Chap. II. ] general topography and geology. 29 



boulders. These are easily recognized by their mineral character as 

 belonging to the Talchir group.* 



2. Above the Talchir group comes a great thickness of beds con- 



taining coal. By both mineral character and 

 Damuda rocks. 



fossil contents, these are recognized as of the 



Damuda group. f Reasons will hereafter be given for concluding that 



in this field only the lower portion represents that group as developed 



in neighboring localities, as on the flanks of the Rajmahal Hills, and in 



Orissa. To this portion will be restricted the name of Lower Damuda. 



Above the Lower Damuda sub-division are found beds markedly 



distinct in mineral character, and at the base 

 Ironstone shales. 



of which there is a considerable thickness of 



carbonaceous shales, with ironstones, the band already alluded to as the 

 ironstone shales. In the presence of coal in large quantities, and, des- 

 pite some minor distinctions, in their fossil contents, these beds are 

 closely allied to the Lower Damuda rocks, and they might well have 

 been named " Upper Damuda," had not that term been already 



applied to a series of beds occurring in the 

 Raniganj rocks. 



Nerbudda district, which there is every reason to 



suppose are distinct from, and more recent than, the upper portion of 



the Damuda group in the Raniganj field. For these, therefore, 



as they contain all the most important coal seams now worked 



in the neighborhood of Raniganj, and as they are well developed 



around that station, the term " Raniganj series" appears appropriate. 



3. The Damuda group is over-laid by grey and greenish sandy 

 shales, and upon these rest coarse false-bedded sandstones, with deep 

 red clays.J These beds are clearly quite distinct from the true Damuda 



* See Memoirs, Vol. I., pp. 46—56, 76—80, &c, Vol. II. 



f Jour. Asiat. Soc, Beng., Vol. XXV, p. 249. Mem. Geo. Surv., India, Vols. I. and II. 



% These are termed marls by Mr. Williams in the same way as the clays of the Trias (which 

 the beds of the Panchet group much resemble,) are known as " New Eed Marls" in England. 

 The term, however, is not quite correctly applied in either case, the clay not being calcareous. 



