468 CLASS REPTILIA. 



like a Y. ; it is embodied in the muscles, and seems in 

 some measure to represent the marsupial bones of the dil- 

 delphis. 



Under the body of the caudal vertebrae, from the thir- 

 teenth, is observable a small transverse lamina directed ob- 

 liquely backwards, and pierced with a hole at its base. 



There is but a mere vestige of the sternum, and it is more 

 membranous than cartilaginous. The ribs are so short, that 

 they seem to be mere transverse processes of the vertebras, 

 having but a single point of articulation on which they are 

 but triflingly moveable. These rudimentary bones are twelve 

 in number on each side. 



The shoulder is very curious, from the prompt synostosis 

 of its three bones into a single one, which bears the glenoid 

 fossa on its posterior edge, sends towards the spine a quadri- 

 lateral lobe, widened above, which is the omoplate, and 

 furnishes to the breast a rounded disk, composed of the 

 clavicle and coracoid bone, separated by a suture. 



This disk is constantly pierced by a small hole and sur- 

 rounded with a large cartilaginous plate of a crescent form, 

 which, under the breast, crosses with its congener. 



The spinal edge of the omoplate is surmounted by a carti- 

 laginous appendage. 



The scapulary head of the humerus is rounded. Below it 

 may be observed a compressed and obtuse tuberosity, and a 

 thick pointed process ; the first turned forward, and the 

 second backward. The two bones of the fore-arm are situated 

 one above the other. 



The carpus is composed of five bones, and two cartilages, 

 all flat and angular. The metacarpus has four short bones, 

 flat, and contracted in their centre. The toes are only four : 

 the first has but one ossified phalanx, the third has three, 

 and the second and fourth have two each. 



