72 



LAND AND FRESH-WATER SHELLS OF N. A. [pART IV. 



Fig. 138. 



Observations. — This is a very remarkable species, having a high 

 subcylindrical spire and a small aperture. Six from the Oosteuaula 

 are all more or less striate, two of them having a well defined revolv- 

 ing band near the base on the inside, one has an obsolete 

 band, and the remaining three are without a band. Three 

 of these specimens are of a bright horn-color, the others 

 are dark brown, and one has indistinct bands above the 

 dark one. The thickened part of the columella in three 

 specimens is of a light salmon. Three of the four from 

 Cahawba Eiver are slightly striate, the fourth smooth. 

 These have no bands and are all white on the columella. 

 The aperture is about one-fourth the length of the shell. 

 I have great pleasure in naming this after Dr. Showalter, who has 

 done so much in the development of the Mollusca of his State. 



This species is closely allied to Melania (Trypanos'.oma) Ordii 

 (nobis), but it is more attenuate and more cyliudrical. — Lea. 



C. Angulate, striate below the periphery. 

 16. P. Thorntonii, Lea. 



Trypanosloma Thorntonii, Lea, Proc. Acad. Nat. Sci., p. 170, 1862. Jour. Acad. 

 Nat. Sci., V, pt. 3, p. 284, t. 36, f. lOG. Obs., ix, p. 106. 



Description.— ^\iG\\ carinate, pyramidal, rather thick, horn-color, 

 banded or not banded; spire regularly elevated; sutures somewliat 

 impressed ; whorls about ten, flattened ; aperture rather small, rhom- 

 bic, white within ; outer lip acute, very sinuous ; columella j.jg jg^^ 

 thickened below and very much twisted. 



Operculum ovate, dark brown, with the polar point near 

 to the base. 



Jia&iiaf.— Tuscumbia, Alabama ; L. B. Thornton, Esq. 

 and Rev. G. White : Chattanooga, Tennessee ; J. Clark. 



Diameter, '62; length, 1-37 inches. 



Observations. — This appears to be a common species 

 about Tuscumbia and up the Tennessee River. I have 

 about sixty specimens before me. They came with a large 

 number mixed up with Mel. {Trypanostoma^ ^mdulata, Say, but were 

 easily separated from that species. They are always smaller, and 

 none have undulations. Like tindnlata they are usually banded ; only 

 eight are without bands entirely. Some specimens have a single 



