100 CARBONIFEROUS CORALS AND BRACHIOPODS 
“ Corallum flat, free or encrusting ; calices of the 
same mass equal and regularly hexagonal, stellar ; the 
upper tabulae which form the floor of the calyx are almost 
horizontal and strongly granulated ; there are, apparently, 
28 vertical striae ; the large diagonal of the calices varies 
from 5 to 7 mm. or even more.” 
Their specimens were derived from the Devonian. 
In all the main characters our specimens agree, both 
with the above definition and with the figures given by 
the authors. The calices average 4 to 5 mm. in diagonal, 
and are usually almost perfect hexagons ; the walls are 
thick and granular, but, when well preserved, show a thin 
central ridge along their middle line ; there are four or five 
grooves running across each wall in all those specimens 
which have been worn down by weathering (these 
grooves represent tubular channels through the walls) ; 
the floor is almost horizontal and granular. (The granu- 
lation of walls and floor indicates clearly the trabecular 
structure of the vesicular tissue, the possession of which 
characterizes the genus Cleistopora). The specimens are 
derived only from the lowest beds (L. L. Shales). 
The figure is a much weathered example, selected to 
show many calices, and is natural size. 
This fossil has usually been named Microcyathus 
cyclostoma, to v/hich, however, it bears practically little 
resemblance. 
Zaphrentis ( = Cyathopsis of McCoy = Zaphrentis of 
Ed. and H., omitting Zaphrentis cylindrica and its 
allies, which are here included in Caninia). 
This genus, as thus restricted, is one of the most inter- 
esting and also one of the most prolific in the Carboniferous 
Limestone of the Bristol area, but is represented in the 
collection by three specimens only. 
