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UNIVERSITY OF TORONTO
STUDIES

GEOLOGICAL SERIES

No. 4: THE STROMATOPOROIDS OF THE
GUELPH FORMATION IN ONTARIO By
W. A. PARKS

THE UNIVERSITY LIBRARY, 1907: PUBLISHED BY
THE LIBRARIAN
UNIVERSITY OF TORONTO STUDIES
COMMITTEE OF MANAGEMENT

 

Chairman ; PROFESSOR Maurice Hurtron, M.A., LL.D.,
Acting President of the University.

PROFESSOR W. J. ALEXANDER, Ph.D.

Proressor W. H. Exuis, M.A., M.B.

PROFESSOR A. KIRSCHMANN, Ph.D.

PROFESSOR J. J. MACKENZIE, B.A.

PROFESSOR R. Ramsay WRIGHT, M.A., B.Sc., LL.D.
PROFESSOR GEORGE. M. Wrone, M.A.

General Editor: H. H. LaAneton, M.A., Librarian of the
University.
THE STROMATOPOROIDS
QF THE GUELPH FORMATION IN ONTARIO

BY

WILLIAM ARTHUR PARKS, Pu.D.

ASSOCIATE PROFESSOR OF GEOLOGY
w77
PAS+
PREFATORY NOTE

The following article on the Stromatoporoidea of the
Guelph dolomites is the first of a series of publications which
it is proposed to issue on the Stromatoporoids of America.
Palaeontologists have long felt the need of a revision of these
forms, for most of the descriptions are contained in journals
of early date which are more or less inaccessible. In many
cases also the descriptions were written before the group was
as well understood as it is at present, and, if illustrated at all,
the figures are imperfect and on different scales of magnifi-
cation. The most important means for the identification of
species is a series of sections, vertical and tangential, on a
uniform scale of magnification so that comparisons may be
readily instituted. An attempt will be made to produce such a
set of plates.

Since the appearance of Nicholson’s monograph on the
British Stromatoporoids we have an adequate and admirable
basis on which to proceed with the classification of forms.
The reader is referred to that volume for all generic descrip-
tions, for a historical review of the subject and for a complete
discussion of the anatomy of Stromatoporoids in general.

Owing to the incomplete preservation of many examples,
the impossiblity of obtaining the type specimens, and the
insufficiency of collections, numerous errors will occur and,
in time, be detected, but I have proceeded on the principle
that no better material may ever be found and that a pro-
visional description is better than none.

My thanks are due to Dr. B. E. Walker, of Toronto, for
advice, encouragement and the presentation of specimens,
and to Professor J. M. Clarke, of Albany, for the loan of sec-
tions and other kindnesses.

W. A. PaRKs.
UNIVERSITY OF TORONTO
Dec. 20th, 1906
THE STROMATOPOROIDS
OF THE
GUELPH FORMATION IN ONTARIO

The Guelph dolomites typically exposed at Galt, Durham,
Glenelg, Elora and a few other places in the western peninsula
of Ontario are particularly rich in the remains of the puzzling
and interesting group of the Stromatoporoids. The identi-
fication of these organisms is attended with peculiar difficulties,
even in the case of well preserved material such as may be
obtained from the Devonian rocks of Kelly’s Island and
numerous other points throughout the Corniferous and Ham-
ilton exposures of Ontario and Ohio. In the case of the Guelph
forms, added difficulty is encountered on account of the ex-
cessive crystallization and dolomitization which in the vast
majority of cases have rendered the minute structure of the
skeleton indeterminable or at least of very doubtful inter-
pretation. Authors have persistently avoided the description
of these forms on account of the difficulty of rigidly defining
the species. The examination of a large number of specimens
has led me to believe that the different species may be iden-
tified with reasonable certainty, although it may be impossible
to frame a thoroughly scientific description of the minute
structure. It is readily admitted that some of the following
notes are based on poor material, but as it seems unlikely
that any better will ever be discovered the attempt seems to
be justified.

The amount of destruction wrought in these delicate
skeletons by the forces of mineralization vary greatly, being
least in some specimens of Stromatopora, and greatest in the
examples of the genus Labechia. The different types of alter-
ation may be considered under the following heads :—

(a) Interstitial crystallization—While the skeleton fibre
is but little altered in some examples, it is found that the
interspaces between the laminae and pillars are filled with

[137]
6 PARKS : STROMATOPOROIDS OF THE GUELPH

large crystals to such an extent as to displace the elements
of the skeleton. Examined with a lens the surface of such
specimens appears to be made up of a continuous mass of
crystals with no appearance of organized structure whatever.
Thin sections however reveal in a general way the character
of the reticulation, but the minute structure of the skeleton
fibre is not determinable.

(b) Complete crystallization—In this class of specimens
the crystallization has invaded the fibre itself. The minute
structure may be absolutely lost or may be apparent only by
slight differences in colour. The surface resembles that of
the type described above. Thin sections are quite useless,
as the slight colour differences are not at all perceptible under
the microscope. The only means of dealing with these speci-
mens is to take advantage of polished surfaces on which the
outline of the skeleton is sometimes shown by reason of a
slightly greater density where the skeletal matter had existed.

(c) Complete reversion (Pl. II, Fig. 6; Pl. ITI, Figs. 1, 2, 5,6)
—In many cases, particularly with examples of Labechia,
the original skeleton has been surrounded by an infiltered
matrix after which the fibre has been replaced by clear crys-
talline calcite ; the outline of the reticulation is therefore
apparent in thin sections as clear interspaces while the true
interlaminar cavities appear as darker spots. In some ex-
amples the original skeleton seems to have been surrounded
by a thin layer of concretionary calcite or dolomite while the
rest of the interlaminar cavities were filled by less dense and
more crystalline matter. The true skeleton has then been
replaced by calcite as described above. The visible result of
this process is that on polished surfaces the cross section of
a lamina appears as two delicate parallel lines while the pillars
similarly cut present the appearance of rings. Thin sections
show however that the concretionary calcite is sharply bounded
towards the skeletal matter but that it fades gradually into

[138]
PARKS : STROMATOPOROIDS ‘OF THE GUELPH G7

the substance filling the interlaminar cavities. Care is re-
quired in examining polished surfaces of this kind of specimen
as the concretionary calcite presents much the same appear-
ance as original skeletal fibre,so that there is a grave danger
of interpreting pillars as tubes and single laminae as double
(Plate II, Fig. 6).

(d) Partial reversion—Specimens are found in which
the above process has not been uniformly performed through-
out the coenosteum. ‘These are so extremely difficult to inter-
pret that they are best thrown aside.

(e) Reversion and subsequent solution—When specimens
wholly or partly reversed have been subjected to the action
of surface waters the secondary calcite occupying the place
of the original skeleton is dissolved. Total disintegration
may result or the solution may be only partial. This fre-
quently happens in the case of reversed specimens of Labechia
so that the position of the pillars is indicated by minute holes,
presenting an appearance which has given rise to the name
‘ Pin-hole fossils”. This condition is also often encountered
in specimens of corals from the Guelph dolomite (Pl. VI, Fig. 1).

(f) One other peculiarity has been observed which is
liable to give rise to erroneous conclusions. In several speci-
mens the skeletal matter is seen to be surrounded at a little
distance by a dark line which is separated from the skeleton
by clear crystalline calcite. This line seems to be caused by
a segregation of the colouring matter much in the same manner
as the banded structure arises in mineral veins. In photo-
graphic reproductions of thin sections care must be taken to
properly interpret this phenomenon (PI. VI, Fig. 2).

Owing to the imperfect state of preservation it was found
impossible properly to represent the anatomy by means of
photo-micrographs. The accompanying plates have been
reproduced from drawings which were made in the following
way. Thin sections of varying thickness were prepared and

[139]
8 PARKS : STROMATOPOROIDS OF THE GUELPH

such of these as presented the most distinct outlines were
photographed on a uniform magnification of ten diameters.
A tracing was then made on drawing paper by placing the
photographic print and paper before a strong light. It was
found that by using a drawing paper of the proper density
the outline of the skeleton appeared in greater perfection
than in the photographic print itself as the less dense images
of foreign particles and refraction lines were obscured. The
detail of the drawing was then filled in partly by reference to
the original thin section and partly by comparison with a
polished surface of the specimen under review. Some of the
figures are not continuous, i. e. they do not represent a con-
tinuous portion of the section but are made up from obser-
vations on different parts of the same surface. While these
drawings may therefore lack the exactitude which can be ob-
tained by direct photographic reproductions from good ma-
terial they are infinitely better than the almost useless photo-
graphs which might be prepared from the badly preserved
Stromatoporoids of the Guelph dolomite.

