E. L. Troxell — Entelodonts in Marsh Collection. 437 



deep valleys on the molars and the low cusps, the strong 

 angle on the inner face of P 3 , the very irregular and pitted 

 premolars, the great breadth of the nose anterior to the 

 orbits, the broad smooth frontals without foramina, and 

 especially the lack of a notch on the anterior side of P 4 

 and the extraordinarily large and oddly shaped dependent 

 process from the zygomatic arch. 



Megachcebtts latidens Group. 

 Megachoerus latidens, sp. nov. 



Holotype, Cat. No. 10009, Y. P. M. Probably Upper Oligocene, near 

 Cheyenne Biver, South Dakota. 



This, like specimen No. 10008, is a very large animal ; of 

 it there is preserved the central portion of the skull with 



Dp 



Mf- Hs PI Py rr 



Fig. 17 '.— Megachoerus latidens, sp. nov. Holotype. Cat. No. 10009. 

 Crown view of upper molars and premolars. Note the deciduous premolar, 

 Dp 4 , still in place. One-fifth nat. size. Dp 4 and P 4 , deciduous and perma- 

 nent fourth premolars ; M 1 , first true molar. Cn, cingulum ; Be, deutero- 

 cone; Hs, hypostyle; Hy, hypocone (on M 2 closely associated with the 

 metaconule) ; Me, metacone; Mt, metaconule; Pa, paracone; PI, proto- 

 conule; Pr, protocone. 



the molars and premolars (fig. 17), except P 1 , and both 

 rami (fig. 18). These are the remains of a young entelo- 

 dont which still retains some of the milk teeth and of 

 which the last molars are just cutting through. 



But few details of the skull itself are worth noting : the 

 infraorbital foramen has its edge over the anterior root of 

 P 4 and opens slightly upward. The upper rim of the 

 orbit was probably rather smooth like most of the surface 

 of the frontals. One small foramen is visible near the 

 center line, where appears a slight fold possibly due to 

 crushing. 



All the permanent teeth of this young animal are uni- 

 formly corrugated on the surfaces which have not been 

 exposed, but it is evident that the sides soon wear smooth, 



