154 MR. W.*P. PYCRAFT ON THE MORPHOLOGY AND 
those described by myself in the Tinamous [81]. The young of Caswarius bear traces 
of similar denticles. 
Podotheca.—The acropodium is made up of small reticulate plates which gradually 
fuse to form ten large transverse scutes, covering its distal third. These are widest in the 
middle of the series. The border region, between the acrotarsium and the acropodium, 
is clothed with tiny granulate plates; these extend downwards so as to clothe the 
proximal half of both outer and inner toes—the remaining region of these, like the 
whole of the middle toe, being protected by large scutes. The inner claw is not 
elongated as in Caswarius. The planta is covered with small reticulate plates. 
It is interesting to note that the podotheca and the cere are mottled with black 
pigment, so as to carry out the general scheme of coloration which characterizes the 
feathers. This mottling is most distinctly marked ina ripe embryo (fig.28). Ina stage 
earlier than this, and in the nestling, they are not nearly so distinct. 
The Uropygium is distinctly traceable in this nestling: in the ripe embryo it is 
much more easily demonstrable. Here it is represented by a small rounded oval mass 
partly embedded in the skin and lying immediately above the cloacal aperture, as in 
Apterya. 
Neither in this nestling nor in the embryos is there any trace of a separate, detachable, 
egg-tooth, as is found in the Meognathe ; but the region of the beak in which this is 
usually borne is, in the embryos, produced into a small conical elevation of a whitish 
colour. Perhaps we should be correct in regarding it as a non-detachable egg-tooth 
becoming absorbed after hatching. In the Neognathe it is detachable, and falls off 
after this event. 
RHEIDA. 
RHEA AMERICANA. 
Apteria :— 
A. spinale.—In one adult and a three-months old nestling this was divided into two 
portions—more or less distinctly—an anterior and a posterior; thus recalling the form 
of this tract in some Tinamous, e. g. Calodromas elegans. The anterior space was 
cordiform in shape, with its base towards the head. Its greatest width was nearly 
2 in., its greatest length about the same. A more or less perfectly feathered area 
of about 4 in. in length divided this from the posterior apterion which is continued 
to the tail. It was at first about % in. wide, narrowed to 14 in., contracting again to 
1 in. for the rest of its course. In another adult and three-months old nestling the 
anterior apterion was very small, 
In other adults, and seven young birds ranging from embryos to half-grown 
specimens, the anterior space was wanting. 
* Figures in brackets refer to Bibliography at end of paper. 
