CARBONIFEROUS CORALS AND BRACHIOPODS 111 
Shape. 
External 
Rings op 
Growth. 
Calyx. 
Septa. 
TABUL.E. 
■C. Murchi- 
soni. 
very long, 
slightly 
compressed. 
! 
' mere ridges 
, at nearly 
regular in- 
tervals of 
5 m.m. 
1 
(not described). 
nearly 
equal, more 
numerous. 
very small, 
fairly re- 
mote. 
C. Stutch- 
buryi. 
short or 
long. 
very 
strong, at 
unequal 
intervals. 
centre of floor 
frequently occu- 
pied by an 
elevation which 
has a depres- 
sion at its top : 
rudimentary 
“ fossula.” 
alternate, 
very 
straight, 
stronger. 
greatly de- 
veloped. 
The calyx in C. Murchisoni is not described, as the 
figured specimen (PL 33, Fig. 3), which is preserved in 
the British Museum, had evidently been broken across 
whilst still in the rock, and the flat cross section, thus' 
produced, was subsequent^ exposed and weathered. 
Exactly similar specimens (i.e. specimens exhibiting the 
same type of external rings and the same number and 
proportion of ^epta) with their calices well preserved are 
not by any means uncommon, and these show a shallow 
central depression surrounded by a broad flat rim ; the 
floor of the central depression may be almost perfectly 
flat, but it almost invariably exhibits a rudimentary 
fossula and, when the depression is considerable, a central 
elevation of its floor which bears a shallow depression on 
top is of very common occurrence. The only striking 
differences observable in the calyx are the presence or 
absence of this central elevation and the angle of slope 
of the rim from the outer wall to the boundary of the central 
depression. From an examination of hundreds of speci- 
mens, I am convinced that it is utterly impossible to 
separate the two species on differences in the calices, seeing 
that these differences vary continuously in degree, and 
