Chap. VII.] trichinopoly ursTRicx — trichinopoly group. 115 



The bottom beds along the Eastern out-crop of the group are chiefly limestones and shales, 

 Character of Eastern out- ^^^ rest on the coral-reef ridges lapping round their extremities, 

 "•°P' and dipping away from them at angles of 20° and 30", but this 



high dip only obtains in the bottom beds, and rarely extends more than a tew yards. They are 

 rai-ely fossiliferous, but a few characteristic species are met with. Near the patch of coral- 

 limestone, a mile to the South-east of Veraicoopay, I found some Acteonellas, apparently of the 

 same species as those of the Ootatoor beds at Kolokaimuttom, but associated with Chemnitzia 

 undosa, and other characteristic Trichinopoly forms. This was the only spot at which I met 

 with this genus in the Trichinopoly group. 

 ' Just North of this spot and on the boundary of the group is a great accumulation of shingle 



and small boulders, apparently the remains of some ancient beach. 

 Shingle deposit. 



I could not determine satisfactorily that it dippsd beneath or 



passed into the gypseous shales, which represent the Trichinopoly group to the West of it, but 



to the North it appeared to pass into some white and ferruginous sands, which in some places, 



and notably to the South-west of Malarasure, rest with local unconformity on these gypseous 



shales. 



We are here upon the confines of the Arrialoor group, and were it not that throughout this 



area the irregularities of the bedding are such, that no local 

 Beds of doubtful age. 



unconformities, such as the above, can be treated as of any import- 

 ance, I shoiild be strongly disposed to regard the beach and the associated sands as marking the 

 base of this groxrp, the more so that near Malarasure the sands spread out and overlap the 

 gypseous shales and pass Northward, with many irregularities, into beds which, at Skutambaudy 

 and Kannanore, contain characteristic Arrialoor fossils. But, on the other hand, similar sands, 

 chiefly of granitic origin, are common in the Trichinopoly beds around, and wherever such 

 occur, they almost invariably present a local unconformity. 



All attempts to fix a stratigraphical boundary between the sands in question and the mass of 

 Obscurity of boundary be- ^^^ Trichinopoly group failed, and such fossUs as I met with 



tween Trichinopoly andAn-ia- between Moulvoy and Malarasure were of species common to the 

 loor groups. "^ '- 



two groups, so that the precise limit of the Arrialoor group in this 



neighboiu-hood, and the age of the beach deposit, still remain somewhat doubtful. I may 



here mention, that further North, where the Arrialoor boundary is clear and distinct, it is 



marked o.ily by the first appearance of its peculiar fossils, or at most by a slight chano-e in 



the mineral character of the beds. Local unconformity of bedding is nowhere met with at 



its base, except perhaps at Veragkoor, though the fact of its overlapping the Trichinopoly beds 



at both extremities of the district, taken in connection with the Palseontological evidence, 



sufficiently proves its unconformity on the large scale and its distinctness as a group. 



Crossing the narrow strip of plant-beds already described, the Trichinopoly beds consist of 



ii'regular alternations of shales with granitic sands, and occasion- 

 Beds South of Moulvoy. -,, . , i , -n , •, 



ally with conglomerate, the Jiastward dip greatly predominatin"-. 



Fossils, including most of the characteristic species of the group, are met "with at a few 

 localities, and these are chiefly Gasteropoda and Bivalves. Ammonites here first appeal-, but 

 are extremely rare. 



Returning for a moment to the Western out-crop of the group between Paroovalapoor 



Beds of Western out-crop. ^^^ Alundanapuram, we meet with similar irregularities to 



North of Paroovalapoor. ^j^^^g akeady described. A fine mass of shingle, chiefly granitic 



in its materials, and including many pebbles 5 or 6 inches in diameter, occurs at the base 



