KING-CRAB, the name given to an Arachnid, belonging to the order Xiphosurae, of the grade Delobranchia or Hydropneustea. King-crabs, of which four, possibly five, existing species are known, were formerly referred to the genus Limulus, a name still applied to them in all zoological textbooks. It has recently been shown, however, that the structural differences between some of the species are sufficiently numerous and important to warrant the recognition of three genera—Xiphosura, of which Limulus is a synonym, Tachypleus and Carcinoscorpius. In Xiphosura the genital operculum structurally resembles the gill-bearing appendages in that the inner branches consist of three distinct segments, the distal of which is lobate and projects freely beyond the margin of the adjacent distal segment of the outer branch; the entosternite (see [Arachnida]) has two pairs of antero-lateral processes, and in the male only the ambulatory appendages of the second pair are modified as claspers. In Tachypleus and Carcinoscorpius, on the other hand, the genital operculum differs from the gill-bearing appendages in that the inner branches consist of two segments, the distal of which are apically pointed, partially or completely fused in the middle line, and do not project beyond the distal segments of the outer branches; the entosternite has only one pair of antero-lateral processes, and in the male the second and third pairs of ambulatory limbs are modified as claspers. Tachypleus differs from Carcinoscorpius in possessing a long movable spur upon the fourth segment of the sixth ambulatory limb, in having the postanal spine triangular in section instead of round, and the claspers in the male hemichelate, owing to the suppression of the immovable finger, which is well developed in Carcinoscorpius. At the present time king-crabs have a wide but discontinuous distribution. Xiphosura, of which there is but one species, X. polyphemus, ranges along the eastern side of North America from the coast of Maine to Yucatan. Carcinoscorpius, which is also represented by a single species, C. rotundicauda, extends from the Bay of Bengal to the coast of the Moluccas and the Philippines, while of the two better-known species of Tachypleus, T. gigas (= moluccanus) ranges from Singapore to Torres Straits, and T. tridentatus from Borneo to southern Japan. A third species, T. hoeveni, has been recorded from the Moluccas. But although Xiphosura is now so widely sundered geographically from Tachypleus and Carcinoscorpius, the occurrence of the remains of extinct species of king-crabs in Europe, both in Tertiary deposits and in Triassic, Jurassic and Cretaceous strata, suggests that there was formerly a continuous coast-line, with tropical or temperate conditions, extending from Europe westward to America, and eastward to southern Asia. There are, however, no grounds for the assumption that the supposed coast-line between America and Europe synchronized with that between Europe and south Asia. King-crabs do not appear to differ from each other in habits. Except in the breeding season they live in water ranging in depth from about two to six fathoms, and creep about the bottom or bury themselves in the sand. Their food consists for the most part of soft marine worms, which are picked up in the nippers, thrust into the mouth, and masticated by the basal segments of the appendages between which the mouth lies. At the approach of the breeding season, which in the case of Xiphosura polyphemus is in May, June and July, king-crabs advance in pairs into very shallow water at the time of the high tides, the male holding securely to the back of the female by means of his clasping nippers. No actual union between the sexes takes place, the spawn of the female being fertilized by the male at the time of being laid in the sand or soon afterwards. This act accomplished, the two retreat again into deeper water. Deposited in the mud or sand near high-water mark, the eggs are eventually hatched by the heat of the sun, to which they are exposed every day for a considerable time. The newly hatched young is minute and subcircular in shape, but bears a close resemblance to its parents except in the absence of the caudal spine and in the presence of a fringe of stiff bristles round the margin of the body. During growth it undergoes a succession of moults, making its exit from the old integument through a wide split running round the edge of the carapace. Moulting is effected in exactly the same way in scorpions, Pedipalpi, and normally in spiders. The caudal spine appears at the second moult and gradually increases in length with successive changes of the skin. This organ is of considerable importance, since it enables the king-crab to right itself when overturned by rough water or other causes. Without it the animal would remain helpless like an upturned turtle, because it is unable to reach the ground with its legs when lying on its back. Before the tail is sufficiently developed to be used for that purpose, the young king-crab succeeds in regaining the normal position by flapping its flattened abdominal appendages and rising in the water by that means. The king-crab fishery is an industry of some importance in the United States, and in the East Indies the natives eat the animal and tip their lances and arrows with the caudal spine. They also use the hollow empty shell as a water-ladle or pan—hence the name “pan-fish” or “saucepan-crab” by which the animal is sometimes known. Fossil king-crabs have been recorded from strata of the Tertiary and Secondary epochs, and related but less specialized types of the same order are found in rocks of Palaeozoic age. Of these the most important are Belinurus of the Carboniferous, Protolimulus of the Devonian, and Hemiaspis of the Silurian periods. These ancient forms differ principally from true king-crabs in having the segments of the opisthosoma or hinder half of the body distinctly defined instead of welded into a hexagonal shield.

