. Bulletin of the British Museum (Natural History), Geology. . - JfcflL, . â Fig. 18 a-i, Shumardia (Shumardia) gadwensis sp. nov. Middle Arenig (Whitlandian, G. gibbsii Biozone); a, b, cranidium, internal mould but well-preserved, with original relief preserved on right side, dorsal and anterior views, Afon Ffinnant Formation, loc. 17, x 12, It. 19576; c, cast from holotype, somewhat compressed small dorsal exoskeleton, mudstones in Nant-y-Gadwen, Llyn, north Wales, x 12, ; d, poorly-preserved but not distorted dorsal exoskelton, showing thoracic segments, Penmaen Dewi Formation, near
. Bulletin of the British Museum (Natural History), Geology. . - JfcflL, . â Fig. 18 a-i, Shumardia (Shumardia) gadwensis sp. nov. Middle Arenig (Whitlandian, G. gibbsii Biozone); a, b, cranidium, internal mould but well-preserved, with original relief preserved on right side, dorsal and anterior views, Afon Ffinnant Formation, loc. 17, x 12, It. 19576; c, cast from holotype, somewhat compressed small dorsal exoskeleton, mudstones in Nant-y-Gadwen, Llyn, north Wales, x 12, ; d, poorly-preserved but not distorted dorsal exoskelton, showing thoracic segments, Penmaen Dewi Formation, near intrusion, north of Whitesand Bay, x 6, ; e, g, pygidium () and cranidium () on same slab, internal mould and latex cast from counterpart showing undistorted proportions of pygidium; note occipital spine on small cranidium, loc. as Fig. 18a, x 15; f, h complete exoskeleton, slightly distorted by tectonic extension, dorsal and lateral views, locality as holotype, Fig. 18c, x 14, ; i, small exoskeleton, internal mould, Dwyrhos Quarry, Llyn, north Wales, x 20, It. 19578. j-k, Shumardia (Shumardia) sp. A. Upper Arenig (Fennian); j, pygidium, Pontyfenni Formation, (S. abyfrons Biozone), loc. 38, x 14, ; k, cranidium, same locality, x 12, 1, Leioshumardia sp. A; dorsal view, Middle Arenig, Whitlandian, Afon Ffinnant Formation, loc. 17, x 14, It. 19583. The smaller complete specimen apparently shows five thoracic segments. The larger (Fig. 180 one is not well preserved but shows a ring-like structure behind the occipital ring which could be interpreted as evidence of a sixth segment. A poorly preserved but otherwise undistorted specimen from Whitesand Bay (Fig. 18d) shows six thoracic segments also, as does a small specimen (Fig. 18i) from Dwyrhos Quarry, Llyn. None is macropleural. The axis tapers back- wards after the third segment. Pleural furrows are short, not extending onto the downturned, faceted pleural tips. Axial taper cont
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