254 Transactions.— Zoology. 
General Remarks. 
The study of Notornis suggests certain questions of interest as to 
flightless birds in general, and especially as to that group of preeminently 
flightless birds, the Ratite, and their relations on the one hand to the 
Carinate, and on the other to the reptilian ancestors of the class. 
The Ratite are usually regarded, from certain undoubted reptilian charac- 
teristics, as being nearer the reptilian stock from which birds sprang, than 
the Carinate, and there seems to bea general opinion that large ratite birds 
of some sort formed the actual connecting link between reptiles of a dino- 
saurian type and the Carinate. 
But it appears to me that there are serious difficulties in the way of this 
view. The Ratite, in many of the most distinctive avian characteristics, 
approach no nearer to reptiles than do the Carinate. For instance, in the 
characters of the vertebre:, the femur, the tibio-tarsus, the tarso-metatarsus, 
the pelvis and sacrum, and, in the case of Dinornis and Apteryx, of the 
small, backwardly-directed hallux. 
The chief skeletal characters, except those of the skull, in which 
the Ratite differ from the Carinate, are :— 
a. The absence of a keel to the sternum : 
6. The great width, and, except in Rhea, the extreme flatness of 
the sternum, i.e. the openness of the transverse sternal angle. 
e. The comparatively small size of the scapula and coracoid. 
d. The coraco-scapular angle is equal to two right-angles. 
e. The axis of the coracoid is vertical or inclined backwards. 
f. The fareula is rudimentary or absent. 
If the Ratite are to be looked upon as in any way an ancestral group, these 
characters must be considered of primary importance, that is, as having @ 
true phylogenetic significance. But in all these points, the Ratite merely eX- 
aggerate what we find in the flightless members of the Carinate order. 
There is no more keel to the sternum ‘in Stringops or Cnemiornis than 10 
Struthio, and the transverse sternal angle of Rhea is very considerably less 
than in the flightless Carinate. In these, also, there is a progressive diminu- 
tion in size of the coracoid and seapula in passing from good fliers to flightless 
members of the same class, and at the same time a gradual rotation back- 
wards of the dorsal end of the coracoid, and increase of the coraco-scapular 
angle. In fact, with the exception of the foramen in the coracoid of the 
ostrich, I know of no character in the shoulder-girdle of Ratite which can 
be pointed out as distinctively reptilian. One important distinction betwee? 
the shoulder-girdle of reptiles and that of birds, is the position of the bones- 
In reptiles the coracoid passes from its sternal articulation outwards and 
slightly upwards, and the scapula (including the supra-scapula), from its 
