Measurements.—Measurements of a female from Nicolás, a male from eight miles north of Tula, and a female and a male from four miles north of Jaumave are as follows: 158, 147, 145, 144; 59, 58, 55, 55; 22, 21, 22, 22; 21, 20.5, 18, 18; condylobasal length, 24.4, 23.1, 23.9, 23.7; interorbital constriction, 4.1, 4.4, 4.3, 4.5; length of nasals, 10.6, 10.5, 10.5, 10.1; length of maxillary tooth-*row, 3.8, 3.6, 3.7, 3.7; breadth of braincase, 11.8, 11.3, 11.3, 11.0; weight in grams, 32.5, 26.0, 25.0, 25.0.
Records of occurrence.—Specimens examined, 6: 4 mi. N Jaumave, 2; Nicolás, 56 km. NW Tula, 5500 ft., 2; Tajada, 23 mi. NW Tula, 5200 ft., 1; 8 mi. N Tula, 4500 ft., 1.
Additional records (Hollister, 1914:475): Miquihuana; Jaumave.
Sigmodon hispidus
Hispid Cotton Rat
This species, as is known, is active by day and by night. It occurs mainly in grassy areas and most of the specimens examined were trapped there. But, one mile east of La Pesca, specimens were taken on a beach having sparse grass. Neotoma micropus and Spermophilus spilosoma, but no smaller rodents, were taken there. Also, many crabs were found in the traps. Possibly only the relatively large rodents are able to compete successfully with the crabs. The specimen from one kilometer east of El Barretal was caught in a rat-trap set in front of small hole in a fence of dead brush that surrounded a cornfield. The area outside the fence supported mesquite and ebony trees (10-12 feet high) and the ground was covered with cat claw. Six miles north and six miles west of Altamira, the two young specimens were taken on a small grassy island surrounded by mud.
According to natives, Sigmodon injures corn and sugar cane. Probably other species of rodents are responsible for some or all of such damage since other kinds of rodents were taken in the same areas.
Dice (1937:245) reported females from the Sierra San Carlos that carried 8 embryos of 18 mm., 5 × 33, 7 embryos very small, and 8 × 20. Females were collected on July 22, 29, and 30.
Sigmodon hispidus berlandieri Baird
1855. Sigmodon berlandieri Baird, Proc. Acad. Nat. Sci. Philadelphia, 7:333, type from Río Nazas, Coahuila.
1902. Sigmodon hispidus berlandieri, V. Bailey, Proc. Biol. Soc. Washington, 15:106, June 2.