P. ulyssiponensis with typical low shell, but some P. vulgata have equally low shells. Found feeding on red algal turf with P. vulgata which also had orange interiors but additionally a silver-grey vertex patch diagnostic of P. vulgata (see images Pv05 & Pv07). Sculpture, aperture outline, interior colours and centrality of apex vary and overlap with those of some P. vulgata. Length 17 mm, North Yorkshire, September 2014.