SKELETON. 41 



when quite young these Batrachians present a con- 

 dition similar to that which persists throughout life in 

 the other families. 



A cartilage in the median line in front, supported 

 by a bony style in Bana, is the so-called omosternum ; 

 a larger one behind is the sternum. This is also 

 provided with a bony style in Rana s Pelodytes, and 

 Pelobates ; or a portion of it may be calcified, as in 

 Hyla and Bufo. In the Discoglossidse the sternum is 

 produced into two posteriorly diverging cartilaginous 

 or calcified styles. 



The shoulder-blade is divided into two parts, the 

 ossified scapula proper and the supra-scapula, carti- 

 laginous or incompletely ossified, bent over at an angle 

 to the scapula. 



The prascoracoid enters the glenoid cavity in the 

 Discoglossidx, Bufonidse, and Hylidse, but not in the 

 three other families, where the cavity is formed by 

 the scapula and coracoid. 



The humerus is a feebly curved bone with a globular 

 distal condyle and a strong prasaxial crest, which is 

 more developed in males than in females, and which 

 in the former may be supplemented by a second crest 

 lower down. The head is replaced by an epiphysis, 

 which calcifies late, or never as in the Discoglossidse and 

 Pelobatidss. The radius and ulna are fused to a single 

 bone, which is shorter than the humerus. The ulnar 

 part projects beyond the radius at the articulation 

 with the humerus. 



The carpal bones vary from six to eight. In the 

 more primitive carpus, such as is represented by the 

 Discoglossidse (Fig. 17, a), we find, following the 

 nomenclature of Howes and Ridewood, two elements 

 in contact with the radius-ulna, the radiale and ulnare ; 

 two, regarded as centralia, in the second row; and 

 four, plus a vestigial ligamentous fifth, in the third 

 row. The fourth distal carpale may fuse with the 

 outer centrale, as in Pelodytes (b), or also with the 

 third distal element, as in Bufo, Hyla, and Bana (c). 



