CAENIVORA. 947 



The crowns of the premolars are simple, and narrow anteroposteriorly, 

 and without posterior lobe. They expand at the base both fore and aft, 

 but do not present basal tubercles. In the sectorial, tlie median cusp is 

 much more elevated than the anterior. Its posterior face is flattened- 

 convex, while its anterior cutting edge is acute. The cutting edge of the 

 anterior cutting ridge is horizontal, and is separated from that of the larger 

 cusp, by a deep closed notch. No trace of internal cusp. The heel is 

 shorter than the anterior lobe, and is about as wide as long. The inner 

 side of the median keel is concave, and is bounded below by a cingulum, 

 while the external side is convex, and has no cingulum. The second true 

 molar has two roots, and is longer than wide. It narrows posteriorly. Its 

 median cutting edge curves a little inwards anteriorly, and the external 

 base forms a small angle of the opposite side. No cingula. 



The deciduous sectorial differs from the permanent, in having a con- 

 cave heel (perhaps jjartly worn), and a slight angular trace of the internal 



cusp. 



Measurements. 



M. 



Length of four last molars on bases - 0140 



Length of permanent sectorial fore and aft 0050 



Length of heel of do 0010 



Elevation of anterior cnsp do 00;!0 



Elevation of median ctisp do 0045 



Diameters tubercular molar ^ '^"*^^°P°*'''"°^ ^'^- 



( transverse 0013 



Diameters sectorial of No. 2 ^ ' ^ 



( vertical of median cusp 0040 



Depth of ramus mandibuli, No. 2, at sectorial 0070 



Fi'om the White River beds of Northeastern Colorado, found by myself 

 with bones of Perathermm, Eiimys, Palceolagus, etc. It is quite possible 

 that the animal from the same locality which I named Canis osomm (see 

 Plate LXVII a), is the same, or a second species of the genus. The typical 

 specimen is not in a good state of preservation. 



NIMRAVID^. 



The dental characters of the Nimravidce are in general those of the 

 Felidce, the higher genera having the same dental formula. Descending the 

 scale, the number of molar teeth increases at both ends of tlie series in the 

 lower jaw, and anteriorly only in the upper, but the number of the true 



