The Yuriyagai: J. Malacozool. Ass. Yamaguchi, 4(1/2). October 1996

Original Articles

Opisthobranchia of Yamaguchi Prefecture, western Honshu, Japan Part 1. Species of the Notaspidea, Nudibranchia, Dendronotacea, Arminacea, and Aeolidacea from the coast of the Japan Sea (1)

Shigeo HORI and Hiroshi FUKUDA

Abstract From the Japan Sea coast in the northern part of Yamaguchi Prefecture, western Honshu, Japan, the following 31 species of the Notaspidea, Nudibranchia, Dendronotacea, Arminacea, and Aeolidacea are recorded: Berthellina citrina (Rüppell & Leuckart, 1831), Pleurobranchaea japonica Thiele, 1925, Kaloplocamus ramosus (Cantraine, 1835), Gymnodoris inornata (Bergh, 1880), Chromodoris aureopurpurea Collingwood, 1881, C. obsoluta (Rüppell & Leuckart, 1831), C. orientalis Rudman, 1983, Hypselodoris festiva (A. Adams, 1861), H. maritima (Baba, 1949), H. sagamiensis (Baba, 1949), Noumea purpurea Baba, 1949, Rostanga bifurcata Rudman & Avern, 1989, Rostanga sp., Actinocyclus japonicus (Eliot, 1913), Trippa spongiosa (Kelaart, 1858), Homoiodoris japonica Bergh, 1881, Discodoris sp., Carminodoris armata Baba, 1993, Thordisa parva Baba, 1938, Platydoris scabra (Cuvier, 1804), Dendrodoris arborescens (Collingwood, 1881), D. rubra Kelaart, 1858, D. guttata (Odhner, 1917), Melibe pilosa Pease, 1960, Dermatobranchus otome Baba, 1992, D. striatellus Baba, 1949, Madrella sanguinea (Angas, 1864), Catriona pinnifera (Baba, 1949), Phyllodesmium serratum (Baba, 1949), Pteraeolidia ianthina (Angas, 1864), and Herviella affinis Baba, 1960. Among them, Chromodoris orientalis [as C. pallescens (Bergh, 1875)], Chromodoris obsoleta [as C. obsolta (Rüppell & Leuckart, 1831)], Hypselodoris festiva, Dendrodoris ar-borescens [as D. nigra (Stimpson, 1855)] were already reported from Yamaguchi Prefecture, but all the remainders are newly recorded from the Prefecture herein. Actinocyclus japonicus, Carminodoris armata, Dendrodoris guttata, Madrella sanguinea, and Pteraeolidia ianthina are new to the Japan Sea, and Rostanga bifurcata and Trippa spongiosa are newly recorded from Japan. Japanese specimen of Platydoris scabra is first illustrated in this paper. For the latter 3 species, the present record is the northern limit of their distribution.

Key words: Aeolidacea, Arminacea, Dendronotacea, Japan Sea, Notaspidea, Nudibranchia, Opisthobranchia, Yamaguchi Prefecture.


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A revision of the species previously known as Hawaiia minuscula in Japan and the discovery of the Helicodiscidae, the family new to Japan

Yasunori KANO

Abstract The anatomy and taxonomy of the minute land snails which were known as Hawaiia minuscula (Binney, 1840) in Japan are revised. They include three species of Helicodiscus Morse, 1864, a genus of the endodontoidean family Helicodiscidae in addition to the true Hawaiia minuscula. One species is He. (Hebetodiscus) singleyanus inermis Baker, 1929, and the other two have probably been undescribed. This is the first record of Helicodiscidae in Japan. Helicodiscus are naturally distributed in North and Central Americas, and the Japanese species must have been introduced from there. It is clear that He. (Heb.) singleyanus inermis is ovoviviparous. This is the first example of an ovoviviparous species in helicodiscids. The fossil shells of Hawaiia from Akiyoshi-dai, Yamaguchi Prefecture are described with brief discussion of the origin of the Japanese Hawaiia .

