THE EURYPTERIDA OF NEW YORK 143 
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 
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 isa 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 stigmatain P. hunteri, notwithstand- 
ing the fact that the ventral side is exposed, it may be mentioned that Fritsch [r1904, 
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. Never- 
theless Pocock’s view of the aquatic habit of Palaeophonus is of interest in con- 
nection 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. 
