from Wiktionary, Creative Commons Attribution/Share-Alike License
- proper n. A taxonomic order within the class Merostomata — distinguished from all other chelicerates by having compound eyes. The only living xiphosurans are the horseshoe crabs.
This extraordinary crustacean is one of the oldest of living animals in its history, as it is closely related to the Xiphosura and even the Trilobites of the Primary Epoch, which existed millions of years ago.
Crustacea; nor the Xiphosura and Trilobites, because, having never investigated them myself, I knew too little about them, and especially because I am unacquainted with the details of the explanations given by
Phyllopoda and Xiphosura, furnished a long and varied, and at the same time intimately connected series, such as was at my command in no other class.