12 THE FISHES OF OHIO. 



ment of the lower pharyngeal teeth that constitutes the particular 

 " bete noire " of the uninitiated, but this must be mastered or 

 many identifications will be impossible. The lower pharyngeal 

 bones form the fifth pair of gill arches and usually bear teeth on 

 their inner surfaces, and to examine these it is necessary to 

 remove the bones. This is most easily done in the case of the 

 minnows and other -small species by lifting the opercleand insert- 

 ing a small hook behind the gills. In the sunfish and suckers 

 and other larger forms it is best to run a scalpel around them 

 before attempting to remove them. The teeth when removed are 

 usually covered, more or less, with broken tissues, which can be 

 removed by cleaning carefully with a fine-pointed needle, or with 

 a soft brush under water. In case the teeth have been broken 

 off, as frequently happens, the bases can be distinguished. A 

 good hand lens is essential. In native minnows the pharyngeal 

 teeth are in one or two rows, and their number and arrangement 

 is expressed by a formula — thus 1,4-4, 2 > meaning that on one 

 side the small, inner row consists of one tooth, and on the oppo- 

 site of two, while the teeth of the outer row are the same on both 

 sides. The fins are composed of stout spines, or soft rays or s-f 

 both. In the fin formula the number of spines is expressed by 

 Roman characters, and the rays by the Arabic figures. Thus the 

 formula, " D. X, 14," indicates that the dorsal fin is composed of 

 ten spines and fourteen rays. If the dorsal fin were in two parts 

 the formula would read " D. X-14." In counting the number 

 of rays the undeveloped rudimentary ones are not usually consid- 

 ered except in the case of the catfish. A little allowance may be 

 made for variation in number of rays. In small specimens where 

 the rays are not always easy to count, a good way to determine 

 the number is to draw the point of a pin forward over the fin 

 near the base of the rays. A good lens is also useful. The 

 dorsal fin is usually referred to in descriptions as simply the 

 dorsal, and other fins in like manner. They are further abbrevi- 

 ated by using D. , A. , C. , V. and P. to stand for dorsal, anal, caudal, 

 ventral and pectoral fins respectively. The scalis are counted 

 along the lateral line (a longitudinal row of scales each with a 

 small pore in most fishes) from behind the opercle to the base of 

 the caudal fin, and the transverse rows are counted from the front 



