Paeker. — On Notornis mantelli. 



253 



of any importance to this rule are in respect of the length of the scapula 

 and of the sternum, both of which are proportionally longer in Notornis 

 than in Trihonyx, instead of shorter, as they would be if the rule held good 

 throughout. As regards the sternum and shoulder-girdle, Notornis is 

 intermediate between Forphyrio — or rather Trihonyx — and Ocydromus, but in 

 the character of the pelvis it differs far more from the normal ralline type 

 than does Ocydromus. 



It has always been acknowledged that Notornis is a degenerate rail, its 

 special and aberrant characteristics being due to structural modification con- 

 nected with the disuse of the wings and the assumption of purely cursorial 

 habits. And I think it is impossible to avoid the conclusion that we have in 

 Porphyria the nearest living representative of the typical ralline ancestor of 

 Notornis, and in Trihonyx the nearest living representative of an important 

 intermediate stage in the process of degeneration. 



The degenerate character of Ocydromus is equally evident, but this genus 

 must be looked upon as descended from a strictly ralline, not from a porphy- 

 rionine ancestor; in other words, as having come along an entirely 

 different line of descent from Notornis, with which it must have, therefore, 

 only a collateral relationship. 



I regret that the absence of specimens in this Museum prevents my 

 instituting a comparison with Aptornis, but judging from Professor Owen's 

 figures, it seems to me that this largest of rails is a further development, by 

 degeneration, of an ocydromine type. For instance, the short sternum, 

 narrowing posteriorly, seems a sort of exaggeration of that of Ocydromus, 

 and the pelvis approaches in its proportions to the same genus, having a far 

 less proportional breadth than in Notornis. 



These conclusions are expressed in the following diagram : — 



Aptornis. 



Ocydromus. 



Notornis. 

 Tribonyx. 



Porphyrio. 



