Escharoides mamillata is an encrusting bryozoan, rarely found in the British Isles. The colonies form sub-circular patches composed of a single layer of autozooids. Autozooids are broadly oval to quadrangular and strongly convex. They range in size from 0.5-0.8 by 0.4-0.6 mm.
Fossil records of Escharoides mamillata are known from the Pliocene Coralline Crag of East Anglia and the Low Countries. Recent specimens of the species were recorded from the Antrim coast, Orkney, the west coast of Scotland, the coast of Galicia, Spain and the Gulf of Marseilles.
The species is able to colonise shells and calcareous organisms. The species is little-known and rarely reported, but assumed to be restricted to offshore environments.