Shell very large, thick, conical, with numerous flat-sided whorls sculptured with spiral grooves; shell base with concentric cords and deep channel around columellar pillar. Aperture narrowly ovate, tangential (perpendicular) to shell axis with twisted, channeled columella, and outer lip curved toward centrally placed, short siphonal canal. Operculum corneous, circular and multispiral with central nucleus. Lateral tooth with broad lateral lamella. Snout very long with small buccal mass and very small taenioglossate radula. Rachidian tooth ovoid with broad cen¬tral cusp. Mantle with siphonal light-sensory organ (pallial eye). Ovipositor on right side of foot in females. Pallial gonoducts completely open, highly complex. Zygoneurous nervous system. Egg capsules deposited in gelatinous strings.

Telescopium telescopium and Campanile symbolicum Iredale, 1917, have convergent shell morphologies and were placed in the same group in some of the older monographic literature. The shells of many extinct Campanile species also resemble Telescopium, but recent studies have shown that the campanilid group constitutes a superfamily of its own (Houbrick, 1989). Telescopioidea Sacco, 1895:56 (Type species, by o.d.: Cerithium charpentienBasterot, 1825) and Campanilopsis Chavan, 1948 (Type species, by o.d.: Cerithium ceres Orbigny, 1847) were proposed as subgenera of Telescopium, but both should be excluded from it because their respective type species are members of Campaniloidea. A number of Italian Tertiary fossils lacking apertures were allocated to Telescopium by Sacco (1895), who noted that they differed sufficiently from Recent Telescopium to warrant establishment of a subgenus, Telescopioidea Sacco, 1895, to accommodate them. Sacco (1895) noted that they more closely resembled living Campanile symbolicum than they did Telescopium; examination of these taxa confirms that they should be regarded as members of the Campanilidae. Authors such as Adams & Adams (1858:291) frequently included Campanile symbolicum Iredale, 1917 (cited as Cerithium laeve Quoy & Gaimard, 1834) in the genus Telescopium.

Telescopium was thought to date from the Late Cretaceous (Turonian) by Cossmann (1906:123), but most of the fossils attributed to this genus are campanilids. The earliest species that appears to belong to Telescopium as now understood is a Miocene fossil, Telescopium pseudobeliscus (Grateloupe, 1832). Recent Telescopium is a monotypic genus. The genus appears never to have been speciesrich, but some fossil species have been described.