Here's the scoop!

  

Quite a few folks guessed correctly that last night's mystery close-up (above) is a worm tube.  Here's the entire tube as we found it washed up on the beach:

 

 

Meet Pectinaria californiensis!  These interesting worms are commonly called "ice cream cone worms."  Perhaps you can see why in the next photo:

 

 

 

 

Although I'm holding the tube with the wider end up, the worm lives buried in the sand with the broader end of the cone facing downward, as in the illustration below:

 

Modified from Gordon, D.C.  1966.  The effects of the deposit feeding polychaete Pectinaria gouldii on the intertidal sediments of Barnstable Harbor.   Limnology and Oceanography 11: 327-332. 

The worm's head extends outwards from the wide end of the tube.  They are deposit-feeders, so they'll use their tentacles to gather sand particles, pass them to their mouth, remove organic material, and then eject the particles from the narrow end of the tube at the surface.

Although the older illustration below shows the worm on the surface, you can see the relationship between the worm and its tube.  (For those of you who spend time along freshwater streams, this is somewhat similar to a caddisfly.)

Modified from Sowerby, J.  1806.  The British Miscellany: or, Coloured figures of new, rare, or little known animal subjects; many not before ascertained to be inhabitants of the British Isles. London.

I appreciated how the grains of sand were painted in the plate shown above.  The tube with its cemented sand grains is quite a work of art -- with the light behind it, it looks a bit like stained glass:

 

 

 That's the scoop on the ice cream cone worm!