Chiastozygus spissus

Chiastozygus spissus Bergen in Bralower & Bergen, 1998

In plan view under crossed polars, the wall, proto inner wall, and outer rows of the diagonal cross exhibit whitish-grey interference colours, whereas the median rows of the diagonal cross remain in constant extinction in the same orientation.

Species of Chiastozygus are characterised by a single wall and a proto inner wall enclosing a central area that is almost completely occupied by a diagonal cross whose arms consist of three rows of longitudinal segments. The median row is markedly narrower than the adjacent rows.

Bralower, T. J. & Bergen, J. A. 1998. Cenomanian–Santonian calcareous nannofossil biostratigraphy of a transect of cores drilled across the Western Interior Seaway. In: Dean, W. E. & Arthur, M. A. (Eds.) Stratigraphy and paleoenvironments of the Cretaceous Western Interior Seaway. SEPM Concepts in Sedimentology and Paleontology. 59–77.