STKEPHOBASIS. 45 



Habitat. — Tennessee Eiver, four miles above Chattanooga; Wra. 

 Spillman, M. D. 



Diameter, -41 ; length, -95 of an inch. 



Observations. — I owe to the kindness of Dr. Spillman a number of 

 this remarkable shell, to which he gave the habitat of Tennessee Kiver, 

 but did not designate from what part. Fortunately, there were some 

 young specimens which, with those approaching maturity, gave 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 being dark brown, while others again 

 are greenish. All which I have seen are more or less banded, some 

 of them so thickly 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 

 th« mature specimens before me have perfect spires, and therefore 

 the proportion cannot be correctly ascertained. There are six or 

 seven 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 fl.ow through other districts as well as his own. — Lea. 



6. S. cornea. Lea. 



Strephobasis cornea, Lea, Proc. Acad. Nat. Sci.,p. 9G, 18G1. Jour. Acad. Nat. Sci.> 

 y, pt. 3, p. 265, t. 35, f. 75. Obs., ix, p. 87. 



DestTijj^t'on. — Shell smooth, cylindrical, thick, horn-color; spire 

 obtuse ; sutures irregularly impressed ; whorls slightly convex above, 

 the last one constricted ; aperture rhombo-quadratc, yellowish-white 

 within; outer lip acute, sinuous; columella sinuous, thickened and 

 channelled backward at its base. 



