Our British Snails

by J. W. Horsley

I am now, therefore, writing about our British land shells, “slugs and snails” in common speech, with the hope that it may add a new interest to the country walks of lads and lasses.

I could show you a wall-case I made for a school. It contains specimens of all the British land shells with the exception of the slugs, which (with the exception of one of which I shall speak in its place) have no external or covering shell, although a small sort of shell, or at any rate some chalky grains, is found inside most of them. You would see that some are as small as a pin’s head although full grown, and they would require a magnifying glass to distinguish one from the other. The largest is Helix pomatia (figured on [pp. 11 and 12]), which often goes by the name of “the edible snail.” All snails are edible and nutritious; but this is the one cultivated in snail farms and sold as food abroad. Sometimes it is called “the Roman snail,” from an idea, probably wrong, that it was introduced by Cæsar’s soldiers, although as a matter of fact it is unknown in South Italy. Sometimes also it is called “the apple snail,” partly because it is as large as a middle-sized apple, and partly because people thought the name pomatia came from the Latin pomum, “an apple,” whereas it really comes from the Greek πῶμα. This word means a lid, or closing arrangement, and this mollusc makes a hard front door for itself when it hibernates, i.e. suspends active life and buries itself in the winter.

H. pomatia, half natural size.

It is much to be regretted that in most cases scientific names fail to give much information to the young student, and in some cases they give none at all. The first or generic name is supposed to be formed from Greek, the second, or specific, from the Latin, but there are some hybrids and many mere “nonsense names” to puzzle beginners. Thus the slug Limax gets its name from limus, “mud”; but a scientist, who ought to have known better, when wanting a name for another kind of slug, transposed the initial letters and made Milax! Vitrina is a sensible and descriptive name, the Latin for glassy, given to a shell like thin glass; but the Greek Arion recalls either a certain musician or a certain swift steed, neither of whom naturally suggests a slug. For Balea at least four derivations have been suggested—none of them probable. Two facts concerning the life or appearance of a mollusc we should learn from its two names, but this is not the case with Agriolimax agrestis, which is by interpretation “the field slug inhabiting fields.” Nor are we helped by the specific name virgata or striped when so many land shells are striped or banded, and still less by terrestris for one land shell when all land shells are terrestrial.

You would note, however, in this wall-case that the species are not many (a good many of the specimens are varieties, not separate species), and that, therefore, one can collect with the hope of speedily forming a complete collection without that inevitable absence of finality found when one collects postage stamps, or, still more, picture postcards, of which one might secure thousands, only to find that fresh thousands were brought out next year. Here, however, is no impossible ideal of perfection. There are but eighty-two land and forty-five freshwater shells in Britain.

Dextral H. aspersa and H. pomatia. The right-hand shell at the bottom shows the winter epiphragm of H. pomatia.

Let us imagine we are starting for an afternoon snailing near London. Which way? To Oxshott? To Caterham? To the latter for choice, since it is on the chalk, whereas the former is on the sand. Snails require lime to make shells, and only on chalk or limestone will you find an abundance. Here, too, as at Box Hill, we shall find the big Helix pomatia, only found in a few English counties, and very local there. If we were very fortunate, we might find a sinistral, or “left-handed” specimen. In the case of the pomatia on the right hand there is shown the thick epiphragm which the mantle secretes before the mollusc hibernates. It hardens on exposure to the air like plaster-of-paris; but is not a true operculum, for that is a constant possession of the shells which have it. Opercula are mainly found in marine or fluviatile shells, and may be either horny (like the winkle) or stony. Amongst our British land shells Cyclostoma elegans and Acicula lineata alone have true opercula, though others form some thin epiphragm for the exclusion of cold air and enemies when they hibernate.