GENERAL CLASSIFICATION 157 



TABLE OF FISHES. 

 OjRDER 1. — Cartilaginous Fishes. 



Vertebral column soft and cartilaginous ; no true ribs in a great 

 number. 



(1) No operculum, over the gills, and no membrane. 



Trematopneans. [Hole-breathing. H. E.] 

 Respiration through round holes. 



1. Cyclostomes. 

 Gasterobranchus (hagfish, myxine). 

 Lamprey. 



(2) No operculum over the gills, but a membrane. 

 Chismopneans. [Cleft-breathing. H. E.] 



Oills opening by clefts at the sides of the neck ; four paired fins. 



3 



Batrachus [Teleost. H. E.]. Balistes [Teleost. H. E.]. 



Lophius (frog-fish) [Teleost. H. E.]. Chimaera [Elasmobranch. H. E.]. 



(3) An operculum over the gills, but no membrane. 



Eleutheropomes. [Free operculum. H. E.] 

 Four paired fins ; mouth under the snout. 



4 



Polyodon [Ganoid. H. E.]. 



Pegasus [Teleost. H. E.]. 



Accipenser (sturgeon) [Ganoid. H. E.]. 



(4) An operculum and a membrane over the gills. 



Teleobranchs. [Complete gills. H. E.] 



[Teleosts. H. E.] 



Gills complete, with an operculum and a membrane. 



5. Aphyostomes. [Sucking-mouth. H. E.] 

 Macrorhyncus. 

 Solenostoma. 

 Centriscus (snipe-fish). 



6. Pteroptera. [United fins. H. E.] 

 Cyclopterus (lump-sucker). 

 Lepadogaster. 



