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smithsonian contributions to the marine sciences • number 41

Phymatolithon

(Melobesioideae, Hapalidiales) 

in the Boreal–Subarctic 

Transition Zone of the 

North Atlantic

A Correlation of Plastid DNA Markers with 

Morpho-Anatomy, Ecology, and Biogeography

Walter H. Adey, Jazmin J. Hernandez-Kantun, 

Paul W. Gabrielson, Merinda C. Nash, 

and Lee-Ann C. Hayek
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smithsonian contributions to the marine sciences • number 41

Phymatolithon

(Melobesioideae, Hapalidiales) 

in the Boreal–Subarctic 

Transition Zone of the 

North Atlantic

A Correlation of Plastid DNA Markers with 

Morpho-Anatomy, Ecology, and Biogeography

Walter H. Adey, Jazmin J. Hernandez-Kantun, 

Paul W. Gabrielson, Merinda C. Nash, 

and Lee-Ann C. Hayek

WASHINGTON D.C.

2018
ABSTRACT

Adey, Walter H., Jazmin J. Hernandez-Kantun, Paul W. Gabrielson, Merinda C. Nash, and Lee-Ann C. Hayek. Phymatolithon (Melobesioideae, Hapalidiales) in the Boreal–Subarctic Transition Zone of the North Atlantic: A Correlation of Plastid DNA Markers with 

Morpho-Anatomy, Ecology, and Biogeography. Smithsonian Contributions to the Marine Sciences, number 41, viii + 90 pages, 21 figures, 11 plates, 5 tables, 1 appendix, 2018.—Species of the coralline algal genus Phymatolithon are the dominant algal calcifiers in the 

rocky intertidal and shallow photic sublittoral zone of the Boreal–Subarctic transition zone that stretches across the North Atlantic from 

the Gulf of Maine and the southern Canadian Maritimes to southwestern Iceland and the Norwegian outer coast. In this paper, we use 

extensive field and laboratory data on the biology, physiology, and ecology of Phymatolithon species, supported by statistical analysis 

and DNA sequence data, to develop a multiscale view of this key genus of the ecosystems of this region. We demonstrate that species 

of Phymatolithon that occur in the Boreal–Subarctic transition zone in the North Atlantic can be segregated systematically by a statistical/developmental analysis of their morpho-anatomical characters. We show these results to be congruent with DNA sequence-based 

methods. Six species are recognized: Phymatolithon laevigatum, P. rugulosum (P. lamii), P. squamulosum (P. lenormandii), P. investiens, 

P. borealis sp. nov. (P. polymorphum), and P. nantuckensis sp. nov.). Based on paraffin section, compound microscope, and EDS-SEM 

analysis, we show that coralline anatomy comprises a diversity of both tissue types and high magnesium carbonate wall structure. 

Variations in vegetative tissue morphology, particularly with respect to cell division and elongation patterns, as well as variation in conceptacle (reproductive structure) location and development, are the result of a complex of genetic and environmental factors. Some of 

these factors can be linked to adaptation to environmental and biogeographical niches, providing a basis for experimental analysis of the 

mechanisms of adaptation. We have analyzed conceptacle development in Phymatolithon and demonstrated the linkage between genetic 

control and concurrent vegetative growth; these parameters interact to produce considerable variation in some characters of final gross 

morphology but not in others. These results strongly demonstrate that morpho-anatomical research in the broader Corallinophycideae 

requires greater biological sophistication, with utilization of quantitative population-level data, if success in correlating it with DNA 

sequence data is to be generally achieved.

Cover images: Left, Maine coast Phymatolithon rugulosum specimen with bi-tetrasporangial conceptacle seen from the surface; SEM 

by W. H. Adey. Center, dive crew preparing for a coralline station in northern Newfoundland: (left to right) Alok Mallick, Walter Adey, 

and Alex Miller; photo by Karen Loveland Adey. Right, northern Norwegian Phymatolithon investiens young female conceptacle seen 

in stained microtome section; compound light microscope image by W. H. Adey.

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Library of Congress Cataloging-in-Publication Data

Names: Adey, Walter H., author. | Smithsonian Institution Scholarly Press, publisher.

Title: Phymatolithon (Melobesioideae, Hapalidiales) in the Boreal–Subarctic Transition Zone of the North Atlantic : a correlation of plastid DNA 

markers with morpho-anatomy, ecology, and biogeography / W. H. Adey [and four others].

Other titles: Correlation of plastid DNA markers with morpho-anatomy, ecology, and biogeography | Smithsonian contributions to the marine sciences ; 

no. 41

Description: Washington, D.C. : Smithsonian Institution Scholarly Press, 2018. | Series: Smithsonian contributions to the marine sciences ; number 41 | 

Includes bibliographical references.

Identifiers: LCCN 2017059107

Subjects: LCSH: Phymatolithon—North Atlantic Ocean | Coralline algae—North Atlantic Ocean.

Classification: LCC QK569.C8 A34 2018 | DDC 571.592989—dc23 | SUDOC SI 1.41:41

LC record available at https://lccn.loc.gov/2017059107

ISSNs: 1943-667X (online); 0196-0768 (print)

Publication date (online): 6 April 2018

Ó The paper used in this publication meets the minimum requirements of the American National Standard for Permanence of Paper for Printed Library 

Materials Z39.48–1992.
Contents

LIST OF FIGURES v

LIST OF TABLES vii

INTRODUCTION 1

MATERIALS AND METHODS 2

RESULTS 18

DISCUSSION 43

CONCLUSIONS 50

PLATES 1–11 51

APPENDIX: SUPPLEMENTARY MATERIALS 75

REFERENCES 85

INDEX 89

Figures

1. Phylograms inferred from maximum likelihood (ML) analyses of 

psbA and rbcL plastid markers for selected species of Phymatolithon 19

2. Mean hypothallial cell shape (length/diameter) as a function of 

hypothallial thickness 20

3. Change in mean cell length (pit to pit) of perithallial cells as a 

function of cell position 22

4. The coefficient of variation of cell length as a function of cell position 23

5. Change in cell diameter (width mid-cell lumen) as a function of cell 

position and positive slope of deeper cell diameter 24

6. Cell diameter coefficient of variation as a function of cell position 25

7. Ratio of cell length to cell diameter as a function of cell position 26

8. Percent of cells with fusions as a function of cell position and mean 

cell length at each cell position 27

9. Mean staining body diameter as a function of cell position 28

10. Bi-tetrasporangial conceptacle height to crust surface (pore plate 

surface height above or below crust surface) as a function of 

conceptacle cavity diameter 30

11. Conceptacle dimensions as a function of conceptacle pore plate 

diameter for Phymatolithon laevigatum 31

12. Development of female carpogonium from formation to 

carpospores after fertilization 34

13. Distribution of Phymatolithon laevigatum in Boreal–Subarctic Atlantic 35

14. Distribution of Phymatolithon rugulosum in Boreal–Subarctic Atlantic 36

15. Distribution of Phymatolithon squamulosum in Boreal–Subarctic Atlantic 37

16. Distribution of Phymatolithon borealis in Boreal-Subarctic Atlantic 38

17. Distribution of Phymatolithon investiens and P. nantuckensis in 

Boreal–Subarctic Atlantic 39

Appendix Figures

A1. Phymatolithon tree of all utilized samples 76

A2a. Station locality information for Phymatolithon laevigatum 77

A2b. Station locality information for Phymatolithon rugulosum, 

P. squamulosum, and P. nantuckensis 78

A2c. Station locality information for Phymatolithon borealis and 

P. investiens 79

Tables

1. Phymatolithon stations in the Boreal–Subarctic transition zone of the 

North Atlantic 4

2. Dimensions of asexual conceptacles of Phymatolithon 29

3. Dimensions of female conceptacles of Phymatolithon 32

4. Dimensions of cystocarpic conceptacles of Phymatolithon 33

Appendix Table

A1. DNA specimen information, station locality data, and museum/

herbarium acquisition codes 80

INTRODUCTION

Since the last decade of the nineteenth century, when a basic knowledge of coralline 

biology and subsequently classical taxonomy fully developed (e.g., Foslie, 1895; Heydrich, 1897a,b), it was assumed that features of surface morphology were sufficient to 

define species. Even though Darwin’s (1859) Origin of Species had been published nearly 

four decades earlier, there was still little understanding of the role of natural selection. 

Because there was virtually no direct access to the subtidal environment, coralline ecology and the potential factors driving natural selection were rarely even contemplated. 

One result, among many, was that numerous branching species of Lithothamnion Heydrich were described for the Norwegian coast of the North Atlantic Ocean based solely 

on the gross morphology of the branches (Foslie, 1895). Later, based on a realization that 

the apparent “branching characters” of these species graded into each other, many of the 

names became disused. Nevertheless, new species, which did not appear to match earlier 

proposed species, continued to be described on the basis of a broader, biosystematic 

understanding (Adey, 1970a).

