The present area is situated in the southeastern part of the western half of the Ryoke belt in the Kinki district. The area is mainly composed of granitic rocks. On the southern side, the granitic rocks are in contact with the Late Cretaceous Izumi Group in fault relation. This fault belongs to the fault system of the Median Tectonic Line and therefore the granitic rocks are mylonitized in various grades within 2-2.5 km width from the Median Tectonic Line. The granitic rocks are divided into ten masses on the basis of their rock-facies and also into two groups different in the stage of intrusion, as follows : The first stage granite: Ryumon-dake quartz diorite (11), Takihata gneissose granodiorite (10), Ashihara gneissose quartz diorite (9) and Mochio granodiorite (8). The second stage granite: Takatori-yama adamellite (7), Imaki quartz diorite (6), Michaya adamellite (5), coarse-grained granodiorite (4), fine-grained biotite adamellite (3) and aplitic granite (2). (Numbers in parentheses correspond to the key of the geologic map, Fig. 2). The gneissose structure is generally conspicuous in the first stage granite. On the contrary, in the second stage granite it is missing or, if any, weak and local. Matadiabasic inclusions are well developed in the first stage granite, but are scarce in the second stage granite. Some of these granitic masses can be lithologically correlated to ones in the Ryoke belt of the Chubu district, where granitic activities are divided into nine phases. The Ryumon-dake quartz diorite and the Takihata gneissose granodiorite, probably including the Ashihara gneissose quartz diorite, are surely correlated to some of the granitic masses of the first to the second phases. Moreover, the Imaki quartz diorite, the Michaya adamellite and the fine-grained biotite adamellite are probably correlated to some of the granitic masses from the third to the seventh phases. Accordingly, the history of the granitic activities seem to have been similar in both districts. On the other hand, in respect to the distribution of these granitic masses, those two districts show some differences. In the Chubu district, the socalled older granite with gneissose structure is almost exclusively distributed along the Median Tectonic Line. But in the present area the second stage granite without gneissose structure is intruded between the Median Tectonic Line and the gneissose granite. This difference is more conspicuous in the northern Shikoku and the Setouchi districts, where the so-called older granite is almost lacking. The present area is the transitional part between the two different parts, the Chubu and the northern Shikoku-Setouchi districts of the Ryoke belt. The further study of the present area may elucidate this different geologic condition in the granitic activities of the Ryoke belt.

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Development of mathematical geology and recent activities of IAMG reported at "Symposium on Data Processing in Geological Sciences" held at Tokyo, Oct. 19, 1973, are briefly summarized. MATHEMATICAL GEOLOGY : Geologist studies multivariate problems by setting up models and sometimes by running them. Among the models used in mathematical geology, some examples of geometrical model, probabilistic model, Markovchain model and simulation model are described (Figs. 1-6). IAMG: Concurrent with the expansion of the mathematical method and with increased facilities of employing electronic computers, so many works have been published in the field of mathematical geology, and there has been a growing trend towards organization of international association of mathematical geologists. Birth and the activities of the International Association for Mathematical Geology (IAMG) are outlined with some discussions on papers and authors having contributed to the Journal of IAMG (Fig. 7 and Table 1). STUDIES AND EDUCATION: Some problems of studies of mathematical geology and education of mathematics carried on in colleges and universities are also discussed.

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