VI PREFACE. 



The plates have been carefully improved; and three, 

 containing upwards of eighty figures, have been added. 



On the whole, it will be found that the amount of matter 

 has been nearly doubled ; all the defects, as far as they have 

 been discovered, have been removed, and every means used 

 of making the present edition as useful as possible. 



PEEFACE TO THE FOURTH EDITION. 



In this edition many synonyms have been rectified, some 

 dates have been given, a few doubtful or unnecessary defi- 

 nitions have been altered or expunged ; descriptions of many 

 additional genera, illustrated by new figures, have been 

 inserted, and the work made as complete as its purely con- 

 chological character will admit. 



G. B. S. 

 July, 1852. 



