Nomenclatural changes for three preoccupied Trilobites generaAbstract : Three junior homonyms were detected amongst the Trilobites genera and the following replacement names are proposed: Proacanthocephalus nom. nov. for Acanthocephalus Qiu, 1983; Paleonelsonia nom. nov. for Nelsonia Palmer & Gatehouse, 1972 and Paleoaethia nom. nov. for Aethia Qian & Zhou. Accordingly, new combinations are herein proposed for the species currently included in these genera respectively: Proacanthocephalus longispinus (Qiu, 1983) comb. nov.; Paleonelsonia schesis (Palmer & Gatehouse, 1972) comb. nov. and Paleoaethia rectangula (Qian & Zhou, 1984) comb. nov.