1S60.] On the rocks of the Damuda group. 355 



Rajmahal hills, besides their occurrence in the fields of Raniganj and 

 Ramghar. 



The Damdda series, thus named from its extensive development on 

 the banks of the river Damdda, comprises, with perhaps one exception, 

 all those rocks from which coal has been obtained in Bengal ; the 

 coal bearing rocks of the Himalaya, Khasi hills and Burma being, 

 however, distinct. This series is divided in the Raniganj field by a 

 mass of black shales, containing beds of clay ironstone, and attaining 

 a total thickness of about 1,500 feet. There is evidence of uncon- 

 formity between these shales and the Lower Damudas, but none is 

 clearly made out between them and the upper series or Raniganj beds, 

 with which they are in consequence classed. 



The Upper Damudas of Raniganj must be carefully distinguished 

 from those beds in Central India which have been called Upper 

 Damudas,* Mem. Greol. Survey of India, Vol II. pp. 176, 312. 

 The Raniganj beds differ from the Lower Damudas in mineral 

 character, and also slightly, so far as is at present known, in fossil 

 remains. The upper beds consist mainly of very thick false bedded 

 sandstones, with seams of coal frequently continuous over considerable 

 areas. The lower beds are much coarser and more conglomeritic, and 

 are rarely false-bedded ; their coal seams are numerous, but very vari- 

 able in quality, and frequently thin out, or change into shale, or 

 even sandstone, within very short distances. 



The most characteristic fossil distinction between the two groups 

 consists in the abundance of a species of plant referred by Mr. 

 Oldham to Schizonema, in the upper division, which has not been 

 found in the lower. No animal remains have as yet been discovered 

 in the Damiida beds. 



The upper or Raniganj series is not known to be represented 

 beyond the Damdda field. The lower group is also found in Orissa, 

 and along the Western side of the Rajmahal hills. The superiority 

 of the coal of Raniganj is perhaps partly explained by the circum- 



* This name was given for good geological reasons, as will be seen by reference 

 to Vol. II. of the Memoirs of the Geological Survey. It has however proved an 

 unfortunate appellation, as it conveys an incorrect idea of the relations of the 

 beds, which contain a flora completely distinct from that of the true Damudas. 

 see Mem. Gcol. Survey, Vol II. p. 176. 



3 A 



