angle to rostrum; supraoccipital rounded
+posteriorly rather than indented on each side of foramen magnum;
+cranium, relative to length of rostrum, more nearly square;
+interparietal large relative to size of cranium. Average and extreme
+measurements of five adults from 2 mi. SSE Autlan are as follows: total
+length, 100.0 (93-107); length of tail vertebrae, 40.0 (37-44); length
+of body, 60.0 (56-63); length of hind foot, 14.0 (14); length of ear
+from notch, 10.5 (10-11); occipitonasal length, 17.3 (16.8-17.9);
+zygomatic breadth, 9.1 (8.7-9.4); postpalatal length, 6.3 (6.0-6.6);
+least interorbital breadth, 3.4 (3.3-3.5); length of incisive foramina,
+3.9 (3.8-4.0); length of rostrum, 5.5 (5.2-5.8); breadth of braincase,
+8.6 (8.0-8.9); depth of cranium, 6.4 (6.0-6.7); alveolar length of
+maxillary tooth-row, 3.0 (2.8-3.1); for photographs of skull, see Plate
+1_i_ and Plate 4_a_.
+
+_Comparisons._--For comparisons with _B. t. canutus_, see account of
+that subspecies. From _B. t. analogous_, _B. t. allex_ differs in:
+external and cranial dimensions less; dorsal coloration paler; tail and
+ears paler and less hairy; dorsum and belly paler; dorsal and ventral
+parts of forefeet and hind feet paler; median parts of incisive foramina
+less constricted on either side of midline and wider open laterally;
+interparietal larger in relation to skull; interorbital breadth greater
+relative to occipitonasal length.
+
+_B. t. allex_ differs from _B. t. paulus_ as follows: dorsum gray with
+yellowish-brown wash rather than fawn to buff; tail unicolored in most
+series, less hairy; hind feet flesh-colored to light sooty, rather than
+whitish; rostrum slightly longer relative to occipitonasal length;
+incisive foramina differ from those of _paulus_ in much the same way as
+from _analogous_.
+
+_Remarks._--Osgood (1909:255-256) dismissed as taxonomically unimportant
+the differences in color of pelage and size of cranium that he observed
+between the specimens from Colima (City), Colima, representative of
+_allex_ and those representing _paulus_ and chose to synonomize _allex_
+with _paulus_. The differences that Osgood (_loc. cit._) deemed "...
+scarcely worthy of recognition ...," are, in fact, not only worthy of
+recognition, but also important in an understanding of the evolution of
+_Baiomys taylori_ (see speciation p. 659). Recently, I (1958b:17-18)
+studied ten specimens from Colima (City), Colima, and chose to regard
+_Peromyscus [= Baiomys] allex_ as a subspecies. I suggested (_loc.
+cit._) that the geographic range of _B. t. allex_ might encompass the
+southern part of Nayarit, and western Jalisco. Subsequent study of
+specimens from these areas reveals that the populations there are
+referable to _allex_. Most of the specimens obtained from these areas,
+however, merit special comment.
+
+In color of pelage, those populations from south of the Rio Grande de
+Santiago and northwest of Guadalajara (4 mi. SE Ahuacatlan; 1 mi. E
+Ixtlan; Etzatlan) show evidence of intergradation with _paulus_ to the
+east and south (Magdalena, Tequila, and Tala, Jalisco), and with
+populations more closely adjacent to the south bank of that river.
+Intergradation is indeed complex in this area. Specimens from some
+localities seem to be intergrades between _allex_ and _paulus_; from
+other localities, some specimens are referable to _allex_, and the
+others to _paulus_; from still other localities, all specimens are
+referable to _allex_.
+
+A series of 39 specimens from 1 mi. SSE Ameca, 4000 ft., Jalisco, are
+uniformly grayish-brown. This series averages grayer than paratypes of
+_allex_. There is little, if any, difference between the series from 1
+mi. SSE Ameca and paratypes of _allex_ in external size of body, hind
+foot, length of ear, and size and conformation of the cranium.
+Populations from Ameca and vicinity might be expected to average
+considerably larger inasmuch as they occur at higher altitudes (see
+Bergman's Rule, p. 609) then the material from the lower coastal plains
+to the south in Colima and Michoacan, and at lower elevations in the
+west in Jalisco and Nayarit. The means of external and cranial
+measurements are not significantly different between the specimens from
+the highlands and those from the lowlands. In the area of Ameca where
+the two species _B. musculus_ and _B. taylori_ occur together,
+interspecific competition seems to have limited, perhaps even reduced,
+size of external and cranial parts of _taylori_ (see p. 660).
+
+In color, specimens from the northern part of the valley of the Rio
+Tepalcatepec (10 mi. S, 1 mi. W Apatzingan) in Michoacan resemble
+paratypes of _allex_. Intergradation probably occurs to the north with
+_analogous_.
+
+In the eight specimens from 13 mi. E and 1 mi. N Talpa de Allende, the
+skull, as reflected in occipitonasal length and zygomatic breadth
+relative to length of body, is larger than in other specimens here
+assigned to _allex_. The median part of the belly of the eight specimens
+is buff-colored rather than whitish-gray as in typical _allex_; the
+mid-dorsal region also averages darker than in any other specimens
+referred to _allex_. Additional specimens are needed from this and
+closely adjacent areas, especially to the west on the coastal plain, in
+order to determine more accurately the taxonomic status of the mice
+there. At present, it seems best to refer them to _allex_. Possibly the
+population represented by the eight specimens is an incipient
+subspecies.
+
+There is no evidence of hybridization or intergradation of populations
+of _B. t. allex_ with any population of _B. musculus_ where the two
+species occur together.
+
+_Specimens examined._--Total 233, all from the Republic of Mexico,
+distributed as follows: NAYARIT: 3 mi. SE Mirador, 7; _2 mi. S.
+Compostela_, 2900 ft., 5; _4 mi. N Santa Isabel_, 3800 ft., 2[25]; _2 mi.
+N Santa Isabel_, 3800 ft., 22[25]; _4 mi SE Ahuacatlan_, 5200 ft., 2[26];
+_1 mi. E Ixtlan_, 4000 ft., 13[25]; 1 mi. E Ixtlan del Rio, 3700 ft., 1;
+2 mi. WNW Valle de Banderas, near sea level, 1. JALISCO: Arroyo de
+Gavalan, 16[28]; Etzatlan, 6[27]; _Mascota_, 3900 ft., 6[27]; _7 mi W
+Ameca_, 15[25]; _6 mi. W Ameca_, 15[25]; _3 mi. W Ameca_, 5[25]; Ameca,
+4000 ft., 11[27]; _1 mi. SSE Ameca_, 4000 ft., 38; 2 mi. N Resolana, 1500
+ft., 28[25]; 13 mi. E, 1 mi. N Talpa de Allende, 8; 2 mi. SSE Autlan, 5;
+1 mi. N San Gabriel, 4000 ft., 1[25]; Las Canoas, l[28]. COLIMA: Type
+locality, 10[27] (including the type). MICHOACAN: 9 mi. S Lombardia, 1500
+ft., 1; _3 mi. W Apatzingan_, 1000 ft, 1; Apatzingan, 3[25]; 10 mi. S, 1
+mi. W Apatzingan, 800 ft., 10.
+
+_Marginal records._--NAYARIT: 3 mi. SE Mirador; 1 mi. E Ixtlan del Rio.
+JALISCO: Etzatlan; Ameca; 2 mi. N Resolana; Las Canoas. MICHOACAN: 9 mi.
+S Lombardia; 10 mi. S, 1 mi. W Apatzingan. COLIMA: type locality.
+NAYARIT: Valle de Banderas.
+
+[25] Univ. Michigan, Museum of Zoology.
+
+[26] California Academy of Sciences.
+
+[27] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[28] American Museum of Natural History.
+
+
+=Baiomys taylori analogous= (Osgood)
+
+    _Peromyscus taylori analogous_ Osgood, N. Amer. Fauna, 28:256,
+       April 17, 1909 (part); Elliott, Check-List Mamm., N. Amer. Cont.,
+       West Indies and Neighboring Seas, Suppl., Amer. Mus. Nat. Hist.,
+       p. 44, January 8, 1917.
+
+    _Baiomys taylori analogous_, Miller, Bull. U. S. Nat. Mus., 79:137,
+       December 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:318, April 29,
+       1924; Ellerman, The Families and Genera of Living Rodents, British
+       Mus. Nat. Hist., 2:402, March 21, 1941; Poole and Schantz, Bull.
+       U. S. Nat. Mus., 178:259, March 6, 1942; Davis, Jour. Mamm., 25:394,
+       December 12, 1944; Hooper, Jour. Mamm., 28:50, February 15, 1947;
+       Hall and Villa-R., Univ. Kansas Publs., Mus. Nat. Hist., 1:460,
+       December 27, 1949; Hall and Villa-R., Anal. del Inst. Biol., 21:196,
+       September 28, 1950; Goldman, Smith. Miscl. Coll., 114:373, July 31,
+       1951 (part); Hall and Kelson, Univ. Kansas Publs., Mus. Nat. Hist.,
+       5:367, December 15, 1952 (part); Villa-R., Anal. del Inst. Biol.,
+       23:435, May 20, 1953; Miller and Kellogg, Bull. U. S. Nat. Mus.,
+       205:512, March 3, 1955; Hooper, Occas. Papers Mus. Zool. Univ.
+       Michigan, 565:13, March 31, 1955; Packard, Proc. Biol. Soc.
+       Washington, 71:17, April 11, 1958.
+
+    _Peromyscus musculus brunneus_, Elliot, Field Columb. Mus. Publ.,
+       115(8):203, 1907 (part).
+
+    _Peromyscus musculus_ [_musculus_], Osgood, N. Amer. Fauna, 28:258,
+       April 17, 1909 (part).
+
+    _Baiomys musculus musculus_, Hall and Villa-R., Univ. Kansas Publs.,
+       Mus. Nat. Hist., 1:460, December 27, 1949 (part); Hall and Villa-R.,
+       Anal. del Inst. Biol., 21:196, September 28, 1950 (part).
+
+    _Baiomys taylori taylori_, Dalquest, Louisiana State Univ. Studies
+       (Biol. Sci. Ser.), 1:155, December 28, 1953 (part); Hall and Kelson,
+       The Mammals of North America, 2:660, March 31, 1959 (part).
+
+    _Baiomys taylori allex_, Hall and Kelson, The Mammals of North
+       America, 2:659, March 31, 1959 (part).
+
+    _Baiomys musculus musculus_, Hall and Kelson, The Mammals of North
+       America, 2:661, March 31, 1959 (part).
+
+_Type._--Adult male, skin and skull; No. 120261 U. S. Nat. Mus. (Biol.
+Surv. Coll.); Zamora, Michoacan, Republic of Mexico, obtained on January
+15, 1903, by E. W. Nelson, and E. A. Goldman, original number 15764.
+
+_Range._--Central and eastern Jalisco south into Michoacan, east through
+Guanajuato, Queretaro, thence into Estado Mexico, and Distrito Federal,
+and west-central Veracruz, see Figure 11. Zonal range: approximately the
+Transverse Volcanic Biotic Province of Moore (1945:218) and of Goldman
+and Moore (1945:349). Occurs from 5000 feet, 7 mi. S Ocotlan, Jalisco,
+up to 8000 feet in Ixtapalapa, Distrito Federal.
+
+_Diagnosis._--Size large for the species; dorsum dark Sepia to near
+blackish medially in freshly taken specimens (Sepia fading to near
+Fuscous in prepared specimens); belly slaty-gray, hairs Deep Neutral
+Gray near tips and Dusky Neutral Gray at bases; hairs on back
+black-tipped with subterminal band of Ochraceous-Tawny (guard hairs
+blackish to base); hairs of throat and chin white-tipped, gray at bases;
+dorsal vibrissae black, ventral and anteriormost vibrissae white; hairs
+on face and sides black-tipped, and Ochraceous-Tawny at base; ears
+sparsely haired, individual hairs grayish, blackish, and ochraceous;
+tail sooty to blackish dorsally, lighter ventrally; forefeet and hind
+feet sooty brown on dorsal and ventral surface. Skull relatively broad
+interorbitally; zygoma broad and squared; cranium larger in all
+dimensions than in most other subspecies. Average and extreme
+measurements of 10 adults from 1 mi. S, 11 mi. W Zamora, 5400 ft.,
+Michoacan, are: total length, 109.4 (102-121); length of body, 64.3
+(58-72); length of tail, 44.9 (39-51); length of hind foot, 14.6
+(14-15); occipitonasal length, 18.0 (17.5-18.6); zygomatic breadth, 9.4
+(9.1-9.7); postpalatal length, 6.6 (6.2-7.2); least interorbital
+breadth, 3.5 (3.3-3.8); length of incisive foramina, 4.0 (3.8-4.2);
+length of rostrum, 6.2 (5.8-6.5); breadth of braincase, 8.7 (8.5-8.9);
+depth of cranium, 6.6 (6.3-6.9); alveolar length of maxillary tooth-row,
+3.1 (3.0-3.3); for photographs of skull, see Plate 2_a_ and Plate 4_b_.
+
+_Comparisons._--For comparisons with _B. t. allex_, _B. t. canutus_, _B.
+t. paulus_, and _B. t. fuliginatus_, see accounts of those subspecies.
+From _B. t. taylori_, _B. t. analogous_ differs as follows: sides and
+dorsum darker, differing most in freshly prepared specimens; dorsal
+surface of forefeet and hind feet darker; basal part of hairs on belly
+darker gray; frontal bones less constricted, causing less taper
+anteriorly in interorbital space; interparietal wider transversely;
+basioccipital more expanded laterally, narrowing more abruptly at suture
+between basioccipital and basisphenoid.
+
+_Remarks._--The pelage of _analogous_ becomes paler with wear as pointed
+out by Osgood (1909:257). A paratype, U. S. Nat. Mus. 120260, and
+several specimens from 1 mi. S, 11 mi. W Zamora, Michoacan, are grayish
+rather than brownish-black. All of these are old adults having the
+terminal black parts of the hairs on the dorsum nearly worn away.
+Excluding such grayish individuals, _B. t. analogous_, like _B. t.
+subater_ and _B. t. fuliginatus_, is uniformly brownish-black. Both
+_analogous_ and _fuliginatus_ occur in relatively high mountainous
+country on dark soils or pedregals, and all three of the aforementioned
+subspecies occur in zones of high relative humidity.
+
+_B. t. analogous_ intergrades with _B. t. paulus_ (see account of that
+subspecies) and _B. t. allex_ south and west of Lago de Chapala in
+Jalisco. Additional specimens are needed from Queretaro and San Luis
+Potosi in order to ascertain whether or not _B. t. analogous_
+intergrades with _B. t. fuliginatus_ or _B. t. taylori_. Specimens from
+western Jalisco, in the past referred to _B. t. analogous_, are
+referable to _B. t. allex_ (see account of that subspecies). Specimens
+obtained west of, and bordering, the Rio del Naranjo in Jalisco show a
+mixture of characters of both _B. t. allex_ and _B. t. analogous_. For
+example, specimens from 2 mi. N Ciudad Guzman resemble _analogous_ on
+the dorsum, whereas, on the belly, the individual hairs are
+white-tipped, pale gray at the base, and in over-all appearance are
+whitish-gray, unlike typical _analogous_ (being like _allex_ instead).
+The dorsal surface of the forefeet are sooty to light brownish (as in
+_analogous_), whereas, the hind feet are flesh-colored (as in _allex_).
