FIGURES 49–54 in Surirella arctica comb. et stat. nov. (Bacillariophyta)-a rare arctic diatom

FIGURES 49–54. Surirella arctica, internal views, SEM. Fig. 49 Internal valve view with a broken off girdle band. Fig. 50 Detail of a thickened median area and irregularly spaced transverse costae. Fig. 51 Valve apex with a partial valvocopula sitting on small platforms at the origin of each costa. Fig. 52 Detail of the rectangular portula with a visible raphe canal. Fig. 53 Small specimen with a poorly developed median area. Costae are noticeably irregularly spaced, supporting the valvocopula. Fig. 54 Small valve with noticeably irregularly spaced costae, having one to six rows of striae in between each pair. Small platforms at the origins of each costa are well visible. Scale bars = 10 µm (Fig. 49) or 1 µm (Figs 50–54).