Walked down to Lower Largo today and noticed on the pier what I thought at first were clumps of tangled cord or part of a fishing net. Then I thought they were clumps of seaweed, which I thought had been washed on to the pier in the storm the previous night. On closer inspection, however, I found that the clumps were made up of the skeletons of dozens of these creatures.
They are brittle-stars. They differ from starfish in that they have an obvious circular central disc from which arise the five thin, very flexible arms which break easily, hence the name. They often occur in large number under stones lying on gravel and rough sand between large rocks. Perhaps the previous night's storm disturbed some rocks and hence these ended up stranded on the pier.
Update 13.11.08. I think I may have discovered why there were so many brittle-stars on the pier. There was a collection of lobster creels sitting there which also contained clumps of brittle-stars, so I think they must have been carried in with them.