268 BULLETIN 56, UNITED STATES NATIONAL MUSEUM. 



Mcdsiirciiiciils of i2 spccinicns of SciuniK (/riKCiis diitlioinii. 



" American Museum of Natural History. 



" Type. 



Subgenus AR^IOSCIURUS Nelson (1899). 

 SLENDER saUIRRELS. 



Ar(rosciurii.9 Nelson, Proc. Washington Acad. Sci., I, p. 29, pi. i, fig. 3. May 

 9. 1S99 (Revision of the Squirrels of Mexico and Central America). 



Dent!t!on.—l. jEj; P. ^; M. —^ = 20. 

 The following is the original description : 



Type Sciurus ociilatiis Peters, from eastern Mexico. 



Distrlhnilon. — Mountains bordering the tableland of Mexico from the vol- 

 canoes of Orizaba and Tolnca north to central Arizona and west-central New 

 Mexico. Transition zone. 



External characters. — Size large; body rather slender; tail usually long, 

 sometimes exceeding length of head and body; upper parts gray or yellowish; 

 underparts white or yellowish. 



Cranial characters. — Premolars }. Skull rather short, depressed; brain case 

 broadened at parietals ; occiput low and broad ; front of skull depressed at base 

 of rostrum (more arched in Parasciiinis) ; rostrum light', nassils narrow, 

 slightly tapering posteriorly ; upper end of pi-emaxill;e narrow. 



