Chapter III: Part 3

Two of the three specimens (KU 63052 and 63055) are the darkest of a series in which the palest are inseparable from _B. m. pallidus_. Goodwin, who kindly compared the three specimens with the type of _nebulosus_, mentioned (_in. litt._) that the skull of the type has a slenderer rostrum. Included in the series of skulls of _B. m. pallidus_ from 3 mi. W Mitla are several adults (not seen by Goodwin) with slender rostra. _B. m. nebulosus_ is judged to be a synonym of _B. m. pallidus_.

Populations of pygmy mice occurring in partially isolated areas of highland in Oaxaca seem to me to be incipient subspecies.

_Specimens examined._--Total 824 all from the Republic of Mexico and distributed as follows: PUEBLA: 2 mi. S Atlixco, 5800 ft., 1; _1 mi. SSW Tilapa_, 5800 ft., 2; _6 mi. SW Izucar de Matemores_, 7; _Piaxtla_, 3900 ft., 4[18]; Acatlan, 4100 ft., 1. MORELOS: 5 mi. W Tepoztlan, 6000 ft., 7[19]; _1 mi. W Tepoztlan_, 6000 ft., 9[19]; _2 mi. SW Tepoztlan_, 7000 ft., 1[20]; _Cuernvaca_, 9[19]; _6 mi. W Yautepec_, 4500 ft., 1[20]; _Yautepec_, 12[19]; _3 mi. N Alpuyeca_, 4000 ft., 2[20]; _Puente de Ixtla_, 2[19]; _Tetecala_, 4[21]; _2 km. S Jonacatepec_, 4500 ft., 6[20]; _type locality_, 6 (including the type). GUERRERO: _Yerbabuena_, 1800 m., 1; _Cueva de tia Juana_ [= _1.5 km. SSW Yerbabuena_], 1; _Laguna Honda_, 1840 m. [= _1.5 km. S Yerbabuena_], 3; 9 mi. SE Taxco, 3800 ft., 1[22]; _17 km. S Taxco_, 4000 ft., 2[20]; _Iguala_, 5[19]; _3.2 km. SSE Iguala_, 970 m., 1; 1 km. SSE Texcaizintla, 1600 m., 2; _Teloloapan_, 20[19], 5[24]; _1 km. N Chapa_, 1470 m., 6; _Chapa_, 1470 m., 5; El Limon, 3[18]; 2-1/2 mi. W Mexcala, 2100 ft., 1[20]; _Rio Balsas_, 1[18]; Ayusinaha [= Ayotzinapa], 1[18]; _Tlapa_, 3900 ft, 1[18]; _2.5 mi. S Almolonga_, 5600 ft., 13[20]; _1 km. N Zihuatanejo_, 1; Zihuatanejo Bay, 4[19]; _Las Gatas_ [= _2 km. S. Zihuatanejo_], 2; _2 km. SSE Zihuatanejo_, 9; _4 mi. W Chilpancingo_, 5800 ft., 3[20]; _Chilpancingo_, 4800 ft., 14[18], 21[19], 45[21]; _2 mi. N Tixtla_, 4400 ft., 3[20]; _3.2 km. S Chilpancingo_, 4; _Cd. Chamilpa_ [= _12 km. ESE Chilpancingo_], 5; _Tlalixtaquilla_, 4200 ft., 2[18]; _15 km. S. Chilpancingo_, 4300 ft., 10[20]; _1 mi. SW Colotlipa_, 2700 ft., 16[20]; _2 mi. SW Colotlipa_, 2700 ft., 1[20]; _Achuitzotla_, 2800 ft., 7[20]; _8 mi. SW Colotlipa_, 1[20]; _5 mi. S Rincon_, 2600 ft., 2[20]; _8 mi. SW Tierra Colorado_, 600 ft., 1[20]; Rio Aguacatillo, _30 km. N Acapulco_, 1000 ft., 3[20]; 5 mi. ESE Tecpan, 50 ft., 9; _Ejido Viejo_, _12 km. NNW Acapulco_, 1; _2 mi. NNW Acapulco_, 7; Acapulco, 3[18], 3[21]; Omentepec, 200 ft., 7[18]. OAXACA: _4 mi. E Huajuapam_, 5000 ft., 1; 2 mi. NW Tamazulapan, 6550 ft., 1; Yalalag, 3000 ft., 5[18]; _11 mi. NW Oaxaca_ [_City_], 1; _Yaganiza_, 3900 ft., 1[18]; Oaxaca [City], 5000 ft., 15, 7[21], 7[19], 5[24]; _3 mi. ESE Oaxaca_ [_City_], 30; _4 mi. ESE Oaxaca_ [_City_], 5050 ft., 1; _10 mi. SE Oaxaca_ [City], 1[22]; _Cerro Ocotepec_, 1[23]; Tepantepec, 9[23]; _1 mi. E Tlacolula_, 5500 ft., 53[19]; _3 mi. W Mitla_, 11; Jalapa, El Campanario, 1[23]; _2 mi. SE Matalan_, 5950 ft., 14; _Lachiguiri_, 2[23]; _Tres Cruces_, 10[23]; _Agua Blanca_, 11[23]; _San Jose_, 1[23]; Reforma, 30[19], 7[21], 10[23], 6[24] _Totolapa_, 1[18]; _Nejapa_, _85 km. WNW Tehuantepec_, 500 m., 12[19], 6[24]; _Chicapa_, 2[18]; _Gueladu_ [= _Jalapa_], 6[23]; _Juchitan_, _Laguna Superior_; Manteca, 8[23], 1[23]; San Bartolo, 3000 ft., 1[18]; _Ejutla_, 1400 m., 21[19]; _El Bambita_, _Tequisitlan_ 4[23]; _Mixtequilla_, 2[23]; _Guiencola_, 5[23]; _Tehuantepec_, 200 ft., 26[18], 11[19]; _Sola de la Vega_, 26[19], 3[24]; Huilotepec, 13[18], 3[23]; _Santa Lucia_, 24[23]; _Cerro de Paste_, _Tenango_, 7[23]; _Sta. C. Quieri_, 3[23]; _Santa Marie Ecatepec_, _Zarzamora_, 13[23]; _Rincon Bamba_, 11[23]; _3 mi. W Miahuatlan_, 5300 ft., 1; _Miahuatlan_, 12[19], 1[23], 6[24]; _San Juan Acaltepec_, 5[23]; _Zapotitlan_, 1[23]; _Llano Grande_, 3[18]; Pinotepa, 700 ft., 2[18]; Juquila, 8[18]; _Arroyo_, _San Juan_, _north of Cerro Otate_, 1[23]; Cerro Otate, 3[23]; 3 mi. S Candelaria, 1.

_Marginal records._--MORELOS: 5 mi, W Tepoztlan, 6000 ft. PUEBLA: 2 mi. S Atlixco, 5800 ft.; Acatlan, 4100 ft. OAXACA: 2 mi. NW Tamazulapan, 6550 ft; Tepantepec; Oaxaca [City], 5000 ft; Yalalag, 3000 ft; Jalapa, El Campanario; Reforma; Huilotepec; 3 mi. S Candelaria; Cerro Otate; Pinotepa, 700 ft. GUERRERO: Acapulco; Zihuatanejo Bay; El Limon; 9 mi. SE Taxco, 3800 ft.

[18] U. S. Nat. Museum (Biol. Surv. Coll.).

[19] Univ. Michigan, Museum of Zoology.

[20] Texas A & M, Cooperative Wildlife Research Collection.

[21] Chicago Natural History Museum.

[22] California Academy of Sciences.

[23] American Museum of Natural History.

[24] University of Florida Collections.

=Baiomys musculus pullus= Packard

_Baiomys musculus pullus_ Packard, Univ. Kansas Publs., Mus. Nat.
Hist., 9:401, December 19, 1958.

_Baiomys musculus grisescens_, Goodwin, Bull. Amer. Mus. Nat. Hist.,
79(2):161, May 29, 1942 (part); Miller and Kellogg, Bull. U. S. Nat.
Mus., 205:513, March 3, 1955 (part); Hall and Kelson, The Mammals of
North America, 2:661, March 31, 1959 (part).

_Type._--Adult female, skin and skull; No. 71605 University of Kansas Museum of Natural History; 8 mi. S Condega, Esteli, Nicaragua, obtained on July 15, 1956, by A. A. Alcorn, original number 4218.

