to consider these cylinders as proximal or distal, but 
it seems that the latter is the more likely explanation, 
and that none of them can be regarded as spitzes. Indi- 
cations of the mode of origin of Exocyathus may per- 
haps be gathered from specimens figured in 133 B and 
134 A, B. In Plate LII, Fig. 209, is shown a thin, scaly, 
more or less circular patch of what appears definitely 
to be a parasitic growth on the inner wall of an ex- 
-panded fragment of Paranacyathus margarita. The sur- 
face of this is concentrically smeared and round the 
edge is seen a ring of small plates regularly and radially 
arranged. This cannot be actually identified as an 
early stage of Exocyathus, but it is suggestive of that 
genus, and it may indicate the mode of origin of other 
forms such as Labyrinthomorpha and Ajacia. The 
smeared pellis of this specimen resembles the coating 
often met with on the lower parts of various Archaeos, 
particularly Metacyathina. This specimen is the nearest 
"approach we have seen in this group to anything which 
might be taken to correspond with the spitz of normal 
ا‎ in the sense that it shows growth from a 
central point; but here the growth is Gent? instead 
of conical. On grinding through the pellis (Fig. 5 
B) structural elements could not be traced to the centre, 
and pores of the Paranacyathus wall were exposed. 
In Plate LI, Fig. 208, are given four successive sec- 
tions of an irregular outgrowth from the outer wall 
near the base of a Metacoscinus. In the first section A 
the striated pellis of the outgrowth is seen at the right, 
and internally is seen a series of partly regular oriented’ 
plates and partly irregular tissue, having no resemb- 
lance to the “wire-netting” septa of Metacoscinus. In 
the fourth section D the peculiar tissue of the outgrowth 
has given place to the normal basal structure of Meta- 
coscinus. This specimen seems to be best interpreted 
as a parasitic growth allied to the group under dis- 
cussion, growing on Metacoscinus. 
Metaldetimorpha. 
A description and several figures of this genus are 
given in our fourth memoir. Some: of the specimens 
show three or more concentric zones of growth, see Fig. 
130 A and C. The greater part of the tissue in these 
Zores is of a vesicular character, with several rows of 
vesicles to the zone, and without marked elongation 
of the vesicles lengthways; in this respect the structure 
- differs considerably from that of the concentric zones 
` of Exocyathus. In some of the specimens the successive 
zones are separated from one another by a remarkable 
type of wall. which thus has vesicular tissue on each 
side of it. It is especially to be noted that these walls 
are tangential in their orientation, parallel to the outer 
surface, in contrast with the transverse tabulae and 
` radial senta found in other 'Árchaeos; apart from the 
outer and inner walls of other Archaeos this appears 
to be the only instance of such tangential structures ` 
. within the intervallum. Such a tangential wall is seen 
in Fie. 127 bh. and 127 C bb in transverse section; a 
in Plate XLI, Fig. 159 B, 
has, in, longitudinal section, a regular honeycomb struc- 
the name Calathium anstedi or crassum. 
rough sketch of his figure in Plate LIT. Fig. 208. He — 
“the whole fossil appears to be composed 0۶۵ 
His generic description, a 
tangential, view of a | similar wall is shown 
The tissue near the wall 
surface, i.e., 
ture and the wall itself is formed by an oriented thick- 
ening of all the radial walls of the honeycomb, thus 
encroaching on the lumina and forming a porous sheet, 
the pores of which become progressively smaller to- 
wards the centre of the sheet; each pore would thus 
have an hour-glass shape when seen in a transverse — 
section of the organism. 
Some Metaldetimorpha specimens show remarkable 
patches of coarse septa-like structure lying with various ` 
orientations among the vesicular tissues; see Plate 
XXXII, Figs. 128, 130 A, 130 B, and BUN XXXIII, 
Fig. 130 F, G. 
“Archaeocyathus profundus.” 
Billings’ original description and figures published i in. 
1865 refer to a large Archaeo species which attained a 
length of more than a foot with a diameter of from 
two to four inches. 
anulations like those of Pycnoidocyathus; it had clearly 
defined radial septa, thin and closely crowded together, 
and the figures show a few synapticulae. The outer 
wall and the thin inner wall were mentioned, but evi- 
dently the preservation was not sufficiently good for 
detailed description. 
In 1886 appeared two او و‎ and sets of plates 
by Walcott and Bornemann respectively which intro- 
duced complications. Walcott figured in his Plate I, Figs. - d 
la and I an outline and enlargement “of a portion ofa — 
transverse section of a specimen in which the growth 
appears to have been in layers. 
Museum.” Walcott appears to have confused one or 
two other species with that of Billings. 
fusion is evident in the beautiful photograph published 
by Bornemann as of Archaeocyathus profundus in his 
Plate 32. We give in Plate LIT, Fig. 210, a crude sketch 
of this photograph. | Bornemann’s specimen was from 
Billings’ tvpe locality. Anse au Loup, Canada; he says, 
“The ole arrangement shows a concentric structure 
like the annual rings of plants.” It is not easy to 
reconcile even the central part of this specimen with 
Billings’ description. 
concentric layers which surround the central Archaeo, 
thev have decided resemblance to some of our specimens | 
of Metaldetimorpha; on the other hand. it may be said 
that they have little resemblance to Exocvathus. 
for the concentric arrangement. 
EROR 
Billings, in be 1865 memoir, describes, p. 337, as hes 
325, a fossil from Pistolet Bay, Newfoundland, under 
Says, 
number of concentric laminae. 
of Calathium does not appear to contemplate a. con- 
55 
ei ۸ ` j 0 - » bs 
The outer surface was thrown into. 
Collection U.S. National ` 
A similar con- 
As regards the more or less 
except. 
We give a |. 
