RIBS. 



49 



Excepting the first, all the trunk vertebrae are usually provided 

 with ribs in Urodeles : ribless (lumbar) vertebrae are met with very 

 rarely (Spelerpes). 



Reptiles, Birds, and Mammals. In these, well-developed 

 ribs are always present, and more or fewer of them almost always 

 unite ventrally with a breast-bone or sternum. Those which 

 unite with the sternum are sometimes spoken of as "true," the 

 others as " false " ribs. 



FIG. 36. SKELETON OF THE TRUNK or A FALCON. 



S, scapula ; G, glenoid cavity for humerus ; Ca, coracoid, which articulates with the 

 sternum (St) at t ; Fu(Cl), furcula (clavicles) ; Cr, keel of sternum ; V, vertebral, 

 and Sp, sternal, portion of rib ; Un, uncinate process. 



The ribs of Snakes show the least amount of differentiation 

 for, without giving rise to a sternum, they extend along the whole 

 trunk from the third cervical vertebra to the anus, and retain 

 throughout a similar form and size. In Lizards, where a dorsal 

 bony and a ventral cartilaginous portion can be distinguished, three 



