This is the most common species of the genus _Peromyscus_ in Tamaulipas. It and _Liomys irroratus_ are the two rodents most easily trapped throughout the state. In general _P. l. texa.n.u.s_ occurs in forested and brushy areas especially under 1200 feet in elevation, as was noted in the Sierra de Tamaulipas, where _P. l. texa.n.u.s_ was taken commonly at elevations of up to 1200 feet. Above this elevation the species was rare and _P. pectoralis_ and _P. boylii_ were more abundant than at lower elevations. The three specimens of _P. l. texa.n.u.s_ from 12 kilometers north and four kilometers west of Ciudad Victoria were trapped in a line of 110 traps set near tree stumps. Small burrows in the ground were noted here. The forest at this locality was composed of mesquite, ebony, acacias, a few yuccas and "nopales" (= cactuses); the ground was covered by cat claw.

Of the many young taken, 15 specimens were saved from Ejido Santa Isabel where _P. leucopus_ was abundant in an area of chaparral consisting of wild "tomate," "zapote," "huizache" and "salvadora." Most of the specimens caught at this locality were taken between 7:30 and 9:30 p. m. in traps baited with a mixture of rolled oats, peanut b.u.t.ter and banana. Specimens from 53 kilometers north of El Limon were taken along with _Liomys irroratus_; the specimen from two kilometers west of El Carrizo was trapped near a dead mesquite log. _Reitrodontomys fulvescens_ was taken in the same area. Four specimens of _P. leucopus_ were taken at Rancho Pano Ayuctle, around a big pile of old firewood in an abandoned sugar mill. At the locality six miles north and six miles west of Altamira, _P. leucopus_ was found in cultivated fields and along the gra.s.sy roadsides; in the vicinity of Tampico specimens were taken in an area of forested cactus-thorn. The specimen from seven kilometers south and two kilometers west of San Fernando was found in a trap set at the base of "nopal" cactus, which was surrounded by bushes and small trees (10-12 feet high).

Breeding records are as follows: Rancho Pano Ayuctle, on February 15, one female carried 2 embryos of 23 mm. in crown-rump length; Jaumave, July 26 to 29, five females, averaging 4.6 (3-6) embryos of 7 (3-15) mm., two females lactating, one on May 25 and the other on July 26; Ejido Santa Isabel, on January 20 to 25, three females lactating; Soto la Marina, on May 16, one female lactating.

Average weights were as follows: from Jaumave four pregnant females, 28.0 (25-33), eight males, 23.4 (21-27); from the Sierra de Tamaulipas, eight females non-pregnant, 21.2 (18-26), 14 males, 22.0 (19-27); from 6 mi. N, 6 mi. W Altamira, six males, 23.5 (21-27).

All specimens examined from Tamaulipas are a.s.signed to _P. l. texa.n.u.s_ because their coloration is pale. Even so the color varies some according to locality; specimens from Rancho Pano Ayuctle and the Sierra de Tamaulipas have much of the cinnamon color that is characteristic of _P. l. incensus_ from farther south, but even so specimens from the two localities last mentioned are paler than those from Veracruz that are typical _incensus_.

Goldman (1942:158) reported specimens from Altamira as _P. l.

incensus_, in which subspecies Ingles (1959:397) included specimens from two miles west of Tampico, but specimens examined from the same area do not differ from individuals from far north thereof; for this reason I identify specimens from these localities as _texa.n.u.s_. Osgood (1909:131) and Hooper (1953:7) also referred specimens from the southern part of Tamaulipas to _texa.n.u.s_. These two authors examined 156 specimens and did not find any intergradation between _texa.n.u.s_ and _incensus_, but to me, the cinnamon tones of specimens from Rancho Pano Ayuctle and the Sierra de Tamaulipas, suggest intergradation between the two subspecies.

Osgood's (1909:265) measurements of _P. l. texa.n.u.s_, from Brownsville, Texas, and those of 40 specimens from different localities in Tamaulipas are about the same except that the anterior palatine foramina average longer in Tamaulipas. Baker's (1956:262) specimens from Coahuila, averaged larger even than Tamaulipan specimens. Another difference between Osgood's measurements and Baker's was the shorter 3.4 (3.0-3.7) maxillary tooth-row in Tamaulipan specimens.

Hooper (1953:7) recorded specimens from General Teran, as in Tamaulipas; actually this locality is in Nuevo Leon.

