146 CRETACEOUS ROCKS OF S. INDIA. [PaRT II, § 2. 



coarse arenaceous limestone, with thin irregular 'partings of a dark clay, 

 are seen in the bank of the nullah, and cropping out on the surface of 

 the ground above. The bottom bed contains a few gneiss pebbles, and 

 immediately on it rests a band of calcareous grit, in which a Trigonia, 

 T. semiculta, and one or two large species of Spondylus and Pecten 

 5-costatus occur in considerable numbers. Resting on this is a bed of 

 similar mineral composition, the fossils of which consist almost exclusively 

 of two species of Pecten (P. quinquecostatus and P. Verdachellensis) 

 both in great abundance. A few other species are associated ; but on the 

 whole the locality is an unproductive one. The fossils are either species 

 peculiar to the locality, (as P. Verdachellensis, which, although so abund- 

 ant at this place, has not been met with elsewhere,) or they are such as 

 are common to the Arrialoor beds of Trichinopoly and Pondicherry. Among 

 the species noted as from Verdachellum in Professor E. For bes's Mono- 

 graph and also in Mr. Kaye's Collection in the Madras Museum, there are 

 many species which belong exclusively and characteristically to beds of 

 . the Trichinopoly group, of which I have found no trace in the neighbour- 

 hood of Verdachellum. If therefore the reference of these forms to 

 Verdachellum be not erroneous, and due to their accidental admixture in 

 Mr. Kaye's collection, there must be some small outlier of the Trichino- 

 poly beds which I have not succeeded in discovering ; but this I think 

 highly improbable. The matrix in which these fossils are imbedded is 

 quite different from that of the Arrialoor beds of Pulliyur, and resembles 

 the Garoodamungalum limestone, a form of rock frequently occurring, as 

 at Garoodamungalum, at the base of the Trichinopoly group. 



From the Pulliyur nullah, the out-crop of the limestone is very distinct 

 Bottom bed near Pulli- ^OT about half a mile to the North ; it then passes 

 y^^- in the thick red soil jungle to the East of Pulliyur, 



the thorny Acacias of which render any attempt to trace it a matter of 

 no small labor; besides which the thick accumulation of red sand entire- 

 ly conceals it, except at one or two spots, where the ground is broken by 



