868 The American Naturalist. | [October, 
following summary of the characters supporting the view that Apteryx 
has been derived from a flying bird: The presence of an alar mem- 
brane or patagium ; of pteryle and apteria; of remiges and tetrices 
majores; the attitude assumed during sleep ; the presence of two 
articular facets on the head of the quadrate; of a pygostyle; of ves- 
tigial acromial, procoracoid and acrocoracoid processes ; the extreme 
variability of the sternum, shoulder girdle and wing, indicating degen- 
eration; the occasional occurrence of a median longitudinal ridge or 
vestigial keel on the sternum; the position of the shoulder girdle and 
sternum in Stage E; the fact that the skeleton of the fore limb is that 
of a true wing in Stage F ; the early assumption of undoubted avian 
characters in the pelvis; the typically avian characters, both as to 
structure and development, of the vertebral column and hind limb; 
the fact that the brain passes through a typical avian stage with lateral 
optic lobes ; and the relations of the subclavius muscle. 
On the other hand the total absence of rectrices tells against this 
ew. 
The following characters indicate descent from a more generalized 
type than existing birds. The characters of the chondrocranium, 
‘especially in the earlier stages, but many of these peculiarities, e. 9. 
the absence of interorbital septum, may, however, be correlated with 
the diminished eyes and the enlarged olfactory organs ; the presence of 
an operculum in early stages (as this structure has not been described 
in reptiles, it either proves nothing or too much); the presence of a 
‘well marked procoracoid in comparatively late embryonic life; and 
the characters of the pelvis. 
Again, the early assumption of their permanent position by the 
limbs; the late appearance and obviously degraded character of the 
hyoid portion of the tongue bone; the position of the nostrils and the 
peculiar mode of development of the respiratory portion of the nasal 
chamber and the total absence of clavicles are characters in which the 
Apteryx exhibits greater specialization than other birds. - ; 
The general balance of evidence seems to point to the derivation of 
‘both Ratitæ and Carinatæ from an early group of typical flying birds _ 
or Protocarinate. 
Tt has always seemed to me that on the hypothesis of its development 
from an ordinary reptilian fore limb, e. g., that of a Dinosaur, the 
wing is one of the most striking examples of the uselessness of incip- 
lent structures. If, on the other hand, we suppose it to have been 
„evolved from a patagium which gradually diminished part passu with 
