18 
long-oval, round-oval, almost completely circular, or nearly quadrangular. 
The autopores are always tabulate ; and when septal spines are present, they 
occur in these tubes. 
( b ) Mesopores.— These tubes vary very much in form and size. In 
the Chillagoe and Tasmanian corals, possibly identical, mesopores seem to be 
absent ; but as the specimens I have seen are not in too good a state of 
preservation, I do not lay great stress on this point. In H. orthopteroides 
the mesopores are reduced to mere slits; in II. australis, II. cratus, 
II. lithostrotonoides, and II. pycnoblastoides, the outline varies from quad- 
rangular to oblong (parallelogrammatic). In II. peristephesicus, these tubes 
are oblong only, and in II. Snssmilchi triangular, quadrangular, or oblong. 
In the last species, and in II. gamboolicus, they are sometimes double. The 
outlines of any of the mesopores arc sometimes modified, so far as the angles are 
concerned, by subsequent thickening, or secondary siliceous alteration. The 
presence of more than one mesopore between two autopores is interesting, 
because it tends to bear out statements to this effect made by other authors. 
Fischer-Benzon figured 1 double and even treble mesopores in his II. cavernosa , 
and Steinmann copied 2 his figure, referring it to II. catenularius , Linu. 
Weissermel also described 3 the presence of more than one mesopore between 
two autopores in the same species; and he also figured 4 two between the 
autopores in a specimen referred to II. appro ximdta, Eichw. At the same 
time, the more complex mesoporal structures figured by Fischer- Benzon have 
not come under my notice. The mesopores arc invariably the smallest zooids 
in the corallum, and there is not the least approach to the remarkable equality 
in diameter between them and the autopores figured by Lambe in his 
II. catenularius, var. amplitabulata . 5 
( c ) Gonopores. — I employ this term to distinguish the corallites, more 
often than not, occupying the angles of the fenestrules, and from which in 
nearly every case new chains arise ; they always lie between two autopores. 
I find that, within certain limits, they are of a different shape to either the 
autopores or mesopores of a given species, and are always either intermediate 
in size, or nearly equal to that of the autopores. Furthermore, in some cases, 
although not in all, the tabulae are differently spaced to those of the other 
1 Fischer-Benzon, Abhandl. Gebeite Naturwis. Verein Hamburg, V, 2 Abth., 1871, t. 1, f. 2. 
2 Steinmann, Elemente Pal., 1890, p. 109, f. 3 A. 
* Weissermel, Zeit. Deutsehen Geol. Gesellsch., XLVII, 3 Heft, 1894, p. 661. 
4 Weissermel, Ibid., p. 662, f. 4. 
5 Lambe, Contrib. Canadian Pal., IV, Pt. 1, 1899, pi. iv, f. 4a. 
