Dr L. Mandl oti the Scales of Fishes. 121 



tes, Lophobranches, Goniodontes, Silures, and Sturgeons. 3d 

 Order : The Ctenoides. — The scales are formed of plates pec- 

 tinated on their posterior edge ; the pectinations of these nu- 

 merous plates superimposed on each other so that the margin 

 of the under one projects beyond that above it, rendering these 

 scales rough to the touch. This structure is particularly re- 

 markable among the Chenodontes and Pleuronectes. Here 

 likewise are arranged the Percoides, Polyacanthes, Scienoides, 

 Sparoides, Scorpionoides, and the Aulostomes. We shall after- 

 wards have an opportunity of learning that these combs are very 

 far from being simple plates, so arranged that the under ones al- 

 ways project beyond the upper : we shall see that they are true 

 teeth, all the development of which admit of being traced. This 

 stnicture must needs have escaped M. Agassiz's observation, in 

 consequence of the insufficiency of the means he employed. For 

 the same reason, this distinguished observer has not discovered 

 the form of the teeth in many of the families he has placed in 

 the following order. 4th Order : The Cycloides. — The fa- 

 milies belonging to this order have scales formed of simple 

 plates, with a smooth border ; a structure which does not pre- 

 vent their surface being frequently ornamented with various 

 designs, imprinted at once on all the scales on their outer 

 part, which is not covered. Here we must place the Labroi- 

 des, Muges, and Atherines, Scomberoides, Gadoides, Gobi- 

 oides, Mm-enoides, Lucloides, Salmones, Clupese, and Cyprini. 

 We shall subsequently see that this order contains famihes 

 whose scales present the most strongly marked differences. 

 Assuredly we cannot assimilate the scales of the Cyprini to 

 those of the Gobioides, nor arrange the Muges with the Athe- 

 rines ; the Muges present distinct teeth, although it may be 

 true that the scales are not rough to the touch. In the family 

 of the Cyprini there is room for sub-divisions. In this case 

 also, a simple magnifying glass produced quite an insufficient 

 (iulargement of the objects for such investigations. We shall 

 revert to thi.'s interesting point, whicii has acquired great im- 

 portance since M. Agassiz's inquiiies regarding the form of 

 scales. 



In finishing the history of researches into the structure of 

 scales, we shall only remark, that nearly all authors have 



