148 



PROTOZOA. 



jaspers with Radiolarians are considered by Haeckel as of the nature 

 of true " silicified deep-sea Radiolarian ooze." Many forms of Radi- 

 olarians have also been yielded by the so-called " Radiolarian copro- 

 lites " of the Lias of Hanover. These are " roundish or cylindrical 

 bodies, which may attain the size of a goose-egg ; they probably 

 originated from Fish or Cephalopods, which had fed upon Crustacea, 

 Pteropoda, and similar pelagic organisms, whose stomachs were al- 

 ready full of Radiolarian skeletons " (Haeckel). 



The Radiolarians which have hitherto been discovered in the 

 Cretaceous rocks are few in number, but Zittel has described several 



Fig. 46. — Types of Polycystina. a, Podocyrtis Scho7>iburgii ; b, Dictyomitra Montgolfieri ; 

 c, Haliomma. dixiphos ; d, Dictyocha Jfessauetisz's ; e, Eucyrtidium elegans ; f, Lychnoca?iium 

 lucerna. d is living, and is after Haeckel ; the remaining are Tertiary, and are after Ehrenberg. 

 All the figures are greatly enlarged. 



species from the Upper Chalk of Germany. The Cretaceous genera 

 Dictyomitra (fig. 46, b) and Stylodictya (fig. 45, a) are represented 

 in both Tertiary and recent seas. 



In formations belonging to the Tertiary period, Radiolarians are 

 found in vast abundance in certain deposits (marls and clays), which 

 may be regarded as "fossil Radiolarian oozes." These Tertiary 

 Radiolarian clays and marls appear to be very widely distributed, 

 but the most famous of these deposits is the Polycystine Marl of 

 Barbados, the age of which is Miocene. The so-called " Barbados 

 earth " is a friable, earthy or chalky marl, which rises to heights of 

 over 1000 feet above the level of the sea, and is more or less 

 extensively composed of the shells of Radiolarians, with a variable 

 proportion of the calcareous tests of the Foraminifera. According 



