Shell size small, 4.0 to 6.7 mm, shape elongate, ovate to fusiform. Protoconch of 1.5 to 2 bulbous brownish glossy whorls. Teleoconch of 4.5 to 5.5 convex whorls with steep to flat subsutural ramps. Axial sculpture is consisted of a central elevated belly and bilateral depressed slender branched threads. Sutures crenulated and well defined. Siphonal fasciole with 2 to 6 oblique cords. Columella with 4 folds which decrease in size anteriorly. Aperture shorter to much shorter than spire; inner lip thin and smooth; outer lip simple and with lirae, extending externally, inferiorly then medially. Siphonal canal short and wide; siphonal notch distinct. Shell ornamented with two broad deep-colored bands overlying the depressed zone of branched slender riblets, below the suture and on lower half of each whorl. One broad white band overlying elevated central bulk of axial ribs.

REMARKS
"supra costellis plurimis et infra costis latis-instructis" C. B. Adams described the axial arrangement of Mitra exigua with numerous tipper riblets and broader lower ribs. Axial ribs in the extant costellariid genera are raised solitarily and retain gent height and width throughout their length except at the intersection enhanced or deducted by spiral sculpture. The genus Atlantilux n. gen. bears distinct axial ribs of elevated central belly with depressed bilateral branched threads. The axial rib is raised at central part in proportion to the enhancement of spiral cords and is spontaneously split into branched threads at its depressed ends. The numbers of adapical and abapical branched threads show an interspecies variation and range from 1 to 3.
A small Vexillum originally described from Western Australia is mentioned here. Vexillum sinuosum Turner, 2008 is firstly noted for its richly wrinkled subsutural ramp of the whorls, an unequalled character in shells of the Indo-Pacific. The Atlantilux n. gen. differs distinctly through more or less convex whorls, rounded axial ribs enhanced with minute to nearly invisible spiral threads, branched axial threads lacking spiral grooves at both ends of the rounded axial belly, and larger papillose protoconch.

RANGE AND HABITAT
Widely distributed in the Caribbean fauna and adjacent North Atlantic Ocean; from the intertidal zone to the epipelagic zone, fine mud and sand.