The Devonian Colonial 

Coral Genus Billinpsastraea o

and Its Earliest Known 

Species

GEOLOGICAL SURVEY PROFESSIONAL PAPER 483-B
The Devonian Colonial 

Coral Genus Billingsastraea 

and Its Earliest Known 

Species

By WILLIAM A. OLIVER, JR.

CONTRIBUTIONS TO PALEONTOLOGY

GEOLOGICAL SURVEY PROFESSIONAL PAPER 483-B

The geographic and stratigraphic distribution of 

Billingsastraea with a redescription of B. affinis 

its earliest known species

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1964
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, B.C., 20402
CONTENTS

Page

Abstract___________________________________________ Bl

Introduction.______________________________________ 1

Distribution of Billingsastraea-------.---,-------.---- 1

Genus Billingsastraea Grabau._______________________ 2

B. affinis (Billings)____________________________ 3

References cited-___________________________________ 4

ILLUSTRATIONS

PLATES 1, 2. Billingsastraea affinis (Billings)_______-Follow B5

TABLES

TABLE 1. Correlation of the New York stratigraphic

section with the European stages._________ Bl

2. Standard statistics of holotype corallum______ 4

695-563 O 64
CONTRIBUTIONS TO PALEONTOLOGY

THE DEVONIAN COLONIAL CORAL GENUS BILLINGSASTRAEA AND ITS EARLIEST

KNOWN SPECIES

By WILLIAM A. OLIVER, JR.

ABSTRACT

In North America, the compound rugose coral genus Billingsastraea ranges in age from late Early Devonian (middle 

Coblenzian) to latest Middle Devonian (late Givetian) ; it is not 

certainly known outside of North America, although it may occur in Europe and Australia. The genus is composed of 

astraeoid, thamnastraeoid, and aphroid corals with disphyllid 

structure. The oldest known species, B. aflinis, is redescribed.

INTRODUCTION

In the course of a study of the compound rugose 

corals from the Middle Devonian Onondaga Limestone 

in New York, the holotype and only known specimen of 

BiUwgsastraea affims (Billings), from the early 

Devonian Grande Greve Limestone in the Gaspe area; 

Quebec, was borrowed for comparison. B. affinis is of 

special interest because it is the oldest species of the 

genus now known.

The specimen of B. affinis was collected by Robert 

Bell in 1862. Since that time no additional specimens 

have been found although several field studies have been 

made in the area (Gumming, 1959, p. 1-6). The present description is of the holotype corallum. It is hoped 

that additional specimens will eventually permit an 

adequate description of the species.

The specimen is the property of the Geological Survey of Canada and is numbered GSC 3270. Thin sections were made by W. C. Pinckney, Jr.; photographs 

were made by E. H. McKinney (exteriors) and the author (thin sections). The typescript was critically 

read by D. J. McLaren and L. M. Gumming, Geological 

Survey of Canada and J. T. Dutro, Jr., and W. J. 

Sando, U.S. Geological Survey.

DISTRIBUTION OF BILLINGSASTRAEA

Billingsastraea affinis (Billings) is from the Indian 

Cove Member of the Grande Greve Limestone (limestone No. 8 of Logan, 1863, p. 393). The Grande 

Greve has generally been correlated with the Oriskany 

Formation (Billings, 1874, p. 2; Clarke, 1908, p. 250; 

Cooper and others, 1942, chart), although Cooper (in 

Cooper and others, 1942, p. 1762-1763) suggested that

"in all probability the top division is higher than any 

Oriskany exposed in New York.*' More recently, 

Boucot (1959, p. 738-739) suggested that the upper part 

of the Grande Greve (limestone No. 8 of Logan) falls 

within his Esopus Stage (1959, p. 738-739) which overlies the Deerpark (Oriskany) Stage and underlies the 

Schoharie (table 1).

Specimens of Billingsastraea are widespread but uncommon in the somewhat younger rocks of Schoharie 

age. Poorly preserved indeterminate specimens are 

known from the Schoharie Formation (Elckard Hill 

Member of Johnsen, 1957) in eastern New York. At 

Innerkip, Ontario, better specimens have been collected 

from the lower part of the Bois Blanc Formation, which 

Oliver (1960, p. 173) correlated with the Schoharie. 

