112 AMERICAN SPECIES OF VERTIGO. 



thin, and typically by having more teeth. V. binneyana is 

 a paler, slightly more slender species, having a more distinct 

 crest, and a deeper external impression over the palatal folds. 

 All of these forms appear to be closely related, and are dis- 

 criminated with some difficulty. 



The type is no. 118419 A. N. S. P. A paratype has been 

 placed in the collection of S. S. Berry. 



In the topotypic lot the following tooth-mutations were 

 found in adult specimens : 



1. Angular, parietal, columellar, basal, upper and lower 

 palatals. 



2. Angular, parietal, columellar, upper and lower palatals 

 (type). 



3. ... parietal, columellar basal, upper and lower palatals. 



4. ... parietal, columellar, . . . upper and lower palatals. 

 The second arrangement is much the more abundant, the 



first, or complete tooth formula, and the third being rare, 

 one of each out of 27 specimens. 



The presence of a basal fold is therefore exceptional in 

 shells from around Bluff Lake. 



20. VERTIGO STERKH n. sp. PI. 11, figs. 2 to 5. 



The shell is imperforate, with a curved umbilical crevice, 

 ovate, chestnut-brown, glossy, slightly striate, but becoming 

 distinctly striate behind the lip. The whorls are moderately 

 convex, the last without any trace of a crest or contraction be- 

 hind the lip, having a short, inconspicuous impression behind 

 the auricle. The aperture has three teeth (or sometimes two) . 

 The parietal lamella is low and short. Columellar lamella 

 small, obtuse and deeply placed. The lower palatal fold is 

 small, tuberculiform (and wanting in some examples). There 

 is no palatal callus. The peristome is thin, brown, and well 

 expanded, having a slight prominence inwardly above the 

 middle of the outer margin, above which it is narrower. 



Length 2.1, diam. 1.25 mm. ; 4i/ 2 whorls. Type, fig. 3. 



Length 2, diam. 1.23 mm. 



Length 1.8, diam. 12 mm. 



California : Funston Meadow, Kern Eiver, Tulare Co., type 



