216 THE AMERICAN MONTHLY [Au 



Palaeozoic types of Radiolarians is still very incomplete. 

 Dr. Rusk gives various types of Polycystina in rocks as 

 old as the Silurian, even the Cambrian. M. Cayeux has 

 found them also in the Silurian. The remains of Radio- 

 larians have been indicated as occaring in the Carbonif- 

 erous Limestone of England where they are known as 

 Calcisphserse. These are composed of carbonate of lime 

 but were originally siliceous and were changed. 



In the Mesozoic systen they are also found. From the 

 Jurassic system in particular, numerous fossil Polycys- 

 tina have been described by Zittel, Dunikonski and Rust. 

 In the marls of the island of Barbadoes, which are placed 

 in the Miocene, but should be Oligocene, they are found 

 in abundance, also at the islands of Trinidad, Hayti, and 

 Cuba and the recent seas thereabout. Many of the Juras- 

 sic Radiolarians occur in jasper, flint or chert, but they 

 are especially abundant in what have been termed "Radio- 

 larian quartzes." They are present in this at Monterey, 

 Cal. They are considered by Hseckel as of the nature of 

 the "silicifled deep-sea Radiolarian oozes." They are 

 found as "Radiolarian coprolites" in the Lias of Hanover. 

 The Barbodoes earth is well known to microscopists as 

 are the "tripoli" of Sicily, Calabria, Greece and Algiers. 

 Another deposit of the same nature is the tripoli or Radi- 

 olarian clay of the Nicobar islands, which rise to an ele- 

 vation of about 2,000 feet above the level of the sea and 

 is probably of Miocene or Oligocene age. They are found 

 in all quarters of the globe where Tertiary rocks or clay 

 are, and present the spectacle of a vast continent or up- 

 rising which bear forms exactly the same as one that 

 was recently found in the Lower Silurian. The Radio- 

 larians existed then without being evoluted. Lately, and 

 in fact in November, 1895, Dr. C. J. Hind has shown that 

 Radiolaria are common in the Lower carboniferous meas- 

 ures of the Devonian age in Devonshire, England, and 

 sends me a paper on the Radialarian rocks of that region. 



