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.    From Wordnik.com.  [Pioneers in Canada] Reference

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.    From Wordnik.com.  [Facts and Arguments for Darwin] Reference

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.    From Wordnik.com.  [Facts and Arguments for Darwin] Reference

Xiphosura.    From Wordnik.com.  [Facts and Arguments for Darwin] Reference