14 



NOETH AMERICAN FAUNA. 



[No. 36. 



nent, often large, more or less hairy; soles of hind feet 6-tubercu- 

 late; mammae, 6 — P^, If; no cheek pouches. Skull with smoothly 

 rounded braincase, more or less inflated, without prominent ridges; 

 zygomata slender; outer wall of anteorbital foramen a broad thin plate; 

 anterior palatine foramina relatively large, forming long narrow slits 

 separated by a thin septum, sHghtly narrower anteriorly, terminating 

 about at the plane of anterior border of tooth row; posterior border 

 of palate square, often with a sHght median spine, terminating at 

 plane of posterior border of tooth row; pterygoids nearly parallel; 

 audital bullse more or less inflated, longer than broad, and obliquely 

 situated. Descending process of mandible a broad flattened plate, 

 strongly deflected inward, the lower portion twisted into a nearly 

 horizontal position and the inner margin raised, leaving a distinct 

 depression in the ramus ;^ coronoid process short. Upper incisors 

 with a deep longitudinal groove near the middle of the tooth. Molars 

 brachyodont, tuberculate, the tubercles arranged in two longitudinal 

 series; first upper molar with five principal tubercles, an anterior 

 median one, and two pairs of lateral ones; w} and w? with or without 

 accessory tubercles or enamel loops in the principal angles; upper 

 molars normally three-rooted, but in some species four-rooted; lower 

 molars two-rooted. 



List of Species and Subspecies, with. Type Localities. 

 Subgenus REITHRODONTOMYS. 



"R. humulis group: 



Reithrodontomys humulis humulis (Bachman). .Charleston, S. C. 



humulis impiger Banga White Sulphur Springs, W. Va. 



humulis merriami Allen Alvin, Tex. 



albescens albescens Cary 18 miles northwest of Kennedy, 



Nebr. 



albescens griseus Bailey San Antonio, Tex. 



R. megalotis group: 



Reithrodontomys montanus (Baird) ''Rocky Mountains, latitude 38°" 



[=San Luis Valley, Colo., near 

 San Luis Lakes]. 



megalotis meg alotis (Baiid) ''Between Janos, Sonora [=Chi- 



huahua] and San Luis Spring" 

 [New Mexico]. 



megalotis aztecus Allen La Plata, N. Mex. 



megalotis dychei Allen Lawrence, Kans. 



megalotis nigrescens nobis Payette, Idaho. 



megalotis longicaudus (Baird) Petaluma, Cal. 



megalotis peninsulas Elliot San Quintin, Lower California. 



megalotis cinereus Merriam Chalchicomula, Puebla. 



1 Less importance is to be ascribed to this character in distinguishing Reiihrodontomys from Peromyscus 

 than the remarks of Baird (Mamm. N. Am., p. 447) and Coues (Mon. N. Am. Rodentia, p. 122) would 

 indicate, for although typical Peromyscus differs noticeably on the average from Reithrodontomys in the 

 shape of the descending process, yet certain species of the subgenus Haplomylomijs show practically the 

 same condition as Reithrodontomys. 



