Oct. 1847.] 288 



minute, spire very short ; suture somewhat channelled ; umbilicus rather largt . 

 Length 4-10. 



Sigaretus Mississippiensis. 



Obliquely oval, with fine very closely arranged wrinkled revolving lines ; 

 whorls convex ; no umbilicus. Length 8-10. 



This species is usually much smaller than the specimen described. 

 scarcely differs from a species of Claiborne, Alabama. Not very common. 



1. Natica $Iississippiensis. 



Subglobose, body whorl flattened above ; suture channelled ; spire little pro- 

 minent; base profoundly callous; aperture moderate. Length 8-10. 

 This rare species I found about 7 or 8 miles N. W. of Vicksburg. 



2. Natica Vicksburgensis. 



Subglobose, whorls 4 or 5, convex; umbilicus large; columella straight; la- 

 bium callous. Length 6-10. 

 This species is common. 



Scalaria trigintanaria. 



Turreted, whorls convex, cancellated with numerous prominent lines, the 

 longitudinal one lamellaeform and elevated towards the suture, about 32 in 

 number on the body whorl, which is obtusely carinated ; revolving lines equally 

 prominent with the longitudinal, but thicker; base below the carina with 

 minute revolving lines. Length 9-10. Very rare. 



Turritella Mississippiensis. 



Subulate, volutions flattened, with seven revolving lines on the larger ones 

 the penultimate line large and prominent ; longitudinal wrinkles fine, approxi- 

 mate, much curved, crenulating the revolving lines ; the whorls near the apex 

 generally with two prominent distant revolving lines, and a less prominent one 

 margins the suture. Length 3 inches. Not abundant. 



1. Terebra divisurum. 



Subulate, with nineteen flattened volutions, obscurely turreted ; polished and 

 with longitudinal curved ribs, dislocated by an impressed line above the middle 

 of each whorl ; ribs obsolete on the body whorl below the impressed line. 

 Length 2 inches. Common. 



The ribs are sometimes obsolete on the larger whorls, or replaced by co 

 wrinkles, which are generally distinct on the body whorl. 



2. Terebra tantula. 



Subulate, with longitudinal ribs dislocated by an impressed line ; whorls with 

 minute revolving lines. 



Very similar to the preceding, but narrower, far less in size, and distinguished 

 by the revolving lines and by the ribs on the body whorl, which extend to the 

 beak. Length . Rare. 



1. Pleurotoma poreellana. 

 Fusiform, smooth and polished ; whorls 11, convex, with two revolving lines 

 near the upper margin ; the interstices transversely striated ; body whorl with 



