Beautiful symmetry

We went to the Liverpool World Museum today and in the aquarium section, are lots of beautiful fish. On the side was a cabinet with these shells in it that nobody looked at. Most people more fascinated by the moving, colourful fish.

A small child pointed at them and asked "What are these?" and the mother said "Oh, they are just shells." and they hurried past them.

I think it's worth just taking a closer look...