Shell tall-spired hut with a rather short and recurved anterior canal. Protoconch polygyrate, narrowly conic, with 4 densely, axially costate whorls. Spire whorls sculptured with a broadly rounded, median carina studded with prominent, laterally compressed nodules. Spiral sculpture consisting of 2 or 3 threads between the upper suture and the peripheral carina, 2 or 3 threads below the carina and 3 strong, smooth cords on the upper part of the base, followed by about 9 threads over the neck and anterior canal. The uppermost of the 3 main basal spirals is emergent over the last whorl. The Insinuate nature of the outer lip exhibited by the type specimen has been shown above to be an abnormality. Colour pale yellowish. Height 33 mm. Width 11,5 mm.

The species is rather similar to the closely related G teschi (Powell) (see below). The main differences are that, in G. bisinuata, the subsutural rib is clear, thin, straight or slightly wavy, without nodules; the sutures are poorly seen and very shallowly impressed. In G. teschi, the subsutural rib is very weakly developed or absent (or there is a weak to moderate subsutural fold), covered with nodules which are the continuation of axial folds; the sutures are clear, more or less channelled. Additionally, the spiral ribs on the shell base in G. bisinuata are clear and prominent; two lower ribs out of three upper ones are much stronger than the other. In G. teschi, the ribs are thinner, more uniform, more

East Africa. From Gulf of Aden to Madagascar.

Off East Africa, Somaliland to Zanzibar, 818 to 1362 metres.