the Structure of Hierococcyx ^c. 603 
simplified ventral feather-tracts^ would also possess a syrinx 
arranged on the tracheo-bronchial plan. This, again, is exactly 
the form of syrinx which that genus of Cuckoos does possess, 
and the following is a more detailed description of it. The 
syrinx of Hierococcyx varius is displayed in the annexed 
illustrations (figs. 16, 17, p. 602). 
The last tracheal ring and the first three bronchial serai- 
rings are very plainly to be distinguished from the preceding 
tracheal rings and the succeeding bronchial semi-rings. They 
are obvious and dififerent from them on account of their red 
colour. As will be gathered from this colour, the rings and 
semi-rings in question are ossified. But so also, though 
diff'ering in colour, are the tracheal rings which precede. 
On the other hand, the bronchial semi-rings which follou' 
after the first three are soft and cartilaginous. The pessulus 
of this syrinx is quite well developed. It marks by its origin 
on both sides of the windpipe the last ti'acheal ring. The 
three strong semi-rings which follow are thus plainly bronchial 
in spite of their resemblance to split tracheal rings, and their 
great difference from the soft cartilaginous bronchial rings 
which immediately ensue. Or, to be probably more accurate, 
they are really rings belonging to the tracheal section of the 
windpipe which have taken on the characters of bronchial 
semi-rings. This matter, however, will be referred to agairj 
in considering other forms of syrinx in this family of birds. 
Hierococcyx possesses the usual pair of intrinsic syringeal 
muscles, which are thin and not easy to see. These muscles 
fan out at their insertion, which is on the third bronchial 
semi-ring, of the three that are ossified, of course. 
I shall now proceed to compare the windpipe of Hierococcyx 
with that of the closely related genus Cuculus. I gave in my 
earliest paper upon Cuckoo anatomy a brief account of the 
syrinx of Cuculus canorus. I may supplement this by a more 
detailed account of the svrinx of the Eastern Cuculus micro- 
ft' 
pterus, a specimen of which, presented to the Zoological 
Society by Mr. E. W. Harper, of Calcutta, died in the 
Society's Gardens last year. The syrinx of this bird presents 
an interesting and significant departure in structure from 
