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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: ASCII
+
+*** 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 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
+
+
+ ALLEN, J. A.
+
+ 1903. 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.
+
+
+ ALLEN, J. A., and CHAPMAN, F. M.
+
+ 1897. On a collection of mammals from Jalapa and Las Vigas, state of
+ Veracruz. Bull. Amer. Mus. Nat. Hist., 9:197-208, June 16.
+
+
+ AXELROD, D. I.
+
+ 1950. 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.
+
+
+ BAILEY, V.
+
+ 1905. Biological survey of Texas. N. Amer. Fauna, 25:1-222, 16 pls.,
+ 24 figs., October 24.
+
+
+ BAKER, R. H.
+
+ 1951. Mammals from Tamaulipas Mexico. Univ. Kansas Publ., Mus. Nat.
+ Hist., 5:207-218, December 15.
+
+
+ BLAIR, W. F.
+
+ 1941. Observations on the life history of _Baiomys taylori subater_.
+ Jour. Mamm., 22:378-383, 1 fig., November 14.
+
+ 1942. Systematic relationships of _Peromyscus_ and several related
+ genera as shown by the baculum. Jour. Mamm., 23:196-204, 2 figs.,
+ 1 table, May 14.
+
+ 1952. Mammals of the Tamaulipan Biotic Province in Texas. Texas
+ Jour. Sci., 4:230-250, 1 fig., 2 tables, June 30.
+
+ 1953. Population dynamics of rodents and other small mammals. Advances
+ in Genetics, 5:1-41, 1 table.
+
+
+ BLAIR, W. F., and BLOSSOM, P. M.
+
+ 1948. Variation in the pygmy mouse (_Baiomys taylori_) from Texas and
+ Arizona. Contrib. Lab. Vert. Biol., Univ. Michigan, 40:1-7, 3
+ tables, March.
+
+
+ BLOSSOM, P. M., and BURT, W. H.
+
+ 1942. A new race of pygmy mouse (_Baiomys_) from Arizona. Occas.
+ Papers, Univ. Michigan, 465:1-4, October 8.
+
+
+ BOOTH, E. S.
+
+ 1957. 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.
+
+
+ BROWN, W. L.
+
+ 1958. Some zoological concepts applied to problems in evolution of the
+ hominid lineage. Amer. Scientist, 46:151-158, 1 fig., June.
+
+
+ BROWN, W. L., JR., and WILSON, E. O.
+
+ 1956. Character displacement. Soc. Syst. Zool., 5:49-64, 6 figs., June.
+
+
+ BURT, W. H.
+
+ 1936. A study of the baculum in the genera _Perognathus_ and
+ _Dipodomys_. Jour. Mamm., 17:145-156, 6 figs., 2 tables, May 14.
+
+ 1938. Faunal relationships and geographic distribution of mammals in
+ Sonora, Mexico. Miscl. Publ. Mus. Zool., Univ. Michigan, 39:1-77,
+ 2 tables, 26 maps, February 15.
+
+
+ CLARK, F. H.
+
+ 1941. Correlation and body proportions in mature mice of the genus
+ _Peromyscus_. Jour. Genetics, 26:283-300, 8 tables, May.
+
+
+ COLLINS, H. H.
+
+ 1918. Studies of normal moult and of artificially induced regeneration
+ of pelage in _Peromyscus_. Jour. Exper. Zool., 27:73-95, 3 figs.,
+ 2 pls., October.
+
+ 1924. Studies of the pelage phases and of the nature of color variations
+ in mice of the genus _Peromyscus_. Jour. Exper. Zool., 38:45-107,
+ 57 figs.
+
+
+ DALQUEST, W. W.
+
+ 1953. Mammals of the Mexican state of San Luis Potosi. Louisiana
+ State Univ. Studies, Biol. Ser., 1:1-229, 1 fig., December 28.
+
+
+ DAVIS, W. B.
+
+ 1944. Notes on Mexican mammals. Jour. Mamm., 25:370-403, 1 fig.,
+ 3 tables, November 12.
+
+
+ DAVIS, W. B., and RUSSELL, J. R., JR.
+
+ 1954. Mammals of the Mexican state of Morelos. Jour. Mamm., 35:63-80,
+ February 10.
+
+
+ DETERRA, H., ROMERO, J., and STEWARD, T. D.
