Heimdallia chatwini Bradshaw, 1981

Description: Vertical or steeply inclined backfilled burrows measuring 6-25 mm in width (measured in horizontal plane) but usually 10 mm wide, and descending approximately 130 mm down into the sediment (Fig. 40). Internal structure of concavo-convex packets of sediment 3--4 mm thick, vertical or inclined towards the concave face (suggested direction of movement) (Fig. 41). Internal structure not always visible and burrows often weather out on bedding planes as featureless straight to gently curved ribbons (Fig. 42) traceable for up to 3 m. Sudden changes of direction are not uncommon (Fig. 43, 44) and probably occurred to avoid adjacent burrows. When visible, the bottom of the trace is slightly irregular with local deeper "pits" (Fig. 45). In 1 instance, a backfilled burrow, 17 mm wide, was seen to terminate in a shallow circular pit of the same width (Fig. 40).