562 



STRUCTURE OF VERTEBRATES 



coracoid. In modern forms it is sometimes the coracoid 

 and sometimes the precoracoid which is missing, but as the 



names were given to the 



Prepubic 

 process . 



Obturator 

 foramen. 



I a urn. 



bones before the original 

 tripartite division was 

 known, any ventral element 

 is usually called coracoid, 

 irrespective of which bone 

 it represents. The three 

 bones in each girdle all 

 contribute to the articular 

 surface for the limb — glenoid 

 in the shoulder and acetab- 

 ulum in the hip. 



The ventral element in 

 the frog's shoulder girdle is 



/schium. 

 ^Acetabulum. 



Fig. 439— Right half of pelvic girdle of lizard ^ precoracoid. By Contrast 

 (Uromastix) in ventral view. the pubis remains Cartil- 



aginous, but the most 

 striking thing in the pelvic girdle is the great length of the ilia 

 which stretch forward to join the ninth vertebra. Such a junction 

 between hip girdle and backbone is called a sacrum. It is common 



Presp/nous fossa 



Clavicle 



Coracoid 



Head of humerus. 



Scapula 



7Ea*/ 



Fig. 440. — Shoulder girdle of man, from the side and slightly from the front. 



for the pubes and ischia to meet in a ventral symphysis, but 

 such a junction of the coracoids as occurs in the frog is unusual. 

 The reptiles have various types of shoulder girdle, but in general 

 in modern forms the scapula, precoracoid, clavicle, and inter- 

 clavicle are well developed (Fig. 438). The same is true of the 



