144 



the merycqidodontim: 



Foramina: The infraorbital foramina lie above P 4 , and the supraorbitals are 25 mm. apart. 

 The condylar foramen is normal and separated from the foramen lacerum fosterius by a ridge from 

 the paroccipital process. The foramen lacerum medium is large and occupies a position correspond- 

 ing to that in Eporeodon. The large foramen ovale is oval in shape. It is located relatively much 

 farther anterior to the bulla than in Merycoidodon. Only one specimen, Cat. No. 10154, in the 

 Marsh Collection, shows a foramen rotundum, and in this one it is so small that it could not have 

 been functional. Hence I believe it justifiable to consider that this foramen is obsolete in the John 

 Day Promerycochoeri, as it is in Eforeodon. The posterior palatine foramina are not visible. 



Fig. 105. — Promerycochcerus temporalis (Bcttany) = P. suferbus. Inferior view of skull. HT. 

 2/5 nat. size. (Drawn from Woodwardian Museum photographs.) 



Cat. No. 3298 W.M. 



Dentition: There is a narrow internal cingulum on all of the superior molars and P 4 , and the 

 metastyle of M 3 is large and robust, forming an abrupt angle with the hypocone, and it is almost in 

 an anteroposterior plane with the paracone. P 1 is isolated. The metastylid of M 3 is also very 

 large. The inferior premolars are slightly crowded, and P 2 and P 3 are placed somewhat obliquely. 

 The canine is posteriorly flat and anteriorly rounded, while that of P. macrostegus is more oblong 

 to square, with the long diameter transverse to the sagittal plane. Cat. No. 10983 Y.P.M. has acces- 

 sory styles on M 3 . The left style is a hypostyle, an integral part of the hypocone, whereas the right 

 style is developed from the cingulum alone. Cat. No. 10978 Y.P.M. has partly deciduous denti- 

 tion, which shows the order of succession of the permanent dentition to be M 1 , M 2 , M 3 , P 4 , P 3 , and 

 P . P 1 , C, and the incisors are broken away, so that determination of their order cannot be made 

 from this specimen. The superior molar-premolar index is 0.80 and that of the lower 0.98. 



Skeleton: The sacrum of Cat. No. 10991 consists of three ankylosed vertebras, with parts of 

 both ilia attached. A fourth sacral was formerly present. The length of the ankylosed vertebras is 

 82 mm., and the transverse diameter of sacral I is 124 mm. The dorsal spines are not large. The 

 maximum length of the centrum of the last lumbar is 35 mm., while the transverse processes are 

 about the same in length. The height of the neural canal is 18 mm. Cat. No. 10989 Y.P.M. has 



