These are the shells of the Dog Whelk, and if you wait until the tide is quite low, and then hunt about on the weed-covered rocks close to the edge of the sea, you will very likely find some of the living animals crawling about. They feed upon the sea-weeds by means of a curious organ called the tooth-ribbon. This is just a narrow strip of gristle, set with row upon row of very tiny hooked teeth; and by drawing this backwards and forwards over the leaves of the weeds the animal scrapes off very tiny pieces, which it then swallows.
In the tooth-ribbon of one of these whelks there are about a hundred rows of teeth, with about nine teeth in each row: so that the animal has nearly a thousand teeth altogether. But of course you can only see them by means of a powerful microscope.
Although this creature is called a “winkle” it is really one of the whelks. It is very common, and you may often find its empty shell lying upon the shore. It is white, or yellowish white, in colour, and is generally about an inch and a half in length, with several high ridges running down it from the top to the bottom, and a number of smaller ridges running crosswise between them.
You would not think that this could be a very dangerous creature, would you? It looks as harmless as it can possibly be, and certainly you need not be in the least afraid to pick up a sting winkle if you find one crawling about, for it cannot injure human beings. But to other shell-bearing molluscs it is a very terrible foe indeed. I dare say that you have often noticed, when you have been picking up shells on the sea-shore, that a good many of those shells had small round holes bored through them. Well, those holes were pierced by a sting winkle. For this animal is a creature of prey, and feeds entirely on other animals which live in shells; and when it meets with one it fastens itself to its victim’s shell, and drills a hole right through it by means of its tooth-ribbon. It then pokes the tooth-ribbon through the hole into the body of the animal inside, and draws it back again. As it does so, of course, the sharp hooked teeth drag away little bits of the animal’s flesh, which the sting winkle swallows. It then pokes its tooth-ribbon down again into the body of the victim, and so on, over and over again, until its hunger is satisfied.
Of course you know the Periwinkle very well indeed by sight—and very likely by taste, too! So there is no need for me to describe it. But perhaps you did not know that there are two different kinds of periwinkles. One of these is the Common Periwinkle, which is very plentiful indeed on many parts of the coast. You may find it in thousands and thousands if you hunt about on the weed-covered rocks near the water’s edge when the tide is out, and no matter how many of them are caught, there always seem to be just as many again next day. This is the periwinkle which is used for food.
The other is the Dog Periwinkle. It is rather larger, and has a stouter shell. If you want to find it, you must look on the rocks about half-way between high and low water-marks, and there you will generally find it crawling about in numbers. But it is not good for food, because it often has a quantity of eggs inside its body, and inside these eggs the shells of the baby periwinkles are already formed, which make it dreadfully gritty. Thrushes, however, as well as a good many of the shore birds, do not mind this in the least, and they devour so many of both these kinds of periwinkles that it is quite a wonder that any are left alive.
In size and shape this very common creature is rather like the dog periwinkle. But its shell is white in colour instead of bluish black, and generally has two or three bands of light yellowish brown running round it. You may often find it crawling about on the weed-covered rocks when the tide is out.