116 Mr. G. M. Mathews on the [Ibis, 



the genus Barnardius I recognize two. Other workers have 

 acknowledged many more species, but I regard these forms 

 as subspecies only, my most recent criticism recording 

 between twenty-five and thirty subspecific forms. Before I 

 undertake the consideration of these I woukl remark upon 

 some remarkable features of the members of the genus 

 Platycercus. Though the species are now well established, 

 and in many cases the subspecies are also fixed, there is a 

 peculiar plasticity seen in the group — albinos, aberration, 

 and hybrids constantly occurring. Further, there has been 

 recorded, more than once, what is apparently dimorphism 

 in the immature stage : that is, the immature taking on the 

 adult plumage in the nest, though the immature plumage is 

 different fi'om that of the adult. 



The whole group is confined to Australia, no member 

 ranging into New Guinea or the islands to the north, nor are 

 the species represented there by any form at all comparable. 



Two species of the genus Platycercus occur in Tasmania, 

 and these well merit special consideratioxi, as one is the 

 least developed and the other the most developed, as regards 

 coloration as distinct from colour-pattern. It might be 

 farther noticed that in the extreme south-west a species has 

 developed from the Barnardius group a structural feature 

 which long ago claimed generic rank (^Purpureicephalus), 

 and this will be dealt with towards the end of these remarks. 



As we have here a peculiar well-marked group isolated 

 in Australia, we are given factors which are not interfered 

 with by extra-limital and unknown complications. Some 

 workers have in other Continents ranked as subspecies 

 forms which were really representative species. In many 

 cases the diff'erence between a subspecies and a representa- 

 tive species is difficult to determine, and a great deal is left 

 to the personal equation. In the peculiar case now before 

 us, I can show that while we have species representing each 

 other we have also subspecies, and in this instance these are 

 well-marked groups of different value. 



In the genus Platycercus I admit seven species, viz. : 

 caledonicus, elegans^ flaveolus, icterotis, adscitus, venustus, 

 and eximius (see PI. III.). While the first six are more 



