MIDDLE DEVONIAN AND CARBONIFEROtTS COKALS — ETHERIDGE. 257 



secondary stereoplasmic thickening one is accustomed to see encas- 

 ing primary septa in many rugose corals." The absence of this 

 primary line, and the uncertain development of the protuber- 

 ances, detracts from the latter possessing a septal nature. 



The vesicular tissue is clearly separable into an outer and inner 

 tissue. The vesicles forming the peripheral zone are always 

 smaller than those in the centre, and in form are usually semi- 

 lunar, each with a long convex inner face and two concave outer 

 faces, very much resembling the corallites in some species of 

 Alveolites ; this peripheral zone is always the wider of the two. 

 Irrespective of their larger size the central vesicles are remark- 

 able for diversity of form, as already explained, the polygonal 

 outline being traceable both in transverse and longitudinal sections. 



In one particular corallite there is even a line of demarcation 

 between the two sets of vesicles, caused by the tissue of the inner 

 or convex edges of the innermost circlet of the peripheral vesicles 

 becoming much thickened. 



The stereoplasmic investment of the walls when present is 

 dense and structureless, and the same may be said of the layer 

 at times seen within the vesicles, and the line of demarcation in 

 the single corallite just described. 



This coral has so far been observed in New South Wales only in 

 limestone masses, from which it has been found impossible to 

 dissassociate it, but Queensland examples from the Reid's Gap 

 Limestone, near Townsville, are sometimes met with in the round 

 and even with traces of the epitheca preserved.^ This appears to 

 have been concentrically striated. Growth accretion swellings 

 also existed, and at times a sub-pedunculate base. 



The relation to Cystiphyllum is shown in the highly vesicular 

 nature of the corallites, and the presence of the endothecal spines. 

 On the other hand, if the obtusely conical inward peripheral pro- 

 jections are of a septal nature, hardly possible, however, I think, 

 a transition to Microplasma is indicated. The distinction between 

 Cystiphyllum and Microplasma has been very clearly explained 

 by Dr. Clemens Schluter, who says that the radially arranged 

 endothecal striations of the former are not the equivalents of the 

 stunted septa around the wall of the latter. If, therefore, the 

 projections described in this coral are not of a septal nature, we 

 are here dealing with a Cystiphyllum ; if, on the contrary, they 

 partake of the characters of septa, our coral would appear to 

 occupy a position intermediate between the two genera. 



Amongst Cystiphylla the present species is otherwise allied to 

 C. cylindricu7n, Lonsd. (no7i Edw. and Haime), C. americanum, 

 Edw. and H., and similar elongated cylindrical stem-like forms. 



7 An excellent illustration of this is given by Nicholson (Manual Pal., 

 3rd Edit., i., 1889, p. 247, f. 127 B. and C.) 



8 Etheridge— Geol. Pal. Q'land, &c., 1892, pi. 3, f. 13. 



