Jason A. Dunlop¹ and James C. Lamsdell^2
1Museum für Naturkunde Berlin, Leibniz-Institute für Evolutions- und Biodiversitätsforschung an der Humboldt-Universität zu Berlin, Invalidenstraße 43, 10115 Berlin, Germany
²Department of Geology and Paleontological Institute, University of Kansas, 1475 Jayhawk Boulevard, Lawrence, KS 66045, USA

The genus level systematics of the eurypterid family Carcinosomatidae (Chelicerata Eurypterida) is briefly reviewed, with particular reference to some nomenclatural problems associated with homonyms and their replacement names. Eusarcus scorpionis Grote & Pitt, 1875 is the type species of both Eusarcana Strand, 1942 and Paracarcinosoma Caster & Kjellesvig-Waering, 1964. Although Strand's name has been completely overlooked in the eurypterid literature, it remains the oldest available (and valid) name associated with Eusarcus scorpionis. It should be noted that Strand replaced a homonym under circumstances when this was not really necessary, but the Principle of Priority means that we are forced to reclassify three Paracarcinosoma species under his genus name as Eusarcana scorpionis (Grote & Pitt, 1875), Eusarcana acrocephala (Semper, 1898) and Eusarcana obesa (Woodward, 1868); all comb. nov.

Key words: Eurypterida, Fossil, Nomenclature, Homonyms, Embrik Strand.