Looking like a sponge

While doing a little tidepooling this morning, I came across several nudibranch egg ribbons attached to the rock:

 

When you find egg ribbons, the nudibranch that laid them is often still in the area, so I started scanning to see if I could locate the species that produced these eggs.

I was looking around, noticing coralline algae, sea squirts, sponges, and not finding any nudibranchs, but then I paused.  Something looked a little different here:

 

Aha!  Two nudibranchs!  They were so transparent and blended in so well with the general background community that I hadn't seen them at first.

Zooming in for a closer look, I realized this isn't a species that we see very often.  Meet Chan's Dorid (Hallaxa chani):

 

Eric got the best picture (above), where you can see the translucent coloration, bumpy dorsal surface, rhinophores (sensory appendages at the front end) with subtle reddish-brown tips, and an unusual gill plume (that to my eye looks like a little pom-pom). 

Hallaxa chani feeds exclusively on the sponge Halisarca.  It has a more northern distribution, and it's apparently relatively rare at the southern end of its range.

Here are a couple more pictures for the record: