270 STRUCTURE AND CLASSIFICATION OF. BIRDS 



Subf. (4.) Arinae. Ara, Gonurus, Bolborhynchus, 

 Galea, Psittacus, Posocephalus, Nestor. 

 Div. 6. Ambiens absent. 



Subf. (5.) Pyrrhurinse. Pyrrhura, Lathamus, Gora- 



copsis, Pyrrhulopsis. 

 Subf. (6.) Platycercinse. Furcula lost. 



Platycercus, Psephotus, Gyanorhamphus, Psit- 

 tacula. 

 Subf. (7.) Chrysotinge. Oil gland lost. 

 Ghrysotis, Pionus, Brotogerys. 



A phylogenetic tree accompanies Garrod's scheme, in 

 which it is assumed that the ancestral parrot possessed the 

 normally running carotids, an ambiens, an oil gland, and a 

 complete furcula. From this the main stems are given off, 

 in one of which the carotids remained normal, while in the 

 other the left became superficial. The loss of the other 

 characters leads to further branching of both main branches. . 



The Stringopinse, especially Stringops itself, are the 

 nearest living representatives of the ancestral stem. 



FuHBRiNGBR ' also argues for the low position of Strin- 

 gops, in contradiction to Marshall, who holds that it is an 

 extremely modified form. Its owl-like plumage, defective 

 carinal keel, and associated loss of the power of flight are 

 undoubtedly modifications, but it seems more probable that 

 they are modifications of an ancient than of a modern type 

 of parrot. Fuebringer's views are chiefly based upon the 

 flexibility of its anatomical characters. I have already 

 referred to the variability of the ambiens : the sternum offers 

 another fact of the same kind ; sometimes it is entire, without 

 notches or foramina, sometimes there are one or two upon 

 one or the other side, and occasionally two incisurse, one 

 upon each side. This variability must not be associated, as 

 variability may often be associated, with a rudimentary 

 structure ; the xiphostern'um is not rudimentary, though 

 the keel is. 



' ' Binige iJemerkungen iiber die Stellung von Stringops,' &o., Journ. f. 0. 

 1889, p. 236. 



