Onoba semicostataOnoba semicostata is a species of minute sea snail, a marine gastropod mollusk or micromollusk in the family Rissoidae.ClassificationTurbo semicostatus Montagu, 1803 is probably another species than those which is mostly understand by that name. According to Warén Turbo shepeianus could be the valid name for this species found off Belgium. Further research is necessary, therefore we use the more commonly used name Onoba semicostata.TaxonomyJanssen mentioned two subspecies: O. s. semicostata and O. s. aculeus. Thorson, Warén and Fretter & Graham are followed who both consider O. s. semicostata and O. s. aculeus as separate species.DistributionThis marine species occurs in the Baltic Sea, the North Sea, the Northern and Northeast Atlantic Ocean and in the Mediterranean Sea.