Borsonella
Shell with a small, blunt nucleus of one or two whorls, sculpture chiefly spiral, feeble, except for one or two spiral carinae, sometimes with a few small riblets or beads on the principal carina; periostracum conspicuous, smooth or vermiculate; canal wide and very short; outer lip sharp, simple, arcuate; pillar solid, with one strong, nearly horizontal plait continuous upon the whole axis; axis impervious, opei-culum absent. Type Pleurotoma (Borsonia) dalli Arnold, 1903. [= Borsonella omphale Dall, 1919].
There is never more than one plait in Borsonella ; in Cordieria, as restricted by Cossmann, there are never less than two. In Rouaultia the anal sulcus is narrow, sharp, and situated at the shoulder iu the peripheral carina. Both Cordieria and typical Borsonia have a long and slender canal and the general aspect of Gemmula, while Borsonella resembles an Autiplanes with a strong plait on the proximal part of the pillar.