203 
outward manifestation in the calico 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 Mat 
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 calico. Hut 
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, hut of a much 
larger mesh than in the higher portion of the com, Mum; and again 
the indistinct septa, but the cardinal septum is not to be seen. 
One specimen has a partially preserved operculum in situ, 
sufficient remaining to show that it had a similar method of 
articulation to that described by l)r. Lindstrbm on the bottom 
valve of ( ronidphyllwu , and the single valve of Calccola* Neither 
the nucleus nor the sculpture are preserved. 
Rfiizophyllum auetraia appears to have for its nearest ally 
A\ elonyatum, Lindstrbm, from the Upper Silurian of Gotland 
and China. 
Locality and Horizon* Hatton’s Corner, near Yass ; Upper 
Silurian, probably Weniock (J. A. Wall). 
Collections. Australian Museum, and J. A. Wall. 
lihizophyllum interpunctatum, Dc Koninck. 
(PL xxx., figs. 7 15.) 
Rhizophyllum inlerpunctatum, Do Koninck, Uoss. Pal. Nouv. 
Galles du Sud, Pt. 1, 1876, p. 61, t. 1, f. 10. 
Rkizophyllwin auatrale, Etheridge, til., Journ. U. Soc. N.S. Wales 
for 1880 [1881 1, xiv., pi., f. 8 (2 figs.), non Mg. 7. 
Rhizophyllum amtrale (pars), Lindstrbm, Bihang K. Vet. A kail. 
Mandl. Stockholm, 1882, vii. No. 4, p. 29. 
Sp. Clear. Coral I urn semi-conate, curved, short, moderately 
expanded above, acutely pointed below, generally C&lcaolaA ike ; 
section semi-circular; lateral angles generally sharp, but occa- 
sionally rounded and obtuse ; dorsal and ventral surfaces as in 
the last species. Calico 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 calico beneath the vesicles ; cardinal septum not apparent; 
counter septum large, projecting forwards as a triangular knob, 
placed in a shallow fossula. Operculum unknown. Epitheca 
* Gcol. Mag., 1871, viii., p. 124. 
