TURDINA. 197 
Tn order to divide the Passerid@ 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 Passeride may be arranged 
in the following subfamilies :— 
Turpriv&, or Thrushes. SrurNIN», or Starlings. 
Sytvunz, or Warblers. FRINGILLINA, or Finches. 
Parin&, or Tits. HirunDININ», or Swallows. 
CorvIN&, or Crows. MoTaciLuinz®, or Wagtails. 
Lan, or Shrikes, ALAUDIN#, or Larks, 
AMPELIN#, or Waxwings. 
The order in which these subfamilies should be arranged and their 
mutual relationship remain a mystery. The Alaudine and the Hirundinine 
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 Turdine, Sylviine, Corvine, and Fringilline have equal claims 
to the distinction. 
Subfamily TURDIN&, orn 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 he found in some of the smaller Tits and Warblers, especially in 
old birds, where the scutella 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 
