Vol. XXII, pp. 157-164 July 28, 1909 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



THE SCALES OF SOME AMERICAN CYPRINIDtE. 

 BY T. D. A. COCKERELL AND EDITH M. ALLISON. 



The sculpture of a Cyx>riuid scale consists of radiating and 

 concentric lines, winch we term radii and circuit. In Salmo 

 only the circuli are found, hut in no Cyprinid have we found 

 the radii wliolly al)Sent. In the Catostoniida^ the radii are hoth 

 hasal and apical, hut in the American Cyprinida? the hasal radii 

 are usually ahsent, while the apical ones are often greatly reduced 

 in numher. The circuli are always present, hoth apical and 

 hasal, in thest' fishes; hut in the Characinid Cheirodon insignis, 

 from Panama, they are confined to the hasal half of the scale.* 



The herhivorous genus Chrosomus lias the radii extending all 

 around the scale, as in Catostouuis. Among the genera usually 

 referred to Leucisciuffi l)asal radii occur in Rhinichthijs and 

 Af/osict, closely related genera which form a distinct trihe or 

 suhfamily. They are also well developed in some, but not 

 all, of the scales of Leuciscus orcutti, which therehy stands apart 

 from the otlier American species ascril)ed to Leuciscus, and 

 nearer to the pala?arctic species. The European Miocene Leu- 

 ciscus ceningensis (Agassiz) from G^^ningen, has radii strongly 

 developed all around, a scale very much more like that of 

 Chrosomus than those of the ordinary American so-called Leu- 

 cisci. In the Japanese Paraeheilognathus rhomheus (Schleg.) 

 there are no basal radii, but the apical radii are strongly zigzag, 

 an extreme exaggeration of a character never more than slightly 

 indicated in the American Cyprinids. Species of Lciheo, Chelx- 

 thiops, Barilius and Barbus, from the River Nile, all have basal 

 as well as apical radii. In Barbus perince Riipp. the scale is 



*In Fundulus, Apomotis, etc., the radii are all basal. 



21— Pkoc. Biol. Soc. Wash., Vol. XXII, I'JO'J. (157) 



