OSTEOLOGY OF BIRDS 



263 



Either head very gradually tapers off to a point, and these pro- 

 duced ends ride over the scapulae when the arch is articulated. 



Projecting from their upper borders we find a single distinct and 

 vertical process of bone that is quite characteristic. In the eider 

 it is in cartilage, but otherwise the fourchette is formed in this 

 duck very much the same as in the merganser. 



In a coracoid we find the summit of the bone much produced 

 above its articulation with the scapula, and compressed in the same 

 plane with the shaft below it in such a manner that when articulated 

 with the sternum the front of the bone is directed forward and 

 outward. 



The sternal extremity of the bone is very much expanded, and it 

 also is found in the same plane with the general compression of 

 the shaft. 



Behind, it is scarred by muscular lines, and shows a large luniform 

 facet for the groove on the sternum. 



The scapular process of the coracoid is to a great extent aborted ; 

 its superior margin being insufficient to accommodate the entire 

 width of the scapula. 



Nothing of importance distinguishes the glenoid cavity, it being 

 formed, as in most birds, in the proportion of one third on the part 

 of the scapula and the remainder by the bone under consideration. 



In the Hooded merganser, the most striking feature of the cora- 

 coid is the extent to which it is flattened in the anteroposterior 

 direction ; this compression being very marked. I noticed this 

 character, too, in a number of the fossil Anatidae from the Equus 

 beds of Oregon. 



The scapula is much arched, and nearly of an equal width the 

 entire length of its blade, its apex being rounded off. We find the 

 bone considerably compressed in the vertical direction throughout, 

 and the length of the chord measured between its extremities less 

 than the length of the coracoid, the reverse of this being the case 

 in Lopliodytes, or in other words, the imaginary line measured be- 

 tween the ends of the scapula is in this last named species, longer 

 than the long axis of the coracoid of the same individual. 



Pelvis and caudal vertebrae [fig. 7, 8] . In order to better 

 illustrate the fact that the pelvis in the mergansers is constructed 

 upon the same plan as that bone in other anserine birds, I have con- 

 trasted it, in my memoir entitled Observations upon the Osteology 

 of the North American Anseres [U. S. Nat. Mus. Proc. 1888. p. 226, 

 fig. 7, 8] with the pelvis of the American eider duck. It will be 

 seen that all the characters present in the latter are also to be found 



