Stenosoma are elongated Idoteids with no distinct pleon somites, so that the pleon and the telson are completely fused. The triangular coxal plates give S. lancifer a serrated shape, a pattern continued into the pleotelson, which narrows then expands before narrowing sharply to an elongated point. Males grow to 22.4 mm, with females being smaller. It is a reddish colour, sometimes with pale medial dots or stripe.
Distribution and Habitat
This species is found amongst algae (especially red algae) and under stones at LWM. It is restricted to the south coast of England and the Channel Islands.
Naylor, E. & A. Brandt. 2015. Intertidal Marine Isopods. Synopses of the British Fauna (New Series), No. 3. Field Studies Council, for The Linnean Society of London.