OCT. 1895. VERTEBRAL COLUMN OF AMIA HAY 13 



Kolliker's figures and descriptions cover twelve vertebral bodies, 

 the prolongation of the vertebral axis behind these, and the arches 

 and other parts connected with these two regions. Of the centra 

 described and figured, the anterior seven are called "complete," in- 

 asmuch as they are provided with fully developed neural and haemal 

 arches. The last five are "incomplete," that is, they have haemal 

 arches but not ossified neural arches. Belonging to the seven com- 

 plete vertebras there are, however, only six neural arches, since the 

 second arch, counting from before, is situated over the articulation 

 between the second and third centra, and belongs equally to both. 

 As was first shown by Franque and later by Kolliker, the so-called 

 intercalated vertebral bodies are no longer developed in this portion 

 of the vertebral column. Shufeldt's figure represents the alternation 

 of pleurocentra and intercentra as ending in front of the tenth ver- 

 tebra from the tip of the ossified part of the vertebral axis. This 

 failure of the "intercalated" centra to develop is only a part of the 

 degeneration which has affected this region and been associated with 

 the production of the heterocercal tail of Amia. 



In the case of three specimens examined by myself I find that 

 the vertebra called by Kolliker the last complete one, being the last 

 one furnished with an osseous neural spine, shows a different state of 

 affairs. There is no osseous neural arch, but there are two cartilag- 

 inous plates present, which meet, or nearly meet, above the 

 spinal cord. These are also segmented off from the cartilage 

 which represents the next segment behind. Shufeldt represents 

 this vertebra as having a neural spine, and hence we may conclude 

 that the spine is sometimes developed, sometimes not. 



As Kolliker has shown, the haemal arch of the vertebra just men- 

 tioned is different from those which precede it. The latter all have 

 conspicuous cartilaginous bases, one on each side of the haemal canal, 

 and, as shown by sections, penetrating to the center of the vertebral 

 body. The former arch, represented by a haemal spine, or hypural 

 bone, is co-ossified to the lower side of the corresponding centrum. 



The five terminal vertebrae have ossified centra, and each has its 

 own haemal arch, but there are no distinct neural arches. In the 

 place of these there is a continuous band of cartilage which roofs over 

 the spinal canal, and is prolonged posteriorly to the end of the noto- 

 chord, some distance beyond the distal ends of the hypural bones. 

 The last five vertebrae are more or less reduced in size as we proceed 

 backward, while the portion of the vertebral axis represented by 

 them is turned strongly upward. That portion of the continuous 

 cartilage which overroofs the last five vertebrae represents, as Kolli- 



