Genus METALDETES (Taylor). 
Metaldetes conicus (Bedford). 
See part l., page 5, 
Figs. 26, 28, 31. 
A fragment of a large cup is shown natural size in 
Plate XVIIL, Fig. 77. This specimen is rather rugged 
and irregular, some others are more regularly conical. 
Taylors Archaeocyathus grandipora is probably the 
upper part of this or a nearly related species. 
Metaldetes superbus, N.Sp. Plate XVIII., Fig. 78. 
This handsome form is shown natural size, it differs 
from other species in the very wide intervallum; co- 
efficient 15 mm.: 50 mm.  Metaldetes conicus and 
superbus are two of the largest and most striking species 
found at the Ajax. 
Metaldetes spiralis, N.Sp. Plate XVIIL, Fig. 79. 
The base of this species is irregular, without central 
cavity, similar to Plate V. Fig. 31. The general shape 
is shown in Fig. 79 A. At 30 mm. above the base inner 
wall and central cavity are well seen, but the septal 
structure (Fig. 79 D, D) is still irregular, having much 
the appearance seen in Spirocyathus rete, and a few 
synapticulae being present, but there are indications of 
the septa becoming more regularly radial at a slightly 
higher level. The outer wall is shown in Fig. 79 C. 
The inner wall, Fig. 79 E, has the characteristic structure 
of Metaldetes, being an irregular network totally 
different from the large channels leading upwards and 
inwards into the central cavity of Spirocyathus rete and 
its allies. 
Genus METACYATHUS (Bedford). 
Metacyathus Taylori. See Part L, page 5, Fig. 30. 
A reconstructed view, natural size, of this striking 
form is shown in Plate XVIII. Fig. 80. e 
New Family METACOSCINIDAE. |— سس‎ 
Archaeos which grow from an irregular base filled 
with irregular trabecular and disseptimental tissue with- 
out septa, inner wall or central cavity; at a higher level 
radial septa occur together with tabulae or structures , 
resembling tabulae. The typical genus is Metacoscinus 
(Bedford) (see Part I.), but two new genera, Paracos- 
cinus and Pycnoidocoscinus, with regular tabulae, are 
placed provisionally in the family. 
Genus METACOSCINUS (Bedford). 
Metacoscinus reteseptatum. See Part I., page 6, Fig. 27. 
Some additional particulars are now figured. Plate 
XIX., Fig. 83 A, shows a reconstruction of the complete 
organism, nalural size. B is a sketch of the upper part 
of a specimen showing the natural rim of the cup; this 
specimen shows several of the tabula-like structures at 
TT (see also 27 a, b). Fig. 83 D shows the inner wall 
of a specimen in which the inner wall mesh is covered 
with numerous small tubercles. 
Plate XX., Fig. 84. 
This fragment, shown natural size in Fig 84 A, has an 
outer wall thrown into large and deep corrugations; the 
outer wall is exceedingly thick a full mm., and has a 
labyrinthine porous structure seen in transverse section 
in Fig. 84 B and in surface view in Fig. 84 C; this thick 
outer wall contrasts strongly with the delicate structure 
of the remainder of the skeleton. The intervallum is 
wide, ranging from 6 mm. in the hollows of the outer 
wall to 12 mm. in the bulges; intervallum co-efficient 
averages 9 mm.: 35 mm. The septa are straight and 
have the same open network as is seen in Metacoscinus 
reteseptatum (Fig. 84 D). The inner wall is similar in 
structure to the latter species; it shows numerous small 
tubercles projecting inwards from the mesh into the 
central cavity (upper left corner of Fig. 84 E). Only 
one fragment has been found; it does not show tabulae, 
and the base has not been found, but the nature of the 
septa and inner wall clearly place it in the genus 
Metacoscinus. 
Metacoscinus insigne, N.Sp. 
New Genus PARACOSCINUS. Plate XX., 
Figs. 85 and 86. 
The genus is made for an unusual Coscinocyathus-like 
form which we have difficulty in placing elsewhere, 
though it must be admitted that the affinity to 
Metacoscinus is not very obvious. The genus may be 
tentatively defined as having clearly defined septa and 
closely-set curved tabulae; growing from an irregular 
base; the outer wall consisting of a finely porous layer 
supported by an irregular trabecular mesh. Only one 
species has been found: the genotype Paracoscinus 
mirabile. 
Paracoscinus mirabile, N.Sp. 
Characters as above. The type specimen is shown 
natural size in Fig. 85 A. The shape is an irregular 
cone becoming more cylindrical above. Intervallum 
co-efficient 4 mm.: 13 mm. The outer wall shows small 
pores, usually obscured, carried by an irregular mesh, 
the latter being 3 mm. or so in thickness; Fig. 85 D 
(lower figure) shows the outer wall, outer view; Fig. 
85 D (upper figure) and H show the same, inner view. 
Septa in the upper part are well defined and numerous, 
averaging 1 mm. apart; septal pores are rather difficult 
to make out, aparently they are very small and numerous 
(Fig. 85 C). Tabulae are numerous and closely set, 
averaging 1 mm. apart, openly porous with irregular 
pores (Fig. 84 B); they are strongly arched upwards, 
the periphery sloping downwards to unite with the mesh 
which underlies the outer wall (Fig. 85C). The inner 
wall has numerous regular pores, about two to 1 mm.; 