_Range._--West-central Nicaragua, from Matagalpa northwest into the valley of the Rio Esteli, east as far as Jinotega, see Figure 10. Zonal range: Upper Tropical Life-zone.

_Diagnosis._--Size medium to small for the species; dorsum Fuscous-Black, individual hairs black-tipped with a subterminal band of Ochraceous-Buff, Neutral Gray at base; some hairs on dorsum all black to Neutral Gray at base; hair on sides Neutral Gray tinged with blackish; face blackish, becoming buffy on sides of head, and white on throat; vibrissae black; tail unicolored Chaetura Black; forefeet and hind feet sooty to dusky-white; mid-ventral region of venter white, hairs white to base; in region of anus and throat, hairs white-tipped, Neutral Gray at base; average and extreme external and cranial measurements of the type and 16 paratypes are as follows: total length, 117.3 (111-121); length of tail vertebrae, 47.2 (44-50); length of body, 70.4 (66-74); length of hind foot, 15.5 (14-17); length of ear from notch, 11.9 (10-13); occipitonasal length, 19.3 (18.9-19.8); zygomatic breadth, 10.2 (9.7-10.6); postpalatal length, 7.0 (6.8-7.3); least interorbital breadth, 3.9 (3.8-4.1); length of incisive foramina, 4.3 (4.0-4.6); length of rostrum, 7.0 (6.5-7.4); breadth of braincase, 9.6 (9.3-10.0); depth of cranium, 7.0 (6.8-7.3); alveolar length of maxillary tooth-row, 3.1 (3.0-3.2); for photographs of skull, see Plate 1_h_, and Plate 3_h_.

_Comparisons._--From _B. m. grisescens_, _B. m. pullus_ differs in: dorsum and tail darker; sides and lateral parts of venter grayish instead of buffy-brown, thus forming distinct mid-ventral white stripe; average length of body and tail significantly longer, thus total length greater; maxillary tooth-row significantly shorter; slightly larger in other cranial and external dimensions.

From _B. m. nigrescens_, _B. m. pullus_ differs in: dorsum slightly darker; face grayish, not sooty; mid-ventral white stripe (absent in most specimens of _nigrescens_) present and becoming grayish laterally; tail darker, less hairy, and averaging significantly longer; smaller in most external and cranial dimensions.

_Remarks._--_B. m. pullus_ resembles _B. m. nigrescens_ in size and color but can readily be distinguished from _nigrescens_ by the shorter tail. _B. m. pullus_ intergrades with _nigrescens_ as shown by specimens, referable to _B. m. nigrescens_, from 1 mi. NW San Salvador and from 1 mi. S Los Planes, El Salvador. In color of the dorsum, specimens from these localities are intermediate between _nigrescens_ and _pullus_.

The mid-ventral white stripe characteristic of _pullus_ is present in three of 28 adults from El Salvador. Goodwin (1942:160) reported white hairs on the pectoral region of several topotypes of _B. m. grisescens_. The areas of white hairs on the venter of _grisescens_ occur in approximately 10 per cent of the specimens examined, whereas in _pullus_, the frequency of occurrence is 90 per cent. The areas of white hairs in _grisescens_ are in broad patches on the pectoral region, while in _pullus_, a white stripe passes from the pectoral region to the inguinal region in both males and females. I know of no selective advantage that the presence of this white stripe would confer on the mice.

_Specimens examined._--Total 46, all from NICARAGUA, and distributed as follows: Type locality, 32 (including the type); _9 mi. NNW Esteli_, 8; _8 mi. NNW Esteli_, 3; San Rafael Del Norte, 1 (Amer. Mus. Nat. Hist.); _1 mi. NW Jinotega_, 1; Matagalpa, 1 (Amer. Mus. Nat. Hist.).

_Marginal records._--NICARAGUA: San Rafael Del Norte; Matagalpa; type locality.

=Baiomys taylori=

Northern Pygmy Mouse

(Synonymy under subspecies)

_Type._--_Hesperomys_ (_Vesperimus_) _taylori_ Thomas, Ann. Mag. Nat. Hist., Ser. 5, 19:66, January, 1887.

_Range._--Southeastern Arizona and southwestern New Mexico, south into Chihuahua and Durango, just east of the Sierra Madre Occidental, thence southeast through Zacatecas, Aquascalientes, Jalisco, Queretaro, and Guanajuato; two fingerlike projections extend northward, one on the west along the coast of Sinaloa into southern Sonora, and the other on the east covering eastern San Luis Potosi, Tamaulipas, eastern Coahuila, Nuevo Leon, into south, southeast, and north-central Texas. Southern margin of range in central Mexico approximates the 19th degree of latitude (see Figure 11). Arid lower and arid upper subdivisions of the Tropical Life-zone in south; principally Lower Sonoran and Lower Austral life-zones in north.

_Characters for ready recognition._--Unless otherwise noted, characters are usable for the age-categories of adult and old adult. Differs from _B. musculus_ in: hind foot less than 16 millimeters; occipitonasal length less than 19 millimeters; zygomatic breadth less than 10 millimeters; rostrum deflected ventrally at frontoparietal suture rather than curving gradually toward anteriormost point of nasals; cingular ridges and secondary cusps on teeth reduced or absent; basihyal having entoglossal process much reduced or absent, shoulders of basihyal not protruding anteriorly, but more flattened (characteristic of all age categories); baculum having narrower shaft, knob-shaped tip, wings at base projecting laterally, baculum less than 3 millimeters long; short process of incus attenuate; muscular process of posterior crus of stapes reduced.

_Characters of the species._--Size small (extremes in external measurements of adults: total length, 87-123; length of tail vertebrae, 34-53; length of hind foot, 12-15; length of ear, 9-12). Upper parts pale drab or reddish-brown to almost black; underparts grayish to cream-buff.

_Geographic variation._--Eight subspecies are here recognized (see Figure 11). Features that vary geographically are mostly the same as those that do so in _B. musculus_ (see page 609).

External and cranial size is less in _B. t. allex_, the southernmost subspecies, and progressively more in _B. t. paulus_, _B. t. taylori_, _B. t. ater_, _B. t. subater_, _B. t. fuliginatus_, _B. t. canutus_, and _B. t. analogous_. Size is largest in subspecies that occur at higher altitudes. Those subspecies are _B. t. analogous_ and _B. t. fuliginatus_. The correlation with Bergman's Rule is less exact in _B. taylori_ than in _B. musculus_. It is noteworthy that the smallest subspecies, _B. t. allex_, occurs in the area where the two species are sympatric.

There is close correlation in _B. taylori_, as also in _B. musculus_, of darker pelages with zones of high relative humidity. The subspecies having dark pelages are: _analogous_, _fuliginatus_, and _subater_. The two first-mentioned subspecies occur at high altitudes, and the other, _subater_, occurs in the humid coastal region of Texas. The paler subspecies, _taylori_, _canutus_, and _allex_, occur at lower altitudes. Two subspecies that occur at relatively high altitudes, _ater_ and _paulus_, are reddish-brown. The color of pelage in these subspecies resembles the color of soil upon which they live. Blair and Blossom (1948:5) demonstrated close correlation of color of soil with color of pelage in _B. t. ater_ by use of an Ives tint photometer.

1. _B. t. allex_
2. _B. t. analogous_
3. _B. t. ater_
4. _B. t. canutus_
5. _B. t. fuliginatus_
6. _B. t. paulus_
7. _B. t. subater_
8. _B. t. taylori_]

_Natural History_

_Habitat and numbers._--The habitat occupied by the northern pygmy mouse ranges from sparse grassy areas along rock walls in central Mexico (see Davis, 1944:394), and mesquite-cactus associations in southern Texas (Blair, 1952:242) to heavy stands of grasses such as _Bouteloua_ sp., _Andropogon_ sp., _Hilaria_ sp., and sacaton grass intermixed with _Yucca glauca_ in New Mexico, Arizona (see Hoffmeister 1956:281), and Chihuahua. Baker (1951:213) reports the species from 2 km. W El Carrizo, Tamaulipas, in dense grass and weeds at the edge of a cornfield. Hooper (1953:7) recorded the northern pygmy mouse in a cultivated field overgrown with herbaceous vegetation at Pano Ayuctle, Tamaulipas. In the State of Sinaloa, Hooper (1955b:13) obtained specimens in grass and among shrubs and vines bordering a fallow field. The northern pygmy mouse, in general, lives in situations more xerophytic and more grassy than does the southern pygmy mouse.

