OF NORTH AMERICA. 455 



ville, mentioned by Dall (p. 71) are referred by the writer to binneyi 

 (see page 443). 



Galba alaskensis Baker. Plate XLVI, figures 14-15. 



Limnaa scalaris WESTERLUND, Nach. Mial. Ges., IV, p. 165, 1883; Vega 

 Exped., Vert. lakt., IV, pp. 163, 170, 201, pi. 4, fig. 13, a, b, 1885 (not scalaris 

 A. Braun, 1853, or Sowerby, 1872). 



Lymnaa emarginata DALL, Alaska Moll., p. 69, 1905. 



SHELL : Elongated, thin, fragile, pellucid ; periostracum light horn 

 colored; surface shining, sculpture of coarse growth lines crossed by 

 impressed spiral lines; whorls 6, convex, especially the body whorl; 

 sutures deeply impressed; spire long, acute; the spire whorls are ab- 

 ruptly narrowed and constricted above the body whorl ; aperture long 

 ovate or semicircular, a trifle shorter than the spire, roundly arched 

 above, subtruncated below; inner lip narrow below, widening above 

 to form the columellar callus which is heavy ; the inner lip is appressed 

 tightly at its junction with the parietal wall and forms a distinct as- 

 cending plait; the umbilical chink is narrowly open and is emargined 

 by the inner lip. 



Length. Breadth. Aperture length. Diameter. 

 22.00 10.00 9.00 6.00 mill. 



23.00 12.00 10.50 .... " 



TYPES: Location not ascertained. 



TYPE LOCALITY : Port Clarence, Alaska. 



ANIMAL, JAW, RADULA and GENITALIA: Unknown. 



RANGE: Alaska. A species of the Yukonian region and of the 

 Arctic life zone. 



RECORDS. 



ALASKA: Port Clarence (Westerlund). 



GEOLOGICAL DISTRIBUTION : Unknown. 



ECOLOGY : Not recorded. 



REMARKS: Alaskensis (scalaris) is undoubtedly a valid species 

 and not a synonym of emarginata, as thought by Dr. Dall. Its narrow 

 shell, acute spire, very deep sutures, causing tumid whorls, and its 

 regularly long, ovate or semicircular aperture will at once separate it 

 from any form of Galba emarginata canadensis, to which race it has a 

 superficial resemblance. It is totally unlike Say's figure of emarginata 

 besides which it occupies an entirely different river system. Young 

 specimens might be confused with juvenile forms of randolphi, but 

 could be easily distinguished by the more tumid whorls, deeper sutures 

 and generally narrower shell and aperture. It somewhat resembles 

 petersi, but may be known by its narrow shell and more tumid body 

 whorl, besides differing in the form of the inner lip. 



