164 THE MAMMALIA OF THE DEEP RIVER. BEDS. 



Measurements. 



M. 



Length of molar-premolar series 064 



Length of premolar series 029 



P. 1, length . 005 



P. 1, width 004 



P. 2. length 007 



P. 2, width 005 



P. 3, length 008 



P. 3, width 006 



P. 4, length 007 



P. 4, width 007 



Length of molar series 037 



M. 1 , length 009 



M. 1, width 010 



M. 2, length 013 



M. 2, width 010 



M. 3, length 015 



M. 3, width 009 



The type of this species was found by Mr. E. Stevenson in the upper beds. 



PlTHECISTES Cope. 



Proceedings Araer. Philos. Soc, Vol. XVII, p. 219. 



In this genus, which is as yet very imperfectly known, the Leptauclienia series 

 of oreodonts appears to have reached its culmination. The lower incisors are reduced 

 to one, the canine has resumed its original functions, and the caniniform premolar 

 has disappeared. The other premolars are greatly reduced in size and the mandible 

 is extremely shortened in consequence. . 



Found only in the upper beds of the Deep River valley. 



Mutual Relations of the Oreodont Genera. 



In my paper upon this family (No. 32), lack of material compelled me to leave 

 many questions with regard to the mutual relations of its genera unsolved and even 

 unattempted. The newly discovered material will. enable us to answer some of these 

 questions with a reasonable degree of probability. We may first consider the origin 

 of Merychyus. 



The relationship of Mesoreodon to the typical Eporeodons of the Oregon John 

 Day is very obvious and need not be dwelt upon, the only difference of taxonomic 

 value between the two genera being in the structure of the manus, and indeed there 

 is much to be said in favor of giving Mesoreodon only subgcneric rank. Neverthe- 

 less, in the skull and, to a less degree, in the dentition, we may observe numbers of 



