137 



Helisoma trivolvis, Say. 



Pond between the Animas and La Plata 10 specimens. 



There is a long list of recorded localities from all the Territories, as 

 well as British America and the Pacific coast, so that it seems univer- 

 sally distributed over this continent. 



Eemarks. — This pond was entirely isolated, and of several acres in 

 extent, resorted to by vast flocks of wild fowl, and inhabited by all sorts 

 of fresh-water and amphibious life. The bottom was muddy, and nearly 

 the whole expanse choked with luxurious vegetation. 



All of the shells, which were quite abundant, seem to belong to this 

 species, although there are scarcely two alike. One resembles closely 

 P. viacrostomus, Whiteaves,* another is near P. tumens, Cpr. ; a third 

 variety might be identified as P. glabratus, Say, if that shell were dex- 

 tral; yet, while all differ in development and in color, all agree in being 

 very fragile, which may be owing partly to scarcity of lime in the water, 

 and partly to the soft bottom ; and in having a short vertical diameter, 

 which peculiarity may have been acquired by them from the necessi- 

 ties of their habitat, since snails having shells with small breadth of 

 beam could most advantageously pass between the stalks of standing- 

 water-plants which everywhere crowd the pond. 



Helisoma ccmmon, Gld. — Colorado Desert {Blalce) ; Klamath Lake, Ore- 

 gon, and Ehett Lake, California (N'eivberry) ; east of Fort Colville, 

 Washington Territory {N'orthwestern Boundm^y Survey). 



Helisoma Trasliei, Lea, is probably a synonym of the above. 



Helisoma corpulentus, Say. — Oregon and Washington Territory ( United 

 States Exploring Expedition) ; Lake Osoyoos, Washington Territory 

 {2larsli) ; British Columbia {Lord) ; Okanigan Iliver, Washington Terri- 

 tory {Cooper). It seems doubtful whether this is not a synonym of H. 

 trivolvis. 



Flanorhis oregonensis, Tryon. — Pueblo Valley, on the boundary between 

 Oregon and ISTevada {sic), " from a thermal spring, water above blood- 

 heat" {Gahh). 



Planorhis subcrenatiis, Cpr. — Oregon {l^uttall)', Washoe, ]!^evada 

 {Neivcomh) ; Sumass Prairie, British Columbia {Lord). 



Planorhis 5or/iM, Tryon, Utah {Sur. ^Y.ofl{)htllM.)■, Truckee Eiver, 

 ;N"evada {Carlton). 



Planorhis gracilentus, Gld. — Colorado Desert ( Wehh). Seems to be a 

 northern form of P. Liehmanni, Dunker. 



Gyraulus parvis, Say. 



Camp 9 : Hot Sulphur Springs v 1 specimen. 



Arkansas Eiver, ten miles below Granite 5 specimens. 



Between Eio Animas and Eio La Plata 2 specimens. 



Saint Mary's Lake, Antelope Park , 50 specimens. 



It occurs also in Hell-Gate Eiver, Montana {Cooper) ; Coeur d'Alene 

 Lake, Montana {Hemphill) ; Euby Valley, Utah {Simpson) ; and along 

 the Yellowstone {Smiths. Gatal.). 



Gyraulus vermicularis, Gld. — Truckee, Nevada, altitude 5,866 feet, 

 rare; Dalles, Oregon {Cooper). 



POMPHOLIGIN^. 



Pompholx effusa, Lea. — Near White Pine, Nevada {Hemphill) ; North- 

 eastern California {Neicherry). 



Carinifex Newherryi, Lea. — Klamath Lake, Oregon {Neicherry). 



