P. inconspicua is frequently found on Zostera with R. membranacea but, because of its tiny maximum size (varies locally 1.3 to 3mm), it is only likely to be confused with the smallest juveniles of R. membranacea. A tiny, purple, apical spot (1), confined to a single embryonic whorl, is diagnostic of P. inconspicua when present, but absent from some. The posterior of the snout often has a broad medial blackish or brown-umber band that extends onto head and body, but the pigment does not extend to near the tip of the snout (2) or onto its side (3) where it is darkest on R. membranacea. Left: Brighton, England. 1997. Leg. J.Light. Centre & right: Llŷn Peninsula, Wales. March 2015.

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