116 THE ORIGIN OF SPECIES 



"and to constitute connecting links with the aquatic 



carnivora." 



Even the wide interval between birds and reptiles has 

 been shown by the naturalist just quoted to be partially 

 bridged over in the most unexpected manner, on the one 

 hand, by the ostrich and extinct Archeopteryx, and on 

 the other hand, by the Compsognathus, one of the Dino- 

 saurians — that group which includes the most gigantic of 

 all terrestrial reptiles. Turning to the Invertebrata, Bar- 

 rande asserts — a higher authority could not be named 

 — that he is every day taught that, although paleozoic 

 animals can certainly be classed under existing groups, 

 yet that at this ancient period the groups were not so 

 distinctly separated from each other as they now are. 



Some writers have objected to any extinct species, 

 or group of species, being considered as intermediate 

 between any two living species, or groups of species. 

 If by this term it is meant that an extinct form is 

 directly intermediate in all its characters between two 

 living forms or groups, the objection is probably valid. 

 But in a natural classification many fossil species cer- 

 tainly stand between living species, and some extinct 

 genera between living genera, even between genera be- 

 longing .to distinct families. The most common case, 

 especially with respect to very distinct groups, such as 

 fish and reptiles, seems to be, that, supposing them to 

 be distinguished at the present day by a score of char- 

 acters, the ancient members are separated by a somewhat 

 lesser number of characters; so that the two groups for- 

 merly made a somewhat nearer approach to each other 

 than they now do. 



It is a common belief that the more ancient a form 



