PHYLUM CHORDATA 



471 



-fi 



-ts.mlls 



E'-S 



backwards from their dorsal or acetabular ends, and lie 

 nearly parallel. Neither is- 

 chium nor pubis unites ven- 

 trally with its fellow to form 

 a symphysis. 



In the hind-limb the femur 

 (Fig. 284,/^) is a compara- ye- 



tively short bone. Its proxi- 

 mal extremity bears a promi- 

 nent trochanter (tr) and a 

 rounded head (hd) . Its dis- 

 tant end is produced into 

 pulley-like condyles. Articu- 

 lating with the femur is a 

 very long bone, the tibio- m s . 



tarsus (ti. ts) ; its distal end 

 is pulley-like, not concave 

 like the corresponding ex- 

 tremity of the tibia of other 

 Amniota. The study of its 

 development shows that the 

 pulley-like distal end of the 

 bone (Fig. 285, ti 1 ) con- 

 sists of the proximal tarsals, 



— astragalus and calcaneum, 7ruh.i 



— which at an early period 

 unite with the tibia and give fik./ } 

 rise to the compound shank- 

 bone of the adult. The fibula 

 (Fig. 284,7?) is verv small, 

 much shorter than the tibia, 

 and tapers to a point at its 

 distal end. 





