Inside and out

This is two views of the same ammonite. It has been sliced through the middle, then the cut surface was polished. It shows the beautiful chambered shell – notice the long body chamber which takes up the last half of the outer whorl. Part of that chamber is filled with mud washed in from the open end, and part is filled with calcite crystal. The chambered shell is filled with crystal only, giving the creamy, red and brown colours.

On the outside, most of the shell itself has come away, exposing the chamber walls (the darker section). Look closely and you can see the wavy patterns – these are suture lines where the chamber walls met the shell and folded like a curtain. Towards the centre, the shell remains in place and that obscures the suture lines. 

Find out more about ammonites on the molluscs pages.

Common name


Scientific name



Molluscs > Cephalopods


Lower Lias

Time period

Lower Jurassic


195 million years

Where found

Lyme Regis

Found by



Dorset County Museum, Dorchester

Accession number