The northern pygmy mouse, as the southern pygmy mouse, is locally abundant in its geographic range. Stickel and Stickel (_op. cit._: 145) pointed out that on the third night of live-trapping in Bexar County, Texas, there was a sudden increase in unmarked pygmy mice trapped. This increase in numbers, after the resident population was seemingly marked, followed a one-half inch rainfall. Collectors from the University of Kansas, myself included, have had similar experiences in trapping these mice. In the Mexican states of Guanajuato, Queretaro, and Jalisco, _B. taylori_ is one of the commonest small mammals. In New Mexico and Arizona and the Mexican states of Sonora and Sinaloa, nevertheless, these mice are rare.

Stickel and Stickel (_loc. cit._) thought that the home range normal for _B. taylori_ in a grassy habitat was less than 100 square feet, but Blair (1953:10) thought that a complete home range had not been recorded by Stickel and Stickel.

_Behavior._--The northern pygmy mouse is crepuscular to nocturnal and where I trapped in northern Mexico was one of the first small rodents to appear in my traps in the evening. Hall and Villa-R (1949:460) recorded this habit in Michoacan. Observations of wild-taken _B. taylori_ held in captivity, lend support to its being crepuscular. Captives were rarely active in bright lights, but in diffuse or dim lights the same mice were active.

Blair (1941:381) pointed out that captive _B. t. subater_ were much more tolerant of one another than mice of the genus _Peromyscus_. He pointed out also that males aided in care of young. In one litter born in captivity in the course of my study, the female killed the male when the young were four days old. In another instance, the female and two eight-day-old young were killed by the male. Until that time, the male, female, and young had lived together peacefully. In other litters born in captivity, adult males did not harm the other mice.

I have noted, as Blair (_loc. cit._) did, that _B. taylori_ utters high-pitched squeals in a "singing" posture resembling that of the coyote, yet remains silent when being handled.

The northern pygmy mouse makes runways in the grass, in miniature resembling those of _Microtus_, and often uses runways constructed by _Sigmodon_. A small firm nest of finely shredded plant material (mostly grasses) is constructed in burrows or under logs, rocks, or fallen cactus plants. Thomas (1888:447) recorded nests of fine curly grass and cornsilk. Secondary refuge nests are not uncommon. Thomas (_loc. cit._) states, "If other mice live in the same place, the individuals of _Baiomys_ watch till others disappear, then suddenly steal part of the other nest and run to their own with it."

_Enemies and food._--Little is recorded of the animals that prey upon the northern pygmy mouse. Twente and Baker (1951:120) found remains of _B. taylori_ in 16 per cent of barn owl pellets (_Tyto alba pratincola_) collected 21 mi. SW Guadalajara, Jalisco. Presumably most of the crepuscular and early nocturnal raptorial birds and carnivorous mammals feed on these mice.

Food of _B. taylori_ consists in part of grass seeds and leaves, prickly pear (_Opuntia_ sp.) and the softer exposed parts of roots of vegetation among which the mice reside.

_Reproduction._--The northern pygmy mouse breeds throughout the year. The only months in which I have not recorded pregnant females or females with young are June and October. Forty-one records of embryos or young per litter average 2.48 (less than in _B. musculus_), and range from as few as one to as many as four per litter.

=Baiomys taylori allex= (Osgood)

_Peromyscus allex_ Osgood, Proc. Biol. Soc. Washington, 17:76-77,
March 21, 1904; Elliot, Field Columb. Mus. Publ., 105(6):135,
July 1, 1905; Lyon and Osgood, Bull. U. S. Nat. Mus., 62:124,
January 15, 1909.

_Baiomys taylori allex_, Packard, Proc. Biol. Soc. Washington,
71:17, April 11, 1958; Hall and Kelson, The Mammals of North
America, 2:659, March 31, 1959 (part).

[_Peromyscus_] _allex_, Elliot, Field Columb. Mus. Publ., 95(4):175,
July 15, 1904.

_Peromyscus taylori paulus_, Osgood, N. Amer. Fauna, 28:255, April
17, 1909 (part).

_Baiomys taylori paulus_, Miller, Bull. U. S. Nat. Mus., 79:137,
December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317,
April 29, 1924 (part); Ellerman, The Families and Genera of Living
Rodents, British Mus. Nat. Hist., 2:402, March 21, 1941 (part);
Poole and Schantz, Bull. U. S. Nat. Mus., 178:259, March 6, 1942;
Goldman, Smith. Miscl. Coll., 115:373, July 31, 1951 (part); Miller
and Kellogg, Bull. U. S. Nat. Mus., 205:512, March 3, 1955 (part);
Hall and Kelson, The Mammals of North America, 2:659, March 31, 1959
(part).

_Baiomys taylori analogous_, Hall and Kelson, Univ. Kansas Publs.,
Mus. Nat. Hist., 5:367, December 15, 1952 (part).

_Type._--Adult male, skin and skull; No. 33429/45452 U. S. Nat. Mus. (Biol. Surv. Coll.); Colima (City), Colima, Republic of Mexico, obtained on March 7, 1892, by E. W. Nelson, original number 2029.

_Range._--Colima, western lowlands of Michoacan and Jalisco, thence north into southern half of Nayarit, see Figure 11. Zonal range: arid lower tropical, approximates northern half of the Nayarit-Guerrero Biotic Province of Goldman and Moore (1945:349). Occurs from near sea level in Nayarit, up to 4000 feet in Jalisco.

_Diagnosis._--Size small for the species; dorsal ground color pale grayish-brown, near Isabella color; mid-dorsal region washed with blackish, individual guard hairs black to base, other hairs black-tipped with subterminal light olive bands, Neutral Gray at base; laterally, black-tipped hairs less abundant, hairs grayish-white to base; venter Pale Gull Gray to whitish, distal half of individual hairs white, proximal half Neutral Gray; hairs in regions of throat and chin white to base; facial region colored like dorsum, becoming paler below eye; in region of mouth, hairs white to base; dorsalmost vibrissae black to base, others white to base; ears flesh-colored, sparsely haired; tail unicolored, sparsely haired for the species; dark blotches on tail of some series (particularly the paratypical series); dorsal and ventral parts of forefeet and hind feet flesh-colored, whitish to gray in some series. Slightly smaller in most cranial dimensions. Maxillary part of zygoma forming almost a right angle with rostrum, rather than tapering at less than a right angle to rostrum; supraoccipital rounded posteriorly rather than indented on each side of foramen magnum; cranium, relative to length of rostrum, more nearly square; interparietal large relative to size of cranium. Average and extreme measurements of five adults from 2 mi. SSE Autlan are as follows: total length, 100.0 (93-107); length of tail vertebrae, 40.0 (37-44); length of body, 60.0 (56-63); length of hind foot, 14.0 (14); length of ear from notch, 10.5 (10-11); occipitonasal length, 17.3 (16.8-17.9); zygomatic breadth, 9.1 (8.7-9.4); postpalatal length, 6.3 (6.0-6.6); least interorbital breadth, 3.4 (3.3-3.5); length of incisive foramina, 3.9 (3.8-4.0); length of rostrum, 5.5 (5.2-5.8); breadth of braincase, 8.6 (8.0-8.9); depth of cranium, 6.4 (6.0-6.7); alveolar length of maxillary tooth-row, 3.0 (2.8-3.1); for photographs of skull, see Plate 1_i_ and Plate 4_a_.

_Comparisons._--For comparisons with _B. t. canutus_, see account of that subspecies. From _B. t. analogous_, _B. t. allex_ differs in: external and cranial dimensions less; dorsal coloration paler; tail and ears paler and less hairy; dorsum and belly paler; dorsal and ventral parts of forefeet and hind feet paler; median parts of incisive foramina less constricted on either side of midline and wider open laterally; interparietal larger in relation to skull; interorbital breadth greater relative to occipitonasal length.

_B. t. allex_ differs from _B. t. paulus_ as follows: dorsum gray with yellowish-brown wash rather than fawn to buff; tail unicolored in most series, less hairy; hind feet flesh-colored to light sooty, rather than whitish; rostrum slightly longer relative to occipitonasal length; incisive foramina differ from those of _paulus_ in much the same way as from _analogous_.

