sll.UMAN SYSTEM 



171 



in Radnorshire and West Shropshire liy Miss G. L. Elles" and 

 M. H. Wood, 8 the former dealing with tin- Wen lock succession 

 and tlu> latter with the Lower Ludlmv. 



The country round Builth may be taken as the type of this 

 graptolitic fades of tin- \Vcnlock Series, and Miss Elles has shown 



Fig. M. MAP OF THE U'Di.oW DISTRICT. 



that it contains a fauna of twenty-three species and varieties of 

 graptolites, by means of which it can be divided into six zones. 

 The succession of the beds is shown in Fig. 5">, which is taken 1-y 

 permission from her paper. The total thickness appears to be 

 about 2500 feet, but tin-re are two partial breaks in the 

 for the flagstones of zone 4 overlap the beds below, so that in one 

 place they rest on the lower part of zone 2, and again, t! 



