INTRODUCTORY REMARKS. vii 



I have not had occasion to describe any Ecliinoderm from our Pleistocene Strata, 

 I think, however, it is very probable, that we shall find Echinus negledus in these beds in 

 Britain, even as it has been found elsewhere in beds of corresponding age and origin. Of 

 all the species of its genus, it is the one which ranges most nearly to the North Pole, and 

 is a truly Arctic and Boreal type. 



I have to return many thanks to the naturalists who have kindly and readily con- 

 tributed the materials for this Monograph. For that portion which concerns the Crag, I 

 have especially to thank Mr. Searles Wood, Captain Alexander, Mr. Charlesworth, 

 Miss Alexander, Miss Ransom, Mr. Brown of Stanway, Mr. Bunbury, Mr. Morris, and 

 Mr. Bowerbank. 



For that portion which relates to the London Clay, many thanks are due, especially to 

 Mr. Frederick Edwards, Mr. Bowerbank, Mr. Wetherell, Mr. Charles Stokes, and Mr. 

 D'Urban. 



Of the greater number of species recorded in this memoir, examples are displayed in 

 the Collections of the Museum of Practical Geology, thanks to the public spirit and 

 liberality of many of the gentlemen whose names I have just recorded. Mr. Edwards 

 has most generously presented the originals of all the species described from his 

 Collection. 



EDWARD FORBES. 



