CALFGUS, a genus of Entomostracous Crustacea, separated by Muller, in which Latreille,and Lamarck include the genus Fondants of Leach, but which Desinarest places under the fourth sub-division or race of Pcecilopoda : namely, those which have fourteen feet, of which the six anterior are unguiculated, the fifth pair being bifid with the last joints fringed with fine hairs in the form of cilia.
It has the body depressed, having its anterior portion covered by a membranous shell in the form of a shield, narrowed posteriorly. Abdomen narrower, of an elongated oval or nearly square shape, and terminated by two elongated antenna;-like processes, cylindrical and simple. There are two small conical antennm situated on the anterior border of the head, and directed laterally, and at the internal base of these are placed the two distant eyes. Beneath the head there is an obtuse beak.
Ca1 igua, together with degas& and other of its congeners of the family Spite/memo's/a, sue commonly known among the fishermen sus Fish-Lice. But Caligua is without the cupping-glass-like suckers, by which A rgulms adheres to its slipper" supporters ; and the hooks of the anterior pairs of feet are theprincipal organs by which the former holds on to the fish. [Anort.rs.] A Tulsa and are now usually regarded as types of distinct families A rgulithr and Cal ighbr. A rgulus is the only genus in the family A rgellidm. With Cal are included the following British genera, Lepeopthirom, Chalimuo, Trebitis.
Dr. ltaird, in his 'Iliatory of the British Entomostmeous Crustacea,' describes four species of Caligus as natives of Great Britain. C. Malleri is found parasitic upon the Cod (Morrhua ralgaria) the Brill or Brett (Rhomtua rulgaris) and upon several other fishes. The following description is from
Baird :— Female.—Carapace oval, rather longer than broad, narrower at upper extremity ; frontal plates of considerable size, notched in the centre ; lemules well developed ; antenna of considerable size ; basal joint large. Thorax shorter than the cara pace, about half the size ; penultimate joint very small, of an elongate diamond shape ; last joint nearly quadrilateral, and lobed at the posterior ex tremity. On each lobe there are two very small tubercles, each of which gives off two short Bette. Abdomen very short and rounded, broader than long; caudal plates terminated by three tolerably long plumose set--e; internal fork with simple short obtuse branches ; second pair of foot-jaws very long, the last joint being narrow, long, and termi nated by two curved claws, one longer than the other ; fourth pair of legs stout, the first joint broad and thick, tho last ending in one long stout curved claw, which is serrated on its inner edge, and two short ones ; oviferous tubes of considerable length.
Male.—In the male the last joint of thorax is considerably smaller than in the female and more rounded ; the lobes much sharper, and terminated by the same tuberelea, but of a larger size. Abdomen about two-thirds the size of the last joint of thorax ; second pair of foot-jaws large.
C. diaphanua is found on the turbot, the gurnard, the mackerel, the plaice, the bolibut, and other fish.
C. rapa.v has been taken on the gurnard, Lough Neagh trout, brill, whiting, dory, and common dab.
C. centrodonti, has been found on the fins and tail of the common Sea-Bream (Pagellus centrodontus) alone.