The Middle Cambrian paradoxidid trilobite Hydrocephalus from Jämtland, central Sweden

A new paradoxidid species, Hydrocephalus vikensis, is described from the lower Middle Cambrian praecurrens Zone in Jämtland, central Sweden. It is contrasted with typical Hydrocephalus species and shows features that recall Paradoxides. The genus Hydrocephalus Barrande is discussed; the validity of the related genus Rejkocephalus Kordule is considered to be doubtful. The associated fauna is listed and an agnostoid that differs slightly from Condylopyge regia (Sjörgen) is illustrated.