76 THE MAMMALIA OF THE DEEP RIVER BEDS. 



The sectorial is very like that of Cynodesmus ; it is marked by a very short 

 (antero-posteriorly) paraconid and high conical protoconid, which has a very steeply 

 inclined anterior edge; the talon, however, is somewhat more modernized by the 

 increase in size of the entoconid, which bears about the same proportion to the hypo- 

 conid as in Canis latrans, and, as in that species, a minute cusp is present between 

 the base of the metaconid and the entoconid, which does not occur in Cynodesmus. 

 The second molar is like that of C. latrans, except for the larger size of the ento- 

 conid, which in the modern species is reduced to a mere ridge. The third molar is 

 missing, but its alveolus shows it to have been larger than in the coyote, and the 

 fragment of mandible displays a deeper and thicker horizontal ramus than in that 

 species. 



Measurements. 



M. 



Length of first lower molar (anteroposterior) 017 



Length of second lower molar .008 



Length of third lower molar alveolus 006 



Depth of mandible beneath m. 1 021 



The type specimen of this species was found in : the Cyclopidius beds of the Deep 

 Eiver by Mr. I. Benet. 



RODENTIA. 



Castoridae. 



STENEOFIBER 



This genus may be distinguished from the nearly allied Castor not only by the 

 simpler pattern and less markedly prismatic character of the molar teeth, but also 

 by the absence of coossification between the fibula and tibia. In the American spe- 

 cies the humerus always has an epicondylar foramen. 



STENEOEIBER MONTAGUS Scott. 

 Amer. Naturalist, 1893, p. 660. 



This species is most like the S. (Castor) peninsulatus Cope, from the typical 

 John Day horizon, but differs from it in some details of molar construction. In the 

 upper molars, except mj?, there are but two fossettes, both of which are anterior to 

 the external enamel inflection; the latter also is nearer to the posterior border of the 

 crown than in the other species of the geuus. In the lower molars there is, as in the 

 other species, "a deep external enamel inflection and three transverse lakes on the 

 inner side;" but different from any of the other members of the group, the external 