+Another series of specimens from 4 mi. W Leon, Guanajuato, are
+intergrades between _B. t. analogous_ and _B. t. paulus_. These
+specimens are grayish to brownish on the dorsum, have sooty forefeet and
+hind feet (more nearly as in _analogous_ than in _paulus_), are
+grayish-white on the venter, and have a distinctly bicolored tail
+(resembling that of _paulus_ more than that of _analogous_). When the
+average of cranial characters is considered, both series are best
+referred to _analogous_.
+
+Hooper (1947:50) pointed out that specimens from the pedregal San
+Geronimo, Distrito Federal, were more nearly black than topotypes and
+generally showed less brownish hues typical of _analogous_. I have
+examined this series and several others from this area (see Specimens
+examined, p. 640) and am convinced that these populations average
+darker. Actually, the dorsum is more nearly black and the venter is more
+buffy than in typical _analogous_. The hairs of these individuals
+average longer than in other populations of _analogous_. Skulls of the
+specimens from the pedregal are indistinguishable from those of
+paratypes of _analogous_. The populations from the Distrito Federal seem
+to be incipient subspecies.
+
+_Specimens examined._--Total 696, all from the Republic of Mexico,
+distributed as follows: SAN LUIS POTOSI: Hacienda Capulin, 5[33]; _3.3
+mi. N Tamazunchale, by-road_, 2[34]; 1 mi. N Tamazunchale, 700 ft., 1[35].
+VERACRUZ: Acultzingo, 4[29], 1[31]. JALISCO: 1 mi. S Jalostotitlan, 5700
+ft., 5; 7 mi. NW Tepatitlan, 3[29]; _6 mi. N, 4 mi. E Tepatitlan_, 6400
+ft., 25; _2-1/2 mi. E Tepatitlan_, 6200 ft., 15; _2 mi. S, 1/2 mi. W
+Tepatitlan_, 9; _near Tepatitlan_, 2; _5 mi. SW Arrandas_, 6700 ft., 6;
+_2 mi. E Zapotlanejo_, 23; _2-1/2 mi. E Puente Grande_ (_5-1/2 mi. SW
+Zapotlanejo_), 3; _8 mi. S Guadalajara_, 10[29]; _3 mi. ENE Santa Cruz de
+las Flores_, 9; _4 mi. NE Ocotlan_, 5050 ft., 18; _13 mi. S, 9-1/2 mi. W
+Guadalajara_, 1; _2 mi. WNW Ocotlan_, 5000 ft., 15; 13 mi. S, 15 mi. W
+Guadalajara, 2; _Ocotlan_, 5000 ft., 8[30]; _1 mi. S Ocotlan_, 5000 ft.,
+12; 27 mi. S, 12 mi. W Guadalajara, 9; _1-1/2 mi. N Mazatmitla_, 6[29];
+_1/2 mi. NW Mazatmitla_, 4; _3 mi. WSW Mazatmitla_, 4; 2 mi. N Ciudad
+Guzman, 5000 ft., 18. GUANAJUATO: 4 mi. N, 5 mi. W Leon, 7000 ft., 25; 5
+mi. S Salamanca, 2[29]; _5 mi. E Celaya_, 6000 ft., 6; _1 mi. E Yuriria_,
+5725 ft., 3; Salvatierra, 5775 ft., 8; _NE edge Acambaro_, 6050 ft., 10;
+_Acambaro_, 3[30]. QUERETARO: Toliman, 7[30]; 6 mi. E Queretaro, 6550 ft.,
+37. HIDALGO: Tula, 2050 m., 1[31]. MICHOACAN: _2 mi. E La Palma, SE side
+Lago de Chapala_, 7; type locality, 4000 ft., 10[30] (including the
+type); _9 mi. E Zamora_ (_Camenaro_), 2[29]; _1 mi. S, 11 mi. W Zamora_,
+5400 ft., 17; S Cuitzeo, 36[29]; _Jiquilpan_, 4800 ft., 15; _11 mi. W
+Jiquilpan_, 6700 ft., 2; _1 mi. E Jiquilpan_, 7; _1 mi. E Zinapecuaro_,
+6300 ft., 17; _4-1/2 mi. NE Tarequato_ (_Tarecuato_), 6600 ft, 1;
+_Tanganciguaro_ (_Tangancicuaro_), 5500 ft., 4; _2 mi. N Tarecuato_,
+7200 ft., 1; _2 mi. S Maravatio_, 6650 ft, 6; _2 mi. SE Zacapu_, 6600
+ft., 11; _1 mi. N Tinquindin_ (_Tinguindin_), 6300 ft., 2; _3 mi. E
+Morelia_, 6600 ft., 3; _11 mi. E, 2 mi. S Morelia_, 1; 2 mi. SE Hidalgo
+(Villa Hidalgo), 6; _1-1/2 mi. N Los Reyes_, 1; _E Los Reyes_, 18[29];
+_Los Reyes_, 8[30]; _3 mi. W, 1 mi. N Patzucuaro_, 6600 ft., 2; _N
+Patzucuaro_, 2[29]; _Patzucuaro_ 9[31], 4[30], 4[29]; Uruapan, 1[29]; _E
+Uruapan_, 12; _2-1/2 mi. E Uruapan_ (_La Presca_), 2[29]; 2 mi. SW
+Zitacuaro, 1; 1 mi. E, 6 mi. S Tacambaro, 4000 ft., 11[37]; _La Huacana_,
+1[30]. MEXICO: Templo del Sol, Pyramides de San Juan, Teotihuacan, 8000
+ft., 1; _31 km. E Mexico City_, 7500 ft., 11[36]; _17 km. E Mexico City_,
+7500 ft, 1[36]; _Cerro La Caldera, 11 mi. ESE Mexico_, 2350 m., 5; 4 km.
+ENE Tlalmanalco, 2290 m., 9; _Hacienda Cordoba_ (_Cordova_), 6. MEXICO,
+D. F.: _Cerro de la Estrella, Ixtapalapa_, 2450 m., 1; _3/4 mi. S, 1 mi.
+E Churubusco_, 2400 m., 2; _5 km. S Mexico City, South of Cd.
+Universitaria_, l[32]; _Pedregal San Angel_, _2.6 mi. S Monumento a
+Obregon, 2_; _El Pedregal, 1 km. S San Angel_, 2260 m., 1; _Falda SW
+Cerro Zacatepec, 3.9 mi. SW Monumento a Obregon_, 1; _2 mi. N Tlalpan,
+Zacayuca_, 2380 m., 5; _Tlalpan_ (_Pedregal_), 2400 m., 21[31]; _San
+Geronimo_, 37[29], 6[38]; _Santa Rosa_, 2700 m., 1[32]; _Tlalpan_, 8; _3/4
+mi. SW Las Fuentes, Tlalpan_, 2450 m., 25[30]; _Tepepan_, 6[29]; _Rancho
+La Noria, 1 mi. W Xochimilco_, 2270 m., 4; _500 meters N Xochitepec_,
+2250 m., 7; 200 m. N San Mateo Xalpa (Jalpa), 2390 m., 2.
+
+_Marginal records._--SAN LUIS POTOSI: Hacienda Capulin; 1 mi. N
+Tamazunchale. HIDALGO: Tula, 2050 m. MEXICO: Templo del Sol, Pyramides
+de San Juan, Teotihuacan. VERACRUZ: Acultzingo. MEXICO: 4 km. ENE
+Tlalmanalco. MEXICO, D. F.: 200 m. N San Mateo Xalpa (Jalpa), 2390 m.
+MICHOACAN: 2 mi. SW Zitacuaro; 1 mi. E, 6 mi. S Tacambaro; Uruapan.
+JALISCO: 2 mi. N Ciudad Guzman; 27 mi. S, 12 mi. W Guadalajara; 13 mi.
+S, 15 mi. W Guadalajara; 7 mi. NW Tepatitlan; 1 mi. S Jalostotitlan,
+5700 ft. GUANAJUATO: 4 mi. N, 5 mi. W Leon. QUERETARO: 6 mi. E
+Queretaro, 6550 ft.; Toliman.
+
+[29] Univ. Michigan, Museum of Zoology.
+
+[30] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[31] Chicago Natural History Museum.
+
+[32] American Museum of Natural History.
+
+[33] Museum of Natural History, Louisiana State University.
+
+[34] Univ. Illinois, Mus. Nat. History.
+
+[35] The Museum, Michigan State Univ.
+
+[36] Texas A & M, Cooperative Wildlife Research Collection.
+
+[37] Univ. California, Mus. Vert. Zoology.
+
+[38] University of Florida Collections.
+
+
+=Baiomys taylori ater= (Blossom and Burt)
+
+    _Baiomys taylori ater_ Blossom and Burt, Occas. Papers Mus. Zool.,
+       Univ. Michigan, 465:2, October 8, 1942; Blair and Blossom, Contrib.
+       Lab. Vert. Biol., Univ. Michigan, 40:1, March, 1948; Hoffmeister and
+       Goodpaster, Ill. Biol. Monogr., 24(1):115, December 31, 1954; Miller
+       and Kellogg, Bull. U. S. Nat. Mus., 205:511, March 3, 1955;
+       Hoffmeister, Amer. Midland Nat., 55:281, April, 1956; Packard, Jour.
+       Mamm., 40:146, February 20, 1959; Hall and Kelson, The Mammals of
+       North America, 2:659, March 31, 1959 (part).
+
+    _Peromyscus taylori paulus_, Osgood, N. Amer. Fauna, 28:256, April
+       17, 1909 (part).
+
+    _Baiomys taylori_ [_ater_], Justice, Jour. Mamm., 38:520, November
+       20, 1957.
+
+_Type._--Adult male, skin and skull; No. 85425, University of Michigan,
+Museum of Zoology; 7 mi. W Hereford, Cochise County, Arizona, obtained
+on March 25, 1941, by Philip M. Blossom, original number 2195.
+
+_Range._--Southeastern Arizona, north to Graham County, thence east to
+the Animas Valley, Hidalgo County, New Mexico; south to northern
+Chihuahua and northwest to the southern border of Cochise County,
+Arizona, see Figure 11. Zonal range: largely lower Sonoran (Apachian
+Biotic Province of Dice, 1943:56). Occurs from 4300 feet in Chihuahua up
+to 6200 feet in New Mexico.
+
+_Diagnosis._--Size medium for the species; dorsum between Mummy Brown
+and Prouts Brown; individual tips of hairs intermixture of black and
+Ochraceous-Tawny, bases of all hairs slate-gray; sides of body and face,
+Buffy Brown to Cinnamon Brown; belly Cinnamon Buff, proximal half of
+individual hairs Deep Neutral Gray, distal half white; in region of
+throat, proximal fourth of individual hairs gray, distal three-fourths
+white; dorsal vibrissae black to base, ventral vibrissae white to base;
+tail brownish above, gray below; dorsal and ventral surface of forefeet
+and hind feet buffy to gray; interparietal somewhat compressed
+anteroposteriorly. Average and extreme cranial measurements of 15 adults
+from 9-1/2 mi. W New Mexico State Line, 5-1/2 mi. N Mexican border,
+Cochise County, Arizona, are as follows: occipitonasal length, 18.0
+(17.5-18.6); zygomatic breadth, 9.5 (9.2-9.9); postpalatal length, 6.6
+(6.0-7.1); least interorbital breadth, 3.6 (3.4-3.8); length of incisive
+foramina, 4.0 (3.8-4.2); length of rostrum, 6.1 (5.7-6.4); breadth of
+braincase, 8.6 (8.4-9.1); depth of cranium, 6.5 (6.3-6.9); alveolar
+length of maxillary tooth-row, 3.2 (3.1-3.4). Average and extreme
+external measurements for six adults from 9 mi. W Hereford, Cochise
+County, are as follows: total length, 106.3 (98-115); length of tail
+vertebrae, 42.3 (39-46); length of body, 64 (59-69); length of hind
+foot, 13.6 (13-14.2); length of ear from notch, 11.1 (10.5-11.5); for
+photographs of skull, see Plate 2_b_, and Plate 4_c_.
+
+_Comparisons._--For comparisons with _B. t. canutus_, see account of
+that subspecies. From _B. t. paulus_, the subspecies to the southeast,
+_B. t. ater_ differs in: dorsum darker brown; tail less strikingly
+bicolored; belly buffy rather than whitish to white-gray; forefeet and
+hind feet darker dorsally and ventrally; posterior margin of
+basioccipital bowed anteriorly in a broad U-shape with a secondary small
+median anteriorly directed U-shaped curve, rather than bowed anteriorly
+in a simple U-shape; interparietal more compressed anteroposteriorly;
+coronoid process of mandible so acutely recurved that tip of coronoid
+points posteroventrally and appears sickle-shaped.
+
+_Remarks._--Blossom and Burt (1942:1) described _B. t. ater_ as the
+darkest of the known subspecies. It is dark, but specimens from some
+parts of the ranges of _B. t. analogous_, _B. t. fuliginatus_, and _B.
+t. subater_ exceed in melanins the darkest individuals of _ater_. Blair
+and Blossom (1948:5) also concluded by the use of an Ives tint
+photometer that _B. t. subater_ was significantly darker than _B. t.
+ater_.
+
+When paratypes of _ater_ and specimens of _B. t. paulus_ are compared,
+the darkest individuals of _ater_ exceed but slightly the darkest of
+_paulus_. The darkest specimens of _paulus_ occur in southern Zacatecas,
+and northern Jalisco, and the palest of the series are in northern
+Durango and southern Chihuahua. When paratypes of _ater_ and _paulus_
+are compared, the difference in color is readily distinguishable.
+Specimens from 1-1/2 mi. N San Francisco, in northern Chihuahua, appear
+to be intermediate in color between _ater_ and _paulus_ except for a
+faint tinge of buff ventrally. In characters of the crania, these
+specimens resemble _ater_ and are referred to that subspecies. A
+slightly different pattern of color is present in pygmy mice from the
+Peloncillo Mountains and the Animas Valley of New Mexico; the upper
+parts resemble those of paratypes of _ater_, but the venter has only the
+faintest suggestion of the buffy wash. Crania of these specimens from
+New Mexico are inseparable from those of paratypes of _ater_, and the
+specimens are, therefore, referred to _ater_.
+
+When specimens are arranged by localities from Arizona east into
+southern New Mexico, thence south into Chihuahua and Durango, gradual
+intergradation in color is evident from dark in the north to pale browns
+in the south, whereas, size and shape of interparietal and size and
+shape of coronoid process of the lower jaw divide quite distinctly into
+two morphological types in central Chihuahua.
+
+Cranial variation in size and proportion among adults is slight
+throughout the range of _ater_ compared to variation detected in other
+subspecies of _Baiomys taylori_. Perhaps such a relatively stable
+pattern of characters of the crania reflects the homogeneity of the gene
+pool, with respect to these characters, of the populations sampled. The
+fact that the color of the pelage of this subspecies varies considerable
+throughout its known range and that the crania do not is perhaps a clue
+to the mode of inheritance of characters in these mice. Seemingly, color
+of pelage is inherited independently of characters of the cranium. The
+relative lack of variability in the crania of _ater_ may result from
+uniform environmental conditions, which have served to select for
+uniform characters in the populations. All of the other wide-ranging
+subspecies of _B. taylori_ occupy more diverse habitats than _ater_.
+Secondly, the rather abrupt change in the cline of measured characters
+of the crania between _ater_ and _paulus_ in central Chihuahua suggests
+a secondary zone of intergradation. The probable cessation of gene flow
+in the past between these two subspecies, allowing _ater_ to be isolated
+for a time, may also, in part, account for the relative lack of
+variability in the crania of _ater_.
