198 University of Washington Publications in Biology [Vol. 2. 



GLOSSARY 



Explanations of Terms, Counts and Measurements Most 

 Frequently Used in Keys and Descriptions 



Abdomen. Belly, the cavity containing the digestive and reproduc- 

 tive organs. 



Abdominal. Pertaining to the belly; said of the ventral fins of fishes 

 when inserted considerably behind the pectorals, the pelvic 

 bones to which the ventral fins are attached having no connec- 

 tion with the shoulder girdle. 



Abortive. Remaining or becoming imperfect. 



Accessory caudal rays. Short, procurrent rays on the upper and 

 lower (rather than posterior) part of the caudal peduncle. 



Accessory pelvic scale. An enlarged scale or fleshy appendage on the 

 upper side at the base of the pelvic fin. 



Actinosts. A series of bones at the base of the rays of the paired 

 fins. 



Acuminate. Tapering gradually to a point. 



Acute. Sharp-pointed. 



Adipose fin. A fleshy fin-like projection behind the rayed dorsal fin, 

 on the back of certain fishes, usually lacking typical fin rays. 



Adnate. Adhering or grown together. 



Adidt. A mature animal. 



Agape. In a gaping state. Jaws open. 



Air bladder or swim bladder. A sac filled with gas situated in the 

 body cavity beneath the backbone and corresponding to the 

 lungs of higher vertebrates. 



Alisphenoid. A small bone on the anterior lateral wall of the brain 

 case. 



Ammocoetes. A name applied to the larval form of lampreys. 



Amphicoelian. Double-concave ; concave at both ends ; said of verte- 

 brae. 



Anadromous. Running up ; said of marine fishes which run up riv- 

 ers to spawn; used in a broader sense any fish entering fresh 

 water or going from deeper water to shallow water for the 

 purpose of spawning. 



Anal. Pertaining to the anus or vent. 



Anal fin. The fin on the ventral median line behind the vent. 



Anal fin III, 10 etc. — three spines and ten soft rays. 



Anal papilla. A protuberance in front of the genital pore and behind 

 the vent in certain groups of fishes, corresponding to the penis 

 of higher vertebrates. 



Anchylosed. Grown firmly together. 



