Triceratium lineatum f. biangulata (labelled as Triceratium lineatum on the slide) from Forrester’s Hill, Oamaru, New Zealand. Single example on the slide. Mounted in Naphrax and dated 13/10/[19]71. Prepared by Richard Gosden. Olympus BHB microscope using 450nm LED light. 40x Leitz Pl Apo NA 1.00 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 46 images stacked in Zerene (Pmax). I couldn’t get close enough with the 63x Leitz Pl Apo NA 1.4 objective, so resolution is slightly limited in this image.
Triceratium lineatum f. biangulata Laporte & Lefebure, 1930. Original description: Laporte, L.J. & Lefébure, P. (1930). Diatomées rares et curieuses, Vol. 2. Paris, pls 16-30. Plate 26, Figure 185. Also see Trigonium lineatum f. biangulata (Laporte & Lefebure) Desikachary & Sreelatha, 1989. I think this is also known as Trigonium lineatum var. lineatum f. biangulata.