_Remarks._--Osgood (1909:255-256) dismissed as taxonomically unimportant the differences in color of pelage and size of cranium that he observed between the specimens from Colima (City), Colima, representative of _allex_ and those representing _paulus_ and chose to synonomize _allex_ with _paulus_. The differences that Osgood (_loc. cit._) deemed "... scarcely worthy of recognition ...," are, in fact, not only worthy of recognition, but also important in an understanding of the evolution of _Baiomys taylori_ (see speciation p. 659). Recently, I (1958b:17-18) studied ten specimens from Colima (City), Colima, and chose to regard _Peromyscus [= Baiomys] allex_ as a subspecies. I suggested (_loc. cit._) that the geographic range of _B. t. allex_ might encompass the southern part of Nayarit, and western Jalisco. Subsequent study of specimens from these areas reveals that the populations there are referable to _allex_. Most of the specimens obtained from these areas, however, merit special comment.

In color of pelage, those populations from south of the Rio Grande de Santiago and northwest of Guadalajara (4 mi. SE Ahuacatlan; 1 mi. E Ixtlan; Etzatlan) show evidence of intergradation with _paulus_ to the east and south (Magdalena, Tequila, and Tala, Jalisco), and with populations more closely adjacent to the south bank of that river. Intergradation is indeed complex in this area. Specimens from some localities seem to be intergrades between _allex_ and _paulus_; from other localities, some specimens are referable to _allex_, and the others to _paulus_; from still other localities, all specimens are referable to _allex_.

A series of 39 specimens from 1 mi. SSE Ameca, 4000 ft., Jalisco, are uniformly grayish-brown. This series averages grayer than paratypes of _allex_. There is little, if any, difference between the series from 1 mi. SSE Ameca and paratypes of _allex_ in external size of body, hind foot, length of ear, and size and conformation of the cranium. Populations from Ameca and vicinity might be expected to average considerably larger inasmuch as they occur at higher altitudes (see Bergman's Rule, p. 609) then the material from the lower coastal plains to the south in Colima and Michoacan, and at lower elevations in the west in Jalisco and Nayarit. The means of external and cranial measurements are not significantly different between the specimens from the highlands and those from the lowlands. In the area of Ameca where the two species _B. musculus_ and _B. taylori_ occur together, interspecific competition seems to have limited, perhaps even reduced, size of external and cranial parts of _taylori_ (see p. 660).

In color, specimens from the northern part of the valley of the Rio Tepalcatepec (10 mi. S, 1 mi. W Apatzingan) in Michoacan resemble paratypes of _allex_. Intergradation probably occurs to the north with _analogous_.

In the eight specimens from 13 mi. E and 1 mi. N Talpa de Allende, the skull, as reflected in occipitonasal length and zygomatic breadth relative to length of body, is larger than in other specimens here assigned to _allex_. The median part of the belly of the eight specimens is buff-colored rather than whitish-gray as in typical _allex_; the mid-dorsal region also averages darker than in any other specimens referred to _allex_. Additional specimens are needed from this and closely adjacent areas, especially to the west on the coastal plain, in order to determine more accurately the taxonomic status of the mice there. At present, it seems best to refer them to _allex_. Possibly the population represented by the eight specimens is an incipient subspecies.

There is no evidence of hybridization or intergradation of populations of _B. t. allex_ with any population of _B. musculus_ where the two species occur together.

_Specimens examined._--Total 233, all from the Republic of Mexico, distributed as follows: NAYARIT: 3 mi. SE Mirador, 7; _2 mi. S. Compostela_, 2900 ft., 5; _4 mi. N Santa Isabel_, 3800 ft., 2[25]; _2 mi. N Santa Isabel_, 3800 ft., 22[25]; _4 mi SE Ahuacatlan_, 5200 ft., 2[26]; _1 mi. E Ixtlan_, 4000 ft., 13[25]; 1 mi. E Ixtlan del Rio, 3700 ft., 1; 2 mi. WNW Valle de Banderas, near sea level, 1. JALISCO: Arroyo de Gavalan, 16[28]; Etzatlan, 6[27]; _Mascota_, 3900 ft., 6[27]; _7 mi W Ameca_, 15[25]; _6 mi. W Ameca_, 15[25]; _3 mi. W Ameca_, 5[25]; Ameca, 4000 ft., 11[27]; _1 mi. SSE Ameca_, 4000 ft., 38; 2 mi. N Resolana, 1500 ft., 28[25]; 13 mi. E, 1 mi. N Talpa de Allende, 8; 2 mi. SSE Autlan, 5; 1 mi. N San Gabriel, 4000 ft., 1[25]; Las Canoas, l[28]. COLIMA: Type locality, 10[27] (including the type). MICHOACAN: 9 mi. S Lombardia, 1500 ft., 1; _3 mi. W Apatzingan_, 1000 ft, 1; Apatzingan, 3[25]; 10 mi. S, 1 mi. W Apatzingan, 800 ft., 10.

_Marginal records._--NAYARIT: 3 mi. SE Mirador; 1 mi. E Ixtlan del Rio. JALISCO: Etzatlan; Ameca; 2 mi. N Resolana; Las Canoas. MICHOACAN: 9 mi. S Lombardia; 10 mi. S, 1 mi. W Apatzingan. COLIMA: type locality. NAYARIT: Valle de Banderas.

[25] Univ. Michigan, Museum of Zoology.

[26] California Academy of Sciences.

[27] U. S. Nat. Museum (Biol. Surv. Coll.).

[28] American Museum of Natural History.

=Baiomys taylori analogous= (Osgood)

_Peromyscus taylori analogous_ Osgood, N. Amer. Fauna, 28:256,
April 17, 1909 (part); Elliott, Check-List Mamm., N. Amer. Cont.,
West Indies and Neighboring Seas, Suppl., Amer. Mus. Nat. Hist.,
p. 44, January 8, 1917.

_Baiomys taylori analogous_, Miller, Bull. U. S. Nat. Mus., 79:137,
December 31, 1912; Miller, Bull. U. S. Nat. Mus., 128:318, April 29,
1924; Ellerman, The Families and Genera of Living Rodents, British
Mus. Nat. Hist., 2:402, March 21, 1941; Poole and Schantz, Bull.
U. S. Nat. Mus., 178:259, March 6, 1942; Davis, Jour. Mamm., 25:394,
December 12, 1944; Hooper, Jour. Mamm., 28:50, February 15, 1947;
Hall and Villa-R., Univ. Kansas Publs., Mus. Nat. Hist., 1:460,
December 27, 1949; Hall and Villa-R., Anal. del Inst. Biol., 21:196,
September 28, 1950; Goldman, Smith. Miscl. Coll., 114:373, July 31,
1951 (part); Hall and Kelson, Univ. Kansas Publs., Mus. Nat. Hist.,
5:367, December 15, 1952 (part); Villa-R., Anal. del Inst. Biol.,
23:435, May 20, 1953; Miller and Kellogg, Bull. U. S. Nat. Mus.,
205:512, March 3, 1955; Hooper, Occas. Papers Mus. Zool. Univ.
Michigan, 565:13, March 31, 1955; Packard, Proc. Biol. Soc.
Washington, 71:17, April 11, 1958.

_Peromyscus musculus brunneus_, Elliot, Field Columb. Mus. Publ.,
115(8):203, 1907 (part).

_Peromyscus musculus_ [_musculus_], Osgood, N. Amer. Fauna, 28:258,
April 17, 1909 (part).

_Baiomys musculus musculus_, Hall and Villa-R., Univ. Kansas Publs.,
Mus. Nat. Hist., 1:460, December 27, 1949 (part); Hall and Villa-R.,
Anal. del Inst. Biol., 21:196, September 28, 1950 (part).

_Baiomys taylori taylori_, Dalquest, Louisiana State Univ. Studies
(Biol. Sci. Ser.), 1:155, December 28, 1953 (part); Hall and Kelson,
The Mammals of North America, 2:660, March 31, 1959 (part).

_Baiomys taylori allex_, Hall and Kelson, The Mammals of North
America, 2:659, March 31, 1959 (part).

_Baiomys musculus musculus_, Hall and Kelson, The Mammals of North
America, 2:661, March 31, 1959 (part).

