Grantarhabdus meddii Black, 1971a
Gephyrorhabdus Hill, 1976
The placolith comprises a cretarhabdid pelaga sloping towards the central area, formed of inclined segments that are predominantly weakly clockwise-imbricated, becoming rarely non-imbricate, and a distally arched central area characterised by a diagonal cross supporting a solid distal process. The intercross area lacks lateral bars or pores.
The placolith generally displays first-order, greyish-white interference colours; however, it becomes dimmer towards the periphery, where only the inner layer of the distal shield is developed. In plan view under crossed polars, the outer layer of the distal shield exhibits inclined extinction and length-fast (–) elongation.
Black, M. 1971a. Coccoliths of the Speeton Clay and Sutterby Marl. Proceedings of the Yorkshire Geological Society 38: 381-424.
Hill, M. E. 1976. Lower Cretaceous calcareous nannofossils from Texas and Oklahoma. Palaeontographica Abteilung B Palaeophytologie. 156: 103-179.