Sustergichnus Chamberlain, 1971

Description.-Intergenic and endogenic preserved as hyporelief and full relief. A two part, narrow, sinuous, sand filled burrow that usually follows the sand mud interface up to 40mm and seldom goes totally into the underlying mud. Some endogenic specimens cross the interface obliquely without following the interface. Gallery, 1 to 2.5 mm wide, and 1 to 3 mm high; some range from 4 mm wide and 9 mm high to 10 mm wide and 7 mm high. Inner structure is always present. It has an almond-shaped crosssection with vertical apices and a smooth external surface. The outer structure is not always present. It is seldom distinguished on endogenic specimens and may be totally or partially absent on intergenic specimens. The outer structure is in the form of a partial sheath on the inner structure. It is thickest in the middle and thins towards the apices. Numerous fine striae on the exterior cross the surface obliquely, and terminate near the bottom apex. Forward motion is implied as in the direction that the striae convergewith the lower apex.