Zoologica Scripta. Vol. 10, 255-257, 1981 A New Species of Ilyodromus Sars (Crustacea, Ostracoda) from the Philippines REGINALD VICTOR and C. HERBERT FERNANDO Department of Biology, University of Waterloo, Waterloo, Ontario, Canada Reccived 1980-05-06 Victor, R. & Fernando, C. H. 1981. A new species ofllyodrornus Sars (Crustacea, Ostracoda) from the Philippines. -Zoo/. Scr. 10: 255-257. The genus Zlyodrornus Sars, 1895 is recorded for the first time in the Oriental Region. Ilyodromus lanaoensis sp.n. is described from Mindanao, the Philippines and compared with the other species of the genus for differential diagnosis. Reginald Victor & C . Herbert Fernando, Department of Biology, University oj Waterloo, Waterloo, Ontario, Canada N2L 3GI. Introduction Recently, Danielopol & McKenzie (1977) redefined the genus Ilyodromus Sars, 1895. At present, Ilyodromus s.str. includes mainly Australasian species, whereas the European species, earlier assigned to this genus, were transferred to Psychro- dromus Danielopol & McKenzie, 1977. Two species from Europe and North America formerly assigned to this genus, can no longer be retained in Ilyodromus s. str., but their generic status is not clear. The distributional affinities of Ilyodromirs s. str. is southern and it has never been recorded in Africa or the Oriental Region. The only valid record of this genus is from European ricefields where it has probably been introduced from elsewhere. In the present study, Ilyodromirs is recorded for the first time in the Oriental Region; a new species is described from Mindanao, the Philippines. Terminology of setae and spines as in Danielopol & McKenzie (1977). Diagnosis and description Ilyodromus lanaoensis sp.n. (Figs. 1-15) Type .\prcirnens. Female holotype (no. 21608) and one paratype fe- male (no. 21609) are submitted in the National Museum of Natural Sciences, Ottawa, Canada. Type locality. Five females were found in a zooplankton sample collected by Dr. D. G. Frey, Indiana University, Bloomington, Indiana, U.S.A., from a pond at the entrance to Bocolod Chico, Lake Lanao, Mindanao, the Philippines, on 9 November 1967. Dcrivntion of nnmr. For Lake Lanao, Mindanao, the Philippines. Diagnosi.c. Length of valves less than 1 mm. Valve surface with lateral striations; dorsum smoothly convex with greatest height postero-medially; fused zone of the inner lamella with branched and simple pore canals. Sensory club Y, of the antenna two-segmented. The y spine of the mandibular palp absent. Fourth endopodite segment of the first thoracic leg with an unusually long, claw-like posterior seta. Furca curved with a faintly pectinate, claw-like posterior seta and a spinose posterior margin. De J crip t ion Fonale. Carapace compressed. Valves unequal, left valve slightly larger than the right. In lateral view, valves elongate. Hinge adont. Dorsum smoothly convex: greatest height slightly posterior to the middle. Ventral margin slightly con- cave in internal view. Anterior and posterior margins round- ed; anterior, posterior and ventral margins hairy. Inner lamel- la more wide anteriorly than posteriorly; the fused zone narrow with branched and simple pore canals; selvage poorly developed. Valves thinly calcified, transparent, smooth with fine lateral striations on the surface (Figs. 1, 2). Natatory setae of the antenna six in number, well de- veloped reaching beyond the tips of the terminal claws; 6th seta longer than others; terminal claws faintly pectinate at the central 1/3 in higher magnification (Fig. 3); sensory club Y, two-segmented (Fig. 4); sensory seta Y, prominent (Fig. 3); second endopodite segment not separated (Fig. 3). Man- dibular gnathobasis strongly dentate (Fig. 5); palp with seven rays, three of which with long hairs, one short with stiff bristles; endopodite with three strong terminal setae: bristle present; p spine bristled and y spine absent (Fig. 9). Rake- like organ with eleven teeth, one end tooth bifid (Fig. 6). Maxillular spines of the third palp with two smooth spines and three setae (Fig. 10): respiratory plate with twenty-two plumose setae. Maxillary endopodite with four unequal setae, the shortest seta probably aberrant (Fig. 8); respiratory plate with six hairy setae: masticatory process with four stout spines in addition to slender setae; a, b and d setae present (Fig. 7). First thoracic leg (the walking limb) with an end claw, faintly pectinate in higher magnification (Fig. 11) little shorter than the combined lengths of second, third and fourth endo- podite segments; second and third endopodite segments separated: fourth endopodite segment with a strongly de- veloped claw-like posterior seta, about twice the length of that segment (Fig. 1 I); all anterior setae smooth: anterior margin of first endopodite segment hairy; posterior margin spinose. Terminal segment of the second thoracic leg (the cleaning limb) with a curved claw, well-developed pincers and a smooth reflexed seta (Fig. 12). Furcal rami short, sym- metrical and curved; terminal and subterminal claws faintly pectinate; posterior seta stout, claw-like, faintly pectinate, approximately half the length of the subterminal claw; termi- nal seta short, smooth about half the length of the posterior seta; posterior margin of the ramus finely spinose (Fig. 15). Furcal attachment branched proximally (Fig. 13) and broad-