Epistomia bursaria is an erect branching bryozoan. The colonies form small, very delicate tufts, 2 – 3 cm high. They are composed of regular dichotomously dividing branches with a serrated outline that is typical of many hydroids. The branches are white in colour and curl at their extremities. Autozooids are arranged in pairs and lack spines. They consist of a triangular tip and an elongated tubular proximal portion, of equivalent lengths. Each autozooid arises as a bud from the top right hand corner of the previous autozooid, passes along the inner edge of the succeeding autozooid and expands immediately above it to produce the inflated triangular portion towards the tip.
The species is able to colonise hard substrates and small red algae in shallow subtidal waters.
The distribution of Epistomia bursaria is patchy. In Britain, it has been recorded from Cromer in the east, to south Devon. The species was traditionally considered rare, however Hincks (1880) reported it as extremely abundant at Swanage, where it is still found. It has also been reported from the north-western Mediterranean, on the decapods Pisa and on calcareous and brown algae, from depths of 20 – 40 m.