368 Mr. C. Lapworth on the Geological 



Table IX. Showing the Kange of the Salopian 

 lihabdophora. 



Wenlock, or in the so-called Lower Ludlow shales, where 

 Monograptidae alone have hitherto been detected. The mem- 

 bers of this family are tolerably abundant in the lower zones 

 of the Wenlock ; but specifically they are far less numerous 

 than in the populous Birkhill shales of the Lower- Valentian 

 era. In the Lower Ludlow, Monograptidse are not uncommon 

 upon certain horizons ; but the species are few and of few 

 types. Above this subformation the sandy strata of the 

 lJowntonian formation suddenly set in ; and beyond the occa- 



