﻿Vol. 6 I.] SEQUENCE IN THE BRISTOL AEEA. 275 



fossula is merely indicated as a narrow septal break, occupied by a 

 single primary septum of shorter length than the others, and by the 

 small, inward shift of the tabular intersections in that region (as 

 in the representation, on a contoured map, of a valley in a hillside) . 

 The fossula is much more strongly marked in the young form. 



(3) External form : 



The general form is an elongated cone. 



The middle of the floor of the calyx is flat, in the few specimens 

 in which I have been able to see this feature. 



Discussion. — Fig. 4, pi. xxxiii, Edwards & Haime, 'Monogr. 

 Brit. Eoss. Cor.' undoubtedly represents the species that I am 

 here describing ; but, as I have shown in Proc. Bristol Nat. Soc. n. s. 

 vol. x (1903) pp. 110 et seqq., Oyathophyllum Stutchhuryi, Edwards 

 & Haime (as originally defined i by certain external characters), 

 is identical with 0. Murchisoni, Edwards & Haime. 



In their later work, 2 Edwards & Haime give an almost iden- 

 tical definition of the species, although they draw attention to the 

 vertical section, which almost certainly belongs to a specimen of 

 Oyathophyllum (j>. 



They group, however, under 0. Stutchhuryi certain short, tur- 

 binate forms, with a broad everted rim to the calyx. I have 

 examined the vertical sections of similar forms, and I find that the 

 central structure is purely vesicular, and agrees entirely with that 

 characteristic of Cyatliophyllum regium. These forms I have there- 

 fore separated, as simple forms of C. regium. 



Under these circumstances, it does not seem possible to adopt 

 0. Stuichburyi as the name of our species, and I have tentatively 

 represented it by Oyathophyllum <p. 



Cyathophyllum Murchisoni, Edwards & Haime. 



Besides 0. Murchisoni, as defined and figured by Edwards & 

 Haime, ' Monogr. Brit. Eoss. Cor/' pt. iii (1852) p. 178 & pi. xxxiii, 

 figs. 3-3 6, I include here all those elongate specimens of 0. 

 Stutchhuryi which have not an essentially-tabulate structure. 



The characters of this species that essentially distinguish it 

 from Oyathophyllum <p, are the predominance of purely-vesicular 

 structure in the central space and the extreme reduction of tabu- 

 late structure. A full account of this species is given in Proc. 

 Bristol Nat. Soc. n. s. vol. x (1903) pp. 110-14. 



Cyathophyllum regium, Phil. 



I here include : — 

 Cyathophyllum regium, Edwards & Haime, ' Monogr. Brit. Foss. Cor. 



pt. iii (1852) p. 180 & pi. xxxii, figs. 1-4 a. 

 Cyathophyllum Stutchhuryi, Edwards & Haime, ibid. pi. xxxi, figs. 1 & 1 a. 



In Proc. Bristol Nat. Soc. n. s. vol. x (1903) pp. 114-15, I 

 have given reasons for regarding the short, turbinate type of 



1 ' Polypiers Foss. Paleoz.' 1851, p. 373. 



2 'Monogr. Brit. Foss. Cor.' pt. iii (1852) p. 179 & pi. xxxi, figs. 1-2 a. 