In the Report of Progress, Geol. Sur. Can., 1863, no
mention is made of Stromatoporoids in the chapter on the
Guelph formation. On reference to the Index of Reports
1863-1884, it is found that no account is given of the Stro-
matoporidae of the Guelph formation up to that date. The
first reference to Stromatopora in this formation ap-
pears to have been made by Professor Nicholson in the An-
nals and Magazine of Natural History, Series 4, Vol. xii, 1873.
A description with two figures is there given of Stromatopora
ostiolata, Nich. (Pl. II, Figs. 1, 2). In the Report of the Pal-
aeontology of Ontario, 1875, Professor Nicholson gives a
lengthy account of Stromatopora ostiolata which at that time
he was inclined to regard as a sponge. Stromatopora concen-
trica, Goldfuss, is also mentioned, but the author expresses
doubt as to the identification of this species.

[140]
PARKS : STROMATOPOROIDS OF THE GUELPH 9

In the year 1867, Winchell (Proc. Am. Ass. Ad. Sci.)
established the genus Coenostroma, which name was adopted
by Sir J. W. Dawson in his description of a new species from
the Guelph, Coenostroma galtense. (‘‘ Life’s Dawn on the
Earth,” p. 160, 1875.) Reference to this species is also made
by Dawson in the Quarterly Journal of the Geological Society,
Vol. xxxv, p. 52, 1879. In the above mentioned article in the
Quarterly Journal of the Geological Society Dawson deals
at length with the question of the minute structure of Stro-
matoporoids and closes with a list of American species in which
only two are mentioned from the Guelph, Stromatopora os-
tiolata, Nich.,and Coenostroma galtense, Dawson. This latter
species therefore replaces Stromatopora concentrica, Gold., in
the opinion of the author. Dr. Whiteaves mentions no new
Stromatoporoids in his article on Guelph fossils (Palaeozoic
Fossils, Vol. III, Pt. i, Geol. Sur. Can., 1884). In Part ii of
the above publication which appeared from the pen of the
same author in 1895, the following list is given—

Clathrodictyon ostiolatum, Nich.

Clathrodictyon jfastigiatum, Nich.

Labechia, Species undeterminable.

Stromatopora galtensis, Dawson.

Stromatopora antiqua, Nich. and Murie.

Stromatoporella, Species undeterminable.

These same species are given by Whiteaves in his list of
Canadian Stromatoporoids in the Canadian Record of Science,
1896. Clarke and Ruedemann mention Stromatopora galiensis,
Dawson, and Clathrodictyon ostiolatum, Nich. as occurring in
the State of New York. (Guelph Fauna in the State of New
York, N. Y. State Museum, Memoir 5, 1903.) Finally in
Part iv, Vol. III of Palaeozoic Fossils, which has just appeared,
Dr. Whiteaves repeats his former list of Guelph species. Two
species only have therefore been recognized as characteristic
of the Guelph while two others have been regarded as common
to it and other Upper Silurian formations.

[141]
10 PARKS : STROMATOPOROIDS OF THE GUELPH

ORDER—STROMATOPOROIDEA, Nicholson and Murte
Section A. (Hydractinoid Group)

Family—ACTINOSTROMIDAE, Nich.
Genus—ACTINOSTROMA, Nich. and Murie
ACTINOSTROMA VULCANA, sp. nov. Plate I, Figures 1, 2, 5

Coenosteum massive, known only by fragments, com-
posed of delicate curving horizontal laminae and continuous
radial pillars. The laminae occur to the number of seven or
eight in the space of one mm. The pillars are slightly stouter
but are practically the same distance apart. The species is
characterized by a most peculiar structure observed in one
specimen only. Growing on what was at one time the surface
of the coenosteum is a volcano-like prominence composed of
laminae and pillars like the general skeletal matter but pro-
vided with a central, distinctly differentiated portion pre-
senting an inverted cone-in-cone structure. A vertical section
of this internal pipe shows it to have an almond-shaped out-
line with a rounded lower termination while the cone-in-cone
arrangement of its constituent parts makes a cup-like depres-
sion at the top, at once suggesting a volcanic crater. The
resemblance to a volcano is further emphasized by the arrange-
ment of the laminae around the “ pipe”’, for they appear
exactly like a series of successive flows from a central vent
(Pl. I, Fig. 5). This structure is eventually covered by the
ordinary growth of the coenosteum. The whole elevation
shows a height of ten mm. and a width of fifteen, while the
“ pipe ”’ is five mm. high and two mm. wide.

Vertical sections of the coenosteum (Pl. I, Fig. 2) show
it to be composed of well defined, delicate, horizontal laminae,
seven or eight of which appear in the space of one mm. The
laminae are connected by vertical pillars which are slightly
stouter than the horizontal components but practically the
same distance apart, so that the general appearance is that

[142]
PARKS : STROMATOPOROIDS OF THE GUELPH II

of a square network, but certain of the squares are somewhat
rounded as if by the presence of astrorhizal canals. The
astrorhizal systems are delicate and appear to be superim-
posed, as a wall-less axial canal can be made out on parts of
a vertical surface. The pillars are continuous and, in good
sections, may be traced through as many as ten laminae.

Tangential sections (Pl. I, Fig. 1) exhibit the round ends
of the radial pillars and very faintly, owing to imperfect preser-
vation, the whorls of connecting arms typical of the genus
Actinostroma. Astrorhizal canals are present but appear
to be extremely delicate ; the sections are not sufficiently
good to afford a full description of these structures.

The character of the skeletal matter is extremely like that
of Actinostroma stellulatum, Nich. Although this species
is European and Devonian, I should be inclined to place the
present example under the same head were it not for the pe-
culiar volcano-like structures above described, which, as far
as I am aware, have not previously been observed in any
Stromatoporoid.

From Clathrodictyon ostiolatum and from C. striatellum
the species under review is distinguished by the more numerous.
laminae in a given space, seven ur eight occurring in a mm.
while only five occur in the Clathrodictyons. The continuity
of the radial elements is of course convincing, but unless the
section is strictly vertical mistakes may easily occur. Tan-
gential sections show distinctly the much greater size of the
cut ends of the radial pillars. At first I was much confused
by the volcano-like structures, thinking them to be the cylin-
ders of Nicholson’s C. ostiolatum. However I am now con-
vinced that they are not even analogous, for Nicholson’s
cylinders are composed of concentric laminae wound around
the long axis, while the structures here described are quite
different in the arrangement of the laminae. The species is
founded on three fragments from Durham, Ont.

[143]
12 PaRKS : STROMATOPOROIDS OF THE GUELPH
Genus—CLATHRODICTYON, Nich. and Murie

CLATHRODICTYON OSTIOLATUM, Nich.—Plate II, Figs. 1-2 ;
Plate V, Figs. 7-8

STROMATOPORA OsTIoLaTa, Nich., An. and Mag. Nat. Hist., ser. 4, 12 : go,
pl. $8: ia, 1873.
STROMATOPORA osTIOLATA, Nich., Palaeontology Prov. of Ontario, pl. i,
fig. 1, 1a, 1874 ; p. 63, 1875.
‘CLATHRODICTYON OSTIOLATUM, Nich., Monograph British Stromatoporoids,
pt. i, p. 14, 1886.
CLATHRODICTYON oOSTIoLATUM, Nich., An. and Mag. Nat. Hist., ser. 5,
19: 12, pl. 3, figs. 1-3, 1887.
CLATHRODICTYON OSTIOLATUM, Whiteaves, Palaeozoic Fossils, vol. iii, pt. 2,

P. 52, 1895. . i
CLATHRODICTYON OSTIOLATUM, Whiteaves, Can. Rec. Sci., vol. vii, No. 3,
1896.

CLATHRODICTYUM OsTIOLATUM, Clarke and Ruedemann, Guelph Fauna
State of New York, N. Y. State Museum
Memoir 5, p. 37, Pl._1, figs. 10-12, 1903.

CLATHRODICTYON OSTIOLATUM, Whiteaves, Palaeozoic Fossils, vol. iii, pt. iv,
Pp. 328, 1906.

