72 



OSTEOLOG1CAL GALLERY. 



for swimming, as are those of the second group. The zygoma is 

 broad and powerful, in correlation with the great development of 

 the biting-muscles, and the lower jaw is articulated to the cranium 

 by a closely fitting transverse hinge, which gives great strength and 

 firmness to the joint, but entirely deprives the animal of the power 

 of moving this jaw backwards and forwards, or from side to side, its 

 only motion being in a vertical direction. The varied and highly- 

 developed dentition differs from that of other Mammals by the 

 development of the last premolar of the upper jaw and the first - 

 molar in the lower into the so-called " sectorial " teeth, which are 

 specially adapted for cutting up animal food. The shape of these 

 teeth is highly characteristic of the different genera. 



The Cats, or Felidce (Case 4, Divs. A to D), the most highly 

 developed of the Carnivores, have unusually long and powerful 

 canine teeth, admirably suited for seizing and killing their prey, 

 and sharp-edged scissor-like sectorial teeth, equally well adapted 

 for cutting up flesh or breaking and crushing bones, which form 

 an essential part of their food. The actual number of teeth, 

 however, is much reduced, the dental formula being 1. 1, C. ], 



Fig. 31. 



'a a 



Bones of toe of Cat. A, with retracted, and B, with extended claw. 



, tendon of extensor muscle ; b, retractor ligament ; me, metacarpal ; 

 ph (1, 2, and 3), 1st, 2nd, and 3rd phalanges ; s, bony sheath, into 

 which the claw is fixed. 



Pm. f , M. \ x 2= 30 ; and the whole jaw is shorter in comparison 

 with the length of the head, and therefore proportionally stronger. 



