ANIMAL RELATIONSHIPS. 
245 
ent groups which now repeat some of their most im¬ 
portant characteristics. Well-known examples of these 
forms are the Pterodactyl, a flying reptile, and the 
archaeopteryx, a reptile-like bird. 
We do not know that any living birds or reptiles 
have descended directly from the archaeopteryx, but it 
Fig. 198.—A Pterodactyl 
certainly seems probable that birds and reptiles are in 
some manner related by descent. However we may 
interpret the records in the rocks, it is certain that no 
accurate classification of animals based on kinship can 
be made without a careful study of fossils. 
