Two new species of the marine monostiliferous hoplonemertean genus Zygonemertes (Nemertea : Enopla) are fully described and illustrated from specimens collected in Hokkaido, northern Japan. Zygonemertes shintai sp. nov. is characterised by a posteriorly lobed central stylet basis, ten proboscis nerves, and anterior pouches of the intestinal caecum that do not reach the ganglionic lobes of the brain. Zygonemertes jamsteci sp. nov. is distinguished from the most similar species, Z. virescens (Verrill, 1879), by having a proboscis as long as the body and a mixed type of pre-cerebral septum. All stages of oogenesis are present simultaneously in mature females of Z. jamsteci. Their oocytes seem to originate from the ganglionic cells of the lateral nerves. All six sectioned specimens of Z. jamsteci were infected by large numbers of unidentified acephaline eugregarines.
A new tanaidacean species of the family Metapseudidae, Curtipleon heterochelatum, is described and illustrated on the basis of one male and five female specimens from the Andaman Sea. A significant asymmetry in the male chelipeds was observed. The new species can be separated from C. carinatoides (Bacescu, 1976) by the absence of spines on the anterior margin of the cephalothorax, and from C. carinatum (Makkaveeva, 1971) by the many spines on the cheliped basis and the distally directed subdistal spine on the dorsal surface of the male cheliped carpus. A revised diagnosis to Curtipleon and a key to the species of the genus are included.
The monotypic genus Paragrandidierella (Crustacea : Amphipoda : Aoridae) is erected with P. minima sp. nov. from Osaka Bay, central Japan, as its type species. Paragrandidierella closely resembles Chevreuxius Bonnier, 1896, Grandidierella Coutiere, 1904, and Orstomia Myers, 1998 in having a carpochelate male gnathopod 1 and uniramous uropod 3 ; however, it can be distinguished readily by the non-spinose inner plate of the maxilliped, the reduced uropods, and the short telson with a pair of dorsal swellings.
The Asian stilt bug genus Yemmatropis Hsiao is reviewed and the type species, Y. dispar (Hsiao, 1974), and the new species, Y. erectus, are described. An adult habitus illustration of Y. erectus, scanning electron micrographs of selected structures and male parameres of both species, and a key are provided to assist in identification.
Two new species of hyocrinid stalked crinoids from deep waters of the Pacific Ocean are described. Thalassocrinus alvinae n. sp. was collected on the Gorda Ridge and represents the first record of the genus from the Eastern Pacific. Thalassocrinus mironovi n. sp. was found on the bathyal slope off New Caledonia (southwestern Pacific). A short revision of the genus Thalassocrinus is given and affinities between the four known species are discussed.
An astropectinid starfish with a unique habit of brooding, Trophodiscus almus Fisher, 1917, has been previously reported to be endemic to the northern part of the Sea of Okhotsk. Recently 11 specimens of this species were obtained from the northern Sea of Japan at depths of 290-295 m off Ajigasawa in Aomori Prefecture, far to the south of the Sea of Okhotsk, and 18 specimens from off Kushiro, Hokkaido, in the Pacific Ocean at depths of 153-252 m. These occurrences of T. almus represent the first records from Japanese waters, and the Sea of Japan is a new southern range limit. A detailed redescription of the species is provided along with color photographs and scanning electron micrographs. The distribution patterns of starfishes known from the Sea of Okhotsk are reviewed in relation to the zoogeographical significance of T. almus.