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Leuciscus Rond.; Klein.; Cuv., Regne anim. ed. 1a II p. 194; Heck., fisch. Syr. p. 49; Heck. Kner, Fisch. oestreich. Mon. p. 169 = Leucos Heck., Fisch Syr p. 48 = Squalius Bp., Faun. Ital., = Telestes Bp., F. Ital. – White-fish.
Body oblong or elongate, compressed or slightly terete, covered with large or medium-sized scales, back elevated to low. Jaws covered by thin, terete, simple lips, upper lip slightly protrusable. No barbels. Snout obtuse or slightly obtusely convex, short, not to hardly anterior to the mouth. Mouth anterior, gape more or less oblique, ending anterior to the eye. Eyes superior or slightly posterior, not covered by palpebral membrane. Lateral line moderately to strongly curved. Belly not keeled anterior to ventral fins. Dorsal fin with few rays, starting above or hardly behind ventral fins and ending anterior to the anal fin, posterior simple ray completely cartilaginous. Anal fin with few rays, hardly longer to no longer than dorsal fin. Pharyngeal teeth grinding 6/5 or 5/5, or predatory 2.5/5.2 or 2.5/4.2.
Remark. The relationship of Leuciscus, as it is described above, with Abramis is so large that the assertion of Mr Valenciennes concerning the not generic differences between Abramis and Leuciscus, if only applied on the species of Leuciscus and Leucos, as this genus is understood by the more recent 465 ichthyologists, in my opinion would be very acceptable. Leuciscus then would stand in the same relationship to Abramis, as Rohtichthys to Rothee, or, if one would reverse the relationship of the lengths of the dorsal fin and the anal fin, as Cyclocheilichthys (Siaja) microlepis to the remaining species of Cyclocheilichthys. Abramis obtains then even hardly the value of a subgenus in relation to Leuciscus, and still other genera of the Leusicini erected by the more recent ichthyologists with regard to their generic value stand in an approximately similar relationship.
Without accepting the genera in this way, I have only mentioned them here with the characters attached to them by the ichthyologists, to keep a clear view at least in the chaos of related species of the large genus Leuciscus. Leucos Heck. differs in nothing from Leuciscus Heck., unless by a tooth less in the left pharyngeal bone, and therefore is here united with Leuciscus. I was also of the opinion that the genus Squalius Bp. is not essentially different from Leuciscus. Indeed it would not differ in anything essentially from Leuciscus unless by a change in the dentition (dentes raptatorii 2.5/5.2), a change that is not represented externally by any character. Moreover Heckel has placed some species in his genus Squalinus, like Squalinus berag and Squalinus lepidus, which show entirely the habitus of Aspius, and also, at least Squalius lepidus, have the shape of the jaws entirely corresponding to that of Aspius, from which genus they were separated by Heckel only on the basis of peculiarities in the dentition.
Telestes Bp. can be separated with just as little reason from Squalinus and Leuciscus. To the blackish longitudinal band on the body, which would narrows down to be the character of the genus, in any case cannot be attached more than specific value.
Leuciscus, accepted in the above described sense as a nominal genus, in essence only differs from Abramis, as the dorsal fin starts above or hardly behind the origin of the pelvic fins and is not or only a little shorter than the anal fin.