205 
Stenopoka. Jackii, Nidi, and Mh.fil., PI. 0, ligs. 11-13. 
l>tenopom Jachii, Nicholson and KtU. fih, Ann. and Mag. Nat. Hist., 1S79, iv., p. 270, f. la-c, p. 275. 
„ Nicholson, Tabulate Corals Pal. Period, 1S79, p. 73, f. 25(t-c. ' ’ 
„ Nicholson and Kth. fil., Ann. and Mag. Nat. Hist., 1880, xvii., p. 181. 
Sp. Ghar. Corallum ramose, dividing at wide intervals, the branches cylindrical, 
averaging about two linos in diameter, and gradually tapering to their free extremities. 
The corallites are nearly vertical in the axial portion of their course, but ultimately 
bend outwards nearly at right angles to the imaginary a.xis of the branches, and 
open^ on the surface by rounded calices which are free from any oblitxuity. As the 
terminations of the branches are approached the angle of deflection of the corallites 
becomes less and less, and the horizontal portion becomes shorter and shorter, until 
at the extremity the whole of the corallites are nearly vertical. Average diameter 
of the corallites from yV to -g-V inch, smaller tubes being intercalated among those of 
average size as the surface is approached. Annular thickenings of the horizontal 
portions of the tubes narrow and ring-like, about five occupying one line, this being 
the total length, in general, of the airnulatcd portions of the corallites. Surface not 
observed. 
Obs. This is a graceful and well-marked species, easily distinguished from 
ovata and S. tasmaniensis of Lonsd.alo by its habit and general proportions. We 
8 lould have been inclined to refer it to Sfenopora ( Oliceteles) gracilis, Dana, which it 
jery closely resembles outwardly, had it not been for the fact that Dana lays stress upon 
10 length of the tubes in the hitter species, as well as upon the remarkable paucity of 
fi'iinulations in the same. 
_ In the present species, on the other hand, the annulations of the tubes, in the 
orizontal portions of their course, are much more numerous than in 8. tasmaniensis, 
onsd., while it differs conspicuously from 8. ovata, Lonsd., and other species, in its 
and general proportions. The presence of minute, irregularly placed mural pores 
^as formerly believed to be readily made out in specimens which are longitudinally 
raetured, by an examination of the exterior of the tubes under low powers of the 
^icroscope. A study of additional specimens, however, in the Mining and Geological 
usetim, renders tliis point exceedingly doubtful, and it is more than probable that 
^*iey do not exist. 
. corallum of 8. Jadcii is from three to six millimetres wide, the latter just 
^ revious to bifurcation. Two tnbes occupy the sjtaco of one millimetre, when seen in 
j^^Situdinal section. The mode of growth seems to be very regular and characteristic 
• Jackii, the corallum bifurcating at wide intervals, and retaining a uniform thickness 
roughout, until quite near the apices of the branches, when it tapers off to a 
^®paratively fine termination (PI. 6, fig. 11). 
_ Loo. and Horizon, Coral Creek, Bowen Biver (f?. L. Jadii ) — Middle or Marine 
Bowen Eiver Coal Field. 
^'’ith be more convenient to describe hero a Coral having many points in common 
Sent differing in one or two very important particulars. This is repre- 
bifut*^ ™ mode of growth is the same, repeated simple 
five intervals ; the size of the corallum almost identical, from three to 
The ®®fres in width; whilst two tubes similarly occupy the space of one millimetre. 
®iUch^ I®,’ however, this fundamental difference, that in this coral the tubes, although 
1 h ^^ohened, are simjfle and apiparently non-aunulate. Since the figures wore drawn 
fieeid°i ^ ®ome excellent sections prepared, which demonstrate this feature in a very 
lucre ^ hope in a Supplement to this W ork to illustrate this form much 
