26 THE VERTEBRATE SKELETON. 



transverse processes of the sacral vertebrae, by means of 

 rudimentary ribs. The pubes and ischia generally meet in 

 ventral symphyses. 



2. THE LIMBS. 



It will be most convenient to defer a discussion of the 

 limbs of fishes to chap. vm. 



All vertebrates above fishes have the limbs divisible into 

 three main segments : 



Anterior or Fore limb. Posterior or Hind limb. 

 Proximal segment. upper arm or brachium. thigh. 



Middle segment. fore-arm or antibrachium. shin or cms. 



Distal segment. manus. pes. 



The proximal segments each contain one bone, the hume- 

 rus in the case of the upper arm, and the femur in the case 

 of the thigh. The middle segments each contain two bones, 

 the radius and ulna in the case of the fore-arm, and the tibia 

 and fibula in the case of the shin. 



The manus and pes are further subdivided into 



(a) two or three proximal rows of bones forming the 

 wrist or carpus in the case of the manus, and the ankle or 

 tarsus in the case of the pes. 



(b) a middle row called respectively the metacarpus 

 and metatarsus. 



(c) a number of distal bones called the phalanges 

 which form the skeleton of the fingers and toes, or digits. 



Typically the manus and pes both have five digits (pente- 

 dactylate). The first digit of the manus is commonly called 

 the pollex, and the first digit of the pes the hallux. 



In a very simple carpus such as that of Chelydra, there 

 are nine bones. They are arranged in a proximal row of 



