v. Haast.—On the Geological Structure of the Southern Alps. 388 
The lowest beds on the western slope are gneiss-granites, overlaid by 
mica, chlorite and other metamorphic schists of similar origin. These 
rocks are followed by clay-slates, semi-crystalline sandstones and felstones, 
which in some instances form not only the summits of the central chain, 
but even reach several miles aeross to its eastern slopes. They generally 
contain quartz veins. Upon them reposes the great sandstone, conglome- 
rate, clay-slate and shale formation, of which the greatest portion of the 
Provincial District of Canterbury is composed, and which in many instances 
ean be followed for nearly seventy miles to the east. I have named this 
extensive series of rocks the Mount Torlesse formation. On the eastern 
side of the great anticlinal it forms a succession of huge folds, dipping 
throughout at high angles, but these folds have been so much destroyed 
during numberless ages, that at present their synclinals generally form the 
summits of the mountains, while the deep broad valleys often run along 
their anticlinals. Besides this folding a great deal of crumpling has taken 
place, so that, although the general character of the arrangement has been 
preserved, over a short space of ground the strata often strike and dip in 
all directions of the compass. During my first journey to the head-waters 
of the river Rangitata, in 1861, I discovered in the Clent Hills a series of 
beds containing numerous impressions of plants, and some twelve miles dis- 
tant in the Rangitata Valley at Mount Potts other beds containing fossil 
shells and saurian bones. Professor F. MeCoy, in Melbourne, to whom I 
sent the collections made, for identification and description, informed me 
that the plants were of Jurassic and the molluscs mostly brachiopods of 
Upper Devonian or Lower Carboniferous age, both being identical with 
exuvie found in the coal fields of New South Wales. However, judging 
from the position and sequence of the strata in both localities, agreeing 
with each other in a remarkable manner, though the Mount Potts beds are 
of much greater thickness, I could not accept this conclusion, being con- 
vinced that they were of the same age. Since that time it has been proved 
by a number of experienced geologists, that the beds in New South Wales, 
to which Professor McCoy alluded, are interstratified, and that consequently 
they must be of the same age. 
Both palwontologists and geologists have agreed that if there exist in 
any geological horizon beds containing a marine fauna of an older together 
with a terrestrial flora of a younger aspect, the former will more correctly 
indicate the age of the beds. Thus, if the fossil shells of any given fornia 
tion have a paleozoic and the plants a mesozoie character, the beds in 
which both occur have to be classified as palæozoic. 
It would be foreign to the object of this paper were I to enter more fully 
into this important question, but I may observe that both in India and 
