BY PROFESSOR STEPHENS, M.A., F.G.S. 



939 



" Independently of the presence of the Estheria, which has been 

 shown by Professor Rupert Jones to be essentially a fresh (or 

 brackish) water genus, there can he little doubt that all the beds 

 of the Raniganj held were deposited in fresh water, and I believe 

 the larger portion to have been the valley or alluvial deposits of a 

 great river. The total absence of marine remains, and of mollusca 

 of any kind, the extreme rarity of limestone, the constant 

 traces of rapid currents shown by the oblique lamination of 

 the sandstone, all favour this view. Lacustrine or estuarine 

 conditions may perhaps have prevailed during the deposition of the 

 Talchirs and of the basement beds of the Panchets, possibly even 

 of the Damudas (though of this I am extremely doubtful), but I 

 am convinced that the mass of the Panchet beds are a fluviatile 

 deposit. The universal evidence of current actions in the sandstones 

 precisely resembles those which may happen in the valley deposits 

 of the great Indian rivers, in which also stratification of fine clay 

 is frequent, while the first named phenomenon is totally 

 inconsistent with deposition in lakes of any size. The recent 

 distribution of Estheria and similar Crustacea, especially in India, 

 is in favour of their Panchet prototype having been an inhabitant 

 of shallow pools, rather than of extensive deep basins of fresh 

 water. Large marshes, more or less permanent, frequently disap- 

 pearing almost completely during the dry season, abound in the 

 valleys of large rivers, indeed after heavy rains the greater portion 

 of the river-valley becomes an immense marsh, in which fine clays 

 may accumulate. 



" During how great a period of geological time even small rivers 

 may occupy the same valleys has been shown by Mr. H. B. 

 Medlicott, in his memoir on the Sub-Himalayan rocks, and when it 

 is borne in mind that it is only in periods of general subsidence, 

 continuous or intermittent, that strata can be accumulated in river 

 valleys, it is easy to conceive that a mere discontinuance of move- 

 ment during a geological period may suffice to cause such changes 

 as are observed between the Talchir and Damuda, and between the 

 latter and the Panchet series; while, unless elevation has taken 

 place, but little denudation will have been caused." 