Key words: anatomy, Hawaiia, Helicodiscidae, Helicodiscus, Japan, ovoviviparity, Zonitidae


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Rediscovery of Terebra pumilio (E. A. Smith, 1873) from the Inland Sea of Japan (Neogastropoda: Terebridae)

Hiroyoshi YAMASHITA

Summary Terebra pumilio (E. A. Smith, 1873), which is a terebrid described together with T. tantilla (E. A. Smith, 1873), has been regarded as a synonym of T. tantilla and invalid name. However, pumilio is valid because it is described in the earlier page than the enumaration of tantilla. This nomenclatorial problem is discussed herein. Although the type locality of T. tantilla is Japan, it has never been recorded in Japan and its adjacent seas. Recently I rediscovered this species from the subtidal zone of the western part of the Inland Sea of Japan. The redescription of the species is given on the basis of the Japanese specimens.

Key words: Inland Sea of Japan, nomenclature, rediscovery, Terebra pumilio, Terebra tantilla, Terebridae


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Discovery of a population of an endangered brackish-water snail Stenothyra japonica (Gastropoda: Neotaenioglossa: Stenothyridae) and characteristics of the accompanied molluscan fauna in Onoda City, Yamaguchi Prefecture, western Japan, with a comment on the conservation value

Ken-Ichi HOSAKA and Hiroshi FUKUDA

Abstract A new population of an endangered stenothyrid snail Stenothyra japonica Kuroda, 1962 was found in an estuary of Ushiro-gata, Onoda City, Yamaguchi Prefecture, western Japan, in 1995. Although this species was widely distributed in Japanese mainland, there are few recent records except in two localities of Niigata and Chiba prefectures. The shell, operculum, radula and head-foot of this snail are described on the basis of specimens of Onoda City. The present population was found in a small canal for farming neighboring to the estuary of the Asa River. It is noticeable that this snails lived in brackish-water in contrast with the freshwater habitats of other two recent localities in Japan. In observed canal, S. japonica is commonly found, forming the largest population in Japan. The molluscan fauna around the habitat is characterized by high species diversity occurrence of several species endangered in most of regions of western Japan. Therefore the environment of the estuary of the Asa River appears to be preserved in good condition. The conservation value of the estuary ecosystem favoring many endangered molluscan species including S. japonica is discussed herein.

Key words: conservation, molluscan fauna, Stenothyra japonica of the Asa River, Yamaguchi Prefecture.


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Shell morphology and anatomy of Xenostrobus atratus (Lischke, 1871) (Bivalvia: Mytilidae)

Taeko KIMURA

Abstract The present paper reports morphological features, particularly diagnostic features in the shell morphology and anatomy of mytilid, Xenostrobus atratus, from the mouth of the Asa River of Yamaguchi Prefecture and the Koajiro Bay of Kanagawa Prefecture. No differences in shell morphology or anatomy were detected between X. atratus specimens collected from Yamaguchi and Kanagawa prefectures. The shell morphology of the present X. atratus specimens are similar to those of X. mangle and X. balani described by Ockelmann (1983). X. atratus, with branching papillae in part on the mantle lobe as indicated in the present study, has folds on the labial palp less than those of X. mangle and X. balani. X. atratus and X. mangle are distinguished from X. balani based on features of the posterior byssus retractor muscle.

Key words: anatomy, Mytilidae, shell morphology, Xenostrobus atratus


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A taxonomic revision of Amaea thielei and "A." ogaitoi (Gastropoda: Neotaenioglossa: Epitoniidae)

Shoichi KIMURA

Summary Two Japanese epitoniids of the genus Amaea H. & A. Adams, 1854 are revised conchologically and taxonomically. It is clarified that the shell of Amaea thielei (de Boury, 1912) is highly variable especially in the condition of the longitudinal ribs and varices, and Scalaria (Acrilla) densicostata Yokoyama, 1920, Scalaria picturata Yokoyama, 1922, and Scala (Acrilla) ojiensis Yokoyama, 1927 are regarded as the junior synonyms of A. thielei (syn. nov.). Amaea ogaitoi Masahito & Habe, 1975 sensu Fukuda et al., 1990 is also a juvenile of A. thielei. The true A. ogaitoi is redescribed on the basis of the type specimens. A. ogaitoi lacks the basal disk which is one of the most important characters of Amaea, and hence the generic position remains uncertain.

