The gelatinous pseudoconch of Corolla spectabilis, a pelagic snail, washed ashore on 2 January 2017.
For an introduction to Corolla, review the post from 11 August 2012 ("Gelatinous thimbles"). There are also pictures in the posts from 19 November 2012 ("Crystals on the beach") and 25 January 2014 ("Gelatinous assortment").
P.S. Interestingly, I didn't see as many Corolla pseudoconchs washing up during the last two years while the water temperature was above average. Now that the water has cooled down, they have been much more obvious (and numbers have been noticeably higher). Their abundance might not be connected to water temperature, but I thought I'd make a note for the record.