Similarly, new genera were proposed based on features that could easily be observed, 

primarily focused on surface morphology, especially of reproductive structures. Thus, 

Phymatolithon Foslie was separated from Lithothamnion on the basis of the presence of 

sunken conceptacles. Clathromorphum Foslie also had sunken conceptacles, but differed 

from Phymatolithon in early development by having “slightly convex light dots” over 

the conceptacles. Subsequent authors, recognizing that the depth of conceptacles graded 

widely between genera and that the “white spots” also appeared in Phymatolithon, 

either rejected both genera (for Lithothamnion) or used one or the other, depending 

on the author (see Adey, 1964). Beginning 70 years later, for all three genera, complex, 

Phymatolithon (Melobesioideae, Hapalidiales) 

in the Boreal–Subarctic Transition Zone of the 

North Atlantic

A Correlation of Plastid DNA Markers with 

Morpho-Anatomy, Ecology, and Biogeography

Walter H. Adey,1* Jazmin J. Hernandez-Kantun,1

Paul W. Gabrielson,2 Merinda C. Nash,1 and Lee-Ann C. Hayek3

1 Department of Botany, National Museum of 

Natural History, Smithsonian Institution, Washington, DC, 20013-7012, USA.

2 Department of Biology and Herbarium, University of North Carolina, Chapel Hill, North 

Carolina, USA.

3 Statistics and Mathematics, National Museum 

of Natural History, Smithsonian Institution, 

Washington, DC, 20013-7012, USA.

* Correspondence: adeyw@si.edu

Manuscript received 23 January 2017; accepted 

5 October 2017.
2 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

based sampling of more than 12,000 specimens, including six 

Phymatolithon species from more than 300 stations, across 

this entire region in the North Atlantic Ocean. In addition, we 

introduce carbonate cell wall ultrastructure and chemistry to the 

morpho-anatomical characterization of these species.

MATERIALS AND METHODS

Collections and Preparation

Specimens were sampled from 278 stations with collections 

from 125 intertidal sites, 728 dive zones of 3–6 m range (to 

depth 35 m), and 44 dredge sites at depths greater than the 35 m 

dive limit employed (Table 1). The collecting effort, primarily by 

scuba, required approximately 25 summer months and 50 winter days. Four research vessels (R/V Pelion and R/V Bjorneng of 

author W.H.A., the chartered vessel R/V Akpatok, and Tromso 

Marinbiologisk Station R/V Asterias) were employed. Approximately 40 of the stations (18 in Iceland) were worked from shore 

with a Boston Whaler independent of a larger research vessel.

Most specimens were taken by scuba as representative samples of station substrate and consisted of rocks, pebbles, or shells 

encrusted with species mosaics of corallines. More than 12,000 

specimens were collected and more than 40,000 species area measurements (in cm2

, reported as % of total coralline cover) were 

taken, mostly while on station (see detailed description in Adey 

and Steneck, 2001). Most samples were tentatively identified 

while alive and fresh in research vessels or at local shore-based 

laboratories. Subsamples were taken for preservation in paraffin and subsequent microtome sectioning, and coralline surface 

areas were measured with clear plastic grids for biogeographical 

and ecological analysis. A number of specimen fragments were 

preserved and sectioned by microtome for stained slide viewing 

within several days of collecting. Based on these sections, a relatively small proportion of the identifications (10%–20%) were 

corrected while still in the field. Later, mostly during the following winter season, collections were reviewed again and “final” 

identifications applied. This procedure as confirmed by DNA 

analysis was more than 95% successful.

Collections are permanently stored in the Coralline Collection of the U.S. National Herbarium (US). During the past 

two decades, many specimens from the extensive dried collections, as well as specimens on loan from other herbaria, have 

been mounted for scanning electron microscopy (SEM) and 

examined using a Leica 440. All numerical data were collected 

manually, either directly with a compound microscope or from 

SEM images. More than 200 paraffin blocks of preserved specimens produced over 1,000 slides from which measurements and 

more than 200 micro-images were obtained; 30 SEM mounts 

were made that produced more than 250 images. For cell dimensions and other characters, the numbers of stations/plants/

filaments measured (i.e., for each data point) are as follows: 

Phymatolithon rugulosum, 25/41/52; P. laevigatum, 33/44/47; 

quantifiable, and statistically significant patterns of anatomy were 

identified; included was a newly described intercalary meristem 

(an uncommon feature in red algae) underlying the superficial 

morphology (Adey, 1964, 1965; Adey et al., 2001, 2005, 2013, 

2015a,b). The evolution of the diverse anatomy in these genera 

was hypothesized, in large measure, to be a defense against mollusk grazing (Steneck, 1982, 1992); different genera and species 

showed a wide variety of anatomical strategies to counter that 

grazing. Furthermore, with the advent of scuba, the ecological 

and biogeographical distributions of these Northern Hemisphere 

species and genera studied by Adey (1964, 1965, 1966a,b, 1968, 

1971) provided quantitatively recognizable patterns.

In the several decades before the application of DNA 

sequencing to corallines, their taxonomy became a shifting 

arena of personal opinion as to what characters were or were 

not taxonomically informative and at what ranks they should 

be applied (Woelkerling, 1988; Irvine and Chamberlain, 1994). 

These opinions were not based on a broader use of statistically 

characterized morpho-anatomical characters in the framework 

of ecological and biogeographical knowledge, with some exceptions (Lebednik, 1977; Steneck, 1982). With the advent of DNA 

sequencing, genera and species of the more intensively studied 

non-geniculate corallines, especially in Subarctic and Boreal 

waters in the North Atlantic, have been supported by DNA 

sequencing and phylogenetic reconstructions (Adey et al., 2015). 

This support has not proved true for many coralline genera and 

species in the rest of the world, where DNA sequencing is revealing a multitude of undescribed taxa (e.g., Basso et al., 2015; 

Hind et al., 2015, 2016; Hernandez-Kantun et al., 2016; Peña 

et al., 2015a,b; Rosler et al., 2016).

The region treated herein that we call the Boreal–Subarctic 

transition zone is that part of the coastal North Atlantic that 

has shallow, warmer-water Boreal species underlain by deeper, 

colder-water Subarctic species. Adey and Hayek (2011) showed 

that this distribution is characteristic for the entire macroalgal 

flora of this zone, a feature revealed only by depth-calibrated 

collections. Adey and Steneck (2001) treated this as a welldefined transition (unnamed zone) between the Subarctic and 

the Boreal (Celtic). It is notable that the transition becomes more 

geographically distributed than depth distributed in Norway 

(Adey, 1971), where the inner fjords are Subarctic and the outer 

coast, with only a weak thermocline, is mostly Boreal in coralline 

composition. Based on the rocky bottom area covered, Boreal 

and Subarctic non-geniculate coralline species together provide 

roughly 80% of the coralline flora in the Boreal–Subarctic transition zone that we cover in this paper (Table 1; Adey and Steneck, 

2001); Phymatolithon species are about half of that value (Adey, 

1964, 1968, 1971). The Boreal species Lithophyllum orbiculatum (Foslie) Foslie in shallow water and Lithothamnion sonderi

Hauck in deep water make up the remaining 20%. In shallow 

to midphotic depths (intertidal to ~20 m; to depth ~30 m on the 

outer Norwegian coast), Phymatolithon species are the dominant crustose elements of the rocky bottom flora. We present an 

extensive set of DNA analyses applied to a very large ecologically 
NUMBER 41 • 3

psbAF1 (forward) and psbA600R (reverse, Yoon et al., 2002). 

The PCR and sequencing mixes and thermocycler protocols followed Adey et al. (2015b).

The DNA analysis included type material from the holotype of Phymatolithon investiens (Foslie) Foslie, the holotype 

of Phymatolithon laevigatum (Foslie) Foslie, an isotype of Phymatolithon rugulosum W. H. Adey, an isotype of Phymatolithon

squamulosum (Foslie) W. H. Adey, J. J. Hernandez-Kantun & 

P. W. Gabrielson, and the holotypes of the newly described species Phymatolithon borealis W. H. Adey, J. J. Hernandez-Kantun 

& P. W. Gabrielson sp. nov. and Phymatolithon nantuckensis

W. H. Adey, J. J. Hernandez-Kantun & P. W. Gabrielson sp. nov. 

Sequences from previous publications included Lithothamnion

spp., Sporolitihon tenue R. G. Bahia, G. M. Amado-Filho, G. W. 

Maneveldt & W. H. Adey, and Phymatolithon spp. (Adey et al., 

2015b; Peña et al., 2015b; Appendix Figure A2); the first two 

were used as the outgroup.

Data sets were initially produced for psbA and for rbcL, 

including all sequences from Genbank and those obtained from 

the North Atlantic. Removing identical sequences for both markers generated two more data sets. All datasets were aligned with 

ClustalW in Mega version 5 (Tamura et al., 2011) using default 

settings and refined by eye. This software was also employed 

to analyze rbcL and psbA data sets with identical sequences by 

using the unweighted pair group method with arithmetic mean 

(UPGMA) with uncorrected p-distances and 1,000 resamplings 

for statistical support. Phylogenetic analyses were applied to 

rbcL and psbA data sets without identical sequences using maximum likelihood (ML) in RAxML 1.3 (Mac version; Silvestro and 

Michalak, 2012). The psbA and rbcL datasets were partitioned 

by codon position and analyzed using the general time-reversible 

(GTR) model with invariant sites and gamma distribution for 

each of the partitions; bootstrap analyses with 1,000 resamplings 

were used for statistical support. The same mentioned partition 

strategy and model were used for Bayesian inference in MrBayes 

v. 3.2.2 (Huelsenbeck and Ronquist, 2001). Four Monte Carlo–

Markov chains were run for 5 million generations, and tree sampling was done every 1,000 generations. Tracer v.1.5 (Rambaut 

and Drummond, 2007) was used to verify the stationary distribution of the runs; 1,250 trees were discarded as burn-in for the 

50% majority rule consensus trees.