(R. I. P.)

Fig. 1.
1, Limulus polyphemus, adult (dorsal aspect).
2, Limulus polyphemus, young (dorsal aspect).
3, Prestwichia rotundata, Coal M., Shropshire.
4, Prestwichia Birtwelli, Coal M., Lancashire.
5, Neolimulus falcatus, U. Silurian, Lanark.
6, Hemiaspis limuloides, L. Ludlow, Leintwardine, Shropshire.
7, Pseudoniscus aculeatus, U. Silurian, Russia.

KINGFISHER (Ger.[1] Königsfischer; Walloon Roi-péheux = pêcheur), the Alceḍo ispida of ornithologists, one of the most beautiful and well-known of European birds, being found, though nowhere very abundantly, in every European country, as well as in North Africa and South-Western Asia as far as Sindh. Its blue-green back and rich chestnut breast render it conspicuous as it frequents the streams and ponds whence it procures its food, by plunging almost perpendicularly into the water, and emerging a moment after with the prey—whether a small fish, crustacean, or an aquatic insect—it has captured. In hard frosts it resorts to the sea-shore, but a severe winter is sure to occasion a great mortality in the species, for many of its individuals seem unable to reach the tidal waters where only in such a season they could obtain sustenance; and to this cause rather than any other is perhaps to be ascribed its general scarcity. Very early in the year it prepares its nest, which is at the end of a tunnel bored by itself in a bank, and therein the six or eight white, glossy, translucent eggs are laid, sometimes on the bare soil, but often on the fishbones which, being indigestible, are thrown up in pellets by the birds; and, in any case, before incubation is completed these rejectamenta accumulate so as to form a pretty cup-shaped structure that increases in bulk after the young are hatched, but, mixed with their fluid excretions and with decaying fishes brought for their support, soon becomes a dripping fetid mass.

The kingfisher is the subject of a variety of legends and superstitions, both classical and medieval. Of the latter one of the most curious is that having been originally a plain grey bird it acquired its present bright colours by flying towards the sun on its liberation from Noah’s ark, when its upper surface assumed the hue of the sky above it and its lower plumage was scorched by the heat of the setting orb to the tint it now bears.[2] More than this, the kingfisher was supposed to possess many virtues. Its dried body would avert thunderbolts, and if kept in a wardrobe would preserve from moths the woollen stuffs therein laid, or hung by a thread to the ceiling of a chamber would point with its bill to the quarter whence the wind blew. All readers of Ovid (Metam., bk. xi.) know how the faithful but unfortunate Ceyx and Alcyone were changed into kingfishers—birds which bred at the winter solstice, when through the influence of Aeolus, the wind-god and father of the fond wife, all gales were hushed and the sea calmed so that their floating nest might ride uninjured over the waves during the seven proverbial “Halcyon days”; while a variant or further development of the fable assigned to the halcyon itself the power of quelling storms.[3]

