W2 ZYGOGEOMYS. THOMOMYS. 



each; upper premolar with four enamel plates; third upper molar 

 incomplete double prism, crown longer than broad; sulcus on 

 middle of outer side only, inner enamel plate covering two-thirds or 

 three-fourths of inner side of tooth, reaching end of heel posteri- 

 orly; outer enamel plate covering about half of outer side of tooth, 

 its anterior bent strongly outward; upper incisors bisulcate, prin- 

 cipal sulcus on inner side of median line, (ex Merr., 1. c.) 



334 trichopus (Zygogcomys) , Merr., Mon. Geomyidae, N. Am. Faun., 



No. 8, 1895, P- Z 9^' pl s - an d figs. 

 PINE ZONE POCKET GOPHER. 



Type locality. Nahuatzin, State of Michoacan, Mexico. 



Geogr. Distr. Sierra Nevada, State of Michoacan, Mexico. Alti- 

 tude, 6,800 to 9,500 feet. 



Genl. Char. Size large; tail long, naked; naked pad on nose; 

 feet covered with hair; other characters as in genus. 



Color. Dark slate to seal brown, washed with ferrugineous on 

 upper parts; under parts plumbeous, tinged with fulvous; white 

 patch on throat; hind feet whitish or dark gray. 



Measurements. Total length, 346; tail vertebrae, 115; hind foot, 

 46. Skull: basal length, 46.5-58.5; Hensel, 43-54; zygomatic width, 

 35-39 ; interorbital width, 8-9.5 > length of upper molar series, 10.5-1 2 ; 

 length of single half of mandible, 33-42. 



The genus THOMOMYS is distinguished from Gcomys and the 

 allied genera by the absence of median grooves on the incisors, by 

 the smaller and more feeble claws, and by even larger cheek pouches. 

 The habits of the species are the same, and they often prove as great 

 pests to the agriculturalist as do their relatives of the other genera. 

 While usually of smaller size than the species of Geomys, there is one, 

 T. bulbivorus, from the northwestern portion of the United States, 

 which equals the largest member of that genus. The Gophers feed 

 upon all kinds of herbage and bulbous roots. They are irascible, 

 bite severely, are very quick in their movements, alert to each 

 danger that threatens, and fertile in methods for avoiding it. 



7O. Tliomoiuys. Pocket Gophers. 



I.S;P.S;M. = ,o. 



Thomomys Wied, Nov. Act. Phys. Med. Akad. Caes. Leop. Carol., 



xix, 1839, p. 377. Type Thomomys rujesccns Wied. 

 Diplostoma Rich., Faun. Bor. Amer., i, 1829, p. 206. (nee Rafin.) 

 Oryctomys Ed. & Gerv., Mag. Zool., vi, 1836, p. 23. (Part.) 



