The 104 Forms type slide created by Klaus Kemp is still with me and I found the opportunity to experiment a bit more with darkfield, an 100x iris objective and (circular) oblique light. After a lot of fiddling around I found a setup that provided images with detail as well as a more 3-dimensional appearance. Here are the first six:
1 Arachnoidiscus ornatus
2 Auliscus sculptus
3 Triceratium favus
4 Amphitetras antediluviana
5 Eupodiscus radiatus
6 Coscinodiscus jonesianus
And next:
7 Artinoptychus splendens
8 Actinoptychus senarius
9 Stephanodiscus niagarae
10 Cocconeis pediculus upper valve (l) and lower.
11 Triceratium pentacrinus
12 Stephanodiscus hantschii
And to conclude, three more with differential interference contrast: