We have other species of stone crabs, one or two of which resemble the last species, and belong to the same genus, but the others are very different in general appearance. The Northern Stone Crab (Lithodes), found principally on and off the coasts of Scotland and Ireland, has a spiny covering with a long beak. Another species—Dromia vulgaris—is somewhat similar in habit, though it can hardly be termed a stone crab, since it inhabits deep water, and apparently lives among the sponges, sea firs, and weeds that cover the bottom.
Fig. 212.—Dromia vulgaris
Fig. 213.—The Hermit Crab in a Whelk Shell
The remainder of the Peculiar-tailed Decapods belong to the Soldier or Hermit Crabs, and constitute the genus Pagurus.
Every one who has searched a few rock pools will have seen the familiar Hermits, and will probably have been interested in their varied antics. First you observe the shell of a mollusc—a Trochus, Periwinkle, or a Whelk—travelling at an abnormal rate for a member of its class. You approach closely to make an inquiry into the matter, when the motion suddenly ceases, and the shell instantly drops into position with its mouth close to the surface below. If left undisturbed for only a short time, the rapid and somewhat jerky motion is resumed, only to cease as suddenly as before as soon as the inhabitant is again threatened.
On examining the shell we find that it is the home of a species of crab, and that the animal within it is completely hidden with the exception of its head, stalked eyes and long, slender antennæ, one very large claw, and a few walking legs.