ent individuals. Those from M. Pfeiffer are, I think, the young of V. cristata, and the others (I forget from whom, but with the name of Draparnaud) the young of V. piscinalis. Mr. Miller introduced V. minuta into his catalogue of the land and freshwater shells of the environs of Bristol, but no specimen of it is preserved in the Bristol Museum. Dr. Turton says, that his V. minuta is the Helix serpuloides of Montagu. This is well known to be a marine shell, referrible to the genus Skenea of Fleming. Mr. Thompson of Belfast has, however, favoured me,” continues Mr. Alder, "with the examination of a shell which may possibly turn out to be the V. minuta Drap., though I suspect it to be marine."

ORDER II. PNEUMONOBRANCHIATA.

THE respiratory organs consisting of a number of pulmonary vessels spread over an open or closed baglike cavity on the back of the neck, they breathe free air, and either live constantly on the land or in the water, in which latter case they come periodically to the surface to respire.

The shell is rarely wanting.

This order is divided into families in the following

manner:

Sect. I. Inoperculated. Edge of the mantle adherent to the back of the neck, forming a closed pulmonary chamber, leaving a hole for the entrance and exit of the air; operculum none; hermaphrodite. A. Terrestrial. Tentacles cylindrical, retractile; upper pair having the eyes at their tip.

Fam. 1. Arionida. Head and tentacles retractile; end of the tail truncated, bearing a mucous gland.

Fam. 2. Helicida. Head and tentacles retractile; end of tail simple, conical.

B. Aquatic, Tentacles contractile, with the eyes at or near their base.

Fam. 3. Auriculide.

Head elongated into a

rugose muzzle; tentacles subcylindrical, eyes near the inner side of their base.

Fam. 4. Limnaida. Head bifid; tentacles compressed, with the eyes on the outer side of their base.

Sect. II. Operculated. Mantle edge separate from the back of the neck, leaving the pulmonic cavity open; tentacles contractile; dioecious; operculum distinct.

Fam. 5. Cyclostomida. Muzzle ringed; tentacles two; operculum spiral.

Sect. I. INOPERCULATED. (Inoperculata.)

The edge of the mantle adherent to the back of the neck of the animal, forming a closed pulmonary chamber, leaving only a hole for the entrance and exit of the air, which is closed by an external valve on the side of the cavity.

They are all destitute of any operculum, but close the shell, during the torpidity of the animal, with a lid or epiphragm formed of its inspissated humours, and sometimes hardened with a little calcareous matter.

They are all hermaphrodite, but require mutual impregnation, and feed on vegetables; but some few have carnivorous propensities, and others, when they live near man, acquire bad habits, and eat paper and dead animal matter.

They may be divided into two groups, by the form of their tentacles, which conform to their more or less aquatic habits.

A. The terrestrial animals have cylindrical retractile tentacles, the upper pair the longest, having the eyes at the tip; the lower pair smaller, sometimes wanting. They are truly terrestrial, and are divided into two families.

Fam. 1. ARIONIDE.

Head and tentacles retractile* into the skin, which covers them as a sheath, being drawn into the cavity of the body; the end of their tail is as it were truncated, and furnished with a gland on its upper edge; the respiratory cavity is in the front of the body, with the hole in the front of the mantle's edge; and the orifice of the generative organs is placed on the right side, near, or immediately under, the respiratory aperture. (p. 103. f. 1.) The shell is presented in very different degrees of development in the different genera,—it is very rudimentary in the only English one.

6.1. ARION Férus. (Land Soles.)

Body elongate, lanceolate, united its whole length to the foot; mantle shield-like, anteriorly ovate, granular; the orifice of the generative organs is immediately under the respiratory aperture. Shell distinct, oblong, sometimes only spongy, or only a few granules in the subtance of the mantle.

*Shell none, or hemispherical and spongy.

9. 1. ARION ater. Black Arion. Tentacles black; the

*

Ehrenberg proposes to call the tentacles of snails tentacula, and those of pond snails, which do not bear eyes, vibracula,