150 THE MAMMALIA OF THE DEEP RIVER BEDS. 



rowed inferiorly and expanding into a transverse oval above. The premaxillaries 

 have a high and broad alveolar portion which forms an abruptly truncated muzzle ; 

 the two bones are ankylosed at the symphysis. The ascending rami are short and 

 have broad, flattened anterior faces. The palatine processes of the premaxillaries 

 are very limited, while the incisive foramina are quite large and extensively emargin- 

 ate the palatine plates of the maxillaries. The last-named processes are both long 

 and broad and of nearly uniform width, the two series of teeth diverging but little 

 posteriorly. The palatines are very large and form nearly half of the roof of the 

 mouth. Transversely, they extend almost to the molar alveoli, and anteriorly they 

 are carried as far as the middle of m. 1 ; they are of uniform width, except behind the 

 molars, where they are constricted by the broad palatine notches. The posterior 

 nares are not indicated in the specimen, but obviously they were placed far back, as 

 the palatines are preserved for some distance behind the last molar. 



Measurements. 



M. 



Length of molar-premolar series 084 



Length of premolar series 041 



Length of ik2_. 010 



Width of p_2. 000 



Length of p^3. 011 



Width of pj? 011 



Length of p^4 009 



Width of p^4 012 



Length of true molar series 043 



Length of m. 1 012 



Width of m. 1 012 



Length of m. 2 017 



Width of m. 2 013 



Length of m. 3 020 



Width of m. 3 014 



MERYCOCIKERUS Leidy. 



Proceeds. Acad. Nat. Sci. Vltila., 1858, p. 24. 



The collection contains nothing from the lower Deep River beds which can be 

 confidently referred to this genus, but there can be no doubt that they occur in those 

 beds because of their abundance both in the John Day and in the Loup Fork. On 

 the other hand, the upper strata of the Deep River valley yielded specimens of Mery- 

 cochcerus in profusion. Among these specimens there is great variation in size, and 

 other characters as well, so great as apparently to indicate more than one species, but 

 the only one which can be definitely identified is the M. montanus Cope. 



