492 THE SNAKES OF SOUTH AFRICA. 
he was obliged to he down for hours at a time. These symptoms 
grew less and less severe as time wore on, and have now almost 
disappeared, although at times when he is out for long in the 
hot summer sun, he feels faint and dizzy. 
Although the snake escaped, there is no doubt about it being 
a Boomslang, as Pretorius knows a Boomslang as well as I do. 
He informs me that the snake glided up a dense mass of prickly 
pears and rapidly slid away out of sight amongst them. This 
is rather remarkable when it is realized that a hedge of prickly 
pears is smothered with long, sharp, straight thorns sticking out 
at all angles. 
E. 
THE ISOLATION OF MADAGASCAR AND AUSTRALIA. 
There is very strong evidence for believing that Madagascar 
was, in remote times, joined to the mainland of Africa, and that 
Australia was a part of Asia. Now, even the study of snakes 
helps us in coming to such a conclusion, and even suggests the 
period at which the separation took place. 
In Madagascar there are no front-fanged (Proteroglypha) 
snakes such as the Vipers and Cobras. They are all of the 
hind-fanged (Opisthoglypha) and solid-toothed (Aglypha) species. 
This indicates that snakes had not evolved a typical poison 
apparatus prior to the separation of Madagascar from Africa, 
otherwise we should have found them there, for Africa is teeming 
with the front-fanged species of snakes. This fact leads us to 
conclude that Madagascar was isolated at a very remote period 
of time, and that the separation of Australia from the mainland 
of Asia occurred at a more recent period, because we find numbers 
of species of front-fanged, typically venomous snakes in that 
country. We thus infer it was isolated after snakes had fully 
evolved their poison apparatus. 
Moreover, in Australia, there are no snakes of the viper (adder) 
family, although there are plenty of them on the mainland of 
Asia. This fact would seem to indicate that the viper family 
of snakes have evolved at a more recent period than the Colubrine 
group of venomous snakes. 
Further, snakes have never been known in New Zealand. 
