OSTEOLOGY OF BIRDS 283 



a character very commonly present in this, the first segment of the 

 spinal column, throughout this group of fowls. 



An open carotid canal is provided for by the 6th to the 12th 

 vertebrae, after which a strong median hypapophysis takes its place, 

 and this becomes tricornuted in the 16th segment and first dorsal, 

 while in the 18th and 19th it is a long median plate. 



The fifth and sixth cervicals usually have the best marked spines, 

 which is in each case a long, though not high, median crest. The 

 lateral canals in the first half of the cervical region are long and 

 tubular, while the parapophyses are coossified for nearly their en- 

 tire lengths with their sides. Anatinae possess the " heterocoelous " 

 type of articulation among the centra of the spinal column. A 

 strong hypapophysis is found on the second and third cervical verte- 

 brae, to be much reduced in the succeeding one, while the follow- 

 ing segments in the skeleton of the neck are notably broad and 

 rather long. In this region the brevity of the pre- and postzyga- 

 pophyses has the effect of very materially reducing the size of the 

 intervertebral spaces or apertures. 



In the dorsal region the vertebrae are not only locked together 

 by their close fitting neural spines, but a very extensive system of 

 metapophysial and other bony spiculae render the strapping still 

 more efficient. The transverse processes are very wide, too, so that, 

 notwithstanding the fact that these segments are all free, the mobil- 

 ity enjoyed by this division of the column is very much com- 

 promised. Pneumaticity is but very imperfectly extended to the 

 vertebrae of the column, especially in the cervical region. 



The ribs seem always to be nonpneumatic, with large anchylosed 

 unciform processes, being wide and flat in the body above the points 

 where they are attached, Clangula is notorious for both of these 

 characters. 



Spatula has on one side seven ribs that connect with the sternum 

 by costal ribs;. one pair behind these, where the haemapophysis 

 fails to reach that bone, and, finally, a small floating haemapophysis 

 clinging to the posterior margin of the latter. The last two pairs 

 of vertebral ribs come from the sacrum and are without unciform 

 processes. 



This arrangement of the ribs prevails also in Oner q u e d u 1 a 

 cyanoptera, while in Clangula the series leads off with two 

 pairs of free ribs, one on the 16th and one on the 17th vertebra, the 

 following' six connecting with the sternum, and three pairs coming 

 from the consolidated sacral vertebrae, making in all nine pairs of 

 ribs to each side, the last three not bearing unciform processes. 



