﻿276 DR. A. VATIGHAN ON THE PAL2EONTOLOGICAL [May I905, 



Cyathophyllum, with broad everted rims, as the simple form of 

 0. regium. 



The essential structure consists in the vaulted arrangement of 

 fine vesicles in the central space, and in the absence of tabulae. 



Evolution and Mutation of the Carboniferous 

 Cy athojphylla. 



All the forms that we have just considered constitute a single 

 gens, in the exact sense in which that term is here employed. 



It seems probable that, at the top of Z 2 or in y, occurred the 

 ancestral Zaphrentis-like form, from which Caninia, Lithostrotion, 

 the Carboniferous Cyathophylla, and the Clisiophyllids were evolved. 

 Cyathophyllum d, from just below y, only differs from Zaphrentis 

 in the development of a vesicular external area. The relationship 

 of such a form to Zaphrentis aff. cornucopia? is, in reality, very 

 close ; for, if a horizontal slice of Z. aff. cornucopice be examined 

 under a microscope, the thick wall is seen to be veined by wavy, 

 discrete, dark lines which run between the ends of adjacent septa, 

 and the dense wall is due to the deposit of stereoplasma on each 

 side of these dark lines. It is, then, possible that the dense wall 

 of Zaphrentis aff. cornucopice differs from the vesicular one of 

 Cyathophyllum 0, only in the amount of the deposit of stereoplasma. 



Cyathophyllum 0, which characterizes the Syringothyris-Zone 

 and reaches its maximum at d, resembles Caninia in the character 

 of its tabulae. It is, therefore, an interesting instance of parallel 

 development and coaeval assimilation. 



Cyathophyllum Murchisoni shows a further divergence from the 

 simple tabulate structure. It reaches its maximum at the bottom 

 of D r 



In Cyathophyllum regium, which is confined to D , the original 

 tabulate structure is entirely lost, and the Clisiophyllidan tendency 

 is exhibited in the vaulted layers of fine vesicles which occupy the 

 central space. 



Campophyllum, Edwards & Haime (non Thomson). 



This genus is distinguished from Caninia by the following 

 characters : — 



(1) Almost perfect radial symmetry, due to the uniformly-developed ring of 



short, thick septa. 



(2) The absence, or very feeble development, of a fossular depression. 



(3) The uniformly- thick shell of vesicles between the two walls. 



(4) The strongly-developed outer wall. 



[See also Proc. Bristol Nat. Soc. vol. x (1903) p. 102.] 



Campophyllum aff. Muechisoni, Edwards & Haime. 

 I here include, tentatively : — 



(1) Campophyllum Murchisoni, Edwards & Haime, ' Monogr. Brit. Foss. 



Cor.' pt. iii (1852) p. 184 & pi. xxxvi, figs. 2, 2 a, 3. 



(2) Campophyllum aff. Murchisoni, Vaughan, Proc. Bristol Nat. Soc. n. s. 



vol. x (1903) p. 116 & pi. i, fig. 5. 



It will be safer to wait for more material, before attempting to 



