Two examples of Actinocyclus pruinosus from New Hebrides (Republic of Vanuatu, South Pacific). No makers name but I understand this is by JA Long. Olympus BHB microscope using 450nm LED light. As well as the arrangement I imaged the left one using 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. 41 images stacked in Zerene (Pmax). An underside view with the rim upwards towards the coverslip.
Actinocyclus pruinosus Castracane 1886. Published in: Castracane, [C.A.] F. (1886). Report on the Diatomaceae collected by H.M.S. Challenger during the years 1873-76. In: Report on the Scientific Results of the Voyage of H.M.S. Challenger during the years 1873-76. Botany. Vol. II. (Murray, J. Eds), pp. [1]-178. Page 144, Plate IV [4], Figure 2.