Ultrastructure of Carbonate Walls

Crusts were fractured using shears and mounted in superglue. After low-magnification imaging of fractured crusts, they 

were prepared as follows for scanning electron microscopy–

energy dispersive spectroscopy (SEM-EDS) measurements. Samples were polished using 2,000 gsm (grams/square meter) wet or 

dry sandpaper, then sonic cleaned in unbuffered deionized water 

for 2 min. This cleaning method very lightly etches the surface, 

allowing differentiation between different magnesium calcite 

morphologies without altering the measured Mg content. Specimens were then coated with platinum.

P. squamulosum, 22/27/33; P. nantuckensis, 1/2/10; P. borealis, 

18/28/31; and P. investiens, 17/29/31. The numerical data for 

bi-tetrasporangial conceptacles were taken from stations/plants/

conceptacles (i.e., for each data point from a single conceptacle) 

as follows: P. rugulosum, 11/13/53; P. laevigatum, 14/16/43; 

P. squamulosum, 14/16/35; P. nantuckensis, 1/2/10; P. borealis, 

5/5/20; and P. investiens, 1/1/6. These data, on 25 Excel spreadsheets, were transferred to the graphing program Origin 2016 to 

create the figures presented herein.

Statistical Methods

All data for each species, either by cell position or by 

selected morphological measurements, were subjected to descriptive statistics and tests of both means and medians plus variances. General linear models (GLM) of analysis of variance 

(ANOVA), regression, and repeated-measures/paired t tests were 

developed and tests of full versus restricted models constructed. 

Assumptions were tested for each model and data transformed 

when necessary for either distributional or variance adjustment. 

For the ratio variables of cell length to cell diameter (L/D), we 

transformed to the difference of logarithms for testing. However, we report herein original values for clarity. For more than 

two groups, we examined one degree of freedom vectors and cite 

Scheffé’s test results in text.

DNA Extraction, PCR Amplification, and Sequencing

Genetic material was successfully obtained and amplified 

from 92 specimens in the herbaria BM, NCU, and US (Appendix 

Figure A1); herbarium acronyms follow Thiers (2017, continuously updated) and are defined therein. All protocols were performed following recommendations of Saunders and McDevit 

(2012) and Hughey and Gabrielson (2012) to prevent contamination. Small fragments (~3 mm3

) were removed from larger 

specimens left as herbarium vouchers. Under a stereomicroscope, fragments were inspected to remove algal epiphytes and 

later crushed to powder in clean foil. Extraction of total genomic 

DNA for specimens in the US and BM herbaria followed the 

modified protocol by Broom et al. (2008) of the Qiagen DNeasy 

Blood and Tissue Kit (Qiagen, Crawley, UK); for specimens in 

NCU, the protocol was as in Gabrielson et al. (2011).

Plastid-encoded rbcL and psbA genes were analyzed using 

negative controls. The rbcL gene was initially amplified by 

polymerase chain reaction (PCR) by two pairs of primers, F57 

(forward) – R753 (reverse) and F753 (forward) – RrbcS start 

(reverse, Freshwater and Rueness, 1994). If none of these pairs 

resulted in a PCR product, we used a pair of primers, F1150Cor 

(forward, Sissini et al., 2014) and RrbcS (reverse, Freshwater and 

Rueness, 1994), to amplify a shorter fragment (trimmed to 296 

base pairs). The psbA gene was amplified initially using the primers psbAF1 (forward) and psbAR2 (reverse, Yoon et al., 2002). If 

PCR product was lacking, a second run was made using primers 
4 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

TABLE 1. Presence of Phymatolithon by species and depth at stations in the Boreal–Subarctic transition zone of the North Atlantic. 

Abbreviations: Int = intertidal zone; rhodos = rhodoliths; Tr = trace. A dash (-) indicates not present or data not available; a question 

mark (?) indicates indeterminant specimen.

Station no. Date Locationa Latitude Longitude

61-1 7/13/1961 Sally Island, off Corea, ME, USA 44 24.1N 67 56.7W 

61-3 7/19/1961 Andrews Island, W Deer Isle, Thorofare, ME, USA 44 8.8 N 68 42.2W 

61-4 7/20/1961 Benner Island, Muscongus Bay, ME, USA 43 52.8 N 69 19.3 W 

61-5 7/22/1961 Small Point, Cape Small, ME, USA 43 42.2N 69 50.3W 

61-6 7/23/1961 Richmond Island, Cape Elizabeth, ME, USA 43 32.4N 70 13.8W 

61-7 7/24/1961 Smutty Nose Island, Isles Shoals, NH, USA 42 59.0N 70 36.4W 

61-8 7/27/1961 Stellwagen ledge, Scituate, MA, USA vic 42 16N 70 46 W 

61-9 7/28/1961 Naushon Island, Buzzards Bay, MA, USA 41 30.1N 70 44.1W 

61-10 7/29/1961 Vineyard Sound, Norton Rock, Martha’s Vineyard, MA, USA 41 26.1N 70 42.3W 

61-11 7/30/1961 Nashawena Island, S Central, MA, USA 41 25.2N 70 52.5W 

61-12 8/1/1961 Nantucket Harbor, Coatue & 2nd, MA, USA 41 18.0N 70 4.4W 

61-13 8/4/1961 Newport Neck, Sheep Point, RI, USA 41 27.6 N 71 18.0 W 

61-14 8/5/1961 Bartlet Reef, NNW Race, Long Island Sound, CT, USA 41 16.3 N 72 8.1 W 

61-15 8/7/1961 East side Block Island, Grace Point, RI, USA 41 10.0N 71 32.6W 

61-16 8/9/1961 High Pine ledge, off Plymouth, MA, USA 42 1.9 N 70 36.5 W 

61-17 8/9/1961 Pickworth Point, off Manchester, MA, USA 42 33.7 N 70 45.9 W 

61-18 8/10/1961 Cape Neddick, ME, USA 43 10.1N 70 35.6W 

61-19 8/12/1961 Outer Heron Island, Boothbay Harbor, ME, USA 43 46.2N 69 35.1W 

61-20 8/13/1961 Otter Island, off Vinalhaven, ME, USA 44 0.3 N 68 48.0 W 

61-21 (+ 62-32,87) 8/17/1961 Western Head, Isle au Haut, ME, USA 44 0.4N 68 39.1W 

61-22 8/20/1961 Shingle Island, W Jericho Bay, ME, USA 44 9.2 N 68 35.0 W 

61-23 8/23/1961 Wooden Ball Island, off Penobscot Bay, ME, USA 43 53.5N 68 44.3W 

61-24 8/23/1961 Wooden Ball Island, off Penobscot Bay, ME, USA 43 53.5N 68 44.3W 

61-25 8/23/1961 Matinicus Rock, ME, USA 43 47.0N 68 51.4W 

61-26 8/27/1961 Great Duck Island, SE Muscongus Bay, ME, USA 43 52.6N 69 7.3W 

61-27 8/29/1961 Upper Herring, Steele Harbor Island, ME, USA 44 29.1 N 67 31.7 W 

61-28 8/30/1961 SW Head, Grand Manan Island, NB, Canada 44 36.5 N 66 59.8 W 

61-29 8/31/1961 Spruce Point, Cross Island, ME, USA 44 35.9N 67 18.7W 

61-30 9/5/1961 Baccarro Point, Barrington Bay, NS, Canada 43 27.8N 65 29.6 W 

61-31 9/6/1961 Beaver Point, Outer Beaver Harbor, NS, Canada 44 53.4 62 25.0 W 

61-32 9/7/1961 Livingston Cove, Cape George, NS, Canada 45 52.1 N 61 58.9 W 

61-33 & following 9/23/1961 Merchant Island, off Deer Isle, ME, USA 44 6.3N 68 39.3W 

61-34 9/24/1961 Northwest Harbor, Deer Isle, ME, USA 44 13.7 N 68 41.2 W 

61-35 9/30/1961 Merchant Island, off Deer Isle, ME, USA 44 6.3N 68 39.3W 

61-36 10/5/1961 Hurricane Island, off Vinalhaven, ME, USA 44 2.0 N 68 53.5 W 

61-37 10/7/1961 Lower head, Marshall Island, ME, USA 44 5.8 N 68 30.4 W 

61-38 10/17/1961 Merchant Island, off Deer Isle, ME, USA 44 6.3N 68 39.3W 

61-39 10/22/1961 Kimball Head, Kimball Island, ME, USA 44 4.5 N 68 40.3 W 
NUMBER 41 • 5

Depth (m); x = depth zone collected % P. 

laevigatum 

0–25 m

% P. 

rugulosum 

5–30 m

% P. 

squamulosum

Int–3 m

% P. 

nantuckensis

% P. 

borealis 

0–30 m

% P. 

