100 VERTIGO. 



Length 2 mm., diam. 0.9 mm. ; 5 to 5y2 whorls. 

 Loess of Mona, St. Louis Co., Missouri. Type and para- 

 types 160362 A. N. S. P., collected by Mr. Leslie Hubrieht. 



Vertigo iDxVhoensis, n. sp. PL 22, figs. 9, 10, 11. 



The shell is ovate, rimate, with eonvexly conic spire and 

 obtuse summit ; cinnamon-brown, the spire paler ; glossy, with 

 extremely weak and rather sparse lines of growth and a faint 

 microscopic granulation. The whorls are strongly convex, 

 the last having an impression at the lip-point, a very low, 

 hardly noticeable crest, and behind it a deep pit over the 

 lower-palatal fold. The peristome is distinctly bent in above 

 the middle of the outer margin, well expanded below the point. 

 Columellar margin reflected. There are four teeth : a well 

 developed parietal lamella, a somewhat oblique columellar 

 lamella, and two palatal folds rather near together, as in 

 y. ventricosa and its allies, the lower-palatal being decidedly 

 larger and a little further in. There is no palatal callus. 



Length 2 mm., diam. 1.2 mm. ; 4i/^ whorls. 



Meadows, Adams Co., Idaho, along a creek east and north- 

 east of the old town. Type and paratypes 158670 A. N. S. P., 

 collected by H. Burrington Baker, Sept. 12-15, 1929. 



The whorls are more convex and the suture deeper than in 

 y. ventricosa, V. columhiana or V. andrusiana, and it differs 

 from all of these by the much deeper external pit over the 

 lower-palatal fold, the other species mentioned having the 

 whorl only somewhat flattened there. The teeth are much the 

 same in this whole ventricosa series, the palatal folds being 

 nearer together than in the V. modesta series. The develop- 

 ment of angular lamella and basal denticle is variable in some 

 forms of the ventricosa group, but neither is present in speci- 

 mens of V. idahocnsis seen. 



Vertigo modesta sculptilis, new mutation. PL 24, figs. 2, 3, 4. 



The shell has rather sharp sculpture on the penult and ante- 

 penult whorls of the spire, as in V. m. insculpta, but it differs 

 by the reduced size of the teeth ; small parietal, columellar and 

 lower-palatal being present in the specimen taken as type ; in 



