Fossiliferous beds near Pondicherry. 229 



No. 11. Several casts of a slightly curved chambered shell, with 

 annular markings, probably referrible to the order of Hamite were found. 

 The drawing represents the chamber as seen in the section ; but the ra- 

 diated marking is probably owing to crystallization. 



No. 12 is a cast in limestone of a bivalve shell. 



It is no easy thing to name fossils, even to those who are most accus- 

 tomed to geological researches, this department forming in general a 

 separate branch of the science. Many of the fossils, however, described 

 in the above lines are of so marked a character, that in those instances 

 where we have ventured to name them with any degree of certainty, we 

 can hardly have been mistaken. I have not neglected either to consult 

 those who were best able to give an opinion on the subject, and have 

 also carefully compared the specimens with the best drawings and au- 

 thorities I could meet with. To Mr. Frederick Burr, I am particularly 

 indebted for the valuable assistance and information he has afforded 

 me. If we do not err therefore very widely from the mark, we have, 

 even on the information already obtained, very good prima facie evi- 

 dence that the Pondicherry beds are the equivalents of the upper 

 secondary formations of Europe, and the fossils point especially to 

 those of the chalk and green sand. 



It is a well known fact, that during the formation of the cretaceous 

 beds in England, a great quantity of silex held in solution by water 

 must have been poured out ; which, by the process of chemical affinity 

 having collected around various organic nuclei such as corals, sponges, 

 and other zoophytes, has formed continuous and extensive layers of 

 flint, interstratified with chalk, almost every nodule of which contains 

 and derives its shape from the enclosed remains of some organized body 

 in a state of complete petrifaction. We observed no vestige of flints in 

 the limestone at Seedrapett, and all the fossils collected there consist of 

 carbonate of lime, and effervesce freely with acid ; but the vast quantity 

 of silicified wood in the neighbouring formation of red sand, seems to 

 point to some phenomenon similar to what must have existed during the 

 deposition of the cretaceous beds of Europe.* 



Lieut. Newbold, in the last number of the Journal, suggested that the 

 fossiliferous beds of Pondicherry probably extended into the Terdaehel- 

 lum talook of South Arcot. I have made inquiries, but have not yet 



* " Flints so commonly enclose the remains of sponges, alcyonia, and other zoophytes, 

 that some geologists are of opinion that the nucleus of every nodule was originally an organic 

 body : that this has been the case in most instances is very evident : and in Sussex 

 there are but few flints that do not possess traces of zoophytical organization." — Mantell's Geo- 

 logy of Sussex, 144. 



