256 ELEMENTS OP OENITHOLOGY. 



jaw joins the skull by the intervention of a quadrate bone. The 

 right auriculo-ventricular valve of the four-chambered heart is 

 muscular, and there is a single aortic arch which arches over the 

 right bronchus. The optic lobes of the brain are lateral and 

 depressed, and reproduction is in all cases oviparous. 



We put forward, in our initial chapter, a sketch which we 

 hoped might serve as an introduction to the whole Class of Birds. 

 But in our treatment of the subject we deliberately adopted 

 modes of grouping which we thought might be acceptable to 

 the beginner, and which had spontaneously suggested themselves 

 to the first teachers and classifiers of our science. 



Now that we have, however, made acquaintance with the 

 anatomy of Birds, the time has come to put away the notions 

 wherewith we began, in favour of more advanced views. 



We spoke ' of Pigeons immediately after Fowls and Phea- 

 sants, and of such they were formerly regarded as allies ; but 

 now the study of anatomy has separated these groups widely. 

 We treated ^ of the Penguin in connection with the Auk, for at 

 first sight these erect flightless Birds present obvious resem- 

 blances. Advanced Ornithology, however, places them poles 

 asunder. Close after the Cormorants we have spoken of ' those 

 yet more familiar coast-birds, the Gulls, and after them the 

 Petrels ; but we shall see that there is no real affinity between 

 them, though they at first seem alike. Neither has the Frigate- 

 bird any close relationship with the Albatross. The Flamin- 

 goes and the Herons, the Storks and the Cranes naturally seem 

 to the beginner akin, but they must be widely separated by the 

 advanced student, and the Homed Screamer of the South- 

 American forests will by him be brought down to the level of 

 the Goose. 



The Curlew and the Ibis *, with their long bills, look alike, 

 but mature study shows us that the Curlew is a Plover ; while 

 Coursers and the Tinamous ', however to the popular eye they 

 may seem to run in couples, are seen by the scientific observer 

 to have hardly anything in common save their bird-nature and 

 mode of locomotion. However like to an ordinary Plover a 

 Stone-curlew {(Edicnemus) may look, it turns out in reality to 

 be far more of a Bustard. 



For the sake of the beginner, we have mentioned ' the stream- 



> See ante, p. 12. » P. 22. ' P 28 



* See ante, p. 53. « Pp. 50 & 51. » P. 69". 



