702 R. F. TOMES ON THE OOLITIC 
successive periods of growth, when the under surface becomes more 
or less convex, the calicular surface always remaining flat. 
The calice is circular and the margin clearly defined but not pro- 
jecting. 
The wall is completely clothed with epitheca, which extends quite 
to the margin of the calice, but does not conceal the several stages 
of growth. 
The septa are few in number, very stout, swollen, and without 
projections or ornamentation of any kind. 
There is no appearance of endotheca, but it is quite possible that 
a vertical section would reveal tabulz corresponding with the periods 
of growth. 
The only recognized genera to which the present species could 
with any degree of consistency be referred, at least so far as external 
characters are concerned, are Monitlivaltia and Epismilia. But the 
former, under no condition of wear, has septa resembling those of the 
present genus, which differs from both Montlivaltia and Epismilia in 
having no dissepimental tissue. And although the coralluam becomes 
more or less massive by the addition of superimposed layers, yet each 
one of these really represents the corallum for the time being; and 
this mode of increase is quite unlike that of rejuvenesence, and is 
attributable to an entirely different cause. No such mode of growth 
occurs to my knowledge in either Montlivaltia or Epismilia. 
It may be added that the general character of the septa is so very 
similar to that of the septa of Bathycenia and another genus here 
described under the name of Scyphocenia, as to leave little doubt 
that the present species represents a genus of simple corals which 
should be placed in the same family with those genera. 
Discoc@NIA BONONTENSIS, n.s. Pl. XXXII. figs. 1, 2. 
The corallum is depressed and has a somewhat discoid form; but 
the calice is flat and its outer margin is well defined. The under 
surface has a moderate degree of convexity, somewhat as in 
Montlivaltia Labechet. The calice is circular, and the fossula is 
small and a little elongated. The septa are stout, but thin where 
they spring from the wall. They speedily increase in size, are a 
little flexuous, and the upper margins as well as the inner ends of 
all are smooth, and have a rounded or swollen appearance, which is 
most strongly pronounced in those which approach the centre and 
form the fossula. These latter come into contact with each other 
laterally at their inner ends but do not unite, and the fossula though 
very small is nevertheless distinct. The loculi are shallow, their 
depth being successively determined by the several periods of growth. 
As many as six of these are indicated by a corresponding number 
of superimposed layers, which are all of equai depth and are very 
shallow. There are forty septa. Of these the first two cycles are 
scarcely distinguishable the one from the other; the septa of the 
third are half the length of those of the first and second; and those 
of the fourth are wanting in some of the systems, and are very short 
in the others. 
