126 REPORT OF NEW JERSEY STATE MUSEUM. 



most difficult groups in natural history in which to distinguish 

 genera and species. Our genera are mostly very closely related 

 and are separated by characters which, although reasonably con- 

 stant, are often of slight structural importance. The spring or 

 breeding dress of the male fish is often peculiar. The top of 

 the head and often the fins, or various portions of the body, are 

 covered with small tubercles, outgrowths from the epidermis. 

 The fins and lower parts of the body in spring males are often 

 charged with bright pigment, the prevailing color of which is 

 red, although in some genera it is satin white, yellowish or black. 

 The young are usually more slender than the adults of the same 

 species and the eye is always much larger. They also frequently 

 show a black lateral stripe and caudal spot which the adults 

 may not possess. The fins and scales are often, especially in 

 specimens living in small brooks or still pools, covered with 

 small round black specks, immature trematodes. These should 

 not be taken for true color markings. No progress can be made 

 in the study of these fishes without careful attention to the teeth. 

 The pharyngeal teeth of the smaller species may best be hooked 

 out through the gill-opening under the shoulder-girdle. They 

 are very brittle, however, and care should be exercised in their 

 removal, as they easily break off. In most cases a principal 

 row of 4 or 5 larger teeth will be found, in front of which is a 

 set of I or 2 smaller ones. The two .sides are usually -hut not 

 always symmetrical. 



Key to the genera. 



a. Chondrostomatin^. Intestinal canal elongate, usually more than twice 

 length of body; teeth i-rowed with grinding surface well developed; peri- 

 toneum usually black; herbivorous. 



b. First rudimentary dorsal ray slender, firmly attached to first devel- 

 oped ray. hybognathus 



bb. First rudimentary dorsal ray somewhat enlarged, blunt, and con- 

 nected by membrane with first developed ray. pimephales 

 aa. Leuciscin^. Intestinal canal short, less than twice length of body ; 

 teeth I or 2-rowed ; peritoneum usually pale ; carnivorous or partly so. 



c. Lower jaw normally formed, dentary bones curved, free from each 

 other, except at symphysis. 



d. Teeth in main row 5-5 or 4-5, lesser row sometimes absent. 

 e. Postventral region transversely rounded, scales passing over 

 it or its edge not forming a scaleless ridge ; anal base generally 

 short. 



