VATJGHAN : CUSIOPHYLLUM INGLETONENSE. 255 
External Area. 
This area is typically Cyathophylloid in aspect, completely septate, 
without considerable thickening of the inner wall, and packed with 
small interseptal vesicles. 
Vertical section, Fig. 26. 
Central Area. 
A thin mesial plate is suggested, but is discontinuous. 
There is no differentiation of nucleus and aureole. l The whole area 
is traversed by close-set vaulted tabulae, undeflected by the lateral 
lamellae, but slightly ridged where they cross the medial lamella. 
The boundary of central and medial areas is strongly marked 
owing to the vertical descent of the tabulae. 
Medial Area : — 
Traversed by concave, horizontal tabulae which are obviously- 
continuous with those of the central area. 
External Area : — 
Composed of several rows of vesicles, which are elongated vertically. 
Ancestors of the Species. 
C. omaliusi exhibits such marked Cyathophylloid characters, that 
it is unnecessary to look further than to Cyathophyllum for its origin. 
In the coronate group of Devonian Cyathophylla (C. helianthoides 
and its kin), the tabulae are raised centrally and the inner portions of 
the long septa differentiated by thickening. Steeper upraising of the 
tabulae, so that they descend vertically on all sides, would result in the 
strong differentiation of central and medial areas which is characteristic 
of the genus Clisiophyllum. 
EXPLANATION OF PLATE. 
Fig. 1. — Clisiophyllum ingletonense sp. nov. 
Basement Beds of the Carboniferous Limestone 
C2-S1, Ingleton (N.W. Yorkshire). 
Fig. la. — Horizontal section at adult stage ; x 2J. 
Fig. 16. — at earlier stage; x IJ. 
Fig. Ic. — at young stage; x IJ. 
Fig. Id. — of a variant, showing distinct double 
nucleation ; x 1 J. 
Fig. le. — Diagrammatic representation of one-half of a vertical 
section ; x 2J. 
Fig. 2. — Clisiophyllum omaliusi Haime. 
Zone d'Etroeungt (Kg). Transition Beds from 
Devonian into Carboniferous. Avesnes (N.E. France). 
Fig. 2a. — Horizontal section at adult stage ; x 1 J. 
Fig. 2b. — Vertical section (incomplete on left hand side) same 
specimen; x 2 J. 
I Clisiophyllum kayseri described by Freeh from the Uppermost Devonian of Velbert im 
Bergischer (Zeitschr. Deutsch. Gec.l. gesellsch., Vol. 37 (1885), p. 92, PI. 8. figs. 2, 2a) has a very 
similar horizontal section (but showing, apparently, no trace of nucleus), whereas the vertical 
section has an aureole of broad descending vesicles and a nucleus composed of flattened-arches, 
one within and under another. 
