(Alder & Hancock, 1854)
Description:
This species may reach 25 mm in length; the body is white, suffused with pink. The pallial rim bears a number of long, tapering processes, four in front of the rhinophores, seven or eight on either side of the body. The two most posterior processes are bifid. Inside the pallial rim on each side are numerous shorter but still conspicuous tubercles. The rhinophores bear numerous fine lamellae. Up to eleven pinnate gills around the anal papilla.
Habitat:
It is a rare species, found on muddy sand seabeds usually in deep water. The diet of O. leachii is not certainly known, but probably this species feeds on burrowing ascidians such as Molgula occulta .
Distribution:
It has a restricted boreal distribution, but is restricted to the British coast in the North Sea (Distr. O. leachii).