236 CEYLON PEARL OYSTER REPORT. 



melobesioides, Chondrilla nucula, Chondrosia reniformis, Leucosolenia darwini, 

 Sycon raphanus, Leucandra primiyenia, Leucandra pulvinar, of which all but five 

 (( 'lathria Jrondifera, Acanthella jiabelliformis, Spirastrella vagabunda, Leucosolenia 

 darwini, and Leucandra pulvinar) are so widely distributed that their occurrence is 

 of little significance. A few other Red Sea species, however, are very closely related 

 to Ceylon forms, and it is not improbable that two or three which have been described 

 by Keller under new names may be identical with Ceylon species, as will appear 

 from the descriptive part of this report. Amongst the Australian Sponge-Fauna also 

 a number of species occur which are very nearly related to Ceylon species, and which 

 have not been taken account of in the above comparison. 



A considerable number of sponges have also been described from South and East 

 African waters outside the Red Sea. The " Challenger " made collections in the 

 neighbourhood of the Cape of Good Hope, and Kikkpatrick (17) has lately described 

 45 species collected by Dr. Gilchrist. Keller (61) also gives a considerable list of 

 species from the East African area, in which, however, while excluding South Africa, 

 he includes the islands of the Western Indian Ocean visited by the " Alert." In 

 spite of these researches only four Ceylon sjjecies appear to have been met with 

 along the African Coast itself (outside of the Red Sea), viz. .Phyllospongia 

 papyracea (Mozambique), Ciocalypta tyleri (Port Elizabeth), Tedania digitata 

 (Mozambique), and Spmigelia fragilis (Zanzibar), the last two being cosmopolitan. 

 On the other hand, a number of Ceylon species extend, as we have seen, to the 

 islands of the Western Indian Ocean, viz. : Hippospongia intestinalis, Euspongia 

 irregularis, Cacospongia cavernosa, Spongelia (?) conica, Aplysina fusca, Tedania 

 digitata, lotrochota baculifera, Lotrochota purpurea, Clathria frondifera, Acarnus 

 ternatus, Agelas mauritiana, Chondrilla nucula, Samus anonymus, Leucandra 

 primigenia. These species have very possibly spread south-westwards from Ceylon 

 along the chain of small islands formed by the Maldives, Seychelles, Chagos, 

 Amirantes, &c. 



Even if we make allowance for errors and omissions in identification and doubtful 

 species, and also for the important fact that many more species are known from 

 Australasian waters than from the Red Sea and East African Coast, it appears 

 probable from the above data that the Sponge-Fauna of Ceylon is more closely 

 related to that of the eastern side of the Indian Ocean than it is to that of the 

 western side, and the Ceylon region may be safely included zoo-geographically in our 

 Indo-Australian area. The similarity of the Sponge-Fauna of Ceylon to that of 

 Australia is doubtless to be accounted for by the facilities of distribution and suitable 

 habitats afforded by the broken coast line which extends between the two, for it is 

 probable that, owing to the brief duration of their free-swimming larval condition, 

 shallow- water sponges are rarely able to traverse wide areas of deep ocean. 



A few other points concerning the geographical relationship of the Ceylon Sponge- 

 Fauna are, perhaps, worth noticing in this place. The Sponge-Fauna of the Azores 



