(Alder & Hancock, 1848)
This drab species does not usually exceed 10 mm in length, but exceptional individuals have been reported from the Isle of Man (15 mm) and the Netherlands (18 mm). The body is grey or yellowish white, with speckles and larger blotches of brown or olive green; there are no extensive areas of white superficial pigment on the dorsum or the sides of the body. The sparse cerata (up to 10 on each side in British specimens) are inflated, urn-shaped and smooth. The shape of these cerata is very variable from minute to minute, but they are never knobbly; their colour matches that of the body, with brown or olive green pigment forming 2-3 vague rings. The tip of each ceras usually bears a ring of chalk-white pigment which obscures the cnidosac within; there is usually a small band of brown apical to this. The hepatic lobes are pale brown, deepening in colour towards the tip. The tentacles are white-tipped, and have 1-2 subterminal bands of brown (E. exiguus-drawing).
This species feeds upon a variety of hydroids, including Obelia geniculata , O. dichotoma , O. flabellata , Laomedea flexuosa , Hydrallmania falcata and Kirchenpaueria pinnata . It is euryhaline (down to 5-7 ä, in the Netherlands).
It has been recorded from scattered shallow sublittoral localities all around the British Isles as well as from the White Sea, Massachusetts, Connecticut, Norway, the Baltic, Atlantic and Mediterranean coasts of France, Italy to 140 m (Distr. E. exiguus).