IJV T. \\. EDGEWORTII DAVID. 557 



The red jasper from Sicily contains numberless radiolarian 

 shells, coloured red, in a translucent siliceous groundmass. 



Fairl}- well preserved radiolaria have been found in red jasper 

 of Lower Devonian age. 



At Cabrieres, in Languedoc, a ver}' hard black siliceous schist 

 of Ordovician age contains r-adiolaria, mostly in a bad state of 

 preservation. In the phosphorite of Cabrieres, however, dark, 

 porous to dense, concretions contain numerous radiolaria. 



The following is an analysis of the phosphorite : — 



Water r08 - 



Lime phosphate 73"6o 



Silicate alumina 2;5'27 



100- 



The radiolarian shells were black, yellow, or colourless. No 

 sponge spicules were present. In pieces of rock (siliceous shale) 

 from Saxony, poor in radiolaria, fragments of graptolites are 

 numerous. 



Black radiolarian fragments have been observed in fairly hard 

 clay shale of Cambrian age. Others occur in flinty pebbles, but 

 not sufficiently well preserved to admit of the species being- 

 determined. Fragments of graptolites and graptogonophores 

 were associated. 



The fact must be emphasized that it is chiefly in concretions 

 containing phosphoric acid that the radiolaria are best preserved. 



It often happens in all flinty rocks, not onl}^ Palaeozoic but also 

 Mesozoic, that the quartz filling the original hollows of the radio- 

 larian shells shows a radial habit, and has the form of perfect 

 spherulites exhibiting dark fixed interference crosses in polarized 

 light when the objective is rotated. 



In most cases the latticed shell has disappeared. Occasional!}', 

 however, the pore openings of the shell are preserved, or one sees 

 a dark circle Ijounding a clear space, with small regularly j^laced 

 dark indentations on the inner side. 



Very often 2:)erfect crystals are developed inside and around 

 these little quartz spheres. Generally' these are opaque 



