[[p. 333]] These islands must not be confounded with the Soloo Islands, between Borneo and Mindanao. On our maps they are written Zula, or Xulla; but as neither of these gives the correct pronunciation, I write the name exactly as it is pronounced by the natives. The group consists of three islands, Sula Mangola to the east, Sula Taliabo to the west, and Sula Bessi to the south. They lie nearly equidistant between Celebes and the Moluccas, being about eighty miles from the nearest part of Celebes, but with several intervening islands; only forty from Bouru, but a clear sea between them; and about ninety from Batchian, with the Obi Islands intervening. The two larger of the Sula Islands are each about fifty miles long and twelve to fifteen wide.

     Islands so small, and so surrounded by others whose productions are more or less known, might be expected to be not worth visiting by the naturalist, as it would seem most probable that they would contain only the common species of the surrounding islands. [[p. 334]] Believing such to be the case, I should probably have taken no trouble to obtain a collection from thence, had I not been told by many of the natives who trade to Sula that a beautiful little bird of the Parrot family was found there and in no other place. In consequence of this and other more or less vague information about its productions, I arranged with my assistant, Mr. Allen, to go there for two months. Owing to bad weather, ill health, and the usual troubles about boats, men, and provisions, he obtained but a very small collection, made on the southern and eastern islands. Only forty-eight species of birds were obtained, yet out of these there were seven new species, which appear to be altogether peculiar to this little group of islands; five or six others are rare birds of the Moluccas or Celebes, and the remainder the commoner species from the same countries.

     But although the Sula Islands show a mixture of the forms of Celebes and the Moluccas, yet these countries have not contributed towards its fauna in anything like an equal proportion. Deducting ten species which have a wide range over a large portion of the Archipelago, and even beyond it, and dividing the remainder into two portions--those that may be supposed to have been derived from Celebes on the one hand, and from the Moluccas and islands to the east and south of them on the other,--we shall find that the Celebesian forms are almost exactly double the rest. Twenty species are identical with birds found in Celebes, and five new species are of Celebesian forms; whereas only eleven species are found also in the Moluccas, and but two of the new species can be affiliated to Moluccan types. Twenty-five of the species of the Sula Islands must therefore have been derived from Celebes, and only thirteen from the Moluccas. The accompanying Table (p. 335) shows the species distributed according to their derivation.

     It is further interesting to remark that all the Raptores and all the Pigeons and Parrots, but one of each group, are Celebesian species or forms; while among the Moluccan species are many active but weak-flying birds, including five species of Flycatchers, which would be most likely to be carried over by strong winds. Further, the birds derived from the Moluccas contain three genera which do not occur in Celebes.

     From these facts it seems to me clear that the Sula Islands are really an outlying portion of Celebes, and must at some former period have had a much closer connexion with that great island than at present. The Moluccan species must therefore be considered as immigrants, many of them from Bouru, which is only forty miles distant; and the fact that some of these early Moluccan immigrants have already become modified into distinct forms, some of which may be classed as species, others as varieties, shows for how long a period of time the small and scattered islands of the Moluccas must have remained in their present disconnected state.

     The following Table shows the geographical affinities of the birds of the Sula Islands:--

     [[p. 336]] There are in all thirteen new species described in the present paper, a few of which are also in my collections from Celebes and the Moluccas. In many cases I have given, from my own notes, the colours of the feet, bill, and iris, as well as the dimensions, from the fresh-killed specimens of rare or interesting species which have been previously described. In the following list of the species I have followed the arrangement of Bonaparte's 'Conspectus,' a work which is in the hands of every ornithologist.