30 
size, quadrangular, polygonal, often of irregular and rounded outline ; sizes 
from 3x3 m. up to 15 x 15 m., with intermediate gradations; margins plain, 
in one alignment, non-fluctuating ; walls flat, or with faint broad rihs or 
corrugations. Complete corallites unknown, but apparently of no great 
length. Epitheca with delicate, fine, transverse striation. Corallite chains 
simple, narrow, farcimentiform only in the smallest degree. Autopores 
oval to long oval, with rounded ends, two to twelve on each corallite 
chain, the average being from four to six, from three-quarters to one 
millimetre in longest diameter by half to three-quarters of a millimetre in 
width ; walls very thick, solid, often presenting the appearance as if the 
zooids were sunk in them ; septal spines well developed, long, from one to 
three cycles in each visceral chamber, according to the distance apart of the 
tabulae, all but meeting at the calicinal centres ; pseudo-columella not 
observed ; visceral chambers transversely elongate (parallelogrammatic), very 
variable in longitudinal diameter ; tabulae complete, close or distant, horizontal 
or oblique, from three to six in the space of one millimetre vertical. Gonopores 
large and polygonal, here and there triangular, round, or irregular ; walls as 
thick as those of the mesopores ; tabulae complete, horizontal, half a millimetre 
apart. Mesopores transversely oblong and narrow, the corallites pipe-like to 
quadrangular and large ; visceral chambers longitudinally elongate as a 
general rule ; tabulae complete and equidistant, horizontal, half a millimetre 
apart. 
Obs. — H. australis is of large and rambling growth, and very variable 
in some of its characters, particularly the distance apart of the autoporal 
tabulae. A large specimen from Molong, in the Geological Survey Collection, 
indicates that it grew in arborescent bunches commencing from a number of 
centres of growth, the corallites of one bunch as they grew intermingling 
with those of another cluster ; a colony of this description is nine inches by 
eight. 
In my former description I stated that H. australis was devoid of 
spiniform septa, but by the acquisition of further specimens, and the 
preparation of a number of additional sections, I find that septal spines are 
present, but very variable in their development. Some specimens, although 
possessing all the other features of this species do not exhibit spiniform septa 
at all, in others they are visible only in the longitudinal sections, and again 
in a third set are more particularly noticeable in transverse sections. The 
spines are as usual twelve in a cycle, five springing from each autoporal wall, 
and one from each meso-autoporal wall, as figured by Eischer-Benzon in 
