PREFACE. 



In submitting the accompanying Monograph to the scientific public, I feel assured 

 that the careful and conscientious manner in which Dr. Hinde has performed the 

 very arduous task entrusted to him will meet with the well-earned recognition of 

 all those who consult this work. 



The earlier methods of classification of both the recent and fossil Spongidae by 

 their external form and habit of growth having been thoroughly tested and proved 

 to be unreliable, the only sure method to be pursued — that of classifying them 

 according to their intimate microscopic structure — has been adopted by Dr. Hinde, 

 who, himself a pupil of the distinguished palaeontologist Prof Dr. Karl Zittel of 

 Munich (one of our highest authorities in this class of organisms), has followed 

 patiently the careful methods of research set forth in the ' Beitrage zur Systematik 

 der fossilen Spongien ' and other of Zittel's works. 



It is no small gratification to knoAv that the determination of this very difficult 

 group of fossil organisms has now been so far completed, and that the types 

 of those species not heretofore described are now all carefully figured in the Plates 

 accompanying this Monograph, and the original specimens are preserved in the 

 British Museum of Natural History. 



British Mttsetjm (Natural History), 

 December 26ih, 1883. 



HENRY WOODWARD, 



Keeper of the Department of Geology. 



