b PEELIMINARY REPORT 



gill-rakers which yavj greatly, in the different species of fish (Fig. 

 IV., G. R.). Occasionally the nature and the number of the gill- 

 rakers borne on the first gill arch is important in identification. If 

 a description should state that the gill-rakers were 5+15 this would 

 indicate that there were 5 above the posterior angle (Fig. IV., P. A.) 

 of the arch and 15 below it; if X+15 it would indicate that the 

 number above the posterior angle was indefinite and the number 

 below 15. The gill-rakers can be counted in most fishes by lifting 

 the opercular flap. 



The bones of the fourth gill arch and those of the fifth arch are 

 modified and bear teeth, the former being known as the upper 

 pharyngeals and the latter as the lotver pharyngeals. In the perch 

 these teeth are very numerous, fine, and set in several masses, 

 usually two masses in the upper and two in the lower. It is often 

 necessary to know the nature of the lower pharyngeal bones and 

 teeth in identification, especially in the suckers, minnows and sun- 

 fish. In the suckers these teeth are arranged in a single row on 

 each side, each row containing numerous teeth which are in some 

 species all of about the same size; in others the lower teeth are 

 very large, graduating to smaller ones as they proceed upwards. 

 In the minnows they may be either in one or two rows, but in any 

 case the outer row contains the largest teeth and scarcely ever more 

 than five of them. Teeth in this row may have developd on each 

 a grinding surface and in some species of fish they are hooked. 



It will be necessary for those who expect to identify minnows 

 to make themselves acquainted with the different kinds of pharyn- 

 geal teeth. These teeth may be removed from a fish without mutil- 

 ating its general appearance by lifting up the gills and loosening 

 the nearest pharyngeal bone with a strong needle and lifting the 

 bone out. If the teeth are stout they may at once be freed from 

 the adhering flesh with a needle or brush, but if they are weak, as is 

 the case with most minnows, the mass of the flesh had better be re- 

 moved gently and then the bone be laid aside until the remainder 

 dries; otherwise some of the teeth will be removed in the opera- 

 tion and the conclusion will be incorrect. The teeth in the second 

 row are very liable to be broken in cleaning. In examining a fresh 

 fish some prefer to boil the bones with the flesh before attempting 

 to remove the latter. In describing the various species of fish the 

 pharyngeal teeth are generally indicated by a formula. Thus, 2, 

 4-5, 2 signifies that there are two teeth in the lesser row on one side, 

 four in the main row on the same side, five in the main row on the 

 other side and two in the lesser; 4-4 signifies that there are two 

 ipain rows with four teeth in each. 



