. Bulletin of the British Museum (Natural History), Geology. 258 R. A. FORTEY & R. M. OWENS Strachan & Khashogji 1984), although how many 'species' it applies to is not resolved. If Jenkins' (1983) wide degree of intraspecific variation is accepted, spinulosus will acquire several synonyms. However, such characters as the shape of the stipe expansion diagram may prove important in discrimination of species, and multivariate statistical treatment of pendents may help in the recognition of species with overlapping ranges of variation. For example, the range of 11 to 25 distal thecae in 1
. Bulletin of the British Museum (Natural History), Geology. 258 R. A. FORTEY & R. M. OWENS Strachan & Khashogji 1984), although how many 'species' it applies to is not resolved. If Jenkins' (1983) wide degree of intraspecific variation is accepted, spinulosus will acquire several synonyms. However, such characters as the shape of the stipe expansion diagram may prove important in discrimination of species, and multivariate statistical treatment of pendents may help in the recognition of species with overlapping ranges of variation. For example, the range of 11 to 25 distal thecae in 10mm shown by Jenkins (1983: text-fig. 1) is extraordinarily large for a single species, but could be produced by overlap of two or more normal curves of lesser span. In any case, we cannot apply any name other than D. spinulosus Perner to these early Llanvirn pendents from the Llanfallteg Formation. Didymograptus (Didymograptus) artus Elles & Wood 1901 (Figs 112b-d, 113) 1901 Didymograptus (Didymograptus) artus Elles & Wood: 48^49, fig. 30; pi. 4, figs 6a-d. 1931 Didymograptus artus Elles & Wood; Bulman: 31, text-fig. 9. 1932 Didymograptus artus Elles & Wood; Boucek: 128, text-fig. 3d-f. 1947 Didymograptus artus Elles & Wood (pars); Ruedemann: 326-327; pi. 54, figs 3-7, 9 [non figs 8, 10]. 1967 Didymograptus artus Elles & Wood; Skwarko: 171-190; pis 21-23. 1973 Didymograptus artus Elles & Wood; Boucek: 85-87, fig. 26e-g; pi. 15, fig. 7. 1976 Didymograptus artus Elles & Wood; Legg: 28; pi. 9, figs 1-6. 1979 Didymograptus cf. artus Elles & Wood; Mu et al.\ 64; pi. 21, fig. 2. Holotype. SM A17772, as specified by Elles & Wood (1901: 49). Type locality and horizon. Early Llanvirn; Thornship Beck, Shap, Cumbria. Occurrence in south Wales. Llanfallteg Formation, the first pendent to appear at the Arenig-Llanvirn boundary. On type section, loc. 52, and at loc. 50, Cefn-maen-llwyd. Elles & Wood figured the species from Ramsey Island, and if s
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