Diagnosis: Fusiform, whorls with a strong median keel, body whorl with a feeble second keel, rest of surface with fine spiral lirae; translucent, suffused with light brown, keels pale; length about 18 mm.
Description: Fusiform, aperture slightly longer than spire; spire whorls with a median keel, shoulder slope gently concave, basal slope straight; body whorl weakly bicarinate, base tapering, rather produced; anal sinus shallow, subsutural, forming a sinuous L-shape, labrum thin, slightly incurved, smooth inside, labium simple, columella long and straight, meeting paries at a slight angle, labial callus uniform, well defined, without a parietal nodule. Early whorls smooth save for fine growth lines and the sharp median spiral keel; from about the 3rd whorl weak spiral lirae develop and growth lines coarsen; penultimate whorl with 9-12 thin spiral lirae basally, crossing fine irregular axial riblets, anterior part of shoulder slope smoother, with finer, much weaker spiral threads; peripheral keel weaker on body whorl, which bears a second very feeble keel at the level of suture of the labrum; body whorl anterior to periphery with 44-56 thin spiral lirae, pricked by pliculate growth lines.
Translucent white, suffused with light brown, showing as axial lines in places and forming sinuous flames on the shoulder slope; keels paler than ground colour, forming two white lines on body whorl; labial callus white, protoconch yellowish.
Protoconch damaged apically, 2,5 whorls remaining; each whorl sculptured by curved subsutural plicules and diagonally cancellate threads; basal diameter about 0,7 mm. Teleoconch whorls about 5,5. Dimensions: 17,7 mm x 7,1 mm (holotype).

lsodaphne albolineata is closely allied to I. perfragilis (Schepman, 1913) from Indonesia, but has a much stronger shoulder keel and a weak second one on the body whorl. ‘Mangilia’ tetartemoris Melvill, 1910, from the Persian Gulf is also somewhat similar and probably congeneric, but has distinct, widely spaced axial ribs.

Distribution: Known only from off Monte Belo, Limpopo River mouth, SOUTHERN MOZAMBIQUE, in 230 fathoms, which is here designated as the type locality. Type material: Holotype G2520/T2096, trawled off Mozambique, don. Mrs H. Boswell. Paratype (worn) A70/T2099, trawled off Monte Belo, 230 fathoms, leg. G. Scott.