46 



LAND AND FRESU-WATEK SHELLS OF N. A. [pART IV. 



Operculum small, ovate, spiral, dark browu, with the polar point 

 near the base. 



Habitat. — Tennessee River, four miles above Chattanooga; William 

 Spillman, M.D. 

 Diameter, -41 ; length, '88 of an inch. 



Observations. — Among the previously described species from Dr. 

 Spillmau were two of this, which, while it has a close resemblance, 

 still may easily be distinguished from it. They totally 

 differ in the color of the epidermis and the cornea is 

 without any bands. The substance of the shell is stouter 

 and the channel below not quite so well pronounced. 

 There is al o a disposition to thickening on the upper part 

 of the columella which the other has not. In both of the 

 specimens before me there is a thickening following the 

 inner edge of the outer lip. The lines of growth in both are well 

 marked, and iu all cases they begin below the antecedent one. 

 The length of the aperture would, I presume, be rather less than 

 half the length of the shell, but both specimens being decollate, the 

 true length of the shell cannot be ascertained, nor can the character 

 of the apical whorls be observed. — Lea. 



Fig. 93. 



7. S. Lyonii, Lea, 



Strephobasis Lyonii, Lea, Proc. Acad. Nat. Sci. .5, 18(U. Obs., xi, 107. 



Description. — Shell smooth, subcylindrical, thick, dark horn-color 

 or olive, rarely banded ; spire obtusely conical ; sutures impressed ; 

 whorls ciglit, somewhat convex; aperture somewhat 

 constricted, rhomboidal, whitish within, rarely banded; 

 outer lip acute, somewhat sinuous; columella thickened 

 below and channelled and drawn back at the base. 



Habitat. — Ilolston River at Knoxvillc, East Tennessee. 



Diameter, -48; length, -92 of an inch. 



Observations. — I have about a dozen, of various ages, of 

 this well characterized species, which is nearly allied to SpiUmanii 

 (nobis). It diflers iu having a sliorter aperture, in being rather larger, 

 and in not being so cylindrical. In the young of the two there is a 

 marked difference in outline, Lyonii being much more conical. Some 

 of the less cylindrical specimens approach olivaria (nobis), but that is 

 a smaller species, of a darker color, aud almost always having two 