+
+_Specimens examined._--Total 58, distributed as follows: ARIZONA:
+_Graham County_: 1-1/2 mi. SW Ft. Grant, Graham Mts., 1[39]; _Pima
+County_: 1-1/2 mi. ENE Greaterville, Thurber Ranch, 2[39]; _Santa Cruz
+County_: Patagonia, 3[39]; _Cochise County_: _9 mi. W Hereford_, 10[43];
+type locality, 2[43] (including the type); _5 mi. W Hereford_, 5[43];
+9-1/2 mi. W New Mexico State Line, 5-1/2 mi. N Mexican border, 20[42]; _3
+mi. E, 1 mi. N Chiricahua_, 1[42]. NEW MEXICO: _Hidalgo County_: 18 mi.
+S, 2 mi. W Animas, 2; _22 mi. S, 2 mi. W Rodeo_, 6000 ft., 1[40]; _22 mi.
+S, 2 mi. E Rodeo_, 6000 ft., 3[40]; 25-1/2 mi. S Animas, 6200 ft. (in Big
+Bill Canyon), 1[40]. CHIHUAHUA: _5-1/2 mi. N, 2 mi. W San Francisco_,
+5100 ft., 1; _2-1/2 mi. N, 3 mi. W San Francisco_, 5200 ft., 1; 1-1/2
+mi. N San Francisco, 5100 ft., 4; Casas Grandes, 4300 ft., 1[41].
+
+_Marginal records_--ARIZONA: 1-1/2 mi. SW Ft. Grant, Graham Mts. NEW
+MEXICO: 18 mi. S, 2 mi. W Animas; 25-1/2 mi. S Animas (in Big Bill
+Canyon). CHIHUAHUA: 1-1/2 mi. N San Francisco; Casas Grandes. ARIZONA:
+Patagonia; 1-1/2 mi. ENE Greaterville, Thurber Ranch.
+
+[39] University of Illinois, Museum of Natural History.
+
+[40] University of New Mexico.
+
+[41] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[42] University of Arizona.
+
+[43] Univ. Michigan, Museum of Zoology.
+
+
+=Baiomys taylori canutus=, new subspecies
+
+    _Peromyscus taylori paulus_, Osgood, N. Amer. Fauna, 28:255, April
+       17, 1909 (part).
+
+    _Peromyscus musculus_ [_musculus_], Osgood, N. Amer. Fauna, 28:256,
+       April 17, 1909 (part).
+
+    _Baiomys taylori paulus_, Miller, Bull. U. S. Nat. Mus., 79:137,
+       December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317,
+       April 29, 1924 (part); Burt, Miscl. Publ., Mus. Zool., Univ.
+       Michigan, 39:54, February 14, 1938; Goldman, Smith. Miscl. Coll.,
+       115:373, July 31, 1951 (part); Miller and Kellogg, Bull. U. S. Nat.
+       Mus., 205:512, March 3, 1955 (part); Hooper, Occas. Papers Mus.
+       Zool., Univ. Michigan, 565:13, March 31, 1955; Hall and Kelson, The
+       Mammals of North America, 2:659, March 31, 1959 (part).
+
+    _Baiomys musculus musculus_, Goldman, Smith. Miscl. Coll., 115:336,
+       July 31, 1951 (part).
+
+_Type._--Adult male, skin and skull; No. 62075, University of Kansas,
+Museum of Natural History; 1 mi. S Pericos, Sinaloa, Republic of Mexico;
+obtained on June 14, 1954, by A. A. Alcorn, original number 1754.
+
+_Range._--Central Nayarit northward through western Sinaloa, to as far
+north as south-central Sonora, see Figure 11. Zonal range: Lower arid
+tropical, closely approximating the Sinaloan Biotic Province of Goldman
+and Moore (1945:349). Occurs from near sea level at Escuinapa (43 feet),
+Sinaloa, to 3200 feet at a place 2 mi. WNW Tepic, Nayarit.
+
+_Diagnosis._--Dorsal ground color Buffy Brown (some specimens near Olive
+Brown); proximal fourth of individual guard hairs of dorsum
+black-tipped, distal three-fourths dark grayish; dorsal underfur
+black-tipped having subterminal band of Buffy Brown; hair around eyes
+buffy to base; belly Pallid Neutral Gray with overtones of buff;
+individual hairs in region of chin whitish-gray to bases; vibrissae
+blackish to bases except ventralmost, those being white to base; tail
+Dark Olive above, slightly paler below. Average and extreme external
+measurements of 13 adults from 15 mi. N Rosario, Chele, Sinaloa, 300
+ft., are as follows: Total length, 109.6 (99-120); length of tail, 43.4
+(38-49); length of body, 66.2 (58-75); length of hind foot, 11.2
+(10-12). Average and extreme cranial measurements of 19 adults from the
+same place are as follows: occipitonasal length, 18.2 (17.7-18.9);
+zygomatic breadth, 9.6 (9.2-10.1); postpalatal length, 6.9 (6.5-7.3);
+least interorbital breadth, 3.6 (3.4-3.8); length of incisive foramina,
+3.9 (3.5-4.2); length of rostrum, 5.9 (5.5-6.6); breadth of braincase,
+8.7 (8.3-8.9); depth of cranium, 6.5 (6.2-6.7); alveolar length of
+maxillary tooth-row, 3.1 (3.0-3.2); breadth of zygomatic plate, 1.8
+(1.6-2.0); for photographs of skull, see Plate 2_c_, and Plate 4_d_.
+
+_Comparisons._--From _B. t. ater_, _B. t. canutus_ differs in: dorsum
+slightly grayer; belly whitish to pale-gray with only faint tones of
+buff, rather than cinnamon-buff to buff-gray; forefeet and hind feet
+flesh-colored to grayish above instead of whitish to flesh-colored; tail
+paler above, less hairy, scales more evident; interparietal relatively
+larger from anteriormost to posteriormost points; incisive foramina
+tapering less abruptly posteriorly, not constricted towards midline;
+over-all size of body and cranium somewhat larger.
+
+From _B. t. paulus_, _B. t. canutus_ differs in: dorsum grayish-brown
+rather than fawn-colored (not differing appreciably from extremes of
+darker brown specimens of _paulus_); forefeet and hind feet
+flesh-colored to grayish above rather than white above; tail less
+hairy, unicolored to faintly bicolored rather than distinctly bicolored;
+braincase slightly larger; alveolar length of maxillary tooth-row
+slightly less.
+
+From _B. t. analogous_, _B. t. canutus_ differs in: dorsum paler, less
+of dark brown hues; belly paler; forefeet and hind feet slightly paler,
+less sooty above; tail less hairy, paler and having scales evident;
+jugal of zygoma extending ventrally to a point immediately above,
+instead of below, level of alveolus of upper molars; nasals more nearly
+truncate anteriorly; infraorbital foramina less deeply notched toward
+midline of skull; body and skull averaging smaller throughout.
+
+From _B. t. allex_, _B. t. canutus_ differs in: dorsal ground color
+grayish rather than fawn color having grayish overtones; underfur on
+dorsum darker gray; dorsal surface of forefeet and hind feet
+flesh-colored to grayish rather than flesh-colored; incisive foramina
+tapering to a point posteriorly rather than rounded posteriorly;
+interparietal relatively smaller; body and skull averaging larger
+throughout.
+
+_Remarks._--Burt (1938:54) reluctantly assigned specimens from Ciudad
+Obregon to _B. t. paulus_, probably being influenced by the resemblance
+in size. He suggested that, perhaps, a distinct subspecies occurs in the
+State of Sonora. Study of larger series of specimens than were available
+to Burt reveals that populations of pygmy mice inhabiting the northwest
+coastal plains of Mexico are indeed distinct.
+
+The darkest of the material assigned to _canutus_ is from Nayarit (for
+specific localities see specimens examined). According to Tamayo
+(1949:Carta de Suelos), color of soil changes from chestnut in northern
+Sinaloa to black in southern Sinaloa and northern Nayarit. There seems,
+therefore, to be a close correlation between color of pelage and color
+of soil in this area. In Nayarit, particularly in the central and
+southern parts, the mice are intermediate in color between the paler,
+grayer population to the north and the more brownish samples,
+representative of _allex_ to the south. The coastal vegetation changes
+from the arid tropical thorn forests of the north and central parts of
+Sinaloa to a savannah in Nayarit, thence to a tropical deciduous forest
+farther south (see Leopold, 1950:508).
+
+In size and color, specimens from 3 mi. SE Tepic and 2 mi. SW Rosa
+Morada are intermediate between the larger, grayer _canutus_ and the
+smaller, light-brownish _allex_. In size of cranium, these specimens are
+more nearly like _canutus_, and are referred to that subspecies. Mice
+from the western coastal plain are relatively homogeneous as regards
+size of body and skull, except that those from 13.5 mi. S Acaponeta,
+Nayarit, average somewhat larger.
+
+_B. t. canutus_, like _B. t. subater_, is predominantly a lowland or
+coastal subspecies. The pallor of the former, that lives on generally
+paler soils, presumably is of adaptive value.
+
+Pygmy mice are seemingly rare in the northern part of the range of this
+subspecies. J. Raymond Alcorn and Albert Alcorn were successful in
+collecting only two specimens from the type locality after three
+successive nights of trapping with 100 traps set each night. Only six
+specimens are known from Sonora. These were obtained in the irrigated
+regions of Ciudad, Obregon, and Navajoa. Charles Sibley obtained one
+specimen 10.6 mi. SE Ciudad Obregon in a "maguey field." I obtained one
+specimen 1 mi. NNW Navajoa in a sparse grassway, 20 feet wide, bordering
+an open sewer, which coursed northward into the Rio Mayo. Irrigated
+wheat fields bordered the grassway and ditch.
+
+_Specimens examined._--Total 70 all from the Republic of Mexico and
+distributed as follows: SONORA: [Ciudad] Obregon, 4[44]; 10.6 mi. SE
+[Ciudad] Obregon, 1[45]; 1 mi. NNW Navajoa, 1. SINALOA: type locality, 2
+(including the type); Culiacan, 175 ft., 2[46]; Mazatlan, 1[48]; _15 mi. N
+Rosario, Chele_, 300 ft., 35[47]; Rosario, 3[46]; Escuinapa, 5[48];
+_Railroad Station Escuinapa_, 43 ft., 2[45]. NAYARIT: Acaponeta, 4[46];
+_13.5 mi. S Acaponeta Junction_, 6[49]; 2 mi. SW Rosa Morada, 2; _2 mi.
+WNW Tepic_, 3200 ft., 1; 3 mi. SE Tepic, 1.
+
+_Marginal records._--SONORA [Ciudad] Obregon. SINALOA: type locality;
+Escuinapa. NAYARIT: Acaponeta; 3 mi. SE Tepic. SINALOA: Mazatlan.
+
+[44] Coll. Univ. California, Los Angeles.
+
+[45] Univ. California, Mus. Vert. Zoology.
+
+[46] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[47] Univ. Michigan, Museum of Zoology.
+
+[48] American Museum of Natural History.
+
+[49] Univ. Illinois, Mus. Nat. History.
+
+
+=Baiomys taylori fuliginatus=, new subspecies
+
+    _Baiomys taylori taylori_, Dalquest, Louisiana State Univ. Studies
+       (Biol. Sci. Ser.) 1:155, December 28, 1953 (part).
+
+    _Baiomys taylori taylori_, Booth, Walla Walla Publs. Dept. Biol.
+       Sci., 20:15, July 10, 1957 (part).
+
+_Type._--Adult male, skin and skull; No. 36765, University of Kansas,
+Museum of Natural History; 10 mi. E, 2 mi. N Ciudad del Maiz, 4000 ft.,
+San Luis Potosi, Republic of Mexico; obtained on January 17, 1950, by J.
+R. Alcorn, original number 10400.
+
+_Range._--Occurs in the Sierra Madre Oriental of the northeastern third
+of San Luis Potosi. Zonal range: Upper Tropical (see Dalquest, 1953:10);
+approximates a part of the Sierra Madre Oriental Biotic Province of
+Goldman and Moore (1945:349, 356). Occurs from 2000 feet at El Salto up
+to 4000 feet at Ciudad del Maiz.
+
+_Diagnosis._--Size large for the species; ground color of dorsum
+Chaetura Drab; individual guard hairs of dorsum black to base, distal
+fourth of hairs of underfur in posterior half of dorsum tipped with
+grayish-brown, proximal three-fourths Dark Neutral Gray; in anterior
+region of dorsum, posterior to ears, distal third of hairs grayish-brown
+and proximal two-thirds Dark Neutral Gray to base; sides slightly paler
+than dorsum; ground color of belly Neutral Gray, individual hairs of
+belly and throat tipped with Pallid Neutral Gray, basally Deep Neutral
+Gray to Dark Neutral Gray; tips of individual hairs of face
+Ochraceous-Tawny; lateral vibrissae whitish, dorsal and ventral
+vibrissae black to base; forefeet and hind feet sooty above and below,
+thigh bearing some white-tipped hairs; tail near Chaetura Drab above,
+Pale Neutral Gray below; anterior part of jugal projecting slightly
+ventrally and forming small protuberance at point of articulation with
+maxillary part of zygoma; jugal extending anteriorly nearly to lacrimal.
+In most cranial measurements averaging as large as _B. t. analogous_.
+Average and extreme measurements of the type and three additional
+paratypes, all adults, are: total length, 105.5 (101-109); length of
+tail, 39.8 (35-42); length of body, 65.8 (63-68); length of hind foot,
+14.3 (14-15); length of ear from notch, 11 (11); occipitonasal length,
+18.1 (18.1-18.8); zygomatic breadth, 9.6 (9.3-9.8); postpalatal length,
+6.5 (6.0-6.7); least interorbital breadth, 3.4 (3.3-3.6); length of
+incisive foramina, 4.0 (3.8-4.2); length of rostrum, 6.3 (6.1-6.4);
+breadth of braincase, 8.8 (8.6-8.9); depth of cranium, 6.7 (6.5-6.8);
+alveolar length of maxillary tooth-row, 3.2 (3.1-3.3); for photograph of
+skull, see Plate 2_d_, and Plate 4_e_.
+
+_Comparisons._--From _B. t. taylori_, _B. t. fuliginatus_ differs in:
+dorsum slightly darker than in darkest _taylori_; tail densely haired,
+bicolored rather than unicolored; belly sooty to grayish rather than
+grayish to whitish; forefeet and hind feet sooty to grayish rather than
+flesh-colored; incisive foramina less bowed laterally, more nearly
+straight; interparietal compressed anteroposteriorly, less
+diamond-shaped.
+
+From _B. t. paulus_, _B. t. fuliginatus_ differs in: dorsum dusky to
+blackish rather than fawn color; belly sooty to grayish rather than
+buffy to whitish-gray; forefeet and hind feet sooty to grayish rather
+than whitish; zygoma more nearly forming a right angle with rostrum or
+skull, less tapered anteriorly; anterior part of jugal possessing
+ventral projection; jugal extending nearly to lacrimal on posterior
+surface of maxillary part of zygoma.
+
+From _B. t. analogous_, _B. t. fuliginatus_ differs in: mid-dorsal
+region blacker, less brownish; tail distinctly bicolored rather than
+unicolored to faintly bicolored; incisive foramina not constricted
+medially; presphenoid broader (at narrowest point); jugal differs much
+the same as it does from _paulus_; nasals anteriorly truncate instead of
+rounded.
+
+_Remarks._--Dalquest (1953:155-157) and Booth (1957:15) assigned all of
+the pygmy mice that they examined from the state of San Luis Potosi to
+_B. t. taylori_. Examination of all of the material that was available
+to Dalquest, plus additional specimens at the University of Kansas
+Museum of Natural History, reveals that there are three subspecies in
+San Luis Potosi. _B. t. taylori_ occurs in the eastern part of the State
+at lower altitudes; _B. t. analogous_ occurs to the southeast at higher
+altitudes; _B. t. fuliginatus_ occurs in the northeastern part of the
+State in the Sierra Madre Oriental.
+
+Specimens obtained from Ebano, Pujal, and Tamuin, representative of _B.
