OCR Text |
Show 1885.] DR. H. GADOW ON THE SPECIES OF RHEA. 319 The number of tracheal rings in Rh. macrorhyncha is 185, in Rh. darwini 152 ; and the rings themselves are comparatively broader and thicker in the latter species, thus making up for their considerably smaller number, as the length of the whole trachea does not show any important differences in the two species. The syringeal muscle described by Forbes exists in all the specimens dissected by me; however, in level of the 9-11 th last tracheal rings, the upper end of the tracheo-bronchial muscle passes into the lower end of the Fig. 9. Fig. 10. Rh. macrorhyncha. Rh. darwini. Dorsal view of tongue, larynx, and syrinx. JS", branch of hypoglossal nerve. lono- m. cerato-trachealis, which runs down from the cerato-hyal along the side of the trachea. Both these muscles and the m. tracheo-sternalis are supplied by branches of the descending ramus of the hypoglossal nerve, thus leaving no doubt as to their common origin from muscles of the hyoid arches. In all other respects the syrinx of m y specimens of Rhea darwini and R. macrorhyncha agrees with the description given by Forbes. The slight modifications concerning the partial fusion of the last tracheal rings are easily explained by differences of age and individual variation. The same, I am sorry to say, applies to the vascular and genital systems. |