NEW MELANID2E OF THE UNITED STATES. 265 



being dark brown, while others again are greenish. All which I have seen are more 

 or less banded, some of them so thickly so as to make the specimen almost black. 

 These bands are all apparent on the inside. The length of the aperture is naturally, 

 I presume, about half the length of the shell, but none of the mature specimens before 

 me have perfect spires, and therefore the proportion cannot be correctly ascertained. 

 There are 6 or 7 whorls. 



I have great pleasure in dedicating this interesting species to Dr. Spillman, to whom 

 I am not only indebted for this, but for very many of the mollusks which he has so 

 successfully discovered in the streams which flow through other districts as well as 

 his own. 



Strephobasis cornea. PI. 35, fig. 75. 



Testa, lsevi, eylindracea, crassa, cornea, ; spira obtusa ; suturis irregulariter impressis ; anfractibus superne 

 convexiusculis, ultimo eonstrieto ; apertura rbombo-quadrata, intua luteo-alba ; labro acuto, sinuoso ; 

 columella sinuosa, ad basim inerassata et retro-canaliculata. 



Shell smooth, cylindrical, thick, horn-color ; spire obtuse ; sutures irregularly im- 

 pressed ; whorls slightly convex above, the last one constricted ; aperture rhombo- 

 quadrate, yellowish white within ; outer lip acute, sinuous ; columella sinuous, thick- 

 ened and channelled backward at its base. 



Operculum small, ovate, spiral, dark brown, with the polar point near the base. 



Strephobasis cornea, Proc. Acad. Nat. Sci., 1861, p. 96. 



Hab. — Tennessee River, four miles above Chattanooga, Wm. Spillman, M. D. 



My cabinet and cabinet of Dr. Spillman. 

 Diam. '41, Length -88 inch 



Remarhs. — Among the previously described species from Dr. Spillman, 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 also 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 in 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 apicial whorls be observed. 



Strephobasis Clarkii. PI. 35, fig. 76. 



Testa lsevi, eylindracea, subtenui, luteo-cornea, trivittata; spira valde obtusa,, curta ; suturis irregulari- 

 ter impressis; anfractibus quinis, superne convexiusculis, ultimo eonstrieto; apertura subgrandi, 

 quadrats,, intus albida, valde vittata; labro acuto; columella sinuosa, ad basim alb&, inerassata et 

 retro-canaliculata. 



68 



