GEOLOGICAL AGE 47 



the siliceous marls and shales of the Tertiary 

 age which occur in Barbados, Cuba, Trinidad, 

 Kichmond in Virginia, Sicily, and the Nicobar 

 Islands. 



The Eadiolaria in these deposits retain the 

 glassy silica of their shells, and for the most 

 part they are in as perfect condition as recent 

 forms, and many are of the same species as 

 those now living. 



Recent researches in geology show that 

 Radiolaria may be of great geological age, and 

 that they occur in siliceous rocks of all forma- 

 tions from the Cambrian upwards. 



There need be no difficulty in obtaining 

 specimens for examination, as will be seen 

 from a subjoined list of rocks in which they 

 are to be found in abundance. 



Localities and rocks in which Eadiolaria have recently 

 been found: 



Cambrian strata in Thuringia. 



Reddish rocks of Ordovician age in the South of Scotland. 



Shales in Languedoc and Saxony. 



Jaspers of Devonian age in Siberia. 



Kieselshiefer of Hesse and Nassau. 



Lower Culm or Carboniferous strata of Devon and 

 Cornwall, 



