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Imperial Gazetteer of India, v. 1, p. 52.

52 TIIE IN.DIAN EMPIRE [CHAP. that the lowest coal measures in India were being formed during Upper Palaeozoic times. Cornpara- On the other hand, among marine fossils, especially such tiremitof freely migrating forms as cephalopods, we have in general life in the a tendency to wide geographical distribution with a very limited ocean. vertical range. The recognition, therefore, of the species of marine fossils in Indian formations permits a more precise correlation of Indian strata with those of Europe than is possible in the case of the fresh-water strata. The marine formations enable us to fix the chief landmarks in Indian geological history, and, having established these, we can con- sider the associated fresh-water and unfossiliferous rocks. Want of Before settling down to the description of the Indian rocks, strict con- teripora- there is one more stratigraphical principle of which the reader neity in should be reminded: it is necessary to explain how it is that, geological in our attempts to express Indian stratigraphy in European terminology, we never attain full success. In consequence of the way in which most areas have been alternately immersed below the sea to receive deposits of sedi- ment, and raised to the denuding action of atmospheric agents, the sedimentary record in any country is marked by inter- ruptions at irregular intervals in the scale. These interruptions or 'breaks' are not on the same horizons for all parts of a large area, for one part may be below water and receiving sediment when another is exposed and being cut into by the weather. Thus the dominant breaks in the Indian stratigraphical scale can only by an infinitesimal chance be strictly contemporaneous with those in Europe. In employing such breaks in the succession to define the upper and lower limits of stratigraphi- cal units, we obtain series of strata which cannot correspond precisely to the units in the European scale; and for these Use of series we are driven, therefore, to employ, in the first instance, localstrati- local names which may cover parts of two or more European graphical names. units. In Southern India, for instance, we have a series of strata answering generally to the Upper Cretaceous of Europe; but the four natural subdivisions in India do not correspond precisely with the European subdivisions. The lower part of the Utatur stage of Southern India corresponds to the cenomanian of Europe, while its uppermost beds contain a turonian fauna. The lower beds of the next succeeding stage, the Trichinopoly beds, are turonian, while its higher beds are senonian (see Bibliography, paper No. I 1). This circumstance, 1 Figures in parentheses and printed in antique type refer to the papers quoted in the Bibliography at the end of the chapter.