Author: Ian Smith. June 2012
Up to 20mm long. Edge of reduced mantle indistinct. Dorsal surface densely covered with large spiculose clubbed tubercles [image 1], each with an apical red-brown or black spot. Minute translucent white papillae  on tubercles cryptically soften their outline. Dorsal ground colour  buff to brown with spots of darker brown and dense white speckling. Several discs of rufous brown with about six black-brown spots peripherally and a brilliant central spot iridescing between azure blue and emerald, as the light varies. Juveniles usually paler than adults.
Smooth cylinder, slightly laterally compressed, with blunt double apex, arising from cylindrical sheath . Tall tubercles on outer, anterior and posterior rim of sheath. Rhinophore yellowish with two or three weakly defined transverse bands, the whole sprinkled with white specks.
Three, on highest point of dorsum. Partially tripinnate, similar colour to tubercles. Not retractile, but often concealed by three protective tuberculated lobes  when not fully expanded.
Indistinct. Tubular mouth and indistinct small rounded oral tentacles in space between foot and oral veil. Veil with 8 to 10 lobes, visible from below, pale buff sprinkled with white .
Translucent cream. No propodial tentacles, but corners of squarish propodium produced into sharp angles . When animal viewed laterally, upper surface of foot periphery forms translucent white band  sprinkled with opaque white around base of body.
Brilliant iridescent azure blue/emerald green spots .
No other British member of the Polyceroidea has brilliant blue-green spots.
On lower shore and sublittorally to 100m feeding on Leucoselenia botryoides [EML] . Cryptic structure and colour make it difficult to detect on shore. Most easily found by examining L. botryoides in water. Simultaneous hermaphrodite. Spawns in June and July. Spawn mass a spiral ribbon attached by edge. Veliger larvae live as plankton before metamorphosing.
Widespread around Britain and Ireland, but probably under recorded because of its camouflage. (U.K. interactive distribution map.NBN).
The map provided here shows the distribution of the species based on Conchological Society data.