Type locality: northern part of the bay of Biscay,
Description. Shell solid, chalky white, consisting of 4-5 whorls, roughly ovate in outline. Apex blunt, almost smooth although very fine spiral lines appear under the microscope. The sculpture consists of axial, nearly straight, ribs crossed by fainter spiral threads, giving the surface a reticulate appearance. Sinus zone not marked. Whorls convex in their upper half, more cylindrical below. Suture deep. Aperture ovate, angulated at the junction between body whorl and columella. Siphonal canal comparatively long, curved towards the columella. Dimensions: height of the shell 7.35 mm, breadth 3.7 mm; height of the aperture 3.9 mm, breadth 1.35 mm.
Remarks. An operculum is present. The animal is blind. O. dictyophora resembles O. tenuicostata a little but is easily separated from that species by having straight ribs instead of curved ones. From O. ovalis, it can be separated by having reticulated instead of mainly spiral sculpture.