The stratigraphy and structure of the Silurian (Wenlock) rocks south-east of Hawick, Roxburghshire, Scotland

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Abstract
From Dr R. B. Rickards: Work on the Cautley area undertaken during the last few years, and completed since the reading of Dr Warren's paper, has shown that the graptolite zones recognized by Watney & Welch (1911; and see Warren 1964, p. 207) are in need of considerable revision. Cyrtograptus rigidus of Watney & Welch is very close to C. symmetricus Elles (1900 ). But it has been shown that the latter species is conspecific with C. rigidus Tullberg ( v . Gortani 1922 ); and this has been confirmed by other workers (e.g., Bouèek 1933 ). The species described by Elles (1900) and Elles & Wood (1913) as C. rigidus is distinct from C. rigidus Tullberg (1883) and has been renamed C. ellesi by Gortani (op. cit.). The zones established by Elles in the Welsh Borders, therefore, now read, from the base up: C. murchisoni, M. riccartonensis, C. rigidus, C. linnarssoni, G. ellesi, G. lundgreni (see Bouèek, 1933 ; Evans 1961 ). However, although rigidus sensu Watney & Welch is very close to rigidus Tullberg, it is intermediate in some characters between the latter and C. ellesi Gortani. Furthermore, as shown below, it occurs at an intermediate horizon, namely the zone of C. linnarssoni, and may represent an evolutionary stage leading from rigidus Tullberg to ellesi Gortani. Its intermediato nature was appreciated by Watney & Welch (1911, p. 234) and also by Elles herself, since a specimen in the Sedgwick Museum (a 22459) presented by Wood, is labelled ' C. symmetricus mut. cautleyensis Elles MS'. The

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