Chap. XI.] cuddalore sandstones. 167 



beds, to judge from the outliers which cap the Cretaceous rocks, at about 



the same level, at several places to the West of the main formation. 



It will not be necessary to enter into much detail in the descrip- 



_,.,,, . ,. „ tion of the Cuddalore group, as it presents few 

 Detailed description of o i j i 



S^(>^^P- features of interest, beyond those already noted ; 



and I shall confine myself to a brief notice of the principal localities at 

 which it may be studied within the limits of our area. 



In the neighbourhood of Tanjore are some coarse grits and conglo- 

 merates, which I have referred to this group. 

 At Tanjore. 



although, as stated in a previous chapter, I can- 

 not consider their age as indisputably settled. They are exposed to 

 a considerable extent in the neighbourhood of Vellum, and the moat 

 of the old fort exhibits a fine section of them to a depth of about 20 feet. 

 They consist of false-bedded sandstones and grits, mottled with irregular 

 ferruginous infiltrations, and in some places passing into laterite to a 

 depth of 6 or 8 feet from the surface. Where laterite is formed the rock 

 appeared to be more argillaceous than elsewhere. Bands of conglome- 

 rate are also intercalated, chiefly containing quartz-pebbles of various 

 tints, (cairngorum, amethyst, and rock crystal,*) and at one spot several 



great blocks of cretaceous chert, similar to those 

 Enclosed chert boulders. 



m the sandstones near Thaloor (page 142), and 

 containing a few fossils. Messrs. King and Foote, who first noticed 

 these, obtained from them some specimens of Cidaris spines, (impressions) 

 and a cast of a terebratula and some other small fossils (all of which were 

 subsequently lost in the ship which was conveying them to Calcutta). 

 These blocks of chert are, I think, imbedded in the conglomerate, and 

 have not been formed in situ, inasmuch as although of large size, (mea- 

 suring 3 or 4 feet in diameter,) they contain no pebbles, and their sandy 

 base appears to be of finer grain than that of the conglomerate bed in 

 which they are enclosed. 



* These are collected by the natives, and several lapidaries in the village of Vellum find 

 emplojinent in cutting and polishing them for sale. 



