264 NEW MELANIDiE OF THE UNITED STATES. 



more solid shell. The aperture is about one-half the length of the shell. Dr. Sho- 

 walter says in his letter that " this is the most uniform species in his collection." 



Genus STREPHOBASIS.* 



Testa cylindracea. Apertura subquadrata. Columella infern6 inerassata et retro-canaliculata. Oper- 

 culum corneum, ad spiram pcrtinens. 

 The mollusk, for which I propose this genus, was sent to me by Wm. Spillman, 

 M. D., of Columbus, Mississippi, and I have before me over a dozen specimens from 

 a third to nearly an inch in length. The very great number of species of the genus 

 Melania makes it desirable to eliminate any group, with characters sufficiently dis- 

 tinct to permanently recognize it. The very remarkable retrorse callus at the base 

 of the column, causing a lateral sinus, is characteristic of this genus. 



Strephobasis Spillmanii. PI. 35, fig. 74. 



Testa laevi, cylindracea, crassiuseula, vel tenebrosc~fusc& vel virente, vald<5 vittata, nitida ; spira obtusa, 

 curta, ad apicem carinata ; suturis irregulariter impressis ; anfraetibus superne eonvexiusculis, ultimo 

 constricto ; apertura subgrandi, subquadrata,. intus cserulescenti et valde vittata ; labro acuto, sinuoso ; 

 columella sinuosa, ad basim inerassata et retro canaliculata. 



Shell smooth, cylindrical, somewhat thick, dark brown or greenish, shining, very 

 much banded ; spire obtuse, short, carinate at the apex ; sutures irregularly im- 

 pressed ; whorls slightly convex above, the last one constricted ; aperture rather large, 

 somewhat square, bluish and much banded within ; outer lip acute, sinuous ; col- 

 umella sinuous, thickened at the base and channelled backward. 

 StrepTwhasis Spillmanii, Proc. Acad. Nat. Sci., 1861, p. 96. 



Hab. — Tennessee River, 4 miles above Chattanooga. Wm. Spillman, M. D. 



My cabinet and cabinets of Dr. Spillman, Dr. Showalter and Dr. Lewis. 

 Diam. -41, Length -95 inch. 



Eemarhs. — I owe to the kindness of Dr. Spillman a number of this remarkable 

 shell, to which he gave the habitat of Tennessee River, but did not designate from 

 what part. Fortunately, there were some young specimens which with those ap- 

 proaching maturity gives, us the advantage of tracing the great difference between 

 the old and young. The old are decollate, and present, by the body whorl being 

 flattened, an almost perfect cylindrical form, while the young, which have the spire 

 entire or nearly so, are almost perfectly oval and do not present a quadrate aperture, 

 but an ovato-rhombic one. The callus at the base of the columella is strong, and 

 amounts nearly to a fold, below which the channel suddenly turns backwards. The 

 upper portion of the whorl, immediately below the suture, is tumid, and hence it has 

 a bulbous appearance. This portion is usually lighter colored than the other parts of 

 the whorl. The color differs in some of the specimens, some being more disposed to 



* 3-T§i<pa>, I turn, and tfaait, base. 