+
+ 1949. Tepexpan Man. Viking Fund Publ. in Anthropology, 11:1-160, 22
+ figs., 37 pls., 10 tables.
+
+
+ DICE, L. R.
+
+ 1943. The biotic provinces of North America. Univ. Michigan Press,
+ Ann Arbor, viii + 78 pp., 1 map.
+
+ DICE, L. R., and LERAAS, H. J.
+
+ 1936. A graphic method for comparing several sets of measurements.
+ Contrib. Lab. Vert. Genetics, Univ. Michigan, 3:1-3, 1 fig., July.
+
+
+ DOBZHANSKY, T.
+
+ 1951. Genetics and the origin of species. Columbia Univ. Press,
+ x + 364 pp., 23 figs., 15 tables.
+
+
+ DUELLMAN, W. E.
+
+ 1958. A monographic study of the colubrid snake genus _Leptodeira_.
+ Bull. Amer. Mus. Nat. Hist., 114(1):1-152, 25 figs., 31 pls.,
+ 25 maps, 30 tables, February 24.
+
+
+ DUNN, E. R.
+
+ 1940. Some aspects of herpetology in lower Central America. Trans.
+ New York Acad. Sci., 2:156-158, April.
+
+
+ ELLERMAN, J. R.
+
+ 1941. 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.
+
+
+ FELTEN, H.
+
+ 1958. Nagetiere (Mammalia, Rodentia) aus El Salvador. Senckenbergiana
+ Biologica, 39:133-144, August 30.
+
+
+ FINDLEY, J. S.
+
+ 1955. Speciation of the wandering shrew. Univ. Kansas Publ., Mus.
+ Nat. Hist., 9:1-68, 18 figs., 1 table, December 10.
+
+
+ GAZIN, C. LEWIS
+
+ 1942. The late Cenozoic vertebrate faunas from the San Pedro Valley,
+ Ariz. Proc. U. S. Nat. Mus., 92(3155):475-518.
+
+
+ GIDLEY, J. W.
+
+ 1922. 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.
+
+
+ GOLDMAN, E. A.
+
+ 1951. Biological investigations in Mexico. Smiths. Miscl. Coll., 115:
+ xiii + 476, frontispiece, 71 pls., 1 map, July 31.
+
+
+ GOLDMAN, E. A. and MOORE, R. T.
+
+ 1945. The biotic provinces of Mexico. Jour. Mamm., 26:347-360, 1 fig.,
+ November 14.
+
+
+ GOODWIN, G. G.
+
+ 1934. Mammals collected by A. W. Anthony in Guatemala, 1924-1928.
+ Bull. Amer. Mus. Nat. Hist., 68:1-60, pls. 1-5, December 12.
+
+ 1942. Mammals of Honduras. Bull. Amer. Mus. Nat. Hist., 79:107-195,
+ May 29.
+
+ 1959. A new pygmy mouse of the genus _Baiomys_ from Oaxaca, Mexico.
+ Amer. Mus. Novit., 1929:1-2, March 5.
+
+
+ HALL, E. R.
+
+ 1959. Geographic distribution of contemporary organisms, pp. 371-373,
+ _in_ Zoogeography. Publ., Amer. Assoc. Adv. Sci., 55:x + 509 pp.
+ January 19.
+
+
+ HALL, E. R., and KELSON, K. R.
+
+ 1959. The mammals of North America. 2 Vols., xxx + 1083 pp. (79 pp.
+ index), 553 figs., 500 maps, March 31, 1959.
+
+
+ HALL, E. R., and VILLA-R., B.
+
+ 1949. An annotated check list of the Mammals of Michoacan, Mexico.
+ Univ. Kansas Publ., Mus. Nat. Hist., 1:431-472, pls. 4-5, 1 fig.,
+ December 27.
+
+
+ HERSHKOVITZ, P.
+
+ 1944. A systematic review of the neotropical water rats of the genus
+ _Nectomys_ (Cricetinae). Miscl. Publ. Mus. Zool., Univ. Michigan,
+ 58:1-101, 4 pls., 5 figs., 2 maps, 19 tables, January 4.
+
+ 1955. South American marsh rats Genus _Holochilus_ with a summary of
+ sigmodont rodents. Fieldiana-Zool., Chicago Nat. Hist. Mus.,
+ 37:639-673, 6 figs., 29 pls., 5 tables, June 19.