+t. taylori_, are much paler on the belly and on the ventral surface of
+the forefeet and hind feet than are specimens from Ciudad del Maiz,
+representative of _B. t. fuliginatus_. The tail in _B. t. taylori_ is
+nearly unicolored and less hairy than in the paratypical series of
+_fuliginatus_. Specimens from 4 km. NE Ciudad Valles are nearly
+intermediate in color of the belly, dorsum, forefeet and hind feet, and
+tail, between the palest mice from the coastal plain and the darker mice
+in the mountains of the northeastern part of the State (specimens from
+El Salto average paler, however, than the type and paratypes). These
+specimens seem to be intergrades between _B. t. taylori_ to the east on
+the coastal plain and _fuliginatus_ to the northwest in the mountains.
+It seems best to refer the mice from 4 km. N Ciudad Valles to _B. t.
+taylori_ on the basis of the average of external and cranial characters.
+Specimens from 6 mi. SW San Geronimo, Coahuila, also referred to _B. t.
+taylori_, resemble in color the mice from 4 km. N Ciudad Valles. When
+more specimens are obtained from the front range of the Sierra Madre
+Oriental, at lower altitudes, the manner in which these two subspecies
+intergrade with one another will be better understood. At present,
+populations from higher altitudes in the mountains seem to represent a
+dark subspecies; populations from the coastal plain represent a pale
+subspecies, and those from the lower slopes and high valleys seemingly
+are intergrades. _B. t. fuliginatus_ occurs in a somewhat limited strip
+of chernozem soil (or suelos negros of Tamayo, 1949: Carta de Suelos).
+The populations occurring at lower altitudes on the coastal plain are on
+generally paler soils.
+
+_Specimens examined._--Total 39, all from the Republic of Mexico, as
+follows: SAN LUIS POTOSI: El Salto, 24 Mus. Nat. Hist., Louisiana State
+Univ., 7 Amer. Mus. Nat. Hist.; type locality, 8 (including the type).
+
+_Marginal records._--See specimens examined.
+
+
+=Baiomys taylori paulus= (J. A. Allen)
+
+    _Peromyscus paulus_, J. A. Allen, Bull. Amer. Mus. Nat. Hist.,
+       19:598, November 12, 1903; Elliot, Field Columb. Mus. Publ.,
+       105(6): 136, July 1, 1905.
+
+    _Baiomys taylori paulus_, Miller, Bull. U. S. Nat. Mus., 79:137,
+       December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317,
+       April 29, 1924 (part); Ellerman, The Families and Genera of Living
+       Rodents, 2:402, March 21, 1941 (part); Goldman, Smith, Miscl. Coll.,
+       115:373, July 31, 1951 (part); Hall and Kelson, Univ. Kansas Publs.,
+       Mus. Nat. Hist., 26:367, December 15, 1952; Goodwin, Bull. Amer.
+       Mus. Nat. Hist., 102:318, August 31, 1953; Miller and Kellogg, Bull.
+       U. S. Nat. Mus., 205:511, March 3, 1955 (part); Packard, Proc. Biol.
+       Soc. Washington, 71:17, April 11, 1958; Packard, Jour. Mamm.,
+       40:146, February 20, 1959; Hall and Kelson, The Mammals of North
+       America, 2:659, March 31, 1959 (part).
+
+    [_Peromyscus_] _paulus_, Elliot, Field Columb, Mus. Publ.,
+       95(4):136, July 15, 1904.
+
+    _Peromyscus taylori paulus_, Osgood, N. Amer. Fauna, 28:255, April
+       17, 1909 (part).
+
+    _Peromyscus musculus_ [_musculus_], Osgood, N. Amer. Fauna, 28:256,
+       April 17, 1909 (part).
+
+    _Baiomys taylori_ [= _paulus_], Twente and Baker, Jour. Mamm.,
+       32:121, February 15, 1951.
+
+    _Baiomys musculus musculus_, Goldman, Smith. Miscl. Coll., 115:336,
+       July 31, 1951 (part).
+
+    _Baiomys taylori allex_, Hall and Kelson, The Mammals of North
+       America, 2:659, March 31, 1959 (part).
+
+_Type._--Adult male, skin and skull; No. 21165, American Museum of
+Natural History; Rio Sestin, Durango, Republic of Mexico; obtained on
+April 15, 1903, by J. H. Batty, original number 455.
+
+_Range._--Central Chihuahua south through Durango (west to eastern edge
+of Sierra Madre Occidental), to Zacatecas and Aguascalientes, thence
+west into northern and northwestern Jalisco, see Figure 11. Zonal range:
+Lower Sonoran, approximately the Chihuahua Desert Biotic Province of
+Goldman and Moore (1945:349). Occurs from 4000 feet 2 mi. ESE Tequila,
+Jalisco, up to 6700 feet 2 mi. W Minaca, Chihuahua.
+
+_Diagnosis._--Size medium to small for the species; dorsum Buffy Brown
+to fawn color; dorsal ground color of unworn pelage of adults varying
+from Buffy Brown in darkest series (especially those from higher
+altitudes) to Avellaneous with grayish overtones in palest series; worn
+pelage in mid-dorsal region of adults fawn to grayish; terminal parts of
+individual hairs buffy, gray basally; guard hairs on dorsum
+black-tipped, grayish basally; belly Light Gull Gray, distal half of
+hairs white, proximal half Neutral Gray; hairs in region of throat and
+chin white to base (some specimens with faint buffy overtones); forefeet
+dusky below, whitish above; hind feet whitish above, ventral surface
+whitish to dusky; dorsal and lateral vibrissae black, other vibrissae
+white. Average and extreme measurements of six adults from the type
+locality are as follows: total length, 109 (106-117); length of tail,
+44.5 (43-48); length of body, 63 (57-69); length of hind foot, 13.1
+(12.7-14.0); occipitonasal length, 17.5 (17.4-18.0); zygomatic breadth,
+9.3 (9.1-9.5); postpalatal length, 6.6 (6.2-6.9); least interorbital
+breadth, 3.5 (3.4-3.6); length of incisive foramina, 3.8 (3.6-4.1);
+length of rostrum, 5.9 (5.7-6.0); breadth of braincase, 8.6 (8.5-8.8);
+depth of cranium, 6.6 (6.2-6.9); alveolar length of maxillary tooth-row,
+3.2 (3.1-3.4); for photographs of the skull, see Plate 2_e_ and Plate
+4_f_.
+
+_Comparisons._--For comparisons with _B. t. allex_, _B. t. canutus_, _B.
+t. ater_, and _B. t. taylori_, see accounts of those subspecies. From
+_B. t. analogous_, _B. t. paulus_ differs as follows: dorsal color paler
+having more reddish-brown than blackish-brown tones; venter whitish to
+buffy, instead of gray to light-gray; tail bicolored (not unicolored),
+usually having more hairs; hind feet white (not sooty) above. Cranially,
+_B. t. paulus_ differs from _B. t. analogous_ in: skull slightly smaller
+in all dimensions; maxillary part of zygoma narrowing and forming
+oblique angle rather than a near right angle with rostrum; anterior
+incisive foramina constricted posteriorly; tips of nasals truncate (less
+rounded).
+
+_Remarks._--J. A. Allen (1903:599) correctly pointed out that young
+specimens, in first pelage, were gray brown; young adults were darker
+and more varied with some blackish; adults and old adults were buffy to
+grayish. The change in color of pelage with increasing age is more
+pronounced in _paulus_ than in other subspecies of _B. taylori_. Of two
+males collected on April 12, 1949, one, an adult, is buffy brown, and
+the other, an old adult with worn pelage, is grayish-brown. In mice in
+the earlier stages of adulthood, underfur of the dorsum is buffy at the
+tips and gray basally. With increased wear, the buffy tip is lost.
+Consequently, mice in the later stages of adulthood are grayish.
+
+_B. t. paulus_ intergrades with _ater_ to the north in Chihuahua (see
+account of that subspecies), with _analogous_ to the south in Jalisco,
+and with _allex_ (see account of that subspecies) to the southwest in
+Nayarit and Jalisco. The zone of intergradation between _paulus_ and
+_analogous_ in Jalisco approximately borders the Rio Grande de Santiago
+from the western part of the State to the northwest shore of Lago de
+Chapala. Nineteen specimens from 2 mi. WNW Lagos de Moreno in northwest
+Jalisco seem to be intermediate between _paulus_ and _analogous_ in
+color, averaging slightly grayer than typical _paulus_. The series of 19
+is referable to _paulus_ on the basis of cranial characters.
+
+A series of 34 specimens from 3 mi. W La Venta, Jalisco (referable to
+_paulus_), is indistinguishable in color of pelage from two series of
+_paulus_ from 5 mi. N Durango, and from 8 mi. NE of Durango, except that
+the antiplantar surfaces of the hind feet are sooty as in _analogous_.
+Seemingly, features of color mentioned above as diagnostic of the two
+subspecies are either present or absent and there is no tendency toward
+intermediacy in color in the population from 3 mi. W La Venta.
+
+The Rio Grande de Santiago may have acted in the past as a physical
+barrier reducing gene flow between _allex_ and _paulus_ and in
+separating completely the two populations for limited periods.
+
+_Specimens examined._--Total 176, all from the Republic of Mexico and
+distributed as follows: CHIHUAHUA: Rancho Sanignacio, 4 mi. S, 1 mi. W
+Santo Tomas, 1; El Rosario, 6700 ft., 1; 2 mi. W Minaca, 6900 ft., 11;
+Balleza, 1[50]. DURANGO: Rosario, 1[51]; type locality, 14[51] (including
+the type); _San Gabriel_, 2[51]; _Rancho Santuario_, 2[51]; 1 mi. N
+Chorro, 6450 ft., 1; _8 mi. NE Durango_, 6200 ft., 2; 5 mi. N Durango,
+6400 ft., 2. ZACATECAS: Valparaiso, 6500 ft., 10[50]. AGUASCALIENTES: _18
+mi. W, 2 mi. S Aguascalientes_, 6000 ft., 1; 16 mi. S Aguascalientes,
+5[52]. JALISCO: 1 mi. NE Villa Hidalgo, 6500 ft., 1; 2 mi. WNW Lagos de
+Moreno, 6370 ft., 19; _2 mi. ESE Tequila_, 4000 ft., 11; _3 mi. W La
+Venta_, 33, 1[53]; _12 mi. W Guadalajara_, 3[54]; _Atemajac_, 12[50]; 4 mi.
+W Guadalajara, 5100 ft., 3; _2 mi. N, 1/2 mi. W Guadalajara_, 11; 2 mi.
+NW Magdalena, 4500 ft., 7[50]; _1 mi. N Tala_, 4400 ft., 3; 3 mi. W Tala,
+4300 ft., 18.
+
+_Marginal records._--CHIHUAHUA: Rancho Sanignacio, 4 mi. S, 1 mi. W
+Santo Tomas; El Rosario; Balleza. DURANGO: Rosario, 6700 ft.; 1 mi. E
+Zarca (Blossom and Burt, 1942:1); 1 mi. N Chorro, 6450 ft. ZACATECAS:
+Valparaiso, 6500 ft. AGUASCALIENTES: 1 mi. N Chicalote (Blossom and
+Burt, 1942:4). JALISCO: 2 mi. WNW Lagos de Moreno, 6370 ft.; 4 mi. W
+Guadalajara, 5100 ft.; 3 mi. W Tala, 4300 ft.; 2 mi. NW Magdalena, 4500
+ft. DURANGO: 5 mi. N Durango, 6400 ft.; type locality. CHIHUAHUA: 2 mi.
+W Minaca, 6900 ft.
+
+[50] United States National Museum (Biol. Surv. Collections).
+
+[51] American Museum of Natural History.
+
+[52] Univ. Illinois, Mus. Nat. History.
+
+[53] The Museum, Michigan State Univ.
+
+[54] Univ. Michigan, Museum of Zoology.
+
+
+=Baiomys taylori subater= (V. Bailey)
+
+    _Peromyscus taylori subater_, V. Bailey, N. Amer. Fauna, 25:102,
+       October 24, 1905; Lyon and Osgood, Bull. U. S. Nat. Mus., 62:139,
+       January 15, 1909; Osgood, N. Amer. Fauna, 28:255, April 17, 1909;
+       Elliot, Check-List Mamm. N. Amer. Continent, West Indies and
+       Neighboring Seas, Suppl., Amer. Mus. Nat. Hist, p. 44, January 8,
+       1917.
+
+    _Baiomys taylori subater_, Miller, Bull. U. S. Nat. Mus., 79:136,
+       December 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:317, April 29,
+       1924; Anthony, Field Book of North American Mammals, p. 348, 1928;
+       Baker, Jour. Mamm., 21:223, May 14, 1940; Ellerman, The Families and
+       Genera of Living Rodents, 2:402, March 21, 1941; Blair, Jour. Mamm.,
+       22:378, November 14, 1941; Poole and Schantz, Bull. U. S. Nat. Mus.,
+       178:259, March 6, 1942; Blair, Jour. Mamm., 23:196, May 14, 1942;
+       Blair and Blossom, Contrib. Lab. Vert. Biol., Univ. Michigan, 40:1,
+       March, 1948; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:511,
+       March 3, 1955; Hall and Kelson, The Mammals of North America, 2:659,
+       March 31, 1959.
+
+    _Baiomys taylori_ [= _subater_], Taylor and Davis, Texas Game, Fish
+       and Oyster Comm. Bull., 27:56, August, 1947 (part).
+
+_Type._--Subadult female, skin and skull; No. 32616/44539 U. S. Nat.
+Mus. (Biol. Surv. Coll.); Bernard Creek, near Columbia, Brazoria County,
+Texas; obtained on February 25, 1892, by W. Lloyd, original number 1122.
+
+_Range._--Southeastern Texas, north of Matagorda Bay west to Lavaca
+County, north to Brazos and Walker counties thence east to Jefferson
+County, see Figure 11. Occurs from near sea level in Brazoria and
+Galveston counties, up to 500 feet in western part of range. Zonal
+range: Humid division of lower Austral (the western part of the
+Austroriparian Biotic Province of Dice, 1943:18-21).
+
+_Diagnosis._--Size medium to large for the species; mid-dorsal region
+Clove Brown (sooty in freshly captured specimens); some parts of
+mid-dorsal region all blackish; individual guard hairs of dorsum
+black-tipped, Deep Neutral Gray basally; underfur black-tipped with
+subterminal band of light buff, Neutral Gray at base; belly
+grayish-white, laterally Isabella Color; distal three-fourths of hairs
+in region of throat and chin white, proximal fourth light gray; in
+median region of belly distal half of individual hairs white, proximal
+half dark gray; vibrissae in most specimens black to base. Average and
+extreme cranial measurements of six adults from 7 mi. S La Belle are as
+follows: occipitonasal length, 18.9 (17.5-19.4); zygomatic breadth, 9.6
+(9.1-9.9); postpalatal length, 6.8 (6.2-7.2); least interorbital
+breadth, 3.7 (3.4-3.9); length of incisive foramina, 4.0 (3.6-4.2);
+length of rostrum, 6.5 (6.1-6.8); breadth of braincase, 8.7 (8.3-8.9);
+depth of cranium, 6.7 (6.6-6.8); alveolar length of maxillary tooth-row,
+3.1 (2.9-3.2). Average and extreme external measurements of four adults
+from Richmond are as follows: total length, 111.5 (108-118); length of
+tail vertebrae, 43.5 (41-47); length of body, 68 (67-71); length of hind
+foot, 14 (13-15); for photographs of the skull, see Plate 2_f_, and
+Plate 4_g_.
+
+_Comparisons._--Because _B. t. subater_ intergrades only with _B. t.
