456 TIIK CHICAGO academy of sciences. 



\\'esterlund"s original Latin description is as follows : 



"Testa aperte rimata, elongata, tenuis, f ragilis, pellucida. irregu- 

 lariter striatula, pallide cornea, spira longa, supra anfractum penulti- 

 muni tumidum abrupte angustata, valde contorta, apice acuta ; anfr. 

 6, perconvexi, sutura profundissima perobliqua disjunct!, superne sub- 

 truncati, tumidi. basin versus forte declivi, attenuati ; apertura dimid- 

 iam testae non attingens. verticalis, subsemicircularis. margine exteriore 

 forte arcuato. superne sinuato. medio producto. (columella cum) mar- 

 gine columellari substricto. verticali. late reflexo, umbilicum semite- 

 gente ; columella incisura obliqua sat profunda, plica lata appressa." 



YVesterlund compares his species with Galba traski Tryon but is in 

 error as that species belongs to a different group. 



Galba petersi (Dall). Plate XXX. figure 29. 



Lymtuea petersi Dall, Alaska Moll., p. 66, pi. 2, fig. 3. 1905. — Pilsbry, 

 Nautilus, XIX, p. 95, 1905. 



"Shell: Extremely thin, of five or more tumid rapidly enlarg- 

 ing whorls ; spire acute, the sutures deep ; whorls rounded, the periph- 

 ery nearer the preceding suture ; shell of a blackish brown, polished, 

 finely, sharply, spirally striate; periostracum brownish, darker at rent- 

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

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



Height. Breadth. Aperture length. Breadth. 



16.00 8.00 8.50 5.20 mill. Type. 



Types: Smithsonian Institution, two specimens. Xo. 180332. 



Type Locality : Koyukuk River, north of the Yukon in Alaska. 



AnimaLj Taw, Radula and Genitalia: Unknown. 



Range : Alaska, north of Yukon River ; a species of the Yukon- 

 ian region. 



RECORDS. 



Koyukuk River, north of the Yukon in Alaska (W. J. Peters). 



Geological Range: Unknown. 



Ecology: Xot recorded. 



Remarks: "This very delicate and pretty species appears to be- 

 long to the typical Lymiicca 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.''' I Dall |. 



Petersi can scarcely belong to the typical Lymnaeas. Its close re- 

 semblance to young specimens of Galba randolphi would lead to the 

 assumption that its proper position is near that species. A camparison 



