58 CLASS AVES. 



proportion, and which fly with the greatest rapidity. 

 Their tail is forked ; their feet, very short, have this 

 very peculiar character, that the thumb is directed 

 forward almost like the other toes, and that the 

 middle and external toes have each but three pha- 

 langes like the internal. 



The shortness of theu' humerus, the breadth of its 

 apophyses, their oval furca, their sternum without 

 indention towards the bottom, indicate, even in the 

 skeleton, to what a degree these birds are organized 

 for a vigorous flight ; but the shortness of their feet, 

 joined to the length of their wings, prevents them 

 when they are on the ground from taking their spring. 

 Accordingly, they pass, so to say, their entue hves in 

 the air, pursuing, in flocks, and with vociferous cries, 

 the insects in the highest regions. They nestle in 

 the holes of walls and rocks, and climb with rapidity 

 along the smoothest surfaces. 



The common species, Hirundo Apus : L. En. 

 542. 1 ; 



is black, with a white throat. 



The species of the high mountains. Hirundo 

 Melba. L. Edw. 27- Vail. Afric. 243. 



is the largest ; brown above, white beneath, with a 

 brown collar under the neck. 



This is the Swift of Latham. The Micropus Mura- 

 rius and Brachypus Murariiis of Meyer, and the 

 Cypselus Murarius of Temminck. 



