Onoba semicostata

Onoba semicostata is a species of minute sea snail, a marine gastropod mollusk or micromollusk in the family Rissoidae.

Classification
Turbo 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.

Taxonomy
Janssen (1975) mentioned two subspecies: O. s. semicostata and O. s. aculeus (Gould, 1841). Thorson (1941), Warén (1973, 1974) and Fretter & Graham (1978) are followed who both consider O. s. semicostata and O. s. aculeus as separate species.

Distribution
This marine species occurs in the Baltic Sea, the North Sea, the Northern and Northeast Atlantic Ocean and in the Mediterranean Sea.