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point to a powerful post-eocretaceons mountain-building by which 

 the deep-seated Radiolai-ia-deposits were uplifted beyond the sea- 

 level, while in the Tertiary the mountains were entirely denuded 

 again. 



In the foregoing Radiolaria-bearing deposits have been described 

 from three levels of the series of sediments of Cuba: a fourth level 

 can still be added. Between Bacuranao and the boring-field which 

 is located to the north of this village, green sediments were observed 

 in the centre of the serpentine-area. These sediments are distinctly 

 seen to dip away below the serpentine. Under the microscope they 

 appeared to be in part volcanic tutfs, in part remarkable radiola- 

 rites, which consist chiefly of skeletons of Radiolaria, but also 

 contain spiculae of sponges, while the „silicic acid of the Radio- 

 laria as well as of the sponges spiculae is still perfectly amorphous 

 (fig. 3). These sibceous sediments are closely connected with the 

 volcanic tuffs; not only do the Radiolaria-layers and the tuffs possess 

 equal dip and equal strike, but sometimes the siliceous sedi- 

 ments contain s|)linters of plagioclase, and in one of the micro- 

 scopical sections the tuff even passes into the siliceous sediment. 

 These Radiolarites of Bacuranao certainly belong to an older level 

 than the tertiary Radiolarites, as the former dip away below the 

 serpentine, whereas the whole tertiary is more recent than the 

 serpentine, whose water-worn fragments are found here and there 

 in the tertiary limestones and calcareous sandstones. They belong- 

 moreover to anotlier level than the red Radiolarites of Viüales and 

 Matanzas, for the thick limestones bearing the red Radiolarites of 

 Vinales are not found near Bacuranao. The siliceous sediments are 

 closely related to the (yuban serpentines. 



Now it is very remarkable that in Cuba such extreme deposits 

 as Radiolarites appear in four different levels. Even when not 

 assuming that Radiolarites are ti'ue deepsea deposits, we must be 

 convinced that the formation of these calcium-free or calcium-}>oor 

 siliceous sediments requires conditions that do not exist in the shallow 

 epi-continental seas. At all events the occurrence of these deposits 

 in at least four levels of the island of Cuba justifies the conclusion, 

 that the area in which the island is now situated, was in the latter 

 half of the Mesozoicum an extreniely restless region, where now 

 deposits of a shallow epicontinental sea (sandstones in the Chalk, 

 Nummulites and Orbitoide-bearing limestones in the Tertiary), then 

 again such peculiar sediments as Radiolarites^) could be formed. 



b One more fact may be adduced to confirm the conception that at least one 

 level of the Radiolaria bearing deposits in Cuba is formed, if not in a true deep- 



