CLASSIFICATION OF BIRDS. Si9 



vertebrre are biconcave ; the ribs are very thin ; the sternum is broad, 

 and perhaps had a keel ; there seem to have been abdominal ribs. The 

 three digits of the hand have separate metacarpals, and are clawed ; 

 the bones of the pelvis are not fused, there are only a few sacral vertebra, 

 perhaps there was an ischial symphysis, there is a complete fibula with 

 its distal portion in front of the tibia, the metatarsals are incompletely 

 fused ; the tail was long like that of a lizard, with about a score of 

 vertebrae, and no ploughshare bone. 



Of an American bird, Laopteryx, also found in Jurassic strata, very 

 little is certainly known. 



Order 2. Ratitce. Running-Birds with raft-like unkeeled breast-bone. 



(a) With teeth. Odontolcoe.— Extinct types from N. American 

 Cretaceous strata. 



Hesperornis, the only certain type, seems to have been like a swim- 

 ming Ostrich. Its sharp teeth, sunk in a groove, suggest a carnivorous 

 habit ; it had four toes all turned forward ; its tail of about a dozen 

 vertebrae and without a ploughshare bone, perhaps served as a rudder in 

 the water. The fore-limb is much reduced ; the vertebrae are like those 

 of modern birds. The rami of the lower jaw were separate. One species 

 measures between five and six feet in length. 



{b) Without teeth. 



The African Ostrich (Struthio) is represented by two or three species, 

 at home in the plains and deserts of Africa, and notable for their size, 

 swiftness of foot, and beauty. There are but two toes, the third and the 

 fourth, the latter clawless. The pubes form a ventral symphysis. The 

 ostrich is monogamous, and at the breeding season the hen lays its eggs, 

 at intervals of two days, in a hollow dug out in the sand by the male. 

 The eggs are incubated by the parents alternately, the male sitting 

 during the night, but in the hottest regions they are sometimes left 

 during part of the day simply covered by the sand. 



The American Ostrich [Rhea) is represented by three species in the 

 S. American Pampas. In the Rhea there are three toes, all clawed, and 

 the ischia form a ventral symphysis. Only here among Ratitse is there 

 a well-developed syrinx. The male excavates a shallow nest in the 

 ground, and there, surrounded by a few leaves and grasses, the numerous 

 eggs are usually laid. It seems that the male bird alone hatches the 

 eggs. Single eggs are often laid here and there on the plains, but these 

 are not incubated. 



The Emu {DromcEus) is represented by two species in Australian 

 deserts and plains. The fore-limb is greatly reduced, the feathers have 

 ' long after-shafts. Nearly related are the Cassowaries ( Casuarius) living 

 in the Austro-Malayan region, eight species in the Papuan Islands, one 

 in N. E. Australia, and one in Ceram. They live in the forests and 

 scrub. The fore-limb is very small, with the shafts of the wing feathers 

 reduced to spines ; the ordinary feathers have long after-shafts. On the 

 top of the skull there is a horny helmet covering a core of light spongy 

 bone ; this protects the bent head as the bird rushes through the scrub. 

 There are three toes, the inner one with a long sharp claw — a formidable 

 weapon. 



