176 PROCEEDINGS OF THE ACADEMY OF 



feet veiy long. 1st and 5th toes subequal and veiy short ; fore- 

 feet not half as long as the hind. Tail nearly naked. Dental and 

 cranial characters slight. I can find but one species. 



1. Sigmodon hispidus, Say and Ord. 



Stn. Sigmodon hi^ridum, Say and Orel, J. A. N. S. P. iv. 1825, 354, pi. 



X. f. 5, G, 7, 8 ; and of authors. 

 Arvicola hispidus, Godm., Am. Nat. Hist. ii. 182G, 68. 

 Armeola Jiortensis, Harlan, Fn. Amer. 1825, 138. 

 Arvicola ferrugineus, HarL, Am. Journ. Sc. x. 182G, 285 (rnsty var. ). 

 Arvicola texiana, And. and Bach., Q. N. A. ill. 1853, 229, pi. cxlvii. 



fig. 2 (not A. texiana, Id., ibid. 319, which is Hesperomys leucopus). 

 Sigmodon berlandieri, Bd., P. A. N. S. P. vii. 1855, 333; M. N. A. 



1857, 504 ; Mex. B. Surv. ii. 1859, 44, pi. yi. f. 2, 2a (Texas and 



Mexico). Tomes, P. Z. S. 18G1, 281 (Guatemala). 

 Hesperomys {Deilemys) toltecus, De Saussure, R. & M. Z. 18G0. p. , 



pi. ix. f. 3a (Vera Cruz). 



Hab. Southern United States and Mexico, especially coastwise. 

 South to Guatemala. 



068. Occupying a considerable stretch of countr}' tliat affords 

 ver3" different climatic conditions, this species changes insensibly' 

 from reddish-brown lined with black, beneath whitish, tail rarely 

 equalling the body alone, and hind foot not over 1.30 or under 

 1.10 (typical hisjndus), to a grayer brown, with purer white under 

 parts, tail sometimes equalling bod}'^ and head, hind foot some- 

 times 1.37 i^'' berlandierV ) ; and this to an animal like the first in 

 colors and proportionate length of tail, but the hind foot not over 

 1.10, sometimes only 0.95 {'^toUecus'''). 



Genus IV. HESPEKOMYS," Waterh., emend. 



Stn. 3Tus, sp.. And. Arvicola, sp., Harl., Am. Monthly Journ. 1832, 

 44G (nu.ttalli) ; Aud. & Bach., Q. N. A. (sonoriensis Le C, texana, 

 Woodh., AM^oryzidora, Aud. and Bach.). Uypudceus, sp., Maxim., 



' In proposing Hesperomys, Waterhouse obviously intended only to sepa- 

 rate the New World mice collectively from those of the Old World, on the 

 difference in the dentition. This is evident throughout his article in the 

 Voyage of the Beagle. Though treating only of South American species, 

 he is at pains to say in one place that " Mus leucopus, Neotoma and Sigmodon 

 certainly belong to the same group." As instituted, Hesperomys is pre- 

 cisely coequal with the tribe or series Sigmodontes as contrasted with 

 typical Old World Mures. It includes in South America, Calomys {Eligmo- 

 dontia, F. Cuv.), Habrothrix, Phyllotis, Scapteromys, Oxymicterus, Holo- 

 clieilus, and Reithrodon ; in North America, the '' Hcsjjeromys'''' of our 

 authors, OnycJiomys, Oryzomys, '' Eeithrodon'''' of our authors, Sigmodon 