_Records of occurrence._--Specimens examined, 149: 4.5 mi. S Nuevo Laredo, 1; 3 mi. SE Reynosa, 2; 7 km. S, 2 km. W San Fernando, 1; Villa Mainero, 1700 ft., 1; Rancho Santa Rosa, 25 km. N, 13 km. W Cd. Victoria, 260 m., 2; 9.5 mi. SW Padilla, 800 ft., 2; 15 mi. N Cd. Victoria, 2; 4 mi. N La Pesca, 1; Soto la Marina, 11; La Pesca, 1; 12 km. N, 4 km. W Cd. Victoria, 3; 7 km. NE Cd. Victoria, 1; Sierra de Tamaulipas, 10 mi. W, and 2 mi. S Piedra, 1200 ft., 31; Ejido Eslabones, 10 mi. W, 2 mi. S Piedra, 1200 ft., 6; Jaumave, 20; Ejido Santa Isabel, 2 km. W Pan-American Highway, 2000 ft., 15; 53 km. N El Limon, 12 km. S Rio Guayalejo, 5; Rancho Pano Ayuctle, 25 mi. N El Mante, 3 km.

W Highway, 300 ft., 16; Rancho Pano Ayuctle, 6 mi. N Gomez Farias, 300 ft., 7; 8 km. W, 10 km. N El Encino, 400 ft., 3; 8 mi. N Tula, 4500 ft., 2; 2 km. W El Carrizo, 3; 6 mi. N, 6 mi. W Altamira, 9; 16 km. N Tampico, 1; 7 km. N Tampico, 3.

Additional records (Osgood, 1909:131, unless otherwise noted): Nuevo Laredo; Mier; Camargo; near Bagdad; Sierra San Carlos (Hooper, 1953:7); Matamoros-Victoria Highway (_ibid._); Charco Escondido (Baird, 1858:464); Hidalgo; Cd.

Victoria; 10 mi. NE Zamorina (Hooper, 1953:7); Gomez Farias (Goodwin, 1954:12); Chamal (_ibid._); Tula (Hooper, 1953:7); Antiguo Morelos (_ibid._); Altamira (Goldman, 1942:158); 2 mi. W Tampico (Ingles, 1959:397); Tampico.

=Peromyscus boylii=

Brush Mouse

Specimens examined were obtained at higher elevations in the oak-tree zone of the Sierras in traps set among rocks, trees and in gra.s.sy areas. _Peromyscus boylii_ was trapped in the same area as was _P.

pectoralis_ and no habitat distinction between the two was noted. Some behavioral differences, however, are pointed out in the account of _P.

pectoralis_. Morphological differences between these two species in Tamaulipas were reported by Hooper (1952:372).

A female taken on August 5 in the Sierra Madre Oriental carried two embryos 15 mm. in crown-rump length.

For the taxonomic status of _P. boylii_ in Tamaulipas see Alvarez (1961).

=Peromyscus boylii ambiguus= Alvarez

1961. _Peromyscus boylii ambiguus_ Alvarez, Univ. Kansas Publ. Mus. Nat. Hist., 14:118, December 29, type from Monterrey, Nuevo Leon.

_Distribution in Tamaulipas._--Known only from the Sierra San Carlos.

_Record of occurrence._--Specimens examined, 7 (UMMZ), all from La Vegonia, Sierra San Carlos.

=Peromyscus boylii levipes= Merriam

1898. _Peromyscus levipes_ Merriam, Proc. Biol. Soc.

Washington, 12:123, April 30, type from Mt. Malinche, 8400 ft., Tlaxcala.

1909. _Peromyscus boylii levipes_, Osgood, N. Amer. Fauna, 28:153, April 17.

_Distribution in Tamaulipas._--Central and southern parts of state.

Weights of 19 males and 18 females from the Sierra Madre Oriental are, respectively, 25.2 (22-30) and 23.6 (20-29); weights of eight males and five females from the Sierra de Tamaulipas are 24.9 (22-32) and 29.6 (24-31).

_Records of occurrence._--Specimens examined, 54: Sierra Madre Oriental, 8 mi. S, 6 mi. W Victoria, 4000 ft., 37; 5 mi. S, 3 mi. W Victoria, 1900 ft., 2; Ejido Eslabones, 10 mi. W, 2 mi. S Piedra, 1200 ft., 1; Sierra de Tamaulipas, 11 mi. W, 8 mi. S Piedra, 2000 ft., 13; 2 km. W El Carrizo, 1.

Additional records: Rancho del Cielo (Hooper, 1953:7); 3 mi.

NW Acuna (_ibid._); Rancho Viejo (Goodwin, 1954:12); Santa Maria (_ibid._); Joya de Salas (_ibid._).

