270 RECORDS OF THE AUSTRALIAN MUSEUM. 



truding round the periphery. The thyrostome being far below 

 in the tube of the peristome is not clearly visible ; it is appar- 

 ently oval, and on the summit of some of the peristomes there 

 are two very minute circular avicircularia. The central portion 

 of the base of the zoarium is concave and mamillated, with 

 minute circular avicularia on the summit of the mamillse (or 

 pores where they are broken away) ; the zooecia are ranged 

 round the circumference of the zoarium. 



Obs. — This is a very remarkable species. Viewed from above 

 the central portion shows a convex calcareous surface with a few 

 small circular avicularia with a bar, or small pores ; round the 

 margin are seen the long tubular peristomes radiating from the 

 centre ; there are two rows of them in the adult specimens. 



In the " unsorted " material I found two small very young 

 zoaria which I have mounted with the others ; the)' show a star- 

 like arrangement of zooecia with a few avicularia and mamillse 

 in the central calcified part. 



The figures drawn show a half of the upper and under sur- 

 faces of two different specimens of medium size and the upper 

 and under surfaces of two young zoaria. 



Bipora (Conescharellina?) eburnea, sp.nov. 



(Plate lxxvii., figs. 6a, 6b.) 



Zoarium disc-shaped ; 4 to 5 mm. in diameter ; concave in 

 upper surface which is covered with low, large, irregularly dis- 

 posed mamillse which appear to have no correlation to the indivi- 

 dul zooecia; the whole surface being minutely granulated. 

 Zooecia totally immersed and undefined. Thyrostome depressed, 

 transversely elliptical with a deep sinus in the lower margin ; a 

 very small oval avicularium on each side above. Under surface 

 of the younger zoaria mamillated with small round avicularia 

 on the summits. In the older zoaria the under surface is flat, 

 with thick reticulated ridges with small round avicularia (some- 

 times absent) in the centre of the intervening flat circular 

 depressions and in many of the depressions the calcareous surface 

 is wanting so that they appear as large round perforations. 



Obs. — This is probably referrible to D'Orbigny's genus 

 Conescharellina. 



BlPORA MAMILLATA, Sp.HOV. 



(Plate lxxvii., fig. 7.) 



Zoarium flat, irregularly oval in shape. Zooecia totally 

 immersed and undefined. Thyrostome orbicular with a slightly 



