Page 359, 
482 ON THE TRACHEA OF THE GALLINA. 
and ossify into a mass whose lower border descends but little below 
the level of the inferior margin of the unmodified last ring for the 
articulation of the anterior extremities of the first bronchial semirings. 
Posteriorly the pessulus joins. the penultimate ring, the two hinder 
ends of the last ring being well separated. The first bronchial semi- 
ring is large and strongly convex downwards from the development 
at each of its ends of upturned articulating processes, at the junction 
of which with the horizontal portion of the tube the second semiring 
articulates along its lower border. The interval between each _ 
lateral element of the last tracheal ring and its corresponding first 
bronchial semiring is considerable, tending to a quadrate form, whilst 
that between the first and second semiring is much narrower and 
meniscoid. The second semiring itself is strongly convex downwards, 
articulating behind by its extreme end with the ring above, but in 
front continuing onwards as a triangle beyond the articular point into - 
the internal bronchial membrane a short distance. The anterior 
terminations of the few lower bronchial semirings are similarly 
pointed; and posteriorly they run inwards (especially the fourth 
and fifth) considerably more than do semirings one and two. 
Polyplectron chinquis so closely resembles Argus in all respects that 
no description of it is needed. The first and second bronchial semi- 
rings are proportionately a little stronger; the antepenultimate 
tracheal ring does not actually fuse with the penultimate, and in one 
specimen the pessulus, instead of blending with the penultimate ring 
behind, runs upwards cuneately between the separated ends of that 
ring to touch the lower margin of the antepenultimate ring. From 
this and other facts pointing in the same direction, to be mentioned 
subsequently, it may, with much probability, be inferred that this 
arrangement just mentioned is the typical one, consolidation of the 
pessulus with the posterior extremities of the penultimate tracheal 
ring having occurred in those cases where, among the Galline, that 
bar is found connected with it. 
In Ithaginis geoffroti (6 adult) there is a transversely fusiform 
median interannular interval between the lower tracheal rings an- 
teriorly, entirely absent behind. The antepenultimate and penulti- 
mate rings are slightly separated throughout, most at the sides, whilst 
between the penultimate and last rings—fusing though they do in the 
middle line anteriorly—there is a slight elongated oblong interval on 
either side of the fused isthmus, extending outwards as far as the 
lateral margin of the tube, but not further backwards. The pessulus 
gives no indication of separation from the penultimate tracheal ring 
posteriorly, whilst anteriorly it springs from the last ring, between 
which and the first bronchial semiring there is a considerable interval. 
This semiring is somewhat squared, sending up processes (an anterior 
