(Ehrenberg)
Shell conical to campanulate. Cephalis subspherical, sparsely perforated, usually with 2 spines. Thorax conical to cylindrical, with circular (proximally) to quadrate (distally) pores increasing in size toward the base. Abdomen, when present, flared out, wider than thorax, with quadrate pores.
Petrushevskaya (1967) described 3 subspecies of this form, of which Cycladophora davisiana (Ehrenberg) davisiana Petrushevskaya (Cycladophora davisiana 2, left drawing) and Cycladophora davisiana (Ehr.) cornutoides (Petrushevskaya) (Cycladophora davisiana 2, right drawing) are often used in current literature (the last one is probably synonymous with Artostrobus jorgenseni). Shell height: ca. 100 µm.
Ref.: Riedel (1958), Petrushevskaya (1967), Bjørklund and Ciesielski (1994).