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

[1] 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.

[1] 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.