Article: Trilobites from the Coniston Limestone Group (Ashgill Series) of the Lake District, England

Five trilobite species from the Coniston Limestone Group of the southern Lake District are redescribed, on the basis of type and topotype material, and one new genus, four new species, and one new subspecies erected. A lectotype of Sphaerexochus? boops Salter is designated and topotype material described; the species is placed in Pseudosphaerexochus. Encrinurus kingi Dean is redescribed and placed in Erratencrinurus, for which a type species is designated; this represents the first record of this genus in Britain. A lectotype of Calymene subdiademata McCoy is selected; material from northern England previously assigned to C. marginata (Shirley) is referred to C. subdiademata. Chasmops marri (Reed) is redescribed and placed in a new genus, Toxochasmops; the pygidium and hypostome are described for the first time. The thorax and hypostome of Acidaspis magnospina Stubblefield are described for the first time and a lectotype designated. Ascetopeltis apoxys sp. nov., Paraharpes whittingtoni sp. nov., Gravicalymene susi sp. nov., Primaspis bucculenta sp. nov., and Tretaspis convergens Dean deliquus subsp. nov. are described. The evolution of T. convergens in northern England and its distribution and relationships with other contemporaneous species of Tretaspis are discussed. Trilobites from the Coniston Limestone Group described by McCoy (1851) are re-evaluated.