REPORT ON ZOOLOGY. 183 



this department of zoology. Thus, he adopts but four orders, 

 in each of which are to be found both osseous and cartilaginous 

 fishes, — both Acanthopterygians and Malacopterygians, — both 

 apod and abdominal genera, — and, in two out of the four, tho- 

 racic and jugular genera besides. Hence it will be seen that his 

 principal divisions are founded neither on the degree of ossifica- 

 tion of the skeleton, nor on the structure of the vertical fins, nor 

 on the position of the ventrals, as is the case in those systems 

 which have been hitherto most generally adopted. M. Agassiz 

 thinks he finds in the differences of the scales the most exact 

 indication of the natural affinities of all fish. Accordingly it 

 is from the scales that he has drawn the diagnostic characters 

 of his four orders, (which bear respectively the names of Pla- 

 coides, Ganoides, Ctenoides, and Cycloides,) although in form- 

 ing them he has kept in view all the rest of the organization. 

 Ichthyologists will doubtless be impatient to see the full deve- 

 lopment of a system founded upon views so entirely opposed to 

 all those which they had previously entertained on the subject. 

 The science of ichthyology has been so little cultivated, that 

 there are but few individuals to whom it is necessary to refer in 

 this Report, besides those who have been already mentioned. 

 Many have made great contributions to the anatomy of fish, 

 amongst whom Geoffroy St. Hilaire stands preeminent ; but I 

 allude to such only as have thrown light upon the affinities of 

 the larger groups, or helped us to a better knowledge of their 

 zoological characters. I must not, however, omit to mention 

 an important paper on the fishes of the Lake of Geneva by 

 M. Jurine, published in 1825, in the third volume of the Mem. 

 de la Soc. de Phys. et d'Hist. Ahit. de Geneve. It is not merely 

 valuable as a local catalogue, but as containing several new cha- 

 racters for distinguishing the species of Cy2)rinidce, which is per- 

 haps one of the worst understood families in the whole class *. 

 This memoir is accompanied by i-emarkably accurate figures of 

 all the species found in the above locality. The scales of fish 

 were, some years back, particularly studied by M. Kuntzmann, 

 whose memoir t on this subject will have acquired fresh interest 

 since naturalists have had their attention again directed to it by 

 M. Agassiz. M. Kuntzmann has not only entered into consi- 

 derable details with respect to the structure of these organs in 



• Cuvier lias somewhere observed that in general the freshwater fishes, at 

 least those of foreign counuies, are much less known and understood tlian those 

 lound on the coasts. 



+ Verhandlung der Gesell. Nat. Freunde in Berlin, vol. i. No. 5, 1824, p. 269. 

 1 am, however, only acquainted with the analysis of it in Bull, des Set. Nat. 

 1826, torn. vii. p. 118. 



