44 CLASSIFICATION OF BIRDS. 
Subclass STRUTHIONIFORMES. 
The Struthioniformes combine two characters not known to be combined in any other 
birds :— 
A. The keel of the sternum has become obsolete. B. Basipterygoid processes very 
large, and placed on the basisphenoid rather than on its rostrum. 
This diagnosis may be strengthened by many other characters :— 
C. Oil-gland absent. D. Plumage of neck continuous. 










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There has been much diversity of opinion as to the precise boundaries of the Ratite. 
The widest scheme places the Struthiones, the Casuarii, the Rhee, the Apteryges, and the 
Crypturi together under the name of Dromeognathe (Stejneger, Stand. Nat. Hist. iv. p. 31), 
because they are all supposed to have the ilium posteriorly separated from the ischium, and 
are assumed to resemble each other in the details cf their palates. A more restricted 
scheme excludes the Crypturi (Huxley, Proc. Zool. Soc. 1867, p. 426), because the keel of 
their sternum is so fully developed ; whilst the most restricted scheme excludes the Apteryges 
also (Firbringer, Morph. und Syst. Vogel, p. 1467), which are removed with the Crypturi to 
the Alectorornithes. The great variations in the so-called dromsognathous palate, and the 
facts that in the Crypturi the ilium is posteriorly united to the ischium by cartilage, and 
that in many skeletons (presumably of old birds) of Caswarius they are united by bone, are 
probably sufficient grounds for rejecting the widest scheme. 
