Heterorhabdus sinuosus Noël 1970
Retecapsa Black, 1971a
Placoliths are constructed of cretarhabdid shields and a tube cycle with radial, non-imbricate segments surrounding a large central area spanned by an axial cross that supports a distal process.
The inter-cross area is occupied by lateral bars that delimit pores arranged in a single complete concentric cycle, a feature characteristic of Heterorhabdus.
The number of pores is used to distinguish species of Heterorhabdus.
The entire placolith exhibits first-order, greyish-white interference colours. The pelaga of Heterorhabdus shows inclined extinction and length-fast (-) elongation in their natural settling position, in plan view under crossed polars.
Black, M. 1971a. Coccoliths of the Speeton Clay and Sutterby Marl. Proceedings of the Yorkshire Geological Society 38: 381-424.
Noël, D. 1970. Coccolithes Crétacés: La Craie Campanienne du Bassin de Paris. - Éditions du Centre National de la Recherche Scientifique, Paris. 1-129