P R E F A C E. 



When the Authors of the present work commenced their task of monographing this 

 curious and extinct group of Echinodermata, they did not contemplate the production 

 of an official publication, but a Memoir on the Blastoidea to be presented to one of 

 the learned Societies. 



As their illustrations had, however, been largely taken from specimens in the 

 British Museum, it was suggested that the work should be submitted to the Trustees 

 to appear as one of the series of Museum Catalogues. 



At this time sixteen of the twenty Plates illustrating the work had already been 

 drawn upon stone and paid for out of the Government Grant Fund of the Royal 

 Society. These Plates were, however, with the approval of the Council, transferred 

 to the Trustees, at whose cost they have been printed off, and also four additional 

 Plates drawn and added to the series, together with seven illustrative woodcuts. 



Science is greatly indebted to the Authors for their very careful and patient 

 labours, not only in the study and comparison of external forms both of recent and 

 fossil Echinodermata, but in preparing sections showing the internal structure of 

 these organisms, involving long and patient examination with the microscope, by 

 means of which they have been largely assisted in working out the morphology of this 

 obscure and but little understood group. 



HENRY WOODWARD, 



Keeper of the Department of Geology. 



British Museum (Natural History). 

 Jult 1st, 1886. 



