42 
AYlien acantliopores are present in nntlnckened corallitc walls tlieir 
position is usually at the angles between the corallites, hut I have before me 
some remarkable instances both of New South Wales and Tasmanian 
specimens in which they are plentifully distriljuted along the course of the 
proper wall, without the latter showing the slightest trace of deposited 
sclerenchyma. In this position the acanthoporcs are separated by intervals 
of the wall, or are sufliciently close for their peripheries to he in contact. 
AVlien in what may he termed their normal position, that is, at the angles of 
the corallites, the acanthopores may appear either as dark spots, in the initial 
stage, or as round masses of semi-transparent, fil)ro-concentric sclerenchyma. 
Those met with on the nuthickened proper wall are also in this state, and 
sometimes, in addition, as hollow bodies occupied by a clear sparry infilling. 
On some highly-thickened walls the acanthopores are indicated as irregularly- 
distributed small openings without distinctive features, such as now lie before 
me in a Tasmanian *S'. oDctta, and the Queensland S. Leichliardti. In a very 
instructive tangential section (PL YII, Pig. 8) of the last-named species, 
taken slightly obliquely to the surface, the acanthoporcs appear as definite 
tubes, Avith determinate Avails passing through the substance of the thickened 
corallite walls. 
The acanthopores, Avhen more fully developed, arc formed by similar 
fibro-laminar sclerenchyma to the thickened corallite Awalls, deposited concen- 
trically. They appear either as depressions Avith a perspective concavity, or 
papillar eminences Avith a dark central spot. At times the thickened rod-like 
mass seems to occupy the centre of an ill-defined triangular space (same as 
visible in PI. VII, Pig. 3) in the angles of the corallites, but separated from 
edge of the former by a minute infilling of matrix. The structure AAdthiii 
the perspective concavity even differs, and may consist of a ring of matrix, 
or even secondary deposit, folloAvcd by a mass of sclerenchyma, Avith a dark 
central nucleus, or a Avacuity filled aa ith clear calcite. Another modification 
observed consists in the perspective cavity filled Avith a clear sclerenchymous 
deposit, itself bearing a dark spot, central or excontric. In the latter case 
the clear ring is not continuous all round, but, like the secondary deposit in 
the corallites of S. ans( rails, is deficient at some part of its course. A similar 
instance has been figured by Messrs. Waagenand lYentzel in their GeinilzeUa, 
crassa, Lonsd., sp.^ A feAV instances have presented themselves in Avhich 
the acanthopores are situated quite on the margin of an interstice, and Avhen 
* Pal. Indica, Salt Range Fossils, 1886, A’ol. I, Part 6, t. 114, f. Ic. 
