Chap. II.] general des«ription or country. 23 



best seen and most extensive, these groups are five in number, three of 



which are undoubtedly of Cretaceous age. Taken 

 In Trichinopoly district. 



in descending order, they may be enumerated as, 



{The Cuddalore sandstones ? Exocjenous plant 

 remains m rondicherry, 

 /' The Arrialoor Group, highly fossiliferous. 

 Cretaceous ... ] „ Trichinopoly Group, ditto ditto. 

 \ „ Ootatoor Group, ditto ditto, 



{The Ootatoor plant beds : plant remains, other fossils 

 doubtful ? 

 and to these we may add a very remarkable and interesting formation, 

 the " Coral reef limestone," which occurs at a few points at the base of 

 the Ootatoor Group, apparently formed under somewhat different condi- 

 tions, but physically associated with it. 



The lowest and therefore oldest beds, the "Plant beds," are seen 

 in the neighbourhood of Ootatoor, cropping out irregularly from 

 beneath the base of the Ootatoor Group, and occupying the South- 

 western corner of the sedimentary area. From this point, if we proceed 

 either Eastward across the strike, or North-eastward along the general 

 boundary of the sedimentary rocks, we meet with all the members of 

 the above series successively overlapping each other, and dipping at a 

 low angle with much regularity to the East. The highest group, a mass 

 of coarse, ferruginous grits of unknown thickness, which we have termed 

 the Cuddalore sandstones, occupy a large area to the North-east, 

 including nearly the whole of the WodiarpoUiam talook, and they 

 re-occur in Tanjore to the South of the Cauvery, where they rest 

 immediately on the gneiss. A few outliers of these rocks are scattered 

 here and there over the Cretaceous rocks to the West of the principal 

 formation, and are in general easily recognizable by their coarse 

 grain, their mottled colors, and the universal absence of any fossil 

 remains. 



