part 2] rugose corals from the burindi series. 169 



The Australian species, as a whole, differ from the British species 

 in the following characters : — 



(1) Columella. This is usually very much stouter than in British 



species (PI. IX, figs. 3 & 6). 



(2) Tabulae. The tabulae in the Australian species are, to a great 



extent, replaced by strongly-arched tabellas, or are sharply bent as 

 in Cionodendron (PI. IX, fig. 6). 



(3) Septa. The septa exhibit a marked tendency to become disunited to 



the epitheca in the adult stage. 

 ■(4) Dissepiments. Dependent upon the disruption between the septa 

 and the epitheca, the external dissepiments (not being intersected by 

 the septa) frequently form an outer zone entirely built up of coarse 

 dissepimental tissue, as in Lonsdalem x (PL IX, fig. 3, corallite b). 



It is the prevalence and the combination of these characters, 

 and not the presence of any one of them, that distinguishes the 

 Australian from the British forms, since in the less typical 

 examples among the British species such features may occasionally 

 be noted. 



The occurrence of a non-columellate form among the Australian 

 members of the genus, in which the columella is usually so 

 pronounced a feature, is of considerable interest. 



A specimen of ' Diphyphyllitm ' 3 was included in the collection 

 examined. It came from the parish of Moorowarra near Somerton, 

 and consisted of a large number of broken and isolated corallites 

 embedded in limestone. 



This form calls for no special comment ; it very closely approxi- 

 mates to ' _D.' lateseptatitm M'Coy, and suggests a non-columellate 

 specimen of L. arundineum. Diameter of corallite = 5 - 5 mm. 

 Number of septa, about 18 to 20. Tabulae fairly widely spaced. 



Among these broken corallites of ' Diphypliylhim" 1 one solitary 

 corallite of Cionodendron was observed, and. has been previously 

 mentioned (p. 167). 



EXPLANATION OF PLATES VIII & IX. 

 Plate VIII. 



AjIYGDALOPHYZLUSr AND ClONODENDRON. 



Fig. 1. Amygdalophyllum etheridgei Dun & Benson. Burindi Series, Babbin- 

 boon (N.S.W.). Transverse section, X 2. The character and 

 structure of the columella is here well shown ; note that the dissepi- 

 mental tissue in the upper part of the figure is not traversed by 

 septa. F in figs. 1 & 3 indicates the position of the cardinal fossida. 

 2. The same. Longitudinal section, X 2. The fibrous structure of the 

 columella, the tabellas, and the wide zone of dissepiments (extrathecal 

 region) are clearly illustrated by this figure. (See p. 162.) 



1 S. Smith, Q. J. G. S. vol. lxxi (1915-16) p. 228. 



2 No 4510 or 4515, Coll. Geol. Surv. N.S.W. Sections R 20872 & R 2199S, 

 British Museum (Natural History). 



