522 



LAND MAMMALS IN THE WESTERN HEMISPHERE 



One {\Pachycyon) , from a cave in Virginia, had remarkably 

 short, stout and strongly curved limb-bones, which suggest otter- 

 like habits ; the other {]Hijcenognathus), from California, had 

 a very short face and extremely massive lower jaw and very 

 heavy teeth ; it was probably like a hyena in appearance. 



As far back as the Blanco stage of the middle Pliocene, 

 remains occur which are assigned to the modern genus Canis, 

 though better preserved specimens would probably require their 

 removal from that genus. In the lower Pliocene the phylum 

 of the true wolves was represented by '\Tephrocyon, which, so 

 far as it is known, differed only in minor details from Canis, 



Fig. 255. 



-Skull of tCynodesmus thooides, a lower Miocene wolf. Princeton University 

 Museum. Compare with Fig. 7, p. 62. 



and '\Tephrocyon went back to the middle Miocene. What 

 would appear to be its direct ancestor is "fCynodesmus, of the 

 lower Miocene, which, in view of the long lapse of time involved, 

 differed less from the modern wolves than one would have 

 supposed, but the differences are significant, as pointing back 

 to a far more primitive type of structure. ^Cynodesmus was 

 a small animal, intermediate in size between a Red Fox and 

 a Coyote. The dental formula was the same as in Canis, 

 but the teeth were relatively smaller and more closely crowded, 

 as the face and jaws were shorter and the cranium, though 

 longer, had a less capacious brain-chamber. The cast of 

 this chamber, which very perfectly reproduces the form of 

 the brain, shows that the latter was not only smaller but less 



