426 ■ PROCEEDINGS OF SECTION C. 



is represented by a few more or less globular loculi (H), seen imme- 

 diately above the rhizoid tissue. Cross sections of small calices usually 

 show a similar arrangement of a few globular loculi separated by septa, 

 and occupying the space between a coarsely perforate inner wall (G) 

 and a more highly perforate outer wall. 



A cross section half way along the cup would show that the septa 

 have become more numerous and the loculi are rectangular. Tabulae 

 are present, though somewhat remote, in the younger (and possibly 

 faster growing) types. The septa, cut somewhat obliquely, are clearly 

 represented in fig. 1. It will be noticed that they are rather solid, the 

 pores being smaller and further apart than in the walls. 



The upper portion of the inter-mural space is completely closed by 

 the curved perforate plate (at A). This is the growing point of the 

 organism, and probably represents the latest tabula connecting the 

 outer and inner walls. It is improbable that the inter-mural sarcode 

 in the older loculi was in the form of a definite zooid, since we should 

 then reasonably expect the tabulae to show some well-defined central 

 orifice (as in many tabulata), whereas it is uniformly perforate. Reasons 

 will be given later for the theory that the Archaeocyathinse were com- 

 pound organisms, and not simple zooids like Zaphrentis, &c., though one 

 is at first tempted to place them among the simple corals from close mor- 

 phological resemblance of the main structures to those Rugosa provided 

 with a (somewhat indefinite) inner wall, as for example Catn'po'ph'jih.mi. 



Probably the relation between the Rugosa and the Archseocyathinae is 

 of the same type as that between the mollusca and brachiopoda — a sort 

 of parallelism of development as regards skeleton on the part of the two 

 phyla, which is not in the least accompanied by a biological kinship. 



Reverting now to the second specimen (see Plate I., fig. 1), a 

 more advanced stage of the turbinate calice than that in fig. 1 is repre- 

 sented in longitudinal section. This photograph gives a very good idea 

 of the matrix of many of the Beltana specimens. On the left may be 

 seen siliceous replacements of indefinite tubes, which have been regarded 

 as Girvanella — but which are probably in some cases simple Sycon- 

 like sponges. On the right occurs a triangular patch of " concentric " 

 calcite, with a curious " Stromatoporoid " appearance, but which is 

 almost certainly of inorganic origin. 



The turbinate caUce (28 m.m. long) has been sectioned medially 

 and then etched rather deeply with acid. Almost the whole structure 

 typical of the simple Archseocyathinae is revealed at a glance. The 

 most prominent feature is undoubtedly the symmetrical arrangement 

 of the convex tabulae. These " sieve-like platforms " appear to be 

 present in all the Archaeocyathinae examined, and are not peculiar, it 

 would appear, to the genus Coscinocyathus, as claimed by Bornemann 

 and Hinde. The arrangement of the pores in the radiating septa is 

 very clearly shown, and also the intercalation of a septum is recog- 

 nisable in the upper left of the calice. 



The inner wall, as usual, is coarsely perforated, each pore being sunk 

 at the bottom of a " dimple," giving a rugged appearance to the surface. 

 The outer wall can be made out in the lower right hand portion of the 

 calice, and the pores are seen to be smaller than in the inner wall. 



