Ctenostomata

Ctenostomata, a sub-order of Bryozoa, in which the (Zoarium) colony is never calcareous, and the orifice is closed by a series of processes or setae. The best known English species is Alcyonidium gelatinosum (Linn.), popularly known as "Pipe-weed," "Pudding-weed," or "Sea Ragged Stuff"; this is common all round the English coasts, and may be recognised by its fleshy, gelatinous consistency, its yellowish brown colour, dotted over with the small stellate points that mark the openings of the individual polypides and its irregular tuft-like mode of growth. The small delicate tufts of the "Sea Silk Coralline" (Vesicularia spinosa, Linn.) and the dense encrusting masses of the "Nit. Coralline" (Amathia lendigera, Linn.) are also well known members of the group, which includes over thirty English species. The recent discovery of spicules in Alcyonidium suggests that this sub-order was derived from a form that had a calcareous skeleton.