AMPHIBIA. ANURA. 137 



The quadrate is not generally ossified. A pre-dentary or 

 mento-meckelian bone is commonly present in the mandible, 

 and a single bone represents the angular and splenial. The 

 branchial arches are much reduced in the adult, and the distal 

 ends of the cornua unite to form a flat basilingual plate of a 

 comparatively large size. 



Ribs are very little developed. Clavicles are present. 

 The ilia are very greatly elongated. The anterior limb has 

 four well-developed digits and a vestigial pollex, and is of 

 moderate length ; the radius and ulna have fused. The 

 posterior limb is greatly elongated and is pentedactylate ; the 

 tibia and fibula are fused, while the calcaneura and astragalus 

 are greatly elongated, and it is largely owing to them that 

 the length of the limb is so great. The group includes the 

 Frogs and Toads, the predominant Amphibia of the present 

 time. 



