188 PROCEEDINGS OF THE MAL.VCOLOGICAL SOCIETY. 



Sliell larpje, globose, sub-perforate, epiilerniis green-brown, spire 

 but little elevated, sutures not appreciably impressed, wliorls deep; 

 habitat streams and springs. 



Klamath and Nevada Systems. 



Varies much in size ; specimens from springs are prevailingly 

 dwarfed. 



Fluminicola (Heatuilla) MERUiAMr, Pilsbry & Beecher. 

 F. Merriami, Pilsbry & Boeclier, 1892. 



Shell small, giobose-turbinate, perforate, epidermis horu-coloured, 

 sutures somewhat impressed, whorls ratlier deep; habitat springs. 



Mojave System. 



Fldminicola (Heathilla) eryturopoma, Pilsbry. 

 F. fnsca, var. minor, Stearns, 1893 (nude name, not used in a strictly 

 varietal sense) ; F. enjthropoma, Pilsbry, 1899. 

 Shell small, giobose-turbinate, sub-perforate, epidermis silvery 

 corneous, sutures somewhat impressed, wliorls fairly deep, operculum 

 with slowly increasing volutions and sub-central nucleus; habitat 

 springs. 



Mojave System. 



Fluminicola (Heathilla) Columbiana, Pilsbry. 

 F. Columbiana, 'Hemphill MS.,' Pilsbry, 1899. 



Shell of moderate size, sub-globose, barely perforate, epidermis 

 dark purplish-black, spire moderately elevated, sutures well impressed, 

 whorls not deep ; habitat streams. 



Columbia System (locally). j 



Fluminicola (Heathilla) minutissima, Pilsbry. ^ 



F. minutissima, Pilsbry, 1907. 



Shell minute, broadly obli(][uely globose, perforate, epidermis olive- 

 yellow, sutures impressed, whorls strongly inflated but not deep ; 

 habitat streams. 



Columbia System (locally). 



Genus Pyrgulopsis, Call & Pilsbry. 

 Pyrgula (sp.), Wolf, 1869 (P. scalar if ormis, Wolf); Pyrgulojjsis, 

 Call & Pilsbry, 1886 {Pijri/ula Nevadensis, Stearns). 



Type, Pyrgula Nevadensis, Stearns. 



Shell varying from small to large size, averaging 5 mm. in altitudi% 

 turreted-conic, imperforate or sub-umbilicate, epidermis pale horn- 

 coloured, whorls somewhat inflated, rounded in adolescent stage, 

 rounded, coronate, or peripherally carinate in adult, the carina 

 frequently becoming obsolete in senile condition, sutures more or less 

 impressed in rounded stages, apex usuallj- small and obtuse, aperture 

 ovate, peritreme continuous ; habitat chiefly confined to lakes. 



Pyrgulopsis is an interesting group on account of the pronounced 

 shortening up of the sculptured stage; specimens in each species 

 frequently pass directly from the juvenile to the senile round- whorled 

 stage with but a barely appreciable development of the carina, and 

 in no instance does it occupy a considerable period. 



