I38 THE HABITAT OF THE EURYPTERIDA 



the brachiopods, pelecypods, etc.? If the eurypterids lived in the 

 marine waters, why are their remains not found with those of the 

 other marine organisms? Band D contains many genera, species, 

 and individuals of brachiopods, pelecypods, gastropods, cephalopods, 

 Crustacea, crinoids, trilobites, corals, the first three groups being 

 especially well represented, the last three by only two or three species. 

 But not a trace of a eurypterid is found in this fauna which, accord- 

 ing to the criteria given on p. 76 is a typical marine fauna. More- 

 over, why should their appearance be so sudden and so localized? 

 The eurypterid band dies out within a few yards of Gutterford Burn, 

 and in the other sections where one would expect to find eurypterids 

 again, for the associated marine fossils occur, there is not even a frag- 

 ment? I must confess that such anomalies in distribution are not 

 compatible with a marine habitat for the organisms so affected. 

 Again, why should the eurypterids have suffered such maceration, 

 while the remains of the other organisms were entombed in a perfect 

 state? Wonderfully preserved starfishes and trilobites are found in 

 one of the beds, the marvellous brachiopod fauna of Band D has been 

 described and figured by Davidson, and his book amply attests to 

 the abundance and fine preservation of the molluscoidea; but the 

 eurypterids are broken up, often unidentifiable and never what the 

 palaeontologist would consider good material. These questions have 

 been, or will be, fully treated in the appropriate sections on the 

 bionomy and distribution of the eurypterid faunas. We are here 

 concerned only with the lithogenesis of the beds so far as that may be 

 separated from faunal considerations. From the study of the sec- 

 tions, and the lithological characters of the rocks, I offer the follow- 

 ing interpretation for the eurypterid-bearing horizons of the Wenlock 

 of southern Scotland. 



It will be remembered that the Tarannon marked a period of 

 retreat of the sea toward the south, the shoreline being at the end of 

 that time somewhere in the central part of the Central Belt, while 

 there must have been an embayment in the Girvan area where con- 

 tinuous marine sedimentation was active. The Wenlock sea which 

 covered the greater part of western, central, and northern England 

 at least, advanced over the terrestrial beds which were deposited 

 during Tarannon time. Unfortunately, the most critical areas of 

 deposition of the Wenlock have been removed by subsequent erosion. 

 The Southern Belt was in the region of continuous marine deposition 

 from Tarannon into Wenlock time, as the sections in many places 