The genus also occurs in the Spirifer pinyonensis zone 

of the Nevada Limestone, considered late Early 

Devonian (presumably Schoharie age) by Cooper and 

others (1942, chart), by House (1962, p. 252-253), and 

by Johnson (1962).

TABLE 1. Correlation of the New York stratigraphic section 

with the European stages

[Based on Cooper and others (1942), Boucot (1959), Oliver (1960), and House (1962)]

Upper Devonian

Middle Devonian

Lower Devonian

European stage

Frasnian 

1

Givetian

 ? 

Eifelian

Coblenzian

Qedinnian

Silurian

Standard New York 

section

Qeneseo Shale 

Tully Limestone 

Moscow Shale

Ludlowville Shale 

Skaneateles Shale

Marcellus Shale 

Onondaga Limestone

Schoharie Grit 

Esopus Shale

Oriskany Sandstone 

Helderberg Group

North American stage (Cooper 

and others, 1942)

Taghanic

Hamilton 

Group

Esopus Stage 

of Boucot, 

1959

Tioughnioga

Cazenovia

Onesquethaw

Deerpark

Helderberg

Bl
B2 CONTRIBUTIONS TO PALEONTOLOGY

In rocks of Middle Devonian age, specimens of Billingsastraea are widespread and more common. Three 

species occur in the Edgecliff Member of the Onondaga 

Limestone in New York (Eifelian age, Oliver, 1960); 

these and other species are known from equivalent and 

younger Middle Devonian formations in Missouri, 

Iowa, Indiana, Kentucky, Ohio, Michigan, southwest 

Ontario, New York, the Hudson Bay lowlands, 

Ellesmereland, and Northwest Territories.

The latest known specimens of Billingsastraea are 

from the lower part of the Cedar Valley Limestone in 

Iowa (Solon Member of Cooper, 1942) and the Tully 

Limestone in New York. Both of these formations 

have been assigned a Late Devonian (Frasnian) age at 

one time or another, but both are now considered as 

more probably of Middle Devonian age. The Cedar 

Valley is assigned to the late Middle Devonian by most 

recent workers (Cooper and others, 1942, p. 1750-1751; 

Downs and Youngquist, 1950, p. 667-668; Collinson and 

Scott, 1958, p. 5). The age of the Tully is still disputed 

and the most recent assignment is to the early Late 

Devonian (House, 1961; 1962, p. 255-256). Tully 

corals, however, are dominantly Middle Devonian 

(Hamilton) species, with a very few species that are 

limited to the Tully and none of the typical Upper 

Devonian forms. Brachiopod and conodont workers 

(for example Cooper, in Cooper and others, 1942, p. 

1786-1788; and Hass, 1959, p. 1615) reported similar 

dominance of Tully faunas by Middle Devonian species.

Billingsastraea, therefore, ranges from rocks of Early 

Devonian (Coblenzian) to late Middle Devonian (Givetian) age. An early Late Devonian (Frasnian) 

extension of this range is possible.

In Europe, species from rocks of Early to Late Devonian age haye been assigned to Billingsastraea. 

Prantl (1951) described two Lower Devonian species 

from Bohemia in which the septa are virtually limited 

to the tabularia which are surrounded by broad dissepimentaria. Most American species have complete septa 

extending from tabularia to the periphery of the corallites; some species show incomplete septa locally. The 

Bohemian species may represent an extreme example 

of the latter trend, although their Early Devonian age 

suggests that they may represent instead an independent development, not closely related to Billingsastraea.

Schouppe (1958) showed that the type species of 

Phillipsastraea has horseshoe-shaped dissepiments and 

that Phillipsastraea is therefore a senior synonym of 

Pachyphyllum. He proposed that species without 

horseshoe dissepiments, which had been placed in Phillipsastraea, be assigned to Billingsastraea. These species, however, differ from species of Billingsastraea by 

possessing a zone of septal thickening just outside of

the tabularium, whereas specimens of Billingsastraea 

have uniformly attenuate septa. Furthermore, the 

thickened-septa species are mostly of Late Devonian 

age. Schouppe failed to show that the "Phillipsastraea" type was polyphyletically derived from species 

of Billingsastraea, or indeed, that there was any relationship at all. On morphologic grounds, it seems necessary to keep the dominantly Middle Devonian 

Billingsastraea separate from the Late Devonian 

' ' Phillipsastraea."

