170 MR. W. P. PYCRAFT ON THE MORPHOLOGY 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 Carinatw ; so also it does in the softness of 
the neossoptiles. 
Rhea 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 prepenne 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 Caswarius or Apteryx, 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: hooklets 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 Paleognathe 
as follows :— 
All the flightless Palwognathe agree, and differ from the Meognathe, in having 
the under surface of the wing naked }, and in that all the feathers have discontinuous 
vanes. 
A. ADULTS. 
Dromeus, Casuarius, and Apteryx have no ala spuria. Lacking a pollex. 
The teleoptiles of Dromeus and Casuarius have a large aftershaft. There is no oil-gland. 
Dromeus 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 Apteryx have no aftershaft and a large oil-gland; it has few remiges— 
13 in all—and these have a long calamus. Apteria are larger. Rictal bristles are of 
great length. 
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 and the Crypturi are the only Paleognathine lacking a sternal callosity. 
1 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. 
