290 Unwersity of California Publications in Zoology  \Vou. 18 
As shown above, they resemble the ostriches in many details, and 
are unquestionably more nearly related to them than to any other 
Ratitae. In the general arrangement of feathers and in the form 
of the barbules, while probably, like ostriches, at the end of a 
short separate path of evolution, they appear to be nearer the line 
of descent of carinate birds. Special attention is drawn to the fact 
that the barbules which approach most nearly a pennaceous type, 
are in the positions where pennaceous barbules are most likely to 
be found at the height of their development in carinate birds, i. e., 
on the basal portion of barbs beyond the middle of the feather. 
c) Summary 
In addition to common ratite characters, Rheiformes are char- 
acterized by the following in common with ostriches: 
(1) Absence of aftershafts. 
(2) No under wing coverts (one row in ostriches). 
(3) Unusually large number of primaries. 
(4) A type of barbule which is intermediate between a downy 
and a pennaceous type, differing, however, from ostriches. 
They are further characterized by: 
(1) Differentiation of the barbules of different portions of 
feathers. 
(2) Highest developed barbules with flattened base provided with 
barbicels on ventral edge only, and filamentous pennulum with prongs 
similar to those of typical down feathers of penguins. 
(3) Less highly developed barbules with basal portion reduced, 
thus becoming still more like the down barbules of penguins. 
8. Order CASUARIFORMES 
1G I ERE By 
The birds of this group differ very considerably from the ratite 
birds previously studied, but agree with them in the several important 
characters common to all ratites. Although Nitzsch (1867) described 
filoplumes from a cassowary, he was undoubtedly mistaken in his 
identification of them (see Part I, p. 260), for filoplumes are as com- 
pletely absent in this group as in any of the other Ratitae. Unlike 
those of the ostriches and rheas, the primaries are greatly reduced, 
hardly differentiated at all in Dromaeidae, and reduced to five or six 
stiff black spines in Casuariidae, representing, according to Beebe 
