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diff --git a/38290-8.txt b/38290-8.txt new file mode 100644 index 0000000..552d609 --- /dev/null +++ b/38290-8.txt @@ -0,0 +1,5739 @@ +The Project Gutenberg EBook of Speciation and Evolution of the Pygmy Mice, +Genus Baiomys, by Robert L. Packard + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Speciation and Evolution of the Pygmy Mice, Genus Baiomys + +Author: Robert L. Packard + +Release Date: December 13, 2011 [EBook #38290] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK SPECIATION AND EVOLUTION OF *** + + + + +Produced by Chris Curnow, Tom Cosmas, Joseph Cooper and +the Online Distributed Proofreading Team at +http://www.pgdp.net + + + + + + + + + + UNIVERSITY OF KANSAS PUBLICATIONS + + MUSEUM OF NATURAL HISTORY + + + Volume 9, No. 23, pp. 579-670, 4 pls., 12 figs. in text + + June 16, 1960 + + + Speciation and Evolution of the + Pygmy Mice, Genus Baiomys + + BY + + ROBERT L. PACKARD + + UNIVERSITY OF KANSAS + LAWRENCE + 1960 + + + + + UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY + + Editors: E. Raymond Hall, Chairman, Henry S. Fitch, + + Robert W. Wilson + + Volume 9, No. 23, pp. 579-670, 4 pls., 12 figs. in text + Published June 16, 1960 + + + UNIVERSITY OF KANSAS + Lawrence, Kansas + + + PRINTED IN + THE STATE PRINTING PLANT + TOPEKA, KANSAS + + 1960 + + [Illustration: Look for the Union Label] + 28-3030 + + + + +Speciation and Evolution of the Pygmy Mice, Genus Baiomys + +BY + +ROBERT L. PACKARD + + + + +CONTENTS + + + PAGE + Introduction 583 + Materials, Methods and Acknowledgments 584 + Paleontology of the Genus 587 + _Baiomys sawrockensis_ 588 + _Baiomys rexroadi_ 589 + _Baiomys kolbi_ 590 + _Baiomys brachygnathus_ 590 + _Baiomys minimus_ 591 + Phyletic trends 592 + Non-Geographic Variation 595 + Variation with age 595 + Secondary sexual variation 597 + Individual variation 597 + Pelage and molts 598 + Taxonomic Characters and Relationships 600 + External parts 600 + Pelage 600 + Skull 600 + Teeth 601 + Hyoid apparatus 601 + Baculum 603 + Auditory ossicles 605 + Genus Baiomys 607 + Systematic Accounts of Species and Subspecies 608 + _Baiomys musculus_ 608 + _Baiomys musculus brunneus_ 612 + _Baiomys musculus grisescens_ 614 + _Baiomys musculus handleyi_ 617 + _Baiomys musculus infernatis_ 618 + _Baiomys musculus musculus_ 620 + _Baiomys musculus nigrescens_ 623 + _Baiomys musculus pallidus_ 625 + _Baiomys musculus pullus_ 628 + _Baiomys taylori_ 630 + _Baiomys taylori allex_ 633 + _Baiomys taylori analogous_ 637 + _Baiomys taylori ater_ 640 + _Baiomys taylori canutus_ 643 + _Baiomys taylori fuliginatus_ 645 + _Baiomys taylori paulus_ 647 + _Baiomys taylori subater_ 650 + _Baiomys taylori taylori_ 651 + Evolution and Speciation 655 + Formation of the Recent Species 658 + Areas of present differentiation 661 + Zoogeographic position 661 + Conclusions 664 + Literature Cited 665 + + + + +INTRODUCTION + + +Pygmy mice (_Genus Baiomys_) are the smallest cricetine rodents in North +America. They occur from Nicaragua in Central America into the +southwestern United States. The principal part of the geographic range +of the pygmy mice lies in the Republic of México. They are notably +common in central México, but are only locally common to the north and +to the south, and then only in certain seasons. + +Pygmy mice were first brought to the attention of biologists in 1887 +when Oldfield Thomas described a diminutive species of cricetine rodent, +_Hesperomys_ (_Vesperimus_) _taylori_. The description was based on a +specimen obtained by William Taylor from San Diego, Duval County, Texas. +C. Hart Merriam (1892:70) described _Sitomys musculus_ on the basis of +specimens from Colima [City of], Colima, México. Merriam (_loc. cit._) +mentioned that the two kinds of mice, _Hesperomys taylori_ and _Sitomys +musculus_, "in general appearance look almost precisely like the common +house mouse (_Mus musculus_) but are still smaller and have shorter +tails." He placed the two species in the genus _Sitomys_. Frederick W. +True in 1894 regarded them as composing a distinct subgenus of _Sitomys, +Baiomys_. According to True (1894:758), _S. taylori_ and _S. musculus_ +possessed a different combination of characters (ascending ramus of +mandible short and erect, condyle terminal, coronoid process +well-developed, uncinate, and near the condyle, size small, tail short, +plantar tubercles six, soles hairy) than either _Vesperimus_, or +_Onychomys_ (which had been considered as a subgenus of _Hesperomys_ +until 1889). In 1907, E. A. Mearns accorded _Baiomys_ generic rank. +Osgood (1909:252) treated _Baiomys_ us a subgenus of _Peromyscus_, +whereas, Miller, in 1912, regarded _Baiomys_ as a distinct genus. Most +recent students of North American mammals have followed Miller, but +usually with reservations. Ellerman (1941:402) emphasized that the +taxonomic position of the genus was uncertain, and wrote that _Baiomys_ +"... seems to be considerably distinct from _Peromyscus_, and may +perhaps be a northern representative of _Hesperomys_ or one of the small +South American genera." + +Only two comprehensive analyses of geographic variation and +interspecific taxonomic relationships have been made; the first was by +Osgood (1909) who had fewer than a fourth of the specimens of _Baiomys_ +available to me; the second was by Hooper (1952a:90-97) who contributed +importantly to understanding the relationships of the two living species +in central México. No attempts heretofore have been made to correlate +and understand the relationships of the five fossil species to one +another and to the living species assigned to the genus. + +Six objectives of the following report are to: (1) list characters +taxonomically useful in recognizing species and subspecies; (2) record +amount of variation within and between populations; (3) correlate +observed variations with known biological principles; (4) show +geographic ranges of the two living species; (5) indicate relationships +between fossil and living species of the genus; and (6) clarify the +systematic position of the genus. + + + + +MATERIALS, METHODS AND ACKNOWLEDGMENTS + + +This report is based on the study of approximately 3,520 museum study +skins, skulls, complete skeletons, and entire animals preserved in +liquid. Most specimens examined were accompanied by an attached label +bearing data on locality and date of capture, name of collector, +external measurements, and sex. In addition, 49 fossil specimens +referable to _Baiomys_ were studied. Nearly two-thirds of the specimens +were assembled at the University of Kansas Museum of Natural History; +the remainder were examined in other institutions. + +Specimens studied were grouped by geographic origin, sex, age, and +season of capture. Individual variation was then measured in several of +the larger samples of each living species and in measurable fossil +material. External measurements used were those recorded by the +collectors on the labels attached to the skins. Twenty cranial +measurements employed in the past in the study of _Baiomys_ and closely +related cricetine rodents were statistically analyzed. The coefficient +of variation was calculated for each of the 20 measurements in order to +determine which varied least. In general, measurements having the least +coefficient of variation were used in comparing samples from different +geographic areas. Figure 1 shows the points between which measurements +were taken. + +_Occipitonasal length._--From anteriormost projection of nasal bones to +posteriormost projection of supraoccipital bone. _A_ to _A'_ + +_Zygomatic breadth._--Greatest distance across zygomatic arches of +cranium at right angles to long axis of skull. _B_ to _B'_ + +_Postpalatal length._--From posterior margin of hard palate to anterior +margin of foramen magnum. _C_ to _C'_ + +_Least interorbital breadth._--Least distance across top of skull +between orbits. _D_ to _D'_ + +_Length of incisive foramina._--From anteriormost point to posteriormost +point of incisive foramina. _E_ to _E'_ + +_Length of rostrum._--The distance in a straight line from the notch +that lies lateral to the lacrimal to the tip of the nasal on the same +side. _F_ to _F'_ + +_Breadth of braincase._--Greatest distance across braincase, taken at +right angles to long axis of skull. _G_ to _G'_ + +_Depth of cranium._--The distance from the dorsalmost part of the +braincase to a flat plane touching tips of incisors and ventral border +of each auditory bulla. A glass slide one millimeter thick was placed on +the ventral side of the skull. One jaw of the caliper was on the lower +surface of the slide and the other jaw on the dorsalmost part of the +braincase. The depth of the slide was subtracted from the total reading. +_H_ to _H'_ + +_Alveolar length of maxillary tooth-row._--From anterior border of +alveolus of M1 to posterior alveolus of M3. _I_ to _I'_ + + [Illustration: FIG. 1. Three views of the skull to show points + between which measurements were taken. Based on _B. m. pullus_, + adult, female, No. 71611 KU, 8 mi. S Condega, Estelí, Nicaragua. + × 1-1/3.] + +Capitalized color-terms refer to Ridgway (1912). Color terms without +initial letters capitalized do not refer to any one standard. + +The names of the cusps and ridges of the teeth (see Figure 2) are those +suggested by Wood and Wilson (1936:389-390). Terminology of the enamel +grooves and folds is that of Hershkovitz (1944:17) and Hooper +(1952b:20-21). + +Because secondary sexual variation was not significant (see page 597), +both males and females of like age and pelage were used in comparisons +of samples designed to reveal geographic variation. + +The species are arranged from less to more progressive; the subspecies +are arranged alphabetically. + +In the synonymy of each subspecies, the plan has been to cite: (1) the +name first proposed; (2) the first usage of the name combination +employed by me; (3) all other name combinations in chronological order +that have been applied to the subspecies concerned. + +The localities of specimens examined are listed by country from north to +south. Within a country, the listing is by state, beginning with the +northwesternmost state and proceeding by tiers (west to east) to the +southeasternmost state. Within a state of the United States, the listing +is by counties in the same geographic order as described for states. +Within any county in the United States, within any state in México, and +within any country in Central America, the listing of localities is from +north to south. When more than one locality is on the same line of +latitude, the westernmost locality is listed first. Marginal localities +for each subspecies are listed in a paragraph at the end of each +account. Each marginal locality is mapped by means of a circle. The +circles are listed in clockwise order, beginning with the northernmost. +When more than one of these localities lies on the same line of +latitude, the westernmost is cited first. Localities not represented on +the distribution maps, so as to avoid undue crowding of symbols, are +italicized in the lists of specimens examined. + + [Illustration: FIG. 2. Occlusal views of molars. × 13. + + A. _B. taylori analogous_, subadult, female, No. 28102 KU, 4 km. + ENE Tlalmanalco, 2290 meters, Estado de México. Right, upper + molars. + + B. _B. musculus musculus_, subadult, male, No. 45456 USNM, Colima, + Colima, México. Left, upper molars. + + A'. _B. taylori analogous_, subadult, female, No. 28102 KU 4 km. + ENE Tlalmanalco, 2290 meters, Estado de México. Left, lower + molars. + + B'. _B. musculus musculus_, subadult, male, No. 45456 USNM, Colima, + Colima, México. Right, lower molars.] + +The largest single collection of pygmy mice is in the University of +Kansas Museum of Natural History, and, unless otherwise indicated, +specimens cited in the taxonomic accounts beyond are there. + +I am indebted to the following named institutions and persons for making +specimens available for study: + + American Museum of Natural History, G. G. Goodwin and R. G. VanGelder. + + Carnegie Museum, J. K. Doutt. + + California Academy of Sciences, Robert T. Orr. + + Chicago Natural History Museum, Phillip H. Hershkovitz. + + Cleveland Museum of Natural History (Collection now a part of Museum of + Zoology, University of Michigan, W. H. Burt, E. T. Hooper). + + Louisiana State University, Museum of Natural History, George H. Lowery, + Jr. + + Los Angeles County Museum, Charles A. McLaughlin. + + United States National Museum (Biological Survey Collections), David A. + Johnson, and Viola S. Schantz. + + United States National Museum, Division of Vertebrate Paleontology, + C. Lewis Gazin. + + University of Arizona, E. L. Cockrum, and G. VR. Bradshaw. + + University of California, Museum of Vertebrate Zoology, Seth B. Benson, + and W. Z. Lidicker. + + University of Illinois, Museum of Natural History, Donald F. + Hoffmeister. + + University of Michigan, Museum of Zoology, W. H. Burt, E. T. Hooper, and + Claude W. Hibbard. + + University of New Mexico, James S. Findley. + + University of Texas, Frank W. Blair. + + Texas A & M, Cooperative Wildlife Research Collection, W. B. Davis. + + The Museum, Michigan State University, Rollin H. Baker. + + University of Florida Collections, James N. Layne. + +I am especially grateful to Professor E. Raymond Hall who guided me in +my study and gave critical assistance with the manuscript. Additional +appreciated suggestions were made by Professors A. Byron Leonard, Robert +W. Wilson, Henry S. Fitch, Ronald L. McGregor, and fellow graduate +students. For the illustrations, I am indebted to Mrs. Lorna Cordonnier, +Miss Lucy Remple and Mrs. Connie Spitz. Mr. B. J. Wilks of the +University of Texas, Department of Zoology, provided a number of living +pygmy mice for study in captivity. Mr. J. Raymond Alcorn and his son, +Albert, collected a large share of specimens of pygmy mice now in the +University of Kansas, Museum of Natural History. My wife, Patricia, +aided me in secretarial work and typing of the manuscript. + +For financial assistance, I am indebted to the National Science +Foundation when I was a Research Assistant, to the Sigma Xi-RESA +Research Fund for a Grant-in-Aid, and to the Kansas University Endowment +Association through its A. Henley Aid Fund, and the Watkins Fund for +out-of-state field work by the Museum of Natural History. + + + + +PALEONTOLOGY OF THE GENUS + + +Five fossil species, all extinct, have been assigned to the genus and +range in time from early late Pliocene (Saw Rock Canyon fauna of +Hibbard, 1953:408) to Mid-Pleistocene (see Hibbard, 1958:25, who +assigns the Curtis Ranch fauna to late Kansan or early Yarmouth). + +I examined all known fossil material and compared it with Recent +material. When the antiquity of the genus is considered, the degree of +difference between the oldest fossil species and the two living species +is much less than might be expected. + + +=Baiomys sawrockensis= Hibbard + + _Baiomys sawrockensis_ Hibbard, Papers Mich. Acad. Sci., Arts and + Letters, 38:402, April 27, 1953. + +_Type._--No. 27506, Univ. Michigan; left mandibular ramus bearing m1-m3 +and incisor; Saw Rock Canyon, early late Pliocene, XI member of the +Rexroad formation, sec. 36, T. 34 S, R. 31 W, Seward County, Kansas +(University of Kansas, Locality 6). + +_Referred material._--Univ. Michigan, Nos. 25781, 27503-27505, +28159-28165, 29708-29715, 31015. + +_Diagnosis._--Ramus of medium size to small for the genus; lower incisor +broad, moderately recurved; diastemal region broad; anterior median fold +between anterior labial conulid and anterior lingual conulid of m1 deep; +primary first fold between anteroconulid and protoconid of m2 deep; +cingular ridge (ectolophid) at entrance to posteroexternal reëntrant +valley (major fold, see Figure 2) between protoconid and hypoconid of m1 +and m2; average and extreme measurements of lower molar row of eight +specimens are, 2.65 (2.5-2.7). + +_Comparisons._--For comparisons with _B. brachygnathus_, see account of +that species. From _B. rexroadi_, _B. sawrockensis_ differs in: anterior +median fold of m1 deeper; incisor narrower; diastemal region broader; +coronoid process broader and better developed; cingular ridges +(ectolophids and mesolophids) more pronounced in their development; +incisors less proödont, more retrodont. + +From _B. kolbi_, _B. sawrockensis_ differs in: crowns of molars +narrower; incisors less proödont; cingular ridges (ectolophids and +mesolophids) of m1 and m2 more pronounced in their development. + +From _B. minimus_, _B. sawrockensis_ differs in: incisor less +procumbent; masseteric ridge extending farther anteriorly; anterior +cingulum of m2 slightly larger. + +From _B. musculus_, _B. sawrockensis_ differs in: over-all size of jaw +and molar row less; diastema more acutely curved; incisors shorter; +anterior median fold of m1 slightly deeper. + +From _B. taylori_, _B. sawrockensis_ differs in: m1 and m2 smaller; +cingular ridges in m1 and m2 more pronounced; anterolingual conulid +farther forward; incisors shorter, more proödont; molar teeth depressed, +less hypsodont; diastemal region broader, more acutely curved; +masseteric ridge not extending so far anteriorly. + +_Remarks._--_B. sawrockensis_ is the oldest known pygmy mouse. The +extreme development of the anterior median fold between the +anterolingual conulid and the anterolabial conulid is regarded as a +primitive feature in the pygmy mice. In this character, the Recent +species can be traced back in time through _B. minimus_ to _B. +sawrockensis_. _B. sawrockensis_ resembles _Calomys laucha_ of South +America in general conformation of jaw and tooth structure. The molars +of _sawrockensis_ are smaller than those of _C. laucha_, and the +anterolingual conulid of _sawrockensis_ is farther forward. + + +=Baiomys rexroadi= Hibbard + + _Baiomys rexroadi_ Hibbard, Amer. Midland Nat., 26:351, September, + 1941; Hibbard, Contrib. Mus. Paleo., Univ. Michigan, 8(2):145, + June 29, 1950 (part); Hibbard, Papers Mich. Acad. Sci., Arts + and Letters, 38:403, April 27, 1953. + +_Type._--No. 4670, Univ. Kansas; left mandibular ramus bearing m1-m3, +and incisor; Rexroad fauna, Locality no. 2, Upper Pliocene, Meade +County, Kansas. + +_Referred material._--Univ. of Michigan Nos. 24840, 24851, 27493, 27496, +27501, 28862-28867. + +_Diagnosis._--Ramus medium in size for the genus; incisors small, +proödont; anterior median fold of m1 slight; cingulum of all molars +poorly developed; average and external measurements of lower molar row +of seven specimens are, 2.7 (2.6-3.0). + +_Comparisons._--For comparisons with _B. sawrockensis_ and _B. minimus_, +see accounts of those species. From _B. kolbi_, _B. rexroadi_ differs +in: over-all size of mandibular ramus, incisors, and molars smaller; +anterior median fold of m1 present, though poorly developed. + +From _B. brachygnathus_, _B. rexroadi_ differs in: over-all size of +mandibular ramus smaller; m3 larger; posterior cusps (hypoconid and +entoconid) elongated; diastema shorter, less acutely recurved; incisors +less proödont; cingular ridges of m1 and m2 less well-developed. + +From _B. musculus_, _B. rexroadi_ differs in: over-all size of +mandibular ramus less; cingular ridges of m1 and m2 less well-developed; +incisors smaller, more proödont; molars less depressed. + +From _B. taylori_, _B. rexroadi_ differs in: m3 more triangular, +posterior part narrower; mental foramen closer to anterior root of m1; +masseteric ridge closer to alveolus of m1; incisor shorter, more +proödont; molars more depressed. + +_Remarks._--Two maxillary tooth-rows and associated parts were studied. +On one of these specimens, the M2 has a well-developed mesostyle; the +anterior median fold of M1 is also well-developed. The other specimen +possesses a low cingular ridge (enteroloph) between the protocone and +the hypocone, a reduced cingular ridge (mesoloph) between the paracone +and metacone of M1. On the second molar, M2, a mesostyle joins with the +mesoloph somewhat in the fashion indicated by Hooper (1957:9, encircled +number 2). + + +=Baiomys kolbi= Hibbard + + _Baiomys kolbi_ Hibbard, Trans. Kansas Acad. Sci., 55:201, June 18, + 1952; Hibbard, Papers Mich. Acad. Sci., Arts and Letters, 38:403, + April 27, 1953. + +_Type._--No. 24846, Univ. Michigan; right mandibular ramus bearing m1-m3 +and incisor; Fox Canyon, upper Pliocene, Rexroad formation, Rexroad +fauna, Univ. Michigan Locality K1-47, sec. 35, T. 34 S, R. 30 W, XI +Ranch, Meade County, Kansas. + +_Referred material._--Univ. Michigan Nos. 24845-24848, 27494, 27497, +27499, 28566, 28861, 28878, 28880-28882, 28884, 28886. + +_Diagnosis._--Ramus of medium size to large for the genus; lower incisor +short, narrow transversely, proödont; anterior median fold of m1 reduced +or absent; cingular ridges of m1 and m2 moderately well-developed; m3 +large relative to m1 and m2; average and extreme measurements of lower +molars of seven specimens are, 3.0 (3.0-3.1). + +_Comparisons._--For comparisons with _B. sawrockensis_ and _B. +rexroadi_, see accounts of those species. From _B. brachygnathus_, _B. +kolbi_ differs in: molar row longer; m3 and jaw larger; diastema longer; +masseteric ridge not so far forward; molars more depressed. + +From _B. minimus_, _B. kolbi_ differs in: molar row longer; m3 larger; +jaw larger; diastema not so acutely curved; incisor shorter, narrower +transversely, more proödont. + +From _B. musculus_, _B. kolbi_ differs in: anterior median fold of m1 +slightly developed or absent, instead of well-developed; m3 larger (not +reduced), external reëntrant valley broad and extending farther across +crown of tooth; incisor smaller, and more proödont; cingular ridges of +m1 and m2 less well-developed. + +From _B. taylori_, _B. kolbi_ differs in: molars larger, more depressed; +incisor shorter, more proödont; m3 smaller relative to m1 and m2; +external reëntrant valley of m3 broad, extending farther across crown of +tooth. + +_Remarks._--The slight development or absence of the anterior median +fold in _kolbi_ suggests that it was specialized. The anterior median +fold is well-developed in all species of _Baiomys_ save _B. +brachygnathus_ and _B. taylori_, in which the fold is only slightly +developed or absent. _B. kolbi_ may have paralleled _B. taylori_ in +specialization for a diet of grasses and for a life in open country. + + +=Baiomys brachygnathus= (Gidley) + + _Peromyscus brachygnathus_ Gidley, U. S. Geol. Surv. Prof. Papers, + 131:124, March 15, 1922. + + _Baiomys brachygnathus_, Hibbard, Amer. Midland Nat., 26:352, + September, 1941. + + _P. [eromyscus] brachygnathus_, Wilson, Carnegie Inst. Washington + Publ., 473:33, May 21, 1936. + +_Type._--No. 10501, U. S. Nat. Mus.; right mandibular ramus bearing +m1-m3, and incisor; 2 mi. NE Curtis Ranch house, near a line between +sec. 28 and 29, T. 18 S, R. 21 E, Mid-Pleistocene (Hibbard, 1958:25), +Cochise County, Arizona. + +_Referred material._--None. + +_Diagnosis._--Ramus small for the genus; m3 reduced; jaw reduced +anteroposteriorly; incisor short, slender, proödont; cingular ridges +well-developed, posterior ectolophid continuous from protoconid to +hypoconid in m1 and m2; diastema short; length of molar row 2.8 mm. + +_Comparisons._--For comparisons with _B. rexroadi_ and _B. kolbi_, see +accounts of those species. From _B. minimus_, _B. brachygnathus_ differs +in: jaw not so slender anteriorly; masseteric ridge not so far anterior; +cheek-teeth slightly broader, less depressed, therefore, more hypsodont; +incisor shorter, more proödont. + +From _B. sawrockensis_, _B. brachygnathus_ differs in: molar row +slightly longer; teeth slightly less depressed; masseteric ridge extends +farther anteriorly; incisors more proödont. + +From _B. musculus_, _B. brachygnathus_ differs in: jaw smaller; molar +row slightly shorter; molars less depressed; incisors slender, shorter, +narrower, and more proödont. + +From _B. taylori_, _B. brachygnathus_ differs in: incisor more slender, +shorter, more proödont; diastema shorter. + +_Remarks._--The molar teeth of _B. brachygnathus_, although worn, +resemble those of _B. taylori_ more than those of any known fossil +species. Gidley (1922:124) stated that the absence of the divided +anterior lobe of the first molar (anterior median fold) in +_brachygnathus_ was one of the chief characters separating +_brachygnathus_ from _taylori_. In _taylori_, the anterior median fold +characteristically is only slightly developed, and in some specimens is +absent. _B. brachygnathus_ differs from _taylori_ chiefly in proödont +incisors, which feature seems to preclude _brachygnathus_ being +ancestral to _taylori_. _B. brachygnathus_ may have been a specialized +divergence from _B. minimus_. + + +=Baiomys minimus= (Gidley) + + _Peromyscus minimus_ Gidley, U. S. Geol. Surv. Prof. Papers, + 131:124, March 15, 1922. + + _Baiomys minimus_, Hibbard, Amer. Midland Nat., 26:352, September, + 1941; Gazin, Prof. U. S. Nat. Mus., 92(3155):488, 1942. + + _P. [eromyscus] minimus_, Wilson, Carnegie Inst. Washington Publ., + 473:33, May 21, 1936. + +_Type._--No. 10500, U. S. Nat. Mus.; left mandibular ramus bearing m1-m3 +and incisor; 2 mi. S Benson, sec. 22, T. 17 S, R. 20 E, Late Pliocene +(Blancan, Gazin, 1942:482), Cochise County, Arizona. + +_Referred material._--None. + +_Diagnosis._--Ramus small for the genus; molar teeth depressed; cingular +ridges (ectolophids) of m1 and m2 well-developed; anterior median fold +present (appearing larger owing to chip of enamel missing); external +reëntrant fold of m3 progresses half way across crown of tooth; diastema +short; incisor moderately large, recurved; length of molar row, 2.6 mm. + +_Comparisons._--For comparisons with _B. brachygnathus_, _B. kolbi_, and +_B. sawrockensis_, see accounts of those species. From _B. rexroadi_, +_B. minimus_ differs in: anterior median fold deeper; incisor longer, +more recurved, less proödont; molars slightly more depressed (though +worn). + +From _B. musculus_, _B. minimus_ differs in: over-all size of jaw and +molars smaller; incisors shorter; masseteric ridge more depressed. + +From _B. taylori_, _B. minimus_ differs in: anterior median fold +slightly deeper; molar teeth more depressed; cingular ridges on m1 and +m2 better developed; masseteric ridge more depressed. + +_Remarks._--Gidley (1922:124) stated that _B. minimus_ differed +considerably from _B. taylori_ in that the coronoid portion of the +ascending ramus diverges at a wider angle from the alveolar part of the +jaw. Study of large samples of lower jaws of _B. taylori_ reveals +considerable individual variation in the angle formed between the +coronoid part of the jaw and the alveolar part. + +_B. minimus_, except for its small size, is like _B. musculus_ and is +considered to be ancestral to that species. + + + + +PHYLETIC TRENDS + + +It seems that the important trends in phyletic development in the pygmy +mice have been from an ancestral stock (see Figure 3) that possessed +relatively brachydont teeth having raised cingular ridges (ectolophids +and mesolophids) and relatively short orthodont to proödont incisors, to +species having teeth more hypsodont on which cingular ridges were +reduced, stylids were isolated or completely absent, and incisors were +longer and more recurved or retrodont. _Baiomys sawrockensis_, or an +unknown stock resembling it, might have been ancestral to the other +known species. Of the four remaining fossil species, _B. kolbi_ seems +least likely to have been ancestral to the two living species, owing to +its proödont incisors, reduction of cingular ridges, loss of an anterior +median fold in m1, and long mandibular tooth-row. _B. kolbi_ may have +been an early, specialized derivation from the ancestral stock. From his +knowledge of the habitats of _B. musculus_, the larger species, and _B. +taylori_, the smaller species, Hibbard (1952:203) suggests that _B. +kolbi_, a large species, might have inhabited lowlands, and _B. +rexroadi_, a small species, highlands. I have no evidence to dispute +this suggestion except that _B. musculus_ has more prominent cingular +ridges (or at least vestiges of this lophid condition) than either _B. +kolbi_ or _B. rexroadi_. _B. musculus_ (see page 610) is less of an open +grassland inhabitant than is _B. taylori_. Therefore, both _B. kolbi_ +and _B. rexroadi_, because of their poorly developed cingular ridges, +might be expected to have lived in a relatively open grassland habitat. + +The relationship of _B. rexroadi_ to fossil species other than _B. +kolbi_ is not clear. Superficially, the former resembles _B. taylori_, +but, owing to the specialized development of the molars of _rexroadi_, +it could hardly have been ancestral to either of the living species. The +resemblance of _B. rexroadi_ to _B. taylori_ may result from each having +occupied the same ecological niche in different periods. The incisors of +_B. rexroadi_, however, are much shorter than those of _B. taylori_ and +suggest somewhat different food habits. + +_B. minimus_ seemingly is more closely related to _B. sawrockensis_ and +_B. musculus_ than to the other described species. The development of +the cingular ridges leads one to suspect that _B. minimus_ was the +ancestor of _B. musculus_. _B. minimus_ may have been derived from a +_sawrockensis_-like stock and probably gave rise to _B. musculus_. + +Hershkovitz (1955:643-644) suggests that "... primitive brachydont, +buno-mesolophodont cricetines have survived ... in forested parts of the +range," whereas "... the progressive branch of cricetines with mesoloph +absent or vestigal, has become increasingly specialized for life in open +country and a diet of grasses." Species of the genus _Baiomys_ can be +divided into two morphological groups. One group, composed of _B. +sawrockensis_, _B. minimus_, and _B. musculus_, includes those species, +the teeth of which were relatively brachydont and had prominently +developed cingular ridges (ectolophids or mesolophids) or, at least, +showed some development of these ridges. _B. sawrockensis_ probably +lived in semi-wooded to shrubby habitats. According to Hibbard +(1953:409), "The Saw Rock Canyon fauna lived in that area at a time when +conditions were comparable to the conditions at the time the Rexroad +fauna lived." The conditions in which the Rexroad fauna lived are +discussed by Hibbard (1941:95). Presumably, there were at least some +well-wooded situations, and the climate was warm. _B. sawrockensis_ +probably inhabited denser vegetation than did _B. minimus_ or than does +_B. musculus_. The teeth of the second group (_B. kolbi_, _B. rexroadi_, +_B. brachygnathus_, and _B. taylori_) lack cingular ridges or have them +much reduced and have more hypsodont molars. The three fossil species +probably inhabited relatively open grassland. This assumption is based +largely on the known habitat of _B. taylori_ (see page 632). + +The suggested grouping, based on supposed similarities in niches +inhabited by the extinct species, does not necessarily indicate degree +of relationship. _B. taylori_ probably was not derived from an ancestor +like _B. rexroadi_ or _B. kolbi_, although, in certain characters, the +three species resemble one another. _B. kolbi_ and _B. rexroadi_ were +already specialized in Blancan times, probably for living on grassland. +_B. taylori_ shows only