MAMMALS OF THE \II.\KAX BOUNDARY. 249 



dd. Median area of upper and under side of tail broad and distinct, 

 yellowish ochraceous above and grayish white below; general 

 color slightly yellower and less rufescenl above. 



Sciurus fremonti grahamensis (p. 261 I. 

 cc. Pelage mostly grayish above Sciurus meartisi (p. 262). 



bb. Total length of skull more than 60 nun. 



e. pm 1 large; Lnterpterygoid fossa short, about equaling the three upper 

 true molars; incisive foramina short, nearly as wide as long; skull 



measuring 61 by 36 nun Sciurus aberti (p. 250). 



vc. i>m' small: interpterygoid fossa longer, measuring, from base of ptery 

 .void, more than the three upper true molars. Skull measuring 68 by 



:!!> mm Sciurus griseus anthonyi (p. 264). 



mi. Species with only one upper premolar. 

 f. Size small. 



.'/. Skull measuring 51 by 34 mm. in greatest dimensions. 



Sciurus alleni i p. 269). 

 tin. Skull measuring <;i by 35 mm. in greatest diameters. 



Sciurus rufiventer texianus (p. 2S1). 

 ff. Larger. 



//. Skull high, measuring 63 by .T7 to 65 by 88 mm. ; brain case 

 inflated and bulging behind the orbits, where the frontal bone 

 forms the anterior portion of its roof. 

 i. Skull smaller: rusty yellow band continuous from occiput to 



root of tail Sciurus arizonensis arizonensis (p. 27"). 



ii. Skull larger; rusty yellow dorsal band interrupted ante- 

 riorly Sciurus arizonensis huachuca (p. 277). 



hh. Skull low, measuring 65 by 37 mm. ; brain case less inflated. 



sciurus apache (p. 270). 



Subgenus 0T0SCITJRUS Nelson (1899). 



TUFT-EARED PINE SQJJIRRELS. 



Otosciurus Nelson. Proc. Washington Acad. Sci., I. p. 28, May 9, 1899. 



Dentition.— 1. \~_\\ P. jE?; M. \ :j=22 



Type.— Sciurus <i/>cr/i Woodhouse. 



Type-locality. — San Francisco Mountain, Arizona. 



Characters. — Compared with other North American arboreal squir- 

 rels, the skull is short and broad; frontal area flattened; brain case 

 depressed, inflated laterally (but loss so than in typical Sciurus) ; 

 rostrum and nasals long, the latter equaling interorbital breadth; 

 premolars f; ears long and broad, very heavily tufted in winter; 

 color usually mainly gray above, white below, with a lateral line more 

 or less distinctly black. 



This subgenus i> very closely related to typical Sciurus, of which 

 Sciurus vulgaris Linnaeus is the type, only differing in color in the 

 greater length of the rostrum, in the more swollen, elevated, and 

 laterally expanded brain case, and the shorter and broader interp- 

 terygoid fossa. 



