PROMERYCOCHCERUS 



13 



in any John Day form in the genus. The nasal bones are nearly straight in anteroposterior profile 

 and are transversely convex and narrow. The size of the -pars facialis of the lacrimal cannot be deter- 



Fig. 71. — Promerycochcerus chelydra (Cope). Skull. HT. Cat. No. 7430 A.M.N.H. 4/9 nat. size. 



(After Peterson, 1914.) 



mined from the type, as it is a very old individual, with the sutures closed. The antorbital fossa is 

 large and well marked but not deep, gradually fading out anteriorly. The frontals are flat, unre- 

 duced, and medium in width, with decurved supraorbital borders, but to a lesser degree than in 



Fig. 72. — Promerycochartts chelydra (Cope). Superior view of skull. HT. Cat. No. 7430 A.M.N.H. 1/3 nat. size. 



(After Peterson, 1914.) 



P. suferbus. The orbits are more oblique than in the latter species, and their vertical diameter is 

 the greater. The prominent temporal ridges unite rapidly, so that the thickened narrow and high 

 sagittal crest is nearly a third of the skull length. The supraoccipital crest is lower than the sagittal 