_Type._--Adult male, skin and skull; No. 120261 U. S. Nat. Mus. (Biol. Surv. Coll.); Zamora, Michoacan, Republic of Mexico, obtained on January 15, 1903, by E. W. Nelson, and E. A. Goldman, original number 15764.

_Range._--Central and eastern Jalisco south into Michoacan, east through Guanajuato, Queretaro, thence into Estado Mexico, and Distrito Federal, and west-central Veracruz, see Figure 11. Zonal range: approximately the Transverse Volcanic Biotic Province of Moore (1945:218) and of Goldman and Moore (1945:349). Occurs from 5000 feet, 7 mi. S Ocotlan, Jalisco, up to 8000 feet in Ixtapalapa, Distrito Federal.

_Diagnosis._--Size large for the species; dorsum dark Sepia to near blackish medially in freshly taken specimens (Sepia fading to near Fuscous in prepared specimens); belly slaty-gray, hairs Deep Neutral Gray near tips and Dusky Neutral Gray at bases; hairs on back black-tipped with subterminal band of Ochraceous-Tawny (guard hairs blackish to base); hairs of throat and chin white-tipped, gray at bases; dorsal vibrissae black, ventral and anteriormost vibrissae white; hairs on face and sides black-tipped, and Ochraceous-Tawny at base; ears sparsely haired, individual hairs grayish, blackish, and ochraceous; tail sooty to blackish dorsally, lighter ventrally; forefeet and hind feet sooty brown on dorsal and ventral surface. Skull relatively broad interorbitally; zygoma broad and squared; cranium larger in all dimensions than in most other subspecies. Average and extreme measurements of 10 adults from 1 mi. S, 11 mi. W Zamora, 5400 ft., Michoacan, are: total length, 109.4 (102-121); length of body, 64.3 (58-72); length of tail, 44.9 (39-51); length of hind foot, 14.6 (14-15); occipitonasal length, 18.0 (17.5-18.6); zygomatic breadth, 9.4 (9.1-9.7); postpalatal length, 6.6 (6.2-7.2); least interorbital breadth, 3.5 (3.3-3.8); length of incisive foramina, 4.0 (3.8-4.2); length of rostrum, 6.2 (5.8-6.5); breadth of braincase, 8.7 (8.5-8.9); depth of cranium, 6.6 (6.3-6.9); alveolar length of maxillary tooth-row, 3.1 (3.0-3.3); for photographs of skull, see Plate 2_a_ and Plate 4_b_.

_Comparisons._--For comparisons with _B. t. allex_, _B. t. canutus_, _B. t. paulus_, and _B. t. fuliginatus_, see accounts of those subspecies. From _B. t. taylori_, _B. t. analogous_ differs as follows: sides and dorsum darker, differing most in freshly prepared specimens; dorsal surface of forefeet and hind feet darker; basal part of hairs on belly darker gray; frontal bones less constricted, causing less taper anteriorly in interorbital space; interparietal wider transversely; basioccipital more expanded laterally, narrowing more abruptly at suture between basioccipital and basisphenoid.

_Remarks._--The pelage of _analogous_ becomes paler with wear as pointed out by Osgood (1909:257). A paratype, U. S. Nat. Mus. 120260, and several specimens from 1 mi. S, 11 mi. W Zamora, Michoacan, are grayish rather than brownish-black. All of these are old adults having the terminal black parts of the hairs on the dorsum nearly worn away. Excluding such grayish individuals, _B. t. analogous_, like _B. t. subater_ and _B. t. fuliginatus_, is uniformly brownish-black. Both _analogous_ and _fuliginatus_ occur in relatively high mountainous country on dark soils or pedregals, and all three of the aforementioned subspecies occur in zones of high relative humidity.

_B. t. analogous_ intergrades with _B. t. paulus_ (see account of that subspecies) and _B. t. allex_ south and west of Lago de Chapala in Jalisco. Additional specimens are needed from Queretaro and San Luis Potosi in order to ascertain whether or not _B. t. analogous_ intergrades with _B. t. fuliginatus_ or _B. t. taylori_. Specimens from western Jalisco, in the past referred to _B. t. analogous_, are referable to _B. t. allex_ (see account of that subspecies). Specimens obtained west of, and bordering, the Rio del Naranjo in Jalisco show a mixture of characters of both _B. t. allex_ and _B. t. analogous_. For example, specimens from 2 mi. N Ciudad Guzman resemble _analogous_ on the dorsum, whereas, on the belly, the individual hairs are white-tipped, pale gray at the base, and in over-all appearance are whitish-gray, unlike typical _analogous_ (being like _allex_ instead). The dorsal surface of the forefeet are sooty to light brownish (as in _analogous_), whereas, the hind feet are flesh-colored (as in _allex_). Another series of specimens from 4 mi. W Leon, Guanajuato, are intergrades between _B. t. analogous_ and _B. t. paulus_. These specimens are grayish to brownish on the dorsum, have sooty forefeet and hind feet (more nearly as in _analogous_ than in _paulus_), are grayish-white on the venter, and have a distinctly bicolored tail (resembling that of _paulus_ more than that of _analogous_). When the average of cranial characters is considered, both series are best referred to _analogous_.

Hooper (1947:50) pointed out that specimens from the pedregal San Geronimo, Distrito Federal, were more nearly black than topotypes and generally showed less brownish hues typical of _analogous_. I have examined this series and several others from this area (see Specimens examined, p. 640) and am convinced that these populations average darker. Actually, the dorsum is more nearly black and the venter is more buffy than in typical _analogous_. The hairs of these individuals average longer than in other populations of _analogous_. Skulls of the specimens from the pedregal are indistinguishable from those of paratypes of _analogous_. The populations from the Distrito Federal seem to be incipient subspecies.

