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I'm not convinced at all by the "frog". This seems to be the same as http://www.ispot.org.uk/node/233962?nav=latest_obs_thumbnail_grid I still think the most likely is some type of slime mold http://www.google.co.uk/search?q=slime+mold&hl=en&safe=off&prmd=imvns&tb... or http://herbarium.usu.edu/fungi/FunFacts/slimemold.htm
This appears every year in the press. Theories are numerous and arguments go back and forth ad-infinitum. I am personally of the opinion that it is the predated remains of a frog as I have found this on numerous occasions next to more easily identifiable frog remians (skin, legs etc.) and have also found it in early spring with the black eggs either within the jelly or next to the jelly. An easy way of ruling out a slime mold is to go back a few days after you first observe it. A slime mold will 'go over' and start to turn to dust. Frog spawn will not do this but will gradually decompose or dessicate. A Google search for 'star jelly' will bring up various pages of stories and theories about this stuff. I'm yet to be convinced by any other than the frog spawn theory - which as I say - is based on personal experience.
I started a discusion about this on UK Climbing http://www.ukclimbing.com/forums/t.php?t=484727&v=1#x6659268 there is certainly support there for the "remains of frogs" suggestion, but I'm more convinced by "nostic a cyanobacteria", see also http://www.worldwidewords.org/weirdwords/ww-nos1.htm
The debate is certainly interesting. Its made all the more interesting by the fact that there does not seem to be any scientific consensus either way! I suppose that the issue is complicated by the fact that there may well be more than a single explanation / origin of slime-like deposits such as this. It is entirely possible that all theories are correct!
Just had a look at the discussion you started on UK Climbing. To my mind the fact its been found on a stile and a bare rock, and in association with frog remains, only firms up the frog theory (although please note I'm still accepting this is just a theory!). I'm by no means a slime mold or cyanobacteria expert, but I would expect these organisms to grow out of the substrate, which might not be likely in the case of the slime found on a rock. Having said that, I have previously posted a picture on Ispot of cyanobacteria I found free floating in a river - so not apparently growing out of anything. I'm going to dig through an old hard drive and find pics of the examples I have previously found which have led me to the frog conclusion.. I'll post a link when I get round to it!
Lat/Lng: 53.12487, -4.05182
OS grid ref: SH627606
Grassy ridge between Y Garn and Foel Goch (Glyderau). I have observed similar "stuff" on the Moelwynion and Dartmoor.