175 



we are able to ascertain, these composed tlie most ancient 

 Fauna of the ocean. They were soon afterwards followed 

 by the Cephalopoda, and many other classes. The only 

 class of comparatively recent introduction is Cirrhipedia. 

 The sessile Cirrhipedes are only fomid in Cainozoic strata, 

 becoming so abundant towards its close, and now so 

 universally spread over the world that the present time 

 might be styled the " Age of Cirrhipedes." * 



The first evidence of the vertebrata, in the upper 

 Silurian, has been already adverted to in the occurrence 

 of Placoid Fishes, in the Ludlow Shales. The earliest 

 Reptiles in the Devonian and Carboniferous systems shew 

 how long that class existed before it arrived at its 

 maximum in the Mesozoic period. The first trace of 

 Birds seems indicated by their footprints in the Trias, 

 though the earliest undoubted examples are in Wealden 

 and Eocene strata. The first Mammals appear in the 

 Inferior Oolite, more frequently in the Wealden ; their 

 present importance in the economy of nature being coin- 

 cident with the commencement of the Cainozoic period, 

 in every region where such strata have been identified. 

 With the accumulated observations of geologists to rely 

 upon, and the very general manner the subject has been 

 treated, I hope to have correctly placed it before you. 

 The object has been to shew a correct tabulation of facts, 

 and their relation, according to the present state of our 

 information. 



* Darwin. 



