80 Million

Different shots of the same thing. Trying to catch the winter light on the ridged and matt surface of this piece of a piece of fossilised shell I found down on the beach yesterday where a massive chalk rockfall is being gradually eroded by the sea into a solution of chalk and flint shingle.
 
The shell is part of an inoceramid bivalve that lived in the warm seas that created the chalk about 80 million years ago. These bivalves were the clams and mussels of their day and could be a metre across.

These huge shells were often colonised by oysters and are sometimes found with the remains of fossilised pearls attached.  There are some marks on the shell fragment I found to suggest something was attached to it.

A bit more about it on my blog.