 Her work on the taxonomy and evolution of graptolites, using material from North Wales and the Skiddaw Slates of the Lake District, England and from the Wenlock Shales of the Welsh borders, was of fundamental importance.One of her innovations was to examine fossil communities rather than only individuals.She also worked on the stratigraphy of the Lower Palaeozoic, using graptolites as a tool to delineate time-zones.