468 J. FRANK DANIEL 
A study of the finer structure of these vertebrae is of interest. 
At the end of the vertebra the calcified tissue appears as a 
whitish ring like the walls of a funnel (cl.r., figs. 18 and 21). 
In this funnel is to be found primitive gelatinous notochordal sub- 
stance which at the ends also forms an intervertebral pad. As 
the sections pass farther toward the middle of the centrum this 
calcified ring becomes smaller and smaller, and there pass off 
from it numerous radiating calcified plates (cl.p.). As the 
middle of the centrum is reached (figs. 20 and 23) the apex of the 
funnel appears as a tiny circlet of calcified tissue containing the 
constricted part of the notochord (ch.). The calcified ring (cl.r.) 
may here be likened to a hub from which the calcified plates 
radiate like the cogs of a wheel. It will be noticed that the 
calcified ring diminishes in thickness as well as in size and that 
the cogs decrease in number the nearer we approach the middle 
of the centrum (compare figs. 19-20, also 22-23), showing that 
some of these do not extend the entire length of the centrum. 
It is also to be seen that the cogs are not so numerous in the 
region of the fifty-third vertebra as in the region of the fifth. 
Other calcifications of less importance also appear in the 
vertebrae. These are confined principally to the lining of the 
neural canal, to the outside circle around the body of the cen- 
trum (not shown in the figures), and to the roof and sides of the 
haemal canal. 
Considerable interest attaches to the region of the spinal 
column between rib-bearing and the haemal arch segments. 
This area, which may be designated as a transition between the 
body and the caudal regions, may be represented by a section 
of the column extending from the thirtieth vertebra—the last 
but one to bear ribs—to the thirty-eighth, usually the second to 
form a complete haemal arch (fig. 16). In such an area there is 
a sudden change in length of centrum, the centra of the non- 
rib-bearing vertebrae being markedly shorter than those of a rib- 
bearing nature. This change begins usually with the thirty- 
second vertebra but in one case I found that the thirty-second 
was still fused with the succeeding vertebra dorsally, although 
the two were separate ventrally. On the opposite side, however, 
