Perhaps this is the commonest of the British spider crabs. Indeed, it is so plentiful at Bognor, and at other places on the southern coast of England, that when a crab pot is taken out of the water as many as twenty or even thirty of these creatures are sometimes found in it. They are called by the fishermen “sea-spiders,” and are generally so clothed with those odd sea-weeds called “corallines” that you can hardly see any part of their “shells” at all. In this crab the carapace is drawn out in front into a very long beak indeed, which has four horns upon it, and the whole upper surface is covered with short, sharp spikes and stout hairs. [Illustration: PLATE XXIV 1. THE LONG-BEAKED SPIDER CRAB. 2. THE FOUR-HORNED SPIDER CRAB.] PLATE XXV THE PEA CRAB (1) This is a very odd crab indeed. In the first place it is extremely small. Even when it reaches its full size it is scarcely ever so much as half-an-inch across, while its body is so round that it really does remind one very much of a pea. Only it is not quite the right colour for a pea, for it is creamy yellow instead of green. And, in the second place, this crab lives in a very odd place--namely, inside the shells of living mussels, or pinnas, or even cockles! What it does there nobody seems quite to know. It does not appear to injure the animal to whom the shell belongs, although it is very fond of the flesh of mussels, and if it finds one of those creatures lying dead will certainly devour it. Perhaps it only creeps inside its shell for the sake of safety. At any rate, it is a very timid little crab, and if you open a mussel and find a pea crab lying hidden inside it, it will tuck up all its legs quite close to its little round body and lie perfectly still for several minutes in the hope that you will think that it is dead. On some parts of the coast pea crabs are so plentiful, that three out of four mussels are found to have one of these odd little creatures inside it. PLATE XXV CRAB CATERPILLARS (2 and 2 A) I dare say you did not know that crabs have caterpillars, just as insects have. We call these crab caterpillars “zoeas,” and they are not in the least like their parents. There are a great many different kinds, of course, for every crab has its own zoea, just as every butterfly and moth has its own caterpillar, and some of them are not very much like some of the others. But they are always very tiny indeed--they are scarcely as large, in fact, as the smallest grains of sand--and they always have a very long curved horn in front of the body and another one behind, and long waggly tails. And they swim in the oddest way possible--by turning somersaults in the water, over and over again!