Page:The Eurypterida of New York Volume 1.pdf/149

 presents a condition intermediate between that of the typical scorpions and of Limulus or Eurypterus. Likewise, it is shown that the comb is structurally intermediate between a typical scorpion comb and the outer branch of one of the metasomatic appendages of Limulus. Finally Pocock doubts that Palaeophonus possessed spiracles or was an air breather but suggests that it was still aquatic and may have possessed branchial lamellae attached to sternites.

We have above pointed out the features which the larvae of Limulus and the eurypterids have in common. The supposed close relationship of the eurypterids to Scorpio, makes it desirable to compare the larval stages of the two.

The embryology of the scorpions has been investigated by Metschnikoff and more recently by Laurie [1890] and Brauer [1895]. We copy here for comparison one of Metschnikoff's [from Balfour's Treatise on Comparative