a slight advance in specialization of molar +structures compared to either of the aforementioned species but is +slightly smaller and does have longer and more recurved incisors. If +only morphological criteria of lower jaws were considered, without +recourse to other data derived from the study of many samples of +populations of the living species, time alone might account for the +differences among _B. taylori_, _B. rexroadi_, and _B. kolbi_. The +available evidence (see page 658) suggests, however, that _B. taylori_ +was derived from the _B. sawrockensis_-_B. minimus_-_B. musculus_ line. + + [Illustration: FIG. 3. Diagram indicating probable relationships + of living and extinct species of pygmy mice.] + +_Baiomys_ seems to have undergone little basic evolutionary and +morphological change since Late Pliocene time. According to Simpson +(1945:207), hesperomine rodents as a group have undergone little basic +evolution, and "The rapid evolution of new genera was more a matter of +segregation of characters in a group with a great variation than of the +origin of significantly new characters." Perhaps, the living southern +pygmy mouse retains many basic characteristics of one of the early North +American cricetine-like stocks that emigrated to South America near the +end of the Pliocene epoch. There is much to suggest close relationship +of the pygmy mice to certain species of South American hesperomine +rodents of the genus _Calomys_. + + + + +NON-GEOGRAPHIC VARIATION + + +Non-geographic variation in pygmy mice (variation in a single population +resulting from age, individual, seasonal, and secondary sexual +differences) has been but little studied in the past. Mearns (1907:381) +figured progressive stages of wear on the teeth of _B. taylori_; Osgood +(1909:252) and Blair (1941:380) referred to changes in dentition, +weights, and pelages. + +The largest samples available for this study were 47 _B. taylori_ from +the vicinity of Altamira (6 mi. N, 6 mi. W; 5 mi. N, 5 mi. W; 1 mi. S), +Tamaulipas, and 44 _B. musculus_ from El Salvador (1 mi. S Los Planes, +and 1 mi. NW San Salvador--two localities 3 miles apart). + + +VARIATION WITH AGE + +Specimens of both species were segregated into five categories: +Juveniles, young, subadults, adults, and old adults. Juvenal and young +pygmy mice are readily separable from the other three categories; +subadults are less easily distinguished from adults. In order to obtain +an accurate understanding of geographic variation in these mice, only +adults should be used in making taxonomic comparisons. + +_Juveniles._--Nestling mice yet unweaned; sutures in cranium +incompletely closed; bony parts of skull fragile; M3 and m3 not erupted +or only partly erupted and not protruding above margins of alveoli. + +At birth, juveniles are pink, without pelage except for the mystacial +vibrissae and a few hairs about the eye. Blair (_op. cit._:381) recorded +changes with age in color of the skin of new-born and suckling pygmy +mice. Data obtained by me from three litters born in captivity agree +with his findings. Pygmy mice are weaned when 17 to 24 days old. At that +time, the mice possess a fine, but not dense, dusky-gray fur. + +_Young._--Weaned mice; cranium fragile; sutures between frontals and +parietals, interparietal and parietals, basioccipital and basisphenoid, +basisphenoid and presphenoid, premaxillaries and maxillaries widely +open; M3 and m3 erupted beyond margins of their alveoli (molars erupt +from anterior to posterior; M3 and m3, therefore, are last to erupt); in +some specimens, molars slightly worn; pelage still dusky and relatively +fine and sparse. + +_Subadults._--Sutures between bones of skull less widely open than in +young; epiphyses of long bones incompletely coalesced to shaft; relative +to length of skull, braincase higher and rostrum shorter than in adults; +all cusps worn, but dentine not occlusally confluent; primary first and +second folds of third upper molars present; primary first fold and major +fold of lower molars visible; pelage a subtle mixture of colors of young +and adult, but resembling most that of adult; molts into postjuvenal +pelage between 46 and 50 days. + +_Adults._--Sutures of skull, and those between epiphyses and shaft of +long bones obliterated except that, in some mice, sutures of skull +persist between frontoparietal, and interparietal; cusps of molars so +worn that dentine occlusally confluent; small island of enamel in third +upper and lower molars of some specimens; relative to length of skull, +cranium lower, rostrum longer, and interorbital region narrower than in +subadult; cranium appears to be more flattened dorsoventrally; between +subadult and adult stages, principal growth occurs in basioccipital, +basisphenoid, frontals, and parietals; nasals grow less. + +Although all bones of the skull grow in the subadult and early adult +stages (see table 1), the above-named bones grow faster than others and +thus cause the general flattening of the skull, typical of adults +(similar to that reported by Hoffmeister, 1951:7). The body continues to +lengthen, accounting for the increase in total length of the adult (see +table 1). Hind foot, tail and ear, reach their maximum lengths by +subadult stage. Adult pelage has been acquired, and the color is +brighter than in either subadults or old adults. + +_Old Adults._--Characterized principally by well-worn molars; only thin +peripheral band of enamel along with slight evidence of any primary or +secondary folds on any teeth remain; all bones of skull coalesced; +epiphyses and shafts of long bones ankylosed; small bony protuberances +on many skulls; pelage usually ragged, tips of the hairs being worn +away; white flecking and spotting not common, but occurs in some adults. + + TABLE 1.--Average and Extreme Measurements (in Millimeters) of + Skulls of Five Age-groups of Baiomys taylori from vic. + (see p. 595) Altamira, Tamaulipas, Mexico. + + =============+===========+===========+===========+===========+=========== + Age groups | Juvenile | Young | Subadult | Adult | Old adult + -------------+-----------+-----------+-----------+-----------+----------- + Number | | | | | + examined | 3 | 3 | 14 | 19 | 8 + | | | | | + | | | | | + Total length | 77.0 | 92.6 | 97.6 | 99.9 | 101.6 + | (74-79) | (89-96) | (91-103)| (93-105) | (98-107) + | | | | | + | | | | | + Length | 27.3 | 39.3 | 40.4 | 39.8 | 40.9 + of tail | (24-29) | (37-41) | (36-43) | (35-45) | (38-45) + | | | | | + | | | | | + Length | 49.6 | 53.3 | 57.0 | 60.0 | 60.7 + of body | (49-50) | (52-55) | (51-61) | (56-67) | (57-67) + | | | | | + | | | | | + Length of | 11.0 | 13.6 | 14.3 | 14.5 | 14.2 + hind foot | (11) | (13-14) |(13.5-15.0)| (14-15) | (13-15) + | | | | | + | | | | | + Occipitonasal| 14.2 | 16.3 | 17.1 | 17.7 | 17.8 + length |(13.6-15.2)|(15.8-16.9)|(16.7-17.6)|(17.2-18.3)|(17.6-18.1) + | | | | | + | | | | | + Zygomatic | 8.1 | 8.7 | 8.9 | 9.3 | 9.4 + breadth | (7.8-8.6) | (8.6-8.8) | (8.6-9.3) | (9.0-9.6) | (9.1-9.6) + | | | | | + | | | | | + Interorbital | 3.4 | 3.4 | 3.4 | 3.6 | 3.5 + breadth | (3.3-3.5) | (3.3-3.6) | (3.3-3.6) | (3.4-3.8) | (3.3-3.6) + | | | | | + | | | | | + Incisive | | | | | + foramina | 2.9 | 3.5 | 3.7 | 3.9 | 3.9 + (length) | (2.8-2.9) | (3.4-3.6) | (3.6-3.9) | (3.6-4.1) | (3.5-4.0) + | | | | | + | | | | | + Depth | 5.9 | 6.5 | 6.5 | 6.7 | 6.8 + of cranium | (5.6-6.2) | (6.3-6.8) | (6.2-6.8) | (6.4-7.0) | (6.5-7.1) + | | | | | + | | | | | + Alveolar | | | | | + length, | 2.7 | 2.9 | 2.9 | 3.0 | 3.0 + upper molars | (2.5-2.8) | (2.9-3.0) | (2.8-3.1) | (2.9-3.2) | (3.0-3.1) + | | | | | + | | | | | + Postpalatal | 4.8 | 5.9 | 6.2 | 6.5 | 6.5 + length | (4.5-5.3) | (5.8-6.0) | (5.8-6.6) | (6.2-7.2) | (6.3-6.7) + | | | | | + | | | | | + Breadth | 8.1 | 8.5 | 8.4 | 8.6 | 8.6 + of braincase | (7.8-8.7) | (8.5) | (8.0-8.7) | (8.3-8.9) |(8.4-8.8) + -------------+-----------+-----------+-----------+-----------+----------- + + +SECONDARY SEXUAL VARIATION + +The method employed by Dice and Leraas (1936:2) was used to measure the +secondary sexual differences, if there were any, in each of several age +classes. As pointed out by Hooper (1952b:11), individual variation in +small samples can obscure secondary sexual differences. The samples of +_B. taylori_ from the vicinity (see page 595) of Altamira, Tamaulipas, +and the samples of _B. musculus_ from El Salvador (table 2) were large +enough to prevent individual variation from obscuring sexual +differences. Nevertheless, no significant secondary sexual differences +were found in either _B. taylori_ or _B. musculus_ (see table 2). +Therefore, the sexes have been considered together for purposes of +geographic studies. + + TABLE 2.--Analysis of Secondary Sexual Variation in Adult B. taylori + Vicinity of (see p. 595) Altamira, Tamaulipas, and Adult B. + musculus from El Salvador (see p. 595). (One Standard Deviation + on Either Side of the Mean is Given.) + + ==============+==========================+============================ + | Baiomys taylori | Baiomys musculus + Character +------------+-------------+-------------+-------------- + | 21 Males | 18 Females | 17 Males | 13 Females + --------------+------------+-------------+-------------+-------------- + | | | | + Total length |98.4 ± 2.95 |100.5 ± 4.72 |112.04 ± 5.49|113.12 ± 4.23 + | | | | + Length of tail|40.1 ± 2.31 | 40.3 ± 2.39 | 47.12 ± 2.95| 45.70 ± 2.92 + | | | | + Length of body|57.83 ± 1.65| 60.10 ± 4.13| 66.67 ± 3.97| 67.75 ± 2.38 + | | | | + Length of | | | | + hind foot |14.21 ± .53 | 14.44 ± .51 | 15.60 ± .49 | 15.38 ± .64 + | | | | + Length of ear |10.00 ± .00 | 10.00 ± .00 | 11.80 ± .65 | 12.00 ± .41 + | | | | + Occipitonasal | | | | + length |17.48 ± .40 | 17.47 ± .47 | 19.32 ± .35 | 19.04 ± .44 + | | | | + Zygomatic | | | | + breadth | 9.17 ± .33 | 9.15 ± .30 | 9.84 ± .21 | 9.91 ± .28 + | | | | + Least | | | | + interorbital | | | | + breadth | 3.53 ± .11 | 3.48 ± .11 | 3.88 ± .08 | 3.88 ± .12 + | | | | + Postpalatal | | | | + length | 6.35 ± .19 | 6.38 ± .30 | 7.11 ± .15 | 6.95 ± .20 + | | | | + Depth | | | | + of cranium | 6.65 ± .24 | 6.61 ± .17 | 7.10 ± .18 | 7.08 ± .18 + | | | | + Incisive | | | | + foramina | | | | + (length) | 3.82 ± .15 | 3.81 ± .18 | 4.43 ± .11 | 4.35 ± .14 + | | | | + Length | | | | + of rostrum | 5.87 ± .20 | 5.88 ± .21 | 6.81 ± .16 | 6.66 ± .31 + | | | | + Breadth | | | | + of braincase | 8.54 ± .23 | 8.52 ± .12 | 9.84 ± .38 | 9.52 ± .20 + | | | | + Alveolar | | | | + length, | | | | + upper molars | 2.98 ± .08 | 3.01 ± .08 | 3.20 ± .09 | 3.24 ± .10 + --------------+------------+-------------+-------------+-------------- + + +INDIVIDUAL VARIATION + +Length of tail varied more than any other measurement used by +me in taxonomic comparisons. Clark (1941:298), Hoffmeister +(1951:16), and Van Gelder (1959:239) point out that external +measurements generally are more variable than measurements of +the cranium, probably because different techniques of measuring +are employed by different collectors. As can be noted in table 3, +females varied more than males. + +In the 3520 specimens examined, an extra tooth was observed in +only one (see Hooper, 1955:298). The left mandibular tooth-row +of an adult male (USNM 71539) from Omentepec, Guerrero, is +worn more than the right one. Irregularities in number of teeth +and abnormalities in individual teeth seem to be rare in pygmy +mice. + + TABLE 3.--Individual Variation: Coefficients of Variation for + Dimensions of External and Cranial Parts in a Population of + B. Musculus and B. Taylori. + + =====================+=========================+========================= + | Baiomys taylori | Baiomys musculus + +-------------------------+------------------------- + | Vic. (see page 595) | Vic. (see page 595) + Measurement | Altamira, Tamaulipas | El Salvador + +-----------+-------------+------------+------------ + | 21 Males | 18 Females | 17 Males | 13 Females + | C. V. | C. V. | C. V. | C. V. + ---------------------+-----------+-------------+------------+------------ + | | | | + Total length | 3.0 | 4.7 | 4.9 | 3.7 + Length of tail | 5.7 | 5.9 | 6.2 | 6.4 + Length of body | 2.8 | 5.0 | 5.9 | 3.5 + Length of hind foot | 3.7 | 3.4 | 3.0 | 4.1 + Length of ear | 0.0 | 0.0 | 5.5 | 3.3 + | | | | + Occipitonasal length | 2.2 | 2.7 | 1.8 | 2.3 + Zygomatic breadth | 3.6 | 3.3 | 2.2 | 2.7 + Interorbital breadth | 3.2 | 3.3 | 2.2 | 2.9 + Incisive foramina | | | | + (length) | 3.8 | 4.6 | 2.5 | 3.2 + Depth of cranium | 3.6 | 2.5 | 2.5 | 2.5 + Alveolar length, | | | | + upper molars | 2.7 | 2.5 | 2.8 | 3.2 + Postpalatal length | 3.1 | 4.7 | 2.1 | 2.9 + Length of rostrum | 3.3 | 3.6 | 2.4 | 4.7 + Breadth of braincase | 2.7 | 1.4 | 4.0 | 4.9 + ---------------------+-----------+-------------+------------+------------ + +The posterior margin of the bony palate varies from semicircular to +nearly V-shaped. The suture between the nasals and frontals varies from +V-shaped to truncate to W-shaped. The maxillary part of the zygoma +varies from broad to slender in dorsoventral width in both species. + + +PELAGE AND MOLTS + +There are three distinct pelages, juvenal, postjuvenal, and adult. The +sequences of molt and change of pelage from the juvenal, to the +postjuvenal, and from it to adult, are essentially as reported for +_Peromyscus_ by Collins (1918:78-81; 1924:58-60) and Hoffmeister +(1951:5). The juvenal pelage is uniformly dusky gray throughout except +for the paler gray on the venter. In most juvenal mice, the yellow to +ochraceous pigments of the subterminal bands are reduced or absent. +Unlike _Peromyscus_, _Baiomys_ has bright brownish hairs on the head as +the first evidence of the postjuvenal molt (see Figure 4, part a). Blair +(1941:381) reports adult pelage in pygmy mice being evident first at an +age of 46 days. Two of my juveniles born in captivity began the +postjuvenal molt on the 38th and 40th days. The area of new hairs on the +head spreads most rapidly posteriorly. New hair appears ventrally and +laterally at the end of 46 days (see Figure 4, part b). Hair replacement +proceeds more slowly after the "saddle back" stage (described in +_Peromyscus_ by Collins, 1918:80) has been reached. That stage was +reached in two pygmy mice at 52 days (see Figure 4, part c). Areas +immediately posterior to the ears, in the scapular region, molt last. +The postjuvenal pelage was seemingly complete in one captive pygmy mouse +at the end of 60 days. Another captive failed to complete its growth of +new pelage until two additional weeks had elapsed. Length of time +required to molt in pygmy mice is about the same as that reported by +Layne (1959:72) in _Reithrodontomys_. + + [Illustration: FIG. 4. Diagrams showing progress of the postjuvenal + molt in pygmy mice. For explanation of a, b, and c, see text. + All approximately 2/3 natural size.] + +If, after the postjuvenal molt, a distinct adult pelage is acquired it +is difficult to separate it from the annual replacement of pelage in +adults at the beginning of the rainy season. Adults of both species have +been found in molt in all months of the year. To the north, in Texas, +the pelage of winter-taken specimens is denser and slightly more reddish +than that of specimens taken in spring and summer. In the two last +mentioned seasons, the pelage is more uniformly gray. To the south, in +México, the pelage is heavy and long in most specimens taken in the +rainy season. The percentage of specimens in molt immediately before the +rainy season and immediately before the dry season is slightly higher +than in specimens taken at other times of the year. The adult or +seasonal molt (both loss of old pelage and growth of new) resembles that +in _Peromyscus truei gilberti_, described by Hoffmeister (1951:6) as +proceeding "posteriorly as a wave over the entire back." The new hair is +slightly brighter than the old. Old adults are usually in ragged pelage +regardless of season; possibly only one regular annual change of pelage +occurs in most animals before they die. Only one case of melanism was +observed among all the specimens of both species examined. It was a +young male _B. t. taylori_, KU 35943, from 6 mi. SW San Gerónimo, +Coahuila, possessing black hairs throughout. Its hairs are longer and +finer than those on specimens of comparable age and sex. No albino was +found, although Stickel and Stickel (1949:145) record one--an adult male +of _B. taylori_. + + + + +TAXONOMIC CHARACTERS AND RELATIONSHIPS + + +_External parts._--Length of body, foot, ear, and tail are useful when +considered together in distinguishing species and subspecies. I found as +Hooper (1952a:91) did that length of ear in combination with length of +hind foot suffices to identify nearly all specimens to species, +especially where the two species occur together. + +_Pelage._--Color in adults is of especial value in subspecific +determination; the manner in which it varies geographically is described +on pages 609, 630. + +_Skull._--Difference in occipitonasal length and zygomatic breadth, both +having low coefficients of variation, are useful in separating species, +especially where they are sympatric. Shape of presphenoid, nasals, +interparietal, frontoparietal sutures, and length and degree of the +openings of the incisive foramina are useful in delimiting subspecies. +The rostrum of _B. taylori_, in front of the frontonasal suture, is +deflected three to five degrees ventrally in 85 per cent of the adults +examined, and in _B. musculus_ is less, or not at all, deflected. + +_Teeth._--Alveolar length of the upper and lower molar tooth-rows aids +in distinguishing fossil and Recent species, and to a lesser degree in +delimiting subspecies. Occlusal pattern is useful in estimating the +relationship of fossil and living species. Degree of development of the +mesostyle, mesostylid, mesoloph, and mesolophid have been useful in +determining relationship between fossil and living species as well as +useful in separating the living species. Rinker (1954:119) and Hooper +(1957:48) have shown the degree of variation in dental patterns in +_Peromyscus_, _Sigmodon_, and _Oryzomys_, mice thought to be closely +related to _Baiomys_. In pygmy mice, however, the dental patterns are +relatively constant. The lophs and styles are subject to some geographic +variation but, nevertheless, are useful in estimating relationships. + + [Illustration: FIG. 5. Ventral view of hyoid bones. × 18. + + A. _Baiomys musculus brunneus_, adult, female, No. 30182 KU, + Potrero Viejo, 1700 feet, Veracruz. + + B. _Baiomys taylori analogous_, adult, female, No. 36761 KU, + 2 mi. N Ciudad Guzmán, 5000 feet, Jalisco.] + +_Hyoid apparatus._--Shape and, to a lesser extent, size of the hyoid +apparatus differentiate nearly all specimens of _B. taylori_ from all +those of _B. musculus_. The hyoid of _B. taylori_ differs from that of +_B. musculus_ principally in the shape of the basihyal. It possesses an +anteriorly pointed entoglossal process in _B. musculus_, and is not +rounded to completely absent as in _B. taylori_ (see Figure 5). The +shoulders of the basihyal protrude anteriorly in _B. musculus_, and are +not flattened as in _B. taylori_. The total length was measured in a +sample of 55 basihyals of _B. musculus_, and was compared to the total +length of a sample of 80 basihyals of _B. taylori_. The means of the two +samples differ significantly at the 95 per cent level; the mean plus two +standard errors of _B. musculus_ and _B. taylori_, are, respectively, +2.43 ± .02; 2.18 ± .03. There is sufficient overlap of the samples +(mean plus one standard deviation of _B. musculus_ and _B. taylori_, +respectively: 2.43 ± .15; 2.18 ± .15) to make the total length of the +basihyal of only secondary importance in distinguishing species, but +shape and total length of the basihyal, when considered together, serve +to identify all specimens to species. When length of the basihyal is +plotted against occipitonasal length (see Figure 6), all specimens +studied, regardless of age or geographical origin, were separated at the +level of species. The hypohyals of _B. taylori_ seemingly remain +distinct throughout life; those of _B. musculus_ completely fuse in some +adults. The ceratohyals are highly variable in shape and of little +taxonomic use. + + [Illustration: FIG. 6. Relationship of length of basihyal to + occipitonasal length of skull. Black symbols, all below the curved + line, represent measurements of _B. taylori_; open symbols, all + above the curved line, represent measurements of _B. musculus_.] + +The degree of geographic variation in shape of basihyal is not great. +Specimens of _B. musculus pallidus_ from 1 km. NW Chapa, Guerrero, have +a small indentation on the anteriormost part of the entoglossal process. +The shoulder of the basihyal is directed less forward in specimens of +_B. taylori taylori_ from 6 mi. N, 6 mi. W Altamira, Tamaulipas, than in +other specimens of the species. The variations observed seemed not to be +clinal. + +According to White (1953:548) the hyoid, like the baculum (Burt, +1936:146), is little influenced by changes in external environment and +may serve to clarify intergeneric relationships. Hyoids of both species +of _Baiomys_ are smaller than hyoids of all subgenera of _Peromyscus_. +In shape, the hyoids of _Baiomys_ resemble those of _Ochrotomys +nuttalli_ (as explained on page 605, _Ochrotomys_ is here accorded +generic, instead of subgeneric, rank). In size, the hyoid of both +species of _Baiomys_ resembles that in _Reithrodontomys_. Sprague +(1941:304) reports a resemblance in shape between the ceratohyals of +_Baiomys_ and _Reithrodontomys_. The thyrohyals differ from those of +_Reithrodontomys_, being less boot-shaped, and having a slight terminal +expansion as in _Ochrotomys_ (see Sprague, _loc. cit._). In shape, the +large basihyal of _Onychomys_ resembles the smaller one of _B. +musculus_. The basihyal of _Oryzomys_ lacks the entoglossal process +present in _Baiomys_. On the basis of shape of hyoid, _Baiomys_ seems to +be most closely related to _Ochrotomys_. + + [Illustration: FIG. 7. Dorsal view of bacula. × 16. + + A. _B. musculus brunneus_, adult, No. 24336 KU, 3 kms. + W Boca del Río, 10 feet, Veracruz. + + B. _B. taylori taylori_, adult, No. 35937 KU, 6 mi. + SW San Gerónimo, Coahuila.] + +_Baculum._--Of _Baiomys_, 166 bacula were processed, using the method of +White (1951:125), and studied. They provide characters of taxonomic +worth at the level of species and aid in evaluating generic +relationships. + +The baculum of _B. taylori_ differs from that of _B. musculus_ in: shaft +narrow; wings anterior to base projecting dorsolaterally instead of +anteriorly; anterior part knob-shaped having indentation at tip, instead +of anterior part spatulate-shaped (in some) to knob-shaped (see Figure +7), without indentation; significantly shorter (see Table 4). + + TABLE 4.--Length of Bacula + + ==============+===========+=========+==========+===========+========== + | Number of | Average | 3 × | 1 | + Species | specimens | length | standard | standard | Range + | | | error | deviation | + --------------+-----------+---------+----------+-----------+---------- + _B. taylori_ | 108 | 2.535 | .078 | .274 | 2.00-3.12 + | | | | | + _B. musculus_ | 58 | 3.324 | .090 | .233 | 2.80-3.88 + --------------+-----------+---------+----------+-----------+---------- + +In each of the two species, individual and geographic variation in the +baculum is slight; its length varies insignificantly according to age. +Excluding juveniles contained in Table 4, but including young and +subadults, only three bacula of _B. taylori_ were longer than 3 mm., and +only one baculum of _B. musculus_ (a young) was shorter than 3 mm. The +total length of the baculum, considered together with its shape, serves +to identify to species all specimens examined by me. + +The bacula of both species of _Baiomys_ were compared with bacula of +_Akodon_, _Scotinomys_, _Holochilus_, _Oryzomys_, _Zygodontomys_, +_Reithrodontomys_, _Thaptomys_, and _Calomys_ and illustrations of +bacula by Blair (1942:197, 200) of _Peromyscus_ (subgenera _Peromyscus_, +_Haplomylomys_, _Podomys_), _Ochrotomys_, and material at the University +of Kansas Museum of Natural History of _Megadontomys_. Shape of baculum +most resembled that of _Ochrotomys_ and _Calomys_. The bacula of +_Baiomys_, as pointed out by Blair (_op cit._:203), differ as much from +those of the genus _Peromyscus_ as do the bacula of _Reithrodontomys_ +and _Onychomys_. In size of baculum, _Baiomys_ resembles _Ochrotomys_. +Blair (_op. cit._:202) pointed out that the length of the baculum of _B. +taylori subater_ was contained in the length of the animal's body 20.3 +times, and 24.2 times in the length of that of _Ochrotomys nuttalli_. +The length of the baculum of _B. musculus_ (average of 58 specimens +without regard to subspecies) is contained in the length of the body (of +specimens from which the bacula were removed) 22.7 times, a figure +approaching that in _Ochrotomys_. When bacula of both species of +_Baiomys_ were compared to those of _O. nuttalli_, bacula of _B. +musculus_ were found to most closely resemble those of _O. nuttalli_. +The baculum of a single specimen of _Calomys_ (_C. laucha_) was +contained in the length of the body 15.5 times. In general shape, as +well as in possession of an anterior knob and the position of the +expanded posterior wings, the baculum of _C. laucha_ resembles the +baculum of _Ochrotomys_ and _Baiomys musculus_. + +Blair (_op. cit._:201) considers generic _versus_ subgeneric rank for +_Ochrotomys_, and on the basis of studies of the phallus Hooper +(1958:23) stated that "it is clear that _nuttalli_ should be removed +from _Peromyscus_ and should be listed as _Ochrotomys nuttalli_ +(Harlan)." I agree with Hooper (_loc. cit._) and point out that on the +basis of the baculum, there is less of a hiatus between _Baiomys_ on the +one hand, and _Ochrotomys_ and _Calomys_ on the other hand, than there +is between any one of those three genera and _Peromyscus_. + +White (1953:631) reported that the baculum of chipmunks might indicate +relationships more clearly than do skulls and skins. He thought that +skulls might more quickly than bacula reflect the habitus of the animal. +The resemblance in cranial morphology between _Peromyscus_ and _Baiomys_ +is judged to be the result of such a convergence of habitus and the +baculum in _Baiomys_ is thought to reflect relationships more accurately +than does the skull. + +_Auditory ossicles._--Examination of a number of auditory ossicles of +_Baiomys_ reveals constant interspecific differences in the malleus and +incus. There is only slight individual variation, slight variation with +age, and no secondary sexual variation. In _Baiomys taylori_ the +orbicular apophysis of the malleus (see Figure 8, A) is rounded to +nearly ovoid; the anterior process is pointed, and the neck is short, +being slightly recurved. The body of the incus is round and the short +process is elongate. The sides of the long limb of the incus are nearly +parallel. The lenticular process is relatively large. The posterior and +anterior crus of the stapes are bowed, and the muscular process is +either absent or much reduced. + +In _Baiomys musculus_, the orbicular apophysis of the malleus (see +Figure 8, B) is round to oblong, and less ovoid than in _B. taylori_; +the anterior process is less acutely pointed than in _B. taylori_, and +the neck is long, less recurved than in _B. taylori_. The body of the +incus, though tending to be round, is more flattened, and the short +process is knob-shaped, not elongated. The sides of the long limb of the +incus are not parallel. The lenticular process is, relative to the size +of the incus, small. The posterior and anterior crus of the stapes are +more nearly straight than in _taylori_. A prominent muscular process +occurs on the posterior crus. + +The auditory ossicles of representative species of all the subgenera of +_Peromyscus_ were studied as were the ossicles of _Onychomys_, +_Ochrotomys_, _Oryzomys_, _Akodon_, _Thaptomys_, _Zygodontomys_, +_Calomys_, _Reithrodontomys_, and _Holochilus_. + + [Illustration: FIG. 8. Lateral views of auditory ossicles. × 20. + + A. _B. taylori analogous_, adult, female, No. 28104 KU, 4 kms. + ENE Tlalmanalco, 2290 meters, Estado de México. + + B. _B. musculus pallidus_, adult, male, No. 28346 KU, Cahuilotal, + Sacacoyuca, 960 meters, Guerrero.] + +The general plan of structure of the auditory ossicles in _Baiomys_ +resembles that in _Calomys_, _Akodon_, and _Thaptomys_. The ossicles of +_Calomys_ and _Thaptomys_, in particular, closely resemble the auditory +ossicles of _Baiomys musculus_. The short process of the incus is +knoblike in _Calomys_ and _Thaptomys_, and the general conformation of +malleus and stapes in those two genera is nearly identical to that in +_B. musculus_. In _Akodon_, the anterior and posterior crus of the +stapes is more rounded than in _B. musculus_, resembling that in _B. +taylori_. + +_Reithrodontomys_ differ from _Baiomys_ in having a more elongate +orbicular apophysis on the body of the malleus, an elongated short limb +on the incus, and a stapes having anterior and posterior crura bowed as +in mice of the genus _Peromyscus_. + +In _Ochrotomys_, the orbicular apophysis of the malleus resembles the +orbicular apophysis of _B. musculus_, but the short process of the incus +is longer, resembling the short process of _B. taylori_. In general +conformation of the malleus, incus, and stapes, _Ochrotomys_ shows +closer resemblance to _B. taylori_ than to _B. musculus_. + +In _Holochilus_ the anterior crus and posterior crus of the stapes are +similar to those in _B. musculus_, but in shape and size of malleus and +incus, _Holochilus_ differs considerably from _B. musculus_ and _B. +taylori_. + +In _Zygodontomys_, size and shape of the ossicles differ greatly from +those of _Baiomys_. + +In the genus _Peromyscus_, only _Peromyscus floridanus_ (subgenus +_Podomys_) possesses a knoblike short process on the incus similar to +that in _B. musculus_; representatives of the other subgenera examined +possess an elongated short limb on the incus. The conformation of the +ossicles of both _Onychomys_ and _Oryzomys_ appears to be more nearly +like that in _Peromyscus_ than that of _Baiomys_. + +On the basis of shape and size of auditory ossicles, _Baiomys_ resembles +South American hesperomines (_Calomys_ and _Thaptomys_) rather than +North American hesperomines. + + + + +Genus =Baiomys= True + + + 1894. _Baiomys_ True, Proc. U. S. Nat. Mus., 16:758, February 7. + Type, _Hesperomys (Vesperimus) taylori_ Thomas. + +_Diagnosis._--Size small (total length in adults, 93-135); tail shorter +than head and body; hind foot in adults 12-17; ears small (8-12) and +rounded; upper parts blackish sepia to ochraceous-buff; underparts slaty +gray to white or pale buffy; eyes small; hind feet having six plantar +pads, soles nearly naked except for some hairs on anterior parts of +soles and anteriorly to base of toes and between toes; occipitonasal +length of skull in adults, 17.0-21.5; zygomatic breadth, 9.0-11.5; +coronoid process of mandible well developed, strongly recurved; +ascending ramus of mandible short and erect; anterior palatine foramina +(incisive foramina) long, usually terminating posterior to plane of the +front of first molars; posterior palatine foramina nearly opposite +middle