Alder and Hancock, 1870
Description
External appearance
Solitary. Body globular, ovoid or conical, up to 15 mm in height and 20 mm in diameter. Test thin and translucent, bearing fibrils with some adhering sand, shells, etc.
Characters
Oral siphon 6-lobed; atrial siphon 4-lobed. Siphons are well-separated. About 20 branched branchial tentacles of variable size. Branchial sac with numerous rows of curved and spirally arranged stigmata; seven small branchial folds on each side (however, the dorsal fold on either side may be reduced or absent); longitudinal bars present. Gut left of branchial sac; stomach small and narrow, not marked off from the rest of the gut, but bearing many diverticula forming a complex liver. One gonad on each side, consisting of an ovoid ovary and a compact group of male follicles concentrated at the end opposite to the oviduct. Oviduct short and directed towards the oral siphon (M. complanata morphology).
Habitat
Attached to hard substrata; from lower shore to depths of more than 500 metres;
Distribution
Arctic-Boreal distribution.