HERMIT CRAB, the common appellation of a large family (pagurida) of crustaceans, of the order decapoda, and sub-order-an-mount (see CRAB). having the abdominal or tail segments much more largely developed 'than in true crabs, -but undefended by hard plates, and not forming an organ for swimming, as in -lobsters, prawns, and other, macroura. The soft and tender tail requires a -protective covering, which the instinct of the hermit crabs leads them to find in some turblnated univalve shell of suitable size. The most common British species (pagurus bernhardus) is an interesting object to every visitor of the sea-shore, and may be found in abundance wherever little pools are left by the tide on a rocky or shelving coast. Shells of whelks, periwinkles, etc., may be seen moving about in the pools in a manner very different from that in which they were carried by their original molluscous owners, having now become the property and habita tions of hermit crabs, by which, perhaps, the mollusks were eaten. On the slightest alarm, the hermit crab retires into the shell, guarding the aperture of it with one claw, which is much larger than the other, the hard points of the feet also projecting a little.
The whole structure of the animal is adapted to such a habitation. The part which in the lobster becomes a finlike expansion at the end of the tail, becomes in the hermit crab an appendage for firmly holding by the shell; and so firmly does the hermit crab hold, that it may be pulled in pieces, but cannot be . pulled out. Some species have suckers to render the hold more perfect. Increase of size, however, renders it necessary fur hermit crabs to relinquish their old shells and seek new ones. Hermit crabs are very interesting inmates of the aquarium, but their locomotive habits and their voracity make them unsuitable for an aquarium otherwise very finely stocked. They feed on mollusks. and on all the animal garbage of the sea-shore.—Some of the hermit crabs of warmer climates are much larger than the British species; some of them (genus ecenobita) inhabit land-shells, and some are found even at a distance from the sea.