228 Shufeldt, Osteology of Cereopsis novce-hollandice. [ist'^'A^rii 



serves to keep the coracoid of either side safe in its articu- 

 lation. 



There is no manubrium on the sternum of the Cape Barren 

 Goose, while quite a prominent one is found in Branta, which is 

 short and peg-] ike in Chen. 



Immediately over the anterior border, in the median line 

 posteriorly, there is always present a circumscribed, rather deep 

 and sizable concavity, the base of which is perforated with a 

 numerous group of small foraminal openings for the admission 

 of air into a large part of the anterior portion of the sternum. 



On either side of this median pit, occurring as it does on both 

 Chen and Branta, there are collections of small pneumatic 

 foramina, extending around as far as the base of either costal 

 process. These do not exist in the sternum of Cereopsis, where 

 all this part of the sternum is smooth and unbroken, not having 

 the thickened posterior rim so prominent in Branta canadensis, 

 and nearly as much so in Chen hyperboreus and C. ccerulescens. 



In Olor columhianus and other Swans this is quite different, 

 there being no median pneumatic concavity just over the anterior 

 border ; while in place of it there is an elevation of some size, its 

 middle part being thickened, and extends up to merge with the 

 anterior border in the median line. As a matter of fact, the 

 sternum of a Swan is so unlike that bone in Cereopsis in so many 

 particulars that a comparison would avail us nothing beyond a 

 demonstration of the decided osteological differences existing 

 between an average Goose and one of the Cygnince in this part 

 of their skeletons. 



The sternal carina in Cereopsis is ample and deep anteriorly, 

 while it slopes away gradually as we proceed backward, to be 

 finally lost on the mid-xiphoidal process at a distance of some 

 2 centimetres from its hinder border. Anteriorly, the border of 

 this keel is thickened and concaved, more so than in either Chen 

 or Branta. Likewise, the lower border of this keel is thick and 

 smooth, being evenly convex outward from the carinal angle in 

 front to where it is lost on the surface of the bone posteriorly. 

 (Fig. 25, Plate XXXIII.) 



The ventral surface of the sternal body is smooth and convex, 

 presenting for examination but the single muscular line on either 

 side of the carina, extending from the middle point of the cora- 

 coidal groove, backward, to be lost on the surface of the bone 

 between the "notch" and the termination of the keel. This 

 muscular line is very strong and elevated in Branta, and more or 

 less in all the A^iseriiue. It is the boundary-line between the 

 three pectoral muscles of the breast (" Myology of the Raven," 

 p. 71, fig. 25). 



A similar " muscular line " traverses either side of the keel, 

 running from a point on the anterior border, at the junction of 

 its middle and lower thirds, to be lost on the surface of the bone, 

 near the end of the carina, in Cereopsis ; but in Branta canadensis 

 distinctly joining the termination of the line (in a rounded curve) 



