FAMILY ARCTOMID^E. 67 



(EXTRA-LIMITAL.) 



Genus Spermophilus, F. Olivier. Ample cheek pouches, commencing at the commissure of the lips, 

 and extending to the sides of the neck ; the anterior ridge on the upper cheek teeth nearly obso- 

 lete, and the internal spur much developed. Tail long and linear, hushy. 



S. tredecimlineatus, Mitchill. (Richardson, pi. 14.) Six to eight yellowish longitudinal stripes, the 



intermediate spaces with black spots. Length 8-10 inches. St. Peters River. 

 S. lateralis. (Say, Long's Exped. Vol. 2, p. 4(3. Richardson, pi. 13.) A yellowish white stripe 



on each flank, bordered with black. Length 10 — 12. Rocky Mountains. 

 S. douglasii. (Richardson, Vol. 1, p. 172.) Hoary brown above, with a black stripe between the 



shoulders; pale brown behind, with indistinct black marks. Length 12 - 13. Columbia River. 

 S. beecheyi. (Richardson, pi. 12. b.) Above reddish varied with blackish, beneath brownish yellow. 



Tail long, bushy and round. Length 17 inches. California. 

 S.franklini. (Richardson, pi. 12.) Yellowish brown above, thickly spotted with black; greyish 



white beneath. Tail long. Length 16 inches. Arctic Regions. 

 S. richardsoni, Sabine. (Richardson, pi. 11.) Yellowish grey above, varied with black; beneath 



pale orange; very short ears. Length 16 inches. Arctic Regions. 

 S. grammurus. (Say, Long's Exp. Vol. 2, p. 72.) Cinereous tinged with reddish ; fur coarse and 



flattened. Three black lines on the tail. Length 21 inches. Rocky Mountains. 

 S. guttatus, Temminck. (Richardson, Vol. 1, p. 162.) Clove-brown above, spotted with white; 



beneath and feet ochraceous; no external ears, and short tail. An Spermophilus ? Length 10 



inches. Rocky Mountains. 

 S. parryi. (Richardson, pi. 10.) Greyish above, pale rust-color beneath; face chesnut-color ; ears 



short; tail flat. Length 16 - 18 inches. Hudson's Bay, Behring's Straits. 

 S. ludovicianus, Ord. (Godman, Vol. 2, p. 114, plate.) Prairie Dog. Reddish brown above, 



mixed with grey and black ; beneath soiled white. Tail short, banded with brown near the tip. 



Length 19 inches. Missouri. 



GENUS ARCTOMYS. Linneus. Gmelin. 



Form, habits and teeth of the preceding. Cheek pouches rudimentary. Living in societies. 

 Fore feet with four distinct toes and the rudiments of a thumb ; hind feet with five toes, 

 and all furnished with strong hooked and compressed nails. Tail bushy. 



Obs. The distinction between this and the preceding genus is exceedingly obscure. 



