HISTORY OF THE CARNIVORA 533 



one of the great modern cats, such as the Lion or Tiger; 

 with extremely shortened face, heavy and widely expanded 

 zygomatic arches and very prominent sagittal crest. The 

 tympanic bullae were large and inflated, each divided by a 

 septum into two chambers, but were not visible from the side, 

 being covered externally by very large processes, which served 

 for the attachment of some of the great muscles of the neck. 

 The short, rounded, bullet-head of the true cats was thus 

 repeated, but there were in the skull several interesting dif- 

 ferences of detail, which it is not worth while to enumerate 

 here. Sufl&ce it to say, that some of these differences were due 

 to the retention of primitive characters in the skull of ^Smilo- 

 don, which have been lost in the modern feUnes, and others to 

 special developments, in which the true cats did not share. 

 The lower jaw had on each side a small, descending flange for 

 the protection of the tusks, which, however, projected well 

 below these flanges when the jaws were shut. The neck 

 was heavy and the structure of its vertebrae was such as to 

 suggest the presence of unusually powerful muscles ; the back 

 and loins were also uncommonly stout, in the larger species 

 heavier than in the Lion or Tiger, but, in marked distinction 

 from those modern forms, the tail was short. The hmbs were 

 shorter and much heavier in relation to the size of the body 

 than in the great existing cats and must have been extremely 

 powerful. The humerus usually had no epicondylar foramen, 

 which all the true felines possess, though it was sometimes pres- 

 ent. The feet also were very stout and armed with large retrac- 

 tile claws ; the base of each claw was covered by a thin bony 

 hood, an outgrowth of the ungual phalanx, which is very char- 

 acteristic of the entire family. The hind foot had five digits, 

 whereas no existing cat has more or less than four. The ap- 

 pearance of these animals must have been very much hke that 

 of the Lion or Tiger, aside from the unknown factors of mane 

 and colour-markings, but differed in the great tusks, the short 

 tail and the shorter and more massive legs and feet. 



