544 



LAND MAMMALS IN THE WESTERN HEMISPHERE 



in the upper jaw. The upper sectorial has a large shearing 

 blade, with well-developed anterior accessory cusp, and the 

 inner cusp, which in ^Smilodon had almost disappeared, is 

 quite large and carried on a separate root. The lower sectorial 



is composed of two cusps only, all traces 

 of the heel and of the inner cusp having 

 disappeared. The single upper molar 

 is very small and usually concealed 

 by the sectorial. The skull is very 

 short and broad, and the shortening of 

 the jaws gives great power to the biting 

 muscles, because of the more favourable 

 leverage. The zygomatic arches are 

 very stout and curve out boldly, con- 

 tributing much to the rounded shape 

 of the head ; the orbits are almost encircled in bone. The 

 large tympanic bullae are two-chambered and there is no ali- 

 sphenoid canal, but in several other respects the base of the 

 cranium differs markedly from that of fSmilodon. The lower 



Fig. 269. — Dentition of Lynx 

 (/y. rufus), left side. i. 3, 

 external upper incisor, i. 1 , 

 first lower incisor, c. = canine. 

 p. 3, p. 4, third and fourth 

 premolars, m. 1, first molar. 



tj--^.7 



Fig. 270. 



Upper teeth of Puma {Felis concolor), left side. p. 4, fourth 

 premolar, m. 1, first molar. 



jaw is without flanges and there is no angle between front 

 and sides. 



The neck is short, the body long and the tail is long in most 

 of the species, but short in the lynxes. The limbs are relatively 

 longer and less massive than in ^Smilodon, and there are five 

 toes in the manus, four in the pes ; the claws are hooded and 

 retractile. 



