OSTEOLOGY OF THE CROCODILE. 677 



the dorsal and sternal ribs are, moreover, united by intervening cartilages, 

 which, as they are generally more or less perfectly ossified in the adult 

 Crocodile, might almost be regarded as additional elements of the thorax. 



(1884.) The posterior dorsal ribs are far less perfectly developed than 

 those situated more anteriorly; and it is not a little interesting to 

 observe how gradually, even in the same skeleton, the transition is 

 effected from the simple condition already noticed in the ribs of fishes, 

 in which each rib is merely appended to the extremity of the transverse 

 process of a vertebra, to ribs perfectly adapted to enter into the com- 

 position of a true thoracic cavity, and united by a double articulation 

 both with the transverse processes and the bodies of the vertebraa. The 

 head of the last rib of the Crocodile is, in fact, simple, and merely 

 articulated with the apex of the transverse process of the corresponding 

 vertebra ; the next is slightly bifid at its origin, but both the divisions 

 are still connected with the transverse process; as we advance still 

 further forwards, the division of the origin of the rib becomes more and 

 more decided, until at length, at about the fifth rib, we have two 

 distinct heads, one firmly articulated with the body of the vertebra, the 

 other with the transverse process presenting an arrangement precisely 

 similar to that met with in the structure of the thorax of a bird. 



(1885.) The sternal apparatus is not less interesting to the osteo- 

 logist. The anterior extremity of the sternum is osseous, and consider- 

 ably prolonged forwards, to be articulated with the clavicles, and thus 

 afford a support to the anterior extremity. Behind this it becomes 

 cartilaginous, and affords attachment to the sternal ribs, which enter 

 into the composition of the thorax : it does not, however, terminate at 

 the posterior margin of the thoracic cavity, but is continued along the 

 mesial line of the abdomen quite to the pubis, and gives off eight abdo- 

 minal sternal ribs t to which no dorsal correspondents are met with. 

 These abdominal ribs serve to support the muscles of the abdomen, and 

 here present their maximum of development : rudiments of them are, 

 however, still met with in the higher animals ; and even in the human 

 subject we find, in the transverse tendinous bands which intersect the 

 substance of the reetus muscle of the abdomen, the last remains of these 

 appendages to the sternal portion of the skeleton. 



(1886.) In the anterior extremity of the Crocodile we have most of 

 the parts enumerated as entering into the composition of a perfect or 

 typical skeleton : the shoulder, however, is composed of only two pieces, 

 the scapula and the clavicle, the last of which articulates with the 

 sternum; the bones of the arm, fore-arm, and hand are completely 

 developed. 



(1887.) The posterior extremities are fully formed, the pelvis being 

 connected by means of the ossa ilii to the transverse processes of two 

 vertebrae, which therefore, as we have seen, constitute the sacrum. 



(1888.) In examining the bones which enter into the composition of 



