30 
very little oblique ; labrum simple ; umbilicus small, nearly con- 
cealed by the base of the labrum. 
Length rather more than one-tenth of an inch. Inhabits the 
North-west Territory. 
The elevated lines on this shell give it a very handsome appear- 
ance, and readily distinguish it from any of our native species 
that I have seen. The European analogue is the aculeata of 
Muller, but our shell is destitute of recurved points on the lamel- 
liform lines. PI. 15, f. 1. 
H. PORCiNA. — Shell depressed, yellowish brown ; epidermis 
rugose, with minute, very numerous bristles ; whorls rather more 
than four, depressed above, beneath rounded, forming a very 
obtuse angle rather above the centre of the whorl ; umbilicus 
open, rather small, profound ; labrum simple. 
Breadth rather more than three-tenths of an inch. Inhabits 
North-west Territory. PI. 15, f. 2. 
H. PRATERNA. — Shell coiivcx, brownish horn color, minutely 
hirsute ; whorls five, rounded ; umbilicus partially or entirely 
closed by the termination of the labrum ; region of the umbilicus 
indented ; aperture much contracted by the labrum ; labrum 
reflected, white, unarmed ; its outer edge not projecting beyond 
the curve of the whorl ; its inferior angle extends to the centre of 
the base of the shell , labium with a strong, prominent, com- 
pressed, white tooth. 
Breadth one-third of an inch. Inhabits Pennsylvania. 
I obtained a specimen of this shell several years ago, but sup- 
posing it to be an accidental variety of the hirsuta^ I laid it aside 
without further notice. Since then, however, Messrs. Hyde and 
Mason have presented numerous specimens of the same species to 
the Academy, having found it rather common ; I therefore no 
longer hesitate to consider it as a distinct species. It resembles 
Helix monodon of Mr. Rackett (Trans. Linn. Soc. London, vol. 
xiii., pi. 5), in the conformation of the aperture, but that shell is 
represented as being largely umbilicated, and its labrum does not 
extend near to the centre of the base, as it does in our shell. PI. 
15, f. 3. 
H. DiODONTA. — Shell somewhat depressed ; spire convex, very 
little elevated ; whorls five, rounded, regularly, but not promi- 
nently wrinkled, and grooved transversely ; aperture moderate ; 
