CXXX FISHES OF ILLINOIS 



Plicate. With wrinkle-like folds. 



Postclavicle. An element of the shoulder girdle. 



Postfrontal. A roofing bone of the skull. 



Post-temporal. The element of the shoulder girdle which connects it with the skull. 



Prefrontal. An anterior roofing bone of the skull. 



Premaxillary. The paired bone forming the front of the upper jaw. (Fig. 1 , pmx.) 



Preopercle. A bone of the cheek. (Fig. 1 , po.) 



Preorbital. A large bone lying in front of the eye. 



Prociirrent, Coming forward. Said of small accessory caudal rays encroaching on 

 the caudal peduncle in front of the base of the caudal fin. 



Protractile. Capable of being drawn forward. Said of premaxillaries which are ex- 

 tensible forward and are separated (when retracted) from the skin of the fore- 

 head by a groove. 



Pseudobranch. A rudimentary gill-like structure, not functioning as a gill, devel- 

 oped on the upper inner side of the opercle, differing from true gills in the fact 

 that it is supplied with arterial rather than venous blood. The pseudobranch 

 may be exposed in the branchial cavity (as in the perch) or covered entirely by 

 skin or hidden in the spiracular cavity (as in sturgeons and the paddle-fish). 

 (See spiracle and opercular gill.) 



Pterygoids. Paired bones of the roof of the mouth. (See ento -pterygoid and ecto- 

 pterygoid.) 



Pubic bones. (See pelvic girdle.) 



Punctulate. Dotted. 



Pyloric cceca. (See caecum.) 



Quadrate. One of the chain of bones connecting the lower jaw with the skull. 



Jiay. An articulated cartilaginous rod supporting the membrane of a fin. (Fig. 1, 

 d2r. See spine.) 



Retrorse. Turned backward. 



Rudimentary. Undeveloped. 



Scapular arch. (See shoulder girdle.) 



■Scute. A bony or horny plate. 



Shoulder girdle. The framework of bones, in most fishes connected with the skull, 

 to which the pectoral fins arc attached, including the post-temporal, clavicle, 

 postclavicle, hypercoracoid, and hypocoracoid. 



Soft dorsal. That dorsal fin or portion of it which consists of soft rays only. (Fig. 

 I,d2r. See spinous dorsal.) 



Spine. Fin rays which are unbranched and unarticulated, and, as a rule, more or 

 less stiffened and sharpened apically. (Fig. 1, d2s. See ray.) 



Spinous dorsal. The dorsal fin or portion of it which consists of unbranched, un- 

 articulated spines only. (Fig. I,d2s. See soft dorsal.) 



Spiracle. An opening in the head, anterior to and above the opercular opening, 

 representing a primitive gill-cleft, in paddle-fishes and in some sturgeons. 



Spiral valve. A spiral infolding of the wall of the intestine in ganoid fishes. 



Subopercle. The bone below the opercle. (Fig. 1, so.) 



Suborbitals. (See infraorbitals.) 



Subulate. Awl-shaped. 



Supplemental maxillary. A small bone lying on the upper posterior edge of the 

 maxillary. 



Supraoccipital. The unpaired bone at the back of the skull, usually with a crest 

 above. 



Supraoral. Above the mouth. 



Symphysis. The point of junction of the two parts of the lower jaw in front ; the tip 



of the chin. 

 Symplectic . A bone connecting the hyomandibular and quadrate. 



