690 
DR W. T. GORDON ON CAMBRIAN ORGANIC REMAINS 
So far the pores on skeletal members other than the inner wall have only been 
mentioned incidentally : it remains to examine the porous Structures in more detail. 
On the outer wall the pores are much smaller than those on the inner, there being 
8 per mm. as compared with 5 per mm. On the outer wall the pores are arranged 
in rows, two or three to the interseptum, but they alternate in the rows, and thus 
an hexagonal outline is impressed on each individual pore (PI. II, fig. 21). 
Although only a rather oblique section of a septum has been obtained, it will 
suffice to give some idea of the arrangement and size of the septal pores. These 
latter seem (PI. II, fig. 23) to run in vertical lines, but rather more irregularly than 
the pores of the inner wall. That these apertures are not in absolutely parallel 
rows may be proved by reference to transverse sections (PI. II, fig. 20, e), where 
the pores on one septum are not exactly opposite those on its neighbours. As com- 
pared with the Australian specimen represented in fig. 24, the arrangement of pores 
is identical. In every particular except size this type agrees with Thalamocyathus 
trachealis as described by Taylor or shown by the section of his material which 
is figured (PI. II, fig. 24). 
In one particular, however, these new forms differ from the Australian species 
with which I have grouped them. That is the occurrence in the interior of the 
cup of a coralloidal type of infilling material. The resulting tissue is very evidently 
connected with the inner, walls (PI. II, fig. 25), and similar material has only beem 
recorded in a few types. Bornemann, Hinde, and Taylor have each noted such 
a feature in some type or another, but only in Taylor’s Somphocyathus does it 
become prominent. In that latter genus the general form (coralloidal) is quite 
comparable with that discovered in T. trachealis. The tissue has been noted in 
two examples, and in each was found near the base of the cup. As will be seen later, 
a similar infilling has been observed in practically all the W eddell Sea specimens ; 
it only occurs near the base of the cup ; it differs in type, and so may be diagnostic 
in value, but, from the position in which it occurs, I am inclined to consider it a 
gerontic feature, since wherever it has been noted it is always present in a region 
where the walls are thickened and the pores more or less closed by callus growth. 
No evidence of rooting processes has been obtained. In the lowest section 
available the diameter was -9 mm. and there were 12 septa, but it could not have 
been far above the extreme point, and any processes below this level could not 
have been very effective in balancing the whole cup. It may be that the form 
had no special rooting processes. As regards details of measurement, the largest 
specimen was 25 to 30 mm. in length, tapering to a point. The “ intervallum 
coefficient,” i.e. the ratio of width of intervallum to width of central cavity, has 
been found of little use. In PI. II, fig. 17, it is 1/1 ; in PI. II, figs. 20 and 25, 1/1 '5 ; 
in PI. II, fig. 18, 1/4. 
An emended description based on the above new facts . is as follows : — Cup, in 
small specimens, a tapering cone, in larger forms more cylindrical. Constrictions 
