APPENDIX.
257
2.  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, fig. 2.
3.  H. fraterna. Shell convex, brownish-horn colour, 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, oblique, compressed, white tooth.
Breadth one-third of an inch.
Inhabits Pennsylvania.
I obtained a specimen of this shell several years ago, but supposing it to be an accidental variety of the hitsuta, 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 mono-don of Mr. Racket, (Trans. Linn. Soc. Lond. vol. 13, 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 species. PI. 15, fig. 3.
4. H. diodonta. Shell somewhat depressed; spire convex, very little elevated; whorls five, rounded, regularly