Rubbery spongelike creatures washed in from Irish Sea
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If this is a sponge, it should have a noticeable aperture (the osculum). Did you see this? Other possibilities could be an egg mass or even something non-biological like boat sealant. Also, do you have an approximate measurement?
I'm fairly certain it's not boat foam - I'm a sailor and very familiar with the stuff. They were a bit rubbery and I am uploading another photo (not very good) which shows what might be aperatures. There were hundreds of the things on the beach.
Size would be about an inch, or inch and a half (about 20-25 mm in Christian measurements!).
Popped down to the local beach and found a single remaining specimen which I will again photograph as well as doing a bit of dissection to view the internal structure.
One sure thing is they appear to be four lobed and there's a sort of fishy smell. However an osculum(s)is/are not very evident although it may be closed up for some reason.
Will upload better photo this evening as well as report of dissection.
Ta for the updates - good to rule out boat foam! It'll be intersting to see what the dissection brings - in the meantime, I'll have a think...
I looked them up as Dead Man's Fingers and it certainly fits the description. I've posted new photos taken tonight which show relative size compared to my fingers. You can also see the porou nature of the surface, each pore presumably leading to the home of separate polyp. DIssected they show a sort of fibrous structure with the pores leading toward the surface of the finger tips.
Wonder why we got such a large mass stranding. Looked it up on the atlas mentioned above and there appears to be only a single "square" off the Skerries coast so perhaps it was unlucky to get hit by some vigorous trawling activity?
With the scale and new photos, I agree with you - regarding distribution, they are found all round the British coast so could have been washed from further afield. Ta for the revisions!
Lat/Lng: 53.6, -5.9
OS grid ref: SB4619