A MONOGRAPH 



BJRITISH FOSSIL SPONGES. 



INTRODUCTION. 



Though Fossil Sponges are mentioned in some of the earliest works in which 

 fossils are treated of, and descriptions of them appear in nearly all subsequent works 

 on palaeontology, their true characters, until a comparatively recent date, were 

 completely misunderstood, and their history was a mass of hopeless confusion. In 

 the absence of any clear ideas as to the real nature of these organisms, the most 

 heterogeneous materials were relegated to the group, and indeed it might be said to 

 have been the practice — not altogether obsolete even now — to regard as a Sponge 

 any fossil whose structure was too obscure to be satisfactorily placed elsewhere. 

 One of the principal reasons for the chaos which existed was the erroneous idea, 

 enunciated more particularly by D'Orbigny and Fromentel, that fossil Sponges 

 belonged to an entirely extinct group, of a different nature to those now living, and 

 consequently that no clue could be obtained to their original structures by a 

 comparison with those of living forms. 



Acting on this mistaken idea, those who studied the fossil forms did not attempt 

 to carry out a systematic investigation of their skeletal structures, like that which 

 had been so successfully applied to existing Sponges, but they were content to limit 

 their investigations to the external form and the superficial canal structures, 

 features possessed in common by many Sponges whose skeletal characters are 

 essentially diverse. The classification thus based, was for the most part valueless 

 and misleading. Here and there observers were not wanting who noticed the 

 importance of the skeletal structures of these fossils, and amongst these Etallon 

 deserves special mention ; but no thorough attempt was made to apply the principle 

 of the character of the skeleton, as the basis of classification*, until that successfully 

 carried out by Professor Zittel in 1877-78. Since the publication of Zittel's 



