PREFACE. 



The dates of the accompanying descriptions by Sir Philip de 

 Malpas Grey Egerton, Bart., have been retained to show when 

 they were respectively completed ; but the Decade itself was not 

 published in consequence of a desire of the late Professor Edward 

 Forbes to issue Decade Y. at the same time. The appointment of 

 Professor Forbes to the Chair of Natural History in Edinburgh 

 interfered with this arrangement, and a further delay was expe- 

 rienced at his death from the inability to discover the MSS. 

 amongst his papers. The original MS. is now published after 

 having been passed through the press by its author. 



H. T. De la Bechk 



2ncl April 1855. 



