OP CONCHOLOaY 311 



52a. P. cylindraceum, Lea. Fig. 101. Smooth, sub- 

 cylindrical, thick; spire elevated; suture irregularly im- 

 pressed; whorls 7 — 8, planulate, slightly impressed, the 

 last narrow, obtusely angulate; aperture small, rhomboidal, 

 with a broad fuse below. Horn-color, with or without bands. 

 Boane Co., E. Tenn. 



g. Smooth species, not angulated. 



53. P. glandulum, Anth. Figs. 102, 103. Ventricose- 

 Gonic, smooth, thick; spire short, acuminate; suture well 

 marked; whorls 8, convex, rapidly increasing; body whorl 

 bulbous; aperture moderate, elliptical, with a well-defined 

 channel. Dark olive, with narrow white suture; aperture 

 reddish within. Ten7i. 



53a. P. subrobustum, Lea. Fig. 104. Smooth, pyrami- 

 dal, thick; spire elevated; suture impressed; whorls 9, flat- 

 tened, the last whorl large, wide, flatly convex, not angled at 

 the periphery; aperture small, obliquely oval, with a well- 

 marked, broad, recurved fuse. Dark horn-color. Holston 

 River, E. Tenn. 



54. P. Christyi, I^ea. Fig. 105. Elongately conical, some- 

 what thick; spire much elevated ; suture regularly impressed ; 

 whorls 10, slightly convex; aperture small, rhomboidal, with 

 a short, broad, recurved fuse. Horn-color, rarely banded, 

 whitish within. Cane Creek, Tenn. 



105a. P. Roanense, Lea. Fig. 106. Pyramidal, smooth, 

 thick; spire pyramidal, elevated; suture impressed; whorls 9, 

 flattened; aperture small, rhomboidal. Dark horn-color. 

 Holston River, E. Tenn. 



105b. P. univittata, i^ea. Fig. 107. Obtusely conical, thick ; 

 spire elevated; suture impressed; whorls 7, flattened, the last 

 sloping, convex, large; aperture moderate, a little produced 

 below. Light olivaceous, with a single band on the periphery. 

 Cahawha River ^ Ala. 



55. P. labiatum, Lea. Figs. 108, 109. Acutely conical, 

 smooth, rather thick, shining; spire attenuate, sharp-pointed; 

 suture regularly impressed; whorls 10, somewhat convex, 

 carinate towards the apex, the last whorl rather large ; aper- 

 ture somewhat small, rhomboidal ; outer lip much dilated and 

 very sinuous. Greenish horn-color, whitish within. Big 

 Miami River, Ohio. 



55a. P. pallidum, Lea. Figs. 110, 111. Attenuately coni- 

 cal, smooth, rather thick; spire much elevated; suture much 

 impressed; whorls 11, slightly convex, somewhat geniculate 

 above; aperture rather small, sub-rhomboidal; outer lip sharp, 

 sinuous; fuse very wide and truncate. Pale horn-color. 

 Niagara Falls. 



