172 FOSSIL REPTILES. 



tance, because its study enables us to form clear ideas on that 

 of the fishes, concerning which numerous and discordant 

 systems have been proposed. 



Relative to this point, we shall find that the successive sim- 

 plification and final disappearance of the auricular apparatus 

 in the batracian reptiles, and also the gradual development of 

 that of the hyo'id, notwithstanding the existence of a larynx 

 and sternum, will lead us to the idea that the bones of the ear 

 do not re-appear in the osseous fishes under the form of 

 opercula ; that the bronchial apparatus has no need to com- 

 plete its complicated formation by the intercalation of sternal, 

 laryngian, or costal pieces; and, in short, that the operculary 

 apparatus is one specially peculiar to the animals to which 

 nature has accorded it. 



As to the bones which compose the other parts of the body 

 of reptiles, the pieces which constitute them are so far from 

 being multiplied, like those of the head, that, in youth, they 

 not unfrequently want those portions of their extremities 

 called epiphyses. 



In the crocodiles and tortoises, the extremities of the bones 

 and their principal eminences are clothed with cartilages of 

 greater or less thickness, which harden and ossify with age. 

 They do not, however, as in the mammifera, form an osseous 

 nucleus, separated for a time from the body of the bone or 

 diaphysis by a suture. This is singular enough, as the sau- 

 rian reptiles, and particularly the monitors, exhibit epiphyses 

 strongly marked. 



Without a thorough investigation of the osteology of existing 

 reptiles of every genus, and without reducing this osteology 

 to general rules, it was impossible for the Baron to conduct 

 his researches on the fossil reptiles in a satisfactory manner. 

 The necessity of this led to views and details much more 

 extensive than those which the bones of mammiferous animals 

 had suggested. We shall accordingly (in proportion to our 

 limits) follow him more extensively into this department. 



