34 KANSAS rN'IVI-.KSl I \- (JC.\R ih;ki.\-. 



sharper. The outer posterior cusp sends a similar ridge to connect 

 with a heel-cusp. This posterior cusp is much lower than the pre- 

 ceding cusps, is sim])le, that is, it has no subordinate cusps, but is 

 convex outwards and ])Osteriorly, and forms an ascending marginal 

 ridge to the inner side. Its highest point is situated very nearly in 

 the middle of the tooth transversely. Between the two cusps of the 

 fust ridge in front and behind, there is a minute cusj), the posterior 

 one uniting with the ridges running from the posterior outer cusp to 

 form the cross ridge. 



The first ui)per molar scarcely differs, save in si/e, from the last 

 milk molar. The posterior inner cusp sends a stronger ridge upward 

 to the posterior edge of the basal margin, and has a similar, but 

 smaller ridge, nearly jiarallel with it, on the outer side. 



The second upper molar has its cusps yet more approximated at 

 the expense of the inner surface. There is a sharp and i)rominent 

 basal ridge on tlie outer side of the valley and posterior transverse 

 ridge, continuous with tlie sharp ridge running from the ai)ex of the 

 inner posterior cusp. The corresj)onding tooth of /'. i/iiU-i-o/'S, as 

 figured by Leidy shows much resemblance to that of the same age, 

 ])ut differs in having a distinct basal ridge on the outer side of the 

 first trans\-erse ridge, and across the inner side of the valley. The 

 third molar is more elongate, but has the same structure as in the 

 second, wherein it differs distinctly from the corresirjuding tooth of 

 I/iiU-i-o/'S. In the present species, the sharj) ridge from the inner 

 posterior cusp is convex and directly continuous with th:^ thin edge 

 of the basal ridge, which is narrower. In macrops there is a deep 

 incision, as in the last molar of the lower jaw, and the basal ridge is 

 much broader. 



The premolars, both above and below, are not very different from 

 the corresponding teeth of P. iitacrops as figured by I.eidy. 



In the adult skulls most of the characters of the teeth that have 

 been given are (jf little a\ail, as the teeih are so worn as to mask 

 most of the important features, and the teeth, except the last premo- 

 lars, are not much unlike those of Dicotvlcs when worn. 



The canines show no grooves, or at most a very slight one, on the 

 outer side. The permanent canines appear at the anterior and inner 

 side of the deciduous teeth, and are broader and Ifatter when first 

 erupted than are their predecessors. The ])ermanent canines of the 

 upper jaws which had reached nearly their full length while yet the last 

 true molars had not yet appeared through the gums, have the hind margin 

 thinner than the anterior, and less concave than in the milk canines. 

 In the lower jaw of the same skull the canines had begun to be ■worn 

 on the back surface near the tip. They are moderately curved, the 



