GENERAL DISCUSSION 1 3 



The nomenclature is brought up to date as far as possible. 

 The absence from the list of certain names which appear in the 

 memoirs of Schrenck, Middendorff, and others, is only apparent ; 

 they are really present under their revised names. I have 

 accepted Simpson's determination of the Naiades, and retain, for 

 the variety of Unto pictoru?n which occurs in eastern Siberia, the 

 early name adopted by Rossmassler from Ziegler's MS., rather 

 than the very recent one which has been proposed by Wester- 

 lund. The list of Amurland mollusks in the Vega Expedition 

 report includes several which belong only to the Lena province 

 or western Siberia and do not occur on the Amur. 



The material examined from which this and the preceding 

 tables have been prepared, has been derived from several 

 sources. The collections of the National Museum containing 

 the boreal shells upon which the work of W. G. Binney was 

 partly founded, have been of great help. I have also had the 

 kind cooperation of Dr. J. F. Whiteaves of the Geological and 

 Natural History Survey of Canada. My own collections from 

 1865 to 1899 in Kamchatka and Alaska have furnished much 

 material. I have also had interesting collections from Messrs. 

 Randolph, McGregor, Stoney, Hepburn, Arnheim, Krause, 

 Palmer and others who have visited Alaska for pleasure or in 

 the Government service. The collections actually made during 

 the Harriman Expedition were more interesting than extensive, 

 but have helped considerably, especially those due to the 

 energy of Prof. Trevor Kincaid, of Seattle, while engaged in 

 his entomological researches. 



