430 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxvi. 



species, one of which, Coregonus oregonius differs widely from the 

 others, and is not known to be represented in any other basin. Core- 

 gonus william.soni occurs also in streams to the northward of the 

 Columbia, and in the Great Basin of Nevada. It is represented east 

 of the divide in Montana b}^ a slightly differentiated form, Coregonus 

 (jouesi," of the Saskatchewan, which probably includes Coregonus 

 cisTfiontanus'^ of the Upper Missouri. The third species, Coregonus 

 coulteri (Eigenmann, from the TJiDper Columbia River, Kicking 

 Horse River at Field), of which Ave have specimeus from Diamond 

 Lake, Washington, is a species well-distinguished by its slender body 

 and large scales, there being but (50 in the lateral line. Its relation- 

 ships are not close to any other known species. 



Farther east, this group or genus Prosopium^ to which all these 

 species belong, is represented by the ]\Icnominee whitefish, Coregonus 

 quad r Hat cralh. Prosopium is distinguished from Coregonus proper 

 by the short, few gill-rakers, the slender body, and the small, inferior 

 mouth, above which are the large preorbitals, which ]\Iilner compared 



to a mask, TrpoamirLOV. 



«Rept. U. S. Fish Commission for 1S72, 1874. p. 88; Milner, Chief Mountain 

 Lalie. 



^Jordan, I'.iill. TT. S. Fish Commission, IX, 1889, p. 49, pi. ix, fig. 89; Horse- 

 thief Creek, Montana. 



