85 
are generally closely packed, although at times separated from one another 
by intervals of some extent. They are either erect or a little curved, and, 
when clustered, are freely united to one another by numerous fistulae, which 
seem to he developed at regular intervals, tier above tier (PI. XIII, fig. 1), 
and practically on the same level throughout the corallum. 
The points chiefly relied on for specific separation are : —(1) Small 
number of the septal laminae, and brevity and delicacy of the spines ; 
(2) plentitude and regularity of the fistulae. 
When compared with some other species of this genus, the tabulae 
present a far more regular appearance than most, with the exception of 
those of T. columnaris and T. dendroidea, which resemble them. This is 
one of the species in which the tabulae, when viewed from above, exhibit 
the peripheral nicks, the impressions of the septal spines. 
The gemmation is not fully known ; two buds were certainly developed 
at one and the same time, but whether or no these were all, I am unable 
to say. 
Microscopic sections reveal the presence of a very thin theca, visible 
only in well-preserved specimens, with a narrow stereoplasmic lining, which 
completely invests the laminae, and coats the primordial spines. Here and 
there the latter thickening has the usual delicate cone-in-cone structure ; 
but, in other instances, it is like the stereoplasmic wall lining, grey in colour, 
and structureless. 
Localities . — Derrengullen Creek, a branch of the Yass River, and 
Barber’s Creek, a branch of Derrengullen Creek, near Bowning, County 
King ( A . J. Shearsby — Australian Museum; C. A. Silssmilch — Technical 
College, Sydney). 
Tryplasma coltjmnaris, sp . nov. 
(Plate XY, Figs. 6 ; PL XIX, Fig. 5 ; PI. XXIY, Figs. 2-5.) 
Specific Characters. — Corallum in the form of solitary corallites, so 
far as known. Corallites long, columnar-cylindrical, straight or sometimes 
slightly curved, attaining a diameter of twenty-five millimetres; base 
obtusely pointed. Epitlieca ornamented with fine, concentric, close, wavy 
lines. Rugae in the form of obtuse rounded ridges. Bourrelets as fine 
concentric rings, the edges crenulated by the rugae, irregularly spaced apart, 
but often close, sometimes developing into obtuse swellings rendering the 
