28o Roosevelt Wild Life Annals 



Cheek. The fleshy area behind and beldw the eye and anterior to the opercle. 



Fig. 179. 

 Chin. Region between the hmbs of the lower jaw. Fig. 179. 

 Compressed. Flattened from side to side, as in the case of the sunfish. 

 Crauiuin. The part of the skull enclosing the brain. 

 Ctenoid secdcs. Scales with minute spines on their distal exposed portions. The 



spines can be felt by gently rubbing the fish with the finger, or they can be 



seen with a lens. 

 Cyeloid scales. Scales without spines, Init with concentric lines called circuli and 



annuli. Scales are smooth to the touch. 

 Dcntary bones. The principal or anterior bones of the mandibles. They usually 



bear teeth. Fig. 179. 

 Depth of fish. The greatest vertical diameter; usually taken just in front of the 



dorsal fin. 

 Depressed. Flattened in the up and dnwn direction, with body low and broad. 

 Disk teeth. Tooth-like tubercles on the oral disk of lampreys, surrounding the 



mouth. 

 Dorsal fins. Unpaired fins of the back. Fig. 179. 

 Emarginate fin. Fin with the margin containing a shallow notch as in the caudal 



fin of the Rock Bass. See Fig. 179. 

 Fin foriunla. A formula showing the number and kinds of rays in a fin, e.g., 



D.X., 12. The capital letter represents the name of the fin (dorsal): the 



Roman numeral, the number of spines: and the Arabic numeral the number 



of soft rays. \Mien there are two dorsals present this fact is indicated by 



means of a dash; D, XII -II, 12. 

 Forked tail. Tail fin conspicuously notched or divided into two similar lobes, each 



with an acute tip. Fig. 180. 

 Fusiform. Spindle-shaped. Applied to the bndy when it tapers at each end and 



is but slightly compressed. 

 Ganoid Scales. Rhomboid scales or plates covered with an enamel-like substance, 



or ganoin. 

 Gills. Breathing organs of fish; typically composed of a bony supporting arch, 



\\-ith two rows of gill filaments on its posterior side and a row of gill rakers 



on its anterior side. 

 Gill clefts or .<:lits. Spaces between the gills, connecting the pharyngeal cavity 



with the gill chamber. 

 Gill cover. The tlap-like covers of the gills and gill chambers: the opercles. 



Fig. 7. 

 Gill openinfis. As here u.sed, meaning the external openings of the gill chambers, 



A single ])air is present in all true fishes found in fresh w-ater. Fig, 179. 

 Gill rakers. Fine rods or tulsercles on the anterior face of a gill arch. 

 Grinding surface. .\ flattened contact area of a tooth. 

 Giihrr plate. The flat, oblong plate on the chin of the Rowfin. 

 Head. Region of the fish anterior to the gill oiienings. measured from the tip 



of the snout to the iwsterior edge of the opercle. 



