122 



THE MAMMALIA OE THE DEEP EIVEE BEDS. 



nenee of a line, examples of which may be found abundantly in every horizon. In 

 the case of Ancliitlierium, it may seem that I have excluded it from the main phylum 

 on very trivial grounds, deviations which are no greater than the elbow joint of 

 Metohippus. But in the teeth of Anchitherium we find that characters which are 

 constant in all the genera before and after it, characters in the continual development 

 of which lies the peculiarity of the evolving equine dentition, are reduced or entirely 

 lost. Of itself, perhaps, this fact would be insufficient to justify us in excluding the 

 genus from the direct line, but it coincides, as we have seen, with many other facts, 

 all of which point to the same conclusion. 



The following table expresses concisely the relationships of the various Oligoeene 

 and Miocene equine genera, according to present information. 



Loup Fork, 

 Deep River, 

 (Hiatus), . 

 John Day, . 

 White River, 



Protoliippus. Hipparion. 



An cliiilierium . Protoliippus. 



? Ancliitlierium. Desmatijypus. 



. Mioliippus. 

 Mesoliippus. 



Rhinoceridae. 



CuENOPUS? Cope. 



The rhinoceroses of the lower beds of the Deep River valley are represented in 

 the collection only by some portions of mandibles which contain much mutilated 

 teeth. These remains are altogether too uncharacteristic to admit of generic ref- 

 erence. 



APHELOPS Cope. 



Bull. U. S. Oeol. and Geogr. Surv., No. 1, 1874, p. 13. 



The upper beds yielded some fragmentary remains of a large rhinoceros which 

 almost certainly belong to Aphelops. The best preserved of these is a portion of a 

 skull, including the occiput, zygomatic arch and roof of the cranium, together with 

 fragments of the molar teeth and superior maxillary bone, but, in the absence of 



