? EQUUS ZEYLANICUS. 267 
Fringing the western and southern coasts of this country 
is a well-marked “ reef” of sandstone containing the fossil 
remains of existing species of mollusca. This rock is 
exposed in many places, generally between high- and low- 
water levels, and will serve as a good geological datum. 
It is often very hard, and is locally used as building stone. 
The consolidation of this rock probably took place after 
the loose sand was elevated above sea level; the cement 
is carbonate of lime, as was probably derived from marine 
shells. It is an interesting fact that whereas the fossils belong 
to recent species, they indicate a distribution somewhat 
different from that which obtains to-day. At Chilaw, for 
instance, Cyprea is a very eemmon fossil genus, but the only 
Cypreas which I was able to discover on the present beach at 
Chilaw were derived from the sandstone. Cyprea, however, 
is common as a living form further north—on the western 
shores of the Calpentyn Peninsula, for example. After eleva- 
tion the sandstone was evidently depressed, for in many places 
a sea-worn surface may be exposed under more modern 
accumulations. The rock is of no great width, and passes 
inland into unconsolidated sand, with which it is doubtless 
contemporaneous. Both the sandstone and the soft sand are 
overlain by other beach or swamp accumulations and blown 
sand of later date. The hard rock was probably formed on 
flats above high-water level, just as similar rocks are tending 
to form at the present day (7.e., on the eastern shores of the 
Puttalam lake). That between the time oi its consolidation 
and the present day it was depressed below the surface of the 
sea is evident, not only from the erosion of its surface, but also 
from the fact that dead corals, now above water, may often 
be seen adhering to it. 
The earth movements chronicled by the coastel sandstone 
were of the nature of vertical uplifts and depressions ; but, as 
may be expected over so large an area as the western and 
southern coast belts, local tilting has occurred. From the 
mouth of the Kelani-ganga to Chilaw the slightest perceptible 
tilt to the west is to be seen, while near Galle the dip is much 
more apparent. On the whole, however, tilting is very slight, 
and for all practical purposes may be ignored. A glance 
13 6(9)16 
