An arrangement labelled “Diatoms selected from Oamaru deposit, Jackson’s Paddock” and “Triceratium lineatum (2 and 3 angles)”. Mounted in Styrax (very yellowed which made imaging with 450nm light ‘interesting’). More on the name in a minute. No makers name. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo 1.4, oil immersion for the smaller one, and 40x Leitz Pl Apo NA 1.00 objective, oil immersion for the larger one. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monbochrome converted Nikon d850 camera. Image stacks prepared in Zerene (Pmax).
Back to names. The slide is labelled “Triceratium lineatum“. Initially I thought there were 2 diatoms on here, but there is a third which is edge on. The two main diatoms look similar, but I think these are different.
The smaller one is I think Trigonium lineatum (the new name for Triceratium lineatum). It is an underside view, with the rim towards the coverslip. 79 images stacked.
The larger one is I think Trigonium taeniatum (as is the one on it’s edge, visible in the 10x objective image). This is top side upwards (rim downwards). 112 images stacked. Trigonium lineatum has also been referred to as Trigonium lineatium var. taeniatum.
Why do I think these are different? It comes down to the bands in each of the three apices on the diatoms. T. lineatum has 3, which T. taeniatum has 4 (see Desikachary and Sreelatha’s Oamaru book or the Oamaru Diatoms website – here) for examples. In fact the T. taeniatum has the start of a 5th band in 2 of its apices. So, basically a really nice slide showing examples of two similar but not identical diatoms.