Pseudofusulina vulgaris globosaのphrenotheca
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概要
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A term "phrenotheca" was proposed by THOMPSON (1948) for diaphragm-like partition in chambers of fusulinids. Search on various literatures reveals that the phrenotheca exists in almost all species of Pseudo-fusulina, a part of the species of Parafusulina, Schwagerina and Paraschwagerina, but not in all species of Triticites and Pseudoschwagerina, and many species of Parafusulina and Schwagerina likewise. In order to clarify the shape and nature of "phrenotheca" the author selected several free specimens of Pseudofusulina vulgaris globosa (SCHELLWIEN) from Akiyoshi, Southwest Japan for study. The specimens have been ground down at the regular intervals of 0.025 mm, so as to keep that ground surfaces are either parallel to the coiling axis of specimens or vertical to that axis. Each ground and polished surface is then etched by 3% NH_4Cl, and replicas of Bioden RFA film are taken to record successive figures of internal morphology. Phrenotheca in the species here treated is well developed throughout the shell, except for full grown outer volutions and one or two innermost volutions, where it is rather difficult to trace phrenotheca if it presents. Phrenotheca is especially well developed in central region of chambers near tunnel. Plate I shows serial axial and tangential sections of Pseudofusulina vulgaris globosa at the intervals of 0.025 mm. Plate II shows a series of sagittal, as well as parallel sections of the same species at the intervals of 0.05 mm. These two sets of sections well exemplify the successive change of the shape of phrenotheca. Namely, in each chamber the phrenotheca is bulged towards polar regions from the central part around tunnel to make continuous small chamberlet like cave which is also supported by wall and fluted septa. This chamberlet has irregular bulge and swelling at places, owing to change in the width of chamber accompanied by the intensity of septal fluting. Thus it forms a closed space by itself or in contact with wall and septa, except for tunnel region. Chamberlet formed by phrenotheca in each chamber is connected by tunnel with each other. Therefore, phrenotheca is nothing but a name for the "shell" of small cave-like chamberlet existing in chambers. Author calls this chamberlet "inner chamber". The existence and the shape of this inner chamber could be a criterion in classifying genera and species of Schwagerininae.
- 地学団体研究会の論文
- 1964-09-30