Identification help brought to you thanks to "archman" on the Marine Life forum on ScubaBoard:
"I showed the picture to my boss. She identified it as a thaliacean the second I brought the image up, ran back to her office to get a book, and had it tagged to genus within four minutes.
The critter in the photo is most likely Thetys, a salpid thaliacean (true salp) found throughout the world's oceans. The little red patch on the left speciment is probably rhodopsin pigment.
Thetys' integument is described as "spiny looking" and "firm". Obviously the spines are visible in the photo. The circular muscle bands are not visible.
The book that was referenced is gorgeously endowed with color photos of various jelly plankton. It's the "Pacific Coast Pelagic Invertebrates", co-authored by Claudia Mills up at Friday Harbor marine lab. She knows her stuff."