Key words: Amaea thielei, "Amaea" ogaitoi, Epitoniidae, taxonomic revision, variation of conchological characters Museum.


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A revision of the family Assimineidae (Mollusca:Gastropoda: Neotaenioglossa) stored in theYamaguchi Museum. Part 3: Subfamily Assimineinae (2) Angustassiminea and Pseudomphala

Hiroshi FUKUDA and Teruhisa MITOKI

Abstract With the specimens of the family Assimineidae stored in the Yamaguchi Museum, the following three species of the subfamily Assimineinae are revised morphologically and taxonomically: Genus Angustassiminea Habe, 1943: A. castanea (Westerlund, 1883), A. satumana (Habe, 1942); Genus Pseudomphala Heude, 1882: P. latericea miyazakii (Habe, 1943). The shell, opercular, radular and head-foot characters of them are redescribed. The SEM photographs of the radulae and opercula of A. castanea and P. l. miyazakii are published for the first time. Their generic and specific status is preliminarily discussed.

Key words: Angustassiminea, Assimineidae, morphology, Pseudomphala, taxonomic revision, Yamaguchi Museum.


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A revision of the family Pyramidellidae (Mollusca: Gastropoda: Heterostropha) from the northern district of Yamaguchi Prefecture deposited in the Hagi City Museum

Shigeo HORI

Summary The Hagi City Museum has a large collection of mollusks collected mainly from the northern district of Yamaguchi Prefecture (the Japan Sea coast of northern part of Yamaguchi Prefecture). The collection consists of two series of specimens, viz. the original series of the Museum and the series donated by the late Mr. Takeichi Tada. Of these specimens, the ones belonging to the family Pyramidellidae from the northern district of Yamaguchi Prefecture are revised. Although most of these species are common to northern district of Yamaguchi Prefecture, most of them had previously been misidentified by various authors. Since the correct re- recognition of these species would be needed for taxonomical or faunal studies of pyramidellids in this region, these species are identified according to type materials and reliable literature, and re-described in detail and illustrated. As a result, the following 33 species are recognized: Odostomia omaensis Nomura, 1938, O. desimana Dall & Bartsch, 1906, O. tenera A. Adams, 1861, O. sinuosa Nomura, 1937, Chrysallida caelatior (Dall & Bartsch, 1906), C. mariellaeformis Nomura, 1938, C. gloria Nomura, 1938, C. affectuosa (Yokoyama, 1927) (comb. nov.), C. pupula A. Adams, 1861, C. pseudalveata Nomura, 1936, C. casta A. Adams, 1861, C. sp., Miralda circinata (A. Adams, 1867), Syrnola cinctella A. Adams, 1860, S. subcinctella Nomura, 1936, S. cinnamomea (A. Adams, 1863), S. brunnea (A. Adams, 1854), S. taeniata (A. Adams, 1863), Turbonilla misella Yokoyama, 1922, T. hiradoensis Pilsbry, 1904, T. mumia (A. Adams, 1861), T. yoritomoi Nomura, 1938, T. sp. A, T. sp. B, Cingulina cingulata (Dunker, 1860), C. laticingula (Dall & Bartsch, 1906), C. inequicingulata Nomura, 1938, C. terebra (Dunker, 1860), C. triarata (Pilsbry, 1904), Mormula philippiana (Dunker, 1860), Tropaeas castaneus (A. Adams, 1863), Tiberia pulchella (A. Adams, 1854), and T. pusilla (A. Adams, 1854). Followings are major taxonomical changes and new distribution records made in the present study: The shell proportion of Pyramidella lischkei Dall & Bartsch, 1906 is continuous to that of Syrnola taeniata (A. Adams, 1863) via several variety forms. Therefore P. lischkei is regarded as a junior synonym of S. taeniata (syn. nov.). Odostomia tenera A. Adams, 1860, of which type locality is off Mishima Island, Hagi City, Yamaguchi Prefecture, was re-discovered from the northern district of Yamaguchi Prefecture including Mishima Island for the first time. Chrysallida gloria Nomura, 1938 is newly recorded in Yamaguchi Prefecture. Chrysallida affectuosa (Yokoyama, 1927), Chrysallida pseudalveata Nomura, 1936, and Turbonilla yoritomoi Nomura, 1938 are new to Yamaguchi Prefecture and the Japan Sea. Further, the latter two were re-discovered for the first time since the original descriptions. Abbreviations used in this paper are as follows: HCM, Hagi City Museum; NSMT, National Science Museum; Tokyo; SH, shell height; SHKM, Saito Ho-on Kai Museum; SW, shell width; UMUT, University Museum, University of Tokyo.

