OCR Text |
Show 1879.] TRACHEA OF THE GALLING. 363 as a short distance posteriorly into the middle of the lower border of the penultimate ring, from the fair-sized bony pessulus. The last tracheal ring sends downwards a thick short process from its hinder end on either side, to articulate with the equally developed upturned posterior extremity of the first bronchial semiring, the anterior upward- and inward-directed terminal limb of which is proportionately long, at the same time that the angle it makes with the main element of the ring is very abrupt. The second semiring is nearly in contact superiorly with the first throughout its length. Anteriorly it ends in a point, as do the lower semirings, which extends a short distance into the inner membranous wall of the bronchus. Posteriorly it is slightly enlarged and rounded, ceasing a short distance outside the posterior angle of the semiring above, with which it is in contact. Turning to the genus Euplocamus, in Euplocamus swinhoii the last four tracheal rings become slightly enlarged from above downwards. Between the simple antepenultimate ring and the one above it there is a slight interval, except in the middle line behind, where a general fusion of the last three rings occurs, as in all Euplocami. The penultimate ring sends downwards a narrow tongue-shaped median process anteriorly, which touches, but does not join, the upper margin of the there indented terminal tracheal ring. Its upper margin is also slightly irregular. The last ring is peculiar in front. Besides the shallow and broad concavity in the middle of its upper border, it sends downwards a deep and transversely considerable semi-ovoid process, notched at its apex, which is lowermost, to form the median element of the actual bifurcation of the tube. On either side of this notch, just beyond it, the anterior extremity of the first bronchial semiring articulates by its triangularly expanded end, the lower angle of which is jointed witb the not much specialized second semiring, which posteriorly articulates by its somewhat expanded termination with the first semiring also. The hinder extremity of the first semiring fuses with the last tracheal, as does the posterior termination of the pessulus, to form a continuous cartilage along the back of the tube as high as the upper border of the antepenultimate tracheal ring. Antero-laterally the annular interval between the penultimate and last rings is well developed, and bent downwards near the middle line on account of the presence of the process and notch above described. The interval between the last tracheal ring and the first bronchial semiring is very large and deep on account of the great size of the descending process of the former. The interval between the first and second semirings is ovate and slightly deeper than those which follow. The pessulus is narrow. Euplocamus preelatus, E. nychlhemerus, and E. albocristatus differ from E. swinhoii in that anteriorly the median process from the lower border of the penultimate ring blends with the upper border of the last tracheal, as does the upper border, but by a more slender isthmus, with the antepenultimate. In E. nychthemerus and E. albocristatus there is a further fusion of the anterior extremity of the |