Unknown Crustacean

This weeks blips will be a bit autobiographical. The lump of rock in this blip was found on a beach in Dorset. Anorakky fossil hunter that I am it was with some irritation that I saw my ( at the time) 10 year old pick this out from a lump of mud.
If you look closely you can see it looks a bit like a piece of prawn.
We sent it to The Natural History Museum in response to a photo we emailed them. After some weeks it was returned with the label ' unknown crustacean'