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



otlier hand, Opis, a genus not met with in the Ootatoor Group, is essea- 

 tially Mesozoic, and the Cretaceous /acies is fully borne out by the abund- 

 ance of Rostellaria, and the recurrence of Pleurotomaria, Acteonella, 

 Inoceramus and Trigonia, in smaller numbers. Among the Brachio- 

 poda, Terebratula and Rhynchonella are still the only genera, and I have 

 only noticed one species of each, but these, in the one or two localities 

 where they occur, are in vast numbers, offering a great contrast to the 

 heterogeneous assemblage of species which characterizes most of the beds. 

 The fossil flora of the Trichinopoly beds is, like that of the associated 



groups, remarkable for the preponderance, if not 



Fossil flora. . 



the almost exclusive occurrence of exogenous or 

 cycadeous forms, as indicated by the wood which is abundant in the lower 

 beds of the group, and is met with in drifted logs of many feet in length. 

 I have not noticed a single undoubted specimen of endogenous wood 

 among the numerous specimens noticed in the field. 



Details of the Geological Structure. 



In desciibing the Ootatoor beds in the preceding pages, I have frequently alluded to 

 the outliers of Trichinopoly beds which range along the South- 

 ern faulted boundary of the Ootatoor group, between Tripatoor 

 and Paroovalapoor. These beds consist for the most part of coarse unfossiliferous sands and 

 con"-lomerates, with large included boulders of gneiss, aU evidencing shallow water, and breaker 

 action, as the conditions of their accumulation. They cover the extremity of the Ootatoor beds 

 to within a few yards of the coral-reef limestone of Tripatoor, and the bottom bed on their 

 Northern out-crop is a coarse conglomerate full of blocks of the limestone, and of the cream- 

 colored concretionary clay nodules of the Ootatoor beds. A good section of these beds is seen 

 in a small nullah that crosses their strike obliquely near the Western extremity, exposing thick 

 beds of sands, Avith psbble-beds, and thin partings of fine silt without fossils. The ridge 

 between the Tripatoor and Seraganoor nullahs is covered with blocks of conglomerate belong- 

 ing to these beds, and in a small nullah to the North-west of Seraganoor their base is exposed, 

 resting on the gneiss at an angle of 25°, In the bed of the large nullah close by some 

 large boulders of the local gneiss (a schistose homblendic rock) are seen imbedded in this 

 conglomerate with fragments of the Ootatoor beds. One of these boulders, which I mea- 

 siu'ed, was not less than 1 2 feet in length. 



Again in a little nullah half a mile North of Seraganoor, that mentioned at page 79, a pebble 



FossUif.rous conglomerate Conglomerate of the Trichinopoly beds is seen resting on the 



North of Seraganoor. vertical sUt of the Ootatoors, and the ground beyond for about 



half a mile to the North is covered with blocks of calcareous grit and conglomerate, containing a 



