A replacement name is proposed for genus Dayus Gerken, 2001 (Crustacea: Peracarida: Cumacea), preoccupied by Dayus Mahmood, 1967 (Insecta: click here Hemiptera: Cicadellidae).The following changes are proposed: Jennidayus new replacement name = Dayus Gerken, 2001 (nec Mahmood 1967); Jennidayus pharocheradus (Gerken, 2001), comb.n.= Dayus pharocheradus Gerken, 2001; Jennidayus acanthus here (Gerken, 2001), comb.
n.= Dayus acanthus Gerken, 2001; Jennidayus makrokolosus (Gerken, 2001), comb.n.= Dayus makrokolosus Gerken, 2001.