The white speckled brown form of Acanthodoris pilosa is sometimes confused with O. bilamellata. It is distinguished by no concentration of brown on the rhinophores, gills and dorsal panel between them, by soft, tall, slender, conical tubercles and by its tripinnate gills which, when contracted, form a small oval, open at the posterior.
Length 4.8 mm. North Yorkshire, England. September 2014.