38 THE FROG 



231. The urostyle (coccyx) represents the fused caudal 

 vertebrae. Note the small apertures by which the 

 tenth spinal nerve emerges. 



Examine the breast bone from the ventral aspect, identify- 

 ing the following bones: 



232. At the cephalic end is the episternum, with a carti- 

 laginous plate projecting from it cephalad. At the 

 caudal end it articulates with 



233. two derm-bones (not part of the sternum proper), 

 the clavicles, which run laterad to the scapulae 

 (236). 



234. Caudad of the clavicles are two stout transverse 

 bones, the coracoids, elements of the pectoral girdle. 



235. The most caudal structure is the sternum, terminat- 

 ing in a cartilaginous plate. 



Examine the pectoral appendage, shoulder and arm, and 

 identify the following bones. The girdle consists of the 

 coracoid (2Z^), and a cartilaginous procoracoid partially 

 covered by the clavicle (2ZZ), and two other elements (^236 

 and 237j. 



236. The scapula is a lateral element bearing on its 

 lateral margin a notch, the glenoid fossa, the re- 

 mainder of which is formed by the coracoid. 



237. The dorsal bone is the suprascapula. 



The free appendage contains twenty-three bones; identify 

 the following: 



238. The proximal bone is the humerus, fitting into the 

 glenoid fossa. 



239. Distal to this is the radio-ulna, resulting from the 

 fusion of the radius and ulna of the embryo. 



240. This is followed by the carpus or wrist containing 



