Cockerell and Allison. — The Scales of American Cyprinidse. 159 



are frequently irregular and broken; in Semotllus they are fur- 

 ther modified, being very distinctly angled in the median line, 

 or inversely V-shaped. Couesius, which is almost the same as 

 Semotilus, and should stand next to it in the system, has just 

 the same characteristic angled circuli. On the other hand, 

 Ptychocheilus grandis is entirely different, with the apical circuli 

 flattened rather than angled mediallj^ Phenacobius mirahilis 

 has strongly angled apical circuli as in Semotilus, the scales 

 closelj^ resembling those of Semotilus corporalis. Hyhopsis gclida 

 has the circuli as in Phychocheilus , and is not related to Phena- 

 cobius. Nocomis kentuckiensis, usually referred to Hybopsis, but 

 certainly not congeneric with it, has angulate apical circuli, as 

 in Semotilus and Couesius. 



In the account of the scales of different genera which follows, 

 it is to be understood that unless the contrary is specified, they 

 have been taken from near the lateral line, at the level of the 

 beginning of the dorsal fin. Scales from other parts of the 

 body will show modifications; thus those on the caudal peduncle 

 are often long and narrow. 



Leuciscus Anctt. Amer. 



These fij^hes are proba])ly nut congeneric with the J^uropean Lenci'^cus 

 leuciscus, but as we do not at present possess any of the Old World species 

 of the geni;s, we are not i)i a position to revise the nomenclature. The 

 following key separates the species examined by us : 



Basal radii present, though not on all of the scales ; basal circuli very 

 much closer and more numerous than in margarita (which, thoi;gh 

 placed by Jordan and Evermann in the same immediate group, is not 

 at all related); apical radii numerous (]."> to 29, counting the partly 

 developed ones); peritoiwiim reddish-l)lack, with dots very thickly 

 strewn on a silver ground . . . L. orcutti (Eigenmann c^ Eigenmann). 



Santa Ana R. , Calif. 

 Basal radii absent on all the scales 1. 



1. Scale much longer tlian broad 2. 



Scale subcircular, or broader than long o. 



2. Scale large; radii numerous (12 to 14); subcentral apical circuli ex- 



tremely irregular, but not angled; peritoneum silvery, with a pro- 

 fusion of small spots, most of them brown, some black 



L. nigrescens (Girard). 

 Alamosa, Colo. 

 Scale very small; radii less numerous (7 to 9); peritoneum brown on 

 a silvery substratum, as in Orthodon, and Acrocheilus 



L. intermedium (Girard). 

 Tempe, Arizona. 



