NEW MELANIDiE OF THE UNITED STATES 2G7 



shows the specimen to have been very imperfect in the aperture. Having subse- 

 quently received a number of perfect specimens (except in the apex), and finding its pro- 

 per place to be in the genus Strephobasis, I have made a new description, and propose 

 to give a more perfect figure. The specimens before me, more than a dozen, vary 

 much in outline, some being more cylindrical than others. One of them has two 

 obscure bands, visible inside and out. Another has an indistinct band inside at the 

 base of the columella ; others are white. Two from Kentucky have two broad dark 

 bands, and two are of an olive color, with a purple spot at the base of the columella. 

 In mature specimens the inner edge of the outer lip is thickened. Some of the mature 

 specimens have a broad furrow round the body whorl. The length of the aperture is 

 usually about the third of the length of the shell. 



Genus NERITINA. 

 Neritina SnowALTERir. PI. 35, fig. 78, 78a. 



Testa lajvi, rotundata, diaphana, hiteo-cornea, ; spira valde depressa ; suturis lovitcr imprests ; auiVactibus 

 trims, inflatis; apertura semirotunda ; labio dilatato, albo, incrassato, edentulo et iueurvato; labro 

 dilatato, tenui, rnargine acuto. 



Shell smooth, rounded, semi-transparent, yellowish horn-color ; spire very much 

 depressed ; sutures slightly impressed ; whorls three, inflated ; aperture semi-rotund ; 

 inner lip dilated, white, thickened, without teeth and incurved; outer lip acute, 

 dilate and thin. 



Operculum ? 



JSferitina Showalterii, Proc. Acad. Nat. Sci., 1861, p. 55. 



Hob. — Coosa River, ten miles above Fort William, Shelby County, Alabama. 

 E. R. Showalter, M. D. 



My cabinet and cabinets of Dr. Showalter and Dr. Lewis, and Academy of Natural 

 Sciences. 

 Diam. -22, Length -18 inch. 



Remarks. — The discovery of this shell by Dr. Showalter marks the first notice, I 

 believe, of the genus Neritina being observed in our fresh waters. His very close ob- 

 servation and active investigations of the waters of central and northern Alabama, 

 have enabled him to lay the naturalists of this country under many obligations by new 

 discoveries, and this is certainly one of much importance. We now see for the first 

 time that this genus, which is common in Europe, Africa, Asia, South America and 

 the West Indies, also inhabits our southern rivers. I have great pleasure in naming 

 the species after the discoverer. This species is not closely allied to any which has 

 come under my notice. It is more rotund than usual, has a clear horn-colored epider- 

 mis, smooth and shining. The substance of the shell is so thin as to permit the col- 

 umn to be visible through it. The inner lip is broad and slightly notched where it is 

 in contact with the body whorl. It is to be regretted that among the four specimens 



