Shell to 25.0 mm in length, form and sculpture as in S. erythrogramma; teleoconch of 7 whorls, protoconch missing, sculptured with angulate, elevated spiral cords which number 2 on the penultimate and body whorl with 9-12 cords, some individuals with a fine, thin intermediate spiral thread; interspaces broad and concave, weakly or distinctly axially striate. Aperture equal in height or slightly longer than the spire, smooth within, outer lip fluted on edge, columella narrowly calloused and with 3 oblique folds, anterior fold feeble, siphonal canal straight. White in color, spiral cords lined with brown, holotype with faint brown axial streaks, interior of aperture orange-brown.

On shell characters alone it is difficult to separate the species from S. erythrogramma (Tomlin), except that the body whorl band of dilacerated blotches and axial streaks are almost absent in S. edithrexae. However, in a small percentage of specimens of Z. erythrogramma the color banding and axial streaks were also absent. The holotype of S. edithrexae also has faint brown axial streaks. The radula of S. edithrexae as figured by the author differs quite prominently from the radula of S. erythrogramma and resembles the radula of the tropical Indo-Pacific Z. pretiosa most closely. In Z. edithrexae, the rachidians have 6 cusps and the 4 central ones are about the same size, whereas in the interlirata-erythrogramma group of species the rachidian has two very long central teeth and 2-3 small intermediate denticles. In S. erythrogramma, the third or fourth anterior cusp of the lateral is very long but is considerably reduced in typical Ziba and S. edithrexae.

Range - Galapagos Islands. Subtidal, from 3-30 m.