Glossary 



Adipose fin. A small median fin between the caudal fin and the dorsal fin. (See Fig. 43.) Not 



present in all fishes. 

 Anal fin. A median fin on the ventral surface of the body just back of the posterior opening of 



the alimentary canal. (See Fig. 43.) 

 Anal opening. The posterior opening of the alimentary canal. 

 Apical radii. Grooves in the free or exposed portion of a scale, running from the center of the scale 



to its margin. (See Fig. 61.) 

 Barbels. Cylindrical, membranous processes extending from the angle of the mouth or the top of 



the head. Best shown in the catfish. (See Fig. i.) 

 Basal fulcra. Rudimentary, spine-like or bony rays at the base of the caudal fin. (See Fig. 36.) 

 Basal radii. Grooves in the basal or covered portion of a scale. Opposed to apical radii. (See 



Fig. 57-) 

 Caudal fin. The large fin at the posterior end of the body; the tail. (See Fig. 43.) 

 Caudal peduncle. The narrowed portion of the body bearing the caudal fin. (See Fig. 43.) 

 Cheeks. The sides of the head. 

 Ctenoid. Scales with teeth on the apical portion. 



Cycloid. Scales of bony fishes, without apical teeth. Opposed to ctenoid. 

 Dentary bone. The anterior portion of the lower jaw. 

 Depressed. Flattened dorso-ventrally. 



Dorsal profile. The dorsal outline of the body when seen from the side. 

 Ductus pneumaticus. A small duct connecting the air bladder with the alimentary canal. 

 Emarginate. Slightly forked or cut away along the margin. 

 Entire. With the margin complete and not forked. 

 Falcate. Scimitar-shaped along the margin; deeply but irregularly forked, one lobe being longer 



than the other. 

 Fingerling. A young fish, about the length of one's finger or less. 

 Fontanelle. An opening between two or more bones of the skull. 

 Frontal bone. That forming the front of the top of the head. 

 Fusiform. Spindle-shaped. 



Gill opening. That just back of the posterior margin of the operculum. 



Inlerorbital distance. That across the top of the head between the upper margins of the two orbits. 

 Intromittent organ. A male reproductive organ developed in some viviparous fishes from the 



modified anal fin. 

 Lateral line. A series of pores, usually in the scales, along the middle of each side of most fishes, 



connected with special nerves. 

 Maxillary barbel. That barbel attached to the edge of the maxillary bone. 

 Maxillary bone. That forming the lower portion of the upper jaw of most fishes. 

 Ocellated. With a central round spot; usually of one large spot which contains a central spot of 



another color. 

 Operculum. The large shield-shaped bone covering the gills, on the side of the head. (See Fig. 



43.) 

 Ovoviviparous. Producing eggs which hatch within the body of the female but are independent of 



the female. 

 Opercular flap. A membranous flap at the posterior margin of the operculum, supported in some 

 species by a bony stay. 



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