The land snail fauna of the Uji-gunto, consisting of two islands, Muko-jima and Ie-jima, located at 129°29′E, 30°12′N, was surveyed in 1981 and 1983. In total, 27 species belonging to 24 genera of 13 families were collected. One subgenus, one species and one subspecies are described as new to science. The land snails of the Uji-gunto contains seven species which are regarded as Osumi elements. But, Nomura-Simpson's Coefficient (NSC) between the Uji-gunto and Yaku-shima, the Osumi Islands, is relatively small (Ie-jima-Yaku-shima : 0.455 ; Muko-jima-Yaku-shima : 0.478), compared with NSC (0.560) between Yaku-shima and Kyushu (Kagoshima-ken). Percentage of endemism in this Island group is very high, namely, one genus and six species, i.e., 22.2% are endemic at species level. For this reason, Uji-gunto is considered to be very peculiar in the land snail fauna and to have been isolated from adjacent land masses for a long period.

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Statistical analyses were made for geographical variation in a camaenid land snail, Satsuma tanegashimae (Pilsbry) which is distributed in the northern parts of the Ryukyu Islands. This species is suitable for the study on intraspecific variation for the following reasons : (1) It has been known only from islands ; island populations are, in general, considered to be units of evolution.(2) It is possible to study most of the populations.(3) It shows a remarkable geographical variation. Fourteen parts of shell were measured and six ratios were calculated (a total of 20 characters were used for study). Discriminant analysis was made to detect distances (MD : Maharanobis Dsquare) between populations. Cluster analysis using MD values suggests the existence of four groups (Uji, Kusagaki, Mishima-Tokara, Tane-Yaku) within this species. The Uji population is quite peculiar, and rather similar to Satsuma myomphala (Martens), a close relative of S. tanegashimae. In the Kusagaki population the shell is very big, ranging from 28.7 to 35.6 mm in width. The individuals from Kuro-shima are on the contrary very small in shell size (20.0-27.1 mm in width). Moreover, a slight difference is observed among the demes inhabiting this island. The populations of Take-shima and Io-jima are similar to that of Kuro-shima in shell shape. All the biota of the former two islands are thought to have been extinguished by a volcanic explosion about 6300 years ago. Considering all these facts the populations of S. tanegashimae inhabiting these two islands may have been introduced from Kuro-shima through the recent human activities. The land snail fauna of the Tokara Islands, southern parts of the northern Ryukyus, is usually considered to be similar to that of the Osumi Islands, northern parts of the northern Ryukyus. The populations of the Tokara Islands are, however, rather different from those of Yaku-shima and Tanega-shima, main islands of the Osumi group. This suggests that the Tokara Islands might have connected with the Osumi-mass but later formed a separate land-mass or an island group.

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Karyotypes in eight species of the Mytilidae have been studied. In the subfamily Mytilinae, Mytilus coruscus and Crenomytilus grayanus have the same chromosome number n=14, and their karyotypes resemble each other. Six species of the subfamilies, Modiolinae, Musculinae, and Lithophaginae, have the chromosome numbers ranging from n=14 to n=16. The karyotypes of these species are clearly different in the same genus or the same subfamily.

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Through the courtesy of Mr. J. F. Peake, senior scientist of Department of Zoology and by the permission of the British Museum (N. H.), I have observed the type specimens of three Japanese clausilid species from Kinnayama (=Kennoyama=Tsurugisan), Shikoku, described by E. R. Sykes and housed in the British Museum (N. H.). The results of my observation on them are as follows : 1. Clausilia (Hemiphaedusa) schmackeri Sykes is a good species and the corrected name is Pinguiphaedusa schmackeri (Sykes, 1895). 2. Clausilia (Hemiphaedusa) ignobilis Sykes is a senior synonym of Tyrannophaedusa (Decolliphaedusa) abei Kuroda, 1980 and the corrected name is Pinguiphaedusa ignobilis (Sykes, 1895). 3. Clausilia (Megalophaedusa) fultoni Sykes is a good species and the corrected name is Mesophaedusa fultoni (Sykes, 1895).

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One of the syntype specimens of Loligo sumatrensis d'Orbigny, 1835 was re-examined to clarify its identity. The results of re-examination revealed that L. sumatrensis is a senior synonym of Nipponololigo kobiensis (Hoyle, 1885).

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The karyotype of Lunella coronata coreensis was examined. The diploid chromosome number in this species is 2n=36, and its karyotype is formulated as follows : 2n=36=26M+6SM+4ST, NF=72

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