Amphicocconeis catharinensis Riaux-Gobin & Garcia. SEM

Amphicocconeis catharinensis Riaux-Gobin & Garcia. SEM, Figs 7–17. Table 1 Description:— SEM.Valves robust, oval-elliptic, with round apices. Valve length 18 ± 3 µm, 14–22 µm. Valve width 11 ± 2 µm, 9–13 µm; n = 10 (SEM) (Table 1). SV: surface convex, striae radiate and regularly spaced, uniseriate, composed of large rectangular areolae. On the valve face, each areola is positioned on the bottom of a depression with opening bordered by digit flaps (Figs 8–9). Areolae are internally closed by hymenes (Figs 10–12). On the mantle, each oblong areola is separated from the next by a granular and concave plain structure of triangular to rectangular shape (Figs 8–9, arrows). Short marginal striae not observed. 11 ± 1 SV stria in 10 µm. SVVC relatively narrow with big pores corresponding to each areola. RV: surface flat, striae radiate, composed of macro-areolae (large along the margin, short along the raphe, with short areolae dispersed in between, Fig. 13). Terminal-distal raphe endings strongly curved on same side (Figs 13, 15). Proximal raphe endings slightly enlarged and curved on same side (opposite to the terminal raphe endings, Fig. 16). 26 ± 2.5 RV stria in 10 µm. RVVC 1/4 of the valve width, with marginal transapical oblong pores corresponding to each macro-alreola (Fig. 17, twin arrowheads). Remarks:—The SV of Amphicocconeis catharinensis was illustrated as being the SV of Psammococconeis disculoides in Garcia (2001: figs 21, 23). The specific ornamentation of the SV mantle, with a concave structure in between each oblong areola (Figs 8–9) seems unique. The RV of A. catharinensis has some similarities with that of A. disculoides and A. debesi (large area with short radiate macro-areolae), but these short areolae in median-area are in very low density in A. catharinensis (Fig. 13), furthermore the SV of A. catharinensis is highly dissimilar to that of Amphicocconeis disculoides (Hustedt) De Stefano & Marino (figs 2–3, 6– 7 in De Stefano & Marino 2003; Figs 1). Type locality:—Zimbros, Peninsula do Porto Belo, Santa Catarina State, Brazil. Holotype:—Stub 4 19/06/2020, BM001222889. Holotype specimen illustrated in Fig. 7. Etymology:—The epithet refers to the location of the type habitat of this taxon in Brazil (locality Santa Catarina State).