Alder and Hancock, 1848
Description
External appearance
Solitary. Body globular to ovoid, up to 18 mm in diameter. Test hard, coloured grey-green, naked or with few attached particles.
Characters
Oral siphon short and 6-lobed; atrial siphon short and 4-lobed. Siphons are well separated. About 14 branched branchial tentacles of variable size. Branchial sac with numerous rows of curved and spirally arranged stigmata; seven branchial folds on each side; longitudinal bars present. Gut left of branchial sac; stomach narrow and small, not marked off from the rest of gut but bearing many diverticula forming a complex liver. One ovoid gonad on each side, consisting of a central ovoid ovary and marginal male follicles. Oviduct long and narrow, directed towards the atrial siphon (M. citrina morphology).
Habitat
Attached to hard substrata; usually in shallow water but occasionally below 200 metres.
Distribution
Arctic-Boreal, down to the Channel coast of France.