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071 a Nexv Classification of Fishes, and on the Geological 

 Disti'ibution of Fossil Fishes. By Professor Agassiz of 

 Neufchatel. 



In a memoir lately read before the Geological Society of Lon- 

 don, the author begins by stating that the science of Ichthyology 

 had obliged him to undertake an examination of recent fish, for 

 the sake of comparing them with the fossil species, and, in doing 

 so, he had arrived at a classification of fish, in general differing 

 considerably from the various arrangements previously adopted 

 by naturalists. One of the essential characters of fish is, to have 

 iheir skin covered with scales of a peculiar form and structure". 

 This covering, which protects the animal without, is in direct 

 relation with its internal organization ; and Mr Agassiz has 

 found, that, by attentive examination of the scales, fishes may be 

 divided into more natural orders than had hitherto been esta- 

 blished. In this manner, he has established four orders, which 

 bear some relation to the divisions of Artedi and Cuvier, but 

 one of which, hitherto completely misunderstood, is almost ex- 

 clusively composed of genera whose species are only found in 

 the older strata of the crust of our globe. These four orders 

 are the Placoidians, which comprehend the cartilaginous fish of 

 Cuvier, with the exception of the sturgeon : the Ganoidians, 

 which comprehend above fifty extinct genera, and to which 

 we must refer the Plectoganathes, Syngnathus, and Acipenser ; 

 thirdly, the Ctcnoidians, which aretheAcanthopterygians of Cu- 

 vier and Artedi, with the exception, however, of those which 

 have smooth scales, and with the addition of the Pleuronectes ; 

 lastly, the Cycloidians, which are principally Malacopterygians, 

 but which comprehend besides all those families excluded from 

 the Acathopterygians of Cuvier, and from which we must take 

 the Pleuronectes, already placed in the preceding order. 



If we estimate the number of fish, now known to amount to 

 about 8000, we may state that more than three-fourtlis of this 

 number belong to two only of the above mentioned orders ; 

 namely, the Cycloidians and Ctenoidians, whose presence has 

 not been discovered in the formations below the chalk. The 

 other fourth part of living species is referable to the orders Pla- 



