Vol. XXII, pp. 215-218 December 31, 1909 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



THE NOMENCLATURE OF THE AMERICAN FISHES 

 USUALLY CALLED LEUCISCUS AND RUTILUS. 



BY T. D. A. COCKERELL. 



The structure of the scales in European Leuciscus and Rutilus 

 is so different from that of the American fishes assigned to these 

 genera, that the latter must evidently be separated. It will be 

 useful, for the sake of comparison, to briefly describe the char- 

 acters of the scales of the principal European groups: 



(1) Leuciscus Cuvier. 



L. leuciscus (L. ). Scale ratlier broad; latero-basal angles strong; 

 lateral circuli extremely numerous; aj)ical circuli about half as 

 many; Vjasal radii well developed; apical radii about five, very 

 strong, with several incomplete ( peripheral ) ones between ; nuclear 

 area a short distance basad of middle, with no granular patch. 

 (Gefle, Sweden; Wheelwright; B. Mus.) 



(2) Rutilus Raf. 



L. rutilus (L. ). Scale very large, diameter about 12 mm.; latero- 

 basal angles strong; lateral circuli extremely numerous; apical 

 circuli not different fro7n lateral ; basal radii strong, but few; api- 

 cal radii about iive, speading, very strong, with intermediate ones 

 suggested l)y obscured grooving and marginal crenulation ; nuclear 

 area central, circulate nearly to middle. (Salisbury, England; 

 Ogden Smith ; B. Mus. ) 



(3) Pigus Bp, 



L. pigus. Scale much as in L. rutilus, but not so large; nuclear 

 area basad of middle, apical grooves and crenulations very dis- 

 tinct. This undoubtedly falls in the same group as L. rutilus. 

 (Lombardy; B. Mus.) 



(4) Cephalus Bp. (= Squalius Bp.?) 



L. cephalus (L. ) . Scale like L. leuciscus, but (at least in specimens 

 examined) larger. Nuclear area conspicuoushj apicad of middle; 

 almost no marginal rudiments of apical radii ; apical circuli not 



36— Proc. Biol. Soc. Wash., XXII, 1909. (215) 