of M2; interorbital space wide relative to widest part of +frontals; nasals projecting only slightly over incisors; condyle +terminal; upper incisors relatively heavy; primary first fold of M3 +obliterated at an early stage of wear; major cusps of upper and lower +anteriormost two molars alternating, more so in m1-m2 than in M1-M2, +dental formula I/i, 1/1; C/c, 0/0; P/p, M/m, 3/3 = 16. + +For distribution of the genus, see Figure 9. + + [Illustration: FIG. 9. Geographic distribution of the genus + _Baiomys_. Black area shows where the two species occur together. + Black dot (Acultzingo, Veracruz) shows locality where _Baiomys + taylori_ occurs within the range of _B. musculus_, but _B. musculus_ + is not known to occur at that locality.] + + + + +SYSTEMATIC ACCOUNT OF SPECIES AND SUBSPECIES + + +=Baiomys musculus= + +Southern Pygmy Mouse + +(Synonymy under subspecies) + + _Type._--_Sitomys musculus_ Merriam, Proc. Biol. Soc. Washington, + 7:170, September 29, 1892. + +_Range._--Southern Nayarit, Michoacán, México, Morelos, Puebla, and +central Veracruz, southeastward to western Nicaragua, but unknown from +southern Veracruz, Tabasco, and the Yucatán Peninsula (see Figure 10); +occurs principally in the arid upper and lower divisions of the Tropical +Life-zone. + +_Characters for ready recognition._--Unless otherwise noted, characters +are usable only for the two age-categories of adult and old adult. +Differs from _B. taylori_ in: hind foot 16 millimeters or more; +occipitonasal length, 19 millimeters or more; zygomatic breadth, 10 +millimeters or more; rostrum not deflected ventrally at frontoparietal +suture but, instead, curving gradually toward anteriormost point of +nasals; cingular ridges and secondary cusps on teeth more pronounced; +basihyal having anterior pointed entoglossal process, shoulders of +basihyal protruding anteriorly (characteristic of all age categories); +baculum having broader shaft, spatulate to knob-shaped tip, wings at +base projecting anteriorly; baculum more than 3 millimeters long; short +process of incus knob-shaped rather than attenuate; muscular process of +posterior crus of stapes prominent. + +_Characters of the species._--Size large (extremes in external +measurements of adults; total length, 100-135; length of tail vertebrae, +33-56; length of hind foot, 14.1-17; length of ear, 9-12); upper parts +dark reddish brown, or ochraceous-buff to nearly black; underparts pale +pinkish buff to white or pale buffy. + +_Geographic variation._--Eight subspecies are here recognized (see +Figure 10). Features that vary geographically are external size, color +of pelage, certain cranial dimensions (occipitonasal length, zygomatic +breadth, least interorbital breadth, length of rostrum, length of +incisive foramina, depth and breadth of cranium, and alveolar length of +upper molar tooth-row). + +External and cranial size (except for _B. m. handleyi_) is less in the +southernmost subspecies, _B. m. pullus_, _B. m. grisescens_, _B. m. +nigrescens_, and more in the northernmost subspecies, _B. m. musculus_, +_B. m. brunneus_, and _B. m. infernatis_. Increase in size from south to +north is in keeping with Bergman's Rule that within a species, smaller +individuals occur in warmer parts of its geographic range. Southern +pygmy mice at high altitudes average larger than those from low +elevations, except where the two species are sympatric. There the +Southern Pygmy Mouse is uniformly larger, regardless of altitude. + +Osgood (1909:257, 259) suggested that degree of relative humidity might +in some way control color of pelage in both _B. taylori_ and _B. +musculus_. In _B. musculus_, the darker subspecies, _B. m. brunneus_, +_B. m. nigrescens_, and _B. m. pullus_, occur in zones of rather +constant high relative humidity, whereas the paler subspecies +_infernatis_, _musculus_, _handleyi_, and to a less extent _grisescens_ +and _pallidus_, occur in zones of lower relative humidity. This is in +keeping with Gloger's Rule, which states that melanins increase in the +warm and humid parts of the range of a species, and reddish or +yellowish-brown phaeomelanins prevail in arid climates. _B. m. musculus_ +ranges into areas where relative humidity is such that darker pelages +might be expected, but this is in the area where the two species are +sympatric, and color of pelage may be an important character of +recognition. + + [Illustration: FIG. 10. Distribution of _Baiomys musculus_. Known + localities of occurrence are represented by circles and black dots; + the former denote localities that are peripheral (marginal) for the + subspecies concerned. + + 1. _B. m. brunneus_ + 2. _B. m. grisescens_ + 3. _B. m. handleyi_ + 4. _B. m. infernatis_ + 5. _B. m. musculus_ + 6. _B. m. nigrescens_ + 7. _B. m. pallidus_ + 8. _B. m. pullus_] + +_Natural History_ + +_Habitat and numbers._--In Veracruz, Dalquest obtained the southern +pygmy mouse in stands of tall grass (_Spartina?_) in sandy loam soil +bordering, and in, dense vegetation; Davis (1944:394) found the species +living in dense stands of grasses and seemingly utilizing underground +burrows. Near Chilpancingo, Guerrero, rocky situations seemed to be the +preferred habitat. Davis (_loc. cit._) believed that the species has a +wide tolerance to kinds of habitats. In Morelos, Davis and Russell +(1954:75) found these mice to be abundant along rock fences separating +cultivated fields, and in arid lowlands. In Colima, Hooper (1955b:13) +obtained specimens from an open thorn forest in sparse grass and rocky +hillside bounding a stream and in litter below shrubs on the floor of a +nut-palm forest; in Michoacán, these mice were taken in cane grass, +shrubs, and mesquite near an irrigation ditch. From Guatemala, Goodwin +(1934:39, 40) records specimens from Sacapulas, a hot, dry, sandy area +where cactus and sparse grasses are present, and from La Primavera, on +the edges of pine-oak-alder forests. Felten (1958:137) has taken +_musculus_ from bushy areas in El Salvadore. In 1955, I obtained the +southern pygmy mouse 6 mi. SW Izucár de Matemores, Puebla, along a +stream in heavy grass bordered by cypress, willow, fig, bamboo, and in +rocky grazed area near sugar cane fields. + +The southern pygmy mouse seems to be locally abundant in certain parts +of its geographic range, and in other parts, scarce. For example, +Dalquest (_in. litt._) recorded the pygmy mouse as common at a place 2 +km. N Paraje Nuevo, 1700 feet, Veracruz, where, by means of 50 traps, he +took 14 of these mice in one night. The species was scarcer, although +the habitat seemed suitable, 3 km. N Presidio, 1500 feet, Veracruz, +where he caught only two pygmy mice in several days of trapping. Six +miles southwest of Izucár de Matemores, the pygmy mouse was the most +common rodent. I have trapped for it in Oaxaca and Veracruz in habitats +that seemed almost identical to those mentioned by Dalquest, and also +that at Izucár de Matemores, Puebla, with almost no success. The reason +for the seeming disparity in numbers at different localities having +nearly the same kind of habitat is unknown to me and bears further +investigation. + +_Behavior._--Little is recorded concerning the behavior of this species. +David and Russell (_op. cit._:76) found that of small mammals _B. +musculus_ was the first to appear at night. I caught mice of this +species by hand in the afternoon in Puebla. They seemed to be active +from noon until dark. Albert Alcorn wrote in his field notes that +specimens were taken near noon at a place 9 mi. NNW Estelí, Nicaragua. +My impression is that _musculus_ is diurnal to crepuscular. + +_Enemies and food._--Owl pellets (thought to be those of a barn owl, +_Tyto alba_) from within the geographic range of _B. musculus_, from 6 +mi. SW Izucár de Matemores, yielded mandibular tooth-rows belonging to +_musculus_. Presumably, most of the carnivorous mammals and raptorial +birds within the range of the southern pygmy mouse could be listed as +enemies. Diurnal to crepuscular habits of this mouse may protect it from +some of the nocturnal carnivorous mammals and raptorial birds. + +Food of the southern pygmy mouse includes nuts, bark, grass seeds, and +leaves. Dalquest (MS) writes that bits of banana proved to be useful +bait in trapping these mice in Veracruz. + +_Reproduction._--Notations concerning lactation and embryos on specimen +labels of females suggest that the southern pygmy mouse breeds in all +months. I have records of pregnant or lactating females in every month, +save January, April, May, and June. The average of 26 counts of embryos +or young per litter is 2.92 (1-4). + + +=Baiomys musculus brunneus= (J. A. Allen and Chapman) + + _Peromyscus musculus brunneus_ J. A. Allen and Chapman, Bull. Amer. + Mus. Nat. Hist., 9:203, June 16, 1897; Elliott, Field Columb. Mus. + Publ., 105(4):136, July 1, 1905; Elliott, Field Columb. Mus. Publ., + 115(8):203, 1907; Osgood, N. Amer. Fauna, 28:259, April 17, 1909. + + _Baiomys musculus brunneus_, Miller, Bull. U. S. Nat. Mus., 79:137, + December 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:318, April 29, + 1924; Ellerman, The Families and Genera of Living Rodents, 2:402, + March 21, 1941; Goldman, Smith. Miscl. Coll., 115:437, July 31, + 1951; Goodwin, Bull. Amer. Mus. Nat. Hist., 102:318, August 31, + 1953; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:512, March 3, + 1955; Booth, Walla Walla Publs., Dept. Biol. Sci., 20:15, July 10, + 1957; Hall and Kelson, The Mammals of North America, 2:661, March + 31, 1959 (part). + + [_Peromyscus musculus_] _brunneus_, Elliott, Field Columb. Mus. + Publ., 95(4): 176, 1904. + + _Peromyscus musculus_ [_musculus_], Osgood, N. Amer. Fauna, 28:258, + April 17, 1909 (part). + + _Baiomys musculus musculus_, Davis, Jour. Mamm., 25:394, December + 12, 1944 (part); Goldman, Smith Miscl. Coll., 115:437, July 31, + 1951; Hooper, Jour. Mamm., 33:97, February 18, 1952 (part); Hall and + Kelson, The Mammals of North America, 2:661, March 31, 1959 (part). + + _B._ [_aiomys_] _m._ [_usculus_] _brunneus_, Hooper, Jour. Mamm., + 33:96, February 18, 1952. + + _Baiomys taylori_, Hooper, Jour. Mamm., 33:97, February 18, 1952 + (part). + +_Type._--Adult female, skin and skull; No. 12535/10845 American Museum +of Natural History; Jalapa, Veracruz, Republic of México; obtained on +April 13, 1897, by F. M. Chapman, original number 1203. + +_Range._--Central Veracruz, coastal plains and eastern slopes of the +plateau of Central México, see Figure 10. Zonal range: Upper Tropical +Life-zone (Lowery and Dalquest, 1951:537), parts of the Veracruz and +eastern Transverse Volcanic biotic provinces of Goldman and Moore +(1945:349). Occurs from near sea level at Boca del Río, Veracruz, up to +5500 feet 3 km. SE Orizaba. + +_Diagnosis._--Size medium to large for the species; ground color of +dorsum of paratypes near Olive Brown; darkest of specimens of this +subspecies examined (from Potrero Viejo, Veracruz) between Prouts Brown +and Mummy Brown; distal two-thirds of guard hairs of dorsum black, +proximal third dark gray to sooty; hairs of dorsum black-tipped having +subterminal band of Ochraceous-Tawny; sides paler (less of dark brown) +than dorsum; venter Deep Olive Buff to clay color, individual hairs pale +olive buff at tips, dark gray basally; region of throat and chin sooty +gray; ventralmost vibrissae white to base, other vibrissae black to +base; ears dark brown, sparsely haired; forefeet and hind feet +flesh-colored in palest specimens, sooty in darkest; tail pale brown, +slightly paler below than above; presphenoid only slightly constricted +towards midline; average and extreme external and cranial measurements +of 10 adults from Cerro Gordo, Veracruz, are as follows: total length, +118.9 (112-127); length of tail vertebrae, 45.1 (42-50); length of body, +74.0 (69-78); length of hind foot, 16.0 (16); length of ear from notch, +12.8 (12-13); occipitonasal length, 19.5 (19.0-20.0); zygomatic breadth, +10.3 (10.0-10.8); postpalatal length, 7.1 (6.7-7.5); least interorbital +breadth, 3.9 (3.7-4.0); length of incisive foramina, 4.4 (4.1-4.6); +length of rostrum, 6.9 (6.5-7.2); breadth of braincase, 9.5 (9.2-9.7); +depth of cranium, 7.1 (7.1-7.4); alveolar length of maxillary tooth-row, +3.3 (3.2-3.3); for photographs of skull, see Plate 1_a_, and Plate 3_a_. + +_Comparisons._--For comparisons with _B. m. nigrescens_, see account of +that subspecies. From _B. m. pallidus_, _B. m. brunneus_ differs in: +dorsal, lateral, and facial coloration deeper reddish brown, more +melanins present; venter darker; buff gray rather than whitish buff to +gray as in paratypical series; vibrissae black rather than brownish to +white; tail sooty, less flesh-colored; forefeet and hind feet averaging +slightly grayer; most external and cranial dimensions averaging slightly +larger; nasals less attenuated; presphenoid less hour-glass shaped, +sides more nearly straight. + +From _B. m. infernatis_, _B. m. brunneus_ differs in: side of face and +neck deep reddish-brown rather than yellowish-gray (the differences in +dorsal colorations are greater between _brunneus_ and _infernatis_ than +between _brunneus_ and _pallidus_); venter darker buff-gray; tail +brownish rather than flesh-colored; forefeet and hind feet average +slightly grayer; most external dimensions averaging slightly larger; +cranial dimensions nearly the same except length of incisive foramina, +which is smaller; presphenoid differs in much the same way as from +pallidus. + +_Remarks_.--Specimens from Chichicaxtle, Puente Nacional, 3 km. W Boca +del Río, 1 km. E. Mecayucan, and Río Blanco (20 km. WNW Piedras Negras), +are all paler than the paratypical series and other specimens from +within the assigned range of _B. m. brunneus_. All these specimens from +the coastal plain average considerably paler than those from the front +range and slopes of the mountains. Specimens from Puente Nacional are +intermediate in color between paler, grayish brown, specimens from the +coastal plains and the darker, brown, specimens from the mountains. When +Allen and Chapman (1897:203) described _brunneus_, they did so on the +basis of the darker brown mice from the higher altitudes. The name, +_brunneus_, _sensu stricto_, could be restricted to those mice from the +higher altitudes of central Veracruz. However, when the mice of +intermediate color from Puente Nacional are considered, it seems best to +include the material from the coastal plain with _brunneus_. Crania from +the higher altitudes are slightly larger than, but not significantly +different from, crania of specimens from the coastal plains. Specimens +examined from the coastal plains resemble the darker series of _B. m. +pallidus_ to the west in central México. But there is no evidence of +gene flow between the paler coastal specimens and _B. m. pallidus_ to +the west. In fact, these paler brown mice on the coastal plain grade in +color into the darker brown mice from the mountains. The paler mice from +the coast may be an incipient subspecies. + +The type and paratypes seem to have faded somewhat since they were +described by Allen and Chapman (_loc. cit._) and by Osgood (1909:259). +However, the color of the paratypes and other specimens herein assigned +is the feature most useful for distinguishing _brunneus_ from all other +subspecies of _B. musculus_. + +_Specimens examined._--Total 187 all from VERACRUZ, Republic of México, +and distributed as follows: type locality, 4400 ft., 16[1] (including +the type), 6[2], 1[3]; _Cerro Gordo_, 1500 ft., 19; _Teocelo_ +[= _Texolo_], 4500 ft., 1; _2 mi. NW Plan del Río_, 1000 ft., 14[4]; +_Plan del Río_, 1000 ft., 2[5]; _Carrizal_, 4[2]; Chichicaxtle, 3[2]; +_Puente Nacional_, 500 ft., 1[5], 2; _Santa Maria, near Mirador_, 1800 ft., +10[2]; Boca del Río, 10 ft., 1[5], 8; _Córdoba_ [= _Córdova_], 14[1]; +_4 km. WNW Fortín_, 4; _Río Atoyac, 8 km. NW Potrero_, 1; _2 km. N. +Paraje Nuevo_, 1700 ft., 9; _El Xuchil_, _1 mi. W. Paraje Nuevo_, 6[6]; +Potrero Viejo, 1700 ft. 15; _Cautlapán_ [= _Ixtaczequitlán_], 4000 ft., +16; _Micayucan_, 1; 3 km. SE Orizaba, 5500 ft., 3; Río Blanco, 20 km. +WNW Piedras Negras, 400 ft, 7; _29 km. SE Córdoba, Presidio_, 15[4]; +_3 km. N Presidio_, 1500 ft., 2; Presidio, 600 meters, 6[3]. + +_Marginal records._--VERACRUZ: type locality; Chichicaxtle; Boca del +Río, 10 ft.; Río Blanco, 20 km. WNW Piedras Negras, 400 ft; Presidio; 3 +km. SE Orizaba, 5500 ft. + +[1] American Museum of Natural History. + +[2] U. S. Nat. Museum (Biol. Surv. Coll.). + +[3] Chicago Natural History Museum. + +[4] Univ. Michigan, Museum of Zoology. + +[5] Texas A & M, Coop. Wildlife Res. Coll. + +[6] Univ. Illinois, Mus. Nat. History. + + +=Baiomys musculus grisescens= Goldman + + _Baiomys musculus griesescens_ Goldman, Proc. Biol. Soc. Washington, + 45:121, July 30, 1932; Ellerman, The Families and Genera of Living + Rodents, 2:402, March 21, 1941; Poole and Schantz, Bull. U. S. Nat. + Mus., 178:259, March 6, 1942; Goodwin, Bull. Amer. Mus. Nat. Hist., + 79(2):160-161, May 29, 1942 (part); Miller and Kellogg, Bull. U. S. + Nat. Mus., 205:513, March 3, 1955 (part); Felten, Senck. Biol., + 39:136, August 30, 1958; Packard, Univ. Kansas Publs., Mus. Nat. + Hist., 9:401, December 19, 1958; Hall and Kelson, The Mammals of + North America, 2:661, March 31, 1959 (part). + +_Type._--Adult female, skin and skull; No. 257083 U. S. Nat. Mus. (Biol. +Surv. Coll.); Comayabuela [= Comayaguela] just south of Tegucigalpa, +3100 feet, Honduras; obtained on March 6, 1932, by C. F. Underwood, +original number 838. + +_Range._--Central to south-central Guatemala, east to south-central +Honduras. Zonal range: Lower parts of the Merendon Biotic Province of +Smith (1949:235). Occurs from 3200 feet at a place 1/2 mi. N and 1 mi. W +Salama, Guatemala, up to approximately 4500 feet at Monte Redondo, +Guatemala. + +_Diagnosis._--Size medium to small for the species; general ground color +of dorsum between Olive Brown and Buffy Brown; distal fourth of +individual guard hairs of dorsum black-tipped, proximal three-fourths +gray, underfur black-tipped with subterminal band of Vinaceous-Buff, +gray basally; facial region below eye Olive-Buff to Deep Olive-Buff; +regions of flanks without black-tipped guard hairs, therefore, appearing +paler brownish-buff than dorsum; venter Pale Olive-Buff to whitish in +midline, hairs there white to base, laterally grayish basally; hairs in +region of throat and chin resemble those of underparts; forefeet and +hind feet flesh-colored with grayish suffusion; ears dusky brown; tail +almost unicolored, slightly darker brown above than below; coronoid +process less acutely falcate than in other subspecies; zygoma bowed. +Average and extreme external and cranial measurements of 14 adults from +La Piedra de Jesús Sabana Grande, Honduras, are as follows: Total +length, 110.7 (100-123); length of tail vertebrae, 44.0 (32-55); length +of body, 66.7 (60-70); length of hind foot, 14.1 (12-15); length of ear +from notch, 11.8 (10-13); occipitonasal length, 19.3 (18.9-19.8); +zygomatic breadth, 10.1 (9.8-10.4); postpalatal length, 6.8 (6.2-7.3); +least interorbital breadth, 3.9 (3.8-4.1); length of incisive foramina, +4.3 (4.0-4.5); length of rostrum, 6.9 (6.6-7.2); breadth of braincase, +9.6 (9.2-10.1); depth of cranium, 7.0 (6.8-7.3); alveolar length of +maxillary tooth-row, 3.2 (3.0-3.4); for photographs of skull, see Plate +1_b_, and Plate 3_b_. + +_Comparisons._--For comparisons with _B. m. pullus_ and _B. m. +handleyi_, see accounts of those subspecies. From _B. m. nigrescens_, +_B. m. grisescens_ differs in: dorsum less blackish (dark brown to +buffy); face buffy below eye rather than brownish-black; venter buffy to +whitish in midline, not sooty gray; forefeet and hind feet flesh-colored +with gray overtones, not dusky to sooty; zygoma bowed, sides less +parallel; braincase and bony palate slightly broader. + +_Remarks._--Goodwin (1942:160) mentioned that a specimen from the type +locality of _grisescens_ was as dark as specimens of _B. m. nigrescens_ +from Guatemala. However, all specimens from Guatemala, other than those +from Sacapulas, were referred by Goodwin (1934:40) to _B. m. +nigrescens_. My studies reveal a grayish-brown population in central +Honduras near to and including the type locality. This population +appears to grade into a slightly paler, particularly as concerns color +of hind foot and tail, group of Guatemalan mice from 1 mi. S Rabinal, +from 1/2 mi. N, 1 mi. E Salama, and from Lake Atescatempa. Specimens +from western Guatemala at Nentón and Jacaltenango, on the other hand, +are darker brownish-black, more nearly like the paratypical series of +_nigrescens_ from the Valley of Comitán, Chiapas, Republic of México. +This darker brownish-black color of the back persists in specimens from +southern Guatemala and El Salvador (see specimens examined of _B. m. +nigrescens_ for localities), and they are best referred to _nigrescens_. +_B. m. grisescens_, in color and certain cranial characters, therefore, +seems to grade into two different subspecies: (1) _B. m. handleyi_, pale +mice in the Río Negro valley in central Guatemala, and (2) _B. m. +nigrescens_, dark mice from southern Guatemala, and parts of El +Salvador. + +Felten (1958:136) referred all _B. musculus_ from El Salvador to _B. m. +grisescens_. Although I have not examined the specimens reported on by +Felten (_loc. cit._), I have examined specimens from Lake Atescatempa, +Guatemala (which I refer to _grisescens_), not too distant from Cerro +Blanco, and Finca Las Canarias, Department of Ahuachapan, and Laguna de +Guija, Department of Santa Ana (localities listed by Felten). It would +seem that specimens from these localities might indeed be _grisescens_. +However, specimens that I examined from 1 mi. S Los Planes, and 1 mi. NW +San Salvador were considerably darker than paratypes of _grisescens_ and +were nearly intermediate in color between _nigrescens_ and _pullus_. I +refer the specimens from 1 mi. NW San Salvador, and 1 mi. S Los Planes +to _nigrescens_ rather than to _grisescens_. + +There is no positive evidence that _B. m. grisescens_ intergrades with +_B. m. pullus_ to the south in Nicaragua. But, there is a suggestion +that intergradation occurs between these subspecies in a series of 76 +skins from La Piedra de Jesús Sabana Grande, Honduras, referable to +_grisescens_. A total of 16 of 76 skins from this locality (21 per cent) +possess the mid-ventral white stripe found in 18 of 20 skins (90 per +cent), from the type locality of _pullus_ in Nicaragua. Further +collection in areas between central Honduras and western Nicaragua may +yield specimens of _B. musculus_ that are intermediate in characters +between _grisescens_ and _pullus_. + +_Specimens examined._--Total 149, distributed as follows: GUATEMALA: 1 +mi. S Rabinal, 3450 ft., 14; 1/2 mi. N, 1 mi. E Salama, 3200 ft., 10; +Lake Atescatempa, 10[7]. HONDURAS: Cementario, Gracias, 1[8]; Monte +Redondo, 1[8]; El Caliche, Cedros, 1[8]; _La Flor Archaga_, 2[8], 1[9]; +Hatillo, 1[8]; _type locality_, 7[8], 6[7] (including the type), 3[9]; +_El Zapote_, _Sabana Grande_, 4[8]; La Piedra de Jesús Sabana Grande, +76[8]; _Cerro de las Cuches Sabana Grande_, 5. + +_Marginal records._--GUATEMALA: 1/2 mi. N, 1 mi. E Salama, 3200 ft. +HONDURAS: El Caliche, Cedros; Hatillo; La Piedra de Jesús Sabana Grande; +Cementario. GUATEMALA: Lake Atescatempa; 1 mi. S Rabinal, 3450 ft. + +[7] United States National Museum (Biol. Surv. Collections). + +[8] American Museum of Natural History. + +[9] Univ. Michigan, Museum of Zoology. + + +=Baiomys musculus handleyi= Packard + + _Baiomys musculus handleyi_ Packard, Univ. Kansas Publs., Mus. Nat. + Hist., 9:399, December 19, 1958. + + _Baiomys musculus musculus_, Goodwin, Bull. Amer. Mus. Nat. Hist., + 68(1):39-40, December 12, 1934 (part); Miller and Kellogg, Bull. + U. S. Nat. Mus., 205:512, March 3, 1955 (part). + + _Baiomys musculus nigrescens_, Hall and Kelson, The Mammals of North + America, 2:661, March 31, 1959 (part). + +_Type._--Adult female, skin and skull; No. 275604 U. S. Nat. Mus. (Biol. +Surv. Coll.); Sacapulas, El Quiche, Guatemala; obtained on April 24, +1947, by Charles O. Handley, Jr., original number 991. + +_Range._--Known only from the type locality in the valley of the Río +Negro. Zonal range: Part of the Chimaltenangan Province of Smith +(1949:235). + +_Diagnosis._--Size medium to large for the species; dorsum Wood Brown in +some series to Buffy Brown; guard hairs of dorsum black-tipped, color of +underhairs Avellaneous; hairs white to base in region of chin, throat, +and median venter; in lateral region, hairs Neutral Gray at base; dorsal +surfaces of forefeet and hind feet and ankles white; tail white below, +brownish above; nasals truncate anteriorly; frontoparietal suture +forming an obtuse angle with the suture separating the parietals; +alveolar length of upper molar tooth-row and tail long. Average and +extreme external and cranial measurements for nine adults from the type +locality are as follows: Total length, 121.4 (115-128); length of tail +vertebrae, 50.7 (49-54); length of body, 70.8 (66-77); length of hind +foot, 15.3 (15-16); occipitonasal length, 19.6 (18.8-20.7); zygomatic +breadth, 10.5 (10.2-11.0); postpalatal length, 6.9 (6.4-7.4); least +interorbital breadth, 4.0 (3.9-4.0); length of incisive foramina, 4.2 +(4.0-4.5); length of rostrum, 7.2 (7.0-7.7); breadth of braincase, 9.8 +(9.7-10.2); depth of cranium, 7.1 (6.8-7.2); alveolar length of +maxillary tooth-row, 3.5 (3.4-3.6); for photographs of skull, see Plate +1_c_, and Plate 3_c_. + +_Comparisons._--From _B. m. nigrescens_, _B. m. handleyi_ differs as +follows: everywhere paler; forefeet and hind feet whitish instead of +dusky to sooty; hairs of anterior part of face white instead of brown; +tail bicolored instead of unicolored; anterior tips of nasals truncate +rather than rounded; frontoparietal suture forming obtuse angle with +suture separating parietals instead of forming right angle; tail and +upper molar tooth-row longer. + +From _B. m. grisescens_, _B. m. handleyi_ differs in: slightly paler +above and below, primarily as a result of lacking buff-colored hairs; +forefeet and hind feet white, not flesh-colored with gray overtones; +tail bicolored, not unicolored; anterior tips of nasals truncate rather +than flaring; tail and upper molar tooth-row longer. + +_Remarks._--_B. m. handleyi_ seems to be restricted to the valley of the +Río Negro, in the region of Sacapulas, Guatemala. Stuart (1954:7) points +out that the Río Negro drops down into a gorge at a place near Sacapulas +and flows northward through a deep canyon for approximately 60 +kilometers. The Río Negro, then, flows onto the lowlands of the Yucatán +Peninsula. The habitat is xerophytic in the valley of the Río Negro near +Sacapulas. Stuart (_op. cit._:10) suggests that this xerophytic habitat +may be continuous to a place to the north of Chixoy, Chiapas, where the +vegetation then becomes more mesic. The mesic conditions to the north in +Tabasco and Yucatán probably have restricted the movement of pygmy mice +to the north. No specimens of this mouse are known from the Yucatán +Peninsula or from the State of Tabasco, México. _B. m. handleyi_ +intergrades with _B. m. grisescens_ to the south. Specimens from 1 mi. S +Rabinal, and those from a second locality 1/2 mi. N and 1 mi. E Salama, +Guatemala, are intermediate in color of pelage between _handleyi_ and +_grisescens_. Stuart (_op. cit._:5) mentions the continuity of habitat +and tributaries from the Salama Basin into the valley of the Río Negro. +Absence of physiographic and biotic barriers in the corridor between +these two basins probably allows for some gene flow between _handleyi_ +and _grisescens_, and results in populations intermediate in color. To +the north and northwest of Sacapulas, the Sierra de los Cuchumatanes +rises abruptly and separates the known geographic range of _handleyi_ +from that of _nigrescens_ to the north, while to the west the +cactus-mesquite habitat of _handleyi_ gives way to the oak-pine timber +that, so far as known, does not support _Baiomys_. The difference in +elevation and flora seems to restrict gene flow between _handleyi_ and +the more northern _nigrescens_. The only evidence of integration between +these two subspecies is provided by one specimen from Chanquejelve, +Guatemala. That specimen is intermediate in color between the pale +_handleyi_ and blackish-brown _nigrescens_. + +The subspecies closest, geographically, to _B. m. handleyi_ is _B. m. +nigrescens_, from which _B. m. handleyi_ differs more in color than from +any of the other named subspecies, except _B. m. pullus_. There is a +close correlation of pallor of mice and the xeric Río Negro Valley, and +the darkness (melanistic color) of mice and the mesic mountains and +valleys to the north. + +_Specimens examined._--Total 49, from GUATEMALA: type locality, +including the type: 12 (U. S. Nat. Mus., Biol. Surv. Coll.), 37 (Amer. +Mus. Nat. Hist.). + + +=Baiomys musculus infernatis= Hooper + + _Baiomys musculus infernatis_ Hooper, Jour. Mamm., 33:96, February + 18, 1952; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:512, + March 3, 1955; Hall and Kelson, The Mammals of North America, + 2:661, March 31, 1959. + + _Baiomys musculus musculus_, Hooper, Jour. Mamm., 28:50, February + 15, 1947 (part). + +_Type._--Adult male, skin and skull; No. 91497 Univ. of Michigan, Museum +of Zoology; Teotitlán, Oaxaca, Republic of México, obtained on February +24, 1947, by Helmuth O. Wagner, original number 2702. + +_Range._--Southeastern Puebla, in the basin drained by the Río Salado +and Río Quiotepec, into northern Oaxaca. Zonal range: Arid Tropical in a +part of the Orizaba-Zempoaltepec Faunal District of the Transverse +Volcanic Biotic Province of Moore (1945:218). Occurs from 3100 feet in +Oaxaca up to 6000 feet in Puebla. + +_Diagnosis._--Size medium for the species; dorsum Drab, terminal parts +of individual guard hairs black, Neutral Gray basally, distal parts of +underfur Pinkish Buff, proximally Neutral Gray; sides same color as +dorsum; hairs in region of throat and chin white to base; venter whitish +to Neutral Gray with tinges of Pinkish Buff; dorsal parts of forefeet +and hind feet whitish with flesh-colored undertones, ventral parts +whitish to dusky-gray; tail bicolored, grayish-brown above, white below; +tip of tail not bicolored, instead grayish-brown throughout; ears pale +brown, sparsely haired; incisive foramina long, not constricted +posteriorly. Average and extreme external measurements for 9 adults from +the type locality are as follows: total length, 113.9 (106-122); length +of tail vertebrae, 44.1 (41-48); length of body, 71.0 (65-79); length of +hind foot, 14.8 (13-16); length of ear, 11.9 (11-12). Average and +extreme cranial measurements of 7 adults from the type locality are as +follows: Occipitonasal length, 20.1 (19.7-20.4); zygomatic breadth, 10.4 +(10.2-10.6); postpalatal length, 7.3 (7.0-7.7); least interorbital +breadth, 4.2 (4.0-4.4); length of incisive foramina, 4.8 (4.4-5.6); +length of rostrum, 7.2 (6.6-7.5); breadth of braincase, 9.6 (9.5-9.8); +depth of cranium, 7.4 (7.1-7.6); alveolar length of maxillary tooth-row, +3.3 (3.1-3.4); for photographs of skull, see Plate 1_d_, and Plate 3_d_. + +_Comparisons._--For comparisons with _B. m. nigrescens_ and _B. m. +brunneus_, see accounts of those subspecies. From _B. m. pallidus_, _B. +m. infernatis_ differs in: sides, ears, and dorsum paler (less of dark +brown); venter whitish gray rather than gray with tinge of buff and +brown; forefeet and hind feet paler; tail bicolored, not unicolored; +incisive foramina longer and not constricted posteriorly; mastoid +process turning dorsally and sickle-shaped at posteriormost point rather +than capitate. + +_Remarks._--_B. m. infernatis_ resembles _B. m. handleyi_ more than any +other subspecies in color of pelage and in external and cranial +dimensions. The resemblance in color between _B. m. pallidus_, in +certain parts of its range, and _B. m. handleyi_ may have resulted from +nearly parallel selective forces that gave rise to two subspecies, +widely separated geographically. The same relation obtains between _B. +m. infernatis_ and _B. m. handleyi_. Both inhabit arid river basins. In +them, pale soil and low relative humidity are important passive factors +of selection that give adaptive value to the pale colors of pelage of +both _infernatis_ and _handleyi_. + +Specimens from 6-1/2 mi. SW Izucár de Matemores, and 1 mi. SSW Tilapa, +Puebla, are intergrades between _B. m. infernatis_ and _B. m. +pallidus_. These specimens are intermediate in color and cranial +characters between the aforementioned subspecies but possess more of the +pale brown overtones seen in paratypes of _pallidus_, and are best +referred to that subspecies. + +_Specimens examined_ (All in Univ. Michigan, Mus. Zool.).