LYMNJEIDJE OF NORTH AMERICA. 457 



of the type (plate XXX, fig. 29) with juvenile specimens of randolphi 

 (plate XLVIII, figs. 7-8) well illustrates the relationship of the two 

 species. Additional material of petersi is needed to satisfactorily de- 

 termine its position. Until the animal of this species and that of at- 

 kaensis is examined the correct position of these species must remain 

 purely conjectural. The form of the axis is that of the emarginata 

 group of Galba rather than of typical Lymncea. 



Galba atkaensis Dall. PI. XLVIII, figures 13-14. 

 Limncea ovata var. atkaensis Dall, Proc. Nat. Mus., VII, p. 343, 1884. 

 Limnceus atkinensis Clessin, Conch. Cab., p. 390, taf. LIII, fig. 11, 1886 

 (figure not typical). 



fLimncea ovata Dall, Report Fur Seal Inves., Ill, p. 544, 1866; Nautilus, 

 XIII, p. 132, 1900. 



Lymncea atkaensis Dall, Alaska Moll., p. 66, pi. 2, figs. 7, 9, 1905. 

 Shell : "With about four ovate whorls rapidly increasing, of a 

 dark olive sometimes purplish tint, very thin, malleated, miscroscopi- 

 cally reticulated, with obscure revolving ridges ; the aperture ovate, 

 not expanded, the margins thin, that on the pillar narrowly reflected ; 

 pillar gyrate, pervious, in the early whorls widely so, a condition con- 

 cealed in the adult." (Dall). 



Length. Breadth. Aperture length. Breadth. 



26.50 16.50 16.50 10.50 mill. 4 whorls, Dall. 



24.00 13.00 14.00 9.20 " 3J4 



17.00 11.50 11.20 7.50 " 4J^ 



22.00 16.00 15.50 9.00 " Type 29031. 



Types: Smithsonian Institution, two specimens, No. 29031. 



Type Location: See records. 



Animal, Jaw, Radula and Genitalia: Unknown. 



Range : Aleutian Chain, Alaska ; a species of the Alaskan region. 



RECORDS. 



Lake on the Island of Atka, Aleutian Chain, near Korovin Bay (Dall). 



Geological Distribution : Unknown. 



Ecology: Not recorded. 



Remarks : "This form grows in a region containing little lime, 

 and the shells are extremely thin and often eroded into holes, which 

 exhibit the peculiarities of the axis by which the species is relegated 

 to the typical Lymnaeas though externally it has much the appearance 

 of a small Radix." (Dall). 



This is a wider species than petersi, with less rotund whorls and a 

 shorter spire, and with a rounder aperture. The writer cannot agree 

 with Dr. Dall in placing this species in Lymncea. The axis is more of 



