(31.) The cray-fish frequents rocky places, the crab[2561] spots which present a soft surface. In winter they both choose such parts of the shore as are exposed to the heat of the sun, and in summer they withdraw to the shady recesses of deep inlets of the sea. All fish of this kind suffer from the cold of winter, but become fat during autumn and spring, and more particularly during the full moon; for the warmth of that luminary, as it shines in the night, renders[2562] the temperature of the weather more moderate. CHAP. 51.—THE VARIOUS KINDS OF CRABS; THE PINNOTHERES, THE SEA URCHIN, COCKLES, AND SCALLOPS. There are various kinds of crabs,[2563] known as carabi,[2564] astaci,[2565] maiæ,[2566] paguri,[2567] heracleotici,[2568] lions,[2569] and others of less note. The carabus differs[2570] from other crabs, in having a tail: in Phœnicia they are called hippoi,[2571] or horses, being of such extraordinary swiftness, that it is impossible to overtake them. Crabs are long-lived, and have eight feet, all of which are bent obliquely. In the female[2572] the first foot is double, in the male single; besides which, the animal has two claws with indented pincers. The upper part only of these fore-feet is moveable, the lower being immoveable: the right claw is the largest in them all.[2573] Sometimes they assemble together in large bodies;[2574] but as they are unable to cross the mouth of the Euxine, they turn back again and go round by land, and the road by which they travel is to be seen all beaten down with their foot-marks. The smallest crab of any is that known as the pinnotheres,[2575] and hence it is peculiarly exposed to danger; its shrewdness, however, is evinced by its concealing itself in the shell of the oyster; and as it grows larger, it removes to those of a larger size. Crabs, when alarmed, go backwards as swiftly as when moving forwards. They fight with one another like rams, butting at each other with their horns. They have[2576] a mode of curing themselves of the bites of serpents. It is said,[2577] that while the sun is passing through the sign of Cancer, the dead bodies of the crabs, which are lying thrown up on the shore, are transformed into serpents.