investiens 

Int 0–3 3–9 9–15 15–21 21–28 28–37 >37 0–35 m

- - x x - - - - 12 17 - - - -

- x x - - - - - 0 0 - - - -

x - - - - - - - - - Present - - -

- x x x - - - - 32 21 - - - -

- - x x - - - - 24 5 - - - -

- - - x - - - - 0 0 - - - -

- - - x - - - - 46 Tr - - - -

- - x x - - - - 100 0 - - - -

- x x - - - - - 90 0 - - - -

- x x x - - - - 100 0 - - - -

- - x - - - - - ? 0 - 100 - -

- - - x - - - - 100 0 - - - -

- - x - - - - - 100 0 - - - -

- - x - - - - - 100 0 - - - -

- - x - - - - - 46 <1 - - - -

- x x x - - - - 28 1 - - - -

- x x x - - - - 14 12 - - - -

- - x x x - - - 28 5 - - - -

- - x x x - - - 4 15 - - - -

- - - x - - - - - - - - - -

- x - - - - - - - - - - - -

x x - - - - - - - - Absent - - -

- - - - x x - - 0 0 - - - -

- - x x - - - - 6 5 - - - -

- x x x - - - - 2 3 - - - -

- - x x x - - - 11 2 - - - -

- - x x x - - - 1 Tr - - - -

- - x x x - - - 2 <1 - - - -

- - x - - - - - 10 28 - - - -

- - x x x - - - 4 0 - - - -

- - x x x - - - - - - - - -

x x x x - - - - 2 32 Absent - - -

x - - - - - - - - - Absent - - -

- x x - - - - - - - - - - -

- x x x - - - - 3 11 - - - -

- x x x - - - - 0.4 27 - - - -

- x x - - - - - - - - - - -

- x x - - - - - 3 4 - - - -

TABLE 1. (Extended)
6 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

Station no. Date Locationa Latitude Longitude

61-40 10/23/1961 Northwest Harbor, Deer Isle, ME, USA 44 13.7 N 68 41.2 W 

61-41 11/2/1961 Merchant Island, off Deer Isle, ME, USA 44 6.3N 68 39.3W 

61-42,46; 62-4,21 11/5/1961 NW Great Spoon Island, ME, USA 44 2.7N 68 33.5W 

61-43 11/17/1961 N Vineyard S, Woods Hole, MA, USA 41 31.0 N 70 39.4 W 

61-44 11/19/1961 Halibut Point, Cape Ann, MA, USA 42 41.7 N 70 37.9W 

61-45 12/2/1961 Merchant Island, off Deer Isle, ME, USA 44 6.3N 68 39.3W 

61-46 12/3/1961 NW Great Spoon Island, ME, USA 44 2.7N 68 33.5W 

62-1 1/3/1962 W Deer Isle, Dunham Point, ME, USA 44 13.3 N 68 44.0 W 

62-2 1/6/1962 Merchant Island, off Deer Isle, ME, USA 44 6.3N 68 39.3W 

62-3 2/10/1962 Merchant Island, off Deer Isle, ME, USA 44 6.3N 68 39.3W 

62-4 2/16/1962 NW Great Spoon Island, ME, USA 44 2.7N 68 33.5W 

62-5 2/28/1962 NW Deer Isle, ME, USA 44 16.0 N 68 40.5 W 

62-6 3/5/1962 NW Little Deer Isle, ME, USA 44 18.5 N 68 44.8 W 

62-7 3/7/1962 NW Harbor, Deer Isle, ME, USA 44 13.4 N 68 40.9W 

62-8 3/11/1962 Lane Cove Breakwater, Cape Ann, MA, USA 42 40.8 N 70 39.7 W 

62-9 3/16/1962 S Saddleback Island, W Jericho Bay, ME, USA 44 8.6 N 68 34.8 W 

62-11L 3/17/1962 Brace Cove, SE Cape Ann, MA, USA 42 35.6 N 70 38.9 W 

62-12 3/29/1962 Sheephead Island, off Deer Isle, ME, USA 44 12.3 N 68 34.0 W 

62-13 3/30/1962 E Wbster Head, North Haven Island, ME, USA 44 11.1 N 68 50.6 W 

62-14 4/3/1962 Rich’s Point, Isle au Haut, ME, USA 44 5.2 N 68 36.0 W 

62-15 4/11/1962 Fog Island, off Deer Isle, ME, USA 44 5.7 N 68 34.4 W 

62-16 4/12/1962 Merchant Island, off Deer Isle, ME, USA 44 6.3N 68 39.3W 

62-17 4/15/1962 Stave Island, Egemoggin Reach, ME, USA 44 17.3 N 68 41.3 W 

62-18 4/17/1962 Pressey Cove to NW Harbor, Deer Isle, ME, USA 44 14.3 N 68 42.5 W 

62-19,23 4/28/1962 NE Eagle Island, E Penobscot Bay, ME, USA 44 13.2 N 68 46.2 W 

62-20 5/2/1962 Off Bartlett Harbor, North Haven Island, ME, USA 44 8.4 N 68 55.6 W 

62-21 5/11/1962 NW Great Spoon Island, ME, USA 44 2.7N 68 33.5W 

62-23 5/12/1962 NE Eagle Island, Penobscot Bay, ME, USA 44 13.2 N 68 46.2 W 

62-24 5/16/1962 Orrs Cove, Cape Rosier, Penobscot Bay, ME, USA 44 19.6 N 68 49.4 W 

62-25 5/17/1962 Negro Island, Bagaduce River, N Penobscot, ME, USA 44 24.2 N 68 46.4 W 

62-26 5/17/1962 Turtle Cove, Long Island, Penobscot Bay, ME, USA 44 23.1 N 68 53.7 W 

62-27 5/29/1962 NE Mount Desert Rock, ME, USA 43 58.2 N 68 7.6 W 

62-28 5/31/1962 Great Spruce Thoro, Roque Island, ME, USA 44 33.9 N 67 30.7 W 

62-29 5/31/1962 Cow Point, Mack Cove, Englishmen Bay, ME, USA 44 35.8 N 67 27.6 W 

62-30 6/1/1962 W Almore Cove, off Cutler, ME, USA 44 39.7 N 67 11.2 W 

62-31 6/2/1962 Deep Cove, Cobscook Bay, ME, USA 44 53.7 N 67 6.7 W 

62-32,87 6/8/1962 E Western Ear, Isle au Haut, ME, USA 44 0.3 N 68 39.1 W 

62-33 6/8/1962 Central S Isle au Haut, ME, USA 44 0.8 N 68 38.3 W 

62-35 6/14/1962 Popplest Cove, Great Wass Island, ME, USA 44 27.5 N 67 34.2 W 

TABLE 1. (Continued)
NUMBER 41 • 7

Depth (m); x = depth zone collected % P. 

laevigatum 

0–25 m

% P. 

rugulosum 

5–30 m

% P. 

squamulosum

Int–3 m

% P. 

nantuckensis

% P. 

borealis 

0–30 m

% P. 

investiens 

Int 0–3 3–9 9–15 15–21 21–28 28–37 >37 0–35 m

x - - - - - - - - - Absent - - -

- x x - - - - - - - - - - -

- x x x - - - - 6 13 - - - -

- x x - - - - - 90 - ? - - -

- x x x - - - - 22 6 - - - -

- x - - - - - - - - - - - -

- - x - - - - - - - - - - -

x - - - - - - - - - Present - - -

- x x - - - - - - - - - - -

- x x - - - - - - - - - - -

- - x - - - - - - - - - - -

x - - - - - - - - - Present - - -

x x - - - - - - 11 6 Abundant - - -

x - - - - - - - - - Absent - - -

- x x - - - - - 12 Tr - - - -

- x x - - - - 0.9 13 - - - -

- - x - - - - - - - - - - -

x - - - - - - - - - Abundant - - -

- x - - - - - - 2 10 - - - -

- - x - - - - - 3 Tr - - - -

- x x - - - - - 0.5 2 Absent - - -

- x x - - - - - - - - - - -

x - - - - - - - - - Present - - -

x x x - - - - - 0 20 Present - - -

- x x x - - - - 7 4 - - - -

x x x - - - - - 6 4 Present - - -

- - - x - - - - - - - - - -

- x x x - - - - - - - - - -

x x x - - - - - 0.8 Tr Abundant - - -

- x x x - - - - 19 0 - - - -

x x x - - - - - 31 0.5 Abundant - - -

- - - x x - - - 7 1 - - - -

x x - - - - - - 1 0 Absent - - -

x x x x - - - - 4 0 Absent - - -

x x x - - - - - 6 Tr Absent - - -

x x x - - - - - Tr 2 Absent - - -

- - x x x x - - 18 6 - - - -

- x x - - - - - 0 6 - - - -

x x x x x - - - 5 0 Absent - - -

TABLE 1. (Extended)
8 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

Station no. Date Locationa Latitude Longitude

62-36 6/15/1962 Grand Manan Channel, East Head, NB, Canada 44 49.9 N 65 55.6 

62-37 6/16/1962 Passamaquoddy Bay, Deer Isle, NB, Canada 44 47.5 N 66 57.0 

62-38 6/17/1962 N Nancy Head, Campobello Island, NB, Canada 44 55.0 N 67 53.5 

62-39 6/18/1962 Cambell Point, Dipper Harbor, Bay of Fundy, NB, Canada 44 5.2 N 66 24.6 W 

