508 HISTORICAL PAL/EONTOLOGY. 



3. CAMBRIAN. 



a. Lower Cambrian. British Longmynd group of Shropshire ; Harlech 



Grits ; Llanberis Slates ; Green and purple slaty rocks of Wicklow, 

 containing Oldhamia. Foreign Fucoidal Sandstone of Sweden, with 

 Eophyton ; Etages A and B of Barrande in Bohemia ; Huronian series 

 of Canada (?). 



b. Upper Cambrian. British Lingula Flags of Shropshire and Wales. 



Tremadoc Slates (?). Skiddaw Slates (?). Foreign "Primordial 

 zone" of Bohemia; Alum-schists of Sweden and Norway; Potsdam 

 Sandstone and Calciferous Sand-rock of North America ; Quebec 

 group of Canada (?). 



4. SILURIAN. 



a. Lower Silurian. 



Britain. 

 Lower Llandeilo or Arenig Group. 



2. Upper Llandeilo or Llandeilo Flags. 



3. Caradoc, Bala, or Coniston Group. 



4. Lower Llandovery Group. 



North America. 



1. Trenton Period (comprising the Chazy, Birds-eye, Black River, 



and Trenton Limestones). 



2. Hudson Period (comprising the Utica Shales and Hudson River 



Group). 

 Bohemia. 

 \ Etage D of Barrande. 



b. Upper Silurian. 



Britain. 



/I. Upper Llandovery (comprising the Tarannon Shales and May 

 Hill Sandstone). 



j 2. Wenlock Group (comprising the Woolhope Limestone, Wen- 

 lock Shale, and Wenlock Limestone). 



I 3. Ludlow Group (comprising the Lower and Upper Ludlow 



V formations). 



North America. 



1. Niagara period (comprising the Oneida Conglomerate, Medina 



Sandstone, Clinton Group and Niagara Limestone). 



2. Salina period (comprising the Guelph Limestone and Onondaga 



Salt Group). 



3. Lower Helderberg period (comprising the Tentaculite and Water- 



lime Groups, the Lower Pentamerus Limestone, the Delthyris 

 Shaly Limestone, and the Upper Pentamerus Limestone). 

 Bohemia. 

 Etage E. 



G. , 



H. 



5. DEVONIAN. 



Lower Devonian. British Arbroath Paving Stones of Scotland ; Lin- 

 ton Group of Devonshire. Foreign Oriskany Sandstone (?) and 

 Comiferous series of North America. 



Middle Devonian. British Bituminous Schists of Caithness ; Ilfra- 

 combe Group of Devonshire. Foreign Eifel Limestone of Europe ; 

 Hamilton series of North America. 



