1903] 



Gidley, Species of Platygonus from Texas. 



479 



containing the complete upper molar-premolar series, parts 

 of the alveoH of the canines and incisors, and a portion of 

 the upper anterior part of the skull. 



Though coming from a later horizon,' the somewhat primi- 

 tive quadritubercular character of the molars suggests in this 

 species a close relationship to P. rex Marsh.- However, com- 

 paring it with a cast of Marsh's type, which the writer has at 

 hand, the following differences are very clearly shown: (i) 

 The four principal cusps of the molars are proportionally 

 shorter. (2) The cusps are subequal in the anterior and pos- 



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Fig. 3. — Platygonus vetus. Leidy. Amer. Mas. No. 2724. X i. 



terior pairs, and are comparatively wide apart at their sum- 

 mits. In P. rex the cusps of the outer side of tlie molars 

 are perceptibly higher than those of the inner side. (3) The 

 posterior heel of m^ is much more strongly developed. It is 

 very weakly represented in P. rex. (4) The size of the molars 

 indicates a species larger than P. rex. 



Compared with P. vetus Leidy (Figs. 3 and 4)the chief dis- 

 tinctions are as follows : ( i ) The cones of both the molars and 

 premolars are proportionally lower and, in the molars, more 



> The type locality of Platygonus rex Marsh is eastern Oregon. Marsh k'ives the 

 horizon as Pliocene, but it is almost certainly Upper Miocene. 

 »Am. Jour. Sci. (,?) xlviii, 1894, p. 273. 



