(Savigny, 1816)
Description
External appearance
Colonial, with zooids immersed. Colonies forming hard, thin, encrusting sheets. Test white, yellow, grey or violet, densely packed with calcareous stellate spicules (D. maculosum spicules).
Characters
Zooids about 1 mm in length; body divided into thorax and abdomen. Oral siphon 6-lobed and large; atrial opening without a siphon. Branchial sac bearing 4 rows of straight stigmata; no longitudinal bars. Lateral thoracic organ (LTO) near the atrial opening, between the third and fourth row of stigmata. Retractor muscle long, extending from the posterior end of thorax. Gut abdominal; stomach smooth. Gonads located in the gut loop. Testis single; sperm duct coiled (D. maculosum zooid).
Habitat
Attached to hard substrata; from shallow water to depths of about 300 metres.
Distribution
Arctic-Boreal distribution, including Sogn, Helgoland, Faeroes, S & W Britain and Bretagne.