1886.} TRACHEA AND SYRINX IN CERTAIN BIRDS. 323 
In the Ardeidz, on the other hand (including the Herons, Bitterns, 
and Seopus, which to this extent is a Heron’), the syrinx has what 
may perhaps be called a more typical form. The bronchi are short, 
and the rings which compose them are only half-rings, and are com- 
pleted on the inner side by membrane; there is a pair of intrinsic 
muscles arising beneath the sterno-tracheal muscles and inserted 
on to the first bronchial semiring ; the bronchidesmus only commences 
at about the level of the fourth or fifth bronchial semiring ; anteriorly, 
therefore, there is a free communication between the upper and lower 
surface of the bronchi: the first two bronchial rings are more or less 
ossified and closely connected with each other and with the preceding 
tracheal rings; the latter undergo no modifications such as those 
which exist in the Storks, but are of uniform thickness, closely 
Syrinux of Ahdimia sphenorhyncha. 
applied and often ossified. The foregoing account does not of course 
pretend to be a detailed description of the syrinx in the two families, 
but it is sufficient to indicate the main differences and to serve as a 
basis for comparison of them with tbe syrinx of Xenorhyncius sene- 
galensis and of Abdimia sphenorhyncha, which are in some respects 
intermediate between the two types. 
In Xenorhynchus there is a transition to the Ardeine syrinx in 
that the upper rings of both bronchi are incomplete and are (fig. 3) 
closed by membrane on the inner side. 
It appears therefore that the syrinx of Xenorhynchus agrees with 
that of other Storks in the peculiar arrangement of the lowermost 
' See F. E. Beddard, “ A Contribution to the Anatomy of Scopus umbretta,” 
P. Z.S. 1884, p. 543. 
