OCR Text |
Show .] MR. W. A. FORBES ON LEPTOSOMA DISCOLOR. 473 be done in birds. As far as I can make out, they do not, however, fuse, but m*e continued up to the head and there diverge. In Opis-thocomus1 Prof. Garrod found a somewhat similar condition, though he says nothing about the vessels being minute. In Leptosoma they have the appearance of white fibrous cords, and they may possibly be, like the carotids of Bucorvus2, no longer functional as blood-channels. But satisfactorily to decide this, as well as the ultimate termination of these carotids, fresh or injected specimens will be necessary. In both the Cuculidae and Coraciidae there are two equisized carotids, which are as free as usual. As regards the vocal organs, there are present but one pair of extrinsic muscles, which diverge to be attached to the "costal processes " of the sternum. The syrinx possesses a single pair of Fig. 4. Fig. 5. Fig. 4. The syrinx of Leptosoma seen from in front, the muscles of the left side having been removed. Fig. 5. The same, from behind. (Both are twice the natural size.) intrinsic muscles, as usual. This organ having been previously unknown in Leptosoma, I here take the opportunity of describing and figuring it. The tracheal rings, which, as usual, interlock with each other for the greater length of the trachea, are well ossified, and only separated by narrow intervals. They gradually narrow as they approach the thorax, the last two being the narrowest of all. The penultimate tracheal ring is produced downwards in a triangular way behind, as is the terminal one in front; behind, this last ring bears the anteriorly- directed narrow pessulus, which intervenes behind between the inturned ends of the first pair of bronchial semirings, but in front does not appear, stopping short before it reaches the anterior surface of the bifurcating trachea. Like the tracheal rings, the first three bronchial semirings are well ossified, and separated from each other only by very narrow interannular intervals. They are nearly straight, with only a very slight concavity upwards, and increase in depth as they descend. In front the semirings of opposite sides are separated from each other by i P. Z. S. 1879, p. 112. 3 Vide Mr. Ottley's paper on this bird, P. Z. S. 1879, pp. 461-467. |