Hectok. — On the Anatomy of Flight of certain Birds. 285 



1. The Antipodes Paerakeet (Pezoporus fairchildii) . 

 A comparison has been made of the structure of the sternum 

 and scapular appendages with those of the red-topped parra- 

 keet, which is also found in the Antipodes Island, but is con- 

 jectured to have been a more recent introduction. The ana- 

 tomical peculiarities bear out this view. In the New Zealand 

 form, which is smaller in size, the sternum has a larger keel, 

 but the marginal area external to the supporting ridge is largely 

 developed, while in the Antipodes Island form this marginal 

 area is almost wanting. On the other hand, the body of the 

 sternum is more massive, broader, and more complete than in 

 the New Zealand red-topped Platycercus, the large foramina 

 being almost obliterated. The shape and angle of articulation 

 of the acromions and scapulae are the same in both, but there 

 is a marked difference in the representative of the clavicles. 

 The true furculum formed by the thorough anchylosis of the 

 clavicles in the mesial plane is well known to be totally absent 

 in Platycercus and its allies, but it is represented in some 

 forms, such as Pezoporus, or the ground-parrakeet of Australia, 

 by a band of fibrous tissue that braces the sternum to the 

 distal extremity of the coracoid, thus supporting the articula- 

 tion of the wing. It thus performs one function of the 

 furculum, but not its chief function, which is that of a power- 

 ful spring, reacting against the downward stroke of the wing 

 in powerful flight. 



Now, in the Antipodes Island parrakeet there is a marked 

 development of the fibrous bond between the sternum and 

 the coraco-humeral articulation, and, following in the same 

 direction, we find in the kakapo (Stringops habroptilus), which 

 is a parrot without proper flight, that the keel of the sternum 

 is almost obliterated, while the fibrous sterno-coracoid has 

 been enormously developed and ossified, so that it forms a 

 wide bony process, which on each side is attached to the 

 sternum. If, as is probable, and has always hitherto been 

 accepted, these processes represent clavicles, then it must be 

 conceded that this clavico-sternal form of articulation more 

 resembles that of animals which use the fore-limb for pro- 

 gression by thrust rather than by flight. 



If this view be correct, there is good ground for supposing 

 that the Antipodes Island parrakeet is an ancient form which 

 has in some degree lost its power of flight, and has de- 

 generated toward the condition of the kakapo. 



2. WlNG-BONES OF THE AlBATBOS. 



The means by which the albatros maintains its remarkable 

 flight for long periods and at all various angles to the wind 

 without any apparent recovery of its initial velocity by the 

 flapping of its wings has been the subject of much contro- 



