18 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY III. 



surface is more or less creuate, especially in young individuals; (c) the 

 anal fin is always short, containing from seven to nine rays; (d) the 

 dorsal fin is never inserted very far behind the ventrals ; (e) the lateral 

 line is developed and continuous. 



The species differ much among themselves in size, nuptial dress, and 

 general appearance, notably in the squamation, the scales of the typical 

 species of Luxllus being closely imbricated and much higher than long, 

 while in the group called Hudsonim the two dimensions of the scales are 

 nearly equal. The scales themselves, in Hudsonius, are thin and loosely 

 imbricated. Within certain limits, the position of the dorsal varies also. 

 In Hudsonius, its first ray is in advance of the insertion of the ventrals; 

 in Luxilus and Alburnops, usually directly opposite ; in Photogenis and 

 Hydroplilox, distinctly posterior. The form of the mouth varies largely : 

 in L.coccogeniSj it is wide and oblique, the lower jaw projecting. In 

 the typical species of Alburnops and Hudsonius, the mouth is small and 

 more or less inferior. 



The species may be provisionally grouped as follows, under five groups, 

 four of which may be considered as distinct genera. Those species 

 whose position is doubtful are indicated by a mark of interrogation : 

 A. LUXILUS Rafinesque. (Scales very closely imbricated, much deep- 

 er than long: teeth 2, 4-4, 2, entire: dorsal fin inserted directly op- 

 posite veutrals: mouth terminal: size large: nuptial dress 

 peculiar ; type Cyprinus cornutus Mit.) 



cornutus Mit. coccoyenis Cope. 



selene Jor. 



B. PHOTOGENIS Cope. (Scales pretty closely imbricated, deeper than 

 long: teeth 1, 4-4, 1, more or less crenate (rarely one-rowed ?): 

 dorsal fin behind ventrals, always with a black spot on the last 

 rays behind : males in spring tuberculate, the lower fins and the 

 tips of the vertical fins filled with satin-white pigment in spring: 

 mouth terminal, the upper jaw longest : size medium ; type P. 

 spilopterus Cope = Cyprinella analostana). 



analostanus Girard. niveus Cope. 



galacturus Cope. iris Cope (?). 



leucopus J. & B. 



C. HYDROPHLOX Jordan. (Scales less closely imbricated, somewhat 

 deeper than long; teeth usually 2, 4-4, 2, often more or less 

 crenate : dorsal fin distinctly behind ventrals, unspotted : breed- 

 ing dress peculiar, thema'es almost always red : mouth terminal, 



