| OCR Text |
Show 570 ON THE ANATOMY OF PASSERINE BIRDS. [June 20, syringeal muscle whatsoever. The box has a well-developed anteroposterior pessular piece. The bronchial rings are throughout of quite simple form, and are separated by but narrow intervals. None are modified in form to serve for the insertion of a vocal muscle, as the latter terminates higher up, as already described, on the tracheal box, and therefore quite out of the region of the bronchi. The lateral position of the single syringeal muscle is that characteristic of all the Mesomyodian Passeres, though in most of these it terminates on one of the bronchial rings, and not, as in the birds under consideration, on the sides of the trachea. This may easily be seen by comparing the accompanying figures of Xenicus with the A B Syrinx of Xenicus longipes, much enlarged. A. From in front. B. From behind. m. Lateral tracheal muscle. beautiful series given by Johannes Miiller of the syrinx of many of Neotropical Mesomyodi \ with those of Garrod of Pitta ~, or my own of Eurylamus, Cymbirhynchus6, aud Philepitta4. In fact it resembles rather that of Todus, as lately described and figured by myself5. Externally the non-oscine nature of Xenicus and Acanthisitta is at once proclaimed by the structure of their wings, which have a " first " 6 (tenth) primary nearly as long as the preceding one, and by the non-bilaminate tarsus. The latter is covered almost completely by a single large scute, with only some very obsolete traces of transverse division below, whilst behind its edges are contiguous for the greater length of the tarsus, leaving only small areas at each end of that bone, which are covered by very small scutellae of irregular form. The digits are slender and compressed, the foot being slightly syndactyle by the union of the fourth toe to the third for the greater part of its two most basal joints. The tail is short and weak; and there are only ten rectrices in- each of m y specimens. As there is no evidence of a pair more having been present, this number 1 Vocal Organs of Passeres : Garrod's ed., Oxford, 1878. 2 Coll. Papers, pl. xxvi. 3 P. Z. S. 1880, pp. 384, 385. * L. c. p. 389. « Antca, p. 444. 6 Sundevall is in error in assigning to these birds only nine remiges (Tentamen, p. 47). |
