No interactions present.
I've a similar, but without the grey stuff on the stalk, which was quite green further down, but not on Ispot yet as no photos of cup coral stalks to be found on the net to compare species, but mine was very hard as well.
Have just put on at http://www.ispot.org.uk/node/329120
I agree this is 'Devonshire cup coral' which I have seen in Devon, but I cannot remember if the column was grey. The smooth curved ridges of the calcareous skeleton differentiate it from Balanophyllia regia which is more porous spongy and brittle. I can convince myself that I can see, in close-up, that the tentacles just visible in the centre do end in a prominent knob.
It is reported as having an epizoic barnacle, Megatrema anglicum on the stalk, but I cannot see any here.
there's another devon c.c. with a similar grey 'crud' coating at aphotomarine (not tested by my McAfee but can see it in google images)
Andy can you add the Tag ProjectM1 if you'd like to see this in the Marine Project.
THREE MARINE PROJECTS
Lat/Lng: 57.60989, -7.15362
OS grid ref: NF923694