170 ME. W. P. PTCEAFT ON THE MOEPHOLOGY AND 



Apteryx should be placed next. It has lost the aftershaft to the feathers ; the 

 prepenna has a well-developed rhachis. In the large size of the apteria and in the 

 possession of an oil-gland it resembles the Carinatce ; so also it does in the softness of 

 the neossoptiles. 



Ehea and Struthio are undoubtedly the most highly specialized of the group. One 

 of the chief pieces of evidence of this, from the point of view of pterylological 

 characters, is the fact that the prepennae has neither aftershaft nor rhachis. The fact 

 that the wing is larger in these two than in the remainder of the group, only means 

 that the need for this organ remained longer, and is not to be regarded as an advance 

 upon that of Casuarius or Apterycc, as the case may be. In them the decline of the 

 wing set in earlier. 



The structure of the teleoptiles in these last two is more complex than in the other 

 groups : booklets are feebly represented. These have lingered longer, just as the power 

 of flight. 



We may briefly sum up the salient features of the pterylosis of the PalceognatJm 

 as follows : — 



All the flightless Palceoguathce agree, and differ from the Neognathce, in having 

 the under surface of the wing naked ^, and in that all the feathers have discontinuous 

 vanes. 



A. Adults. 



DronuEUS, Casuarius, aud Apteryx have ao ala spuria. Lacking a pollex. 



The teleoptiles of Dromaus and Casuarius have a large aftershaft. There is no oil-gland. 

 DromcBHS has numerous though greatly degenerate remiges — 17 in all. 

 Casuarius has few remiges — -6 in all. These are degenerate and peculiarly modified 

 to form elongated porcupine-like quills, representing only the calamus of 

 ordinary feathers. 

 The teleoptiles of Apferyx have no aftershaft aud a large oil-gland; it has few remiges — 

 13 in all — aud these have a long calamus. Apteria are larger. Rictal bristles are of 

 great leugth. 

 Rhea and Struthio have a large ala spuria. 



The teleoptiles of Rhea and Struthio have no aftershaft : there is no oil-gland. Remiges are 

 numerous and large. 



The remiges of Rhea number 28; metacarpo-digitals 12. There are no rectrices. 

 The remiges of Struthio number 32 ; metacarpo-digitals 16. There are large rectrices. 

 Apteryx aud the Crypturi are the only Palseognathinse lacking a sternal callosity. 



' The naked under surface of the wing of the flightless Struthious birds is probably a secondary feature due 

 to the suppression of the feathers by the long continued application of the wing to the side of the body. 



