"70 Recherches stir Ics Poissons Fossiles. 



scales, an exact means of tracing the natural affinities of all 

 fishes. It is quite indisputable, that the animals of this class 

 have in their squamous integuments, a peculiar character 

 which forms a distinct and independent system, enveloping 

 the animal, and entering into the most intimate relations 

 between the being and the external world by which it is 

 environed, as the feathers of birds and the hair of Mammaha, 

 etc. We conceive, therefore, that parts which change with 

 the condition of existence, in which the beings live, should 

 possibly, for this reason, correspond also with all the pe- 

 culiarities of internal organization, and therefore lead to cor- 

 rect conclusions. 



Here are the orders and the names of the principal families 

 comprised in our classification : — 



First Order : The Placoides. — So named, because of the 

 irregularities presented in the solid parts of their integu- 

 ments; these are deposits of enamel, of considerable dimen- 

 sions, or in numerous little points, as the shagreen of Rais, 

 Sharks, etc. 



The family of Cestraciontes, Agassiz, only contains a sin- 

 gle genus of which there are any species at present existing 

 on the earth, the genus Cestracion : the others are fossil, the 

 Hybodentes^ Agassiz, are also fossils ; then come the Squales 

 or Sharks, the Rais and the Cyclostomes. 



Second Order : The GANoiDES.— This division contains fa- 

 milies in appearance very different, but which have, however, 

 much affinity when examined closely, and arranged according 

 to their habits. The character which they all possess in com- 

 mon is, the angular form of their scales, which are composed 

 of two substances ; namely, horny or bony plates deposited 

 one under the other, and covered by a thick bed of enamel. 

 These scales are formed exactly as the teeth. 



We must place here the Lepidoides, Agass. which are all 

 fossils, the Sauroids id. likewise fossil, except two genera, the 

 Lepidostes of Bichir ; and the PycnodontSy Agass. also fossil ; 



