1920] Stock: An Early Tertiary Vertebrate Fmina 271 



CAENOPUS? or DICEEATHERIUM?, sp. indet. 



Three fragmentary superior teeth pertaining to a single rhinoceros, 

 no. 23614, figures 4 and 5, are available for study. These specimens 

 represent P- and apparently P- and P-. They correspond fairly closely 

 in size with similar teeth of Oligocene rhinoceroses and particularly 

 with those of Caenopus occidentalis as figured by Osborn.^ In the 

 character of size they are comparable also to some specimens belong- 

 ing to rhinoceroses from the John Day. The teeth from the red beds 

 of Tecuja Canon do not seem to have acquired a noticeably greater 



Figs. 4 and 5. Caenopus? or Diceratherium?, sp. indet. Superior cheek teeth, 

 no. 23614, occlusal view, natural size. Fig. 4, Pi; fig. 5, P^? and P-. Red beds, 

 Tecuja Caiion, California. 



degree of hypsodonty than that possessed by teeth of Oligocene 

 rhinoceroses of the John Day. 



In F- (fig. 4) the parastyle is broken away, but the rest of the 

 crown remains intact. It exhibits a postprotoconal valley and a post- 

 fossette as in the corresponding tooth of Oligocene aceratheres. The 

 transverse diameter across the posterior side is somewhat greater than 

 in C. occidentalis. As remarked by Osborn, P^ in the Oligocene forms 

 is subject to considerable variation. 



The two remaining teeth (fig. 5) of the rhinoceros from Tecuja 

 Canon are badly injured. From the parts which remain a size is 

 indicated which would place them rather with the premolars than with 

 the molars of the superior dentition. They are considered as pre- 

 molars in the present discussion, having been determined tentatively 

 as P- and P-. The cingulum is well developed in these teeth along the 

 preserved portions of the anterior and po.sterior borders. An interest- 



3 Osborn, H. F., The extinct rhinoceroses, Amer. Mus. Mem., vol. 1, pt. 3, pi. 

 13, fig. 5, 1898. 



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