VI PREFACE. 



It is hoped that the satisfactory manner in which this 

 work has been accomplished may result in the issue of other 

 equally valuable monographs under the auspices of the 

 Trustees, by the staff of the Museum, dealing with similar 

 geographical units hitherto neglected. 



HENRY WOODWARD. 



Geological Department, 



British Museum (Natural History), 

 February, 1900. 



