HAP. Xil.] 



BIFFEBENT KINDS OF GATS. 



433 



individuals of this genus, tlic first inferior premolar may have but 

 one root, or may even be wanting altogether, thus carrying the 

 reduction of lower teeth to an extreme. In the development of the 

 upper canines the Machccrodonts are separated from the general 

 condition of the cat tribe, not merely in that they were so immense, 

 but that their length necessitated a pecuhar mode of use, so that 



Fi". 184.— Skull of Mach^rodus smilodon. 



these creatures may be said to have initiated a new and very special 

 modification of cat-existence. 



§ 16. Another fossil form of cat has been named IIoplophoneus * 

 by Professor Cope, who represents it as like Machaerodus in having 

 the mandible vertically expanded and the upper canines more or less 

 largely developed, but as difiering from it and from all existing cats 

 in that the inferior sectorial has a posterior lobe or " heel," while 

 the superior sectorial has no anterior lobe, such as that which exists 

 (Figs. 12 and 46) in all living cats. Its upper molar is largely 

 developed (Fig. 185, B) and there is no inferior tubercular molar. 



It is a miocene genus, founded on fossils from the White Rivers of 

 Nebraska and Colorado. 



* See Annals and Magazine of Natural 

 History for Januaiy, 1880, p. 39 ; see 

 also Bulletin of the United States Geo- 



logical Survey, 7tli Eeport, p. 509 ; and 

 the Proceedings of the Acad, of Nat. So. 

 of Philadelphia, July 8, 1879. 



F F 



