Report on the zoological collections made in the Indo-Pacific Ocean ...

584 COLLECTIONS FROM THE WESTERN INDIAN OCEAN.Indian Oceau sliallow-water faunas, wo find 16 out of the 56 speciesobtained in the latter region to be identical with Australianspecies, a proportion to the whole of 2 : 7, or 28 per. cent. It isstill more remarkable to find that of these, three (viz. Carterispongiaotahitica, lotrocJiota purpurea^ Clathria frondifera) occur abundantlyin both places.Had Dr. Coppinger's researches enabled meto add more species to the list, I have little doubt that still greaterproofs would have been forthcoming of a former communicationbetween these two widely remote districts. As might almost havebeen expected, 14 of these identical species occur in tropical watersin Australia also (chiefiy from Torres Straits or N. Queeusland, butone third of the number from Port Darwin).Of the mutual relations of the different localities in the district atpresent under notice I have little to say, as the investigation of themmust be admitted not to be sufficient for a satisfactory comparison.In spite of its much more westerly longitude and of its separationfrom the other localities by much open sea and in part by that greatbody of land, the island of Madagascar, we find no decided difli'erencesbetween the fauna of Mozambique and that of the rest of thedistrict ;perhaps the Mozambique current partly accounts for this.On the other hand, we find that 7 out of the 13 species recordedfrom the Seychelles were not found in the other localities: probablythis is partly duo to the fact that here alone was dredging regularlycarried out. The Amirante Islands have the greatest number ofspecies (26).Taxonowy.—Of the strictly taxonomical aspects of this part ofthe collection little has to be said which has not been already said inthe Melanesian portion of this Ileport. I therefore refer those interestedin the subject to that part of the Ileport for most questionsrelating to the general zoology of the Group and to the bearing ofthese collections on classification and morphology. The full descriptionsof new species and genera which are represented also in theMelanesian collection will be found in the Ileport on that collection ;they are not noticed at length in this place. This collection fromthe Western Indian Ocean is remarkable for the large proportion(31 per cent, of the whole) which the Ceratose sponges bear to theremaining groups : this is no doubt largely due to the number of" beach specimens " included in the collection, representing, as suchspecimens naturally would, most chiefiy this less perishable order.This proportion probably more closely resembles that which wouldbe obtained in the South-west of Australia than that found by the' Alert ' in the Eastern and Northern parts of that continent (whichwas about 18 per cent.) ; but the species are smaller than the generalityof those which contribute so largely to the shore gatheringsat Freeman tie, West Australia.No species of the order Ceratosa call for special notice here.Of the MonactinelUd SUicea none of the Families are strongly represented,the RenieridDS, with 7 species, being the most abundant,and yet maintaining only about the same proportion (15 per cent.) tothe remainder of the Sponges as in the Melanesian collection.