Nicholson’s description of this very remarkable form is
in part as follows ——‘‘ Fossil forming large hemispherical
masses, several inches in diameter, composed of innumerable
delicate laminae, arranged concentrically, and separated by
interspaces which are broken up by numerous slender vertical
pillars, giving the whole a finely reticulate structure. The
laminae are as thin as writing paper ; and, with the intervening
interspaces, there are about ten of them in the space of one line.
The upper surface of the mass is undulated and is quite smooth,
except for the presence of rounded or conical elevations, per-
forated at the apex with rounded openings, and arranged with
tolerable regularity in diagonal lines. These elevations have
a width of half a line and appear to be of the nature of ex-
hhalent apertures or oscula........ Laterally the laminae
and osculiferous surfaces instead of being concentrically
arranged as regards the entire mass, terminate in a series of
rounded, nipple-shaped prominences, each of which is com-
posed of thin concentric laminae which scale off like the coats
Of Al. ONION. 6 ose snus In the present species, intercalated
among the general enveloping concentric laminae of the mass

[144]
PARKS : STROMATOPOROIDS OF THE GUELPH 13

is a series of cylindrical masses, each composed of laminae
concentric with its long axis, and each terminating (probably
at both ends though this is not shown) in a rounded nipple-
shaped extremity. Superiorly these laminated cylinders are
enveloped by laminae concentric to the whole mass, so that
the outermost surface is simply undulating.” (Pl. II, Fig. 1.)

Nicholson’s amended description as contained in the
Annals and Magazine of Natural History, 1887, is in part as
follows -—‘‘ Coenosteum massive, composed of concentrically
laminated parallel cylinders, which are more or less enveloped
by laminae concentric with the entire colony, and which
terminate superficially in blunt nipple-shaped prominences.
Under surface unknown. Surface of the laminae smooth or
with exceedingly fine granulations, without tubercles or
mamelons. Astrorhizae well developed, each system having
a vertical, wall-less axial canal, which opens on the surface
of the laminae by a slightly projecting round aperture. As
regards internal structure, the skeleton is composed of ex-
ceedingly delicate laminae, about five of which occupy the
space of 1 millim. The laminae are curved in conformity
with the curvature of the fossil, and are not at all, or but slight-
ly, inflected or crumpled. Each lamina gives off downwards
numerous close-set and delicate radial pillars, which may or
may not reach the lamina below. The interlaminar cells
are thus more or less quadrangular in shape, though often
incomplete.”’ (Pl. II, Fig. 2.)

Nicholson’s description of the skeletal matter of C. ostto-
latum conforms very closely to that given for C. striatellum.
Both species have five very delicate laminae to the mm. and
in both some of the pillars fail to reach the next lamina. It
would appear that the laminae are less crumpled in C. ostio-
latum, but this feature is very difficult to determine. Further,
although not mentioned in the text, Nicholson’s figure of
C. ostiolatum shows the double-based pillars given for C.

[145]
14 ParKS : STROMATOPOROIDS OF THE GUELPH

striatellum. It seems highly probable that the species C.
ostiolatum would not have been founded on the minute struc-
ture of the skeleton alone, it must therefore depend for its
existence on the presence of the characteristic cylinders and
their nipple-like projections. Most of the specimens which,
from a study of their minute structure, might be ascribed to
either species do not show the cylinders even over vertical
sections as large as eight inches by four inches. It seems
justifiable therefore to conclude that both species are present
and to restrict the name C. ostiolatum to those specimens
which show distinct evidence of being composed of a series
of parallel cylinders enveloped in the general tissue of the
coenosteum. It should also be noted that, according to
Nicholson, astrorhizal systems are well developed in C. ostio-
Zatum but absent in C. striatellum.

The type specimen of C. ostiolatum is probably lost, for
Nicholson states that it was the property of the University
of Toronto. The disastrous fire of 1890, which injured the
University museum, must therefore have destroyed this type
together with other valuable material. Besides specimens
from different localities in the Guelph the museum contains
a specimen from the Upper Niagara near Hamilton, Ont.,
which apparently belongs to this species.

CLATHRODICTYON STRIATELLUM, D’Orb. Plate I, Figs. 3-4 ;
Plate VI, Fig. 8

STROMATOPORA CONCENTRICA, Lonsdale, Silurian System, p. 680, pl. xv,

fig. 31, 1839. :
STROMATOPORA STRIATELLA, D’Orbigny, Prodrome de Paléontologie, t. 1,
I, 1850.
STROMATOPORA MAMMILLATA, Fr. Qhmide Sil. Form. von Ehstland.
Pp. 232, 1858.
STROMATOPORA MAMMILLATA, von Rosen, Ueber die Natur der Stroma-

toporen, p. 71, pl. viii, figs. 1-5, 1867.
STROMATOPORA MAMMILLATA, Ferd. Roemer, Lethaea Palaeozoica, part 1,
Pp. 531, fig. 125, 1883.
CLATHRODICTYON STRIATELLUM, Nicholson, Ann. Nat, Hist., ser. 5, vol.
xix, p. 6, pl. 1, figs. 9 and 10, 1887.
CLATHRODICTYON STRIATELLUM, Nicholson, Mon. British Stromatoporoids,
p. 156, pl. 1, fig. 1; pl. v, fig. 3, pl. xix,
figs. 6-12.

[146]
PARKS : STROMATOPOROIDS OF THE GUELPH 15

Nicholson’s description in the last article cited above is
as follows —‘‘ The coenosteum in this species is mostly
laminar or hemispherical with a concentrically wrinkled
epitheca. The surface is more or less undulated, but without
definite eminences or ‘‘ mamelons”, the concentric laminae
usually exfoliating concentrically round elevated points.
Astrorhizae are apparently wanting.

“As regards internal structure, vertical sections (Pl. I,
Fig. 4) show that the concentric laminae are comparatively
remote, about four interlaminar spaces, and therefore five
laminae, occupying the space of 1 mm.; but the interlaminar
spaces are wider over the convexities of the undulated laminae.
The concentric laminae are thrown into successive undulations,
which are more pronounced in some specimens than in others,
but are always gentle and regularly curved. The laminae
are also regularly crumpled in the same manner as in C. vesa-
culosum, but less completely, so that there is no appearance
in vertical sections of rows of lenticular vesicles, such as are
so characteristic of the latter species. Each infolding of the
lamina is, however, prolonged downwards into the interlaminar
space below in the form of a more or less complete radial pillar.
Some of the radial pillars are quite short, others project about
half-way into the interlaminar space ; others cross the space
and become connected with the lamina below ; finally, a few
spring from the upper sides of the laminae. A further very
characteristic point about the radial pillars is that they are
very commonly double at their bases, where they spring from
their producing lamina.

‘“‘Tangental sections (Pl. I, Fig. 3; Pt. VI, Fig. 8) of
this species are much more characteristic than is usual in the
genus Clathrodictyon. Where such a section traverses an
interlaminar space, the cut ends of the radial pillars are seen
in the form of dark granular masses, of considerable size,
and usually of a more or less elongated or oval shape. Where

[147]
16 PARKS : STROMATOPOROIDS OF THE GUELPH

the section more or less closely coincides with a concentric
lamina, the cut ends of the radial pillars are more closely
set and larger in size, and often form a sort of mosaic pave-
ment, or at other times a loose reticulation. Tangential sec-
tions are also unlike similar sections of most species of this
genus in the apparent absence of astrorhizal canals.

‘“ Obs.—In its general features Clathrodictyon striatellum
can hardly be confounded with any other member of the
genus. In external and superficial characters it makes a close
approach to C. regulare, Rosen, but its size is usually much
greater, its general texture is coarser, and its internal structure
is quite different. Its most distinctive characters are the
gentle and regular undulation of the concentric laminae, and
the peculiar form of the radial pillars which spring, very com-
monly by a double base, from the under sides of the laminae,
and often fall short of the upper surface of the lamina next
below. The exposed surfaces of the concentric laminae in
well preserved examples show, much more clearly than is
usual in the genus, the presence of innumerable zooidal pores.
The radial pillars produce no connecting processes or ‘‘ arms ”’;
whereas these structures are occasionally developed in C.
regulare. Lastly, the present form shows a more complete
absence of the astrorhizal system, so far as my observation
goes, than is the case in any related form of Clathrodictyon.

