In the fourth paper of a series, the authors treat the remaining valid named taxa in the fasciolariid genus Fusinus Rafinesque, 1815 that belong to the Japanese fauna. The species that Tokubei Kuroda originally intended to describe as F. grabaui is here described as F. amadeus n. sp. A second species that previously bore a Kuroda manuscript name is described as F. teretron n. sp. The genus Propefusus Iredale, 1924 is synonymized with Fusinus, and due to resulting homonymy its type species, Pyrula undulatus Perry, 1811, is renamed Fusinus pyrulatus (Reeve, 1847).

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The Pectinoidea species collected on the coral reefs around the Berau Islands (East Kalimantan, Indonesia) were studied. Nineteen species (four Propeamussiidae, fifteen Pectinidae) are listed from the Berau Islands. Three pectinoidean species are new to science, of which two are described herein: Parvamussium caesicium n. sp. and Talochlamys inaequalis n. sp. Two pectinid species (Pascahinnites coruscans coruscans and Palliolum minutulum) are new records for Indonesia.

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Jouannetia (Pholadopsis) spinosa n. sp. is described as the second species in the West Pacific and the sixth species of the subgenus Pholadopsis. It lives in weakly consolidated mud and sand blocks obtained from relatively deep waters in Japan and the Philippines. J. (P.) spinosa n. sp. is characterized by a small spherical shell with dense spiny sculpture, remarkably concave posterior portion of the anterior slope, a siphonoplax with claw-like spines on the posterior margin, and red pigmentation on the translucent mantle collar at the base of the siphon. It has been collected from depths ranging from 50 to 180 m, and shows a marked difference in depth range compared to the intertidal congener Jouannetia (Pholadopsis) globulosa in the West Pacific. The structure of the mesoplax in the subfamily Jouannetiinae is also discussed in detail.

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A new species of septibranch bivalve is described from the Tsugaru Strait and Otsuchi Bay, northern Japan at depths ranging from 25 m to 200 m. The systematic status and species affiliation of Rhinoclama are briefly reviewed in this paper, to place the new species in the context of the genus. Rhinoclama is here found to contain 3 species groups, mainly based on rostrum morphology; the brevirostris species-group (= subgenus Austroneaera, with poorly developed rostrum), alta species-group (= species of Rhinoclama s.s., with straight developed rostrum) and adamsi species-group (= species of Rhinoclama s.s., with developed and upturned rostrum). R. tsugaruensis fits in the last species group, and differs from R. adamsi and R. rugata by the absence of concentric sculpture on the shell disc. This small- sized Cuspidariid is here described as Rhinoclama (Rhinoclama) tsugaruensis n. sp.

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Tokubei Kuroda's collection comprises one of the most important records of the land snail fauna of Taiwan. Among the 35 new and available species-group names described by Kuroda, the types of 22 species have been catalogued and pictured previously. The present article presents the type series of ten further species: Diplommatina dandanensis Kuroda, 1941, D. karenkoensis Kuroda, 1941, Gastrocopta ooi Kuroda, 1941, Thaumatoptyx crassilamellata (Kuroda, 1941), Reinia eastlakeana tayalis Kuroda, 1941, Otesiopsis taiwanica (Kuroda, 1941), Plectopylis ishizakii Kuroda, 1941, Satsuma nux sericata (Kuroda, 1941), S. succincta rubrotincta (Kuroda, 1941) and Aegista taiwanica Kuroda, 1941. This leaves three species described by Kuroda still untraceable. Two diplommatinid subspecies are raised to full species status.

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Age determination of Margaritifera laevis was carried out in the Chubu-Nougu River, at Omachi in Nagano Prefecture, Japan. There were many juvenile mussels in the brook of Chubu-Nougu River. The relationship between age and shell length in juvenile mussels was investigated. In juvenile mussels, the annual rings on the shell surface roughly indicated the true age, but the rings of the ligament did not. Therefore, it is suggested that the growth rings of the ligament should not be used in age determination of juvenile mussels.

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Abnormal changes in reproduction such as a female-biased sex ratio or melanism and atrophy of the testis have been observed in Sinotaia quadrata histrica in Lake Kasumigaura, middle Japan. These changes are thought to have been induced by water pollution. In order to examine the possibility of abnormal changes of reproduction in females, we studied changes in the number of shelled embryos in the brood pouch between different seasons and regions. Females examined were collected at four sites (Ogawa, Ishida, Hasugawara, and Takayama) within the lake and at a fish farm on the lakefront as a control once a month from April 2001 to March 2002. At each collection, about 20 females were selected at random and the number of shelled embryos in the brood pouch was counted. The average number of shelled embryos during a year was 14.1 at the fish farm and 5.9 to 9.9 at the four lake sites. A clear seasonal difference between spring-summer and autumn-winter was observed at the fish farm, but only a slight difference at Ishida and Hasugawara, and no differnce at Ogawa and Takayama. In autumn-winter, the average number of shelled embryos at the fish farm was significantly different from those at Ogawa, Ishida and Takayama. These seasonal and regional differences between the fish farm and four sites in the lake suggest the possible effect of changes in environmental conditions such as water pollution.

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[in Japanese]

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