204 SYSTEM OF AGASSIZ. 



The task of arranging all this disorder has at length been 

 undertaken by an individual, to whose hands Cuvier at once 

 consigned the materials he had himself collected for this im- 

 portant work. The able researches of Professor Agassiz 

 have already extended the number of fossil Fishes to two 

 hundred genera, and more than eight hundred and fifty spe- 

 cies.* The results of this inquiry throw a new and most im- 

 portant light on the state of the earth, during each of the 

 great periods into which its past history has been divided. 

 The study of fossil Ichthyology is therefore of peculiar im- 

 portance to the geologist, as it enables him to follow an en- 

 tire Class of animals, of so high a Division as the verte- 

 brate, through the whole series of geological formations; 

 and to institute comparisons between their various conditions 

 during successive Periods of the earth's formation, such as 

 Cuvier could carry only to a much more limited extent in 

 the classes of Reptiles, Birds, and Mammifers, for want of 

 adequate materials. 



The system upon which M. Agassiz has established his 

 classification of recent Fishes is in a peculiar degree appli- 

 cable to fossil Fishes, being founded on the character of the 

 external coverings, or Scales. This character is so sure 

 and constant, that the preservation even ofa single scale, will 

 often announce the genus and even the species of the animal 

 from which it was derived ; just as certain feathers announce 

 to a skilful ornithologist the genus or species of a Bird. It 

 follows still farther, that as the nature of their outward 

 covering indicates the relations of all animals to the external 

 world, we derive from their scales certain indications of the 



Cuvier; and one great proof of this imperfection is that they have led to no 

 general results, either in Natural History, Physiolog^y, or Geology. 



* No existing genus is found among the fossil Fishes of any stratum 

 older than the Chalk formation. In the inferior chalk there is one living 

 genup, Fislularia; in the true chalk, five; and in the tertiary strata of 

 M. Bolca, thirty-nine living genera, and lliirty.eight which are extinct. — 

 Agassiz. 



