PAIRED LIMBS 



557 



plantigrade insectivore such as a hedgehog, although even here 

 there are speciahsations such as the loss of the centrale (present 

 in the mole) and the fusion of radiale and intermedium. The 

 commonest type of development is an elongation of the hands 

 and feet, so that the animal walks on the phalanges of its digits 



Fig. 434. — Skeleton of Pterodactyl X i. (Guide to Fossil Birds, Reptiles, etc., 



British Museum [Natural History], I934-) 

 (a) Pubic bone. 



(digitigrade) or on the nails at their tips (unguligrade) . The rabbit 

 (Fig. 335) is a rather bad example of a digitigrade animal, the 

 cat or dog (Fig. 435) is a better one. The limbs are capable of 

 Httle movement except in the fore and aft plane, so that there 

 is a tendency for fusion of the bones of forearm and shank, and 

 for the development of pulley-like joints. The chief unguligrade 

 mammals are the artiodactyls and perissodactyls, which show a 

 reduction of digits which is achieved in different ways in the 



