Some Silurian Stromatoporoids from Northwestern Baffin Island

SOME SILURIAN STROMATOPOROIDS FROM NORTHWESTERN BAFFIN ISLAND

A. A. Petryk SOME SILURIAN STROMATOPOROIDS FROM NORTHWESTERN BAFFIN ISLAND

Allen Alexander Petryk, B.Sc.

A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of

Master of Science

Department of Geological Sciences

McGill University

Montreal

1965 CONTENTS

Page

INTRODUCTION------l

Scope------1

Area------2, 2a

Acknowledgments------3

STRATIGRAP.HY------4

Previous work------4

Ordovician and Silurian stratigraphy of North western Baffin Island------6

Table of formations------5

Description of formations------6

Brodeur group------6

Baillarge formation------6

Cape Crauford formation------16

A COMPARISON OF THE TIME-STRATIGRAPHIC RELA.TIONSHIPS OF THE STROMATOFOPDIDS AND THE ASSOCIATED FAUNAS IN THE BPDDEUR GROUP 'Z7

METHODS------38

Field collecting------38

Preservation------38

Preparation of thin sections------4o

IMPORTANCE OF STHOMATOFOROIDS------41 Page

GENERAL PALAEONTOLOGY------42

Stromatoporoidea------42

General - definition; time; biological relationship ecology------42

Previous workers - classifications------42

SYSTEMATIC PALAEONTOLOGY------45

Family CLATHRODICTYIDAE------45 Genus CLATHRODICTYON------··------45 Clathrodictyon lenticulare n. sp.------46 Clathrodictyon vajgatschense Yavorsky------48 Clathrodictyon miniapse n. sp.------51 Clathrodictyon Linnarsonni Nicholson------53

Genus ECCLIMADICTYON------57 Ecclimadictyon fastigiatum (Nicholson)------57 Ecclimadictyon microvesiculosum (Riabinin)------61 Ecclimadictyon sp. A.------63

Genus INTEXODICTYON------66 Intexodictyon brodeurense n. sp.------67

Family ACTINOSTROMATIDAE------70 Genus GERRONOSTROMA------70 ? Gerronostroma juvene n. sp.------70

Family STROMATOPORIDAE------75 Genus STROMATOPORA------76 Stromatopora baffinensis n. sp.------76 Stromatopora aspectabilis Yavorsky------81 Stromatopora sp. A.------85 Stromatopora baillargensis n. sp.------87

Genus ACTINODICTYON------89 Actinodictyon crispatum n. sp.------89 CONTENTS

Page

INTRODUCTION------·------1

SCOPE------1 AREA------2, 2a ACKNOWLEDGMENTS------3

STRATIGRAPHY------4

Previous work------4

Ordovician and Silurian Stratigraphy of North western Baffin Island------6

Table of for.mations------5

Description of formations------6

Brodeur group------6

Baillarge formation------6

Cape Crauford formation------16

A Comparison of the Time-Stratigraphic Relationships of the Stromatoporoids and the Associated Faunas in the Brodeur Group.------27

Methods------38

Field Collecting------38

Preservation------38

Preparation of thin sections------4o

Importance of Stromatoporoids------41 Page

GENERAL PALAEONTOLOGY------42

stromatoporoidea------42

General - definition; time; biological relationship ecology------42

Previous workers - classifications------42 SYSTEMATIC PALAEONTOLOGY------45

Family CLATHRODICTYIDAE------45 Genus CLAT.HRODICTYON------45 Clathrodictyon lenticulare n. sp.------46 Clathrodictyon vajgatschense Yavorsky------48 Clathrodictyon miniapse n. sp.------51 Clathrodictyon Linnarsonni Nicholson------53

Genus ECCLIMADICTYON ------57 Ecclimadictyon fastigiatum (Nicholson)------57 Ecclimadictyon microvesiculosum (Riabinin)------61 Ecclimadictyon sp. A.------63

Genus INTEXODICTYON------66 Intexodictyon brodeurense n. sp.------67

Family ACTINOSTROMATIDAE------70 Genus GERHONOSTROMA------70 ? Gerronostroma juvene n. sp.------70

Family STBOMATOFORIDAE ------75 Genus STROMATOFORA ------76 stromatopora baffinensis n. sp. ------76 Stromatopora aspectabilis Yavorsky------81 Stromatopora sp. A. ------85 Stromatopora baillargensis n. sp.-~------87

Genus ACTINODICTYON ------89 Actinodictyon crispatum n. sp.------89 Page

ILLUSTRATIONS - Figures; Tables; Plates------95

REFERENCES CITED------96

APPENDIX - Index of fossil localities------103

PLATES------1

INTroDUCTION

SCOPE

This thesis is concerned with the taxonomy of a collection of

Stromatoporoidea from Baffin Island.

Fossils were collected from a great thickness of carbonate

strata found at Brodeur Peninsula, the northvTestern ti:p of the island.

A detailed review of the Ordovician and Silurian stratigra:phy of

northwestern Baffin Island is included.

A brief statement on the importance of stromato:poroids in

stratigraphie correlation is gi ven.

The :problems of collection, preservation and :preparation of thin

sections of stromatoporoids are mentioned.

The general and systematic palaeontology of stromatoporoids is preceeded by a comparative study of their time-stratigrapbic relationship

to the rest of the fauna identified from the same strata. 2

AREA

The Geological Survey of Canada, "Operation Admiralty11 team, of which the writer was a member, mapped the area between, latitude 700 N and 74° N, and longitude 8oOW and 910W, on northwestern Baffin Island.

(~Fig. 1)

The party was landed at Arctic Bay in June 1963 by uotter11 air craft1 specially equipped with low pressure tires. Two helicopters and a small 11 Piper Cub 11 aircraft, with low pressure tires, vTere used in daily work. Two base camps were established in the map-area. The first, was located about 5 miles southeast of the Arctic Bay settlement and the

second1 at Jungersen Bay, at the head of Admiralty Inlet.

Topographically, northwestern Baffin Island is part of a dissected plateau (about 1800 feet above sea-level) called, the Jones-Lancaster

Plateau(Y. O. Fortie~ 1957). Castell ated cliffs whose summits rise

1000 to l8oO feet above the sea, have sufficient talus slopes to allow the geologist to do thorough sectioning.

From mid-June to July, daytime temperatures ranged between 30°-

50oF. The climate is dry. Ablation is high in the surmner months; only a few snowfields persist. A combination of extensive exposure, cool, dry climate and continued light makes the summer months in the Arctic very suitable for geological exploration. 2a

1---- ~

0 100 200 300 400

MILES

!Ui/i!/J ICE CAPS

Figure 1.

Geograph:ïl;atmap of the Arctic Islands showing location of map area. 3

ACKNOWLEDGEMENTS

I am indebted to Professer C. W. Stearn for his assistance and advice throughout this and ether studies at McGill University.

Special thanks are due to Dr. H. P. Trettin for suggesting this study for his encouragement and assistance in collecting some of the stromatoporoids described in this thesis and whose un published maps and stratigraphy have been used to complete this study.

I am indebted to Miss Regina Kouri for her patience in typing and for her help in preparing this manuscript.

I am grateful to the Palaeontology Division, Geological

Survey of Canada for making the specimens available, and also to the Ministère des Richesses Naturelles, ~êbec and National

Research Council, for supporting the writer during this research. 4

STRATIGRAPHY

PREVIOUS WORK

Only recently has the regional stratigraphy of the Archean,

Proterozoic and Paleozoic rocks been studied, but exploration for minerals began in 1906, when a Canadian Government Expedition (Bernier,

1909) traversed the 1ength of Admiralty Inlet.

R. R. H. Leman and R. G. Blackadar (1963) defined three groups in the vicinity of Admiralty Inlet. H. P. Trettin and the writer ex amined the h.ighest, Admiralty group, in 1963. Leman and Blackadar cal1ed the youngest limestone unit in the region the Bai.llarge formation.

It was said to be in excess of 460 feet in thickness. Fossils from the formation were assigned to the 'Arctic Ordovician fauna', by G. W.

Sinclair (~, Leman and Blackadar ibid, p. 72) (Stromatoporoids were not reported.) H. P. Trettin (~press) measured a complete section on the northeast coast of Brodeur Peninsula; the total thickness was about

1600 feet. The Baillarge formation was found to be succeeded through a transition zone, by limestones of the newly erected Cape Crauford formation. Trettin (op. cit.) defined the Brodeur group to include both formations. As the stromatoporoids studied for this report were all collected from the Brodeur group, only its stratigraphy is described in the following section. 5 TABLE OF FORMATIONS*

Group and Formation and approximate approximate System thickness thickness Lithology (feet) (feet) '

Quaternary Silts, gravels elavs Disconformity

Cape Crauford formation Limestone, follili- Middle ferous dolomitized Brodeur 1341 lime stone dolomite Silurian group ~2940 Baillarge Lime stone, fossili- Late Middle formation ferous dolomitic Ordovician + 1600 limestone,shale Disconformi ty (1) in northwest Borden Peninsula; conformi ty ( 1) at Baillarge Bay Ship Point formati-on Flaggy dolomite, 920 fossiliferous Middle and Admiralty Turner Cliffs Sandstone, Middle- formation siltstone, Upper group .±350 mudstone Ordovician +1870 Gallery formation Sandstone +6oo

Slight angular unconformity

Gabbroic dykes; divided Proterozoic and/or Early Cambrian and Archaean.

* revised by A. A. Petryk 6

OROOVICIAN AND SIWRIAN ST.RATIGRAPHY OF NW BAFFIN ISLAND

DESCRIPI'ION OF FORMATIONS

Brodeur group

The Brodeur group bas been proposed by Trettin to include the

Baillarge formation and the newly erected Cape Crauford formation.

This followed the revision of the Baillarge formation and the dis covery of a younger unit, the Cape Crauford formation. A. W. Norris

(1963) had assigned this youngest unit to the Read Bay formation; the Cape Crauford formation is now believed to be stratigraphically lower than the Read Bay formation; details are on p. 26.

Baillarge Formation

General.-- The uppermost division of the Adrniralty Group, was defined by Lemon and Blackadar (1963, p. 70) from exposures near Baillarge Bay on the east coast of Admiralty Inlet. Although the nature of its top or bottom was not definitely known, the Baillarge formation was believed to be more than 460 feet thick. Trettin found a well exposed complete section of limestones, about 16 miles south, southwest of Cape Crauford on the western coast of Admiralty Inlet. At this reference section the 7

top of the Baillarge formation (~ loc. D, Fig. 2) was set at the first significant and mapable change in lithology which is a sequence of thinly stratified calcareous dolomitic and microcrystalline lime stones. When Trettin traced the formation around the northern coast of Brodeur Peninsula, he found that it included most of the strata assigned by A. W. Norris (1963) to the lower limestone unit of the Read

Bay Formation.

Distribution.-- Outcrops of the Baillarge formation are found in 3 parts of the map-area: in scattered areas of northwestern Borden

Peninsula, in a belt extending from Cape Crauford to Agu Bay and south of the head of Milne Inlet. (see Fig. 2)

Lithology.-- At the reference section, the Baillarge formation is about 1600 feet thick. Two members A and B are defined. The lower 277 feet of the type section are equivalent to member A (~Table 2).

Member A.-- Everywhere, seree from member A, covers the contact between the Baillarge and underlying Ship Point formations. The member thickens rapidly westward from the reference section and thins progres sively southeastward in the central map area to less than 50 feet thick in places.

The lower 335 feet is dark blue-grey in colour and contains thinly interbedded shale, dolomite and limestone. The shale is medium to dark grey, partly silty, dolomitic or calcareous and thinly lami nated or bedded. The limestone is medium light grey, microcrystalline 8

to cryptocrystalline, partly argillaceous, thinly laminated to thin

bedded and partly carbonaceous. Desiccation breccias are rairly cam

mon. The dolomite is pale yellowish grey to pale olive, partly cal

careous, microcrystalline and thinly lamina.ted. Low-angle cross

laminations and desiccation breccias are common. The calcite-dolomite

ratio changes vertically, but is constant within the lamina.e. Rhythmic

sequences or dolomite and limestone, several millimeters in thickness

have been recognized by Trettin. As the proportion of dolomite in

creases the proportion of microcrystalline limestone and bituminous

matter decreases. The upper surface of the rhythmic sequence is sharp

and shows signs of erosion. Silt-sized detrital mineral grains con

sist of quartz and feldspar, including some plagioclase, but are present

in trace quantities only.

The upper 126 feet is more resistant than the lower part of

member A, but less so than the overlying member B. Four yellow, lami

nated to very thick-bedded medium crystalline to predominantly micro

crystalline dolomite ledges are separated by darker coloured, reces

sive in tervals of shaly carbonates. 11 Ghost 11 fossil and breccia tex

tures reveal replacement processes. Only traces of carbonaceous matter occur in the dolomite.

Member B.-- At the reference section this member is about 1200

feet thick. It is characterized by very light grey-brown, resistant

steep cliffs of massive dolomitic limestone, separated by a few reces- 9

sive intervals of thin bedded argillaceous dolomitic limestone. Bed ding, except in the argillaceous dolomites, is vague. Numerous light yellowish coloured stringers and tubes eut the rock. Some are rich in dolomite others are devoid of this mineral. If broken, the rock omits a strong fetid odour. Fossils are abundant in some beds, rare in ethers. The lower 350 feet contains the Arctic Ordovician fauna.

The upper 470 feet is rich in brachiopods, corals and stromatoporoids.

Echinoderm columnals occur throughout the section. Most fossils are broken and seem to have been transported. In the upper levels of member B, brachiopod co~uinas, isolated stromatoporoids and corals appear to be virtually, in place. Intraclasts (Folk, 1959) measuring less than about 2 millimeters, maximum length, are rare. Fecal ( ?) pellets are very rare. The matrix is mainly anhedral cryptocrystalline calcite with scattered patches of stromatactis and clear secondary cal cite (Folk, 1962, p. 69). The percentage of dolomite is generally small, however, some areas contain more than 6o~. Inclusions are cam mon in euhedral zoned dolomite crystals. The dolomite crystals average a few tens of microns in diameter and form stringers parallel to bedding or patches or pervade the whole rock. A solution breccia occurs 783 feet above the base of the member.

At the composite reference section (loc. D, Fig. 2 and loc. Fs3,

Fs4, F-lg. 4), the following sub-units exist: 10

Feet above base of member

790-ll35 Generally resistant, but the upper 15 :feet are (345) recessive; sparsely to richly :fossili:ferous; the intervals 790-845 and 873-890 are very rich in brachiopods; colonial corals and stromatoporoids occur throughout the section; several extensively dolomitized units, lighter in colour and more re cessive in profile than the other beds, occur in the interval 845-945.

783-'790 Brecciated laminae of yellowish brown microcrysta.l line limestone interlaminated with clear, seconda.ry calcite; overlain by wavy beds; resembles solution breccias of Cape Crau:ford Formation.

6ll-783 Alternations of resistant and recessive units pro (172) ducing a step-like profile; interval 663-745 richly fossiliferous with eup corals, stromatoporoids, etc.; most fossils seem to be transported; recessive inter vals at 648-655 and 778-783 feet.

566-611 Recessive unit forming ledges and plateaux, argil (45) laceous, thin-bedded, partly covered; at 596-6ol some lamina.ted very :finely microcrystalline, cal careous dolomite.

349-566 Generally resistant but with a minor recessive (217) interval at 361-371; sparsely fossiliferous, mostly 'Wi th echinoderm columnals.

284-349 Recessive unit forming ledges or plateaux; weathering (65) with a light greenish hue; argillaceous, thin- to very thin-bedded; bedding planes show small undulations; rich Arctic Ordovician :fauna.

0-284 Resistant unit; sparsely fossiliferous with Arctic (284) Ordovician fauna; light grey weathering beds, a few feet thick, with the bases at 23 and 43 :feet.

