The Fenestella sensu lato on the left has barbed spines which were probably used as grappling hooks to stabilise the colony. A really nice example. The pinnate colony is Ptylopora. Could they be Carboniferous?

La Barde dawn last Friday for comparison.

There are meshes too but not attached to the screws do they might be other genera of Fenestrata.

Any chance that this is a microconchid rather than a baby nautiloid? It would be interesting if this were so as microconchids are rare in the Jurassic.

Any chance of this being a microconchid rather than a baby nautiloid? It would be an interesting find if so.

I think it was taken from the foreshore beneath the cliffs south of Whitby harbour.

I think your fossil is more likely to be an ammonite than a nautiloid, and my guess is that it is Jurassic in age.