Diagnosis: Shell of moderate size, depressed conical, weakly carinate peripherally, fragile, brilliantly iridescent under very thin outer porcelaneous layer, color brassy; spire almost flat-sided, sutures weakly impressed; whorls with 2 weak carinae at periphery, visible only on last whorl, with numerous spiral threads above peripheral cords, strongest on first 3 whorls, obscure subsequently; axial sculpture of low riblets on first 1,5 whorls, thereafter almost absent; base weakly convex, with numerous spiral threads, umbilicate; umbilicus wide, defined by strong, smooth spiral cord, aperture rhomhoidal; lips thin with broad, V-shaped posterior sinus, and broad, very shallow. U-shaped basal sinus; anterolateral sinus, if present, probably narrow. shallow and U-shaped, columella thin, very weakly sigmoid, edentate. Type-species: Basilissa lampra Watson. 1879; here designated.
Remarks: The shell of the type-species of this genus is most similar to those of species of Seguenziella Marshall, 1983. Rotellenzia lampra, however, lacks the strong mid-whorl and peripheral carinae which characterize Seguenziella. Moreover, if Schepman's illustration of the radula of R. lampra is accurate, the odd structure of the cusps of the rhachidian and laterals further separates the two genera. However the two genera undoubtedly are closely related, and on the evidence of the radula, both are more closely allied to Seguenzia Jeffreys,1876, than to other genera with similar shell shapes, such as Carenzia Quinn, 1983. If the similarities of shells hold between Rotellenzia and Seguenziella, a narrow, U-shaped anterolateral labral sinus probably exists. However the chipped lip of the holotype of R. lampra prevents direct observation of this feature, and the growth lines give no additional indication, a situation also found in Seguenziella.