Epiphysis

Isn't the tinterweb a wonderful place. Whilst checking out the Westray figurine I came across a photo of a strange object. One that I have in my collection of seashore finds. 

I thought it was the inside of a shell, perhaps the top of a anemone or even perhaps a piece of pot. 

No. This apparently is an epiphysis. Or the end part of a long bone, initially growing separately from the shaft. This must have belonged to a juvenile because it had not fused yet. 

I'm sure there are a couple of experts out there who could tell me what kind of animal it belonged to. A challenge for you Blipmates.