PHYLOGENY OF THE PALZOGNATHZ AND NEOGNATHZ. 169 
detail. Prepenne only are represented. In the Crypturi only is there a distinct after- 
shaft, and this is of great size, equal, indeed, to the main shaft. In these particulars, 
and in the complexity of the main shaft, it is unique. In Casuarius, Dromeus, and 
Apteryx, these havea well-developed rhachis. An aftershaft appears to be represented 
only in the two former, and here it consists only of a few sessile rami without any trace 
of arhachis. The remiges of the adult Apterya show how the loss of this may have 
come about (Pl. XLV. fig. 13). In Rhea and Struthio the prepenna is umbelliform, and 
thereby differs from that of the other Palwognathe: the aftershaft is represented, as in 
Casuarius, by a few sessile rami. In Struthio, however, the number of these is very 
great. In both Rhea and Struthio the main shaft is represented by 3 thickened rami, 
which in the latter are produced forwards beyond the rest of the feather to form broad, 
hollow, ribbon-shaped laminz, recalling in form the nestling-down of the Crypturi 
(Pl. XLV. fig. 2). 
The following point involves a mystery which I am anxiously endeavouring to solve. 
The prepenne are regarded by some as nothing more than portions of the distal 
extremities of the developing rami of the teleoptiles below. If this is so, how comes 
it that the prepenne of Casuarius and Dromeus have a scarcely recognizable aftershaft, 
whilst in the teleoptile it is of such great length as to be hardly distinguishable from 
the main shaft? In the Tinamous these relations are exactly reversed. The aftershaft 
in the adult feather is very small or wanting, and in the nestling it is as long as the 
main shaft! 
A further most serious objection to the probability of the truth of this view is the 
fact that in Apterya the nestling-down feathers are not driven out by the teleoptiles. 
These arise at the side of the prepenne, the ultimate fate of which my series of 
nestlings is not large enough to show. It is probable that they are shed as soon as the 
definitive feathers have completed their growth. The peculiar downy nature of these 
feathers does not seem to have been recorded before. 
The discovery of a uropygium in Dromeus and Rhea is a point of some interest. 
The podotheca appears to be of some slight value for systematic purposes. Dr. Gadow 
[25] long since pointed out the differences between the three species of Rhea. I have 
not succeeded in finding any appreciable difference between the different species of 
Cassowary, or in distinguishing that of Caswarius from Dromeus. Casuarius lorie 
seems to differ from the other species in this respect and to form a type of its own 
(fig. 2B, p. 155), just as Apteryx australis mantelli seems to differ from the other 
Apteryges in having, as a rule, the acrotarsium clothed with transverse scutes in place 
of small rounded plates. 
Dromeus represents the less specialized of all the Palwognathe.  Casuarius 
undoubtedly comes next ; though in the brilliant coloration of its head and ueck, its 
remarkable casque, spine-like remiges, and elongated claw on its inner toe it has made 
a distinct advance upon Dromeus. 
