0)1 Streptelasma Profimdum. — Sardeson. 287 
margin of the newly formed tabula rather than upon the cen- 
tre. Only exceptional!}', tabulae formed above the ends of the 
septa across the base of the calyele (fig. 6, pi, XVI). They 
are numerous when formed regularly (fig. 4, pi. XVII), but 
the number, form, and thickness are very variable in spec- 
imens from any horizon and locality, and it does not appear 
that they are really different in any supposed species of this 
coral, S. 2^i'ofi(>nlam. The tabula? are more inconstant than 
the septa. 
Edwards and Ilaime (op. cit.) record the fact that the sides 
of ths septa, as s?en in the cell opening or calyele of course, 
are striated, a feature that is well seen in a few specimens. 
The small ridges or "strife" on the sides of the septa were 
developed strongest and most regularly near the bases of the 
septa, aiid became irregular gradually, hence the}'' are regular 
at the cell margin and confused near the bottom of the calyele. 
There are one tf) Four in 1 mm. Their origin is probably found 
in the transverse rings or lines which are seen on the outside 
of the theca, since they appear to be no more than the struc- 
tural projection of these rugosities, inward through successive 
increments of the corallum. At first thej^ are arranged in 
circles parallel to the cell margin, but deeper in the calyele 
they are increasingly irregular. In thin sections I have de- 
tected evidence of them near the bases of the septa only, but 
on silicified specimens and on interior casts in limestone they 
are sometimes seen to be continuous with denticulations on 
the free edges of the septa. The septa had evidently both 
striated faces and serrated margins and especially at the base 
of the calyele they were deeply serrate. 
In nearly complete specimens, the alternating large and 
small septa are readily observed.' Kunth has pointed out that 
in cf>rals of this type the major septa (first order) are not old- 
er necessarily than the minor ones (second order). At the 
calyele margin of this species all septa are nearly equal in size, 
but with distance from the margin those of the first order in- 
crease the more rapidly, and unite or "wind" together in the 
bottom of the calyele, while those of the second order become 
buried in the "false wall" before reaching the calyele bottom. 
This gives the appearance in the cell opening as if the minor 
s?pta developed simultaneously from between the major ones, 
