Shell for ID

[goosey]

If this hadn't been upturned when I found it I would have just thought it was a stone. Probably the reason I have never seen a shell like this before.
It is 4cm x 3cm, and is very textured. The bit on the end which is 'bald' is striated and smooth and there is no ridge from one bit to the other. It has quite a weight to it.

1. 2.

[goosey]

On a later visit I have found another shell which I think is possibly the same type. I reckon that the textured surface you see in images 3 + 4 has been eroded away to an extent resulting in what you see in image 1 + 2.
On the underside of image 4. you can see a bare patch a bit like the one in image.1

Now I am thinking that this is some sort of life form that has covered the shell the way baracles and limpets do and not a shell in it's natural form? (does this make sense )

3. 4.

[goosey]

It's strange the answer's you find when you aren't looking at all. I have found the ID for these, they are Snail furs - Hydractinia echinata