‘My identification of this form as the one which D’Or-
bigny had in view in establishing his Stromatopora striatella
is based upon an examination of Lonsdale’s original specimen,
which served as the type of the species to the French palaeon-
tologist, and which is now in the British Museum. My iden-
tification of Stromatopora mammillata, Fr. Schmidt, with
D’Orbigny’s species, is based upon specimens of the former
kindly given me by Magister Schmidt himself. I have figured
a portion of the surface, and also tangential and vertical sec-
tions of one of these specimens. These will show that there

[148]
PARKS : STROMATOPOROIDS OF THE GUELPH 17

exists no substantial difference between the Russian and the
British specimens, which I have here included in the present
species. Any apparent differences which are present may
probably be accounted for by the fact that the Esthonian
specimens are silicified, and have therefore undergone con-
siderable alteration.

“ Dastribution.—Clathrodictyon  striatellum, D’Orbigny,
occurs in the Ordovician rocks of Esthonia (in the ‘‘ Bork-
holm’sche Schichten ’’); but elsewhere it is only known as a
Silurian species. It is common in the Wenlock Limestone
of Britain (Dudley, Ironbridge, Dormington, &c.), and it is
also found in the Wenlock Limestone of Wisby, Gotland.”

It should also be noted that Nicholson was originally
of the opinion that C. striatellum occurred in the Niagara
for he mentions the species in the report on the Palaeontology
of Ontario as being common in the Niagara at Thorold and
rare at Rockwood. Later he seems to have altered his opinion
for it is not mentioned in his monograph. I am forced to the
conclusion that many examples hitherto ascribed to C. ostio-
latum belong properly to this species. The skeletal fibre is
remarkably similar, so much so, that it is impossible to make
a distinction. The main difference seems to be that the lam-
inae in C. striatellum are more crumpled than in the other
species. With such material as we have it is impossible to
make this distinction ; furthermore some specimens from the
European localities are not more crumpled than undoubted
examples of C. ostiolatum. Nicholson himself admits that
considerable variation occurs in this respect. However the
crucial test is the presence of the ‘‘ cylinders’. Without these
structures it seems impossible to ascribe a specimen to C.
ostiolatum. Many of the specimens examined are entirely
without this typical arrangement of the laminae ; these are
not parts only, but large pieces, four inches by eight. Fur-
ther, large specimens of perfect hemispherical shape show

[149]
18 PARKS : STROMATOPOROIDS OF THE GUELPH

nothing but the regularly curved laminae thoughout the whole
coenosteum. The most serious difficulty in the identification
of C. striatellum in the Guelph is the fact that Nicholson states
that astrorhizal systems are absent, while in the Guelph ex-
amples they appear to be present. However only one system
was observed in a considerable number of sections, so that it
is reasonable to suppose they were overlooked by Nicholson.
If my conclusions are correct, C. striatellum is much more ab-
undant than C. ostiolatum and occurs at all the typical local-
ities.

CLATHRODICTYON FASTIGIATUM, Nich.—Plate I, Fig. 6

CLATHRODICTYON FaAsTIGIATUM, Nicholson, Mon, Brit. Strom., pt. x1,
Pp. 43, fig. 3, 1886.

CLATHRODICTYON FASTIGIATUM, Aiaveleest Ann. Nat. Hist., ser. 5, vol. xix,
p. 8, pl. 2, figs. 3 and 4, 1887.

CLATHRODICTYON FaSTiG1aTUM, Nicholson, Mon. Brit. Stromatop., pt. 2,
p. 152, pl. 19, figs. 1-5, 1888.

CLATHRODICTYON FASTIGIATUM, Whiteaves, Pal. Fossils, vol. iii, pt. ii,

Pp. 52, 1895.

CLATHRODICTYON FASTIGIATUM, Wosbaves, Coit Rec. Sci., vol. vii, No. 3,
Pp. 135, 1896.

CLATHRODICTYON FASTIGIATUM, Whiteaves, Pal. Fossils, vol. ili, pt. iv,
Pp. 328, 1906.

Nicholson’s description of the above species as given in
his monograph (op. cit.) is as follow: -—

“The coenosteum in this species is laminar and cake-like,
of variable size, but of small thickness, full-grown examples
having a diameter of 15 cm. or more, with a thickness in the
centre of from 2 to 3cm. ‘The under surface is covered with a
ccncentrical y wrinkled epitheca. The superior side of the
coenosteum is flat, or slightly undulated, but is quite free
from ‘‘mamelons’’ The surface exhibits, when well pre-
served, numerous vermiculate and inosculating ridges formed
by rows of elongated tubercles. Small and remote astror-
hizae may sometimes be recognized in thin section but their
development is imperfect, and I have not detected their
presence on the free surface.

[150]
PARKS : STROMATOPOROIDS OF THE GUELPH 19

“As regards its internal structu e, the coenosteum is
composed of bent and crumpled concentric laminae, of which
about five (or four interlaminar spaces) usually occupy the
space of 1mm. As shown by vertical sections (Pl. I, Fig. 6)
the laminae are bent in two ways. _n the first place they are
bent into numerous chevron-like foldings, no traces of which
appear on the surface of the coenosteum. In the second place
each lamina is minutely crumpled or inflected in such a way
that the interlaminar spaces are constricted into rows of very
imperfect and more or lessopen vesicles. The radial pillars
are developed from the point of inflection of the laminae,
but are thin and largely imperfect. Hence, in vertical sec-
tions, the bent and crumpled laminae are far more conspicuous
than the radial pillars. Tangential sections exhibit the ir-
regularly sinuous and vermiculate edges of the transversely
divided and folded laminae, the cut ends of the radial pillars
appearing in these as dark rounded dots. Occasionally we
may also recognize in tangential sections scattered points
round which rows of dots are disposed in a radiating manner.
Such points represent the centres of small astrorhizae.

‘OB8s.—C. fastigiatum has certain relationships with C.
variolare, Rosen sp., and specimens occasionally occur which
present a mixture of the characters of the two forms. In
typical examples, however, the present beautiful species
cannot readily be confounded with any other known member
of the genus Clathrodictyon. It is distinguished from its near-
est allies (viz. C. vari lare, Rosen, ‘nd C. vesiculosum, Nich.
and Mur.) by the greater remoteness of the concentric laminae,
and by the peculiar and constant chevron-like and angular
folds into which the laminae are thrown. The appearances
presented by tangential sections are also exceedingly character-
istic, and quite unlike those seen in any other species of Clath-
rodic yon with which I am acquainted. The very imperfect
development of the astrorhizae is also a point in which the

[151]
20 PARKS : STROMATOPOROIDS OF THE GUELPH

present species is separated from the forms above alluded to.
Lastly, as far as I have seen, the coenosteum of C. fastigiatum
always has the form of a thin, cake-like expansion, with a
concentrically wrinkled epitheca below.

“ Distribution.—C. fastigiatum occurs abundantly in the
Wenlock Limestone of Britain, and I have specimens of it
from Jronbridge, Dudley, Much Wenlock, and Dormington.
I have also collected examples of this species in the Silurian
(‘‘ zone of Pentamerus esthonus’’) of Kattentack, Esthonia.
By the kindness of Mr. Whiteaves, I have have also been
enabled to examine specimens of this species belonging to
the collection of the Geological Survey of Canada. The
specimens in question are from Glenelg Township, near Dur-
ham, Ontario, and occur in a Magnesian Limestone belonging
to the Guelph formation.”’

To this description there is nothing to be added. The
species is well marked and easily identified. The University
Museum possesses specimens from Elora and from Aboyne
as well as from the Township of Glenelg.

Family—LABECHIIDAE, Nicholson
Genus—LaBEcHIA, Edwards and Haime

LABECHIA DURHAMENSIS, sp. nov. Plate II, Figs. 4-6 ; Plate
V1, Figs. 1, 2

Coenosteum massive, growing from a finely wrinkled
concave epitheca, and reaching a width of a foot or more.
Extreme thickness not observed, but cannot be less than eight
or ten inches. Mode of growth distinctly latilaminar, the
layers having an average thickness of five mm.

The vertical elements are well marked pillars of large
size which appear to have been hollow. The average width
of a pillar is 4% mm. and the average interspace % mm., but
considerable variation is to be observed. The pillars are

[152]
PARKS : STROMATOPOROIDS OF THE GUELPH Oe

connected by horizontal bars at irregular intervals, from eight
to ten occurring in the distance of four mm.

Tangential sections (Plate II, Fig. 5; Pl. VI, Fig. 2)
present a series of rounded dots representing the cut ends of
the pillars. Occasionally the pillars are seen to be connected
by bars in the manner typical of the genus Labechia. The
hollow character of the pillars is seen only in exceptionally
well preserved examples.

