The present report describes the ontogenic development of a Middle Cambrian trilobite : Ehmaniella burgessensis Rasetti from the Burgess Shale, Yoho Park, British Columbia. The morphogenesis of this trilobite during its early growth stages are similar to those of Sao hirsuta Barrande, Crassifimbra walcotti (Resser), Glyphaspis cf. parkensis Rasetti, Yuknessaspis santaquinensis Hu, Trymataspis convexus Hu, and Ehmaniella sp. etc. whereas in the late ontogenic stage the instars are similar to most of its fellow member except for those of Crassifimbra walcotti and Trymataspis convexus. These phenomena possibly indicate that these trilobites are derived from the same common ancestor but differentiated into different groups in later descendants.

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Several thick limestone layers are exposed in the Setogawa terrain. Well-preserved planktonic foraminifers were recovered from most of these limestone layers. Planktonic foraminifers consisting of a total of 23 species were discovered at seven limestone localities and in one mollusca-bearing sandstone of the Setogawa Group. These limestones of the Setogawa Group are assignable to three different horizons corresponding to Blow's zones of P.12 to P.13, P.14 and P.16, and are dated to range from the Middle to Late Eocene.

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Uranium-series analyses of seventy-four coral samples imply that the Pleistocene Riukiu Limestone (Hanzawa, 1935) on Hateruma, Ryukyu Islands, were formed during at least four stages of high sea stand, two interstadials (ca.81 and 103 ka B. P., respectively) and two interglacials (the last and penultimate ones). The oldest coral date was 300⁺⁴⁰_-30ka obtained from a Porites sample which was collected at a locality of about 33m above the sea. Maybe this date is suggestive that the coral reef has already formed at the time of an another high sea stand (correlative to the stage 9 of the marine oxygen isotope record) in the place where the island is at present. The tidal flat around the coast of the island is likely to have been built since the last thousands years. The Riukiu Limestone on Hateruma is thus correlative with some of Pleistocene uplifted coral reefs on Barbados (Bender et al., 1979), New Guinea (Bloom et al., 1974) and Kikai (Konishi et al., 1974) dated previously, and the tidal flat limestone with the Raised Coral Reef Limestone on Kikai (Ota et al., 1978) and with the reef complex I on the Huon Peninsula, New Guinea (Bloom et al., 1974). Among marine terraces which were divided into eight steps (T1 through T8) by Ota et al. (1982), T2 and lower five terraces (T4 to T8) are inferred to be erosional in origin, based on the results of ²³⁰Th/²³⁴U age determination of corals which were collected on the same surface of the terraces. Ota et al. (1982) documented that the former shoreline of each terrace shows progressive westward tilting. The maximum uplift rate of approximate 0.3m/ka is calculated in the eastern part of the island, assuming the constant rate of tectonic uplift and a sea level 6m higher of the present one at the time of T3 terrace formation (ca. 128ka B. P.). Accordingly, Hateruma is considered to have been situated tectonically in the compressive field since the last interglacial.

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In this paper selected eight species of Hemiaster from the Upper Cretaceous of Japan are described. They are assigned to the subgenera Hemiaster (5 species), Leymeriaster (2 species) and Mecaster (1 species). Among them, one is new, another is a hitherto described Japanese species, and some of the rest are provisionally comparable with but distinct from certain foreign species, but I postpone to establish new taxa until more and better material is obtained. Some brief remarks are given on the Hemiaster faunal aspect, the mode of occurrence and the inferred mode of life.

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