110 



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



Fig. 208. 



53 a. P. subrobustum, Lea. 



Trypanostomn subrobustum, Lea, Proc. Acad. Nat. Sci., p. 4, 1834. Jour. Acad. 

 Nat. Sci., vi, p. 141, t. 23, f. 50, 1SG7. 



Description. — Shell smooth, pyramidal, dark horn-color, thick; 

 spire pyramidal and elevated ; sutures impressed; whorls about nine, 

 flattened ; apei'ture small, rhomboidal ; outer lip sharp 

 and very sinuous ; columella thickened and very much 

 twisted. 



Operculum ovate, dark-brown, with polar point near 

 the base on the left side. 



Habitat. — Holston Eiver, at Knoxville, East Ten- 

 nessee. 



Diameter, -Gl ; length, 1-25 inches. 

 Observations. — A single specimen only, with an imper- 

 fect outer lip and much eroded spire, was received. 

 This is greatly to be regretted, as such a fine large species ought to be 

 well represented. This specimen has no bands and is without stria?. 

 It belongs to the group of which Hartmanii may be considered the 

 type, but may be distinguished by its being a larger and more robust 

 species, with a much larger body-whorl. The aperture is about oue- 

 third the length of the shell. — Lea. 



Fig. 309. 



54- P. Christyi, Lea. 



Trypanostoma Christyi. Lea, Proc. Acad. Nat. Sci., p. 173, 1862. Jour. Acad. Nat. 

 Sci., V, pt. 3, 272, t. 30, f. 83. Obs., ix, p. 94. 



Description. — Shell smooth, elongately conical, somewhat thick, 

 horn-color, rarely banded; spii'e very much elevated; sutures regu- 

 larly impressed; whorls about ten, slightly convex; aper- 

 ture small, subrhomboidal, whitish within; outer lip acute, 

 sinuous ; columella white and twisted. 



Operculum subovate, dark-brown, with polar point near 

 to the basal mai'gin. 



Habitat. — Cane Creek, Tennessee ; Prof. D. Christy. 



Diameter, -48; length, 1-12 inches. 



Obso-vations. — I am indebted to the late Joseph Clark 

 for many specimens from the above habitat, brought by 

 Prof. Christy. It is allied to Estabrookii, herein described, but it is a 

 larger and heavier shell, has a larger aperture, a much more twisted 



