121 
wall of 7'rematotrochus are well-represented by the radial pores 
on the base of Stephanophyllia. 
In the following revised diagnosis of the genus I have noted 
what appear to be its essential attributes. 
Genus Trematorrocuus, 7’, Woods (emend). 
Corallum simple, conical, free. Calice circular or elliptical 
with distinct margin. Costz prominent. Septa in six systems, 
solid, and continuous with coste. The inner ends of some are 
lobed and united to hard nodular tissue, which occupies the axial 
space and constitutes the columella. The highest cycle of septa is 
small or even rudimentary and corresponds to well developed coste. 
Wall incomplete in the intercostal spaces, which are regularly 
fenestrated. Neithere ndotheca nor synapticule present. No 
e pitheca. 
Trematotrochus Clarkii spec. nov. PI. iii, figs. 2 a, dD. 
The corallum is smali and roundly conical in shape. It is 
slightly contracted at the calice, which is circular, with a sub- 
plane surface. 
The septa are in six systems with four cycles. The primaries 
are free and of nearly the same thickness throughout. I select 
these as primary because they are continued on the wall by costie 
which evidently constitute the original framework of the coral. 
Usually there is but one tertiary developed in each system and 
this joins the secondary at from one-third to a half from the wall. 
A single one of my specimens shows two tertiaries in four of the 
systems, the additional one present aiso joining the neighbouring 
secondary. Before uniting, the tertiaries and secondaries equal 
the primaries in thickness, but their fused portions are much 
stouter. In most examples, as in the one figured, there are thus 
18 equal septa at the margin of the calice, but in the exceptional 
one mentioned there are 22. In all cases, however, the inter- 
spaces are approximately equal. Each of these is at the circum- 
ference medially divided by a cycle of rudimentary septa just as 
in 7. fenestratus. These are very small, and, in fact, only 
occasionally visible in the calice as extremely short needle-like 
spikes. The septa of the three first orders are solid, exsert, and 
minutely granular on their sides ; the secondaries are much lobed 
and indented in their thickened portions. 
The columella is formed by hard nodular tissue, which occupies 
a small but well marked area between the opposite ends of the 
_ principal septa at the centre of the calice. The secondaries, and 
the primaries also in well preserved examples, unite with it, the 
thickened and lobed ends of the former rising slightly above its 
upper surface. It is continuous downward nearly, if not quite, 
