Facelina auriculata:
Cerata rarely more than 25% of body length so only slightly overlap adjacent clumps, which are usually neat, compact and more clearly defined than on F. bostoniensis.
Subapical, opaque white on cerata is amorphous (1), not shield-shaped. Frequently, there are white pigment splashes down the front of cerata (2).
Usually, but not always, some blue iridescence on cerata (3) and, often, on head and body.
Length 17 mm. Menai Strait, Wales. February 2011.