--Total 18, all +from the Republic of México and distributed as follows: PUEBLA, +Tepanaco, 6000 ft., 3, Tehuacán, 5400 ft., 3. OAXACA: Type locality, +3100 ft., 12 (including the type). + +_Marginal records._--See specimens examined. + + +=Baiomys musculus musculus= (Merriam) + + _Sitomys musculus_ Merriam, Proc. Biol. Soc. Washington, 7:170, + September 29, 1892; Lyon and Osgood, Bull. U. S. Nat. Mus., + 62:135, January 15, 1909. + + _Baiomys musculus_ [= _musculus_], Mearns, Bull. U. S. Nat. Mus., + 56:381, April 13, 1907; Hooper, Jour. Mamm., 36:29, May 26, 1955. + + _Peromyscus musculus_ [_musculus_], J. A. Allen and Chapman, Bull. + Amer. Mus. Nat. Hist., 9:203, June 16, 1897; Elliot, Field Columb. + Mus. Publ., 105(4):135, July 1, 1905; Osgood, N. Amer. Fauna, + 28:257, April 17, 1909 (part). + + [_Peromyscus_] _musculus_, Trouessart, Cat. Mamm., 1:518, 1898. + + [_Peromyscus_] _musculus_ [_musculus_], Elliot, Field Columb. Mus. + Publ., 95(4):175, July 15, 1904. + + _Baiomys musculus musculus_, Miller, Bull. U. S. Nat. Mus., 79:137, + December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:318, + April 29, 1924 (part); Ellerman, The Families and Genera of Living + Rodents, 2:402, March 21, 1941; Poole and Schantz, Bull. U. S. Nat. + Mus., 178:258, March 6, 1942; Davis, Jour. Mamm., 25:394, December + 12, 1944 (part); Hooper, Jour. Mamm., 28:50, February 15, 1947 + (part); Hall and Villa-R., Univ. Kansas Publs., Mus. Nat. Hist., + 1:460, December 27, 1949 (part); Hall and Villa-R., Anal. del Inst. + Biol., 21:196, September 28, 1950 (part); Goldman, Smith. Miscl. + Coll., 115:336, July 31, 1951 (part); Miller and Kellogg, Bull. + U. S. Nat. Mus., 205:512, March 3, 1955 (part); Hooper, Occas. + Papers Mus. Zool. Univ. Michigan, 565:13, March 31, 1955; Hall and + Kelson, The Mammals of North America, 2:661, March 31, 1959 (part). + + _B._ [_aiomys_] _m._ [_usculus_] _musculus_, Hooper, Jour. Mamm., + 33:97, February 18, 1952 (part); Packard, Univ. Kansas Publs., + Mus. Nat. Hist., 9:400; December 19, 1958. + + _Baiomys taylori allex_, Hall and Kelson, The Mammals of North + America, 2:659, March 31, 1959 (part). + +_Type._--Adult female, skin and skull; No. 33437/45460 U. S. Nat. Mus. +(Biol. Surv. Coll.); Colima (City), Colima, Republic of México, obtained +on March 9, 1892, by E. W. Nelson, original number 2055. + +_Range._--Southwestern Nayarit and northwestern Jalisco, south into +Colima, thence eastward into Michoacán. Zonal range: part of arid Lower +Tropical Subzone of Goldman (1951:330); approximates part of the +Nayarit-Guerrero Biotic Province of Goldman and Moore (1945:349). Occurs +from near sea level in Colima up to 5800 feet in Jalisco. + +_Diagnosis._--Size large for the species; dorsum Olive-Brown in darkest +series to Buffy Brown with tones of Fawn Color in the palest series; +guard hairs of dorsum black-tipped, gray basally (in some specimens, +guard hairs gray-tipped with subterminal black band, and gray base); +underfur of dorsum black-tipped with subterminal band of fawn to buff, +Neutral Gray basally; face and head paler than back because of greater +number of fawn-colored and buff-colored hairs; hairs on throat and chin +white to base; venter and flanks Pale Olive-Buff in palest series to +Gray (Pale Gull Gray) in darkest series; individual hairs of venter +tipped with white to buff, basally Gray (Dark Gull Gray); forefeet and +hind feet white to gray with flesh-colored undertones; tail faintly +bicolored, individual hairs above black, below white; nasals flared +anteriorly; zygoma and zygomatic plate thick. Average and extreme +external and cranial measurements for 8 adults from Armeria, Colima, are +as follows: total length, 125.5 (115-135); length of tail vertebrae, +47.5 (42-54); length of body, 75.6 (68-81); length of hind foot, 16.5 +(16-17); occipitonasal length, 20.3 (19.8-20.7); zygomatic breadth, 10.7 +(10.3-11.1); postpalatal length, 7.4 (7.1-7.7); least interorbital +breadth, 4.0 (3.9-4.1); length of incisive foramina, 4.3 (4.1-4.5); +length of rostrum, 7.3 (6.9-7.6); breadth of braincase, 9.8 (9.4-10.0); +depth of cranium, 7.1 (6.7-7.2); alveolar length of maxillary tooth-row, +3.4 (3.3-3.6); for photographs of skull, see Plate 1_e_, and Plate 3_e_. + +_Comparisons._--For comparisons with _B. m. brunneus_, _B. m. +infernatis_, and _B. m. pallidus_, see accounts of those subspecies. +From _B. m. nigrescens_, _B. m. musculus_ differs in: dorsum paler +throughout (less of blackish brown); region of face and ears paler, more +buff and fawn-colored hairs rather than blackish-brown to grayish hairs; +vibrissae paler; venter paler, less dark gray and less of sooty-colored +undertones, tips of hairs whitish to pale Olive-Buff rather than light +gray at tips becoming darker basally; forefeet and hind feet paler, +whitish to pale buff-color with flesh-colored undertones, not +sooty-colored to dark brown; tail paler below; nasals flaring outward, +not tapering toward midline at anteriormost point; zygoma more massive; +larger in external and cranial dimensions. + +_Remarks._--Merriam (1892:170) described _Sitomys_ [= _Baiomys_] +_musculus_ on the basis of 23 specimens (from Colima City, Colima; +Armeria, Colima; Plantinar, and Zapotlán, Jalisco). According to the +original description, _B. musculus_ resembled a small house mouse and +was smaller than any known species of _Sitomys_ except _S. taylori_ [= +_Baiomys taylori_]. From _taylori_, _musculus_ differed in being larger +[in size of body], and in having longer ears and tail, and larger hind +feet. When Allen and Chapman (1897:203) described _Peromyscus_ [= +_Baiomys_] _musculus brunneus_ from Jalapa, Veracruz, the specimens +described by Merriam from Colima and Jalisco became representative of +the nominal subspecies _B. m. musculus_. Osgood (1909:258) assigned +specimens from Colima, Guerrero, Jalisco, Michoacán, Morelos, Oaxaca, +Puebla, Sinaloa, Veracruz, and Zacatecas to the subspecies _musculus_. +Subsequently, Russell (1952:21) named the subspecies _pallidus_ from the +arid lowlands of Morelos; Hooper (1952:96) described the subspecies +_infernatis_ from northern Oaxaca and southeastern Puebla; and Goodwin +(1959:1) described a new subspecies _nebulosus_ from the Oaxaca +highlands. Each of the subspecies mentioned immediately above was +described from within the geographic range assigned to _B. m. musculus_ +by Osgood (_loc. cit._). Hall and Kelson (1959:661) mapped the range of +_B. m. musculus_ so as to include Colima, parts of Jalisco, Michoacán, +Guerrero, Oaxaca, and Veracruz. Lukens (1955:159), in a study of the +mammals of Guerrero, has shown that the characters attributed to _B. m. +pallidus_ are not significantly different from those of pygmy mice +studied from Guerrero. He (_loc. cit._) concluded that: (1) if the +specimens of pygmy mice from central Guerrero were typical of the +subspecies _musculus_, then _pallidus_ did not deserve subspecific +recognition, or; (2) the name _B. m. musculus_ should be restricted to +the larger pygmy mice inhabiting the lowlands immediately adjacent to +the Pacific Coast and the area to the north. My data (see Figure 12) +show pygmy mice from southwestern Nayarit, northwestern and central +Jalisco, Colima, and parts of Michoacán to be significantly larger in +certain cranial and external measurements than pygmy mice from Guerrero, +Oaxaca, Morelos, and parts of Puebla. This finding essentially +corroborates Hooper's (1952a:96) findings. It seems advisable, +therefore, to restrict the range of _B. musculus musculus_ to the large +mice inhabiting west-central México and the coastal lowlands of Colima +and Michoacán. The name _pallidus_ is applicable to the smaller mice +occupying Morelos, southwestern Puebla, Guerrero, Oaxaca, and +southwestern Chiapas. + +_B. m. musculus_ intergrades with _B. m. pallidus_ in eastern Michoacán +and central and western Guerrero. Specimens from San José Prura and 12 +mi. S Tzitzio, Michoacán, though referable to _B. m. musculus_ because +of slightly larger size of crania are intermediate in size and color +between the smaller and slightly darker _pallidus_ to the south and east +and the larger, slightly paler _musculus_ to the northwest. + +_Specimens examined._--Total 156 all from the Republic of México, and +distributed as follows: NAYARIT: 3 mi. NNW Las Varas, 150 ft., 1. +JALISCO: 7 mi. W Ameca, 4000 ft., 2[10]; _6 mi. W Ameca_, 4300 ft., 3[10]; +_10 mi. S Ameca_, 5800 ft., 1[10]; _13 mi. S, 15 mi. W Guadalajara_, 3; +_13 mi. S, 9-1/2 mi. W Guadalajara_, 1; _3 mi. ENE Santa Cruz de las +Flores_, 1; 27 mi. S, 12 mi. W Guadalajara, 1; _4 mi. NE Autlán_, 3000 +ft., 5[10]; _Sierra de Autlán_, 5000 ft., 2[10]; _2-1/2 mi. NNE Autlán_, +3000 ft., 8; 2 mi. SSE Autlán, 1; _5 mi. S Purificación_, 2; Chamela +Bay, 1[10]; _2 mi. N La Resolana_, 1500 ft., 6[10]; _1 mi. N San Gabriel_, +4000 ft., 32[10]; 2 mi. N Cuidad Guzmán, 5000 ft., 1; 3 mi. E Navidad, +4300 ft., 10[10]. COLIMA: _type locality_, 10[11] (including the type); _3 +mi. SE Colima_ (_City_), 5[10]; _4 mi. SW Colima City_, 1; Armeria, 200 +ft., 8[11]; _Paso del Río_, 20[10]. + +MICHOACÁN: 12 mi. S Tzitzio, 6[10]; San José Prura, 4[12]; 1 mi. E, 6 mi. +S Tacámbaro, 4000 ft., 3[13]; La Salada, 3[11]; 1/2 mi. SE Coalcomán, +15[10]. + +_Marginal records._--NAYARIT: 3 mi. NNW Las Varas, 150 ft. JALISCO: 3 +mi. E Navidad, 4300 ft.; 27 mi. S, 12 mi. W Guadalajara. MICHOACÁN: 12 +mi. S Tzitzio; San José Prura; 1/2 mi. SE Coalcomán. COLIMA: Armeria, +200 ft. JALISCO: Chamela Bay. + +[10] Univ. Michigan, Museum of Zoology. + +[11] U. S. Nat. Museum (Biol. Surv. Coll.). + +[12] Chicago Natural History Museum. + +[13] Univ. California, Mus. Vert. Zoology. + + +=Baiomys musculus nigrescens= (Osgood) + + _Peromyscus musculus nigrescens_ Osgood, Proc. Biol. Soc. + Washington, 17:76, March 21, 1904; Elliot, Field Columb. Mus. Publ., + 105(4):136, July 1, 1905; Lyon and Osgood, Bull. U. S. Nat. Mus., + 62:135, January 15, 1909; Osgood, N. Amer. Fauna, 28:259, April 17, + 1909. + + _Baiomys musculus nigrescens_, Miller, Bull. U. S. Nat. Mus., + 79:137, March 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:318, + April 29, 1924; Goodwin, Bull. Amer. Mus. Nat. Hist., 68(1):40, + December 12, 1934; Ellerman, The Families and Genera of Living + Rodents, 2:402, March 21, 1941; Poole and Schantz, Bull. U. S. Nat. + Mus., 178:259, March 6, 1942; Hooper, Jour. Mamm., 28:50, February + 15, 1947; Goldman, Smith. Miscl. Coll., 115:357, July 31, 1951; + Miller and Kellogg, Bull. U. S. Nat. Mus., 205:513, March 3, 1955; + Booth, Walla Walla Publs., Dept. Biol. Sci., 20:15, July 10, 1957; + Hall and Kelson, The Mammals of North America, 2:661, March 31, 1959 + (part). + + [_Peromyscus musculus_] _nigrescens_, Elliot, Field Columb. Mus. + Publ., 95(4):176, 1904. + + _B._ [_aiomys_] _m._ [_usculus_] _nigrescens_, Goodwin, Bull. Amer. + Mus. Nat. Hist., 79(2):160, May 29, 1942; Hooper, Jour. Mamm., + 33:97, February 18, 1952 (part); Packard, Univ. Kansas Publs., + Mus. Nat. Hist., 9:399, December 19, 1958. + + _B._ [_aiomys_] _m._ [_usculus_] _musculus_, Booth, Walla Walla + Publs., Dept. Biol. Sci., 20:15, July 10, 1957 (part). + +_Type._--Adult female, skin and skull; No. 76827 U. S. Nat. Mus. (Biol. +Surv. Coll.); Valley of Comitán, Chiapas, Republic of México, obtained +on December 9, 1895, by E. W. Nelson and E. A. Goldman, original number +8719. + +_Range._--Southern coastal region and eastern parts of Chiapas, +southeastward into central and southern Guatemala, thence south into El +Salvador (see Figure 10). Zonal range: parts of Lower Austral; also +occurs in parts of the arid division of the Upper Tropical Life-zone, +and in parts of the arid division of the Lower Tropical Life-zone; +approximates a part of the Chiapas Highlands Biotic Province of Goldman +and Moore (1945:349), and parts of the Guatemalan Subregion of Smith +(1949:235). + +_Diagnosis._--Size medium to small for the species; dorsum Vandyke Brown +mixed with blackish, individual hairs black-tipped with a subterminal +band of Warm Buff, Neutral Gray at base; guard hairs of dorsum black +distally, Neutral Gray basally; hairs on sides grayish-brown, facial +region like dorsum; chin buffy-brown; vibrissae brown, ventrally some +white; venter creamy-buff to grayish, individual hairs creamy-buff at +tips, gray basally; in region of throat and chin, hairs tipped with +Ochraceous-Buff; dorsal surface of forefeet and hind feet dull whitish +gray to brownish-black; tail indistinctly bicolored, dusky above, +grayish to brownish below; incisive foramina short, wide medially; +average and extreme external and cranial measurements of 15 adults from +6 mi. NW Tonalá, Chiapas, are as follows: total length, 107.5 (100-116); +length of tail vertebrae, 41.1 (33-48); length of body, 66.1 (62-73); +length of hind foot, 15.0 (14-16); length of ear, 10.9 (10-12); +occipitonasal length, 18.9 (18.4-19.7); zygomatic breadth, 9.8 +(9.4-10.2); postpalatal length, 6.9 (6.6-7.4); least interorbital +breadth, 3.7 (3.5-3.8); length of incisive foramina, 4.4 (4.1-4.8); +length of rostrum, 6.7 (6.1-7.1); breadth of braincase, 9.2 (9.0-9.4); +depth of cranium, 6.9 (6.5-7.3); alveolar length of maxillary tooth-row, +3.1 (2.9-3.2); for photographs of skull, see Plate 1_f_, and Plate 3_f_. + +_Comparisons._--For comparisons with _B. m. handleyi_, _B. m. +grisescens_, _B. m. musculus_, _B. m. pallidus_, and _B. m. pullus_, see +accounts of those subspecies. + +From _B. m. brunneus_, _B. m. nigrescens_ differs in: dorsum +blackish-brown rather than reddish to ochraceous brown; face and ears +brownish-black rather than brownish with tinges of ochraceous; vibrissae +darker; forefeet and hind feet darker; venter with more grayish tones; +dorsalmost part of zygomatic plate projects farther anteriorly; +interparietal oval to diamond-shaped and narrower anteroposteriorly; +zygomata narrower at anteriormost part; slightly smaller in most cranial +and external measurements. + +From _B. m. infernatis_, _B. m. nigrescens_ differs in: dorsum darker; +region of face and ears darker; venter buffy to gray rather than +whitish-buff; vibrissae darker; forefeet and hind feet darker; tail +darker above and below; incisive foramina shorter, more constricted +laterally; cranium slightly smaller in most dimensions. + +_Remarks._--Hooper (1952a:93-94) reported specimens from the coastal +strip of southern Chiapas as the most intensely pigmented, whereas, +specimens from central and western Chiapas were distinctly paler. Crania +of specimens from the coastal region of southern Chiapas were smaller +than crania from the central highlands and mountains of Chiapas. My +studies essentially corroborate the findings of Hooper. The gradation of +color between the pale brown _pallidus_ to the north in Oaxaca, and the +brownish-black _nigrescens_ to the south in Chiapas is extremely +gradual. Specimens from the central and western parts of Chiapas (see +Figure 10 for localities) are difficult to assign to either _pallidus_ +or _nigrescens_. Equal justification exists for assignment to either +subspecies. I have assigned the specimens to _nigrescens_ because they +are geographically closer to the type locality of _nigrescens_. +Specimens from Reforma, Oaxaca (assigned by Hooper, 1952a:93-94, to +_nigrescens_), are nearly identical in size and color to paratypes of +_pallidus_. I assign the Reforma specimens to _pallidus_. + +The darkest of all the specimens examined and assigned to _nigrescens_ +are from 1 mi. NW San Salvador and 1 mi. S Los Planes, El Salvador. The +variations in color in this subspecies closely correspond to degree of +relative humidity; the palest samples are from areas of low relative +humidity and the darkest are from areas of high relative humidity. In +view of the present state of differentiation of specimens from the +southern coastal areas of Chiapas and mountainous areas of El Salvador, +it would seem that populations there might be incipient subspecies. + +_Specimens examined._--Total 319. CHIAPAS: _17 mi. W Bochil_, 1[14]; _15 +mi. W Bochil_, 1[14]; _14 mi. W Bochil_, 1[14]; Bochil, 6[15]; Ocuilapa, +3500 ft., 5[16]; _5 mi. NNW Tuxtla Gutiérrez_, 9; _11 km. W Tuxtla +Gutiérrez_, 800 m., 2[15]; _10 km. W Tuxtla Gutiérrez_, 800 m., 2[15]; +_Tuxtla Gutiérrez_, 2600 ft., 8[16], 11; _Ocozocoautla_, 10[15], 2[16]; 25 +mi. E Comitán, Las Margaritas, 1250 m., 5[17], 24[15]; Cintalpa, 555 m., +1[14], 18[15], 3[17]; _Jiquilpilas_, 2000 ft., 1[16]; San Bartolome, 3[16]; +_type locality_, 5700 ft., 26[16] (including the type); 15 mi. SW Las +Cruces, 1; Villa Flores, 600 m., 12[15]; _23 mi. S Comitán_, 1[14]; _15 +mi. S, 2 mi. E La Trinitaria_, 4; _30 mi. S Comitán_, 2[14]; 35 mi. S +Comitán, 1[14]; _3 mi. E Arriga_, 1[14]; 6 mi. NW Tonalá, 19; _Tonalá_, +8[16]; _Los Amates_, 1[14]; Pijijiapan, 10 m., 7[15]; Mapastepec, 45 m., +25[15], 4[17]. + +GUATEMALA: Chanquejelve, 1[14]; _Nentón_, 3000 ft., 1[16]; Jacaltenango, +5400 ft., 8[16]; La Primavera, 5[14]; 4 mi. S Guatemala City, 4700 ft., 3; +_5 mi. S Guatemala City_, 4050 ft., 10; _6 mi. S Guatemala City_, 4680 +ft., 1; _Lake Amatitlán_, 4500 ft., 13[16]; El Progresso (Distrito Santa +Rosa), 3[15]; _2 mi. N, 1 mi. W Cuilapa_, 2980 ft., 1[14]; _1 mi. WSW El +Molino_ (_Distrito Santa Rosa_), 2; _2-1/2 mi. W, 2-1/4 mi. N San +Cristobal_, 2900 ft., 1; El Zapote, 1[15]. + +EL SALVADOR: 1 mi. NW San Salvador, 29; 1 mi. S Los Planes, 15. + +_Marginal Records._--CHIAPAS: Bochil; 25 mi. E Comitán, Las Margaritas, +1250 ft. GUATEMALA: Chanquejelve; La Primavera; Jacaltenango, 5400 ft.; +4 mi. S Guatemala City, 4700 ft.; El Progresso. _El Salvador_: 1 mi. NW +San Salvador; 1 mi. S Los Planes. GUATEMALA: El Zapote. CHIAPAS: +Mapastepec, 45 m.; Pijijiapan, 10 m.; 6 mi. NW Tonalá; 15 mi. SW Las +Cruces; Cintalpa, 555 m.; Ocuilapa, 3500 ft. + +[14] American Museum of Natural History. + +[15] Univ. Michigan, Museum of Zoology. + +[16] U. S. Nat. Museum (Biol. Surv. Coll.). + +[17] University of Florida Collections. + + +=Baiomys musculus pallidus= Russell + + _Baiomys musculus pallidus_ Russell, Proc. Biol. Soc. Washington, + January 29, 1952; Davis and Russell, Jour. Mamm., 35:75, February + 10, 1954; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:512; Hall + and Kelson, The Mammals of North America, 2:662, March 31, 1959. + + _Peromyscus musculus brunneus_, Elliot, Field Columb. Mus. Publ., + 115(8):203, 1907 (part). + + _Peromyscus musculus_ [_musculus_], Osgood, N. Amer. Fauna, 28:257, + April 17, 1909 (part). + + _Baiomys musculus musculus_, Miller, Bull. U. S. Nat. Mus., 79:137, + December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:318, + April 29, 1924 (part); Davis, Jour. Mamm., 25:394, December 12, 1944 + (part); Hooper, Jour. Mamm., 28:50, February 15, 1947 (part); + Goldman, Smith, Miscl. Coll., 115:336, July 31, 1951 (part); Miller + and Kellogg, Bull. U. S. Nat. Mus., 205:512, March 3, 1955 (part); + Booth, Walla Walla Publs., Dept. Biol. Sci., 20:15, July 10, 1957 + (part); Hall and Kelson, The Mammals of North America, 2:661, + March 31, 1959 (part); Goodwin, Amer. Mus. Novitates, 1929:1, + March 5, 1959. + + _B._ [_aiomys_] _m._ [_usculus_] _musculus_, Hooper, Jour. Mamm., + 33:97, February 18, 1952 (part). + + _B._ [_aiomys_] _m._ [_usculus_] _nigrescens_, Hooper, Jour. Mamm., + 33:97, February 18, 1952 (part). + + _Baiomys musculus nebulosus Goodwin_, Amer. Mus. Novitates, 1929, + March 5, 1959. + +_Type._--Adult female, skin and skull; No. 4501 Texas A&M Cooperative +Wildlife Collection; 12 kms. NW Axochiapán, 3500 feet, Morelos, Republic +of México, obtained on July 28, 1950, by W. B. Davis, original number +5112. + +_Range._--Guerrero thence eastward into Morelos and west central Puebla +along the southern edge of the Transverse Volcanic Biotic Province +(Goldman and Moore, 1945:349), south into Oaxaca, see Figure 10. Zonal +range: largely Arid Lower Tropical Subzone of Goldman (1951:330). Occurs +from near sea level in Oaxaca and Guerrero up to 6550 feet in Oaxaca. + +_Diagnosis._--Size medium for the species; dorsum Buffy Brown in palest +series to Olive-Brown in darkest series, individual hairs Warm Buff, +Neutral Gray basally, some with black tips and a subterminal band of +Warm Buff, guard hairs of dorsum black-tipped, gray basally; hairs on +sides creamy-buff, gray basally; face same color as back fading to white +on throat; vibrissae white-tipped, pale brown basally; venter, whitish +with tinges of buff on lower throat, individual hairs having tips white +to buffy-white, light gray basally; dorsal surface of forefeet and hind +feet whitish to flesh-color; tail indistinctly bicolored, brownish +above, grayish brown below; zygoma bowed as in _B. m. grisescens_; tail +short; average and extreme external and cranial measurements for 17 +adults from Tehuantepec, Oaxaca, are: total length, 117.3 (110-126); +length of tail vertebrae, 46.9 (41-51); length of body, 70.4 (65-76); +length of hind foot, 15.8 (15-16); occipitonasal length, 18.9 +(18.2-20.1); zygomatic breadth, 10.1 (9.7-10.6); postpalatal length, 6.9 +(6.6-7.5); least interorbital breadth, 3.8 (3.6-3.9); length of incisive +foramina, 4.4 (4.2-4.7); length of rostrum, 6.7 (6.3-7.2); breadth of +braincase, 9.3 (8.7-9.7); depth of cranium, 6.6 (6.4-6.8); alveolar +length of maxillary tooth-row, 3.2 (3.1-3.4); for photographs of skull, +see Plate 1g, and Plate 3g. + +_Comparisons._--For comparisons with _B. m. brunneus_ and _B. m. +infernatis_, see accounts of those subspecies. + +From _B. m. musculus_, _B. m. pallidus_ differs in: dorsum more +olive-gray and brown, less ochraceous on either side of mid-dorsal +region; face below eye grayish, not buffy; sides gray with buffy +overtone, not creamy with light yellow overtones; venter grayish-white +rather than an olive-buff; zygomata more tapering anteriorly; maxillary +part of zygoma narrower when viewed from above; external and cranial +dimensions smaller. + +From _B. m. nigrescens_, _B. m. pallidus_ differs in: dorsum paler, +fewer black hairs medially; face paler, less sooty; vibrissae brownish +with white tips rather than black with brownish tips; venter paler; +dorsal surface of forefeet and hind feet whitish to flesh-colored rather +than sooty to dusky-white; tail paler; nasals slightly more attenuated; +averaging slightly larger in external and cranial measurements. + +_Remarks._--Russell (1952:21) described _pallidus_, on the basis of +specimens from the arid Balsas Basin, of Morelos, as pale gray dorsally. +After examining the original material from Morelos, I find the dorsal +color of _pallidus_ to be much closer to a buffy brown than a pale +grayish. Even so, smaller size differentiates _pallidus_ from +_musculus_. _B. m. infernatis_, not _B. m. pallidus_, is the most pallid +of all named subspecies of _B. musculus_. + +_B. m. pallidus_ intergrades to the northwest with _B. m. musculus_, to +the northeast with _B. m. infernatis_, and to the southeast with _B. m. +nigrescens_. + +According to Goodwin (1959:2), _B. m. nebulosus_ (named on the basis of +one specimen) differs from _B. m. musculus_ [= _pallidus_] from southern +Oaxaca in: darker and longer pelage; larger skull; interorbital region +broader and less constricted posteriorly. From _B. m. nigrescens_ and +_B. m. brunneus_, _B. m. nebulosus_ differs as follows: pelage longer +and softer; skull larger. + +Study of specimens of _B. musculus_ from Oaxaca reveals considerable +variation in external and cranial measurements as well as color, +corresponding to that reported by Goodwin (_loc. cit._). Specimens from +higher altitudes average somewhat darker and larger in external and +cranial size than those at lower elevations. These differences seem to +be microgeographic and not of subspecific rank. Among specimens that I +have studied in Oaxaca are several from different localities (KU 63052, +an adult male, from 3 mi. W Miahuatlán; KU 68964, an adult male from 3 +mi. W Mitla, 6000 ft.; KU 63055, an adult female from 3 mi. S +Candelario, 1200 ft.) that, according to Goodwin (_in. litt._) match +_nebulosus_ in reported color, size of body and skull (except for the +region of the rostrum). + +Two of the three specimens (KU 63052 and 63055) are the darkest of a +series in which the palest are inseparable from _B. m. pallidus_. +Goodwin, who kindly compared the three specimens with the type of +_nebulosus_, mentioned (_in. litt._) that the skull of the type has a +slenderer rostrum. Included in the series of skulls of _B. m. pallidus_ +from 3 mi. W Mitla are several adults (not seen by Goodwin) with slender +rostra. _B. m. nebulosus_ is judged to be a synonym of _B. m. pallidus_. + +Populations of pygmy mice occurring in partially isolated areas of +highland in Oaxaca seem to me to be incipient subspecies. + +_Specimens examined._--Total 824 all from the Republic of México and +distributed as follows: PUEBLA: 2 mi. S Atlixco, 5800 ft., 1; _1 mi. SSW +Tilapa_, 5800 ft., 2; _6 mi. SW Izucár de Matemores_, 7; _Piaxtla_, 3900 +ft., 4[18]; Acatlán, 4100 ft., 1. MORELOS: 5 mi. W Tepoztlán, 6000 ft., +7[19]; _1 mi. W Tepoztlán_, 6000 ft., 9[19]; _2 mi. SW Tepoztlán_, 7000 +ft., 1[20]; _Cuernvaca_, 9[19]; _6 mi. W Yautepec_, 4500 ft., 1[20]; +_Yautepec_, 12[19]; _3 mi. N Alpuyeca_, 4000 ft., 2[20]; _Puente de +Ixtla_, 2[19]; _Tetecala_, 4[21]; _2 km. S Jonacatepec_, 4500 ft., 6[20]; +_type locality_, 6 (including the type). GUERRERO: _Yerbabuena_, 1800 +m., 1; _Cueva de tia Juana_ [= _1.5 km. SSW Yerbabuena_], 1; _Laguna +Honda_, 1840 m. [= _1.5 km. S Yerbabuena_], 3; 9 mi. SE Taxco, 3800 ft., +1[22]; _17 km. S Taxco_, 4000 ft., 2[20]; _Iguala_, 5[19]; _3.2 km. SSE +Iguala_, 970 m., 1; 1 km. SSE Texcaizintla, 1600 m., 2; _Teloloapán_, +20[19], 5[24]; _1 km. N Chapa_, 1470 m., 6; _Chapa_, 1470 m., 5; El Limón, +3[18]; 2-1/2 mi. W Mexcala, 2100 ft., 1[20]; _Río Balsas_, 1[18]; Ayusinaha +[= Ayotzinapa], 1[18]; _Tlapa_, 3900 ft, 1[18]; _2.5 mi. S Almolonga_, +5600 ft., 13[20]; _1 km. N Zihuatanejo_, 1; Zihuatanejo Bay, 4[19]; _Las +Gatas_ [= _2 km. S. Zihuatanejo_], 2; _2 km. SSE Zihuatanejo_, 9; _4 mi. +W Chilpancingo_, 5800 ft., 3[20]; _Chilpancingo_, 4800 ft., 14[18], 21[19], +45[21]; _2 mi. N Tixtla_, 4400 ft., 3[20]; _3.2 km. S Chilpancingo_, 4; +_Cd. Chamilpa_ [= _12 km. ESE Chilpancingo_], 5; _Tlalixtaquilla_, 4200 +ft., 2[18]; _15 km. S. Chilpancingo_, 4300 ft., 10[20]; _1 mi. SW +Colotlipa_, 2700 ft., 16[20]; _2 mi. SW Colotlipa_, 2700 ft., 1[20]; +_Achuitzotla_, 2800 ft., 7[20]; _8 mi. SW Colotlipa_, 1[20]; _5 mi. S +Rincón_, 2600 ft., 2[20]; _8 mi. SW Tierra Colorado_, 600 ft., 1[20]; Río +Aguacatillo, _30 km. N Acapulco_, 1000 ft., 3[20]; 5 mi. ESE Tecpán, 50 +ft., 9; _Ejido Viejo_, _12 km. NNW Acapulco_, 1; _2 mi. NNW Acapulco_, +7; Acapulco, 3[18], 3[21]; Omentepec, 200 ft., 7[18]. OAXACA: _4 mi. E +Huajuapám_, 5000 ft., 1; 2 mi. NW Tamazulapán, 6550 ft., 1; Yalalag, +3000 ft., 5[18]; _11 mi. NW Oaxaca_ [_City_], 1; _Yaganiza_, 3900 ft., +1[18]; Oaxaca [City], 5000 ft., 15, 7[21], 7[19], 5[24]; _3 mi. ESE Oaxaca_ +[_City_], 30; _4 mi. ESE Oaxaca_ [_City_], 5050 ft., 1; _10 mi. SE +Oaxaca_ [City], 1[22]; _Cerro Ocotepec_, 1[23]; Tepantepec, 9[23]; _1 mi. E +Tlacolula_, 5500 ft., 53[19]; _3 mi. W Mitla_, 11; Jalapa, El Campanario, +1[23]; _2 mi. SE Matalán_, 5950 ft., 14; _Lachiguiri_, 2[23]; _Tres +Cruces_, 10[23]; _Agua Blanca_, 11[23]; _San José_, 1[23]; Reforma, 30[19], +7[21], 10[23], 6[24] _Totolapa_, 1[18]; _Nejapa_, _85 km. WNW Tehuantepec_, +500 m., 12[19], 6[24]; _Chicapa_, 2[18]; _Gueladu_ [= _Jalapa_], 6[23]; +_Juchitán_, _Laguna Superior_; Manteca, 8[23], 1[23]; San Bartolo, 3000 +ft., 1[18]; _Ejutla_, 1400 m., 21[19]; _El Bambita_, _Tequisitlán_ 4[23]; +_Mixtequilla_, 2[23]; _Guiencola_, 5[23]; _Tehuantepec_, 200 ft., 26[18], +11[19]; _Sola de la Vega_, 26[19], 3[24]; Huilotepec, 13[18], 3[23]; _Santa +Lucia_, 24[23]; _Cerro de Paste_, _Tenango_, 7[23]; _Sta. C. Quieri_, +3[23]; _Santa Marie Ecatepec_, _Zarzamora_, 13[23]; _Rincón Bamba_, 11[23]; +_3 mi. W Miahuatlán_, 5300 ft., 1; _Miahuatlán_, 12[19], 1[23], 6[24]; _San +Juan Acaltepec_, 5[23]; _Zapotitlán_, 1[23]; _Llano Grande_, 3[18]; +Pinotepa, 700 ft., 2[18]; Juquila, 8[18]; _Arroyo_, _San Juan_, _north of +Cerro Otate_, 1[23]; Cerro Otate, 3[23]; 3 mi. S Candelaria, 1. + +_Marginal records._--MORELOS: 5 mi, W Tepoztlán, 6000 ft. PUEBLA: 2 mi. +S Atlixco, 5800 ft.; Acatlán, 4100 ft. OAXACA: 2 mi. NW Tamazulapán, +6550 ft; Tepantepec; Oaxaca [City], 5000 ft; Yalalag, 3000 ft; Jalapa, +El Campanario; Reforma; Huilotepec; 3 mi. S Candelaria; Cerro Otate; +Pinotepa, 700 ft. GUERRERO: Acapulco; Zihuatanejo Bay; El Limón; 9 mi. +SE Taxco, 3800 ft. + +[18] U. S. Nat. Museum (Biol. Surv. Coll.). + +[19] Univ. Michigan, Museum of Zoology. + +[20] Texas A & M, Cooperative Wildlife Research Collection. + +[21] Chicago Natural History Museum. + +[22] California Academy of Sciences. + +[23] American Museum of Natural History. + +[24] University of Florida Collections. + + +=Baiomys musculus pullus= Packard + + _Baiomys musculus pullus_ Packard, Univ. Kansas Publs., Mus. Nat. + Hist., 9:401, December 19, 1958. + + _Baiomys musculus grisescens_, Goodwin, Bull. Amer. Mus. Nat. Hist., + 79(2):161, May 29, 1942 (part); Miller and Kellogg, Bull. U. S. Nat. + Mus., 205:513, March 3, 1955 (part); Hall and Kelson, The Mammals of + North America, 2:661, March 31, 1959 (part). + +_Type._--Adult female, skin and skull; No. 71605 University of Kansas +Museum of Natural History; 8 mi. S Condega, Estelí, Nicaragua, obtained +on July 15, 1956, by A. A. Alcorn, original number 4218. + +_Range._--West-central Nicaragua, from Matagalpa northwest into the +valley of the Río Estelí, east as far as Jinotega, see Figure 10. Zonal +range: Upper Tropical Life-zone. + +_Diagnosis._--Size medium to small for the species; dorsum +Fuscous-Black, individual hairs black-tipped with a subterminal band of +Ochraceous-Buff, Neutral Gray at base; some hairs on dorsum all black to +Neutral Gray at base; hair on sides Neutral Gray tinged with blackish; +face blackish, becoming buffy on sides of head, and white on throat; +vibrissae black; tail unicolored Chaetura Black; forefeet and hind feet +sooty to dusky-white; mid-ventral region of venter white, hairs white to +base; in region of anus and throat, hairs white-tipped, Neutral Gray at +base; average and extreme external and cranial measurements of the type +and 16 paratypes are as follows: total length, 117.3 (111-121); length +of tail vertebrae, 47.2 (44-50); length of body, 70.4 (66-74); length of +hind foot, 15.5 (14-17); length of ear from notch, 11.9 (10-13); +occipitonasal length, 19.3 (18.9-19.8); zygomatic breadth, 10.2 +(9.7-10.6); postpalatal length, 7.0 (6.8-7.3); least interorbital +breadth, 3.9 (3.8-4.1); length of incisive foramina, 4.3 (4.0-4.6); +length of rostrum, 7.0 (6.5-7.4); breadth of braincase, 9.6 (9.3-10.0); +depth of cranium, 7.0 (6.8-7.3); alveolar length of maxillary tooth-row, +3.1 (3.0-3.2); for photographs of skull, see Plate 1_h_, and Plate 3_h_. + +_Comparisons._--From _B. m. grisescens_, _B. m. pullus_ differs in: +dorsum and tail darker; sides and lateral parts of venter grayish +instead of buffy-brown, thus forming distinct mid-ventral white stripe; +average length of body and tail significantly longer, thus total length +greater; maxillary tooth-row significantly shorter; slightly larger in +other cranial and external dimensions. + +From _B. m. nigrescens_, _B. m. pullus_ differs in: dorsum slightly +darker; face grayish, not sooty; mid-ventral white stripe (absent in +most specimens of _nigrescens_) present and becoming grayish laterally; +tail darker, less hairy, and averaging significantly longer; smaller in +most external and cranial dimensions. + +_Remarks._--_B. m. pullus_ resembles _B. m. nigrescens_ in size and +color but can readily be distinguished from _nigrescens_ by the shorter +tail. _B. m. pullus_ intergrades with _nigrescens_ as shown by +specimens, referable to _B. m. nigrescens_, from 1 mi. NW San Salvador +and from 1 mi. S Los Planes, El Salvador. In color of the dorsum, +specimens from these localities are intermediate between _nigrescens_ +and _pullus_. + +The mid-ventral white stripe characteristic of _pullus_ is present in +three of 28 adults from El Salvador. Goodwin (1942:160) reported white +hairs on the pectoral region of several topotypes of _B. m. grisescens_. +The areas of white hairs on the venter of _grisescens_ occur in +approximately 10 per cent of the specimens examined, whereas in +_pullus_, the frequency of occurrence is 90 per cent. The areas of white +hairs in _grisescens_ are in broad patches on the pectoral region, while +in _pullus_, a white stripe passes from the pectoral region to the +inguinal region in both males and females. I know of no selective +advantage that the presence of this white stripe would confer on the +mice. + +_Specimens examined._--Total 46, all from NICARAGUA, and distributed as +follows: Type locality, 32 (including the type); _9 mi. NNW Estelí_, 8; +_8 mi. NNW Estelí_, 3; San Rafael Del Norte, 1 (Amer. Mus. Nat. Hist.); +_1 mi. NW Jinotega_, 1; Matagalpa, 1 (Amer. Mus. Nat. Hist.). + +_Marginal records._--NICARAGUA: San Rafael Del Norte; Matagalpa; type +locality. + + +=Baiomys taylori= + +Northern Pygmy Mouse + +(Synonymy under subspecies) + +_Type._--_Hesperomys_ (_Vesperimus_) _taylori_ Thomas, Ann. Mag. Nat. +Hist., Ser. 5, 19:66, January, 1887. + +_Range._--Southeastern Arizona and southwestern New Mexico, south into +Chihuahua and Durango, just east of the Sierra Madre Occidental, thence +southeast through Zacatecas, Aquascalientes, Jalisco, Querétaro, and +Guanajuato; two fingerlike projections extend northward, one on the west +along the coast of Sinaloa into southern Sonora, and the other on the +east covering eastern San Luis Potosí, Tamaulipas, eastern Coahuila, +Nuevo León, into south, southeast, and north-central Texas. Southern +margin of range in central México approximates the 19th degree of +latitude (see Figure 11). Arid lower and arid upper subdivisions of the +Tropical Life-zone in south; principally Lower Sonoran and Lower Austral +life-zones in north. + +_Characters for ready recognition._--Unless otherwise noted, characters +are usable for the age-categories of adult and old adult. Differs from +_B. musculus_ in: hind foot less than 16 millimeters; occipitonasal +length less than 19 millimeters; zygomatic breadth less than 10 +millimeters; rostrum deflected ventrally at frontoparietal suture rather +than curving gradually toward anteriormost point of nasals; cingular +ridges and secondary cusps on teeth reduced or absent; basihyal having +entoglossal process much reduced or absent, shoulders of basihyal not +protruding anteriorly, but more flattened (characteristic of all age +categories); baculum having narrower shaft, knob-shaped tip, wings at +base projecting laterally, baculum less than 3 millimeters long; short +process of incus attenuate; muscular process of posterior crus of stapes +reduced. + +_Characters of the species._--Size small (extremes in external +measurements of adults: total length, 87-123; length of tail vertebrae, +34-53; length of hind foot, 12-15; length of ear, 9-12). Upper parts +pale drab or reddish-brown to almost black; underparts grayish to +cream-buff. + +_Geographic variation._--Eight subspecies are here recognized (see +Figure 11). Features that vary geographically are mostly the same as +those that do so in _B. musculus_ (see page 609). + +External and cranial size is less in _B. t. allex_, the southernmost +subspecies, and progressively more in _B. t. paulus_, _B. t. taylori_, +_B. t. ater_, _B. t. subater_, _B. t. fuliginatus_, _B. t. canutus_, and +_B. t. analogous_. Size is largest in subspecies that occur at higher +altitudes. Those subspecies are _B. t. analogous_ and _B. t. +fuliginatus_. The correlation with Bergman's Rule is less exact in _B. +taylori_ than in _B. musculus_. It is noteworthy that the smallest +subspecies, _B. t. allex_, occurs in the area where the two species are +sympatric. + +There is close correlation in _B. taylori_, as also in _B. musculus_, of +darker pelages with zones of high relative humidity. The subspecies +having dark pelages are: _analogous_, _fuliginatus_, and _subater_. The +two first-mentioned subspecies occur at high altitudes, and the other, +_subater_, occurs in the humid coastal region of Texas. The paler +subspecies, _taylori_, _canutus_, and _allex_, occur at lower altitudes. +Two subspecies that occur at relatively high altitudes, _ater_ and +_paulus_, are reddish-brown. The color of pelage in these subspecies +resembles the color of soil upon which they live. Blair and Blossom +(1948:5) demonstrated close correlation of color of soil with color of +pelage in _B. t. ater_ by use of an Ives tint photometer. + + [Illustration: FIG. 11. Distribution of _Baiomys taylori_. Known + localities of occurrence are represented by circles and black dots; + the former denote localities that are peripheral (marginal) for the + subspecies concerned. + + 1. _B. t. allex_ + 2. _B. t. analogous_ + 3. _B. t. ater_ + 4. _B. t. canutus_ + 5. _B. t. fuliginatus_ + 6. _B. t. paulus_ + 7. _B. t. subater_ + 8. _B. t. taylori_] + +_Natural History_ + +_Habitat and numbers._--The habitat occupied by the northern pygmy mouse +ranges from sparse grassy areas along rock walls in central México (see +Davis, 1944:394), and mesquite-cactus associations in southern Texas +(Blair, 1952:242) to heavy stands of grasses such as _Bouteloua_ sp., +_Andropogon_ sp., _Hilaria_ sp., and sacaton grass intermixed with +_Yucca glauca_ in New Mexico, Arizona (see Hoffmeister 1956:281), and +Chihuahua. Baker (1951:213) reports the species from 2 km. W El Carrizo, +Tamaulipas, in dense grass and weeds at the edge of a cornfield. Hooper +(1953:7) recorded the northern pygmy mouse in a cultivated field +overgrown with herbaceous vegetation at Pano Ayuctle, Tamaulipas. In the +State of Sinaloa, Hooper (1955b:13) obtained specimens in grass and +among shrubs and vines bordering a fallow field. The northern pygmy +mouse, in general, lives in situations more xerophytic and more grassy +than does the southern pygmy mouse. + +The northern pygmy mouse, as the southern pygmy mouse, is locally +abundant in its geographic range. Stickel and Stickel (_op. cit._: 145) +pointed out that on the third night of live-trapping in Bexar County, +Texas, there was a sudden increase in unmarked pygmy mice trapped. This +increase in numbers, after the resident population was seemingly marked, +followed a one-half inch rainfall. Collectors from the University of +Kansas, myself included, have had similar experiences in trapping these +mice. In the Mexican states of Guanajuato, Querétaro, and Jalisco, _B. +taylori_ is one of the commonest small mammals. In New Mexico and +Arizona and the Mexican states of Sonora and Sinaloa, nevertheless, +these mice are rare. + +Stickel and Stickel (_loc. cit._) thought that the home range normal for +_B. taylori_ in a grassy habitat was less than 100 square feet, but +Blair (1953:10) thought that a complete home range had not been recorded +by Stickel and Stickel. + +_Behavior._--The northern pygmy mouse is crepuscular to nocturnal and +where I trapped in northern Mexico was one of the first small rodents to +appear in my traps in the evening. Hall and Villa-R (1949:460) recorded +this habit in Michoacán. Observations of wild-taken _B. taylori_ held in +captivity, lend support to its being crepuscular. Captives were rarely +active in bright lights, but in diffuse or dim lights the same mice were +active. + +Blair (1941:381) pointed out that captive _B. t. subater_ were much more +tolerant of one another than mice of the genus _Peromyscus_. He pointed +out also that males aided in care of young. In one litter born in +captivity in the course of my study, the female killed the male when the +young were four days old. In another instance, the female and two +eight-day-old young were killed by the male. Until that time, the male, +female, and young had lived together peacefully. In other litters born +in captivity, adult males did not harm the other mice. + +I have noted, as Blair (_loc. cit._) did, that _B. taylori_ utters +high-pitched squeals in a "singing" posture resembling that of the +coyote, yet remains silent when being handled. + +The northern pygmy mouse makes runways in the grass, in miniature +resembling those of _Microtus_, and often uses runways constructed by +_Sigmodon_. A small firm nest of finely shredded plant material (mostly +grasses) is constructed in burrows or under logs, rocks, or fallen +cactus plants. Thomas (1888:447) recorded nests of fine curly grass and +cornsilk. Secondary refuge nests are not uncommon. Thomas (_loc. cit._) +states, "If other mice live in the same place, the individuals of +_Baiomys_ watch till others disappear, then suddenly steal part of the +other nest and run to their own with it." + +_Enemies and food._--Little is recorded of the animals that prey upon +the northern pygmy mouse. Twente and Baker (1951:120) found remains of +_B. taylori_ in 16 per cent of barn owl pellets (_Tyto alba pratincola_) +collected 21 mi. SW Guadalajara, Jalisco. Presumably most of the +crepuscular and early nocturnal raptorial birds and carnivorous mammals +feed on these mice. + +Food of _B. taylori_ consists in part of grass seeds and leaves, prickly +pear (_Opuntia_ sp.) and the softer exposed parts of roots of vegetation +among which the mice reside. + +_Reproduction._--The northern pygmy mouse breeds throughout the year. +The only months in which I have not recorded pregnant females or females +with young are June and October. Forty-one records of embryos or young +per litter average 2.48 (less than in _B. musculus_), and range from as +few as one to as many as four per litter. + + +=Baiomys taylori allex= (Osgood) + + _Peromyscus allex_ Osgood, Proc. Biol. Soc. Washington, 17:76-77, + March 21, 1904; Elliot, Field Columb. Mus. Publ., 105(6):135, + July 1, 1905; Lyon and Osgood, Bull. U. S. Nat. Mus., 62:124, + January 15, 1909. + + _Baiomys taylori allex_, Packard, Proc. Biol. Soc. Washington, + 71:17, April 11, 1958; Hall and Kelson, The Mammals of North + America, 2:659, March 31, 1959 (part). + + [_Peromyscus_] _allex_, Elliot, Field Columb. Mus. Publ., 95(4):175, + July 15, 1904. + + _Peromyscus taylori paulus_, Osgood, N. Amer. Fauna, 28:255, April + 17, 1909 (part). + + _Baiomys taylori paulus_, Miller, Bull. U. S. Nat. Mus., 79:137, + December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317, + April 29, 1924 (part); Ellerman, The Families and Genera of Living + Rodents, British Mus. Nat. Hist., 2:402, March 21, 1941 (part); + Poole and Schantz, Bull. U. S. Nat. Mus., 178:259, March 6, 1942; + Goldman, Smith. Miscl. Coll., 115:373, July 31, 1951 (part); Miller + and Kellogg, Bull. U. S. Nat. Mus., 205:512, March 3, 1955 (part); + Hall and Kelson, The Mammals of North America, 2:659, March 31, 1959 + (part). + + _Baiomys taylori analogous_, Hall and Kelson, Univ. Kansas Publs., + Mus. Nat. Hist., 5:367, December 15, 1952 (part). + +_Type._--Adult male, skin and skull; No. 33429/45452 U. S. Nat. Mus. +(Biol. Surv. Coll.); Colima (City), Colima, Republic of México, obtained +on March 7, 1892, by E. W. Nelson, original number 2029. + +_Range._--Colima, western lowlands of Michoacán and Jalisco, thence +north into southern half of Nayarit, see Figure 11. Zonal range: arid +lower tropical, approximates northern half of the Nayarit-Guerrero +Biotic Province of Goldman and Moore (1945:349). Occurs from near sea +level in Nayarit, up to 4000 feet in Jalisco. + +_Diagnosis._--Size small for the species; dorsal ground color pale +grayish-brown, near Isabella color; mid-dorsal region washed with +blackish, individual guard hairs black to base, other hairs black-tipped +with subterminal light olive bands, Neutral Gray at base; laterally, +black-tipped hairs less abundant, hairs grayish-white to base; venter +Pale Gull Gray to whitish, distal half of individual hairs white, +proximal half Neutral Gray; hairs in regions of throat and chin white to +base; facial region colored like dorsum, becoming paler below eye; in +region of mouth, hairs white to base; dorsalmost vibrissae black to +base, others white to base; ears flesh-colored, sparsely haired; tail +unicolored, sparsely haired for the species; dark blotches on tail of +some series (particularly the paratypical series); dorsal and ventral +parts of forefeet and hind feet flesh-colored, whitish to gray in some +series. Slightly smaller in most cranial dimensions. Maxillary part of +zygoma forming almost a right angle with rostrum, rather than tapering +at less than a right angle to rostrum; supraoccipital rounded +posteriorly rather than indented on each side of foramen magnum; +cranium, relative to length of rostrum, more nearly square; +interparietal large relative to size of cranium. Average and extreme +measurements of five adults from 2 mi. SSE Autlán are as follows: total +length, 100.0 (93-107); length of tail vertebrae, 40.0 (37-44); length +of body, 60.0 (56-63); length of hind foot, 14.0 (14); length of ear +from notch, 10.5 (10-11); occipitonasal length, 17.3 (16.8-17.9); +zygomatic breadth, 9.1 (8.7-9.4); postpalatal length, 6.3 (6.0-6.6); +least interorbital breadth, 3.4 (3.3-3.5); length of incisive foramina, +3.9 (3.8-4.0); length of rostrum, 5.5 (5.2-5.8); breadth of braincase, +8.6 (8.0-8.9); depth of cranium, 6.4 (6.0-6.7); alveolar length of +maxillary tooth-row, 3.0 (2.8-3.1); for photographs of skull, see Plate +1_i_ and Plate 4_a_. + +_Comparisons._--For comparisons with _B. t. canutus_, see account of +that subspecies. From _B. t. analogous_, _B. t. allex_ differs in: +external and cranial dimensions less; dorsal coloration paler; tail and +ears paler and less hairy; dorsum and belly paler; dorsal and ventral +parts of forefeet and hind feet paler; median parts of incisive foramina +less constricted on either side of midline and wider open laterally; +interparietal larger in relation to skull; interorbital breadth greater +relative to occipitonasal length. + +_B. t. allex_ differs from _B. t. paulus_ as follows: dorsum gray with +yellowish-brown wash rather than fawn to buff; tail unicolored in most +series, less hairy; hind feet flesh-colored to light sooty, rather than +whitish; rostrum slightly longer relative to occipitonasal length; +incisive foramina differ from those of _paulus_ in much the same way as +from _analogous_. + +_Remarks._--Osgood (1909:255-256) dismissed as taxonomically unimportant +the differences in color of pelage and size of cranium that he observed +between the specimens from Colima (City), Colima, representative of +_allex_ and those representing _paulus_ and chose to synonomize _allex_ +with _paulus_. The differences that Osgood (_loc. cit._) deemed "... +scarcely worthy of recognition ...," are, in fact, not only worthy of +recognition, but also important in an understanding of the evolution of +_Baiomys taylori_ (see speciation p. 659). Recently, I (1958b:17-18) +studied ten specimens from Colima (City), Colima, and chose to regard +_Peromyscus [= Baiomys] allex_ as a subspecies. I suggested (_loc. +cit._) that the geographic range of _B. t. allex_ might encompass the +southern part of Nayarit, and western Jalisco. Subsequent study of +specimens from these areas reveals that the populations there are +referable to _allex_. Most of the specimens obtained from these areas, +however, merit special comment. + +In color of pelage, those populations from south of the Río Grande de +Santiago and northwest of Guadalajara (4 mi. SE Ahuacatlán; 1 mi. E +Ixtlán; Etzatlán) show evidence of intergradation with _paulus_ to the +east and south (Magdalena, Tequila, and Tala, Jalisco), and with +populations more closely adjacent to the south bank of that river. +Intergradation is indeed complex in this area. Specimens from some +localities seem to be intergrades between _allex_ and _paulus_; from +other localities, some specimens are referable to _allex_, and the +others to _paulus_; from still other localities, all specimens are +referable to _allex_. + +A series of 39 specimens from 1 mi. SSE Ameca, 4000 ft., Jalisco, are +uniformly grayish-brown. This series averages grayer than paratypes of +_allex_. There is little, if any, difference between the series from 1 +mi. SSE Ameca and paratypes of _allex_ in external size of body, hind +foot, length of ear, and size and conformation of the cranium. +Populations from Ameca and vicinity might be expected to average +considerably larger inasmuch as they occur at higher altitudes (see +Bergman's Rule, p. 609) then the material from the lower coastal plains +to the south in Colima and Michoacán, and at lower elevations in the +west in Jalisco and Nayarit. The means of external and cranial +measurements are not significantly different between the specimens from +the highlands and those from the lowlands. In the area of Ameca where +the two species _B. musculus_ and _B. taylori_ occur together, +interspecific competition seems to have limited, perhaps even reduced, +size of external and cranial parts of _taylori_ (see p. 660). + +In color, specimens from the northern part of the valley of the Río +Tepalcatepec (10 mi. S, 1 mi. W Apatzingán) in Michoacán resemble +paratypes of _allex_. Intergradation probably occurs to the north with +_analogous_. + +In the eight specimens from 13 mi. E and 1 mi. N Talpa de Allendé, the +skull, as reflected in occipitonasal length and zygomatic breadth +relative to length of body, is larger than in other specimens here +assigned to _allex_. The median part of the belly of the eight specimens +is buff-colored rather than whitish-gray as in typical _allex_; the +mid-dorsal region also averages darker than in any other specimens +referred to _allex_. Additional specimens are needed from this and +closely adjacent areas, especially to the west on the coastal plain, in +order to determine more accurately the taxonomic status of the mice +there. At present, it seems best to refer them to _allex_. Possibly the +population represented by the eight specimens is an incipient +subspecies. + +There is no evidence of hybridization or intergradation of populations +of _B. t. allex_ with any population of _B. musculus_ where the two +species occur together. + +_Specimens examined._--Total 233, all from the Republic of México, +distributed as follows: NAYARIT: 3 mi. SE Mirador, 7; _2 mi. S. +Compostela_, 2900 ft., 5; _4 mi. N Santa Isabel_, 3800 ft., 2[25]; _2 mi. +N Santa Isabel_, 3800 ft., 22[25]; _4 mi SE Ahuacatlán_, 5200 ft., 2[26]; +_1 mi. E Ixtlán_, 4000 ft., 13[25]; 1 mi. E Ixtlán del Río, 3700 ft., 1; +2 mi. WNW Valle de Banderas, near sea level, 1. JALISCO: Arroyo de +Gavalán, 16[28]; Etzatlán, 6[27]; _Mascota_, 3900 ft., 6[27]; _7 mi W +Ameca_, 15[25]; _6 mi. W Ameca_, 15[25]; _3 mi. W Ameca_, 5[25]; Ameca, +4000 ft., 11[27]; _1 mi. SSE Ameca_, 4000 ft., 38; 2 mi. N Resolana, 1500 +ft., 28[25]; 13 mi. E, 1 mi. N Talpa de Allendé, 8; 2 mi. SSE Autlán, 5; +1 mi. N San Gabriel, 4000 ft., 1[25]; Las Canoas, l[28]. COLIMA: Type +locality, 10[27] (including the type). MICHOACÁN: 9 mi. S Lombardia, 1500 +ft., 1; _3 mi. W Apatzingán_, 1000 ft, 1; Apatzingán, 3[25]; 10 mi. S, 1 +mi. W Apatzingán, 800 ft., 10. + +_Marginal records._--NAYARIT: 3 mi. SE Mirador; 1 mi. E Ixtlán del Río. +JALISCO: Etzatlán; Ameca; 2 mi. N Resolana; Las Canoas. MICHOACÁN: 9 mi. +S Lombardia; 10 mi. S, 1 mi. W Apatzingán. COLIMA: type locality. +NAYARIT: Valle de Banderas. + +[25] Univ. Michigan, Museum of Zoology. + +[26] California Academy of Sciences. + +[27] U. S. Nat. Museum (Biol. Surv. Coll.). + +[28] American Museum of Natural History. + + +=Baiomys taylori analogous= (Osgood) + + _Peromyscus taylori analogous_ Osgood, N. Amer. Fauna, 28:256, + April 17, 1909 (part); Elliott, Check-List Mamm., N. Amer. Cont., + West Indies and Neighboring Seas, Suppl., Amer. Mus. Nat. Hist., + p. 44, January 8, 1917. + + _Baiomys taylori analogous_, Miller, Bull. U. S. Nat. Mus., 79:137, + December 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:318, April 29, + 1924; Ellerman, The Families and Genera of Living Rodents, British + Mus. Nat. Hist., 2:402, March 21, 1941; Poole and Schantz, Bull. + U. S. Nat. Mus., 178:259, March 6, 1942; Davis, Jour. Mamm., 25:394, + December 12, 1944; Hooper, Jour. Mamm., 28:50, February 15, 1947; + Hall and Villa-R., Univ. Kansas Publs., Mus. Nat. Hist., 1:460, + December 27, 1949; Hall and Villa-R., Anal. del Inst. Biol., 21:196, + September 28, 1950; Goldman, Smith. Miscl. Coll., 114:373, July 31, + 1951 (part); Hall and Kelson, Univ. Kansas Publs., Mus. Nat. Hist., + 5:367, December 15, 1952 (part); Villa-R., Anal. del Inst. Biol., + 23:435, May 20, 1953; Miller and Kellogg, Bull. U. S. Nat. Mus., + 205:512, March 3, 1955; Hooper, Occas. Papers Mus. Zool. Univ. + Michigan, 565:13, March 31, 1955; Packard, Proc. Biol. Soc. + Washington, 71:17, April 11, 1958. + + _Peromyscus musculus brunneus_, Elliot, Field Columb. Mus. Publ., + 115(8):203, 1907 (part). + + _Peromyscus musculus_ [_musculus_], Osgood, N. Amer. Fauna, 28:258, + April 17, 1909 (part). + + _Baiomys musculus musculus_, Hall and Villa-R., Univ. Kansas Publs., + Mus. Nat. Hist., 1:460, December 27, 1949 (part); Hall and Villa-R., + Anal. del Inst. Biol., 21:196, September 28, 1950 (part). + + _Baiomys taylori taylori_, Dalquest, Louisiana State Univ. Studies + (Biol. Sci. Ser.), 1:155, December 28, 1953 (part); Hall and Kelson, + The Mammals of North America, 2:660, March 31, 1959 (part). + + _Baiomys taylori allex_, Hall and Kelson, The Mammals of North + America, 2:659, March 31, 1959 (part). + + _Baiomys musculus musculus_, Hall and Kelson, The Mammals of North + America, 2:661, March 31, 1959 (part). + +_Type._--Adult male, skin and skull; No. 120261 U. S. Nat. Mus. (Biol. +Surv. Coll.); Zamora, Michoacán, Republic of México, obtained on January +15, 1903, by E. W. Nelson, and E. A. Goldman, original number 15764. + +_Range._--Central and eastern Jalisco south into Michoacán, east through +Guanajuato, Querétaro, thence into Estado México, and Distrito Federal, +and west-central Veracruz, see Figure 11. Zonal range: approximately the +Transverse Volcanic Biotic Province of Moore (1945:218) and of Goldman +and Moore (1945:349). Occurs from 5000 feet, 7 mi. S Ocotlán, Jalisco, +up to 8000 feet in Ixtapalapa, Distrito Federal. + +_Diagnosis._--Size large for the species; dorsum dark Sepia to near +blackish medially in freshly taken specimens (Sepia fading to near +Fuscous in prepared specimens); belly slaty-gray, hairs Deep Neutral +Gray near tips and Dusky Neutral Gray at bases; hairs on back +black-tipped with subterminal band of Ochraceous-Tawny (guard hairs +blackish to base); hairs of throat and chin white-tipped, gray at bases; +dorsal vibrissae black, ventral and anteriormost vibrissae white; hairs +on face and sides black-tipped, and Ochraceous-Tawny at base; ears +sparsely haired, individual hairs grayish, blackish, and ochraceous; +tail sooty to blackish dorsally, lighter ventrally; forefeet and hind +feet sooty brown on dorsal and ventral surface. Skull relatively broad +interorbitally; zygoma broad and squared; cranium larger in all +dimensions than in most other subspecies. Average and extreme +measurements of 10 adults from 1 mi. S, 11 mi. W Zamora, 5400 ft., +Michoacán, are: total length, 109.4 (102-121); length of body, 64.3 +(58-72); length of tail, 44.9 (39-51); length of hind foot, 14.6 +(14-15); occipitonasal length, 18.0 (17.5-18.6); zygomatic breadth, 9.4 +(9.1-9.7); postpalatal length, 6.6 (6.2-7.2); least interorbital +breadth, 3.5 (3.3-3.8); length of incisive foramina, 4.0 (3.8-4.2); +length of rostrum, 6.2 (5.8-6.5); breadth of braincase, 8.7 (8.5-8.9); +depth of cranium, 6.6 (6.3-6.9); alveolar length of maxillary tooth-row, +3.1 (3.0-3.3); for photographs of skull, see Plate 2_a_ and Plate 4_b_. + +_Comparisons._--For comparisons with _B. t. allex_, _B. t. canutus_, _B. +t. paulus_, and _B. t. fuliginatus_, see accounts of those subspecies. +From _B. t. taylori_, _B. t. analogous_ differs as follows: sides and +dorsum darker, differing most in freshly prepared specimens; dorsal +surface of forefeet and hind feet darker; basal part of hairs on belly +darker gray; frontal bones less constricted, causing less taper +anteriorly in interorbital space; interparietal wider transversely; +basioccipital more expanded laterally, narrowing more abruptly at suture +between basioccipital and basisphenoid. + +_Remarks._--The pelage of _analogous_ becomes paler with wear as pointed +out by Osgood (1909:257). A paratype, U. S. Nat. Mus. 120260, and +several specimens from 1 mi. S, 11 mi. W Zamora, Michoacán, are grayish +rather than brownish-black. All of these are old adults having the +terminal black parts of the hairs on the dorsum nearly worn away. +Excluding such grayish individuals, _B. t. analogous_, like _B. t. +subater_ and _B. t. fuliginatus_, is uniformly brownish-black. Both +_analogous_ and _fuliginatus_ occur in relatively high mountainous +country on dark soils or pedregals, and all three of the aforementioned +subspecies occur in zones of high relative humidity. + +_B. t. analogous_ intergrades with _B. t. paulus_ (see account of that +subspecies) and _B. t. allex_ south and west of Lago de Chapala in +Jalisco. Additional specimens are needed from Querétaro and San Luis +Potosí in order to ascertain whether or not _B. t. analogous_ +intergrades with _B. t. fuliginatus_ or _B. t. taylori_. Specimens from +western Jalisco, in the past referred to _B. t. analogous_, are +referable to _B. t. allex_ (see account of that subspecies). Specimens +obtained west of, and bordering, the Río del Naranjo in Jalisco show a +mixture of characters of both _B. t. allex_ and _B. t. analogous_. For +example, specimens from 2 mi. N Ciudad Guzmán resemble _analogous_ on +the dorsum, whereas, on the belly, the individual hairs are +white-tipped, pale gray at the base, and in over-all appearance are +whitish-gray, unlike typical _analogous_ (being like _allex_ instead). +The dorsal surface of the forefeet are sooty to light brownish (as in +_analogous_), whereas, the hind feet are flesh-colored (as in _allex_). +Another series of specimens from 4 mi. W León, Guanajuato, are +intergrades between _B. t. analogous_ and _B. t. paulus_. These +specimens are grayish to brownish on the dorsum, have sooty forefeet and +hind feet (more nearly as in _analogous_ than in _paulus_), are +grayish-white on the venter, and have a distinctly bicolored tail +(resembling that of _paulus_ more than that of _analogous_). When the +average of cranial characters is considered, both series are best +referred to _analogous_. + +Hooper (1947:50) pointed out that specimens from the pedregal San +Gerónimo, Distrito Federal, were more nearly black than topotypes and +generally showed less brownish hues typical of _analogous_. I have +examined this series and several others from this area (see Specimens +examined, p. 640) and am convinced that these populations average +darker. Actually, the dorsum is more nearly black and the venter is more +buffy than in typical _analogous_. The hairs of these individuals +average longer than in other populations of _analogous_. Skulls of the +specimens from the pedregal are indistinguishable from those of +paratypes of _analogous_. The populations from the Distrito Federal seem +to be incipient subspecies. + +_Specimens examined._--Total 696, all from the Republic of México, +distributed as follows: SAN LUIS POTOSÍ: Hacienda Capulín, 5[33]; _3.3 +mi. N Tamazunchale, by-road_, 2[34]; 1 mi. N Tamazunchale, 700 ft., 1[35]. +VERACRUZ: Acultzingo, 4[29], 1[31]. JALISCO: 1 mi. S Jalostotitlán, 5700 +ft., 5; 7 mi. NW Tepatitlán, 3[29]; _6 mi. N, 4 mi. E Tepatitlán_, 6400 +ft., 25; _2-1/2 mi. E Tepatitlán_, 6200 ft., 15; _2 mi. S, 1/2 mi. W +Tepatitlán_, 9; _near Tepatitlán_, 2; _5 mi. SW Arrandas_, 6700 ft., 6; +_2 mi. E Zapotlanejo_, 23; _2-1/2 mi. E Puente Grande_ (_5-1/2 mi. SW +Zapotlanejo_), 3; _8 mi. S Guadalajara_, 10[29]; _3 mi. ENE Santa Cruz de +las Flores_, 9; _4 mi. NE Ocotlán_, 5050 ft., 18; _13 mi. S, 9-1/2 mi. W +Guadalajara_, 1; _2 mi. WNW Ocotlán_, 5000 ft., 15; 13 mi. S, 15 mi. W +Guadalajara, 2; _Ocotlán_, 5000 ft., 8[30]; _1 mi. S Ocotlán_, 5000 ft., +12; 27 mi. S, 12 mi. W Guadalajara, 9; _1-1/2 mi. N Mazatmitla_, 6[29]; +_1/2 mi. NW Mazatmitla_, 4; _3 mi. WSW Mazatmitla_, 4; 2 mi. N Ciudad +Guzmán, 5000 ft., 18. GUANAJUATO: 4 mi. N, 5 mi. W León, 7000 ft., 25; 5 +mi. S Salamanca, 2[29]; _5 mi. E Celaya_, 6000 ft., 6; _1 mi. E Yuriria_, +5725 ft., 3; Salvatierra, 5775 ft., 8; _NE edge Acambaro_, 6050 ft., 10; +_Acambaro_, 3[30]. QUERÉTARO: Tolimán, 7[30]; 6 mi. E Querétaro, 6550 ft., +37. HIDALGO: Tula, 2050 m., 1[31]. MICHOACÁN: _2 mi. E La Palma, SE side +Lago de Chapala_, 7; type locality, 4000 ft., 10[30] (including the +type); _9 mi. E Zamora_ (_Camenaro_), 2[29]; _1 mi. S, 11 mi. W Zamora_, +5400 ft., 17; S Cuitzeo, 36[29]; _Jiquilpan_, 4800 ft., 15; _11 mi. W +Jiquilpan_, 6700 ft., 2; _1 mi. E Jiquilpan_, 7; _1 mi. E Zinapecuaro_, +6300 ft., 17; _4-1/2 mi. NE Tarequato_ (_Tarecuato_), 6600 ft, 