Most of the specimens examined were trapped in brushy areas. On the
Sierra de Tamaulipas, wood rats were caught in steel traps set near or
between rocks. In the vicinity of La Pesca, specimens were trapped on
the beach where _Spermophilus spilosoma_ and _Sigmodon hispidus_ were
taken also.
Two females, obtained on May 19 and June 10 at Soto la Marina and on
the Sierra de Tamaulipas, respectively, each carried 2 embryos that
were 40 mm. in crown-rump length. Dice (1937:254) reported that two
females collected on July 24 and August 16 on the Sierra San Carlos
each carried 2 embryos that ranged from 34 to 36 mm. in crown-rump
length.
_Neotoma micropus_ occurs throughout the Tamaulipan Biotic Province and
is represented in Tamaulipas by two subspecies, each of which has its
type locality in the state. Intergradation between the two takes place
at Soto la Marina.
=Neotoma micropus littoralis= Goldman
1905. _Neotoma micropus littoralis_ Goldman, Proc. Biol.
Soc. Washington, 18:31, February 2, type from Altamira, 100
ft., Tamaulipas.
_Distribution in Tamaulipas._--From the Sierra de Tamaulipas
southward.
Weight of two males and three non-pregnant females was 248, 254, 185,
210, 240 grams, respectively.
_Records of occurrence._--Specimens examined, 14: Sierra de
Tamaulipas, 2 mi. S, 10 mi. W Piedra, 1200 ft., 6; 6 mi. N,
6 mi. W Altamira, 8.
Additional record: Altamira (Goldman, 1910:29).
=Neotoma micropus micropus= Baird
1855. _Neotoma micropus_ Baird, Proc. Acad. Nat. Sci.
Philadelphia, 7:333, April, type from Charco Escondido,
Tamaulipas.
_Distribution in Tamaulipas._--From Soto la Marina
northward.
The weight of five males and four females from Soto la Marina averaged,
respectively, 256.4 (210-317) and 233.0 (195-274) grams.
A specimen (56924) from La Pesca differs from all other specimens of
_N. micropus_ examined in being smaller, having a conspicuously shorter
rostrum, broader intraorbital canal, and lower broader braincase.
External measurements of this specimen are as follows: 347; 155; 39;
--. Its cranial measurements are: greatest length, 44.8; basilar
length, 34.3; zygomatic breadth, 23.6; interorbital constriction, 6.2;
incisive foramina, 6.5; length of maxillary tooth-row, 8.7; width of
mesopterygoid fossa, 4.1.
_Records of occurrence._--Specimens examined, 58: 4 mi. SW
Nuevo Laredo, 900 ft., 14; 4-1/2 mi. S Nuevo Laredo, 1; 3
mi. SE Reynosa, 1; 3 mi. S Matamoros, 2; 33 mi. S Washington
Beach, 1; San Fernando, 180 ft., 1; 7 km. S, 2 km. W San
Fernando, 2; 12 mi. NW San Carlos, 1300 ft., 4; 9-1/2 mi. SW
Padilla, 800 ft., 3; 3 mi. N Soto la Marina, 3; Soto la
Marina, 500 ft., 12; 4 mi. N La Pesca, 3; 1 mi. E La Pesca,
1; La Pesca, 2; 3 mi. NE Guemes, 1; 7 mi. NE Cd. Victoria,
1; Cd. Victoria, 6.
Additional records (Goldman, 1910:28, unless otherwise
noted): Nuevo Laredo; 10 mi. S Nuevo Laredo (Booth,
1957:15); Camargo; Matamoros; Bagdad; 40 mi. S Matamoros
(Hooper, 1953:9); Sierra San Carlos (El Mulato, Tamaulipeca)
(Dice, 1937:254); San Fernando (J. A. Allen, 1891:224);
Forlon.
=Microtus mexicanus subsimus= Goldman