FISHES. 201 



Sub-Class II. Tail lieterocercal ; optic nerves forming a chiasma ; 

 arterial bulb with several rows of valves ; air bladder fre- 

 quently cellular and lung-like ; exoskeleton typically of bony 

 plates. . . .... Ganoidei, page 212. 



ORDERS OF TELEOSTEI. 



Gills pectinated — of the ordinary sort, not tuft-like. 



I. Maxillaries normally developed and normally distinct from 



each other ; gills not in the axils ; typical fishes (characters 

 too various to be here summarized). . Teleocephat.t, Z. 



II. With 4 to 8 long barbels about the mouth, the longest of 



which is a continuation of the incomplete maxillary; 

 subopercle wanting; ventrals abdominal ; usually an adi- 

 pose fin and dorsal and pectoral spines; skin naked or 

 with bony plates ; chiefly in fresh water. 



Nematognathi, AA. 



III. Maxillaries rudimentary or wanting; scapular arch free 

 from skull; body elongated, serpentiform, with a long 

 dorsal and anal, which meet around the tail ; no ventral 

 fins; scales small or none; jaws with teeth; chiefly 

 marine Apodes, BB. 



IV. Carpal bones elongated, forming a kind of arm which sup- 



ports the pectorals, in the axils of which are the small gill 

 openings; ventrals jugular, with 4 or 5 soft rays; body 

 scaleless or tuberculate ; head very large ; marine. 



Pediculati, page 211. 



V. Intermaxillaries immovably united with the maxillaries ; 



skin rough, often covered with spines or ganoid plates; 

 ventral fins wanting; marine. Plectognathi, page 212. 



** Gills small, tuft-like, largest at their free tips ; body covered 

 with bony plates ; mouth small, toothless, at the end of the 

 long snout ; no ventral fins ; marine. 



Lophobranchii, page 212. 



• Z. SUB -ORDERS OF TELEOCEPHALI. 



I. Body flat, unsymmetrical ; both eyes on the upper or colored 



side; ventrals jugular. . . Heterosomata, page 208, 



II. Bones of snout prolonged into a long tube which bears the 



short jaws at the end. . . Hemibranchii, page 209. 



