Bailey — North American Species of Sigmoclon. 103 



Key to Species. 



1. Tail thinly haired; skull relatively long and narrow. 

 2. Size large, hind foot averaging 32 or more. 

 3. Upperparts mainly warm brown. 

 4. Upperparts uniformly brown, size larger - - Jiispidus. 

 A.'. Upperparts brownest on rump, size smaller - spadicipygus. 

 3'. Upperparts light gray, blackish or yellowish gray. 

 4. Upperparts dark gray; much black and no brown littoralis. 

 4''. Upperparts light buffy or yellowish gray. 

 .5. Upperparts pale butfy gray. 



6. Pelage fine and not very hispid - - - eremicus. 

 Q'. Pelage coarse and very hispid, especially in summer. 

 7. Size large, hind foot averaging 40 - - major. 



1'. Size medium, hind foot not over 36. 

 8. Hind foot about 33 - . . . berlandieri. 



S'. Hind foot 35-36 arizoncn. 



5^. Upperparts dark buflfy or yellowish gray. 



6. Upperparts buffy gray; hind foot about 34 mascotensis. 

 6''. Upperparts yellowish gray ; hind foot 41 - tonalensis. 

 1' . Size small, hind foot averaging less than 32. 



3. Upperparts buffy gray texianus. 



3''. Upperparts tawny or dull brownish gray. 

 4. Upperparts tawny or dull yellowish. 



5. Audital bullae wide and flattened . . - borucce. 



5'. Audital bullae high and narrow, rounded or elongated. 

 6. Tail short, averaging 103; audital bullte narrow satttratus. 

 6f. Tail longer, averaging 112; audital bullae short and 



rounded alleni. 



4'. Upperparts dull brownish gray. 



5. Belly white; feet clear gray . - . - toltecus. 



5'. Belly grayish buff; feet yellowish brown - microdon. 



V. Tail well haired; skull short and wide. 

 2. Upper half of outer surface of ear black. 

 3. Size large, hind foot 30-33. 



4. Upperparts grizzled buffy; lowerparts ochraceous ochrogaster. 

 V. Upperparts grizzled tawny; belly rich ferruginous melanotis. 

 y. Size small, foot 28; upperparts gray; belly buffy minimus. 



2'. Outer and inner surface of ears whitish or buffy gray. 



3. Ears buffy gray; nose conspicuously ochraceous ochrognathus. 



y. Ears light gray or whitish; nose not conspicuously ochraceous. 



4. Ears silvery gray; belly white . . . - leucotis. 



4''. Ears darker gray; belly bufl'y. 



5. Upperparts rich tawny gray .... alticola. 



5^. Upperparts dull tawny gray - . - - amoles. 



