The accompanying illustration represents the commonest of the group--the Common Shore Crab (_Carcinus mænas_), which is found plentifully on all our coasts, and even in brackish water far up the estuaries of rivers. It is a very voracious and pugnacious creature, probably the most active of all our crabs, and its movements, whether connected with its feeding, its sports, or its warfare, are always very interesting when observed through clear water. This crab varies considerably in colour, but is usually of the greenish tinge shown in the frontispiece. Another abundant and well-known species is the Edible Crab (_Cancer pagurus_), which is as familiar an object in town as on the sea coast. Unlike the common lobster, its natural colour is not considerably changed by boiling, being only turned from a dull to a brighter red. The finest specimens of this crab are to be caught beyond low-water mark, the usual snare being the basket or pot, baited with fish refuse, but large numbers live among the stones and rocks left exposed at low tide, and sometimes include specimens of considerable size. They should be looked for under large stones that are loosely piled together, or in the narrow chinks of rocks. It is very interesting to compare the habits of the two common crabs just mentioned. The former, when molested, will run off in great haste, but always retreat with its front to the enemy, and its sharp and powerful pincers far apart and wide open, ready for immediate use in its own defence if necessary. The latter species, on the other hand, though strongly built and provided with formidable claws, seldom runs far, and hardly ever attacks one in the act of pulling it out of its hiding-place; but, on the contrary, doubles all its ten legs under its body as if endeavouring to approach, as nearly as possible, the form of a ball, and will allow itself to be rolled about without showing any signs of life. The genus _Xantho_ contains two or three species that are common on the Cornish and Devon coasts, and which may be known by their depressed and deeply-grooved carapace and the presence of three or four prominent tubercles on the latero-anterior margins. The abdomen of the female has seven joints, while that of the male has only five. One of these (_Xantho florida_), shown on Plate VI., is a powerfully built crab, as may be seen when, after being disturbed, it pushes its way among the loose stones of the beach, often lifting masses many times its own weight.