A new species, Solemya tagiri is described from near submarine fumaroles in shallow water in Kagoshima Bay, southern Kyushu, Japan. It is a small species of Solemya (s.s.), with a ligament lying between the postero-dorsal margin and the resilifer and a varnished yellowish periostracum ornamented by fine, reddish radiating lines. This species is associated with a chemosynthetic environment, together with a pogonophoran, Lamellibrachia satsuma.
Two new species of Bathymodiolus, B. hirtus n. sp. and B. securiformis n. sp., are described. They inhabit bathyal chemosynthetic environments around methane seeps on the Kuroshima Knoll, off the Yaeyama Islands, southwestern Japan. B. hirtus n. sp. is characterized by having anteriorly situated umbones and a distinctly hirsute shell surface. B. securiformis n. sp. has an elongate shell with a short and low anterior part, a high and expanded posterior part, and a deep ventral concavity. Some anatomical characters also separate these new species from hitherto known species.
Shell morphology and anatomy of Pisidium conventus aff. akkesiense collected from a fish-culture pond were studied. This species showed similarities to the subgenus Neopisidium with respect to ligament position and gill, resembling P. conventus in anatomical characters.
The new genus Thaluta is proposed for a group of small costellariid gastropods from the Indian and Western Pacific Oceans, with Thala maxmarrowi Cernohorsky, 1980 as the type species. A second species from central Japan that was previously misidentified as T. maxmarrowi is here described as Thaluta takenoko sp. nov. It differs from the type species in part by having a paucispiral rather than a multispiral protoconch. A series of specimens from Australia with an unknown protoconch may represent a third species of Thaluta. The geographic range of T. maxmarrowi is extended to South Africa. Comparison is made with the genera Thala H. & A. Adams, 1853, Mitromica Berry, 1958 and Zierliana Gray, 1847, with particular reference to Z. anthracina (Reeve, 1844)
A new gymnodorid nudibranch, Gymnodoris inariensis, collected from muddy sand in Kagoshima Bay, is described here. External features of the body characterize this species, including its blackish color, very small size, minute rhinophores, and the complete absence of dorsal gills.
In the spring of 2003, aplysiid Opisthobranchia with large swimming parapodia were found in Suruga Bay, Japan. These specimens are here identified as Aplysia (Varria) extraordinaria (Allan, 1932), an Australian species.
A new species of the genus Aegista, A. stenomphala is described from Mt. Gokenzan in Kagawa Prefecture, northeastern Shikoku. This new species is closely related to Aegista mayasana but differs from it in having a densely bristled shell surface.
An isolated cephalopod beak was discovered in the Lower Miocene unit of the Ichishi Group at Iedokoro, Misato Village, Mie Prefecture, central Japan. It measures 39.7mm in maximum length and consists of large outer and short inner horny lamellae, with a conspicuous anterior calcified tip; the outer lamella is divided into a pair of posteriorly elongated wing portions. In the absence of the strongly convex, posteriorly elongated inner lamella that occurs in the upper beaks of all extant cephalopods, the present specimen is identified as the lower beak. The overall morphological features suggest a closer phylogenetic affinity to Recent Nautilus (Nautilidae) than to the coleoids, but the paired wing portions are more elongated than those of the lower beaks of Nautilus. We provisionally refer this cephalopod beak to the genus Aturia, because large mature shells of Aturia cubaensis occur in the same horizon.
An elliptic Fourier analysis was carried out on shell outlines in 63 species of the Pectinidae (Bivalvia). Fourier coefficients and their principal components were used to compare shell shapes among taxonomic subgroups and life habits. This study reveals differences in shell outline between the tribes of byssate and free-living pectinids. Byssally attached species of the Pectininae have more rounded and equilateral shell outlines than those of the byssate Chlamydini and Mimachlamydini. Free-living pectinids generally possess circular and equilateral shells, except for some species of the Decatopectinini. This study suggests that the change of life habit from byssally attached to free living required Chlamydinae to modify their shell outlines considerably, whereas only a minor modification of the outline enabled the byssate Pectininae to adapt to free-living habits. Patinopecten, which represents the only free-living scallop in the Chlamydinae, has a shell outline with a smaller aspect ratio than most of the free-living Pectininae. This suggests that a vestige of the oblong shell shape of typical Chlamydini still remains in the shell of Patinopecten, showing a phylogenetic constraint.