256 STRUCTDEE AND CLASSIFICATION OF BIEDS 



treme type ; in Cacatua cristata, for example, when the syrinx 

 is seen on a lateral view the membrane occupies a great deal 

 of the outer lateral region of the commencement of the 

 bronchus. 



The semi-rings of the bronchus are at first very sinall, and 

 do not extend across the side of the bronchus ; they gradu- 

 ■ally increase in length, until at the sixth or .seventh they 

 come to extend right across the syrinx.*' In Microglossa 

 aterrima the syrinx' is in certain respects less abnormal; 

 the rings are still feeble, but on a lateral view of the organ 

 they extend completely across, and there is on Such a 

 view no bare tract of membrane, such as we have figured 

 in Cacatua. 



Calyptorhynchus Banhsi is intermediate between the 

 two extremes ; the first semi-ring only is iiicoinplete, inas- 

 much as it does not reach from one side of the syrinx to 

 the other — or rather we should say from the anterior to the 

 posterior side. * 



Stringops hahroptilus has the same weak cartilaginous 

 bronchial semi-rings ; but on a lateral view of the syrinx they 

 are seen to extend right across, 



h. The second group contains the following genera :^ . 



Ghrysotis. Tanygnathus. 



Pyrrhulopsis. Eos. 



Trichoglossus. Polyteles. 



Lorius. ' Platycercus. 



Pionus. Poeocephalus. 



Psittacus. 



These genera are differentiated from those of the first 

 division by the fact that the bronchial semi-rings are as a rule 

 ossified, and are frequently more or less fused together ; at 

 the same time the first ring is commonly concave upwairds, 

 whereas in the parrots of the first-rnentioned group the 

 bronchial semi-rings are straight. 



The most extreme type is perhaps offered by Ghrysotis ; 

 of this genus I have seen the following Specifes : — 



