Small to relatively large trivaricate shells (50—200 mm in length), with extremely long siphonal canal, usually as long or longer than length of spire + aperture. Siphonal canal consisting of terminations of previous canals fused into an almost closed tube. Usually nine angulate or rounded ribs on early teleoconch whorls, of which every third is strengthened into a varix leaving, initially, two intervarical nodes. Ornamentation on varices of simple, non-ramose spines. Outer lip of aperture with labral tooth in all species except those in subgenus Promurex. Inner lip usually rather narrow and always smooth. Operculum with terminal to subcentral nucleus, growth lines simple to lamellate. Radula with central teeth having three simple, primary cusps, central longest, with two short intermediate cusps between. No accessory denticles developed. Marginal teeth with expanded, overlapping bases. Ejaculatory duct closed, muscular, usually partly embedded in body wall. Radular sac markedly shorter than buccal mass. Accessory salivary glands very small, possibly absent in some species.