698 
DR W. T. GORDON ON CAMBRIAN ORGANIC REMAINS 
The inner wall is also porous, as may be seen in PI. VI, fig. 69, w.p., but still 
more clearly, in fig. 70 of the same plate. In size these wall pores are very similar 
to the septal pores, but the, wall is not so well preserved as are the septa. The 
outer wall seems to be covered by a thin continuous lamina, but beneath this coating 
a porous structure similar to that on the inner wall may be noted in favourable 
sections. The dissepimental tissue is imperforate. 
So far the specimens might quite well be placed in the genus Archaeocyathus, 
but as they are cut at lower levels changes occur which place them quite outside 
that genus. In PI. VII, fig. 75, there is shown what might be taken for a Proto- 
pharetra with closely set septal plates, and on the upper side, a, a small rooting 
process is attached. The next section is given in fig. 76, but now the septa are almost 
straight from wall to wall. Rooting processes are again shown, but the cup 
has become broken in outline. In fig. 77, from the section succeeding the last, 
the septa are still straighter ; indeed, we now recognise the similarity to the cup 
of PI. VI, fig. 68. At a of this figure a new cup is being formed from the wall 
of the old one, and it becomes more noticeable at a, fig. 78. Thus the form 
shown in PI. VI, fig. 68, can be traced downwards into a rooting portion which 
is very similar to Protopharetra. This is precisely the character of Taylor’s 
genus Metaldetes. It will be readily admitted that the form of fig. 75 cannot 
be correlated with any of Bornemann’s species of Protopharetra, it is a much more 
delicate type than any he has described ; but his contention that some forms of 
Protopharetra are the rooting or basal parts of other genera of the Archseocyathinse 
is substantiated by the above series. 
Dictyocyathidse. 
Dictyocyathus, Bornemann, 1891.* 
Dictyocyatlius, sp. (PI. VI, fig. 67.) 
Among the small cups scattered through the material and only represented by a 
few sections is one shown in PI. VI, fig. 67. There seem to be large pores on the 
inner wall, small ones on the outer wall, and very few septa joining the two walls. 
Too few sections have been cut to admit of a distinct specific description, but it 
constitutes a type quite different from any of the other forms obtained, and in all 
probability is referable to Dictyocyathus. The walls and transverse septal processes 
are thickened by subsequent layers of material, so that the outer wall becomes very 
thick at a level three or four sections below that figured. The only longitudinal 
section available shows the large pores of the inner wall ; those on the outer wall 
are completely obliterated by the secondary growth. 
* “ Verstein. Sardinien,” Nova Acta der Ksl. Leop.-Carol. Deut. Akad. der Nat., vol. lvi, 1891, pi. ii. 
