FIGURES 51–61 in Planothidium incuriatum sp. nov. a widely distributed diatom species (Bacillariophyta) and type analysis of Planothidium biporomum

FIGURES 51–61. Planothidium incuriatum sp. nov. SEM views. 'Croix au Buis' creek (Yvette River basin, Magny-les-Hameaux, France), BR-4315. Fig. 51. External view of rapheless valve. Fig. 52. Internal view of raphe valve. Fig. 53. External view of raphe valve. Fig. 54. Internal view of rapheless valve. Fig. 55. Internal detailed view of raphe valve central area. Fig. 56. External detail of a raphe valve. Two reduced striae at both sides forming an irregular rectangular central area. Drop-like proximal raphe ends. Striae usually formed by three rows of areolae. Fig. 57. Detail of cavum aperture. Open border attached to the neighbour striae. Fig. 58. Detail of raphe ends. Note the groups of two small areolae located in the valve mantle. Fig. 59. Open non-perforated and ligulated connective bands. Figs 60–61. Detail of striae usually triseriate from the rapheless valve, as well as the areolae located in the mantle. Scale bars: Figs 51–53 = 5 µm; Fig. 54 = 10 µm; Figs 55–56, 60 = 4 µm; Figs 57–59 = 3 µm; Fig. 61 = 2 µm.