57 
The corallites, after their divergence from the axial region, lose much 
of their polygonal form, and become to some extent cylindrical. The 
joreservation of the proper wall and line of demarcation between the corallites 
varies much according to preservation, but, as a rule, they can he satisfactorily 
made out. In an exceptionally good section of this species may he seen the 
primordial wall, the secondary organic tliickening, and the inorganic invest- 
ment (PL VII, Pig. 3). There is hut little difference in a transverse axial 
section between this species and S. crinifa, excepting in the size of the 
coralhtos ; there is the same form, same condition of the walls, and the same 
secondary inorganic deposition around the walls. In a transverse section of 
the peripheral region the periodical thickenings succeed one another more 
rapidly in succession, and they are more strictly moniliform, or even pyriform, 
than in S. cr'mita. It is, however, in a longitudinal axial section that the 
greatest differences are observable, the corallites of S. ovata so far examined 
by me being here entirely destitute of constrictions or swellings, and are 
practically non- tabulate also. The moniliform swellings of the walls vary to 
some extent from being moderately distant^ to a rapid succession of one 
another, and they are at times semi-confluent, more especially in Tasmanian 
examples, but in such cases do not entwely lose their moniliform outline, as 
in the case with S. temnemiensis. 
In PL VII, Pigs. 2 and 3, the insensible manner in which the original 
wall passes into a thickened portion, and l:)ecomes lost, is excellently shown, 
but now and then it can be equally distinctly traced in the latter. 
In position and structure the acanthoporcs (PL VII, Pigs. 2 and 4) 
arc very similar to those of S. crinita, and when present usually occupy the 
angles between contiguous cells ; but at times, especially in Tasmanian 
examples, are scattered on the intermediate boundary walls rather thickly, 
although never clustered there as in S. tasmaniensis. They are circular, 
very strongly-developed and with thickened walls, and a distinct lumen. 
In a very interesting section (PL VII, Pig. 3), from a Singleton specimen, 
there is an instance of the development of acanthoporcs in thickened and 
unthickened walls, side by side ; and, lastly, the central aperture usually 
occupies a very large part of the diameter. They have a general papillose 
appearance, the walls being concentric-laminar in structure. In vertical 
sections the acanthopores appear as rods running in the corallite walls, and in 
this species are very persistent. 
' Ann. Mag. Nat. Hist., 1886, XVII t. .3, f. 2. 
