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 dirupta W.Greg. ( Gregory 1857 ) Figs 4 , 35–38 , Table 1 Cocconeis diaphana W.Sm. var. β (“Sidmouth material”). Original description Gregory (1857) : 491, 492, pl. 9, fig. 25 reproduced in Fig. 4 . “Broad short oval to orbicular. Length 25.4 to 61 µm ; breadth 17.8 to 53.3 µm ”. “Valve thick. Median line irregular, like a slit. Wavy longitudinal striae, except the slit. Fine transverse striae. Appearance of a long stauros, which, under a higher power, disappears as such. The striated surface seems to be ‘torn asunder in the middle’. Vertical striae about 26, transverse striae about 60 in 1 c.d.m.”. Type material Lectotype , designated here: slide BM 1420 , labelled “Arran 56” in Greville collection, the only syntype found in BM . Notes Several localities (Glenshira sand, Mr Miles’s Corallina gathering and several dredgings) cited by Gregory in the original description could contain syntypes , but only the one designated as lectotype was found in BM. According to W. Gregory “ C. diaphana […] which was found occurring with C. dirupta […] may perhaps be an imperfect form of C. dirupta […] or possibly [...] the lower valve’ of the latter”, with some further notes that “it is, however equally probable that these forms belong to different species”. LM examination of the type material and completed description Figs 35–38 , from BM 1420: n = 16, valves are 18.3–36.5 (20 ± 6) µm long, 17.2–30.8 (26.6 ± 4.7) µm wide; with 13.5–19.5 (16.6 ± 2) SV striae in 10 µm , and 16–23 (18.9 ± 1.9) RV striae in 10 µm . L/l: 1.12 ± 0.06. Valves thick, round-elliptic to almost discoid. Valves rarely found separate, appearing darkbrown. SV with coarse radiate striae, equidistant, composed of transapically oblong areolae arranged in a zig-zag pattern along longitudinal lines, areolae smaller near the margin. One median stria often shorter on one side of the central area ( Figs 35–36 , arrows). Presence of intercalary short striae near the margin. SV sternum relatively large, fusiform (rarely constricted in its mid-part) with apices often deflected in opposite directions (not illustrated). RV with delicate but clearly identifiable striae, equidistant, strongly bent at the apices, with frequent intercalary short striae near the margin. Raphe almost straight to slightly sigmoid ( Fig. 37 ). RV axial area narrow. Distal raphe fissures close to the margin. Helictoglossae often clearly deflected in opposite directions ( Fig. 37 , arrowheads); presence of a large and narrow transverse fascia (never reaching the margin, formed by one or two shorter striae, Fig. 38 , arrows); proximal raphe endings coarse and relatively close. Figs 35–38. Cocconeis dirupta W.Greg. from BM 1420. 37 . Lectotype illustration. SV sternum lanceolate with apices slightly bent in opposite directions (36), one SV stria lacking on one side (35, 36, arrow), RV striae strongly radiate, RV fascia narrow and extended (38, arrows), helictoglossae deflected in opposite directions (37, arrowheads) and raphe slightly sigmoid (37). Scale bars = 10 µm. Figs 39–44. Cocconeis diaphana W.Sm. isolectotype SEM illustration. Mica labelled as “ Cocconeis diaphana n.sp. , Jersey, Aug. 14. 1852”, deposited in the Van Heurck collection in Meise (BR). SV external view with a reduced central area (39, arrow) and striae composed of transversally elongated alveoli (39). SV internal view (40). Note the SV valvocopula (SVVC) with a smooth edge (40, arrowhead). Detail of the SV apex (41). Detail of a broken SV showing the double layered structure of the alveoli (42). RV external view with the central oblong-elongate central area reaching less than ¼ of the valve width (43, arrow). RV internal view with a low and straight helictoglossa (44, arrow) and the RV valvocopula (RVVC) with a smooth edge (44, arrowhead). Scale bars = 10 µm (39, 40, 43–44), 2 µm (41), 1 µm (42). The complete frustules appear obscure while the separate RV and SV appear translucent, which probably justifies W. Gregory’s hesitation about the existence of a second taxon ( C. diaphana W.Sm. ) in his material. On the other hand the R.K. Greville drawing ( Gregory 1857 : fig. 25) probably superimposed the two valves. Contrarily to the latter drawing ( Gregory 1857 , fig. 25 reproduced in Fig. 4 ), the fascia does not reach the valve margin in the many specimens observed in this study. The slide BM 1420 from Arran 56 (Gregory in Greville collection) is designated here as the lectotype , since nothing else has been traced that could be considered as original material studied by W. Gregory.