Sehr klein, schlank, zylindrisch-spindelförmig. Spira ziemlich hoch (etwa 1/2 der Höhe. Mit gekipptem Apex. Umgänge flach mit tiefen Nähten, fast glatt. Mündung birnförmig, Lippe senkrecht, sehr dünn. Spindel schwach gedreht, unten gestutzt und ausgeschnitten. (F. Nordsieck)

As Lissactaeon:
Shell colorless, slender, with fairly high spire and deep suture, sculptured with fine spiral lines; aperture about half as long as the shell; columella somewhat twisted, swollen above. Animal unknown.
L. exilis (Jeffreys), in the Mediterranean Sea and Atlantic Ocean.
Crenilabium Cossman, 1889, has a similar form; the columellar margin shows a few fine transverse folds.

DIAGNOSIS. — Shell morphology. Shell external, fragile, oval to elongate; spire short or elevated. Aperture longitudinal, anteriorly rounded. Columella with no folds. Operculum present.
Anatomy. Radula with or without a rachidian tooth and unicuspid lateral teeth with or without denticles. Jaw with unicuspid elements with or without denticles.
REMARKS. — The genus Crenilabium was introduced by Cossmann (1889) for Acteon aciculatus Cossmann, 1889, a species of Acteonidae from the Eocene of the Paris Basin with an elongate shell with a very high spire and light sculpture. The following year, Monterosato (1890) described the new genus Lissacteon based on the recent species Acteon exilis Jeffreys, 1870, also characterized by having an elongate shell with a high spire. Pilsbry (1895-96), based on conchological characters, considered Lissacteon to be a synonym of Crenilabium. Bouchet (1975) redescribed A. exilis providing anatomical information that justified the maintenance of this species in its own genus, mainly because of the presence of a rachidian tooth in the radula and unicuspid lateral teeth. Bouchet (1975) also agreed in considering Lissacteon a synonym of Crenilabium but at the same time indicated that this synonymy could not be completely confirmed because of the lack of anatomical information from the fossil species.
I here maintain Lissacteon as a synonym of Crenilabium and use this name for species with a rachidian tooth in the radula and lateral unicuspid teeth. As discussed by Rudman (1971c) and Bouchet (1975) the shell of the Acteonidae does not seem to provide useful systematic information beyond the species level, so species with different shell morphologies are here included in Crenilabium.