KING-CRAB. A large, singular crustacean like animal of the genus Limulus, also called 'horseshoe' and 'helmet' crab. It is, with four other species living in the tropical regions of Eastern Asia from Japan to the East Indian Archipelago. the sole surviving representative of a large group (Merostomata, q.v.) which dates from Cambrian times. The king-crab of our north eastern American coast is a large animal, some times nearly two feet in length, including the caudal spine. Its body is formed of two regions, the head and abdomen or hindbody. the caudal spine being a modification of the ninth or last abdominal segment. The large, broad, lunatc Bead is in general shape like a horse's hoof ; hence the local name given the ani mal. It is composed of six fused seg ments, and bears six pairs of legs, ending in forceps, corre sponding in position to t he antenme, jaws, and maxillae of the lobster or crab. On each side of the head are two compound eyes, In nate in shape, the surface of which is smooth, while there is a pair of minute simple eyes situated one on each side of a low conical spine in the middle near the front edge. The legs are armed on the basal joint with sharp spines pointing inward for retaining the food or prey. The males differ from the females chiefly in respect to the shape of the second pair of legs, which end in a swollen thumb (next to the last joint) and a slender finger (last joint). The abdomen consists of nine segments, which are dis tinct in the larva, but which on hatching be come fused together. It bears six pairs of broad, , leaf-like feet, those of - each pair fused together 1 along the median line, all 1,1111.1111M but the first pair bearing on each side a set of about one hundred leaf-like, flat, thin, oval gills. The abdominal limbs of the first pair are called the 'operculum.' since they form a structure which overlaps the other ab dominal legs, and on the under side bears two papilla. out of which the eggs pass, or, in the male, the seminal fluid.
The internal anatomy is remarkable for the shape of the nervous system, the brain being in front of the which passes through a nerve-ring. which distributes nerves to the appendages. The arteries are very numerous,
dividing into numerous microscopic branches, while the nerve-ring and principal nerves are coated by an arterial membrane, so that the blond bathes the whole nervous system except the brain.
Unlike the crustaeea. the female king-crab buries her eggs in the sand between tide-marks., and then leaves them at the mercy of the waves until the young hatch. They are laid in the Northern States, according to the locality, from the end of May till the end of June—sometimes in July. The young hatch from a month to six weeks after oviposition. The female lays at spring tide at high water. and the eggs are fer tilized by the male after they are extruded, he being slightly attached by his claws to the ab domen of his mate. Before hatching the shell bursts open, w bile the serous membrane within distends. acting as a thin, transparent, vicarious egg-shell. The young or larva just before hatch ing passes through a 'trilobite stage,' the seg ments being distinctly marked and the body di vided into three longitudinal lobes. The caudal spine is rudimentary, becoming longer after each molt. The first molt occurs between three and four weeks after hatching, the shell or skin split ting open around the front.
The king-erab burrows in the sand and mud of quiet bays and shallow estuaries, and is not to be found on the outer rocky shores of New Eng land. It lives on shellfish and worms, seizing them in a haphazard way as it burrows through the soft sand or mud, for which the body is ad mirably adapted. 'When it burrows the head is bent down at right angles to the hindbody, and if disturbed the caudal spine is held vertically, as a means of defense. It is extremely large and abundant in Delaware Bay and on the coast of New Jersey, where after being dried it is used as a fertilizer; it is also fed to swine and poultry. It also serves as a bait for eels and other fish. In the Moluccas the animal may be seen for sale in the market, being eaten by the lower classes of people. In the Southern United States it is called 'casserole-fish.' from its resemblance to a sauce-pan or casserole.