44 THE CLASSIFICATION OF BIRDS 



with great and the latter with small subclavicular processes of 

 the coracoid. These families appear to be so nearly related to 

 each other that there seems to be no reason why the Order should 

 be split iuto suborders. 



The Pindce are almost cosmopolitan. Their range extends as 

 far as the limit of forest- growth, except that they are unknown 

 in Madagascar, Australia, and Polynesia. Of the Capitonidce, the 

 Capitonincc may be described as circumtropical, whilst the In- 

 dicatorince are restricted to tropical Africa, India, and Borneo. 

 The Gfalbulidce and the EliamphastidcK are confined to tropical 

 America. 



The ^Egithornorphas are the predominant birds at the present 

 time, and contain far more species than all the other groups 

 combined. The subclass comprises those birds which are so far 

 typical of the Class that their deep plantar tendons are normal 

 (the flexor perforans digitorum not leading to the hallux but to all 

 the other digits), and their wings are normally developed (the 

 fifth secondary being present, the quills being differentiated from 

 the smaller wing-feathers, and the wings being capable of sus- 

 taining flight). All these characters may be regarded as primitive, 

 and have probably been handed down by the laws of heredity 

 from their primaeval avian ancestors ; nevertheless the group 

 appears to be more highly developed than any of the others. 



The yEgithomorpb.se may be subdivided into four Orders, which 

 may be diagnosed as follows : 



CUCULIFOEMES. /Egithomorphas with desmognathous palates, 

 altrical young, and with the spinal feather-tract forked on the 

 upper back. 



PASSERIFOUMES. ^githomorpl se with free maxillo-palatines, 

 with the young altrices, with the spinal feather-tract well defined 

 on the neck but not forked on the upper back,* and without 

 basipterygoid processes or ambiens muscle. 



TURNICIFORMES. yEgithomorphse with schizorhinal nasals ; 



* The pterylosis of the upper parts in the Passeriformes is subject to some 

 variation. The spinal feather-tract is always well defined on the neck by lateral 

 bare tracts, and always continues uninterruptedly between the shoulders. On 

 the lower back it may be (a) forked as in Hirundo and Eurylccmus, or widened 



