90 



iq-ORTH AMEEICAK FAUKA. 



[NO. 39. 



Distrihiitwn. ^Known only from Boca del Monte and Xuchil, 

 Vera Cruz (fig. 9). 



Characters. — Size medium, hind foot 27-28 mm.; color dichromatic, 

 dtdl umber, brown, or black; skull short and wide with emarginate 

 anterior base of zygoma and strongly projecting incisors; groove on 

 inner margin of incisors very obscure; ears small; claws very slender; 

 mammae in 3 pairs, inguinal 2-2, pectoral 1-1. 



CoZor.— Upperparts in brown phase varying from dull burnt umber, 

 or Front's brown, to nearly black; underparts lightly washed with 

 pale buff or whitish; chin, feet, and tip of tail white. In black phase, 

 slaty black all over except white chin, feet, and tip of tail. 



SlculL — Light and smooth, not ridged or angular, short and wide, 

 with very short rostrum and greatly projecting incisors; anterior 

 base of zygoma emarginate or concave in outline where it joins the 

 frontal; lachrymal long and attached for all or most of its length to 

 zygoma; premaxillae widening posteriorly and terminating approxi- 

 mately even with nasals; palate flat, not arched between molar 

 series; lateral pits deep; base of pterygoids constricted. Dentition 

 light; incisors slender, projecting, pale or whitish, with indistinct or 

 obsolete inner groove; anterior lower incisor with anterior enamel 

 plate minute or often entirely wanting. 



Measurements —-AYersigG of 4 topotypes ( ad.): Total length, 

 193; tail vertebrae, 58; hind foot, 27.2. Average of 3 adult females: 

 195, 57, 27, Slcull ( c? ad.):i Basal length, 33.7; nasals, 12.4; zygo- 

 matic breadth, 24; mastoid breadth, 17.6; alveolar length of upper 

 molar series, 7.3. 



Remarlcs. — It would be useless to list the various species of Tho- 

 momys to which authors have applied the name umhrinus. For over 

 half a century the name was shifted about to one and another species, 

 and proved a stumbling block to every naturalist working on the 

 genus. Fortunately the type is still extant and has been identified 

 with a sufficiently restricted species to give it a definite location. 

 The species thus becomes the type of a well-defined group, including 

 umhrinus, orizdbx, peregrinus, nelsoni, slieldoni, goldmani, perditus, 

 and atrovarius. 



Specimens examined. — Total number, 15, as follows: 

 Vera Cruz: Boca del Monte, 8; Xuchil, 7. 



THOMOMYS UMBRINUS ORIZABA Merriam. 

 Orizaba Pocket Gopher. 



(PI. VI, fig. 15.) 



Thomomys orizabae Merriam, Proc. Biol. Soc. Washington, VIII, 145, Dec. 29, 1893. 



Type. — Collected on Mount Orizaba (9,500 feet altitude), Puebla, 

 Mexico, by E. W. Nelson and E. A. Goldman, April 25, 1903. Type 

 specimen in U. S. Nat. Mus., Biological Survey collection. 



iNo. 66091, U. S. Nat. Mus., from Boca del Monte, Vera Cruz. 



