I found some shells like these on the beach. They appear to be some type of venus clam (family veneridae). Does anyone know the purpose of the spiny protuberances? - Ken Morley

hi Ken, it's look like those spines are for defense against predation. you may want to check some info about this interesting species http://www.edulifedesks.org/class... - Margot

That is so interesting, thanks Margot! - Ken Morley