566 Mr. L. W. Wiglesworth on the Polynesian 



XLV. — On the Polynesian Members of the Genus Ptilopus, 

 By Lionel W. Wiglesworth. 



(Plate XI.) 



The Pigeons of the genus Ptilopus, as distributed among 

 the islands of Polynesia, exemplify on a remarkable scale 

 the formation of new species by geographical separation, 

 which is shown in sach a striking manner in the Parrots, 

 Blackbirds, and Rhipidurae of the Fiji Islands, and above all 

 in the well-known Land-shells of the family Achatinellid<s of 

 the valleys of Oahu. In these cases, however, a narrow pro- 

 jecting mountain-ridge or a few miles of sea are sufficient to 

 prevent the species from interbreeding and losing their iden- 

 tity — as no doubt they would for the most part, could they 

 pass freely from one locality to another ; but with the genus 

 Ptilopus a stretch of unbroken ocean 20U or 300 miles wide is 

 required to serve the same end, in consequence of the good 

 powers of flight of these birds. The eighteen known Poly- 

 nesian species of Ptilopus are therefore spread out over an enor- 

 mous area, in addition to that occupied by the other members 

 of the genus in Australia, Papuasia, and the islands of the 

 Oriental subregion. Ranging more widely than even ^jo/om* 

 and Tatare, the genus Ptilopus is found throughout the Poly- 

 nesian subregion, so far as it is known, except, perhaps, in the 

 Marshall, Gilbert, and Fanning groups, and, of course, in the 

 Sandwich Islands, which form really a subregion in themselves. 

 The distribution of these Pigeons in Polynesia has been well 

 sketched out, in the ' Proceedings ' of the Zoological Society 

 of London for 1874^ by Dr. Finsch, who, with Dr. Hartlaub, 

 must always be regarded as the pioneer in the ornithology 

 of this subregion, and again, in the same ' Proceedings ' 

 for ]878, has been treated of by Mr. Elliot. Unhap- 

 pily, the views expressed in the elaborate monograph of 

 the latter accord so ill — at least with regard to Central 

 Polynesia — with those of Dr. Finsch, Mr. Layard, and other 

 naturalists, that one is puzzled to know which is the most 

 correct authority. As regards localities, however, it is 

 obvious that the collecting naturalist is he who should be 



