DIVING BIRDS. 541. 
an ostrich, lived in Texas and New Mexico, part of a leg- 
bone having been found on the San Juan River. 
Sub-class 4. Carinate.—All other living birds belong to 
this group; they are remarkably homogeneous in form 
and structure, and the subdivisions may be regarded as 
orders. They are characterized by the keeled breast-bone 
or sternum—the wings, as a rule, being well developed. 
The diving birds (Pygopodes) are eminent as swimmers, 
and comprise the penguins, auks, puffins, grebes, and loons. 
The penguins are confined to the antarctic regions. They 
are large birds, and form a characteristic element in a Pata- 
gonian landscape. The bones are solid, not light and hol- 
low, as in other birds; the wings are small, paddle-like, 
with scale-like feathers ; on shore they have an awkward 
gait. They lay but a single egg, and some species do not 
lay their egg on the rocks, but bear it about in a pouch- 
like abdominal fold. The penguins, however, differ so 
much from the other divers that they are now often ranked 
as a separate group of this grade, called Sphenisct. 
The guillemots and auks are characteristic arctic birds 
ranging from Labrador northward, and have great powers 
of flight. The gare fowl, or great 
auk (Alcea impennis, Fig. 462), is 
nearly or quite extinct, being un- 
til lately confined to one or two 
inaccessible islets near Iceland, 
where it has been extinct since 
1844, and to Labrador, though 
formerly it ranged from Cape 
Cod northward, a few survivors 
having lived on the Funks, an 
islet on the eastern coast of New- 
foundland, within perhaps thirty 
years. 
The loons are well known for Fig. 463.—Roseate Tern.—From 
their large size and quickness in 7e™”* 7901087: ; 
diving. They are migratory, laying two or three eggs in 
rushes near the water’s edge. 
The petrels, gulls, and terns (Fig. 463, roseate tern) rep- 
