TURDINtE. 197 



In order to divide the PasseridcB into subfamilies we have to rely entirely 

 upon external characters, many of which may be of very recent origin, 

 and developed by a common cause simultaneously from several centres, so 

 that our classification must be more or less an artificial one, and in many 

 cases, no doubt, not corresponding with genealogical relationship. So 

 unreliable as a test of family connexion are these external characters, that 

 a humorous ornithologist has said " that no external characters are so 

 unreliable as the form of the beak and the feet, except the shape of the 

 wings and tail " ! The wisest course is to acknowledge our ignorance^ and 

 accept an admittedly artificial classification until future discoveries reveal 

 a natural system. 



The British species of birds belonging to the Passerida may be arranged 

 in the following subfamilies : — 



TtTBDiM.-E, or Thrushes. SxtrHNiN^, or Starlings. 



Sylvun^, or Warblers. Fhingillin^, or Finches. 



P.vitiNiE, or Tits. HiEUNDiNiN^, or Swallows. 



OoRA-iN.T!;, or Crows. Motacillin.e, or A\'ag-tail3. 



Laniin.i-;, or Shrikes. Alaudinjo, or Larks. 

 AjiPELix^, or Waxwings. 



The order in which these subfamilies should be arranged and their 

 mutual relationship remain a mystery. The Alaudina and the Hirundiiuiue 

 are probably the most aberrant, and ought perhaps to be placed at the 

 outside. It is impossible to say which is the central or most typical 

 group ; the Turdina, Sylviince, Corvince, and Fringillina; have equal claims 

 to the distinction. 



Subfamily TURDIN^, or THRUSHES. 



The Thrushes and their allies form a large group of birds so nearly related 

 to the Warblers and the Tits, that it is impossible to draw a hard and fast 

 line between them. Their chief character consists in having the front as 

 well as the back of the tarsus covered with one long plate instead of several 

 smaller ones ; but this peculiarity is often absent in young birds, and is 

 also to be found in some of the smaller Tits and Warblers, especially in 

 old birds, where the scutellte become confluent. In the other sub- 

 families the scutellation of the tarsus is generally well marked. The 

 bill in this family is very variable. It is usually slender, a typical 

 insectivorous bill ; but in some genera it is widened to adapt it to catch 

 insects on the wing. It is not always furnished with rictal bristles. 

 There is usually an almost obsolete notch or indentation near the tip, but 