Vertical sections (Plate II, Fig. 4) exhibit the continuous
pillars and the connecting bars ; those cut transversely ap-
pearing as irregular dots while those which happen to follow
the plane of the section are seen as flexuous lines of some
thickness passing from pillar to pillar.

This is a well marked species and capable of easy identi-
fication, when occurring under ordinary conditions. How-
ever the great majority of examples are in the ‘‘ reversed "’
state. In these the substance of the original skeleton has been
surrounded by infiltered matter and the fibre subsequently
replaced by crystalline calcite. The fossil therefore appears
in section as clear white matter traversing a muddy base.
In many examples this calcite has subsequently been dissolved
so that the specimen shows a mass of rock penetrated by
numerous small holes. This peculiarity has given rise to the
popular term “ pin-hole fossils’. (Pl. VI, Fig. 1.)

Tangential sections of the reversed examples (PI. II, Fig. 6)
show the cross sections of these pin-holes which are seen to
be connected by clear spaces corresponding to the original
position of the bars. A rather puzzling appearance is some-
times shown by these specimens ; the infiltered calcite and
dolomite seems to have formed a concretionary layer around
the original skeleton, so that, in thin sections and on polished
surfaces, a dense line is seen to surround the position of the
pillars. First inspection is apt to lead to the conclusion that
these lines represent actual organic tissue but I believe the
explanation to be as indicated above. (PI. II, Fig. 6.)

[153]
22 PaRKS : STROMATOPOROIDS OF THE GUELPH

Vertical sections of the reversed specimens (PI. III, Fig. 1)
show no new features. The peculiar appearance due to the
method of mineralization above described is to be seen on
the face of most polished specimens.

From Labechia conjerta, Lons., the present species differs
in the smaller size and more remote position of the pillars and
in the coarser character of the connecting bars. From L.
canadensis, Nich., it differs in the much finer nature of the
whole coenosteum. Labechia durhamensis occurs in abund-
ance, particularly in the reversed condition, at Durham, Galt,
Guelph, Elora and throughout the Guelph of Ontario.

LABECHIA MINORA, sp. nov. Plate III, Figs. 2, 5, 6

Coenosteum large, spreading, gently undulating, reaching
a width of at least two feet. Thickness unknown but must
have been considerable, perhaps ten inches or a foot. Coenos-
teum composed of distinct latilaminae varying from four to
eight mm. in thickness, The only specimens known are in
the reversed condition so that no information is available
regarding the surface condition of the species.

The coenosteum appears to have been composed of well
marked vertical pillars and flexuous connecting bars. The size
of these pillars cannot be stated with accuracy but they
seem to vary from one-tenth to one-fifth of one mm. in
diameter. The space between the pillars is likewise not to
be stated with certainty as considerable variation was ob-
served. This uncertainty however is doubtless to be attrib-
uted to the poor state of preservation rather than to an organic
difference in the distribution of the pillars.

Vertical sections (Pl. III, Fig. 2) show the clear calcite
filling the cavities left by the solution of the pillars and their
connecting arms.

Tangential sections (PI. III, Figs. 5, 6) show the cut ends
of the pillars as clear spaces, here and there connected by oc-

[154]
PARKS : STROMATOPOROIDS OF THE GUELPH 23

casional openings. The two figures exhibit a considerable
difference in the distance apart of the pillars but this is to be
attributed to a more perfect preservation in the one case.

L. minora is distinctly finer than L. durhamensis and it
is impossible to confuse the two species. The reversed speci-
mens of both species present somewhat the same appearance
as to their ‘‘ pin-hole”’ character, but the larger size of the
pores in the L. durhamensis is at once apparent. A normal
example of L. minora has not been examined ; all the available
specimens being reversed. In this state however the species
is common and occurs in large masses at Elora, Galt, Dur-
ham, Glenroading, etc.

Genus—ROSENELLA, Nich.
ROSENELLA GLENELGENSIS, sp. nov. Plate II, Fig. 3 ; Plate
III, Fig. 4 ; Plate VI, Fig. 5

Coenosteum consisting of a series of flat or undulating
plates of considerable thickness enclosing large lenticular
interspaces. The plates are separated from each other in a
vertical direction by an average interspace of one mm. ‘Their
undulations however bring them in contact in a horizontal
direction at distances varying from almost nothing to as much
as 50mm. Occasionally also contiguous plates are connected by
a single vertical bar or tube. The surface of each layer is minutely
ridged and tuberculated and provided with a rich system of
astrorhizal canals. Occasional large pores penetrate the lam-
inae. ‘These seem to have no distinct distribution, as in some
cases they correspond with the astrorhizal centres and in other
cases are quite distinct. The plates vary somewhat in thick-
ness but average about one-quarter to one-fifth of one mm.
(Pl. ITI, Fig. 4.)

Vertical sections (Pl. II, Fig. 3) slow the cut edges of the
horizontal plates as a series of undulating lines with lenticular
masses of matrix between. The upper surface of the plates,

[155]
24 PaRKS : STROMATOPOROIDS OF THE GUELPH

in many instances, shows a dense border line, which however
can, in other cases,be seen on both sides of the lamina. An
occasional plate shows this dense line towards the centre.
Very fine and indistinct striations cross the plates in a vertical
direction. Although no certain evidence is obtainable, these
striations probably represent minute tubuli. The large pores
already referred to can be seen as distinct openings in the
laminae as viewed in cross section.

Tangential sections are very unsatisfactory, and in fact
reveal nothing further as to the minute structure of the species.
The surface of each plate is marked by numerous little rounded
and ridge-like elevations between which run the horizontal
canals of fine but distinct astrorhizal systems. (PI.VI, Fig. 5.)
The centres of these systems are about 10 mm. apart and are
usually situated in a depression of the plate. The large central
canal is well marked in some examples, but in others is appar-
ently absent. I am inclined to regard the large open axial
canal of the astrorhizal systems as normal and to ascribe its
absence to the process of mineralization.

Many examples of this species have been labelled Stroma-
topora antiqua but I cannot agree with this identification.
If we have to deal with a Stromatopora the horizontal plates
must represent latilaminae. But latilaminae are essentially
distinct from each other which is not the case here. The plates
are also separated from each other by too great an interval
for this explanation to hold good. It may be urged that the
original latilaminae were thicker and have been reduced by
solution. Such a process could not produce the regularity
of separation of the plates nor would it leave the surface in
the excellent condition observed. The fibre of the coenosteum
is dense and not at all of the porous character typical of the
Milleporoid type of Stromatoporoid.

The open lenticular skeleton and the absence of pillars
at once suggests Nicholson’s genus Rosenella, but it must be

[156]
PARKS : STROMATOPOROIDS OF THE GUELPH 25

admitted that differences exist, particularly in the presence
of astrorhizal systems and the absence of even rudiments of
pillars. Rosenella glenelgensis occurs in some abundance at
Durham and Elora.

Section B. (Milleporoid Group.)
Family—STROMATOPORIDAE, Nicholson
Genus—STROMATOPORA, Goldfuss
STROMATOPORA GALTENSIS, Dawson. Plate IV, Figs. 3-4

CoENOSTROMA GALTENSE, Dawson, Life’s Dawn on the Earth, p. 160, 1875:
CoENOSTROMA GALTENSE, Dawson, Quart. Jour. Geol. Soc. Lond., vol.
XXV, Pp. 52, 1879.

Cf. STROMATOPORA CONSTELLATA, Ha. 7. Palaeontol. New York, 3: 324, 1852.

STROMATOPORA GALTENSIS, Nicholson, Mon. Brit. Strom., p. 173, 1891.
STROMATOPORA GALTENSIS, Whiteaves, Pal. Fossils, vol. ili, p. 52, 1895.
STROMATOPORA GALTENSIS, Whiteaves, Can. Rec. Sci., vol. vii, p. 136, 1896.
STROMATOPORA GALTENSIS, Clarke and Ruedemann, N. Y. State Museum,
Memoir 5, p. 36, pl. i, fig. 13, 1903.
STROMATOPORA GALTENSIS, Whiteaves, Pal. Fossils, vol. itl, p. 328, 1906.

Sir William Dawson’s description of this species was made
at a time when the nature of Stromatopora was but little under-
stood; in consequence it is impossible to recognize the species
from any description yet published. In his monograph Pro-
fessor Nicholson refers to a specimen examined by him and
states that the minute structure is much destroyed by min-
eralization but that the species is closely allied or identical
with S. typica, von Rosen. Nicholson is also of the opinion
that both these species are probably identical with S. con-
stellata, Hall. With the view of attempting to clear up this
difficulty I have endeavoured to obtain a view of Dawson’s
type but have been unsuccessful. Professor Clarke of the
New York State Geological Survey has kindly furnished me
with sections of S. constellata from the Cobleskill and Dr.
B. E. Walker has presented to the museum a specimen of
S. typica from the Wenlock limestone of England which had
been identified by Nicholson.

