138 CRETACEOUS ROCKS OF S. IKDIA. [PaRT II. § 1. 



together -with some fragmentary remains of Crustacea, some Shark's teeth, and fossil wood. 

 As is usually the case in the Arrialoor group, the fossils are veiy beautifully preserved, the 

 shells of the Nautili and Ammonites remaining perfect, while, the matrix being soft, they are 

 easily extracted without injury. 



On the summit of the ridge to the North of this place a small nullah that nins down to Vyla- 

 Northern tennination of Vaudj exposes a good deal of the shales near the base of the group 

 lower zone. with their included calcareous concretions. Here also many of 



the fossils above enumerated are to be found with but little search. These beds may 

 be followed down the mtllah to Vylapaudy, where they finally disappear beneath the 

 alluvium. 



Having thus described the whole of the lower fossiliferous zone of the Arrialoor group, we 



Middle 01- unfossiUferous ^^^^ return to the Southern extremity of its out-crop, and follow 

 ^°"°- up, in a similar manner, the broad band of neai-ly unfossiliferous 



sands which succeeds, and separates the former beds from the interesting fossil zone of Sain- 

 thoray and Ninnyoor. 



I have already ( page 134.) mentioned that to the North of theMurdayaur allmium or rather 



of the thick regur deposit occupving the hollow through which that 

 Beds East of Murdayaur. ■, ■, f\~i , . ■, ■, ^ 



stream flows, a narrow band ot Cretaceous rocks is exposed between 



the regur and the Cuddalore sandstones. There is some difficulty at this point in distinguish- 

 ing the two formations, inasmuch as theii' lithological characters are for the most part very simi- 

 lar, and no fossils are found in either group which might aid in determining the relative age of 

 the beds. From near the banks of the Coleroon to Kondamungalum, beds of coarse grit, strong- 

 Grit escarpmeut-Kondamuu- ly stained with iron, (a form of rock highly characteristic of the 

 eaium. lower beds of the Cuddalore sandstones,) fonn a small bluff, 



(evidently an old marine escarpment,) along the margin of the alluvial plain. At Kondamunga- 

 lum it turns off to the Northward, becoming much less abrupt as it retreats and finally merging 

 into a gentle slope, which still preserves, however, something of the character of an in-egular 

 coast line, and follows for 4 miles in a North-west direction, the summit of the ridge which 

 separates the Murdayaur from a small parallel nullah farther to the North. On the 

 Southern or Murdayairr-ward slope of the ridge, the Cretaceous rocks are frequent!}^ exposed, the 



upper beds being chiefly white or tinted shah' sandstones, with 

 Cliaracter of Cretaceous beds. 



large concretions of chert ; the lower beds, fine sands or soft shale 



similar to those of the fossiliferous band below. The former beds are well seen in the upper part of 



tlie \-alley, the di-ainage of which feeds theKeelanirttom tank. In some places thej'' are very coarse 



in texture, consisting of a grit more or less stained with ferruginous infiltrations from above, 



and they are then quite undistinguishable from the grits of the Cuddalore group. Indeed I 



Resemblance to Cuddalore should strongly doubt whether these beds be really Cretaceous 



sandstoues. rocks were it not for their resemblance to beds of less doubtful 



position (and in the general direction of their strike) farther North, and also that they are 



sometimes intercalated with the soft ochreous shales, so characteristic of the Cretaceous 



ormation generally in the Trichinopoly district. As it is, I have not been able satisfactorily to 



determine the lunits of the two groups in this neighbourhood, owing to the high ground being 



evenly covered with red soil, and the line given in the map can only be taken as the best 



approximation to the truth that my local knowledge of the beds, and the data of the locality 



would admit of my making. 