(After Trettin, ~ press) 11

LEGEND

Brodeur Gp. undlfferent.

Cape Crouford Fm.

\ - Boillorge fm ; i B Boollorge Fm. and Ship Point fm. undifferentioted

•A Locolity

·..... ·.._ -.

PENIN S.

1! c

0 50 Scole of Miles

Figure 2. Geological ma.p sho'Wing localities on northwestern Baffin Island. 12

Contacts.-- The Baillarge formation overlies the Ship Point formation with an abrupt, structurally conformable contact which appears to re present a disconformity in the northwestern region of Brodeur Peninsula.

Trettin claims that there is evidence of considerable erosion prior to the deposition of the Baillarge formation. At this time the western part of the area was submerged and recei ving lagooned sediments. The contact is placed at the first thinly stratified calcareous dolomitic and microcrystalline limestone, which lies generally less than 20 feet below a sequence of solution breccias.

Origin.- The rythmic sequences of dolomite-limestone and carbonaceous matter characteristic of the lower beds of member A, the desiccation breccias, the absence of sandy and argillaceous beds, the extremely fine laminations and the authigenic pyrite, suggest that the sediments were deposited in a lagoonal environment. Periodic inflow of sea water was followed by evaporation, precipitation of calcium carbonate and an in creasing rate of penecontemporaneous replacement by dolomite as the chemical composition of the water changed. Replacement by magnesium rich solutions probably took place before any great thickness of se diment was deposited.

Measured sections show that member A is thickest in the western parts of the are a and thinner in the eastern and central parts. Whether this reflects different rates of subsidence or indicates that the cen tral and eastern parts were emergent at the beginning of Baillarge 13

time is unknown.

Characteristics of member B indicate a marked change in depth and composition of the sea water. The map area was completely sub merged at this time. Abundant fossil coquinas, in situ corals and stromatoporoids, the scarcity of laminated dolomite and authigenic pyrite indicate normal salinities, relatively deeper and unrestricted waters. Trettin (in press) states that the scarcity of secondary calcite and the absence of oolites show that the basin of deposition was protected from vigourous waves and currents, perhaps by reefs, banks, shoals, or a wide shallow shelf.

The size of the calcite crystals is generally greater in member A than member B. The reason for this is unknown. Dolomi tiza tion seems to have been preferentially guided along bedding plane partings, worm tubes and other fissures. Replacement patterns are irregular in these strata and are in sharp contrast to the fine laminated penecontemporaneous dolomitization of member A. The source of dolomitizing solutions is unknown.

Correlation and Age.-- Although fossils have not been collected from member A of the Baillarge formation, the stratigraphie position of this member, above early Middle Ordovician rocks and below beds con taining the Arctic Ordovician fauna, agrees wi th a late Middle

Ordovician assignment. Member A is believed to be equivalent to the middle part of the Cornwallis formation which is tentati vely, regarded 14

as Mîddle Ordovician. (Thorsteinsson, 1963, p. 33). The overlying

350 feet of member B of the Baillarge formation contains the Arctic

Ordovician fauna and is probably correlative with the upper part of the Cornwallis formation. The interval 284'-349', characterized by a greenish weathering shaly limestone, is rich in the Arctic Ordovician fauna. G. W. Sinclair considers that Receptaculites sp., Catenipora sp., and Maclurites cf. M. manitobensis (Whiteaves) are representative of the Red River fauna, but that the fauna from GSC No. 58915, interval

750'-780', reference section of Baillarge formation, 'is early Upper

Ordovician and slightly older.'

The upper 500 feet of the Baillarge formation contain Silurian fossils characteristic of the "Shelly facies" of the Allen Bay formation, in the type section on Cornwallis Island, which is Upper Ordovician

(Ashgillian) and, in part, Middle Silurian (Ashgillian to Wenlock)

(Thorsteinsson, 1958, pp. 42-57). A. W. Norris (1963) referred the same sections on western Brodeur Peninsula to the Read Bay formation which is late Wenlockian and Ludlovian in age ( Thorsteinsson, 1958, pp. 47-74). This age assignment was based upon poorly preserved

Atrypella (?). The fossil was not found in the 1963, Operation

Admiralty collections and T. E. Bolton now doubts its presence.

(~Table I, p.30 for the identifications).

Bolton has equated the upper part of member B of the Baillarge formation with two distinct faunal assemblages - 1) Streptelasma 15

kukense - Brachyprion (1) aff. ~· robustum- Favosites cf. !· favosus and 2) Rhipidium sp. A similar assemblage to the first was described from Southampton Island by Teichert (1937) and in Operation Franklin colections from Brodeur Peninsula, (Norris 1963a). The Rhipidium sp. differs from the form described from Duke of York Bay, Southampton

Island. Rhipidium sp. has greater affinities with Conchidium arcticum, from northwest Devon Island (Holtedahl, 1914).

The upper part of the Baillarge formation (and most of the

Cape Crauford formation) is correlated with the Niagaran of North

America, pre-Ludlovian of Europe and pre-Atrypella equivalents of the Read Bay formation.

Early Silurian faunas have not been recognized in northwestern Baffin Island, in Foxe Bas$in or on Southampton Island;

Arctic Ordovician and Niagaran faunas are present (Teichert, 1937;

Burns, 1952).Trettin (~ gress) states that there is no evidence that a hiatus e.xists beneath the Niagaran in the present area. He also suggests that some of the fossils that are elsewhere characteristic of the Niagaran in the present area, range into the Early

Silurian (Albion or early IJ.andoverian). The ranges of Ecclima- dictyon fastigiatum, and Ecclimadictyon microvesiculosum suggest that faunal zone II* ma;yrbe partly Upper IJ.andoverian (lower Niagaran).

* The faunal "zones11 have been established by Trettin and not by Geological Survey of Canada palaeontologists. 16

There is no evidence in the stromatoporoids identified from this faunal zone that i t extends into the early Llandoverian. Stroma toporoids in faunal zone III indicate an early Niagaran age, (~ p. 2.1 for details) •

Cape Crauford Formation

General.- The Cape Crauford formation is the youngest formation in the area. It lies conformably on the Baillarge formation and is overlain, unconformably by q;uaternary unconsolida.ted sediments. The formation is named after Cape Crauford, the northeastern point of

Brodeur Peninsula, discovered by W. E. Parry, in 1820, (Parry, 1821, p. 267). The following rock types are arra.nged in order of abundance; fossiliferous cryptocrystalline, part1y do1omitized 1imestone; vaguely bedded, microcrysta1line dolomite; thinly interstratified microcrystalline limestone and dolomite; and widespread stratified breccias formed in the latter two rock types by solution of originally inter lwninated evaporites.

Distribution.- The formation underlies the central and western parts of Brodeur Peninsula and the unnamed peninsula south of Bernier Bay

(~ Figs. 2 and 4).

Lithologx.-- The composite reference section is about 7,000 feet south and 9,000 feet northwest of Cape Crauford. The formation is 17

1,341 feet thick and has been subdivided by Trettin into 3 members,

A, B, and C which are composed of 3 or less genetic assemblages in

varying proportions. In member B, the original mineralogy and tex

ture has been partly obliterated by secondary dolomitization.

Member A.- This basal member is the most widely distributed unit

of the Cape Crauford formation and is exposed in the central and western parts of Brodeur Peninsula and of the unnamed peninsula

south of Bernier Bay. At the composite type section, the member is

about 616 feet thick. Isopachs based upon 3 sections, (loc. A, B

and C see Fig. 3) suggest a thinning to the Southwest.

Assemblage . - l

Assemblage 1 is similar to the fossiliferous massive dolomitic

lime stone and calcareous dolomite of the Baillarge formation. When broken the rock emits a strong fetid odour. Brachiopods, corals,

stromatoporoids, gastropods, bryozoans and ostracods are present in most beds, however, they are generally broken and less abundant than

in the upper part of the Baillarge formation. Intraclasts and pellets

seem to be more common than in the Baillarge formation and range in

size from about l cm. to about 1 mm., and are similar in colour, com position and texture to the matrix. The pellets are rounded and rich in carbonaceous matter. They differ from the intraclasts in their uniformity in size, in their shape, and in having diameters generally less than 0.2 mm. (Folk, 1962, pp. 64). Dark-grey cherty lenses, 18

argillaceous material and silts are scattered on the beds. Greyish yellow to very pale orange dolomite occurs in stringers, tubes and

irregular patches or pervades the whole rock. Dolomite may be present

in any proportion. In this section, dolomite occurs as euhedral crys tals which range in size from about 15 to lOO microns. Inclusions and zonation are cammon in the crystals.

Assemblage - 2

Assemblage 2 consists of thinly interstratified limestone, dolomitic limestone and calcareous dolomite. As in assemblage 1, a strong fetid odour is emi ted when the rocks are broken. The pale to dark-yellowish brown, finely laminated to thin bedded limestones are least resistant and occur as re ces sive intervals. T'ne only organic remains are fecal ( 'l) pellets and stromatoli tic algal ( 'l) structures.

Carbonaceous matter is concentrated in the stromatolites which en crust aggregates of microcrystalline, partly pelletal limestone.

The encrustations form pisolitic stromatolites (Donaldson, 1963) oncolites or discrete hemispheroids (Logan, Ginsburg and Rezak, 1964).

They vary in size, shape and are commonly multiple and partly a.braided. The limestone is composed of anhedral to subhedral, sub sequent calcite crystals which range in size from a few to lOO microns.

The dolomite is pale orange to pale yellowish brown, calcareous, microcrystalline, very finely laminated to thinly bedded. Dolomite crystals range from a few to about lOO microns in size; they are 19

mostly euhedral, contain inclusions and are often partly zoned.

Minute low angle, cross-laminations are found in some limestone and dolomite strata.

Assemblage - 3

Assemblage 3 is dominated by widely distributed, irregu.larly

stratified, ledge forming breccias with miner undulating beds of thinly interstratified, crenulated limestone, dolomitic limestone and cal careous dolomite typical of assemblage 2. The breccia zones range from a few feet to more than lOO feet in thickness. At Sargent Point about lOO feet of brecciated limestone caps the cliff section. Some units are very extensive and have been traced about 80 miles around the coast of Brodeur Peninsula. Individual fragments range from a fraction of a millimeter to about 2 feet in length; they are flat, sub-equant or rounded. The fragments are apparently, of similar composition and show little displacement one to another; they are welded together by clear secondary calcite or set in a matrix of microcrystalline cal cite and dolomite. The breccias are highly vuggy. Interstices carry bitwninous matter and traces of malachite. Viewed from a distance, the fairly resistant breccia ledges appear as shallow folds not more than 10 feet high. The intervening strata of assemblage 1 appear to be undisturbed. wcally, the folds are distrubed by steeply dipping fractures and faults. Breccias in the fractures contain fragments from all three assemblages; some show mud flow characteristics. 20

These local breccias are believed to be tectonic. The jointing pat tern in the breccias probably controls the formation of such weather ing remnants as stacks and pinnacles.

Figure 3 shows the distribution of the 3 assemblages, in 3 sections of member A, measured on the northeastern most coast of

Brodeur Peninsula. In a section from A to C there is aslight increase in the proportion of assemblages 1 and 3 at the expense of assemblage 2.

Member B.- Member B is found only in northwestern Brodeur

Peninsula. Here it forma the upper part of a prominent plateau. At the type section at Cape Crauford it is about 300 feet thick. In the field member B is a relatively light coloured recessive interval between 2 massive dark brown limestone ledges of members A and C. The member is mostly dolomite with minor limestone and stratified breccia. Secondary dolomitization has largely obliterated primary structures and textures.

Member B probably contained the 3 genetic assemblages which were des cribed in member A. The most common lithology is medium to pre dominantly microcrystalline dolomite which is slightly calcareous, poorly bedded and vuggy. Relict foss:ils, mainly echinoderms and breccia textures, occur in places. Only the fossil, Favosites was collected from this member. Dolomi tization is common in all three assemblages but is least so in assemblage 2.

Approximately the lower 50 feet of this member contains thinly interstratified microcrystalline limestone and dolomite of assemblage 2. li

FEET A LEGE ND ~ Asse-mbloo.e 1 600 ŒilJ]J] Assemblaqe 2 c:::= Assemblage 3 500 Tel'ltottve lsopoch

0 30 MILES

500

400 ------300 -

200 - -

100

FIGURE 3. - COI..UMNAR SECTIONS .f MEMBER-A-CAPE CRAUFORO FORMATION 22

Breccias occur in the lower 145 feet of the member and in the 232-

259 foot interval above its base.

Insoluble residues of silt, mainly quartz and sa:me K- felds:par, albite and white mica and a little clay amount to generally, less than 3% in the intervals 168-177, 232-259, 264-265, and 300-317 feet above the base of member B. The beds between 220-222, contain microcrystalline authigenic pyrite and its alteration products. (Trettin, in ;press) •

Member C.-- This member is preserved only on the northernmost

Brodeur Peninsula. At Cape Crauford it is about 365 feet thick. It is more resistant and in part darker than member B. The base of C is placed at the first fossiliferous limestone ledge overlying several hundred feet of more recessive dolomite. This unit is capped uncon- for.mably by unconsolidated Pleistocene and Recent deposits.

Member C contains lithologies common to member A, but shows greater dolomi tiza.tion. A summary of the lithologies at the type section follows:

Foot above base of member

240-295 MOstly assemblage 2 with sorne 3; the upper part is (55) slightly silty.

27-24o Assemblages 1, 2 and 3; 1 is highly dolomitized. (193)

0-27 Assemblages 1 and 3; individual units a few feet (27) thick; assemblage l contains poorly preserved stroma to:poroids, colonial corals, brachio:pods and is more highly dolomitized than in member A. 23

Contacts.-- The Cape Crauford formation conformably overlies the

Baillarge formation, the contact being placed 1600 feet above the base of the composite reference section. The contact is arbitrarily placed at the base of the lowest beds of assemblage 2 which occur about 20 feet below as sequence of solution breccias. The upper contact is a

Pleistocene to Recent erosion surface overlain by unconsolidated

~aternary deposi ts.

Origin.-- The three type assemblages are found in all three members of the formation. Each assemblage representa a distinctive environment,

(Trettin, in press).

Origin of Assemblage - 1

This lithology is similar to the predominant rock-type of member B of the Baillarge formation and probably originated under similar conditions. The predominance of cryptocrystalline calcite matrix indicates that the environment was sheltered from vigo...,rous waves and currents. (Folk, 1962, p. 69). The intraclasts represent largely muds that were exposed and desiccated at periods of low tides.

Although many fossils are broken and show signs of transportation probably from shelfward banks or reefs, some, like the very delicate fenest e llid . bryozoa, are preserved almost whole and chie:t'ly, in place. Dolomi tization is clearly secondary and may have resulted from the downward seepage of brines from overlying lagoons represented by assemblages 2 and 3, (De:t'feyes, Lucia and Weyl, 1964). 24

Origin of Assemblage 2

The process of dolomitization differed in this environment.

Trettin explains that the fine laminations of dolomite found inter laminated with limestones are due to replacement at the sea water-sediment interface. The homogeneity, fine layering, unifor.m crystal size and cal cite - dolomite ratio wi thin each lamina strongly favours this view.

An opposing interpretation would be that certain beds of the originally layered limestone were selectively replaced. No support is offered for this hypothesis. Except for possible fecal pellets (Purdy, 1963, pp.

342) (Folk, 1962, p. 64) and algal coatings fossils are absent. All the features suggest that the limestone of assemblage 2 is a chemical precipitate. The crystal size of the fossiliferous limestone of member

B of the Baillarge formation and of assemblage 1 of the Cape Crauford formation, is less than 4 microns, whereas, the crystals of member A of the Baillarge formation and of assemblage 2 of the Cape Crauford formation are larger. The relatively high concentration and wide dissemination of carbonaceous matter found in the cryptocrystalline limestones may have retarded crystal growth. The carbonaceous matter may be the decay product of inswept and local planktonic organisms and in situ, algal matting.