1; +_Tanganciguaro_ (_Tangancicuaro_), 5500 ft., 4; _2 mi. N Tarecuato_, +7200 ft., 1; _2 mi. S Maravatio_, 6650 ft, 6; _2 mi. SE Zacapu_, 6600 +ft., 11; _1 mi. N Tinquindin_ (_Tinguindin_), 6300 ft., 2; _3 mi. E +Morelia_, 6600 ft., 3; _11 mi. E, 2 mi. S Morelia_, 1; 2 mi. SE Hidalgo +(Villa Hidalgo), 6; _1-1/2 mi. N Los Reyes_, 1; _E Los Reyes_, 18[29]; +_Los Reyes_, 8[30]; _3 mi. W, 1 mi. N Pátzucuaro_, 6600 ft., 2; _N +Pátzucuaro_, 2[29]; _Pátzucuaro_ 9[31], 4[30], 4[29]; Uruapan, 1[29]; _E +Uruapan_, 12; _2-1/2 mi. E Uruapan_ (_La Presca_), 2[29]; 2 mi. SW +Zitacuaro, 1; 1 mi. E, 6 mi. S Tacámbaro, 4000 ft., 11[37]; _La Huacana_, +1[30]. MEXICO: Templo del Sol, Pyramídes de San Juan, Teotihuacán, 8000 +ft., 1; _31 km. E México City_, 7500 ft., 11[36]; _17 km. E México City_, +7500 ft, 1[36]; _Cerro La Caldera, 11 mi. ESE México_, 2350 m., 5; 4 km. +ENE Tlalmanalco, 2290 m., 9; _Hacienda Córdoba_ (_Córdova_), 6. MEXICO, +D. F.: _Cerro de la Estrella, Ixtapalapa_, 2450 m., 1; _3/4 mi. S, 1 mi. +E Churubusco_, 2400 m., 2; _5 km. S México City, South of Cd. +Universitaria_, l[32]; _Pedregal San Angel_, _2.6 mi. S Monumento a +Obregón, 2_; _El Pedregal, 1 km. S San Angel_, 2260 m., 1; _Falda SW +Cerro Zacatepec, 3.9 mi. SW Monumento a Obregón_, 1; _2 mi. N Tlalpan, +Zacayuca_, 2380 m., 5; _Tlalpan_ (_Pedregal_), 2400 m., 21[31]; _San +Gerónimo_, 37[29], 6[38]; _Santa Rosa_, 2700 m., 1[32]; _Tlalpan_, 8; _3/4 +mi. SW Las Fuentes, Tlalpan_, 2450 m., 25[30]; _Tepepán_, 6[29]; _Rancho +La Noria, 1 mi. W Xochimilco_, 2270 m., 4; _500 meters N Xochitepec_, +2250 m., 7; 200 m. N San Mateo Xalpa (Jalpa), 2390 m., 2. + +_Marginal records._--SAN LUIS POTOSÍ: Hacienda Capulín; 1 mi. N +Tamazunchale. HIDALGO: Tula, 2050 m. MEXICO: Templo del Sol, Pyramídes +de San Juan, Teotihuacán. VERACRUZ: Acultzingo. MEXICO: 4 km. ENE +Tlalmanalco. MEXICO, D. F.: 200 m. N San Mateo Xalpa (Jalpa), 2390 m. +MICHOACÁN: 2 mi. SW Zitacuaro; 1 mi. E, 6 mi. S Tacámbaro; Uruapan. +JALISCO: 2 mi. N Ciudad Guzmán; 27 mi. S, 12 mi. W Guadalajara; 13 mi. +S, 15 mi. W Guadalajara; 7 mi. NW Tepatitlán; 1 mi. S Jalostotitlán, +5700 ft. GUANAJUATO: 4 mi. N, 5 mi. W León. QUERÉTARO: 6 mi. E +Querétaro, 6550 ft.; Tolimán. + +[29] Univ. Michigan, Museum of Zoology. + +[30] U. S. Nat. Museum (Biol. Surv. Coll.). + +[31] Chicago Natural History Museum. + +[32] American Museum of Natural History. + +[33] Museum of Natural History, Louisiana State University. + +[34] Univ. Illinois, Mus. Nat. History. + +[35] The Museum, Michigan State Univ. + +[36] Texas A & M, Cooperative Wildlife Research Collection. + +[37] Univ. California, Mus. Vert. Zoology. + +[38] University of Florida Collections. + + +=Baiomys taylori ater= (Blossom and Burt) + + _Baiomys taylori ater_ Blossom and Burt, Occas. Papers Mus. Zool., + Univ. Michigan, 465:2, October 8, 1942; Blair and Blossom, Contrib. + Lab. Vert. Biol., Univ. Michigan, 40:1, March, 1948; Hoffmeister and + Goodpaster, Ill. Biol. Monogr., 24(1):115, December 31, 1954; Miller + and Kellogg, Bull. U. S. Nat. Mus., 205:511, March 3, 1955; + Hoffmeister, Amer. Midland Nat., 55:281, April, 1956; Packard, Jour. + Mamm., 40:146, February 20, 1959; Hall and Kelson, The Mammals of + North America, 2:659, March 31, 1959 (part). + + _Peromyscus taylori paulus_, Osgood, N. Amer. Fauna, 28:256, April + 17, 1909 (part). + + _Baiomys taylori_ [_ater_], Justice, Jour. Mamm., 38:520, November + 20, 1957. + +_Type._--Adult male, skin and skull; No. 85425, University of Michigan, +Museum of Zoology; 7 mi. W Hereford, Cochise County, Arizona, obtained +on March 25, 1941, by Philip M. Blossom, original number 2195. + +_Range._--Southeastern Arizona, north to Graham County, thence east to +the Animas Valley, Hidalgo County, New Mexico; south to northern +Chihuahua and northwest to the southern border of Cochise County, +Arizona, see Figure 11. Zonal range: largely lower Sonoran (Apachian +Biotic Province of Dice, 1943:56). Occurs from 4300 feet in Chihuahua up +to 6200 feet in New Mexico. + +_Diagnosis._--Size medium for the species; dorsum between Mummy Brown +and Prouts Brown; individual tips of hairs intermixture of black and +Ochraceous-Tawny, bases of all hairs slate-gray; sides of body and face, +Buffy Brown to Cinnamon Brown; belly Cinnamon Buff, proximal half of +individual hairs Deep Neutral Gray, distal half white; in region of +throat, proximal fourth of individual hairs gray, distal three-fourths +white; dorsal vibrissae black to base, ventral vibrissae white to base; +tail brownish above, gray below; dorsal and ventral surface of forefeet +and hind feet buffy to gray; interparietal somewhat compressed +anteroposteriorly. Average and extreme cranial measurements of 15 adults +from 9-1/2 mi. W New Mexico State Line, 5-1/2 mi. N Mexican border, +Cochise County, Arizona, are as follows: occipitonasal length, 18.0 +(17.5-18.6); zygomatic breadth, 9.5 (9.2-9.9); postpalatal length, 6.6 +(6.0-7.1); least interorbital breadth, 3.6 (3.4-3.8); length of incisive +foramina, 4.0 (3.8-4.2); length of rostrum, 6.1 (5.7-6.4); breadth of +braincase, 8.6 (8.4-9.1); depth of cranium, 6.5 (6.3-6.9); alveolar +length of maxillary tooth-row, 3.2 (3.1-3.4). Average and extreme +external measurements for six adults from 9 mi. W Hereford, Cochise +County, are as follows: total length, 106.3 (98-115); length of tail +vertebrae, 42.3 (39-46); length of body, 64 (59-69); length of hind +foot, 13.6 (13-14.2); length of ear from notch, 11.1 (10.5-11.5); for +photographs of skull, see Plate 2_b_, and Plate 4_c_. + +_Comparisons._--For comparisons with _B. t. canutus_, see account of +that subspecies. From _B. t. paulus_, the subspecies to the southeast, +_B. t. ater_ differs in: dorsum darker brown; tail less strikingly +bicolored; belly buffy rather than whitish to white-gray; forefeet and +hind feet darker dorsally and ventrally; posterior margin of +basioccipital bowed anteriorly in a broad U-shape with a secondary small +median anteriorly directed U-shaped curve, rather than bowed anteriorly +in a simple U-shape; interparietal more compressed anteroposteriorly; +coronoid process of mandible so acutely recurved that tip of coronoid +points posteroventrally and appears sickle-shaped. + +_Remarks._--Blossom and Burt (1942:1) described _B. t. ater_ as the +darkest of the known subspecies. It is dark, but specimens from some +parts of the ranges of _B. t. analogous_, _B. t. fuliginatus_, and _B. +t. subater_ exceed in melanins the darkest individuals of _ater_. Blair +and Blossom (1948:5) also concluded by the use of an Ives tint +photometer that _B. t. subater_ was significantly darker than _B. t. +ater_. + +When paratypes of _ater_ and specimens of _B. t. paulus_ are compared, +the darkest individuals of _ater_ exceed but slightly the darkest of +_paulus_. The darkest specimens of _paulus_ occur in southern Zacatecas, +and northern Jalisco, and the palest of the series are in northern +Durango and southern Chihuahua. When paratypes of _ater_ and _paulus_ +are compared, the difference in color is readily distinguishable. +Specimens from 1-1/2 mi. N San Francisco, in northern Chihuahua, appear +to be intermediate in color between _ater_ and _paulus_ except for a +faint tinge of buff ventrally. In characters of the crania, these +specimens resemble _ater_ and are referred to that subspecies. A +slightly different pattern of color is present in pygmy mice from the +Peloncillo Mountains and the Animas Valley of New Mexico; the upper +parts resemble those of paratypes of _ater_, but the venter has only the +faintest suggestion of the buffy wash. Crania of these specimens from +New Mexico are inseparable from those of paratypes of _ater_, and the +specimens are, therefore, referred to _ater_. + +When specimens are arranged by localities from Arizona east into +southern New Mexico, thence south into Chihuahua and Durango, gradual +intergradation in color is evident from dark in the north to pale browns +in the south, whereas, size and shape of interparietal and size and +shape of coronoid process of the lower jaw divide quite distinctly into +two morphological types in central Chihuahua. + +Cranial variation in size and proportion among adults is slight +throughout the range of _ater_ compared to variation detected in other +subspecies of _Baiomys taylori_. Perhaps such a relatively stable +pattern of characters of the crania reflects the homogeneity of the gene +pool, with respect to these characters, of the populations sampled. The +fact that the color of the pelage of this subspecies varies considerable +throughout its known range and that the crania do not is perhaps a clue +to the mode of inheritance of characters in these mice. Seemingly, color +of pelage is inherited independently of characters of the cranium. The +relative lack of variability in the crania of _ater_ may result from +uniform environmental conditions, which have served to select for +uniform characters in the populations. All of the other wide-ranging +subspecies of _B. taylori_ occupy more diverse habitats than _ater_. +Secondly, the rather abrupt change in the cline of measured characters +of the crania between _ater_ and _paulus_ in central Chihuahua suggests +a secondary zone of intergradation. The probable cessation of gene flow +in the past between these two subspecies, allowing _ater_ to be isolated +for a time, may also, in part, account for the relative lack of +variability in the crania of _ater_. + +_Specimens examined._--Total 58, distributed as follows: ARIZONA: +_Graham County_: 1-1/2 mi. SW Ft. Grant, Graham Mts., 1[39]; _Pima +County_: 1-1/2 mi. ENE Greaterville, Thurber Ranch, 2[39]; _Santa Cruz +County_: Patagonia, 3[39]; _Cochise County_: _9 mi. W Hereford_, 10[43]; +type locality, 2[43] (including the type); _5 mi. W Hereford_, 5[43]; +9-1/2 mi. W New Mexico State Line, 5-1/2 mi. N Mexican border, 20[42]; _3 +mi. E, 1 mi. N Chiricahua_, 1[42]. NEW MEXICO: _Hidalgo County_: 18 mi. +S, 2 mi. W Animas, 2; _22 mi. S, 2 mi. W Rodeo_, 6000 ft., 1[40]; _22 mi. +S, 2 mi. E Rodeo_, 6000 ft., 3[40]; 25-1/2 mi. S Animas, 6200 ft. (in Big +Bill Canyon), 1[40]. CHIHUAHUA: _5-1/2 mi. N, 2 mi. W San Francisco_, +5100 ft., 1; _2-1/2 mi. N, 3 mi. W San Francisco_, 5200 ft., 1; 1-1/2 +mi. N San Francisco, 5100 ft., 4; Casas Grandes, 4300 ft., 1[41]. + +_Marginal records_--ARIZONA: 1-1/2 mi. SW Ft. Grant, Graham Mts. NEW +MEXICO: 18 mi. S, 2 mi. W Animas; 25-1/2 mi. S Animas (in Big Bill +Canyon). CHIHUAHUA: 1-1/2 mi. N San Francisco; Casas Grandes. ARIZONA: +Patagonia; 1-1/2 mi. ENE Greaterville, Thurber Ranch. + +[39] University of Illinois, Museum of Natural History. + +[40] University of New Mexico. + +[41] U. S. Nat. Museum (Biol. Surv. Coll.). + +[42] University of Arizona. + +[43] Univ. Michigan, Museum of Zoology. + + +=Baiomys taylori canutus=, new subspecies + + _Peromyscus taylori paulus_, Osgood, N. Amer. Fauna, 28:255, April + 17, 1909 (part). + + _Peromyscus musculus_ [_musculus_], Osgood, N. Amer. Fauna, 28:256, + April 17, 1909 (part). + + _Baiomys taylori paulus_, Miller, Bull. U. S. Nat. Mus., 79:137, + December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317, + April 29, 1924 (part); Burt, Miscl. Publ., Mus. Zool., Univ. + Michigan, 39:54, February 14, 1938; Goldman, Smith. Miscl. Coll., + 115:373, July 31, 1951 (part); Miller and Kellogg, Bull. U. S. Nat. + Mus., 205:512, March 3, 1955 (part); Hooper, Occas. Papers Mus. + Zool., Univ. Michigan, 565:13, March 31, 1955; Hall and Kelson, The + Mammals of North America, 2:659, March 31, 1959 (part). + + _Baiomys musculus musculus_, Goldman, Smith. Miscl. Coll., 115:336, + July 31, 1951 (part). + +_Type._--Adult male, skin and skull; No. 62075, University of Kansas, +Museum of Natural History; 1 mi. S Pericos, Sinaloa, Republic of México; +obtained on June 14, 1954, by A. A. Alcorn, original number 1754. + +_Range._--Central Nayarit northward through western Sinaloa, to as far +north as south-central Sonora, see Figure 11. Zonal range: Lower arid +tropical, closely approximating the Sinaloan Biotic Province of Goldman +and Moore (1945:349). Occurs from near sea level at Escuinapa (43 feet), +Sinaloa, to 3200 feet at a place 2 mi. WNW Tepic, Nayarit. + +_Diagnosis._--Dorsal ground color Buffy Brown (some specimens near Olive +Brown); proximal fourth of individual guard hairs of dorsum +black-tipped, distal three-fourths dark grayish; dorsal underfur +black-tipped having subterminal band of Buffy Brown; hair around eyes +buffy to base; belly Pallid Neutral Gray with overtones of buff; +individual hairs in region of chin whitish-gray to bases; vibrissae +blackish to bases except ventralmost, those being white to base; tail +Dark Olive above, slightly paler below. Average and extreme external +measurements of 13 adults from 15 mi. N Rosario, Chelé, Sinaloa, 300 +ft., are as follows: Total length, 109.6 (99-120); length of tail, 43.4 +(38-49); length of body, 66.2 (58-75); length of hind foot, 11.2 +(10-12). Average and extreme cranial measurements of 19 adults from the +same place are as follows: occipitonasal length, 18.2 (17.7-18.9); +zygomatic breadth, 9.6 (9.2-10.1); postpalatal length, 6.9 (6.5-7.3); +least interorbital breadth, 3.6 (3.4-3.8); length of incisive foramina, +3.9 (3.5-4.2); length of rostrum, 5.9 (5.5-6.6); breadth of braincase, +8.7 (8.3-8.9); depth of cranium, 6.5 (6.2-6.7); alveolar length of +maxillary tooth-row, 3.1 (3.0-3.2); breadth of zygomatic plate, 1.8 +(1.6-2.0); for photographs of skull, see Plate 2_c_, and Plate 4_d_. + +_Comparisons._--From _B. t. ater_, _B. t. canutus_ differs in: dorsum +slightly grayer; belly whitish to pale-gray with only faint tones of +buff, rather than cinnamon-buff to buff-gray; forefeet and hind feet +flesh-colored to grayish above instead of whitish to flesh-colored; tail +paler above, less hairy, scales more evident; interparietal relatively +larger from anteriormost to posteriormost points; incisive foramina +tapering less abruptly posteriorly, not constricted towards midline; +over-all size of body and cranium somewhat larger. + +From _B. t. paulus_, _B. t. canutus_ differs in: dorsum grayish-brown +rather than fawn-colored (not differing appreciably from extremes of +darker brown specimens of _paulus_); forefeet and hind feet +flesh-colored to grayish above rather than white above; tail less +hairy, unicolored to faintly bicolored rather than distinctly bicolored; +braincase slightly larger; alveolar length of maxillary tooth-row +slightly less. + +From _B. t. analogous_, _B. t. canutus_ differs in: dorsum paler, less +of dark brown hues; belly paler; forefeet and hind feet slightly paler, +less sooty above; tail less hairy, paler and having scales evident; +jugal of zygoma extending ventrally to a point immediately above, +instead of below, level of alveolus of upper molars; nasals more nearly +truncate anteriorly; infraorbital foramina less deeply notched toward +midline of skull; body and skull averaging smaller throughout. + +From _B. t. allex_, _B. t. canutus_ differs in: dorsal ground color +grayish rather than fawn color having grayish overtones; underfur on +dorsum darker gray; dorsal surface of forefeet and hind feet +flesh-colored to grayish rather than flesh-colored; incisive foramina +tapering to a point posteriorly rather than rounded posteriorly; +interparietal relatively smaller; body and skull averaging larger +throughout. + +_Remarks._--Burt (1938:54) reluctantly assigned specimens from Ciudad +Obregón to _B. t. paulus_, probably being influenced by the resemblance +in size. He suggested that, perhaps, a distinct subspecies occurs in the +State of Sonora. Study of larger series of specimens than were available +to Burt reveals that populations of pygmy mice inhabiting the northwest +coastal plains of México are indeed distinct. + +The darkest of the material assigned to _canutus_ is from Nayarit (for +specific localities see specimens examined). According to Tamayo +(1949:Carta de Suelos), color of soil changes from chestnut in northern +Sinaloa to black in southern Sinaloa and northern Nayarit. There seems, +therefore, to be a close correlation between color of pelage and color +of soil in this area. In Nayarit, particularly in the central and +southern parts, the mice are intermediate in color between the paler, +grayer population to the north and the more brownish samples, +representative of _allex_ to the south. The coastal vegetation changes +from the arid tropical thorn forests of the north and central parts of +Sinaloa to a savannah in Nayarit, thence to a tropical deciduous forest +farther south (see Leopold, 1950:508). + +In size and color, specimens from 3 mi. SE Tepic and 2 mi. SW Rosa +Morada are intermediate between the larger, grayer _canutus_ and the +smaller, light-brownish _allex_. In size of cranium, these specimens are +more nearly like _canutus_, and are referred to that subspecies. Mice +from the western coastal plain are relatively homogeneous as regards +size of body and skull, except that those from 13.5 mi. S Acaponéta, +Nayarit, average somewhat larger. + +_B. t. canutus_, like _B. t. subater_, is predominantly a lowland or +coastal subspecies. The pallor of the former, that lives on generally +paler soils, presumably is of adaptive value. + +Pygmy mice are seemingly rare in the northern part of the range of this +subspecies. J. Raymond Alcorn and Albert Alcorn were successful in +collecting only two specimens from the type locality after three +successive nights of trapping with 100 traps set each night. Only six +specimens are known from Sonora. These were obtained in the irrigated +regions of Ciudad, Obregón, and Navajoa. Charles Sibley obtained one +specimen 10.6 mi. SE Ciudad Obregón in a "maguey field." I obtained one +specimen 1 mi. NNW Navajoa in a sparse grassway, 20 feet wide, bordering +an open sewer, which coursed northward into the Río Mayo. Irrigated +wheat fields bordered the grassway and ditch. + +_Specimens examined._--Total 70 all from the Republic of México and +distributed as follows: SONORA: [Ciudad] Obregón, 4[44]; 10.6 mi. SE +[Ciudad] Obregón, 1[45]; 1 mi. NNW Navajoa, 1. SINALOA: type locality, 2 +(including the type); Culiacán, 175 ft., 2[46]; Mazatlán, 1[48]; _15 mi. N +Rosario, Chelé_, 300 ft., 35[47]; Rosario, 3[46]; Escuinapa, 5[48]; +_Railroad Station Escuinapa_, 43 ft., 2[45]. NAYARIT: Acaponéta, 4[46]; +_13.5 mi. S Acaponéta Junction_, 6[49]; 2 mi. SW Rosa Morada, 2; _2 mi. +WNW Tepic_, 3200 ft., 1; 3 mi. SE Tepic, 1. + +_Marginal records._--SONORA [Ciudad] Obregón. SINALOA: type locality; +Escuinapa. NAYARIT: Acaponéta; 3 mi. SE Tepic. SINALOA: Mazatlán. + +[44] Coll. Univ. California, Los Angeles. + +[45] Univ. California, Mus. Vert. Zoology. + +[46] U. S. Nat. Museum (Biol. Surv. Coll.). + +[47] Univ. Michigan, Museum of Zoology. + +[48] American Museum of Natural History. + +[49] Univ. Illinois, Mus. Nat. History. + + +=Baiomys taylori fuliginatus=, new subspecies + + _Baiomys taylori taylori_, Dalquest, Louisiana State Univ. Studies + (Biol. Sci. Ser.) 1:155, December 28, 1953 (part). + + _Baiomys taylori taylori_, Booth, Walla Walla Publs. Dept. Biol. + Sci., 20:15, July 10, 1957 (part). + +_Type._--Adult male, skin and skull; No. 36765, University of Kansas, +Museum of Natural History; 10 mi. E, 2 mi. N Ciudad del Maíz, 4000 ft., +San Luis Potosí, Republic of México; obtained on January 17, 1950, by J. +R. Alcorn, original number 10400. + +_Range._--Occurs in the Sierra Madre Oriental of the northeastern third +of San Luis Potosí. Zonal range: Upper Tropical (see Dalquest, 1953:10); +approximates a part of the Sierra Madre Oriental Biotic Province of +Goldman and Moore (1945:349, 356). Occurs from 2000 feet at El Salto up +to 4000 feet at Ciudad del Maíz. + +_Diagnosis._--Size large for the species; ground color of dorsum +Chaetura Drab; individual guard hairs of dorsum black to base, distal +fourth of hairs of underfur in posterior half of dorsum tipped with +grayish-brown, proximal three-fourths Dark Neutral Gray; in anterior +region of dorsum, posterior to ears, distal third of hairs grayish-brown +and proximal two-thirds Dark Neutral Gray to base; sides slightly paler +than dorsum; ground color of belly Neutral Gray, individual hairs of +belly and throat tipped with Pallid Neutral Gray, basally Deep Neutral +Gray to Dark Neutral Gray; tips of individual hairs of face +Ochraceous-Tawny; lateral vibrissae whitish, dorsal and ventral +vibrissae black to base; forefeet and hind feet sooty above and below, +thigh bearing some white-tipped hairs; tail near Chaetura Drab above, +Pale Neutral Gray below; anterior part of jugal projecting slightly +ventrally and forming small protuberance at point of articulation with +maxillary part of zygoma; jugal extending anteriorly nearly to lacrimal. +In most cranial measurements averaging as large as _B. t. analogous_. +Average and extreme measurements of the type and three additional +paratypes, all adults, are: total length, 105.5 (101-109); length of +tail, 39.8 (35-42); length of body, 65.8 (63-68); length of hind foot, +14.3 (14-15); length of ear from notch, 11 (11); occipitonasal length, +18.1 (18.1-18.8); zygomatic breadth, 9.6 (9.3-9.8); postpalatal length, +6.5 (6.0-6.7); least interorbital breadth, 3.4 (3.3-3.6); length of +incisive foramina, 4.0 (3.8-4.2); length of rostrum, 6.3 (6.1-6.4); +breadth of braincase, 8.8 (8.6-8.9); depth of cranium, 6.7 (6.5-6.8); +alveolar length of maxillary tooth-row, 3.2 (3.1-3.3); for photograph of +skull, see Plate 2_d_, and Plate 4_e_. + +_Comparisons._--From _B. t. taylori_, _B. t. fuliginatus_ differs in: +dorsum slightly darker than in darkest _taylori_; tail densely haired, +bicolored rather than unicolored; belly sooty to grayish rather than +grayish to whitish; forefeet and hind feet sooty to grayish rather than +flesh-colored; incisive foramina less bowed laterally, more nearly +straight; interparietal compressed anteroposteriorly, less +diamond-shaped. + +From _B. t. paulus_, _B. t. fuliginatus_ differs in: dorsum dusky to +blackish rather than fawn color; belly sooty to grayish rather than +buffy to whitish-gray; forefeet and hind feet sooty to grayish rather +than whitish; zygoma more nearly forming a right angle with rostrum or +skull, less tapered anteriorly; anterior part of jugal possessing +ventral projection; jugal extending nearly to lacrimal on posterior +surface of maxillary part of zygoma. + +From _B. t. analogous_, _B. t. fuliginatus_ differs in: mid-dorsal +region blacker, less brownish; tail distinctly bicolored rather than +unicolored to faintly bicolored; incisive foramina not constricted +medially; presphenoid broader (at narrowest point); jugal differs much +the same as it does from _paulus_; nasals anteriorly truncate instead of +rounded. + +_Remarks._--Dalquest (1953:155-157) and Booth (1957:15) assigned all of +the pygmy mice that they examined from the state of San Luis Potosí to +_B. t. taylori_. Examination of all of the material that was available +to Dalquest, plus additional specimens at the University of Kansas +Museum of Natural History, reveals that there are three subspecies in +San Luis Potosí. _B. t. taylori_ occurs in the eastern part of the State +at lower altitudes; _B. t. analogous_ occurs to the southeast at higher +altitudes; _B. t. fuliginatus_ occurs in the northeastern part of the +State in the Sierra Madre Oriental. + +Specimens obtained from Ebano, Pujal, and Tamuín, representative of _B. +t. taylori_, are much paler on the belly and on the ventral surface of +the forefeet and hind feet than are specimens from Ciudad del Maíz, +representative of _B. t. fuliginatus_. The tail in _B. t. taylori_ is +nearly unicolored and less hairy than in the paratypical series of +_fuliginatus_. Specimens from 4 km. NE Ciudad Valles are nearly +intermediate in color of the belly, dorsum, forefeet and hind feet, and +tail, between the palest mice from the coastal plain and the darker mice +in the mountains of the northeastern part of the State (specimens from +El Salto average paler, however, than the type and paratypes). These +specimens seem to be intergrades between _B. t. taylori_ to the east on +the coastal plain and _fuliginatus_ to the northwest in the mountains. +It seems best to refer the mice from 4 km. N Ciudad Valles to _B. t. +taylori_ on the basis of the average of external and cranial characters. +Specimens from 6 mi. SW San Gerónimo, Coahuila, also referred to _B. t. +taylori_, resemble in color the mice from 4 km. N Ciudad Valles. When +more specimens are obtained from the front range of the Sierra Madre +Oriental, at lower altitudes, the manner in which these two subspecies +intergrade with one another will be better understood. At present, +populations from higher altitudes in the mountains seem to represent a +dark subspecies; populations from the coastal plain represent a pale +subspecies, and those from the lower slopes and high valleys seemingly +are intergrades. _B. t. fuliginatus_ occurs in a somewhat limited strip +of chernozem soil (or suelos negros of Tamayo, 1949: Carta de Suelos). +The populations occurring at lower altitudes on the coastal plain are on +generally paler soils. + +_Specimens examined._--Total 39, all from the Republic of México, as +follows: SAN LUIS POTOSÍ: El Salto, 24 Mus. Nat. Hist., Louisiana State +Univ., 7 Amer. Mus. Nat. Hist.; type locality, 8 (including the type). + +_Marginal records._--See specimens examined. + + +=Baiomys taylori paulus= (J. A. Allen) + + _Peromyscus paulus_, J. A. Allen, Bull. Amer. Mus. Nat. Hist., + 19:598, November 12, 1903; Elliot, Field Columb. Mus. Publ., + 105(6): 136, July 1, 1905. + + _Baiomys taylori paulus_, Miller, Bull. U. S. Nat. Mus., 79:137, + December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317, + April 29, 1924 (part); Ellerman, The Families and Genera of Living + Rodents, 2:402, March 21, 1941 (part); Goldman, Smith, Miscl. Coll., + 115:373, July 31, 1951 (part); Hall and Kelson, Univ. Kansas Publs., + Mus. Nat. Hist., 26:367, December 15, 1952; Goodwin, Bull. Amer. + Mus. Nat. Hist., 102:318, August 31, 1953; Miller and Kellogg, Bull. + U. S. Nat. Mus., 205:511, March 3, 1955 (part); Packard, Proc. Biol. + Soc. Washington, 71:17, April 11, 1958; Packard, Jour. Mamm., + 40:146, February 20, 1959; Hall and Kelson, The Mammals of North + America, 2:659, March 31, 1959 (part). + + [_Peromyscus_] _paulus_, Elliot, Field Columb, Mus. Publ., + 95(4):136, July 15, 1904. + + _Peromyscus taylori paulus_, Osgood, N. Amer. Fauna, 28:255, April + 17, 1909 (part). + + _Peromyscus musculus_ [_musculus_], Osgood, N. Amer. Fauna, 28:256, + April 17, 1909 (part). + + _Baiomys taylori_ [= _paulus_], Twente and Baker, Jour. Mamm., + 32:121, February 15, 1951. + + _Baiomys musculus musculus_, Goldman, Smith. Miscl. Coll., 115:336, + July 31, 1951 (part). + + _Baiomys taylori allex_, Hall and Kelson, The Mammals of North + America, 2:659, March 31, 1959 (part). + +_Type._--Adult male, skin and skull; No. 21165, American Museum of +Natural History; Río Sestín, Durango, Republic of México; obtained on +April 15, 1903, by J. H. Batty, original number 455. + +_Range._--Central Chihuahua south through Durango (west to eastern edge +of Sierra Madre Occidental), to Zacatecas and Aguascalientes, thence +west into northern and northwestern Jalisco, see Figure 11. Zonal range: +Lower Sonoran, approximately the Chihuahua Desert Biotic Province of +Goldman and Moore (1945:349). Occurs from 4000 feet 2 mi. ESE Tequila, +Jalisco, up to 6700 feet 2 mi. W Miñaca, Chihuahua. + +_Diagnosis._--Size medium to small for the species; dorsum Buffy Brown +to fawn color; dorsal ground color of unworn pelage of adults varying +from Buffy Brown in darkest series (especially those from higher +altitudes) to Avellaneous with grayish overtones in palest series; worn +pelage in mid-dorsal region of adults fawn to grayish; terminal parts of +individual hairs buffy, gray basally; guard hairs on dorsum +black-tipped, grayish basally; belly Light Gull Gray, distal half of +hairs white, proximal half Neutral Gray; hairs in region of throat and +chin white to base (some specimens with faint buffy overtones); forefeet +dusky below, whitish above; hind feet whitish above, ventral surface +whitish to dusky; dorsal and lateral vibrissae black, other vibrissae +white. Average and extreme measurements of six adults from the type +locality are as follows: total length, 109 (106-117); length of tail, +44.5 (43-48); length of body, 63 (57-69); length of hind foot, 13.1 +(12.7-14.0); occipitonasal length, 17.5 (17.4-18.0); zygomatic breadth, +9.3 (9.1-9.5); postpalatal length, 6.6 (6.2-6.9); least interorbital +breadth, 3.5 (3.4-3.6); length of incisive foramina, 3.8 (3.6-4.1); +length of rostrum, 5.9 (5.7-6.0); breadth of braincase, 8.6 (8.5-8.8); +depth of cranium, 6.6 (6.2-6.9); alveolar length of maxillary tooth-row, +3.2 (3.1-3.4); for photographs of the skull, see Plate 2_e_ and Plate +4_f_. + +_Comparisons._--For comparisons with _B. t. allex_, _B. t. canutus_, _B. +t. ater_, and _B. t. taylori_, see accounts of those subspecies. From +_B. t. analogous_, _B. t. paulus_ differs as follows: dorsal color paler +having more reddish-brown than blackish-brown tones; venter whitish to +buffy, instead of gray to light-gray; tail bicolored (not unicolored), +usually having more hairs; hind feet white (not sooty) above. Cranially, +_B. t. paulus_ differs from _B. t. analogous_ in: skull slightly smaller +in all dimensions; maxillary part of zygoma narrowing and forming +oblique angle rather than a near right angle with rostrum; anterior +incisive foramina constricted posteriorly; tips of nasals truncate (less +rounded). + +_Remarks._--J. A. Allen (1903:599) correctly pointed out that young +specimens, in first pelage, were gray brown; young adults were darker +and more varied with some blackish; adults and old adults were buffy to +grayish. The change in color of pelage with increasing age is more +pronounced in _paulus_ than in other subspecies of _B. taylori_. Of two +males collected on April 12, 1949, one, an adult, is buffy brown, and +the other, an old adult with worn pelage, is grayish-brown. In mice in +the earlier stages of adulthood, underfur of the dorsum is buffy at the +tips and gray basally. With increased wear, the buffy tip is lost. +Consequently, mice in the later stages of adulthood are grayish. + +_B. t. paulus_ intergrades with _ater_ to the north in Chihuahua (see +account of that subspecies), with _analogous_ to the south in Jalisco, +and with _allex_ (see account of that subspecies) to the southwest in +Nayarit and Jalisco. The zone of intergradation between _paulus_ and +_analogous_ in Jalisco approximately borders the Río Grande de Santiago +from the western part of the State to the northwest shore of Lago de +Chapala. Nineteen specimens from 2 mi. WNW Lagos de Moreno in northwest +Jalisco seem to be intermediate between _paulus_ and _analogous_ in +color, averaging slightly grayer than typical _paulus_. The series of 19 +is referable to _paulus_ on the basis of cranial characters. + +A series of 34 specimens from 3 mi. W La Venta, Jalisco (referable to +_paulus_), is indistinguishable in color of pelage from two series of +_paulus_ from 5 mi. N Durango, and from 8 mi. NE of Durango, except that +the antiplantar surfaces of the hind feet are sooty as in _analogous_. +Seemingly, features