LILY ENCRINITE. 
423 
We will first examine the contrivances in the 
joints, of the vertebral column, which adapted it 
^or flexure in every direction, and then pi’oceed 
^0 consider the arrangement of other parts of the 
l»ody. 
These joints are piled on each other like the 
^iiasonry of a slender Gothic shaft, but, as a cer- 
tain degree of flexibility was requisite at every 
^I’ticulation, and the amount of this flexure varied 
to different parts of the column, being least at 
the base and greatest at the summit, we find pro- 
portionate variations both in the external and in- 
ternal form and dimensions of each part.* The 
* The body (PI. 49, Fig. 1) is supported by a long vertebral 
‘Column attached to the ground by an enlargement of its base (PI. 
■tQ, Fig. 2). It is composed of many cylindrical thick joints, 
^I’ticulating firmly with each other, and having a central aper- 
like the spinal canal in the vertebra of a quadruped, through 
"'I'ich a small alimentary cavity descends from the stomach to 
base of the column, PI. 49, Fig. 4, 6, 8, 10. The form of 
tke column nearest the base is the strongest possible, viz. cylin- 
'^rical. This column is interrupted, at intervals, which become 
*'5ore frequent as it advances upwards, by joints of wider diameter 
of a globular depressed form (PI. 49, Fig. 1. and Figs. 3,4, 
a, a, a.) Near the summit of the column, (PI. 49, Figs. 3, 4,) 
^ series of thin joints, c, c, c, is placed next above and below each 
''‘rgest joint, and between these two thin joints, there is intro- 
'^uced a third series, b, b, b, of an intermediate size. The use 
these variations in the size of the interpolated joints was to give 
'ftcreased flexibility to that part of the column, which being near- 
®®t to its summit required the greatest power of flexion. 
At Plate 49, Figs. 6, 8, 10, are vertical sections of the 
'columnar joints 5, 7, 9, taken near the base ; and show the in- 
'•^tnal cavity of the column, to be arranged in a series of double 