Origin of Assemblage 3

As noted above, this assemblage is characterized by numerous breccia units. R. Thorsteinsson (1958, p. 38) noted similar breccias 25

in the Cornwallis formation over the center of Cornwallis Island.

Here the strata areaf limited areal extent and form lenticular bodies.

Some brecciaed zones grade laterally into masses of gypsum. The position of the breccias was probably occupied earlier by evaporites.

A. W. Norris (1963) explained the breccias on the west coast of

Brodeur Peninsula on the basis of the solution of inferred, inter- calations of evaporites with carbonates. Trettin, found additional evidence to support the solution hypothesis. He noted that certain larninated strata of assemblage 2 and 3 of member A showed solution casts of bladed gypsum. (For additional discussion the reader is referred to Trettin; ~press). Evaporites probably made up less than

10of; of the type section of member A. The pseudomorphs of calcite after gypsum and the presence of small undulatory algal stramatolites

of in assemblage 3, indicate an environmentAvery shallow protected waters

(Logan, Ginsburg and Rezak, 1964). Reef banks or ahoals are believed to l1ave extended seaward, that is, to the north or northeast of the present area. In~flow, outflow and evaporation was controlled by these barriers.

Correlation and Age.-- The lower 996 feet of the Cape Crauford formation contain Silurian fossils characteristic of the Allen Bay formation which, in the type section on Cornwallis Island, ranges from Late

Ordovician to Middle Silurian (Asgillian to Wenlockian ) - ( Thorsteinsson,

1958, pp. 42-47). 26

No distinctly late, Late Ordovician and Early Silurian (Albion) faunas have been identified in the Brodeur group.* Only 290 feet of strata seem to represent this range in age at the reference section near Cape Crauford. Why this unit is so thin compared to the 1500 feet or more of strata presumed to be Middle Silurian in age, is not understood. There is no evidence to support slow sedimention in the Late

Ordovician and Early Silurian or a hiatus may exist.

As Atrypella (~) (Norris, 1963 p. 152) is now believed not to exist in the Cape Crauford formation, (~p. 14) the Cape Crauford formation and the Baillarge formation are considered to be older than late

Wenlockian. Members A and B of the Cape Crauford formation are gi ven a Middle Silurian age. The upper unfossiliferous 344 feet of the Cape

Crauford formation may include strata correlative with the base of

Read Bay formation, (Wenlockian to early and middle I.udlovian) on the east-central coast of Cornwallis Island (Thorsteinsson, 1963, p. 48)

(Trettin ~press).

* Faunal zone II (see p. n ) is below a collection with Reticularia('l) undulata Poulsen whlchba.s been described (Poulsen, 1934) from the Cape Schuchert formation of northwestern Greenland. This formation is Middle lJ.andoverian on the basis of Monograptus convolutus ( Poulsen, 1934) • These facts suggest that faunal zone II is partly early Silurian ( early lJ.andoverian or Albion) in age. 27

A COMPARISON OF THE TIME-STRATIGRAPHIC REIATIONSHIPS

OF THE STROMATOR>ROIDS AND THE ASSOCIATED FAUNAS IN THE BRODEUR GROUP

The stromatoporoids from northwestern Baffin Island, have stratigraphie ages similar to the associated faunas (brachiopods, cephalopods, corals, etc.) identified by T. E. Bolton, palaeontologist, at the Geological Survey of Canada. Clathrodictyon Linnarsonni

Nicholson, and Ecclimadictyon microvesiculosum (Riabinin), are found lowest in the Brodeur group. The former species is found in the

Wenlock limestone, Visby, Gotland, (Sweden) and the latter species is found throughout the Llandoverian in the Estonian SSR. Both species occur in, faunal zone II, of the Baillarge formation, which Bolton considera as probably Niagaran. f. Linnarsonni occurs throughout faunal zone II and near the top of faunal zone III. Ecclimadictyon fasti giatum (Nicholson and Murie) which occurs only in faunal zone III, ranges from Upper L.landoverian to Wenlockian. The fact that f.

Linnarsonni occurs in faunal zone II and III, (about 218 feet of strata separate these zones) suggests that no hiatus exists between these zones. The ranges of E. fastigiatum and !· microvesiculosum 28

suggest that faunal zone II may be Upper Llandoverian (lower Niagaran).

There is no evidence to show that faunal zone II extends into the early Llandoverian, as Trettin suggests, (see, p. 15).

Considerable diversification of species occurred during Baillarge time. All the genera mentioned in this thesis except, Actinodictyon are found in the Baillarge formation, faunal zone III. ~ne new species,

2..:.. miniapse, ranges throughout faunal zone III. Again, Q. Linnarsonni, and !!· fastigiatum indicate that faunal zone III is probably early

Niagaran. Trettin (~ press) has correlated most of the Baillarge formation ( faunal zone III) wi th the Cape Schuchert formation on northwestern Greenland. The formation is Middle Llandoverian or early

Niagaran on the oasis of Monog_raptus convolutus (Poulsen, 1934).

The marine conditions during Cape Crauford time must have been considerably different from those in the Baillarge seas for the stromatoporoid species are different. All are new species except,

Stromatopora aspectabilis Yavorsky (l96l)* which was collected from the highest stratum, (faunal zone IVe) in the Cape Crauford formation.

The genu~ Actinodictyon occurs only in the Cape Crauford formation.

* Unfortunately, the occurrence of the species given by Yavorsky is simply, Silurian. 29

The stromatoporoids in the Cape Crauford formation are insufficient to give any specifie age assignment. The Cape Crauford formation is considered to be Niagaran, pre-late Wenlockian, on the basis of the absence of Atrypella, (Trettin, ~press).

The distribution, number, stratigraphie position of the

tramatoporoids species described in this dissertation are set in

Tables 2, p.34, and 3, p.35. The lithology and biostratigraphy of the Brodeur group is included in Table I. 30

TABLE I: LITHOIDGY AND BIOSTRATIGRAPHY OF THE BRODEUR GROUP (Tb accompany Figs. 2, 3 and 4)

LI.THOIDGY

1: fossiliferous cryptocrystalline limestone 2: thinly interstratified microcrystalline limestone and dolomite 3: strata of type 2 brecciated by solution of evaporites and associated undulatory stromatolites sh: shale, shaly impurities st; silty impurities d: cross-cutting and thickly stratified dolomite

Note: The lithology column in Table Z shows rock types expressed on a percentage basis.*

BIOSTRATIGRAPHY

Faunal zone IVe (1 coll., loc. A): Stromatopora baffinensis n. sp.,

Stromatopora aspectabilis Yavorsky, Streptelasma kukense Teichert,

Favosites cf. ,!. favosus (Goldfuss) from Stanley Point (Teichert, 1937, pp. 129), Halysites, sp., Porpites aff. !• michiganensis (Bassler), orthoconi tic cephalopod.

Faunal zone IVb (1 coll., loc. B): Favosites cf.,!. favosus (Goldfuss).

Faunal zone IVa (8 coll. at loc. B, 3 coll. at loc. C): Clathrodictyon

* After Trettin (in press); stramatoporoid identifications have been added by the author. 31

lenticulare n. sp., Stromatopora sp. A, Actinodictyon crispatum n. sp.,

Streptelasma kukense Teichert, Favosites cf. F. favosus (Goldfuss)

from Stanley Point, eystiha1ysites sp., Catenipora sp., Brachyprion

aff. ~· robustum Twenhofel, StegerhlOchus {7) sp., strophomenid brachio pod, Clarinda (7) sp. or Glassia (?) sp., Pterinea sp., Holopea, sp.,

Horrootoma sp., Leperditia sp.

Comments re faunal zone IV: Niagaran, ;pre-late Wenlockian, on the basis of absence of Atrypella.

F"i,P'lal zone III (2 coll. at loc. D, 3 coll. near loc. A): Clathrodic tyon vajgatschense Yavorsky, Clathrodictyon miniapse n. sp., Clathro dictyon Linnarsonni Nicholson, Eccl:imad.ictyon fastitÉ-atum (Nicholson and Murie), Intexodictyon brodeurense n. sp., 1 Gerronostroma juvene n. sp., stromatopora baillargensis n. sp., Favosites sp. same sp. as in zone II, "Ftychop!Vllum" or "~" sp., Rhipidium sp. same sp. as in zone II, strophomenid brachiopod, "Reticularia ( î) 11 undulata Poulsen,

Clarinda (?) s;p., Leperditia sp.

Comments: "Reticularia { 'l) 11 undulata was described by Poulsen from the Cape Schuchert Fm. on NW Greenland. The formation is Middle

IJ.andoverian or early Niagaran on the basis of Monogra;ptus convolutus

(Poulsen, 1934). 32

Faunal zone II (8 coll., loc. D): Clathrodictyon Linnarsonni Nicholson,

Ecclimadictyon microvesiculosum ( Riabinin), Ecclimadictyon sp. A,

Favosites sp. same sp. as in zone III, Palaeofavosites sp., Vacuopora

11 n.sp., n Ptychophyllum" or "Naos sp., Rhipidium sp. close to Conchi

~ arcticum from NW Devon Island (Holtedahl, 1914), Brachyprion cf.

~· philomela Billings of Southampton Island (Teichert, 1937, p. 139),

Homortoma sp. sorne with large whorls.

Comments: Faunal zone II shares several elements with III and is considered by Bolton as probably Niagaran. The position of this zone, however, below nReticularia ( 'l) 11 undulata suggests that i t may extend into the early Llandoverian.

Faunal zone Ic (1 coll., loc. D): Receptaculites cf.~. arcticus

Etheridge, Streptelasma sp., Grewingk.ia. sp., Calapoecia sp., Plasmo

~ora cf'. P. lambei Schuchert, Catenipora sp., crinoid fragments incl. sg_uare columnals, Arthroclema. cf. !:_. arma.ta Ulrich, Helo;pora sp.,

Rhinidictya sp., Austinella sp., Le;pta.ena s;p., Tri;plesia sp.,

Beloitoceras s;p., illaenid trilobite, Ceraurus (ï) s;p., cf. Lepidoco-

~sp.

Comments: Arctic Ordovician fauna., ea.rly Late Ordovician and slightly older. 33

Faunal zone Ib (l coll., loc. F): Receptaculites sp., Catenipora sp.,

Ma.cluri tes cf. _!':!. mani tobensis (Whi teaves)

Comments: Arctic Ordovician fauna, Red Ri ver representative.

Faunal zone Ia (I coll., about 2 mi. SW of loc. D): Catenipora sp.,

Calapoecia cf. Q. canadensis Billlngs, Plasmopora sp., Batostoma sp.

Comments: Arctic Ordovician fauna.

Identification and correlation of Faunal zone I: G. W. Sinclair, Faunal zones II, III and IV: T. E. Bolton. 34

FEET STOOMATORlOOIDS FA UNA AGE LITHOLOGY FORM. l -2800 Middle Si lu rion st '1 and/or younoer Id ' 2d 3d i ~-2600 ~romatopora oaffinensis n. s~. Ne IStromatopora aspectabilis Yavorsky '1, 0 - J Ct: 0 d LI.. -2400 : J :::> <( 1 i i Ct: Nb 2~ (.) (l)d 2 IJJ -2200 a. <( (.)

1 Middle Silurien -2000 (Nioooron) .. sp. ~Clathrodictyon lenticulare n. Id 2 3 1 f-- 1800 ~lathrodict~on lenticulare n, sp. ._ No

~ctinodictyon crisgatum n. sp, r-- IGqo ~atopora sp. A, / Clathrodictyon vajgatschense Yavorsky Clathrodictyon miniapse n, sp. m Ecclima.dictyon fastigiatum (Nicholson) Id

!- 1400 ua.~--tromatopora baillargense'"~· n. sp. 1 lathrodictyon Linnarsonni.. Nicholson"·

1 Middle and/or .J;cclima.dictyon fastigiatum (Nicholso

- 400 Id 2 sh

Lote Middle <( Ordovicien 1 - 200- 2 sh i l .. Table z. straœ.toporoids, f'aune.l zones, age and lithology of' the Brodeur group, 3S

,...... := ...... := Il .., ~ 0 ., • ..... •1< 8 >- ..... ~ 0 • ' 0 '-' > ..... < .r: 0 ...... g • u .. ~ • z < ci .. .:= ..... • "" .:= ::s Il •.:= "" .:= .:= Il u 1< Il c:i ...... , .r: ...... := ...... u .. Il Il ::s ~ .:= 1< > u ....• .. Il ::s 0 ..... 1< .:= Il < 1< .... ~ ..... < 'tl u .:= • .... 0 ..... Il ; .....â +' .... m 1< .. s ..... > 41 .., "" ~ ...l .., .:= ~.:= .:= .:= .:= .:= ~ ~ "' • ~ .:= .:= "" 1< s:l ~ ~ ~ ~ ~ ~ ~ ~ 0 ...... ~ ..... 1< ...... u u u u ..u u ...... Il 0 ...... u ..... 'tl 'tl 'tl 'tl 'tl 'tl ..... 5~ ., g ., 0 0 0 'tl 0 ::s 1< ; s 1< 1< 1< 0 ...lZ e 1< ~ ...... ] .r: .r: .r: 1< Il Il Il ...... r:.... {.) .... Cl .... u u u ., ., .:= .:= u u 0 ...... "' ..... ~ .... .,...... ll

58902 1000-20 x3 x2

58935 315 xl - 58905 57-207 xl 58928 170 1 xl 58945 1-50 ~3 ~p c~u OR F~. xl 1585-96 ~I ~I.A !teE FM xl x2 x2 x~ 58916 J -·--

58913 1 x2 x3 x4 58911 1575-85 xl l it]. ' 58918 1560-70 -- xl 58942 1550 .. ~- ---~ ~l 58912 1531 i 1 xl l '"Xl 58919 1470 IX 1 x2 Al --- -- xl 58917 1456 - -- f-- 58934 1426 i ~~ 1 xl 58936 1208 l 1 ! 58910 1179 -- !X2 58929 1176 Xl! 1 x3 , x3 58932 1 xl 1100-10 ·- t .f-- covered f l

* The number denotes the number of apecimens ~f a species collected at a particular interval and from which thin sections have been prepared.

TABLE 3. STRATIGRAPHie DISTRIBUTION OF STROMATOPOROIDS • e

~ 54ryent R:Mt

il CareCrauford 1

LEGENO

F'O~I'fArt""'S ~ CAPE CRAUFORD}8RODEUR GROUP BAIL LARGE

SHIP POINT

->'VW'A FAULT

---;. APPARENT DIP DIRECTION

--+--?- PLUNGE OF FOLO AXES

Figure ~.Geologicalmap showing fossil localities and sections on northwestern Brodeur PeninsuJa.

~ 37

Ma.p kev Section localitv GSC Nn Posi +.inn

Fl Tm-63-14c-F 58925 lower part member B

"'" ----

F2 B 58947 member A - ----· ~ 58915 member A and part F3 D 58929-34 ~f2 member B 58939-41 ~ -----

D2 58936 ~ upper part member B ~4 ~ Pl

Fs5* Tmp-63-27a-d 58918 upper part member B

'-·--- ' - ----

Fs6 Tm-63-18b 58942 upper part member B

upper part member Fs7 c A of columnar 58927-28 A section.p. 58946 li'= 0 ------' lower member B and Fs8 .H locality F 58902 12 upper member C § 58937 g 58903-07

Fs9 G B of columnar 58938 0~ lower member B and section. p. 58926 member A

0~ ------~--·---·· -

FslO R C of columnar 58943-45 part of member A section. p.

Table 4.General index to Map 4.of fossil localities and sections from northwestern Brodeur Peninsula.

