^^^ M. Agassiz on Fishes. 



and the best of the more modern, leave us in the midst of the in- 

 vestigation. Accordingly, I have had to pursue my researches, in 

 a great degree, independently of every thing which was previously 

 accomplished, in establishing an equilibrium in the various branches 

 of ichthyology, and in making the whole of this labour nothing more 

 than a simple introduction to the examination of those fosil species 

 I sought to determine ; for it will now be readily conceived, that those 

 memoirs concerning Ichthyolites whicli were published some twenty 

 years ago, do not now exhibit results in keeping with the knowledge 

 which may be easily acquired regarding the existing species, in the 

 many great collections throughout Europe. 



From this state of things, and from the manner inwhich I have been 

 obliged to study living lishes, that I might compare them with fossil 

 ones, a great advantage has resulted in the complete independence 

 I was required to maintain concerning all the former reputed alliances 

 of different lishes ; because the great number of new species which 

 have been discovered since the commencement of the present century, 

 for the most part represented in the licgne AnhnaL of Cuvier, and 

 which it was necessary to insert in the groups of the natural families 

 of this class, has caused all the alliances proposed by the older ichthyo- 

 logists entirely to disappear. In afresh reviewing their characters, 

 1 have been led to adopt a classification which differs considerably from 

 any arrangement which has hitherto been proposed, and which is 

 founded upon important considerations which have hitherto been ne- 

 glected. 



It admits of no doubt, that one of the distinctive characters of the 

 class of fishes, consists in the skin being possessed of scales of a pecu- 

 liar form and structure. This covering, which protects the animal 

 externally, has, according to all the observations I have made up to 

 the present moment, the most direct relation to its interior organiza- 

 tion, and to the external circumstances in which the animal is placed. 

 So that, in this point of view, the scales acquire a primary import- 

 ance, and may be regarded as a superficial reflection of all that passes 

 within and around the fish. Accordingly, upon attentively examin- 

 ing them, I have found that fishes may be arranged in an order much 

 more natural than any hitherto proposed, by allowing ourselves to be 

 regulated by the structure of the scales. Acting on this principle, I 

 have established four orders, which present some resemblance to the 

 great divisions of Artedi and Cuvier, but one of which, hitherto al- 

 most wholly unknown, is nearly exclusively formed of genera, the 

 species of which are found solely in the older strata of the crust of 

 the globe. These four divisions are — the Placdides, which includes 

 all the cartilaginous fishes of Cuvier, with the exception of the Stur- 

 geons ; the Ganu'ides, which comprehends more than fifty extinct 

 §enera, and with which it is necessary to ally the Plectognathes, the 

 yngnatlies, and the Acipenser ; the Ctendides, which are the Acan- 

 thopterygiens of Cuvier and Artedi, to the exclusion, however, of all 

 those which have smooth scales, and including with them the Pleuro- 

 nectes ; and, lastly, the Cyclu'ides, which are principally the IMalacop- 

 terygiens, but which likewise comprehend all the families which are 

 excluded from the Acanthopterygiens of Cuvier, and from which it 

 is necessary to separate his Pleuronectcs, that they may be carried 

 back to the preceding order. 