62-40 6/21/1962 Macomber Point, Quaco Bay, Bay of Fundy, NB, Canada 45 21.4 N 65 31.0 W 

62-41 6/22/1962 Quaco Ledge, Bay of Fundy, NB, Canada vic 45 17 N 65 20 W 

62-42 6/23/1962 Broad Cove, off Digby, NS, Canada 44 41.3 N 65 46.5 W 

62-43 6/25/1962 N Swallowtail Point, Grand Manan, NB, Canada 44 46.4 N 66 45.0 W 

62-44,50 6/26/1962 Arey Cove, Schoodic Point, ME, USA 44 20.0 N 68 3.6 W 

62-45 6/20/1962 NE Butter Island, E Penobscot Bay, ME, USA 44 14.2 N 68 47.4 W 

62-46 7/1/1962 SE Pickering Island, E Penobscot Bay, ME, USA 44 15.6 N 68 44.7 W 

62-47 7/2/1962 Deer Isle Mill Pond, ME, USA 44 13.6 N 68 41.1 W 

62-48 7/2/1962 SW Eagle Island, E Penobscot Bay, ME, USA 44 12.3 N 68 47.1 W 

62-49 7/9/1962 SE Vinalhaven, ME, USA 44 1.9 N 68 49.0 W 

62-50 7/12/1962 Arey Cove, Schoodic Point, ME, USA 44 20.0 N 68 3.6 W 

62-51 7/13/1962 S Parker Head, Roque Island, ME, USA 44 34.7 N 67 32.4 W 

62-52 7/14/1962 S shore Outer Wood Island, NB, Canada 44 36.3 N 66 49.1 W 

62-53 7/16/1962 SW Cape Fourchu, West, NS, Canada 43 47.8 N 66 10.0 W 

62-54 7/17/1962 SW St Ann Point, Pubnico, NS, Canada 43 35.7 N 65 48.6 W 

62-55 7/18/1962 E Cat Point, Baccaro Point, NS, Canada 43 27.4 N 65 27.9 W 

62-56 7/19/1962 E Cape Roseway, NS, Canada 43 37.7 N 65 15.7 W 

62-57 7/20/1962 Green Point, W Port Latour, NS, Canada 43 29.9 N 65 31.7 W 

62-58 7/23/1962 Whipple Point, Brier Island, NS, Canada 44 13.5 N 66 22.3 W 

62-59 7/30/1962 Kimble Island, ME, USA 44 4.5 N 68 40.3 W 

62-60 7/30/1962 Eggemoggin in Egg, Reach, ME, USA 44 18.6 N 68 44.0 W 

62-61 8/3/1962 NW Flint Island, Flint Island Narrows, ME, USA 44 28.8 N 67 47.8 W 

62-62 8/4/1962 Pinkham Island, Harrington Bay, ME, USA 44 32.6 N 67 49.8 W 

62-65 8/11/1962 Deep Cove, Long Island, Blue Hill Bay, ME, USA 44 21.7 N 68 31.4 W 

62-67 8/12/1962 Seal Cove, Bartlett Island, Blue Hill Bay, ME, USA 44 20.3 N 68 27.0 W 

62-68 8/13/1962 Long Porc/Hop, Frenchmen Bay, ME, USA 44 24.6 N 68 9.3 W 

62-69 8/12/1962 Freese’s Island, W Deer Isle, ME, USA 44 12.3 N 68 43.3 W 

62-70 8/16/1962 E Metinic Island, ME, USA 44 52.3 N 69 7.1 W 

62-71 8/17/2015 Cranberry Island, Muscongus Bay, ME, USA 43 56.2 N 69 21.8 W 

62-72 8/18/1962 Stage Island, Cape Porpoise, ME, USA 43 21.7 N 70 24.9 W 

62-73 8/19/1962 Flat Point, E Cape Ann, MA, USA 42 38.9 N 70 35.4 W 

62-74 8/20/1962 Center Hill Point, Cape Cod Bay, MA, USA 41 51.6 N 70 31.3 W 

62-75 8/21/1962 N Clark Island, Duxbury Bay, MA, USA 42 0.8 N 70 38.2 W 

62-76 8/21/1962 W Calf Island, off Boston Harbor, MA, USA 42 20.4 N 70 53.9 W 

62-77 8/23/1962 Wood Island, off Biddeford, ME, USA 43 27.5 N 70 19.5 W 

TABLE 1. (Continued)
NUMBER 41 • 9

Depth (m); x = depth zone collected % P. 

laevigatum 

0–25 m

% P. 

rugulosum 

5–30 m

% P. 

squamulosum

Int–3 m

% P. 

nantuckensis

% P. 

borealis 

0–30 m

% P. 

investiens 

Int 0–3 3–9 9–15 15–21 21–28 28–37 >37 0–35 m

- x x x - - - - 2 0.7 - - - -

x x x x - - - - Tr 33 Absent - - -

- x x x - - - - 0.2 8 - - - -

x x x - - - - - 7 8 Absent - - -

x x x - - - - - 34 3 Absent - - -

x x x - - - - - 9 9 Absent - - -

- x x - - - - - 31 0.2 - - - -

x x x x x - - - Tr 6 Absent - - -

- x x - - - - - Tr 21 - - - -

- x - - - - - - - - - - - -

- x x - - - - - 0 25 - - - -

x x - - - - - - - - Absent - - -

- x - - - - - - 0 30 - - - -

- x x - - - - - - - - - - -

- - x x - - - - - - - - - -

x x x - - - - - 16 0 Absent - - -

x x x - - - - - 4 0 Absent - - -

x x x x - - - - 7 57 Abundant - - -

x x x - - - - - 58 1 Abundant - - -

- - x - - - - - - - - -

- - - x x - x - 0.3 37 - - - -

x x x - - - - - 3 20 Present - - -

x x x - - - - - 4 0.8 Present - - -

x x x - - - - - 0.4 31 Absent - - -

x - - - - - - - Present - - -

x x x - - - - - 3 Tr Absent - - -

x - - - - - - - Absent - - -

x x x x - - - - 1.7 20 Absent - - -

x x x x - - - - 4 65 Absent - - -

x x x x - - - - Tr 23 Absent - - -

x - - - - - - - Present - - -

x x x x x - - - 7 4 Abundant - - -

x x x - - - - - 1 0 Abundant - - -

x x x x - - - - 3 0 Absent - - -

x x x x x - - - 10 4 Abundant - - -

x x x - - - - - 79 0 Absent - - -

x x x - - - - - 48 0 Absent - - -

x x x - - - - - 5 0 Absent - - -

x x x x - - - - 45 Tr Absent - - -

TABLE 1. (Extended)
1 0 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

Station no. Date Locationa Latitude Longitude

62-78 8/24/1962 N of Rockland Breakwater, W Penobscot, ME, USA 44 7.1 N 69 4.6 W 

62-79A 8/26/1962 NW Moose Island, SW Deer Isle, ME, USA 44 9.0 N 68 41.2 W 

62-79B 8/27/1962 Carter Point, Eggemoggin Reach, ME, USA 44 16.7 N 68 37.6 W 

62-79C 8/27/1962 Naskeag Harbor, ME, USA 44 13.7 N 68 31.8 W 

62-79D 8/20/1962 Harriman Point, Blue Hill Bay, ME, USA 44 18.1 N 68 31.9 W 

62-79E 8/20/1962 Thompson Cove, Eggemoggin Reach, ME, USA 44 15.8 N 68 39.1 W 

62-79F 8/21/1962 W Lazygut Island, off Deer Isle, ME, USA 44 10.9 N 68 33.9 W 

62-79G 8/21/1962 SW E Mark Island, Jericho Bay, ME, USA 44 10.1 N 68 34.9 W 

62-80 8/28/1962 W Bradbury Island, E Penobscot Bay, ME, USA 44 14.7 N 68 45.9 W 

62-82 8/29/1962 W Cape St Mary, NS, Canada 44 5.3 N 66 12.9 W 

62-83 8/30/1962 Cape D’or, Bay of Fundy, NS, Canada 45 18.1 N 64 45.7 W 

62-84 9/1/1962 L’Etete Pass, Green Point, Passam, NB, Canada 45 2.4 N 66 53.6 W 

62-87 9/4/1962 Western Ear, Isle au Haut, ME, USA 44 0.3 N 68 39.1 W 

62-88 9/6/1962 Dice Head, N Penobscot Bay, ME, USA 44 22.9 N 68 49.4 W 

E62-6 10/20/1962 N & Little Deer Isle, ME, USA vic 44 17N 68 41W 

63-1 7/17/1963 E Point off Scituate, MA, USA 42 12.4 N 70 43.0 W 

63-2 7/18/1963 Orrs Island, Harpwell Sound, ME, USA 43 47.6 N 69 56.8 W 

63-3 7/21/1963 S Merchant Island cove, ME, USA 44 6.3N 68 39.3W 

63-5 7/22/1963 Pemaquid Point, ME, USA 43 50.1 N 69 30.4 W 

63-6 7/24/1963 Brant Rock, Mass Bay, MA, USA 42 5.6 N 70 38.5 W 

63-7 7/24/1963 Woods Hole, Marine Biological Lab Beach, MA, USA 41 31.6 N 70 40.5 W 

