‘ 
CONCHOLOGICAL WRITINGS. 23 
4, Sub-genus. Shell transverse, thick, not truncated, knobby or 
warty. 18. P. gibbosus; 19. P. verrucosus ; 20. P. tubercularis ; 
21. P. nodosus. 
5. Sub-genus. Shell rounded or longitudinal. 22. P. pusillus ; 
23. P. subrotundus; 24, Potamilus obovalis. Raf. 
IJ. G. Puevrocera. Univalve. Shell variable oboval or conical, 
mouth diagonal crooked, rhomboidal, obtuse aud nearly reflexed at 
the base, acute above the connection, lip and columelle flexuose 
entire. Animal, with an operculum membranaceous, head separated 
from the mantle inserted above it, elongated, one tentaculum on each 
side at its base, subulate acute, eyes lateral exterior at the base of 
the tentacula. 6 species. 1. Pl. retusa; 2. Pl. saxatilis; 3. Pl. 
fasciata; 4. Pl. coneola; 5. Pl. angulata; 6. Pl. turricula. 
Raf. 
III. G. Amstoxts. Univalve. Shell thick oboval, mouth oval, 
ronnded at the base, obtuse above with a thick appendage of the lip, 
columelle flexuose, a small rugose ombilic. 2 Species, 1A, eburnea ; 
2. A. ventricosa. Raf. 
[From the American Monthly Magazine and Critical Review, Vol. IV, 
page 39, New York, 1818.] 
Farther Account of Discoveries in Natural History, in the Wes- 
tern States, by Constantine Samuel Rajinesque, Esq., com- 
municated in a Letter from that Gentleman to the Kuitor. 
[42] 
8. N. G. Exurpsroma. (Univalve Shell. Nat. fam. Neritinia. ) 
Shell oval, obtuse, mouth oblique, elliptical entire, thick lips, the 
inner one plaited, smooth covering the columella and ombilic, de- 
current and notched outside the mouth, below the columella. Three 
species. 
8. N. Sp. Eilipstoma gibbosa. 4 spires, a large knob behind the 
outward lip. From the Ohio and Wabash, length half an inch. 
9 N. Sp. Lllipstoma zonalisa. 3 spires, smooth, 3 transverse, 
zones violet. Kentucky river. 
10. N. Sp. £llipstoma rugosa. 5 spires, smooth, sutures. 
wrinkled. Ohio river. 
[106] 
General Account of the Discoveries made in the Zoology of the 
Western States. By C. F. Rafinesque, in 1818. 
(107) J ° 
8. Montiusca. As many as 25 new genera, and 212 species, 
(mostly new) have been discovered; many of which, however, are 