_Specimens examined._--Total 696, all from the Republic of Mexico, distributed as follows: SAN LUIS POTOSI: Hacienda Capulin, 5[33]; _3.3 mi. N Tamazunchale, by-road_, 2[34]; 1 mi. N Tamazunchale, 700 ft., 1[35]. VERACRUZ: Acultzingo, 4[29], 1[31]. JALISCO: 1 mi. S Jalostotitlan, 5700 ft., 5; 7 mi. NW Tepatitlan, 3[29]; _6 mi. N, 4 mi. E Tepatitlan_, 6400 ft., 25; _2-1/2 mi. E Tepatitlan_, 6200 ft., 15; _2 mi. S, 1/2 mi. W Tepatitlan_, 9; _near Tepatitlan_, 2; _5 mi. SW Arrandas_, 6700 ft., 6; _2 mi. E Zapotlanejo_, 23; _2-1/2 mi. E Puente Grande_ (_5-1/2 mi. SW Zapotlanejo_), 3; _8 mi. S Guadalajara_, 10[29]; _3 mi. ENE Santa Cruz de las Flores_, 9; _4 mi. NE Ocotlan_, 5050 ft., 18; _13 mi. S, 9-1/2 mi. W Guadalajara_, 1; _2 mi. WNW Ocotlan_, 5000 ft., 15; 13 mi. S, 15 mi. W Guadalajara, 2; _Ocotlan_, 5000 ft., 8[30]; _1 mi. S Ocotlan_, 5000 ft., 12; 27 mi. S, 12 mi. W Guadalajara, 9; _1-1/2 mi. N Mazatmitla_, 6[29]; _1/2 mi. NW Mazatmitla_, 4; _3 mi. WSW Mazatmitla_, 4; 2 mi. N Ciudad Guzman, 5000 ft., 18. GUANAJUATO: 4 mi. N, 5 mi. W Leon, 7000 ft., 25; 5 mi. S Salamanca, 2[29]; _5 mi. E Celaya_, 6000 ft., 6; _1 mi. E Yuriria_, 5725 ft., 3; Salvatierra, 5775 ft., 8; _NE edge Acambaro_, 6050 ft., 10; _Acambaro_, 3[30]. QUERETARO: Toliman, 7[30]; 6 mi. E Queretaro, 6550 ft., 37. HIDALGO: Tula, 2050 m., 1[31]. MICHOACAN: _2 mi. E La Palma, SE side Lago de Chapala_, 7; type locality, 4000 ft., 10[30] (including the type); _9 mi. E Zamora_ (_Camenaro_), 2[29]; _1 mi. S, 11 mi. W Zamora_, 5400 ft., 17; S Cuitzeo, 36[29]; _Jiquilpan_, 4800 ft., 15; _11 mi. W Jiquilpan_, 6700 ft., 2; _1 mi. E Jiquilpan_, 7; _1 mi. E Zinapecuaro_, 6300 ft., 17; _4-1/2 mi. NE Tarequato_ (_Tarecuato_), 6600 ft, 1; _Tanganciguaro_ (_Tangancicuaro_), 5500 ft., 4; _2 mi. N Tarecuato_, 7200 ft., 1; _2 mi. S Maravatio_, 6650 ft, 6; _2 mi. SE Zacapu_, 6600 ft., 11; _1 mi. N Tinquindin_ (_Tinguindin_), 6300 ft., 2; _3 mi. E Morelia_, 6600 ft., 3; _11 mi. E, 2 mi. S Morelia_, 1; 2 mi. SE Hidalgo (Villa Hidalgo), 6; _1-1/2 mi. N Los Reyes_, 1; _E Los Reyes_, 18[29]; _Los Reyes_, 8[30]; _3 mi. W, 1 mi. N Patzucuaro_, 6600 ft., 2; _N Patzucuaro_, 2[29]; _Patzucuaro_ 9[31], 4[30], 4[29]; Uruapan, 1[29]; _E Uruapan_, 12; _2-1/2 mi. E Uruapan_ (_La Presca_), 2[29]; 2 mi. SW Zitacuaro, 1; 1 mi. E, 6 mi. S Tacambaro, 4000 ft., 11[37]; _La Huacana_, 1[30]. MEXICO: Templo del Sol, Pyramides de San Juan, Teotihuacan, 8000 ft., 1; _31 km. E Mexico City_, 7500 ft., 11[36]; _17 km. E Mexico City_, 7500 ft, 1[36]; _Cerro La Caldera, 11 mi. ESE Mexico_, 2350 m., 5; 4 km. ENE Tlalmanalco, 2290 m., 9; _Hacienda Cordoba_ (_Cordova_), 6. MEXICO, D. F.: _Cerro de la Estrella, Ixtapalapa_, 2450 m., 1; _3/4 mi. S, 1 mi. E Churubusco_, 2400 m., 2; _5 km. S Mexico City, South of Cd. Universitaria_, l[32]; _Pedregal San Angel_, _2.6 mi. S Monumento a Obregon, 2_; _El Pedregal, 1 km. S San Angel_, 2260 m., 1; _Falda SW Cerro Zacatepec, 3.9 mi. SW Monumento a Obregon_, 1; _2 mi. N Tlalpan, Zacayuca_, 2380 m., 5; _Tlalpan_ (_Pedregal_), 2400 m., 21[31]; _San Geronimo_, 37[29], 6[38]; _Santa Rosa_, 2700 m., 1[32]; _Tlalpan_, 8; _3/4 mi. SW Las Fuentes, Tlalpan_, 2450 m., 25[30]; _Tepepan_, 6[29]; _Rancho La Noria, 1 mi. W Xochimilco_, 2270 m., 4; _500 meters N Xochitepec_, 2250 m., 7; 200 m. N San Mateo Xalpa (Jalpa), 2390 m., 2.

_Marginal records._--SAN LUIS POTOSI: Hacienda Capulin; 1 mi. N Tamazunchale. HIDALGO: Tula, 2050 m. MEXICO: Templo del Sol, Pyramides de San Juan, Teotihuacan. VERACRUZ: Acultzingo. MEXICO: 4 km. ENE Tlalmanalco. MEXICO, D. F.: 200 m. N San Mateo Xalpa (Jalpa), 2390 m. MICHOACAN: 2 mi. SW Zitacuaro; 1 mi. E, 6 mi. S Tacambaro; Uruapan. JALISCO: 2 mi. N Ciudad Guzman; 27 mi. S, 12 mi. W Guadalajara; 13 mi. S, 15 mi. W Guadalajara; 7 mi. NW Tepatitlan; 1 mi. S Jalostotitlan, 5700 ft. GUANAJUATO: 4 mi. N, 5 mi. W Leon. QUERETARO: 6 mi. E Queretaro, 6550 ft.; Toliman.

[29] Univ. Michigan, Museum of Zoology.

[30] U. S. Nat. Museum (Biol. Surv. Coll.).

[31] Chicago Natural History Museum.

[32] American Museum of Natural History.

[33] Museum of Natural History, Louisiana State University.

[34] Univ. Illinois, Mus. Nat. History.

[35] The Museum, Michigan State Univ.

[36] Texas A & M, Cooperative Wildlife Research Collection.

[37] Univ. California, Mus. Vert. Zoology.

[38] University of Florida Collections.

=Baiomys taylori ater= (Blossom and Burt)

_Baiomys taylori ater_ Blossom and Burt, Occas. Papers Mus. Zool.,
Univ. Michigan, 465:2, October 8, 1942; Blair and Blossom, Contrib.
Lab. Vert. Biol., Univ. Michigan, 40:1, March, 1948; Hoffmeister and
Goodpaster, Ill. Biol. Monogr., 24(1):115, December 31, 1954; Miller
and Kellogg, Bull. U. S. Nat. Mus., 205:511, March 3, 1955;
Hoffmeister, Amer. Midland Nat., 55:281, April, 1956; Packard, Jour.
Mamm., 40:146, February 20, 1959; Hall and Kelson, The Mammals of
North America, 2:659, March 31, 1959 (part).

_Peromyscus taylori paulus_, Osgood, N. Amer. Fauna, 28:256, April
17, 1909 (part).

_Baiomys taylori_ [_ater_], Justice, Jour. Mamm., 38:520, November
20, 1957.

_Type._--Adult male, skin and skull; No. 85425, University of Michigan, Museum of Zoology; 7 mi. W Hereford, Cochise County, Arizona, obtained on March 25, 1941, by Philip M. Blossom, original number 2195.

_Range._--Southeastern Arizona, north to Graham County, thence east to the Animas Valley, Hidalgo County, New Mexico; south to northern Chihuahua and northwest to the southern border of Cochise County, Arizona, see Figure 11. Zonal range: largely lower Sonoran (Apachian Biotic Province of Dice, 1943:56). Occurs from 4300 feet in Chihuahua up to 6200 feet in New Mexico.

_Diagnosis._--Size medium for the species; dorsum between Mummy Brown and Prouts Brown; individual tips of hairs intermixture of black and Ochraceous-Tawny, bases of all hairs slate-gray; sides of body and face, Buffy Brown to Cinnamon Brown; belly Cinnamon Buff, proximal half of individual hairs Deep Neutral Gray, distal half white; in region of throat, proximal fourth of individual hairs gray, distal three-fourths white; dorsal vibrissae black to base, ventral vibrissae white to base; tail brownish above, gray below; dorsal and ventral surface of forefeet and hind feet buffy to gray; interparietal somewhat compressed anteroposteriorly. Average and extreme cranial measurements of 15 adults from 9-1/2 mi. W New Mexico State Line, 5-1/2 mi. N Mexican border, Cochise County, Arizona, are as follows: occipitonasal length, 18.0 (17.5-18.6); zygomatic breadth, 9.5 (9.2-9.9); postpalatal length, 6.6 (6.0-7.1); least interorbital breadth, 3.6 (3.4-3.8); length of incisive foramina, 4.0 (3.8-4.2); length of rostrum, 6.1 (5.7-6.4); breadth of braincase, 8.6 (8.4-9.1); depth of cranium, 6.5 (6.3-6.9); alveolar length of maxillary tooth-row, 3.2 (3.1-3.4). Average and extreme external measurements for six adults from 9 mi. W Hereford, Cochise County, are as follows: total length, 106.3 (98-115); length of tail vertebrae, 42.3 (39-46); length of body, 64 (59-69); length of hind foot, 13.6 (13-14.2); length of ear from notch, 11.1 (10.5-11.5); for photographs of skull, see Plate 2_b_, and Plate 4_c_.

