120 SWALLOWS, MARTINS AND SWIFTS 



structural features, is quite distinct, causing it to be 

 grouped by Huxley with the Trochilidcc or humming- 

 birds and the Caprimulgidce or nightjars in the sub- 

 order CypselomorphcB. The specific name apus, Greek 

 for ' footless,' bestowed by Linnaeus upon the common 

 swift, is less appropriate than most of the titles chosen 

 by that great classifier. In truth, the swift not only 

 has a pair of serviceable feet, but they differ in con- 

 struction from those of almost every other kind of bird. 

 The four toes on each foot are all directed forward, and 

 differ in the number of joints in each toe from the 

 arrangement universal, or all but universal, among 

 birds, even including, as Professor Newton has pointed 

 out, the fossil Arckceopteryx from the Upper Jurassic 

 limestone of Solenhofen in Bavaria. 1 The normal 

 arrangement of phlanges or joints on the feet of birds 

 being 2, 3, 4, 5, that in the swifts is 2, 3, 3, 3. 



In heraldry the martlet, representing either a 

 swallow, a martin, or a swift, is represented as footless, 

 and is therefore assigned as the mark of cadency for a 

 fourth son, who might be assumed to be without 

 expectation of substantial inheritance ; and so, to quote 

 the words of an old writer, ' the martlet is an agreeable 

 mark of difference for younger sons, to put them in 

 mind to trust to the wings of virtue and merit, and not 

 to their legs, having no land of their own to set their 

 feet upon.' 



A remarkable feature in the swift family consists in 



1 The Archseopteryx is the earliest form of bird yet discovered. 

 It retains many features of its reptilian ancestry, having teeth in 

 both jaws of its powerful bill and a tail formed of 2Q vertebrae, 



