Article: The atrypidine brachiopod Dayia navicula (J. de C. Sowerby)
The atrypidine brachiopod Dayia navicula (J. de C. Sowerby) is described and a neotype is designated. The musculature is reinterpreted and shown to differ from previous interpretations. Comparisons are made between Dayia navicula s. str. and other forms referred to the species. Between the Ludlow and the Lower Devonian the shells increase in size and incurvature of the umbo becomes less marked.