Trace fossils include biogenic structures such as burrows, tracks, borings, coprolites and some others. The formal naming of trace fossils is provided by ICZN. Ichnotaxnomic classification is based on the morphology of trace fossil, refering to their behavioral significance.
 From the view of ichnology, the substrate consistency are divided into follows. 1) soupeground is highly watery sediment and fluid, therfore almost traces are deformed out of recognition. 2) looseground (sandy sediment) and softground (muddy sediment), which are aquatic and bioturbated mostly, and related to Skolithos, Cruziana, Zoophycos and Nereites ichnofacies. 3) firmground consists of dewatered and companted sediments, which are related to Glossifungites ichnofacies. 4) hardground, rockground and shellground are related to Trypanites ichnofacies, which are eroded by boring or etching. 5) Woodground is woody (xylic) substrate, which is related to Teredolites ichnofacies.

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 Rock-boring trace fossils are characterized by boring organisms such as bivalves, gastropods, brachiopods, barnacles, polychaete annelids, sponges, bryozoans, etc. In general, these trace fossils are used as indicators of ancient rocky shores, and are useful for reconstruction of paleoenvironments. A Trypanites ichnofacies, typical hard substrates ichnofacies, are characterized by ichonogenus Trypanites. Subsequently Trypanites ichnofacies are divided into two ichnofacies, Entobia ichnofacies and Gnathichnus ichnofacies, based on tiering and ichonofabrics. These new recognition give good indications of paleobathymetry, rate of burial, depositional environments, and paleoproductivity. The rock-boring trace fossils, Gastrochaenolites ispp. and Meandropolydora isp., are reported from the Cenozoic and the Cretaceous of Hokkaido.

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 A dredged fossil rostrum of Mesoplodon from the bottom of the ocean (550-1050m in depth) off the Midway Islands (lat. 27-32N., long. 170-172E.) has a lot of borings made by boring shells. Inhabitants in the borings have not been identified yet. Fresh fragments of boring shells had remained in the borings. Therefore, the borings were made in the near past, after the strata were eroded and the fossil rostrum lay on the sea bottom. The rostrum shape is slender like a rod with mesorostral ossification and the fossil is quite different from living species of Mesoplodon. The fossil rostrum is similar to that of extinct species Mesoplodon longirostris in some aspects, but the fossil’s protuberance of mesorostral ossification is higher than that of M. longirostris. Therefore, the fossil has not been also identified yet. The big question is where the fossil rostrum is derived from.

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 The writer studied borings made by some kind of Polydora in the shells of Babylonia japonica (Reeve) collected from the Pleistocene formation, Crassostrea gigas (Thunberg) and Mactra (M.) chinensis Philippi from the inner site of Tokyo Bay.
 In this short paper, he described the morphological characters of them with special remarks on the difference of above three specimens. After the penetration, it makes very thin shell layer secondarily. Especially in case of Mactra and Crassostrea, they make a dome respectively inside of the shell. He made some considerations about the boring behavior of Polydora in the shell layer.

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 Magilus antiquus Montfort is a boring gastropod belonging to the Family Coralliophilidae. This paper reports the occurence of this species in the coral reef along the coast of Efate Island of the New Hebrides in the South Pacific. A single specimen in hand consists of two parts, the anterior turbinate cone with 4 to 5 whorls, and the posterior tubular pseudo-shell. The height of the shell is 37mm, and the width is 30mm. The tubular part has a ventral keel extended from the inner lip of aperture to the tip. The length of the tube is 70mm, and it is twisted at the two-thirds of its length. The terminal aperture of the tube is covered with a small subcircular semi-transparent operculum. The comparative characters with allied species and boring mechanism in the coral body are described. However, the mechanism of secondary deposit of calcareous materials in the shell and burrows of Magilus antiquus have not been cleared yet, so it should be studied in future.

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 Charles Lyell visited North America 4 times between 1841 and 1853. During those trips, he made geological observations and collected a variety of fossils with the collaboration of Canadian and American researchers. He was also interested in trace fossils, and made special visits to the sites where those fossils had been discovered. His travels resulted in 2 books and a number of lectures and research papers. In this review, four topics, i. e., fossil footprints of birds, fossil footprints of reptiles, ‘fossil’ rain-marks, and the lecture on the Canadian lower Silurian fossil footprints have been selected and Lyell’s thoughts on those fossils are introduced.

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 The bipedal walking of birds shows great variability and includes head-bobbing and non-bobbing walking. These two types of walking were different in kinematic gait characteristics. Previous studies showed that head-bobbing has visual functions, and that head-bobbing affect the gait characteristics by enhancing stability of walking. Head bobbing probably is related to how animals stabilize their walking, so that it affects the gait characteristics. As an ultimate cause, the strategy of stabilizing walking or head bobbing may be determined in relation to the foraging behavior in which birds walk at relatively slow speed and seek foods at the place relatively near to the birds. Human also walk in bipedal. The bipedal walking of human is more like non-bobbing walking than of head-bobbing walking in several gait parameters. It may be explained from the viewpoint of how human and birds stabilize their walking.

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 Vertebrate teeth and bones consist largely of biological apatite crystals. Octacalcium phosphate (OCP) has been speculated to be a potential candidate for a constituent of the central dark lines in biological apatite crystals. However, if OCP and the central dark line can be shown not to be identical, then some pathway other than the OCP one might operate to produce the apatite crystals. In this study we used transmission electron microscopy and X-ray diffraction to look for possible differences between the central dark line and OCP. X-ray diffraction analysis revealed that the sharp reflection peak of 1.855 nm in d-value, characteristic of OCP, disappeared after the synthetic OCP had been heated up to 150°C for 1 hour. However, electron micrographs provided clear evidence that the central dark lines persisted in the examined biological apatite crystals even after heating at 600°C. These findings indicate that OCP cannot be a candidate for a constituent of the central dark lines in the biological apatite crystals in vertebrate teeth and bones.

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 The goblin shark, Mitsukurina owstoni Jordan (Lamniformes: Mitsukurinidae) is a rarely caught but widely distributed shark. Based on four specimens from Japan (110-335 cm total body length, TL), the relationship between tooth crown height (CH) and TL for each tooth in M. owstoni is examined using regression analysis. The results suggest that the CH for most teeth can be used to predict the TL, where an increase in the CH of each tooth through replacement is proportional to the increase in TL. Distally located teeth show a proportionally greater size increase in comparison to mesially located teeth.
 Most mitsukurinid fossils are represented only as isolated teeth. The regression equations obtained in this study may be used to estimate the TL of extinct mitsukurinids (e.g., Scapanorhynchus Woodward) from their teeth. Calculations suggest that most Scapanorhynchus individuals did not exceed 415 cm TL, although some individuals may have attained 670 cm TL.
 The sole specimen of eastern Pacific Mitsukurina owstoni is represented only by the head. Previous TL estimates of this individual ranged from 2.18 m TL to 3.75 m TL. A reassessment of its TL based on our 36 independent, tooth-based regression equations strongly suggests that the shark was about 2.7 m TL.

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[in Japanese]

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