*Fs denotes stromatoporoids present. 38

METHODS

Field Collecting.-- Palaeontologists have considered the Stroma

toporoidea as obscure organisms, systematically difficult to study

and understand. For this reason, they have been neglected in fossil

collecting. In the field, stromatoporoids may be confUsed with algal

structures, but with some training, discrimination is possible even

wi thout the aid of a hand lens.

Preservation.-- The preservation of both the gross structures and microstructures of most of the coenostea from the Brodeur Peninsula

is good. Penmineralization by calcite bearing solutions has com pletely infiltrated the coenostea, so that, no prima-~ porosity re mains. Dolomitization is locally present in the Brodeur group, but it has not significantly obliterated stromatoporoid structures. De-

structive recrystallization has occurred in the specimens collected

from weathered and leached zones.

Tne crystal boundries show no relationship to the tissue.

Crystals are large (50 to 300 microns) and their boundries cross the pillars and laminae indiscriminately. In places, the jagged contacts between the coarse crystals, roughly divide the galleries. Locally, in vertical sections, small intracrystalline movements have revealed close-set parallel cleavage planes. Where these cleavage planes pass 39

through the tissue, they give it the appearance of being transversely

porous.

The most poorly preserved specimens, those collected from re-

latively deep weathered zones, have been subjected to wlde temperature

changes which have strained the crystal mosaic. Minute fractures and

partings between crystal boundries have provided access for solutions

to leach and reprecipitate a fine calcite druse in galleries ~~d other

openings. The tissue is no longer distinct, but appears faded; only

11 ghosts 11 remain.

In most of the Brodeur Peninsula specimens, the epitissue and

endotissue* are distinguishable wi thin the same thin section. In

some sections where preservation is best, the epitissue masks the

endotissue. (Microreticulate tissue (Stearn, ~ Rress) completely masks endotissue). If the epitissue is poorly deve1oped or preserved,

specifie and generic assignment is complicated. Indeed, in species

with maculate or melanospheric tissue, (Stearn, ibid) the gross

* C. W. Stearn (~ Rress) has written at length about tissue types and preservation. He has substituted the term, 11 secondary tissue" (Ga11oway, 1957) by 11 c1othing or coating" tissue. Professer Stearn states that the adjective "secondary", carries the suggestion of tissue deposited by inorganic agencies after the organism was dead. The writer agrees with Professer Stearn, however, the writer has substituted the words, epitissue and endotissue, for 11primary" and nsecondary11 tissue, because they are c1ear and concise. The Shorter Oxford Eng1ish Dic tionary (1933, p. 2199) defines tissue (01d French, ~; Latin, texo, 4o

structure may appear entirely different in a specimen ~th a poorly preserved epitissue, from a specimen with a fully devéloped epitissue.

If carbonate muds are trapped within a coenosteum, the normal structural growth is unchanged. Solutions from the carbonate muds entombing a coenosteum have infiltrated some specimens. Only the margin of the coenosteum is changed to a golden-brown hue. The presence of microstylolites and compressed structural elements attest to this conclusion. Most often the structure remains intact, but the tissue is obliterated; tissue reversai (Stearn, ibid.) is uncarnmon.

Preparation of thin sections.- A vertical (radial) and tangential

(horizontal) thin section are required of each specimen. The first refers to sections which are parallel to the pillars and which eut the concentric laminae at right angles, and the second refers to sections which are parallel to the concentric laminae and eut whatever vertical structures are present.

weave), in the biological sense as 'the substance, structure or texture of which an animal or plant body or any part or organ of i t is com posed ••••• it may be an aggregate of similar cells'. ~ and endo- are the common Greek prefixes for upon and within, respectively. These words have been used in the Descriptive Palaeontology of this paper. PAI..AIDN'IDLOGY 41

IMroRT.ANCE OF STROMATOIDROIDS

Stramatoporoids are abundant fossils in the Ordovician, Silurian

and Devonian systems yet they have been least studied of any cammon

fossils in America. A great number of Silurian species have been de

scribed in the Soviet Union. (Yavorsky, 1929, 1931,1932, 1943, 1950,

1955, 1957, 1961, 1963) but studies of Si1urian stramatoporoids in

America have not been extensive1y studied; most work has been on stromatoporoids of Devonian age.

Stramatoporoids are gaining importance in time-stratigraphy.

Their nature and distribution in biostromes and bioherms of lower and iniddle Palaeozoic age make them important to petro1eum geo1ogists in search of petroleum in ancient organic reefs.

There is a prevalent, but inaccurate opinion that fossi1s of sessile organisms, because they are in situ, facies fossils, are of little value in correlation. J. St. Jean, Jr., (1960, p. 240) suggests that the microstructures in stromatoporoids are genetic characteris tics and appear to be little affected by environmental changes. If this is true, then intercontinental correlation is possible providing the microstructure of the stromatoporoids is tully understood. 42

GENERAL PALAEX)N'IOI.DGY

STROMA'IO:OOROIDEA

General definition

Stromatoporoidea are layered, calcareous, organic bodies composed of thin laminae, pillars and curved plates, occurring in marine deposi ts of Ordovician, Silurian and Devonian age. They fre quently occur in large beds and make organic reefs or bioherms. They occur in profusion in North America, Europe, Asia, Australia and

Morocco, but have not been reported from South America. (Ga.lloway,

1957 p. 345).

T,ypical stromatoporoids appeared in the Middle Ordovician; expansion and diversification occurred in the Silurian. They reached their acme in forms and numbers in the Devonian, at the end of which they became extinct.

The Stromatoporoidea have been assigned to many different groups by different authors. Lecompte (1951) has summarized the different views. Stromatoporoids have been assigned to the algae, foraminifera, porifera and hydrozoa. Since Carter's {1877, 1878) comparison of stromatoporoids with calcareous hydrozoa, all writers of the present century, except Parks (1935) and Twinchell, (1928-29), have recognized that stromatoporoids are an extinct order of

Hydrozoa, possibly the ancestors of Upper Paleozoic and Mesozoic order Sphaeractinoidea which evolved into the Uydrozoa of the

Cenozoic and Recent.

Ecological factors controlling stromatoporoid growth are mostly that of tropical to subtropical reefal conditions.

stromatoporoids are often associated with corals and algae. Stroma toporoids and calcareous algae were the principal agents in reef construction, however, they are also commonly found with normal marine invertebrates in interreefal beds. The lack of variety of reef organisms in ancient reefs may reflect the encrusting habit of many of the stromatoporoids and algae. The distribution of fossil stromatoporoids in reef cores and talus slopes indicate shallow, high energy, turbulent waters, conditions similar to those of present reefs.

Sorne of the stromatoporoids from Brodeur Peninsula are found tumbled with subhemispheroidal coral heads; others are irregular lenticular masses, measuring about 3 to 10 inches across, encrusting brachiopod co~uinas. Because most of the coenostea are whole and in place, the marine environment must have been ~uiet, protected from vigourous waves and currents, perhaps by a wide shallow shelf. (see p. l~)

H. A. Nicholson (1886 to 1892) in his great monograph, studied and classified the Stromatoporoids of Britain. W. A. Parks

(1907 to 1936) and Galloway and St. Jean (1955 to 1957) classified 44

many stromatoporoids from Canada and the United States.

Today, the works of Yavorsky (1955), Lecompte (1956)

and Galloway (1957) are best known. All three have proposed different

classifications. The writer follows Galloway's classification.

The microstructures of the tissues are important in

separating families and genera. Dr. c. w. Stearn (Microstructure of the StromatoKoroidea,~ press)* has reviewed the meaning of micro-

structures to different specialists. He has listed and defined 14 microstructures and gives their equivalent terms in German, Russian

and French. These definitions of tissue are used in the descriptive palaeontology of this dissertation.

* Stearns revised generic descriptions are used except, that of Ecclimadictyon, Nestor 1964, Intexodictyon Yavorsky, 1963, Actinodictyon Parks, 1909; the writer has amended the latter descriptions. SYSTEMATIC PALA.IDN'IDIDGY Fami1y CLATHRODICTYIDAE Kuhn, 1939

1939 Fami1y Clathrodictyonidae no. faro., Kuhn, p. 338. 1939 Familia Clathrodictyonidae Kuhn, p. A42. 1957 Fami1y C1athrodictyidae Kuhn, Galloway, p. 432.

Coenosteum laminar to massive, composed of cysts side by side in concentric layers, or of laminae, which are gener ally parallel, and short pillars. Gal1eries higher than the laminae are thick; foramina may occur between super posed galleries. Pillars normally present, confined between two laminae, but may be incidenta1ly superposed. Tissue compact, fibrous or tubulose, especially the primary laminae, the secondary tissue on the laminae and pil1ars either compact, finely fibrous or tubulose or containing vacuoles, not maculate. Astrorhizae present or absent.

Genus CLAT.HRODICTYON Nicholson and Murie, 1878

1878 Clathrodictyon Nicholson and Murie, p. 220. 1886 Clathrodictyon Nicholson, vol. 39, p. 77; vol. 42, p. 147 1887 C1athrodictyon Nicholson, p. 1. 1927 Clathrodictyon Twenhofel, p. 107. 1937 C1athrodictyon Ripper, p. 1. 19 39 Clathrod.i ctyon - Kuhn, p. A42. 1951 C1athrodictyon Lecompte (part), p. 129. 1955 Clathrodictyon Yavorsky, pp. 39-49 1957 Clathrodictyon Galloway, p. 433.

T,ype species: Q. vesiculosum Nicholson and Murie

Coenosteum composed of imperforate, con tinuous, 1aminae commonly undulant or crumpled and short pillars that are con fined to an interlaminar space. The pillars and laminae are a single uniform layer of compact, cammonly speckled, tissue. Where the laminae are bent the pillars extend from their downward in f1ections in cylindrical form. 46

Clathrodictyon lenticulare n. sp.

Pl. I, figs. 1, 2.

Three specimens of this species were collected from the Cape

Crauford formation on Brodeur Peninsula, sections c, H and G.

Exterior.-- The bulbous coenosteum is 9 cm. diameter and 6 to 9 cm. in height; the surface is smooth.

Vertical sections.-- The structure is characterized by a dense vesi cular network of irregularly space laminae and pillars and relatively large lens-like cysts.

Laminae are straight and continuous except where they appear to bulge over large lens-like galleries or where they are folded over trapped foreign matter; the cyst plates extend horizontally by im bricating with each ether; in ether areas they appear irregularly superposed suggesting that astrorhizae are responsible for their expansion. Laminae curve down over the lens-like cysts to join the laminae below. At high magnification the laminae are seen to be the result of cyst plates arranged side-by-side. There are 16 to 20 laminae in 2 mm. (average 17);they are 20 to 50 micronsthick, compact tissue.

Pillars are spool, cylindrical or conical in form. They are irregularly developed; most are perpendicular to the laminae, but many are oblique. Minuteness, variability in form and preservation make the pillars difficult to measure; 10 to 15 occur in 2 mm. and they are 20 to 50 microns thick. Pillar tissue is generally, less compact than that of the laminae.

Astrorhizal canals are very rarely seen in longitudinal section.

This suggests that the system of tubes is highly sinuous and that the predominant trend is parallel to concentric laminae.

Galleries vary in size and shape. The isometric form is com moner than the cystic form.

About 4o% of the section is occupied by gallery space.

Tangential sections.-- The concentric laminae appear as curved bands composed of dark dots of tissue which are the eut ends of pillars, in a relatively light background of tissue. These bands alternate with clear interlaminar zones which contain relatively smaller dots of tissue. The dots range from 50 to lOO microns in size. Where the section lies closest to the plane of the laminae the dots are densely packed about lOO microns apart.

The dendritic branches of the astrorhizal system radiate out from what appears like a tripartite or compound center of tubes. The tubes are oval in cross-section; they range from 200 to 300 microns, long diameter, lOO to 150 microns, short diameter and are comparable to the lens-shaped galleries seen in vertical sections. Apparently, the lens-shaped galleries are tangentially eut astrorhizal canals.

About 7 canals radiate from an astrorhizal center; the centers are about 4 mm. apart. 48

Discussion.-- This species is similar to Q. vesiculosum Nicholson and

Murie, 1878, except for the relatively wide lens-like galleries, which

reflect the oval shape of the astrorhizal canals, and straighter and more widely spaced laminae. The species is named Q. lenticulare be-

cause of the presence of the wide lens-like galleries.

Occurrence.-- Three specimens of this species were collected from

the Cape Crauford formation, faunal zone !Va; GSC Nos. 58928-1;

58905-1; 58935-2. The holotype is GSC No. 58905-1.

Clathrodictyon vajgatschense Yavorsky

Pl. I, figs. 3, 4.

1961 Clathrodictyon variolare Rosen var. vajgatschense Yavorsky, p. 27, pl. XIV, figs. 1-3.

This species is represented in the collections by four specimens from Brodeur Peninsula, locality Tmp-63-27a.

Exterior.- The bulbous coenosteum measures 8 to 10 cm. diameter and

5 to 8 cm. in height, measured from the center of the base to the highest point on the coenosteum. The surface is smooth to monticular.

About 6 latilaminations occur in 2 cm.

Vertical sections.-- The structure is characterized by vesicular galleries and regularly wavy laminae of different sizes and shapes. The center of each wave contains a small astrorhizal tube. Laminae are continuous but irregularly spaced. Closely and widely spaced laminar zones appear to alternate somewbat regularly.

This irregu.larity of laminar spacing reflects a varying ,·or inter rupted growth rate. The variable thickness of the laminae attest to this probability. There are fi ve latilaminations in 2 mm. The laminae are sharply upturned at astrorhizal tubes, thereby producing small columns which on surface appear as monticules. The monticules are about 4oo microns in diameter, rise about 200 microns and are 1 mm. apart. Eight to 10 laminae occur in 2 mm.; they are 30 to 70 microns thick; tissue is compact.

Cylindrical to spool-shaped pillars are confined to one inter laminar space. Their spacing and thickness is highly irregular;

4 to 8 in 2 mm. and 30 to 100 microns thick. At high magnification the structure of laminae and pillars appears to be the result of an orderly arrangement of dissepiments or cyst plates. Pillar tissue is compact.

A.strorhizal tubes are conspicuous in vertical sections. They appear as minute (lOO to 200 micron diameter) tubes about 1 mm. apart.

The tubes are not straight but are slightly bent. They connnonly ex tend about 2 mm. in a section. Horizontal branching :from these tubes is rarely seen.

Galleries are unequal in size and shape. They are oval, round or cystic; some appear isometric, ethers rectangular. Dissepiments, 50

20 microns thick, extend locally through the gallery spaces. About

50~ of the section is gallery. Foreign matter is concentrated in the dark latilaminar zones.

Tangential sections.-- The structure is characterized by irregular sized dots of dark tissue in a background of lighter tissue and con spicuously meandering astrorhizae. The dots are eut pillars (20 to 50 microns). Some pillars are joined by dissepiments. Astrorhizal branches 100 microns in diameter rarnifY densely throughout the section; dark tissue lines some of the tubes. Locally, clear oval or circular spots are the remains of trapped organisms.

Discussion.-- The species differs from Q. lennuki Nestor, 1964, in having a greater range in the number of laminae and pillars, more widely spaced laminae, and pillars which are not as thick; Q. variolare

Rosen has many more laminae, and smaller galleries wlùch alternate with larger ones. The values for laminae, pillars and galleries are iden tical to Q. variolare Rosen var. vajgatschense Yavorsky, 1961, however, the astrorhizal systems are apparently, more closely set in the specimens from Brodeur Peninsula. This latter point is not considered of specifie importance, in this case. Yavorsky's variety is elevated to species status.

Distribution.-- ~ne species is found near the Urals, in rock of

Silurian age.

Occurrence.-- The species is represented in the collections by four 51

specimens from the Baillarge formation, faunal zone III, GSC Nos.

