CARBONIFEROUS CORALS AND BRACHIOPODS 107 
Calices nearly equal, averaging a little over 11 mm. 
diagonal ; walls very sharp and crenulated by the thick 
ends of the strongly marked septa ; each calyx extremely 
shallow with a somewhat deeper, central, circular cup (of 
diameter a little over 4 mm,) ; from the floor of the calyx 
projects a prominent columella, which is compressed and 
somewhat fusiform in section. 
In a horizontal section, the columella is non-prominent, 
thin, and never markedly fusiform ; the inner portion is 
nearly free from vesicles ; the outer is occupied by close, 
small vesicles ; the boundary of the vesicles forms an 
inner wall whose diameter bears a variable ratio to that of 
the corallite (1 to 2J up to 1 to 3), being usually greater, 
the smaller the corallite. 
The septa are markedly alternate, the longer reaching 
nearly to the columella, the shorter only extending to the 
inner wall and occasionally falling short of it, whilst, in 
some examples, they poke a little beyond ; the number of 
the septa seldom exceeds forty, and may sink to thirty-six, 
whilst occasionally it rises to forty-six. 
In the majority of cases the septa are more prominent 
than the vesicular tissue which they traverse, but pxamples 
are not uncommon in which the reverse is the case. There 
are also examples in which the vesicular tissue is con- 
spicuous almost to the centre of the corallite. 
In a vertical section, the central area is occupied by 
conical tabulae, whose apices lie on the columella ; near 
the inner wall each tabula usually forks ; the outer area 
is occupied by rows of small vesicles, which ascend 
obliquely to the outer wall. (There are usually four 
vesicles in a row, but the number is variable.) 
The specimens are all derived from a very limited number 
of beds, the Aranea beds of Stoddart, in the lower part of 
the Great Quarry. 
This form is undoubtedly a mere local mutation of 
