SPONGES. 237 



lias lately been worked out in great detail by TOPSENT (48, 62), who records eight 

 species from that area which are also met with in Ceylon, while two of these, Dotona 

 pulchella and Rhrtbdoploca unispiculifera, have not yet been met with elsewhere. 

 The genus Petromica, also, is only known as yet from the Azores and from Ceylon, 

 the two species being almost identical. Hence, in spite of the great difference in 

 point of distance, the Sponge-Fauna of the Azores appears to resemble that of Ceylon 

 nearly as much as does that of the Red Sea ! 



There also appears to be a certain amount of affinity between the Sponge-Fauna of 

 Ceylon and that of the American coast of the North Atlantic, especially amongst the 

 horny sponges (<'.</., Hi/>j><>xj><>n</i'< (him), though, perhaps, some of the identifications 

 in this group are a little doubtful. The Lithistid genus Aciculites, however, has, so 

 far as I am aware, only been recorded from Ceylon and Havannah, and the two 

 species in these two remote localities are closely similar. 



Very nearly two-thirds of the total number of species are, however, so far as is 

 known at present, peculiar to the Ceylon area, and, although the number of such 

 species (at present 140) will certainly be largely decreased by future identifications 

 and discoveries in other localities, it will, on the other hand, also be augmented by 

 fresh additions to the list of the Ceylon Sponge-Fauna. My investigations of the 

 Sponge-Fauna of other parts of the world also lead me to believe that while a 

 considerable number of species enjoy a very wide geographical range, the majority 

 have comparatively small areas of distribution. I strongly suspect, however, that a 

 large number of our so-called " species " will ultimately be found to be so closely 

 connected by intermediate forms that it will no longer be possible to separate them 

 sharply from one another. In the meantime they must be distinguished by separate 

 names, and, if the different forms are fully and properly described, it should be easy 

 for future workers to trace out their true relationships. 



REFERENCE LIST OF LITERATURE. 



(1.) RIDLEY and DEXDY.' Report on the Monaxonida collected by H.M.S. "Challenger,"' 1887. 



(2.) DEXDY. "The Sponge-Fauna of Madras. A Report on a Collection of Sponges obtained in the 



Neighbourhood of Madras by EDGAR THURSTOX, Esq." ' Ann. and Mag. Nat. Hist.' (5), xx., 



p. 153. 1887. 

 (3.) DEXDY. " Report on a Second Collection of Sponges from the Gulf of Manaar." ' Ann. and Mag. 



Nat. Hist.' (6), in., p. 73. 1889. 

 (4.) CARTER. "Report on Specimens dredged up from the Gulf of Manaar .and Presented to the 



Liverpool Free Museum by Captain W. H. CAWNE WARREN." 'Ann. and Mag. Nat. Hist.' (5), 



v., p. 437 ; (5), vi., pp. 35 and 129. 1880. 

 (5.) CARTER. " Supplementary Report on Specimens dredged up from the Gulf of Manaar," &c. ' Ann. 



and Mag. Nat. Hist.' (5), vii., p. 361. 1881. 

 (6.) ESPER. ' Fortsetzung der Pflanzenthiere,' Part 2. 1798-1806. 



