133 
As the only part which geologists are likely to find, except 
in special circumstances, is the calcareous shell, this has for 
me the most interest, hut as I have recently entered into 
the points which I more fully examined, it will not he 
necessary to do more than briefly review a few points con- 
cerning the shell. 
Through the shell of most there are tubes passing from the 
interior to the exterior, and these tubes are filled with the 
chylaqueous fluid of the animal, and upon these perforations 
or pores depends for the most part the sculpturing of the shell. 
There is an external growth which is most apparent in 
Eschara, Myriozoon, &c., and this takes place independently 
of the life of the polypide, as is shown by a considerable ex- 
ternal growth over the opercula. 
The stalk of the Ctenostomata is divided by diaphragms 
in which there are minute perforations through which the 
funiculus above and below is connected, and in the same 
way each polypide is joined with the main funiculus. In 
the walls of the Cheilostomata there are similar thin por- 
tions, which have been called by Reichert “ rosettenplatte,” 
and the object of my recent communication, to which I 
have referred, was to show that the position and form of 
these rosettenplatte should be given as a character, since 
they differ very much in various species. The points to be 
noticed are their number, position, and if they are separated 
by dividing ridges. Part of the characters it will be seen 
can be made out in fossil species, and therefore it is most 
important that it should be mentioned, as thus the position 
of an internal organisation is recorded in the shell. 
Although this is an important point that may be learnt 
by an examination of thin sections of the shell, it is by no 
means all, for sections will show the shape of the cell, mode 
of growth, varying structure of the shell, from which in 
some cases even the general sculpturing of the exterior 
would be revealed. Nor is it probably with the more recent 
