FROM A DREDGING IN THE WEDDELL SEA. 
689 
Here, the outer wall — a continuous, porous lamina — is seen at a ; and at b the inner 
wall is evidently not continuous, but a comparison of figs. 20 and 23 clearly 
shows that it consists of a series of broad rings set one above the other and soldered 
to the septa. As mentioned above, the rings are not thick and are grooved on their 
upper surfaces. 
At c (fig. 23) a septum appears cut longitudinally, and near the top of the 
figure the attachment of four rings to this septum is shown. A longitudinal 
section at right angles to the plane of fig. 23 demonstrates that the pores of the 
inner wall are delimited by the vertical septa and the horizontal ring-platforms 
(PI. II, fig. 22, a). This figure represents the vertical septa at d crossed by the 
horizontal platforms b, the spaces between the intersections constituting the pores 
(a). Such pores ought to be square in section, but increased growth at the fused 
corners, and to a certain extent all round the pores, has given a circular shape to 
the aperture. Such increase in thickness of the septa in this region accounts for 
the swollen inner ends so apparent at a in fig. 19. Eeverting to fig. 22, however, 
it seems difficult at first sight to determine which are the septa and which the 
ring-platforms, but a closer examination soon indicates a means of distinction 
even in such a section. At c in that figure, and again at a in fig. 19, a series of 
small dots may be noted which are in each case continuations of the platforms. 
The explanation of this row of dots is given by fig. 23, where (at b) on the under 
surface of each platform a small projection is shown. Now, turning again to 
fig. 19, the origin of the row of dots is quite clear. They represent a series of 
small peg-like projections or denticles on the under surface of each platform. They 
are again shown, more highly magnified, in PL III, fig. 26, where at a the denticles 
are very evident, at s the swollen end of a septum is equally so, and aty? a septal 
pore is conspicuous. The denticles are so close together that in the thickness of 
a section more than one would be included, or, to put it otherwise, no section 
could be cut thin enough to pass between two denticles; consequently any 
longitudinal section of the ring-platforms will always show the denticle on the 
lower surface of each. 
Unfortunately, such a characteristic feature is not mentioned by Taylor in his 
original description of the species, but this was due to the method he employed 
of etching the skeleton out by dissolving the matrix in hydrochloric acid. Such 
minute denticles were broken off. That such must have been the case is shown 
in PI. II, fig. 24, where a longitudinal section is represented which was prepared 
from material kindly given me by Mr Taylor some years ago. The identity 
of this type with that of fig. 23 is undoubted. At b, in each, the denticles are 
shown, at c, a porous septum, and at a, the finely porous outer wall. It is true 
that the Australian specimen is distinctly more robust and larger (a point which 
will be referred to later), but there is no doubt that the two are specifically 
identical. 
TRANS. ROY. SOC. EDIN., YOL. LII, PART IV (NO. 27). 
107 
