Cardioichnus planus Smith et Crimes, 1983

Description. Hypichnial mound, subquadrate in outline, with rounded angles and a median longitudinal depression bounded by two low semicircular ridges. The mound is 18 mm long an 16 mm wide. In specimen no. 4017 (Fig. 9E), C. planus is 20 mm wide, 38-43 mm long, and is continuous with Scolicia isp.

Remarks.Cardioichnusis a resting trace of irregular echinoid burrows (Smith and Crimes, 1983).