86 THE NAUTILUS. 



by boat down the Coosa from Rome, Ga., to Widtiska Shoals, Shelby 

 county, Ala., in 1904-5, have been worked up, it is not at present 

 possible to say how far up the river any of these species extend. 



SOMATOGYRUS DECIPIENS n. sp. PI. vi, figs. 10 and 11. 



Shell obtusely conic, imperforate, thick, solid, light greenish- 

 yellow, smooth, lines of growth very fine and inconspicuous. Spire 

 elevated, obtuse; whorls 4, roundly shouldered below the suture, 

 which is well impressed ; body whorl large, shouldered above, flat- 

 tened on the sides and obliquely angled below and descending to the 

 axis. Aperture very oblique, obovate, obtusely angled above and 

 widening toward the base, which is slightly emarginate. Columella 

 concave, with a heavy, wide, flattened callus which extends over the 

 parietal wall. Lip sharp, heavily thickened within. 



Alt. (fig. 11) (apex eroded) 3^, diam. 2^ mm. 



Types (No. 28431, Coll. Walker) from the Coosa River at The 

 Bar, Chilton county, Ala. Co-types in the collections of T. H. 

 Aldrich, G. H. Clapp, John B. Henderson, Jr., and the Philadelphia 

 Academy. Also from the Coosa at Cedar Island, Butting Ram 

 Shoals, Higgins Ferry, Duncan Riffle and other points in Coosa and 

 Chilton counties, collected by Smith, and from the Coosa at 

 Wetumpka, five miles above Wetumpka, "Wilsonville, Fort William, 

 and Montevallo, collected by Hinkley. 



A careful study of many hundreds of specimens has convinced me 

 that under the description of Somatogyrus hinkleyi (NAUTILUS, xxii, 

 p. 135) I confounded two distinct species, one imperforate, and the 

 other perforate. As both the figured types of hinkleyi fortunately 

 belong to the same form, the perforate one, that species will retain 

 the name under the amended description given below. The imper- 

 forate form is the species here described as decipiens. The dis- 

 tinctive characters of the two species are so marked that, once 

 appreciated, there is no difficulty in separating them at sight, and it 

 is a matter of some chagrin that the difference was not realized in 

 the first instance. 



S. decipiens is a smaller, thicker species than hinkleyi, and 

 always imperforate, without any suggestion of an axial groove. 

 While both species are alike in the elevation of the spire, decipiens 

 is at all stages of growth distinctly biangulate, with the intervening 

 side of the whorl flattened ; in some instances the lower angulation 

 becomes a distinct carina, but this is not usual. 



