10 Proceedings of the Royal Physical Society. 



Ludlow type of fossils in any particular area serves to indi- 

 cate that the upward movements which converted portions of 

 the Silurian sea into a continental area with inland lakes 

 had begun to manifest themselves, but such shore conditions 

 may have been contemporaneous with marine conditions in 

 other areas. 



In support of the contention that the Ludlow facies of 

 fossils indicates shore conditions, and, in particular, that the 

 Eurypterids were shore animals, I may point to the fact that 

 the oldest air-breathinor arachnids have been obtained from 

 beds containing these fossils. These are Palmophoneus 

 nuncitts from Gothland ; another Palseophoneus from Lesma- 

 hagow ; and a third scorpion has been described by Professor 

 "Whiteaves from the Water-lime group of America, long 

 known as the deposit in which the Eurypterus remipes 

 occurs. Though I have mentioned the Swedish specimen 

 first because it was first described, I believe that the Ameri- 

 can specimen was first discovered, so that the latter country 

 is justly entitled to the honour of priority of discovery. The 

 presence of air-breathers in these strata points to proximity 

 of land, and I have no doubt that our knowledge of the 

 plants and land animals of that ancient period will yet be 

 largely increased when the beds occupying this horizon are 

 subjected to more minute examination. The occurrence of 

 the peculiar phyllopods (Ceratiocaris) in such numbers in 

 strata of this age has an important bearing on this question ; 

 for all the recent forms are either fresh-water or confined to 

 inland seas and lakes. It is highly probable, therefore, that 

 their representatives in Upper Silurian times may have b^en 

 confined to shallow water along the margin of the Silurian 

 sea, or to estuaries. 



The Lower Old Eed Sandstone, as developed in Scotland, 

 was deposited in a series of lakes or inland seas formed by 

 the elevation of portions of the old Silurian sea-floor. This 

 conclusion is based partly on the character of the strata, the 

 absence of undoubtedly marine fossils, and, in particular, on 

 the peculiar facies of the fish fauna of the Moray Firth basin 

 and of the Midland valley. The enormous thickness of these 

 deposits in the central basin points to prolonged subsidence 



