120 THE HABITAT OF THE EURYPTERIDA 



can be followed through in the same way for the Kokomo, the most 

 marked difference between the two formations being the local char- 

 acter and diverse source of the latter. The Kokomo waterlime lacks 

 the lateral and vertical persistence characteristic of the Bertie and in 

 this respect is similar to the waterlimes of Oesel which in many out- 

 crops appear as thin bands intercalated between limestone beds (see 

 section, fig. 7 above, and description). Indeed, the section revealed 

 at Kokomo is the counterpart of what theoretically we should expect 

 to find in the southward continuation of the Bertie in Pennsylvania 

 where the waterlimes merged into the marine deposits. • 



The second difference between, the Kokomo and Bertie waterlime 

 is that of origin, for while the latter was derived from the north the 

 former must have come from the west since the sea covered the Michi- 

 gan area during Monroe time and precluded the derivation of sedi- 

 ments from the Canadian region. It is difficult to arrive at an expla- 

 nation of the lithogenesis of such a formation when so few outcrops 

 are visible, but yet we can determine enough to show that the Kokomo 

 sediment was river-borne and came from a continent to the 

 west (see map, fig. 8). A study of the faunas convincingly shows the 

 distinctness of the source of the material and organisms found at 

 Kokomo (see below, pp. 253-256). 



7. THE TARANNON-WENLOCK BEDS OF SOUTHERN SCOTLAND 



Distribution of Formations. The clearest conception of the 

 lithogenesis of the eurypterid-bearing Wenlock beds of southern Scot- 

 land is to be obtained from a survey of the palaeographic condi- 

 tions existing in Great Britain from the end of Ordovicic time on 

 through the Siluric. The outcrops in Wales, in the hilly areas of 

 Cumberland and in innumerable outliers in Westmoreland and else- 

 where, as well as those of the southern uplands of Scotland, indicate 

 that throughout the Ordovicic the sea covered Wales, the greater 

 part of western and central England and southern Scotland as far 

 north as the great northeast-southwest fault line delimiting the north- 

 ern edge of the tableland. The central and northern portions of Scot- 

 land formed a part of the old land which, rising to the east in the Scan- 

 dinavian shield, extended westward through North Britain and Ire- 

 land on into the northern Ailantic, and which throughout the Palae- 

 ozoic furnished the sediments which were deposited either in the sea 

 to the south of that ancient shoreline, or on the land to the north of 



