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. CarinatcB. 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 Sphenisci. 



The guillemots and auks are characteristic arctic birds 

 ranging from Labrador northward, and have great powers 

 of flight. The gare fowl, or great 

 auk (Alca 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 coasfc of New- 

 foundland, within perhaps thirty 

 years. 



The loons are Well known for Fig. 463. Roseate Tern. From 

 1 1 i -I i Tenney's Zoology. 



their large size and quickness in 



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- 



