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107 



Older XXXI. PxVSSERIFORMES. Pi;u( iiiMi-T?ii<i'-. 



This order, coiuprisiiig the rest of the living nienibers of the chl^^ 

 Avcs, includes between five and six thousand speeies, nearly all beiui;- 

 birds of small size. 



The feet are adapted for perching, three of the toes being directed 

 forwards and one backwards. The front toes are generally separate 

 from one another to the Ijase. The hind toe is long, inserted low down 

 and moved by a separate tendon from that which serves the front toes, 

 so that it is capable of being powerfully opposed to them, like a thumb. 

 The palate is tegithognathous, the vomer being broad and truncate and 

 the maxillo-palatiue bones separate from one another (Appendix, 

 p. 209). This arrangement of the deep plantar tendons of the foot, 

 which is termed " passerine," combined with the icgithognathons palate, 

 is characteristic of the Order. 



Passerine birds are divided into two sections, the Acrontijodi or 

 Singing-Birds, and the Mcsoi/ii/oi/i or Songless Passercs. This division, 

 however, is based on the anatomical strncturc of the syrinx or lower 

 larynx, in which the voice is produced, rather than on the actnal power 

 of producing melodious notes in a certain se(iuencc. In the Arroniijodi 

 the intrinsic mnsclcs of the syrinx arc complex and consist of numerous 

 pairs fixed to the t-nds of the bronchial semi-rings; while in the Meso- 

 iiiijodi the muscles are simple, consisting in many cases of only one pair, 

 inserted into the viidd/c of the bronchial semi-rings (Appendix, p. ."il^). 



All our song-birds belong to the Acromyodian group, but there are 

 numerous Passerine birds possessing the less complicated ]\Icsomyodeau 

 apparatus which can utter notes more deserving of the term song than 

 some, such as the Crows, referred to the former division. 



Section A. MESOMYODI. Songless Bikos. 



The Mesomyodean Passeres are further divided into two groups — 

 Trachtoiiliomc and Oli(j(imijod(e — the formei' having the lower end of the 

 trachea modified to form an organ of song, while in the latter the 

 reverse obtains. 



Group I. THACHEQPUOXJE. 



Four families are recognised, characterised by the shape of the 

 sternum and by the structure of the tarsal scutes. In the Pteruptochkue 

 and ConojMphagldce the sternum has four posterior notches, in this 

 respect differing from all other Passeres ; while in the For mica riidce and 

 lieiidrocohi/jtidd' there are only two notches. 



