﻿462 DE. A. VAUGHAN ON THE FAIJNAL SUCCESSION [Aug. IQoSr 



Lithostrotion. 



LiTHOSTEOTiON cf. AFFiNE (Martin), Ed. & H. (PI. XLIX, fig. 10.) 



Compare Litliostrotion affiiie (Martin), as figured by Edwards & Haime in 

 'Monogr. Brit. Foss. Oor,' pi. xxxix, fig. 2 ; and compare also Lithostrotion 

 cyathophylloides, Vaughan, figured in the ' Eush paper ' pi. xxx, 

 figs. 1 & 1 a. 



The spacing of the major septa agrees with LitJiostrotion affine ; 

 their continuation to the columella with L, cyatliophylloides. 



The corallites are very often in close union — a character unknown 

 in the coral of the megastoma-hedL^. Again, the calyx is sharp- 

 rimmed, whereas L. cyathophylloides has its calicular wall as broad 

 as in a Cyatlio-pliyllum. 



Occurrence. — This species is abundant at the top of the 

 CyatTiaa^onia-'Beds, where it characterizes a peculiar faunal phase. 



The same form occurs in the CyatJiaxonia-Beds of the Western 

 Midlands. 



Diphyphylloid variant of Lithosteotion ieregiilake from P 

 (L 10 6). 



Cf. DiphypliylluQii gracile, M'Coy. 



The tabulae are convex and smooth, the columella being usually 

 wanting. (The central cylinder is commonly found detached, 

 and suggests an OrtJioceras.) 



This form is common in D^ of the Avon section. 



Liiliostrotion-l i k e Clisiophyllids. 

 The general characters of this large group are : — 



(1) A dense axial nucleus confined to the middle of the central area, and 



enclosing a prominent columellar plate. 



In the calyx the whole nucleus is usually cemented into a solid, 

 smooth-sided, strongly-projecting axial spike. PI. XLIX, fig. 3, is a 

 section of a young example of this group (probably Glisiophyllum 

 ciirkeenense), cut immediately above the floor of the calyx in order to 

 show this character. 



(2) A narrow external vesicular ring. 



(3) Major and minor septa strongly developed within the vesicular ring, 



and extending without appreciable thinning to the wall. 



The group can be divided into two sections : — 



I. Corals with a short and stout columella, from which short 

 radiating lamellae project and become rapidly merged in the 

 loose and irregularly-reticulated intersections of the broad 

 central area. 



CUsiojphylluon cur'keenense, Yaughan (' Eush paper ' p. 320 & 

 pi. xxx, fig. 2), in which the medial and external areas are very 

 strongly differentiated, is the most highly-specialized member of 

 this group. 



