LOMAS : ox THE ORIGIN OF THE TRIAS. 
17 
places where water is more or less permanent. We should 
naturally expect to find plant life and aquatic animals more 
abundant in those places. A salt pan near Riverton, in South 
Africa, I found to be swarming with the little Crustacean 
Estheria (the most common and most widely distributed fossil 
in our Trias), and larger animals coming there to drink leave 
their footprints and other remains in the mud. 
Xow to apply these principles to our Trias. It is generally 
accepted that the material forming out Triassic rocks was 
originally river borne. I shall not stop now to discuss the 
origin or courses of these rivers, but, given the deposits and 
a desert or semi-desert condition of climate, we can see how 
wind would in places concentrate the coarser fragments, forming 
deposits like the Pebble Beds of the Midlands. Some localities 
may have escaped the sifting, and the Pebble Beds of Lancashire 
and Cheshire, in part, may represent these. In the latter counties 
we find very thick masses of sand, false bedded, in a way which 
suggests dunes rather than river deposits, and lenticular patches 
of pebbles interspersed at all horizons and very inconstant in 
extent. I have not made careful calculations, but it strikes me 
that if the pebbles in the Lancashire and Cheshire areas were 
concentrated as in the Midlands, they would make up a deposit 
quite as thick and of a similar nature. It has been asserted that 
the pebbles of the ^lidlands are larger in size than those further 
north. I know places in Lancashire and Cheshire where they 
range up to 6 in. or 8 in. in diameter, and my experience in Cannock 
Chase and other places in the Midlands is that assemblages of a 
larger size than this require looking for. Large pebbles are 
exceptional and do not characterise the beds as a whole. 
On this h^^othesis, the Pebble Beds of the Midlands and 
further Xorth may differ only in one having been subject to the 
concentrating influence of wind and the other having to a large 
extent preserved its original character, and being abnormally 
thickened by the importation of fine material from the Midlands. 
We should naturalty expect that the stones over which sand has 
drifted in the course of concentration would be etched or planed 
to form dreikanter. These are found in the Pebble Beds but are 
not common. Neither are they in existing deserts. 
B 
