Lower Palaeozoic Pocks of the South of Scotland. 43 
consequently very few in comparison with the numbers which 
may be obtained from a recent ooze or from loose fossil 
material. 
With two or three doubtful exceptions the forms which I 
have been able to determine in this chert may be all included 
in one of the four legions or subclasses into which Haeckel 
has divided the Radiolaria, viz. that of the Spumellaria or 
Peripylea. Within this subclass but two suborders, the 
Beloidea and the Sphseroidea, are represented. In the first 
of these there is no connected siliceous test ; but the skeleton 
consists of numerous solid siliceous spicules irregularly scat- 
tered in the soft structures surrounding the central capsule. 
Spicules of similar form and proportions to those of the exist- 
ing members of this group, represented in plates ii. and iv. of 
Haeckel’s 1 Challenger ’ Report, are abundant in the chert. 
Some of them with three- or four-pointed rays (woodcut, a-f 
p. 56) are very similar in form to the spicules of Calcisponges ; 
others, however, with a central rod giving off divergent rays 
from its extremities (woodcut, g ) are quite distinct from any 
known type of sponge-spicule. These detached spicules 
are in the same condition as the lattice-like Radiolaria with 
which they are intermingled, and there can be no doubt that 
like these latter they were originally siliceous. Though now 
detached from their normal positions, the inevitable result of 
the decay of the soft structures, yet instances are not unfre- 
quent in this chert wdiere several of these Beloid spicules 
occur in close proximity to each other, forming small groups, 
much in the same way as we should expect to be the case if 
forms like the recent Lampoxanthium pandora , Haeckel *, 
and Sphcerozoum pandora , H.f, were fossilized under favour- 
able conditions. 
The great majority of the Radiolaria in this chert, how- 
ever, belong to the more normal types of the suborder Sphae- 
roidea, in which the test consists of one or more rounded shells 
with a lattice-like or irregularly reticulate, sorcalled u spongy'’ 
structure. The simplest forms of these, in which the test is 
without spines or with only very minute secondary spines, 
are comparatively rare (PI. III. figs. 1, 2). Tests in which 
there is a single large radial spine, with or without secondary 
spines, are abundant. In some the outer or cortical test con- 
sists of simple lattice-like structure with subcircular or irre- 
gular meshes (PI. III. figs. 3, 4, 5, PI. IV. fig. 3) ; in others 
the structure is “ spongy ” (PI. III. fig. 7), whilst in another 
genus with the same structure there is a concentric inner or 
medullary test (Pi. III. figs. 8, 9). Shells with three or with 
* Chall. Report, pi. ii. fig. 1. t Ibid. pi. iv. fig. 6. 
