Penion benthicolus: Although this species agrees with the ormesi series in sculpture and shape, it has an operculum without the white callus along the outer margin of the muscle scar, and apparently has a white protoconch. Thus it comes between the two series of Powell (1947). Fleming (1954. p. 1057) has shown that Penion should be used for the group of shells previously known as Verconella.

Penion benthicolus: Shell small for the genus, rather like chathamensis Powell but with much finer sculpture. Whorls 7,5 in holotype, protoconch missing; the smaller paratype has a protoconch of 3,5, slightly convex, white whorls followed by 6 shell whorls. Height of aperture plus canal. 1,14 to 1,19 times the height of the spire (holotype 1,17). Whorl outline strongly convex, slightly subangled below the suture. The sculpture consists of very hue spiral grooves which are comparatively equally developed, there being no primary spirals. These spirals number from 20 to 30 per centimetre on the penultimate whorl. There are also low, regular, vertical axial folds on the spire whorls, becoming obsolete across the body whorl. The larger paratype is somewhat worn and loses these axials earlier. There are 16 to 19 axials on the penultimate whorl. The columella is strongly twisted. Colour chalky white in the holotype (living shell) and larger paratype, light orange in the smaller paratype. Colour of aperture and the inner lip orange in the smaller paratype. The holotype has a raised tooth-like callus high up on the parietal wall, but this is obviously the result of an injury. Spire angle 42° (holotype), 40° and 41° in paratypes. Holotype : Height: 102 mm. Diameter 38 mm.; Spire 47 mm.