126 The Platycercine Parrots of Australia. [Ibis, 



features. This genus extends over southern and south-central 

 Australia, but not into Tasmania. Two representative species 

 appear recognizable (B. barnardi and B. zonarius, PI. III. 

 fig. 9 & Text-fig. 1, b. & z.), and the variation is marked. It 

 appears that the normal green survived more conspicuously, 

 though cyanism seems to have been the most dominant factor ; 

 erythrism, melanism, and xanthochroism are all seen, but 

 in subordinate features, while the peculiar scalloped back 

 has never been produced. The evolution of the feature in 

 Platycercus is inexplicable at present, and in the present 

 genus it has never heen developed, though apparently both 

 groups are referable to allied ancestral sources. 



A red forehead only appears sporadically throughout the 

 genus, which otherwise has suppressed the erythristic element. 

 The chief difference between the two species appears to be 

 the possession by the western form of a wholly black head : 

 the eastern form has the crown of the head pale green, the 

 nape brown; in some cases the brown predominates, in others 

 the green. Generally, however, the chief feature is the 

 bluish shade of the green back, rump, and breast ; the 

 xanthochroistic element seems confined to a yellow band 

 across the belly, which is variable in size, sometimes extend- 

 ing from the breast to the vent, at others only appearing as 

 a spot on the abdomen. The variation in size is noteworthy 

 and needs careful study. The speciesseem peculiarly plastic, 

 as subspecies can be distinguished with ease if few speci- 

 mens are examined, but more material tends to confuse the 

 judgment, probably because the birds are wanderers to some 

 extent and the subspecies are limited in breeding-areas. 



Speculation as to the origin of these species is handicapped 

 by the survival in the south-west of a species commonly 

 referred to a distinct genus, Purpureicephalus (PI. III. fig. 6 & 

 Text-figure 2, A), on account of a structural difference in the 

 bill. Otherwise it is a Barnardius as regards colour-pattern, 

 the erythristic element, which has been almost entirely 

 eliminated in that genus, having maintained itself, as the 

 bird has a red head and is mauve underneath with red under 

 tail-coverts. I must note that the cheek-patch, seen in the 

 genus Platycercus, is present in the genus Barnardius in a 



