Lower Palaeozoic Rocks of the South of Scotland . 47 
single species. The preservation of the Radiolaria in this 
Ordovician chert, which has evidently been subjected to con- 
siderable disturbance, is an indication that if these organisms 
had entered largely into the composition of other beds of chert 
in this country they would probably ere now have been recog- 
nized in them. The observations of Dr. Rust * have led him 
to conclude that on the continent in the majority of cases chert 
and other siliceous rocks may be attributed to Radiolaria ; but 
in this country, according to present experience, similar rocks 
are mainly derived from the remains of siliceous sponges and 
very exceptionally from those of Radiolaria. 
Description of Species . 
In attempting to classify these ancient Radiolaria I have 
followed as far as possible the latest system of Prof. Haeckel, 
contained in the * Challenger ’ Report on this group. In this 
elaborate work the limits assigned to genera are extremely 
narrow and precise, and it is no wonder therefore that even 
with the greatest desire for comprehension it should be found 
impracticable to fit all these fossils into the divisions, nume- 
rous though they are, which have been already established, 
and I have therefore reluctantly been obliged to propose 
additional genera to include some of them. 
Class RADIOLARIA , Muller. 
Subclass SPUMELLARIA, Ehrenberg. 
Order SPHiERELLARIA, Hseckel. 
Suborder Sph^eroidea, Haeckel. 
Family Liosphaerida, Haeckel. 
Sphaeroidea without radial spines on the surface of the 
spherical shell ; living solitary (not associated in colonies). 
(‘ Challenger ’ Report, part i. p. 59.) 
Genus Styptosph^era, Hseckel. 
Liosphaerida forming a solid sphere of spongy framework, 
without enclosed medullary shell and without central cavity. 
(Chall. Rep. part i. p. 86.) 
Styptosphcera antiqua , sp. n. (PI. III. fig. 1.) 
The irregularly reticulate or spongy framework appears to 
* Jahresb. d. naturhist. Gesellsch. zu Hannover, 1883-87 (1888), p. 56. 
