51 F. B. Loomis — Ehinocerotidce of the Lower Miocene. 



Tims, the largest species of the Diceratheres is characterized 

 by the simplicity of the dental pattern, the crista and the 

 crochet being absent on the second and third molars, and only 

 the crochet faintly indicated on the first molar. The premolars 

 are without the crochet but have the crista incipient. Around 

 the premolars the cingulum is well developed along the front, 



Fig. 2. Diceratherium annatum M. 

 men, one-half nat. size. 



premolars and molars of type speci- 



back and internal face of the tooth; but in the first molar it 

 is interrupted opposite the protocone and hypocone. 



As noted above, in the simplicity of the dental pattern and 

 in the development of the cingulum, D. annatum shows a 

 strong affinity to such Aceratheres as A. tridactylum and A. 

 occidentale. 



Diceratherium annectens Marsh. 



This Journal, vol. v, p. 4, 1873. 



The type is No. 10,001 of the Yale Museum from the " John 

 Day valley, Oregon." The type is composed of the incisor, 

 first and third premolars, and the first and second molars, of 



*Fig. 3. Diceratherium, annectens M. ; third premolar, first and second 

 molar of type specimen, one-half nat. size. 



the upper right jaw, apparently all belonging to one individual. 

 Of these the second molar is marked "type," but the others 

 are included in the description. 



This small species is readily distinguished by the fact that 

 on the molars the protoconule and the hypocone are so closely 



