694 
DR W. T. GORDON ON CAMBRIAN ORGANIC REMAINS 
the Archseocyathinae.* A consideration of the specimens now figured indicates 
that the early stages in Spirocyathus and Protopharetra are very similar ; but I 
believe they can be distinguished, and hold with Taylor t that they may be 
independent forms belonging to the same group. 
In the above-mentioned figure (fig. 39) there is another important feature, namely, 
the occurrence at a, b, and c of small structures not unlike the cup itself, except 
that there is no central cavity. The structure at b is in continuity with the 
thickened wall of the cup, but the others are separated from it. Similar continuity 
between such a strand and the cup is indubitable in PI. IV, fig. 40, a. These con- 
stitute the rooting processes of this form. Here (fig. 40) the Spirocyathus character 
is very evident in the cup, and it is the second section- above that of fig. 39. The 
lower half of this figure still shows a remarkable resemblance to Protopharetra , but 
the upper part to Spirocyathus. Even in PI. IV, fig. 41, the Protopharetra affinities 
are still marked, though the regular septa near the inner wall place it with Spiro- 
cyathus cf. S. irregularis , Taylor. PI. IV, fig. 37, shows a section at a still higher 
level in the cup, and the relation to Spirocyathus atlanticus is now evident, although, 
in parts, the Protopharetra character persists. The central cavity in figs. 39, 40, 
and 41 is crossed by irregular strands which are clearly outgrowths from the inner 
wall and continuous with the septa. 
The porous nature of the inner wall is shown in PI. IV, fig. 42, a and b. (The 
figure is really on its side ; a is the top and b the bottom of the section.) The 
central cavity is cut obliquely, so that the inner wall on the one side is exposed on 
the right-hand side of the figure, and again at a higher level on the left-hand side. 
The pores are evidently hexagonal in outline (a), but become more circular by 
thickening round the edges, while rod-like synapticulse divide each pore horizontally 
(PI. IV, fig. 42, a and b). The breadth' of the pore is the whole space between two 
septa. The septa themselves are so porous that the wall is a meshwork of rods 
rather than a porous lamina. A section through the wall thus shows a row of 
circular dots, some of which may be connected when the section has coincided with 
the rod-like portion of the wall between adjacent pores (PI. IV, fig. 42). This is also 
indicated at a and b, fig. 38. 
Another interesting feature is the occurrence of dissepiments in the central 
cavity near the base of the cup. In PI. IV, figs. 39, 40, and 41, the ends of the 
septa are seen to cross the inner wall, and a certain amount of dissepimental tissue 
to be developed between them. Some of the longer outgrowths from the septa 
pass completely across the central space (figs. 40 and 41). 
The discovery of the rooting processes in the above species is of interest, 
especially as these processes are not very unlike the cup in character, and it is 
possible that Bornemann had obtained some such similar forms, which he named 
* Nova Acta der Ksl. Leop.-Carol. Deut. Akad. der Nat., vol. li, pp. 47, 48. 
t Mem. Boy. Soc. S. Australia, vol. ii, part ii, 1910, p. 113. 
