ACANTHOPTERYGIOUS FISHES. f203 



aa. Two dorsal fins. 



b. Head armed. 



c. Head armed with spines. 



d. Ventrals thoracic. 

 Perca. 

 Sciaena. 



dd. Ventrals jugular. 

 Trachinus. 

 Lophius. 



cc. Head armed with a coat of mail, by the extension of 

 the suborbital bone : gill lid spinous. 

 Trigla. 

 Cataphractus. 

 Cottus. 

 bb. Head without armature. 



c. Ventral fins thoracic 

 Mullus. 



cc. Ventral fins abdominal. 

 Mugil. 

 Atherina. 



Sect. VI. Scales small, often scarcely perceptible, unless at the extremity of the 

 lateral line, where they sometimes form a ridge. In other cases 

 this ridge is formed by a protuberance of tlie skin, supported by 

 transverse processes, 

 a. Two dorsal fins. 



b. The first dorsal fin entire. 

 Scomber. 

 Trachurus. 

 Zeus. 



bb. Spines of the first dorsal fin without a connecting mem- 

 brane. Ventrals consisting of a single spine each. 

 Spinachia. 

 Gasterosteus. 



aa. One dorsal fin, elevated at its origin and termination. No 

 teeth. 

 Lampris. 

 Xiphias. 



VII. Mouth tubular. 

 Centriscus. 



