214 * THE HISTORY OF CREATION, 
A very peculiar class of Vertebrate animals, long since 
extinct, and which appears to have lived only during 
the secondary epoch, is formed by the remarkable Sea- 
dragons (Halisauria, or Enaliosauria, also called Nexipoda, 
or Swimming-footed animals). These formidable animals 
of prey inhabited the mesolithic oceans in great numbers, 
and were of most peculiar forms, sometimes from thirty 
to forty feet in length, From many and excellently pre- 
served fossil remains and impressions, both of the entire 
body of Sea-dragons as well as of single parts, we have 
become very accurately acquainted with the structure of 
their bodies. They are usually classed among Reptiles, 
whilst some anatomists have placed them in a much lower 
rank, as directly allied to Fish. Gegenbaur’s recently 
published investigations, which place the structure of their 
limbs in a true light, have led to the surprising conclusion 
that the Sea-dragons form quite an isolated group, differ- 
ing widely both from Reptiles and Amphibia as well as 
from Fish. The skeleton of their four legs, which are 
transformed into short, broad, paddling fins (like those of 
fish and whales) furnishes us with a clear proof that the 
Halisauria branched off from the main-stock of Vertebrata at 
an earlier period than the Amphibia. For Amphibia, as well 
as the three higher classes of Vertebrata, are all derived 
from a common primary form, which possessed only jive toes 
or fingers on each leg. But the Sea-dragons have (either 
distinctly developed or in a rudimentary condition as 
parts of the skeleton of the foot) more than five fingers, 
as have also the Selachians or Primeval fish. On the other 
hand, they breathed air through lungs, ike the Dipneusta, 
although they always swam about in the sea. They, 
