THE LIMBS. 189 



speaking, flat, but its surface has a considerable 

 curve from side to side, and also, though in a less 

 degree, in its long diameter. 



In those animals which belong to the typically 

 unguiculated or clawed groups the bone of the last 

 phalanx is long, but compressed from side to side, 

 curved, and pointed, and the two sides of the nail 

 bend completely round, so that their edges nearly 

 meet at the middle line of the back or under surface 

 of the finger or toe. In this way the nail becomes 

 converted into a claw, which forms a sheath sur- 

 rounding the bone. Usually, however, especially 

 near the base, the edges do not quite meet, and there 

 is a groove between them, filled up by softer epi- 

 dermic material. As it is important for the due ful- 

 fillment of the function of claws that they should 

 not be blunted by contact with the ground in walk- 

 ing, they are, in their most perfect condition, raised 

 at their ends, the toes resting on bare cushions or 

 pads placed beneath the joint between the middle 

 and ungual phalanx. 



When the horny covering of the last phalanx is 

 modified into a hoof, on which the animal habitually 

 rests and walks, the bone is generally broader and 

 shorter, and the nail is curled round into the form 

 of a short cylinder obliquely truncated, but with its 

 edges not meeting behind, and with the interval filled 



