188 BRITISH BIRDS. 



varies in different species, in some the anterior part being 

 slightly developed or absent, in others the posterior part. 

 The breadth is greatest in the lumbar region. This tract is 

 present in all species examined except the Blue Tit (see note 

 under this species). 



The ulnar tracts consist of small pre-pennse on the ulnar 

 margin of each wing. Each pre-penna is replaced later by 

 the secondaries, and in some cases by the secondary coverts. 

 These tracts are absent in the Wheatear, Robin, all four Tits, 

 and Wren. 



The femoral tracts are situated laterally on each side just 

 beneath the femur. The pre-pennse never seem to be long, 

 and are more closely approximated to each other than in some 

 of the other tracts. This tract is absent in the Thrushes and 

 Robin, the Tits, Swallow, and Sand-Martin. 



The ventral tract is situated laterally on each side of the 

 abdomen, and runs obliquely from the middle line towards 

 the upper end of the femoral tract. In character it resembles 

 the femoral tract, and is widest posteriorily. This tract is 

 present in the Meadow- Pipit, Starhng, and in all the Fringillince 

 examined which have down. 



The crural tract consists of a few small inconspicuous pre- 

 pennse forming a circle round the lower end of the crus, just 

 above the ankle joint. It was noted in the Red-throated 

 Pipit, all the Fringillince examined which have down, and 

 in the Snow- Bunting. 



I am indebted to my friend, Mr. J. L. Bonhote, for notes 

 or specimens of the Bearded Tit, Red-throated Pipit, Tree- 

 Sparrow, Brambling, Lesser Redpoll, Snow-Bunting, and 

 Kingfisher. 



MISTLE-THRUSH Turdus viscivorus L. 



Down. Colour. — Greyish white, some pre-pennse having 

 huffish white tips. 



Distribution. — Inner and outer supra-orbital, occipital, 

 humeral, spinal and ulnar. In some there is a pre-penna 

 on the bastard wing. The outer supra-orbital tract is not 

 found in the Blackbird or Song-Thrush. 



Coloration of Mouth. Inside, orange ; no spots ; ex- 

 ternally, flanges lemon-yellow. 



SONG-THRUSH Turdus musicus L. 

 Down. Colour. — Buffish white. 



Distribution. — Inner supra-orbital, occipital, humeral, spinal 



and ulnar. 

 Coloration of Mouth. Inside, orange ; no spots ; flanges 



lemon-yellow. 



