184 EXTINCT | MONSLBTSS: 
latest geological period, known as the Pleistocene. During part 
of that time North America, as well as Northern Europe and 
Asia, were invaded by a great ice-sheet, and an arctic climate 
prevailed. It is therefore very probable that while the mammoth 
and the mastodon were roaming over North America, giant sloths 
and armadillos were monarchs of the southern continent. What 
cause, or causes, led to the extermination of the giant sloths and 
armadillos is stilla matter of speculation. One writer suggests 
an explanation that seems to deserve consideration. The 
southern parts of this great continent are even now subject to 
long-continued droughts, sometimes lasting for three years in 
Fic. 50.—Skeleton of Scelidotherium. {After Capellini.) 
succession, and bringing great destruction to cattle. In fact, 
the discoveries related above were rendered possible by several 
successive dry seasons. It is argued that the upright position 
of most of the skeletons found zz situ seems to suggest that 
the creatures must have been mired in adhesive mud sufficiently 
firm to uphold the ponderous bones after the flesh had decayed. 
A long drought would bring the creatures from the drained 
and parched country to the rivers, reduced by want of rain to 
slender streams running between extensive mud-banks; and it 
is possible that, in their anxious efforts to reach the water, 
they may have only sunk deeper and deeper in the mud until 
