MEMOIRS OF THE KYANCUTTA MUSEUM 
No. 3 
KYANCUTTA, South Australia, 
September, 1936. 
Further Notes on ۱ 
Cyathospongia (Archaeocyathi) 
and other organisms 
From the LOWER CAMBRIAN of Beltana, South Australia 
By R. & J. Bedford 
NOTE:—The paper we have in hand on the families | 
Archaeocyathidae and Coscinocyathidae is still not ready 
for the press; the present paper deals with a few of the 
more unusual types. Unless otherwise stated, all 
specimens are from the Ajax Mine, Beltana. 
? PORIFERA. 
Associated with the silicified Archaeos in the Ajax 
limestone we have found several specimens of a minute, 
straight or slightly curved, conical tubular organism. 
The fossil is about 12 mm. long by 14 mm. diameter at 
the larger end, and tapers to a point. The wall is 
unsilicified, about 1/5 mm. thick at the larger end, and 
is, for the most part, only distinguishable from the matrix 
by being slightly more soluble in acid; from the outer 
surface a large number of minute silicified oval studs 
project inwards within the substance of the wall, and 
these may be regarded as probably representing casts 
in silica of a system of minute pores. The studs are 
oval in section, about + mm. in longest diameter, and 
become progressively smaller towards the point of the 
cone. As a rule, they do not appear to penetrate right 
through the thickness of the wall; each stud appears to 
become smaller in section as it penetrates the wall. 
This suggests either that the original structure was a 
series of pits which bottomed within the wall, or else 
that if it consisted of pores these narrowed as they passed 
inwards and the inorganic filling of silica became 
jammed and failed to penetrate the entire depth of the 
pores. The fossils are often surrounded partially or 
wholly by inorganic siliceous deposits in the limestone, 
and in this case the studs become continuous outwardly 
with the surrounding silica. Occasionally also the 
lumen of the tube is partly occupied by silica, but the 
inner ends of the studs have not yet been observed 
continuous with such infilling. «The studs are very 
closely packed and are regularly arranged in longitudinal 
rows, the longer diameter of each stud being at a right 
angle to the rows, and the studs of each row alternating 
with those of adjoining rows. 
The lack of silicification of the wall substance of the 
fossils suggests that they were of different composition 
from normal Archaeo walls, but not necessarily that 
they were of such extreme difference as that between 
Silica and Calcite. The preservation of the fossils in a 
single fragment of the typical Ajax limestone is very 
capricious. An unsilicified Archaeo may lie side by 
side with silicified specimens. In typical material of 
the best quality some 90 per cent. of the usual Archaeos 
may be silicified and 10 per cent. unsilicified, whilst a 
few specimens will show silica porecasts and nothing 
else. In such material Uranosphaera is silicified or 
unsilicified in about equal proportions; Heterocyathus is 
more than half in the form of pore-casts, but a few 
fragments are normally silicified; isolated sponge 
spicules are usually well silicified. 
New Genus and Species Tunkia incerta. 
We propose the name те ineerta:for:the fossil 
described above. The gemeric«name:diszfrom;a:black- 
fellow word “tunki,” meaning little." In its conical 
form and single wall it resembles the Monocyathina, 
but the latter are generally well silicified, and the doubt 
whether the structure was actually pitted or porous makes 
its correlation difficult. However, it seems to be an 
interesting little form, and its publication may lead to its 
identification by some other worker in Cambrian 
palaentology. The fossil is shown on Plate XXI, fig. 
88. (А) a specimen natural size; (B) a fragment 
enlarged 15 diameters; this shows a mass of surrounding 
silica in white, and also a plug of the same within the 
lumen; the unsilicified wall-substance is shown by ver- 
tical shading, the unsilicified matrix outside by cross 
hatching; (C) is a reconstruction of the organism 
enlarged 10 diameters. 
