lvi Field Columbian Museum — Zoology, Vol. V. 



Head. 13. Spinous portion of dorsal fin. 



Snout. 14- Soft portion of dorsal fin. 



Eye. 15. Base of dorsal fin. 



Premaxillary. 16. Pectoral fin. 



Maxillary. 1 7 . Anal fin. 



Supplemental maxillary. 18. Ventral fin. 



Mandible, or lower jaw. 19. Base of caudal fin (last vertebra). 



Symphysis. 20. Caudal fin. 



Cheek. 21. Lateral line. 



Preopercle, 1 22. Depth of the fish. 



Opercle, J> Gill covers. 23. Depth of caudal peduncle. 



Subopercle, J 24. Caudal peduncle. 



The profile of the fish, unless otherwise mentioned, is the curve 

 from the highest point on the back to the tip of the snout. The 

 origin of the dorsal or anal fin is the insertion of its first spine 

 or ray. 



Fishes in general, and especially those treated of in this work, 

 breathe by means of gills, which are fine hair-like projections 

 (branchiae) usually supported on the outer curves of cartilaginous 

 or bony arches known as gill arches; in the true fishes the normal 

 number on each side is four. The gill rakers are a series of bony 

 appendages variously formed along the inner edge of the anterior gill 

 arch. 



The gill membranes usually serve to attach the gill covers 

 to the isthmus, which is the thick, fleshy projection between the gill 

 openings. The branchiostegal membranes are attached to the 

 lower posterior portions of the gill covers; the cartilaginous or bony 

 supports of this membrane are the branchiostegal rays. 



The pseudobranchi^e are small or imperfectly developed gills 

 on the inner side of the opercle, near its junction with the preopercle. 



The pharyngeal bones are behind the gills and at the beginning 

 of the oesophagus; in true fishes they represent a fifth gill arch. 



In general the teeth of fishes are conical and pointed; frequently 

 some are incisor or molar-like. Occasionally, as in some of the 

 killifishes (Characodon, Goodea, and Skiffia, etc.), the incisor-like teeth 

 are bicuspid or (Cypriuodoit) tricuspid. The upper teeth of fishes may 

 be attached to one or more of the following bones: premaxillary, 



MAXILLARY, PREFRONTAL, VOMER, PALATINE, PTERYGOID, and UPPER 



pharyngeals; lower, to the mandible, tongue, and lower pharyn- 

 geals. In some fishes treated of in this work, as the Large-mouth 

 Black Bass, teeth are present on nearly all of the parts of the mouth 

 and pharynx as above mentioned; in the suckers and minnows teeth 

 are present only on the pharyngeal bones. Fishes do not masticate 

 their food ; the teeth are used chiefly for catching, holding, and break- 



