118 CARBONIFEROUS CORALS AND BRACHIOPODS 
:and often rudimentary ; the outer vesicular zone is very 
narrow. 
Two distinct mutations may be included here : — 
( 1 ) Short turbinate specimens with broad, everted rims, 
and (2) elongated, narrow, conical forms. In both forms the 
cup is deep and its floor is occupied by a large, rounded 
oval eminence with a prominent crest extending almost 
across it, whilst sharp ridges ascend the sides of the 
eminence towards the crest. 
This assemblage of characters corresponds, in all essen- 
tial points, with the definition given by McCoy of C. 
turbinatum, but the specimens he had under observation 
had a wider conical angle, and consequently exhibited a 
greater number of septa. On the other hand, it is evident 
that Edwards and Haime were only acquainted with the 
two forms I have alluded to above. 
[The rounded central boss, the extended mesial crest and 
the more or less obvious concavity of the rows of vesicles, 
seen in the central area of a vertical section, mark out this 
group as members of the section Dibunophyllum (Nich. 
and Thom.)] 
A small turbinate example is labelled “Upr. L. Shales, 
Ashton.” 
The figure represents, natural size, the horizontal section 
of one of the more elongate forms. 
A Clisiophyllid perhaps belonging to the Acrophyllum 
section. 
This is a horizontal section, with a narrow central area 
(about -g- the total diameter) ; a strong mesial plate bisects 
the central area, and on either side of this plate are indis- 
tinct, spiral, concentric intersections. 
The inner septal area is narrow and practically non- 
vesicular ; there are thirty- six strong septa. 
The outer septal area is very broad and crowded with 
