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Show 784 MR. W. A. FORBES O N T H E [June 21, As compared with Struthio and Apteryx, all the tracheal and bronchial rings are much less firm and more cartilaginous in Casuarius, as also in Dromceus. The memBrana tympaniformis completing the trachea below is a simple membrane, passing continuously from one bronchus to the other, with no intervening pessulus. Internally, a very slight thickening of this membrane in an anteroposterior direction, at the bifurcation of the tube, may be seen ; but there is nothing that can be properly called a membrana semilunaris present. The external vocal cord, on the other hand, situated over the first two bronchial semirings, is very well-developed, with a sharply-defined margin. On the internal wall of the bronchus there is, in addition, a second, much slighter and less prominent fold, slightly concave forwards, running somewhat obliquely backwards and downwards, and supported by the anterior ends of the third and sixth bronchial semi-rings. Besides Casuarius galeatus, I have examined tracheae of CC. Bec-carii, Bennetti, uni-appendiculatus (2 specimens), and westermani; and in none of these species can I detect any difference of importance from the arrangement I have described above. In the last-named species (an adult specimen) there is a considerable amount of ossification in the last tracheal and first bronchial rings. The mucous fold on the internal walls of the bronchi varies much in development in different specimens. In adults there is a great accumulation of the fibrous and elastic tissures of the mucous membrane in the region of the tracheal tympanum. Of Droma?us nova?-hollandia I have only, as yet, been able to examine one trachea, and that too from a young specimen. This closely resembles that of Casuarius; but the number of imperfect tracheal rings seems to be considerably smaller, in the specimen in question only the last three being incomplete behind. The third and fourth bronchial semirings are considerably stronger than the first two and the immediately preceding tracheal rings. There is no pessulus ; but the memBrana semilunaris, especially posteriorly, seems to be better developed. The insertion of the stemo-tracheales is as in Casuarius. The lateral tracheal muscles extend down to within about 1 *5 inch of the end of the trachea. In the genus Bhea (as represented by JR. americana and B. ma-crorhyncha) a very different condition of things occurs, there being a highly-specialized and peculiar syrinx, provided with a pair of intrinsic muscles \ 1 I had observed the peculiar syrinx of Bhea some months before I met with M. Alix's short paper on this bird in the " Bulletin " of the Societe Philoma-tique for 1874 (p. 38), in which he points out, for the first time, the fact that Bhea possesses a true syrinx. His account, which I here reproduce, runs as follows :-" II y a chez le Nandou un larynx inferieur. Les cordes vocales sont placees a l'origine des bronches, dont les premiers anneaux sont incomplets, en sort que la paroi interne qui leur correspond a l'aspect d'une membrane tym-paniforme. Le reste des bronches est forme" par des anneaux complets." This description is, as will be seen, very incomplete, and, in the last statement incorrect. ' |