In Europe then, only the specimens from the Lower 

Devonian in Bohemia are possibly assignable to Billingsastraea. Therefore, the genus is rare in Europe, if 

it occurs at all.

Other reported occurrences of Billingsastraea are 

limited to Australia. DeKoninck 1898, p. 53) cited 

Phillipsastraea verneuili (Milne-Edwards and Haime) 

from the Middle Devonian of New South Wales. This 

is the type species of Billingsastraea* originally described from North America. This citation was repeated by Benson (1922, p. 68,), but the two specimens 

have never been illustrated or adequately described. 

Hill (1957, p. 46), in a review of Australian Devonian 

coral faunas, did not mention the occurrence and cited 

no other Australian specimens of Billingsastraea.

Family DISPHYLLIDAE 

Genus BILLINGSASTRAEA Grabau

1851. [part] Phillipsastraea Milne-Edwards and Haime, p. 447.

1917. Phillipsastraea (Billingsastraea) Grabau, p. 957.

1937. Billingsastraea Grabau, Stumm, p. 437-^38.

1949. Billingsastraea Grabau, Stumm, p. 35.

1951. Billingsastraea Grabau, Ehlers, and Stumm, p. 85.

1953. Billingsastraea Grabau, Ehlers, and Stumm, p. 1.

1956. Billingsastraea Grabau, Hill, p. 280.

1958. [not] Billingsastraea Grabau, Schoupp4, p. 235-237.

Type species. By monotypy, Phillipsastraea verneuili Milne-Edwards and Haime, 1851 (p. 447-448, pi. 

10, fig. 5).

Horizon and locality of type species. Stated by 

Milne-Edwards and Haime to be Wisconsin; generally 

assumed to be a drift specimen originating in the Onondaga or Bois Blanc Formations of Ontario or Michigan 

(Stumm, 1949, p. 35).

Diagnosis. Astraeoid, thamnastraeoid, or slightly 

aphroid corals with calices having a central pit and a 

broad horizontal or reflexed peripheral platform. 

Septa are radially arranged and lightly to heavily carinate with zigzag or crossbar carinae. Major and minor 

septa extend from the periphery; minor septa terminate 

at the outer margin of the tabularium; major septa 

commonly extend to or almost to the axis. At their 

peripheral ends the septa abut against those in the adjacent corallite or are continuous into the next corallite.
DEVONIAN COLONIAL CORAL BILLINGSASTRAEA B3

The tabularium is narrow and composed of closely 

spaced, horizontal, complete tabulae. The dissepimentarium is composed of gently to strongly curved dissepiments that are horizontally arranged except next to 

the tabularia where they are inclined toward the 

corrallite axes.

Remarks. The above diagnosis is adapted from that 

of Stumm (1949, p. 35). It differs by the inclusion of 

zigzag and weakly carinate forms. The type species 

of Radiastraea Stumm (1937), R. arachne, has very 

weak zigzag carinae in some corallites, but carinae are 

totally lacking in others. Stumm listed Radiastraea 

in the synonymy of Billingsastraea but did not include 

its characters in his diagnosis.

The name Billing'sastraea was established by Grabau 

(1917, p. 957) by merely using the word in a subgeneric 

sense. The genus was first defined by Stumm (1937, p. 

437-438), and his definition has been generally accepted 

and used by later workers.

Phillipsastraea vern,euili Milne-Edwards and Haime, 

the type species of Billing sastraea, has never been adequately described. Milne-Edwards and Haime (1851, 

p. 447-448, pi. 10, fig. 5) illustrated the surface of a 

single specimen and briefly described it in general terms. 

There is no indication that any subsequent description 

of the species was based on the type specimen. The 

species characters of P. verneuili are not known, but 

there is no reason to think that it doesn't fit the generally accepted generic concept. B. verneuili (MilneEdwards and Haime), 1851, may be a junior synonym 

of B. rugosa (Hall) 1843.

Three groups of astraeoid corals with the following 

characters are sometimes confused :

1. Uniformly attenuate septa: Billing sastraea.

2. Septa dilated at the borders of the tabularia: Phillipsastraea of most authors.

3. Septal dilation at borders of tabularia corresponding 

to row of horseshoe-shaped dissepiments: Pachyphyllum of authors.

