CXXVIU FISHES OF ILLINOIS 



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 taper- 

 ing 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.) 



Gill-membranes. The thin wall of skin, supported by the branchiostegals, and clos- 

 ing the gill-cavity below. (Fig. 8 and 9.) 



Gill-rakers. A series of tooth- or filament-like bony appendages placed along the 

 anterior edge of the first gill arches. (Fig. 2, gr.) 



Graduated. Becoming progressively longer in one direction. Said of the spines in 

 the fins of certain fishes. 



Giilar plate. A bony plate imbedded in the skin between the sides of the lower jaw 

 of certain ganoid fishes. 



Hcemal spine. The lower spine of a caudal vertebra. 



Heterocercal. Unequally lobed. Said of the tail of a fish in which the vertebral 

 column is bent upward posteriorly. (Fig. 4, 5, and 6. See also note under 

 c, of key to families, p. 1.) 



Homocercal. Equally lobed. Said of the tail when the backbone stops (at least 

 apparently) at the middle of the base of the caudal fin. (Fig. 7. See hetero- 

 cercal.) 

 Hyoid. A bone in the floor of the mouth ; tongue bone. (Fig. 5 7 , hy. ) 

 Hyomandibular. One of the chain of bones forming the suspensorium of the lower 

 jaw (i. e., connecting it with the skull). 



Hypercoracoid. An element of the shoulder girdle. 



Hypocoracoid. An element of the shoulder girdle. 



Hypural. The expanded last vertebra. 



Imbricated. Overlapping, like shingles on a roof. 



Infraoral. Below the mouth. Said of the teeth of the mouth disc below the oeso- 

 phageal opening in lampreys. (Fig. 10.) 



Infraorbitals. A chain of small bones below the eye. 



Interneurals. The bones to which the dorsal fin rays are attached. 



Interopercle. A bone of the lower part of side of head. (Fig. 1 , io.) 



Interorbital space. The space between the eyes on top of the head. 



Isocercal. With the vertebrae becoming progressively smaller backward, as in the 

 codfishes. 



Isospondylous. With the anterior vertebrse simple. Said of the herring- and pike- 

 like fishes, which lack the Weberian ossicles found in the suckers, carps, and 

 catfishes. (See Weberian ossicles.) 



Isthmus. The fleshy interspace between the gill-openings. 



Jugular. Pertaining to the throat. Said of the ventral fins or vent when placed in 

 advance of the attachment of the pectorals. 



Keeled. {See carinate.) 



Larva. The young of an animal, if differing in an important way from the adult. 



Lateral line. A series of sensory muciferous tubes along the sides of a fish. 



Leptocephalus. A name applied to the lar\'al form of the eel. 



Lingual. Pertaining to the tongue. 



Lingual teeth. The serrated teeth on the "tongue" (i. e., at the opening of the 



oesophagus) in lampreys. (Fig. 10.) 

 Lunate. With a broad and shallow notch. 



