3 86 THE ANIMAL KINGDOM. 



are hatched well-clothed with downy feathers, able to run or swim and pro- 

 vide for themselves, e. g. gallinaceous birds, waders, Lamellirostres, Ratitae. 

 Such birds are termed Praecoces or Autophagi. But when the food-yolk 

 is small in amount, the young are hatched, either naked or with little 

 down, unable to run or swim, and requiring to be fed by the parents and to 

 be brooded on by the female : e. g. Accipitrine birds, Passeres, and many 

 others. Such birds are termed Altrices or Inses sores. Most of them 

 are monogamous and have few young, while many of the Praecoces are 

 polygamous and their young numerous. 



The classification of Birds presents great difficulties, and many arrangements 

 have been proposed which it is impossible to discuss in a short compass. Three 

 chief divisions are generally recognised Saururae, Ratitae, and Carinatae. The 

 first contains the Jurassic Archaeopteryx^ the second a few living Birds mostly of 

 large size, such as the Ostrich, Cassowary, Emu, &c., incapable of flight and devoid 

 of a keel to the sternum ; the third all Birds capable of flight and with a keel to the 

 sternum. Prof. Dam&s in a recent memoir (Palaeont. Abhandl. Berlin, ii. part 3, 

 1884) has proposed to classify Archaeopteryx in the group of Carinatae. His views 

 have been criticised by Paulow in the Bulletin de la Soc. Imp. des Naturalistes de 

 Moscou, 60, p. 100, 1884, who has pointed out that in several respects Archae- 

 opteryx can hardly be considered as within the line of descent of Carinatae. Re- 

 taining the Saururae as a separate group but following Dames in other points, the 

 classification given below may be adopted as showing the main outlines. For sub- 

 ordinate divisions and discussions on the various systems proposed, the student 

 must refer to an article on ' Ornithology ' by Prof. Newton in the Encyclopaedia 

 Britannica (ed. ix.) xviii. 1885. 



I. Saururae. Vertebrae biconcave ; sternum broad (? a keel), well ossified ; ab- 

 dominal ribs ; tail long with separate caudal vertebrae (i. e. no ploughshare bone) ; 

 three fingers with separate metacarpals, all clawed ; pelvic bones separate ; fibula 

 complete, its distal end in front of tibia ; metatarsals united but not to the degree 

 observable in living birds. Archaeopteryx from the Solenhofen Slates. 



II. Ratitae. Feathers of the adult with free barbs ; an after-shaft to those of the 

 body ; sternum devoid of keel ; anterior limb shortened or rudimentary ; incapable 

 of flight ; teeth when present lodged in a groove (Hesperornis). 



(1) Imperfectly known order Laopteryx from Jurassic strata in America. 



(2) Odontolcae (Marsh). Kami of lower jaw separate ; wing with only a 



humerus. Vertebrae with typical avian centra ; no ploughshare bone. 

 Hesperornis from American Cretaceous strata. 



(3) Post-cretaceous Ratitae. Edentulous; rami of lower with anchylosed 



symphysis. Vertebral centra typical ; wings rudimentary but with 

 humerus, fore-arm and rudimentary hand. Tertiary, Diluvial and 

 living : includes the living Apteryx^ Cassowary, Emu, Ostrich and Rhea> 

 and the fossil Aepyornis from Madagascar, Dinornis (Moa) and Palapteryx 

 from New Zealand. 



III. Carinatae. Contour feathers in the adult ; sternum with a keel ; anterior 

 limb well developed ; capable of flight ; teeth, when present, lodged in sockets 

 (Ichthyornis). 



