Nereites irregularis

Nereites irregularis (formerly Helminthoida labyrinthica and Helminthoida crassa) is a type of trace fossil found on sedimentary rocks. They are relatively small Nereites characterized by large numbers of closely packed deeply meandering trails that tend to coil. The trails are usually horizontal and may be regular to irregular in guidance. The central tunnel is usually thicker than the envelope zone. In dense meanders, the envelope zone may touch or overlap, but it displays low-amplitude lobes in looser meanders.

Nereites irregularis has not been matched with known modern organisms, but they are generally believed to have been grazing trails (pascichnia) made by worms.