PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 114(4):929-937. 2001. A new asellote isopod of the genus Santia Sivertsen & Holthuis, 1980 (Crustacea: Isopoda: Asellota: Santiidae) from Japan Michitaka Shimomura and Shunsuke F. Mawatari Division of Biological Sciences, Graduate School of Science, Hokkaido University, North 10, West 8, Kita-ku, Sapporo 060-0810, Japan Abstract. — Santia longisetosa, a new species of the family Santiidae (Iso-poda: Asellota) is described from the Pacific coast of Shikoku, Japan. The new species differs from its congeners in having a long robust sensory seta distal-ventrally on each propodus of pereopods 2-7, the nearly straight frontal margin of the head bearing some long setae, and 2 long robust sensory setae distal-laterally on article 2 of antenna 1. Santiidae is a small family of four genera and 21 species in the suborder Asellota. Santia Sivertsen & Holthuis, 1980, is the largest genus in the family and includes 15 species (Wolff 1989, Wolff & Brandt 2000, Shimomura & Mawatari 2000), all from marine benthic habitats. Among them only one species, Santia katoi Shimomura & Mawatari, 2000 has been so far described from Japan. Our recent investigation yield-ed an undescribed species of Santia from the subtidal zone of Kochi Prefecture, Shi-koku, the second record of the genus from Japan. Materials and Methods Specimens were obtained from 0.5 m depth of the subtidal zone by filtering sur-face water; specimens were fixed with 5% neutral formalin solution diluted with sea-water, and preserved in 70% ethanol. Each isopod was dissected and prepared for ob-servation using a light microscope equipped with Nomarski differential interference contrast (Shimomura & Mawatari 1999). Total length as indicated in "Material ex-amined" was measured from the tip of the head to the end of the pleotelson. The type specimens are deposited in the Zoological Museum, Division of Biological Sciences, Graduate School of Science, Hok-kaido University (ZIHU), and in the Toya-ma Science Museum (TOYA). Santia longisetosa, new species Figs. 1-4 Material examined. — Murotomisaki-cho, Muroto Cape, Kochi Prefecture, Japan, 33°16'N, 134°7'E, 0.5 m, surface water, subtidal, 27 June 2000: holotype, male, 1.0 mm (ZIHU-01963); paratype, ovig. female, 1.1 mm (TOYA Cr-12877); paratypes, 2 fe-males, 1.1 mm (TOYA Cr-12878), 1.3 mm (ZIHU-01966). Description. — Male: Body (Fig. lA) about 2.4 times as long as maximum width. Head 2.0 times as broad as long, slightly narrower than pereonite 1, with 10 dorsal setae; frontal margin of head nearly straight, with 8 long setae; labrum surpass-ing head anteriorly; posterior margin of head convex between eyestalks. Preocular lobes narrow, with 1 or 2 apical setae. Eyes dorsal lateral, each with 3 ommatidia. Per-eonites 1-4 laterally rounded, each with 4-7 lateral and few dorsal setae; pereonites 5-7 laterally rounded, each with 0-3 lateral and 2 dorsal setae. Pereonites 1, 2 and 4 subequal in length; pereonite 3 slightly shorter than pereonite 2; pereonites 5 to 7 increasing in length. Pereonites 1 and 2 subequal in width; pereonite 3 slightly wid-
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