304 PROCEEDINGS OF THE ACADEMY OF [1892. 



large deuterocone. The upper molars are very simple and consist 

 of a large crescentic protoeone, and low, compressed para- and meta- 

 cones, the latter somewhat the smaller of the two. In the lower jaw 

 pi is very small and simple, implanted b)^ one fang. P^, s and * are 

 all alike, except in size, which increases posteriorly; these teeth 

 consist of a high, acute, trenchant and recurved protoconid, and a 

 low cutting heel, but with no paraconid, except for a rudimentary 

 one on p*. In the lower molars the protoconid is greatly enlarged, 

 compressed, acute and with cutting edges ; the metnconid has almost 

 com])letely fused with the protoconid, from which it is separated 

 only by a very shallow groove ; the paraconid is much reduced and 

 forms a low anterior basal cusp; the talon consists of the hypoconid 

 only, which has a trenchant upper margin. The mandible is slender, 

 with long symphysis which reaches to p^. The posterior thoracic 

 and lumbar vertebrae have the characteristic creodont feature of 

 involuted zygapophyses. In the humerus the en tepi condyle is less 

 prominent than is usual among creodonts, but retains the foramen ; 

 the trochlea is low, but distinctly convex. The ulna has a long 

 olecranon. The head of the radius is transversely oval and displays 

 three humeral surfaces. The astragalus is very slightly grooved, 

 and the trochlear surface extends to the middle of the neck ; distally 

 there is a distinct facet for the cuboid, separated from the navicular 

 surfiice by an angle; the body of the bone is pierced by a foramen. 

 The calcaneum has a long tuber calcis and rather small sustenta- 

 culum. The proximal end of the cuboid exhibits separate facets for 

 the calcaneum and astragalus. The feet were plantigrade and 

 pentadactyl. 



Three species have been referred to this genus : D. tiavajoviits Cope, 

 and D. carnifex Cope are from the Puerco and D. leptognathns 

 Osborn is from the Wasatch, but being known from a single molar 

 only, is provisionally placed in this genus. 



PACHY^NAi Cope. 

 Syn. Mesonyx- Cope, in part. 



If, Cj-, P|, M|. The incisors are small, the canines very robust. 

 Pi is small, single-rooted and separated by a short diastema from 



1 Rep. Vert. Foss. New Mexico, U. S. Geog. Surv. W. 100th Mer., 1874, 

 p. 13. 



■' Mesonyx ossifragus, Tert. Vert. p. 362. 



