AMERICAN SPECIES OF VERTIGO. 137 



high as wide, the columellar border nearly vertical, reflected 

 above, dilated inwardly; outer margin somewhat angular to- 

 wards the insertion, the basal margin semicircular. On the 

 parietal wall a weak, short tooth stands deep within, behind 

 the callus connecting the lip-margins, while the columella is 

 toothless. Behind the aperture there is sometimes a very weak 

 indication of a callus [crest] parallel to the outer margin. 

 Length 2.2, diam. 1.2 mm. (Reinh.). 



Siberia: Chukchi Peninsula, at Pooten (Poot) ; branches of 

 St. Lawrence Bay; Ratmanof Harbor (Krause). Alaska, at 

 Chilkat Inlet. 



P. [upa] krauseana REINH ARDT, S. B. Ges. Nat. Freunde, 

 Berlin, 1883, p. 38. Vertigo krauseana Reinh., DALL, Alaska, 

 Land and Fresh Water Moll., p. 32 (Chilkat Inlet?). 



"Only a few examples show a weak, tubercular eleyation 

 on the columella. The species stands near the Greenlandic 

 P. hoppei Moller, in dentition, but the latter is distinguished 

 by the more plump, ventricose shape, paler color, smoother 

 and glossy surface and greater transparency" (Reinh.). 



This appears likely to prove merely a race of V. modesta, 

 but as it is not known to me autoptically and is smaller than 

 any Alaskan specimens I have seen, it is here allowed specific 

 rank. I have seen modesta and modesta castanea as short as 

 2.3 mm., but they were associated with larger specimens. 



28. VERTIGO DALLIANA (Sterki). PI. 11, fig. 1. 



Shell conic or ovate-conic, of greenish-horn color, transpar- 

 ent, finely irregularly striate in the lines of growth, polished ; 

 whorls 4%, well rounded, with deep suture, rather rapidly in- 

 creasing, the last occupying about % of altit., towards the aper- 

 ture somewhat ascending on the penultimate. Aperture la- 

 teral, somewhat oblique, subovate with just perceptibly flat- 

 tened palatal margin; margins approximate, the ends pro- 

 tracted; peristome shortly but decidedly expanded, with a 

 very fine thread-like lip near the margin, the same continuing 

 as a very fine callus on the apertural wall inside of the line 

 connecting the ends of the margins ; palatal wall quite simple ; 

 no lamellae (Sterki). 



