ON DAVIESIELLA CARINATA (Garwood)

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I. INTRODUCTION. The purpose of this paper is to describe the external and internal characters of the brachiopod Daviesiella carinata (Garwood), characters which are of interest both from a morphological and from a taxonomic point of view. This brachiopod has usually been referred to in the literature as Chonetes carinata Garwood, and it was selected by Professor E. J. Garwood as the index-fossil of the Upper Michelinia Beds in the North-West of England (1, pp. 452 et seq.) In later sections of this paper, some details of variation within the species and of the distribution and zonal value of the species will be given. In 1916, Garwood figured a ventral valve of a brachiopod to which he gave the name Chonetes carinata, but his figure was not accompanied by a description (2, Pl. 14, fig. 4). Not possessing specimens which exhibited internal characters, Garwood naturally referred the brachiopod to the genus Chonetes Fischer von Waldheim upon the external characters which were observable. Apparently, specimens showing details of internal structure have never been forthcoming, and in 1930 M. G. Delepine remarked: “Les caracteres internes de cette forme n’ayant jamais encore pu etre observes” (3, p. 13). Delepine there considered Daviesiella carinata to be a variety of D. comoides (Sow.). II. NATURE OF MATERIAL AND METHOD OF INVESTIGATION. In the course of a detailed study of the British Carboniferous species of the genera Chonetes and Daviesiella, the author has formed a large collection of specimens referable to Daviesiella carinata and he has ...