Navicula cuspidata var. craticula from Warri, Southern Nigeria. Single example on the slide. Prepared by JA Long. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo NA 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 20 images stacked in Zerene (Pmax). Sot sure if the marks on the surface are issues with the adhesive to the coverslip (doesn’t look like this to me) or something else.
As for details on the name, there are a few options.
Navicula cuspidata var. craticula (Van Heurck) H. Peragallo, 1889.
Navicula cuspidata f. craticula M.Peragallo & Héribaud 1893. Published in: Héribaud-Joseph, Frère [J.-B. C.] (1893). Les Diatomées d’Auvergne. pp. [1]-255, 6 pls. Clermont-Ferrand & Paris: Pensionnat des Frères des Écoles Chrétiennes & Librarie des Sciences Naturelle. Page 107, Plate IV, Figure 15.
Navicula cuspidata f. craticula (Ehrenberg) Dippel 1905. Published in: Dippel, L. (1905). Diatomeen der Rhein-Mainebene. pp. [1]-170. Braunschweig: Friedrich Vieweg und Sohn. Page 58.