This member of the Acanthodoris family is a fairly common sighting in the Pacific Northwest.  It is relatively visible as it can get up to 5 cm or 2 inches and its somewhat translucent/whitish body seems to reflect light in a way that is quite striking. Like the Nanaimo Horned Dorid, it has very obvious, tall, somewhat curved rhinophores, a large branchial gill plume and buttery yellow tips to its long, pointed papillae — not to mention an obvious yellow margin on its mantle.  This yellow margin is also found on the Yellow-edged Cadlina, a smaller less common nudibranch.  For more information on the taxonomy of the Hudson’s Dorid, feeding patterns and other photos check out Bill Rudham’s  Sea Slug Forum.