124 TRANSACTIONS—PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
which reveal to us, not alone the constituents of which the rocks 
forming the crust of the earth are composed, but also their micro¬ 
scopic fossil contents, the presence of which had been previously 
unsuspected. 
The discovery of Radiolaria in the Ordovician is a case in point. 
The rocks of the Lower Silurian of Ayrshire and the Grampian 
range, as well as those of West Cornwall, have yielded to the micro¬ 
scope Radiolaria^ whose recent representative the naturalists of the 
“Challenger Expedition” in the South Pacific Ocean have met with 
at depths exceeding five miles (4575 fathoms). 
These discoveries would seem to indicate that pelagic conditions 
obtained in the early Palaeozoic not dissimilar to those occurring at 
the present day, and we have reason to believe that further dis¬ 
coveries may be looked for in the not distant future. 
In following out a similar line of research Sir William Dawson 
and Professor Penhallow have recently placed the subject of our 
paper upon a more scientific basis than it has previously occupied, 
and one such as no unsupported scientific opinion is at all likely to 
overturn. The Parka question, in a word, having emerged from 
the region of opinion and passed into that of well ascertained fact, 
falls to be dealt with upon scientific grounds alone. 
THE HISTORY OF PARKA DECIPIENS. 
In 1831 Dr. Fleming compared this interesting fossil to the seed 
of Jiinais and Sparganiiim.'’" Hugh Miller expressed a similar view, 
while Page regarded Parka and certain associated seed-bodies as ot 
respectively vegetable, molluscan, and crustacean origin. Lyell, 
Powrie, Woodward, and Geikie, on the other hand, believed Parka 
to represent the egg-packets of crustaceans, and latterly geologists 
have apparently settled down into the belief that in the clusters of 
of Parka decipiens we find the spawn of Pterygotiis. 
That these varying opinions, more especially the latter, are but 
plausible conjectures is evident from the fact that in the Upper 
Silurian Pterygotus and allied crustaceans are equally prevalent, 
whilst in the Old Red Sandstone of the counties of Lanark (East), 
Berwick, and Caithness Pterygotus occurs. Yet in neither the former 
nor the latter do we find a trace of Pa^'ka decipiens. 
THE DISCOVERY OF THE VEGETABLE ORIGIN OF PARKA DECIPIENS. 
The papers on Parka by Dawsonf and Penhallow t were based 
upon material obtained by the writer from the Old Red Sandstone of 
* Cheek’s Edinburgh Journal. 
t Trans. Roy. Soc. Canada, 1891. 4 Canada Rec. Science, 1S92 
