ORDER II 



RADIOLARIA 



39 



Contrary to formerly accepted ideas, the geo- 



the aid of special literature. 



logical antiquity of 



the Radiolarians is 



very great ; and they 



also play an important 



part in the composi- 

 tion of many silicious 



and calcareous-silicious 



rocks (quartzites, horn- 

 stone, jasper, phyllites, 



Aptychenschiefer,etc.) 



According to Barrois 



they are the oldest 



known animal organ- 

 isms, since the Spumel- 



laria (Monosphaeroidae) 



occur plentifully in 



the bituminous quart- 

 zites of Bretagne, in- 



terbedded with pre- 



Cambrian gneiss. 



Although the group 



is still very imperfectly 



known, yet, according 



to Rust, fossil Radio- 



laria are by no means 



less abundant and less 



diversified than the 



recent. 



ceptional 



(Miocene of Barbados, 



Oran, Sicily) have the skeletons been preserved unaltered, and still consist of 



amorphous silica. In the 

 older rocks the silica has 

 usually become dissipated 

 in the matrix, being re- 

 placed by lime carbonate, 

 iron, or some colouring 

 agent; in other cases the 

 quartz has become crypto- 

 crystalline, or replaced by 

 a calcite pseudomorph. 



The Cambrian Griffel- 

 schiefer of Sonneberg in 

 FIG. 49. Thuringia contain poorly 



Recent and Tertiary Nasselarians : A, Podocyrtis Schomburgld, Ehrbg. rreserved Svka*roidea : the 



Tertiary marl ; Barbados. B, Cyrtocalpis amphora, Haeek. Recent ; * , .^ 



Mrssma. C, Bothryocnmpe liexfttltalamia, Haeck. Recent; Mediter- USUallV dark, tllOUgh SOniC- 



ranean. D, Petalospyrisforeolata, Ehrbg. Tertiary marl ; Barbados. ,. i , li^ht coloured 



Ordovician strata of Langenstriegis in Saxony, and of Rehau and Steben in 

 Franconia, the red jasper of Abington, Scotland, and the Ordovician silicious 



Recent and Tertiary Spumellarians : A, Actinomma asferacanthium, Haeck. 

 T in v Recent; Messina. B, Stylodictya multispina. Haeek. Recent; Messina. C, 

 ] ex- jf e i iodiscus Humboldti, Ehrbg. Barbados earth (Miocene); Barbados. D, 

 instances HaUomma dixiphos, Ehrbg. Miocene marl ; Caltanisetta, Sicily. E, Astromma 

 ' Aristotdis, Ehrbg. Miocene ; Barbados. 



