1880. ] On the Extinct Cats of America. 853 
Upper, Lower 
Eoc ocene. Miocene 
| Aa 
| Eur. | Eur. Am. 
Upper 
Miocene. | Pliocene. 
Eur.| Am.| 45/2 Am. 
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E R ine 3.1 AELE R TA x 
As already remarked, the genera of the Nimravine and Drepa- 
nodont lines are extinct, and this in spite of the fact that they pre- 
sented the most perfect weapons of destruction in their canine 
teeth, from the earliest times. Their other modifications of 
structure advanced, pari passu, with those of the feline series, and, 
among others, the feet presented in the latter forms at least (e. g., 
Smilodon necator, Gerv.), the most perfect prehensile power of the 
lions and tigers of to-day. As nothing but the characters of the 
canine teeth distinguished these from the typical felines, it is to 
these that we must look for the cause of their failure to continue. 
Prof. Flower’s suggestion appears to be a good one, viz: that the 
length of these teeth became an inconvenience and a hindrance to 
their possessors. I think there can be no doubt that the huge 
canines in the Silodons must have prevented the biting off of 
flesh from large pieces, so as to greatly interfere with feeding, 
and to keep the animals in poor condition. The size of the ca- 
nines is such as to prevent their use as cutting instruments, ex- 
cepting with the mouth closed, for the-latter could not have been 
opened sufficiently to allow any object to enter it from the front. 
