Asterophilia sp.

Comment from expert, Leslie Harris: Ken is right, it's a scaleworm in the family Polynoidae, genus Asterophilia. The scales are translucent so the edges don't show which makes the big papillae look as if they're directly on the body. There are two described species both of which are commensal on sea stars. The differences between the 2 are microscopic so I can't say which species this belongs to.