26o 



NEW YORK STATE MUSEUM 



The pair of free ribs that are attached to the 16th vertebra are 

 long and pointed, with free extremities. They do not, however, 

 bear epipleural appendages. 



Nothing peculiar marks the ribs of the dorsal series nor the 

 haemapophyses that connect them with the sternum. The epipleural 



appendages are large and all 

 are closely, though freely, ar- 

 ticulated with the posterior 

 borders of their ribs. 



The first pair of sacral ribs 

 is like the dorsal ones, ex- 

 cept they have no epipleural 

 appendages. The last two 

 sacral pairs, however, anchy- 

 lose with the pelvis, and their 

 haemapophyses do not reach 

 the sternum. 



Sternum [fig. 3. 4]. Mer- 

 gus has an interesting form 

 of this bone, and it differs in 

 a number of points from the 

 sterna of its supposed nearest 

 allies among the ducks. The 

 body is of an oblong outline 

 and moderately well concaved 

 above. Right over the anter- 

 ior border in the median line 

 there is a single semiglobular 

 pit, but there appear to be 

 no pneumatic foramina of any 

 size at its bottom. 



The costal processes are 

 large, prominent, and quad- 

 rate plates. They extend be- 

 hind the first haemapophysial 

 facet. These latter articula- 

 tions are six in number, and 

 the lateral borders behind them are sharp, curving at first out- 

 ward, before they extend backward, to the xiphoidal margin. 



Upon the convex, pectoral aspect of the bone we are to notice 

 the principal muscular lines. These extend directly backward, one 



Fig. 3 Sternum of Mergus serrator; pec- 

 toral aspect; natural size. Drawn by the author; 

 same skeleton as figures i and 2 