58913-1, 58913-4, 58913-8; 78916-5. The hypotype is GSC No. 58913-1.

Clathrodictyon miniapse n. sp.

Pl. I, figs. 51 6.

Nine specimens of this species were collected from northwest

Brodeur Peninsula, section D2, localities Tmp-63-27a, c, d, and Tm-63-

18b.

Exterior.-- The coenosteum is hemispherical to low-domical in for.m; its outer edge is projected horizontally over the sediments on which it grew.

In sorne vertical sections this basal edge makes wavy apopheses projecting into the sediments. Basal diameters range from 7.5 to 18 cm., (the latter value is taken from a low-domical or discoid.al for.m) and average 10 cm.

Their heights range from 4 to 8 cm. and average 6 cm. The surfaces of most specimens are poorly exposed; an exfoliated or cleaved surface is generally smooth wi th few large, irregular undulations. Mam.el ... ons which measure about 2 mm. in diameter, rise 50 microns and are regularly spaced about 5 mm. apart, occur in sorne surfaces. Latilaminations are indistinct; about 3 to 6 occur in 1 cm.

Vertical sections.-- Laminae are straight, continuous and regularly spaced. The regularity in structure persists over enclosed foreign matter. The laminar spacing of nine specimens ranges from 16 to 22 in

2 mm; average 18.5. Laminar thickness ranges from 20 to 50 microns, 52

and averages 30 microns. Tissue is compact to speckled.

Pillars are conical to cylindrical in shape. The pillars and laminae appear to be for.med by cyst plates which are places side-by side.

Surrounding mamillae or mamelons and along some layers, the cyst plates or dissepiments imbricate. Thickness of laminae and pillars are the same, except where the pillars thicken as they diverge upward into laminae. Fourteen to 18 pillars occur in 2 mm. Tissue is compact to speckled.

Gallaries are subisometric, generally, 1ow vaulted archways. In places the pillars are closely set, creating high vaulted archways.

About 50% of sections is occupied by gallery space.

Monticules are common in the upper 1~ers of the coenosteum.

Some are the resu1t of the doming of tissue over trapped conispiral organisms(~) or sediments. Others are low undulations that can be found everywhere in the coenosteum. Axial canals of astrorhizae are commonly centered in these up bends which measure about 1 mm. diameter and are 2 to 3 mm. apart. In sorne sections monticules are absent.

Astrorhizal axial canals are 150 microns in diameter and are from 2 to

4 mm. apart. The minute branches which measure lOO microns diameter, extend horizontally, or diagonally, through the vaulted galleries.

Tangential sections.-- The concentric laminae appear as dark curved to wavy bands of tissue. These bands alternate with thiner, c1ear inter laminar zones. Evenly distributed and densely packed dots occur in both zones. Astrorhizal centers are 2 to 4 mm. apart; they are 150 53

microns in dia.meter and have dendri tic branches which are 100 microns in

dia.meter. The dark dots or eut pillars are 25 to 75 microns across; 25

to 30 occur in lsquare millimeter. Coiled sha.ped organisms or trapped

sediments are visible in sorne sections.

Discussion.- The above specimens differ from Q. vesiculosum in ha.ving

straighter laminae and pillars; Q. tenerum Yavorsky (1957, p. 17) has

fewer laminae but more widely spaced pillars. The structure is char-

acterized by minute arches or vaults to which the name Q. miniapse is

given.

Occurrence.-- Nine specimens were collected from the Baillarge formation,

faunal zone III, GSC Nos. 58917-1; 58919-8; 58918-1; 58913-3, 58913-6,

58913-7, 58913-9; 58942-1. The holotype is GSC No. 58919-8.

Clathrodictyon Linnarsonni Nicholson

Pl. I, figs. 7, 8;

1887 Clathrodictyon Linnarsonni n. sp. Nicholson, p. 5, pl. I, figs. 7, 8.

Ten specimens of this species were collected from Brodeur

Peninsula, section D.

Exterior.-- T11e coenosteum is, generally, hemispherical; the base is

irregularly convoluted and centrally wrinkled. The upper surface of

the coenosteum extends slightly horizontally at its base, so that, in 54

vertical section it appears bell-shaped. Basal diameters (measured above the horizontally extended base) ranged from 10 to 20 cm., and the height ranges from 5 to 10 cm. The surface is smooth and covered with irregular shaped mamelons upon Which are sparsely scattered monticules.

The sizes of the protuberances increases proportionally with coenos teal growth. Mamelons are 1 to 3.5 cm. diameter, rise 2 to 7 mm. and are 1.5 cm. apart; monticules are 0~7 to 2 mm. diameter and rise 0.7 to

2 mm. and are 8 mm. to 1 cm. apart.

Vertical sections.-- Laminae are straight, continuous and regularly spaced; they are gently inflected into monticules or mamelon columns or they may be curved above foreign matter. In ten specimens the laminar spacing in 2 mm. averaged 12.5 and ranged from 11 to 16.

Laminae range from 20 to 75 microns in thickness, and average 27 microns.

Tissue is compact to speckled. Pillars are cone to spool-shaped and they perpendicularly span only one interlaminar space. They appear to be downward inflections in the laminae. Where dark epitissue has been removed, some pillars appear to be formed by adjacent, down curved dis sepiments or cyst plates which either arise from the laminae or are in timately bound with them. Here they seem to be prolongations of fUnnel-shaped inflections of the laminae. The thickness and separation of pillars is similar to that of the laminae. Pillars range from 9 to

14 and average 11 in 2 mm. Tissue is compact to speckled. Galleries are round to oval in shape and mak.e up about 65~ of sections. They 55

measure lOO to 200 microns vertically, and lOO to Boo microns hori zontally. The structure in mamelon columns is no different from that in any other part of the coenosteum except that astrorhizae are con centrated in and about them. Mamelons are 2 mm. wide, o. 7 to l mm. high and about 8 nnn. a part.

Central astrorhizal canals with diagonal and horizontally spreading branches are connnon. The dia.meters of the central canals and. branches are about the same, 150 to 300 microns. The almost vertical canals are 3 to 7 nnn. apart. Sorne horizontal tubes extend 3 nnn. be tween the la.minae.

Tansential sections.-- Irregularly thickening and thinning d.ark, con centric bands of tissue are separated by thinner clearer zones wi th less tissue. The relatively dark bands are sections which lie in and about the la.minae. Pi.llars appear as irregular oval dots of d.ark speckled tissue. Rarely are d.issepiments seen connecting the pillars.

The pillars measure 75 to 125 microns; about 15 occur in l square millimeter, but more occur within mamelon regions.

Astrorhizal branches rad.iate dendritically from central canals.

Their diameters and separations are as those given in vertical section.

Astrorhizae occur insid.e and outside mamelon areas.

Discussion.-- These specimens differ from typical C. vesiculospum in having generally, more widely spaced laminae. The laminae and pillars are straighter and thicker than those of c. vesiculosum; they form a 56

more regular network of subrectangular to isometric galleries. The range in the number of laminae is less than that of Q. vesiculosum.

Unlike the often diagonal and incomplete pillars in Q. vesiculosum, the above species pillars, perpendicularly span interlaminar space. The species differs from Nicholson's (1889) description of Q. striatellum

D'Orbigny sp. in having astrorhizae and pillars which span an inter laminar space. The species cannet be put into the genus Stromatoporella because it lacks the characteristic tissue called, "ordinicellular"

(stearn, in press) and ring pillars of this genera. The species differs from Q. lennuki Nestor, (1964) in having closer set pillars and 'vell developed astrorhizae in the mamelon columns. Although, Nicholson's description of Q. Linnarsonni lacks detail, it is considered complete enough to make specifie assignments possible.

Distribution.-- This species is found in the Wenlock limestone, Visby,

Gotland and in the Bai11arge formation (Niagaran) of northwestern

Baffin Island.

Occurrence.-- Ten specimens were collected from the Bai11arge formation, faunal zone II and III GSC Nos. 58932-4, 58932-5, 58932-6, 58929-1;

58910-1, 58912; 58934-1, 58934-3, 58934-4; 58918-2. The hypotype is

GSC No. 58932-4. 57

Genus ECCLIMADICTYON Nestor, 1964

1964 Ecclimadictyon gen. nov., Nestor, p. 6o

TYPe species: Clathrodictlon fastigiatum Nicholson, 1886

The laminar to bulbous coenosteum is com posed of strongly zigzag-shaped anasto mosing, continuous to discontinuous lami nae of compact to speckled tissue. Thin irregularly spaced cylindrical pillars are confined to an interlaminar space and appear as dark dots in tangential section.

Ecclimadictlon fastigiatum (Nicholson, 1886)

Pl. II, figs. 1, 2.

1886 Clathrodic~on fastigiatum n. sp. -- Nicholson, p. 43, fig. 3; p. 78, fig. 12 (unwritten). 1887 Clathrodictlon fastigiatum, Nicholson Nicholson, p. 8, pl. II, figs. 3, 4. 1889 Clathrodictyon fastigiatum, Nicholson Nicholson, p. 152, pl. XIX, figs. 1-5. 1895 Clathrodictlon fastigiatum, Nicholson- Whiteaves, p. 52, pl. II. 1896 Clathrodictlon fastigiatum, Nicholson Whiteaves, p. 135. 1906 Clathrodictyon fastigiatum, Nicholson Parks, p. 18, pl. I, figs. 3, 4. 1907 Clathrodictlon fastigiatum, Nicholson Parks, p. 18, pl. I, fig. 6. 19o8 Clathrodictlon fastigiatum, Nicholson Parks, p. 24, pl. VII, fig. 8. 1939 Clathrodictyon fastigiatum, Nicholson Riabinin, p. 6, pl. I, figs. 6-9. 1951 Clathrodictyon fastigiatum, Nicholson partim - Riabinin, p. 20, pl. XIV, fig. l, non 2-6. non 1915 Clathrodictlon fastigiatum, Nicholson Boehnke, p. 169, non 1929 Clathrodictlon fastigiatum, Nicholson Yavorsky, p. 84, figs. 1-3. non 1940 Clathrodictyon fastigiatum, Nicholson Chi, p. 292, figs. la-b. 58

non 1955 Clathrodictlon fastigiatum, Nicholson Yavorsky, p. 44, pl. XV, figs. 7, 8. 1956 Clathrodictlon fastis!atum, Nicholson Stearn, p. 50, pl. II, non 1961 Clathrodictlon fastis!atum, Nicholson Yavorsky, p. 28, pl. XIV, figs. 4-6. 1964 EccJ imadictyon pand.um n. sp. - Nestor, p. 69, diag. 33, pl. XXIII, fig. 6; pl. XXVIII, fig. 6.

Four specimens of this species were collected from northeast

Brodeur Peninsula, localities, Tm-63-27c; Tmp-63-27b; Tmp-63-27a-12.

Exterior .- Coenostea are bulbous, tabular or low domical in form.

The bulbous or hemispherical coenostea, measure 10 to 15 cm. at their

bases. One tabular coenosteum measured 20 cm. diameter and 2 to 4 cm. in

thickness. Surfaces are smooth with low undulations. Protuberances

reflect the presence of trapped organisms or sediments.

Vertical sections.-- Laminae are crumpled into wide, irregular sized,

chevron folds. If a lamina is traced laterally it appears to quickly

join wi th ei ther the lamina immediate!y above or below i t; 8 to 14

laminae occur in 2 mm; the four specimens* averaged 10.5 in 2 mm.

They are about 50 microns thick. Tissue is speckled.

Pillars most often arise from downward pointing inflecting in the

* Minor variations in the number of laminae can occur in the same section. The variations are attributed to adverse periods of growth 11 11 ( dwarfing effect); tissue is often darker and inclusions of detrital matter are common. If the section is slightly obli~ue to the laminae, the zigzag structure is maintained, however, many of the points at which they ordinarily touch appear as small denticles. Also, in some 59

laminae. They are cylindrical to cone-like in form. At high magnification seme pillars appear like dissepiments thinly covered with lighter epitissue. Pillars are, generally, 200 microns apart, 20 microns thick and have speckled tissue. Their structure is amalgamated vith the laminae, but they are less conspicuous than the laminae.

At low magnification, galleries appear irregular in size, but closer observation shows that their for.ms and dimensions are uniformly isometric or pseudopentagonal. Local variations are caused by folding structure about foreign matter or near astrorhizal systems. Dissepi- ments are present, but inconspicuous. About 50~ of sections is gallery.

Low domical monticules are rare. Some continue down in the structure as astrorhizal colu:mns. Astrorhizal systems are difficult to see.

Central tubes are 200 microns vide and 1 ta 2 :nmt. apart; branches measure lOO ta 200 microns in diameter. Longitudinal sections of the central tubes show that they are straight and perpendicular.

Tangential sections.-- Distinction between laminae, sensu stricto, and interlaminar spaces is vague because of the folded nature of the laminae.

sections, the regular zigzag network may be periodically succeeded by disrupted zones in which closely set irregular pillars predominate. These zones are not primary structures, but they reflect the presence of oblique fractures in the specimen from which the section was pre pared. Care must be exercised ta avoid erroneous conclusions about the structural elements present. 60

The tissue fabric is vermiform. Astrorhizae are inconspicuous in the structure; they are 200 microns wide and about 2 mm. apart. Scattered, irregular sized dots (20 to 150 microns) represent the eut ends of pillars or the apices of inflected laminae. Tissue is speckled.

Trapped sediments and coil-shaped organisms occur in sorne sections.

Discussions.-- Nestor (1964) makes Q. fastigiatum the type species of his genus Ecclimadictyon, in which he claims that the laminae are directly connected without the development of pillars. The four specimens studied in this thesis show that laminae are more often con nected by distinct pillars than by direct connection with other laminae.

Nestor also claims that dissepiments and astrorhizae are not present; these structures are present in the species described above. The holo type, Q. fastigiatum Nicholson shows all the above stated features

Nestor claims are absent. His new species E. pandum, has all the above features which he claims are absent in !· fastigiatum and is here placed in synonymy wi th !· fastigiatum.

Distribution.-- The species is found in the Wenlock of Britain in the

"zone of Pentamerus esthonus" of Estonia (Upper llandoverian and

Wenlock) and in the Guelph formation (Upper Middle .Silul:"illll.) of Ontario, and also from the Cedar Lake formation of Manitoba, Canada (Niagaran).

Occurrence.-- Four specimens were collected from the Bail1arge formation, fauna1 zone III, GSC Nos. 58919-5; 58911-1; 58913-2; 58913-5; 58916-1,

58916-4. The hypotype is GSC No. 58916-1. 61

Ecclimadictyon microvesiculosum (Riabinin)

Pl. II, figs. 3, 4.

1951 Clathrodictyon vesiculosum Nicholson and Murie -- Riabinin, p. 14, pl. V, figs. 1, 2; pl. VI, figs. 3,4. 1951 Clathrodictyon microvesiculosum n. sp. -- Riabinin, p. 15, pl. v, figs. 4, 5; pl. VI, figs. 5, 6. 1951 Clathrodictyon microvesiculosum n. sp., partim - Riabinin, p. 15, pl. V, figs. 3; pl. IX, figs. 1, 2. 1964 Ecclimadictyon microvesiculosum -- Nestor, p. 65, pl. XXV, figs. l-4, pl. XXYIII, figs. 1, 2.

This species is represented in the collections by four specimens

from the Brodeur group, section D and D2.

Exterior.-- Coenostea are bulbous, hemispherical to compressed domical

forms with smooth to wavy surfaces; diameters range from 4.5 to 14 cm.

Monticules may be present 2 to 3 mm. apart. La.tilaminations are present in some specimens; 5 to 7 in 2 cm.

