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

'372 COLLECTIOlfS FROM MELANESIA.explanation seems, however, to suggest itself as possibly applicableto some cases of extremely generalized and indefinite types (e. g.Reniera indisiincta and Ht/meniacidon caruncida, which are commonto the British and Australian seas), viz. an independent origin ofthe same species, or of what to a zoologist's eye is the same species,at two different localities. The number of points by which it ispossible to distinguish species of (e. g.) Reniera, Hi/meniacidon, Amorpliina,and Suberites from odo another is so small, and these pointsare so variable and so relative in their character, that it is quitepossible that the same end (^. e. the same specific characters) maybe attained by development in the same direction of two distinctspecies, the result being a zoological but not a natural species, or, inother words, of species which are distinct from each other but whichcannot be shown to be so.2. Distribution of '•Alert ' Species within Australian Seas.List of the Species collected on the Australian coasts, or in the ArafuraSea,by H.M.S. 'Alert,' 1881, with their known distributionin those waters. [The localities for Southern and "WesternAustralia, and in one or two cases for Port Jackson, are givenfrom previous writings ; the rest are those due to the ' Alertinvestigations.]Note.—Where the distribution of a varieiy of a species is given, the distributionof the typical form is also given (when Australian) opposite the name ofthe species. The stars opposite the name of the variety refer exclusively to thevariety.O"^8.5MOrder CARNOSA (not represented).Order CERATOSA.Family SPONGIID^.1. Cacospongia mollior, Schmidtofficinalis, Linne, yar. cavernosa,uov4. septosa (Zamarc/i:?)5. Hippospongia derasa, n. sp(). IStelospongus excavatus, n. sp7. iiuplexus, n. sp