Range — Most warm seas and abundant in the Tertiary, back to the Paleocene. The genus is abundantly represented in the Tertiary of both Europe and North Amerca, but the greatest representation is now in the Indo-Pacific. Very few species still exist in Caribbean-Panamic waters, and now there are none in Mediterranean and West African waters, where Gemmula is replaced by Fusiturris.

Shell rather large, 24-88 mm., elongate-fusiform, with tall spire and long straight unnotched anterior canal. Protoconch tall, conical polygyrate and axially costate. Adult sculpture of spiral keels and cords, the peripheral keel mostly double, often flanged and always studded with gemmules, often cog-like in vertically fused pairs. Sinus deep and narrow, on the peripheral carina. Operculum leaf-shaped, with a terminal nucleus. Radula consisting either of a pair of wishbone-shaped marginals only (G. hombroni), or with the addition of a central tooth, which may be vestigial (G. congener diomedea), to fully formed, unicuspid, with a large broad base (G. gilchristi).
Coloration, usually with peripheral dots of brown alternating with the gemmules and sometimes with the addition of brownish spiral bands and zones.