Vertical sections.-- Laminae are curved in irregular zigzags and are

joined to each other at the apices of the inflections and by small pillars. The structure is like a diagonal net with holes of irregular size. In some thin sections sets of crumpled laminae are separated every 0. 5 to l Imll. by two relati vely straight laminae which form an interlaminar space measuring, 100 to 200 microns. In this space, the pillars clearly project downward from the laminae. The number of

jagged laminations in 2 Imll. ranges from 10 to 19 and averages 15. The laminae and pillars average 4o microns in thickness and are compact.

Galleries are variable in size and shape. Some are ovoid to 62

broad. rectangles, ethers have more than 6 sides. Their àiameters, measured vertically between two zigzag laminae, are less than that of the interlaminar spaces which are spanned by perpendicular pillars.

Galleries account for about 50% of the sections.

Astrorhizae are rare and difficult ta see in vertical section.

They appear as clear, round ta aval spaces measuring 150 to 200 microns in diameter. Tubes rarely disrupt or eut the structure. When a canal is visible its position is vertical to the laminae. Dissepiments are absent.

Tangential sections.-- The concentric structures over mamelon columns are transected laminae out of which project irregularly, curved bars, identical in thickness ta the laminae and which are, in fact, obliquely eut pillars. In the clear spaces, pillars and sections of diagonal laminae appear as dark, 4o micron dots. Astrorhizal canals occur in and outside of the mamelon regions; they are 2 mm. diameter and about

2 mm. apart. The centers of mamelons or monticules are l ta 3 mm. apart.

Discussion.-- The somewhat regular wider interlaminar spaces between the polyhedral galleries may be horizontally branching astrorhizae.

This structure is not everywhere seen, nor is it continuous.

Nestor (1964, pp. 5-8) reviewed Nicholson's, Yavorsky's and

Riabinin 's work on Ordovician and Llandoverian stromatoporoids in

Estonia. He argued that too many new "species 11 of Clathrodictyon were being introduced from studies of vertical sections which have eut structure with varying degrees of obliqueness. Clathrodictyon kudri avzevi Riabinin, Ecclimadictlon microvesiculosum (Riabinin) and others, are subject to wide variation in this respect. Nestor remeasured many of Riabinin's type species and found them to be about one-fifth less than the recorded values. Iliabinin was prone to base lùs separation of species on their stratigraphie occurrence. Tne relatively straight laminae are interpreted by Nestor as dissepiments. Except for a lower average spacing of laminae, the specimens are identical with the type species Q. vesiculosum.

Distribution.-- In Estonia, the species is found throughout the

Llandoverian.

Occurrence.-- Four similar specimens were collected from the Baillarge formation, faunal zone II, GSC Nos. 58932-1, 58932-2, 58932-3 and

58936-1. The bypotype is GSC No. 58932-l.

Ecclimadictlon sp. A

Pl. II, figs. 5, 6.

This species is represented in the collections by one specimen from the Brodeur group, section D.

Exterior.-- Only a fragment of a coenosteum, (10 x 7 x 5 cm.) was col lected. It is a massive, wavy, tabular form, of a light, whitish-buff 64

colour and wi thout clear latilaminations. The surface is wavy and smooth.

Vertical sections.- T'ne predominant elements in the structure are re latively thick, sharp zigzagged laminae which irregularly connect with out the formation of pillars. The laminae can be traced for only a short distance laterally before they join with others.

Wi thin the thick lami.nae are relati vely thin microlaminae. The microlaminae extend horizontally, uninterrupted through the zigzag structure. They are fairly weil spaced ( 4 in 2 mm.) and generally straight. At higher magnification they are seen locally, either to inflect downward before they join the heavy laminae or they may gently curve down and join the microlaminae below. (Because of their con tinuity, they are not called dissepiments). The microlaminae are 200 to 300 microns apart; a relatively dark, endotissue of 1 micron thick ness is covered Ydth light epitissue which makes the total thickness of the microlaminae 5 microns. The epitissue and endotissue are compact.

The heavier, irregular, chevron-folded laminae are lOO microns thick. One side of a zigzag may be 1.5 to 2 mm. long and extend across

3 to 4 of the horizontal microlaminae. The inflection of the laminae form an angle, which ranges from 40 to 6o degrees. Measured vertically Ô5

rrom points or inflection,* 4 to 5 laminae occur in 2 mm. In places the regular, zigzag laminae curve to form thick cyst plates. Such areas appear to contain astrorhizal clusters. In other parts of the section, the laminar complex appears as dots of tissue 100 microns across. The tissue in the laminae is compact to speckled. Minute cleavage planes within the calcite mosaic erroneously, suggest transverse porosity.

The astrorhizal system is d.ifficult to see. It can be traced where the laminae bend or curve, rather than sharply inflect. Some branches have been eut and appear in the plane of section as clear oval to round areas, 300 microns across, surrounded by laminar tissue.

Galleries conform to the irregular nature of the laminae. T'ney are 100 to 200 microns, measured perpendicular between two laminae and extend irregularly. The fine microlaminae cross gallery space. About

55~ of the section is gallery.**

Tangential sections.-- Bands of relatively light tissue appear superimposed upon a dark, irregular, discontinuous vermicular network.

Irregular round dots of dark tissue are conspicuous wi thin clear spaces.

* Nestor (1964) has used the term ncarcasses", it seems to represent the aggregate structure of zigzagged laminae and interlaminar space.

** The structural elements appear different if the section is not vertical or too thin. Several sections were made to verify this point. 66

Where the section is closest to being tangential, the tissue is an ir regular network of sma.ll and large arcs . about lOO microns thick. When sufficient epitissue is removed, by preservation and/or grinding, micro laminae (1 micron thick) are visible extending across and joining wi th the thicker tissue to fo:rm wide arcs. The relati vely light bands of tissue conform to these arcs, which are microlaminae. Tissue in the structural elements is of varying degrees of compactness. About 60% of the sections are tissue.

Discussion.- The above species is grossly similar to Ecclimadictyon porkuni (Riabinin, 1951) however, three significant features distin guish it from the latter species; there are half as many laminae, microlaminae are straight, more continuous and the angle ( 4o0 to 6o0 ) at the point of inflection of the laminae is about half that in !· porkuni.

Astrorbizae are difficult to see in tangential sections; they are recognized as clusters of about 7, clear, oval to round centers

(lOO to 300 micron diameter), surrounded by dark tissue.

Occurrence.-- One specimen was collected from the 1ower part of the

Baillarge formation, faunal zone II, GSC No. 58932-7.

Genus INTEXODIC'l'YON Yavorsky 1963

1963 Intexodictyon Yavorsky, p. 34. 1964 Intexodictyon - Nestor, p. 72.

Lectotype : _:. perplexum Yavorsky

Massive coenosteum camposed of persis tant dense or compact pillars confined to a single interla.minar space. The pillars arise from the laminae and fonn a comple.xi ty interwoven interlaminer te..n gle. Astrorhizae may be present.

Intexodictyon brodeurense n. sp.

Pl. II, figs. 7, 8.

Tnis species is represented in the collections by two specimens

from Brodeur Peninsula, section D.

Exterior.-- The coenosteum, represented by fragments only in the collection, appears massive. The undulating surface is covered with small mamelons, about 2 ta 3 mm. diameter, 1 mm. high and 5 ta 3 mm. apart.

Vertical sections.-- At XlO magnification, the laminae are relatively dark, irregularly spaced, continuous, gently undulant in mamelons. The mamelons may occur on broader and sharper infleéted waves. (~pl. II, fig. 7) Their thickness ranges from 50 ta 70 microns. At higher magnification a denser, compact primary lamina underlies the epitissue.

Iocally, about columns, the primary la.minae appear ta bend dawn ward obliquely ta join with curved dissepiments. A relatively lighter, less compact, discontinuous, irregular, pseudolaminae may occur between the laminae proper. This structure is produced by the joining of irregular pillars and dissepiments which arise mostly from below the laminae. 68

These pseudolaminae and their supporting pillars appear to have caved

down from the laminae proper. There are 5 to 7 lamina proper, in 2mm.

Foreign material in the form of pellets, generally, less than 100 microns diameter, is concentrated locally between laminae. Pillars

are highly irregular in form and spacing. They arise from the base of a lamina and may be perpendicular or oblique to it. Some appear to be the result of a downward inflection in the lamina and appear like tun nels perpendicular or oblique to i t. The curved, oblique pillars may not cross an interlaminar space directly, but instead, they may arch horizontally, entwine with ether pillars or dissepiments which, in turn, cross the interlaminar space and create irregularly shaped smaller galleries. Perpendicular pillars are spaced 3 to 7 in 2 mm; they are

50 to 70 microns across. About 60~ of the section is occupied by gallery space.

The exact nature of the astrorhizal system is unknown. Astre- rhizae_wind in and out of the structure, so that, vertical sections of the tubes are not easily observable. In tangential section they are

200 to 300 microns across. Generally, the canals meander along the laminae. The holotype contains a large 1 mm. circular structure with smaller subsidiary tubes, 200 microns wide leading away from it. This may be an astrorhizal cylinder although there is no evidence of i ts upward extension. Dissepiments are common but obscured by epitissue.

Tangential sections.-- Conspicuous mamelon columns of concentric and radial structure rarely have an axial canal; one canal measured 500 mi crans in diameter. Astrorhi zae extend up wi thin the mamelon columns and a:p:pear, in tangential section, as clear centers about 200 microns in diameter and about 2.5 mm. apart. Wide discontinuous clear regions between the concentric laminae are astrorhizal tubes. Pillars occur as dark compact dots, 70 microns across, some wi th laminae. Curved irregular pillars a:ppear as a network of connected bars in mamelon.

Some intermamelon regions contain a high concentration of pellets which could be confused with pillars. Dissepiments are best seen in regions where the section has eut interlaminar space obliquely.

Discussion.-- Some confusion remains concerning the genus Intexodic tyon (Yavorsky, 1963) and Ha.mmatostroma (Stearn, 196l).Yavorsky es tablished his genus to include largely Silurian and some Devonian species with compact tissue, and irregular, incomplete and almost cys tose pillars. Stearn's genus has fibrous laminar tissue, but speckled pillar tissue. Stearn (personal communication) suggests that the pil lar structures of the two forms ma.y dif:fer. The above form is grossly similar to !· perplexu.m Ya.vorsky, however, the pilla.rs are twice as thick and set twice as far apa.rt. TW.s species is named a:fter Brodeur

Peninsula (and the Brodeur group), where is was col1ected.

Occurrence.-- Two specimens of the species were collected from the

Baillarge formation, :fauna.l zone III, and are coded under the GSC

Nos. 58919-1 and 58916-2. The holotype is GSC No. 58919-1. '(0

Family ACTINOSTROMATIDAE Nicholson, 1886

1886 Family Actinostromidae Nicholson, p. 74. 1922 Family Actinostromatidae Stechow, p. 151. 1957 Family Actinostromatidae Nicholson-- Galloway, p. 437.

Coenosteum laminar or massive, rarely cylindrical, composed of definite laminae and continuous or superposed, strong pillars. The laminae are regular, irregular or irregularly cystose, with much secondary thicken ing tissue. Tissue compact, fibrous, porous or vacuolate, not maculate. Galleries usually superposed. Astro rhizae present or absent. Silurian common. Devonian abundant.

Genus GERRONOSTROMA Yavorsky, 1931

1931 Gerronostroma n. gen. -- Yavorsky, p. 14o6, pl. I, 1941 Gerronostroma Riabinin, p. 91. 1955 Gerronostroma -- Yavorsky, pp. 34-38. 1957 Gerronostroma -- Galloway, p. 438 T,ype species: Q. e1egans Yavorsky

Coenosteum camposed of well defined compact pi1lars and laminae. Laminae persistant and transverse1y porous. Pillars, spool-shaped, composed of porous tissue and conspicuously super posed from one interlaminar space to the next.

1 Gerronostroma juvene n. sp.

Pl. III, figs. 1-4.

This species is represented in the collections by two specimens from Brodeur Peninsula, location Trop 63-27a-12.

Exterior.-- The coenostea are massive, bulbous or tabular in form.

The bulbous form is incomplete, but its estimated measurements are about 10 cm. diameter by 5 cm. radial height, measured through the 71

center of the coenosteum. The undulating surface is rough. Lati laminae are not present in the dark grey-brown coloured coenosteum. The larger light grey-buff, tabular coenosteum measures 30 cm. dia.meter and i ts thickness was greater than 10 cm. Mamelons of irregular size, shape and distribution are sporadically covered with papillae. Mamelons are 5 to 10 mm. in diameter, rise about 1.5 mm. and are about 1 to 2 cm. apart. Papillae are 1 to 1.5 mm. diameter and rise about 0.5 mm. The surface is roughened by the emergence of the ends of the pillars. Small pits about 0.75 mm. diameter and 3 to 4 mm. apart cover the surface.

Vertical sections.-- The general appearance is that of a tattered and broken net or grid. Laminae are discontinuous, broad undulating and generally regularly spaced. Some la.minae appear to have their broken ends turned up or down. The local breaks and swells in the laminae reflects the presence of an astrorhizal network which ramifies through out the structure. Beneath the epitissue is a finer, darker micro lamina of endotissue which is 12 to 50 microns thick. This wide range in thickness is due to an irregular pinching and swelling of the micro laminae. The average thickness of the epitissue and endotissue ranges from 80 to lOO microns. There are 6 to 8 laminae in 2 mm. The gener ally evenly spaced laminae are, in some sections, alternate somewhat regularly with closely spaced wavy laminae and dissepiments; 5 to 8 irregular laminae occur in these 1 mm. thick zones. This zonation reflects latilaminar growth; about 5 latilaminae occur in 1 cm. Under 72

X4o magnification, the microlaminae appear to pass througn the pillars.

Epitissue may completely mask the finer laminar structure. Reversals in the relative preservation of the endotissue of the microlaminae occur in the same section, that is, their tissue may be either darker or lighter than the epitissue. The epitissue and endotissue are of varying degrees of compactness.

The relati vely thick pillars are irregular in spacing and appear to continue through several interlaminar spaces. The irregularity in spacing of pillars is caused by the interlacing astrorhizal system.

Pillars are cylind..~cal to spool-form; the second has a thicker epi tissue than the first. They are confined to one interlaminar space;

5 to 7 occur in 2 mm. Microstructure is similar to that of the laminae, however, the endotissue is thinner and less dense or compact. The endo tissue is about 50 microns in diameter; when epitissue covers the endo tissue the pillars are lOO to 180 microns thick. Some pillars seem to extend out and curve up from their bases in the laminae, that is, they are not straight and perpendicular.

Bread mamelon columns and smaller monticular inflections are in timately connected with astrorhizal growth. Pillars diverge away from the api ces of t'olds but remain perpendicula.r to the lamina.e. Astre· rhizal axial canals dia.gonally wind through the lattice; they are 500 microns in diameter. The 200 to 300 micron diameter astrorhizal branches, either extend into, and are confined by one interlaminar space, 73

or they curve upward and extend across the structure.

Galleries are rectangular; some are round due to the expansion of

spool-shaped pillars. About 45~ of sections is occupied by gallery

spa.ce.

Dissepiments are present in well preserved specimens. They are

gently curved to highly curved nea.r mamelon columns where they imbricate

irregularly to form cysts. Epitissue about these fine (lü micron) fil

aments blends with that of the la.minae and pilla.rs. The dissepiments

pass through pillars as they extend through the galleries. Some appear

to form secondary la.minae between the primary ones. Usually, only one

dissepiment will continue la.terally in the confines of a single inter

laminar space. Trapped foreign matter, muds and pellets, occur in places.

