132 UNIVERSITY OF COLORADO STUDIES 



Palatine bones. Bones on each side of the roof of the mouth. 



Parietal bones. Bones on each side of the top of the head, just back of the frontal. 



Parr marks. Vertical bars of dusky or black on the sides of the young of most species of trout, 

 whitefish and other species of Salmonid fishes. (See Fig. 37.) 



Pearl organs. Small tubercles developed on the scales of males of some fishes during breeding 

 season. Their function is to aid in keeping the two fishes alongside during spawning. 



Pectoral fins. Those just back of the gill opening. (See Fig. 43.) 



Peritoneum. The membranous lining of the abdominal cavity. 



Pharyngeal bones. Bones at the beginning of the esophagus just back of the last pair of gills on 

 each side. (See p. 46.) 



Poikilothermous. Having a temperature of the surrounding medium, popularly known as "Cold- 

 blooded." 



Predorsal region. The region along the middle of the back just in front of the dorsal fin. 



Premaxillary bones. Those forming the front and median portion of the upper jaw, in most fishes. 



Preoperculum. The anterior portion of the operculum. 



Pyloric coeca. Small blind tubes at the lower end of the stomach. 



Radii. Grooves in the scales of many bony fishes. 



Scale formulae. Scales are to be counted in oblique series from the base of the first ray of the dorsal 

 fin to the lateral line, the scale in the lateral fine not being included; next, those in the lateral 

 line from the origin of the lateral line just back of the gill opening to the base of the caudal 

 fin; the third count is of the scales in oblique series between the lateral Une and the base of the 

 first ray or spine of the anal fin, the scale of the lateral line not being included. These counts 

 are conventionally given as 5, 67-70, 3 or 4, meaning 5 scales in obhque series between the base 

 of the dorsal fin and the lateral line, 67 to 70 in the lateral line and 3 or 4 in oblique series 

 between the lateral line and the base of the anal fin. 



Septum of the nostril. The elevated membranous partition between the two halves of the nostril. 



Snout. The portion of the head in front of the eye and above the mouth. (See Fig. 43.) 



Soft dorsal fin. Opposed to spinous dorsal, the supporting structures being soft rays. 



Spinous dorsal fin. The anterior portion of the dorsal fin which is either separate from the posterior 

 soft dorsal or joined with it into a single fin. The supporting structures in the spinous dorsal 

 are bony spines. 



Suborbital bones. A chain of more or less connected bones below the eye. 



Supraocular region. That just above the eye. 



Terete. Rather cyUndrical, having a more or less circular outline in cross-section. 



Ventral fins. Paired fins on the ventral surface of the body in front of the anal fin and behind or 

 below the pectoral fins. (See Fig. 43.) 



Ventral profile. The ventral outline of the body when seen from the side. 



Vomer. The front part of the roof of the mouth. 



Weberian apparatus. A chain of small bones connecting the air bladder with the inner ear. 



