ORDER II RADIOLARIA 
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 (Jonosphaeroidae) 
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 Riist, fossil Radio- 
laria are by no means 
less abundant and less 
Barbados earth (Miocene) ; 
39 
Contrary to formerly accepted ideas, the geo- 

Recent and Tertiary Spumellarians : A, Actinommea asteracanthium, Haeck. 
Recent; Messina. C, 
Barbados. D, 
s : Fic. 48. 
diversified than the 
5 D Recent; Messina. B, Stylodictya multispina, Haeck. 
recent. Only IN €X- Heliodiscus Humboldti, Ehrbg. 
ceptional instances aliommea dixiphos, Ehrbg. 
- Aristotelis, Ehrbg. 
(Miocene of Barbados, 
Miocene marl ; Caltanisetta, Sicily. 
Miocene ; Barbados. 
E, Astromma 
Oran, Sicily) have the skeletons been preserved unaltered, and still consist of 

Fic. 49. 
Recent and Tertiary Nasselarians : A, Podocyrtis Schomburgki, Ehrbg. 
Tertiary marl; Barbados. 
Messina. 
ranean. 
l B, Cyrtocalpis amphora, Haeck. Recent; 
C, Bothryocampe hexathalamia, Haeck. Recent; Mediter- 
D, Petalospyris foreolata, Ehrbg. Tertiary marl ; Barbados. 
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 erypto- 
crystalline, or replaced by 
a calcite pseudomorph. 
The Cambrian Griffel- 
schiefer of Sonneberg in 
Thuringia contain poorly 
preserved Sphaeroidea; the 
usually dark, though some- 
times red or light-coloured 
Ordovician strata of Langenstriegis in Saxony, and of Rehau and Steben in 
Franconia, the red jasper of Abington; Scotland, and the Ordovician silicious 
