136 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



CoRNEocYCLAs ViKGiNiCA (Gmelin). 

 Tellma Virginica, Gmelin, 1788; Ci/clas dubia, Say, 1817. 



Shell large, broadly trigonal-ovate, moderately inflated, iimbones 

 conspicuous and decidedly anterior, hinge fairly developed; habitat 

 lakes and streams. 



Boreal portions of American Province. Yukon System. 



Quaternary : Loess of eastern States ; Yukon Valley, Alaska. 



A species more or less intermediate in character between Pisidium 

 and Corneocyclas, but grouping best with the latter. 



CoRNEOCYCLAS PULCHELLA (Jenyns). 



Pisidium pulchelltim, Jenyns, 1832; P. variahile. Prime, 1851: 



P. Adamst, Prime, 1851 ; P. ferruginenm, Prime, 1851 ; P. nov- 



eboracense, Prime, 1853 ; P. occidetitale, Newcomb, 1863 ; P. itisipie. 



Gabb, 1868; P. Jlarfordiamim, Prime, 1869 (nude name), jf^« 



cotypes ; P.arcticum, Westerlund, 1885 ; P. glaciale, Westerlund, 



1885; P. scutellatum, Sterki, 1890; P. Roper i, Sterki, 1898; 



P. Ashmuni, Sterki, 1903; P. proximum, Sterki, 1906; P. 



Californicum, ' Newcomb MS.,' Perry, 1908 (nude name), fide 



locotypes ; P. Marci, Sterki, 1909. 



Shell of moderate size, prevailing smaller than sub-sp. aldifa 



apparently, sub-trigonal, inflated, beaks prominent and sub-terminal, 



hinge not well developed, teeth sub-obsolete ; habitat springs, marshes, 



lakes, and moist places, infrequent! j' in streams intergrading with ahdita. 



Distribution apparently same as abdita. 



Quaternary : Loess of eastern States ; post-Glacial deposits of 

 Vancouver Island ; Summer Lake beds, Oregon ; Owens Lake beds, 

 California. Pliocene : Cache Lake beds. California. 



The specific and varietal names adopted for this Corneoci/clas and its 

 sub-species are probably not the earliest, but they are the earliest 

 which the wi'iter with the literature and material at hand has been 

 able to satisf}' himself were actually applied to it. 



Corneocyclas compressa (Prime). 

 Pi.sidimn compressttm, Prime, 1851. 



Sliell of small size, distinctly trigonal, inflated, beaks nai'row and 

 high, sub-terminal, hinge moderately developed ; habitat lacustrine. 



jS^earctic Piegiou. Yukon, Eraser, Columbia, Nevada, Klamath, 

 Coast Range, Arizona, and Los Angeles (locally) Systems. 



Quaternary : Loess of eastern States ; Lahontan Lake beds, Nevada. 

 Pliocene : Kettleman, Santa Clara, and Cache Lake beds, California. 

 Miocene : Contra Costa Lake beds, California. 



Corneocyclas rotundata (Prime). 

 Pisidium rotmidatum, Prime, 1851. 



Shell minute, ovate-trigonal, strongly inflated, beaks broad, elevated, 

 and decidedly anterior, hinge much reduced ; habitat lacustrine. 



Poreal portions of American Province. Yukon System. 



