1840.] Observations on the Fossiliferous heds near Pondicherry. 89 



it presents, as has been already stated, an undulating wavy surface, and 

 the stone is found immediately below the turf, and sometimes even ap- 

 pears above it : it is quite hard, and is quarried in large blocks, though 

 to no great depth, for the purposes before mentioned. It is almost every 

 where replete M'ith shells or other organic remain?, which are in general 

 so firmly imbedded in the hard stone that it is impossible to detach 

 theip. -^'the geologist, therefore, who would study with accuracy the nature 

 of this deposit, should endeavour to reside for some period on the spot, 

 many of the shells which are most perfect in the stone, not having yet 

 been discovered in a separate state. In one situation, however, there 

 are several small mounds of a whitish limestone, almost resembling 

 chalk, v/Lere the surface having been abraded and decomposed by v/a- 

 ter, ti.e shells which it contained have been separated, and lie scattered 

 on the surface of the soil, among the debris of the containing rock : it 

 was in this spot that most of the specimens here noticed were col- 

 lected, I will now proceed to describe thetn in the order in which they 

 appear in the Plates. 



PL I. Nos. 1 and 2 — Osfrea carinata — The identity of this shell v/ith 

 that figured by Lyeli and other authors among the fossils of the Eu- 

 ropean chalk cannot be doubted : they are very numerous at Secdra- 

 pett, and are found both in a separate state an.d imbedded in the rock, 

 sometimes very perfect. No. 1 is slightly fractured at the point, but the 

 linear marking, and even the sharp angles of the ribbing on the sides, 

 are beautifully preserved, and the inner surface retains much of its 

 polished enamel. No. 2 is a perfect specimen of the two valves adhering 

 firmly together. 



Nos. 3 and -1 are BacuUtes. This shell is called by Dr. Buckland a 

 straight ammonite, and the same authority states that it is " found in the 

 cretaceous formation alone." We collected many fragments of this shell on 

 the surface of the soil, varying from three inches to half an inch in length : 

 the most perfect specimen being imbedded in a rolled piece of limestone 

 (No. 3), and owing to a longitudinal fracture displaying four of its 

 chambers. All the specimens display the foliated markings at the junc- 

 tion of the v/alls of the chamber with the external shell : they are of a 

 yellowish or reddish brown colour, and the interior is generally filled with 

 beautifully crystallized calcareous spar. No. 5 is the transverse section 

 of a baculite. 



Nos. 6, 7, 8 are bivalve shells, probably referrible to the genus Cardi- 

 um ; they are represented about the natural size ; G and 7 retain the shell 

 itself and appear almost recent, but the interior of No. 7 is filled with 



