ON THE ANATOMY OF CHAUNA DERBIANA. 323 
bronchi. The above-mentioned extremely delicate nature of the 
commencing bronchial tubes is most peculiar. 
The lungs present no special features of interest. 
There are several myological characters which, though small in 
themselves, all go to form the exact definition of any group of birds, 
and aid in the determination of affinities. Among the more important 
of these are the presence or absence of the ambiens muscle* (which is 
of fair size in Chawna), the presence or absence of the femoro-caudal, 
the semitendinosus, and their accessory heads (which are al] four 
found in Chauna). .Having dwelt fully on the importance of these 
muscles in the paper just referred to, all I need remark on the present _ 
occasion with regard to them is, that there is therefore a difference 
between this bird and all the true Anserine birds, in none of which 
is there ever a trace of the accessory semitendinosus. A reference to 
my paper on the muscles of the thigh of birds will show that in 
possessing all the five above-mentioned muscles the Screamers agree 
only with the Galline and their nearest allies, the Rallidw, Muso- 
phagide, Cuculide, Columbe, and some of the Limicole. 
With reference to secondary myological points, there are four 
which, in my estimation, deserve special attention. They are :— 
1. The presence or absence of the expansor secundariorum muscle. 
2. The presence or absence of a special muscular slip from the 
biceps humeri to the patagium. 
3. The area of the origin of the obturator internus. 
4. The degree of development of the tensor-cruris fascie. 
These will be considered separately. 
1. The presence or absence of the Expansor secundariorum muscle, 
Ezxpansor secundariorum is the name which it is my habit to employ 
for a very small and peculiar triangular muscle arising from the quills 
of the last few (generally two or three) secondary remiges at the Page 194. 
elbow. Its remarkably long and slender tendon, which frequently 
traverses a fibrous pulley on the axillary margin of the teres muscle, 
runs up the arm side by side with the axillary vessels and nerves to 
be inserted in the thorax, into the middle of a tendon which runs 
from the inner side of the middle of the scapular element of the 
scapulo-coracoid articulation to near the middle of the thoracic border 
of the sterno-coracoid articulation, at right angles to it when’ the fore 
limb is extended. This arrangement being found very well dif- 
ferentiated in the Storks may, for the sake of convenience, be termed 
Ciconine. In Chauna it is exactly the same, as may be seen from the 
accompanying drawing (Plate [16] XIV. fig. 1, e.s.). 
In the majority of the Gallinaceous birds the expansor secundari- 
* Vide “ Proceedings of the Zoological Society,” 1874, p. 116. (Supra, p. 213:) 
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