63-8 7/14/1963 Cape Cod Canal, MA, at bridges, USA vic41 46 N 70 33.9 W 

63-9 7/26/1963 Great Bald Head, Ogunquit, ME, USA 43 12.5 N 70 35.2 W 

63-10 7/26/1963 Ogungquit, ME, shore off harbor, USA 43 14.0 N 70 35.2 W 

64-1 6/6/1964 Harding Point off Port Hebert, NS, Canada 43 44.8N 64 57.5W 

64-2 6/8/1964 SE Shannon Island, NS, Canada 49 27.4N 63 44.5W 

64-3 6/9/1964 Bald Rock off Ship Harbour, NS, Canada 44 41 N 62 48.4 W 

64-4 6/10/1964 Pass between Liscomb & Hemloe Island, NS, Canada 45 0.4N 61 58.5W 

64-5 6/11/1964 Mill Cape, Bras D’Or Lakes, NS, Canada 45 49.5N 60 41.8W 

64-6 6/15/1964 Pearl Island, Bay of Islands, NF, Canada 49 12.6N 58 15.8W 

64-8 6/16/1964 Pearl Island, NF, Canada 49 14N 58 17W 

64-9 6/21/1964 E Cape St George, NF, Canada 48 29.2N 59 7.3W 

64-10 6/22/1964 SE Cape Ray, NF, Canada 47 37.2N 59 17.7W 

64-11 6/23/1964 St Paul Island, NS, Canada 47 12.8N 60 8.2W 

64-12 6/25/1964 Beaton Point, Mabou, Cape Breton, Canada 46 6.5N 61 28.8W 

64-14 6/27/1964 E Macquarie Point, off Pictou, NS, Canada 45 47.2N 62 50W 

64-15 6/28/1964 Cape Wolfe, W shore, PEI, Canada 46 43.5N 64 24.5W 

64-16 6/29/1964 Fisherman Ledge, off Caraquet, NB, Canada 47 52.5N 64 53.25W 

TABLE 1. (Continued)
NUMBER 41 • 1 1

Depth (m); x = depth zone collected % P. 

laevigatum 

0–25 m

% P. 

rugulosum 

5–30 m

% P. 

squamulosum

Int–3 m

% P. 

nantuckensis

% P. 

borealis 

0–30 m

% P. 

investiens 

Int 0–3 3–9 9–15 15–21 21–28 28–37 >37 0–35 m

x x x x - - - - 5 Tr Abundant - - -

x - - - - - - - - - Present - - -

x - - - - - - - - - Present - - -

x - - - - - - - - - Absent - - -

x - - - - - - - - - Absent - - -

x - - - - - - - - - Present - - -

x - - - - - - - - - Absent - - -

x - - - - - - - - - Absent - - -

x x x x x - - - 5 5 Abundant - - -

x x x - - - - - - - Present - - -

x x x x - - - - 19 12 Abundant - - -

- x x - - - - - 0 31 - - - -

- x x x x - - - 22 7 - - - -

- x x - - - - - 2 12 - - - -

x - - - - - - - - - Present - - -

x - - - - - - - - - Absent - - -

x - - - - - - - - - Abundant - - -

x - - - - - - - - - Abundant - - -

x - - - - - - - - - Abundant - - -

x - - - - - - - - - Absent - - -

x - - - - - - - - - Absent - - -

x - - - - - - - - - Absent - - -

x - - - - - - - - - Abundant - - -

x - - - - - - - - - Present - - -

x x x x - - x x 10 51 Abundant - - -

x x x x x - - - 14 0.4 Abundant - - -

- - - x x - - x 2 1 - - - -

- - x - - - - - 29 0.2 - - - -

- x x - - - - - 100 0 - - - -

x x x x x x x - 5.0 0.1 Present - - -

- - - - - - - x - - - - - -

- x - x - - - - 39 0 - - - -

x - x x - - - - 0 0 Absent - - -

x - x - x x - x 0 Tr Absent - - -

x - x - - - - - 44 0 Absent - - -

- x x - - - - - 53 0 Abundant to 

9 m

- - -

- x x - - x x x 58 0 Present - - -

- - x x x - x - 22 0 - - - -

TABLE 1. (Extended)
1 2 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

Station no. Date Locationa Latitude Longitude

64-17 6/30/1964 NE Bonaventure Island, Quebec, Canada 48 29.8N 64 9.5W 

64-18 7/1/1964 Fame Point, NE Gaspe, Quebec, Canada 49 7N 64 38W 

64-19 7/2/1964 Ile Petite Basque, Quebec, Canada 50 8.3N 66 21.4W 

64-20 7/3/1964 Off Seal River, Moisie Bay, Quebec, Canada 50 15N 65 46W 

64-21 7/4/1964 Eskimo Island, off Havre St P, Quebec, Canada 50 12.9N 63 39.5W 

64-22 7/5/1964 S Ile Longue, Quetachu Bay, Quebec, Canada 50 16.4N 62 48W 

64-23 7/12/1964 North Arm Point, Bay of Islands, NF, Canada 49 11.2N 58 7.1W 

64-24 7/15/1964 Bay of Islands, NF, Canada 49 4-12N 58 12-20W 

64-26 7/21/1964 Bound Head, Humber Arm, NF, Canada 49 2.6N 58 6.8W 

64-27 7/24/1964 Wapitagun Island, Quebec, Canada 50 11.7N 60 0.8W 

64-28 7/25/1964 NE Great Mecatina, Mackinnon Island, Quebec, Canada 50 50.2N 58 50.6W 

64-29 7/25/1964 Red Bay, Strait of Bell Isle, Labrador, NF, Canada 51 42.8N 56 25.8W 

64-30 7/27/1964 NW Camp Islands, Labrador, NF, Canada 52 10.5N 55 39.9W 

64-31 7/28/1964 White Bear Arm Labrador, NF, Canada 52 46.7N 56 0.7W 

64-32 7/31/1964 Cape Harrison, Labrador, NF, Canada 54 52N 57 57W 

64-33 8/1/1964 Hopedale Run, Labrador, NF, Canada 55 26.2N 59 49.1W` 

64-34 8/2/1964 Tunungayualuk Island, Labrador, NF, Canada 56 3.6N 61.13W 

64-35 8/4/1964 Whale Island, Labrador, NF, Canada 56 32N 61 9.2W 

64-36 8/5/1964 Kikkertasoak Island, Labrador, NF, Canada 57 14.3N 61 28W 

64-37 8/7/1964 Saglek Bay, Labrador, NF, Canada 58 32.2N 62 39W 

64-38 8/8/1964 Nachvak Fjord, Labrador, NF, Canada 59 5.5N 63 30.5W 

64-39 8/9/1964 Eclipse Harbor, Labrador, NF, Canada 59 51N 64 10.5W 

64-40 8/10/1964 Ekortiarsuk Fjord, Labrador, NF, Canada 60 6N 64 22.4W 

64-41 8/17/1964 Strait of Belle Isle, NF, Canada 51 32.6N 56 4.2W 

64-42 8/18/1964 James Island, St John Bay, NF, Canada 50 55.5N 57 11.5W 

64-43 8/20/1964 Bay Le Moine, NF, Canada 47 37.3N 58 40.3W 

64-44 8/27/1964 Fish Head, Great Island, Ramea Island, NF, Canada 47 31.7N 57 20.3W 

64-45 8/29/1964 Chap Rouge, Great St Lawrence, NF, Canada 46 53.8N 55 21.7W 

64-46 8/30/1964 Great Island, off Valen, NF, Canada 47 30.0N 54 2.17W 

64-47 9/1/1964 Outer Fermeuse Harbor, NF, Canada 46 57.2N 52 53.5W 

64-48 9/2/1964 Bay Bulls, Baboul Rocks, NF, Canada 47 17.5N 52 46.8W 

64-49 9/6/1964 Trinity Bay, King’s Head Cove, NF, Canada 47 59N 53 19.2W 

64-50 9/7/1964 Trinity Bay, Random Sound, NF, Canada 48 5N 53 38W 

64-51 9/8/1964 Skerwink Head, Trinity Bay, NF, Canada 48 22N 53 19.7W 

64-53 9/11/1964 E side of Change Island, NF, Canada 49 37.5N 54 23W 

64-54 9/13/1964 Cape St Martin, Hardy Harbor, NF, Canada 50 1.5N 55 53W 

64-56 9/27/1964 Scatari Island, NS, Canada 46 1.1N 59 45.5W 

64-57 9/29/1964 SW Arm, Green Island, NS, Canada 45 53.7N 59 59.5W 

TABLE 1. (Continued)
NUMBER 41 • 1 3

Depth (m); x = depth zone collected % P. 

laevigatum 

0–25 m

% P. 

rugulosum 

5–30 m

% P. 

squamulosum

Int–3 m

% P. 

nantuckensis

% P. 

borealis 

0–30 m

% P. 

