A Navicula sp. from Zebu, Philippines. Single example on the slide. Marine material. No makers name. Olympus BHB microscope using 450nm LED light. 63x Leitz Pl Apo NA 1.4 objective, oil immersion. Olympus Aplanat Achromat condenser, oil immersion, oblique lighting. 2.5x Nikon CF PL photoeyepiece. Monochrome converted Nikon d850 camera. 54 images stacked in Zerene (Pmax).
As for what this is, after looking through Schmidt’s Atlas, I think it might be Navicula samoensis. Navicula samoensis Grunow 1877. Published in: Schmidt, A.[W.F.] (1877). Atlas der Diatomaceen-kunde Series II: Heft 13. pp. pls 49-52. Aschersleben: Verlag von Ernst Schlegel. Plate 50, Figures 43,44 (especially 44). Nomen. This name is currently regarded as a synonym of Caloneis samoensis (Grunow) Cleve 1894. Published in: Cleve, P.T. (1894). Synopsis of the naviculoid diatoms. Part I. Kongliga Svenska Vetenskapsakademiens Handlingar Series 4 26(2): 1-194, 5 pls. Page 60. This is present in the Philippines according to Mann, A. (1925). Marine diatoms of the Philippine Islands. Bulletin United States National Museum 100(6, part 1): 1-182, 39 pls.