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THE EURYPTERIDA OF NEW YORK

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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.^[1]

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

↑ His arguments are that the Scottish Palaeophonus hunteri does not show the stigmata, which Peach believed he saw, and that the single stigma seen by Thorell and Lindstrom in P. nuncius is a fortuitous crack. He therefore holds that Palaeophonus had no stigmata and spiracles and that on account of the excellent preservation of the Siluric scorpions in undoubted marine beds, they can not have been land animals, and that the strong sharply pointed legs were admirably fitted, like those of a crab, for maintaining a secure hold amongst the seaweed.
In regard to the supposed absence of stigmata in P. hunteri, notwithstanding the fact that the ventral side is exposed, it may be mentioned that Fritsch [1904, p. 64] has pointed out that the relation of the chelicerae to the frontal margin of the carapace shows that the specimen (of P. hunteri) lies with the dorsal side up and with the ventral organs of the cephalothorax pressed through the mutilated carapace. In that case it can not be expected that the fine slitlike stigmata should be observable, and in all Siluric scorpions which happen to have only the dorsal sides exposed, the question of the presence or absence of stigmata is obviously still an open one. Nevertheless Pocock's view of the aquatic habit of Palaeophonus is of interest in connection with the New York Proscorpius osborni in view of the absence of all other remains of land animals or plants in the waterlime; and especially in view of Brauer's discovery [1895, p. 351] that the ontogeny of Scorpio shows that the lungbooks are derived from gills borne on mesosomatic appendages.

[1] His arguments are that the Scottish Palaeophonus hunteri does not show the stigmata, which Peach believed he saw, and that the single stigma seen by Thorell and Lindstrom in P. nuncius is a fortuitous crack. He therefore holds that Palaeophonus had no stigmata and spiracles and that on account of the excellent preservation of the Siluric scorpions in undoubted marine beds, they can not have been land animals, and that the strong sharply pointed legs were admirably fitted, like those of a crab, for maintaining a secure hold amongst the seaweed.
In regard to the supposed absence of stigmata in P. hunteri, notwithstanding the fact that the ventral side is exposed, it may be mentioned that Fritsch [1904, p. 64] has pointed out that the relation of the chelicerae to the frontal margin of the carapace shows that the specimen (of P. hunteri) lies with the dorsal side up and with the ventral organs of the cephalothorax pressed through the mutilated carapace. In that case it can not be expected that the fine slitlike stigmata should be observable, and in all Siluric scorpions which happen to have only the dorsal sides exposed, the question of the presence or absence of stigmata is obviously still an open one. Nevertheless Pocock's view of the aquatic habit of Palaeophonus is of interest in connection with the New York Proscorpius osborni in view of the absence of all other remains of land animals or plants in the waterlime; and especially in view of Brauer's discovery [1895, p. 351] that the ontogeny of Scorpio shows that the lungbooks are derived from gills borne on mesosomatic appendages.

[1]