In the Guelph collection examined there are two species
of true Stromatopora (omitting S. antiqua) and one or two of

[157]
26 PARKS : STROMATOPOROIDS OF THE GUELPH

Stromatoporella. On ordinary inspection the Stromatoporella
might easily be mistaken for Stromatoporaandas far as Dawson’s
description goes might serve as an example of his S. galtensts.
Nicholson however has stated that the specimen examined
by him resembles S. typica therefore we must conclude that
one of the Stromatopora represents the species. The one most
closely resembling S. ¢ypeca is much finer in grain than the
other and is made the basis for the description here given.
Without an opportunity to inspect the type I can not posi-
tively state that we are dealing with a true example of the
species described by Dawson.

Coenosteum massive, concentric. Neither upper nor
under surface observed with certainty. Latilaminar structure
but faintly indicated. Skeletal matter minutely fibrous.
Pillars and laminae completely fused. The coenosteal tissue
is pierced by numerous, slightly flexuous, tabulate zooidal
tubes which are about one-eighth of a millimetre in diameter.
The tabulae are numerous and distinctly preserved; as many
as ten appearing in the space of one mm. The interspaces
between neighbouring tubes are about one and one-half times as
wide as the tubes themselves. Astrorhizal systems are well de-
veloped and are superimposed, being centred by a continuous
wall-less axial canal. The systems average 6 mm. apart.

Vertical sections exhibit the inosculating fibre of the tissue,
the zooidal tubes, the cut ends of astrorhizal canals and an
occasional vacuity in the skeletal matter which is however
fairly dense. (Pl. IV, Fig. 3.)

Tangential sections show the cut ends of zooidal tubes,
vacuities in the tissue and the astrorhizal canals. (Pl. IV,
Fig. 4.) These various features are typical of true Stroma-
topora ; specific differentiation is largely a matter of fineness
of grain and the character of the zooidal tubes.

In my opinion the present example more closely resembles
S. concentrica than S. typica. It is certainly not the latter,

[158]
ParKS : STROMATOPOROIDS OF THE GUELPH a

but in view of the fact that S. concentrica is said by Nicholson
to be confined to the Devonian and not to occur in America
I hesitate to place our species under that name. From S.
typica the species is easily differentiated by the much coarser
character of the tubes and the connecting tissue. In vertical
sections six tubes and their interspaces occupy thedistance of two
mm. The same dimensions are given by Nicholson for S. concen-
trica. In my specimen of S. typica nine or ten tubes occur in the
same distance. Although not so apparent on limited sections, a
wide view of a vertical surface shows that the tubes of S.
typica are much more nearly parallel than in this example.
Tangential sections exhibit a closeness and coarseness of fibre
much more like S. concentrica than S. typica. In fact the
differences of our species from S. concentrica are hard to find,
the only point observed being that the tabulae of the zooidal
tubes are a little closer together. A comparison of the figures
here given of S. typica and S. constellata prove the identity
of these forms. As they are not found in the Guelph no de-
scription is given. (Plate IV, Figs. 5-8.)

If S. galtensis is not considered to be identical with S.
concentrica it must be placed very near it and may be re-
garded as the American type of that species. There can be
little doubt that it represents the Guelph development of the
Niagaran S. typica. Specimens of S. galtensis are among the
rarest of the Guelph Stromatoporoids, but in this museum,
and I have no doubt in many others, numerous examples of a
species to be described as Stromatoporella elora have been
ascribed to S. galtensts.

Dawson’s type appears to have been lost. Dr. Whit-
eaves assures me it is not now in the collection of the Geo-
logical Survey and Dr. Adams makes the same statement for
the Redpath museum at Montreal. It is very unfortunate
that this should be the case, and I must disclaim any respon-
sibility for the identification here given. Dawson’s specimen

[159]
28 PaRKS : STROMATOPOROIDS OF THE GUELPH

was obtained at Galt ; the Geological Survey had, at one time,
a specimen from Hespeler. The specimens on which the pre-
sent description is based are from Elora and Durham.

STROMATOPORA ANTIQUA, Nicholson and Murte

PACHYSTROMA ANTIQUA, Nich. and Murte, Jour. Linn. Soc., vol. xiv,
p. 224, pl. 4, figs. 2-5, 1879.

STROMATOPORA ANTIQUA, Nicholson, Mon. Brit. Strom., pt. 1, p. 17, pl. 5,
figs. 8-11, 1886.

STROMATOPORA ANTIQUA, Nicholson, Ann. and Mag. Nat. Hist., p. 310,
pl. vii-x, April, 1891.

STROMATOPORA ANTIQUA, Whiteaves, Pal. Fossils, vol. iii, pt. ii, p. 53, 1895

STROMATOPORA ANTIQUA, Whiteaves, Can. Rec. Sci., vol. vii, No. 3, p. 136,
July, 1896.

STROMATOPORA ANTIQUA, Whzuteaves, Pal. Fossils, vol. iii, pt. iv, p. 328, 1906.

Stromatopora antiqua is a Niagara species of very doubt-
ful occurrence in the Guelph. A careful examination of a
large number of specimens which might provisionally be
placed here has resulted in no certain identification of the
species. Many large hemispherical Stromatoporoids occur,
which in the general shape of the coenosteum and in the
distinct latilaminar structure conform to the description of
S. antiqua. In every instance the minute structure is entirely
destroyed. Professor Nicholson states (Ann. and Mag. Nat.
Hist., op. cit.) “‘A poorly preserved specimen in dolomitic
limestone of Niagara age from Durham, Ont., may also pos-
sibly belong to this species.’’ A description of S. antiqua will
be deferred until the Niagara forms are revised.

STROMATOPORA, sp. indet.

There is no doubt that a species of true Stromatopora
differing from S. galtensis or S. antiqua is present but the pre-
servation is so poor that it would be rash to attempt a de-
scription. The coenosteum seems to be composed of coarsely
porous fibre through which run large open canals. No at-
tempt to obtain sections was at all satisfactory, for, although
cuts were made in numerous directions it seemed impossible

[160]
Parks : STROMATOPOROIDS OF THE GUELPH 29:

to locate either a tangential or vertical slice. The general
structure is very much coarser than in S. galtensis or in S.
concentrica, but whether the curving, open canals represent
astrorhizal systems or zooidal tubes I am unable to say.

Genus—STROMATOPORELLA, Nicholson.
STROMATOPORELLA ELORA, sp.nov. Plate III, Fig.3; Plate V,
Hives, 1,3, 4.2 Plate VL, Fig, 6

Coenosteum massive, apparently concentric and hemis-
pherical. Latilaminar structure present but not pronounced
except in weathered specimens. Latilaminae about 4 mm.
thick. Both pillars and horizontal elements are distinct but
are imperfectly fused in the manner described by Nicholson
for the genus. Skeletal fibre minutely porous as in the genus
Stromatopora. Fairly long zooidal tubes penetrate the coe-
nosteum vertically. No very certain evidence of tabulae in
the tubes has been observed, but it is extremely likely that
they existed. Astrorhizal systems are well developed the
centres being from 3 to6mm.apart. A very large axial canal
forms the centre of the system and this canal is surrounded
by a stout “‘ astrorhizal cylinder ’’ in which a vertical arrange-
ment of the tissue is perceptible as well as a faintly defined
central line. The astrorhizal canals are large, round and
strictly superimposed, at least in some cases, as six or eight
of the cut ends may be observed lying one above the other
between the same pair of vertical pillars. About five hori-
zontal laminae with the intervening interspaces occur in one
mm., but in certain parts of a latilamina they are somewhat
more closely crowded. The pillars are, on the whole, more
distinct than the laminae but some sections were observed
where the opposite was true. Four to five pillars occur in the
space of one mm.

A considerable number of vertical sections were prepared
which present a puzzling difference and cause great trouble

[161]
30 PARKS : STROMATOPOROIDS OF THE GUELPH

in photographing. Badly preserved at the best, so that thin
sections are difficult to examine, this species seems to have
a peculiar power to absorb Canada balsam with the result
that the evidence of structure entirely disappears. The best
results were obtained by photographing the polished surface.

