This very curious little species is allied to Pleurotoma opalus and ebur, both of Reeve, and cornea nearer to the first named. In the above description I have endeavoured to touch upon the chief characteristics of these three species. I take the one now being described as the type, and have named it as exhibiting the pentagonal arrangement of the ribs most conspicuously. With the aid of a good lens, if the shell be examined from the apex, taking that as the axis of the five acute and projecting ribs, like the spokes of a wheel, it will be seen how very characteristic they are.
Alt. : 11. Diam. : 3 mm.