. Bulletin of the British Museum (Natural History), Geology. Fig. 57 Pricyclopyge binodosa eurycephala subsp. nov. Upper Arenig, Fennian, B. rushtoni Biozone, Pontyfenni Formation, loc. 23. a, b, holotype, perfectly preserved cephalon, dorsal and lateral views, x 6, ;c,pygidium in full relief, x 3, There is a stratigraphical intergradation, but the two forms are distinct between the rushtoni Biozone and the Llanvirn. The maximum cranidial width of the median cephalic lobe in P. binodosa eurycephala is behind cranidial mid-length, as measured along the sagittal line. On P. b.
. Bulletin of the British Museum (Natural History), Geology. Fig. 57 Pricyclopyge binodosa eurycephala subsp. nov. Upper Arenig, Fennian, B. rushtoni Biozone, Pontyfenni Formation, loc. 23. a, b, holotype, perfectly preserved cephalon, dorsal and lateral views, x 6, ;c,pygidium in full relief, x 3, There is a stratigraphical intergradation, but the two forms are distinct between the rushtoni Biozone and the Llanvirn. The maximum cranidial width of the median cephalic lobe in P. binodosa eurycephala is behind cranidial mid-length, as measured along the sagittal line. On P. b. binodosa maximum width is attained at, or in front of, cranidial mid-length. The glabellar tubercle, and the circular depressions to either side of it, are variably preserved, and no taxonomic importance is attached to their absence on certain specimens. Palpebral rims are always clearly defined. One specimen (Fig. 56e) shows the glabella only gently expanding in width at first near its posterior margin but still attaining maximum cranidial width behind cranidial mid-length. On the entire undistorted cephalon (Fig. 57a) maximum cephalic width of P. b. eurycephala is far forwards in comparison with the perfectly preserved cephala of P. b. prisca illustrated by Marek (1961: pi. 1, fig. 20; pi. 2, fig. 1), on which maximum width is near the back end of the cephalon in dorsal orientation. Specimens of this quality are rare, however. These subtle differences are worth taxonomic recognition, because they are of stratigraphical importance: P. b. eurycephala is apparently confined to the Fennian, where Pricyclopyge is one of the commoner Fig. 58 Pricyclopyge binodosa binodosa (Salter 1859), for comparison with P. binodosa eurycephala subsp. nov. a, axial shield, slightly distorted, showing forward expansion of median glabellar lobe, Llanvirn above Llanfallteg Formation, St Clears, Dyfed, x 2, NMW ; b, transition cephalon between P. binodosa binodosa and P. b. euryce
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