Page 516. 
364 ON THE ANATOMY OF PASSERINE BIRDS. 
of fibrous tissue surrounding the trachea. In its anterior half it is so; 
but behind it descends for some distance on each side to a median 
spot situated below its general level, at a distance beneath it equal to 
the diameter of the tube itself, to blend at the angle thus formed with 
a strong fibro-cartilaginous ribbon, which expands below the level of | 
the bronchial bifurcation, to terminate as a membranous covering to 
the front of the cesophagus. 
From the postero-lateral portion of the horizontal miéieeh of the 
ring just described, and from its descending limb, the posterior 
longitudinal muscle of the syrinx arises, on each side, powerful, and 
in a single mass, of which the longer postero-external fibres, as it 
‘descends, differentiate themselves off to form an independent 
fasciculus, which is inserted into the posterior hooked extremity of 
the third bronchial semiring. The other much larger internal 
portion, composed mostly of much shorter and oblique fibres, is in- 
serted into the posterior triangular surface of the tracheal three- 
way piece (last tracheal ring), and into the posterior extremity of 
the first bronchial semiring, a few of its tendinous fibres of termina- 
tion apparently running on to the back of the membrane between 
the first and second semiring, and perhaps slightly to the back of 
the second semiring itself, although this last seems to be independent 
in this respect. 
The comparatively slender muscuius sterno-trachealis springs from 
the lateral surfaces of the four or five tracheal rings above the last 
two, emerging between the anterior and posterior intrinsic muscles. 
Menwra superba, from the above description, is therefore acromyo- 
dian, although not typically Oscine. 
Atrichia rufescens presents precisely the same arrangement as 
Menura. There are three modified bronchial semirings, the third 
descending posteriorly, and the second expanded a short distance 
before it reaches its anterior termination, the anterior longitudinal 
muscle being there inserted. The posterior muscle, however, does 
not clearly separate into two before it reaches its points of insertion, 
which are identical with those in Menura. The lower tracheal rings 
are different, in that they are not flattened from above downwards; 
they retain the characters of those above them toa great extent. The 
last forms the characteristic three-way piece. In Plate [25] LIL. figs. 
4, 5, and 6 these points are clearly seen. 
Atrichia is therefore also Acromyodian, although far from being 
normally Oscine. It would require but little modification in either 
it or Menuwra to convert their syringeal muscular masses into more 
numerous independent muscles. In the Crow, Starling, and most 
of the other Oscines I have examined, the third semiring is the one 
to which the long anterior muscle runs, the long posterior not going 