The average vertical section presents the appearance
seen in Pl. V, Fig. 1. The vertical pillars are apparent as well
as the horizontal laminae. Zooidal tubes are but indistinctly
seen. A much better preserved portion is seen in Pl. III,
Fig. 3, which was prepared from a polished surface. The
horizontal laminae and the vertical pillars are here quite
distinct as well as the zooidal tubes, which owing to mineral-
ization show but faint evidence of tabulae. The wide open
axial canal of the astrorhizal system is well shown with a
heavy cylinder surrounding it. This cylinder shows indis-
tinct vertical striations and some evidence of a central hollow.
Certain sections show the large axial canals lying one above
another between a pair of pillars. Occasional sections are
cut which show scarcely any sign of the laminae. Such slices
suggest the structure of a true Stromatopora.

Tangential sections are, on the whole, more satisfactory
than the vertical. The coarsely porous character of the fibre
is distinctly seen. The cut ends of the wide axial tubes are
prominent, as well as the ramifying canals of the astrorhizae
A somewhat different appearance is presented according to
the level at which the section is cut. If the line of section
passes through a lamina (PI1.V, Fig. 3) the astrorhizal canals
are conspicuous and the pillars lose their significance, being
fused together by the horizontal elements. Through the
tissue thus formed pass the distinct round zooidal tubes. In
many parts of such sections the pillars are seen to be de-
formed by the zooidal tubes pointing to the assumption that
the latter are the more important elements to which the pillars
have to give place. If the horizontal section is situated at

[162]
ParKS : STROMATOPOROIDS OF THE GUELPH 31

the level of an interlaminar space (PI1.V, Fig. 4) the tissue is
less continuous and presents a ring-like appearance. These
rings are not proper tube walls but are made up of two or more
pillars which are deformed and united into a ring surrounding
the zooidal tube. In some cases they are contiguous so that
the section appears as series of coalesced circles. Occasionally
very delicate lines can be made out connecting the pillars as
in Aciinostroma but in the majority of cases they are united
by their own deformation as described above.

It is apparent from this description that we have to deal
with a form intermediate between Stromatopora and Actinos-
troma. The minute structure of the fibre is distinctly of the:
character ascribed to the Milleporoid group, while the incom-
plete fusion of the vertical and horizontal elements as well
as some sign of delicate connecting arms points to a relation-
ship with the genus Actinostroma. Nicholson’s genus Stroma-
toporella approaches nearer to this species than any other,
but in this example the zooidal tubes are much more numer-
ous and more closely set than in any other Stromatoporella ;
in this respect it approaches closer to the true Stromatopora.

The bad preservation and the diverse appearance of sec-
tions not accurately cut render this species very difficult of
description and identification. However after the examin-
ation of a number of sections one becomes accustomed to the
general aspect and may recognize examples with facility.
It is quite possible that this species is Stromatopora galtensis
of Dawson.

Stromatoporella elora is one of the commonest forms of
the Guelph dolomite and may be obtained at any of the well
known localities.

STROMATOPORELLA ELORA, vay. MINUTA, var. nov. Plate V,
Figs. 2, 5,6; Plate VI, Fig. 7

There are in the University collection a half-dozen of

fragments which have caused me a great deal of uncertainty

[163]
32 PARKS : STROMATOPOROIDS OF THE GUELPH

as to their identity with Stromatoporella elora. The coenosteum
cannot be described as to its external features, for only small
fragments are available, but it seems to have been spreading
in character and to have been bent into sharp folds. The
thickness must have been at least 3 cm. but may have been
much greater. Latilaminar structure is not very pronounced.
The fibre and included calcite are of much the same colour so
that the interpretation of thin sections is almost impossible.
Well polished surfaces are much more satisfactory than thin
sections.

The coenosteum is seen to be made up of a series of com-
paratively stout radial pillars which are connected at frequent
intervals by delicate horizontal arms. ‘These arms are some-
what flexuous, do not arise in whorls, and are very incom-
p:etely continuous so as to form laminae. Passing vertically
through the coenosteum, in part between the horizontal arms,
in part along the sides of the pillars and in part through the
very centre of these elements are delicate zooidal tubes,
apparently devoid of tabulae.

Vertical sections (Pl. V, Fig. 5) show the distinct vertical
pillars, approximately parallel, and distant from each other
about one-eighth of a millimetre so that four pillars and their
interspaces appear in one mm. The connecting horizontal
elements are much more frequent,as many as eight or ten
occurring in the space of one mm. ‘The horizontal elements,
while not strictly formed into laminae, nevertheless show some
regularity in arrangement, enough to justify the terms ‘‘ lam-
inae”’ and “interlaminar spaces.’’ The vertical tubes are
seen most frequently crowded into the side of the pillars,
although some penetrate the coenosteum among the arms.

Tangential sections (Pl. V, Figs. 2, 6; Pl. VI, Fig. 7)
if cut along an interlaminar space show more or less distinctly
the cut ends of the pillars but in no case are they at all com-
parable in clearness of outline with the vertical section. Where

[164]
PARKS : STROMATOPOROIDS OF THE GUELPH 33

the pillars can be made out as distinct dots they are seen to
be connected by very delicate arms suggesting the hexactin-
ellid whorls of Actinostroma. Among these arms, in part
bounded by them and in part squeezed into the sides of the
pillars, are the minute tubes already referred to. In many
parts of a tangential section the pillars are entirely obliterated
by the invasion of these vertical tubules so that it presents
a sort of fine net-like aspect. This appearance is due to the
fact that the part of a pillar left by the occurrence of a tubule
in its centre is of about the same calibre as the connecting
arms.

Tangential sections which are at all thick, in fact all
tangential sections thick enough to be of any value, do not
show the fine connecting arms at all but present the typical
appearance of Siromatopora (Pl. V, Fig. 6). On polished sur-
faces however the structure above described can be made out
Astrorhizal systems of a delicate character throw a ramification
of canals over the whole surface. The centres of these sys-
tems are about 4mm.apart. A somewhat diagrammatic repre-
sentation of a polished tangential surface is shown in Pl. V,
Fig, 2.

This species presents affinities to Actinostroma in the
distinctness of its pillars and in the lack of complete fusion
of its horizontal elements. On the other hand it approaches
Stromatopora in the character of the fibre and in the presence
of zooidal tubes. It seems advisable to include this example
with Stromatoporella elora and provisionally to give it the rank
of a variety. The resemblance to Stromatoporella elora is so
strong that at times I have been tempted to consider the
differences as merely the result of different processes of fossil-
ization. However the vertical pillars in the present variety
are more prominent in vertical section. The tubules are
smaller. The connecting bars are finer. The astrorhizal
systems are smaller and less regular. In fact the whole coe-

[165]
34 PARKS : STROMATOPOROIDS OF THE GUELPH

nosteum is of a more delicate build except for the greater
clearness of the vertical pillars. If the horizontal arms are
at all thickened by secondary matter the resemblance to
Stromatoporella elora is very strong, for the quadrangular
interspaces become rounded and the pillars lose their outline
as in S. elora. In this variety there is a strong suggestion of
Bargatsky’s genus Parallelopora. ‘The vertical section par-
ticularly resembles Parallelopora darlingtonensis. ‘The fibre
does not present the vacuities characteristic of that genus,
unless the minute vertical tubules are morphologically equiv-
alent. Stromatoporella elora minuta is founded on six frag-
ments from Durham collected by Mr. Joseph Townsend, of
Toronto.

Family—IDIOSTROMIDAE, Nich.
Genus—HERMATOSTROMA, Nich.
HERMATOSTROMA GUELPHICA, sp. nov. Plate IV, Figs. 1, 2:
Plate VI, Fig. 4

This species is founded on two very well preserved speci-
mens, bothfrom Elora. Neither of these examples is of suffi-
cient size to render possible any account of the general surface
characters or the size of the coenosteum. One specimen is
three inches long by one and a half inch wide with a thickness
of three-quarters of an inch. On the polished faces of this
piece the pillars are seen to be parallel throughout and the
horizontal elements to be destitute of curving ; from this it
may be deduced that the coenosteum was of a considerable
size and spreading rather than hemispheric in character.
Latilaminar structure entirely absent.

