Porella patula is an encrusting bryozoan that forms brittle sheets, composed of a single layer of autozooids. Autozooids are oval to hexagonal and convex. They are 0.4-0.6 by 0.3-0.44 mm.
Porella patula is a boreal-arctic species that is known from the Barents Sea, Greenland and Canada. In the NE Atlantic it ranges south to western Norway and north-east England, but is absent from the western coasts of Britain.
The species is able to colonise hard substrates including other Bryozoa e.g. Flustra foliacea in offshore habitats.