The tenth chapter is dealt with the history of research in older rocks and Cambro-Ordovician of eastern North America. In last century Pre-Cambrian stratigraphy was started in Canada, while the New York System was instituted around Albany, N. Y. and later it was correlated to the European sequence. Subsequently the Cambrian and Ordovician Systems were classified in detail. Starting with the ventral anatomy of trilobites Walcott made invaluable contributions on the Cambrian geology and palaeontology, i.e. the Olenellus fauna, unique fauna the Burgess shale and so forth. His “Cambrian Fauna of China” 1913 provided a firm basis for the Cambrian of Eastern Asia. The relation of the Cambro-Ordovician faunas of the continent to the European ones in the northern part of the Appalachian geosyncline and their distribution in the Appalachian mountains and further westerly beyond the lower Mississipy river and also in the interior lowland are briefly outlined. These systems in the Cordilleran geosyncline is described in the eleventh chapeter. Stratigraphy in the western sites is followed by notes on the Alaskan faunas in the north which were allied to the Siberian ones at the beginning, but later to the Eastern Asiatic ones also. In the south it is a remarkable fact that the Mexicoan faunas are more related to the Andean ones than those of the United States, particularly in the early Ordovician age. The Circum-Pacific Cambro-Ordovician belt is taken up in the final chapter. The history of this belt's history started in the Sinian period. In the early Cambrian age the eastern side belonged to the Olenellian province, but the other side constitued the Redlichia province. Subsequently, however, trilobites of the two sides became closer related to each other, although the early Upper Cambrian Kushan fauna was quite isolated. Trilobites were intimate between the two sides of the Northern Pacific and also on the southern Pacific side in the early Ordovician age. The aspect of the provinciality in the middle and late Ordovician ages is still obscure, sofar as trilobites are concerned.
In the Miocene Morozaki Group of the Chita Peninsula, there are two types of fold generated under different stresses : left-stepping en echelon fold developed along the southwest coast of the Peninsula, and east-west-trending folds which are found in the east and northwest of this area. The former is a set of folds produced by left-lateral strike slip of the Atsumiwan Fault which is a splay fault at the end of the Median Tectonic Line, extending along the southwest coast of the Peninsula. The latter are folds related to right-lateral strike slip of the Chitawan and Isewan Faults, splay-faults of the Yoro-Isewan Fault which forms conjugate fault set with the Median Tectonic Line. On the basis of the commonly expressed concept that synsedimentary folding has a relation with the thickness of the deposits in the sedimentary basin. Investigation for the lateral variation in thickness of the four major sandstone beds revealed that there are three phases of faulting during the deposition of the Morozaki Group and in the following age of emergence. 1) Right-lateral slip phase of the Chitawan Fault. This phase is contemporaneous with sedimentation of the Himaka, Katana and Toyohama Formations, being characterized by the development of E-W trending folds and E-W or N-S trending elastic dikes. 2) Left-lateral slip phase of the Atsumiwan Fault. These faulting occurred concurrently with the deposition of the Yamami and Utsumi Formations, being related to the development of the left-stepping en echelon fold, the rightstepping en echelon sandstone-dike swarms, the Tsubuteura Olistostrom, the Hazikami Fault and the Utsumi Growth Fault. 3) Right-lateral slip phase of the Isewan Fault. It is the phase of emergence following the deposition of the Utsumi Formation, and the E-W trending folds in the north of Utsumi were caused by these faulting. It is conclusded from the results of this investigation that the sedimentation and tectogenesis of the Morozaki Group took place under the alternating faulting of the Median Tectonic Line and Yoro-Isewan Fault Systems which are in a conjugated relation.
The most noticeable characteristic of the national urban system in Bangladesh is that it has been formed under the influence of international political changes. When the present territory of Bangladesh was separated from India in 1947, the area was much less urbanized with its urban population less than 4 %. Its small cities were just constituent of a partial set divided from the Calcutta-based urban system in the eastern part of British India. Even Dhaka, the present capital, was a local town whose population size was merely one tenth of Calcutta. The process in which those disconnected cities have formed the present urban system would show some essential factors to support a national urban system. The first stage of the process is the domination of the capital after the provincial government of the former East Pakistan was located. Though Dhaka had been a political center of muslims in the east Bengal, it was far from primate in the area at the time of the partition. The population of Dhaka grew more rapidly than that of Chittagong, the second largest city, to become the only nuclear of a political region. It is 2.5 times as large as Chittagong in 1981 and its primacy is still increasing. But thanks to Chittagong and Khulna which have international trade centers, the centralization of population is more or less lightened and hardly called extreme as rank-size distribution illustrates. The second stage is the development of large cities on a national scale by intensive industrial investment to selected centers. Industrialization was first set up with a view of substitution for the jute industries in Calcutta, and the labor-absorbing industries provided growth poles in the initial stage of urbanization. For example, Khulna, the third largest city at present, has developed only since jute mills were established in the 1950's. The top 4 cities (i.e. Dhaka, Chittagong, Khulna and Narayanganj) have not only commercial, transport and administrative function but also have industrial function, which distinguishes them from other local cities as well as population size. The third stage is the growth of local cities with the development of transportation network. The early example is the growth of Mymensing in the 1960's, but this is rather new trend in Bangladesh. Recent change of the means of transportation from vessels to automobiles has promoted the construction of all weather roads radiating from Dhaka, and the secondary local centers (e.g. Barisal, Sylhet, Rangpur) were emerging in each sector. The growth of local trade centers are, at the same time, supported by the recovery of consumer purchasing power after ten year economic difficulties caused by independence war from Pakistan in 1971. Spatial factor of the accessibility to Dhaka is now more effective than political factor of local administrative hierarchy. In connection with the change of the urban system, there are two more factors which seems to be important in the future. One is a regional development plan called “upazila development project”, which includes such projects as construction of paved roads and health care facilities in every upazila, or a local administrative unit. The plan will serve a test case of the influence of regional development on the national urban system in the third world. The other is the international relationship with India. The trade with India is not so much at present, but some manufactured goods flows into Bangladesh through western border. More active economic interchange with Calcutta would stimulate the rise of some cities in the western area. Bangladesh is still on her way of urbanization. The process above mentioned is rather common to most nations than Bangladesh proper, but the speed of change in the urban system is quite rapid and this would be the reflection of a character of Bangladeshi society.