398 NEW YORK STATE MUSEUM 
organisms, than the belief, which I hold, that Palaeophonus lived in 
the sea, probably in shallow water, its strong sharply pointed legs being 
admirably fitted, like those of a crab, for maintaining a secure hold amongst 
the seaweed or on the jagged surface of rocks, and for resisting the force 
of the rising and falling waves.”’ 
We have seen above that Fritsch believed there were indications of 
lung sacs in Proscorpius osborn1i, but inspection of the speci- 
men has failed to reveal any traces of respiratory organs. 
Although the discussions of the authors cited demonstrate that the 
ventral side of the mesosoma is not shown well enough in any of the 
four Siluric scorpions to settle the question of the presence or absence 
of stigmata or the life habit of these scorpions, we feel that Whitfeld’s, 
Laurie’s and Pocock’s suggestion of their probable aquatic habitat is well 
worthy of serious consideration. It is therefore pertinent to summarize 
here the arguments in favor of this view. 
1 All four scorpions have been found in marine beds and in such 
good preservation that it is difficult to assume they drifted out to sea; 
especially since the beds containing them do not afford any other remains 
of land animals or plants. On the other hand, we should note in this 
connection that they all four occur in association with eurypterids, and 
these are considered in this publication as having been principally inhabi- 
tants of estuaries. But this association may, as indicated under 3, have 
rather a phylogenetic than a physical cause. 
2 If the Siluric scorpions agree with the recent ones in respect to 
the body form and arrangement of the prosomatic appendages, then it 
does not follow, as pointed out by Laurie [loc. cit. p. 577], that they have 
reached the same point of specialization in respect to their respiratory 
organs. ‘‘ The terrestrial mode of life and consequent adaptation to air- 
breathing may have come later.’ 
3. As Pocock has shown that the arrangement of the parts consti 
tuting the ventral side of the prosoma in Palaeophonus indicates that the 
latter “occupies an intermediate | position between Limulus and the 
