A new mediterranean species of Haminaea Leach, 1820 (Gastropoda: Opisthobranchia: Cephalaspidea)

A new species of cephalaspidean gastropod from Mediterranean Sea (West Naples Gulf, Italy) is described. This species, Haminaea fusari, is characterised mainly by the presence of short parapodial lobes, which cover only the anterolateral parts of the shell; the prostatic gland has two lobes separated by a narrow and cylindrical zone; the lateral teeth of the radula are all smooth; the penis has a triangular section at the apical zone and a small sharpened tip; and the spawn is horse-shoe-shaped or coiled in a single spiral. This species is compared with all the European species of the genus and a key to identification is provided.