II. Internal features. 



(a). Oral cavity — Expose by making a slit with the scissors 

 from the corner of the mouth to the caudal angle of 

 the operculum. Where do teeth occur ? 

 (b). Types of teeth in fishes: 



(i). Villiform — Study and draw teeth of the com- 

 mon btdlhead. 

 (2). Setiform — Study and draw teeth of the black 



angel fish. 

 (3). Cardiform — Study and draw teeth of the com- 

 mon pike. 

 (4). Canine — Study and draw teeth of the wall- 

 eyed pike 

 (5). Incisor — Study and draw teeth of the sheeps- 



head. 

 (6). Pavement — Study and draw teeth of the ray. 



Write formula. 

 (7). Coalescent — Study and draw teeth of the 

 parrot fish, 

 (c). Oral breathing -valves — Folds of mucosa forming 

 pockets just behind the teeth on both upper and lower 

 jaws. Function? 

 (d) . Vomer — This is a bone forming the middle of the roof of 

 the mouth. Determine its location. Does it bear 

 teeth? Examine a preparation of the brook trout in 

 which the vomer is flat, and the lake trout in which 

 this bone is boat-shaped. 

 (e). Tongue — Compare with the buUhead. 

 (f ) . Gill arches — Determine number, connections, and shape. 

 Identify the gUl rakers and gill filaments. Fim.ction 

 of each. Write the formula for the gill rakers in the 

 perch and whitefish, and make a drawing of each, 

 (g). Pseudobranchiae — Examine the inner surface of the 

 operculum of the striped bass. Near the junction of 

 the operculum with the preoperculum is a small gill- 

 like structure, the psendohranchia. When it is evident 

 as in this species it is said to be exposed. When 

 the pseudobranchia is not apparent, it is said to be 

 concealed. 

 (h). Pharyngeal teeth — Located at the beginning of the 

 esophagus. Upper pharyngeals, above the esophagus, 

 and lower pharyngeals, below the esophagus. 