+taylori_ to the south and west, _subater_ is compared only with
+_taylori_. Young adults of both subspecies in unworn pelage show best
+the colors that differentiate the two subspecies. Old adults of
+_subater_ in worn pelage appear grayish, resembling _taylori_, and at
+that age, only certain cranial characters are of taxonomic use.
+Cranially, _subater_ differs from _taylori_ in: presphenoid not shaped
+like an hour-glass; parapterygoid processes thicker medially;
+interparietal diamond-shaped instead of elongated and compressed. Skull
+slightly larger in most measurements.
+
+
+    [Illustration: PLATE 1
+
+    Photographs of skulls in dorsal view of _Baiomys_. x 2.
+
+    _a._ _B. m. brunneus_, [F] ad., 10834, AMNH, Jalapa, Veracruz.
+    _b._ _B. m. grisescens_, [F] ad., 257080, USNM, Comayabuela, Honduras.
+    _c._ _B. m. handleyi_, [F] ad., 275597, USNM, Sacapulas, Guatemala.
+    _d._ _B. m. infernatis_, [F] ad., 91499, MZUM, Teotitlan, Oaxaca.
+    _e._ _B. m. musculus_, [F] ad., 45462, USNM, Colima, Colima.
+    _f._ _B. m. nigrescens_, [M] ad., 76834, USNM, Comitan, Chiapas.
+    _g._ _B. m. pallidus_, [F] ad., 4802, Texas A & M, Axochiapan, Morelos.
+    _h._ _B. m. pullus_, [F] ad., 71608, KU, 8 mi. S Condega, Nicaragua.
+    _i._ _B. t. allex_, [F] ad., 45453, USNM, Colima, Colima.]
+
+
+    [Illustration: PLATE 2
+
+    Photographs of skulls (_a-g_) in dorsal view of _Baiomys_. x 2.
+
+    _a._ _B. t. analogous_, [F] ad., 120265, USNM, Zamora, Michoacan.
+    _b._ _B. t. ater_, [F] ad., 15056, UI, 1-1/2 mi. ENE Greaterville,
+          Arizona.
+    _c._ _B. t. canutus_, [F] ad., 62076, KU, 1 mi. S Pericos, Sinaloa.
+    _d._ _B. t. fuliginatus_, [F] ad., 36771, KU, type locality.
+    _e._ _B. t. paulus_, [F] ad., 40032, KU, 18 mi. W, 2 mi. S
+          Aguascalientes.
+    _f._ _B. t. subater_, [F] ad., 44543, USNM, type locality.
+    _g._ _B. t. taylori_, [F] ad., 57944, KU, 5 mi. E San Antonio, Texas.
+    _h._ Photo. of captive [M] _B. t. taylori_, 25 mi. E Austin, Texas.
+    x 1.]
+
+
+    [Illustration: PLATE 3
+
+    Photographs of skulls in ventral view of _Baiomys_. x 2.
+
+    _a._ _B. m. brunneus_, [F] ad., 10834, AMNH, Jalapa, Veracruz.
+    _b._ _B. m. grisescens_, [F] ad., 257080, USNM, Comayabuela, Honduras.
+    _c._ _B. m. handleyi_, [F] ad., 275597, USNM, Sacapulas, Guatemala.
+    _d._ _B. m. infernatis_, [F] ad., 91499, MZUM, Teotitlan, Oaxaca.
+    _e._ _B. m. musculus_, [F] ad., 45462, USNM, Colima, Colima.
+    _f._ _B. m. nigrescens_, [M] ad., 76834, USNM, Comitan, Chiapas.
+    _g._ _B. m. pallidus_, [F] ad., 4802, Texas A & M, Axochiapan, Morelos.
+    _h._ _B. m. pullus_, [F] ad., 71608, KU, 8 mi. S Condega, Nicaragua.]
+
+
+    [Illustration: PLATE 4
+
+    Photographs of skulls in ventral view of _Baiomys_. x 2.
+
+    _a._ _B. t. allex_, [F] ad., 45453, USNM, Colima, Colima.
+    _b._ _B. t. analogous_, [F] ad., 120265, USNM, Zamora, Michoacan.
+    _c._ _B. t. ater_, [F] ad., 15056, UI, 1 mi. ENE Greaterville, Arizona.
+    _d._ _B. t. canutus_, [F] ad., 62076, KU, 1 mi. S Pericos, Sinaloa
+    _e._ _B. t. fuliginatus_, [F] ad., 36771, KU, type locality.
+    _f._ _B. t. paulus_, [F] ad., 40032, KU, 18 mi. W, 2 mi. S
+          Aguascalientes.
+    _g._ _B. t. subater_, [F] ad., 44543, USNM, type locality.
+    _h._ _B. t. taylori_, [F] ad., 57944, KU, 5 mi. E San Antonio, Texas.]
+
+_Remarks._--This subspecies retains its chief diagnostic character,
+blackish mid-dorsal region, throughout nearly all parts of its range.
+Specimens from the general area of Matagorda Bay and Lavaca County grade
+into _taylori_ in characters of color and crania. The Colorado and
+Brazos rivers seemingly serve as barriers reducing gene flow between
+_taylori_ and _subater_. These rivers may well have been important
+factors in the origin and the limitation of these two seemingly
+closely-related subspecies.
+
+_Baiomys taylori subater_ is not differentiated in color of pelage and
+characters of crania from _B. t. taylori_ to the same degree that _B. t.
+paulus_ is differentiated from _B. t. analogous_, or that _B. t.
+taylori_ is differentiated from several of the other subspecies of
+_Baiomys taylori_. _B. t. subater_ probably is a more recent occupant of
+the area in which it now lives than is the case with any other one of
+the subspecies of _taylori_. Sufficient time probably has not elapsed to
+allow for formation of more distinctive phenotypic patterns.
+
+_Specimens examined._--Total 65, all from TEXAS and distributed as
+follows: _Brazos County_: 1/2 mi. NW College Station, 1[55]; _3 mi. W
+College Station_, _1 mi. W Easterwood Airport_, 1[55]; _College Station_,
+1[55]. _Walker County_: Huntsville, 1[55]. _Hardin County_: Sour Lake,
+1[57]. _Jefferson County_: 7 mi. S Labelle, 10. _Harris County_: 6 mi. NE
+Crosby, 1[56]. _Colorado County_: _10 mi. N Eagle Lake_, 1[55]; _9 mi. N
+Eagle Lake_, 1[55]; 2 mi. W Eagle Lake, 1; _Eagle Lake_, 1[55], 5. _Fort
+Bend County_: Richmond, 4[57]. _Galveston County_: _Texas City_, 6[58];
+Virginia Point, 1[57]. _Brazoria County_: _Austin Bayou near Alvin_,
+2[57]; 14 mi. SSE Alvin, 2[59]; type locality, 7[57] (including the type).
+_Lavaca County_: 4 mi. W Hallettsville, 1[55]; _1 mi. SW Hallettsville_,
+3[55]; _13.7 mi. SW Hallettsville_, 2[55]; 4 mi. NE Yoakum, 11.
+
+_Marginal records._--TEXAS: Huntsville; Sour Lake; 7 mi. S La Belle;
+Virginia Point; 14 mi. SSE Alvin; type locality; 4 mi. NE Yoakum; 4 mi.
+W Hallettsville; 1/2 mi. NW College Station.
+
+[55] Texas A & M, Cooperative Wildlife Research Collection.
+
+[56] Carnegie Museum.
+
+[57] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[58] Los Angeles County Museum.
+
+[59] American Museum of Natural History.
+
+
+=Baiomys taylori taylori= (Thomas)
+
+    _Hesperomys_ (_Vesperimus_) _taylori_ Thomas, Ann. Mag. Nat. Hist.,
+       ser. 5, 19:66, January, 1887.
+
+    _Baiomys taylori_ [_taylori_], Mearns, Bull. U. S. Nat. Mus.,
+       56:381, April 13, 1907; Stickel and Stickel, Jour. Mamm., 30:141,
+       May 23, 1949.
+
+    Baiomys taylori taylori, Miller, Bull. U. S. Nat. Mus., 79:136,
+       December 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:317, April 29,
+       1924; Anthony, Field Book of North American Mammals, p. 327, 1928;
+       Ellerman, The Families and Genera of Living Rodents, 2:402, March
+       21, 1941; Taylor and Davis, Texas Game, Fish and Oyster Comm. Bull.,
+       27:56, August, 1947 (part); Blair, Texas Jour. Sci., 2:104, March
+       31, 1950; Goldman, Smith. Miscl. Coll., 115:373, 426, July 31,
+       1951; Baker, Univ. Kansas Publs., Mus. Nat. Hist., 5:212, December
+       15, 1951; Blair, Texas Jour. Sci., 4:242, June 30, 1952; Hooper,
+       Occas. Papers, Univ. Michigan, Mus. Zool., 544:7, March 25, 1953;
+       Dalquest, Louisiana State Univ. Studies (Biol. Sci. Ser.), 1:155,
+       December 28, 1953 (part); Blair, Adv. in Genetics, 5:10, January 27,
+       1954; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:511, March 3,
+       1955; Baker, Univ. Kansas Publs., Mus. Nat. Hist., 9:273, June 15,
+       1956; Packard, Proc. Biol. Soc. Washington, 71:17, April 11, 1958;
+       Hall and Kelson, The Mammals of North America, 2:659, March 31, 1959
+       (part).
+
+    _Cricetus_ (_Vesperimus_) _taylori_, Thomas, Proc. Zool. Soc.
+       London, 68:446, November 20, 1888.
+
+    _Sitomys taylori_, Merriam, Proc. Biol. Soc. Washington, 7:170,
+       September 29, 1892.
+
+    _Sitomys_ (_Baiomys_) _taylori_, True, Proc. U. S. Nat. Mus.,
+       16(972):758, February 7, 1894; J. A. Allen, Bull. Amer. Mus. Nat.
+       Hist., 6:181, May 31, 1894.
+
+    _S._ [_itomys_] _taylori_, Rhoads, Proc. Acad. Nat. Sci.
+       Philadelphia, 46:256, October, 1894.
+
+    _Peromyscus_ (_Baiomys_) _taylori_, J. A. Allen, Bull. Amer. Mus.
+       Nat. Hist., 8:65, April 22, 1896.
+
+    [_Peromyscus_] _taylori_, Trouessart, Cat. Mamm., 1:517, 1898.
+
+    _Peromyscus taylori_ [_taylori_], Elliot, Field Columb. Mus. Publ.,
+       105(4):135, July 1, 1905; V. Bailey, N. Amer. Fauna, 25:101, October
+       24, 1905; Elliot, Field Columb. Mus. Publ., 115(8):203, 1907;
+       Osgood, N. Amer. Fauna, 28:253, April 17, 1909.
+
+_Type._--Adult male, skin and skull; No. 87.11.24.1, British Museum,
+Natural History; San Diego, Duval County, Texas; obtained by William
+Taylor.
+
+_Range._--North-central to southeastern Texas, excluding the coastal
+plain north of the region of Matagorda Bay, thence south into the
+southern part of Tamaulipas and west into Coahuila and Nuevo Leon, see
+Figure 11. Occurs from near sea level in Texas up to 1500 feet in
+Coahuila. Zonal range: mostly Lower Austral (in Mexico and southeastern
+half of Texas, the Tamaulipas Biotic Province of Goldman and Moore,
+1945:349, and Blair, 1952:230).
+
+_Diagnosis._--Size medium for the species; dorsum grayish in freshly
+taken specimens to Hair Brown in preserved specimens; individual guard
+hairs of dorsum black-tipped, grayish basally, underfur black-tipped
+with a subterminal band of olive-buff; sides of body pale-grayish near
+venter, individual hairs buffy proximally, grayish basally; belly pale
+grayish, individual hairs white-tipped, Pale Neutral Gray basally;
+throat and chin colored as is belly; forefeet and hind feet sooty-gray
+dorsally, sparsely-haired ventrally, thus appearing flesh-colored; tail
+unicolored gray to sooty-gray. Average and extreme cranial measurements
+of 22 adults from 6 mi. SW San Geronimo, Coahuila, are as follows:
+occipitonasal length, 18.0 (17.4-19.0); zygomatic breadth, 9.6
+(9.2-10.2); postpalatal length, 6.5 (5.9-7.1); least interorbital
+breadth, 3.6 (3.3-3.8); length of incisive foramina, 4.0 (3.6-4.3);
+length of rostrum, 6.1 (5.7-6.7); breadth of brain case, 8.8 (8.5-9.1);
+depth of cranium, 6.5 (6.0-7.0); alveolar length of maxillary tooth-row,
+3.1 (3.0-3.3). Average and extreme external measurements of 19 adults
+from 6 mi. SW San Geronimo are as follows: total length, 102.2 (95-115);
+length of tail vertebrae, 39.4 (21-46); length of body, 62.8 (53-76);
+length of hind foot, 14.0 (12-15); length of ear from notch, 10.7
+(10-12); for photographs of skull, see Plate 2_g_, and Plate 4_h_.
+
+_Comparisons._--For comparisons with _B. t. subater_, _B. t. analogous_,
+and _B. t. fuliginatus_, see accounts of those subspecies. From _B. t.
+paulus_, found to the southwest, _B. t. taylori_ differs as follows:
+dorsum grayish rather than fawn-colored; hairs on dorsal parts of
+forefeet and hind feet sooty-gray (not white to white-brown); venter
+gray to Light Drab-Gray, rather than whitish with gray overtones; tail
+unicolored instead of bicolored; skull averaging slightly larger
+over-all; maxillary part of zygoma forms right angle with rostrum rather
+than obtuse angle; incisive foramina extending posteriorly to anterior
+plane of first upper molars instead of to a transverse plane at middle
+of right and left first upper molars; bullae less inflated; interorbital
+region broader relative to length of skull; rostrum sloping gently from
+frontonasal suture to anterior tip of nasals rather than declining
+abruptly from frontonasal suture to anterior tip of nasals.
+
+_Remarks._--The geographic range of _taylori_ is relatively large, and
+the subspecies is locally variable. Nevertheless, none of the external
+and cranial measurements of specimens assigned to this subspecies
+differs significantly from the corresponding measurements of material
+from the type locality and adjacent areas in southeastern Texas. In
+southeastern Texas, south of the Guadalupe River, south to the coastal
+plain of Tamaulipas, this subspecies differs in color (being paler) from
+_B. t. subater_ with which _taylori_ might be confused. The foothills of
+the Sierra Madre Oriental in western Tamaulipas, north through Nuevo
+Leon and Coahuila, seem to mark the southwestern limit of the range
+assignable to _taylori_.
+
+On December 27, 1958, a specimen, KU 81552, was obtained 3 mi. N Bowie,
+Montague County, Texas. This record station extends the known range of
+_B. taylori_ 65 miles northward from the previous northernmost locality,
+listed by Hunsaker, Raun, and Swindells (1959:447). Two specimens, KU
+81553 and 81554, were collected by the author 2 mi. NE Cedar Hill,
+Dallas County, Texas, on October 31, 1958. These two specimens, plus the
+single specimen from Bowie County are all paler with more buffy bellies
+than either _B. t. taylori_ or _B. t. subater_. They may represent an
+incipient subspecies. I tentatively assign them to _B. t. taylori_
+because of the pale rather than dark (like _B. t. subater_) pelage.
+Additional specimens are needed from these areas and from the hiatus
+between the ranges of _B. t. taylori_ and _B. t. subater_ the better to
+understand the manner in which these two subspecies intergrade.
+
+Among named subspecies of _Baiomys taylori_, _B. t. taylori_ most
+closely resembles _B. t. subater_ to the north in Texas. Nine specimens
+examined from Yoakum are intergrades between _taylori_ and _subater_.