of color mentioned above as diagnostic of the two +subspecies are either present or absent and there is no tendency toward +intermediacy in color in the population from 3 mi. W La Venta. + +The Río Grande de Santiago may have acted in the past as a physical +barrier reducing gene flow between _allex_ and _paulus_ and in +separating completely the two populations for limited periods. + +_Specimens examined._--Total 176, all from the Republic of México and +distributed as follows: CHIHUAHUA: Rancho Sanignacio, 4 mi. S, 1 mi. W +Santo Tomás, 1; El Rosario, 6700 ft., 1; 2 mi. W Miñaca, 6900 ft., 11; +Balleza, 1[50]. DURANGO: Rosario, 1[51]; type locality, 14[51] (including +the type); _San Gabriel_, 2[51]; _Rancho Santuario_, 2[51]; 1 mi. N +Chorro, 6450 ft., 1; _8 mi. NE Durango_, 6200 ft., 2; 5 mi. N Durango, +6400 ft., 2. ZACATECAS: Valparaíso, 6500 ft., 10[50]. AGUASCALIENTES: _18 +mi. W, 2 mi. S Aguascalientes_, 6000 ft., 1; 16 mi. S Aguascalientes, +5[52]. JALISCO: 1 mi. NE Villa Hidalgo, 6500 ft., 1; 2 mi. WNW Lagos de +Moreno, 6370 ft., 19; _2 mi. ESE Tequila_, 4000 ft., 11; _3 mi. W La +Venta_, 33, 1[53]; _12 mi. W Guadalajara_, 3[54]; _Atemajac_, 12[50]; 4 mi. +W Guadalajara, 5100 ft., 3; _2 mi. N, 1/2 mi. W Guadalajara_, 11; 2 mi. +NW Magdalena, 4500 ft., 7[50]; _1 mi. N Tala_, 4400 ft., 3; 3 mi. W Tala, +4300 ft., 18. + +_Marginal records._--CHIHUAHUA: Rancho Sanignacio, 4 mi. S, 1 mi. W +Santo Tomás; El Rosario; Balleza. DURANGO: Rosario, 6700 ft.; 1 mi. E +Zarca (Blossom and Burt, 1942:1); 1 mi. N Chorro, 6450 ft. ZACATECAS: +Valparaíso, 6500 ft. AGUASCALIENTES: 1 mi. N Chicalote (Blossom and +Burt, 1942:4). JALISCO: 2 mi. WNW Lagos de Moreno, 6370 ft.; 4 mi. W +Guadalajara, 5100 ft.; 3 mi. W Tala, 4300 ft.; 2 mi. NW Magdalena, 4500 +ft. DURANGO: 5 mi. N Durango, 6400 ft.; type locality. CHIHUAHUA: 2 mi. +W Miñaca, 6900 ft. + +[50] United States National Museum (Biol. Surv. Collections). + +[51] American Museum of Natural History. + +[52] Univ. Illinois, Mus. Nat. History. + +[53] The Museum, Michigan State Univ. + +[54] Univ. Michigan, Museum of Zoology. + + +=Baiomys taylori subater= (V. Bailey) + + _Peromyscus taylori subater_, V. Bailey, N. Amer. Fauna, 25:102, + October 24, 1905; Lyon and Osgood, Bull. U. S. Nat. Mus., 62:139, + January 15, 1909; Osgood, N. Amer. Fauna, 28:255, April 17, 1909; + Elliot, Check-List Mamm. N. Amer. Continent, West Indies and + Neighboring Seas, Suppl., Amer. Mus. Nat. Hist, p. 44, January 8, + 1917. + + _Baiomys taylori subater_, Miller, Bull. U. S. Nat. Mus., 79:136, + December 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:317, April 29, + 1924; Anthony, Field Book of North American Mammals, p. 348, 1928; + Baker, Jour. Mamm., 21:223, May 14, 1940; Ellerman, The Families and + Genera of Living Rodents, 2:402, March 21, 1941; Blair, Jour. Mamm., + 22:378, November 14, 1941; Poole and Schantz, Bull. U. S. Nat. Mus., + 178:259, March 6, 1942; Blair, Jour. Mamm., 23:196, May 14, 1942; + Blair and Blossom, Contrib. Lab. Vert. Biol., Univ. Michigan, 40:1, + March, 1948; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:511, + March 3, 1955; Hall and Kelson, The Mammals of North America, 2:659, + March 31, 1959. + + _Baiomys taylori_ [= _subater_], Taylor and Davis, Texas Game, Fish + and Oyster Comm. Bull., 27:56, August, 1947 (part). + +_Type._--Subadult female, skin and skull; No. 32616/44539 U. S. Nat. +Mus. (Biol. Surv. Coll.); Bernard Creek, near Columbia, Brazoria County, +Texas; obtained on February 25, 1892, by W. Lloyd, original number 1122. + +_Range._--Southeastern Texas, north of Matagorda Bay west to Lavaca +County, north to Brazos and Walker counties thence east to Jefferson +County, see Figure 11. Occurs from near sea level in Brazoria and +Galveston counties, up to 500 feet in western part of range. Zonal +range: Humid division of lower Austral (the western part of the +Austroriparian Biotic Province of Dice, 1943:18-21). + +_Diagnosis._--Size medium to large for the species; mid-dorsal region +Clove Brown (sooty in freshly captured specimens); some parts of +mid-dorsal region all blackish; individual guard hairs of dorsum +black-tipped, Deep Neutral Gray basally; underfur black-tipped with +subterminal band of light buff, Neutral Gray at base; belly +grayish-white, laterally Isabella Color; distal three-fourths of hairs +in region of throat and chin white, proximal fourth light gray; in +median region of belly distal half of individual hairs white, proximal +half dark gray; vibrissae in most specimens black to base. Average and +extreme cranial measurements of six adults from 7 mi. S La Belle are as +follows: occipitonasal length, 18.9 (17.5-19.4); zygomatic breadth, 9.6 +(9.1-9.9); postpalatal length, 6.8 (6.2-7.2); least interorbital +breadth, 3.7 (3.4-3.9); length of incisive foramina, 4.0 (3.6-4.2); +length of rostrum, 6.5 (6.1-6.8); breadth of braincase, 8.7 (8.3-8.9); +depth of cranium, 6.7 (6.6-6.8); alveolar length of maxillary tooth-row, +3.1 (2.9-3.2). Average and extreme external measurements of four adults +from Richmond are as follows: total length, 111.5 (108-118); length of +tail vertebrae, 43.5 (41-47); length of body, 68 (67-71); length of hind +foot, 14 (13-15); for photographs of the skull, see Plate 2_f_, and +Plate 4_g_. + +_Comparisons._--Because _B. t. subater_ intergrades only with _B. t. +taylori_ to the south and west, _subater_ is compared only with +_taylori_. Young adults of both subspecies in unworn pelage show best +the colors that differentiate the two subspecies. Old adults of +_subater_ in worn pelage appear grayish, resembling _taylori_, and at +that age, only certain cranial characters are of taxonomic use. +Cranially, _subater_ differs from _taylori_ in: presphenoid not shaped +like an hour-glass; parapterygoid processes thicker medially; +interparietal diamond-shaped instead of elongated and compressed. Skull +slightly larger in most measurements. + + + [Illustration: PLATE 1 + + Photographs of skulls in dorsal view of _Baiomys_. × 2. + + _a._ _B. m. brunneus_, [F] ad., 10834, AMNH, Jalapa, Veracruz. + _b._ _B. m. grisescens_, [F] ad., 257080, USNM, Comayabuela, Honduras. + _c._ _B. m. handleyi_, [F] ad., 275597, USNM, Sacapulas, Guatemala. + _d._ _B. m. infernatis_, [F] ad., 91499, MZUM, Teotitlán, Oaxaca. + _e._ _B. m. musculus_, [F] ad., 45462, USNM, Colima, Colima. + _f._ _B. m. nigrescens_, [M] ad., 76834, USNM, Comitán, Chiapas. + _g._ _B. m. pallidus_, [F] ad., 4802, Texas A & M, Axochiapán, Morelos. + _h._ _B. m. pullus_, [F] ad., 71608, KU, 8 mi. S Condega, Nicaragua. + _i._ _B. t. allex_, [F] ad., 45453, USNM, Colima, Colima.] + + + [Illustration: PLATE 2 + + Photographs of skulls (_a-g_) in dorsal view of _Baiomys_. × 2. + + _a._ _B. t. analogous_, [F] ad., 120265, USNM, Zamora, Michoacán. + _b._ _B. t. ater_, [F] ad., 15056, UI, 1-1/2 mi. ENE Greaterville, + Arizona. + _c._ _B. t. canutus_, [F] ad., 62076, KU, 1 mi. S Pericos, Sinaloa. + _d._ _B. t. fuliginatus_, [F] ad., 36771, KU, type locality. + _e._ _B. t. paulus_, [F] ad., 40032, KU, 18 mi. W, 2 mi. S + Aguascalientes. + _f._ _B. t. subater_, [F] ad., 44543, USNM, type locality. + _g._ _B. t. taylori_, [F] ad., 57944, KU, 5 mi. E San Antonio, Texas. + _h._ Photo. of captive [M] _B. t. taylori_, 25 mi. E Austin, Texas. + × 1.] + + + [Illustration: PLATE 3 + + Photographs of skulls in ventral view of _Baiomys_. × 2. + + _a._ _B. m. brunneus_, [F] ad., 10834, AMNH, Jalapa, Veracruz. + _b._ _B. m. grisescens_, [F] ad., 257080, USNM, Comayabuela, Honduras. + _c._ _B. m. handleyi_, [F] ad., 275597, USNM, Sacapulas, Guatemala. + _d._ _B. m. infernatis_, [F] ad., 91499, MZUM, Teotitlán, Oaxaca. + _e._ _B. m. musculus_, [F] ad., 45462, USNM, Colima, Colima. + _f._ _B. m. nigrescens_, [M] ad., 76834, USNM, Comitán, Chiapas. + _g._ _B. m. pallidus_, [F] ad., 4802, Texas A & M, Axochiapán, Morelos. + _h._ _B. m. pullus_, [F] ad., 71608, KU, 8 mi. S Condega, Nicaragua.] + + + [Illustration: PLATE 4 + + Photographs of skulls in ventral view of _Baiomys_. × 2. + + _a._ _B. t. allex_, [F] ad., 45453, USNM, Colima, Colima. + _b._ _B. t. analogous_, [F] ad., 120265, USNM, Zamora, Michoacán. + _c._ _B. t. ater_, [F] ad., 15056, UI, 1 mi. ENE Greaterville, Arizona. + _d._ _B. t. canutus_, [F] ad., 62076, KU, 1 mi. S Pericos, Sinaloa + _e._ _B. t. fuliginatus_, [F] ad., 36771, KU, type locality. + _f._ _B. t. paulus_, [F] ad., 40032, KU, 18 mi. W, 2 mi. S + Aguascalientes. + _g._ _B. t. subater_, [F] ad., 44543, USNM, type locality. + _h._ _B. t. taylori_, [F] ad., 57944, KU, 5 mi. E San Antonio, Texas.] + +_Remarks._--This subspecies retains its chief diagnostic character, +blackish mid-dorsal region, throughout nearly all parts of its range. +Specimens from the general area of Matagorda Bay and Lavaca County grade +into _taylori_ in characters of color and crania. The Colorado and +Brazos rivers seemingly serve as barriers reducing gene flow between +_taylori_ and _subater_. These rivers may well have been important +factors in the origin and the limitation of these two seemingly +closely-related subspecies. + +_Baiomys taylori subater_ is not differentiated in color of pelage and +characters of crania from _B. t. taylori_ to the same degree that _B. t. +paulus_ is differentiated from _B. t. analogous_, or that _B. t. +taylori_ is differentiated from several of the other subspecies of +_Baiomys taylori_. _B. t. subater_ probably is a more recent occupant of +the area in which it now lives than is the case with any other one of +the subspecies of _taylori_. Sufficient time probably has not elapsed to +allow for formation of more distinctive phenotypic patterns. + +_Specimens examined._--Total 65, all from TEXAS and distributed as +follows: _Brazos County_: 1/2 mi. NW College Station, 1[55]; _3 mi. W +College Station_, _1 mi. W Easterwood Airport_, 1[55]; _College Station_, +1[55]. _Walker County_: Huntsville, 1[55]. _Hardin County_: Sour Lake, +1[57]. _Jefferson County_: 7 mi. S Labelle, 10. _Harris County_: 6 mi. NE +Crosby, 1[56]. _Colorado County_: _10 mi. N Eagle Lake_, 1[55]; _9 mi. N +Eagle Lake_, 1[55]; 2 mi. W Eagle Lake, 1; _Eagle Lake_, 1[55], 5. _Fort +Bend County_: Richmond, 4[57]. _Galveston County_: _Texas City_, 6[58]; +Virginia Point, 1[57]. _Brazoria County_: _Austin Bayou near Alvin_, +2[57]; 14 mi. SSE Alvin, 2[59]; type locality, 7[57] (including the type). +_Lavaca County_: 4 mi. W Hallettsville, 1[55]; _1 mi. SW Hallettsville_, +3[55]; _13.7 mi. SW Hallettsville_, 2[55]; 4 mi. NE Yoakum, 11. + +_Marginal records._--TEXAS: Huntsville; Sour Lake; 7 mi. S La Belle; +Virginia Point; 14 mi. SSE Alvin; type locality; 4 mi. NE Yoakum; 4 mi. +W Hallettsville; 1/2 mi. NW College Station. + +[55] Texas A & M, Cooperative Wildlife Research Collection. + +[56] Carnegie Museum. + +[57] U. S. Nat. Museum (Biol. Surv. Coll.). + +[58] Los Angeles County Museum. + +[59] American Museum of Natural History. + + +=Baiomys taylori taylori= (Thomas) + + _Hesperomys_ (_Vesperimus_) _taylori_ Thomas, Ann. Mag. Nat. Hist., + ser. 5, 19:66, January, 1887. + + _Baiomys taylori_ [_taylori_], Mearns, Bull. U. S. Nat. Mus., + 56:381, April 13, 1907; Stickel and Stickel, Jour. Mamm., 30:141, + May 23, 1949. + + Baiomys taylori taylori, Miller, Bull. U. S. Nat. Mus., 79:136, + December 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:317, April 29, + 1924; Anthony, Field Book of North American Mammals, p. 327, 1928; + Ellerman, The Families and Genera of Living Rodents, 2:402, March + 21, 1941; Taylor and Davis, Texas Game, Fish and Oyster Comm. Bull., + 27:56, August, 1947 (part); Blair, Texas Jour. Sci., 2:104, March + 31, 1950; Goldman, Smith. Miscl. Coll., 115:373, 426, July 31, + 1951; Baker, Univ. Kansas Publs., Mus. Nat. Hist., 5:212, December + 15, 1951; Blair, Texas Jour. Sci., 4:242, June 30, 1952; Hooper, + Occas. Papers, Univ. Michigan, Mus. Zool., 544:7, March 25, 1953; + Dalquest, Louisiana State Univ. Studies (Biol. Sci. Ser.), 1:155, + December 28, 1953 (part); Blair, Adv. in Genetics, 5:10, January 27, + 1954; Miller and Kellogg, Bull. U. S. Nat. Mus., 205:511, March 3, + 1955; Baker, Univ. Kansas Publs., Mus. Nat. Hist., 9:273, June 15, + 1956; Packard, Proc. Biol. Soc. Washington, 71:17, April 11, 1958; + Hall and Kelson, The Mammals of North America, 2:659, March 31, 1959 + (part). + + _Cricetus_ (_Vesperimus_) _taylori_, Thomas, Proc. Zool. Soc. + London, 68:446, November 20, 1888. + + _Sitomys taylori_, Merriam, Proc. Biol. Soc. Washington, 7:170, + September 29, 1892. + + _Sitomys_ (_Baiomys_) _taylori_, True, Proc. U. S. Nat. Mus., + 16(972):758, February 7, 1894; J. A. Allen, Bull. Amer. Mus. Nat. + Hist., 6:181, May 31, 1894. + + _S._ [_itomys_] _taylori_, Rhoads, Proc. Acad. Nat. Sci. + Philadelphia, 46:256, October, 1894. + + _Peromyscus_ (_Baiomys_) _taylori_, J. A. Allen, Bull. Amer. Mus. + Nat. Hist., 8:65, April 22, 1896. + + [_Peromyscus_] _taylori_, Trouessart, Cat. Mamm., 1:517, 1898. + + _Peromyscus taylori_ [_taylori_], Elliot, Field Columb. Mus. Publ., + 105(4):135, July 1, 1905; V. Bailey, N. Amer. Fauna, 25:101, October + 24, 1905; Elliot, Field Columb. Mus. Publ., 115(8):203, 1907; + Osgood, N. Amer. Fauna, 28:253, April 17, 1909. + +_Type._--Adult male, skin and skull; No. 87.11.24.1, British Museum, +Natural History; San Diego, Duval County, Texas; obtained by William +Taylor. + +_Range._--North-central to southeastern Texas, excluding the coastal +plain north of the region of Matagorda Bay, thence south into the +southern part of Tamaulipas and west into Coahuila and Nuevo León, see +Figure 11. Occurs from near sea level in Texas up to 1500 feet in +Coahuila. Zonal range: mostly Lower Austral (in México and southeastern +half of Texas, the Tamaulipas Biotic Province of Goldman and Moore, +1945:349, and Blair, 1952:230). + +_Diagnosis._--Size medium for the species; dorsum grayish in freshly +taken specimens to Hair Brown in preserved specimens; individual guard +hairs of dorsum black-tipped, grayish basally, underfur black-tipped +with a subterminal band of olive-buff; sides of body pale-grayish near +venter, individual hairs buffy proximally, grayish basally; belly pale +grayish, individual hairs white-tipped, Pale Neutral Gray basally; +throat and chin colored as is belly; forefeet and hind feet sooty-gray +dorsally, sparsely-haired ventrally, thus appearing flesh-colored; tail +unicolored gray to sooty-gray. Average and extreme cranial measurements +of 22 adults from 6 mi. SW San Gerónimo, Coahuila, are as follows: +occipitonasal length, 18.0 (17.4-19.0); zygomatic breadth, 9.6 +(9.2-10.2); postpalatal length, 6.5 (5.9-7.1); least interorbital +breadth, 3.6 (3.3-3.8); length of incisive foramina, 4.0 (3.6-4.3); +length of rostrum, 6.1 (5.7-6.7); breadth of brain case, 8.8 (8.5-9.1); +depth of cranium, 6.5 (6.0-7.0); alveolar length of maxillary tooth-row, +3.1 (3.0-3.3). Average and extreme external measurements of 19 adults +from 6 mi. SW San Gerónimo are as follows: total length, 102.2 (95-115); +length of tail vertebrae, 39.4 (21-46); length of body, 62.8 (53-76); +length of hind foot, 14.0 (12-15); length of ear from notch, 10.7 +(10-12); for photographs of skull, see Plate 2_g_, and Plate 4_h_. + +_Comparisons._--For comparisons with _B. t. subater_, _B. t. analogous_, +and _B. t. fuliginatus_, see accounts of those subspecies. From _B. t. +paulus_, found to the southwest, _B. t. taylori_ differs as follows: +dorsum grayish rather than fawn-colored; hairs on dorsal parts of +forefeet and hind feet sooty-gray (not white to white-brown); venter +gray to Light Drab-Gray, rather than whitish with gray overtones; tail +unicolored instead of bicolored; skull averaging slightly larger +over-all; maxillary part of zygoma forms right angle with rostrum rather +than obtuse angle; incisive foramina extending posteriorly to anterior +plane of first upper molars instead of to a transverse plane at middle +of right and left first upper molars; bullae less inflated; interorbital +region broader relative to length of skull; rostrum sloping gently from +frontonasal suture to anterior tip of nasals rather than declining +abruptly from frontonasal suture to anterior tip of nasals. + +_Remarks._--The geographic range of _taylori_ is relatively large, and +the subspecies is locally variable. Nevertheless, none of the external +and cranial measurements of specimens assigned to this subspecies +differs significantly from the corresponding measurements of material +from the type locality and adjacent areas in southeastern Texas. In +southeastern Texas, south of the Guadalupe River, south to the coastal +plain of Tamaulipas, this subspecies differs in color (being paler) from +_B. t. subater_ with which _taylori_ might be confused. The foothills of +the Sierra Madre Oriental in western Tamaulipas, north through Nuevo +León and Coahuila, seem to mark the southwestern limit of the range +assignable to _taylori_. + +On December 27, 1958, a specimen, KU 81552, was obtained 3 mi. N Bowie, +Montague County, Texas. This record station extends the known range of +_B. taylori_ 65 miles northward from the previous northernmost locality, +listed by Hunsaker, Raun, and Swindells (1959:447). Two specimens, KU +81553 and 81554, were collected by the author 2 mi. NE Cedar Hill, +Dallas County, Texas, on October 31, 1958. These two specimens, plus the +single specimen from Bowie County are all paler with more buffy bellies +than either _B. t. taylori_ or _B. t. subater_. They may represent an +incipient subspecies. I tentatively assign them to _B. t. taylori_ +because of the pale rather than dark (like _B. t. subater_) pelage. +Additional specimens are needed from these areas and from the hiatus +between the ranges of _B. t. taylori_ and _B. t. subater_ the better to +understand the manner in which these two subspecies intergrade. + +Among named subspecies of _Baiomys taylori_, _B. t. taylori_ most +closely resembles _B. t. subater_ to the north in Texas. Nine specimens +examined from Yoakum are intergrades between _taylori_ and _subater_. +These specimens have the sooty dorsal color of _subater_, but ventrally +are inseparable from topotypes of _taylori_. In length of body and +tail, specimens from Yoakum are like _subater_, but in length of hind +foot, they are intermediate between the two subspecies. Cranially, they +are like _subater_. When all characters are considered, the specimens +are best referred to _subater_. Bailey (1905:103) suggested that +specimens from the southern part of the range, which he ascribed to +_subater_, tended to a more grayish color than topotypes of _subater_, +therefore, grading into _taylori_. The zone of intergradation runs from +Matagorda Bay northwest through Lavaca County, thence north to the +Colorado River, and closely follows the boundary between the Lower +Austral and Humid Division of Lower Austral Life-zone as plotted by +Bailey (_loc. cit._). Findley (1955:44) pointed out that where two +life-zones meet, the resulting populations of shrews are mostly +intergrades. Such is the case between these two subspecies of _Baiomys +taylori_ in an area where life-zones might seem less important than in +the mountainous west. + +In the southern part of the range of _taylori_, intergradation occurs +between _B. t. taylori_ in western Tamaulipas and _B. t. fuliginatus_ in +the mountains of San Luis Potosí. + +Dalquest (1953:156) found no indication of intergradation between the +two species, _B. taylori_ and _B. musculus_, in San Luis Potosí. After +examination of specimens from San Luis Potosí, I am in agreement that +they are all referable to the species _taylori_. + +_Specimens examined._--Total 435. TEXAS: _Montague County_: 3 mi. N +Bowie, 1. _Dallas County_: 2 mi. NE Cedar Hill, 2. _Travis County_: +8 mi. NW Austin, 2[60]; _Austin_, 2[60]; _4 mi. E Austin_, 4[60]; +_5 mi. E Austin_, 3[60]; _6 mi. E Austin_, 16[60], 1; _7 mi. E Austin_, +1[60]; _15 mi. E Austin_, 1[60]; _4 mi. S Austin_, 1[60]. _Bastrop +County_: 25 mi. E Austin, 2. _Kendall County_: Boerne, 1[61]. +_Bexar County_: _1 mi. N Randolph Field_, 3[64]; _5 mi. ENE_ +(_on U. S. Highway 81_) _San Antonio_, 1; _3 mi. NE San Antonio_, 1; +San Antonio, 26[61], 11[62], 1[63]; _5 mi. E San Antonio_, 11; +_4-1/2 mi. E Sayers_, 3. _Gonzales County_: 7 mi. S Luling, 2[60]. +_Wilson County: 4 mi. W LaVernia_, 3; 12 mi. W Floresville, 1. +_Atascosa County_: 9 mi. SW Somerset, 1. _Goliad County_: 8 mi. +NE Goliad, 1[60]. _Bee County_: Beeville, 1[61]. _Aransas County_: +Aransas (Wildlife) Refuge, 1[65]; _5 mi. E Copana Bay_, 1[65]; +_4.6 mi. NE Rockport_, 5[60]; _4.5 mi. NW Rockport_, 2[60]; 3 mi. N, +2 mi. E Rockport, 4; _Rockport_, 1[60], 1[61], 1[63]; _1-1/2 mi. +SW Rockport_, 1[60]; _2 mi. SW Rockport_, 2[60]; _13.4 mi. SW Rockport_, +1[60]; _14 mi. SW Rockport_, 1. _San Patricio County_: Welder Wildlife +Refuge, 7. _Duval County_: type locality, 2[61], 1[66]. _Nueces County_: +Corpus Christi (south Nueces Bay), 1[64] (Cleveland Mus. Coll.). _Kleberg +County_: 2 mi. S Riviera, 3[65]. _Brooks County_: 3 mi. S Falfurrias, +2[65]. _Hidalgo County_: 6 mi. S McAllen, 17[60]. _Willacy County_: 28 mi. +E Raymondville, 10[65]. _Cameron County_: Brownsville, 31[61], 23[62], +5[64]. COAHUILA: 6 mi. SW San Gerónimo, 32. NUEVO LEÓN: Santa Catarina, +1[61]; 14 mi. N Monterrey, 1950 ft., 2[67]; Monterrey, 1[61]; 20 km. N +General Terán, 3[64]. TAMAULIPAS: _Near Headwaters Río Sabinas, 8 km. W, +10 km. N El Encino_, 400 ft., 1; Camargo, 5[61]; Charco Escondido, 20 mi. +S Reynosa, 3[67]; Matomoras, 5[61]; _Ejido Santa Isabel, 2 km. W +Inter-American Highway_, 2000 ft., 7; Hidaglo, 7[61]; _Hda. Station +Engracia_, 4[63]; 4 mi. N La Pesca, 1; 29 mi. N Ciudad Victoria, 1[67]; +Ciudad Victoria, 6[61], 3; Jaumavé, 2400 ft., 6[64], 10; Sierra de +Tamaulipas, 3[64]; _25 mi. N El Manté, 3 km. W Inter-American Highway_ +(_on Rancho Pano Ayuctle_), 300 ft., 4; _6 mi. N Gomez Farias_ (_on +Rancho Pano Ayuctle_), 1; _5 mi. NE Gomez Farias_, 12[64], 1[62]; 70 km. +(by highway) S Ciudad Victoria, 2 km. W El Carrizo, 5[62], 2; Antigua +Morelos, 5[64]; _6 mi. N, 6 mi. W Altamira_, 31; _5 mi. N, 5 mi. W +Altamira_, 4; _Alta Mira_ (_Altamira_), 2[61]; 1 mi. S Altamira, 6; _10 +mi. NW Tampico_, 1. SAN LUIS POTOSÍ: Ebano, 5[68]; _4 km. NE Ciudad +Valles_, 1; Ciudad Valles, 1; _3 km. W Tamuín_, 1[68]; _Tamuín_, 6[68]; +_Pujal_, 300 m., 1[64]. VERACRUZ: Tampico Alto, 50 ft., 1; Potrero Llano, +350 ft., 1; Ozulama, 2; Cerro Azul, 350 ft., 1. + +_Marginal Records._--TEXAS: 3 mi. N Bowie; 2 mi. NE Cedar Hill; 25 mi. E +Austin; 7 mi. S Luling; 8 mi. NE Goliad; Aransas (Wildlife) Refuge; 3 +mi. N, 2 mi. E Rockport; Corpus Christi (South Nueces Bay); 2 mi. S +Riviera; 28 mi. E Raymondville; Brownsville. TAMAULIPAS: Matomores; 4 +mi. N La Pesca; 1 mi. S Altamira. VERACRUZ: Tampico Alto; Ozulama; Cerro +Azul; Potrero Llano. SAN LUIS POTOSÍ: Ciudad Valles. TAMAULIPAS: Antigua +Morelos; 70 km. S Ciudad Victoria, 2 km. W El Carrizo; Jaumavé; Hidalgo. +NUEVO LEÓN: 20 km. N General Terán; Santa Catarina. COAHUILA: 6 mi. SW +San Gerónimo. TEXAS: 9 mi. SW Somerset; Boerne; 8 mi. NW Austin. + +[60] Coll. University of Texas. + +[61] U. S. Nat. Museum (Biol. Surv. Coll.). + +[62] American Museum of Natural History. + +[63] Chicago Natural History Museum. + +[64] Univ. Michigan, Museum of Zoology. + +[65] Texas A & M Coop. Wildlife Res. Coll. + +[66] Carnegie Museum. + +[67] Univ. California, Mus. Vert. Zool. + +[68] Museum of Natural History, Louisiana State University. + + + + +EVOLUTION AND SPECIATION + + +The history of the genus dates back to the early late Pliocene, but +morphological change since then has been slight insofar as can be judged +from lower jaws. _Baiomys_ seems to have been relatively conservative +also in types of habitat occupied. + +According to Wilson (1937:59), the late Pliocene was a time of decided +expansion of myomorph rodents, more particularly cricetines. +Furthermore, at this time, the climate in the interior basin of +southwestern North America presumably was becoming arid, if we can judge +from the spread of elements of the Madro-Tertiary flora. Axelrod +(1950:266) points out that the drier, continental climate initiated in +the early Tertiary probably had its culmination in middle Pliocene time. +Some floras of early late Pliocene of the southwestern United States +reflect a climate slightly cooler and more moist than the climates of +the middle Pliocene. However, late Pliocene times reflect an arid +climate. The flora of the southwestern interior basin of North America +in early late to late Pliocene was intermediate between the previous +grassland floras of the middle Pliocene and the savannah flora of upper +Pliocene. Axelrod (_loc. cit._) suggests that this intermediate flora of +the interior basin of southwestern North America resulted from the +folding of the Cascades and uplifting of the Sierra Nevada and +Peninsular ranges to the south. The development of these mountains +produced greater aridity to the lee of the mountains, thus accounting +for the grassland-savannah flora. Pygmy mice probably originated in that +time, I judge in México, and moved northward and southward in a +grassland-savannah habitat that seemingly existed as far north as what +is now Meade County, Kansas (where the Sawrock fauna lived). Further +evidence for occupancy of a grassland-savannah habitat by ancestral +pygmy mice stems from the distribution of the living species, _B. +taylori_, that at present occupies territory adjacent to parts of the +Sonoran and Chihuahuan deserts. _B. taylori_ seems to be morphologically +more specialized for life in an arid grassland than was _B. +sawrockensis_. + +The geographic range of ancestral pygmy mice possibly extended farther +south in late Pliocene time than the range of _B. musculus_ does now. +Anyhow, _B. sawrockensis_ of the early late Pliocene dwelt in a more +mesic type of habitat than _B. musculus_ does, and such habitat may have +existed from the Pacific lowlands of Central America to the Caribbean +lowlands of northern South America (see Duellman, 1958:136, and Dunn, +1940:156) during late Pliocene times. An ancestral stock of hesperomine +mice, not greatly different from _Baiomys_, may have emigrated from the +North American continent into South America across the continuous land +connection, which Simpson (1950:395) suggests was formed in the +Chapadmalalan age (= Blancan age of North American terminology). The +length of time of interchange of genes between northern and southern +populations of mice across the Central American land connection probably +was brief. Duellman (_op. cit._:129) pointed out that once the +Panamanian portal was closed, the warm counter equatorial current, El +Niño, combined with the uplifting of the Andes, began to produce heavy +rain forests in Central America and northern South America in late +Pliocene or early Pleistocene times. These forests presumably isolated +the stock in North America from that in South America where the latter +probably evolved rapidly into kinds that differed from one another and +from _Baiomys_ in shape of body, type of pelage, and shape of skull. +Internal structures such as hyoid apparatus, auditory ossicles, and +baculum remained almost unchanged, as for example in _Calomys_ now +living in South America. The present resemblance in internal +morphological features between it and _Baiomys_, I judge, reflects +taxonomic relationships more accurately than do shape and conformation +of body and skull that seem to respond more rapidly to external +environmental changes. The cranial characters distinguishing _Baiomys +musculus_ from _Calomys laucha_ are as follows: posterior lacerate +foramina between second, rather than first, upper molars; parapterygoid +fossa shallower; mesopterygoid fossa as wide or wider, instead of +narrower, than parapterygoid processes; burr for attachment of +superficial masseter muscle hypertrophied instead of well-developed. In +other cranial characters studied, the two genera closely resemble each +other. Such similarities of crania between _Calomys_ and _Baiomys_ may +reflect convergence, but the total of internal and external +morphological characters shared, I think reflects true relationships. + +_Peromyscus_ has a large number of living and extinct species and +exhibits a wide range of morphological variation, whereas _Baiomys_ has +a small number (7) of species and exhibits a narrow range of +morphological variation. The small number of known species of pygmy mice +suggests their conservatism in elaboration of morphological characters. +Possibly this is because the habitat, or even the ecological niche, +occupied in geological time by these mice was restricted, geographically +and in kind. If the habitat of the pygmy mice oscillated between +savannah and arid grassland, then an hypothesis can be made possibly +accounting for the origin of species of these mice. My idea is that the +geographical distribution of _Baiomys_ today reflects a predilection on +the part of these mice for a relatively uniform warm climate. Therefore, +in the past, in times of warmer continental climate, these mice moved +toward favorable habitat northward from an area in central and northern +México. In cooler periods, the mice moved southward as habitats to the +north became unfavorable. + +Dr. W. B. Davis (_in. litt._) informs me that _B. taylori_ was uncommon +in Brazos County, Texas, approximately 15 years ago, and suggests that +the abundance there now of this mouse and my taking it in 1958 northward +nearly to the southern border of Oklahoma reflects a definite movement +northward. Movement in the same direction in late years has been +suggested for the nine-banded armadillo and the hispid cotton rat (Hall, +1959:373) that are associated with warm climates to the south. These +movements possibly reflect only minor fluctuations of climate, but in a +long period of warmth movements northward would be expected to be +pronounced and extensive. + +Extinct species of _Baiomys_ may have originated as a result of +extension northward of the geographical range and subsequent retreat +southward of the northern populations, as follows: (1) the range of the +genus moved northward in a warm period; (2) in cooler times, most of the +mice in the north disappeared and only isolated colonies remained in +small patches of remaining habitat still favorable to the mice; (3) the +small populations of isolated pygmy mice after a time changed through +mutations, recombinations and subsequent selection to a degree that +prevented crossbreeding once populations from the south again moved +northward and came in contact with previously isolated stocks; (4) then +competition caused further divergence in morphological characters. Such +an hypothesis would account for the morphological differences between +the extinct _B. kolbi_ and _B. rexroadi_. The extinct _B. +brachygnathus_, presumably a dweller of a xerophytic grassland, may have +had its origin from a _B. minimus_-like stock in the manner outlined. + + +FORMATION OF THE RECENT SPECIES + +The morphological difference between the extinct _B. minimus_ and the +living _B. musculus_ is not great, and musculus seems to be the product +of the _B. sawrockensis-B. minimus_ line of development. Morphological +characters of the parental stock of the two living species, _musculus_ +and _taylori_, may have been intermediate between those of _B. minimus_ +and those of _B. musculus_. The principal part of the range of _Baiomys_ +today is in México, and probably was there through much of Pleistocene +time. Extension northward of the species and retreat southward of those +northern populations of pygmy mice would not only have left isolated +populations in the north, but would have allowed the mice that retreated +south to share a common gene pool. Therefore, populations of pygmy mice +occurring to the south in central México might be expected to maintain a +relatively high degree of heterozygosity in morphological and behavioral +characters. The occurrence of any physical or biotic barrier that would +have separated this homogeneous group would be conducive to speciation. +There is evidence that a barrier occurred in the Pleistocene in central +México sufficient to separate the supposed interbreeding, relatively +homogeneous populations of pygmy mice. According to Sears (1955:529) and +De Terra _et al_. (1949:51), parts of the higher regions in the Valley +of México, and the transverse volcanic zone in central México were +glaciated. On the mountain Ixtaccihuatl, De Terra (_op. cit._:52) found +evidence of four marked advances of ice, from oldest to youngest, as +follows: Salto, ice advanced to 3100 meters; Xopano, ice at 3200-3300 +meters; Trancas, ice to 3400 meters; Ayolotepito, ice to 4350 meters. +The Salto advance is correlated by De Terra (_loc. cit._) with the Iowan +glacial period. The advance of ice down the mountain sides in the +transverse volcanic zone was accompanied by cool moist climates or +pluvial periods. Such climates probably altered habitat formerly +suitable for _Baiomys_. There is no record of _Baiomys_ known to me +exceeding 8000 feet in elevation, although the lower edge of the ice on +Ixtaccihuatl is at approximately 15,300 feet (4600 meters, Sears, _loc. +cit._). Presumably, the advance of ice down the mountains forced the +pygmy mice to move to lower altitudes. Pluvial conditions possibly +rendered the habitat even at lower altitudes uninhabitable for the mice, +with the result that none continued to live in the transverse volcanic +zone, but only north and south thereof. Long-continued separation of +these northern and southern segments allowed species formation to occur. +As climatic and habitat conditions became more favorable in central +México, the two species moved back toward each other, and eventually +their geographic ranges overlapped. + +An analysis of external and cranial characters of pygmy mice (see Figure +12) reveals that both species are essentially largest to the north and +smallest to the south. There are exceptions to this cline in both +species. For example, _B. taylori analogous_ is a large subspecies; it +lives allopatrically in the southern part of the range of the species. +_B. musculus pallidus_ is not the largest subspecies; it lives +allopatrically in the northern part of the range of the species. In +west-central México, where the two species are sympatric, _B. taylori_ +is smaller than elsewhere and _B. musculus_ is larger than elsewhere. +_B. t. analogous_ lives in the mountains of the transverse volcanic zone +in central México. Its large size may be a result of the cooler climate +in the mountains. _B. t. allex_, the smallest subspecies, lives +sympatrically with _B. musculus musculus_ at lower elevations in +west-central México. The small size of _allex_ could be a result of the +warmer climate of the lower elevations. _B. m. pallidus_, at lower +elevations in southern Oaxaca, is smaller than other subspecies of +_musculus_ to the south at higher elevations. _B. m. musculus_ lives at +low elevations along the coast of west-central México. Unlike _B. m. +pallidus_, _B. m. musculus_ is large at lower elevations. It occurs +sympatrically with _B. t. allex_. It is my idea that during the period +of separation, when the two species were evolving, larger subspecies +evolved to the north or at higher altitudes where climates were cooler; +smaller subspecies evolved to the south or at lower elevations; the two +cognate species, _musculus_ and _taylori_, made contact at lower +elevations where individuals of _taylori_ may have been smallest, but +individuals of _musculus_ were not the largest of the species. The +differences, therefore, between the two species in their initial contact +probably were slight. Hybrids, if they occurred, were probably +inviable, sterile, or ill-suited for occupancy of the habitat of either +of the parental stocks. The occurrence of hybrids, therefore, would +result in what geneticists call "gamete wastage," and any further +divergence in the parental stock, either in external characters (size +and shape of body and head), or behavior, useful in recognition of +species, would be favored by natural selection (see Dobzhansky, +1951:225; and Koopman, 1950:147). The two species seem to have diverged +more in external characters where they occur together than in areas +where they live separately (see Figure 12). The two species could be +confused if a sample of adults of _taylori_ from 7 mi. S La Belle, +Jefferson County, Texas, were compared to a sample of adults of +_musculus_ from Tehuantepec, Oaxaca (see Figure 12). No confusion in +species identity would arise, however, if a sample of adults was taken +from the area where the two species live together (see Figure 12). Brown +and Wilson (1956:49) pointed out that where two closely related species +occur together, characters (morphological, ecological, physiological, or +behavioral) of each species are easily distinguished. However, where the +two species are allopatric, the two closely related species so resemble +one another that the species are not easily distinguished. This +phenomenon has been called "character displacement" by Brown and Wilson +(_loc. cit._). + +In the area where the two species of pygmy mice occur together, there +seems to be a disparity in numbers between them. Hooper (1952a:91) has +recorded the collection of both _B. musculus_ and _B. taylori_ in a +single trap line. A series of pygmy mice collected from San Gabriel, +Jalisco, contained one _taylori_ and 33 _musculus_; another sample from +La Resolana, Jalisco, had a ratio of 25 _taylori_ to 6 _musculus_. The +disparity in numbers where the two species occur together has been +further substantiated by collections of the University of Kansas. +Possibly this disparity in numbers is a result of interspecific +competition. Hooper (_op. cit._:90) pointed out that where the range of +_B. musculus_ (typical of arid tropical lowlands) meets that of _B. +taylori_ (typical of arid temperate highlands), the two geographic +ranges interdigitate with parts of the range of _musculus_ extending +into the highlands and parts of the range of _taylori_ extending into +the lowlands. In the lowlands, _musculus_ may be better adapted to +environmental conditions and, therefore, more successful in competition +with _taylori_ for available habitat. The reverse situation may exist in +the highlands. Also, the fact that _musculus_ is more of a diurnal +animal than is _taylori_ may account for the difference in numbers of +individuals of the two species taken in trap lines. Many collectors set +their traps in late afternoon or evening and retrieve them in early +morning. Such a schedule might not yield many _musculus_. If +interspecific competition does occur in the area where the two species +occur, any change in habits or microhabitat by either species that would +reduce this competition would be favored by natural selection (see Mayr, +1949:518; Lack, 1944:262-263; and Brown, 1958:154-155). Brown (_op. +cit._:154), as I understand him, pointed out (taking account of Gause's +principle) that when two species having similar ecological valences move +into the same niche in the same locality, one of three things must +eventually happen: (_a_) the two species occupy different geographic +ranges; (_b_) they compete and one is eventually eliminated; (_c_) the +two species, because of differentiation or specialization, exploit +different aspects of the niche. In _Baiomys_, (_c_) seems to apply. +Natural selection probably would favor a continuation of diurnal +activity in _musculus_ and nocturnal activity in _taylori_, thereby +preventing frequent meeting of the two species. + + +AREAS OF PRESENT DIFFERENTIATION + +In both species of _Baiomys_, the most distinct subspecies, _B. t. +allex_ and _B. m. musculus_, occur in the area where the two species are +sympatric. Seven subspecies, or 44 per cent, occur either in or adjacent +to the transverse volcanic zone. This area is the major area of active +differentiation. Incipient subspecies are also evident in these areas. A +secondary area of differentiation is indicated within the range of _B. +musculus_ in Guatemala, El Salvador and Honduras. Three subspecies occur +in this area (_grisescens, handleyi_ and _nigrescens_) and incipient +subspeciation is in evidence there. + + +ZOOGEOGRAPHIC POSITION + +Hooper (1949:25) regards _Baiomys_ as a member of the rodent fauna of +the arid, western Sonoran region, whereas Hershkovitz (1958:609) +suggests that _Baiomys_ is a nearctic-neotropical varicant (a kind that +occurs in contiguous zoogeographic regions without our knowing in which +region the taxon originated). The findings from my study do not +contradict either of the above suggestions. Because of the close +resemblance of _Baiomys_ to certain hesperomine mice of South America, +it is postulated that _Baiomys_, in more primitive form than now, +occurred farther south in past times than it does now. Fossils show that +primitive stocks of the genus in late Pliocene or early Pleistocene +times occurred also north of the present range of the genus. The belt in +west-central México between nearctic and neotropical regions is the +current center of distribution of the genus and probably has been for a +considerable time. + + [Illustration: + + FIG. 12. Averages of the occipitonasal lengths of skulls of adults + at 19 localities of occurrence (solid symbols) of _Baiomys taylori_, + and at 17 localities of occurrence (open symbols) of _Baiomys + musculus_. Note that the occipitonasal length decreases from north + to south in each of the two species, and that in the region where + the two species occur together, west-central México, _B. taylori_ + is smallest and _B. musculus_ is largest. Average, extremes, number + of specimens averaged (in italic type), and name of locality, from + north to south for each species, are as follows: + + _Baiomys taylori_ + + 18.0 (17.5-18.6) _15_, 9-1/2 mi. W New Mexico state line, Ariz. + 18.9 (18.2-19.4) _6_, 7 mi. S. La Belle, Jefferson Co., Texas. + 18.2 (17.8-18.5) _10_, San Antonio, Bexar Co., Texas. + 18.2 (18.0-18.5) _5_, 2 mi. W Miñaca, Chihuahua. + 18.0 (17.6-19.0) _22_, 6 mi. SW San Gerónimo, Coahuila. + 18.2 (18.1-18.3) _3_, Ciudad Obregón, Sonora. + 18.1 (17.4-18.5) _5_, vic. (see p. 649) Durango, Durango. + 18.1 (17.5-18.5) _9_, Jaumavé, Tamaulipas. + 18.2 (17.7-18.9) _19_, 15 mi. N Rosario Chelé, Sinaloa. + 17.9 (17.4-18.3) _27_, vic. (see p. 655) Altamira, Tamaulipas. + 18.3 (17.9-18.7) _9_, Valparaíso, Zacatecas. + 18.1 (18.1-18.2) _4_, Ciudad del Maíz, San Luis Potosí. + 18.6 (18.3-18.9) _8_, Tepic, Nayarit. + 18.0 (17.7-18.4) _18_, 4 mi. N, 5 mi. W León, Guanajuato. + 18.1 (17.5-18.9) _28_, 6 mi. E Querétaro, Querétaro. + 17.7 (17.1-18.1) _17_, 1 mi. SSE Ameca, Jalisco. + 17.3 (16.8-17.9) _10_, 2 mi. SSE Autlán, Jalisco. + 18.0 (17.5-18.6) _10_, 1 mi. S, 11 mi. W Zamora, Michoacán. + 17.6 (17.4-18.2) _8_, Colima, Colima. + + + _Baiomys musculus_ + + 20.2 (19.9-20.3) _6_, vic. (see p. 622) Ameca, Jalisco. + 20.2 (19.9-20.3) _6_, 2 mi. SSE Autlán, Jalisco. + 19.6 (19.2-20.1) _6_, Jalapa, Veracruz. + 20.3 (19.7-20.9) _9_, Colima, Colima. + 19.5 (19.0-20.0) _10_, Cerro Gordo, Veracruz. + 19.8 (19.4-20.3) _6_, 6 mi. S Izucár de Matemores, Puebla. + 20.0 (18.8-20.5) _7_, Teotitlán, Oaxaca. + 20.1 (19.7-20.7) _7_, 1 km. NW Chapa, Guerrero. + 19.9 (19.4-20.4) _8_, 5 mi. ESE Tecpán, Guerrero. + 19.5 (19.1-20.1) _22_, 3 mi. ESE Oaxaca, Oaxaca. + 19.5 (19.1-19.9) _11_, Valley of Comitán, Chiapas. + 18.9 (18.2-20.1) _17_, Tehuantepec, Oaxaca. + 18.9 (18.4-19.7) _15_, 6 mi. NW Tonalá, Chiapas. + 19.1 (18.8-20.4) _10_, 1 mi. S Rabinal, Guatemala. + 19.7 (18.8-20.4) _10_, Lake Amatitlán, Guatemala. + 19.2 (18.4-19.8) _26_, vic. (see p. 625) San Salvador, El Salvador. + 19.3 (18.9-19.9) _24_, 8 mi. S Condega, Estelí, Nicaragua.] + + + + +CONCLUSIONS + + +1. Two Recent species, each polytypic with eight subspecies, and five +fossil species are recognized. + +2. The phyletic trends in the genus _Baiomys_ have been from an +ancestral stock that possessed relatively brachydont teeth having raised +cingular ridges and orthodont to proödont incisors, to species having +hypsodont teeth with reduced cingular ridges and retrodont incisors. + +3. Reduction of cingular ridges in pygmy mice is associated with an +existence in open grassland (more xeric than mesic), whereas, the +presence of cingular ridges is associated with an existence in a +savannah habitat (more mesic than xeric). + +4. Shifts of geographical range of populations of pygmy mice at and near +the periphery of their geographic range may account for the +differentiation of the extinct species. + +5. The two living species, _B. musculus_ and _B. taylori_, are seemingly +derived from a common ancestor that in morphological structure was +intermediate between _B. minimus_ and _B. musculus_. + +6. The living species of pygmy mice resulted from a geographic +separation, perhaps occurring in the Iowan glacial period (See De Terra, +1949:51) in the transverse volcanic zone of central México. + +7. The two species are now sympatric in west central México, where +morphological characters (size and shape of body and length of skull) +differ most. Where the two species are allopatric, these same +morphological characters differ least. + +8. This is a documented instance of character displacement in mammals. + +9. On the basis of internal morphological characters studied (auditory +ossicles, hyoid apparatus, and baculum), _Baiomys_ seems to be more +closely related to a South American hesperomine, perhaps _Calomys_, than +to any North American cricetine. + +10. Pygmy mice were more widely distributed in the past than they are at +present. Part of the ancestral stock of the pygmy mice may have +emigrated from North America into South America in a brief period in the +Pliocene; if so, it is easy to understand why certain South American +hesperomines resemble _Baiomys_. + +11. The combination of morphological and behavioral characters in the +living pygmy mice warrants generic status for them. If _Baiomys_ were +treated as a subgenus of the genus _Peromyscus_, there would be adequate +justification for including in the genus _Peromyscus_ a number of other +genera, some of them occurring in South America. Such lumping of genera +would reduce our understanding of the natural relationships among this +group of cricetine rodents. + + + + +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 México. 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, México. 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 Potosí. 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 México. 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 México. 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 Michoacán, México. + 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 México. 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, México. 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 México. 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 México. Ecol., 31:507-518, 1 fig., 1 table, + October. + + + LOWERY, G. H., and DALQUEST, W. W. + + 1951. Birds from the state of Veracruz, México. 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, México. Proc. Biol. Soc. Washington, + 7:164-174, September 29. + + + MOORE, R. T. + + 1945. The transverse volcanic biotic province of central México and its + relationship to adjacent provinces. Trans. San Diego Soc. Nat. + Hist., 10:217-236, 1 map, 4 tables, August 31. + + + 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, México. Proc. Biol. Soc. Washington, 65:21-22, + January 29. + + + SEARS, P. B. + + 1955. Palynology in southern North America, Part 4: Pleistocene Climate + in México. Bull. Geol. Soc. America, 66:521-530, 6 figs., 1 pl., + 1 table, May. + + + 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 México 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 México, 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, México, from barn owl + pellets. Jour. Mamm., 32:120-121, 1 table, February 15. + + + VAN GELDER, R. G. + + 1959. A taxonomic revision of the spotted skunks (Genus _Spilogale_). + Bull. Amer. Mus. Nat. Hist., 117(5):229-392, 47 figs., 32 tables, + June 15. + + + WHITE, J. A. + + 1951. A practical method for mounting the bacula of small mammals. + Jour. Mamm., 32:125, February 15. + + 1953. The baculum in the chipmunks of western North America. Univ. + Kansas Publ., Mus. Nat. Hist., 5:611-631, 19 figs., December 1. + + + WILSON, R. W. + + 1937. Pliocene rodents of western North America. Carnegie Inst. + Washington, Publ. 487:21-73, 2 figs., July 23. + + + WOOD, A. E., and WILSON, R. W. + + 1936. A suggested nomenclature for the cusps of the cheek teeth of + rodents. Jour. Paleon., 10:388-391, 2 figs. + + +_Transmitted March 4, 1960._ + + +[] +28-3030 + + + + +UNIVERSITY OF KANSAS PUBLICATIONS + +MUSEUM OF NATURAL HISTORY + + +Institutional libraries interested in publications exchange may obtain +this series by addressing the Exchange Librarian, University of Kansas +Library, Lawrence, Kansas. Copies for individuals, persons working in a +particular field of study, may be obtained by addressing instead the +Museum of Natural History, University of Kansas, Lawrence, Kansas. There +is no provision for sale of this series by the University Library, which +meets institutional requests, or by the Museum of Natural History, which +meets the requests of individuals. However, when individuals request +copies from the Museum, 25 cents should be included, for each separate +number that is 100 pages or more in length, for the purpose of defraying +the costs of wrapping and mailing. + + * An asterisk designates those numbers of which the Museum's supply + (not the Library's supply) is exhausted. Numbers published to date, + in this series, are as follows: + + Vol. 1. Nos. 1-26 and index. Pp. 1-638, 1946-1950. + + *Vol. 2. (Complete) Mammals of Washington. By Walter W. Dalquest. + Pp. 1-444, 140 figures in text. April 9, 1948. + + Vol. 3. *1. The avifauna of Micronesia, its origin, evolution, and + distribution. By Rollin H. Baker, Pp. 1-359, 16 figures in + text. June 12, 1951. + + *2. A quantitative study of the nocturnal migration of birds. + By George H. Lowery, Jr. Pp. 361-472, 47 figures in text. + June 29, 1951. + + 3. Phylogeny of the waxwings and allied birds. By M. Dale + Arvey. Pp. 473-530, 49 figures in text, 13 tables. + October 10, 1951. + + 4. Birds from the state of Veracruz, Mexico. By George H. + Lowery, Jr., and Walter W. Dalquest. Pp. 531-649, + 7 figures in text, 2 tables. October 10, 1951. + + Index. Pp. 651-681. + + *Vol. 4. (Complete) American weasels. By E. Raymond Hall. Pp. 1-466, + 41 plates, 31 figures in text. December 27, 1951. + + Vol. 5. Nos. 1-37 and index. Pp. 1-676, 1951-1953. + + *Vol. 6. (Complete) Mammals of Utah, _taxonomy and distribution_. + By Stephen D. Durrant. Pp. 1-549, 91 figures in text, + 30 tables. August 10, 1952. + + Vol. 7. *1. Mammals of Kansas. By E. Lendell Cockrum. Pp. 1-303. + 73 figures in text, 37 tables. August 25, 1952. + + 2. Ecology of the opossum on a natural area in northeastern + Kansas. By Henry S. Fitch and Lewis L. Sandidge. + Pp. 305-338, 5 figures in text. August 24, 1953. + + 3. The silky pocket mice (Perognathus flavus) of Mexico. + By Rollin H. Baker. Pp. 339-347, 1 figure in text. + February 15, 1954. + + 4. North American jumping mice (Genus Zapus). By Philip H. + Krutzch. Pp. 349-472, 47 figures in text, 4 tables. + April 21, 1954. + + 5. Mammals from Southeastern Alaska. By Rollin H. Baker and + James S. Findley. Pp. 473-477. April 21, 1954. + + 6. Distribution of Some Nebraskan Mammals. By J. Knox Jones, + Jr. Pp. 479-487. April 21, 1954. + + 7. Subspeciation in the montane meadow mouse. Microtus + montanus, in Wyoming and Colorado. By Sydney Anderson. + Pp. 489-506, 2 figures in text. July 23, 1954. + + 8. A new subspecies of bat (Myotis velifer) from southeastern + California and Arizona. By Terry A. Vaughan. Pp. 507-512. + July 23, 1954. + + 9. Mammals of the San Gabriel mountains of California. + By Terry A. Vaughan. Pp. 513-582. 1 figure in text, + 12 tables. November 15, 1954. + + 10. A new bat (Genus Pipistrellus) from northeastern Mexico. + By Rollin H. Baker. Pp. 583-586. November 15, 1954. + + 11. A new subspecies of pocket mouse from Kansas. By E. Raymond + Hall. Pp. 587-590. November 15, 1954. + + 12. Geographic variation in the pocket gopher, Cratogeomys + castanops, in Coahuila, Mexico. By Robert J. Russell and + Rollin H. Baker. Pp. 591-608. March 15, 1955. + + 13. A new cottontail (Sylvilagus floridanus) from northeastern + Mexico. By Rollin H. Baker. Pp. 609-612. April 8, 1955. + + 14. Taxonomy and distribution of some American shrews. + By James S. Findley. Pp. 613-618. June 10, 1955. + + 15. The pigmy woodrat, Neotoma goldmani, its distribution and + systematic position. By Dennis G. Rainey and Rollin H. + Baker. Pp. 619-624, 2 figures in text. June 10, 1955. + + Index. Pp. 625-651. + + Vol. 8. 1. Life history and ecology of the five-lined skink, Eumeces + fasciatus. By Henry S. Fitch. Pp. 1-156, 26 figures in + text. September 1, 1954. + + 2. Myology end serology of the Avian Family Fringillidae, + a taxonomic study. By William B. Stallcup. Pp. 157-211, + 23 figures in text, 4 tables. November 15, 1954. + + 3. An ecological study of the collared lizard (Crotaphytus + collaris). By Henry S. Fitch. Pp. 213-274, 10 figures in + text. February 10, 1956. + + 4. A field study of the Kansas ant-eating frog, Gastrophryne + olivacea. By Henry S. Fitch. Pp. 275-306, 9 figures in + text. February 10, 1956. + + 5. Check-list of the birds of Kansas. By Harrison E. + Tordoff. Pp. 307-359, 1 figure in text. March 10, 1956. + + 6. A population study of the prairie vole (Microtus + ochrogaster) in northeastern Kansas. By Edwin P. Martin. + Pp. 361-416, 19 figures in text. April 2, 1956. + + 7. Temperature responses in free-living amphibians and + reptiles of northeastern Kansas. By Henry S. Fitch. + Pp. 417-476, 10 figures in text, 6 tables. June 1, 1956. + + 8. Food of the crow, Corvus brachyrhynchos Brehm, in + south-central Kansas. By Dwight Platt. Pp. 477-498. + 4 tables. June 8, 1956. + + 9. Ecological observations on the woodrat, Neotoma floridana. + By Henry S. Fitch and Dennis G. Rainey. Pp. 499-533, + 3 figures in text. June 12, 1956. + + 10. Eastern woodrat, Neotoma floridana: Life history and + ecology. By Dennis G. Rainey. Pp. 535-646, 12 plates, + 13 figures in text. August 15, 1956. + + Index. Pp. 647-675. + + Vol. 9. 1. Speciation of the wandering shrew. By James S. Findley. + Pp. 1-68, 18 figures in text. December 10, 1955. + + 2. Additional records and extensions of ranges of mammals from + Utah. By Stephen D. Durrant, M. Raymond Lee, and Richard M. + Hansen. Pp. 69-80. December 10, 1955. + + 3. A new long-eared myotis (Myotis evotis) from northeastern + Mexico. By Rollin H. Baker and Howard J. Stains. Pp. 81-84. + December 10, 1955. + + 4. Subspeciation in the meadow mouse, Microtus + pennsylvanicus, in Wyoming. By Sydney Anderson. + Pp. 85-104, 2 figures in text. May 10, 1956. + + 5. The condylarth genus Ellipsodon. By Robert W. Wilson. + Pp. 105-116, 6 figures In text. May 19, 1956. + + 6. Additional remains of the multituberculate genus + Eucosmodon. By Robert W. Wilson. Pp. 117-123, 10 figures + in text. May 19, 1956. + + 7. Mammals of Coahuila, Mexico. By Rollin H. Baker. + Pp. 125-335, 75 figures in text. June 15, 1956. + + 8. Comments on the taxonomic status of Apodemus peninsulae, + with description of a new subspecies from North China. + By J. Knox Jones, Jr. Pp. 337-346, 1 figure in text, + 1 table. August 15, 1956. + + 9. Extensions of known ranges of Mexican bats. By Sydney + Anderson. Pp. 347-351. August 15, 1956. + + 10. A new bat (Genus Leptonycteris) from Coahuila. By Howard J. + Stains. Pp. 353-356. January 21, 1957. + + 11. A new species of pocket gopher (Genus Pappogeomys) from + Jalisco, Mexico. By Robert J. Russell. Pp. 357-361. + January 21, 1957. + + 12. Geographic variation in the pocket gopher, Thomomys bottae, + in Colorado. By Phillip M. Youngman. Pp. 363-385, 7 figures + in text. February 21, 1958. + + 13. New bog lemming (genus Synaptomys) from Nebraska. + By J. Knox Jones, Jr. Pp. 385-388. May 12, 1958. + + 14. Pleistocene bats from San Josecito Cave, Nuevo León, + México. By J. Knox Jones, Jr. Pp. 389-396. + December 19, 1958. + + 15. New Subspecies of the rodent Baiomys from Central America. + By Robert L. Packard. Pp. 397-404. December 19, 1958. + + 16. Mammals of the Grand Mesa, Colorado. By Sydney Anderson. + Pp, 405-414, 1 figure in text. May 20, 1959. + + 17. Distribution, variation, and relationships of the montane + vole, Microtus montanus. By Emil K. Urban. Pp. 415-511. + 12 figures in text, 2 tables. August 1, 1959. + + 18. Conspecificity of two pocket mice, Perognathus goldmani and + P. artus. By E. Raymond Hall and Marilyn Bailey Ogilvie. + Pp. 513-518, 1 map. January 14, 1960. + + 19. Records of harvest mice, Reithrodontomys, from Central + America, with description of a new subspecies from + Nicaragua. By Sydney Anderson and J. Knox Jones, Jr. + Pp. 519-529. January 14, 1960. + + 20. Small carnivores from San Josecito Cave (Pleistocene), + Nuevo León, México. By E. Raymond Hall. Pp. 531-538, + 1 figure in text. January 14, 1960. + + 21. Pleistocene pocket gophers from San Josecito Cave, Nuevo + León, México. By Robert J. Russell. Pp. 539-548, 1 figure + in text. January 14, 1960. + + 22. Review of the insectivores of Korea. By J. Knox Jones, Jr., + and David H. Johnson. Pp. 549-578. February 23, 1960. + + 23. Speciation and evolution of the pygmy mice, genus Baiomys. + By Robert L. Packard. Pp. 579-670, 4 plates, 12 figures in + text. June 16, 1960. + + Index will follow. + + Vol. 10. 1. Studies of birds killed in nocturnal migration. By + Harrison B. Tordoff and Robert M. Mengel. Pp. 1-44, + 6 figures in text, 2 tables. September 12, 1956. + + 2. Comparative breeding behavior of Ammospiza caudacuta and + A. maritime. By Glen E. Woolfenden. Pp. 45-75, 6 plates, + 1 figure. December 20, 1956. + + 3. The forest habitat of the University of Kansas Natural + History Reservation. By Henry S. Fitch and Ronald R. + McGregor. Pp. 77-127, 2 plates, 7 figures in text, + 4 tables. December 31, 1956. + + 4. Aspects of reproduction and development in the prairie vole + (Microtus ochrogaster). By Henry S. Fitch, Pp. 129-161, + 8 figures in text, 4 tables. December 19, 1957. + + 5. Birds found on the Arctic slope of northern Alaska. By + James W. Bee. Pp. 163-211, pls. 9-10, 1 figure in text. + March 12, 1958. + + 6. The wood rats of Colorado; distribution and ecology. + By Robert B. Finley, Jr. Pp. 213-552, 34 plates, + 8 figures in text, 35 tables. November 7, 1958. + + 7. Home ranges and movements of the eastern cottontail in + Kansas. By Donald W. Janes. Pp. 553-572, 4 plates, + 3 figures in text. May 4, 1959. + + 8. Natural history of the salamander, Aneides hardyi. + By Richard F. Johnston and Schad Gerhard. Pp. 573-585. + October 8, 1959. + + 9. A new subspecies of lizard, Cnemidophorus sacki, from + Michoacán, México. By William E. Duellman. Pp. 587-598, + 2 figures in text. May 2, 1960. + + 10. A taxonomic study of the Middle American Snake, Pituophis + deppei. By William E. Duellman. Pp. 599-612, 1 plate, + 1 figure in text. May 2, 1960. + + Index will follow. + + Vol. 11. 1. The systematic status of the colubrid snake, Leptodeira + discolor Günther. By William E. Duellman. Pp. 1-9, + 4 figs. July 14, 1958. + + 2. Natural history of the six-lined racerunner, Cnemidophorus + sexlineatus. By Henry S. Fitch. Pp. 11-62, 9 figs., + 9 tables. September 19, 1958. + + 3. Home ranges, territories, and seasonal movements of + vertebrates of the Natural History Reservation. By Henry + S. Fitch, Pp. 68-326, 6 plates, 24 figures in text, + 8 tables. December 12, 1958. + + 4. A new snake of the genus Geophis from Chihuahua, Mexico. + By John M. Legler. Pp. 327-334, 2 figures in text. + January 28, 1959. + + 5. A new tortoise, genus Gopherus, from north-central Mexico. + By John M. Legler. Pp. 335-343. April 24, 1959. + + 6. Fishes of Chautauqua, Cowley and Elk counties, Kansas. + By Artie L. Metcalf. Pp. 345-400, 2 plates, 2 figures in + text, 10 tables. May 6, 1959. + + 7. Fishes of the Big Blue River Basin, Kansas. By W. L. + Minckley. Pp. 401-442, 2 plates, 4 figures in text, + 5 tables. May 8, 1959. + + 8. Birds from Coahuila, México. By Emll K. Urban. Pp. 443-516. + August 1, 1959. + + 9. Description of a new softshell turtle from the southeastern + United States. By Robert G. Webb. Pp. 517-525, 2 pls., + 1 figure in text, August 14, 1959. + + 10. Natural history of the ornate box turtle, Terrapene ornata + ornata Agassiz. By John M. Legler. Pp. 527-669, 16 pls., + 29 figures in text. March 7, 1960. + + Index will follow. + + Vol. 12. 1. Functional morphology of three bats: Eumops, Myotis, + Macrotus. By Terry A. Vaughan. Pp. 1-153, 4 plates, + 24 figures in text. July 8, 1959. + + 2. The ancestry of modern Amphibia: a review of the evidence. + By Theodore H. Eaton, Jr. Pp. 155-180, 10 figures in text. + July 10, 1959. + + 3. The baculum in microtine rodents. By Sydney Anderson. + Pp. 181-216, 49 figures in text. February 19, 1960. + + 4. A new order of fishlike Amphibia from the Pennsylvanian of + Kansas. By Theodore H. Eaton, Jr., and Peggy Lou Stewart. + Pp. 217-240, 12 figures in text. May 2, 1960. + + More numbers will appear In volume 12. + + + + +Transcriber's Notes + +The text presented is that of the original printed version except for +the revisions below and a few assumed typesetting errors. The subsection +headers under "VARIATION WITH AGE" were converted to italic only to +match the rest. All other section title formatting retained as printed. +The words Miscellaneous and Monograph were abbreviated as Miscl. and +Mongr. respectively. Except for the two variant spellings of one word +(Mexico/México) which were retained, the most prevalent form of accented +words was used. + +Both decimal and whole plus fractional part of numbers (i.e., 9-1/2) +were retained as printed. The male and female symbols are represented by +[M] and [F] respectively. Footnotes were all placed at the end of each +species account. The list of KU Publications were compiled after the +article's text. + + +Typographical Corrections + + Page Correction + ==== ==================== + 591 proödent => proödont + 694 hesperomyines => hesperomines + + +Text Emphasis + + _Text_ - Italic + + =Text= - Bold + + + + + +End of the Project Gutenberg EBook of Speciation and Evolution of the Pygmy +Mice, Genus Baiomys, by Robert L. 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