Nereites (trace fossil) irregularis (Schafhäutl, 1851)

Description. A tightly meandering horizontal ribbon composed of a central, wide zone (the faecal string) and narrow, rarely observed side zones (the envelope zone). In most cases only the central part is visible on the rough surfaces as a ribbon, which is 0.7-2.0 mm wide. The envelope, if visible, is very thin, less than 1 mm wide, with an uneven outer margin and filled with darker sediment than the surrounding rock (locality no. 2). The amplitude of meanders ranges from 13 to 110 mm. Some of the ribbons display a strong tendency to coiling about 70 mm wide (Fig. 8D) which can give an impresion of spiralling (Fig. 8B, locality no. 20). Meanders touch or are rarely separated by up to 10 mm. Very rarely, crossings of the ribbons appear in the same level (Fig. 8C).