_Comparisons._--For comparisons with _B. t. canutus_, see account of that subspecies. From _B. t. paulus_, the subspecies to the southeast, _B. t. ater_ differs in: dorsum darker brown; tail less strikingly bicolored; belly buffy rather than whitish to white-gray; forefeet and hind feet darker dorsally and ventrally; posterior margin of basioccipital bowed anteriorly in a broad U-shape with a secondary small median anteriorly directed U-shaped curve, rather than bowed anteriorly in a simple U-shape; interparietal more compressed anteroposteriorly; coronoid process of mandible so acutely recurved that tip of coronoid points posteroventrally and appears sickle-shaped.

_Remarks._--Blossom and Burt (1942:1) described _B. t. ater_ as the darkest of the known subspecies. It is dark, but specimens from some parts of the ranges of _B. t. analogous_, _B. t. fuliginatus_, and _B. t. subater_ exceed in melanins the darkest individuals of _ater_. Blair and Blossom (1948:5) also concluded by the use of an Ives tint photometer that _B. t. subater_ was significantly darker than _B. t. ater_.

When paratypes of _ater_ and specimens of _B. t. paulus_ are compared, the darkest individuals of _ater_ exceed but slightly the darkest of _paulus_. The darkest specimens of _paulus_ occur in southern Zacatecas, and northern Jalisco, and the palest of the series are in northern Durango and southern Chihuahua. When paratypes of _ater_ and _paulus_ are compared, the difference in color is readily distinguishable. Specimens from 1-1/2 mi. N San Francisco, in northern Chihuahua, appear to be intermediate in color between _ater_ and _paulus_ except for a faint tinge of buff ventrally. In characters of the crania, these specimens resemble _ater_ and are referred to that subspecies. A slightly different pattern of color is present in pygmy mice from the Peloncillo Mountains and the Animas Valley of New Mexico; the upper parts resemble those of paratypes of _ater_, but the venter has only the faintest suggestion of the buffy wash. Crania of these specimens from New Mexico are inseparable from those of paratypes of _ater_, and the specimens are, therefore, referred to _ater_.

When specimens are arranged by localities from Arizona east into southern New Mexico, thence south into Chihuahua and Durango, gradual intergradation in color is evident from dark in the north to pale browns in the south, whereas, size and shape of interparietal and size and shape of coronoid process of the lower jaw divide quite distinctly into two morphological types in central Chihuahua.

Cranial variation in size and proportion among adults is slight throughout the range of _ater_ compared to variation detected in other subspecies of _Baiomys taylori_. Perhaps such a relatively stable pattern of characters of the crania reflects the homogeneity of the gene pool, with respect to these characters, of the populations sampled. The fact that the color of the pelage of this subspecies varies considerable throughout its known range and that the crania do not is perhaps a clue to the mode of inheritance of characters in these mice. Seemingly, color of pelage is inherited independently of characters of the cranium. The relative lack of variability in the crania of _ater_ may result from uniform environmental conditions, which have served to select for uniform characters in the populations. All of the other wide-ranging subspecies of _B. taylori_ occupy more diverse habitats than _ater_. Secondly, the rather abrupt change in the cline of measured characters of the crania between _ater_ and _paulus_ in central Chihuahua suggests a secondary zone of intergradation. The probable cessation of gene flow in the past between these two subspecies, allowing _ater_ to be isolated for a time, may also, in part, account for the relative lack of variability in the crania of _ater_.

_Specimens examined._--Total 58, distributed as follows: ARIZONA: _Graham County_: 1-1/2 mi. SW Ft. Grant, Graham Mts., 1[39]; _Pima County_: 1-1/2 mi. ENE Greaterville, Thurber Ranch, 2[39]; _Santa Cruz County_: Patagonia, 3[39]; _Cochise County_: _9 mi. W Hereford_, 10[43]; type locality, 2[43] (including the type); _5 mi. W Hereford_, 5[43]; 9-1/2 mi. W New Mexico State Line, 5-1/2 mi. N Mexican border, 20[42]; _3 mi. E, 1 mi. N Chiricahua_, 1[42]. NEW MEXICO: _Hidalgo County_: 18 mi. S, 2 mi. W Animas, 2; _22 mi. S, 2 mi. W Rodeo_, 6000 ft., 1[40]; _22 mi. S, 2 mi. E Rodeo_, 6000 ft., 3[40]; 25-1/2 mi. S Animas, 6200 ft. (in Big Bill Canyon), 1[40]. CHIHUAHUA: _5-1/2 mi. N, 2 mi. W San Francisco_, 5100 ft., 1; _2-1/2 mi. N, 3 mi. W San Francisco_, 5200 ft., 1; 1-1/2 mi. N San Francisco, 5100 ft., 4; Casas Grandes, 4300 ft., 1[41].

_Marginal records_--ARIZONA: 1-1/2 mi. SW Ft. Grant, Graham Mts. NEW MEXICO: 18 mi. S, 2 mi. W Animas; 25-1/2 mi. S Animas (in Big Bill Canyon). CHIHUAHUA: 1-1/2 mi. N San Francisco; Casas Grandes. ARIZONA: Patagonia; 1-1/2 mi. ENE Greaterville, Thurber Ranch.

[39] University of Illinois, Museum of Natural History.

[40] University of New Mexico.

[41] U. S. Nat. Museum (Biol. Surv. Coll.).

[42] University of Arizona.

[43] Univ. Michigan, Museum of Zoology.

=Baiomys taylori canutus=, new subspecies

_Peromyscus taylori paulus_, Osgood, N. Amer. Fauna, 28:255, April
17, 1909 (part).

_Peromyscus musculus_ [_musculus_], Osgood, N. Amer. Fauna, 28:256,
April 17, 1909 (part).

_Baiomys taylori paulus_, Miller, Bull. U. S. Nat. Mus., 79:137,
December 31, 1912 (part); Miller, Bull. U. S. Nat. Mus., 128:317,
April 29, 1924 (part); Burt, Miscl. Publ., Mus. Zool., Univ.
Michigan, 39:54, February 14, 1938; Goldman, Smith. Miscl. Coll.,
115:373, July 31, 1951 (part); Miller and Kellogg, Bull. U. S. Nat.
Mus., 205:512, March 3, 1955 (part); Hooper, Occas. Papers Mus.
Zool., Univ. Michigan, 565:13, March 31, 1955; Hall and Kelson, The
Mammals of North America, 2:659, March 31, 1959 (part).

_Baiomys musculus musculus_, Goldman, Smith. Miscl. Coll., 115:336,
July 31, 1951 (part).

_Type._--Adult male, skin and skull; No. 62075, University of Kansas, Museum of Natural History; 1 mi. S Pericos, Sinaloa, Republic of Mexico; obtained on June 14, 1954, by A. A. Alcorn, original number 1754.

_Range._--Central Nayarit northward through western Sinaloa, to as far north as south-central Sonora, see Figure 11. Zonal range: Lower arid tropical, closely approximating the Sinaloan Biotic Province of Goldman and Moore (1945:349). Occurs from near sea level at Escuinapa (43 feet), Sinaloa, to 3200 feet at a place 2 mi. WNW Tepic, Nayarit.

_Diagnosis._--Dorsal ground color Buffy Brown (some specimens near Olive Brown); proximal fourth of individual guard hairs of dorsum black-tipped, distal three-fourths dark grayish; dorsal underfur black-tipped having subterminal band of Buffy Brown; hair around eyes buffy to base; belly Pallid Neutral Gray with overtones of buff; individual hairs in region of chin whitish-gray to bases; vibrissae blackish to bases except ventralmost, those being white to base; tail Dark Olive above, slightly paler below. Average and extreme external measurements of 13 adults from 15 mi. N Rosario, Chele, Sinaloa, 300 ft., are as follows: Total length, 109.6 (99-120); length of tail, 43.4 (38-49); length of body, 66.2 (58-75); length of hind foot, 11.2 (10-12). Average and extreme cranial measurements of 19 adults from the same place are as follows: occipitonasal length, 18.2 (17.7-18.9); zygomatic breadth, 9.6 (9.2-10.1); postpalatal length, 6.9 (6.5-7.3); least interorbital breadth, 3.6 (3.4-3.8); length of incisive foramina, 3.9 (3.5-4.2); length of rostrum, 5.9 (5.5-6.6); breadth of braincase, 8.7 (8.3-8.9); depth of cranium, 6.5 (6.2-6.7); alveolar length of maxillary tooth-row, 3.1 (3.0-3.2); breadth of zygomatic plate, 1.8 (1.6-2.0); for photographs of skull, see Plate 2_c_, and Plate 4_d_.

