220 OSTEOLOGY OF ANSERES. 



second vertebra does not perforate the cup of the atlas from behind, 

 but both these segments, in common with many Ducks, present the in- 

 teresting condition of having- the lateral vertebral canals at the outer 

 sides of their centra, for the protection of the vessels that pass through 

 them. This canal is a very prominent feature through all of these cer- 

 vical vertebrae through the twelfth; in the tirst five or six it has a fe- 

 nestra in its lateral wall on either side. With the exception of the last 

 tew vertebrae in which it occurs, it extends nearly the full length of the 

 centra, while its inferior wall includes the greater part of the parial 

 parapophyses, and these latter being rather widely separated, we have 

 as a result a broad area at the under side of all of these vertebra' where 

 this construction obtains. 



The byapopbysial canal is found in the sixth to the twelfth, inclusive, 

 but in none of these does it close in entirely, though the processes ap- 

 proach each other very near in the last-mentioned vertebra. 



Axis vertebra has a prominent hyapophysis, but it is missing in the 

 third vertebra, and this process does not make its appearance again 

 until we find it as a conspicuous median plate in the thirteenth. In 

 the fourteenth it is smaller, and although still in the vertical plane, evi- 

 dently moved slightly to the left of the median line. This last condi- 

 tion is more pronounced in the fifteenth, while in the sixteenth, where 

 it still possesses considerable size, it is carried so far to the left as to 

 be nearly in the same plane with the side of the vertebra, though it 

 still remains vertical. Sixteenth vertebra also has lateral hyapophysial 

 cornua, which makes this peculiar shifting of its mid-process all the more 

 striking. I am unable to say at present whether this is a constant con- 

 dition of affairs or not. The dorsal series also have hyapophysial proc- 

 esses ; these are at first short, with spreading cornua, to gradually be- 

 come longer and lose their terminal bifurcation, and again grow shorter, 

 to finally disappear on the first sacral, or dorso lumbar. 



Axis has a thick and heavy neural spine. In the following six or 

 seven segments this gradually becomes longer, lower, and thinner, to 

 be absent entirely in the tenth cervical vertebra. In the fourteenth it 

 re-appears, and from it, backward, it gradually assumes the broad, ob- 

 long plate which is perfected in the dorsal series. The vertebra? of this 

 latter region are restricted in their movements upon one another by the 

 many interlacing tendinal and metapophysial spicuhc among them. 



In the cervical region the neural canal is cylindrical in form, and 

 owing to the fact that neither the pre- or postzygapophysial facets are 

 upon spreading limbs, in its anterior division this tube is wonderfully 

 well protected, its walls being nearly continuous from one vertebra to 

 the next. This condition does not obtain in the latter half of the cer- 

 vical region, however, where the prolongation of the aforesaid apophy- 

 ses lend to the dorsal aspects of the vertebrae, when viewed from above, 

 that familiar capital-letter -of-X appearance, with the extremities of the 

 lines alternately articulating above and below. 



