Diagnosis. Shell of medium size, fusiform, covered by brown periostracum. Protoconch multispiral. with 1.7 smooth initial volutions and 1-1.4 whorls with arcuate axial ribs. Subsutural fold weaker than the peripheral keel, especially on later whorls, flattened, with a relatively narrow gemmulate cord. Sutural fissure formed by subsutural fold, is narrow. Spiral cords on the body whorl usually rather narrow and rounded, with wide interspaces, and granular. Columellar pleat distinct to obsolete. Anal sinus deep. U-shaped.

Description of holotype. The shell is fusiform and rather thick and strong. The protoconch is missing and the upper teleoconch whorls are eroded. The teleoconch consists of at least 10 whorls separated by deeply channelled sutures. The profile of spire is flat. Whorls bear a rather wide subsutural fold which is prominent and markedly narrower than the peripheral keel on initial whorls, but becomes wider, much flattened, and with indistinct border on last whorls. The subsutural fold is covered by rounded blunt tubercles, which occupy the whole fold on early whorls, but on later whorls they are confined to a relatively narrow and flattened cord in the middle of the subsutural fold. There is a wavy cord at the upper edge of the subsutural fold, that forms a fissure above the adapical suture. The peripheral keel is strong and bears longitudinally elongate gemmules (25 on the body whorl and 22 on the penultimate), which becomes arcuate on the last whorls. The gemmules more or less correspond to tubercles on the subsutural fold. The keel is bordered by two cords, the upper being strongly wavy. On the two last whorls, these cords become more distant from the keel, and their place is occupied by two narrow riblets. One more cord is situated in the middle of the interspace between the keel and the subsutural fold. The keel is covered by three rather indistinct spiral cords, the upper is the strongest and is thickened at intersections with gemmules. The keel on all whorls is set at a small distance from the upper edge of the subsutural fold. This distance is slightly less than the interspace between the keel and the subsutural fold. The body whorl comprises 55% of the shell height. Its periphery below the keel and the shell base is covered by rather narrow granular cords, sometimes with a thinner cord in the broad interspaces between cords. The cords on the canal are weaker and narrower. There are 25 cords below the keel. The aperture is narrow, and its width slowly decreases to rather short and obliquely truncated canal. The inner lip is smoothly curved in its upper part and almost straight at the columella. It is covered by a white callus with fine longitudinal wrinkles. The columellar pleat encircles the columella obliquely and is well seen inside the aperture. The outer lip projects strongly forward below the sinus. The anal sinus is deep, U-shaped, with diverging branches. The sinus is directed slightly adapically.
Shell height 32.6 mm, body whorl height 18.0 mm, aperture height 14.3 mm, shell diameter 9.8 mm.
The shell is covered by light-brown perio¬stracum.

The species is rather variable in the shell sculpture. The subsutural fold may be stronger and narrower than in the holotype, with a well-expressed cord bearing tubercles. The position of the tuberculate -cord may also vary. The peripheral keel may be set lower and closer to the suture, and sometimes it has a sloping profile. The sutural fissure formed by the subsutural fold, varies in width, but usually it is rather shallow. The interspace between the fold and the keel is covered by up to 6 cords. Cords on the shell base can also vary in number, width, and prominence. They may be weakly to heavily gemmulate. The lower and upper branches of the anal sinus may be almost parallel or diverging. The prominence of the columellar pleat varies from well-expressed to obsolete, even in shells from the same sample.
The species is very similar to G. didyma, and it is sometimes difficult to distinguish these species in the absence of shells with a more or less intact protoconch. G. moosai differs from G. didyma in having a larger shell with usually weaker and narrower spiral cords on the shell base and a weaker subsutural fold, which bears small and rounded tubercles occupying only a portion of the fold on last whorls. The sutural fissure formed by the subsutural fold, is much narrower than in G. didyma.
The species is also similar to G. fierstinei, while differs in having a larger and somewhat narrower shell with a higher spire, a typically weaker and narrower subsutural fold, and a less developed columellar pleat.

Distribution. Tanimbar Islands (Banda and Arafura seas), the Philippines, and Mozambique Channel, at 288-575 m.