President's Address. 17 
actually publish to the world the discovery of Radiolarians 
in Paleozoic deposits was Rothpletz, who showed that in 
unquestionable Silurian rocks in Saxony there occurred 
certain cherts or “lydites” charged with the remains of 
Radiolarians (Zeitschr. d. deutsch. Geol. Gesell., 1880). The 
cherts in question are associated with tuffs and diabases, the 
latter showing a characteristic and peculiar “spheroidal” 
structure. Rothpletz further pointed out that cherts of a 
very similar character occurred in the Ordovician series of 
the same region, though he was not able to demonstrate the 
actual presence of the tests of Radiolarians in these. 
The occurrence of beds of Radiolarian chert in the 
Ordovician series of the southern uplands of Scotland was, 
I think, first noted by myself (Zrans. Edin. Geol. Soc., vol. vi., 
p. 56, 1890) ; and a detailed account of the forms present in 
these deposits was given by my friend Dr Hinde, in the 
same year (Ann. and Mag. Nat. Hist., 1890). The Radiolarian 
cherts in question are most extensively developed in Lanark- 
shire, though they seem to be present over a large area in 
the south of Scotland; and the most important beds occupy 
a definite zone near the summit of the Glenkiln series. 
There are, however, other bands (as in Dobb’s Linn and at 
Hartfell), which appear to be placed at higher horizons. As 
seen in Lanarkshire, the Radiolarian cherts are accompanied 
by red and green mudstones, which forcibly recall to our 
minds the red or coloured muds of modern deep-sea deposits, 
They are also associated with basic lavas, which show the 
peculiar “spheroidal” structure above referred to. Dr 
Hinde (op. cit.) points out that the Radiolarians of these 
ancient deposits “do not differ in any striking respect from the 
existing forms of the group;” and he finally concludes that 
“this Ordovician chert may, therefore, be fairly considered 
to be due to the accumulation of the tests of Radiolarians, 
and is thus a pure Radiolarian rock, equally as much as the 
Tertiary beds of Barbados and the Nicobar Islands, which, 
according to Heckel, correspond to the recent Radiolarian 
ooze, and ‘are certainly of deep-sea origin, having probably 
been deposited at depths greater than 2000 fathoms.” In 
this conclusion I fully concur; and I may mention that Dr 
VOL. XUL B 
