It was first named as Tryblidium unguis and described by Gustaf Lindström in Latin from the Silurian deposits of Gotland in Sweden, in 1880.

The central space of the interior surface is surrounded by an oval ring of six pairs of muscular scars, open anteriorly.

The uppermost pair is more complicated and consists, as in the kindred species, of a more shallow, elongated interior portion, and of a larger exterior one, from the inner corner of which there projects a narrow sinuous groove, directed obliquely upwards and leaving a small, smooth space between itself and the opposite similar one.

The lower, interior part of this upper, muscular scar is pearshaped, wide below, with a narrow, stalklike neck upwards and its surface is finely reticulated by shallow pits and intervening ridges.

Some dark, narrow streaks are directed from the enclosed central space of the shell towards the interstices between the muscular scars.