xxi] 



SKELETON OF THE LIMBS 



551 



proved to be composed of a portion budded off by the conjoined 

 epicoracoids. The sternum is supposed to be the first sign of the 

 breast-bone of higher Vertebrates, and it is almost certainly formed 

 as a piece budded off from the conjoined epicoracoids behind. 



In the arm the two points to be noticed are the complete fusion 

 of the radius and ulna into one bone, and the reduction of the 

 carpus, in which there are only six bones, three of the distal small 

 bones having coalesced and the centrale being absent. The first 

 digit or pollex is rudimentary. 



In the pelvic girdle there is no epipubis : the ilium is a very 

 long cylindrical bone : the ischiurn ossifies most of the ischiopubic 



FIG. 272. Shoulder-girdle and sternum of 



A. An old male Common Frog, Rana temporaria. 



B. An adult female Toad, Docidophryne gigantea. To illustrate the difference 

 in structure between Firmisternia and Arcifera. Both figures after Parker. 



In both A and B the left suprascapula is removed. The parts unshaded 

 are ossified ; those marked with small dots consist of hyaline cartilage, those 

 marked with large dots of calcified cartilage. 



1. Calcified cartilage of suprascapula. 2. Ossified portion of suprascapula. 



3, Scapula. 4. Coracoid. 5. Epicoracoid. 6. Precoracoid. 



7. Clavicle. 8. Glenoid cavity. 9. Coracoid foramen. 10. Epi- 



sternum. 11. Omosternum. 12. Sternum. 13. Xiphisternum. 



cartilage and is closely applied to its fellow. In the leg the tibia 

 and fibula are fused into one bone, which is about the same length 

 as the femur. The ankle is remarkably elongated, the tibiale arid 

 the fibiale being long cylindrical bones, easily mistaken for the 

 middle segment of the limb. The distal bones of the tarsus have 

 nearly disappeared, only two or three small nodules being present 

 on the axial side. The longest toe is the fourth, that correspond- 

 ing to the human big toe (hallux) is the shortest. It is a matter 

 of great interest to see on the inner side of the foot a spur 

 supported by a small bone which may be the vestige of a sixth 



