Peterson: The Osteology of Promerycoch(erus. 201 



and, as in the other species mentioned, situated quite close to the 

 median line. 



The palatal bones in general are like those in P. carrikeri, though 

 the posterior extension of the palatine plate gives the inner nares a 

 more backward position than in that species, as has already been 

 pointed out. 



A feature which is characteristic not only of the genus Promery- 

 cochcerns, but of many other genera of this family is well displayed in 

 the present species, namely, the division of the external face of the 

 maxillary into two fossae by a broad and inflated ridge (a deep and 

 large pre-orbital fossa above and a shallower depression below the ridge 

 and above the premolars, somewhat analogous to many of the early 

 camels) which includes the anterior portion of the jugal and extends 

 more or less prominently to the border of the anterior nares. In 

 Merycoidodon this ridge is also very prominent, but the superior fossa 

 is confined to an area nearer the orbit (the lachrymal pit) while the 

 inferior fossa is broad, shallow, and extends well back above the 

 molars. In Promerycochcerus and Merycoidodon there was therefore 

 a similarity in the arrangements of the naso-labial and maxillo-nasal 

 muscles. In Merycochcerus on the other hand the facial region is, as 

 already stated, entirely different. In the first place the nasals are 

 laterally constricted in the median antero-posterior region, and secondly 

 the inflated ridge referred to above is practically absent, so that the 

 large fossa on the side of the face, though not regularly concave, is 

 nevertheless uninterrupted from the nasals to the lower limit im- 

 mediately above the alveolar border of the maxillary. This change of 

 the facial region indicates a different distribution of the labial and nasal 

 muscles, the animal having perhaps had a lip with considerable power 

 of prehension or possibly a proboscis as was originally suggested by 

 Leidy. 



As in P. carrikeri the infra-orbital foramen is small and located above 

 P-. The premaxillaries are slightly more produced beyond the an- 

 terior faces of the canines than in the latter species and, as stated 

 before, the borders which form the sides of the anterior nares are more 

 oblique upwards and backwards. The large anterior palatine fora- 

 mina are separated in the median line of the premaxillaries by a heavy 

 bony septum, their lateral borders nearly reaching the internal face 

 of the canines, thus the two foramina together display a pear-shaped 

 outline. As stated above, the jugal is much inflated anteriorly and the 



