Fig. 53.—Pelvic vertebre of young Alligator. 
Fig. 55.—Pelvic vertebrze of Bald Eagle. In the reptile, where there is no need 
for rigidity, only two typical pelvic vertebre are joined together; in the birds 
many dorsal and caudal vertebra are joined with these to make a rigid frame 
for flight and for bipedal locomotion. 76 
