GLOSSARY OF TECHNICAL TERMS CXXXlll 



CcECutn. A blind sac, or tubular diverticulum, connected with the alimentary canal. (Fig. 



2, pyl.) 

 Canines. Conical teeth (in jaw) which are larger than the rest, as in the pike-perch. 

 Cardiform. Said of teeth which are coarse and sharp, like wool-cards. 



Carinate. Keeled; having a sharp median ridge. Said of the belly of certain herring-like fishes. 

 Catadromous. Going down to the sea to spawn, as does the common eel. 

 Caudal. Pertaining to the tail or caudal fin. 



Caudal peduncle. The fleshy (usually tapering) end of the body, between the anal and caudal 

 fins. (Fig. 1, cp.) 



Centrum. The body of a vertebra. 



Chiasma. The union of the trunks of the optic nerves, in ganoid fishes. In teleostean fishes 



(recent bony forms) the optic nerves cross or interlace without uniting to form a solid 



chiasma. 



Chin. The space between the two rami of the lower jaw. 



Chondrocranium. The rudimentary cartilaginous cranial skeleton, corresponding to the primi- 

 tive skull of cartilaginous fishes, of which traces remain in recent bony forms. 



Clavicle. An element of the shoulder girdle. 



Compressed. Flattened from side to side. 



Conus arteriosus. A muscular and contractile bulb between the ventricle and the root of the 



aorta. It is furnished interiorly with one or more transverse rows of pocket-shaped valves 



to prevent a backward flow of the blood. (Fig. 2, aob.) 



Coracoid. (See hyper- and hypo-coracoid.) 



Ctenoid. With the posterior edge pectinated. Said of the scales in most spiny-rayed fishes. 



Cycloid. Smooth-edged. Said of the concentrically striated (not ctenoid) scales of typical 



soft-rayed fishes. 

 Dentary. An element of the lower jaw, usually bearing teeth. 

 Dentate. With tooth-like notches. 

 Depressed. Flattened from above downwards. 



Depth. The vertical diameter or distance through, as of the body or head of fishes. 

 Dorsal. Pertaining to the back. 



Dorsal fin. The fin on the back, in front of the adipose fin, if that is present. (Fig. 1, dl, 



and d2.) 

 Ectopterygoid. A paired bone of the roof of the mouth. (Fig. 1 and Fig. 56, ecp.) 

 Emarginate. With a slight, shallow notch at the tip. Said of the caudal fin of fishes. (Fig. 7.) 

 Entopterygoid. A paired bone of the roof of the mouth, behind the ectopterygoid. (Fig. 56, enp.) 

 Falca'e. Scythe-shaped. 

 Falciform. {See falcate.) 



Fauna. The assemblage of animals inhabiting a region. 

 Filament. Any slender or thread-like structure. 

 Fi'amentous. Slander or thread-like; said of certain elongated fin-rays in some fishes. 



Fontanelle. An unossified space in the roof of the skull, filled with cartilage or covered with 



membrane. 

 Foramen. A hole or opening. 



Frontal. One of the anterior bones of the roof of the skull. 



Fulcra. Spine-like structures bordering the anterior rays of the fins in ganoid fishes. 

 Furcate. Forked. 

 Fusiform. Spindle-shaped. Said of the form of fishes which have the body tapering both 



anteriorly and posteriorly, and but little or not at all compressed. 

 Ganoid. A term applied to scales or plates of bone covered by enamel. Those of the gars are 



examples. 

 Ganoid fishes. A name applied to the families of sturgeons, paddle-fishes, gars, etc. (See 



analytical key to the orders of Teleostomi, p. 13.) 

 Gill-arches. The bony axes of the gills. (Fig. 2, ug and Ig.) 



