570 ON THE ANATOMY OF PASSERINE BIRDS. [JuDC 20, 



syringeal muscle whatsoever. The box has a well- developed antero- 

 posterior 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 charac- 

 teristic 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 



Syrinx of Xenicus longipes, much enlarged. 

 A. Prom in front. B. From behind. 



m. Lateral tracheal muscle. 



beautiful series given by Johannes Miiller of the syrinx of many of the 

 Neotropical Mesomyodi ', with those of Garrod of Pitta ", or my own 

 oi Eurykemus, Cymbirhynchus\ and Philepitta^. In fact it resembles 

 rather that of Todus, as lately described and figured by myself 5. 

 Externally the non-oscine nature of Xenictts and Acanthisitta is at 

 once proclaimed by the structure of their wings, which have a " first ""^ 

 (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 scutelise of irregular 

 form. The digits are slender and compressed, the foot being slightly 

 sy'udactyle 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 my specimens. As 

 there is no evidence of a pair more having been present, this number 



' Vocal Organs of Passeres : Garrod's ed., Oxford, 1878. 

 ^ Coll. Papers, pi. xxvi. 



^ P. Z. S. 1880, pp. 384, 385. * L. c. p. 389. ^ ^nte'a, p. 444. 



^ Suudevall is iu error in assigning to these birds only nine remiges (Ten- 

 tamen, p. 47). 