The common kingfisher of Europe is the representative of a well-marked family of birds, the Alcedinidae or Halcyonidae of ornithologists, which is considered by most authorities[4] to be closely related to the Bucerotidae (see [Hornbill]); but the affinity can scarcely be said as yet to be proved. Be that as it may, the present family forms the subject of an important work by Bowdler Sharpe.[5] Herein are described one hundred and twenty-five species, nearly all of them being beautifully figured by Keulemans, and that number may be taken even now as approximately correct; for, while the validity of a few has been denied by some eminent men, nearly as many have since been made known, and it seems likely that two or three more described by older writers may yet be rediscovered. These one hundred and twenty-five species Sharpe groups in nineteen genera, and divides into two sub-families, Alcedininae and Daceloninae,[6] the one containing five and the other fourteen genera. With existing anatomical materials perhaps no better arrangement could have been made, but the method afterwards published by Sundevall (Tentamen, pp. 95, 96) differs from it not inconsiderably. Here, however, it will be convenient to follow Sharpe. Externally, which is almost all we can at present say, kingfishers present a great uniformity of structure. One of their most remarkable features is the feebleness of their feet, and the union (syndactylism) of the third and fourth digits for the greater part of their length; while, as if still further to show the comparatively functionless character of these members, in two of the genera, Alcyone and Ceyx, the second digit is aborted, and the birds have but three toes. In most forms the bill does not differ much from that of the common Alcedo ispida, but in Syma its edges are serrated, while in Carcineutes, Dacelo and Melidora the maxilla is prolonged, becoming in the last a very pronounced hook. Generally the wings are short and rounded, and the tail is in many forms inconspicuous; but in Tanysiptera, one of the most beautiful groups, the middle pair of feathers is greatly elongated and spatulate, while this genus possesses only ten rectrices, all the rest having twelve. Sundevall relies on a character not noticed by Sharpe, and makes his principal divisions depend on the size of the scapulars, which in one form a mantle, and in the other are so small as not to cover the back. The Alcedinidae are a cosmopolitan family, but only one genus, Ceryle, is found in America, and that extends as well over a great part of the Old World, though not into the Australian region, which affords by far the greater number both of genera and species, having no fewer than ten of the former and fifty-nine of the latter peculiar to it.[7]

In habits kingfishers display considerable diversity, though all, it would seem, have it in common to sit at times motionless on the watch for their prey, and on its appearance to dart upon it, seize it as they fly or dive, and return to a perch where it may be conveniently swallowed. But some species, and especially that which is the type of the family, are not always content to await at rest their victim’s showing itself. They will hover like a hawk over the waters that conceal it, and, in the manner already described, precipitate themselves upon it. This is particularly the way with those that are fishers in fact as well as in name; but no inconsiderable number live almost entirely in forests, feeding on insects, while reptiles furnish the chief sustenance of others. The last is characteristic of at least one Australian form, which manages to thrive in the driest districts of that country, where not a drop of water is to be found for miles, and the air is at times heated to a degree that is insupportable by most animals. The belted kingfisher of North America, Ceryle alcyon, is a characteristic bird of that country, though its habits greatly resemble those of the European species; and the so-called “laughing jackass” of New South Wales and South Australia, Dacelo gigas—with its kindred forms, D. leachi, D. cervina and D. occidentalis, from other parts of the country—deserve special mention. Attention must also be called to the speculations of Dr Bowdler Sharpe (op. cit., pp. xliv.-xlvii.) on the genetic affinity of the various forms of Alcedinidae, and it is to be regretted that hitherto no light has been shed by palaeontologists on this interesting subject, for the only fossil referred to the neighbourhood of the family is the Halcyornis toliapicus of Sir R. Owen (Br. Foss. Mamm. and Birds, p. 554) from the Eocene of Sheppey—the very specimen said to have been previously placed by König (Icon. foss. secliles, fig. 153) in the genus Larus.

(A. N.)