44 



covered. By the information thus acquired, it is possible to determine whether a 

 fish inhabited river, lake, or pond, the open sea, or the shallow waters ; whether 

 it lived on the surface, or frequented the great depths. These indications may 

 serve to determine divers important circumstances in the formation of rocks. 



Another peculiar advantage resulting from the study of Fossil Fishes is, that 

 the examination invariably makes us acquainted with the whole organization, and 

 affords a perfect idea of its pristine condition. Such researches must consequently 

 lead to results much more satisfactory than the study of the Mollusca, of which 

 only the shells have been preserved ; and more general than that of the Mammi- 

 fera, the whole skeleton of which is rarely discovered, and that only in the most 

 recent strata. The Reptiles, even when more generally known, can scarcely emu- 

 late the fishes in importance : since they are of rarer occurrence, and were deve- 

 loped at a later period in the series of creations. 



Fossil Fishes differ according to the great geological formations in which they 

 are found ; and exhibit, in each, a peculiar character of organization sufficient for 

 their determination. They differ the more widely from the fishes of the existing 

 period, as they are found in formations of a more ancient date. All the bony 

 fishes anterior to the chalk, are referrible to genera, which have no longer repre- 

 sentatives in the present world : they are invariably characterized by rhomboidal 

 scales covered with enamel. Those of the same formations, which, in the present 

 System, would be associated with the Chondropterygii, possess, like the genus 

 Cestracio, flattened, dotted, or differently plaited teeth. 



Comparisons thus multiplied, justify, in the opinion of the Professor, an alte- 

 ration in the arrangement of Fishes ; which will frequently indicate affinities 

 hitherto unknown : and the new classification, which he advocates, is intended to 

 expose the whole of the natural relations of fishes with each other, and their suc- 

 cession in the series of formations. General geological considerations, moreover, 

 drawn from the study of these fossils, will exhibit the connection which exists be- 

 tween the organic development of the earth, and that of the different Classes of 

 animals. These ideas will be completed by the organic representation of each of 

 the great geological periods. 



Great pains have evidently been taken, by Professor Agassiz, in examining 

 the various organs of fishes found in a fossil state, and in discovering the charac- 

 ters proper for their distribution into families, genera, and species. With this 

 view, he has applied himself, in an especial manner, to the study of the skeleton 

 of fishes, and to the microscopic inspection of several thousands of scales belong- 

 ing to more than two hundred species of different genera and families. 



As regards the publication of the work, the first volume will be devoted to an 

 examination of all the general questions. It will contain an Introduction to the 

 study of Fossils ; an indication of the sources from which the Professor has 

 drawn, in the prosecution of his researches ; and the general anatomy of the 



