Animal, vegetable, mineral?

In the 18th century, Swedish botanist Carl Linnaeus developed a system of taxonomy, his Systema Naturae, that attempted to classify everything on Earth by separation into three distinct kingdoms: animal, vegetable and mineral, or as he called them, Regnum Animale, Regnum Vegetabile and Regnum Lapideum.

I wonder what he would have made of this "creature" that I found washed up on the salt marshes this morning?