CYPKINTDJS. cvm. 269 



tichthyS) -with one or two exceptions, show no special 

 variations in the breeding season, but this matter needs 

 further investigation. 



The genera given below appear to be well character- 

 ized, although several are very closely related, and the 

 occurrence of intermediate forms may require them to 

 be reunited. Lythrurus and Plargyrus are properly 

 sub-genera of Luxilus, but they show so many external 

 peculiarities that I have, for the present, given them 

 generic rank. Most of the species here admitted have 

 been pretty thoroughly tested by the author, though 

 there are several, particularly under Hybopsis^ which I 

 do not like to indorse. 



NOTE.- -Young CyprinidcB usually are more slender than 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. Spots on the fins are generally charac- 

 teristic. The following artificial key will generally hold good for 

 adult fishes, but only great patience and long and careful observa- 

 tion will enable the student to identify the young. The accounts 

 of the pharyngeal teeth are taken from Prof. Cope's invaluable 

 "Monograph of the Cyprinidm of Pennsylvania," but most of 

 them have been verified by the author. It has been thought best 

 to make the dental characters subordinate in the present work, 

 but the student is strongly advised to examine the teeth of these 

 fishes, as the actual characters of the genera are largely drawn 

 from them. 



* Native species ; fins without serrated spines. 



f Dorsal preceded by a short, spinous ray, which is connected 

 by a membrane to the soft rays (about half the height of 

 the fin, and appearing as if broken off) ; snout short and 

 blunt, overlapping the small mouth ; front of muzzle with 

 about a dozen large tubercles in spring males; fins low; 

 dorsal with a black spot in front, about half way up ; peri- 

 toneum black ; intestines long, two to three times length of 

 body ; teeth one-rowed, 4-4, with masticatory surface. 



