FLIGHTLESS BIRDS. 
555 
evident they were derived from flying-birds quite independently of the modern 
flightless birds. 
Eocene Flightless As they may possibly have some connection with the Stereor- 
Birds. nithes, although it is almost as probable they may form a group by 
themselves, it may be convenient to mention here certain giant extinct birds from 
the Lower Eocene of France, England, and the United States, which constitute the 
family Gastornithidce. All have a bony bridge at the lower end of the tibia, 
while in the European Gastornis the component bones of the skull remained 
separate throughout life, and it is possible that there may have been a large tooth 
on each side of the upper jaw, while the symphysis of the lower mandible was 
short. In North America the group is represented by Diatryma. 
The Flightless or Ostrich-Like Birds. 
Subclass Ratitse. 
With the exception of certain specially modified species like the dodo, in 
which the power of flight has been lost, the existing birds hitherto treated are 
characterised by the circumstance that the breast-bone is provided with a strong 
vertical median keel, to afford support for the muscles necessary for flight, while 
both the scapula and metacoracoid are separate elongated bones, forming an acute 
or right angle at their junction. On account of this general presence of a keel to 
the breast-bone, the foregoing orders are brigaded together into a single assemblage 
or subclass, known as the Carinatce, which may be anglicised into Carinates. As a 
rule, the Carinates possess to a greater or less degree the power of flight; and 
they are further generally characterised by the circumstance that in the pelvis the 
bones known as the ilium and ischium are united at their outer extremities so as 
to enclose a foramen 1 ; while the head of the quadrate bone, by which the lower 
jaw articulates with the skull, is double ; and in the palate the vomer (except in 
the tinamus) is not fused with the neighbouring bones, or interposed between them 
and the rostrum of the sphenoid. On the other hand, in the birds now to be con¬ 
sidered the breast-bone is invariably devoid of a keel, while the metacoracoid is short 
and united with the scapula, and the two bones form a very obtuse angle at their 
junction 2 ; moreover, the furcula is incomplete, so that its two branches remain quite 
separate. All these birds further agree in having their wings greatly reduced, so as 
to be utterly useless for flight. They are also characterised by the extremities of the 
ilium and ischium (except in very old individuals of the rheas and emeus) remaining 
distinct 3 ; and likewise by the single head of the quadrate bone, as they are by the 
vomer, which is broad behind, being interposed between the other bones of the palate 
and the rostrum of the sphenoid, and also frequently fused with some of them. 
Other features of the group are the absence of an oil-gland, and of any marked 
distinction between feathered and unfeathered areas on the skin; while the hook- 
1 This circular foramen or vacuity is shown in the pelvis of the skeleton of the parrot figured on p. 292 oi 
Vol. III. 
2 This arrangement is shown in the figure on p. 294 of Vol. III., which is taken, by the way, from an aberrant 
Carinate. 
3 See figure in Vol. III. p. 290. 
