GENERAL. Shell of medium size, length 27.9 mm, moderately thin but solid. Shape slender with acute spire; whorls convex; body whorl rather stretched, with weak shoulder. Axial sculpture dominant. Colour pale brown, tending to orange, spire whorls with one moderately broad, slightly darker band, body whorl with 3 such bands, one suprasutural primary spiral cord clearly paler; axial and spiral sculpture accentuated by slightly paler knobs on top of axial ribs, varices and some axials slightly paler to white.
PROTOCONCH . Pale multispiral, consisting of about 4 whorls, tip usually slightly eroded or chipped, 1.5 mm high, diameter 1.2 mm; colour yellowish to pale brown, spiral bands slightly darker. First whorls smooth, glossy; third whorl with weak angulation at mid-whorl, turning into 2 spiral cords; spiral cords gradually more abapically situated, fourth whorl with 2 brown spiral cords; last 1/6 whorl with a few strongly opisthocline axial riblets adapically of those spiral cords. Transition to teleoconch marked by a single red-brown opisthocline axial line.
TELEOCONCH. Consisting of 7 convex whorls. First teleoconch whorl with 4 primary spiral cords, interspaces broad with 1 fine secondary spiral thread. Fifth primary spiral cord appearing along abapical suture of second teleoconch whorl, interspaces with 3 secondary spiral cords of which middle one usually slightly stronger. Middle secondary spiral cords gradually increasing in strength, resulting in 23 alternating fine and finer spiral cords on penultimate whorl, including 5 slightly stronger ones (primary spiral cords) with 3 slightly finer, but unequal in strength, secondary spiral cords in interspaces. Body whorl with 15 primary and 34 secondary spiral cords, on base towards siphonal canal growing larger. First teleoconch whorl with 11 sharp axial ribs including 1 slightly stronger varix, second and third whorl with 12 axial ribs including 1 (on second whorl) or 2 (on first whorl) slightly stronger varices. Their number only weakly increasing, penultimate whorl with 13 axial ribs, occasionaly with a single weak varix. Body whorl with 19 axial ribs, including 4 that form a broad prelabral varix.
APERTURE. Columella rather straight, gently curved towards an also straight parietal part. Adapical border of aperture broad, formed by shoulder of body whorl. Columella smooth, transition to siphonal canal with 1 weak columellar fold. Outer lip with 14 thin but moderately sharp internal lirae, extending far into aperture. Outer lip thick, edge sharp, with weak notch along siphonal canal. Aperture with siphonal canal about 1/3 of total shell length. Siphonal canal twisted, short, broad, open, on outside covered by sharp sculpture. Holotype: MADAGASCAR • dd (27.9 mm long); off Fort Dauphin, ATIMO VATAE stn CP3509; 25° 15' S, 47°07' E; depth 78-79 m; Apr. 2010; ATIMO VATAE exped.; MNHN IM-2000-35086 (Figs 3A-C, 8).

Phos geminus sp. nov. is a large species, up to 37 mm long, characterized by its slender shape with an acute spire and rather narrow body whorl and by the sharp, cancellate sculpture.
Little variability in shape and sculpture is observed. The middle secondary spiral cords may become almost as strong as the primary spiral cords (see holotype), resulting in 23 alternating fine and finer spiral cords on the penultimate whorl; in other specimens these middle secondary spiral cords may be only slightly stronger, resulting in 5 primary spiral cords with 3 finer secondary spiral cords in the interspaces . The number of columellar folds at the transition to the siphonal canal may vary from 1 (holotype) to, occasionally. The colour, however, may range from white and yellowish over pink and orange or purplish to dark chocolate brown .
All authors working with African Photinae have until now referred specimens of this species to Phos roseatus Hinds, 1844. This misidentification is listed in almost every work that covers the Indo-Pacific Ocean. However, P. roseatus from the eastern Indian Ocean and western Pacific differs from P. geminus sp. nov. in its sligtly broader shape, with axial ribs that are slightly broader on the penultimate and body whorls and fewer in number. The weak conchological differences between P. geminus sp. nov. and P. roseatus are the reason why the new species has escaped the attention of most scientists and collectors. The differences in shape and axial sculpture, however, are consistent and one is able to recognize and separate both morphotypes even with a limited amount of material.

This species is restricted to the western Indian Ocean along the East Africa coast, from South Africa in the south to the Red Sea in the north, living in sand, it is syntopic with Phos retecosus Hinds, 1844 off Chagos Archipelago (KF 1636), with P. rhodostoma Von Martens, 1880 at Nacala Bay (KF 2232, KF 3035, KF 4763) and with P. ladoboides sp. nov. at the Seychelles (REVES-2 stn 5 and KF6126).