+These specimens have the sooty dorsal color of _subater_, but ventrally
+are inseparable from topotypes of _taylori_. In length of body and
+tail, specimens from Yoakum are like _subater_, but in length of hind
+foot, they are intermediate between the two subspecies. Cranially, they
+are like _subater_. When all characters are considered, the specimens
+are best referred to _subater_. Bailey (1905:103) suggested that
+specimens from the southern part of the range, which he ascribed to
+_subater_, tended to a more grayish color than topotypes of _subater_,
+therefore, grading into _taylori_. The zone of intergradation runs from
+Matagorda Bay northwest through Lavaca County, thence north to the
+Colorado River, and closely follows the boundary between the Lower
+Austral and Humid Division of Lower Austral Life-zone as plotted by
+Bailey (_loc. cit._). Findley (1955:44) pointed out that where two
+life-zones meet, the resulting populations of shrews are mostly
+intergrades. Such is the case between these two subspecies of _Baiomys
+taylori_ in an area where life-zones might seem less important than in
+the mountainous west.
+
+In the southern part of the range of _taylori_, intergradation occurs
+between _B. t. taylori_ in western Tamaulipas and _B. t. fuliginatus_ in
+the mountains of San Luis Potosi.
+
+Dalquest (1953:156) found no indication of intergradation between the
+two species, _B. taylori_ and _B. musculus_, in San Luis Potosi. After
+examination of specimens from San Luis Potosi, I am in agreement that
+they are all referable to the species _taylori_.
+
+_Specimens examined._--Total 435. TEXAS: _Montague County_: 3 mi. N
+Bowie, 1. _Dallas County_: 2 mi. NE Cedar Hill, 2. _Travis County_:
+8 mi. NW Austin, 2[60]; _Austin_, 2[60]; _4 mi. E Austin_, 4[60];
+_5 mi. E Austin_, 3[60]; _6 mi. E Austin_, 16[60], 1; _7 mi. E Austin_,
+1[60]; _15 mi. E Austin_, 1[60]; _4 mi. S Austin_, 1[60]. _Bastrop
+County_: 25 mi. E Austin, 2. _Kendall County_: Boerne, 1[61].
+_Bexar County_: _1 mi. N Randolph Field_, 3[64]; _5 mi. ENE_
+(_on U. S. Highway 81_) _San Antonio_, 1; _3 mi. NE San Antonio_, 1;
+San Antonio, 26[61], 11[62], 1[63]; _5 mi. E San Antonio_, 11;
+_4-1/2 mi. E Sayers_, 3. _Gonzales County_: 7 mi. S Luling, 2[60].
+_Wilson County: 4 mi. W LaVernia_, 3; 12 mi. W Floresville, 1.
+_Atascosa County_: 9 mi. SW Somerset, 1. _Goliad County_: 8 mi.
+NE Goliad, 1[60]. _Bee County_: Beeville, 1[61]. _Aransas County_:
+Aransas (Wildlife) Refuge, 1[65]; _5 mi. E Copana Bay_, 1[65];
+_4.6 mi. NE Rockport_, 5[60]; _4.5 mi. NW Rockport_, 2[60]; 3 mi. N,
+2 mi. E Rockport, 4; _Rockport_, 1[60], 1[61], 1[63]; _1-1/2 mi.
+SW Rockport_, 1[60]; _2 mi. SW Rockport_, 2[60]; _13.4 mi. SW Rockport_,
+1[60]; _14 mi. SW Rockport_, 1. _San Patricio County_: Welder Wildlife
+Refuge, 7. _Duval County_: type locality, 2[61], 1[66]. _Nueces County_:
+Corpus Christi (south Nueces Bay), 1[64] (Cleveland Mus. Coll.). _Kleberg
+County_: 2 mi. S Riviera, 3[65]. _Brooks County_: 3 mi. S Falfurrias,
+2[65]. _Hidalgo County_: 6 mi. S McAllen, 17[60]. _Willacy County_: 28 mi.
+E Raymondville, 10[65]. _Cameron County_: Brownsville, 31[61], 23[62],
+5[64]. COAHUILA: 6 mi. SW San Geronimo, 32. NUEVO LEON: Santa Catarina,
+1[61]; 14 mi. N Monterrey, 1950 ft., 2[67]; Monterrey, 1[61]; 20 km. N
+General Teran, 3[64]. TAMAULIPAS: _Near Headwaters Rio Sabinas, 8 km. W,
+10 km. N El Encino_, 400 ft., 1; Camargo, 5[61]; Charco Escondido, 20 mi.
+S Reynosa, 3[67]; Matomoras, 5[61]; _Ejido Santa Isabel, 2 km. W
+Inter-American Highway_, 2000 ft., 7; Hidaglo, 7[61]; _Hda. Station
+Engracia_, 4[63]; 4 mi. N La Pesca, 1; 29 mi. N Ciudad Victoria, 1[67];
+Ciudad Victoria, 6[61], 3; Jaumave, 2400 ft., 6[64], 10; Sierra de
+Tamaulipas, 3[64]; _25 mi. N El Mante, 3 km. W Inter-American Highway_
+(_on Rancho Pano Ayuctle_), 300 ft., 4; _6 mi. N Gomez Farias_ (_on
+Rancho Pano Ayuctle_), 1; _5 mi. NE Gomez Farias_, 12[64], 1[62]; 70 km.
+(by highway) S Ciudad Victoria, 2 km. W El Carrizo, 5[62], 2; Antigua
+Morelos, 5[64]; _6 mi. N, 6 mi. W Altamira_, 31; _5 mi. N, 5 mi. W
+Altamira_, 4; _Alta Mira_ (_Altamira_), 2[61]; 1 mi. S Altamira, 6; _10
+mi. NW Tampico_, 1. SAN LUIS POTOSI: Ebano, 5[68]; _4 km. NE Ciudad
+Valles_, 1; Ciudad Valles, 1; _3 km. W Tamuin_, 1[68]; _Tamuin_, 6[68];
+_Pujal_, 300 m., 1[64]. VERACRUZ: Tampico Alto, 50 ft., 1; Potrero Llano,
+350 ft., 1; Ozulama, 2; Cerro Azul, 350 ft., 1.
+
+_Marginal Records._--TEXAS: 3 mi. N Bowie; 2 mi. NE Cedar Hill; 25 mi. E
+Austin; 7 mi. S Luling; 8 mi. NE Goliad; Aransas (Wildlife) Refuge; 3
+mi. N, 2 mi. E Rockport; Corpus Christi (South Nueces Bay); 2 mi. S
+Riviera; 28 mi. E Raymondville; Brownsville. TAMAULIPAS: Matomores; 4
+mi. N La Pesca; 1 mi. S Altamira. VERACRUZ: Tampico Alto; Ozulama; Cerro
+Azul; Potrero Llano. SAN LUIS POTOSI: Ciudad Valles. TAMAULIPAS: Antigua
+Morelos; 70 km. S Ciudad Victoria, 2 km. W El Carrizo; Jaumave; Hidalgo.
+NUEVO LEON: 20 km. N General Teran; Santa Catarina. COAHUILA: 6 mi. SW
+San Geronimo. TEXAS: 9 mi. SW Somerset; Boerne; 8 mi. NW Austin.
+
+[60] Coll. University of Texas.
+
+[61] U. S. Nat. Museum (Biol. Surv. Coll.).
+
+[62] American Museum of Natural History.
+
+[63] Chicago Natural History Museum.
+
+[64] Univ. Michigan, Museum of Zoology.
+
+[65] Texas A & M Coop. Wildlife Res. Coll.
+
+[66] Carnegie Museum.
+
+[67] Univ. California, Mus. Vert. Zool.
+
+[68] Museum of Natural History, Louisiana State University.
+
+
+
+
+EVOLUTION AND SPECIATION
+
+
+The history of the genus dates back to the early late Pliocene, but
+morphological change since then has been slight insofar as can be judged
+from lower jaws. _Baiomys_ seems to have been relatively conservative
+also in types of habitat occupied.
+
+According to Wilson (1937:59), the late Pliocene was a time of decided
+expansion of myomorph rodents, more particularly cricetines.
+Furthermore, at this time, the climate in the interior basin of
+southwestern North America presumably was becoming arid, if we can judge
+from the spread of elements of the Madro-Tertiary flora. Axelrod
+(1950:266) points out that the drier, continental climate initiated in
+the early Tertiary probably had its culmination in middle Pliocene time.
+Some floras of early late Pliocene of the southwestern United States
+reflect a climate slightly cooler and more moist than the climates of
+the middle Pliocene. However, late Pliocene times reflect an arid
+climate. The flora of the southwestern interior basin of North America
+in early late to late Pliocene was intermediate between the previous
+grassland floras of the middle Pliocene and the savannah flora of upper
+Pliocene. Axelrod (_loc. cit._) suggests that this intermediate flora of
+the interior basin of southwestern North America resulted from the
+folding of the Cascades and uplifting of the Sierra Nevada and
+Peninsular ranges to the south. The development of these mountains
+produced greater aridity to the lee of the mountains, thus accounting
+for the grassland-savannah flora. Pygmy mice probably originated in that
+time, I judge in Mexico, and moved northward and southward in a
+grassland-savannah habitat that seemingly existed as far north as what
+is now Meade County, Kansas (where the Sawrock fauna lived). Further
+evidence for occupancy of a grassland-savannah habitat by ancestral
+pygmy mice stems from the distribution of the living species, _B.
+taylori_, that at present occupies territory adjacent to parts of the
+Sonoran and Chihuahuan deserts. _B. taylori_ seems to be morphologically
+more specialized for life in an arid grassland than was _B.
+sawrockensis_.
+
+The geographic range of ancestral pygmy mice possibly extended farther
+south in late Pliocene time than the range of _B. musculus_ does now.
+Anyhow, _B. sawrockensis_ of the early late Pliocene dwelt in a more
+mesic type of habitat than _B. musculus_ does, and such habitat may have
+existed from the Pacific lowlands of Central America to the Caribbean
+lowlands of northern South America (see Duellman, 1958:136, and Dunn,
+1940:156) during late Pliocene times. An ancestral stock of hesperomine
+mice, not greatly different from _Baiomys_, may have emigrated from the
+North American continent into South America across the continuous land
+connection, which Simpson (1950:395) suggests was formed in the
+Chapadmalalan age (= Blancan age of North American terminology). The
+length of time of interchange of genes between northern and southern
+populations of mice across the Central American land connection probably
+was brief. Duellman (_op. cit._:129) pointed out that once the
+Panamanian portal was closed, the warm counter equatorial current, El
+Nino, combined with the uplifting of the Andes, began to produce heavy
+rain forests in Central America and northern South America in late
+Pliocene or early Pleistocene times. These forests presumably isolated
+the stock in North America from that in South America where the latter
+probably evolved rapidly into kinds that differed from one another and
+from _Baiomys_ in shape of body, type of pelage, and shape of skull.
+Internal structures such as hyoid apparatus, auditory ossicles, and
+baculum remained almost unchanged, as for example in _Calomys_ now
+living in South America. The present resemblance in internal
+morphological features between it and _Baiomys_, I judge, reflects
+taxonomic relationships more accurately than do shape and conformation
+of body and skull that seem to respond more rapidly to external
+environmental changes. The cranial characters distinguishing _Baiomys
+musculus_ from _Calomys laucha_ are as follows: posterior lacerate
+foramina between second, rather than first, upper molars; parapterygoid
+fossa shallower; mesopterygoid fossa as wide or wider, instead of
+narrower, than parapterygoid processes; burr for attachment of
+superficial masseter muscle hypertrophied instead of well-developed. In
+other cranial characters studied, the two genera closely resemble each
+other. Such similarities of crania between _Calomys_ and _Baiomys_ may
+reflect convergence, but the total of internal and external
+morphological characters shared, I think reflects true relationships.
+
+_Peromyscus_ has a large number of living and extinct species and
+exhibits a wide range of morphological variation, whereas _Baiomys_ has
+a small number (7) of species and exhibits a narrow range of
+morphological variation. The small number of known species of pygmy mice
+suggests their conservatism in elaboration of morphological characters.
+Possibly this is because the habitat, or even the ecological niche,
+occupied in geological time by these mice was restricted, geographically
+and in kind. If the habitat of the pygmy mice oscillated between
+savannah and arid grassland, then an hypothesis can be made possibly
+accounting for the origin of species of these mice. My idea is that the
+geographical distribution of _Baiomys_ today reflects a predilection on
+the part of these mice for a relatively uniform warm climate. Therefore,
+in the past, in times of warmer continental climate, these mice moved
+toward favorable habitat northward from an area in central and northern
+Mexico. In cooler periods, the mice moved southward as habitats to the
+north became unfavorable.
+
+Dr. W. B. Davis (_in. litt._) informs me that _B. taylori_ was uncommon
+in Brazos County, Texas, approximately 15 years ago, and suggests that
+the abundance there now of this mouse and my taking it in 1958 northward
+nearly to the southern border of Oklahoma reflects a definite movement
+northward. Movement in the same direction in late years has been
+suggested for the nine-banded armadillo and the hispid cotton rat (Hall,
+1959:373) that are associated with warm climates to the south. These
+movements possibly reflect only minor fluctuations of climate, but in a
+long period of warmth movements northward would be expected to be
+pronounced and extensive.
+
+Extinct species of _Baiomys_ may have originated as a result of
+extension northward of the geographical range and subsequent retreat
+southward of the northern populations, as follows: (1) the range of the
+genus moved northward in a warm period; (2) in cooler times, most of the
+mice in the north disappeared and only isolated colonies remained in
+small patches of remaining habitat still favorable to the mice; (3) the
+small populations of isolated pygmy mice after a time changed through
+mutations, recombinations and subsequent selection to a degree that
+prevented crossbreeding once populations from the south again moved
+northward and came in contact with previously isolated stocks; (4) then
+competition caused further divergence in morphological characters. Such
+an hypothesis would account for the morphological differences between
+the extinct _B. kolbi_ and _B. rexroadi_. The extinct _B.
+brachygnathus_, presumably a dweller of a xerophytic grassland, may have
+had its origin from a _B. minimus_-like stock in the manner outlined.
+
+
+FORMATION OF THE RECENT SPECIES
+
+The morphological difference between the extinct _B. minimus_ and the
+living _B. musculus_ is not great, and musculus seems to be the product
+of the _B. sawrockensis-B. minimus_ line of development. Morphological
+characters of the parental stock of the two living species, _musculus_
+and _taylori_, may have been intermediate between those of _B. minimus_
+and those of _B. musculus_. The principal part of the range of _Baiomys_
+today is in Mexico, and probably was there through much of Pleistocene
+time. Extension northward of the species and retreat southward of those
+northern populations of pygmy mice would not only have left isolated
+populations in the north, but would have allowed the mice that retreated
+south to share a common gene pool. Therefore, populations of pygmy mice
+occurring to the south in central Mexico might be expected to maintain a
+relatively high degree of heterozygosity in morphological and behavioral
+characters. The occurrence of any physical or biotic barrier that would
+have separated this homogeneous group would be conducive to speciation.
+There is evidence that a barrier occurred in the Pleistocene in central
+Mexico sufficient to separate the supposed interbreeding, relatively
+homogeneous populations of pygmy mice. According to Sears (1955:529) and
+De Terra _et al_. (1949:51), parts of the higher regions in the Valley
+of Mexico, and the transverse volcanic zone in central Mexico were
+glaciated. On the mountain Ixtaccihuatl, De Terra (_op. cit._:52) found
+evidence of four marked advances of ice, from oldest to youngest, as
+follows: Salto, ice advanced to 3100 meters; Xopano, ice at 3200-3300
+meters; Trancas, ice to 3400 meters; Ayolotepito, ice to 4350 meters.
