. Bulletin of the British Museum (Natural History), Geology. ARENIG IN SOUTH WALES 125 of the cranidial margin. The front of the glabella is almost bluntly rounded about the mid-line, or with a faint suggestion of a point (Fig. 19d). Posterior border furrow deep, not reaching cranidial margin; border widens laterally. Thorax with axis nearly three times as wide as thoracic pleurae; we have found no evidence of a macropleural segment. Structure of pleurae typically shumardiid, with depressed front margin fitting beneath preceding pleura, transverse pleural furrows near back of pleura, and deep,
. Bulletin of the British Museum (Natural History), Geology. ARENIG IN SOUTH WALES 125 of the cranidial margin. The front of the glabella is almost bluntly rounded about the mid-line, or with a faint suggestion of a point (Fig. 19d). Posterior border furrow deep, not reaching cranidial margin; border widens laterally. Thorax with axis nearly three times as wide as thoracic pleurae; we have found no evidence of a macropleural segment. Structure of pleurae typically shumardiid, with depressed front margin fitting beneath preceding pleura, transverse pleural furrows near back of pleura, and deep, downturned facet. Axis hardly tapers backwards. Pygidia in relief are two-thirds to three-quarters as long as wide (long (sag.) half-ring is excluded); flattened examples may appear a little longer as the postaxial field is extended. The axis is very wide (tr.)—half pygidial width at first ring—and transversely convex, with only gentle backward taper to a broadly rounded termination at about 0-7 of pygidial length (again half-ring excluded). Four axial rings are defined by furrows which are distinctly fainter medially (the fourth may be hard to discern); the first three rings are of equal length (sag.). The three pairs of pleural furrows are progressively shorter backwards, the third pair being very short. In the relief material the postaxial field slopes down to a narrow (sag.) flattened border, which becomes narrower away from the mid-line and does not extend to the anterolateral margins. This may be obliterated on crushed material. The holotype shows the extent of the doublure where it is impressed on the dorsal surface; wide on the mid-line, and narrowing rather abruptly to the second pair of pleural Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original British Museum (Natural History). London :
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