264 



Correspondence. 



and one typical order. Consequently I arrange the class as follows 

 into orders : — 



1. PLAGIOSTOMI, 



Cuv. 



Aberrant Group. 

 CTENOBRAN- 

 CHII. 

 Gills pectinated. 



I 



I 2 ' 



Normal Group. f 



Fish breathing by | 



gills not pectinated. J 



ACTENOBRAN- ', 



CHII. I 



STURIONES, 



Cuv. 

 OSTINOPTERY- 

 GII, M'Leay. 



LOPHOBRAN- 

 CHII, Cuv. 



5. CYCLOSTOMI, 



Cuv. 



Cartilaginous fish, with fix- 

 ed branchiae leading to 

 Mammalia. 



Cartilaginous fish with free 

 branchiae. 



Bony fish with free bran- 

 chiae leading to Amphibia. 



Bony fish breathing by tufts 

 arranged in pairs along 

 the branchial arches. 



Cartilaginous fish breathing 

 by a series of cells. 



Now this arrangement differs from that of Swainson, in making the 

 vast majority of fishes an aberrant group ; but it is the structure, not 

 the number of species it contains, that determines the plan of a group 

 in nature. The group Ungulata is just as important now when contain- 

 in gcomparatively few genera, as it was in the antediluvian ages, when 

 it contained an immense number of them. Besides, I will venture to 

 say, that the above circular arrangement of fishes, expresses their place 

 among Vertebrata better than that of Swainson. I shall differ from him 

 still further as I go on. But in the mean time I must observe, that the 

 above, and following new names, are merely used, in order that you may 

 the better understand my meaning. I have been obliged to invent a 

 technical name for bony fishes, with pectinated gills, viz. 



OSTINOPTERYGII. 



Which may thus be divided into tribes : — 



Aberrant Group. 

 ACANTHOPTE- 

 RYGII. 



Artedi. 



[ 



1. BALISTINA, 

 Plectognathi, 



Cuv. 



Spines in first dor- ^ 2. PERCINA. 

 sal hard. 



Maxillary bones soldered 

 to the intermaxillaries, 

 and both to the palatine 

 arch. Opercula and gills 

 concealed under the skin. 



Bones of the jaws free and 

 complete. Operculum dis- 

 tinct. Operculum or pre- 

 operculum generally with 

 dentated edges, or with 

 spines. 



