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wellingtonensis * 1 , I wrote as follows when speaking of an intra -marginal ring in 
some of the corallites : — “ 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 (PL XXI, Figs. 11 and 12) 
an inner ring is visible which might he taken for a further series of dissepi- 
ments ; it is, however, a second corallite springing from within the outer 
one.” I have not seen any reasons to alter this view. 
The almost total absence of dissepimental tissue at once recalls to mind 
the genera Amplexus and Tycnostylus , and a number of other Rugose genera 
with complete septal lamellae 2 . 
14. Tabula. — One of the most conspicuous features of the corallum 
in all the species. The distance apart of these floors is of too variable a 
nature to be a reliable factor in specific description, except in one or two 
instances. In a comparative sense the tabulae may be either distant or much 
crowded together, and in one species ( T. Lonsclalei ) this crowding occurs in 
clusters so constantly as to become of specific importance. The tabulae are 
both complete and incomplete in all but one species, the complete often 
largely predominating over the incomplete. The complete tabulae extend 
entirely across the corallites, from wall to wall, and may be either horizontal, 
concave, oblique, convex, or rolling, and more than one of these characters 
may be common to a species. 
In the descriptions of two of the already known species ( T. welling- 
tonensis and T. Lonsdalei), I questioned the actual union of the complete 
tabulae with the corallite walls, but I am now convinced that a union is the 
case invariably. Dybowski described the tabulae as ceasing at the inner or 
distal ends of the septal spines without reaching the proper wall ; but he was 
probably misled, like myself, by deceptive appearances. He accounted for 
this, however, on the supposition that the spines are too closely packed to 
permit of the floors joining the wall, but it is now quite evident to me that 
the latter had a connection with the wall of their corallite as a support. 
The incomplete tabulae invariably give rise to a vesicular tissue, but 
this must not be confounded with the general vesicular structure of the 
Cystiphvlloidea, particularly that of the operculate division ; and herein 
lies one of the fundamental differences between this group and the 
1 Etheridge — Rec. Geol. Survey N. S. Wales, 1895, IV, Pt. 4, p. 162. 
i See Sherzer — American Gcol., 1891, VII, No. 5, pp. 281, 287. 
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