THE LAURENTIAN AND HURONIAN PERIODS. 75 
traces of life have been detected, which may subsequently 
prove of great interest and importance. ‘Thus, Principal 
Dawson has recently described under the name of Archeo- 
spherine certain singular rounded bodies which he has dis- 
covered in the Laurentian limestones, and which he believes 
to be casts of the shells of Foraminifera possibly somewhat 
allied to the existing G/obigerine. ‘The same eminent palzeon- 
tologist has also described undoubted worm - burrows from 
rocks probably of Laurentian age. Further and more extend- 
ed researches, we may reasonably hope, will probably bring 
to light other actual remains of organisms in these ancient 
deposits. 
THE HURONIAN PERIOD. 
The so-called Muronian Rocks, like the Laurentian, have 
their typical development in Canada, and derive their name 
from the fact that they occupy an extensive area on the borders 
of Lake Huron. They are wholly metamorphic, and consist 
principally of altered sandstones or quartzites, siliceous, fels- 
pathic, or talcose slates, conglomerates, and limestones. They 
are largely developed on the north shore of Lake Superior, 
and give rise to a broken and hilly country, very like that 
occupied by the Laurentians, with an abundance of timber, 
but rarely with sufficient soil of good quality for agricultural 
purposes. They are, however, largely intersected by mineral 
veins, containing silver, gold, and other metals, and they will 
ultimately doubtless yield a rich harvest to the miner. The 
Huronian Rocks have been identified, with greater or less 
certainty, in other parts of North America, and also in the 
Old World. 
The total thickness of the Huronian Rocks in Canada is 
estimated as being not less than 18,000 feet, but there is con- 
siderable doubt as to their precise. geological position. In 
their typical area they rest unconformably on the edges of 
strata of Zower Laurentian age ; but they have never been seen 
in direct contact with the Uffer Laurentian, and their exact 
relations to this series are therefore doubtful. It is thus open 
to question whether the Huronian Rocks constitute a distinct 
formation, to be intercalated in point of time between the 
Laurentian and the Cambrian groups; or whether, rather, they 
should not be considered as the metamorphosed representa- 
tives of the Lower Cambrian Rocks of other regions. 
_ As regards the fossils of the Huronian Rocks, little can be 
said. Some of the specimens of Lozoon Canadense which have 
