OCR Text |
Show 1879.] TRACHEA OF THE GALLINAE. 359 ring 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 semirings 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 Gallinae, that bar is found connected with it. In Ithaginis geoffroii (<$ adult) there is a transversely fusiform median interannular interval between the lower tracheal rings anteriorly, entirely absent behind. The antepenultimate and penultimate 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 and a posterior) of no great length to articulate with the last tracheal ring, the second semiring (scarcely differing from tbe third) just touching its two angles sufficiently for it to be said that it does articulate with it. In this species the lateral sterno-tracheal muscle terminates inferiorly in a peculiar manner. It is constituted of two parts, an outer and an inner. Of the inner, which is also divided below into two, the median portion ceases at the twelfth ring from the bifurcation, opposite which spot its outer moiety sends downwards a special thin extra broad fasciculus to join the undivided outer main element of the muscle just before it leaves the windpipe, opposite its antepenultimate ring. The nerve to these lower fibres is not small; and from being superficial- resting as it does on the muscles under consideration as they descend-it disappears behind the special fasciculus above described at the spot where that begins to run inwards towards its fellow, which it does not meet. In Lophortyx californicus (adult male) there are no interannular |