Peterson: The Osteology of Promerycocikerus. 165 



crown is of the same simple construction as in Mcrycnidodon ciilhcrtsoni, 

 though rclati\'ely smaller and perhai)s more h\ psodont. P- and P- 

 are also like those oi-M. cidbertsoni, but the apices of the crowns are 

 shifted further forward. There is no apparent change in P-. 



The antero-posterior diameter of the molar series in P. carrikcri is 

 somewhat greater in comparison with that of Merycoidodon cnlbertsoni, 

 which is due to the slight reduction of the premolars on the one hand 

 and the elongation of M- on the other. M-ahd M- do not seem to be 

 greatly difil'erent in relative size when compared with A'lerycoidodon, 

 while in MerycochcErus and later genera of the family the whole molar 

 series has become elongated and otherwise modified. In P. carriheri 

 the molars are very little, if any, more hypsodont than in Merycoidodon 

 cidbertsoni. 



the inferior dentition. 

 (Plate XXXVIII). 



The lower incisors, though larger than the upper, are short-crowned 

 and soon become worn down in their sockets to sub-cylindrical pegs. 

 Their position is more procumbent and they are set more closely to- 

 gether than those above. The incisiform canine retains its relative 

 size, while the true incisors are reduced when comj^ared with Mery- 

 coidodon. This is not only true of P. carrikeri, but seems to hold good 

 in many of the later genera of this family. The canine is crowded very 

 closely against the antero-external angle of Py, so that the two teeth 

 greatly overlap one another. The caniniform Pyis typical of the family, 

 but in P. carrikeri the position of the tooth is unusually procumbent and 

 also large in size. From the peculiar wear on the internal lace of 

 the tooth in some individuals CNos. 109, 1047) it seems quite possible 

 that it was used efTectively in stripping branches of their foliage, or 

 perhaps in excavating in soft marshy places. P-j-is isolated by short 

 diastemata and is relatively smaller than in Merycoidodon culbertsoni. 

 P-j and P4 and My and IVIj differ veiy little in form from those in 

 M. cidbertsom; on the other hand the antero-posterior diameter of 

 M^g is equal to My and M 2 together, in natural correspondence with the 

 elongated upper molar. Cingula are absent on the lower molars, 

 or \ery slightly developed. 



