The original genus description (Nomusa 1936), states that Siogamaia is a shell of moderate size with many whorls.

The surface is marked by weak axial ribs that are mostly shown in the earlier whorls.

The Aperture is obliquely ovate with a single distinct columellar fold.

The outer lip is smooth within, Nothing is known about the biology of the members of this genus.

As is true of most members of the Pyramidellidae sensu lato, they are most likely to be ectoparasites.