Descriptions of two new and one poorly known species of the genus Caligus Miiller, 1785 (Copepoda: Siphonostomatoida) G. A. Boxshall & A. R. Gurney British Museum (Natural History), Cromwell Road, London SW7 5BD Introduction Caligus dubius was first described by Scott in 1894 from material collected from the plankton of Loanda Harbour, Gulf of Guinea. Both sexes were present in Scott's material but his inadequate description was based only on the female. The single subsequent record of C. dubius is that of Leigh-Sharpe (1934) who assigned some material from the Siboga expedition to C. dubius. No host or station data are available for Leigh-Sharpe's material. The type material of C. dubius is stored in the collections of the British Museum (Natural History) and reexamination of this material has revealed several significant differences from the specimens described by Leigh-Sharpe (1934). The female of C. dubius is redescribed and the male is described for the first time. Leigh-Sharpe's material is redescribed as a new species, C. sibogae, belonging to a well defined group of species within the genus Caligus. The diagnostic features of this group, called here the macarovi-group, are described and its 28 member species are listed. A second new species, C. antennatus, is described from material sent from Kuwait by Dr I. U. Tareen. This species is also referred to the macarovi-group. Specimens were dissected and examined in lactophenol using phase contrast microscopy. Some specimens of C. antennatus sp. nov. were freeze dried and examined by scanning electron microscopy. Drawings were made either using a camera lucida or by tracing from micrographs. Caligus dubius Scott, 1 894 Caligus dubius T. Scott, 1894 : 130, pi. XIV, fig. 22. nee. Caligus dubius : Leigh-Sharpe, 1934 : 19-21, figs 17, 18. ADULT FEMALE. Dorsal shield (Fig. 1A) subcircular with marked posterior sinuses, and comprising half the total body length. Free margin of thoracic portion of dorsal shield extending beyond posterior tips of lateral portions. Genital complex distorted in preserved syntype but approximately 1 -5 times longer than broad, greatest width near posterior margin and tapering slightly anteriorly (according to Scott, 1894: pi. XIV, fig. 22). Abdomen 1 -segmented, 3 times longer than broad. Caudal rami about 2*5 times longer than broad and armed with 3 long plumose setae and 3 short setae. Body length of syntype female 3'6 mm. Egg strings about 1 mm in length and containing 8 eggs. First antenna of usual structure for genus but with many armature elements missing from syntype. Second antenna (Fig. IF) with a posteriorly directed spinous process on basal segment, middle unarmed, terminal segment subdivided into a basal portion carrying 2 small setae and a claw-like apical portion. Post antennal process (Fig. ID) with a small base bearing 2 multiple setules and a long slender tine. Mandible of usual form for genus. First maxilla (Fig. IE) anterior process with 3 naked unequal setae, posterior process with a simple slender tine. Second maxilla (Fig. 2A) with long flabellum on brachium (see Kabata, Bull. Br. Mus. not. Hist. (Zool.)39 (3) : 161-178 Issued 27 November 1980
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