106 SCIURUS. 
D, Arzosciurus. 
Premolars, —, Skull broad, depressed between orbits; superior 
outline curved greatly at occipital region; orbital region very broad; 
postorbital process curving downward, and pointed; nasals long, 
extending posteriorly to end of premaxille. 
Fic. 16. SciuRUS (ARAZOSCIURUS) NAYARITENSIS. 
No. 4741 Field Columbian Mus, Coll. Nat. size. 
KEY TO THE SPECIES AND SUBSPECIES OF THE SUBGENUS. 
A. Size large. Premolars, - =. PAGE 
a. Back with longitudinal black band...........S. oculatus 107 
b. Back without longitudinal black band. 
a.’ Under parts white. 
a.’ Above gray, washed with blackish; tail 
beneath yellowish gray or brown .......S. 0. toluce@ 107 
b.”” Above grizzled yellowish brown; tail 
beneath grizzled yellowish gray ...........S.allent 108 
