Presenting the letter 'E'

Doesn't take much explaining -- my letter 'E' in my ABC-Along 2008 project. But this next one...
'E' is for 'echinoid.' Are you buying it? "Resembling a sea urchin," says my dictionary (where I sought help when repeated walks yielded nothing 'E'-ish for me). Have I cheated? Or have I expanded my vocabulary? It's a little touch of green for you, nonetheless, in honor of St. Patrick.