OSTEOLOGY OF BIRDS 



285 



are seven free caudal vertebrae. There are live pairs of dorsal ribs 

 and three pairs of pelvic ribs. 



In Somateria m o 1 1 i s s i m a the hrst 15 vertebrae of the 

 trunk are without free ribs, the first pair occurring upon the i6th 

 vertebra, and they have good sized unciform processes. The 17th- 

 to the 2 1 St vertebrae inclusive are true dorsals, and there are but 

 six free caudals. There are five pairs of dorsal ribs, and three 

 pairs of pelvic ribs, the latter being entirely lacking in unciform 

 appendages. Seven pairs of these ribs have their costal ribs articu- 

 lating with the sternum, while in the case of the last pair of the 

 series the haemapophyses, although long, fail to reach the sternal 

 border. 



Upon examining a specimen of Polysticta stelleri, I 

 find that the first 15 cervicals are without ribs, the first free pair 

 ocicurring upon the i6th, and they possess unciform processes. 

 17-21 inclusive are true dorsals, and there are seven free caudals. 

 The arrangement of the ribs is the same as found in N e 1 1 a 

 r u f i n a . This latter statement also applies to O i d e m i a p e r - 

 spicillata, where we also find that there are 15 cervicals that 

 do not support free ribs, which occur for the first time on the 

 1 6th though they are lacking in unciform processes. Again 17-21 

 are dorsals, with seven free caudals, and the ribs as in N e 1 1 a 

 r u f i n a . 



Although I am not especially considering the venebral column 

 of the swans in this place, as that will be more fully done further 

 along, yet it may not be altogether uninteresting to compare here 

 the vertebrae and ribs of a typical swan with the corresponding 

 bones of soime of the ducks we have been examining, and these 

 comparisons are shown in the subjoined table. 



TABLE 



[Compare with data given in table on page 315] 



Now, in the case of Spatula and Clangula, in the specimens 

 before me, the 38th vertebra, though free and really a caudal, lies 



