374 FISHES. 



C. Anacanthini. — Vertical and ventral fins without spinous 

 rays. Ventral fins, if present, jugular or thoracic. Air-bladder, 

 if present, without pneumatic duct. Lower pharyngeals separate. 



D. Physostomi. — All the fin rays articulated ; only the first 

 of the dorsal and pectoral fins is sometimes ossified. Ventral fins, 

 if present, abdominal, Avithout spine. Air-bladder, if present, 

 with a pneumatic duct. 



E. LoPHOBRANCHii. — Gills not laminated, but composed of 

 small rounded lobes, attached to the branchial arches. Gill-cover 

 reduced to a large simple jilate. A dermal skeleton replaces 

 more or less soft integuments. 



F. Plectognathi. — A soft dorsal fin opposite to the anal ; 

 sometimes elements of a spinous dorsal. Ventral fins none, or 

 reduced to spines. Gills pectinate ; air-bladder without pneu- 

 matic duct. Skin with rough scutes, or with spines, or naked. 



FIRST ORDER— ACANTHOPTERYGIL 



Part of the rays of the dorsal, anal, and ventral fins are not 

 articulated, more or less imngcnt spines. The lower pharyngeals 

 are generally separate. Air-bladder, if present, without pneu- 

 matic duct in the adjdt} 



First Division — Acanthopterygii Perciformes. 



Body more or less compressed, elevated or oblong, but not elon- 

 gate ; the vent is remote from the extremity of the tail, behind 

 the ventral fins if they are present. No prominent anal papilla. 

 No supcrbrancliud organ. Dorsal fin or fins occupying the 



^ The Acanthoptcrygians do not form a perfectly natural group, some 

 heterogeneous elements being mixed up with it. Neither are the characters, 

 by which it is circumscribed, absolutely distinctive. In some forms (certain 

 Blennioids) the structure of the fins is almost the same as in Anacanths ; there 

 are some Acanthoptcrygians, as Gems, Pogonias, which possess coalesced 

 pharyngeals ; and, finally, the presence or absence of a pneumatic duct loses 

 much of its value as a taxonomic character when we consider that probably 

 in all fishes a communication between pharynx and air-bladder exists at an 

 early stage of development. 



