On the basis of the radula, operculum, and selected features of shell morphology, the concept of this genus has been broadened to include not only those species with palmately digitate shell projections, as in the type species, but also those with nonpalmate spines, such as H. oxyacantha.
The shells are of moderate size (maximum length 70 mm), and robustly or more narrowly fusiform. The spire is moderately low to moderately high, consisting of a comparatively extensive protoconch and three to five shouldered post-nuclear whorls. The body whorl bears five to ten spinose varices. The spines may be distally palmate or nonpalmate. The suture is unimpressed but is set in an excavated region that is most apparent behind each strongly buttressed varical shoulder portion. The aperture is small to moderate in size and generally subcircular. The canal is lightly scaled by overlapping, or is very narrowly open. The anal sulcus is weakly indicated or entirely lacking. The columellar lip is detached, weakly erect, and smooth; at its anterior end it is thickened into a knob, the thickening resulting in the formation of an oblique sulcus leading directly into the siphonal canal. In profile, the ventral surface is more or less broadly arcuate.
The ocenebrine operculum is generally subcircular. The nucleus on its exterior surface is more or less near the right margin and halfway between the anterior and posterior ends. Opposite the nucleus, the interior surface has an oval, depressed area, and is irregularly, concentrically ridged; the remainder of the interior is somewhat thickened and polished.
The lateral radular teeth are typically muricoid and not unusual in size or other features. The rachidian tooth is muricine but is remarkable for the shortness and bluntness of its cusps. The central cusp is the longest, the laterals are almost as long, and the intermediates are so small and have become fused to such an extent with the laterals that they are generally little more than short appendages or simple lumps on their inner edges.