The scientific Reader will feel that much value has been added 
to the present work, from the whole of the Paleeontology, during 
its progress through the Press, having had the great advantage 
of passing under the revision of Mr. Broderip, and from the 
botanical part having being submitted to Mr. Robert Brown. 
I have also to acknowledge my obligations to Mr. Clift for his 
important assistance in the anatomy of the Megatherium; to 
Professor Agassiz of Neuchatel for his unreserved communica- 
tions of his discoveries relating to Fossil Fishes; to Mr. Owen 
lor his revision of some parts of my Chapter on Mollusks ; and 
to Mr. James Sowerby for his assistance in engi'aving most of 
my figures of radiated animals, and some of those of Mollusks. 
To all these Gentlemen I feel it my duty thus to offer my 
public acknowledgments. 
Many obligations to other scientific friends are also acknow- 
ledged in the course of the work. 
The Wood-cuts have been executed by Mr. Fisher and Mr. 
Byfield, and most of the Steel plates of Mollusks by Mr. Zeitter. 