+
+ 1958. A geographical classification of neotropical mammals.
+ Fieldiana-Zool., Chicago Nat. Hist. Mus., 36:583-620, 2 figs.,
+ 13 tables, July 11.
+
+
+ HIBBARD, C. W.
+
+ 1941. 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.
+
+ 1952. A contribution to the Rexroad Fauna. Trans. Kansas Acad. Sci.,
+ 55:196-208, 2 figs., June 18.
+
+ 1953. The saw rock canyon fauna and its stratigraphic significance.
+ Papers, Michigan Acad. Sci., Arts and Letters, 38:387-411,
+ 5 figs., April 27.
+
+ 1958. Summary of North American Pleistocene mammalian local faunas.
+ Papers, Michigan Acad. Sci., Arts and Letters, 43:3-32, 1 table.
+
+
+ HOFFMEISTER, D. F.
+
+ 1951. A taxonomic and evolutionary study of the pinon mouse, _Peromyscus
+ truei_. Ill. Biol. Monogr., 21:x + 104, 5 pls., 24 figs.,
+ 7 tables, November 12.
+
+ 1956. Mammals of the Graham (Pinaleno) Mountains, Arizona. Amer.
+ Midland Nat., 55:257-288, 7 figs., 1 table, April.
+
+
+ HOOPER, E. T.
+
+ 1947. Notes on Mexican mammals. Jour. Mamm., 28:40-57, February 15.
+
+ 1949. Faunal relationships of recent North American rodents. Miscl.
+ Publ. Mus. Zool., Univ. Michigan, 72:1-28, 5 tables, May 20.
+
+ 1952a. Notes on the pygmy mouse (_Baiomys_), with description of a
+ new subspecies from Mexico. Jour. Mamm., 33:90-97, 3 figs.,
+ February 18.
+
+ 1952b. A systematic review of the harvest mice (genus _Reithrodontomys_)
+ of Latin America. Miscl. Publ. Mus. Zool., Univ. Michigan,
+ 77:1-255, 9 pls., 24 figs., 12 maps, 7 tables, January 16.
+
+ 1953. Notes on the mammals of Tamaulipas, Mexico. Occas. Papers
+ Mus. Zool., Univ. Michigan, 544:1-12, March 25.
+
+ 1955a. Extra teeth in the pygmy mouse, _Baiomys musculus_. Jour. Mamm.,
+ 36:298-299, May 26.
+
+ 1955b. Notes on Mammals of western Mexico. Occas. Papers Mus. Zool.,
+ Univ. Michigan, 565:1-26, November 9.
+
+ 1957. Dental patterns in mice of the Genus _Peromyscus_. Miscl. Publ.
+ Mus. Zool., Univ. Michigan, 99:1-59, 24 figs., 3 tables, March 28.
+
+ 1958. The male phallus in mice of the genus _Peromyscus_. Miscl. Publ.
+ Mus. Zool., Univ. Michigan, 105:1-24, 1 fig., 24 pls., 1 table,
+ December 29.
+
+
+ HUNSAKER, D., RAUN, G. G., and SWINDELLS, J. E.
+
+ 1959. Range expansion of _Baiomys taylori_ in Texas. Jour. Mamm.,
+ 40:477-478, August 20.
+
+
+ KOOPMAN, K. F.
+
+ 1950. Natural selection for reproductive isolation between _Drosophila
+ pseudoobscura_ and _Drosophila persimilis_. Evolution, 4:135-148,
+ 3 figs., 7 tables, June.
+
+
+ LACK, D.
+
+ 1944. Ecological aspects of species formation in passerine birds. Ibis,
+ 86:260-286, July.
+
+
+ LAYNE, JAMES N.
+
+ 1959. Growth and development of the eastern harvest mouse,
+ _Reithrodontomys humulis_. Bull. Florida State Mus., 4:61-82,
+ 5 figs., April 27.
+
+
+ LEOPOLD, A. S.
+
+ 1950. Vegetation zones of Mexico. Ecol., 31:507-518, 1 fig., 1 table,
+ October.
+
+
+ LOWERY, G. H., and DALQUEST, W. W.
+
+ 1951. Birds from the state of Veracruz, Mexico. Univ. Kansas Publ.,
+ Mus. Nat. Hist., 3:531-649, 7 figs., 2 tables, October 10.
