534 LAND MAMMALS IN THE WESTERN HEMISPHERE 



On account of the very incomplete preservation of the 

 material so far collected, little is known of the fsabre-tooth 

 series in North America during the Pliocene and Miocene 

 epochs. Remains of very large cats have been found in the 

 lower Pliocene and upper Miocene, but it is uncertain whether 

 they belong to the feline or the fmachairodont subfamily. Some 



Fig. 263. — Skull of a tsabre-tooth tiger (^Machairodus pcUmidens) from the Miocene 

 of France. (After Filhol.) P. 4> fourth upper premolar, sectorial tooth. 



of the species have been referred to the genus ^Machairodvs, 

 which ranged from the lower Pleistocene to the middle Miocene 

 of Europe, and the reference may be correct, but is uncertain. 

 However, the European representatives of that genus, which 

 are much better known, will serve to show the developmental 

 stage from which ]Smilodon was undoubtedly derived. The 

 dental formula was the same as in the American genus, though 

 there were generally two premolars in the lower jaw and in ^Smi- 

 lodon generally but one ; the individual teeth were formed on 

 the same plan as in the latter, but were relatively smaller, and 

 the very small, rudimentary upper molar was visible externally 



