Chap. V.] trichinopoly district — ootatoor group. 5^ 



corals, similar to those at Maravattoor, testify to the former existence of 

 ft reef somewhere in the vicinity. 



Between Poothoor and Purawoy I met with two instances of the coral- 

 reef limestone, in the one case (that nearest to 

 Poothoor and Puvawoy. 



Poothoor,) restmg on gneiss, and exhibiting the 



characteristic streaks of the now embedded and once encrusting corals. 

 This patch is about 25 yards across, and not more than a few feet in 

 thickness. The other patch occurs at the Southern end of the bund of 

 a small tank, half a mile South of Purawoy, and is still smaller in extent. 

 Close by some blocks of conglomerate in the Ootatoor beds contain large 

 eub-angular fragments of the limestone, some of them upwards of a foot 

 in diameter, and containing the characteristic coral streaks. They are- 

 sandy in structure, similar to the limestone at Maravattoor. Several small 



masses of a similar arenaceous limestone occur ta 

 Bosses at Olapaudy. 



the North of Olapaudy, at the foot of the limestone 



ridge formed by the lower beds of the Ootatoor Group, but no one of them 



is more than a few feet in diameter, and they do not contain any corals. 



All the coral-reef limestone ridges hitherto described, occur unques- 

 tionably at the base of the Ootatoor Group, either resting on gneiss, or 

 on the plant-beds, or, possibly in one or two cases, on some of the first- 

 formed deposits of the Ootatoor Group. We have now to consider soma 

 other cases in which the age of the limestone, so far as can be judged 

 from mere stratigraphic evidence, is open to some doubt, but which, as 

 there is no positive evidence to prove a different epoch of formation, 



I ta f d iibtful ^^^ which, as in all essential characters the lime- 



ys®- stones resemble those above described, I therefore 



consider in this place. 



The first of which I have to speak, is one to which I have already 

 briefly alluded, and which is illustrated in the 



Boss at Maddam. 



wood-cut (page 54). It will be seen on refer- 

 ence to the map, that along the Southern boundary of the strip of 



