Looking like some kind of high-fashion button, the spotted aglaja is really an animal.
It is a member of the sea slug group or, for the more scientifically inclined, a member of the opisthobranch order which, unlike regular sea snails (prosobranch), have minimized their shell or lost it completely.
The head of the animal, sprouting white margined lateral lobes, is oriented to the right side of the photograph. The head and body part covering the front half of the animal, which facilitates burrowing, is called a head shield.
The spotted aglaja has a mall, vestigial internal shell.
At 3/4 of an inch, this animal has reached its average size, but can grow to a little more than an inch.
It is commonly found burrowing in muddy sand where it preys on bubble snails along with other small mud dwellers including copepods.
Lacking a radula or rasping tongue, it sucks in its prey whole.
The spotted aglaja ranges from Southeast Alaska to Southern California inhabiting the low intertidal and shallow subtidal zones. It lays eggs from June to August.