Correcting a 135-year error: Limulidae Leach, 1819 (Chelicerata, Xiphosura) is the proper authority, not Limulidae Zittel, 1885

The horseshoe crab Limulus polyphemus (Linnaeus, 1758) is a famous species, renowned as ‘living fossil’ (Owen, 1873; Barthel, 1974; Kin and Błażejowski, 2014) for its apparently little-changed morphology many millions of years. genus Müller, 1785 was used by Leach (1819, p. 536) the basis new family Limulidae synonymized it with Polyphemus Lamarck, 1801 (Lamarck's proposed but later unaccepted replacement , discussed Van der Hoeven, 1838, 8) Xyphotheca Gronovius, 1764 (later changed to Xiphosura 1764, another junior synonym ). He also included valid modern Tachypleus Leach, 1819 in family. primary authority (1819) widely recognized neontological literature (e.g., Dunlop et al., 2012; Smith 2017). It World Register Marine Species (WoRMS Editorial Board, 2021).