192 CRETACEOUS ROCKS OF S. INDIA. [PaKT II. § 2. 



the level of tlie actual plain the regur gradually ascends to much higher 

 beds, and elevation must have operated slowly in raising these interior 

 ti'acts above the level of the sea. The collateral evidences of upheaval 

 are abundant along this coast. I ha,ve, in a previous part of this Me- 

 moir, described the escarpment which bounds the Eed Hill plateau to the 

 North of Pondlcherry, and have given a drawing of that still finer exam- 

 ple of an old marine escarpment which runs from the neigbourhood of 

 Cuddalore up to the Madras and Trichinopoly road. Another equally 

 fine in point of distinctness, but shorter, runs to the North of the Mur- 

 dayaur, in Trichinopoly, and indeed in many other localities the little 

 plateau of Cuddalore sandstones is bounded by escarpments more or 

 less abrupt and elevated. 



An instance of a somewhat older formation of regur than that of 

 Mercanum is that of the lower valley of the Vellaur. On the left bank 

 of this river, beyond the narrow fluvlatile zone, the regur extends to 

 some miles below Bhonaglrl, (Bhuvanaglri) probably of considerable 

 thickness. Between Bhonaglrl and Porto Novo, three or four old sjiits* 

 of sand run parallel to the coast, the Innermost being not less than 6 

 miles from the present coast line. The regur in its typical form does 

 not extend quite up to these, but becomes sandy and Impregnated with 

 salt and soda, which effloresce on the surface, but the deposit is continu- 

 ous, its mineral character only being changed. To the North-east, near 

 the Cuddalore river, beneath this sandy soda soil, a bed of shells occurs 

 at a depth of 6 feet, and is worked by the natives in the neighbourhood 

 of Kundvamelur for the manufacture of lime. The shells form about 

 half of the mass of the bed, the matrix being a dark sandy mud, and 

 they consist mainly of Cytherea casta, a common existing estuarine 

 species, among which a few other species, more characteristically marine, 

 are intermingled. 



* This locality is of some historic interest as the scene of Sir Eyre Coote's victory over 

 Hyder Ali— the battle of Porto Novo, 



