SKELETON OF THE MUSK-DUCK. 40.J 



In SO far as the length of the wing is concerned, it is hard 

 to say whether it has really undergone reduction, or whether the 

 disproportion between the size of the wing and of the body is 

 not due to an increase in the latter, while the former has remained 

 stationary. While, however, Somateria and Tachyeres agree so 

 closely in the matter of the length of this limb, they differ 

 conspicuously in that the several bones thereof in Tachyeres are 

 much thicker and heavier, and this seems to show that a 

 shortening process has begun. The evidence so far to hand 

 seems to support one view almost as well as the other. Later 

 I propose to enter with some detail into this question, when 

 dealing: with the wings of Struthious birds. 



The Pelvic Limb. 



The hind limb of Biziura presents some interesting evidences 

 of adaptation in the direction of increased swimming powers. 

 It is a noticeable fact, however, that the relative length of the 

 several segments of ihe leg have remained practically unaltered ; 

 indeed there is a singular uniformity in this matter throughout 

 the ducks generally : Anas, for example, on the one hand, the 

 diving ducks on the other, presenting almost the same relative 

 proportions — the femur being about f the length of the tibio- 

 tarsus. 



Unless the pi'esent specimen be abnormal, the femur in 

 Biziura is remarkable for its deep dorso-vertical curvature, and 

 the exceptional development of the scars for the origin and 

 insertion of the muscles. In the curvature of the shaft, Biziura 

 is nearly approached by Erismatura. 



The ecto- and entocnemial crests of the tibio-tarsus are Avell 

 developed. In the form of the entocnemial crest Biziura is 

 peculiar in that it is long and low. (Edemia approximates very 

 closely to this type, but the crest is deeper. Erismatura is inter- 

 mediate in this particular. In Tachyeres the crest is linguiforra 

 and of great size. 



The tarso-metatarsus is flattened antero-posteriorly, grooved 

 in front, and twisted on itself. The hypotarsus is complex. In 

 its general form the tarso-metatarsus approaches very closely to 

 that of Tachyeres, since in both these birds the shaft is unusually 

 stout. In Somateria, for example, the shaft is relatively slender, 

 tapering rapidly from the glenoid mesotarsal articular surface. 



