244 



OSTEOLOGY OF ANSERES. 



the former Duck. On its dorsal aspect the bone is much concaved 

 throughout and presents a single, median, pneumatic foramen just within 

 its anterior border. This aperture, thougb a smaller one, is also seen 

 in the Garrot, bul the sternum of that Duck is a non-pneumatic one. 



It will be observed from Fig. 24 that the sternum of* the Spoon-bill 

 possesses quite a prominent, peg-like manubrium, and that its sharp, 

 anterior carinal border slopes to the front, forming an acute angle with 

 the convex and ribbed inferior margin of the keel at their point of inter- 

 section. 



This keel extends the entire length of the sternal body, and is withal 

 rather a deep one. The usual swell that fortifies it in front is uncom- 

 monly broad. Above the manubrium, in 

 front, the coracoidal grooves unite in the 

 median line, and the common bed thus 

 formed is carried out laterally, on either 

 side, to a point opposite the middle of the 

 base of the costal process. These latter 

 projections are rather lofty and prominent, 

 each being of a broad, quadrilateral outline. 

 Either costal border occupies less than 

 half of the lateral margin, the remainder 

 being somewhat curved and cultrate. 



Regarding this bone from a pectoral as- 

 pect (Fig.2o), we notice that the form of the 

 sternal body is oblong, with a slight out- 

 curving of the lateral xiphoidal processes 

 behind. These latter form the external 

 boundaries to the large subelliptical vacui- 

 ties, one on either side of the hinder ex- 

 tremity of the bone; but they fail to con- 

 vert these apertures into true fenestra 1 , from 

 the fact that their inturned tips never reach 

 the external angles of the mid-xiphoidal 

 prolongation, as shown in the figure. This 

 fig. 25. Under view of sternum of latter projection always has its posterior 



Spatula clypeata; life size. Sam, bone • /> L -n -ii - i i ,.• * ■, 



aashownin Fig. 24. margin fortified by a raised and thickened 



edge, which is continuous witli the rib of 

 the inferior carinal border. 



The principal muscular line seen upon either side of this wall of the 

 sternum, extends directly from the middle point of that lip of bono 

 which undcrlaps the outer end of the coracoidal groove, to follow the 

 inner vA<j,<> of the xiphoidal notch to the apex of the posteroexternal 

 angle of the mid projection, traveling the entire length of the sternum, 



of course, to do so. 



Now Glaucionetta islandica has a sternum of an entirely different 

 'uni from the bone as I have just described it for Spatulq and the Teals. 