Tangential sections.- A good "hexactinellid network tl i s not developed

in the sections studied. There is some suggestion of this texture be tween mamelons, where the plane of section lies in the la.mina.e. Tan

gentially eut laminae a.ppea.r as da.rk concentric bands over the mamelon

columns. The thickness of the bands depends upon the obliqueness of

the plane of section at the laminae and the amount of epitissue on the

laminae. Straight to curved cylindrica.l pillars project from both sides of the la.minae;

Locally, in oblique sections, some pillars span the interlaminar region, others seem to curve up into the plane of section and appear a.s dots. In the clear spaces pillars appear as dots arranged in "single- file", about lOO microns apart, between two adjacent laminae. The cores or endotissue of' the pillars appear as dark, 30 to 4o micron dots; heavy epitissue will thicken them to 150 microns or more. Some pillar centers contain lumina, this again may be tissue reversal, the result of' preser vation. Laminae and pillar tissue vary in degrees of compactness.

Discussion.-- This species may be assigned by different specialists to either the genus Actinostroma or Gerronostroma, depending upon the weight given to certain characters. The following characters from the above description apply to Actinostroma; coenosteum laminar ta globular; surface tuberculate; pillars with or without lumina; tissue compact; astrorhizae present; Silurian and Devonian. However, pillars appear superposed, discontinuous and, in tangential sections, have no radial arms. The last two characters are suggestive of' Gerronostroma, however, the genus bas transversely porous laminae, rare astrorhizae, lumina are absent and is Middle to Upper Devonian in age. The last four cbaracters are not present in the species studied. The f'act that radial arms are not present and that pillars appear superposed favours the genus.

Gerronostroma.

The characteristics described in the two specimens from Brodeur

Peninsula have some affinity to tbat of!· whiteavesii Nicholson (1891), except that in!· whiteavesii astrorhizae are reduced to vertical canals which appear on the coenosteal surface or in tangential section as rosette-like groups; pillars have moderate1y well-developed radial 75

processes. The astrorhizal axes in the species from Brodeur Peninsula have a good branching network, but pillars do not have radial arms in tangential section and there are fewer pillars in 2 mm. (5 to 8) than in A. whiteavessi (10).

The new species from Brodeur Peninsula, is grossly similar to

C. nikitini Yavorsky, (1961, p. 12), however, there are fewer pillars and astrorhizae are present in the new species. Yavorsky 1 s species is found in Middle Devonian rocks of the USSR.

The above factors, coupled with a tentative Middle Silurian age of the strata from which the specimens were collected, justify the in- traduction of a new species. The species is named ? Q. juvene because it is the youngest form of this genus yet described.

Occurrence.-- Two specimens were collected from the upper part of the

Baillarge formation, faunal zone III, GSC Nos. 58916-2, 58916-6. The holotype is GSC No. 58916-2.

Family STROMATOPORIDAE Winchell, 1867

1867 Family Stromatoporidae Winchell, p. 98. 1886 Family Stromatoporidae Winchell Nicholson, p. 74. 1939 Family Stromatoporidae Winchell Kuhn, p. A44. 1957 Family Stromatoporidae Winchell Galloway, p. 445.

Coenosteum massive to laminar, composed of latilaminae, laminae and short and long pillars, the interlaminar spaces more or less filled with secondary tissue; tissue ~inely or coarsely maculate and amalgamated; pseudozooidal tubes common; astrorbizae and mamelons common. Upper Ordovician, Silurian and Devonian.

Genus STROMATO:OORA Goldf'uss, 1826*

TYPe species: ~. concentrica Goldfuss

Coenosteum composed o~ an amalgamate network o~ tissue in which neither laminae nor pillars are easily dis tinguished. Vertical elements {pillars) predominate in the structure and are separated by high galleries called pseudozoidal tubes. Microlaminae com posed o~ a line o~ dark granules, or more rarely a clear path in the tissue, are present in some species. Tangential sections show an irregular continuous network o~ tissue with small galleries and ~ew areas of isolated tissue. The tissue is cellular or microreticulate.

Stromatopçra ba~finensis n. sp.

Pl. III, figs. 5, 6.

This species is represented in the collections by three specimens

~rom Brodeur Peninsula, section H.

Exterior.-- The coenosteum is irregular, long and domical in ~or.m.

The base projects sharply as a wave-like expansion into a mixed fossiliferous calcareous mud. Latilaminations are not present.

* Because the literature on stromatopora is so voluminous, no attempt has been made here to cite it. The reader is re~erred to Galloway {1957, p. 447). 77

Vertical sections.-- The coarse grid is characterized by relatively thick laminae and stout pillars into a regular grid. The concentric laminae are generally straight and continuous. Locally, a thick lamina may appear to be cleaved. The di vided lamina may continue laterally, or it may rejoin to assume i ts original form. Where this occurs, regular stout pillars span the apparent division, so that, the basic structure is maintained. Locally, three relatively thin lamina.e join to form a single thick lamina. The thick laminae, composed largely of a "microreticulate" epitissue (stea.rn, in ;eress) are underlain, in part, by "microlaminae"* and shorter, imbricating dissepiments. At high magnification, where the microreticulate tissue does not mask the primary elements, apparently, the basic elements in the structure are broad imbricating dissepiments. In some sections the broad dissepiments are set, side-by-side in an arrangement which is common to Clathrodictyon.

In the holotype, 4 to 5 laminae occur in 2 mm., but other specimens have 7 laminae. They are lOO to 400 microns thick; the dissepiments or "microlaminae 11 are about 10 to 20 microns thick.

The pillars are spool-shaped, expanded where they merge with the laminae. Dissepiments underlie the microreticulate epitissue. The

* Microlaminae are put in quotes because i t is uncertain whether they exist as continuous sheets of tissue, as Galloway has defined the word. pillars are superposed and regularly spaced; about 5 to 6 occur in 2 mm. and they are 70 to 150 microns thick, discounting the expanded parts.

The microreticulate tissue resembles a checker-board. The light

11 11 11 spots are cellules and the dark centers, "melanospheres ( Stearn, !!! press). The melanospheres are about 25 microns in size; 13 to 14 series of melanospheres {measured horizontally or vertically) occur in 1 mm.

Poor preservation may marr the discreteness of the melanospheres.

Commonly, the melanospheres appear closer to each ether vertically than horizontally. This alignment of melanospheres gives the laminae an appearance of being transversely porous. In ether parts of the section, the melanospheres are horizontally set, so closely that they appear to be continuous. If microlaminae underlie every continuous strand of melanospheres, horizontally, then microlaminae should underlie every series of melanospheres vertically. This obviously does not occur. *

Astrorhizae cannot be clearly distinguished in vertical sections.

The predominant tubular structures are the caunopores. These conspicuous tubes, 80 to 200 microns diameter, eut across the structural elements or lie within them. They are walled with a dark tissue, 12

* Dr. Stearn (personal communication) suggests that the series of melanospheres, (set in contact, horizontally and vertically) create a microlaminar grid-like structure.

** It is uncertain if the tabulae are always separately secreted in the caunopore tubes. 79

microns thick. Some contain tabulae, 20 microns thick. I.ocally, the

tabulae are really dissepiments which extend through the tubes. The

caunopores are set about l mm. apart, but they curve everywhere in the

coenosteum.

The galleries are round and measure lOO to 250 microns diameter.

About 70% of vertical sections is occupied by gallery space.

Tangential sections.-- The laminae appear as concentric zones of dark porous, melanospheric tissue which alternate with clear gallery zones

containing pillars about 1 mm. in diameter. Tangentially or longi

tudinally eut caunopore tubes densely ramifY through the structure.

Where the section lies in the plane of the laminae, 25 micron melanos pheres are evenly and closely set.

Discussion.-- The species described from northwestern Baffin Island,

contains features which are characteristic of both Stromatopora and

Ferestromatopora. In the type species of Stromatopora, ~· concen trica Goldfuss, the pillars or vertical elements predominate in the

structure and are separated by high galleries called, pseudozoidal tubes. Generally, neither laminae nor pillars are easily distin guished. In the species from Brodeur Peninsula, la.minae predominate in the structure, pillars are relatively subordinate, but both elements are easily distinguishable; galleries are small and round.

Galloway (1957, p. 447) re-defined the genus Stromatopora, when he emphasized that microlaminae underlay the maculate tissue. The 80

microlaminae, used in Galloway's sense, do not underlie every series of horizontally disposed melanospheres. Where they cross gallery space they are much more widely separated than the series of melanospheres which compose the laminae. The microlaminae are not straight and con tinuous, but curve to connect with the laminae below. Locally, they appear to be more like dissepiment~ that is, broad onlapping sheets of tissu~ than tru.e microlaminae. Where the melanospheric tissue is not well preserved, broad imbricating dissepiments are observed within the thick laminae. The dissepiments lie in the thick laminae and in the stout pillars proper. The microstructure is similar to the larger structures in the Baffin Island species, however, the cellules, which would correspond to galleries, are larger and the melanospheres, or dark dots of tissue, are closer vertically than horizontally, so that, the vertical element predominates.

Galloway (ibid., p. 448) also claimed that in stromatopora pseudozoidal tubes are dominant over l.a.minae. It is obvious in the new species from Baffin Island that the so-called, pseudozoidal tubes, are subordinate to the laminae.

The new species has some affinities with Ferestromatopora

Yavorsky but they are minor. Both have amalgamate structure, but the species from Brodeur Peninsula has perfect microrecticulation. The horizontal elements predominate over the pillars, but both are well devel.oped. Galleries are relatively small, round and superposed; in 81

Ferestromatopora, galleries are not superposed. Galloway (1957 p. 446) has included the specimens Stromatopora concentrica, illustrated from

Belgiu.m by Le compte, in Ferestromatopora. stearn (in ;press) states:

"Although ty;pical Ferestromatopora is easily distinguished from typical stromatopora on the basis of the absence of pseudozooidal tubes and the dominance of horizontal elements, such species as §.. di vergens Galloway and St. Jean, §.. lami nosa Lecompte, and §.. eumaculosa Galloway and St. Jean whose microlaminae seem to be derived from microreticulate tissue, could be assigned to either genus. Such species can be as signed to Stromatopora if the galleries are superposed for.ming pseudozooidal tubes, and to Ferestromatopora if the tubes are missing. The spli tting of this group wi th microreticulate tissue away from both genera seems to offer a solution to this problem that expresses the biological relationships more satis factorily. 11

The genus Stromatopora should be critically, re-evaluated with the view of establishing a new genus.

The regular nature of the laminar and pillar structure and the

perfectly developed microreticulate tissue1 establishes a unique species.from northwestern Baffin Island.

Occurrence.-- Three specimens were collected from the highest faunal zone, IVe of the Brodeur group; GSC Nos. 58902-2, 58902-4, 58902-5.

The holotype is GSC No. 58902-2.

Stromatopora aspectabilis Yavorsky

Pl. IV, figs. 1, 2;

1961 stromatopora asEectabilis Yavorsky, p. 4o, pl. XXIII, figs. 4-7. 1961 stromatopora vorkutensis Yavorsky, p. 39, pl. XXIII, figs. l-3. 82

Two specimens were collected from Brodeur Peninsula, section H.

Exterior.-- The coenosteum is a thick, tabular, broad wavy expansion measuring about 8 cm. in thickness and more than 30 cm. in width. One wave length measures 7 cm.

Vertical sections.-- The sections are characterized by an amalgamate network of, generally, continuous, bumpy laminae and pillars which

form a network of round, poorly superposed cyst-like galleries.

Locally, the laminae are discontinuous; where groups of closely set

tubes extend vertically through the coenosteum. In such places the tubes are lined by thick tissue which appears ta bifurcate and join repeatedly about the vertical pseudozoidal tubes. Close observation of the laminae and pillars suggests that their amalgamate nature is dependent upon the basic underlying structural elements, dissepiments. About 7 to 8 laminae occur in 2 mm. and their thickness is similar to that of the pillars, lOO to 150 microns. The laminar epitissue has been secreted upon the dissepiments, so that, the dissepiments curve into the pillar structure.

This gives the pillars the appearance of bifurcating as they extend into laminae. About 6 pillars occur in 2 mm.

The dissepiments commonly extend somewhat horizontally, so that, they have been described as '~icrolaminae" by sorne authors.* The dis-

* The preservation determines what appears as microlaminae or dissepi ments. In the literature, Stromatopora, is described as containing sepiments, apparently, overlap; the line of overlap is usually hidden by the epitissue at the lamina-pillar confluence. They are clearest in the round to cyst-like galleries. They extend undeterred through relatively large vertical caunopore (î) tubes. Dissepiments are about lOO microns apart and 10 microns thick, so that, 16 to 20 occur in 2 mm.

About 45~ of sections is gallery.

Astrorhizae are not easily distinguishable in vertical sections.

They may be connected to the larger tubes in the coenosteum. These larger tubes, which measure about 4oo microns and are about 3 to 4 mm. apart, have 100 to 200 micron thick walls of epitissue. Unlike the astrorhizae which generally branch upward, the large tubes appear as main trunks to a root system of smaller tubes 100 to 200 microns which spread down, then horizontally. Where two tubes join to form the thick trunk, their common wall creates a control core which extends upward.

(~ pl. IV, fig. 1} This pseudocolumn is joined by the tenuous dissepiments which continue horizontally through the main tube, creating

"tabulae" ( î) •

The epitissue of the horizontal and vertical elements is not well preserved. The tissue is murky, however, locally melanospheres are dis- cerably superimposed suggesting a microreticulate pattern. The melanos-

microlaminae and few dissepiments. The species of Stromatopora studied by the author, appear to contain dissepiments, as defined on pages 90 and 91 of this dissertation. 84

pheres are mostly preserved as tattered f1ocks of dark tissue about

20 to 30 microns in size.

Tangential sections.-- The sections are characterized by a carpet of c1osely set dark dots in a background of lighter tissue. About 20,

100 to 150 micron dots occur in one square millimeter. Some dots are connected to form a vermicular network. Dark concentric bands of melanospheric tissue represent transected laminae. Dendritic branching astrorhizal systems are about 3 to 4 mm. apart; the tubes are lOO to

200 microns in dia.meter. La.rger oval to round {about 4oo microns di ame ter) tubes are set 3 to 4 mm.. a part and are surrounded by lOO to

200 microns thick melanospheric tissue. Smaller (200 micron) but similar tubes are irregular1y distributed. The mela.nospheres are clearer in tangential sections; they are 20 to 35 microns in size.

Discussion.-- The characteristics described are essentially that of the species, Stromatopora as~ectabilis Yavorsky, 1961. Three char acteristics, however, are different; the larger tubes 4oo micron diameter with a pseudocolumn have not been recognized in ~. a.spec tabilis; the number of dissepiments is less than in the Russian specimens and the pillars are smaller in diameter. The 1ast two features are similar in ~· vorkutensis Yavorsky, 1961, but the above species ha.s closer set and smaller astrorhizae and the pseudozooida.l tubes are larger. Slight differences in structure may be only the result of different preservation or different growth rates. The basic 85

difference between Yavorsky's two species is the separation between astrorhizae and the number of dissepiments; ~· aspectabilis bas 16 dissepiments in 2 mm., ~· vorkutensis has 22. The species from Brodeur

Peninsula, bas a range of 16 to 20 in 2 mm. The wri ter suggests, after making several sections of the same coenosteum,that these three species are the same. It is not certain if the la.rger tubes in the above specimen are caunopores and if they should be given specifie importance.

Occurrence.- ~· aspectabilis is found in the Silurian of the Russian

Urals. In the Baffin Island collections two specimens were taken from the same large samp1e, from faunal zone IVe of the Brodeur group; GSC

Nos. 58902-1; 58902-3. The b:ypotype is GSC No. 58902-1.

Stromatopo ra sp. A

Pl. IV, figs. 3, 4.

Exterior.- The coenosteum is a la.minar wavy expansion about 6 to 7 mm. thick and 10 cm. wide. About 6 latilaminations occur in 1 cm.

The surface was unavailable for study.

One specimen was collected from northern Brodeur Peninsula.

