29O NEW YORK STATE MUSEUM 



This latter character is almost entirely absent in the pelves of the 

 species of the genus Marila, and the bone as a whole is not so 

 strikingly long and narrow as it is in N e 1 1 a r u f i n a , as com- 

 pared with what we find in Spatula. But it gains in vertical depth, 

 and this has the effect nevertheless of rendering the pelvic basin 

 on the ventral aspect both narrow and deep. Passing to the pelvis 

 of H a r e 1 d a hyemalis it is again seen to be different, for 

 it is in this species a very delicate, light structure, with a general 

 resemblance to the pelvis of some of the smaller auks or gulls. 

 It is much compressed from above, downward, thus causing the 

 pelvic basin to be very shallow. The parial interdiapophysial rows 

 of foramina are of much larger size than usual, especially those 

 next to the centra of the sacral and prosacral vertebrae. We find 

 no notches of any kind on the smooth even borders of the ilio- 

 ischiac bones behind, while beyond these, on either side, extend the 

 very long postpubic elements ; they each curve almost immediately 

 downward and inward, and are of uniform width. The preace- 

 tabular part of this pelvis is short and narrow, with the ilia hori- 

 zontally disposed, and somewhat concaved upon their dorsal as- 

 pects. A minute, though distinct, propubis exists, and the obturator 

 foramen is exceedingly small with the obturator space long and 

 remarkably narrow. This last is also the case in Polysticta 

 s t e 1 1 e r i , but here in this species the pelvis resembles quite 

 closely the bone as I have described it for Spatula. It however 

 has the distal free ends of the postpubic elements expanded, and 

 the posterior margins of the bone smooth and unnotched. An- 

 teriorly, the ante ro external angles of the ilia are not as much 

 rounded off as they are in Spatula. Somateria mollis- 

 s i m a , S . v . nigra, and S . dresseri all belong to a genus 

 of ducks that possess pelves that in form approach the pelvis of 

 Mergus serrato r , though they are not as narrow, and 

 there are some other not highly important differences. This state- 

 ment applies with even more truth to the pelvis of O i d e m i a 

 perspicillata, and above all others as applied to the pelves 

 of O i d e m i a d e g 1 a n d i and O . americana. In these 

 last named species the pelves are wonderfully like the bone as it 

 is found in Mergus. 



Spatula possesses, in common with all true ducks, a completely 

 nonpneumatic shoulder girdle. In it we find a broad, U-shaped 

 furcula, devoid of hvpocleidium and with its long, pointed, clavi- 

 cular heads extending almost directly backward. On the upper 



