. Bulletin of the British Museum (Natural History). 16 M. G. LOCKLEY & A. WILLIAMS. Figs 31-34 MonoboUna plumhea (Salter). Fig. 31, paralectotype B5917, latex cast of internal part of exfoliated brachial valve x 2-5; Fig. 32. lectotype GSM 16909, latex cast of internal part of exfoliated pedicle valve x2-5; both from Mytton Flags, White Grit Mine, Shropshire. Figs 33a. b, BB 14404, partially exfoliated valve x 3. and detail of ornament x 8, from Llanvirn Beds, Abereiddy Bay, Dyfed. Fig. 34, B 14376, latex cast of external mould of a ? pedicle valve x4, from Arenig Beds, Tremanhire, St Davi
. Bulletin of the British Museum (Natural History). 16 M. G. LOCKLEY & A. WILLIAMS. Figs 31-34 MonoboUna plumhea (Salter). Fig. 31, paralectotype B5917, latex cast of internal part of exfoliated brachial valve x 2-5; Fig. 32. lectotype GSM 16909, latex cast of internal part of exfoliated pedicle valve x2-5; both from Mytton Flags, White Grit Mine, Shropshire. Figs 33a. b, BB 14404, partially exfoliated valve x 3. and detail of ornament x 8, from Llanvirn Beds, Abereiddy Bay, Dyfed. Fig. 34, B 14376, latex cast of external mould of a ? pedicle valve x4, from Arenig Beds, Tremanhire, St David's, Dyfed. , Figs 35^1 MonoboUna crassa sp. nov. Figs 35a, b, B 5918, latex cast of external mould of a pedicle valve x4, with detail of ornament x8, from Llandeilo shales, Wellfield, Builth. Figs 36-38 and 40, GSM 16902, 16918, 16901 and 16900 respectively, internal moulds of brachial valves all x 2, from Llandeilo shales, Wyeford, Builth. Fig. 39, holotype SM A. 104412, latex cast of internal mould of a brachial valve x2, from Llandeilo shales. Pen Cerrig, Builth. Fig. 41, SM , exterior of a pedicle valve x2, from Nemagraptus gracilis shales, Gwern-y-fed, Builth. no evidence to suggest that the specimens are distinguishable from the type species. The large, thick-shelled paralectotypes are better preserved than the lectotype and exhibit 7 and 9 costellae respectively at 5 mm anteromedially of the umbones; B 14404 also exhibits the distinctive concentric fila characteristic of the type species. Indeed, having examined over 150 recognizable MonoboUna specimens in an old Geological Survey collection from Abereiddy Bay, we have selected twelve specimens (GSM Zs 6259-70) which exhibit the outline, ornament and ventral muscle platform impressions characteristic of the type species M. plumbea. The lectotype (B 14376) of M. plitmbea var. plicata which Davidson. Please note that these images are extracted from scanned page images that may have been digitally enhanced for reada
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