52 CRETACEOUS ROCKS OF S. INDIA. [PaRT II. § 1. 



the plant-beds' at Ootatoor and* elsewhere, aud as being quite distinct 

 from the Ootatoor beds which cap them, notwithstanding any local 

 appearance of conformity. 



The actual geological age of these plant-beds cannot be decided from 

 this district alone, and there is no use in entering upon the question here. 



I should mention that in one or two of the layers close to the gneiss, 

 there occur sparsely disseminated a few casts of a small bivalve, like a 

 Cyclas, but they are poorly preserved, and being solely casts, are not 

 recognizable. 



T. OLDHAM. 

 November ]861. 



Chapter V. — Ootatoor Grotfp. — fa) Coral Reef Limestone. 



The peculiar formation which I have thus designated occurs in 

 Occixrs at base of Oo- isolated ridges and bosses at several pomts along 

 tatooi loup. ^i^g boundary of the Cretaceous rocks, the lowest 



beds of which are heaped around it, and occasionally in a great measure 

 formed of its debris. It rests sometimes on the plant-beds, and some- 

 times, and more frequently, on the gneiss, or on the lowest beds of the 

 Ootatoor Group, and appears to belong exclusively to the earliest portion 

 of the Ootatoor period, during which the clays and argillaceous lime- 

 stone of the Ootatoor Group, abounding in the varied forms of Cretaceous 

 cephalopoda, indicate the existence of a moderately deep sea. In one 

 case indeed, that alluded to in the preceding pages of the limestone 

 at Cullygoody, there is no proof to be derived from stratigrajDhical 

 evidence, that the rock in question is not of posterior date to the 

 formation of the Ootatoor Group ; inasmuch as, while these beds are 

 locally absent, (or such of them as exist underlie the limestone,) those 

 of the Trichinopoly Group rest immediately upon it. This evidence 



