420 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
of the median frontal portion or lip (PI. 4, fig. 8). As the calyx of 
the parent tube grows upward and the lateral angles grow outward, 
the front and sides meet, closing over the lateral extensions and 
converting them into tubes. The various steps are well indicated 
by the lines of growth on the well-preserved specimen figured from 
Eighteen Mile Creek (PI. 4, figs. 9, 10). 
It is evident, from the geometrical growth of the corallum, that 
some of the polypites forming the inside branches must eventually 
interfere with each other. In a nearly perfect specimen from 
Eighteen Mile Creek (PI. 4, fig. 1) the two corallites approaching 
each other are apparently young individuals which have not yet 
reached the calyx-building stage. Even before they can reach this 
stage, they must meet, when one of several things may happen. 
The stronger branch may put out normal buds, preventing the 
weaker one from budding. The corallites may cross each other in 
different planes, each giving off normal branches. Finally the two 
corallites may coalesce. This last method of settling the difficulty 
seems to have occurred, as indicated by intergrown specimens. In 
one specimen (PI. 4, fig. 11) the weaker polypite on the left put 
forth one short bud only, the left one, while the stronger polypite 
on the right put out two buds, at a somewhat distorted angle. The 
shorter of these buds from the right united with the single bud 
from the weaker member on the left, the resulting tube apparently 
being traversed by a continuous canal. In another specimen (PI. 4, 
fig. 12) the branch from the left was also the weaker or younger one, 
the branch from the right in this case succeeding in putting forth 
two normal buds, while the branch from the left put forth a very 
short bud on the left which was soon enveloped by the calyx of the 
stronger branch. The two calices appear to have been united by 
the tube of this bud. It is interesting to observe, that in the com¬ 
plete specimen (PL 4, fig. 1) the branch from the left is also the 
shorter one (the specimen is represented in the figure as seen 
from the flat under side, arid hence with parts reversed), and that 
hence the branch from the right would have succeeded in putting 
forth its buds, before the branch from the left had reached maturity. 
A union, similar to that of the other specimens, would probably have 
taken place, had growth continued. It should be noted that in all 
these cases the branch approaching from the right is the left branch, 
when considered with reference to its maternal corallite, while 
similarly the branch approaching from the left is the right branch 
of its maternal corallite. 
