21 
nati on the Ohio, and at Engineer Cantonment at Council Bluff, 
on the Missouri. 
Besides the above species, I have observed in the western 
regions the following known species, which I described in the 
American edition of Nicholson’s Encyclopaedia, and in the Journal 
of the Academy. 
H. ALBOLABRis. — Common as far as Council Bluff. 
H. THYROIDUS. — On the hanks of the Ohio, Mississippi and 
Missouri. The animal is of a pale whitish or yellowish color, 
immaculate. 
H. ALTERNATA. — On the hanks of the Ohio, Mississippi and 
Missouri Rivers ; this species varies in being somewhat larger, and 
in having a rather more elevated spire. The animal is of a dirty 
yellowish orange color. The foot obtusely terminated behind, 
head and tentacula pale bluish, eyes blackish. Shell nine-tenths 
of an inch in breadth. 
H. HIRSUTA. — Common as far as Council Bluff. 
H. LABTRINTHICA. “ “ “ 
H. 3UNUTA. “ “ “ 
H. PERSPECTIVA. — Occasionally occurs on the banks of the 
Missouri, and other western streams, and in some parts com- 
mon. 
PoETGYRA PLICATA. — Shell convex beneath, depressed above, 
spire slightly elevated ; whorls five, compressed, crossed by nu- 
merous raised, equidistant lines, which form grooves between 
them aperture subreniform, labrum reflected, regularly arquated 
describing two-thirds of a circle j within two-toothed, teeth not 
separated by a remarkable sinus ; labrum with a profound dupli- 
cature, which terminates in an acute angle at the centre of the 
aperture ; beneath exhibiting only two volutions, of which the 
external one is slightly grooved near the suture. 
Inhabits Alabama. Breadth one-fourth of an inch. Cabinet of 
Academy. 
This species is about the same size as P. avara, but, besides 
other characters, it is sufficiently distinguished by the acute fold 
of the labrum. It was sent to the Academy by Mr. Samuel 
Hazard. 
Pupa arjuifera. — Shell dextral j oblong oval, or somewhat 
