MAMMALS 



323 



F. z. ripensis Bailey. Color light brown; size small: Pecos Valley, 

 Texas. 



F. z. cinnamominus Holl. Color pale, with much red: Great Plains 

 from Manitoba to northern Texas; east to central Iowa. 



F. rivalicius Bangs. Color dark brownish black; length 547 mm.; 

 tail 233 mm.; hind foot 78 mm. : coast region of Louisiana; moults twice 

 annually. 



Family 2. Geomyidae. — Pocket gophers. Thick-bodied rodents 

 with short legs, fore feet fitted for digging, small ears and eyes, and a 

 pair of large fur-lined cheek -pouches which 

 are not connected with the mouth but open 

 on the cheeks at the sides of the mouth; 

 dentition i/i, 0/0, i/i, t^IT)-. 9 genera and 

 about 100 species, all American, half of 

 which occur in the southern United States, 

 the rest in Mexico and Central America. 

 The animals live in burrows in the ground, 

 in which they dig with great facility, using 

 both the strong, clawed fore feet and the 

 incisors. Their food consists chiefly of 

 roots, tubers and grasses, and they fre- 

 quently do great damage to potato and 

 vegetable fields. The cheek-pouches are 

 useful in carrying food to their winter store 

 houses, substances being put into them with 

 their fore feet. They are mostly nocturnal 

 and live in communities and do not 

 hibernate; the young number from i to 

 7 in a litter. 



Key to the Genera of Geomyidae of the United States 



ai Outer surface of the upper incisors grooved (Fig. 174). 



bi Upper incisors with 2 grooves each i. Geomys. 



b2 Upper incisor with a single deep groove 2. Cratogeomys. 



a2 Outer surface of the upper incisors not grooved or with a single 



fine groove 3. Thomomys. 



I . Geomys Rafinesque. Upper incisors with a large groove near the 

 middle and one near the median margin; ears rudimentary; fore claws 

 very large: 11 species, all in the United States. 



G. tiiza (Ord.) (Fig. 175). Color brown above, yellowish beneath; 

 tail almost naked; length 249 mm.; tail 89 mm.; hind foot ^^ mm.i 

 Georgia, Florida and Alabama; common. 



iVN\\\ 



Fig. 174. — Incisors of (i) Geomys 

 bursarius and (2) Thomomys tal- 

 poides {from. Merriam). 



