(Savigny, 1816)
Description
External appearance
Colonial, with zooids immersed and arranged in biserial linear systems. Colony flat, encrusting, usually grey, orange or red-brown. Test soft and smooth.
Characters
Zooids up to 3 mm in length; body not divided into thorax and abdomen. Oral siphon unlobed and relatively wide; atrial siphon with no, or only small, dorsal lip. Eight to 16 simple branchial tentacles of variable size. Branchial sac bearing 9 to 15 rows of straight stigmata; three internal longitudinal bars on each side; no folds. Gut left of branchial sac; stomach trumpet-shaped, with 9 to 11 longitudinal folds. Ovary dorsal and posterior to testis; mulberry-like testis lateral on each side (B. leachi zooid).
Habitat
Attached to hard substrata; from shallow water to depths of several hundred metres.
Distribution
From Norway to the Mediterranean.