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Show 544 MR. Vf. A. FORBES ON THE GENUS ORTHONYX. [June 6, 6. Contributions to the Anatomy of Passerine Birds.-Part V.1 On the Structure of the Genus Orthonyx. By W. A. FORBES, B.A., Prosector to the Society. [Received June 5, 1882.] The position in the series of Passeres of the genus Orthonyx has for many years been a moot point with ornithologists, Johannes Miiller having long ago2 surmised that these birds might be tracheo-phones, and so connected with the Neotropical Dendrocolaptidae. Some recent writers (e. g. G. R. Gray, Bonaparte, and Salvadori) have placed them in, or in the neighbourhood of, the Menuridse ; Sundevall, on the other hand3, assigns them a position amongst his Cichlomorphae Brevipennes. Up to the present time the formation of their soft parts, and particularly of the syrinx, has remained unknown-a deficiency in our knowledge I am now able to supply by my dissection of both the Australian and New-Zealand forms. For my specimens of the former (Orthonyx spinicauda) I am indebted to the kindness of Mr. E. P. Ramsay, of the Australian Museum; for a pair of the latter (O. ochrocephala) to that of m y friend Prof. Jeffery Parker, of the University of Otago. Both forms are typical Singing-birds (" Oscines Normales " ) , with a well-developed Oscinine syrinx with its normal complement of four pairs of muscles. Of these the short anterior muscle runs to the anterior end of the third bronchial semiring alone in O. spinicauda ; whilst in O. ochrocephala this ring receives its muscular supply from a fasciculus of the long anterior muscle. They thus differ essentially from Menura, with which they have been associated, that bird having but three pairs of muscles, peculiarly arranged 4. In this, as in all other points examined-with one exception in the case of Orthonyx spinicauda-these birds quite resemble the normal Passeres, as they do in having the bilaminate tarsus and reduced "first" (tenth) primary nearly always associated with the normal Acromyodian syrinx. Orthonyx spinicauda, however, has a peculiarity quite unknown to me in any other bird, inasmuch as its carotid artery, the left alone of these vessels (as in all Passeres) being developed, is not contained anywhere in the subvertebral canal, but runs up superficially in company with the left vagus nerve to near the head, where it bifurcates in the usual manner. This is just the same arrangement as that which occurs in many of the Parrots-all those in fact included in Garrod's '* Psittacidse," 5-save that in them the right carotid artery as well is present, running as usual in the hypapophysial canal. 1 For Part IV. see P. Z. S. 1881, p. 435. 2 In 1848. Vide ' Vocal Organs of Passeres,' Garrod's edition, p. 36. 3 'Tentamen,' pp. 9 & 11. 4 G-arrod, Coll. Papers, pp. 362-364. 6 Coll. Papers, p. 255. |
