Diagnosis "Oval Oichnus tapering subparabolically from a millimetre-sized external opening to a minute inner one. External opening commonly rhomboid in outline"

Diagnosis – (Emended after Bromley, 1993, pp. 170, 171.) Oval Oichnus tapering subparabolically from a relatively large external aperture to a minute inner one.
Description – Rhomboidal forms with side widths averaging 120 μm. The margins are perpendicular to the substrate surfaces. The borings do not appear to fully penetrate the substrate.

Emended diagnosis.: Penetrative or nonpenetrative Sedilichnus tapering conically from a relatively large external opening to a smaller inner one, or terminating in the host shell as a rounded pit. External opening is oval to rounded rhomboid in outline. In the penetrative form, the internal opening is circular to subcircular or oval in outline (after Blissett and Pickerill, 2007; and Zonneveld and Gingras, 2014).