ON THE TRACHEA OF CERTAIN DUCKS. 279 
and of the wing-membrane in insects, appears to me rather to be de- 
pendent on the torsion of the bones or main nervure of the wing, the 
power of lateral flexion in which is proved by M. Marey’s discovery of 
the figure-of-8 action in the insect. A thin wooden lath employed as 
a nervure to an artificial wing, if set with its narrow section vertical 
and fixed to a non-yielding horizontal wing, gives a vertical figure- 
of-8 when moved up and down, the plane changing exactly as it is 
described by M. Marey in the insect. 
44, ON THE FORM OF THE LOWER LARYNX IN 
CERTAIN SPECIES OF DUCKS.* 
THE present communication contains descriptions of the condition of Page 151. 
the lower larynx in some rare members of the Anatide, which are not 
referred to in the works of either Mr. Eyton or Mr. Yarrell. 
1. Sancrp10Ryis MELANONOTA (Gm.): Sclater, Rev. Cat. Vert. p. 241. Page 152. 
To Mr. Eyton, who established the genus to which this peculiar bird 
_ belongs, the visceral anatomy was unknown; and I am not aware of 
_ any subsequent description of it having been published. A pair were 
purchased by the Society on the 18th of September, 1867, the female 
of which died on the 10th of March, and the male on the 18th of 
October last year; these are the specimens which I have examined. 
In both sexes the diameter of the trachea diminishes slightly at its 
lower extremity before it again expands a little to end in the syrinx. 
As in birds generally, the tracheal rings are complete and notched in 
the middle line before and behind, in such a way that where they meet 
the two halves overlap and are overlapped respectively by the rings 
above and below them. The lower tracheal rings, however, in both 
sexes are much thinned in front, as is the case in the male of Harelda 
glacialis ;+ they are not ossified together. 
In the male Sarcidiornis melanonota (fig. 1) there are 20 anterior, 
membrane-covered fenestre, formed in the intervals between these 
thinned rings; in the female (fig. 2) there are only 12 of the same. Page 153. 
In the latter there is no lateral diverticulum from the syrinx; but 
in the former, from the left side, as usual, one is developed, entirely 
a we 
* “ Proceedings of the Zoological Society,’ 1875, pp. 151-6. Read, March 2, 
1875. 
+ Vide figs. Eyton’s “ Anatide,” plate opposite p. 65; Yarrell’s “ Brit. Birds,” 
vol. iii. p. 261. 