Vertical sections.- The diagnostic feature in vertical sections is a regular structure which is essentia.lly like tha.t of microreticulate tissue, on a larger scale. The horizontal and vertical elements are preserved as beads (200 micron in diameter) of tissue, which would 86

be e~uivalent to the melanospheres in microreticulate tissue. The hor izontally disposed beads are set slightly wider apart than the vertical ones, making the vertical element, somewhat, predominant. Between the vertical elements are the so-called, pseudoz~ tubes. Nearly all resemblance of gallery or interlaminar space is lost except for an in termittent broken structure between 1 mm. thick latilaminations. There are 8 to 10 beads set horizontally or verti.cally in 2 mm. About80% of sections is tissue.

The structure is broken by spots of coarse crystallization, same of which are the remains of tubular structures. Some are clearly tan gential sections of round tubes, others are longitudinal sections of tubes disposed horizontally in the structure. The tubes ( caunopores"l) are 200 to 500 microns in diameter.

Dissepiments or microlaminae are rarely visible; some have been preserved; they measure 25 microns in diameter.

TangentiaJ. sections.- The sections are characterized by 200 micron dots of tissue which are evenly spaced about lOO microns apart. Pre servation has made some of the dots of tissue appear fused. This porous structure is penetrated by remnants of 200 to 500 micron dia.meter tubes.

Discussion.-- The tissue structure has not been preserved, but there is a suggestion of melanospheres in otherwise dark compact tissue. Con spicuous dark, 50 micron dots are surrounded by a 150 micron thick, light, fibrous halo. These spots occur in almost every bead of tissue. The spots may be diagenetic concentrates of pigment.

The almost perfect reticulate gross structure has not been des cribed in the literature. Since only one specimen has been collected a new species has not been named.

Occurrence.-- The specimen was collected from the base of the Cape

Crauford formation, faunal zone IVa; GSC No. 58945-1.

Stromatopora baillargensis n. sp.

Pl. IV, figs. 5, 6.

Two specimens of this species were collected from Brodeur

Peninsula, localities, Tm-63-27c; Tm-63-27a-12.

Exterior .- Coenostea are tabular or laminar expansions, about 6 cm. thick and more than 10 cm. wide. The surface is somewhat undulant and is covered with 1 mm. aize monticules. Latilaminae are not visible.

Vertical sections.-- Neither discrete continuous laminae, nor pillars are developed in the structure. The horizontal element is composed of relatively closely set dot-like masses of tissue which give off, above and below, similarly thick vertical to curved, clumps of tissue. Where the section is slightly obli~ue to the structure, the horizontal and vertical elements appear as zones of closely set dots, 1 mm. across, and short curved bars which alternate with clear zones. Locally, the vertical element spans from one laminae, sensu lato, to another; 88

laminae are 200 to 250 microns thick and 3 occur in 2 mm. Und.ulations

in the horizontal elements, have wave lengths of 0.8 to 1.5 mm. Be

tween the vertical elements are discontinuous, pseudozooidaltubes; 5

occur in 2 :mm.. Dissepiments are rarely preserved in the specimens

collected from Brodeur Peninsula. Other tubes appea.r as 200 to 4oo micron clear holes surrounded by 200 microns of tissue. These may be

caunopores. One longitudinal section of a caunopore tube, wi th tabulae

set 500 microns apart, was seen disposed horizontally in the structure.

The tissue is murky and compact, probably due to bad preservation.

Tangential sections.-- The poorly preserved specimen shows vague dark

and light bands of porous tissue. T'ne thick sieve-llke structure is marred by irregularly branching tubes. Some 200 micron caunopore tubes

are discernable. Locally, tissue appears melanospheric.

Discussion.-- The finer structural features have apparently been lost

in preservation. The gross elements are well enough preserved specifie

identification. Similar species have not been described. The new

species is named after the Baillarge formation from which it was col

lected.

Occurrence.-- Two specimens of this species were collected from the

Baillarge formation, faunal zone III; GSC Nos. 58919-4 and 58916-3.

The holotype is GSC No. 58916-3. Genus ACTINODICTYON Parks, 1909

1909 Actinodictyon n. gen., Parks, p. 30. 1915 Actinodictyon Parks -- Bass1er, p. 16. 1928 Actinodictyon Parks Kuhn, p. 25. 1936 Actinodictyon Parks Parks, p. 113. 1951 Actinodictyon Parks Lecompte, p. 149. 1957 Actinodictyon Parks Galloway, p. 453. 1958 Actinodictyon Parks Flugel, p. 142. 1964 Actinodict1on Parks Nestor, p. 80.

Type species: !;. canadense Parks

Coenosteum cylindrical or a wavy ex pansion composed of irregularly crump1ed laminae and through-going pillars. The laminae re semble dis sepiments and are inflected irreg ularly up and down so that they are impersistent and abut against each other or as in some species of C1athrodictlon. Pillars thick, ir regular in cross section. The cam pact epitissue and endotissue of the 1aminae and pillars are amalga.mated.

Actinodict1on crispatum n. sp.

Pl. IV, figs. 7, 8.

Tbree specimens of the species were collected from Brodeur

Peninsula, section R.

Exterior.-- The coenosteum is a wavy laminar expansion, encrusting fossiliferous calcilute. The la.rgest specimen measures 18 x 12 x 5 cm.

The surface i s hUilll1ocky.

Vertical sections.- The gross structure is tha.t of regularly spaced, zigzag laminae*, and somewhat irregularly spaced, atout, slightly curved pillars which extend through several interlaminar spaces. Re-

1atively thin and straight dissepiments pervade the gross structure.

Laminae laterally, either inflect to join with immediately adjacent laminae or extend into the pillars. The laminae gently curve into the points of inflection. This suggests a basic cyst plate structure. At higher magnification, the laminae are seen to be underlain by finer dissepiments. Indeed, the thin dissepiments** are the structural base (the endotissue) upon which tissue was secreted to for.m the thicker laminae. In some thin sections only dissepiments occur. Similarly, the stout pillars are the result of selective secretion of epitissue about an "a.x:is 11 of downward inflected and joined dissepiments. The pillars, therefore, do not have a microaxis of re1atively denser endotissue. The laminae are also joined by relatively smal1 pi1lars which extend downward from inf1ections in the 1aminae. These are really cyst plates or dissepiments upon which little epitissue has been secreted.

* Ga11oway and St. Jean (1957) and Flugel (1958) refer to the laminae as cyst plates or cysts.

** The distinction between micro1aminae and dissepiments is difficult. Throughout this thesis, dissepiments are considered ~s~roadly curved on1apping structures. It is unknown whether these structures are always sheets of endotissue or whether, they are sometimes strands or 91

This structure is amalgamate, for the stout pillars branch into laminae.

Six to eight laminae occur in 2 mm. and they are about 50 microns

thick. Tissue is compact to flocculent; the f'locculent to ragged nature

of' the epitissue in some areas is probably due to diagenetic ef'f'ects.

Some laminae appear transversely porous; these "pores11 are closely-set

calcite cleavage planes. At XlO magnif'ication, the tissue could be er-

roneously interrpreted as being maculate or microreticulate.

The conspicuously stout pillars are about lOO microns thick, 0.2

to 1 mm. apart, and generally 4 to 5 occur in 2 mm. The pillars are

not straight but appear to bend so to maintain a perpendicular relationship with the planes of the laminae as they extend in the struc-

ture. Pillar tissue is like that of the laminae.

Astrorhizae are obscure in vertical section. They extend wi thin

the confines of one interlaminar space and are 200 to 300 microns in diameter. Some clear round areas surrounded by tissue are astrorhizal branches eut by the plane of' section.

Galleries are of' zigzagged, rectangular form. Relatively straignt,

to locally imbricating dissepiments appear to extend uninterrupted

through galleries and laminae; closer observation shows that they in-

threads which wind their way through the coarser structures. When a relatively fine line of' dark endotissue is straight and continuous through the structures i t is called a microlamina. 92

flect into laminae, stout pillars and minute dissepiment or cyst place-type pillars. Dissepiments are l to 2 microns thick, and 150 to

200 microns apart. About 50fo of the section is occupied by gallery space.

Locally, coarse bioclastic and other foreign matter is enclosed by the growth of the coenosteum.

Tangential sections.-- Distinct concentric laminae are not visible.

The most conspicuous structure is that of the dissepiments which join the minute and stout pillars to form an irregular network. Laminae, sensu stricto, are poorly developed. Relatively light, laminar dis sepimental membranes appear to connect and brace the thicker structures in the coenosteum. In some very, thin sections, this tissue is seen only as, scattered patches of relatively light hue.

The stout pillars are large lOO micron dots of dark tissue or crude star-like forma when the section is at the level where the relatively, thick laminae, join the pillars. At this same level, the lamina.e are pierced by lOO to 200 micron diameter "pores11 (Pa.rks, 1909) or astrorhizal tubes which are surrounded by dark tissue. In another section, radiating astrorhizae are conspicuous, but they apparently do not have central canals. Astrorhizal centers are about 6 nnn. apart and their branches are about 200 microns in dia.meter.

Discussion.-- Except for the atout pillars and the numerous dissepiments, the structure is grossly similar to Ecclimadictyon fastigiatum 93

(Nicholson). The relati vely thin horizontal to curved elements dis- cussed above are not true microlaminae, but rather membranes of dissepiments. Flugel (1958, p. 143) states that dissepiments are absent in Actinodictyon, but that they are present in Pseudoactinodictyon

Flugel, 1958*.

In the type species, ~· canadense Parks, dissepiments are subordinate in the structure. Flugel suggests that Parks species, !.· neptuni, and ~· canadense are the same. He also states that !_. keelei is a

Clathrodictyon and only ~· lowi Parka, is a valid species. The writer agrees with the possible synonymy**.

The species described differa from ~. canadense in the following characters; coenosteum is a thin laminar crust; laminae are regularly and more distantly spaced and sharply inflected; dissepiments are very numerous within galleries; astrorhizal systems are closer together. The species is named, A. crispatum, because of the wavy form of both the coenosteum and the laminae-dissepimental elements.

* This latter genus was established by Flugel to separate Devonian species with true laminae, from Silurian species without straight, con tinuous, laminae which Parka included together in Actinodictyon.

** Flugel's (1958, p. 142) diagrams illustrate the apparent variation in the structure depending upon the relative position of the vertical section. Occurrence.-- Three specimens were collected from the lower part of the Cape Crauford formation, faunal zone IVa, GSC Nos. 58945-2, 58945-3,

58945-4. The holotype is GSC No. 58945-3. 95

ILLUSTRATIONS

Figures Page

1 Geographical map of the Arctic Islands showing location of map area 2a

2 Geological map showing localities on northwestern Baffin Island 11

3 Columnal sections of Member A Cape Crauford For-mation 21

4 Geological map showing fossil localities and sections on northwestern Brodeur Peninsula

Tables

Table of Formations 5

1 Lithology and Biostratigraphy of the Brodeur group 30

2 Stromatoporoids, faunal zones, age and lithology of the Brodeur group 34

3 Stratigraphie Distribution of Stromatoporoids 35

4 General Index to Ma.p (Figure) 4 of fossil locali ties and sections from Northwestern Brodeur Peninsula 37

Plates

I to IV 96

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APPENDIX

INDEX OF FOSSIL I.DCALITIES, BAILLARGE FORMATION

Section or Locality Location

Locality Tm-63-14c-F Brodeur Peninsula, NW Baffin Island; S-facing cliffs and plateu, about 30 miles SW of Cape Crauford, one half mile NW of Admiralty Inlet.

Section B Brodeur Peninsula, NW Baffin Island; S-facing cliffs, about 20 miles SW of Cape Crauford, 3 miles NW of Admiralty Inlet.

Section D Brodeur Peninsula, NW Baffin Island: cliffs, facing Admiralty Inlet, about 17 miles SW of Cape Crauford.

Section D2 S-facing cliffs near Admiralty Inlet, about 16 miles SW of Cape Crauford.

Locality Tmp-63-27a-d About 18,000 feet SW of Cape Crauford; in gulleys eut by two adjacent creeks.

Locality Tm-63-l8b Creek eut about one half mile SW of Cape Crauford.

Note: Stromatoporoids were collected only in the last two localities. See Table 4 for GSC numbers. INDEX OF FOSSIL IOCALITIES 1 CAPE CRAUFORD FORMATION

Section location

c NW Baffin Island, Brodeur Peninsula about 6,500 feet SW of Cape Crauford, seaward facing cliffs.

H NW Baffin Island, seaward facing cliffs, about 5 miles NW of Cape Crauford.

G NW Baffin Island, Brodeur Peninsula, about 5 miles ESE of Sargent Point, E-facing cliffs.

R NW Baffin Island, Brodeur Peninsula, SW facing cliffs, about 4 miles NE of Jackson Inlet.

Note: Stromatoporoids were collected in all these sections. See Table 4 for GSC numbers. PLATES Plate I

All figures X 11.

Figures 1, 2. Clathrodictyon lenticulare n. sp., (Page 46) 1, vertical and 2, tangential sections of holotype; section G; GSC No. 58905-1.

Figures 3, 4. Clathrodictyon vajgatschense Yavorsky (Page 48) 4a. 3, vertical and 4, tangential sections of bypotype; GSC locality No. 58916-5; 4a, clearer tangential section of hypotype; locality Tmp-63-27a-10; GSC No. 58913-1.

Figures 5, 6. Clathrodict~:on miniapse n. sp., (Page 51) 5, vertical and 6, tangential sections of holotype; locality Tmp-63-27c-12; GSC No. 58919-8.

Figures 7, 8. Clathrodictyon Linnarsonni Nicholson, (Page 53) 7, vertical and 8, tangential sections of hypotype; section D; GSC No. 58932-4.

Plate II

Al1 figures X 11.

Figures l, 2. Ecclimadictlon fastigiatum (Nicholson and Murie) 1, vertical and 2, tangentia.l sections {Page 57) of hypotype; loca.lity Tm-63-27a-l2; GSC No. 58916-1.

Figures 3, 4. Ecclimadi.ctlon microvesiculosum (Riabinin) (Page 61) 3, vertical and 4, tangential sections of hyptype; section D; GSC No. 58932-l.

Figures 5, 6. Ecc1imadictyon sp. A., (Page 63) 5, vertical and 6, tangential sections of holotype (î) section D; GSC No. 58932-7.

Figures 7, 8. Intexodictyon brodeurense n. sp., (Page 67) 8a. 7, vertical and 8, tangential sections of ho1otype; loca1ity Tmp-63-27c-12; GSC No. 58919-l; 8a, c1earer tangential section of paratype; locality Tmp-63-27c l2; GSC No. 58919-2.

Plate III

Magnifications as indicated.

Figures 1, 2. t Gerronostroma juvene n. sp. (Page 70 ) 1, vertical and 2, tangential sections, X 11, of ho1otype; 1ocality Tm-63-27a-l2; GSC No. 58916-2.

Figures 3, 4. 'l Gerronostroma Juvene n. sp. Same specimen as above, X 20.

Figures 5, 6. Stromatopora baffinensis n. sp. (Page 76) 5, vertical and 6, tangentia1 sections, X 11, of ho1otype; section H; GSC No. 58902-3.

Figures 7, 8. Stromatopora baffinensis n. sp. Same specimen as above, X 20.

Plate IV

All figures X 11.

Figures 1, 2. StromatoR?ra as~ectabilis Yavorsky (Page 81 ) 1, vertical and 2, tangential sections of hypotype; section H; GSC No. 58902-2.

Figures 3, 4. Stromatopora sp. A., (Page 85 ) 3, vertical and 4, tangential sections of holotype (7); section R; GSC No. 58945-1.

Figures 5, 6. Stromatopora baillargensis n. sp. (Page 87 ) 5, vertical and 6, tangential sections of holo type; locality Tm-63-l8b; GSC No. 58916-3.

Figures 7, 8. Actinodictyon crispatum n. sp. (Page 89) 7, vertical and 8, tangential sections of holo type; section R; GSC No. 58945-3.