58 FISH GALLERY. 



gnathi. 3. Anacanthini. 4. Physostomi. 5. Lophobranchii. 

 6. Plectognathi. 



Subclass II. Pal^ichthyes. Heart with a contractile conus 

 arteriosus; intestine with a spiral valve; optic nerves non-decussating 

 or only partially decussating. 



Orders : — 7. Ganoidea. 8. Chondropterygii. 



Subclass III. Cyclostomata. Heart without bulbus arteriosus; 

 intestine simple. Skeleton cartilaginous or notochordal. One nasal 

 aperture only. No jaws ; mouth surrounded by a circular lip. 



Order : — 9. The Lampreys. 



In many works on Fishes a fourth Subclass, Leptocardii, is 

 admitted ; it comprises the Lancelet (Branchiostoma) only, which, 

 however, differs so much not only from the Class of Fishes, but 

 from the general Vertebrate type, that in a strictly systematic 

 account it should be referred to a distinct class. As it is exhibited 

 in this Gallery, it will be mentioned at the end of this Guide. 



TELEOSTEI. 

 Order I. ACANTHOPTERYGII, or SPINY-RAYED FISHES. 



Acanthopterygians are bony fishes in which part of the dorsal, 

 anal, and ventral fins are non-articulated, more or less pungent 



Fig/44. 



The Pike-Perch (Zucioperca) : a Spiny-rayed Fish. 



spines ; the lower pharyngeal bones are generally separated ; the 

 air-bladder, if present, is without pneumatic duct in the adult. 

 This Order, the most numerous in species, is divided into a great 



