92 
difficult to distinguish the remains of the old cups from particularly strong 
and well-marked ‘accretion ridges.’ There is, however, strong reason for 
believing that the production of accretion ridges, and the simple form of 
calicular gemmation just alluded to, are merely different stages of the same 
physiological process.” This explanation can he appreciated by a glance at 
(PI. XVI, figs. 5 and G.) 
Sections prepared for the microscope reveal the presence of a thick 
and dark-coloured outer wall, inwardly invested by an ample stereoplasmic 
layer, which also follows the septal spines, and, in fact, at times represents 
them, without the presence of primordial laminae. 
On the question of dissepiments, I formerly wrote as follows 1 : — “ In a 
coral with such remarkably short and distally free septa, dissepiments would 
not be expected, but at times a single dark plate is developed. ... It 
is, in all probability, not formed by a series of dissepiments in a single line, 
but is the primitive theca in the substance of the outer investment, and septa 
traversing this zone have an intra- and extra thecal portion. In a rather 
more complete section .... an inner ring is visible which might be 
taken for a further series of dissepiments ; it is, however, a second corallite 
springing from within the older one.” 
The principal characters relied on to distinguish this species are — 
(1) form of the corallites ; (2) marked distinction between the two orders 
of the septal lamellae ; (3) simple calicinal gemmation ; (4) non-expansion 
of the calice edge. 
Locality . — Wellington Caves, near Wellington, County Wellington 
(J. Sibbald — Mining and Geological and Australian Museums). 
Tryplasma, sp. 
(Plato XVI, Figs. 1 and 2 ; PI. XXII, Fig. 16 ; PI. XXIII, Fig. 8.) 
Observations . — The subject of the above figure appears to be allied to 
T. welling tonensis, but still presents an important point of difference. The 
corallum evidently consisted of an aggregation of corallites produced by 
repeated budding, which was, I think, calicinal, notwithstanding the 
deceptive parietal appearance of the two corallites, one above the other, in 
the left central line ; the three buds at the lower left-hand corner appear to 
be calicinal also. The septal apparatus consists of stout vertical laminae, 
1 Etheridge — Rec. Geol. Survey N. S. Wales, 1895, IV, Pt. 4, p. 162. 
