Revision of the type material of Diploneis zannii Frenguelli (Bacillariophyceae) Author Vouilloud, Amelia A. División Ficología, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Paseo del Bosque s / n, (1900) La Plata, Argentina Author Sala, Silvia E. División Ficología, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Paseo del Bosque s / n, (1900) La Plata, Argentina Author Heguilor, Santiago Laboratorio de Química Ambiental y Biogeoquímica (LAQAB), Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Av. Calchaquí km 23500 (CP 1888) Florencio Varela, Buenos Aires, Argentina text Phytotaxa 2018 2018-06-06 351 3 239 245 http://dx.doi.org/10.11646/phytotaxa.351.3.5 journal article 10.11646/phytotaxa.351.3.5 1179-3163 13707252 Diploneis zannii Frenguelli (1933: 415 , pl. IV, fig. 10) ( Figs 1–23 ) Description: LM ( Figs 1–16 ). Valves elliptic-lanceolate (length 37.5–57.5 μm, breadth 27–36 μm, L/B: 1.7–2.2). Longitudinal canals occupying 1/3 of valve width, together forming a narrow lanceolate area. Striae uniseriate, slightly radial at valve center (8–10/10 μm), strongly radial at poles (10–11/10 μm), interrupted at canals. SEM ( Figs 17–23 ). Raphe filiform ( Figs 17–19 ) with external proximal ends straight located at bottom of a depression ( Fig. 18 ); distal ends curved in obtuse angle ( Fig. 19 ) to the same side. Longitudinal canals with one row of areolae separated from striae by conspicuous hyaline area ( Figs. 17–19 ). Externally, each alveolus opens as a uniseriate stria composed of equidistant areolae (10–12/10 μm) ( Figs 18–19 ). Internally, raphe straight, running through sunken area between longitudinal canals ( Figs 20–22 ); proximal and distal ends simple, helictoglossae slightly developed ( Figs 21–22 ). Transapical ribs straight delimiting alveoli ( Figs 20–23 ). Transapical ribs fungiform in transverse section ( Fig. 23 , arrows). Areolae open in single foramina ( Figs 21, 23 , arrowheads). Type: — ARGENTINA . Corrientes : Itatí Rincón Lagoon , Esteros del Iberá , 28°42’00’’S ; 58°06’00’’W , J. Frenguelli, 24 February 1941 ( lectotype designated here , Frenguelli Collection! 268, slide 268 (3), England Finder: N 47 (4), here illustrated as Figs 14–16 ; Isolectotype designated here : Frenguelli Collection! 268, Slides 268 (1–3, 6, 8, 15, 16).