XIII PHYLUM CHORDATA 417 



Order 20. — Picari^. 



A somewhat heterogeneous group inchiding the Cuckoos {Gncu- 

 lidce), Plantain-eaters (Micsophagidce), Rollers (Ooraciidcx), Motmots 

 {Momotidce), Kingfishers (Alcedinidce), Bee-eaters (Meropidce), 

 'S.oo^oes (Upiopidm), Goa,t-svickers (Caprimulgi), Swifts {Gypsdidce), 

 Humming Birds (Trochilidai), Colies (Colii), Trogons {Trogones), 

 Woodpeckers, and Hornbills (Pici), &c. ' 



Order 21. — Passeres. 



Including the Lyre-birds (Memora), Larks (Alauiidm), Starlings 

 {SturnidcB), Finches (Fringillidce), Swallows (Ifirimdinidce), Black- 

 birds and Thrushes (Turdidw), Birds of Paradise (Paradiseidce), Crows 

 (Cormdce), &c. 



Systematic Position of the Exam/pie. 



The numerous species of Columba belong to the family Cohcmhidce, 

 of the order Coluinbce. 



The following are the chief characters of the Columbse : — There 

 are eleven primary remiges, the first very small ; the skull is 

 schizognathous (see p. 428) ; the oil-gland has no tuft of feathers ; 

 the vomer is vestigial; there is a large crop; the caeca are 

 vestigial ; and the young are non-precocious. 



Of the two families of Columbse, the Columhidce, or Doves and 

 Pigeons, are distinguished from the Dididce, including the Dodo and 

 Solitaire, by the power of flight and the accompanying typical 

 carinate characters of the sternum and shoulder-girdle. 



In Columba there are twelve rectrices; the second primary 

 remex is longer than the sixth, and the proximal portion of the 

 tarso- metatarsus is feathered. 



3. General Organisation. 



In respect of range of structural variations, the entire class of 

 Birds is hardly the equivalent of a single order of Reptiles. Among 

 existing Birds, the Emu and the Raven, which may be said to 

 stand at opposite ends of the series, present nothing like the 

 anatomical differences to be found between a common Lizard and 

 a Chamseleon, or between a Turtle and a Tortoise. Hence in 

 dividing the class into orders, we find none of those striking dis- 

 tinctive characters which separate the orders of Fishes, Amphibia, 

 and Reptiles, but have to be content with characters which in other 

 groups would be considered insignificant, such as details in the 

 structure of the skull and sternum, in the arrangement of the 

 muscles of the wing and leg, in the form of the foot, and in the 

 peculiarities of the newly-hatched young. It is for this reason 

 that in the preceding classification no diagnoses of the orders are 

 given : to define them adequately would involve a degree of ana- 

 tomical detail quite beyond the scope of the present work. 



