This species of dorid nudibranch (shell-less marine gastopod) is found along the west coast of North America, from Alaska south to California (Santa Barbara) Wikipedia 2011
). It reaches lengths of up to 35 mm, and the body "ranges from translucent white to grey. The mantle is covered in prominent conical papillae which are tipped with milky yellow." (Sea Slug Forum 2011).
View a video of this species.