The chiton is one of the oddest of all the shell-bearing molluscs; for it does not look like a mollusc at all. It looks much more like a kind of sea woodlouse, or a very tiny armadillo. For instead of having a single shell like a whelk or a periwinkle, or a double one like a cockle or an oyster, it has eight shelly plates on its back which overlap one another, just like the tiles on the roof of a house. And if you touch it, it will often roll itself up into a kind of ball, just like the pill-millepedes, or “monkey-peas,” which are so common in our gardens. [Illustration: PLATE XII 1. THE PAINTED TOP. 2. THE GREY TOP. 3. THE COWRY. 4. THE CHITON.] This creature is called the Chiton, and if you want to find it you must go and look on the piles at the end of a pier, or on the rocks which are left bare at very low tides. There you will often find it in hundreds. Generally it is ashy grey in colour, but it varies a good deal in hue, and you will sometimes find examples which are streaked and mottled with pink, and orange, and white, and lilac, and chocolate brown. Before a chiton reaches its perfect form it passes through a kind of caterpillar stage, and then turns into a sort of chrysalis, just as an insect does. And both the caterpillar and the chrysalis, strange to say, have eyes upon their heads, while the perfect chiton has none. But some chitons have eyes all over their shells instead, and in some of these very odd creatures between eleven and twelve thousand eyes have been counted, the shells being almost entirely covered with them; so that the animals may really be said to see with their whole bodies! CHAPTER III BIVALVE MOLLUSCS PLATE XIII THE OYSTER (1) The “bivalve” molluscs are so called because they live in shells made of two parts, or “valves,” which are fastened together by means of a hinge. There are a great many of these, and the Oyster is one of the best known of them all. This creature is only found in places where the bottom of the sea is muddy, because in sandy places the sand is very apt to get into the hinges of the shells and to prevent them from being closed; and in that case the animal very soon dies from suffocation. So oysters are generally found in the mouths of rivers, or in land-locked bays where there is no sand at all. The history of these creatures is a very curious one indeed.