304 AMERICAN JOURNAL 



6. P. nobile, Lea. Fig. 19. Pyramidal, thick; spire ele- 

 vated; whorls 9 — 10, flattened, the last angulate and tubei-<;u- 

 late on the periphery, striate below; aperture rather large, 

 rhomboidal, terminating in a narrow, rather long, twisted 

 canal. Yellowish horn-color. Alabama. 



Distinguished chiefly by the canal. 



7. P. robustum, Lea. Fig. 20. Conical; spire elevated; 

 whorls 10, flattened above, the last stout, convex and chan- 

 nelled, below the channel angled and tuberculate; aperture 

 rather small, rhomboidal; lip sigmoid, channel rather short. 

 Pale horn-color, obscurely banded. Tennessee River, Ala. 



h. Sulcate species. 



8. P. canaliculatum, Say. Figs. 21 — 25. Elevated, 

 conical; whorls 7 — 9, flattened, the last with a broad, shallow 

 groove just above the carinate angular periphery; aperture 

 rhomboidal; canal short. Horn-color, yellowish, brownish or 

 green, with or without baiids; aperture white, or tinged with 

 purple. Ohio River and tributaries, northern and southern. 



9. P. filum, Lea. Figs. 26—31. Conical; whorls 8—10, 

 flattened, the last deeply grooved, and much carinated on the 

 periphery ; base very short, nearly horizontal ; aperture short, 

 rhomboidal. Horn-color, yellowish, brownish or green, some- 

 times banded, white or purple within. Tenn., Ala. 



Shorter, more conical, and more carinate and deeper grooved than ca- 

 naliculatum. 



10. P. ponderosum, Anth. Figs. 32, 33. Pyramidal, 

 thick ; spire much elevated ; whorls 9, concavely flattened, the 

 last one with a raised carina on the periphery. Reddish- 

 brown; pale salmon-color or whitish within, sometimes nar- 

 rowly banded near the base. Tenn. River, Fox River, Tils., 

 North Ala., Oostenaula River, Geo. 



The largest species of the genus. Differs from the above in size and the 

 absence of the groove on the body whorl. Fig. 33 is P. dux. Lea. 



12. P. Troostii, Lea. Figs. 3-1 — 38. Conical or pupseform, 

 very much inflated ; suture irregularly much impressed; whorls 

 9, convex, all of them channelled and carinate, the last in- 

 flated, with a double carina, and excavated between. Yellow- 

 ish horn-color or greenish, with or without bands. Southern 

 Lnd., Term., N. Geo., N. Ala.. 

 Figs. 37 and 38 ai"e P. viride and P. ligatum, Lea. 



12a. P. affine, Lea. Fig. 39. Pyramidal, canaliculate; spire 

 elevated ; whorls 9, flattened, the last convex, deeply canalicu- 

 late in the middle ; base long ; aperture I'homboidal, with a 

 wide, well marked channel. Corneous, with or without bands. 

 Cumberland River, E. Tenn. 



