14 



THE merycqidodontid;e 



crest, which stands well above the level of the frontals, and is much produced beyond the occipital 

 condyles. The wings are widespread. 



The brain case is small, narrow, and elongate, with strong lateral convexities. The small 

 external auditory meatus is in its normal position but is far below the superior surface of the skull. 

 The basicranial axis is moderately steep. The palate is narrow and anteriorly flat, soon becoming 

 gently vaulted. The U-shaped palatonarial border is almost directly beneath the postorbital con- 

 striction. The narrow glenoid surface is nearly uniform in width and is placed somewhat obliquely 

 to the sagittal plane. The short postglenoid process is moderately stout and has nearly the same 



Fig. 73. — Promerycochcerus chelydra (Cope). 



Inferior view of skull. HT. 

 (After Peterson, 1914.) 



Cat. No. 7430 A.M.N. H. 1/3 nat. size. 



dimensions in both diameters, although the transverse is slightly the greater. The bulla? are small 

 and subconical and do not extend anterior to the postglenoid processes nor below their inferior 

 surfaces. The paroccipital process is transversely wide at the base, is then rotated forward, nearly 

 touches the postglenoid process, and gradually becomes slenderer toward the distal end, which is but 

 a relatively short distance below the postglenoid process. Index: 0.73-0.75. 



Foramina: The infraorbitals are above P 4 . The supraorbital foramina are 21 mm. apart and 

 have distinct channels leading forward and laterally downward. The joramen ovale is small. I do 

 not find a joramen rotundnm. The posterior palatine foramina appear to be obsolete or are at least 

 minute. 



Dentition: The teeth are much worn in the type, as the animal was very old. P 1 is isolated 

 by a diastema on either side. The superior molars lack the internal cingulum, but the protocone of 

 M 2 shows one well developed posteriorly. The metastyle of M 3 occupies the same relative posi- 

 tion as in P. superbus. The superior molar-premolar index is 0.88-0.93. 



