Stokes and Broderip, 1828
The Devonshire cup-coral occurs in two forms:
(1) Shallow water form, var. smithii:
Corallum: Solitary subcylindrical, constricted in the lower part, with a broad attached base. Outline of calyx elliptical, more nearly circular in young specimens. Septa exsert, with a finely granulate surface, arranged in four or five cycles with about 6-10 in each of the first two, which are nearly equal in size. Pali form a single series opposite septa of cycle 3. Columella consisting of a series of twisted ribbons, occasionally thickened to form blunt, rod-like structures. Costae well-developed towards the upper margin of theca, obsolete below. Height up to 15 mm, long axis of calyx to 20 mm.
Polyp: Tentacles up to 80 in number, long in full extension, with prominent terminal knobs. Column capable of extending to 30 mm above corallum, forming a tall cylinder. Colour variable, translucent: brown, red, orange, pink, white or vivid emerald green, often different on various regions, usually with a zig-zag ring of contrasting, more opaque colour around the mouth. Tentacles transparent with colour confined to warts, terminal knobs usually white or brown.
(2) Deep water form, var. clavus:
Corallum: Inversely conical with a narrow base which may be attached or secondarily free. Structure otherwise as var. smithii but generally more delicate in texture. Up to 30 mm tall. Polyp similar to var. smithii.
Attached to rocks, shells, worm tubes (see Wilson, 1976), etc. Var. smithii frequently occurs on the shore in shaded places and deep pools around LWST but is generally more common sublittorally, down to about 100 m depending on local conditions. Var. clavus occurs from about 50 m depth to at least 1000 m, its upper limit determined by water turbulence, as the narrow base is vulnerable to breakage. Detached specimens of this form are frequently found living free on the bottom as a consequence of such breakage.
Common and locally abundant on all western coasts of the British Isles as far north as Shetland and Orkney with occasional records from the North Sea on the east coast of Scotland. Abundant around south-west Europe and in the Mediterranean.