19 



connate with its entire length above the alveolus. There is 

 an indistinct cingulum around the entire crown. 



The fourth premolar has a very curious shape. The blade 

 of this tooth resembles the crown of the third, but is smaller- 

 It is inserted by three fangs, the disposition of which is oppo- 

 site to that in Canis, the internal, being on the same transverse 

 line as the posterior external, instead of the anterior, as in 

 Cams. From the internal fang arises a sharp cusp, which is 

 nearly as large as the blade of the tooth, the two are connate 

 at base. The anterior face of the crown is much worn, and 

 there is a small anterior heel formed by the basal ridge. The 

 cingulum is complete all around. 



The maxillary does not show the outward bulge at the 

 third premolar, which is so marked in the fox. The alveolus 

 is straighter, and the palatine plates are comparatively thicker 

 and flatter. The infraorbital foramen is oval, and not so 

 much compressed as in the fox, to which it corresponds very 

 nearly in position, though situated slightly forward as in Hyce- 

 nodon. 



Measure merits. 



Upper Jaiu. M. 



Length of third premolar .007 



Breadth of third premolar .004 



Length of fourth premolar .007 



Breadth of fourth premolar .007 



Lower Molars, from Dr. Leidy. 



Length of last premolar . 0075 



Length of first molar .009 



These exhibit nearly the same proportionate size as in the 

 gray fox. 



Genus . Species . 



Sacrum (Plate IX., Fig. 8). — This peculiar srcrum is com- 

 posed of only one true vertebra ; there may have been one or 

 more pseudo-sacrals, but this is not certain. 



The centrum is very long, strongly depressed, and straight 

 on the inner margin, not curved as in the sacrum of most 

 mammals. The anterior articular face is much depressed, and 



