TWO NEW AMPHIPODS OF THE GENUS EURYSTHEUS FROM JAPAN

Abstract

advices : prticularly to Mr. H. SANDO of T6hoh.1 University, and Mr. T. KIKUCHI of Kydshu University, for sending the useful materials for this study. Eurystheus japonicus n. sp. (Fig. l) &fiIle?-Pleon segments 4 and 5 armed with two minute medio-dorsal teeth o n the hind margin, together with a seta at the base of each lateral tooth. H e a d , lateral Iobes lobate, not pointed apically. Side plate 2 the largest and the deepest. Plean segment 3, lower hind corner with an acute tooth, margin above bulging, then nearly straight. Eyes long oval, reniform and dark. Accessory flagellurn of antmna 1 five-seven jointed. Upper lip with epistome produced acutely a n d right-angularly in front. Gnathopod 1, article 5 slightly longer than article 6 ; palm illdefined ; finger denticulate. Gnathopod 2 larger and powerful ; articles 2 and 5 robust and subequal; the anterodistal corners of article 2 lobate ; a r t i c l e 6 nearly equal to or slightly longer than article 5; palm oblique with three denticles or tubercles of which the middle one in specimens from Seto Inland Sea is t h e largest and projecting across the finger, whereas the appearence of these denticles in Asamushi specimens, rather resemble those of SARS' figures of E. maculatus 11895, pi. 198) ; hind margin of article 6 sometimes shorter than palm, sometimes longer, and nearly parallel with its anterior margin. Peraeopods 3-5 with articles 2 and 4 much variable in shape and the hind margin slightly serrated ; peraeopod 4 longer than or subequal to peraeopod 5 ; peraeopod 3, article 2 well e x p a n d e d and broadened distally, article 4 more or less widened ; peraeopod 4, article 2 well expanded or rather narrow, and its hind margin convex or slightly concave, article 4 less widened; peraeopod 5, article 2 more or less narrowing distally, article 4 normal. The other points typical without any characteristics. Fev~aie-Differing from the male only in peraeon segment 2 and i t s coxal plate, gnathopod 2, and peraeopods 3-4. The breadth of peraeon segment 2 and the depth of its coxal plate normal. Gnathopod 2 not powerful and not variable ; article 2 rather slender ; article 5 much shorter than article 6 of which p a l m with two denticles, widely concave between the two, and bearing a rather strong s p i n e near the defined denticle. Peraeopods 3-5 not variable; article 2 of peraeopod 3 moderately broadened, and those of peraeopods 4-5 narrowing distally ; t h e shapes of article 2 of peraeopods 3-5 in Asamushi specimens are, however, so&-what different from those of specimens from Seto Inland Sea i n the l o n g e r a n d more slender shape to their width. male 8 mm !fiWredI, No. 2055 ; Allotype, ovig. female 6 mm (figured), 2 paratj'pe~, all preserved now in my hand. Occurrence-Seto Inland Sea : Hosonosu, 11 specimens ; Mihara Bay, 10 spec.