CARNIVORA. 399 



of the Felidae, though retaining other skeletal features of a 

 more primitive type. These are the Nimravidse or Machae 

 rodontidae, which survived until the Pleistocene both in 

 Europe and in America and then became extinct. Some of 

 them retain the third trochanter on the femur, and also exhibit 

 traces of the primitive separation of the scaphoid and lunar 

 bones of the carpus. Nevertheless, their dentition is extremely 

 specialized, the upper canines being much enlarged and pro- 

 tected by the peculiar conformation of the anterior end of the 

 lower jaw, which eventually develops a flange (fig. 224). While 

 the upper canines increase in size, those of the mandible are 

 reduced until they are scarcely larger than the incisors. This 

 tribe of cats must have been differentiated quite at the dawn 

 of the Eocene ; for the earliest known form of mandible 

 (Eusmilus) referable to it exhibits the maximum reduction of 

 the teeth, and yet it dates back to the end of the Eocene 

 period. Hoplophoneus and Nimravus may be mentioned as 

 well-known American Miocene types; while Machcerodus is a 

 Miocene, Pliocene, and Pleistocene genus, apparently originating 

 in Europe, and eventually ranging over Europe, Asia, and North 

 and South America. 



Eusmilus. A genus known only by the mandible, and perhaps by 

 some upper teeth. The mandible is slender, with a truncated symphysis 

 which descends into a flange for the protection of the upper canine. There 

 are only two pairs of lower incisors, and the small lower canine immediately 

 adjoins them, being separated by a wide diastema from the cutting teeth, 

 which are reduced to one premolar (pm. 4) and a .sectorial molar (m. 1). 

 The last-mentioned tooth is a two-lobed blade without any trace of an 

 internal tubercle. The typical species is Eusmilus bidentatus, from the 

 Upper Eocene Phosphorites of Quercy, France, with the mandible 0'12 m. 

 in length. A slightly larger species (E. dakotensis) is indicated by a 

 mandibular ramus from the Lower Miocene (White River Formation) of 

 South Dakota, U. S. A. 



Hoplophoneus. This is the best-known Miocene genus of Nimravidse, 

 nearly the whole of the skeleton having been discovered. The dental 



, . i. 3, c. l,pm. 2 3, m. 1 



tormula is -^ , and the much-enlarged upper canine is 



i. o, c. i, pm. L, m. i 



laterally compressed, with finely serrated edges. The upper sectorial tooth 

 is trilobate, but without any internal tubercle ; while the lower sectorial 

 molar has a two-lobed blade, with a low heel behind but no internal 

 tubercle. The skull is very short and rounded, and there is a marked 



