"Although long known as Syrinx aruanus, this combination is grammatically incorrect. The Greek word syrinx (a pipe) is feminine and thus the specific epithet, which in this case is an adjective derived from the Aru Islands and meaning the Aruanan Syrinx, must agree in gender with the genus name. Hence Syrinx aruana is the grammatically correct name. When he proposed the genus name Syrinx, Röding himself used the combination Syrinx aruana (and all the other specific epithets he combined with Syrinx were also feminine). This is a mandatory change following Art. 34.2 of the ICZN Code."
https://www.molluscabase.org/aphia.php?p=taxdetails&id=527732