156 CRETACEOUS ROCICS OF S. INDIA. [PaRT II. § 2. 



calcareous sandstone, has been traced as far to the North-east as the edge 

 of the Mercanum alluvium, while limestone nodules similar to those of 

 Valudayur have never been found elsewhere then below, i. e. to the 

 West of the out-crop of the former bed. 



I have described in some detail the country around Valudayur, 

 not only because it possesses a special interest, as the original locality 

 from which the fossils described by Professor Forbes were obtained, 

 but also because it affords a fair example of the Geology of these rocks, 

 as they occur over the whole of the Pondicherry area, and that a detailed 

 account of the locality explains the reason, that the occurrence of two 

 distinct deposits has escaped the notice of previous observers. Nowhere 

 is any section obtainable exposing the two rocks in absolute superposition, 

 and nowhere can their stratlgraphical structure be traced with such 

 accuracy as to afford a distinct proof of unconformable bedding. 



Of the two groups, it unfortunately happens that the lowest, 

 - Valndaym- group much which in many respccts is the most interesting, 

 obscured by regur. ^^^ ^j^^^^ concerning which information is most 



required, is also that which is most obscured and is least prolific in 

 fossil remains. The first is due to the slight degree of consolidation of 

 the rocks composing it, in consequence of which it has been every- 

 where denuded to a low level, and subsequently covered up by 

 superficial deposits to a depth generally greater than that of the 

 natural drainage system, and for the same reason the artificial sec- 

 tions exposed in irrigation wells, (now pretty numerous,) are generally 

 concealed beneath the water line, and the only materials furnished to 

 the Geologist are the lumps of debris thrown out of such excavations. 

 From an examination of these, and the few nullah courses in 



which the rocks are exposed, it appears that the 

 Lower beds of group. 



lower part of the group, (of a thickness not 



ascertainable but extending over a horizontal area of about 3 miles in 



width,) consists of sand or sandy shale, sometimes argillaceous, and 



