Chap. TII.] trichinopoly district — trichinopoly group. 113 



few corals and some of the characteristic Trichinopoly fossils. I also noticed a few small 

 bones in one block, but the matrix was too tough to permit of my detaching the specimen, 

 which, moreover, was not sufficiently well preserved to render it likely that its character 

 could be satisfactorily determined. The Northern out-crop of this outlier is seen in another 

 small nullah, wiere the bottom bed consists of fine silts resting on the highly inclined Ootatoor 

 beds. 



A quarter of a mile to the East of the Madras road, a fossiliferous conglomerate similar to 

 Fossiliferous conglomerate ^^^ above is again met with, resting on the fossiHferous shales of 

 atMuddam. Muddam, described at page 61. In this conglomerate I found 



several of the most characteristic species of the Garoodamungalum limestone, Strombusco ntortus, 

 Sowerby, Chemnitzia tmdosa, Sow. sp., Gardium Hillanum, Sow., and some others. This con- 

 glomerate is very limited in extent, and the mass of the outlier, of which it is the termination, 

 consists of coarse sand and gravel, containing pebbles of quartz, granite, and gneiss, and some 

 boulders of the latter rock, several feet in diameter. The beds, notwithstanding an occasional 



appearance of dipping, must be nearly horizontal, and deposited on 

 IiTegularity of bottom. 



an uneven bottom, as I noticed gneiss to all appearance in situ 



protruding in the midst of them, upwards of a hundred yards from their boundaiy. This 



outlier is not more than three-quarters of a mile in length, and an interval of about the same 



distance separates it from the next, which commences a quarter of a mile to the "West of the 



Outliers between Muddam Naicolum nullah, and extends down to its bank, as indicated by 

 and Paroovaiapoor. ^.j^g blocks of conglomerate that protrude above the soil. No sec- 



tions are seen, and no distinct bedding, and it is probable that the deposit is quite superficial. 

 In the nullah, which is broad and shallow, nothing but Ootatoor beds are exposed. A few 

 yards above the opposite bank the characteristic gravel and conglomerate of the Trichi- 

 nopoly beds re-appear and cover the ridge that separates the Naicolum nullah from -that of 

 Paroovaiapoor. At their Northern extremity, on the Eastern slope of this ridge, a thick 

 band of conglomeratic blue limestone forms the bottom bed, and is seen resting on the Ootatoor 

 shales, in which, about a hundred yards to the Eastward, a limestone exactly resembling the 

 above is intercalated. Both limestones contain a few fossils, Dentalium, Natiea, Sec, but the 

 only species which I recognized as characteristic, was Chemnitzia undosa in the Trichinopoly 

 bed. Between this point and Paroovaiapoor there is much difficulty in separating the two 

 groups. 



Fine laminated silts, closely resembling those of the Ootatoor beds, become largely iaterca- 



Deceptive dip of beda N. W. lated in the Trichinopoly beds, replacing the sands and gravels ; 

 Paroovaiapooi. ^^^ ^^^ apparent dip of the beds, wherever seen, is so nearly the 



same in both cases, viz., at a low angle to the Northward, that I was long puzzled how to 

 reconcile these appearances with the known facts of supei-position elsewhere. 



It appeared, however, finally, that the inclination of the Trichinopoly beds to the Noi-thward, 



although very regular at an angle of from 10* to 3", (the angle 

 Explanation. 



diminishing Northward,) is due to original deposition, and con- 

 tinues very nearly up to their Northern boundary, where the Ootatoor beds have almost the 

 same dip. The Trichinopoly beds, for about half a mile from theii' Southern boimdary, are 

 sufficiently characteristic, although unfossiliferous, being pale grey sands, with large calcareous 

 concretions, and sometimes conglomerates containing clay-nodules from the Ootatoor beds. 

 Beyond this they assume the form of fine sandy silts, and these continue up to the point where, 

 in a little nullah, I found them resting on the Ootatoor beds, which exactly resembled them 



P 



