312 



AMPHIBIA 



xn. 8- 



extension of the precoracoid cartilages. This structure, although 

 present in some arciferal girdles (e.g. Leptodactylidae), is more usually 

 associated with the firmisternal pattern and a jumping habit. 



The shoulder girdles of modern urodeles are greatly simplified, the 

 only ossification being a scapulo-coracoid encircling the glenoid. The 

 two epicoracoids overlap broadly, and anteriorly are quite free of 

 each other; posteriorly they are usually rather weakly locked by a 



LEPTODACTYLUS 



Fig. 183(a). Leptodactylus pragnathus. Ventral view showing sternal articulation with 

 girdle. The left half of the ventral sternal blade has been removed. Labelling as in Fig. 1 83 . 



cartilaginous sternum. The Apoda, of course, retain no vestiges of 

 either limbs or limb girdles. 



9. Pelvic girdle of Amphibia 



The pelvic girdle is much larger in land animals than the small 

 ventral cartilages found in fishes. It is formed of three main cartilage 

 bones in all tetrapods (Fig. 184), but it is not clear how these origin- 

 ated, nor whether the division has mechanical significance. The dorsal 

 ilium becomes attached to specially modified transverse processes of 

 one or more sacral vertebrae. This ilium can be regarded mechanically 

 as the ossification along a line of compression stress due to the weight- 

 bearing. 



The ventral portion of the girdle consists of an anterior pubis and 

 posterior ischium, the three bones meeting at the acetabulum, where 



