Cytological structures of the two spyrids Acanthodesmia vinculata (Muller) and Lithocircus reticulatus (Ehrenberg) were examined. The cytological features of the two species are obviously different. A. vinculata has a pear-shaped central capsule containing an eccentrically situated nucleus and juxtanuclear axoplast. The fusules are concentrated around the base of the central capsule in a pore field (porocora), which is the most diagnostic feature of nassellarian cytology. In contrast, L. reticulatus possesses a globular central capsule containing a large centrally located nucleus. Of particular interest, fusules of L. reticulatus are distributed radially, all around the central capsule, which previously has been described as a typical feature of spumellarians, not nassellarians. In addition, there are some minor differences in ultrastructure of the capsular wall and fusules between the two spyrids. This evidence indicates that these two species should be separated above the generic level. Beyond these fine structural differences, the two spyrids have some common features of the capsular wall and fusule structure. Their capsular wall is considerably thicker (0.3-0.5μm thick) and multilayered compared to that of the cyrtid capsular wall that is composed of a single osmiophilic layer (0.03-0.05μm thick). Moreover, the spyrid fusules lack an inner osmiophilic zone that is characteristic of the cyrtid fusules. The general shape of the fusules is also different between the spyrids and cyrtids. These features are sufficiently different to validate the suborders Spyrida and Cyrtida as the highest hierarchical division among the nassellarians, and do not support assigning spyrids to a family taxon such as Acanthodesmidae or Trissocyclidae as previously suggested by some workers. The Spyrida and Cyrtida include respectively two and four types of nucleus-axoplast relationships, which appear to be useful for considering family classification. Among them, one relationship named Acanthodesmia-type is recognized both in the Spyrida and Cyrtida. This clearly suggests that convergence occurs frequently in radiolarian evolution. Hence, it is necessary to synthesize cytological, morphological and stratigraphic information to construct a consistent classification scheme of nassellarians.

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Sharpeiceras mexicanum (Bose, 1928) has been recently found in a mudstone unit of Hirotomi in the Monbetsu Valley, south-central Hokkaido. It possesses the adult body chamber, which has not been well shown in the hitherto described specimens of this species. Sharpeiceras kikuae Matsumoto and Kawashita, 1995 is redescribed in this paper, since it was established as an appendix to a stratigraphic paper written in Japanese and seems to have been little noticed. It came from a mudstone member in the lower part of the Middle Yezo Subgroup in the Oyubari area, central Hokkaido. It is somewhat similar to S. florencae Sapth but has a wider umbilicus, less crowded ribs on the septate whorls and more distinctly separated two lateral tubercles. In these respects it seems to resemble S. mocambiquense (Choffat), but the available material is insufficient for exact comparison. The two species described indicate an early Cenomanian age for the fossiliferous mudstone.

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This paper focuses on ceratoikiscid radiolarians from the Devonian Nakahata Formation of the Yokokurayama Group in the Kurosegawa Terrane. The fauna is assigned to the Emsian to Eifelian (late Early to early Middle Devonian). There are 13 species of radiolarians, including 4 new species, which belong to the genera Ceratoikiscum, Glanta, Protoholoeciscus, Circulaforma and Helenifore. The morphology and stratigraphic distribution of the genera suggest that Protoholoeciscus evolved from Ceratoikiscum via Glanta with the process of acquisition of shell.

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Recently many plant taxa have been described from the marine Upper Yezo Group (Coniacian-Santonian). These plant fossils are preserved as permineralized debris in calcareous nodules together with various marine animals. A single bennettitalean specimen was collected from the Upper Yezo Group. It consists of a receptacle, with numerous fertile (seminiferous) and sterile (interseminal) scales. Although the specimen is fragmented, its anatomical features are well preserved. This paper provides a description of a new reproductive organ belonging to Bennettitales. As its affinity to Williamsoniaceae or Cycadeoidaceae and their allies is uncertain, we provisionally place our specimen in the form-genus Bennetticarpus and describe B. yezoites sp. nov. Comparison of Bennetticarpus yezoites with known bennettitalean taxa in other regions is given briefly.

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Lower Triassic coniform conodonts Aduncodina unicosta Ding and Neostrachanognathus tahoensis gen. et sp. nov. from the pelagic limestone of the Taho Formation in Ehime Prefecture, Southwest Japan are newly reconstructed as quadrimembrate apparatuses with the M, Sa, Sb, and Sc elements. A. unicosta Ding, originally described as a form species, is the Sb element of the skeletal apparatus of A. unicosta, newly conceived. Furthermore, the form species Cornudina anterodentata Ding and C. angularis Wang and Cao are referable to the Sa and Sc elements of A. unicosta, respectively. The elements of A. unicosta and N. tahoensis are all coniform types. The M elements of the two species are adenticulated and the Sa, Sb, and Sc elements are denticulated with one to four denticles on the anterobasal margin of the base. The morphologic similarity between Triassic A. unicosta and N. tahoensis and the Early to Middle Paleozoic coniform-type conodonts probably represents an adaptive convergence of the feeding apparatuses. A. unicosta and N. tahoensis indicate the early Spathian.

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A row of oval unpaired, ventral body attachment scars, accompanied by pseudosutures and drag bands, is preserved on surfaces of steinkerns of a lower Chesterian (Mississippian) goniatitid ammonoid, Goniatites multiliratus, from Oklahoma. Many smaller oval and crescentic attachment scars are present in the interspaces between these ventral attachment scars and between pseudosutures. Comparison with the muscle scars of other extant and fossil shelled cephalopods suggests that the unpaired ventral scars of this species represent the attachment sites of the muscle or ligament at the posterior end of the body. The smaller oval and crescentic scars on the ventral and lateral sides of each chamber appear to indicate weaker and less permanent attachments of muscular tissue to the shell wall. These are presumed to have been formed during gradual forward movement of the body.

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Specimens of the Recent species Ophiura sarsii sarsii Lutken, collected from the Late Pliocene Hachioji Formation in Kashiwazaki City, Niigata Prefecture, central Japan, represent the first record of this species from the Pliocene, although this species has been found from the Middle-Late Miocene. The fossil specimens have been compared and contrasted with related species using morphometric characteristics of the disk, basal arm portions and radial shields.

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Ukhtoceras hidense sp. nov. is described from the Lochkovian (Early Devonian) shale of the Fukuji Formation, Gifu Prefecture as the first find of a discosorid cephalopod in Japan. This species also extends the geographic range of the ukhtoceratids into East Asia.

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Haplophragmoides yoshidai Hanagata nom. nov. is proposed as a replacement for Haplophragmoides kushiroensis Yoshida, 1963.

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