CHIEFLY OF THE UNITED STATES. 151 



basis, Trypanostoma and Litliasia, to which genera they seem nearest allied. The 

 operculum of the only one I have seen, gibberosa, is the same as Goniobasis and the 

 Melanidce generally. 



Strephobasis Ltonii. pi. 23, fig. 65. 



Testa laevi, subcylindracea, crassa, tenebroso-coruea vel oliva, raro vittata ; spira obtuso-conica ; suturis 

 impressis ; anfractibus octonis, couvesiusculis; apertura subcoastricta, rhouiboidea, intus albida, raro 

 vittata ; labro acuto, aliquanto sinuoso ; columella inferne iuora<!sata, ad basim caQaliculati et 

 retrorsa. 



Shell smooth, subcylindrical, thick, dark horn-color or olive, rarely banded ; spire 



obtusely conical ; sutures impressed ; whorls eight, somewhat convex ; aperture 



somewhat constricted, rhomboidal, whitish within, rarely banded ; outer lip acute, 



somewhat sinuous; columella thickened below and channelled, and drawn back at 



the base. 



Proc. Acad. Nat. Sci. 1864, p. 5. 



Hab. — Holston River at Knoxville, East Tennessee, JMajor S. S. Lyon, U. S. E. 



My cabinet. 

 Diam. -48, Length -92 inch. 



Remarlcs. — I have about a dozen, of various ages, of this well characterized species, 

 which is nearly allied to Spillmanii, (nobis). It differs in having a shorter aperture, 

 in being rather larger, and in not being so cylindrical. In the young of the two 

 there is a marked difference in outline, Lyonii being much more conical. Some of 

 the less cylindrical specimens approach olivaria, (nobis,) but that is a smaller species, 

 of a darker color, and almost always having two bands. Lyonii is usually without 

 bands. Among the specimens before me two have a single band, one has two bands, 

 one has four bands, and another has five bands. Four have a dark purple mark 

 round the base of the columella. In those before me the color of the epidermis is 

 very variable : several are light horn-color, one young one is almost a cinnamon 

 brown, and three are olivaceous. The old specimens are much eroded at the apex, 

 and this causes a more cylindrical outline. The aperture is about four-tenths the 

 length of the shell. 



I have great pleasure in dedicating this fine species to Major Sidney S. Lyon, of 

 the U. S. Engineer Corps, at this time (1864) in the field in East Tennessee. I .owe 

 to him the possession of these and other interesting species described in this paper. 



Trtpanostoma venustum. PL 23, fig. 66. 



Testa Isevi, acuminata, luteo-cornea, tenui, mucronata, evittata ; spira subelevata ; suturis impressis; an- 

 fractibus novenis, planulatis ; apertura paiTiuscula, subconstricta, elliptica ; labro acuto, subsinuoso ; 

 columella tenui, subcoutorta. 



Shell smooth, acuminate, yellowish horn-color, thin, sharp pointed, without bands ; 



