A strew slide from Griffith Park stream, Fern Dell, Los Angeles, California. Per California Academy of Sciences. Mounted in Aroclor and dated September 1974. Range of species present including Surirella sp. and Hydrosera triquetra. No makers name but this is by Bernard Hartley. Olympus BHB microscope using 450nm LED light. I chose one (a Craticula sp.) for imaging at high magnification. 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. 26 images stacked in Zerene (Pmax).
Craticula sp. I think this is Craticula sardiniana (the ends look too large for it to be C. cuspidata). C. sardiniana published in: Bahls, L. (2013). New diatoms (Bacillariophyta) from western North America. Phytotaxa 82(1): 7-28, 107 figs. C. sardiniana is shown on the Diatoms of North America site here.
There is an entry from Bernard Hartley’s Sample and Strew Slide Collection PDF for this – slide 593 – accessed from here (also screenshotted above).