xii. 6 



VERTEBRAL COLUMN 



305 



Fig. 178. The skeleton of the frog, seen from the dorsal surface; the left 

 suprascapular and scapular have been removed. 



a. astragalus; c. calcaneum; d. suprascapular; e. exoccipital ; /. femur;//), frontoparietal; 

 g. metacarpals; h. humerus; i. ilium; k. metatarsals; /. carpus; m. maxilla; w. nasal; o. pro- 

 otic; p. pterygoid; pm. premaxilla; q. 'quadratojugal'; r. radio-ulna; J. squamosal; se. 

 sphenethmoid; s.v. sacral vertebra; t. tibio-fibula; u. urostyle. 

 (After Marshall, The Frog, Macmillan.) 



attached to the pelvic girdle and acts as a support by which the 

 movement of the hind limbs is transmitted to the rest of the body. 

 There is no longer any sinuous motion and the number of vertebrae 

 is very low (nine in the adult Ra?ia), and behind them is an unseg- 

 mented rod of 'hypochordal' bone, the urostyle. Shortening of the 

 body is a characteristic feature of the change from aquatic to terrestrial 



