An arrangement of three Coscinodiscus excavatus var. semilunaris from Newcastle, Barbados. No makers name, but I think this is by JA Long. Olympus BHB microscope using 450nm LED light. I imaged the one in the top, middle, at higher resolution with a 63x Leitz Pl Apo 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 72 images stacked in Zerene (Pmax).
Coscinodiscus excavatus var. semilunaris Grunow, 1884. Original description: Grunow, A. (1884). Die Diatomeen von Franz Josefs-Land. Denkschriften der Kaiserlichen Akademie der Wissenschaften. Mathematisch-Naturwissenschaftliche Classe, Wien., 48: 53-112, 5 pls. Pages 71,73.
Translation of this:
“C. excavatus var. semilunaris Grun.
With only a slight, crescent-shaped elevation and a barely perceptible depression half-enclosed by it. The central meshes are often somewhat larger than the others, and the remaining meshes on the outside are not as noticeably larger as in C. excavatus and the closely related C. crassus. The extent of the crescent-shaped elevation is highly variable; sometimes it is short and broad, but often it encompasses more than half the shell. Fossil from Newcastle Estate, Barbados.”