with Descriptions of New Species. 225 



part of the hypocone, termed an hypostyle, whereas the 

 right style is developed from the cingulum alone. Both 

 have an average diameter of over 5 mm. 



In the list of synonyms, Merycochoerus temporalis 

 Bettany is intentionally placed at the end, partly not to 

 break the continuity of the P. superhus series, and partly 

 because it was considered as a distinct species until Cope 

 wrote in 1884: ^^I cannot detect any difference between 

 the specimen described by Mr. Bettany as the type of his 

 M. temporalis, and those of the M. superhus in my posses- 

 sion. " There are some minor differences between the 

 type of this species and P. superhus, but they are too 

 unimportant, in the writer's opinion, to consider of speci- 

 fic value, especially when this group shows so much 

 variation. It would be exceedingly difficult to find any 

 two specimens in the group between which many minor 

 differences, at least, could not be detected. 



Pr ornery coclioerus chelydra (Cope). 



Holotype, Cat. No. 7430, Cope Collection, A. M. N. H. Upper 

 Oligocene (upper John Day), Bridge Creek, John Day Eiver, 

 Oregon. Figured by Peterson, Ann. Carnegie Mus., 9, pi. 41, 

 figs. 1, 2 ; pi. 42, fig. 1, 1914. 



Specific characters.— Maxmrnm width of skull anterior 

 to glenoid articular surface, and equal to. distance from 

 paroccipital process to canine ; posterior angle of zygoma 

 rises nearly to level of sagittal crest ; bullae do not extend 

 anterior to postglenoid processes; palate moderately 

 produced; supra-occipital bone presents a wide, flat 

 convexity above foramen magnum ; superior molars lack 

 an internal cingulum ; bullae normally small and subconi- 

 cal; infra-orbital foramen above P^. 



Two skulls in the Marsh Collection, Nos. 10962 and 

 10979, show the characters of this species quite well. In 

 general proportions and appearance they differ not a 

 great deal from P. superhus, except in the much greater 

 bizygomatic diameter of the former. The internal cingu- 

 lum is discontinuous, but is especially well developed on 

 the posterior side of the protocones of M-. The metastyle 

 occupies the same relative position as in P. superhus. 



Cope^ wrote that ^ 'a line drawn through the postglenoid 

 and paroccipital processes makes an angle of 90° with the 



' Proc. Amer. PhHos. Soc, 21, 523, 1884. 



