262 THE VERTEBRATE SKELETON. 



slender curved bones, the abdominal ribs (fig. 46, 4). Each 

 series consists of four or more bones, arranged in a V-like 

 form with the angle of the V directed forwards. They show a 

 considerable amount of variability in number and character. 

 They are really membrane bones, and are in no way homolo- 

 gous with true ribs, but correspond rather with the more 

 posterior of the bones constituting the plastron of Chelonia. 



2. THE APPENDICULAE SKELETON. 



This includes the skeleton of the two pairs of limbs and 

 their respective girdles. 



FIG. 47. LEFT HALF OF THE PECTORAL GIBDLE OF AN ALLIGATOB (Caiman 

 latirostris) x f . (Brit. Mus. ) 



1. scapula. 3. interclavicle. 



2. coracoid. 4. glenoid cavity. 



THE PECTORAL GIRDLE. 



The pectoral girdle of the Crocodile is less complete than is 

 that of most reptiles. It consists of a dorsal bone, the 



