Two Diploneis diatoms. Labelled as LHS Diploneis (smithii) var. rhombica or Diploneis var. dilatata (Navicula smithii var. dilatata), and RHS Diploneis fusca. Prepared by RI Firth and dated September 1970. 63x Leitz Pl Apo 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, slightly oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 29 images stacked in Zerene (Pmax).