(Stimpson, 1852)
Description
External appearance
Solitary. Body globular to ovoid, up to 35 mm in diameter. Test tough, bearing fibrils, heavily coated with sand, mud, shells, etc., except for the area near the siphons.
Characters
Both siphons 4-lobed. From 30-60 simple branchial tentacles of variable size. Branchial sac with numerous rows of straight stigmata; four branchial folds on each side; longitudinal bars present. Gut left of branchial sac; stomach horizontal with longitudinal folds and a single small liver diverticulum. Ten to twenty drop-shaped polycarps scattered over each side of mantle wall (P. fibrosa morphology).
Habitat
Loosely attached to sand or mud; from shallow water down to depths of over 1000 meters.
Distribution
Artic-Boreal distribution.