investiens 

Int 0–3 3–9 9–15 15–21 21–28 28–37 >37 0–35 m

x - x x x - - - 3 0 Absent - - -

x - x - x - - - 0 0 Absent - - -

- - x x x - - - 0 0 - - - -

x x x x - - - - 0 0 Absent - - -

x - x x x - - - 0 Tr Absent - - -

x - x x x x - - 0 Tr Absent - - -

- x x - - - - - 30 0 - - - -

x - - - - - - - - - Present at 

1/11 sites

- - -

- x x x - - - - 24 0 - - - -

x x x x x x x - Tr 0 Absent - - -

x - x - x x - x 0 0 Absent - - -

- - x - x - - x 0 0 - - - -

x - x - x x - x 0 0 Absent - - -

x x x x x - - - 0 0 Absent - - -

x - x - - - - - 0 0 Absent - - -

- - x x x - - - 0 0 - - - -

x x x x x - - - 0 0 Absent - - -

- - x - x x - - 0 0 - - - -

- - x - x x - x 0 0 - - - -

- - - - x - - - 0 0 - - - -

- - x x x x - - 0 0 - - - -

- - x x x - - - 0 0 - - - -

- - x x x - - - 0 0 - - - -

x x x x - x - x 0 0 Absent - - -

x x x x - x - x 18 0 Absent - - -

x x x x x x - x 2 0 Absent - - -

- x x x x x - x 3 0.2 Absent - - -

- x x x x x - x 0.3 3 - - - -

x x x x x x - - 14 2 Absent - - -

x x x x x x - x 0 0 Absent - - -

- - x x x x - x 0 0 - - - -

- - - - - x - - 0 0 - - - -

- x x x x x - x 8 0 - - - -

x x x x x x - x 0 0 Absent - - -

x x x x x x - - 13 Tr Abundant - - -

- x x x x x - x 0.4 0 - - - -

- - x x x - - 7 15 - - - -

- - x - - - - x 20 0 - - - -

TABLE 1. (Extended)
1 4 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

Station no. Date Locationa Latitude Longitude

64-58 9/30/1964 Chedabucto Bay, Durell Island, NS, Canada 45 21N 61 00W 

64-60 10/1/1964 Bald Rock, Whitehaven, NS, Canada 45 12N 61 10.5W 

64-62 10/3/1964 Nichol Island, off Ship Harbor, NS, Canada 44 44.5N 62 45W 

65-2 7/24/1965 Shrewsbury Rocks, NE NJ, USA 40 20.5 N 73 57.1 W 

66-10 6/5/1966 Hvalfjord, mid Iceland 64 20N 21 45W 

66-11 6/6/1966 Hvalfjord, inner Iceland 64 22.5N 21 33W 

66-12 6/10/1966 Kollufjord, Hofsvik, Iceland 64 15.3N 21 52.9W 

66-13 6/17/1966 Breidhafjord, Kolgraf, Iceland 65 1.2N 23 1W 

66-14 6/19/1966 Kolgrafafjord, SW arm, Iceland 64 56.5N 23 6.5W 

66-15 6/25/1964 Steingrimsfjord, Hunafloi, Iceland 65 39N 21 29.5W 

66-16 6/27/1966 Steingrimsfjord, Os, Iceland 65 44.4N 21 41.2W 

66-17 6/28/1966 Kollafjord, Iceland 65 36.4N 21 22 W 

66-18 7/5/1966 Hrutey in Hrutafjord, Iceland 65 16.4N 21 8.3W 

66-19 7/13/1966 Sandesnes in Eyiafjord, Iceland 66 1.4N 18 31W 

66-20 7/14/1966 W shore N of Hangenes, Eyiafjord, Iceland 65 55.9N 18 18.7W 

66-21 7/15/1966 S of Grenivik, Eyiafjord, Iceland 65 56N 18 12.7W 

66-22 7/16/1966 E Hrisey, Eyiafjord, Iceland 65 59.9N 18 21.7W 

66-23 7/26/1966 Thernunes in Reydarfjordur, Iceland 64 58.9N 13 52W 

66-24 7/29/1966 Holmanes, Reydarfjordur, Iceland 65 2.5N 14 0.6W 

66-25 8/4/1966 Vattarnes, outer Reydarfjordur, Iceland 64 56.4N 13 41.5W 

66-26 8/11/1966 Stadhur off Grindavik, Iceland 63 49N 22 31W 

66-27 8/17/1966 Urdharvita, Heimey, Iceland 63 26N 20 15W 

66-28 8/29/1966 Hammerfest-Kvaloy, Norway 70 44.5N 23 48.3E 

66-29 8/31/1966 Kargeneset, Kvaloy, Norway 70 31.4N 23 44.2E 

66-30 9/3/1966 Bringnes, Inner Porsangerfjord, Norway 70 31.5N 25 11E 

66-31 9/4/1966 Kavholme, Langfjord, N Norway 70 06.5N 22 50E 

66-32 9/8/1966 Nordbotn, Kvaloy (Tromso), N Norway 69 40.4N 18 46.2E 

66-33 9/11/1966 Hokey (Tromso), N Norway 69 40.1N 18 50.2E 

66-34 9/11/1966 Sandesund-Tromso, N Norway 69 41.7N 18 55E 

66-35 9/13/1966 Tussoy, off Tromsoy, N Norway 69 41 N 18 7.8 E 

66-36 9/17/1966 Landegodefjord, N of Bodo, Norway 67 20.5N 14 29.6 E 

66-37 9/18/1966 Landegodefjord, off Skjelstad, Norway 67 22.4N 14 31 E 

66-38,42, 43,1,3,4 9/30/1966 Digertmulen, Trondheimsfjord, Norway 63 27.2N 10 18.8E 

66-39 10/13/1966 Beitstadfjord, in Trondheimsfjord, Norway 63 56.7N 11 14 E 

66-40 10/27/1966 Sorfjord, Bergkalnes, Norway 63 43.9N 10 01.1 E 

66-41 10/27/1966 Sorfjord, Bergkalnes, Norway 63 43.1N 10 0.3 E 

66-42 11/23/1966 Digertmulen, Trondheimsfjord, Norway 63 27.2 N 10 18.8 E` 

66-43 12/27/1966 Digertmulen, Trondheimsfjord, Norway 63 27.2N 10 18.8 E 

67-1 2/1/1967 Digertmulen, Trondheimsfjord, Norway 63 27.2N 10 18.8E` 

TABLE 1. (Continued)
NUMBER 41 • 1 5

Depth (m); x = depth zone collected % P. 

laevigatum 

0–25 m

% P. 

rugulosum 

5–30 m

% P. 

squamulosum

Int–3 m

% P. 

nantuckensis

% P. 

borealis 

0–30 m

% P. 

