20 EXTINCT MONSTERS 
seasons, the large rivers of South America are swollen by heavy 
rains, great numbers of quadrupeds are drowned every year. 
Troops of wild horses that graze in the “savannahs,” or grassy 
plains, are said to be swept away in thousands. 
In Java, in the year 1699, the Batavian River was flooded 
during an earthquake, and drowned buffaloes, tigers, rhinoceroses, 
deer, apes, crocodiles, and other wild beasts, which were brought 
down to the coast by the current. 
In tropical countries, where very heavy rains fall at times, and 
rivers become rapidly swollen, floods are a great source of danger 
to man and beast. Probably the greater number of the bodies 
of animals thus drowned find their way into lakes, through 
which rivers flow, and never reach the sea ; and if the growth of 
sediment in such lakes goes on fairly rapidly, their remains may 
be buried up, and so preserved. But in many cases the bones 
fall one by one from the floating carcase, and so may in that way 
be scattered at random over the bottom of the lake, or the bed 
of a river at its mouth. In hot countries such bodies, on reach- 
ing the sea, run a great chance of being instantly devoured by 
sharks, alligators, and other carnivorous animals. But during 
very heavy floods, the waters that reach the sea are so heavily 
laden with mud, that these predaceous animals are obliged to 
retire to some place where the waters are clear, so that at such 
times the dead bodies are more likely to escape their ravages ; and, 
at the same time, the mud with which the waters are charged 
falls so rapidly that it may quickly cover them up. We shall 
find further on that this explanation probably applies to the 
case of the “ fish-lizards,’ whose remains are found in the Lias 
formation (see p. 75). 
But, for several reasons, sedimentary rocks formed in lakes 
are much more likely to contain the remains of land animals 
