650 MR. NEWTON ON A SEXUAL PECULIARITY IN A DUCK. [Nov. /, 



sternums (that of the male) of the species now before me, though 

 the other (that of the female) retains the normal fissures of a fresh- 

 water Duck. However, it may be gathered from remarks which I 

 once contributed to make elsewhere* that I do not attach much 

 importance to this feature. In other respects the sternums present 

 no characters on which I need dwell ; that of the female is somewhat 

 smaller thau that of the male ; but it will be worth ascertaining 

 whether the fenestration in the latter is constant. 



Fig. 1. 



Fig. 1. Left side of posterior end of sternum of Anas punctata, $ , seen from 

 above. 

 2. Corresponding view in the female. 



My surprise, however, was great when I came to see the tracheas. 

 Accustomed as I had been to find in all the freshwater Ducks the 

 trachea of the male with its usual bony enlargement or labyrinth 

 (bulba ossea) situated immediately above the bronchial tubes, and 



Fig. 3. 



Fig. 4. 



Fig. 3. Lower part of trachea of Anas punctata, $ . 

 4. The same, ? . 



this, with the single exception of the Garganey (Anns querqitedula, 



Linn.), of uniform pattern throughout the whole group, the trachea 



* Phil. Trans. 1869, p. 337. 



