10 The Life and Writings of Agassiz. 



therefore, to a certain extent, with Cuvier's division of fishes 

 into Acanthopterygians and Malacopterygians. 



The second order, that of the Ganoidians, seems to have a yet 

 more satisfactory foundation. There have been found in the 

 Nile and in the rivers of North America, two fishes which 

 have always puzzled the ichthyologists ; that of the Nile is 

 known under the name of Bichir {Folypterus Bichir) ; the other, 

 which is found iniAmerica, is called the Garpike (Lepidos- 

 feus), having some resemblance to the Pike. Both these 

 fishes are furnished with scales of very peculiar form and 

 structure. Instead of being arranged in the manner of roof 

 tiles, — as in most fishes, — they are placed simply side by side, 

 the surface being covered with a coat of enamel, making a 

 very solid cuirass. On examining these fishes in an anatomi- 

 cal point of view, M. Agassiz found that the skeleton pre- 

 sented no less striking differences than the scales and the 

 soft parts of the body. Nevertheless, it seemed hazardous 

 to separate them altpgether from the other great families ; 

 and, particularly when the smalless of their number was 

 considered, it seemed contrary to all method to place them 

 in the same rank with the Placoidians on one side, and the 

 Osseous fishes on the other. But the procedure, though not 

 authorised by the study of the living fishes, was justified by 

 an examination of fossil species. Here is displayed a whole 

 ichthyological fauna, having the characters neither of the Os- 

 seous nor of the Cartilaginous fishes, but altogether analo- 

 gous to the Bichir and the Lepidosteus. So that these two 

 genera, apparently mere exceptions in the present creation, 

 in reality constitute a type by themselves, which, though not 

 numerous at present, is, nevertheless, the expression of an 

 entire order of things. : Associating with these fishes the 

 numerous fossil species whose scales have the same struc- 

 ture, M. Agassiz made his division of Ganoidians, which al- 

 ready contains many hundred species, and promises to be- 

 come still larger, since it predominates in all the formations 

 anterior to the chalk. M. Agassiz recognises several dis- 

 tinct families of this order : the two principal ones are the 

 Sauroidians, to which the Lepidosteus and the Bichir belong ; 