+
+
+ LUKENS, P. W., JR.
+
+ 1955. 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.
+
+
+ MAYR, E.
+
+ 1949. Speciation and selection. Proc. Amer. Phil. Soc., 93:514-519,
+ December.
+
+
+ MEARNS, E. A.
+
+ 1907. Mammals of the Mexican boundary of the United States ... Pt.
+ 1, Families Didelphidae to Muridae. Bull. U. S. Nat. Mus.,
+ 56:xv + 530, 13 pls., 126 figs., numerous tables, April 13.
+
+
+ MERRIAM, C. HART
+
+ 1892. Descriptions of new mammals collected by E. W. Nelson in the
+ states of Colima and Jalisco, Mexico. Proc. Biol. Soc. Washington,
+ 7:164-174, September 29.
+
+
+ MOORE, R. T.
+
+ 1945. The transverse volcanic biotic province of central Mexico and its
+ relationship to adjacent provinces. Trans. San Diego Soc. Nat.
+ Hist., 10:217-236, 1 map, 4 tables, August 31.
+
+
+ OSGOOD, W. H.
+
+ 1909. Revision of the mice of the American Genus _Peromyscus_. N. Amer.
+ Fauna, 28:1-285, 8 pls., 12 figs., several tables, April 17.
+
+
+ PACKARD, R. L.
+
+ 1958a. New subspecies of the rodent _Baiomys_ from Central America.
+ Univ. Kansas Publ., Mus. Nat. Hist., 9:397-404, 2 tables,
+ December 19.
+
+ 1958b. The taxonomic status of _Peromyscus allex_ Osgood. Proc. Biol.
+ Soc. Washington, 71:17-20, April 11.
+
+
+ RIDGWAY, R.
+
+ 1912. Color standards and color nomenclature. Published by the author,
+ Washington, D. C., iii + 43 pp., 53 pls.
+
+
+ RINKER, G. C.
+
+ 1954. The comparative myology of the mammalian genera _Sigmodon_,
+ _Oryzomys_, _Neotoma_, and _Peromyscus_ (Cricetinae), with remarks
+ on their intergeneric relationships. Miscl. Publ. Mus. Zool.,
+ Univ. Michigan, 83:1-124, 18 figs., 2 tables, June 4.
+
+
+ RUSSELL, R. J., JR.
+
+ 1952. A new subspecies of pygmy mouse, _Baiomys musculus_, from
+ Morelos, Mexico. Proc. Biol. Soc. Washington, 65:21-22,
+ January 29.
+
+
+ SEARS, P. B.
+
+ 1955. Palynology in southern North America, Part 4: Pleistocene Climate
+ in Mexico. Bull. Geol. Soc. America, 66:521-530, 6 figs., 1 pl.,
+ 1 table, May.
+
+
+ SIMPSON, G. G.
+
+ 1945. The principles of classification and a classification of mammals.
+ Bull. Amer. Mus. Nat. Hist., 85:xvi + 350, October 5.
+
+ 1950. History of the fauna of Latin America. Amer. Sci., 38(3):361-389,
+ 10 figs.
+
+
+ SMITH, H. M.
+
+ 1949. Herpetogeny in Mexico and Guatemala. Ann. Association Amer.
+ Geogr., 39:219-238, 1 fig., 1 table, September.
+
+
+ SPRAGUE, J. M.
+
+ 1941. A study of the hyoid apparatus of the cricetinae. Jour. Mamm.,
+ 22:296-310, 5 figs., August 14.
+
+
+ STICKEL, L. F., and STICKEL, W. H.
+
+ 1949. A _Sigmodon_ and _Baiomys_ population in ungrazed and unburned
+ Texas prairie. Jour. Mamm., 30:141-150, 3 tables, May 23.
+
+
+ STUART, L. C.
+
+ 1954. 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.
+
+
+ TAMAYO, JORGE L.
+
+ 1949. Atlas Geografico general de Mexico, con cartas fisicas,
+ biologicas, demograficas, sociales, economicas, y cartogramas,
+ Mexico, 24 maps, December 12.
+
+
+ THOMAS, O.
+
+ 1888. On the small mammals of Duval County, Texas. Proc. Zool.
+ Soc. London, pp. 443-450.
+
+
+ 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, Mexico, 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 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
+
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