286 The American Geologist. November, i897 
For some distance from the cell beginning, the cell may be 
filled by the septa which coalesce laterally forming a ''false 
wall" which extends to the centre. But in later growth and 
when the growth is irregular, open spaces are left between the 
septa and these are closed by transverse processes, the tabulte. 
The tabuhe are continuous with the septa and sometimes 
with the theca, that is, the increment upon the septa or the 
theca above the position of a tabula is continuous with it in 
structure, (tig. 3, plate XVII), like the tabulae in the Alcyon- 
arian coral Heliopora as described by Moseley( Challenger, 
Report, Zool. vol. 2). Evidently in the growth of Streptelasma 
profundum, the septa filled the entire bottom of the cell when- 
ever the octoderm of the polyp remained in sufficiently con- 
stant relation to the skeleton but whenever the octodermal 
wall shrank away leaving an open space between it and the 
skeleton, skeletal growth began in the new position, resulting 
in the formation of transverse tabula; between the septa. The 
tabulte are either very thin and granular, or thickened more 
or less and vertically striated as seen in sections. The septa 
grew out partly or entirely over the thickened tabula?. 
Spaces between the septa, closed by tabulae are found even 
in the smallest preserved apices in some specimens but as a 
rule the tabuhe characterize that part of the cell which repre- 
sents the later mature or senile growth. This is evidently be- 
cause in the conical earlier portion, the space to be filled ex- 
ceeded but little the deposit, while in the later more cylindri- 
cal portion, the space was increasingly greater but the amount 
of deposit was nearly the same, and hence in this stage open 
spaces remained, as described. To about one inch from the 
apex of the cell the septa may entirely or in some parts fill 
the inner space to the centre without the tabulae. Thereafter 
numerous tabulae and thinner false wall are characteristic, 
(figs. 4 and 7, pi. XVII). 
8. profundum therefore possesses regularly the character- 
istics described of Zaphrentis canadensis, Z. apinis, and Z. 
helUstriata. 
The general direction of the tabuhe is perpendicular to the 
theca, but in the central portion of the cell they arch irregu- 
larly over (fig. 4, pi. XVII) or bend downwards. The deepest 
part of the cell-opening or calycle remains upon the outer 
