280 LAKE SUPERIOR. 



collections now at my command do not contain sufficient materials to 

 limit precisely those 'genera, I shall only mention that such a revision 

 seems desirable, since, as far as I can now judge, the group of 

 which P. catus may be considered as the type, should constitute a 

 first germs, and retain the name of Pimelodus, and that new names 

 should be framed for the other groups of species, of which P. cuclo- 

 pum, albidus, ctenodus, &c., may be considered as the respective 



types. 



If we now admit the generic sections, which I propose for 

 the numerous species of Pimelodus, their study will be by this 

 very fact much simplified ; for when we have once the group to 

 which our species belongs, its comparison with the others will be 

 very easy. Now we have already said that the first group, that 

 which is to retain the name of Pimelodus, will contain the P. 

 Catus as its type, and in addition to it the P. punctulatus Cuv. and 

 Yal., P. coenosus and borealis of Richardson, and P. albidus, 

 nebidosus and ceneus of Lesueur, besides a new species from Lake 

 Superior, to be described below. All authors have not admitted 

 P. ncbnlosus as a species ; the natural history of P. albidus and 

 ceneus leaves also much to be desired, so it is also with P. punctu- 

 latus. So that we are still in doubt about the real number of species 

 which will compose the genus Pimelodus proper. The Pimelodus 

 Catus, which is perhaps the best known, differs considerably from 

 our northern species, so that we need hardly mention the differences ; 

 but P. nebidosus and P. albidus seem to be very closely allied to 

 P. Catus, if we judge by the description which we have before us. 

 The P. ceneus would come near P. punctulatus, which in its turn 

 would remind us of P. Catus. Hence we may see how important 

 it may be to submit anew these species to a close examination, to study 

 them each in its locality and by minute anatomical as well as 

 zoological investigation, to ascertain the value of their characters. 



For the present, however, I cannot undertake this comparative 

 study from want of sufficient materials, but I shall attempt to 

 describe the species we brought from Lake Superior, and com- 

 pare it with P. coenosus and borealis of Richardson, from which, 

 though allied to them, it seems however to differ specifically. 



