366 The American Naturalist. [April, 
GEOLOGY AND PALEONTOLOGY. 
Origin of the Continental Area of Australia.—The follow- 
ing account of the probable origin of the Australian Continent is given 
by Professor David in a presidential address before the Linnean 
Society of New South Wales : 
“ That the movements of the earth’s crust which laid the foundations 
of the Australian Continent commenced in Pre-Cambrian time is con- 
clusively proved by the vast amount of folding to which the Archean 
rocks at Androssan and in the Mount Macdonnell Ranges were sub- 
jected before the deposition of the earliest Cambrian sediments. 
“In Tasmania the crumpling of the crust took place between E. N. 
E. and W. S. W. directions, so that the axes of the fold trend N. N. 
W. and S. S. E. 
‘At St. Vincent’s Gulf, near Adelaide, the folds run chiefly N. E. 
and S. W.,and N. N. E. and S.S. W., so as to meet, if produced, a pro- 
longation of the Tasmanian axes toward the N. W., nearly at right 
angles. In the Macdonnell and Musgrave Ranges, the trend is E. and 
W., and in the Kimberly District of West Australia, N. W. and S. E., 
with a secondary folding S. W. and N. E 
“ It is not certain whether, either in Australia or Tasmania, there 
was any land surface in Archean time, but the conglomerates in the 
Archean and in the succeeding Cambrian, and the ripple-marked 
flaggy quartzites (if they are Archean or Cambrian and not Lower 
Silurian) imply shallow seas, with probably a neighboring land sur- 
face. It is improbable, too, that the Archean strata should have been 
as powerfully folded, as observation shows them to have been, in Pre- 
Cambrian time, without some areas being elevated sufficiently to form 
land. 
“In Australia, therefore, there was probably land and probably con- 
temporaneous life, at all events, in the seas, in Pre-Cambrian time, the 
latter assumption being rendered probable by the occurrence of the 
beds of limestone and contemporaneous (?) iron-ores and graphite in 
the Archean rocks of South Australia, and of limestone and contem- 
poraneous (?) ironstone in the Archean rocks of Tasmania, and also 
by the great diversity of forms of animal life met with in the succeed- 
ing Lower.Cambrian rocks. 
“ The earliest known folding of the Australian region took place in 
Pre-Cambrian time in Australia and Tasmania, and, at least, as far 
