(Berenicea) megastoma with Fistulipora minor. 429 
is probable that it is this outer layer that forms the successive 
tabule in the smaller polygonal tubes, just as the calcareous 
covers found in the larger cells may be the tabule of. these 
tubes; for I find these external characters in all the stages of 
growth. 
The last or oldest stage in which I have found this organ- 
ism is in incrusting patches, varying from 1 to 6 or 8 lines in 
thickness, the thicker specimens often showing several con- 
centric or zonal layers of growth, in which the larger cells 
form erect continuous tubes that open at the surface with 
nearly circular mouths. In all specimens that have their 
structure well preserved the larger tubes are seen to be tabu- 
lated, the tabule, which are nearly horizontal, being some- 
what irregular in their distance from one another: in some 
specimens they are less than the diameter of the tube apart ; 
in others they are much wider, which leads me to think that 
in some cases they have partly disappeared during fossiliza- 
tion. The smaller polygonal tubes, on the other hand, are 
always closely and more strongly tabulated, the tabule being 
generally horizontal, but sometimes curved or vesicular. In 
this, the latest stage of the organism (so far as I am ac- 
quainted with it), it is identical with the Mstulipora minor, 
M‘Coy, which Prof. Nicholson, in his ‘ Tabulate Corals,’ now 
places with the Monticulipore. I now find that all the speci- 
mens that I had formerly identified with /. minor from the 
limestone strata of Western Scotland must be regarded as 
only the more advanced stage of Ceramopera megastoma, 
M‘Coy. ‘This I have been able satisfactorily to determine, 
from the preparation of numerous sections of the organism in all 
its stages of growth that are contained in my own collection, 
as well as from the careful study of a number of beautifully 
preserved specimens from the Braidwood limestone, Carluke, 
Lanarkshire, now in the cabinet of Dr. J. R. 8S. Hunter, of 
that district. 
In Dr. Hunter’s polished sections one is enabled to trace 
clearly, even in the same specimen, the several phases of the 
organism, from its first Ceramopora-stage, in which the cells 
are seen to be reclined and with roundly triangular mouths 
that have thickened, raised lower lips, onwards into the 
Fistulipora-stage, when the larger tubes become erect and 
open at the surface with nearly circular mouths, and have 
their interiors partitioned off by tabule. I have also well- 
preserved specimens from the Ayrshire Carboniferous lime- 
stones showing the same stages of structure; and this leads 
me to remark that, as we have only one species of Ceramopora 
in the Carboniferous strata of Scotland which is also found 
