20 



CTPSBLID^ 



very short ; feet weak, small and usually pamprodactylous {i.e., all 

 four toes anteriorly directed) ; tail of ten feathers only (this latter 

 character an easily recognisable distinction from the Swallows with 

 a tail always of twelve feathers) ; palate aegithognathous, no 



Pig. 12. — Wing of Cypselus africanus. x \. 



Pig. 13. — Poot of Cypselus africanus. x {. 



caecan or semitendinosus muscle. The Swifts are all birds of strong 

 flight and lay elongated white eggs in nests which are partly or 

 wholly composed of the inspissated secretion of the salivary glands. 



The range of the family extends all over the world except the 

 extreme northern and southern regions. 



Key of the Genera. 



A. Tarsus feathered ; tail normal. 



a. All the toes directed forward at equal intervals Cypselus, p. 21. 



b. Toes in pairs, the third and fourth outwards, 



the first and second inwards TacJiornis, p. 28. 



B. Tarsus unfeathered ; tail with the shafts stiffened 



and projecting as spines beyond the webs of 



the feathers Chcetura, p. 29. 



