Ruler worm?

Okay, I don't know the identity of this worm yet, but it's too interesting not to post a picture, and perhaps someone out there can help with the identification.  Eric and I have seen a few of them recently in the low intertidal zone on Bodega Head.

 

This worm is fairly small, ~4 cm long and only a few millimeters wide.  You can see the metallic silver coloration and the very regular black striping (reminiscent of a ruler!).  Note that both the anterior (head) and posterior (tail) ends are patterned slightly differently than the middle section.

Here are two close-ups of the head end:

 

 

If you have any thoughts about the identification, or just want to join in on praising this worm, feel free to submit a comment!

P.S.  You could also suggest a possible common name for the worm.  Ruler Worm? (for the tick marks)  Piano Worm? (for the resemblance to black-and-white keys)