Schouppe (1958) showed that the type species of Phillipsastraea has horseshoe-shaped dissepiments and that 

Phillipsastraea is therefore a senior synonym of Pachyphyllum. Schouppe (1958, p. 2(37) proposed that the 

species of group 2 (Phillipsastraea of authors) be included in Billing sastraea but presented no evidence to 

show that the former (primarily of Late Devonian age) 

were polyphyletically derived from the Middle Devonian Billingsastraea. The morphologic and stratigraphic evidence suggests either no relationship or a 

monophyletic origin instead, and Billingsastraea is here 

restricted to forms with uniform attenuate septa.

Billingsastraea affinis (Billings) 

Plates 1 and 2

1874. Phillipsastraea aflmis Billings, p. 11.

1901. [part] P. verneuili Milne-Edwards and Haime. Lambe,

p. 166.

1908. P. verneuili Milne-Edwards and Haime. Clarke, p. 218. 

1953. Billingsastraea afflnis (Billings). Ehlers and Stumm, p.

6, pi. 2, fig. 4. 

1955. B. affinis (Billings). Stumm, cards 231, 231.1, two new

figs.

Occurrence of type material. "Indian Cove, Gaspe, 

in the Gaspe limestone No. 8" (Billings, 1874, p. 11). 

Gaspe limestone group, Grande Greve Formation, Indian Cove Member of Cumming (1959, p. 4, 24). 

Lower Devonian, Esopus Stage, Etymothyris zone of 

Boucot (1959, p. 737-739).

Diagnosis. Billingsastraea with small corallites and 

calices that are deep and steep sided, with a boss and 

a flat calicular platform. The dissepiments are arranged in arched layers and are smaller and more 

steeply inclined toward the tabularia.

External features. Astraeoid and thamnastraeoid 

colonies of unknown size. The holotype consisted of 

two fragments 7.9 by 7.0 by 2.2 cm, and 6.7 by 5.7 by 3.0 

cm; one horizontal and one vertical slice for thin sections have now been removed from the first of these. 

Corallites are irregularly prismatic and subparallel in 

the preserved parts of the corallum. The distance between adjacent corallite axes (essentially a measure of 

corallite diameter) ranges from 9.6 to 15.6 mm and averages 12.8 mm (table 2).

The surface of the holotype corallum is somewhat 

worn but seems to preserve the shape of several calices. 

The sides of the calicular pits are almost vertical; bottoms are flat with a calicular boss formed by the axial 

ends of the septa; depths to the top of the boss range 

from 3.0 to 3.5 mm. The calicular platforms are flat 

with low radiating septal ridges.

Internal features. The septa are radially arranged. 

Major septa extend from the corallite margin to the 

tabularium where they zigzag and turn slightly; a few 

septa reach the axis or meet other septa. Minor septa 

are commonly limited to the dissepimentarium, although one or two per corallite may be nearly as long 

as the major septa. Peripherally the septa may continue into the next corallite, but commonly they alternate in position forming a zigzag boundary. All septa 

are attenuate and of equal thickness. The number of 

major septa per corallite in the holotype ranges from 

18 to 21 and averages 19.4 (table 2).
B4 CONTRIBUTIONS TO PALEONTOLOGY

TABLE 2. Standard statistics of holotype corallum

[All measurements in millimeters]

Number of corallites____________________ 16 

Number of septa (n) :

Observed range______________________ 18-21 

Mean ____________________________ 19.4 

Standard deviation___________________ 1.1 

Coefficient of variation________________ 5. 6 

Tabularium diameter (d*) :

Observed range______________________ 3. 7-4. 8 

Mean ____________________________ 4. 3 

Standard deviation ___________________ . 3 

Coefficient of variation_________________ 6. 9 

Correlation coefficient (r) of n and d*_..______ .32 

Probability of r being significant____________ . 30 

Axial distance (da ) (mean da is a measure of corallite diameter) :

Observed range______________________ 9. 6-15. 6 

Mean ___________________________ 12. 8

Short zigzag carinae are well developed on all septa 

in the dissepimentarium. At the inner edge of the dissepimeiitarium they are spaced 7 to 10 per 2.5 mm. The 

carinae are very steeply inclined in all but the innermost 

part of the dissepimentarium (pi. 1, figs. 2 and 5).

The dissepimentaria occupy a large part of each corallum. In longitudinal sections the dissepiments form 

an arched pattern, being steeply inclined at the tabularium margins, and nearly horizontal near corallite 

boundaries. The dissepiments tend to increase in size 

away from the tabularium.