+The Salto advance is correlated by De Terra (_loc. cit._) with the Iowan
+glacial period. The advance of ice down the mountain sides in the
+transverse volcanic zone was accompanied by cool moist climates or
+pluvial periods. Such climates probably altered habitat formerly
+suitable for _Baiomys_. There is no record of _Baiomys_ known to me
+exceeding 8000 feet in elevation, although the lower edge of the ice on
+Ixtaccihuatl is at approximately 15,300 feet (4600 meters, Sears, _loc.
+cit._). Presumably, the advance of ice down the mountains forced the
+pygmy mice to move to lower altitudes. Pluvial conditions possibly
+rendered the habitat even at lower altitudes uninhabitable for the mice,
+with the result that none continued to live in the transverse volcanic
+zone, but only north and south thereof. Long-continued separation of
+these northern and southern segments allowed species formation to occur.
+As climatic and habitat conditions became more favorable in central
+Mexico, the two species moved back toward each other, and eventually
+their geographic ranges overlapped.
+
+An analysis of external and cranial characters of pygmy mice (see Figure
+12) reveals that both species are essentially largest to the north and
+smallest to the south. There are exceptions to this cline in both
+species. For example, _B. taylori analogous_ is a large subspecies; it
+lives allopatrically in the southern part of the range of the species.
+_B. musculus pallidus_ is not the largest subspecies; it lives
+allopatrically in the northern part of the range of the species. In
+west-central Mexico, where the two species are sympatric, _B. taylori_
+is smaller than elsewhere and _B. musculus_ is larger than elsewhere.
+_B. t. analogous_ lives in the mountains of the transverse volcanic zone
+in central Mexico. Its large size may be a result of the cooler climate
+in the mountains. _B. t. allex_, the smallest subspecies, lives
+sympatrically with _B. musculus musculus_ at lower elevations in
+west-central Mexico. The small size of _allex_ could be a result of the
+warmer climate of the lower elevations. _B. m. pallidus_, at lower
+elevations in southern Oaxaca, is smaller than other subspecies of
+_musculus_ to the south at higher elevations. _B. m. musculus_ lives at
+low elevations along the coast of west-central Mexico. Unlike _B. m.
+pallidus_, _B. m. musculus_ is large at lower elevations. It occurs
+sympatrically with _B. t. allex_. It is my idea that during the period
+of separation, when the two species were evolving, larger subspecies
+evolved to the north or at higher altitudes where climates were cooler;
+smaller subspecies evolved to the south or at lower elevations; the two
+cognate species, _musculus_ and _taylori_, made contact at lower
+elevations where individuals of _taylori_ may have been smallest, but
+individuals of _musculus_ were not the largest of the species. The
+differences, therefore, between the two species in their initial contact
+probably were slight. Hybrids, if they occurred, were probably
+inviable, sterile, or ill-suited for occupancy of the habitat of either
+of the parental stocks. The occurrence of hybrids, therefore, would
+result in what geneticists call "gamete wastage," and any further
+divergence in the parental stock, either in external characters (size
+and shape of body and head), or behavior, useful in recognition of
+species, would be favored by natural selection (see Dobzhansky,
+1951:225; and Koopman, 1950:147). The two species seem to have diverged
+more in external characters where they occur together than in areas
+where they live separately (see Figure 12). The two species could be
+confused if a sample of adults of _taylori_ from 7 mi. S La Belle,
+Jefferson County, Texas, were compared to a sample of adults of
+_musculus_ from Tehuantepec, Oaxaca (see Figure 12). No confusion in
+species identity would arise, however, if a sample of adults was taken
+from the area where the two species live together (see Figure 12). Brown
+and Wilson (1956:49) pointed out that where two closely related species
+occur together, characters (morphological, ecological, physiological, or
+behavioral) of each species are easily distinguished. However, where the
+two species are allopatric, the two closely related species so resemble
+one another that the species are not easily distinguished. This
+phenomenon has been called "character displacement" by Brown and Wilson
+(_loc. cit._).
+
+In the area where the two species of pygmy mice occur together, there
+seems to be a disparity in numbers between them. Hooper (1952a:91) has
+recorded the collection of both _B. musculus_ and _B. taylori_ in a
+single trap line. A series of pygmy mice collected from San Gabriel,
+Jalisco, contained one _taylori_ and 33 _musculus_; another sample from
+La Resolana, Jalisco, had a ratio of 25 _taylori_ to 6 _musculus_. The
+disparity in numbers where the two species occur together has been
+further substantiated by collections of the University of Kansas.
+Possibly this disparity in numbers is a result of interspecific
+competition. Hooper (_op. cit._:90) pointed out that where the range of
+_B. musculus_ (typical of arid tropical lowlands) meets that of _B.
+taylori_ (typical of arid temperate highlands), the two geographic
+ranges interdigitate with parts of the range of _musculus_ extending
+into the highlands and parts of the range of _taylori_ extending into
+the lowlands. In the lowlands, _musculus_ may be better adapted to
+environmental conditions and, therefore, more successful in competition
+with _taylori_ for available habitat. The reverse situation may exist in
+the highlands. Also, the fact that _musculus_ is more of a diurnal
+animal than is _taylori_ may account for the difference in numbers of
+individuals of the two species taken in trap lines. Many collectors set
+their traps in late afternoon or evening and retrieve them in early
+morning. Such a schedule might not yield many _musculus_. If
+interspecific competition does occur in the area where the two species
+occur, any change in habits or microhabitat by either species that would
+reduce this competition would be favored by natural selection (see Mayr,
+1949:518; Lack, 1944:262-263; and Brown, 1958:154-155). Brown (_op.
+cit._:154), as I understand him, pointed out (taking account of Gause's
+principle) that when two species having similar ecological valences move
+into the same niche in the same locality, one of three things must
+eventually happen: (_a_) the two species occupy different geographic
+ranges; (_b_) they compete and one is eventually eliminated; (_c_) the
+two species, because of differentiation or specialization, exploit
+different aspects of the niche. In _Baiomys_, (_c_) seems to apply.
+Natural selection probably would favor a continuation of diurnal
+activity in _musculus_ and nocturnal activity in _taylori_, thereby
+preventing frequent meeting of the two species.
+
+
+AREAS OF PRESENT DIFFERENTIATION
+
+In both species of _Baiomys_, the most distinct subspecies, _B. t.
+allex_ and _B. m. musculus_, occur in the area where the two species are
+sympatric. Seven subspecies, or 44 per cent, occur either in or adjacent
+to the transverse volcanic zone. This area is the major area of active
+differentiation. Incipient subspecies are also evident in these areas. A
+secondary area of differentiation is indicated within the range of _B.
+musculus_ in Guatemala, El Salvador and Honduras. Three subspecies occur
+in this area (_grisescens, handleyi_ and _nigrescens_) and incipient
+subspeciation is in evidence there.
+
+
+ZOOGEOGRAPHIC POSITION
+
+Hooper (1949:25) regards _Baiomys_ as a member of the rodent fauna of
+the arid, western Sonoran region, whereas Hershkovitz (1958:609)
+suggests that _Baiomys_ is a nearctic-neotropical varicant (a kind that
+occurs in contiguous zoogeographic regions without our knowing in which
+region the taxon originated). The findings from my study do not
+contradict either of the above suggestions. Because of the close
+resemblance of _Baiomys_ to certain hesperomine mice of South America,
+it is postulated that _Baiomys_, in more primitive form than now,
+occurred farther south in past times than it does now. Fossils show that
+primitive stocks of the genus in late Pliocene or early Pleistocene
+times occurred also north of the present range of the genus. The belt in
+west-central Mexico between nearctic and neotropical regions is the
+current center of distribution of the genus and probably has been for a
+considerable time.
+
+    [Illustration:
+
+    FIG. 12. Averages of the occipitonasal lengths of skulls of adults
+       at 19 localities of occurrence (solid symbols) of _Baiomys taylori_,
+       and at 17 localities of occurrence (open symbols) of _Baiomys
+       musculus_. Note that the occipitonasal length decreases from north
+       to south in each of the two species, and that in the region where
+       the two species occur together, west-central Mexico, _B. taylori_
+       is smallest and _B. musculus_ is largest. Average, extremes, number
+       of specimens averaged (in italic type), and name of locality, from
+       north to south for each species, are as follows:
+
+    _Baiomys taylori_
+
+    18.0  (17.5-18.6)  _15_, 9-1/2 mi. W New Mexico state line, Ariz.
+    18.9  (18.2-19.4)   _6_, 7 mi. S. La Belle, Jefferson Co., Texas.
+    18.2  (17.8-18.5)  _10_, San Antonio, Bexar Co., Texas.
+    18.2  (18.0-18.5)   _5_, 2 mi. W Minaca, Chihuahua.
+    18.0  (17.6-19.0)  _22_, 6 mi. SW San Geronimo, Coahuila.
+    18.2  (18.1-18.3)   _3_, Ciudad Obregon, Sonora.
+    18.1  (17.4-18.5)   _5_, vic. (see p. 649) Durango, Durango.
+    18.1  (17.5-18.5)   _9_, Jaumave, Tamaulipas.
+    18.2  (17.7-18.9)  _19_, 15 mi. N Rosario Chele, Sinaloa.
+    17.9  (17.4-18.3)  _27_, vic. (see p. 655) Altamira, Tamaulipas.
+    18.3  (17.9-18.7)   _9_, Valparaiso, Zacatecas.
+    18.1  (18.1-18.2)   _4_, Ciudad del Maiz, San Luis Potosi.
+    18.6  (18.3-18.9)   _8_, Tepic, Nayarit.
+    18.0  (17.7-18.4)  _18_, 4 mi. N, 5 mi. W Leon, Guanajuato.
+    18.1  (17.5-18.9)  _28_, 6 mi. E Queretaro, Queretaro.
+    17.7  (17.1-18.1)  _17_, 1 mi. SSE Ameca, Jalisco.
+    17.3  (16.8-17.9)  _10_, 2 mi. SSE Autlan, Jalisco.
+    18.0  (17.5-18.6)  _10_, 1 mi. S, 11 mi. W Zamora, Michoacan.
+    17.6  (17.4-18.2)   _8_, Colima, Colima.
+
+
+    _Baiomys musculus_
+
+    20.2  (19.9-20.3)  _6_, vic. (see p. 622) Ameca, Jalisco.
+    20.2  (19.9-20.3)  _6_, 2 mi. SSE Autlan, Jalisco.
+    19.6  (19.2-20.1)  _6_, Jalapa, Veracruz.
+    20.3  (19.7-20.9)  _9_, Colima, Colima.
+    19.5  (19.0-20.0) _10_, Cerro Gordo, Veracruz.
+    19.8  (19.4-20.3)  _6_, 6 mi. S Izucar de Matemores, Puebla.
+    20.0  (18.8-20.5)  _7_, Teotitlan, Oaxaca.
+    20.1  (19.7-20.7)  _7_, 1 km. NW Chapa, Guerrero.
+    19.9  (19.4-20.4)  _8_, 5 mi. ESE Tecpan, Guerrero.
+    19.5  (19.1-20.1) _22_, 3 mi. ESE Oaxaca, Oaxaca.
+    19.5  (19.1-19.9) _11_, Valley of Comitan, Chiapas.
+    18.9  (18.2-20.1) _17_, Tehuantepec, Oaxaca.
+    18.9  (18.4-19.7) _15_, 6 mi. NW Tonala, Chiapas.
+    19.1  (18.8-20.4) _10_, 1 mi. S Rabinal, Guatemala.
+    19.7  (18.8-20.4) _10_, Lake Amatitlan, Guatemala.
+    19.2  (18.4-19.8) _26_, vic. (see p. 625) San Salvador, El Salvador.
+    19.3  (18.9-19.9) _24_, 8 mi. S Condega, Esteli, Nicaragua.]
+
+
+
+
+CONCLUSIONS
+
+
+1. Two Recent species, each polytypic with eight subspecies, and five
+fossil species are recognized.
+
+2. The phyletic trends in the genus _Baiomys_ have been from an
+ancestral stock that possessed relatively brachydont teeth having raised
+cingular ridges and orthodont to prooedont incisors, to species having
+hypsodont teeth with reduced cingular ridges and retrodont incisors.
+
+3. Reduction of cingular ridges in pygmy mice is associated with an
+existence in open grassland (more xeric than mesic), whereas, the
+presence of cingular ridges is associated with an existence in a
+savannah habitat (more mesic than xeric).
+
+4. Shifts of geographical range of populations of pygmy mice at and near
+the periphery of their geographic range may account for the
+differentiation of the extinct species.
+
+5. The two living species, _B. musculus_ and _B. taylori_, are seemingly
+derived from a common ancestor that in morphological structure was
+intermediate between _B. minimus_ and _B. musculus_.
+
+6. The living species of pygmy mice resulted from a geographic
+separation, perhaps occurring in the Iowan glacial period (See De Terra,
+1949:51) in the transverse volcanic zone of central Mexico.
+
+7. The two species are now sympatric in west central Mexico, where
+morphological characters (size and shape of body and length of skull)
+differ most. Where the two species are allopatric, these same
+morphological characters differ least.
+
+8. This is a documented instance of character displacement in mammals.
+
+9. On the basis of internal morphological characters studied (auditory
+ossicles, hyoid apparatus, and baculum), _Baiomys_ seems to be more
+closely related to a South American hesperomine, perhaps _Calomys_, than
+to any North American cricetine.
+
+10. Pygmy mice were more widely distributed in the past than they are at
+present. Part of the ancestral stock of the pygmy mice may have
+emigrated from North America into South America in a brief period in the
+Pliocene; if so, it is easy to understand why certain South American
+hesperomines resemble _Baiomys_.
+
+11. The combination of morphological and behavioral characters in the
+living pygmy mice warrants generic status for them. If _Baiomys_ were
+treated as a subgenus of the genus _Peromyscus_, there would be adequate
+justification for including in the genus _Peromyscus_ a number of other
+genera, some of them occurring in South America. Such lumping of genera
+would reduce our understanding of the natural relationships among this
+group of cricetine rodents.
+
+
+
+
+LITERATURE CITED
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+
+_Transmitted March 4, 1960._
+
+
+[]
+28-3030
+
+
+
+
+UNIVERSITY OF KANSAS PUBLICATIONS
+
+MUSEUM OF NATURAL HISTORY
+
+
+Institutional libraries interested in publications exchange may obtain
+this series by addressing the Exchange Librarian, University of Kansas
+Library, Lawrence, Kansas. Copies for individuals, persons working in a
+particular field of study, may be obtained by addressing instead the
+Museum of Natural History, University of Kansas, Lawrence, Kansas. There
+is no provision for sale of this series by the University Library, which
+meets institutional requests, or by the Museum of Natural History, which
+meets the requests of individuals. However, when individuals request
+copies from the Museum, 25 cents should be included, for each separate
+number that is 100 pages or more in length, for the purpose of defraying
+the costs of wrapping and mailing.
+
+    * An asterisk designates those numbers of which the Museum's supply
+      (not the Library's supply) is exhausted. Numbers published to date,
+      in this series, are as follows:
+
+   Vol.  1. Nos. 1-26 and index. Pp. 1-638, 1946-1950.
+
+  *Vol.  2. (Complete) Mammals of Washington. By Walter W. Dalquest.
+                Pp. 1-444, 140 figures in text. April 9, 1948.
+
+   Vol.  3. *1. The avifauna of Micronesia, its origin, evolution, and
+                distribution. By Rollin H. Baker, Pp. 1-359, 16 figures in
+                text. June 12, 1951.
+
+            *2. A quantitative study of the nocturnal migration of birds.
+                By George H. Lowery, Jr. Pp. 361-472, 47 figures in text.
+                June 29, 1951.
+
+             3. Phylogeny of the waxwings and allied birds. By M. Dale
+                Arvey. Pp. 473-530, 49 figures in text, 13 tables.
