360 University of California Publications in Geology [Vol. 7 



In preparing the following' paper the writer has made a re- 

 examination of the type specimen of Tephrocyon, and several 

 figures representing phases of the structure not previously illus- 

 trated accompany this discussion. 



For the loan of the type specimen from the University of 

 Oregon, the writer is much indebted to Professor A. J. Collier 

 and Professor J. P. Bovard. 



Genus Tephrocyon 



Type species Tephrocyon rurestris (Condon). 



Skull of the type specimen short-muzzled, shortening of the 

 muzzle accompanied by backward extension of the premaxillaries 

 beyond the anterior ends of the nasal processes of the frontals. 

 auditory bullae large. Paroccipital process prominent. Man- 

 dible* heavy, uncommonly convex below the anterior border of 

 the masseteric fossa. Crushing region of the molar teeth rela- 

 tively large. M 1 and M 2 with inner lobe relatively wide antero- 

 posteriorly. M, with well-developed metaconid and large heel. 

 M 2 relatively long anteroposteriorly, paraconid ridge or tubercle 

 distinct, antero-extenal ridge of the cingulum strongly marked. 

 Premolars usually relatively short. P 4 with an incipient proto- 

 style in the type specimen of the genus. Posterior opening of 

 the vertebra rterial canal of the atlas situated farther back than 

 in Canis. 



The forms that have been referred to Tephrocyon include the 

 following : 



T. rurestris (Condon). Maseall Beds. Oregon. Middle Mio- 

 cene. 



T. hippophagus Matthew and Cook. Snake Creek, Nebraska. 

 Early Pliocene. 



T. temerarius (Leidy). Sands of the Niobrara River, Snake 

 Creek?, and Whistle Creek, Nebraska; Mohave Beds, Mohave 

 Desert, California. Upper Miocene. 



T. kelloggi Merriam. Virgin Valley Beds, Nevada, Middle 

 Miocene; Cedar Mountain, Nevada, Middle to Upper Miocene. 



T., near kelloggi Merriam. Thousand Creek Beds, Nevada. 

 Early Pliocene. 



