SCHIZOSTOMA. 355 



2, S. castaneum, Lka. 



Schisosfotna castaneum, Lea, Proc. Acad. Nat. Sci., p. 18G, May, 1860. Jour. Acad, 



Nat. Sci., V, pt. 3, t. 35, f. 50. Obs., ix, p. 69. 

 Gyrotoma castanea, Lea, Binney, Check List, No. 311. Brot, List, p. 27. 



Description. — Shell carinate, conical, rather thick, dark brown, im- 

 perforate; spire exserted : sutures very much impressed; whorls six, 

 flattened, with a single carina and four bands ; lip-cut straight, narrow 

 and deep; aperture rather small, elliptical, banded within, rounded 

 at the base ; columella white and thickened ; outer lip acute, slightly 

 sinuous. 



Operculum nearly round, light brown, with the polar point below 

 the middle on the inner side. 



Habitat. — Coosa River, Alabama; E. R. Showalter, M.D. 



Diameter, -32 ; length, -64 of an inch. 



Observations. — Several specimens are before me of nearly the same 

 size. A single, rather obscure carina follows round the middle of the 

 lower whorls, and is exhibited on the upper whorls just above Fig. 672. 

 the suture with more force. The four bands are obscure 

 on the outside, but well defined on the inside. One specimen 

 has but three bands, and another has very pale bands. The 

 impression made by the lip-cut is well defined and forms a 

 narrow, hem- like line below the suture. The aperture is rather 

 small, not being quite half the length of the shell, and is rounded at 

 the base. It is nearest in outline to pagoda (nobis), but may at once 

 be distinguished by the color being usually darker, by being less cari- 

 nate, in having a deeper lip-cut, and in being rounded at the base, 

 instead of being angular there, as that species is. The aperture is 

 rather more than one-third the length of the shell. — Lea. 



This shell is also closely allied to Wehimpkaense., Len, 

 which, however, has a short, wide fissure. I have endeavored 

 in the Synoptical Table of this genus to indicate the close 

 connection of certain species belonging to the opposite groups, 

 namely, those with the short, oblique, and those with the nar- 

 row, direct fissure. It is curious that almost every species 

 in the one section has its analogue in tlie other, with which, 

 perhaps, it has more ailinity than with tlie nearest of its own 

 section. 



