486 



MANUAL OF ZOOLOGY 



as in the cassowaries. In the latter the head is produced 

 into a great horny prominence or " casque," supported by 

 an elevation of the roof of the skull. The cere is frequently 

 absent. The nostrils are placed at the base of the beak, 

 except in Apteryx, in which they are at the tip. 



The essential structure of the wing — apart from its feathers 

 — is very uniform. As a rule all three digits are devoid of 

 claws, as in the pigeon, but the ostrich has claws on all 



Fig. 29s — A.wing of nestling of Opisthocomus ; B, wing of adult Apteryx ; both 

 from the inner (ventral) aspect; cb. 1, first ctibital remex; dg. 1, dg. 2, dg. 3, 

 digits; pr.ptgm, pre-patagium; pt.pgm, post-patagium. (A, after Pycraft; 

 B, after T. J. Parker.) 



three digits; rhea on the first, and sometimes the second 

 and third; the cassowary, emu, and kiwi (Fig. 295, B) 

 on the second ; and the crested screamer ( Chauna) and 

 two other species, and, as a rare abnormality, the common 

 fowl and the goose, on the first. With these exceptions, the 



