The Striped Nudibranch  is a rare sighting for anyone snorkeling or free diving above 30ft subtidal, as its primary prey in the Pacific Northwest is an octo-coral, the Sea Pen.  I was quite surprised to discover these in the upper subtidal. I was turning over kelp leaves on a murky no-viz day when I noticed one on the bottom of the kelp (very unusual) and another in the sand (much more common).  When I returned the next day to see if a second sighting would be possible I found no Armina californica, but I did find the remnants of a yellow Sea Pen, explaining their presence.  These critters bury themselves in the sand and may push their way through the sediment “sniffing” out Sea Pens with only the tips of their rhinophores exposed.  It is not uncommon to find several gathered together munching away on a sacrificial octo-coral.  They lack the typical gills or cerata of many nudibranchs and breathe through gills that are hidden between the dorsum and the foot. Their dorsum is ridged — imagine being a tiny copepod– rather than winding your way through cerata or tubercles, you’d be climbing hills and valleys.