Cocconeis molesta Kütz., C. diaphana W. Sm. and C. dirupta W. Greg. (Bacillariophyta): type material, ambiguities and possible synonymies Author Riaux-Gobin, Catherine CRIOBE-USR 3278 CNRS-EPHE-UPVD, 66000 Perpignan, France. & Laboratoire d’Excellence ‘ CORAIL’, 66000 Perpignan, France. catherine.gobin@univ-perp.fr Author Compère, Pierre Deceased 29 April 2016. Author Jordan, Richard W. Department of Earth & Environmental Sciences, Yamagata University, Yamagata 990 - 8560, Japan. sh081@kdw.kj.yamagata-u.ac.jp Author Coste, Michel IRSTEA, 50 avenue de Verdun, Cestas, France. & The Natural History Museum, Department of Life Sciences, Cromwell Rd, SW 7 5 BD, London, United Kingdom. michel.coste@irstea.fr&j.yesilyurt@nhm.ac.uk Author Yesilyurt, Jovita C. text European Journal of Taxonomy 2016 2016-06-14 204 1 18 journal article 10.5852/ejt.2016.204 9b814d4f-378b-4e95-8144-1e6b183711d5 2118-9773 3840075 Cocconeis molesta Kütz. ( Kützing 1844 ) Figs 1 , 15–20 , Table 1 Cocconeis molesta var. crucifera Grunow ex Cleve (1895: 174) . Type: pl. 30, fig. 23 in Van Heurck ( 1880 –1885). Original description Kützing (1844) : 71, pl. 5, fig. 7. 1–2, reproduced in Fig. 1 “ C. minuta , elliptico-oblonga, densissime aggregata, laevissima; limbo nullo . An Callithamnion cruciatum in den Lagunen von Venedig ! (Laguna Veneta, Italy ) - Länge 1/150–1/140”. – “fig. 1. geglüheten Exemplare, fig. 2. aufgeweichte Exemplare”. Emended description by Van Heurck Van Heurck (1896: 290 , pl. 29, fig. 823) after observation of the original specimen (F.T. Kützing no. 259 in Van Heurck collection): “valves small, elliptic, finely striate; transverse striae about 40 in 1 c.d.m., reaching to the raphe, formed of puncta, distant and consequently capable of forming longitudinal lines undulate or decussate (according to the direction of the illumination). Raphe robust; central nodule elongated into a narrow acute stauros. Length, 1.5 to 2 c.d.m. Breadth, 1 c.d.m. Marine. North Sea”. Type material “An Callithamnion cruciatum in den Lagunen von Venedig ” ( Kützing 1844: 71 ; Kützing 259 , Herbarium sheet BM 000905975 , BM 18381 , holotype ); BR slide IX-43-A13 (Van Heurck collection, Kützing 259 , isotype ). Notes Van Heurck (1896) after studying material from F . T . Kützing, emended the description and stated that the observed specimen “corresponds to the var. crucifera of Grunow ( H . V . H . Atl.: pl. 20, fig. 20)” ( Van Heurck 1880 –1885: pl. 30, fig. 20) and added “it appears to me right to consider it as the type form”. LM examination of the type material and completed description Cf. Riaux-Gobin & Compère (2008) : figs 56–57; Figs 15–17 from BM 18381, Figs 18–20 from slide IX-43- A 13. The frustule is small ( ca. 16.4 µm long, 9.7 µm wide) and strongly arched ( RV concave, SV convex). The RV striation is hardly discernible, with ca. 30 striae in 10 µm ( Fig. 18 , arrowhead). The SV areolae are arranged along axial rows in a zig-zag pattern (22–23 rows in 10 µm , Figs 16, 17, 20 ). The helictoglossae are close to the margin and deflected in opposite directions ( Fig. 15 ), the raphe is straight. The SV sternum is narrow and straight, with a small oblong central area. The RV fascia is narrow and half a valve in length. SEM examination of the Herbarium sheet BM 000905975 The material is very poor and only a broken SV of Cocconeis molesta was observed, with the following morphometrics and features: estimated valve length (> 17 µm ), SV stria density ( 40–42 in 10 µm , Figs 15–20. Cocconeis molesta Kütz. 15–17 . From BM 18381 (15–16: holotype illustration); helictoglossae deflected in opposite directions (15, arrowheads), SV axial rows in a zig-zag pattern (16–17). 18–20 . From IX-43-A13 (H.F. Van Heurck collection), RV striation often difficult to observe (18, arrowhead), RV fascia (19, arrowheads), SV axial rows in a zig-zag pattern (20). Scale bars = 10 µm. areolae small and transversely oblong), apical SV row of areolae, in a zig-zag pattern ( 27.5 in 10 µm ), SV sternum narrow and thickened in internal view, central area slightly enlarged.