1. The Jori Grid Pattern System is characterized by an interval network of paths and ditches, which divide a given area into units measuring approximately 109m square. By the middle of the 8th Century the system consisted of such a grid pattern, with the arable land in each section divided into regular allotments. About the middle of the 8th Century a new system was introduced, by which the entire Jori System was organized into “Jo”, “Ri” and “Tsubo”. The “Tsubo” was the smallest section of the square, consisting of approximately 1.2 hectares, the “Ri” comprised 36 “Tsubo”, or approximately 654m square, and the “Jo” was a liniar arrangement of “Ri”, whose exact organization varied according to region.
In some provinces, such as Settsu, Sanuki and Awa, historical evidence shows that the system of land unit indication followed three stages, as follows: 1) according to former small place names 2) according to the Jori Numbering System with place names attached to it 3) according to the Jori Numbering System only
A number of historical materials show the process from 2) to 3) in Yamato, Yamashiro, Iga, Ohmi and Echizen provinces in accordance with the fixation of the Jori Numbering System. However this Jori Indication System was not introduced at a time. In Yamashiro province, this system was introduced by 743, but in Sanuki, it came after 757 and before 763, and in Settsu, after 756 and before 767.
2. The former type of small place name was divided or changed to fit with the Jori Grid Pattern in stage 1) or 2). This process is shown for Kuso-oki region, Echizen Province in the 8th century (Fig.7). Some of former types of small place names, which were quite extensive (See Fig.7 Left), were divided and changed (See Fig.7 Right) in accordance with increase in arable land.
However all of the former types of small place names were not divided in the 8th century. In the Kinki District (near the Capital of Ancient Japan), the greater part of those place names already fit the Jori grid pattern, as shown in Fig.6, but others fit only partially, as shown in Fig.5.
In the case of Echizen province, not so far from the capital, those place names partly fitted or were in the process of such adaptation as above mentioned. In the case of Etchu province, far from the capital, such place names were not divided as shown in Fig.8. In the last case, the Jori Indication System was established at once, but the enforcement of the Jori Grid Pattern was probably incomplete, and the Jori Indication System does not seem to have been fixed perfectly.
3. After the enforcement of the Jori Grid Pattern and the fixation of the Jori Indication System, the latter began to deteriorate. An early sign of this process was found in the 10th century. In medieval times the small place name began to be used side by side with the Jori Indication System. Almost all these new small place names designated the smallest section of the Jori Grid Pattern. By the end of the Medieval Period, this small place name system became generalized even on the Jori Grid Pattern.
4. The plan of the Jori Grid Pattern was completed in the middle of the 8th century, with the introduction of the Jori Indication System. This plan undoubtedly was connected with Handenshuju, one of the important policies of the ancient “Ritsuryo” period, but “Ritsuryo” was established by 701 at the latest. Accordingly, the plan of the Jori Grid Pattern, especially the Jori Indication System, was not peculiar only to “Ritsuryo”. It was necessary for registry affairs rather than for Handenshuju itself. Since the 8th century, the bureaucratic procedures for distinction between private lands and government owned lands became very important, in accordance with the increase of private land.

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The Kii-tanabe plain, located on the south-western coast of the Kii-peninsula, is a small delta which has filled up the drowned valley of the Aizu river. In this plain, there are many prehistoric and protohistoric remains that can be fortuitously used in estimating the time and paleoenvironment of the alluvial deposits. The auther classified the alluvial surfaces from the viewpoint of landform evolution, and tried to reconstruct the paleogeography based on analysing the physiographic environment and the archeological data of the human remains. The results are as follows:
The alluvial surfaces in this area can be divided into four surfaces: sand bar I, sand bar II, upper delta and lower delta. The paleogeography during prehistoric and protohistoric era had changed according to the steps outlined below.
(1) By the earliest Jomon, Oshigatamon stage (around 8000yrs. B.P.), the sea invaded landward and the shoreline receded about 2km behind that of the present day.
(2) With the progress of transgression, the embayment area spread over the Kiitanabe plain, and the blue-grey clay with shell was deposited on the bay-bottom.
(3) On the open coast, the sand bar I was formed just after the sea-level reached its highest point during the middle Jomon period (around 4400yrs. B.P.), while as to the inland region, it became a lagoonal environment, and humic silt, silt, or peat was accumulated.
(4) After slightly falling once, the relative sea-level rose slightly and the sand bar II was formed in front of the sand bar I. (probably around 2400yrs. B.P.)
(5) A regression which attained more than 2m below the present sea-level during the Yayoi period and which had been known in other regions, caused dissection of the sand bar I, sand bar II and upper delta. The lower delta composed of fluvial sand and gravel was formed along the present river.

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