large spherical urchin, many spines, red and purple colouration.
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With most of my marine observations coming from beach-combing, I see very few urchins - apart from fossil ones! I expect they are just too fragile for anything recognisable to be washed up.
Yes, they are often smitherreened.
Inside the globe is Aristotle's lantern - next time then!
THREE MARINE PROJECTS
Lat/Lng: 50.0, -5.1
OS grid ref: SW8023