36 
Queensland Stenoportc presents some interesting points of study. It is com- 
posed of concentric zones of successively-deposited matter, and, wlien present, 
regularly follows the outline of the corallite, which it assists in filling up. 
This is seen to greatest advantage in S. crinita, and from the varying colours 
of the lamince is best compared to the concentric structure of a nodule of 
clay ironstone, which it much resembles. 
In S. crinita, S. ovata, and S. tasmaniensis it completely follows the 
outline of the tubes, but it is always much less marked in the last-named 
species. In the two first-named the corallite wall is generally succeeded 
by a zone of clear calcite, this by a ring of dark ferruginous deposit of greater 
or less thickness, at times a mere ring, at others broadening into a zone ; this 
again by another layer of clear calcite, which may or may not completely fill 
the visceral chamber. In the latter case its inner or free margin is ragged, 
the centre being occupied by matrix, or a subsequent infiltration of carbonate 
of lime (PI. VI, Pigs. 3 and 4). There are even degrees and variations in 
this structure, for it sometimes happens that beyond the first dark ring the 
whole chamber is filled with clear calcite, or this ring may expand into a 
broad zone completely infilling the tube. In some few examples of S. ovata 
the outline of the tubes is followed immediately by a pale-coloured ring of 
sclerenchyma, of radiately fibrous structure. In vertical sections of /S', crmita 
the moniliform walls are invested in a somewhat similar manner. 
In /S', australis a modification of this secondary investment is seen. 
It is never in contact with the polygonal wall for more than half or two-thirds 
of its circumference, being separated from the remaining part of the tube by 
a distinct and conspicuous interspace, which is filled in the fossil with trans- 
parent calcite. Not only is this partial interspace between the inner ring and 
the outer wall apparently always present, but it seems to be always situated 
upon the same side of all the corallitcs in any particular section.^ 
It has already been mentioned that S. tasmaniensis exhibits this 
filling of the tubes to a far less extent than the other species mentioned ; and 
it is a peculiar fact that in all the Tasmanian species examined by me® the 
deposit is absent, but in the Indian forms of /S', ovata it is to some extent 
developed.^ In the case of Stenopora australis the peculiar appearance there 
' Nicholson & Etheridge, Junr., Ann. Mag. Nat. Hist., 1879, IV, p. 272; Ibid, 18SG, XVII, t. 3, t. 5. 
^ With the exception of Stenopora informis. 
^ Pal. Indic.a, Salt Range Fossils, 1886, Vol. I, Part 6, t. 110, f, Ic. 