+                October 10, 1951.
+
+             4. Birds from the state of Veracruz, Mexico. By George H.
+                Lowery, Jr., and Walter W. Dalquest. Pp. 531-649,
+                7 figures in text, 2 tables. October 10, 1951.
+
+            Index. Pp. 651-681.
+
+  *Vol.  4. (Complete) American weasels. By E. Raymond Hall. Pp. 1-466,
+                41 plates, 31 figures in text. December 27, 1951.
+
+   Vol.  5. Nos. 1-37 and index. Pp. 1-676,  1951-1953.
+
+  *Vol.  6. (Complete) Mammals of Utah, _taxonomy and distribution_.
+                By Stephen D. Durrant. Pp. 1-549, 91 figures in text,
+                30 tables. August 10, 1952.
+
+   Vol.  7. *1. Mammals of Kansas. By E. Lendell Cockrum. Pp. 1-303.
+                73 figures in text, 37 tables. August 25, 1952.
+
+             2. Ecology of the opossum on a natural area in northeastern
+                Kansas. By Henry S. Fitch and Lewis L. Sandidge.
+                Pp. 305-338, 5 figures in text. August 24, 1953.
+
+             3. The silky pocket mice (Perognathus flavus) of Mexico.
+                By Rollin H. Baker. Pp. 339-347, 1 figure in text.
+                February 15, 1954.
+
+             4. North American jumping mice (Genus Zapus). By Philip H.
+                Krutzch. Pp. 349-472, 47 figures in text, 4 tables.
+                April 21, 1954.
+
+             5. Mammals from Southeastern Alaska. By Rollin H. Baker and
+                James S. Findley. Pp. 473-477. April 21, 1954.
+
+             6. Distribution of Some Nebraskan Mammals. By J. Knox Jones,
+                Jr. Pp. 479-487. April 21, 1954.
+
+             7. Subspeciation in the montane meadow mouse. Microtus
+                montanus, in Wyoming and Colorado. By Sydney Anderson.
+                Pp. 489-506, 2 figures in text. July 23, 1954.
+
+             8. A new subspecies of bat (Myotis velifer) from southeastern
+                California and Arizona. By Terry A. Vaughan. Pp. 507-512.
+                July 23, 1954.
+
+             9. Mammals of the San Gabriel mountains of California.
+                By Terry A. Vaughan. Pp. 513-582. 1 figure in text,
+                12 tables. November 15, 1954.
+
+            10. A new bat (Genus Pipistrellus) from northeastern Mexico.
+                By Rollin H. Baker. Pp. 583-586. November 15, 1954.
+
+            11. A new subspecies of pocket mouse from Kansas. By E. Raymond
+                Hall. Pp. 587-590. November 15, 1954.
+
+            12. Geographic variation in the pocket gopher, Cratogeomys
+                castanops, in Coahuila, Mexico. By Robert J. Russell and
+                Rollin H. Baker. Pp. 591-608. March 15, 1955.
+
+            13. A new cottontail (Sylvilagus floridanus) from northeastern
+                Mexico. By Rollin H. Baker. Pp. 609-612. April 8, 1955.
+
+            14. Taxonomy and distribution of some American shrews.
+                By James S. Findley. Pp. 613-618. June 10, 1955.
+
+            15. The pigmy woodrat, Neotoma goldmani, its distribution and
+                systematic position. By Dennis G. Rainey and Rollin H.
+                Baker. Pp. 619-624, 2 figures in text. June 10, 1955.
+
+            Index. Pp. 625-651.
+
+   Vol.  8.  1. Life history and ecology of the five-lined skink, Eumeces
+                fasciatus. By Henry S. Fitch. Pp. 1-156, 26 figures in
+                text. September 1, 1954.
+
+             2. Myology end serology of the Avian Family Fringillidae,
+                a taxonomic study. By William B. Stallcup. Pp. 157-211,
+                23 figures in text, 4 tables. November 15, 1954.
+
+             3. An ecological study of the collared lizard (Crotaphytus
+                collaris). By Henry S. Fitch. Pp. 213-274, 10 figures in
+                text. February 10, 1956.
+
+             4. A field study of the Kansas ant-eating frog, Gastrophryne
+                olivacea. By Henry S. Fitch. Pp. 275-306, 9 figures in
+                text. February 10, 1956.
+
+             5. Check-list of the birds of Kansas. By Harrison E.
+                Tordoff. Pp. 307-359, 1 figure in text. March 10, 1956.
+
+             6. A population study of the prairie vole (Microtus
+                ochrogaster) in northeastern Kansas. By Edwin P. Martin.
+                Pp. 361-416, 19 figures in text.  April 2, 1956.
+
+             7. Temperature responses in free-living amphibians and
+                reptiles of northeastern Kansas. By Henry S. Fitch.
+                Pp. 417-476, 10 figures in text, 6 tables. June 1, 1956.
+
+             8. Food of the crow, Corvus brachyrhynchos Brehm, in
+                south-central Kansas. By Dwight Platt. Pp. 477-498.
+                4 tables. June 8, 1956.
+
+             9. Ecological observations on the woodrat, Neotoma floridana.
+                By Henry S. Fitch and Dennis G. Rainey. Pp. 499-533,
+                3 figures in text. June 12, 1956.
+
+            10. Eastern woodrat, Neotoma floridana: Life history and
+                ecology. By Dennis G. Rainey. Pp. 535-646, 12 plates,
+                13 figures in text. August 15, 1956.
+
+            Index. Pp. 647-675.
+
+   Vol.  9.  1. Speciation of the wandering shrew. By James S. Findley.
+                Pp. 1-68, 18 figures in text. December 10, 1955.
+
+             2. Additional records and extensions of ranges of mammals from
+                Utah. By Stephen D. Durrant, M. Raymond Lee, and Richard M.
+                Hansen. Pp. 69-80. December 10, 1955.
+
+             3. A new long-eared myotis (Myotis evotis) from northeastern
+                Mexico. By Rollin H. Baker and Howard J. Stains. Pp. 81-84.
+                December 10, 1955.
+
+             4. Subspeciation in the meadow mouse, Microtus
+                pennsylvanicus, in Wyoming. By Sydney Anderson.
+                Pp. 85-104, 2 figures in text. May 10, 1956.
+
+             5. The condylarth genus Ellipsodon. By Robert W. Wilson.
+                Pp. 105-116, 6 figures In text. May 19, 1956.
+
+             6. Additional remains of the multituberculate genus
+                Eucosmodon. By Robert W. Wilson. Pp. 117-123, 10 figures
+                in text. May 19, 1956.
+
+             7. Mammals of Coahuila, Mexico. By Rollin H. Baker.
+                Pp. 125-335, 75 figures in text. June 15, 1956.
+
+             8. Comments on the taxonomic status of Apodemus peninsulae,
+                with description of a new subspecies from North China.
+                By J. Knox Jones, Jr. Pp. 337-346, 1 figure in text,
+                1 table. August 15, 1956.
+
+             9. Extensions of known ranges of Mexican bats. By Sydney
+                Anderson. Pp. 347-351. August 15, 1956.
+
+            10. A new bat (Genus Leptonycteris) from Coahuila. By Howard J.
+                Stains. Pp. 353-356. January 21, 1957.
+
+            11. A new species of pocket gopher (Genus Pappogeomys) from
+                Jalisco, Mexico. By Robert J. Russell. Pp. 357-361.
+                January 21, 1957.
+
+            12. Geographic variation in the pocket gopher, Thomomys bottae,
+                in Colorado. By Phillip M. Youngman. Pp. 363-385, 7 figures
+                in text. February 21, 1958.
+
+            13. New bog lemming (genus Synaptomys) from Nebraska.
+                By J. Knox Jones, Jr. Pp. 385-388. May 12, 1958.
+
+            14. Pleistocene  bats from San Josecito Cave, Nuevo Leon,
+                Mexico. By J. Knox Jones, Jr. Pp. 389-396.
+                December 19, 1958.
+
+            15. New Subspecies of the rodent Baiomys from Central America.
+                By Robert L. Packard. Pp. 397-404. December 19, 1958.
+
+            16. Mammals of the Grand Mesa, Colorado. By Sydney Anderson.
+                Pp, 405-414, 1 figure in text. May 20, 1959.
+
+            17. Distribution, variation, and relationships of the montane
+                vole, Microtus montanus. By Emil K. Urban. Pp. 415-511.
+                12 figures in text, 2 tables. August 1, 1959.
+
+            18. Conspecificity of two pocket mice, Perognathus goldmani and
+                P. artus. By E. Raymond Hall and Marilyn Bailey Ogilvie.
+                Pp. 513-518, 1 map. January 14, 1960.
+
+            19. Records of harvest mice, Reithrodontomys, from Central
+                America, with description of a new subspecies from
+                Nicaragua. By Sydney Anderson and J. Knox Jones, Jr.
+                Pp. 519-529. January 14, 1960.
+
+            20. Small carnivores from San Josecito Cave (Pleistocene),
+                Nuevo Leon, Mexico. By E. Raymond Hall. Pp. 531-538,
+                1 figure in text. January 14, 1960.
+
+            21. Pleistocene pocket gophers from San Josecito Cave, Nuevo
+                Leon, Mexico. By Robert J. Russell. Pp. 539-548, 1 figure
+                in text. January 14, 1960.
+
+            22. Review of the insectivores of Korea. By J. Knox Jones, Jr.,
+                and David H. Johnson. Pp. 549-578. February 23, 1960.
+
+            23. Speciation and evolution of the pygmy mice, genus Baiomys.
+                By Robert L. Packard. Pp. 579-670, 4 plates, 12 figures in
+                text. June 16, 1960.
+
+            Index will follow.
+
+   Vol. 10.  1. Studies of birds killed in nocturnal migration. By
+                Harrison B. Tordoff and Robert M. Mengel. Pp. 1-44,
+                6 figures in text, 2 tables. September 12, 1956.
+
+             2. Comparative breeding behavior of Ammospiza caudacuta and
+                A. maritime. By Glen E. Woolfenden. Pp. 45-75, 6 plates,
+                1 figure. December 20, 1956.
+
+             3. The forest habitat of the University of Kansas Natural
+                History Reservation. By Henry S. Fitch and Ronald R.
+                McGregor. Pp. 77-127, 2 plates, 7 figures in text,
+                4 tables. December 31, 1956.
+
+             4. Aspects of reproduction and development in the prairie vole
+                (Microtus ochrogaster). By Henry S. Fitch, Pp. 129-161,
+                8 figures in text, 4 tables. December 19, 1957.
+
+             5. Birds found on the Arctic slope of northern Alaska. By
+                James W. Bee. Pp. 163-211, pls. 9-10, 1 figure in text.
+                March 12, 1958.
+
+             6. The wood rats of Colorado; distribution and ecology.
+                By Robert B. Finley, Jr. Pp. 213-552, 34 plates,
+                8 figures in text, 35 tables. November 7, 1958.
+
+             7. Home ranges and movements of the eastern cottontail in
+                Kansas. By Donald  W. Janes. Pp. 553-572, 4 plates,
+                3 figures in text. May 4, 1959.
+
+             8. Natural history of the salamander, Aneides hardyi.
+                By Richard F. Johnston and Schad Gerhard. Pp. 573-585.
+                October 8, 1959.
+
+             9. A new subspecies of lizard, Cnemidophorus sacki, from
+                Michoacan, Mexico. By William E. Duellman. Pp. 587-598,
+                2 figures in text. May 2, 1960.
+
+            10. A taxonomic study of the Middle American Snake, Pituophis
+                deppei. By William E. Duellman. Pp. 599-612, 1 plate,
+                1 figure in text. May 2, 1960.
+
+            Index will follow.
+
+   Vol. 11.  1. The systematic status of the colubrid snake, Leptodeira
+                discolor Guenther. By William E. Duellman. Pp. 1-9,
+                4 figs. July 14, 1958.
+
+             2. Natural history of the six-lined racerunner, Cnemidophorus
+                sexlineatus. By Henry S. Fitch. Pp. 11-62, 9 figs.,
+                9 tables. September 19, 1958.
+
+             3. Home ranges, territories, and seasonal movements of
+                vertebrates of the Natural History Reservation. By Henry
+                S. Fitch, Pp. 68-326, 6 plates, 24 figures in text,
+                8 tables. December 12, 1958.
+
+             4. A new snake of the genus Geophis from Chihuahua, Mexico.
+                By John M. Legler. Pp. 327-334, 2 figures in text.
+                January 28, 1959.
+
+             5. A new tortoise, genus Gopherus, from north-central Mexico.
+                By John M. Legler. Pp. 335-343. April 24, 1959.
+
+             6. Fishes of Chautauqua, Cowley and Elk counties, Kansas.
+                By Artie L. Metcalf. Pp. 345-400, 2 plates, 2 figures in
+                text, 10 tables. May 6, 1959.
+
+             7. Fishes of the Big Blue River Basin, Kansas. By W. L.
+                Minckley. Pp. 401-442, 2 plates, 4 figures in text,
+                5 tables. May 8, 1959.
+
+             8. Birds from Coahuila, Mexico. By Emll K. Urban. Pp. 443-516.
+                August 1, 1959.
+
+             9. Description of a new softshell turtle from the southeastern
+                United States. By Robert G. Webb. Pp. 517-525, 2 pls.,
+                1 figure in text, August 14, 1959.
+
+            10. Natural history of the ornate box turtle, Terrapene ornata
+                ornata Agassiz. By John M. Legler. Pp. 527-669, 16 pls.,
+                29 figures in text. March 7, 1960.
+
+            Index will follow.
+
+   Vol. 12.  1. Functional morphology of three bats: Eumops, Myotis,
+                Macrotus. By Terry A. Vaughan. Pp. 1-153, 4 plates,
+                24 figures in text. July 8, 1959.
+
+             2. The ancestry of modern Amphibia: a review of the evidence.
+                By Theodore H. Eaton, Jr. Pp. 155-180, 10 figures in text.
+                July 10, 1959.
+
+             3. The baculum in microtine rodents. By Sydney Anderson.
+                Pp. 181-216, 49 figures in text. February 19, 1960.
+
+             4. A new order of fishlike Amphibia from the Pennsylvanian of
+                Kansas. By Theodore H. Eaton, Jr., and Peggy Lou Stewart.
+                Pp. 217-240, 12 figures in text. May 2, 1960.
+
+            More numbers will appear In volume 12.
+
+
+
+
+Transcriber's Notes
+
+The text presented is that of the original printed version except for
+the revisions below and a few assumed typesetting errors. The subsection
+headers under "VARIATION WITH AGE" were converted to italic only to
+match the rest. All other section title formatting retained as printed.
+The words Miscellaneous and Monograph were abbreviated as Miscl. and
+Mongr. respectively. Except for the two variant spellings of one word
+(Mexico/Mexico) which were retained, the most prevalent form of accented
+words was used.
+
+Both decimal and whole plus fractional part of numbers (i.e., 9-1/2)
+were retained as printed. The male and female symbols are represented by
+[M] and [F] respectively. Footnotes were all placed at the end of each
+species account. The list of KU Publications were compiled after the
+article's text.
+
+
+Typographical Corrections
+
+  Page Correction
+  ==== ====================
+  591 prooedent => prooedont
+  694 hesperomyines => hesperomines
+
+
+Text Emphasis
+
+  _Text_ - Italic
+
+  =Text= - Bold
+
+
+
+
+
+End of the Project Gutenberg EBook of Speciation and Evolution of the Pygmy
+Mice, Genus Baiomys, by Robert L. Packard
+
+*** END OF THIS PROJECT GUTENBERG EBOOK SPECIATION AND EVOLUTION OF ***
+
+***** This file should be named 38290.txt or 38290.zip *****
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