THE SKELETON IN AMPHIBIA. ANTERIOR LIMB. 185 



The shoulder-girdle of Anura is however subject to con- 

 siderable variations. In the Toads (Bufonidae) the epicora- 

 coids or unossified ventral ends of the coracoids and pre- 

 coracoids overlap in the middle line (fig. 30, B, 5). This 

 arrangement is called Arciferous. In the Frogs, Ranidae, 

 and other forms belonging to the group Firmisternia, the 

 epicoracoids do not overlap but form a narrow cartilaginous 

 bar separating the ventral ends of the coracoids (fig. 30, A, 5). 



ANTERIOR LIMB. 



In many Amphibia and especially in the Urodela the 

 anterior limb has a very simple unmodified arrangement. 

 The humerus is straight and of moderate length, its ends are 

 rounded for articulation on the one hand with the shoulder- 

 girdle, and on the other hand with the radius and ulna. In 

 the Urodela the radius and ulna are distinct. In the Anura 

 they have fused, though the line of junction of the two 

 is not obliterated. Their proximal ends are hollowed for 

 articulation with the convex end of the humerus. 



The manus in all recent Amphibia agrees in never having 

 more than four complete digits, but is subject to considerable 

 variation, this statement applying especially to the carpus. 



In the larva of Salamandra (fig. 31, A), except that the 

 pollex is absent 1 , the inanus retains completely the condition 

 which is generally regarded as primitive for the higher 

 Vertebrata. It consists of an anterior row of three elements, 

 the ulnare, intermedium, and radiale, and a posterior row 

 of four, the carpalia 2, 3, 4, and 5. Interposed between the 

 two rows is a centrale. Menobranclius has a similar very 

 simple carpus. In most other Amphibia this simplicity is 

 lost. This loss may be due to : 



(a) fusion of certain structures, e.g. in the adult Sala- 

 mandra the intermedium and ulnare have fused, 



1 The first digit present is sometimes regarded as the pollex, but from 

 analogy with Anura it is probable that tbe pollex is the missing digit. 



