688 
DR W. T. GORDON ON CAMBRIAN ORGANIC REMAINS 
Thalamocyathus tubavallum, Taylor, sp. 
1910. Arcliseocyathus tubavallum , Taylor, Mem. Roy. Soc. South Australia, vol. ii, part ii, p. 123, 
text-figs. 28, 29. 
One small specimen from which only three transverse sections were prepared 
could probably be referred to this species. Although Taylor only obtained a 
small fragment of the form, its characters are fairly well marked. The inner 
wall is thick, and consequently the pores seem to be short pipes. The outer wall has 
smaller pores, and is much thinner, while the septa are imperforate. Unfortunately 
Taylor only published drawings of this form, and so correlation is difficult. One 
section of the present specimen is given in PI. I, fig. 15. The thick inner wall is 
marked, as also are the small pores on the outer wall. The septa are imperforate, 
except for stirrup-pores at their inner ends. These are clearly seen at a and b of 
the figure above mentioned. As no longitudinal sections could be prepared, the 
diameter of the pores cannot be clearly seen. Those on the inner wall seem to 
average 7 per mm., and those on the outer wall 10 to 11 per mm. The measurements 
correspond fairly well with Taylor’s text-fig. 29. 
Thalamocyathus trachealis, Taylor, sp. 
1910. Arcliseocyathus trachealis, Taylor, Mem. Roy. Soc. South Australia, vol. ii, part ii, pp. 125, 126, 
pi. i, iii, v, viii, text-fig. 22. 
Three of the specimens discovered could be referred to the above species, 
and, as the material allowed of examination of minute details, Taylor’s description 
of the species will be emended to some extent, and consequently the new examples 
must be described in considerable detail. The largest specimen was probably 
2 '5 to 3 cm. in length, 1 cm. in diameter at the top, and tapering gradually to a 
point. An oblique section near the top' of the cup is shown in PI. II, fig. 18. The 
great number of closely set septa is at once apparent, while the large pores of the 
inner wall and the small pores of the outer (notably at a) are also visible. In 
fig. 17 a much smaller specimen is represented in transverse section, and a distinct 
feature is the breadth of the inner wall, although in some places it has disappeared 
entirely. This latter feature is still more obvious in PI. II, fig. 20, where at a 
the wall is very broad, whereas at b only the inner rim is visible, and the septa 
seem to stop far short of the wall, while their inner ends have become thickened. 
The reason for all these features is indicated in fig. 20. The apparent inner wall 
is really a broad ring of no great thickness, and arched so that a gutter is formed 
on the upper surface. Should the plane of section correspond with that of the ring 
a complete platform is seen, but in general the broad ring is only partly coincident 
with the plane of section, and in the other parts the margin, or part of the margin, 
is alone included. (See also fig. 19.) This will be even more easily understood by 
reference to fig. 23, where a longitudinal section of the same specimen is represented. 