Key words: Hagi City Museum, Mishima Island, northern coast of Yamaguchi Prefecture, Pyramidellidae, Takeichi Tada


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The anatomy of an introduced slug Limax (Limacus) flavus Linnaeus (Gastropoda: Stylommatophora: Limacidae) from Yamaguchi City, western Japan

Yasunori KANO

Summary A specimen of a slug Limax (Limacus) flavus Linnaeus, 1758 (Japanese name: Kiiro-Namekuji) which was collected from Daifu, Yamaguchi City, western Japan in 1963, is described. The anatomical characters of this specimen (radula, jaw plate, alimentary canal and reproductive system) are described. In Japan, there has been no clear record of this species because of the lack of anatomical information in the past reports. Precise identification and description of this species in Japan are first given. This species is naturally distributed in Europe and perhaps have been introduced to Japan in the early 20th Century. This species rapidly increased the distribution range after immigration to Japan, but has recently become very rare or extinct.

Key words: anatomy, Japan, Limax (Limacus) flavus, redescription, Yamaguchi City


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On the shell morphology and distribution of Pupilla (Gibbulinopsis) cryptodon (Gastropoda: Stylommatophora: Pupillidae)

Hiroyoshi YAMASHITA and Hiroshi FUKUDA

Summary Six new localities of a pupillid land snail Pupilla (Gibbulinopsis) cryptodon (Heude, 1880) were found in Yamaguchi, Fukuoka, and Nagasaki prefectures in Japan. On the basis of the specimens collected in these localities, the protoconch and aperture of this species were examined with the SEM for the first time. The protoconch has a prominent branching and anastomosing system on surface. The surface inside the aperture (including the palatal, parietal and columellar teeth) is covered with many minute wart-like sculptures. The conditions of the habitats in new localities of this species are described in detail. In addition to them, the occurrence records in the previous literature are compiled and the pattern of geographical distribution of this species is discussed. This species is chiefly distributed in rather cold areas of Chinese Continent and Korean Peninsula. The distribution area in Japan is discontinuous and restricted to the western part (coasts of the Seto Inland Sea, Japan Sea and East China Sea). Judged from the distribution pattern, the Japanese populations are considered to be relics of the colder age when the Japanese Archipelago was connected with the Chinese Continent. Whereas this species inhabits inland provinces in China, it is restricted to sanhills of seashores in Japan. This seems to be caused by the lack of dry environment preferred by this species in the Japanese inlands where show wet climate.

Key words: habitat, distribution, Pupilla (Gibbulinopsis) cryptodon, sandhill of seashore, shell morphology


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Some molluscs brought from the Yellow Sea, East China Sea and neighboring areas to Port Hagi, Yamaguchi Prefecture, western Japan by the Koshu-Maru

Isao KAWAKAMI and Yasuko ITO

Summary Several noteworthy molluscs, which have been brought from the Yellow Sea, East China Sea and neigh- boring areas by a longline fishing boat "Koshu-Maru", are recorded and illustrated. Since many fishing boats belonging to Yamaguchi Prefecture have sailed out fishing far away from their home ports, many molluscs might have often been brought from foreign seas to the Prefecture and mis-re- cognized as inhabitants in the water of the Prefecture. Thus, if one reports such a kind of specimens, reliable and detailed sampling data must be recorded to avoid the confusion on localities.

