GRITTY SANDSTONES. 41 



exposed in the wells are coarse, mottled reddish-yellow and white^ 

 in generally horizontal beds. Not the slightest trace of any organism 

 could be detected. 



The next outcrop of the gritty sandstones requiring notice is one 

 to be seen 8 miles further to the north-west-by- 

 north, at the junction of the Nambi-Ar or Tiruk- 

 urungudi river with the nalah rising in the Anaikulam tank. The grit is 

 mottled and much false bedded, and petrologically, as well as in the absence 

 of all traces of fossils, greatly resembles the Nagarkoil beds in Travancore. 

 Only a small exposure of this grit is seen resting on the very uneven 

 surface of the gneiss, but it probably extends a considerable distance 

 under the wide alluvial spread east of the Nambi-Ar. It is overlaid by a 

 highly kankarized, and therefore much altered, pebbly sandstone, of 

 probably alluvial origin. 



About a mile to the north-east of this, and about half a mile west of 



the hamlet called Thopevella in the map, is a considerable show of 



typical whitish grits very like those seen at Nagarkoil, and described 



in my paper on the geology of South Travancore (Records G. S. I. 



Vol. XVI 1883, page 38) . These grits are overlaid by a bed of sandy clay 



full of sub-fossil shells of recent species of Ostrea, Area, Cytherea, &c. 



The section is small and not very satisfactory, 

 Yellava Odai section. 



but at one place a band of the clayey sand is 



distinctly included in the gritty sandstone and appears positively to 

 settle its age. The clayey band encloses many specimens of Area 

 granom and of a Cytherea (? castanea). Unfortunately, petrological 

 identity excepted, there is no evidence that the gritty sandstone is posi- 

 tively a representative of the Cuddalore series, else the question of the. age 

 of the Cuddalore beds might be taken as settled for good and all. As it 

 is, further evidence will be necessary before this point can be regarded as 

 definitely settled. If the Cuddalore grits are really of marine origin, 

 and from their geographical position this seems highly probable, it is 

 certainly strange that they have been found to be unfossiliferous over 

 such extensive areas. 



( 41 ) 



