Fossiliferous beds near Pondicherry. 227 



There is a gradual descent from Trivacary towards Seedrapett, and the 

 limestone commences immediately on the boundaries of the red soil : 

 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 purpose before mentioned. It is almost every 

 where replete with shells or other organic remains, which are in general 

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

 them : the geologist, therefore, who would study with accuracy the na- 

 ture 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 

 ehalk, where the surface having been abraded and decomposed by wa- 

 ter, the 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 them in the order in which they 

 appear in the Plates.* 



PI. I. Nos. 1 and 2.* — Ostrea carinata — The identity of this shell with 

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

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

 pett, and are found both in a separate state and 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 4 are Baculites. The 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 

 junction of the walls 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 trans- 

 verse section of a baculite. 



* These references are made to the Madras Journal o/ Literature and Science, No. 28, 

 September, 1840, from which this part of the paper is extracted. 