Key words: East China Sea, longline fishing of the globefish, Port Hagi, shells from Yamaguchi Prefecture


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Biography of malacologists in Yamaguchi Prefecture, western Japan (4). Gorô OKAFUJI (1924- 1978)

Kazuyuki MASHINO

Summary A biography of Gorô Okafuji (1924-1978), who studied palaeontology and malacology mainly in Yamaguchi Prefecture, is given. He surveyed the fossils of the Mine District and clarified the land snail fauna of the area, while he worked at senior high school. His major achievements are as follows: 1. He discovered the semi-fossils of a probable relic population of Cochlicopa lubrica (Müller) (Stylommatophora: Cochlicopidae), which is a land snail distributed chiefly in cold region, in Kojikiana, a limestone cave of Mine City. 2. He surveyed the distribution and habitat of Bythinella (Moria) akiyoshiensis Kuroda & Habe (Neotaenioglossa: Hydrobiidae), a minute limnetic snail.

Key words: biography, Bythinella (Moria) akiyoshiensis, Cochlicopa lubrica, Gorô Okafuji, history of malacology, limestone area, Mine City of Yamaguchi Prefecture


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Brief Communication

Notes on the record of Conus (Virgiconus) lividus Hwass, 1792 (Neogastropoda: Conidae) in Kurae- no-hama, Hagi City, Yamaguchi Prefecture, western Japan

Yasuko ITO

Summary An empty shell of Conus (Virgiconus) lividus Hwass, 1792 was collected in beach drifts of Kuraeno-hama (N344'-25', E1312'-23'), Hagi City, Yamaguchi Prefecture (the coast of the Kita-nagato Kaigan faced to the Japan Sea), in January 1996. In Yamaguchi Prefecture, this species was recorded from five localities in the previous literature, but no voucher specimen of these records has been preserved up to the present time. Therefore, the present shell is the only specimen which certainly indicates that this species is distributed in the Prefecture. The occurrence of this species is one of the good examples of the marine molluscan fauna of the Kita-nagato Kaigan, which is strongly affected by the Tsushima Warm Current. However, it remains uncertain whether C. (V.) lividus is settled or not, because of the rarity of this species.

Key words: Conus (Virgiconus) lividus, the coast of the Kita-nagato Kaigan of the Japan Sea, Kuraeno-hama in Hagi City of Yamaguchi Prefecture, occurrence record, Tsushima Warm Current


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Notes on the intrusion of three non-marine gastropods into Ube City, Yamaguchi Prefecture, western Japan, found in 1996

Ken-Ichi HOSAKA

Summary In 1996, I recorded the intrusions of two terrestrial and one freshwater gastropods into Ube City, Yamaguchi Prefecture, western Japan. They are "Paludinella" debilis (Gould, 1859) (Neotaenioglossa: Assimineidae), Pseudosuccinea sp. (Hyglophila: Lymnaeidae) and Rumina decollata (Linnaeus, 1758) (Stylommatophora: Subulinidae). "P." debilis is recorded for the second time in the Prefecture. Because all the localities hitherto known in the Prefecture are gardening shops, this species seems to immigrate through the transportation of garden plants. Pseudosuccinea sp. is new to the Prefecture. The record of R. decollata is the second one in Ube City, and its distribution range may be increasing in the City. The microsculptures of the shells of "P." debilis and Pseudosuccinea sp. were observed with SEM. Although "P." debilis is conchologically similar to the species of Paludinellassiminea, it is distinguishable from the latter in having the spiral cords on the whorls and in lacking the distinct umbilical keel. The whorls of Pseudosuccinea sp. exhibit many faint spiral cords with tiny periostrucal hairs.

Key words: non-marine gastropods, new intrusion, "Paludinella" debilis, Pseudosuccinea sp., Rumina decollata, Ube City, Yamaguchi Prefecture


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