Fischer P., 1883
Shell external, internal, or absent, in the adult phase; skin often able to secrete a strong acid on abrupt disturbance; operculum absent in post-larval stages; calcareous spicules may be present in the skin; body-shape superficially bilaterally symmetrical; head with a flattened oral veil, and bearing inrolled antero-lateral oral tentacles and dorso-lateral rhinophoral tentacles; mantle cavity widely open on the right side, containing a bipectinate gill; mantle enlarged to form a dorsal disc; foot large, broad, often natatory, sometimes with a conspicuous metapodial gland; non-calcareous spines may be present in the midgut (not in British species); potash-resistant jaws are present, consisting of separate, articulating, masticatory elements; radula always present, rather broad, lacking the median tooth; abraded or broken teeth are discarded, not retained in a special sac; hermaphrodite reproductive system usually lacking an external seminal groove; penis unarmed; impregnation never hypodermic; central nervous system euthyneurous, forming a ganglionic ring around the foregut, behind the buccal mass. In habit the pleurobranchomorphs are epifaunal carnivores, in the North Sea feeding principally upon ascidians, by means of an extensible proboscis.
Source: Thompson, 1988.
The following subtaxa of this order occur in the region:
Family Pleurobranchidae
Genus Berthella
Berthella plumula
Genus Pleurobranchus
Pleurobranchus membranaceus