30 ON THE EXTINCT MAMMALIA OF 



ramus is broken off on both sides, but sufficient remains to indicate that it was con- 

 structed as in the animal just named, and not as in the Gray Fox, Canis virginianus. 

 The measurements of the specimen, in comparison with those of a lower jaw of the 



recent Canis velox, are as follows : 



C. vafer. C. velox. 



Space occupied by the inferior molars, . . .21 lines. 22 lines. 



Depth of the jaw at the sectorial molar, . . . 6 " 6i " 



Depth of the jaw just back of the symphysis, . . 4j " 4 J " 



Antero-posterior diameter of the sectorial molar, . . 5i " 5i " 



Canis Haydeni. 



An extinct species of Wolf, distinguished by the above name, of more robust pro- 

 portions than any now in existence, is indicated by a fragment of the right side of a 

 lower jaw, from the Niobrara Eiver. 



The specimen is represented in figure 10, plate I. The jaw contains the sectorial 

 molar and the preceding two premolars, very much worn, and therefore indicating an 

 aged individual. It also contains the sockets of both tubercular molars. 



The jaw fragment has the same form as the corresponding portion in the American 

 Wolf, Canis occidentalis, or the European Wolf, Canis luptis, except that its ramus 

 ascends a relatively shorter distance from behind the position of the sectorial molar. 

 In consequence of the latter circumstance the tubercular molars appear crowded in 

 position in comparison with their condition in the recent species just mentioned; 

 and the last tooth was even directed forward from the ascending border of the ramus 

 above the level of the worn heel of the sectorial molar. 



The teeth remaining in the specimen, so far as can be judged in their worn con- 

 dition, have had the same form and relative proportions as in the recent Wolves 

 above named. 



The last tubercular molar differed from the corresponding tooth of recent Wolves, 

 and also from that of the extinct allied Amphicyon and Cynodon, in its having had 

 two fangs, well separated, as indicated by the remaining pair of alveoli. The fangs 

 of the first tubercular tooth were widely separated. 



A pair of vasculo-neural foramina, communicating with the inferior dental canal, 

 are situated below the back pair of premolars. 



The huge species of extinct Wolf indicated by the fossil was dedicated to its 

 discoverer, Dr. Hayden. 



The measurements of the specimen, compared with those of the corresponding 

 portion of the jaw and teeth of a large skull of the American Wolf, Canis occidentalis, 

 from Oregon, and a nearly equally large one of the European Wolf, Canis lupus, from 

 Germany, presented to the Academy by Prince Maximilian de Wied, are as follows : 



