Gemmula ambara: Shell moderately broad fusiform, length 30-55 mm. Overall color of the shell is white, flushed with a distinct violet or purplish tone in some specimens (particularly when freshly collected), except for the subsutural area, which is always light amber to dark amber brown in color. The protoconch has 3-4 translucent yellowish-brown to purplish brown whorls, axially costate over the last two protoconch whorls. Post-nuclear whorls 9-10.
The spire whorls are sculptured with a prominent subsutural fold comprising two strong, closely-spaced spiral ribs, immediately adjacent to the suture, with the region in between moderately elevated, such that the two ribs comprise a prominent amber keel that borders the suture. In earlier spire whorls, there are two additional ribs in the anterior subsutural region and as the shell increases in size, the subsutural region can have as many as 6 to 7 spiral ribs, with the two posterior ones comprising a subsutural keel always the strongest. There are axial columns between the spiral ribs, quite strong in some specimens. A diagnostic feature of this species is that the entire subsutural region up to the peripheral sinus rib is amber in color, and the rest of the shell (except the colored protoconch) is white.
In the first few post-nuclear spire whorls, the most prominent features are the amber brown subsutural region and the strongly gemmulate sinus rib. By the fourth post-nuclear whorl, an additional spiral rib anterior to the gemmulate peripheral sinus rib becomes emergent and in mature specimens, two strong additional spiral whorls are found anterior to the sinus rib in the larger spire whorls.
In the body whorl, there are six principal spiral ribs and at the base, numerous weaker spiral ribs surrounding one major, somewhat crenulate rib. There are 16 spiral ribs with a varying number of weak ribs between the principal raised spirals along the canal

Gemmula ambara: Gemmula ambara looks superficially similar to smaller specimens of Gemmula diomedea ; it can readily be distinguished from members of the G. diomedea complex from the Philippines because the entire subsutural region until the sinus rib at the periphery is amber brown. In all of the G. diomedea-like specimens (there are likely to be multiple species in this complex) the one or two raised subsutural ribs are brown but the remainder of the subsutural region has the same white background color as merest of me shell (including the region between the two brown subsutural spiral ribs — white in G. diamedea, amber in G. ambara). When preserved, the protoconch is also diagnostic: brown in G. ambara, generally white and much larger in G. diomedea, (although some varieties of G. diomedea, which may be different species, have a protoconch that is light yellowish). In addition, most Philippine specimens of Gemmula diomedea have a higher and narrower spire, and a proportionately shorter canal than Gemmula ambara. Most specimens of G. diomedea have diameter/length ratio = 0.30-0.32 while for G. ambara it is 0.33-0.35. As noted in the molecular phylogeny section that follows, Gemmula ambara is most closely related to G. rosario and G. lisajoni. G. rosario is a pure brown shell, uniformly straw brown rather than amber and white, while G. lisajoni has a distinctive deeply purplish-violet canal, with a brown body . In contrast to G. ambara, there is no white coloration in either of these species. Other Philippine forms of Gemmula such as G. speciosa, G. kieneri and G. sogodensis are both morphologically and genetically even more distant and would not be mistaken for Gemrnula ambara.

Gemmula ambara: Collected in the Central Philippines, primarly from Balicasag Island, Bohol.