204 Annals of the Carnegie Museum. 



of the specimens at hand. The tooth is more robust than that in 

 P. carrikeri and has the cingula better developed. Both premolars 

 two and three have smaller antero-posterior diameters than those in 

 P. carrikeri, but are transversely wider and have heavier cingula than 

 in the latter species. P- is similar in the two species. M-is absent. 

 The diameters of M- are distinctly greater than those of the cor- 

 responding tooth in P. carrikeri. The diameters of the third molar 

 are correspondingly large. Although the skull is more delicate in its 

 proportions than that of P. carrikeri, the premolar-molar series is 

 more robust, apparently one of the evolutionary features of the 

 phylum. The premolar series occupies a shorter space in the alveolar 

 border than is generally the case in older forms, an advanced ^^ feature. 



THE inferior DENTITION. 



The lower incisors of this species are more spatulate than is 

 usual, are set close together, and have a rather procumbent position. 

 The canine has the usual incisiform character and receives much 

 wear on the external face of the crown by friction with the superior 

 canine. Py is robust, but not nearly as much so as in P. carrikeri, and 

 its position is somewhat les,s inclined outward and forward than in the 

 latter species. Pyhas a similar oblique position immediately back of 

 Py", the tooth is otherwise like that in P. carrikeri. All of the pre- 

 molars are more compactly placed than in P. carrikeri which has P-g- 

 quite isolated. The molars are on an average larger than those in 

 P. carrikeri, so that including the diastemata back and in front of 

 Po in the latter species, the length of the whole dental series is no 

 greater that in P. vantasselejisis. 



Measurements. 



No. 1230 



(Type) 

 Mm. 



Superior dentition, total length 170 



Superior dentition, length from incisors toM- 108 



Superior dentition, length of molar series 78 



Canine, antero-posterior diameter near base 16 



Canine, transverse diameter near base 19 



P- antero-posterior diameter 14 



P - transverse diameter 9 



1' We should not lose sight of the fact that certain forms in the Oligocene as 

 Merycoidodon gracilis have the premolar teeth reduced to very nearly as great a 

 degree as Merychytis from the Upper Harrison beds. 



