Chap. V.] trichinopoly district — ootatoor group. 53 



however, in favor of the latter view is merely negative, and is, I 

 think, overborne by other considerations which will appear in the 

 course of description. To this I now proceed, commencing with the 

 limestone at the Western extremity of the Cretaceous rocks. 



About a mile to the South of Tripatoor, and to the East of the 

 shallow nullah that flows down from that village, 



At Tripatoor. i t i • i 



a broad rocky ridge, rising several leet above the 



level of the surrounding land, marks the boundary of the Cretaceous 



rocks. The rock, of which this ridge is composed, differs strikingly 



both in structure and external appearance, from the ordinary sedimentary 



rocks of the district : it is a compact splintery limestone of a pale pink, 



^, ^ e ^■ or a cream color, sonorous and brittle under the 



Character of Irnie- ' 



^'°^®- hammer, and breaking with a more or less con- 



choidal fracture with equal facility in any direction. In general it exhi- 

 bits no distinct bedding, but occasionally a thick slab-like structure is 

 perceptible over a limited area. Small irregular cavities sometimes occur 

 in it, which are partially or wholly filled -with crystallized calc-spar. Ex- 

 ternally the rock is much eroded, and often deeply 

 Weathered sm-faces. 



honeycombed by the action of the atmosphere ; it 



is sometimes pale, sometimes black on the surface, and rarely exhibits 

 to the naked eye any trace of organic structure. In some places it con- 

 tains a few small bivalves and corals, and occa- 

 Fossil contents. • n 



sionally a coarsely-ribbed pecten of a species pecu- 

 liar to this rock. In other parts, and especially towards the base, it 

 exhibits a mass of irregular white streaks from a few lines to two or 

 three inches in thickness, preserving an irregular parallelism to each 

 other, and never intersectiug. No organic structure is perceptible in 

 these streaks to the naked eye, and the rock shows no tendency to break 



along them ii^ preference to any other direction. 

 Corals. 



but an occasional weathered surface shows that 



they are corals of various species of Astrcea, seen in section, evidently 



