MIDDLE DEVONIAN AND CARBONIFEROUS CORALS — ETHERIDGE. 255 



In viewing a longitudinal section we observe that the peripheral 

 tier of vesicles is often large, followed by two or three tiers of 

 smaller, or the whole septal zone is occupied by four or five tiers of 

 smaller vesicles, all convex upwards, and as a rule semi-lunate in 

 form, although some are quite globular. So marked is this in 

 some corallites that this external zone presents quite the appear- 

 ance of a Cystiphyllum. In certain corallites, although not in all, 

 the " walls " of the innermost tier of vesicles, or that next to the 

 tabulate area, are thickened, presenting the appearance of an 

 inner mural investment, but which is not very apparent in a 

 transverse section. 



The larger mass of each corallite is occupied by the tabulae. 

 These are very variable in character, and in their distance apart 

 from one another. They may be quite distant, moderately close, 

 or very close, in fact quite approximate, and horizontal, oblique, 

 concave, or inosculating, when large and small vesicles are formed, 

 in shape semi-lunate, lenticular, or even globular. Deflection at 

 the edges, when the tabulae are horizontal, is occasionally present, 

 but never marked. The result of this variability is that, in a 

 horizontal section, an absolutely clear old visceral chamber is the 

 exception ; generally the plane of the latter is occupied by one or 

 more cut edges of tabulae. For diversity in form of the tabulse 

 this is one of the most remarkable corals I know of. 



In its mode of growth D. gevimiformis is quite distinct from 

 any Australian form of the genus hitherto described. It is a 

 larger species than D. mitchelensis, mihi,^ with a greater develop- 

 ment of vesicular tissue, and does not possess septa of the second 

 order. It is also distinct from D. robustmn, mihi,^ which is larger 

 and possesses secondary septa. 



Two American species at least, referred by W. J. Davis 

 to Diphyphyllum, assume a composite form of growth, viz., 

 D. bellis, Davis, ^ with the general outward appearance of a Cyatho- 

 phyllum^ which is even more composite than D. geimniformis, and 

 D. conjunctum, Davis.'' Both are very large and compound Middle 

 Devonian forms. 



Loc. — Taemas Bridge Road, north bank of Murrumbidgee 

 River (Aust. Mus.); T. Hughes' selection. Parish of Warroo, Co. 

 Murray, Murrumbidgee River (C Cullen — Geol. and Mining Mus., 

 Sydney); North of Portion 41, Parish of Warroo, Co. Murray, 

 Murrumbidgee River (C. Cullen — ibid.) 



Hor. — Cave Limestone — Middle Devonian. 



3 Etheridge — Geol. Surv. Vict., Progress Report xi., 1899, p. 30, pi. A., 

 f. 6-8 and 12, pi. B., f, 11. 



4 Etheridge— Eec. Geol. Surv. N.S.W., vi., 1899, 3, p. 153, t. 32, f. 1 and 

 2, t. 37, f. 2. 



5 Davis— Kentucky Fossil Corals, pt. 2, 1885, t. 108, f. 2, t. 116, f. 4. 



6 Davis— Loc. cit., t. 116, f. 1 -3. 



