128 AMERICAN SPECIES OF VERTIGO. 



four-toothed: 1 pliciform tooth deep on the parietal wall, 1 

 columellar, the rest smaller, in the palate. Peristome simple, 

 straight, the columellar margin shortly dilated above. Length 

 3, diam. 1.5 mm. Kamchatka (Morelet). 



Pupa borealis MORELET, Journ. de Conchyl. vii, 1858, p. 9. 

 PPR., Monogr. vi, p. 311. W. G. BINNEY, Terr. Moll, v, 

 1878, p. 211; Third Supplement, Bull. M. C. Z. xix, 1890, 

 p. 185, fig. in text ; Man. Amer. Land Sh. p. 483. 



Binney's figure of a specimen from Petropaulovski shows 

 no upper palatal fold, and might be considered identical with 

 V. arctica-, yet the teeth are so variable in these derivatives 

 of modesta that a single specimen is inconclusive. 



Wallenberg's figures of the form he calls V. shuttleworthiana 

 from Lapland look a good deal like modesta, the shells being 

 much larger than the true shuttleworthiana. See Malak. Bl. 

 v, pi. 1. 



25a. Vertigo modesta ultima n. subsp. Page 124, figs. 4, 4a. 



On the north shore of Norton Sound Mr. R. C. McGregor 

 obtained an entirely toothless form, having the shape and 

 striation of V. modesta, and probably merely a terminal mem- 

 ber of the mutation-series represented by the three-toothed 

 form found elsewhere on Norton Sound. Like the latter, it 

 is not distinguishable from the terminal forms of V. m. cas- 

 taneai except by the remote locality. It is smaller than 

 V. arctica extima of central Siberia and differs from V. 

 krausseana by having no teeth and by the somewhat greater 

 size. 



Length 2.6, diam. 1.4 mm. 



Length 2.5, diam. 1.5 mm. 



25&. Vertigo modesta mut. parietalis Ancey. PI. 10, fig. 4. 



" Shell having two teeth on the parietal wall" (Ancey). 

 The shape varies from that of corpulenta to about that of 

 modesta ; whorls about 5. Teeth 5, there being an angular 

 lamella; and the others are larger than in typical corpulenta. 

 The surface is somewhat striate, as in modesta and corpulenta. 

 Length 2.45, diam. 1.3 mm. ; 5% whorls. 



