88 THE NAUTILUS. 



curving regularly into the columella. Columella narrow, thickened, 

 rounded and concave, separated below from the body-whorl by a 

 small but profound umbilicus and a strong axial groove, adnate only 

 on the parietal wall, which is heavily callused. Alt. (apex eroded) 

 4.5, diara. 4.5 mm. 



Types (No. 28432, Coll. Walker) from Coosa River at Duncan's 

 Riffle, Chilton County, Ala. Co-types in the collections of T. H. 

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

 Academy. Also from the Coosa at Wilsonville, Ala. 



This species is about the size and general appearance of S. depres- 

 sus Tryon, and sargenti Pils. It differs from the former in its 

 heavier shell, sub-sutural constriction, large umbilicus and strong 

 axial groove. The latter species is rather larger, not so thick and 

 imperforate. A single specimen from Williamsville was recently 

 sent in by Mr. Hinkley, which was not included in the material sent 

 to me in 1904. 



Named in honor of Mr. J. B. Henderson, Jr., who has been a 

 hearty supporter of Mr. Smith's work on the Coosa. 



SOMATOGYRUS PYGM^US n. sp. PI. vi, fig. 3. 



Shell minute, globose-conic, imperforate, rather thin, light green- 

 ish horn-colored, smooth, lines of growth indistinct. Spire obtusely 

 elevated, whorls 4, convex, suture deeply impressed ; body whorl 

 large, convex, regularly rounded, impressed at the axis. Aperture 

 subcircular, not much expanded. Lip simple, sharp, thin, regularly 

 curved from the upper to the columellar extremity. Columella con- 

 cave. Columellar callus narrow, flattened, closely appressed to the 

 body whorl and extended over the parietal wall to the upper inser- 

 tion of the lip. 



Alt. (apex eroded) 2,5, diam. 2 mm. 



Types (No. 28433, Coll. Walker) from the Coosa River, at The 

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

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

 Academy. 



About twenty-five examples of this diminutive species were col- 

 lected at The Bar. It did not occur elsewhere. I have been wholly 

 unable to identify this form as the young of any of the associated 

 species. Though so small, the shells have every appearance of 

 maturity. Compared with young S. nanus of the same &\ze,pyg7naus 

 differs in the thinner shell, regular convexity of the whorls and 



