32 ESSAY ON CLASSIFICATION. 



upon this globe, and that they were followed by higher 

 and higher types, until man crowned the series. Every 

 geological museum, representing at all the present state 

 of our knowledge, may now furnish the evidence that this 

 is not the case. On the contrary, representatives of nume- 

 rous families, belonging to all the four great branches of 

 the animal kingdom, are well known to have existed 

 simultaneously in the oldest geological formations. 1 Never- 

 theless, I well remember when I used to hear the great 

 geologists of the time assert that the Corals were the first 

 inhabitants of our globe, that Mollusks and Articulata 

 followed in order, and that Vertebrates did not appear 

 until long after these. What an extraordinary change the 

 last thirty years have brought about in our knowledge, and 

 in the doctrines generally adopted respecting the exist- 

 ence of animals and plants in past ages ! However much 

 naturalists may still differ in their views regarding the 

 origin, the gradation, and the affinities of animals, they 

 now all know, that neither Radiata nor Mollusks nor Arti- 

 culata have any priority one over the other, as to the 

 time of their first appearance upon earth ; and that, though 

 some still maintain that Vertebrata originated somewhat 

 later, it is universally conceded that they were already in 

 existence towards the end of the first great epoch in the 

 history of our globe. I think it would not be difficult to 

 show, upon physiological grounds, that their presence 

 upon earth dates from as early a period as any of the 



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System ; London, 1839, 1 vol. 4to. 4to. HALL (JAMES), Palaeontology 



MURCHISON (SiR R. I.), Siluria. The of New York; Albany, 1847-52, 2 



History of the Oldest Known Rocks vols., 4to. BARRANDE (J.), Systeine 



containing Fossils; London, 1854, 1 silurien du centre de la Boherue; 



vol. 8vo. MURCHISON (R. I.), DE Prague and Paris, 1852, 2 vols. 4to. 



VERNEUIL (Eo.), and KAISERLING SEDGWICK (A.), and McCoY (FR.), 



(COUNT ALEX. VON), The Geology of British Palaeozoic Rocks and Fossils; 



Russia in Europe, and the Ural London, 1851-55, 4to., 3 fasc. 



