FROM A DREDGING IN THE WEDDELL SEA. 
687 
bifid. Similar modifications are not unknown among modern hexactinellid spicules, 
but none quite like that of fig. 12 has ever been recorded. 
The sponge remains, or at least the spicules which are probably sponge remains, 
thus parallel in a remarkable manner the resemblances shown among the algse from 
the Beardmore Glacier blocks and the mass dredged in the Weddell Sea (positions 
almost opposite one another with respect to the South Pole). 
Archseocyathinae, Bornemann, 1884.* 
The most important organic remains in this limestone can be definitely placed 
among the Archseocyathinse. Several families are represented, and the different 
species may be grouped as follows — 
Archaeocyathidse, Taylor, I9i0.t 
Arcideocyathus, Bqllings, 1861.J 
Archasocyathus pauciseptatus, sp. nov. 
One exceedingly small specimen is worthy of notice, since it is the only example 
in the material which approximates to the type of A. profundus , Billings. One 
transverse section was obtained, and it is figured in PI. VI, fig. 63. The imper- 
forate outer lamina on the outer wall, the straight septa, and the irregular but 
numerous dissepiments separate the type from Spirocyathus. The septa are few in 
number and perforated as seen in transverse and longitudinal section (PI. VI, fig. 63, 
p, and fig. 64, p, respectively). The dissepimental platforms are very oblique and 
irregular. Their inner ends are continued across the central cavity and unite in an 
irregular tissue (PI. VI, fig. 64). Smaller offsets from these help to fill in the whole 
central cavity. The inner wall is porous, but lack of material has prohibited a 
more accurate description. The only other form which approximates to the 
above is A. dissepimentalis, Taylor, but that species has more numerous septa and 
no tissue in the centre of the cup. 
Thalamocyathus, gen. nov. 
Archseocyathidse with septa straight, perforate or imperforate. No tabulae or 
dissepiments cross the interseptal loculi. Walls simple or modified. Central cavity 
frequently filled by callus growth in the older part of the skeleton, i.e. near the 
base. (The greater number of the species formerly in the genus Archaaocyatlius 
will . fall into this new division. The reasons for erecting a new genus will be 
discussed below.) 
* Geol. Zeitschr., 1884, p. 706. 
f Mem. Roy. Soc. South Australia, vol. ii, part ii, p. 105. 
| Geology of Canada, “ New Species of Lower Silurian Fossils,” p. 3. 
