58 CEYLON PEARL OYSTER REPORT. 



small bulk of the material which he investigated and amongst which he found 

 altogether something like 70 species a notable addition indeed to the 13 or so 

 previously described from the same neighbourhood by Esper (6), Haeckel (7), 



BoWERBANK (8), and HOLDSWORTH (9). 



The collection of sponges (146 species) made by Professor Herdman is, however, far 

 more extensive than any previously obtained in Ceylon waters, and includes not only a 

 large proportion of the species already described by the authors mentioned, but also a 

 considerable number (77 species) of new ones, some of which are of very great interest. 

 With the exception of the Calcarea, which are singularly few in number, and of the 

 Hexactinellida, which are, of course, a deep-water group and not likely to be met 

 with in the neighbourhood of the pearl banks, the collection contains representatives 

 of practically all the important sub-divisions of the Phylum. In dealing with so 

 large a mass of material, the cpiestion of classification has assumed a very formidable 

 aspect, and I have found it desirable to make certain modifications in this respect 

 which I hope may be regarded as improvements. These modifications will be duly 

 explained, and I hope justified, in the proper place. 



Since, in spite of the enormous advances which have been made during the last 

 twenty years in our knowledge of the sponges, our ideas as to taxonomy are not yet 

 by any means in a settled condition, I have considered it desirable to give brief 

 diagnoses of the various sub-divisions with which I have to deal, in order that there 

 may be no mistake as to the sense in which I employ them. We are, undoubtedly, 

 progressing rapidly towards a satisfactory and natural classification of the group, but 

 the problem is an extremely difficult one, and every new collection of any considerable 

 extent, such as the present, must for a long time to come necessitate more or less 

 modification of existing views. The classification which I have adopted may at 

 present be regarded as the latest of these modifications, based principally upon the 

 writings of Sollas, Ridley, Lendenfeld, Topsent, and myself. Topsent, in 

 particular, has done much in the last few years both in arranging and classifying the 

 chaotic mass of information left by earlier writers, and in making notable additions to 

 our systematic knowledge of this difficult but interesting group. 



In order to facilitate reference to the type specimens by future workers and to make 

 the systematic portion of this report as precise as possible, I have adopted the 

 system, already employed in my Catalogue of Non-Calcareous Sponges collected by 

 J. Bracebkidge Wilson, &c. (10), of giving at the end of the description of each 

 species the Register Number (R.N.), which I have attached to each specimen. This 

 method also has the great advantage of enabling one to refer readily to individual 

 specimens in the text. 



At the conclusion of the Report I propose to give as complete a list as possible oi 

 the Sponge-Fauna of Ceylon and to discuss the problem of Geographical Distribution. 

 In the meantime I append a list of the principal memoirs dealing with the subject 

 arranged in chronological order. 



