PHYLOGENY OF THE PAL.EOGNATH.E AND NEOGNATB1E. 169 



detail. Prepennae 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, Dromceus, and 

 Apteryx, these have a 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 a rhachis. The remiges of the adult Apteryx show how the loss of this may have 

 come about (PI. XLV. fig. 13). In Rhea and Strut/no the prepenna is umbelliform, and 

 thereby differs from that of the other Palceognathce : 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 StrutMo 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 laminae, recalling in form the nestling-down of the Crypturi 

 (PI. XLV. fig. 2). 



The following point involves a mystery which I am anxiously endeavouring to solve. 

 The prepennae 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 prepennae of Casuarius and Dromceus 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 Apteryx the nestling-down feathers are not driven out by the teleoptiles. 

 These arise at the side of the prepennae, 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 Dromceus 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 Casuarius from Dromceus. Casuarius lorice 

 seems to differ from the other species in this respect and to form a type of its own 

 (fig. 2 b, 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. 



Dromceus represents the less specialized of all the Palceognathce. Casuarius 

 undoubtedly comes next ; though in the brilliant coloration of its head and neck, its 

 remarkable casque, spine-like remiges, and elongated claw on its inner toe it has made 

 a distinct advance upon Dromceus. 



