Lower Palceozoic Rocks of the South of Scotland. 45 
other suborders of this legion, but also of the important 
Nassellarian Cystellaria, which are extremely abundant both 
in recent deposits and in all Tertiary and Mesozoic Radio- 
larian beds which have as yet been examined. 
With the exception of the Radiolaria very few other 
organisms can be recognized in the sections of this chert-rock. 
There are one or two spicules of Hexactinellid sponges, 
readily distinguishable from the detached Beloid spicules by 
their larger size and distinctive forms, and I have met with a 
few minute toothed plates and detached denticles, which bear 
a certain resemblance to the radute of naked Molluscs ; there 
are further numerous almond-shaped hollow bodies about * * * § 1 
millim. in length, with imperforate siliceous walls, of whose 
nature I am quite ignorant. This Ordovician chert may 
therefore be fairly considered to be due to the accumulation 
of the tests of Radiolaria, and is thus a pure Radiolarian rock, 
equally as much as the Tertiary beds of Barbados and the 
Nicobar Islands, which, according to Haeckel, correspond to 
the recent Radiolarian ooze, “ and are certainly of deep-sea 
origin, having probably been deposited at depths greater than 
2000 fathoms ” *. If the same conclusion is applicable to 
this fossil chert, it represents, as Prof. H. A. Nicholson f has 
already pointed out, a true deep-sea deposit in the Palaeozoic 
period, the existence of which in the geological series has of 
late been disputed. The beds of fine-grained red and green 
mudstones associated with this chert likewise favour the same 
view of its origin in deep water. 
Hitherto only a single species of Radiolaria has been 
described from the entire Palaeozoic series, and this was dis- 
covered by Dr. Rothpletz \ in siliceous shale of Upper Silu- 
rian age at Langenstriegis, in Saxony. This Radiolarian 
shale, like the Scotch chert, is accompanied by beds with 
graptolites. It is only since 1876 that Radiolaria were known 
in any rocks older than Tertiary by the discovery by v. Zittel § 
of a few forms in the Upper Chalk of Germany; since then 
the existence of an abundant and varied Radiolarian fauna in 
beds of chert and jasper of Lower Cretaceous and Jurassic age 
lias been proved by Dr. Rust ||, and v. Dunikowski^[ has 
described numerous species in the Lower Lias of the Tyrol. 
* Chall. Report, vol. xviii. pt. i. p. clxix. 
t Trans. Edmb. Geol. Soc. vol. vi. pt. i. p. 56. 
j Zeitschr. d. deutsch. geol. Gesellsch. Bd. xxxii. (1880) p. 447, pi. xxi. 
§ Ibid. Bd. xxviii. (1876) pp. 75-86, pi. ii. 
|| 1 Palseontographica/ Bd. xxxi., xxxiv. 
If Op. cit . 
