106 AMERICAN SPECIES OP VERTIGO. 



16. VERTIGO TRIDENTATA Wolf. PL 12, figs. 1, 2, 3. 



"Shell narrowly ovate, amber-colored, highly polished; 

 whorls 5, smooth, with three teeth in the mouth, one on the 

 middle of the lower lip, and one on each side, forming a regu- 

 lar triangle" (Wolf). 



The shape varies from ovate to tapering oblong. It is 

 honey-yellow, shading to somewhat browner below, paler 

 above; surface smooth, with only faint indications of striae, 

 glossy. The last whorl is somewhat flattened externally over 

 the lower palatal fold, and has a rather narrow but generally 

 distinct crest behind the lip. The outer lip projects forward 

 and slightly inward near the middle. Parietal lamella high, 

 rather short. Columellar lamella blunt, directed downward. 

 Lower palatal fold strongly developed. Upper palatal fold 

 quite small or sometimes wanting. These folds stand on a 

 more or less distinct palatal callus. Angular lamella and 

 basal fold are never developed. 



Length 2.2, diam. 1.1 mm.; 5% whorls. 



Length 2, diam. 1.1 mm. 



Length 1.85, diam. 1.1 mm.; 4% whorls. 



New York : Troy, Aldrich ; Mohawk, G. H. Clapp ; Syracuse, 

 pleistocene, Burnett Smith. New Jersey: Princeton, A. D. 

 Brown ; near Clementon, Bayard Long. Pennsylvania : Phila- 

 delphia; York Furnace, A. P. Brown; Northampton Co., B. 

 Long. Ohio : New Philadelphia, Sterki. Indiana : Lafayette, 

 Tippecanoe Co., Satterthwait. Illinois: Canton, J. Wolf, 

 type loc. Also reported from Ontario, Minnesota, Michigan, 

 Kansas, Colorado, New Braunfels, Texas, etc. 



Vertigo tridentata WOLF, Amer. Journ. of Conch, v, 

 May 5, 1870, p. 198, pi. 17, f. 1. STERKI, Proc. U. S. Nat. 

 Mus. xi, 1888, p. 375, no. 15, pi. 42, f . 4 ; Nautilus iii, April, 

 1890, p. 135; xxix, 123 (Geneva, 0.). PLEAS, Naut. vii, 68 

 (Henry Co., Ind.). HANHAM, Naut. xi, 111 (Quebec). 

 DANIELS, 27th Ann. Rep. Dep. Geol. and Nat. Ees. Indiana, 

 1902, 632 (Danville and Dunreith, Ind.). HANNA, Naut. 

 xxiii, 95 (Douglas Co., Kansas). WALKER, Moll, of Michigan, 

 1906, p. 518, f. 153 (Ann Arbor and Grand Rapids). J. 



