‘Conical single-walled tubes, with numerous circular 
pores, very uniform and regularly arranged in the typical 
species. 
Monocyathus porosus (Taylor's *Archaeolynthus") Fig. 1. 
A conical tube, often somewhat waved by gentle annu- 
lar constrictions; average diameter 6 mm. Wall thin, 
(.2mm.), pierced by very uniform and regularly arranged 
pores; the pores are spaced about two to the mm., are 
circular, and alternate as the rows are traced longitudin- 
ally but form a square pattern as the rows are traced 
diagonally; this is the most usual arrangement of pores in 
the inner wall of normal Archaeocyathinae. One speci- 
men was noticed in which the rim at wider end is folded ; 
inwards to a depth of a little over 1mm. and about the 
same distance inwards from’ the wall; this suggests that 
the wall may correspond to the outer wall of Archaeocy- 
athinae. 
Family MONOCYATHIDAE (new family). 
to the 
and is 
This form is tentatively assigned by Taylor 
sponges. The wall, however, is not sponge-like, 
almost identical with that of many normal Archaeocya- 
thinae, and particularly with the outer wall of Dokido- 
cyathus (Taylor), 
Monocyathus irregularis (new species). Fig. 2. 
Tubular; average diameter 3mm. Wall thin (.2mm.), 
waved by annular constrictions. Circular pores, irregular 
in size, about one to the mm.; a pore often occupies the | 
centre of a small circular papilla. The resemblance to 
the wall of an Archaeocyathus is much less than in the 
preceding species; we place it in this genus provisionally. 
Family ARCHAEOCYATHIDAE (Taylor). 
Archaeocyathus subacutus (new species). Fig. 3. 
Conical tube. Intervallum coefficient 3mm.: 6mm. (the 
first figure gives the intervallum width, the second figure 
the diameter of central cavity). Septa numerous (about 
50), 6mm. apart. Outer wall has small circular pores, 
one row to intercept, .3mm. apart. Septal pores appear 
to be confined to a single row of rather large pores, about 
.5mm, apart, close to junction with outer wall; but we 
are not quite certain on this point. Inner wall; large cir- 
cular pores, regularly alternating, one row to intercept, 
about .5mm. apart. The regular alternation of the large 
pores of inner wall gives a very characteristic appear- 
ance to the inner ends of the septa as seen in transverse 
section; and also in tangenial section where they become 
sinuous as they approach the inner wall. 
Taylor describes a similar but unsilicified form “in a 
friable limestone . . . . the finer details of the structure 
not well preserved" which he assimilates to Bornemann's 
Archaeocyathus acutus, saying that the material is not 
satisfactory enough to found a new species upon. Our 
specimens are silicified and well preserved, but it is 
impossible to s&y whether they correspond with 'Taylor's. 
We use the name “subacutus” to preserve the association 
with Taylor's provisional correlation of his specimens. 
Archaeocyathus floreus (new species). Fig. 4. 
Conical tube; intervallum coefficient 2mm.: 4mm.; the 
cone tapers downwards to a minute spitz, retaining its 
characteristic structure, and without sign of root tissue. 
The outer wall bulges out longitudinally between the sep- 
ta, giving a fluted exterior to the cone; there are about 
six defined vertical rows of small pores to each intersept. 
The septa are very remote, ten in number at 8mm. diam- 
eter; there is sometimes a vertical row of septal pores 
close to the junction with outer wall, about the same size 
as those of outer wall, and we have seen occasional pores 
(some of larger size) farther away from the outer wall. 
The inner wall has two or three rows of rather large 
pores to the intercept. The species agrees with Archae- 
ocyathus Rensselaericus (Ford) in the fluting of outer 
wall. | 
Archaeocyathus magnipora (new species). Fig. 7. 
Conical Tube; intervallum coefficient 2mm.: 4mm. Septa 
fairly remote, about 18 in number at 8mm. diameter. 
Outer wall; numerous small and rather irregular pores. 
Inner wall; a single row of large pores to each intercept. 
Septa with large circular pores of various sizes. A very 
scarce species. 
Archaeocyathus retevallum (new species). Fig. 6. 
Conical, expanding to an irregular cup; intervallum 
coefficient 3mm.: 20mm. Septa very numerous and close- 
ly set (.5mm.) Outer wall; a row of small pores to each 
intersept. Inner wall a spongy mesh, ./mm. thick, pass- 
ing with no definite perforated membrane into the central 
cavity. Septal pores not identified. The species is 
scarce, only one colony of three individuals having heen 
found, in brown limestone. 
Archaeocyathus tracheodentatus (new species). Fig. 5. 
Conical tube; intervallum coefficient 2mm.: 7mm. Out- 
er wall not well seen, no pores being visible (perhaps 
from secondary silicification). Septa very numerous and 
closely set (.4mm.); pores visible close to outer wall, and 
perhaps elsewhere. The inner wall has a row of circular 
pores to each intercept, and strong annular shelves pro- 
jecting into the central cavity, each shelf giving off into 
the central cavity a regularly arranged series of spines. 
This structure is exactly intermediate between two of 
Taylor’s species, Archaeocyathus trachealis and Ethmo- 
phyllum dentatum, having shelves like the former, and 
spines like the latter, but being without the vesicular 
wall of the latter. A scarce species. 
Ethmocyathus lineatus (new genus and species). Wig. €. 
The unique specimen of this very interesting form has 
an inner wall which is quite unlike that of any other 
member of the ‘Phylum. The septa curve at their inner 
ends and become united to form a regular honeycomb of 
small square cells, diagonally arranged, each cell being 
about .4mm. across and .5mm. deep. The inner face of 
this honeycomb is crossed by an extremely fine grating of 
minute, horizontal, annular bars, about ten to 1mm. The 
organism is conical; intervallum coefficient 2mm.: 10mm. 
Septa very numerous and closely set (.4mm.) Outer 
wall; numerous extremely fine pores about four rows to 
intersept. Septal pores fine and numerous, 
