290 University of California Piiblications in Zoolofjjj (Vol. 13 



As sliowii above, they resemble the ostriches in many details, and 

 are unquestionably mor(; 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 aj^proach most nearly a pennaceous type, 

 are in the positions where peiniaceous 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. 



3. Order CASUARIFORMES 

 PI. 14, Figs. 3, 4. 



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 