=Peromyscus pectoralis=

White-ankled Mouse

_Peromyscus pectoralis_ and _P. boylii_ are closely related morphologically and seem to occupy the same habitat. In the Sierra Madre Oriental, according to the field notes of the collector (Heinrich, June 6 to August 5, 1953), individuals of _P. pectoralis_ had a pinkish coloration on the mouth and forefeet produced by the juice of the "nopal" cactus fruit, on which obviously the mice feed, whereas only a few specimens of _boylii_ were thus discolored. It was noted that _boylii_ was feeding on acorns. Furthermore, the two species may differ in time of breeding; in August, males of _pectoralis_ had the testes well developed when those organs were small in _boylii_ collected at the same locality.

A specimen from 53 kilometers north of El Limon, was shot at a height of 10 feet on a concrete underpa.s.s. Other specimens were taken in a trap line that yielded _Peromyscus boylii_, _P. leucopus_ and _Liomys irroratus_.

Two subspecies of _P. pectoralis_ occur in Tamaulipas: _P. p. collinus_ is widely distributed in the central and western parts of the state and _P. p. eremicoides_ occurs only in the western "corner" of the state.

=Peromyscus pectoralis collinus= Hooper

1952. _Peromyscus pectoralis collinus_ Hooper, Jour. Mamm., 33:372, August 19, type from San Jose, 2000 ft., Sierra San Carlos, 12 mi. NW San Carlos, Tamaulipas.

_Distribution in Tamaulipas._--Along the central and western mountains.

A female obtained on January 21 at a place 53 kilometers north of El Limon, contained three embryos. A lactating female was taken on August 2 in the Sierra Madre Oriental. Males, as previously noted, had well-developed testes in August. The weights of 17 males and 20 females from the Sierra de Tamaulipas were, respectively, 26.6 (24-33), and 25.6 (21-31) grams.

Measurements of specimens from different localities in Tamaulipas averaged about the same, except that those of specimens from Palmillas, averaged smaller. The small size suggests intergradation between the subspecies _collinus_ and _eremicoides_. The latter occurs to the west and differs from _collinus_ in smaller size, more grayish coloration, completely white tarsal joint and relatively longer tail. Hooper (1952:374) reported specimens from Jaumave as intergrades between the two subspecies before mentioned and Osgood (1909:164) identified two specimens from there as _eremicoides_. In the present account, individuals from Palmillas and Jaumave are referred to _collinus_.

_Records of occurrence._--Specimens examined, 101: 7 km. SW La Purisima, 1; Sierra Madre Oriental, 5 mi. S, 3 mi. W Victoria, 1900 ft., 12; Sierra Madre Oriental, 8 mi. S, 6 mi. W Victoria, 4000 ft., 16; Sierra de Tamaulipas, 2 mi. S, 10 mi. W Piedra, 1200 ft., 36; Sierra de Tamaulipas, 3 mi.

S, 14 mi. W Piedra, 1200 ft., 14; 14 mi. N, 6 mi. W Palmillas, 5500 ft., 1; Palmillas, 4400 ft., 3; 53 km. N El Limon, 12 km. S Rio Guayalejo, 5; Joya Verde, 35 km. SW Victoria, 3800 ft., 9; 10 km. N, 8 km. El Encino, 400 ft., 1; 8 km. NE Antiguo Morelos, 500 ft., 3.

Additional records (Hooper, 1952:374, unless otherwise noted): Sierra San Carlos (Marmolejo, 1700 ft., San Jose, 2000 ft., Tamaulipeca, 1500 ft., La Vegonia, 2900 ft.); Villagran, 1300 ft.; Cd. Victoria; near Jaumave, 2400 ft.; Sierra de Tamaulipas, near Acuna, 1600 ft.; La Joya de Salas (Goodwin, 1954:12).

=Peromyscus pectoralis eremicoides= Osgood

1904. _Peromyscus att.w.a.teri eremicoides_ Osgood, Proc. Biol.

Soc. Washington, 17:60, March 21, type from Mapimi, Durango.

1909. _Peromyscus pectoralis eremicoides_, Lyon and Osgood, Bull. U. S. Nat. Mus., 62:128, January 28.

_Distribution in Tamaulipas._--Known only from Miquihuana and vicinity of Tula.

The two specimens from Miquihuana are typical _P. pectoralis eremicoides_ in external and cranial measurements. Specimens from nine miles southwest of Tula are characteristic of _eremicoides_ in cranial measurements but the tail is shorter than usual for this subspecies, in this respect approaching _P. p. lacia.n.u.s_.