236 



University of California Publications. 



[Geology 



referred to a species distinct from the typical T. rurestris of the 

 Mascall formation in the John Day region of Oregon. Through 

 the kindness of Professor John F. Bovard and Professor Arthur 

 J. Collier, the type specimen of the Mascall species was loaned 

 by the University of Oregon for comparison. 



The jaw is of nearly the same length as in the type species, 

 but more slender and the inferior margin not so strongly convex 

 below the anterior end of the masseteric fossa. Inferior pre- 

 molar series longer, and molar series shorter than in T. rurestris. 

 Pj, P 2 , and P 3 of the type specimen without anterior or posterior 

 cusps. P4 with a single posterior cusp. M, with large meta- 

 conid, heel with large crushing hypoconid and entoconid. Tri- 

 gonid of M, with well-developed paraconid. 



The form of the mandible (pi. 32) in this species differs less 

 noticeably from that of the typical Canis than in the type speci- 

 men of Tephrocyon. The inferior margin is not as strongly 

 convex as in T. rurestris, nor is the jaw as a whole quite as 

 massive. The jaw tends, however, to be relatively heavy in the 

 posterior half in comparison with species of Canis. 



The incisor teeth are not present on any specimen, and the 

 canines are represented only by the basal portion of a tooth not 

 showing any peculiar characters. 



The premolars are uncommonly simple in form on the type 

 specimen of this species. There appear to be no subsidiary cusps 

 on the first three premolars, but P 4 has in addition to the princi- 

 pal cone a posterior cusp and an incipient basal tubercle. On 

 another specimen, no. 1147-1, apparently representing this form, 

 P. has a distinct posterior cusp. 



Mj is characterized by the large size of the metaconid and of 

 the broad crushing heel (see pi. 32, fig. 1). The metaconid is 

 larger and more prominent than in T. rurestris. The heel of this 

 tooth is nearly identical in form with that of the type species. 

 The hypoconid and entoconid are of approximately equal size, 

 but the entoconid seems to be slightly more elevated. There is 

 a small but distinct tubercle on the posterior side of the base 

 of the protoconid immediately in front of the hypoconid. An- 

 other small tubercle is faintly developed on the posterior side of 

 the base of the metaconid. 



