A new opisthobranch of the mesopsammic, heteroproct aeolidoidean nudibranch family Pseudovermidae, Pseudovermis thompsoni new species, is described. It has been recorded from coarse sands at three localities in the northern Adriatic Sea and appears to be closely related to three other European species, viz. P. boadeni Salvini-Plawen & Sterrer, P. axi Marcus & Marcus, and P. schulzi Marcus & Marcus. The new species has been observed to feed on the mesopsammic medusa Halammohydra.
Descriptors: HALAMMOHYDRA