In the holotype the tabularia range in diameter from 

3.7 to 4.8 mm and average 4.3 mm. Tabulae are incomplete, forming an arched pattern. Individual tabulae 

are convex in the axial region, convex or concave 

peripherally. They are closely spaced.

Micro structure. Preservation of the holotype is not 

adequate for detailed description of microstructure; 

however, two types of skeletal tissue can be discerned. 

The septa and carinae, except for thin surface layers, 

are composed of dark tissue, in contrast to the dissepiments, tabulae, and thin surface layers of the septa, 

which are uniformly lighter in color. A similar contrast has been noted by the writer in several other 

species of Bitting'sastraea and Heliophyllum. Better 

preserved specimens of other species suggest that the 

darker tissue is composed of pinnately arranged fibers.

Remarks. The above description is based on the 

holotype corallum. Measurements and counts are from 

16 corallites within this 1 colony (table 2).

Billing sastraea affinis differs from other species of the 

genus by the shape of its calice (steep sides, flat peripheral platform) and by the arrangement of its tabulae 

and dissepiments. Other species have raised calice rims 

and lack the calicular boss; both features are reflected 

in dissepiment and tabula arrangements.

Billings (1874, p. 11) first described B. affinis but 

did not illustrate it. Subsequently, Lambe (1901, p. 

166) and Clarke (1908, p. 218) placed the species in 

synonymy with B. verneuili, basing the latter on Onondaga Limestone specimens that are now referred by the 

present writer to B. rugosa (Hall). The holotype corallum of B. affinis falls within the range of B. rugosa in 

corallite and tabularium diameters and number of 

septa but differs by the shape of the calicular pit and 

platform and by the arrangement of the dissepiments.

B. affinis was first illustrated by Ehlers and Stumm 

(1953, pi. 2, fig. 4); a polished longitudinal section was 

illustrated by Stumm (1955, card 231). The holotype 

was not thin sectioned prior to the present work, and no 

illustrations of transverse sections have been published 

previously. All descriptions including this one are 

based on the holotype.

Material. Holotype and only known specimen, 

GSC 3270.

REFERENCES CITED

Benson, W. N., 1922, Materials for the study of the Devonian

paleontology of Australia: New South Wales Geol. Survey,

Recs., v. 10, p. 83-204. 

Billings, Blkanah, 1874, On some of the fossils of the Gaspe

series of rocks: Canada Geol. Survey, Paleozoic fossils,

v. 2, pt. 1, p. 1-64. 

Boucot, A. J., 1959, Brachiopods of the Lower Devonian rocks

at Highland Mills, New York: Jour. Paleontology, v. 33, p.

727-769. 

Clarke, J. M., 1908, Early Devonic history of New York and

eastern North America: New York State Mus. Mem. 9,

366 p. 

Collinson, Charles, and Scott, A. J., 1958, Chitinozoan f aunule of

the Devonian Cedar Valley formation: Illinois Geol. Survey,

Circ. 247, 34 p. 

Cooper, G. A., and others, 1942, Correlation of the Devonian

sedimentary formations of North America : Geol. Soc. America Bull., v. 53, p. 1729-1794. 

Gumming, L. M., 1959, Silurian and Lower Devonian formations

in the eastern part of Gaspe Peninsula, Quebec: Canada

Geol. Survey Mem. 304, 45 p. 

Downs, H. R., and Youngquist, Walter, 1950, Conodonts from

the Cedar Valley limestone of Iowa: Jour. Paleontology, v.

24, p. 667-672. 

Bhlers, G. M., and Stumm, E. C., 1951, Corals of the Middle

Devonian Traverse group of Michigan, part 4, Billingsastraea: Michigan Univ., Mus. Paleontology Contr., v. 9, p.

83-92, pi. 1-3. 

 1953, Species of the tetracoral genus Billing sastraea

from the Middle Devonian of New York and other regions:

Buffalo Soc. Nat. Sci., Bull., v. 21, no. 2, p. 1-11, pi. 1-6. 

Grabau, A. W., 1917, Stratigraphic relationships of the Tully

limestone and the Genesee shale in eastern North America:

Geol. Soc. America Bull., v. 28, p. 945-958. 

