PLEISTOCENE VERTEBRATES FROM CUMBERLAND CAVE 



55 



side, occiput more elevated than in the living species, giving a less 

 convex contour to the cranium. Anterior zygomatic region widely- 

 expanded, with its outer rim strongly turned downward and ex- 

 tending forward well beyond the maxillary-premaxillary suture, 

 thus giving an unusually broad surface for the attachment of the 

 anterior portion of the masseter-laterahs. Jugal relatively deep, 



FiQUEE 30.-Scfwru^ {Tamiasciurus) tenuidens Hay, skuU (U.S.N.M. no. 8164), and mandible (U.S.N.M. 

 no. 12050): a, Dorsal view of skull; 6, lateral view of mandible. X IH. Cumberland Cave Pleistocene, 

 Maryland. 



about one-fourth deeper than the average in the Hving species. Bullae 

 much as in the Uving members of the group but more inflated back- 

 ward and outward, in posterior portion, giving a decidedly flatter 

 appearance to the posterior wall of its mner face and to the outer 

 face directly below the external auditory meatus. External audi- 

 tory meatus smaller than in living species. 



Incisors more robust, with greater anteroposterior diameter than 

 in the living species. Cheek-tooth row of equal length with that of 

 Sciurus fremonti, and of S. hudsonicus from the Fort Yukon district, 

 but teeth slightly narrower. 

 - Lower jaw relatively deep, short, and massive, with broadly ex- 

 panded angle. Anterior portion of masseteric fossa deeper and 



