It's in the details

 

Sometimes I just can't help it.  This is an extreme closeup of a common marine species.  It ends up looking very abstract at this magnification, but I'm drawn in by these detailed views and I'm tempted to share the wonder and beauty of them.

The pale lavender points are short spines.  The smooth, transparent structures are papulae (used for respiration).  And the tiny beak-like jaws (some are open, some are closed) are pedicellariae.

Any guesses yet?

Another hint is the dark brown pentagon shape near the center of the photograph.  This is a clue that the animal has five-part radial symmetry.

If you scan the image above very closely there's another structure that may help you identify this animal.  It's pale yellow and has a few lines crossing through it — in this case, some of the lines form a Y-shape (at least to my eye).

I've circled this structure in the image below:

 

  

That's a madreporite or a sieve plate, through which water can be pulled in to be used in a water vascular system.

Okay, here's the entire animal:

 

It's a juvenile Ochre Sea Star (Pisaster ochraceus).  This is another animal that we encountered in a Bull Kelp holdfast not too long ago.  It was only ~12-14 mm across.