considered B. infundibulum as an Arctic and cold temperate water species, and B. vitrea as a warm water species, typical in the tropics, i.e. the West Indies, Florida and the Mediterranean. In the western Mediterranean close to the Strait of Gibraltar (Alboran Sea), Mills et al. (Mills et al., 1996) found both species: B. infundibulum was observed in deeper waters (274–831 m) and B. vitrea found mostly in surface waters (upper 15 m). Most probably, only the warm water species (B. vitrea, L. Agassiz, 1860) occurs in other Mediterranean areas.