HANMBAL : CALIFORXIAX FRESHWATER MOLLUSCA. 137 



CoUXEOCrCLAS ^QUILATK.RALIS (Plime). 



Pisidium (Bquilaterale, Prime, 1852. 



Sliell of moderate size, inflated, beaks narrow, anterior, and some- 

 what elevated, hinge moderately developed ; habitat chiefly lakes. 



American Province, Siberia. Yukon System. 



Quaternary : Loess of Kotzebue Sound, Alaska. 



CoRXEocTCLAs Idahoensis (Roper). 

 Pisidium Idahoensis, Roper, 1896. 



Shell of very lai'ge size, ovate-trigonal, strongly inflated, beaks 

 broad, elevated, and decidedly anterior, teeth sub-obsolete ; habitat 

 lakes. 



Boreal portions of American Province. Yukon, Fraser, and 

 Columbia Systems. 



Corxeocyclas Trempeki, n.sp. PI. YII, Fig. 22. 



Shell minute, globular-trigonal, beaks anterior, broad, and somewhat 

 elevated, hinge much reduced; habitat marshy lakes. Length 1"4, 

 altitude 1*3 ram. ; depth of valves 1 ram. 



Mojave System. 



Bluff Lake Cienaga, San Bernardino Mountains, California 

 (H. Hannibal). 



jS'amed after Dr. U. H. Tremper, the first conchologist to visit this 

 portion of the San Bernardino Mountains. 



GASTROPODA. 



Superfamily LYM:N0IDE.E (Broderip), 1839. 



The Lymnoidese, which embrace the purely aquatic inoperculate 

 pulmonates of the North Temperate regions and the bulk of those 

 inhabiting the more tropical portions of the world, include a number 

 of families, all simple types, but differing fundamentally in the 

 manner of "whorling and ontogenetic stages. And the anatomy, of 

 which much has been written, but little is actually known that will 

 assist in explaining the internal modifications each group has under- 

 gone, appears to have specialized along dissimilar lines. There are 

 excellent reasons for believing that these groups, like less bizarre 

 types in general, are of considerable antiquity. The Planorbidfe had 

 already reached their present specialization at the dawn of the 

 Cenozoic, while a Physa, P. prisca, AValcott, was described several 

 years ago from the Carboniferous of N^evada, a discovery which carries 

 this genus back to rank as one of the oldest known freshwater 

 molluscs. 



Family LYMX^ID^, Broderip, 1839 (emended). 



Shell of small or moderate size, dextral or sinistral, spire elevated, 

 whorls varying from appressed to inflated, inijierforate to umbilicate, 

 coluraellar axis varying in different sub-families, aperture ranging 

 from succiniform to auriculiform ; animal dextral, hermaphroditic, 



