15 
IV— THE GENERAL STRUCTURE OF AUSTRALIAN 
HALYSITES. 
1. Mode of JP reservation. — All the specimens I have examined are 
calcareo-siliceous, i.e., traces of the original calcareous tissue are retained in 
places, hut the greater portion of each corallum has either been simply 
silicified, or has undergone a secondary change, and is converted, more or less, 
into chalcedony, and Beekite rosettes are often visible on the exterior of the 
walls. The entombing matrix being in a great measure calcareous, the resulting 
weathered specimens are, as a rule, in a beautiful state of preservation. Some 
are far more silicified than others, and in a few exceptional cases secondary 
silicification is carried sufficiently far to obliterate in a great measure structural 
details. 
2. Form and Dimensions. — No absolutely perfect corallum has come 
under my notice. The growth outline of the II 'alt/sites found in N. S. Wales 
appears to be restricted to three types — (a) a lax and spreading shrub — like 
corallum forming masses up to eight inches in height by nine inches in width ; 
( b ) expanding sub-pyriform colonies, the component corallites radiating, 
but not curving, from a comparatively narrow base of attachment (II. 
lithostrotonoides, II. Sitssmilchi, &c.), forming masses up to seven inches high 
by six wide on the upper surface ; (<?) thick tabular masses (H. perestephesicus, 
&c.), ranging up to two feet long by ten inches wide, but the total height 
unknown. I have not seen sufficiently perfect examples of either the 
Queensland or Tasmanian corals to be able to speak with any certainty as to 
their forms, nor have I observed any trace of a Syringopora-Mke growth in 
corals such as referred to by Prof. H. A. Nicholson 1 in connection with II. 
catenularius, var. Fieldeni, Eth. 2 In this instance Ido not quite understand 
my late friend’s remarks. Although referring to the variety as of peculiar 
growth, Mr. Etheridge does not in any way allude to the jiresence of 
connecting tubes between the corallites, and one can only surmise that a 
re-examination of the type revealed these to Prof. Nicholson. 
3. Mode of Attachment. — Dr. Eisher-Benzon says his example of II. 
parallela, E. Schmidt, was attached to a Cyaihophyllum . 3 Of two specimens in 
the Geological Survey Collection one has every appearance of being adherent 
1 Nicholson, Man. Palaeontology, 3rd Edit., 1889, p. 340. 
3 Etheridge, Quart. Journ. Geol. Soc., 1878, XXXIV, p. 583. 
* Fisher-Benzon, Abhandl. Gebeite Naturwis. Verein Hamburg, V, 2 Abth. , 1871, p. 20, 
