﻿274 DE. A. VATTGHAK ON THE PALiEONTOLOGICAL [May 1905, 



The Carboniferous Cyathophylla. 



The characters of the typical members of this single, compre- 

 hensive gens are as follows : — ■ 



(1) Very numerous septa, alternately long and short. 



(2) All the septa are of nearly-equal thickness, and the thickness of each 



septum is almost uniform along its length. 



(3) The long septa reach nearly, or quite, to the centre ; and all the septa 



extend to the wall. 



(4) In the external area, which is radiated by both series of septa, the inter- 



septal spaces are crowded with small vesicles. 



(5) In the medial area, which is radiated only by the long septa, the inter- 



septal spaces contain few vesicles. 



Cyathophylltjm 0. (PI. XXIII, fig. 2.) 



This type may be considered to represent the Zap7irentis-\ike 

 ancestor of the gens. 



Form : short, cornute, and broad-angled. 



The septa are of uniform thickness along their length, and only 

 differ, one from the other, in being alternately long and short ; they 

 are considerably more wide-spaced than is the case in the more 

 typical members of the gens. The long septa do not reach the 

 centre, which is occupied solely by the broad tabulae. 



There is a strongly -marked septal break at the fossula, which is 

 occupied by a single, short septum ; there is, also, a lateral inter- 

 ruption of the septal sequence, marked out by the greater elonga- 

 tion of one of the shorter septa. 



The interseptal vesicles are distributed, as in the typical members 

 of the gens. 



The tabulae are broad and vaulted, with a deep and narrow 

 depression which forms the fossula. 



CrATHOPHrLLTTM 0. (PI. XXIII, figS. 3-3 b.) 



= Cyathophyllum Sttitchburyi, Edwards & Haime ('pars) ' Monogr. Brit. 

 Foss. Cor.' pt. iii, p. 179. 



Besides the characters already noted as common to all the typical 

 members of the gens, the following characters are important : — 



(1) In a vertical section : 



The tabulae are low, broad plates, which occupy the whole region 

 within the inner wall, but only the minority stretch continuously 

 across from side to side ; the majority are merely very broad, low 

 vesicles which overlap one another. In this respect, the vertical 

 section differs from that of a Caninia. 



(2) In a horizontal section : 



The numerous interseptal vesicles in the medial area represent 

 the intersection of the tabular vesicles by the plane of section. 



The centre is usually free of septa, and occupied only by a few 

 curvilinear intersections with the tabular vesicles. In the adult, 

 this area is very reduced in size by the extension of the long septa 

 almost or quite to the centre ; but in the young form (see PI. XXIII, 

 fig. 3 a) there is a broad, central tabular area, free of septa. The 



