FISHES OF LAKE SUPERIOR. 353 



the species of animals are circumscribed within narrow limits in their 

 geographical distribution. From the great number which have already 

 been described, it is plain that almost every lake and every river 

 has species of its own ; but, nevertheless, there is a great uni- 

 formity among these fish all over the world ; for the carps of China 

 and those of Europe are very similar ; so are the little white-fishes 

 of the Nile and those of other basins. But however uniform 

 these fishes may be in the main, we cannot help observing that 

 among them there are peculiar groups, located in particular parts 

 of the world, for instance, the Catostomi, all over the freshwaters of 

 America. The small bearded species are very numerous in Europe, 

 and, in general, in the Old World ; species with beards occur there 

 more extensively than on the American continent.* Again, the types 

 with a large dorsal are Extensively distributed, but are almost all extra 

 American. The species which occur at great altitudes, as those from 

 the lakes of tropical America, are so peculiar as to differ decidedly 

 from all other Cyprinidoe, being devoid of ventral fins. In Lake Supe- 

 rior and the other Canadian lakes there is a considerable variety of 

 these fishes, — Catostomi mixed with European types, and a genus 

 which has only American representatives. 



The Httle group of Cyprinodonts, which have so universally been 

 connected with Cyprinoids, will be found to differ more from Cypri- 

 noids than has been supposed. We need only compare the structure 

 of their mouths to be satisfied of the difference. There are no repre- 

 sentatives of that type in Lake Superior. 



How far it might be advisable to subdivide this family into small 

 groups according to their structural differences, remains to be ascer- 

 tained. The Catostomi, for instance, are very remarkable for the 

 large opening in the centre of their skull, and for the peculiar arrange- 

 ment of the teeth in the pharyngeal bone. 



Rhinichthys, Agass. 



I propose to include in the genus Rhinichthys small Catostomi, 

 whose essential character is, as the name indicates, to have a conical 



* I would mention, as particularly characteristic of the Old World, the genera Barbus, 

 CJobitis, and the allied types. 

 2i 



