584: COLLECTIONS FROM THE WESTERN INDIAN OCEAN. 



Indian Ocean shallow-water faunas, wo find 16 out of the 56 spe- 

 cies obtained in the hitter region to be identical with Australian 

 species, a proportion to the whole of 2 : 7, or 28 per. cent. It is 

 still more remarkable to find that of these, three (viz. Carterispongia 

 otahitica, Iotrochota purpurea, Clathria frondifera) occur abun- 

 dantly in both places. Had Dr. Coppingcr's researches enabled me 

 to add more species to the list, I have little doubt that still greater 

 proofs would have been forthcoming of a former communication 

 between these two widely remote districts. As might almost have 

 been expected, 14 of these ideutical species occur in tropical waters 

 in Australia also (chiefly from Torres Straits or N. Queensland, but 

 one third of the number from Port Darwin). 



Of the mutual relations of the different localities in the district at 

 present under notice I have little to say, as the investigation of them 

 must be admitted not to be sufficient for a satisfactory comparison. 

 In spite of its much more westerly longitude and of its separation 

 from the other localities by much open sea and in part by that great 

 body of land, the island of Madagascar, we find no decided differ- 

 ences between the fauna of Mozambique and that of the rest of the 

 district ; perhaps the Mozambique current partly accounts for this. 

 On the other hand, we find that 7 out of the 13 species recorded 

 from the Seychelles were not found in the other localities: probably 

 this is partly due to the fact that here alone was dredging regularly 

 carried out. The Amirante Islands have the greatest number of 

 species (26). 



Taxonomy. — Of the strictly taxonomical aspects of this part of 

 the collection little has to be said which has not been already said in 

 the Melanesian portion of this Deport. I therefore refer those in- 

 terested in the subject to that part of the Deport for most questions 

 relating to the general zoology of the Group and to the bearing of 

 these collections on classification and morphology. The full descrip- 

 tions of new species and genera which are represented also in the 

 Melanesian collection will be found in the Deport on that collection ; 

 they are not noticed at length in this place. This collection from 

 the "Western Indian Ocean is remarkable for the large proportion 

 (31 per cent, of the whole) which the Ceratose sponges bear to the 

 remaining groups : this is no doubt largely due to the number of 

 " beach specimens " included in the collection, representing, as such 

 specimens naturally would, most chiefly this less perishable order. 

 This proportion probably more closely resembles that which would 

 be obtained in the South-west of Australia than that found by the 

 ' Alert ' in the Eastern and Northern parts of that continent (which 

 was about 18 per cent.) ; but the species are smaller than the gene- 

 rality of those which contribute so largely to the shore gatherings 

 at Frccmantle, West Australia. 



No species of the order Ceratosa call for special notice here. 

 Of the Mbnactinellid Silicea none of the Families are strongly re- 

 presented, the Renieridse, with 7 species, being the most abundant, 

 and yet maintaining only about the same proportion (15 per cent.) to 

 the remainder of the Sponges as in the Melanesian collection. 



