T-ftyS-l The Kent's Hole Machairodus. 221 



Upper. Lower. 



Inner incisor . . 0*63 inch . . . 0*31 inch 



Middle do. . . 079 „ ... 0*39 „ 



Outer do. . . 0*98 „ ... 0*83 „ 



Canine do. . . 5*00 ,, ... 1*02 „ 



In the form of their crowns, the difference between the 

 incisors of the Felidce and Machairodus is very decided ; for, 

 instead of being chisel-shaped as in the former, every one 

 in the latter is thoroughly conical, extends to a simple 

 rounded point, and is slightly incurved throughout, the 

 point itself standing perpendicularly. Close to the point 

 are two more or less sharp edges, which run along both 

 sides of the crown and get thick and callous below. At the 

 bottom of the crown they turn inwards, get weaker, and 

 approach each other at an angle, which includes a blunt 

 and scarcely perceptible tubercle. These edges have also 

 slight notches corresponding to those of the under tusk. 



The conical form of the incisors, as well as the lancet- 

 like upper canines, shows in a high degree the bloodthirsty 

 nature of the Machairodus. Assuming, as very probable, 

 that the objects of his bloodthirstiness were the great 

 Edentata of South America — the Megatherium, Scelidothe- 

 rium, Mylodon, and Glyptodon — it is clear that a sharp 

 long-pointed set of teeth was necessary for killing animals 

 covered with a hard coat of mail, and only a beast of prey 

 like the Machairodus could have been able to kill them. 

 These large animals did not possess the means of adtive 

 defence. Even the powerful claws of their fore-legs were of 

 no use. For defence, they had only their clumsy figures 

 and coats of mail. The Machairodus, therefore, required 

 the long sharp tusks and pointed incisors to be able 

 to take hold of and kill his prey. The tusk of a tiger or 

 lion could not possibly have penetrated the skin of a 

 Mylodon or Glyptodon. It harmonises well with this 

 description that the South American species of Machai- 

 rodus possessed such great upper and relatively small lower 

 tusks ; as it was only there that the coated gigantic animals 

 existed. In Kaup's species the upper tusks were smaller 

 and the lower ones larger ; and Machairodus latidens, as re- 

 presented by Owen, differs still more from M. neogaeus. 

 The incisor figured by Owen has a thicker, but not a 

 shorter, crown than that of the same tooth in the Buenos 

 Ayres skeleton. This shows a much less disproportion in 

 M. latidens in the extent of the incisors and tusks, and 

 enables us to show this characteristic as a necessary con- 

 sequence of a difference of construction for their food. 



