Recherches sur les Poissons Fossiles. 



337 



it is ramified.O) Sometimes these furrows do not commence 

 where the scale is composed of many leaflets ; for example 

 below the middle of its radius ;( 2 ) or more towards the centre 

 of the scale is occupied by the thick leaflets with hardened 

 edges, to which only the furrows extend/ 3 ) or rather the mid- 

 dle of the scale is covered with furrows which are interlaced 

 and form a net, which in other species extends over the 

 whole scale. The leaflets are otherwise perfectly smooth 

 on the whole extent of their surfaces by which they are 

 joined to one other. The furrows are not extended beyond 

 the outer margins of the leaflets of growth ; they are the 

 canals to the border of the external surface which commu- 

 nicate from one leaflet to another : they are multiplied 

 during the growth of the scale, and give rise to all the 

 variations which we have described. The disposition of 

 the furrows varies also the reflections of the fish.* 



Abstract of the families, genera, and species of the order 

 of Gano'ides. Rech. sur les Poiss. Foss. chap. i. vol. ii. 



1st Oiid.— GANOIDES, Agass. (Goniolepidoti, Agass.) 



I place the order of Ganoids at the head of the class of fishes, because 

 of their great peculiarities as compared with the types of the families 

 now predominant. However the order of Placoids is even still more 

 distinct from existing forms ; but I have not yet had sufficient opportu- 



0) Selecta genera, Tab. C. Clupanodon aureus, Tab. D. Chalceus an- 

 gulatus. 



(2) Chichla labrina, 



(3) Serrasalmo Piranha. 



* The chapter here breaks off abruptly ; but although incomplete, 

 these details may be sufficient to show the care with which the 

 principles have been examined on which Professor Agassiz's classi- 

 fication is founded. We shall now afford some examples of the manner 

 n which those principles are applied, and of the results obtained 

 from them in Geology, as well as in Ichthyology.— Ed. 

 I 2 x 