Hall, James, 1843, Geology of New York. Part 4, comprising

the survey of the fourth geological district: Albany, 683 p. 

Hass, W. H., 1959, Conodont faunas from the Devonian of New

York and Pennsylvania [abs.] : Geol. Soc. America Bull., v.

70, p. 1615.
DEVONIAN COLONIAL CORAL BILLING8A8TRAEA B5

Hill, Dorothy, 1956, Rugosa in R. C. Moore, ed., Treatise on invertebrate paleontology, Part F Coelenterata: New York 

and Lawrence, Kansas, Geol. Soc. America and Kansas 

Univ. Press, p. 233-324.

 1957, The sequence and distribution of upper Paleozoic 

coral faunas: Australian Jour. Sci., v. 19, p. 42-61.

House, M. R., 1961, Goniatite zonation of the Frasnian: Royal 

Geol. Soc. Cornwall, 4th Conf. of Geologists and Geomorphologists working in S. W. England, Proc., Abstracts, p. 

14-15.

 1962, Observations on the ammonoid succession of the

North American Devonian: Jour. Paleontology, v. 36, no. 2,

p. 247-284. 

Johnsen, J. H., 1957, The Schoharie formation a redefinition:

Dissert. Abs., v. 17, no. 10, p. 2247. 

Johnson, J. G., 1962, Lower Devonian-Middle Devonian boundary

in central Nevada : Am. Assoc. Petroleum Geologists Bull., v.

46, p. 542-546. 

Koninck, L. G. de, 1898, Descriptions of the Palaeozoic fossils of

New South Wales (Australia) : New South Wales Geol.

Survey, Mem. 6 (Palaeontology), 298 p. 

Lambe, L. M., 1901, A revision of the genera and species of

Canadian Palaeozoic corals: Canada Geol. Survey Contr.

Canadian Palaeontology v. 4, pt. 2, p. 97-197, pi. 6-18.

Logan, W. E., 1863, Geology of Canada: Canada Geol. Survey

Rept. Prog. 983 p. 

Milne-Edwards, Henri, and Haime, Jules, 1851, Monographic

des polypiers fossiles des terraines palaezoiques: Paris, Mus.

Natl. d'histoire nat, Archives, v. 5, 502 p. 

Oliver, W. A., Jr., 1960, Coral faunas in the Onondaga limestone

of New York: U.S. Geol. Survey Prof. Paper 400-B, p.

B172-B174. 

Prantl, Ferdinand, 1951, On the supposed occurrence of the

genus Phillipsastraea d'Orbigny, 1849, in the Devonian of

Bohemia: Prague, Ntirodni Mus. Sbornik, v. 7B, no. 3,

Geologia et Palaeontologia, no. 2, p. 3-17, pi. 1-4. 

Schouppe, Alexander v., 1958, Revision des Formenkreises um

Phillipsastraea d'Orb., "PachypJiyllum" E. & H., Macaeea

(Webst.), "Thamnophyllum" Pen., PenecMella Soshk., und

verwandter Formen: Neues Jahrb. Geologic und Palaontologie, Abh., v. 106, p. 139-244, pi. 5-6. 

Stumm, E. C., 1937, The lower Middle Devonian tetracorals of

the Nevada Limestone: Jour. Paleontology, v. 11, p. 424-

443, pi. 53-55.

 1949, Revision of the families and genera of the Devonian 

tetracorals : Geol. Soc. America Mem. 40, 92 p., 25 pis.

 1955, Type invertebrate fossils of North America 

(Devonian), Division 1, Unit IF, Tetracoralla, part C; 

Wagner Free Inst. Sci., Philadelphia, cards 128-337.
PLATES 1 and 2
PLATE 1

FIGURES 1-5. Billingsastraea affinis (Billings) (p. B3).

Holotype G.S.C. 3270. 

la-b. Surface of two parts of corallum, X 1.

2. Transverse thin section of a part of the corallum in fig. la, X 1-

3. Part of transverse thin section, X 2%.

4. Longitudinal thin section taken at left end of corallum as seen in figure 

la, before thin section in fig. 2 was cut off, X 1%.

5. Part of longitudinal thin section, X 5. Note calice profile in figs. 4 and 5.
GEOLOGICAL SURVEY PROFESSIONAL PAPER 483-B PLATE 1

BILLINGSASTRAEA AFFINIS (BILLINGS)