Chap. IX.] arrialoor group — verdachelltjm area. 149 



beds of the Cuddalore sandstones are un distinguishable lithologically from 

 those of the Arrialoor group. 



Between Yualakappam (Kordirakuppam of the map) and Palkollei, 

 a small nullah flowing down from the Eastward, exposes some of the 

 Cretaceous rocks consisting of shales with large calcareous concretions, 

 exhibiting sometimes the zig-zag structure, similar to those of the 

 Ootatoor and Trichinopoly groups previously described. They are quite 

 unfossiliferous ; at Yualakuppam a soft laminated sandy clay, equally 

 unfossiliferous, is seen in the debris of a well close to the little outlier of 

 Cuddalore beds on which the village is built. Cretaceous rocks of similar 

 character are also seen in the neighbourhoods of Isarikuppam and 

 Korilaveram, close to the overlap of the Cuddalore beds. 



Relations of Arrialoor heels of Verdachellum to those of Trichino- 

 poly. — It is somewhat difficult, owing to the general obscurity of the 

 Arrialoor beds in the Verdachellum area, to correlate them, with any 

 certainty, with those of the same group in Trichinopoly. The area, as a 

 whole, is characterized by the absence of fossils, and only at Pulliyur and 

 Yeramanur do we meet with any distinct representatives of the lower 

 fossiliferous zone. The fine sands with casts of fossils, which occur near 

 the boundary of the group at Killanur and Chendamungalum, remind us 

 of the similar beds in the upper part of the same zone near Coothoor 

 (page 136), and in the same way the unfossiliferous sands and clays which 

 appear to constitute the whole of the beds to the Eastward, may be the 

 continuation of the unfossiliferous zone in Trichinopoly ; as indeed the 

 strike of the bedding would indicate ; but if such be the case, tlie mineral 

 characters of the beds have become much changed in the interval, — the 

 deposits being finer and more argillaceous, and exhibiting less irregularity 

 in their mode of accumulation, than is the case with the white sands and 

 sandy shales of the Northern part of the Trichinopoly district. More- 

 over the deposits have greatly decreased in thickness, or at least the area 

 occupied by their out-crops has become much narrower, (owing to the 



