Chap. VIII.] trichinopoly district — arrialoor group. 125 



the group, as far North as Moulvoy, although shells of the genus are tolera- 

 bly abundant in the neighbourhood of Garoodamungalum and Annapaudy, 

 where the beds become more regular. In the limestone at the base of 

 the group, the fossils are very numerous, as a rule, and very various, 

 numbers of different species being mixed indiscriminately in the rock. 

 In the higher beds this is less frequently the case, and the fossiliferous 

 bands are usually characterized by the exclusive occurrence or the pre- 

 dominance of some one or two species, especially Spondylus and Trigonia. 

 As regards the age of the Trichinopoly Group, little more can be said 

 AgeofTricMnopoly ^^^^ *^^* ^* ^^ considerably newer than the Oota- 

 ^™^^" toor Group, and is decidedly Upper Cretaceous.* 



So far as the fossils have been examined, they tend to confirm Professor 

 E. Forbes's opinion, that it is about of the age of the Upper Greensand, 

 and its relations to the Arrialoor group, (the fauna of which reminds one 

 in many respects of that of the White Chalk,) also support this view : 

 but until the whole fauna has been examined, it would be premature to 

 offer any decided opinion on this matter. 



Chapter VIII. — Arrialoor Group, in Trichinopoly District 



The extent of the Arrialoor group in Trichinopoly alone considerably 

 exceeds that of both the groups previously treated 



Extent of Group. i ti i • 11 



01 ; and unlike them it extends beyond the limits 

 of the district, and occupies a large area to the North of the Vellaur, which 

 will be described in a succeeding chapter. In Trichinopoly it occupies a 

 broad strip of country in the Arrialoor and "Wodiarpolliam sub-divisions, 

 extending from the banks of the Vellaur nearly to those of the Coleroon 



* In the foregoing pages, where the terms Upper and Lower Cretaceous ai-e used 

 I draw the line of separation at the base of the Gault of Europe. By Middle Cretaceous 

 I do not intend to refer to any distinct sub-diTision, but only to position in the Cretaceous series. 



