Shell small, slender, white, eight-whorled; nucleus milk-white, strongly transversely plicate below, above smooth, rounded ; spiral sculpture of (on the last whorl 18) strong rounded threads, of which four or five are visible on the upper whorls; these are slightly swollen, but not keeled, where they pass over the ribs; between these are numerous fine close-set threads slightly marked by inconspicuous lines of growth. The transverse sculpture consists of (on the last whorl 10) rounded rather close stout ribs which pass clear over the whorl and are straight and slightly larger behind ; suture appressed and wavy, conspicuous ; canal stout, slightly twisted, aperture subovate, marginated ; outer lip internally lirate with two or three strong denticles anteriorly; inner lip smooth, or slightly granulous. Max. Ion. of shell, 24.0 mm ; of last whorl, 16.5 mm ; of aperture and canal, 12.5 mm; max. lat. of shell, 9.0 mm.

Shell small (up to 24 mm), solid, whitish, consisting of 7-8 unkeeled convex whorls. Suture wavy, appressed. Protoconch milk-white, consisting of 1 1/4 whorls, smooth, final part (about 1/4 whorl) with strong axial riblets. Diameter: 0.8-1.0 mm. About 7-10 prominent, rounded and broad axial ribs on all whorls reaching from suture to suture; up to 10 on body whorl separated by rather narrow interspaces.
Spiral cords strong and rounded, slightly swollen where they pass over the ribs. About 15-18 spiral cords on body whorl including siphonal canal. On first two teleoconch whorls with 3 cords, 4 on the following whorls, 4-5 on penultimate whorl. Between these cords are numerous fine close-set threads. Both margins of the suture are bordered by a thread and appressed to each other in a wavy line. Aperture ovate, outer lip thickened, with some strong internal lirae and two or three white denticles anteriorly; inner lip slightly crenulated, sometimes smooth. Siphonal canal stout, rather short, about as long as the aperture length.

This species recalls F. bocagei Fischer, dredged by the Travailleur in about 500 fms., but that species, from an authentic specimen, is shorter, stouter, with only seven transverse ribs and three principal spiral threads on the spire. The fine spirals in F. Bocagei are also more conspicuous. F. aepynotus has a little the aspect of F. carolinensis Verrill, especially the young ones, while differing in many details, especially the number and straightness of the ribs. Its nearest relative would seem to be a form named by Borson Fusus lamellosus, from the Tertiary of Modena; but this is merely the young of F. rostratus, and the adult has very different characters.

A common species in the waters around Florida, but rather rare in private collections due to its small size. F. benthalis (Dall, 1889) can be distinguished from F. aepynotus by having a clearly smaller and more slender shell, a larger number of much narrower and weaker axial ribs, a weaker spiral sculpture with usually only three strong spiral cords, and by a different protoconch morphology.
The new species F. thompsoni is smaller in size, has a sharper and different spiral sculpture, the axial ribs are narrower and less numerous, the spire angle is narrower, the suture deeper incised, the whorls more convex, and the protoconch completely different (1 3/4 whorls, first half whorl smooth, 1 1/4 whorls strongly plicated).

Gulf of Mexico, SE Florida, Florida Keys.
Type locality: Florida Keys, off Sombrero Key, (24227,34"N,8P06,40MW), 128 m.