Page 357. 
480 ON THE TRACHEA OF THE GALLINA. 
The adult (male) P. nigripennis differs in that the antepenultimate 
tracheal ring blends anteriorly with the penultimate, at the same time 
that there is a greater fusion between the penultimate and last rings, 
all three apparently blending behind as well. The interannular interval 
between the last tracheal ring and the first bronchial semiring is 
reduced to little more than a line, and the bronchial interannular 
intervals are very small. 
It is to be specially noted that in the genus Pavo the second 
bronchial semiring, by not articulating with the one above it at either 
end, does not participate in the formation of the specialized lower 
larynx. This is a feature indicating non-elaboration of the organ. No 
other Gallinaceous bird with which I am acquainted resembles Pavo 
in this respect. 
In Caccabis rufa the thoracic extremity of the trachea is perfectly 
simple, and all the rings are in contact with those contiguous to them 
throughout their circumference. The lower margin of the penultimate 
ring faces slightly outwards on either side, whilst in the middle line 
in front it fuses with the ring below it, a well-defined semiellipsoid 
ossification developing in the region, upwards as far as the upper 
margin of the penultimate ring, and downwards to the median point 
of bifurcation of the last ring, from which it extends laterally a short 
distance. The pessulus is attached as in Pavo. It is ossified, the 
anterior termination being the ossification just described ; the posterior 
is a triangular extension into the middle of the posterior surface of 
the penultimate ring, the apex of which reaches its superior margin. 
The first bronchial semiring is concave upwards, and in front forms a 
Fig. 3. Fig. 4. 
Front view. Back view. 
Caccabis rufa. 
