236 THE HISTORY OF CREATION. 
orders of Beaked animals represent but a single degenerated 
branch developed on one side—probably possessed a very 
highly developed jaw like the marsupial animals, which 
developed from them. 
Marsupial, or Pouched Animals (Didelphia, or Marsu- 
pialia), the second of the three sub-classes of Mammals, 
form in every respect—both as regards their anatomy and 
embryology, as well as their genealogy and history—the 
transition between the other sub-classes—the Cloacal and 
Placental Animals. Numerous representatives of this group 
still exist, especially the well-known kangaroos, poucLed 
rats, and pouched dogs; but on the whole this sub-class, 
like the preceding one, is evidently approaching its complete 
extinction, and the living members of the class are the last 
surviving remnants of a large group rich in forms, which 
represented the Mammalia during the more recent secondary 
and the earlier tertiary periods. The Marsupial Animals 
probably developed towards the middle of the Mesolithic 
epoch (during the Jura) out of a branch of the Cloacal 
Animals, and in the beginning of the Tertiary epoch again, 
the group of Placental Animals arose out of the Marsupials, 
and the latter then succumbed to the former in the struggle 
for life. All the fossil remains of Mammals known to us from 
the Secondary epoch, belong either exclusively to Marsupials, 
or partly perhaps to Cloacal animals, At that time Marsu- 
pials seem to have been distributed over the whole earth ; 
even in Europe (France and England), well-preserved fossil 
remains of them have been found. On the other hand, the 
last off-shoots of the sub-class now living are confined to a 
very narrow tract of distribution, namely, to Australia, the 
Australasian, and a small part of the Asiatic, Archipelago. 
