NOTES ON THE STRUCTURE OF BIRDS. 
the duplicature does not descend so far, “ descending on the breast 
more than half way before it makes a turn upwards.” It may be 
observed, that in both these birds (the marail and parraka) the 
descent is on the left side, the ascent on the right. 
In Ortalida ruficauda , the trachea, after leaving the furcatorial 
opening, turns down the breast on the left* side of the sternal keel, 
runs for its whole length, takes a simple turn at the extremity, 
and returning parallel with and on the left of the descending 
branch, follows the oesophagus in its usual course. The dupli- 
cature of the trachea is felt from the outside, and on putting 
aside the feathers, its track can be easily traced. On remov- 
ing the skin, it is seen covered with a transparent sheath, and 
in its passage it indents or grooves the muscle of the breast. At 
the furcatorial opening it is bound over by two muscles, arising 
from the centre of the os furcatorius, and joining over the trachea 
with a strong fascia, where there are also transverse fibres. These 
muscles are seen in our plate, dissected off from each side. At 
the lower end, where the duplicature takes place, it is bound down 
by a strong fascia attached to the curve, and giving rise to a mus- 
cular stripe, which is inserted into the extremity of the cartila- 
ginous end of the sternum, and keeps the tracheal curve in its 
place, preventing it from slipping forward. This cartilaginous 
end, or termination, is much elongated, and serves as an admirable 
yielding stay. 
• The bird is supposed to be placed upon its back, with the head from tie 
Cartilaginous End of Sternum. 