_Comparisons._--From _B. t. ater_, _B. t. canutus_ differs in: dorsum slightly grayer; belly whitish to pale-gray with only faint tones of buff, rather than cinnamon-buff to buff-gray; forefeet and hind feet flesh-colored to grayish above instead of whitish to flesh-colored; tail paler above, less hairy, scales more evident; interparietal relatively larger from anteriormost to posteriormost points; incisive foramina tapering less abruptly posteriorly, not constricted towards midline; over-all size of body and cranium somewhat larger.

From _B. t. paulus_, _B. t. canutus_ differs in: dorsum grayish-brown rather than fawn-colored (not differing appreciably from extremes of darker brown specimens of _paulus_); forefeet and hind feet flesh-colored to grayish above rather than white above; tail less hairy, unicolored to faintly bicolored rather than distinctly bicolored; braincase slightly larger; alveolar length of maxillary tooth-row slightly less.

From _B. t. analogous_, _B. t. canutus_ differs in: dorsum paler, less of dark brown hues; belly paler; forefeet and hind feet slightly paler, less sooty above; tail less hairy, paler and having scales evident; jugal of zygoma extending ventrally to a point immediately above, instead of below, level of alveolus of upper molars; nasals more nearly truncate anteriorly; infraorbital foramina less deeply notched toward midline of skull; body and skull averaging smaller throughout.

From _B. t. allex_, _B. t. canutus_ differs in: dorsal ground color grayish rather than fawn color having grayish overtones; underfur on dorsum darker gray; dorsal surface of forefeet and hind feet flesh-colored to grayish rather than flesh-colored; incisive foramina tapering to a point posteriorly rather than rounded posteriorly; interparietal relatively smaller; body and skull averaging larger throughout.

_Remarks._--Burt (1938:54) reluctantly assigned specimens from Ciudad Obregon to _B. t. paulus_, probably being influenced by the resemblance in size. He suggested that, perhaps, a distinct subspecies occurs in the State of Sonora. Study of larger series of specimens than were available to Burt reveals that populations of pygmy mice inhabiting the northwest coastal plains of Mexico are indeed distinct.

The darkest of the material assigned to _canutus_ is from Nayarit (for specific localities see specimens examined). According to Tamayo (1949:Carta de Suelos), color of soil changes from chestnut in northern Sinaloa to black in southern Sinaloa and northern Nayarit. There seems, therefore, to be a close correlation between color of pelage and color of soil in this area. In Nayarit, particularly in the central and southern parts, the mice are intermediate in color between the paler, grayer population to the north and the more brownish samples, representative of _allex_ to the south. The coastal vegetation changes from the arid tropical thorn forests of the north and central parts of Sinaloa to a savannah in Nayarit, thence to a tropical deciduous forest farther south (see Leopold, 1950:508).

In size and color, specimens from 3 mi. SE Tepic and 2 mi. SW Rosa Morada are intermediate between the larger, grayer _canutus_ and the smaller, light-brownish _allex_. In size of cranium, these specimens are more nearly like _canutus_, and are referred to that subspecies. Mice from the western coastal plain are relatively homogeneous as regards size of body and skull, except that those from 13.5 mi. S Acaponeta, Nayarit, average somewhat larger.

_B. t. canutus_, like _B. t. subater_, is predominantly a lowland or coastal subspecies. The pallor of the former, that lives on generally paler soils, presumably is of adaptive value.

Pygmy mice are seemingly rare in the northern part of the range of this subspecies. J. Raymond Alcorn and Albert Alcorn were successful in collecting only two specimens from the type locality after three successive nights of trapping with 100 traps set each night. Only six specimens are known from Sonora. These were obtained in the irrigated regions of Ciudad, Obregon, and Navajoa. Charles Sibley obtained one specimen 10.6 mi. SE Ciudad Obregon in a "maguey field." I obtained one specimen 1 mi. NNW Navajoa in a sparse grassway, 20 feet wide, bordering an open sewer, which coursed northward into the Rio Mayo. Irrigated wheat fields bordered the grassway and ditch.

_Specimens examined._--Total 70 all from the Republic of Mexico and distributed as follows: SONORA: [Ciudad] Obregon, 4[44]; 10.6 mi. SE [Ciudad] Obregon, 1[45]; 1 mi. NNW Navajoa, 1. SINALOA: type locality, 2 (including the type); Culiacan, 175 ft., 2[46]; Mazatlan, 1[48]; _15 mi. N Rosario, Chele_, 300 ft., 35[47]; Rosario, 3[46]; Escuinapa, 5[48]; _Railroad Station Escuinapa_, 43 ft., 2[45]. NAYARIT: Acaponeta, 4[46]; _13.5 mi. S Acaponeta Junction_, 6[49]; 2 mi. SW Rosa Morada, 2; _2 mi. WNW Tepic_, 3200 ft., 1; 3 mi. SE Tepic, 1.

_Marginal records._--SONORA [Ciudad] Obregon. SINALOA: type locality; Escuinapa. NAYARIT: Acaponeta; 3 mi. SE Tepic. SINALOA: Mazatlan.

[44] Coll. Univ. California, Los Angeles.

[45] Univ. California, Mus. Vert. Zoology.

[46] U. S. Nat. Museum (Biol. Surv. Coll.).

[47] Univ. Michigan, Museum of Zoology.

[48] American Museum of Natural History.

[49] Univ. Illinois, Mus. Nat. History.

=Baiomys taylori fuliginatus=, new subspecies

_Baiomys taylori taylori_, Dalquest, Louisiana State Univ. Studies
(Biol. Sci. Ser.) 1:155, December 28, 1953 (part).

_Baiomys taylori taylori_, Booth, Walla Walla Publs. Dept. Biol.
Sci., 20:15, July 10, 1957 (part).

_Type._--Adult male, skin and skull; No. 36765, University of Kansas, Museum of Natural History; 10 mi. E, 2 mi. N Ciudad del Maiz, 4000 ft., San Luis Potosi, Republic of Mexico; obtained on January 17, 1950, by J. R. Alcorn, original number 10400.

_Range._--Occurs in the Sierra Madre Oriental of the northeastern third of San Luis Potosi. Zonal range: Upper Tropical (see Dalquest, 1953:10); approximates a part of the Sierra Madre Oriental Biotic Province of Goldman and Moore (1945:349, 356). Occurs from 2000 feet at El Salto up to 4000 feet at Ciudad del Maiz.

_Diagnosis._--Size large for the species; ground color of dorsum Chaetura Drab; individual guard hairs of dorsum black to base, distal fourth of hairs of underfur in posterior half of dorsum tipped with grayish-brown, proximal three-fourths Dark Neutral Gray; in anterior region of dorsum, posterior to ears, distal third of hairs grayish-brown and proximal two-thirds Dark Neutral Gray to base; sides slightly paler than dorsum; ground color of belly Neutral Gray, individual hairs of belly and throat tipped with Pallid Neutral Gray, basally Deep Neutral Gray to Dark Neutral Gray; tips of individual hairs of face Ochraceous-Tawny; lateral vibrissae whitish, dorsal and ventral vibrissae black to base; forefeet and hind feet sooty above and below, thigh bearing some white-tipped hairs; tail near Chaetura Drab above, Pale Neutral Gray below; anterior part of jugal projecting slightly ventrally and forming small protuberance at point of articulation with maxillary part of zygoma; jugal extending anteriorly nearly to lacrimal. In most cranial measurements averaging as large as _B. t. analogous_. Average and extreme measurements of the type and three additional paratypes, all adults, are: total length, 105.5 (101-109); length of tail, 39.8 (35-42); length of body, 65.8 (63-68); length of hind foot, 14.3 (14-15); length of ear from notch, 11 (11); occipitonasal length, 18.1 (18.1-18.8); zygomatic breadth, 9.6 (9.3-9.8); postpalatal length, 6.5 (6.0-6.7); least interorbital breadth, 3.4 (3.3-3.6); length of incisive foramina, 4.0 (3.8-4.2); length of rostrum, 6.3 (6.1-6.4); breadth of braincase, 8.8 (8.6-8.9); depth of cranium, 6.7 (6.5-6.8); alveolar length of maxillary tooth-row, 3.2 (3.1-3.3); for photograph of skull, see Plate 2_d_, and Plate 4_e_.