66 



LAND AND FRESH WATER MOLLUSKS 



Fig. 42. Lymnaa 



kenzie River; Fort Anderson, Lat. 68° N. ! and Lake Harrison, Lat. 



70° N ! Shawnigan Lake, Vancouver Island ! and Dall River, Lat. 

 66° N. ! of the Yukon drainage in Alaska. The 

 following additional localities are cited from the 

 literature : York Factory, Keewatin, and the Nel- 

 son River ; Egg Lake, Alberta ; Red Deer, McLeod, 

 and Olds ; Lake Isle Lacrosse and Vermilion Lake ; 

 Lake Osoyoos, B. C. (but replaced west of the 

 Cascades by Z.. sufnasst't, according to J. K. 

 Lord) ; Syniakwateen Lake, B. C. ; lakes in the 

 Kenai Peninsula, Alaska (Wossnessenski) ; Stewart 

 River, Yukon district (Canadian Geol. Survey). 



It seems unnecessary to cite the multitudinous 

 varietal names bestowed on the mutations of this 

 species in Europe. In a wide sense it is one of the 

 most easily recognizable of fresh water shells, as 

 it is one of the most conspicuous of circumboreal 

 species. 



Lymnaea petersi n. sp. Plate 11, fig. 3. 



Shell extremely thin, of five or more tumid rapidly enlarging whorls ; 

 spire acute, the suture deep ; whorls rounded, the periphery nearer 

 the preceding suture ; shell of a blackish brown, polished, finely 

 sharply spirally striate ; periostracum brownish, darker at resting 

 stages ; aperture oval, a thin wash of callus on the body ; pillar very- 

 thin, gyrate, the gyrations pervious ; the outer lip not thickened. 

 Height 16; max. diam. 8; height of aperture 8.5 ; width 5.2 mm. 



Range. — Koyukuk River, north of the Yukon in Alaska; W. J. 

 Peters of the U. S. Geological Survey. 



This very delicate and pretty species appears to belong to the typical 

 Lynincea in spite of its small size ; it has much the aspect of a minute 

 L. randolphi., but has more whorls in less than half the height, and is 

 of quite a different color and without angularity to the whorls. 



Lymnaea atkaensis Dall. Plate 11, figs. 8, 10. 



Limna-a atkaensis Dall, Proc. U. S. Nat. Mus., vii, p. 343, 1884. 



Range. — Lake on the island of Atka, Aleutian chain, near Korovin 

 Bay. 



Shell with about four ovate whorls rapidly increasing, of a dark 

 olive sometimes purplish tint, very thin, malleated, microscopically 

 reticulated, with obscure revolving ridges ; the aperture ovate, not 

 expanded, the margins thin, that on the pillar narrowlv reflected; 



