the uninterrupted outline presented by the somites in question, which imparts so natural an appearance to this region, is thus the result of pure accident I find hardly credible. In fact, there is, I think, no reason to doubt that the fifth and sixth mesosomatic somites were united to the metasoma, and shared its unmistakable inversion. Hence the plates in question are sternites. The important point attached to this conclusion is the absence of stigmata on these sternites. Perhaps it was this fact which led Thorell to his decision as to their tergal character.
The above-given reasons justify a sceptical attitude towards the alleged existence of stigmata in the Gotland Palæophonus, at all events until a further examination of the specimen settles the points now under dispute. And since I found no distinct traces of stigmata in the Scotch specimen, I am inclined to believe that Peach fell into error on this point perhaps influenced in part by the alleged presence of stigmata in the Gotland example, perhaps in part by the assumption that a form so closely resembling recent scorpions in other structural details must also resemble them in the nature of its respiratory organs.
To the belief in the presence of stigmata, implying the existence of organs fitted for aërial respiration, coupled with the knowledge of the terrestrial habits of all living scorpions, is traceable the conviction evinced by most previous writers that these Silurian scorpions lived on the land. This belief is less easy to reconcile with the facts that both the known specimens are relatively in an admirable state of preservation, and were met with in strata of undoubted marine origin, containing abundance of admittedly marine organisms, than the belief, which I hold, that Palæophonus 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.
Respiration, as already suggested, may have been effected
