MAMMALS 315 



mouth but open on the cheeks at the sides of the mouth; dentition 

 i/i, 0/0, i/i, 3/3: 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 frequently 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. 



h> Upper incisor with a single deep groove 2. Cratogcomys. 



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



line 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: 16 species and subspecies, all in the United States. 



'U^ 



Fig. 175. — Geomys luza {from Merriani) . 



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

 tail almost naked; length 270 mm.; tail 8q mm.; hind foot t^^ mm.: 

 Georga, Florida and Alabama; common. 



G. t. luza (Bart.). Pine barrens of Georgia; Austroriparian zone. 



G. I. mobilensis Merriam. Color very dark: Alabama and Florida. 



G. t. fioridanus (Audubon and Ba^hman). Size larger; color darker: 

 peninsular Florida. 



G. bursarius (Shaw) (Fig. 174). Color dark reddish brown; feet 

 white; length 27c mm.; tail 80 mm.; hind foot 35 mm.; upper incisors 



