4 DAVENPORT ACADEMY OF NATURAL SCIENCES. 



This quite distinct form was collected in considerable numbers at 

 Symon's Stage Station, near the foot of Pyramid Lake, Nevada. Its 

 nearest congener is A. porata Say, from which it differs in elevation, 

 sculpturing, and dentition. Since this last character is the one of chief 

 importance, the description of the dentition is here given. Comparing 

 the denticle formulae of the two forms, thus : 



A. porata. 



q 1 i I o 



30-18-5- ^ "*" -- 5-18-30,* 



4 + 4 



A. dalli. 

 34_23-7- -7-23-34, 



the dissimilarity is strongly marked. Specimens may be seen in nu- 

 merous private collections, and in the cabinets of the Smithsonian In- 

 stitution, the New York State Museum of Natural History, and the 

 Davenport Academy of Natural Sciences. 



VALVATID^E. 



Genus VALVATA Miiller (1774). 

 Valvata utahensis, sp. nov. 



(Plate I., Fi^s. 1-3.) 



Valvata sincera, var. utahensis. Call. Bull. U. S. Geol. Sur., No. n, p. 44, Plate 

 VI., Figs. 1-3 (1884). 



Shell operculate, narrowly umbilicate, conical, with minute trans- 

 verse striae, shining, somewhat pellucid, yellowish horn color at apex, 

 white below; spire obtusely elevated, flattened at tip; suture well im- 

 pressed ; whorls four, convex, regularly increasing, the uppermost ones 

 with a single well-marked carina, which becomes obsolete on the last 

 whorl ; last whorl equals one-half the whole length of the shell ; aper- 

 ture circular, slightly angled posteriorly; peristome simple, continuous, 

 joined to the next whorl above by a very slight calcareous deposit ; 

 within white. 



Operculum light horn color, corneus, spirally multivolute, slightly 

 produced posteriorly to conform to the shape of the aperture. Denti- 

 tion unpublished. 



Length, 4.80; breadth, 3.2o inm . 



Habitat. Lakz Utah, Utah. 



* After Ctimpson, Smithsonian Misc. Coll., No. 201, p. 14, Fig-. 6; also ibid., No. 144, p. 80, 

 ff. 158- 



