Ascophora

Ascophora is an infraorder under order Cheilostomatida of the Bryozoa. 
They are now considered a synonym of Flustrina. 
Ascophorans are distinguished from other cheilostomes in having a completely calcified wall covering their frontal surface apart from the orifice, and possessing an ascus (hence the name of the suborder). The ascus is a water-filled sac of frontal membrane opening at or near the orifice. It functions as a hydrostatic system by allowing water into the space below the inflexible frontal wall when the zooid everts its polypide (feeding tentacles) by muscles pulling the frontal membrane inwards (non-ascophorans do not need this structure as their frontal wall is not calcified).
The structure of this frontal wall is the basis of distinguishing the four major subdivisions of the Ascophora, each of which is, however, currently under suspicion of being polyphyletic and/or paraphyletic. They are therefore listed here as 'unranked' groupings.
Ascophorans are exclusively marine, but very widespread geographically and ecologically. They grow on various substrates and in a variety of colony shapes.