Ctenophora vertebra (W.Greg.) D.M.Williams & Van de Vijver, comb. nov. (Figs 53–65)

Basionym: Synedra vertebra (vertebrata) W.Greg . 1855 Quarterly Journal of Microscopical Science 3: 41, pl. IV, fig. 22 (= our Fig. 53)

Synonym: Synedra pulchella var. vertebra (W.Greg.) Van Heurck 1896: 309 (see Smith, 1856: 104, “Synedra Vertebra, Greg. Mic. Journ. vol. 3. pi. iv. 22 = S. pulchella, Synop. xi. 84?”)

TYPE:— SCOTLAND, lacustrine sands, Glenshira, near Inverary (BM 24988!, isotype?, https://data.nhm.ac.uk/object/57f0e08a-1cdb-4262- 99e6-a64d88c254ec)

Registration: http://phycobank.org/104112

Valves lanceolate, tapering towards capitate poles; length ca. 44–104μm, width 2–4μm (Figs 54–7). Sternum very narrow, regular, meeting distinctive ovoid central area, buttressed either sides of valve (Figs 54–7). ‘Ghost striae’ present. Sternum meeting virgae, sternum larger than virgae, vimines reduced in size relative to virgae (Figs 54–7). No data on apical pore fields, rimoportulae or girdle.

Only preserved LM specimens of Gregory’s Synedra vertebra have been available for examination and these are limited to one slide from Dickie’s collection in BM (BM 24988). There are no doubt other specimens. Gregory’s own collection is poorly catalogued in BM and hence difficult currently to use, but it is well-known that the Glenshira material was widely circulated.

Gregory noted of Synedra vertebra that “This form, which is very frequent in the deposit, belongs to the same division as S. pulchella and S. acicularis ” (Gregory 1855: 41); Grunow (1862: 385) included it in his ‘2 Gruppe Ctenophora ’; Van Heurck gave a very brief description including it as a variety of Synedra pulchella (Van Heurck 1896: 309) .