BUFFALO SOCIETY OF NATUEAL SCIENCES 151 



THE LUDLOW OF ENGLAND AND THE LUDLOW AND LANARKIAN OF 



SCOTLAND 



Introduction. Although the Siluric of southern Scotland is char- 

 acterized by large eurypterid faunas at successive horizons, the rocks 

 of the same age in England and Wales, where more open marine con- 

 ditions obtained, have yielded only two or three fragments, except in 

 the higher Ludlow beds which mark the transition to the continental 

 deposition characterized by the Old Red Sandstone. Even in the 

 Ludlow the remains which in some strata are abundant show a much 

 poorer preservation than do those from Scotland. Complete indi- 

 viduals are never found and although it is possible from the fragments 

 to determine that different genera are represented, more precise iden- 

 tifications are difficult, and in most cases species have been erected 

 simply in order to have some way of designating the fragments be- 

 longing to the various genera. In order to understand why all of the 

 specimens from the Siluric of England are so much more poorly pre- 

 served than are those from Scotland, it will be necessary briefly to 

 trace the geological changes which were taking place throughout 

 Great Britain during the later Siluric. 



In Scotland the Upper Siluric is marked by the approaching con- 

 tinental conditions as evidenced in the deposits of greywackes and 

 flagstones, some barren, some containing a sparse marine fauna and 

 others only fish and eurypterid remains. The conditions as yet were 

 unstable, showing the alternate dominance now of river-borne sedi- 

 ments and now of shore deposits. To the south, however, the sea 

 still covered most of England, though the muds pouring in from the 

 land had made conditions unfavorable for many of the forms of life 

 which thrived in that region during Wenlock time. Thus the corals 

 no longer built up great reefs and only a few survived in the stifling 

 muds wherein the graptolites were buried in such abundance. Brach- 

 iopods and the majority of molluscs likewise decreased in number as the 

 migration to more favorable waters to the south progressed. Toward 

 the top of the Upper Ludlow rock in England many rill and ripple- 

 marked sandstones are to be found, some of which show trails. Near 

 the top of this series too, occurs the "Bone-bed" which varies from f 

 inch to 6 inches in thickness and is made up largely of fish, eurypterid 

 and crustacean remains, while a few brachiopod shells have been found 

 in places. Geikie has estimated that this bed probably covers an 



