CALCAREOUS SPONGES. 707 



It is now more than forty years since any attempt was made 

 at a complete revision of the Oalcarea, and in the interval 

 the number of known species has increased from 111, described 

 in Haeckel's ' Kalkschwamme,' to 436 recognised by us at 

 the present time. Having recently been engaged in examining 

 collections of Calcarea of considerable importance and extent, 

 we have had impressed upon us the necessity for a complete 

 systematic catalogue of all the known species, the descriptions 

 of which are scattered through an immense number of separate 

 memoirs. In order to supply this want we have had to go 

 througli practically the whole of the literature of the group, 

 and there is not a paper, to the best of our belief, which contains 

 a reference to a new species which we have iiot seen. It is with 

 considerable satisfaction that we find, as a i^esult of this work, 

 that the scheme of classification proposed by one of us twenty 

 years ago [Dendy, 1892 B] is still applicable in its essential 

 respects, and requires comparatively little revision in order to 

 bring it up to date. 



In the present memoir we propose to give diagnoses of all the 

 families and genera employed, and to enumerate all the known 

 species under the genera to which we assign them. We have 

 decided to confine ovirselves to the consideration of living forms, 

 since our knowledge of fossil sponges is at present so unsatis- 

 factory, and the number of described species so great. 



We have had access, during the course of our work, to a large 

 amount of material, comprising a large proportion of the known 

 species. This has consisted chiefly of the collections in the 

 Natural History Department of the British Museum, a large 

 collection brought by one of us from Australia (see Dendy 

 [1891 A and 1892 B]) ; the collections made by Mr. Cyril Cross- 

 land in the Red Sea (see Row [1909]), Zanzibar (see Jenkin 

 [1908 A]), and Cape Yerde (see Thacker [1908]); a collection 

 made by the ' Sealark ' Expedition in the Indian Ocean (see 

 Dendy [1913]) ; and the magnificent collection made by the 

 Hamburg South- Western Australian Expedition in 1905 (see 

 Row [1913 MS.]). In addition, one of us (Row) visited Berlin 

 and Jena in 1912, and obtained valuable information from the 

 study of type specimens at those places. 



With regard to the difficult question of synonymy, and the 

 limits which should be assigned to each species, we have, never- 

 theless, been obliged to rely in most cases upon the published 

 descriptions and determinations of the authors responsible, and 

 we have unfortunately found that these descriptions are fre- 

 quently very inadequate ; while even where they are more com- 

 plete, the fact that they have been prepared from the point of 

 view of a different scheme of classification has sometimes made 

 them difficult to use. We have, however, assumed that all 

 descriptions are correct, except in cases where they have been 

 shown by subsequent authors, from an investigation of type 



Peoc. Zool. Soc— 1913, No. XLVII. 47 



