Hi Sumanta,

You must be knowing that it is very difficult to identify the fossils from their photographs, but the following are just hint and it needs very to verify them.

I am not sure, but the first photo shows affinity to fossil Arctica and the second one is very close to pycnodonte pulaskiensis.

With best wishes.

Thanks for your reply.

I can't understand what did you want to say about the first picture?

But the 2nd picture is not of pyconodont. Pyconodont is a kind of oyster. But this specimen is sure not an oyster. In this specimen ventral margin is smooth. In the external surface concentric ornamentation is clearly seen.

Did u collect this from nearby sea shore or inland area like rock hill....or....? 

These fossils are collected from the early Paleocene rocks of South India. The collection area is approximately 150km. away from the present day coastline.

Hello Sumanta

It is very difficult to say what species are because your photos do

Do you have photos with a better light and resolution.

it looks like Polymesoda sp.

Is the pallial sinus of your species clear? If yes, upload the picture so that I can say the name of estuarine, shore or freshwater mussel/clam?.

If possible put clear photos of  other side of the shell. 

Hi Sumanta, pls upload some high resolution pics of both sides of these fossils,

Thnks

I don't think it is possible to identify these bivalves with any certainty, if the internal features are unknown. The external shape of neither resembles that of Arctica or  Pycnodonte (or indeed any oyster). The upper specimen is in its shape similar to Polymesoda, but this shape is not unique. If correct, you would expect the environment to be brackish, or at least near-coastal marine with influx of lagoonal/ deltaic species. If at all possible, collect specimens showing the inside features..

The rock containing these fossils deposited in an estuarine environment. It is also evident from the presence of Physa (a freshwater gastropod) along with typical marine gastropods like Turritella.

This turreted, robust, strongly noded gastropod is also found to co-occur along with the above bivalves.

Please provide the dorsal /umbonal view of the bivalve to see the lunule and escutcheon as well as inflation. The color also is very unnatural. 

Dorsal and Lateral view of the same species.

The general shape and ornament look somewhat like a Callista in the Veneridae, but the picture of the hinge area is too dark and not zoomed in enough to tell any details. The interior characters are the most important.  Is the original shell structure completely gone, or is it possible to carefully open the shell up to indicate interior features?  

We found a remarkable similar gastropod near Rajahmundry

May be Katelysia opima (Gmelin, 1791)