282 Roosevelt Wild Life Annals 



Pectoral fins. The anterior paired fins, attached to the pectoral arch. Fig. 179. 



Pelvic arch. The bony structure supporting the ventral or pelvic fins. 



Pelvic fins. The same as the ventral fins. 



Peritoncuin. The lining membrane of the body cavity. 



Pharyngeal bones. Bones behind the gill arches, near the entrance of the ceso- 

 phagus. As a rule they bear teeth. 



Pharyngeal teeth. Teeth on the pharyngeal bones. In minnows they may be 

 removed with needles or fine cutting instruments. The pharyngeal bones can 

 be seen, covered with thin mucosa, in the back part of the gill-chamber. 

 The teeth are in one or two rows on each bone, and the tooth formula is 

 written as follows: i, 4-4, 2. This means that there are four large teeth in 

 the outer row, on each bone, while the inner row of one bone bears one tooth, 

 that of the other side, two. The teeth on the lesser row, therefore, are 

 represented by the outer numbers and those of the larger row by the middle 

 numbers on each side of the dash. Sometimes the lesser row is wanting. If 

 the greater row should have four teeth on each bone, the formula would 

 be 4-4. 



Pigment. Coloring matter. 



Plicae. Flat, parallel folds or wrinkles, as on the lips of some suckers. 



Plicate. Possessing plicae. 



Postorbiials. Bones of the orbital series, situated just behind the eyes. 



PremaxiUaries. Anterior pair of bones of the upper jaw, meeting in front and 

 usually bearing teeth. Fig. 179. 



Pseudobranchiae. Small gills on the upper, inner side of the opercle. Called also 

 opercular gills. 



Pterygoids. Bones in the posterior part of the roof of the mouth just back of 

 the palatines. 



Pyloric caeca. Tubular projections from the prehepatic or duodenal part of the 

 intestine. 



Preopercle. The bone in front of the o])ercle and more or less parallel with it. 

 Fig. 179. 



Protractile. Applied to the ])rcnia.\illarics when these are capalile of being ex- 

 tended forward. When jircniaxillaries are retracted, they arc bordered behind 

 by a groove. Fig. 179. 



Radii of scale. Lines on proximal part of a scale, radiating from near center 

 to base. 



Raw .\ supporting rod for a fin. There are two kinds: hard (spines') and 

 soft rays. 



Scale formula. This has three numbers separated by dashes, e.g.. 6-56-12. The 

 first number represents the number of the scales between the lateral line 

 and a point on the middle of the back about halfway between the dorsal fin 

 and the head. The middle number represents the number of scales crossed 

 by the lateral line — or the number in the transverse series if the lateral line 

 is incomplete or absent — beginning near the dorsal edge of the gill opening 

 and extending to the last vertebra. The last number represents the number 

 of scales between the lateral line and the front edge of the anal fin or, in some 

 cases, the base of a ventral fin. 



