Chap. VIII.] arrialoor group — trichinopoly district. 139 



The shales and fine sands which underlie the sandstones above mentioned, are seen in a well 

 at Ambapuram, and in one or two shallow nullahs near the border of the alluvial plain. They 

 are quite unfossilifcrous. 



The highest beds of the fossiUferous zone described at page 135, pass in a N. N. W. direction 

 White sands of Reddipoi- P'^^*' ReddipoUiam, and a little to the North-east of Mauna- 

 liam, Pereya Nagaiore, &c. hudoor, whence they continue Northward to the East of Oota- 



coil. A short distance above (i. e. to the East of) these beds, some unconsolidated white sands 

 are seen in a small nullah North-east of ReddipoUiam, and again in a well at Pereya Nagalore, and 

 these are followed by a considerable thickness of green shaly clay, which is well exposed in 

 the broken ground at the head of the nullah to the East of the latter village. So far as any dip 

 can be observed in these beds, it appears to be at a very low angle to the North-east, but for 

 the most part they are almost horizontal. Still further East, in the broken ground South of Tha- 



„, , . . , loor, these clays pass again into white sands, in which are foiind 



Cliert concretions at Thaloor. ' ^ i. o > 



a few cherty concretions, 1 or 2 feet in diameter. These concre- 

 tions are far more numerous in some beds of argillaceous sand exposed in the small nullah that 

 crosses the WodiarpoUiam road 2 miles East of Thaloor. Some of them are as much as 4 feet 

 in diameter, the chert is grey and opaque, in some parts porous in structure, and enclosing soft 

 ferruginous nodules of concentric structure, which have evidently resisted the silicifying infil- 

 tration. These concretions appear to be characteristic of a particular zone. I have already 

 (page 138) described their occm-rence near Keelanuttom, 5 miles to the South, and Messi's. 



King and Eoote met with them, (containing recognizable fossils.) 

 At VuUam. '^ ' ^ & » V 



imbedded in the conglomeratic grits at Yullam fort, to the South 

 of the Cauvery. In this latter case they vrere probably derived from Arrialoor beds, denuded 

 during the formation of the grits, but if so, it is improbable, from their large size, that they 

 could have been transported from any great distance. 



For 3 or 4 miles to the North of Thaloor, the country is too thickly covered with regur 

 to allow of much rock being seen, the chief exception being that in the nullah that passes by 

 Keelymungalum some nodular calcareous shales are exposed, but containing no fossils. 



Passing on towards the watershed between the Vellaur and Coleroon rivers, a tolerably 



consecutive view of the beds, under consideration, is obtained in 

 ■White sands, &c., at Cullmoad. 



the various small nullahs at the head of the dramage system. 



These beds, here exposed, overlie the highly fossiliferous shales of Ootacoil, described at page 1 35. 

 The red clays, with casts of small fossils, which I have mentioned, (loc. cit.) as succeed- 

 ing the fossil band of Ootacoil, are Avell exposed in the West branch of the nullah which 

 passes Cullmoad, and in the East branch of the same nullah for about half a mile above the 

 village. At this point the nullah is crossed by the out-crop of a bed of sandstone, which 

 rests on the clay, and dips about 4° to the North-east ; and this is succeeded by a mass of 

 white sands and grey sandy clays, which are extensively exposed in the system of gullies 



above, which cut deejily into these soft beds. Imbedded in the 

 Megalosaurian remains. , •, i i i ^ ^ ^ i -xi i 



deposits, large bones are numerous, but so saturated with water 



and so very friable, that it is impossible, even with the greatest cai-e, to extract them in anything 



like a recognizable condition.* Fortunately for their determination I found a single tooth 



* The most perfect bone extracted has somewhat the form of a scapula, but is much splin- 

 tered. It measures 3 feet 3 inches in length, and 1 foot 6 inches across at its broadest cud. 



