New Amphicocconeis (Bacillariophyta) from Raivavae and Tahiti Islands (South Pacific) and Porto Belo (Brazil), with re-examination of Psammococconeis Author Riaux-Gobin, Catherine PSL Research University: CNRS-UPVD-EPHE, USR 3278 CRIOBE & Laboratoire d’Excellence ‘ CORAIL’, University of Perpignan, Perpignan, France Author Garcia, Marinês 0000-0003-3564-8045 Departamento de Botânica, Universidade Federal do Rio Grande do Sul-UFRGS, Campus do Vale, Porto Alegre, RS, Brazil marinesgarciabotanica @ gmail. com; https: // orcid. org / 0000 - 0003 - 3564 - 8045 marinesgarciabotanica@gmail.com Author Witkowski, Andrzej University of Szczecin, Institute of Marine and Environmental Sciences, Szczecin, Poland Author Saenz-Agudelo, Pablo 0000-0001-8197-2861 Universidad Austral de Chile, Instituto de Ciencias Ambientales y Evolutivas Valdivia, Region de Los Rios, Chile pablo. saenzagudelo @ gmail. com; https: // orcid. org / 0000 - 0001 - 8197 - 2861 pablo.saenzagudelo@gmail.com Author Coste, Michel French National Institute for Agriculture, Food, and Environment-INRAE (EABX) Author Daniszewska-Kowalczyk, Genowefa University of Szczecin, Institute of Marine and Environmental Sciences, Szczecin, Poland text Phytotaxa 2021 2021-08-02 513 1 30 54 http://dx.doi.org/10.11646/phytotaxa.513.1.2 journal article 10.11646/phytotaxa.513.1.2 1179-3163 5306935 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 ).