This paper presents a brief discussion on the relationship between the molluscan assemblages and the sediments of the Daishaka Formation, and the inferred sedimentary environment. The stratigraphy and the lithological change in time and space were studied in detail through the correlation using several tuff and pumice conglomerate layers as key beds. The molluscan assemblages of the Daishaka Formation, which belong to the "Omma-Manganjian fauna", are grouped into seven categories, judging from the molluscan fossils regarded as actually or nearly autochthonous. These autochthonous assemblages seem to be very consistent with the sediments representing both the substratum and the water depth at that time. Almost all the sediments were deposited in the sublittoral zone. Generally speaking, the finer sediments, prevailing in the lower parts of the lower and upper units of this formation, were deposited in the lower sublittoral zone, and the remaining coarser sediments in the upper sublittoral zone.

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Several bivalve fossils were newly obtained from the Lower Jurassic Kuruma Group in the eastern part of Toyama Prefecture, north-central Japan. The following species are described in this article : Nuculana (Dacryoma) konishii Hayami, Nuculana (Dacryomya) cf. konishii Hayami, Pteroperna kitadaniensis Goto n. sp., Bakevellia (Neobakevellia) sp.

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This is Part 2 of a monograph of the Cretaceous Nautiloids from Hokkaido being published in series. It contains the description of three species, of which the first is new and assigned to Kummeloceras (established in Part 1), the second is identified with Cymatoceras pseudoatlas (Yabe et Shimizu), originally described on a specimen from Kyushu, and the last is a new species of Cymatoceras allied to and possibly evolved from C. saussureanum (Pictet) of an earlier age. The first two occur in the Lower Santonian Zone of Inoceramus amakusensis and the last in the Middle Campanian Zone of Sphenoceramus schmidti and seems to range down to the Lower Campanian Zone of Sphenoceramus orientalis. Some remarks are given on the Cymatoceratidae, proposing a new genus.

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Palaeoscenidiidae have most basically a bar-centered, eight-spined and polarized spicule. The eight spines consist of four shorter apical spines and four longer basal spines, although the apicals may be reduced to as few as one. It is widely recognized in many species of palaeoscenidiids that one of the apical spines is distinctively developed. Each spine is distinguished by comparative location with the distinctive apical spine and the median bar. Skeletal construction and systematics of palaeoscenidiids are easily understandable in terms of these identifications. Palaeoscenidiidae are composed of Palaeoscenidiinae and Pentactinocarpinae. Palaeoscenidiinae contain the following genera; Palaeoscenidium, Archaeosemantis, Parentactinia, Pactarentinia n. gen. and Tlecerina n. gen., and probably Sepsagon and Parasepsagon. Five new and two indeterminable species of Palaeoscenidium?, Parentactinia, Pactarentinia and Tlecerina are described. Genera of Parentactinia, Pactarentinia and Tlecerina may be simply termed a lattice-shelled Palaeoscenidium. They are distinguished by degree of development of the shell. Each shell is situated under the basal spines in Parentactinia, covers a part of each basal spine in Pactarentinia, and involves the whole of the spicule in Tlecerina. These radiolarians were obtained from a specimen of siliceous shale in the middle part of the G₄ of Mt. Yokokura. The geological age of it is estimated early or middle Devonian on the basis of the stratigraphic relationship between the G₄ and associated fossil-bearing formations and comparisons with known Palaeozoic radiolarians.

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^<230>Th/²³⁴U ages averaging 82, 000±2, 000 years old were determined for three species of ahermatypic solitary corals (Trochocyathus hanzawai, Micrabacia japonica and Flabellum rubrum) from the Riukiu Limestone of grainstone facies in the northern area of Kamikatetsu, Kikai-jima, Ryukyu Islands. It is most likely that this type of limestone was deposited at the water depth of 120 m or less as a forereef sediment, in front of the reef which has been elevated up to 184 m in present altitude by the vertical tectonic movement and is now forming a marine terrace developing to the south of Gusuku. The surface of terrace including the dated grainstone is thought to be partly constructional and partly erosional. Because two types of limestone, coralline limestone and this grainstone formed separately during times of two interstadial high sea stands (approximately 60, 000 and 82, 000 years ago, respectively), are recognized in the terrace deposit distributed at the same altitude.

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