REPORT ON THE RADIOLARIA. 



clxxi 



Eadiolaria which they contain. The white specimens resembling Kieselguhr contained approxi- 

 mately 60 to 70 per cent, by volume of Eadiolarian shells, the yellowish marl 40 to 50 per cent., and 

 the brown and black (bituminous) marl 10 to 20 per cent, or less. Two analyses of the first, which 

 my friend Dr. W. Weber was good enough to carry out, yielded different results from those which 

 are given by Ehrenberg on the basis of Eammelsberg's analyses (L. N. 25, p. 116). The results of 

 both are here given for comparison. 



For further comparison I here add the three different analyses of Miocene Tripoli-marls from 

 Sicily, given by Stohr on the authority of Fremy, Schwager, and Mottura (Tagebl. d. fiinfzigsten 

 Versamml. Deutsch. Naturf. u. Aertzte in Miinchen, 1877, p. 163). 



B. The Eadiolarian marl of the Mediterranean appears, judging by the accounts already pub- 

 lished, to stretch along a considerable part of the coast in the earlier and middle Tertiary forma- 

 tions ; thus it occurs of similar composition in widely separated localities, in Sicily, Calabria, Zante, 

 and Greece ; in North Africa from Tripoli to Oran and probably much farther. So long ago as 

 1854 Ehrenberg, in his Mikrogeologie (L. N. 6) gave a series of important, even if incomplete, com- 

 munications regarding the " chalky white calcareous marl of Caltanisetta " (Taf. xxii.), the " Flatten 

 marl of Zante " (Taf. xx.), the " plastic clay of yEgina " (Taf. xix.), and the " polishing slate of 

 Oran " (Taf. XXL). In 1880 Stohr showed in his fundamental description of the Tripoli from 