The skeleton is composed of a series of parallel pillars of
which about five occur in the space of one mm. The inter-
spaces between the pillars are from one and a half to twice
the thickness of the pillars themselves. The horizontal ele-
ments consist of rods of about the same calibre as the pillars,

[166]
PARKS : STROMATOPOROIDS OF THE GUELPH 35

forming with them an almost square network. These con-
necting structures are not disposed without regularity as in
Labechia but are arranged, if not strictly, at least with a consider-
able degree of continuity into horizontal laminae. Both pil-
lars and horizontal connecting elements appear to be hollow ;
the internal canal is continuous in both the pillars and bars
and is enlarged at the points of junction. Astrorhizal systems
are entirely absent.

Vertical sections (Pl. IV, Fig. 1; Pl. VI, Fig. 4) show
a distinct rectangular network in which the vertical com-
ponents are much more continuous than the horizontal.
Where the section passes through the centre of a pillar or bar
the central cavity appears as a clear space, not filled with
ferric oxide as in Nicholson's description of the type species
of the genus Hermatostroma.

Tangential sections (Pl. IV, Fig. 2 ; Pl. VI, Fig. 3) present
a different appearance according as the plane of section tra-
verses a lamina or interlaminar space. In the former case
the central hollow of the pillar is seen to be enlarged and to
pass into the somewhat curved connecting processes. The
various hollow bars with the cut ends of the pillars give to
this part of a section the appearance of a mass of inosculating
pipes. The interspaces probably represent the habitation
cavities of the zooids. When the section follows an inter-
laminar space the cut ends of the pillars appear as small but
very distinct rings. Astrorhizae are undoubtedly absent
as neither vertical or horizontal sections show any trace of
these structures.

This species appears to me to belong to Nicholson’s genus
Hermatostroma. The general structure of the coenosteum
is identical, except for the absence of the ‘‘ short flexuous
tubes of considerable size, bounded by thin proper walls,
and crossed by occasional tabulae.’’ Although Nicholson
thinks these structures to be part of the Stromatoporoid,

[167]
36 PARKS : STROMATOPOROIDS OF THE GUELPH

he discusses the possibility of their being of the nature of
Caunopora. ‘The net-like character of the coenosteum, and
the existence of more or less distinct laminae removes the
species from Labechia, even if the tubes are not really hollow.
(It is always possible that this appearance is the result of
mineralization.) It is certainly not to be placed under Actin-
ostroma as there is no sign of the hexactinellid arrangement
of the horizontal bars and the resulting angular network.
If my conclusions are correct we have in this species the first
recorded Hermatostroma in America and also the first in the
Silurian. Out of a large collection only two specimens were
found, both from Elora ; it may therefore be concluded that
Hermatostroma guelphica is a rare form.

[168]
PaRKS : STROMATOPOROIDS OF THE GUELPH ah

APPENDIX

It must be admitted as possible that other species occur
in the Guelph dolomite, for numerous specimens were ex-
amined of which the structure could not be made out with
sufficient accuracy for description. Notable is a compact
close-grained example occurring in large (eight to ten inch)
hemispheric masses and exhibiting distinct latilaminar struc-
ture with a fairly constant separation of about 8 mm. An-
other similar species but with the latilaminae much thinner
may be referred to Stromatopora antiqua. Many sections were
also examined in which faint evidence of laminae may be seen.
These may belong to C. striatellwm or some other species of
Clathrodictyon. There also occurs a ramose form exhibiting
slight evidence of the structure of a true Stromatopora but it
is likewise much too poorly preserved to render a description
justifiable.

[169]
Fig.
Fig.
Fig.
Fig.
Fig.

Fig.

Fig.
Fig.
Fig.
Fig.
Fig.
Fig.

Fig.
Fig.
Fig.
Fig.
Fig.
Fig.

Fig.
Fig.

Fig.
Fig.

EXPLANATION OF PLATES

Unless otherwise stated all figures are enlarged ten times

Puiate I
1—Actinostroma vulcana. Tangential section.
2— a in Vertical section.
3—Clathrodictyon striatellum. Tangential section.
4— ” Vertical section.

5—Actinostroma vulcana. Vertical section through one of volcano-like
projections, showing the ‘‘crater’’ and ‘‘pipe,’’x 2.

6—Clathrodictyon fastigiatum. Vertical section.

Figures 1, 2 and 5 are from specimens presented by Dr. B. E. Walker.

Figures 3 and 4 from specimens collected by Mr. Joseph Townsend.

Figure 6 after Nicholson.

Priate II

1—Clathrodictyon ostiolatum. Natural size.
2— n - Vertical section.
3—Rosenella glenelgensis. Vertical section.
4—Labechia durhamensis. Vertical section.
5— - “ Tangential section.

6— e ss Tangential section of reversed specimen,
showing the concretionary calcite surrounding the original position
of the pillars and arms.

Figures 1 and 2 after Nicholson (Paleontology of the Province of
Ontario.)

Figures 3 and 6 from specimens collected by Mr. Joseph Townsend.
Figures 4 and 5 from a specimen presented by Dr. B. E. Walker.

Puate III

1—Labechia durhamensis. Vertical section of reversed specimen.
2—Labechia minora. Vertical section of reversed specimen.
3—Stromatoporella elora. Vertical section from polished surface.
4—Rosenella glenelgensis. Vertical section. Natural size.
5—Labechia minora. Tangential section of reversed specimen.

ce “ce “ “ce «e “

All figures from specimens collected by Mr. Joseph Townsend.

Piate IV

1—Hermatostroma guelphica. Vertical section considerably restored.

2—Hermatostroma guelphica. Tangential section. This section passes
for the most part through an interlaminar space but the laminz are
cut at certain points.

3—Stromatopora guelphensis. Vertical section.

“e ‘

— Tangential section.
(Compare Nicholson’s figures of S. concentrica).

[171]
40

Fig.
Fig.
Fig.
Fig.

Fig.
Fig.

Fig.
Fig.
Fig.
Fig.

Fig.
Fig.

Fig.

Fig.
Fig.

Fig.

Fig.

PARKS : STROMATOPOROIDS OF THE GUELPH

s—Stromatopora typica. Tangential section.

6— Stromatopora consiellata. Tangential section.

4—Stromatoporatypica. Vertical section.

8—Stromatopora constellata. Vertical section.

Figures 1, 2, 3 and 4 from specimens collected by Mr. Joseph Townsend.

Figures 6 and 8 from specimens from the Cobleskill, lent by Professor
J. M. Clarke.

Figures 5 and 7 from a specimen identified by Nicholson in the Wenlock
of England and presented by Dr. B. E. Walker.

PLATE V

1—Stromatoporella elora. Vertical section.

2—Stromatoporella elora minuta, Tangential section, somewhat dia
grammatic, prepared from polished surface to show the connecting
arms and the invasion of the pillars by tubules.

3—Stromatoporella elora. Tangential section through a lamina.

“

4— Tangential section passing largely through an
interlaminar space.

5s—Stromatoporella elora minuta. Vertical section.

6— - Se a Tangential section.
4—Clathrodictyon ostiolaium. Tangential section.
8— “ ee Portion of surface. Natural size.

Figures 1-6 from specimens collected by Mr. Joseph Townsend.
Figures 7 and 8 after Nicholson (An. and Mag. Nat. Hist.)

Prate VI

. 1—Labechia durhamensis. Showing the vertical section partly polished

and partly weathered, also the wrinkled concave epitheca, x 4.
2—Labechia durhamensis. Tangential section showing the cut ends of
the pillars, their hollow centres and the clear crystalline calcite sur-
sounding them.
3—Hermatostroima guclphica. Tangential section.

oe

4— Vertical section. The photograph does
not show the hollow character of the pillars and horizontal elements.

5—Rosenella glenelgcusis, Portion of surface of a plate showing its
ridge-like character and less clearly the ramifications of the fine
astrorhizal canals.

6—Stromatoporella elora. Tangential section from polished surface.

Fig 7—Stromatoporella elora minuta. Tangential section from polished sur-

face. On comparing this figure with Plate IV, Fig. 6, it will be ob-
served that the latter figure, being prepared from a thin section, has
lost many of the fine connecting arms. On the other hand the present
figure has too fine an appearance owing to the photographic repro-
duction of matter not forming part of the coenosteum. Plate V, Fig.
2, is the mean of these two and although considerably restored and
diagrammatic approaches most closely to the real structure of the
coenosteum.

Fig. 8—Clathrodictyon striatcllum. Tangential section.

All figures are produced from un-retouched photographs. Numbers 2,

3, 4.and 8 are from thin sections and numbers 1, 5, 6and 7 from surfaces.

[172]
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UNIVERSITY OF TORONTO STUDIES

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Do. No. 2: The Michipicoten iron ranges, by Professor

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