203 



outward manifestation in the calice of the cardinal septum. The 

 vesicles filling the former extend quite up to its margin. 



The position of the counter septum is indicated on the tlat 

 ventral side by the slightest appearance of a ridge, causing an 

 almost imperceptible angularity to the surface. The same is even 

 the case on the dorsal, or convex side, indicating the position of 

 the cardinal septum, although it is not visible in the calice. But 

 when the epitheca is removed by weathering the counter septum 

 stands out as a thickened ridge extending from the hinge line 

 to the basal apex. This is remarkably well shown in a fractured 

 base, where also the vesicular tissue is apparent, but of a much 

 larger mesh than in the higher portion of the corallum; and again 

 the indistinct septa, but the cardinal septum is not to be seen. 



One specimen has a partially preserved opei'culum in situ, 

 sufficient remaining to show that it had a similar method of 

 articulation to that described by Dr. Lindstrom on the bottom 

 valve of Goniophylluiii, and the single valve of Calceola* Neither 

 the nucleus nor the sculpture are preserved. 



Rhizophyllum australe appears to have for its nearest ally 

 R. elungatum, Lindstrom, from the Upper Silurian of Gotland 

 and China. 



Locality and Horizon. — Hatton's Corner, near Yass ; Upper 

 Silurian, probably ^Yeniock (J. A. Wall). 



Collections. — Australian Museum, and J. A. Wall. 



Rhizophyllum interpunctatum, De Koainck. 



(PI. XXX., figs. 7 - 15.) 



Rldzophyllum interpunctatum, De Koninck, Foss. Pal. Nouv. 

 Galles du Sud, Pt. 1, 1876, p. 61, t. 1, f. 10. 



Rhizophyllum australe, Etheridge, fil., Journ. R. Soc. N.S. Whales 

 for 1880 [1881], xiv., pi., f. 8 (2 figs.), non fig. 7. 



Rhizophyllum australe (pars), Lindstrom, Bihang K. Vet. Akad. 

 Handl. Stockholm, 1882, vii. No. 4, p. 29. 



Sp. Char. — Corallum semi-conate, curved, short, moderately 

 expanded above, acutely pointed below, generally Calceola-\i\s.e ; 

 section semi-circular ; lateral angles generally sharp, but occa- 

 sionally rounded and obtuse ; dorsal and ventral surfaces as in 

 the last species. Calice shallow, highly vesicular, the vesicles 

 large ; margin more or less oblique ; ventral margin sharp, 

 bevelled inwards, and bearing about twenty vertical, granulated 

 septa, and at the lateral angles, and on the dorsal side are about 

 twelve fine and highly granulated curved septa, which all descend 

 into the calice beneath the vesicles ; cardinal septum not apparent; 

 counter septum large, projecting forwards as a triangular knob, 

 placed in a shallow fossula. Operculum unknown. Epitheca 



* Geol. Mag., 1871, viii., p. 124. 



