774 



PHYLUM CHORDATA : CLASS AVES — BIRDS 



SOME CONTRASTS BETWEEN MODERN RATIT/E AND 



MODERN CARINAT^ 



Ratit^. 



Carinat^. 



Running Birds, with wings more 

 or less degenerate and unused in 

 flight, with a keelless raft-like 

 breast-bone. 



The skull is dromseognathous, 

 i.e. the vomer is interposed between 

 the palatines, the pterygoids, and 

 the basisphenoidal rostrum. 



The sutures in the skull remain 

 for a long time distinct. The 

 quadrate articulates with the skull 

 by a single head. 



The long axes of the adjacent 

 portions of the scapula and coracoid 

 lie almost in the same line, or form 

 a very obtuse angle, and the two 

 bones are fused. 



The clavicles are small or absent. 



The ilium and ischium are not 

 united behind, except in old Rheas 

 and Emus. No pygostyle. 



The feathers of the adult have 

 free barbs, the barbules have no 

 hooks. There is no oil gland, 

 except in the kiwi. There are no 

 regularly arranged pterylae. 



The male has a penis. 



The young are always praecoces. 



Flying Birds, with wings almost 

 always well exercised in flight. Math 

 a keeled breast-bone. 



(The keel is rudimentary in the 

 New Zealand parrot Stringops, in 

 the exterminated Dodo (Didus), 

 and in the extinct Aptornis — one of 

 the rails. The penguins do not fly 

 at all ; the Tinamou, the Hoatzin, 

 and some other birds, fly very little.) 



Except in the Tinamous, the 

 skull is never droniEeognathous, 

 i.e. the vomer is not fused with 

 the neighbouring bones of the 

 palate, and the palatines articulate 

 with the basisphenoidal rostrum. 



The sutures in the skull almost 

 always disappear very early. The 

 quadrate articulates by a double 

 head. 



The scapula and coracoid meet 

 almost at right angles, and are 

 connected with one another by 

 ligament only. 



The clavicles are in most cases 

 very well developed. 



The ilium and ischium unite, 

 enclosing a sciatic foramen. Usu- 

 ally a pygostyle. 



The barbs of the feathers are 

 generally united, the barbules have 

 hooks. There is usually an oil 

 gland. 



The male has rarely a penis. 

 The 3^oung may be praecoces or 

 altrices. 



Pedigree. — Birds have many structural affinities with 

 Reptiles ; some of the ancient Dinosaurs present approxi- 

 mations to Birds ; the extinct flying Pterodactyls show that 

 it was possible for flight to be developed among Reptiles ; 

 the oldest bird — Archceopteryx — is in many ways a con- 

 necting link between the two classes ; and the develop- 



