Paeker. — On Kotornis mantelli. 255 



coracoid articulation upwards and somewhat inwards, so that the two pairs 

 of bones form, with the adjacent portions of the sternum and vertebral 

 column, a transverse arch or true shoulder " girdle": in Carinatce, on the 

 other hand, the coracoid passes from the sternum forwards, upwards, and 

 outwards, and the scapula, from its coracoid end, backwards and upwards. 

 In the RatitcB the bones make no closer an approach to reptiles in this than 

 in other characters, the coracoid is still directed upwards and slightly out- 

 wards, the chief alteration in its position being that it has a slight backward 

 inclination, this being, however, only an extreme development of what 

 occurs in Notornis and Ocydronius : the scapula also passes upwards and 

 backwards, and not inwards. Finally, a diminution of the furcula occurs in 

 all birds with functionless wings. 



In a suggestive paper on the phylogeny of Mammals,* Professor Huxley 

 has brought out the fact that it gives a wholly erroneous notion of the 

 pedigree of that class to suppose that either the Marsupials or the Monotremes 

 lie in the direct line of descent of the Monodelphia. He points out that 

 the ancestors of the Monodelphia — the MetatJieria — were probably didel- 

 phous but not marsupial, and that the Marsiqnalia are to be looked upon 

 as an offshoot of the Metatheria, which, while retaining the lower characters 

 of brain and urinogenitals, and the large prs-pubes, have undergone great 

 specialization in other directions. In the same way Professor Huxley sup- 

 poses the Monotremata to be a specially modified offshoot of the Prototheria, 

 the forerunners of the Metatheria. 



It appears to me that a far juster view of the affinities of the Ratitce than 

 that alluded to above, is to be had by considering them as the greatly 

 specialized but degenerate (using that word in the sense in which I have 

 applied it to Notornis and other flightless birds) descendants of Carinate 

 birds. Professor Huxley remarks! that " in all probability the existing 

 RatitcB are but the waifs and strays of what was once a very large and im- 

 portant group." What I wish to insist upon is that this hypothetical group, 

 like the mammalian Metatheria, gave rise to two races of descendants : one 

 continuing the direct line of descent — the Carinatce — the other arising by a 

 gradual modification of structure correlated with disuse of the wings — the 

 Eatitce. Just as the Metatheria gave rise to marsupial descendants which 

 exist now only in the Austro- Columbian and Australian regions, so we 

 may suppose that a widely distributed group of primitive typical birds — 

 Proto-CarinatcB — gave rise to Eatite descendants, now confined to the 

 Austro-Columbian, African, and Australian regions. The fact that such 



* " Nature," vol. xxiii., p. 227. 

 t Proc. Zool. Soc, 1867, p. 419. 



