Stearns' ear?

 

Jim and I were talking about marine snails today, and at one point we discussed this species, Marsenina stearnsii (formerly Lamellaria stearnsii).  It's a small snail that I haven't seen very often, but I don't think I've shown a photo of them before, so here you go.  This one was photographed on Bodega Head in November 2009.  It is sometimes referred to as Stearns' Ear Shell because the shell (which is often hidden by the mantle in live animals) looks a bit like an ear.

A few fun facts about these interesting snails — Their color patterning looks like the tunicates that they eat (so they can be hard to see); they are likely nocturnal (another possible reason they're not observed that often); they have acid glands on the dorsal (top) surface — I'm guessing those are the little points at the top of the rounded area in the middle of the animal.