Original: Xiphosura are traditionally placed in the class Merostomata, although this term was originally intended to encompass also the eurypterids, whence it denoted what is now known to be an unnatural (paraphyletic) group.
Simplified: Xiphosura are traditionally placed in the class Merostomata. This term was originally made for the eurypterids; now, with the Xiphosura added, it is known to be paraphyletic.