Cocherell ami Allison. — TJic Scales of American Ci/prinidx. 161 



Lavinia Girard. 



This genus does not belong to tlie Chondrostomina', I )nt is closely related 

 to the American species of Lenciscus. The teeth are only in one row, bxit 

 tliey are distinctly hooked. It seems probable that the genus is derived 

 from the American Leuciscus, rather than the reverse. 



The scales of Lavinia exilicauda Bairdtt Girard (Coyote Creek, Calif.), 

 are so like those of Leuciscus hi/choplilox from Idaho tliat we can not find 

 any satisfactory difference. The basal circuli are more indistinct and 

 confused in Leiieiscus liydi-ophlox, more distinct and separate in Lavinia 

 exilicauda, but this is perhaps not constant. The scales of the Leuciscus 

 seem on the whole to be broader. Tlie anal fin of the Lavinia seems dis- 

 tinctly longer, but this is not constant. The peritoneum of the Lavinia is 

 similar to that of Leuciscus hydrophJox, but the spots are much more 

 crowded, giving a beautifully marbled effect, with large brown stellate 

 spots and l)lack <lots. (Tliis is wholly difierent from the peritoneum of 

 Orthodon, etc. ) 



Tlie long intestinal canal of the Lavinia is a good generic character, 

 but it has probably been acquired independently of the other herbivorous 

 groups. 



Rutilus Rafincsque. 



R. olivaceus (Cope) stands entirely apart, by its very small scales, with 

 the radii few (7 to 10). R. thalassinus { Co-pe) , according to our material 

 from Pit River, Canby, Calif. (Stanford Univ. Coll.), is distinct by the 

 large broad scale, witli the rather numerous (11 to 15) apical radii very 

 parallel. The others have the scale large and br(^a(l, and are more alike 

 in the form of the radii, which are more convergent, going to a smaller 

 nuclear area than in thalassinus. R. hicolor (Girard) has the least num- 

 ber of radii (5 to S), and compared witli R. oregonensis Snyder has the 

 scale smaller, with the apical radii less spreading. R. syininetricAis (Baird 

 and Girard) has the basal area smaller tlian in R. columbianus Snyder; 

 the basal area of cohimbianns is much larger than that of bicolor. The 

 radii are aljout i) to 13 in columbinnv.s, and 7 to 11 in oregonensis. In R. 

 symmelrirus we found the radii very varial)Ie, 11 to 20, but this includes 

 several difierent fishes from various parts of California and Oregon, which 

 are at least subspecifically separable into four groups. (These segregates 

 from R. symmetricus have been defined and discussed by the senior author, 

 as far as the material permits, but more information is needed before 

 publication. It will especially be necessary to determine the characters 

 of tlie fishes now regarded as synonymous with symmetricus. ) 



Hybopsis Agassiz and Nocomis Gerard. 



Nocomis Girard is a distinct genus. The following table separates the 

 species of Hybopsis and Nocomis seen by us: 



