306 TUE WASATCn AND BRIDGEK FAUN^. 



Length true molars .010; last threepremolars.01,'35; last molar narrow.. i).dajf^-in«ian««. 

 •• Inferior tubercular molar short, subquadrate iu outline. 



Length true molars .Oil ; depth of ramus at sectorial .010 2>. massetericus. 



Length true molars .018; depth of ramus at sectorial .017 X). curtidens. 



DlDYMICTlS HAYDENIANUS Cope. 

 Proceed. Amer. Philos. Soc., leda, p. -IC-J. Paleoutological Bulletiu Xo. 35, p. 464, 1882, Nov. 11. 



Plate XXIII e, C^'s. 12-13. 



This Creodont is represented by parts of the maxillary and mandibular 

 bones of the left side, the former supporting the four and the latter sup- 

 porting the three last molars. The arrangement of the superior molars is 

 much as in D. protenus, the fourth premolar being a true sectorial. The 

 third premolar has no internal lobe, although the section of the base of the 

 crown is narrowly triangular. It has anterior and posterior basal lobes, and 

 a posterior lobe on the cutting edge. In the sectorial the median lobe is a 

 good deal more produced than the posterior, though the two form together 

 the usual blade. The anterior basal lobe is distinct, and the internal is 

 larger and is conic. The first true molar has the anterior external base of 

 the crown produced. Its two external cusps are conic and distinct. The 

 internal part of the crown is rounded and supports a conic internal tubercle, 

 which is separated from the external cones by two small concentric tuber- 

 cles. The second true molar is considerably smaller, and is transverse, its 

 external border being very oblique. It has an acute internal lobe. 



The character of the species is well marked in the inferior true molars. 

 The first has the form seen in other species of Bidymktis. The heel is 

 large, and with a median basin between lateral cutting edges. The two 

 anterior inner cusps are of equal elevation and are near together ; the exter- 

 nal is much larger. The last molar is elongate, but reduced in size. Its 

 anterior three cusps, rudimental in other species, are here elevated, forming 

 the triangular mass seen in the first true molar. They are not so elevated, 

 however, as in that tooth, and thus not so much developed as in Oxyopia, 

 Sh/polopkus, etc. The fourth premolar has a median cutting edge on the 

 short heel. 



