in which the outer wall is thrown into deep horizontal 
bulges. Often synapticulate. Septa in part defined 
and radial, in part wavy, and sometimes giving place 
to irregular trabecular tissue within the bulges. Inner 
wall has large channels leading upwards and inwards 
into the central cavity.” Our classification differs con- 
siderably from Taylor’s. He separated these forms, as 
members of the family “Archaeocyathidae,” from such 
species as Flindersicyathus irregularis, which he placed 
among the “Spirocyathidae,” whereas we regard Pycnoi- 
docyathus as evolved from a form like Flindersicyathus 
- (see our second memoir, pp. 14, 15). 
South Australian species are Pycnoidocyathus synap- 
liculosus and simplex Taylor, and maximipóra, vici- 
nisepta and parvulus Bedford. 
Genus Beltanacyathus Bedford. 
The genus is described in our third memoir, 
24. The genotype is Beltanacyathus tonicus. We place 
it in this family chiefly on account of the very charac- 
teristic inner wall. ‘The spongy outer wall is of a 
nature often met with in Metacyathina, but not 
Ajacicyathina. The spitz has so far only shown Meta- 
cyathine affinity by the presence of dissepiments, but 
more materia! is desirable. In placing this striking 
form in the present family we suggest that the straight 
septa have evolved on the same lines as the similar septa 
of Pycnoidocyathus maximipora. Taylors Archaee- 
cyalhús wirrialpensis appears to belong to this genus. 
Ethmophyllum whitneyi Meeck, and marianum 
Romer have features of resemblance to Beltanacyathus. 
Family Syringocnemidae Taylor. 
Genus Syringocnema Taylor. 
The well-known and clearly defined genotype 
. Syringocnema favus was described by Taylor in 1910 
and details as to the nature of its remarkable structure 
were added in our second memoir, p. 16, Fig. 74. We 
regard this structure as having been evolved from a 
“type comparable to Flindersicyathus ptychophragma. 
` A spitz of Syringocnema is drawn in Plate L, Fig. 
206 and shows an irregular structure near the tip, with 
trabeculae and dissepiments, which has considerable 
resemblance to the Archaeopharetra type; from this 
point it develops rapidly to the characteristic Syringoc- 
nema structure above It is highly probable that the 
tittle spitz drawn in Plate XXX, Fig. 122, is of Syrin- 
 gocnema; the relationship of transverse partitions to 
the developing tubular elements is clearer in this 
specimen and so is its resemblance to the Archaeo- 
pharetra type of spitz: unfortunaetly this spitz does not 
go far enough upwards to make its identity with 
Syringocnema certain. 
New Order CROMMYOCY ATHINA. 
There is a number of problematic forms whose rela- 
A tion to one another and to the better known orders of 
pp: 23; 
in 
79 
Archaeos remains doubtful. Among them growth in 
irregular concentric rings is frequent, and the above 
name is suggested from the resemblance to the suc- 
cessive coals of an onion (Greek—Krommuos) . 
Another frequent character is that of forming an in- 
crusting or parasitic investment to various species of 
ا‎ 
Labyrinthomorpha. 
. Vologdin in 1926/1931 figured one of these incrust- 
ing organisms under the name of Labyrinthomor pha 
tolli, A rough sketch after Vologdin's figures is shown 
in Plate LI, Fig. 207, A being the complete organism, 
here investing two specimens T Coscinocyathus and a 
Ere and B being a sectional view of the 
structure. He described this in 1937 briefly as follows: 
“The forms essentially consist of an irregular network 
of vesicles, sometimes porous"; we have not been able 
to refer to his 1926 description. He made a family 
Vesiculoidae for this genus. 
Ajacia. 
In our second memoir, pp. 9, 10, fig. 37, we described 
a remarkable specimen of an incrustation surrounding 
several different Archaco spitzes under the name Ajacia 
ajax; at first we thought it might be an Alga, but now 
consider that it is in all probability an incrusting. 
Archaeo. Unfortunately fine detail is obscured in this 
specimen, but it is seen to be laminated, the laminae 
following the external mamillated contour. 
. Exocyathus. 
The structure of the genotype, Exocyathus australis, 
is described at length in our fourth memoir, pp. 32-34, 
Figs. 132-136. This was considered by Taylor as roots 
or “exotheca,” but we think that the balance of evi- 
dence definitely favors its being of a parasitic or in- 
crusting nature. The fine structure of Exocyathus, 
which is well brought out by etching the silicified speci- 
mens of the Ajax Mine, seems very different from that 
of any other Archaeo. It consists of narrow radial 
plates, greatly elongated lengthways; in transverse sec- 
tion these, in parts of the organism which are arranged 
in broad concentric lamellae, stretch across the. thick- 
ness of each lamella; as in Fig. 133A; but they also 
tend, in parts of the organism, to bud out from the, 
surface of the lamella as cylindrical columns, as in 
Fig. 135 A and B, and these cylinders may become in- 
dependent distally as in Fig. 146A. The cylindrical 
processes are shown in Fig. 132, A, B, C; in the central 
parts the constituent plates become crumpled and: 
anastomosing, and the structure has something like that 
of sticks of the sweetmeat called “Edinburgh Rock.” 
There is no separate outer wall to these cvlinders. the 
surface being formed simply by the regularly disposed 
outer edges Gr the longitudinal plates, which are here 
united by minute connecting bars. 
"In our former: description we were doubtful whether $ 
1 
