1 PASSERES. 
the classification of the Passeres—as witness the 7% a ee 
Briefly three types of syrinx are recognized—the Tracheo- 
bronchial, the Tracheal and the Prandival: the last two being 
derivatives of the first.. The tracheo- bronchial i is the type found 
in the Oscines and Sub-Oscines. Herein the lower end of the 
trachea has the last four or five rings welded to form a little dice- 
shaped box communicating below with the bronchi. The 
bronchial rings I and II are closely attached to this box, 
while III forms a strong arcuate bar supporting a delicate 
sheet of membrane stretched between rings I and II on the 
one hand and 1V.on the other. The bronchial rings are in- 
complete on their inner aspects, their free ends supporting a 
“tympanic membrane,” which plays an important part in voice 
Syrinx of a Magpie, showing the Diacromyodian attachment of the intrinsic 
muscles at the ends of the bronchial semi-rings. ‘The left-hand figure is a side 
view and the right-hand figure a dorsal view of the syrinx. ‘The membranous 
parts between the bronchial semi-rings and the internal tympaniform membrane 
are dotted ; II, II are the Second and third bronchial semi-rings; 7.7, the 
internal tympaniform membrane ; s¢, the muscle from the side of the trachea 
to the upper end of the clavicle: 1, 2, 5, 4, 5, 6, the syringeal muscles ; there 
isa 7th, which is hidden by the 6th; the 4th is hidden below and between the 
Ist, 2nd, and 3rd. 
production, At the junction of the bronchi with the trachea is a 
bony bar—the “ pessulus.” This supports a thin fold of mem- 
brane whose free edge cuts across the bottom of the dice-shaped 
box of the tracheal tube. By its vibrations it acts like the “ free 
reed” of an organ-pipe. Muscular lips extending from the 
inner surfaces of bronchial semi- ring IIT narrow the aperture on 
either side of the “reed” during the production of the * voice’ 
or song, and thus complete the mechanism of voice production. 
In the Tracheal syrinx a’ variable number of the lower tracheal 
