38 LAND AND FRESH WATER MOLLUSKS 



larger, and of a different tint, and the size of the whorls increases 

 more rapidly. It is less flat and much larger than I', exilis, which is 

 also of a different hue. 



It is the most common land shell on most of the islands of Bering 

 Sea and on the continent near the sea, where it usually occurs, but as 

 we move southward we find it occurring at continually greater eleva- 

 tions and entirely absent from the warm dry plains and valleys. It 

 attains from 7,500 to 10,800 feet elevation in the Sierra and Rocky 

 Mountains. 



*Vitrina exilis Morelet. 



Vitrina exilis MORELET, Journ. de Conchyl., vn, p. 8, 1858. PFEIFFER, 

 Mon. Hel. Viv., iv, p. 799, 1859. BINNEY, Bull. U. S. N. Mus., No. 

 28, p. 178, fig. 172, 1885 ; Terr. Moll., v, pp. 138, 200, pi. n, fig. B. 



Range. Northeastern Asia and adjacent islands, from Japan 

 northeastward . 



Kamchatka, at Petropavlovsk ! Bering Id. (Vega Expd.). 



This is a small species, of a whitish or translucent glassy hue ; 

 smaller and with a more elevated spire than its American representa- 

 tive V. alaskana. According to Binney V. exilis has the jaw and 

 radula as usual in the genus, the transverse rows of teeth numbering 

 37 . i . 371 with seven perfect laterals. 



I have seen no specimens from east of the Commander Islands ; the 

 shells thus identified are probably all V. alaskana. 



Genus Vitrea Fitzinger. 

 Vitrea radiatula Alder. 



Helix radiatula ALDER, Cat. Test. Newcastle upon Tyne, p. 12, No. 50, 

 1830. GRAY, in Turton's Man., p. 173, pi. xii, fig. 137, 1840. 



f Helix hammonis STROM, Trondj., Selsk. Skrift., p. 435, pi. vi, fig. 16, 1765. 



? Zonites viridulus MENKE, Syn., ed. n, p. 137, 1830. 



Helix electrina GOULD, Inv. Mass., p. 183, fig. in, 1841. 



Hyalina viridula BINNEY, Land and Fw. Sh. N. Am., i, p. 34, figs. 41-43, 

 1869 ; not of Menke? 



Hyalina pellucida LEHNERT, Science Record, n, p. 172, June 16, 1884. 



Range. Holarctic. Northern Europe, Asia and America. 



Manitoba, at Lake of the Woods, Carberry and Pembina ; Alberta, 

 at Laggan and Red Deer ; Fort Resolution, Great Slave Lake ! British 

 Columbia, at Departure Bay ! Comox ! and Union Bay ! Alaska, at 

 Killisnoo ! Klukwan ! Portage Bay ! Seduction Tongue ! Anuk ! St. 

 Paul, Kadiak Island ! Unga Island, Shumagins ! Unalaska, Aleutians ! 

 Nulato, Yukon River ! Point Barrow ! Bering Island, Bering Sea ! 

 Petropavlovsk, Kamchatka ! 



