223 | Mr. R. Etheridge and Dr. H. A. Nicholson 
vermicular anastomosing ridges, devoid of any defined direc- 
tion, and equally developed on all parts of the corallum, in- 
cluding the concentrically wrinkled base. Calicular fission 
well displayed in many instances. 
Obs. We have examined upwards of two hundred examples 
of the species, all in a fine state of preservation, and therefore 
feel ourselves in a position to pass a few remarks upon it with 
more than ordinary confidence. First, as to the number of 
cups. Prof. de Koninck has figured * a single cup of P. 
eyclostoma adhering to a Zaphrentis; but, strange to say, out 
of the large number of specimens we have looked over, 
we have only found a few examples of this. ‘The simple 
double cup or cell is, perhaps, with the triple form (Pl. XII. 
figs. 2, 16), the commonest aspect in which this organism is 
presented to us. We have also observed numerous indivi- 
duals in which the cups are four in number (Pl. XII. fig. 1), 
the condition in which P. cyclostoma was figured by Messrs. 
Meek and Worthen under the name of Sphenopotertum enor- 
met. Five, again, is not an uncommon number amongst the 
specimens to which we have had access, corresponding with 
the figure given by Dr. Kunth t as Paleacis (Ptychocharto- 
cyathus) lava, Ludwig. The type example figured by Phil- 
lips § possessed six cells, a number to be found on several 
specimens in the Scotch Survey collection. There are, again, 
others with seven and nine (Pl. XII. fig. 17), whilst the 
largest number we have had an opportunity of observing has 
been twelve; but we see no reason why this number should 
not be considerably exceeded. 
The second point to which we have to draw attention is the 
varied form of the colony. In the simplest state but one in 
which P. cyclostoma has comeunder our observation it is bilobed; 
@. e. there are two cells united, as it were, almost base to base, 
their mouths then looking in contrary directions to one 
another, and set somewhat obliquely to an imaginary vertical 
axis. By the addition of another cup a trilobed appearance 
is assumed (Pl. XII. figs. 2 and 16), whilst a further addition 
of another gives a more or less quadrangular or sometimes 
irregular outline to the colony. It not unfrequently happens 
that after a number of cells have been developed (say six or 
seven), one, perhaps the first formed, assumes a more or less 
central position, and is somewhat elevated above the others, 
and round it the latter appear to radiate, more, perhaps, 
* Nouvelles Recherches, pl. 15. f. 8. 
+ Illinois Report, ii. pl. 14. f. 2 6. 
¢ Zeitschr. deutsch. geol. Gesellsch. xxi. pl. 2. f. 2a. 
§ Geol. Yorksh, ii. pl. 2. f. 9. 