investiens 

Int 0–3 3–9 9–15 15–21 21–28 28–37 >37 0–35 m

- - - - - x - - - - - - - -

x x x x x x - - 26 3 Absent - - -

x x x - - x x x 23 2 Abundant - - -

- - x x - - - - 100 0 - - - -

- x - - - - - - 0 46 - - 0 0

- - x x x - - - 0 4 - - 0 0

x x x x x x - - 1 39 Abundant - 0 0

x x x x x - - - 0 2 Present - 0 0

x x x x - - - - 0 0 Abundant - 0 0

- x x x x x x x 0 0.2 - - 0 0

- x x x - - - - 0 0 - - 0 0

x x x x x x x - 0 0.4 Absent - 0 0

x x x x x x x x 0 0 Absent - 0 0

- - - x - - - - 0 0 - - 0 0

- x x x - - - - 0 0 - - 0 0

x - x x x - - - 0 0 Absent - 0 0

- - x x x - - - 0 0 - - 0 0

x x x x x x x x 0 0 Absent - 0 0

- x x x x x x - 0 0 - - 0 0

x x x x x x x x 0 0.1 Absent - 0 0

x x x x x x x - 0.3 36 Abundant - 0 0

x x x x x x - - 0 61 Abundant - 0 0

x x x x x x x x 0 Tr Present - 0 7

x x x x x x x - 0 0 Present - 0 7

x x x x x - - - 0 0 Present - 0 42

- x x x x x x x 0 Tr Tr - 0 39

x x x x x x x - 5 0 Present - - rhodos, Tr

- - - x x x - - 0 0 - - - rhodos, Tr

- - - - - x - - - - - - - rhodos, Tr

- x x x x - x - 0 4 - - 0 Tr

- x x x x x - - 0 Tr Present - - 17

x - x - x - - - - - Abundant - 0 0

x x x x x x - - 22 0.1 Abundant - 2 10

x x x x x x x - 35 0.6 Abundant - 2 0

x x x x x x - - 33 1 Abundant - - 0

- - x - - - - - - - - - 0 0

x x x x x x x - - - - - - Tr

- x x x x x - - - - - - - -

- x x x x x x - - - - - - -

TABLE 1. (Extended)
1 6 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

Station no. Date Locationa Latitude Longitude

67-2 2/3/1967 Prestvaagen, inner Trondheimsfjord, Norway 63 48.7N 10 39.1E 

67-3 3/11/1967 Digertmulen, Trondheimsfjord, Norway 63 27.2N 10 18.8E 

67-4 4/22/1967 Digertmulen, Trondheimsfjord, Norway 63 27.2N 10 18.8E 

67-5 7/16/1967 Sorfjord, N corner of Daleoren, Norway 63 43 N 10 0 E 

67-6 7/18/1967 E side of Froya-Helskjaeret, Norway 63 45 29.2 8 55 40.4 

67-7 7/21/1967 Nogvafjord-Kjeholmen, Norway 62 41.5 N 6 15.7 E 

67-8 7/21/1967 Veddehl in Asefjord (Alesund), Norway 62 26.7N 6 15.2 E 

67-9 7/26/1967 Lagoyfjord-Indre Solund Tobehl, Norway 61 9.2N 4 48.2 E 

67-10 7/30/1967 Hardangerfjord-Kvindherredsfd, Norway 59 59.5 N 5 57 E 

67-11 7/31/1967 Hardangerford-Samlenfjord, Norway 60 20.2N 6 20.5 E 

67-12 8/2/1967 Espevaer-Ryggen skjaer, Norway 59 34.4N 5 7.9 E 

67-13 8/7/1967 South coast Norway-Hille-Asgard, Norway 57 59.4 N 7 21.2 E 

67-14 8/9/1967 Oslo Fjord, SW Molen, Norway 59 28.9 N 10 29.6 E 

67-15 8/11/1967 Oslofjord Nesodden Baerodden, Norway 59 50.2 N 10 38.2 E 

67-16 8/13/1967 Outer OsloFjord-Tjomoy-Bustein, Norway 59 6.4 N 10 29.5 E 

68-27 9/5/1968 Gaasvaer, Norway 66 4.2 N 12 10.0 E 

68-28 9/6/1968 Alstfjord-Haestadsund, Norway 66 1-2 N 12 28-30 E 

68-29 9/8/1968 Ranfjorden-Leirviken, Norway 66 12.5 N 13 33.6 E 

68-30 9/12/1968 Vestvagoy-Lofoten Island, Brandish, Norway 68 4.3 N 13 38.8 E 

68-31 9/14/1968 E Fjord, Forsahavnet, Norway 68 17 N 16 36.5 E 

68-32 9/18/1968 Hakoy-Sandnessund-Tromsoy, Norway 69 39.7N 18 46.5E 

68-33 9/27/1968 Balsfjord, Hamarvoll, Norway 69 20.8 N 19 13 E 

68-34 10/3/1968 Tromsoy, SW off Biological Station, Norway 69 38.1N 18 54.3E 

68-35 11/13/1968 Tromsoy, SW off Biological Station, Norway 69 38.1N 18 54.3E 

69-1/2 2/19/1969 Tromsoy, SW off Biological Station, Norway 69 38.1N 18 54.3E 

69-8 6/24/1969 Revabotn; Rolfroysund, Norway 71 46.7 N 23 48.5 E 

69-9 6/25/1969 Hjelmsoy-Akkarfjorden-Holmen, Norway 71 5.5 N 24 42 E 

69-11 6/26/1969 Mageroy-Turfjorden-Kaka, Knive, Norway 71 7.1 N 25 31.4 E 

69-12 6/28/1969 Porsangerfjord-Reinoy, Norway 70 44.4N 25 50.3 E 

69-13 6/29/1969 Porsangerfjord-Osterbotn, Norway 70 6.5 N 25 15 E 

69-14 7/2/1969 Syltefjord-Veidnesodden, Norway 70 32.5 N 30 8.5 E 

69-16 7/4/1969 Sor-Varanger-Kjofjord Brasneset, Norway 69 44.8 N 29 39.7 E 

69-17a 7/4/1969 Sor-Varanger, Stransnes, Norway 69 48.0 N 29 44.2 E 

69-17b 7/4/1969 Kjofjord-Straumen, Norway 69 48.6N 29 45.6E 

a

 Location abbreviations: MA = Massachusetts, ME = Maine, NB = New Brunswick, NF = Newfoundland, NJ = New Jersey, NS = Nova Scotia, 

PEI = Prince Edward Island, RI = Rhode Island.

TABLE 1. (Continued)
NUMBER 41 • 1 7

Depth (m); x = depth zone collected % P. 

laevigatum 

0–25 m

% P. 

rugulosum 

5–30 m

% P. 

squamulosum

Int–3 m

% P. 

nantuckensis

% P. 

borealis 

0–30 m

% P. 

investiens 

Int 0–3 3–9 9–15 15–21 21–28 28–37 >37 0–35 m

x x - - - - - - 23 0 Abundant - - -

- x x x x x - - - - - - - -

- x x x x x x - - - - - - -

- x x x x - - - - - - - 0 0

x x x x x x x x Tr 0 Abundant - 58 0

- x x x x - - - 5 4 Present - 35 ?

x x x x x x x x 10 0 Abundant - 38 ?

x x x x x x x x 0 1 Absent - 67 0

- x x x x x x x 18 0 - - 34 0

- x x x x x x x 43 0 Abundant - 10 0

x x x x x x x 0 0 Present - 94 0

x x x x x x x x 9 Tr Present - 57 0

x x x x x x x - 20 0 Abundant - 24 0

- x x x x x x - 53 0 Abundant - 21 0

- x x x x x x - 50 0 Abundant - 8 0

- x x x x x x x 2 11 - - 20 ?

- x x x x x - - - - - - 0 0

- x x x x x - - 4 0.1 - - 0 34

- x x x x x x x 0 0 - - - 77

- x x x x x x - 10 2 - - 0 Tr

- - - - - x - - - - - - 0 rhodos, Tr

- x x x x x x - 0 0 - - 0 rhodos, Tr

- - - - - x - - - - - - 0 Tr

- - - - - - x - - - - - 0 rhodos, Tr

- - - - - x - - - - - - 0 Tr

- - - - - - - x 0 0 - - 0 Tr

- x x x x x - - 0 0 - - 0 34

- - - - - x x x - - - - - 37

- - - - - - x x - - - - 0 0

- x x x x x x - 0 0 - - 0 0

- - x x x x x - 0 11 - - 0 7

- x x x x x x x 0 0 - - 0 0

- - - - - x x - 0 0 - - 0 0

- - - - - x x - 0 0 - - 0 0

TABLE 1. (Extended)
1 8 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

small, narrow, high-magnesium grains oriented more or less perpendicular to the cell lumen and an interfilament layer 0.1–0.4 

μm thick of very small tabular grains (typically 0.2–0.4 μm long 

and 0.05 μm in diameter) that form a glide plane for differential growth, and often produce vertical “stripes” seen on vertical thallus fractures; calcified walls gradually perforated with 

depth to form cell fusions. All conceptacle primordia formed 

adventitiously from cells 30–100 μm deep in the perithallium; 

as the conceptacles develop, overlying perithallium is raised and 

cut off as degenerating discs; mature conceptacles, with floors 

sunken below the crust surface and often with sunken roofs; 

bi-tetrasporangia with thick cap walls (i.e., conceptacles with 

many pores); pore canals not lined by distinctive cells; male 

and female conceptacle roofs formed by overgrowing of lateral perithallial tissue; spermatangia borne in dendroid clusters 

completely clothing conceptacle walls; carpogonial filaments 

unbranched, producing highly fragmented, dendritic fusion cells 

on fertilization and producing typically one-celled gonimoblast 

filaments bearing single large carposporangia, across the entire 

conceptacle floor. In some species, postmature conceptacle cavities are buried by new perithallial growth and remain as cavities 

in thick crusts. Species occur in a wide range of marine/polyhaline estuarine habitats.

Type Species. Phymatolithon calcareum (Pallas) W. H. 

Adey & D. L. McKibbin, 1970:100.

Anatomy

The North Atlantic Boreal–Subarctic transition zone Phymatolithon species are presented as three species pairs based on 

morpho-anatomical similarities, with P. laevigatum and P. rugulosum characterized by adherent thalli with thin hypothalli, P. squamulosum and P. nantuckensis sp. nov. characterized by leafy and 

imbricating thalli, also with thin hypothalli, and P. borealis sp. 

nov. and P. investiens by thick and leafy to cantilevered thalli with 

thick hypothalli (Figure 2A,B). By a paired, two-tailed Welch–

Satterthwaite t test (t = 5.89, df = 2.14, p < 0.005), the thick/thin 

hypothallium differentiation is highly significant (Figure 2C).

Hypothallium

Hypothallial characteristics are critical to understanding 

these species in the North Atlantic Boreal–Subarctic transition 

zone, as is shown in a plot of hypothallial L/D cell ratio versus 

hypothallium thickness (Figure 2). Our ANOVA model showed 

that this relationship is significantly different across the species 

(p < 0.001). Phymatolithon investiens has by far the thickest 

hypothallium (98–350 μm; mean 176 μm), which is thicker than 

P. borealis (50–140 μm; mean 77 μm); the latter is thicker than P. 

squamulosum (15–75 μm; mean 41 μm), which in turn is thicker 

than P. laevigatum (13–55 μm; mean 27.4 μm) and P. rugulosum

(8–50 μm; mean 26.1 μm). Finally, P. laevigatum is significantly 

thicker than P. nantuckensis, the latter with a hypothallium only 

For these analyses, we used a Zeiss UltraPlus field emission 

SEM equipped with an HKL electron backscatter diffraction 

(EDS) housed at the Australian National University, Centre for 

Advanced Microscopy. SEM-EDS was used for spot analyses to 

quantify the elemental composition of representative parts of the 

coralline crust. Usually eight to nine measurements were made 

for each carbonate type. For EDS the operating voltage was 

15 kV with 11 mm working distance. A range of settings were 

used for imaging, including secondary electron and in-lens imaging to show topography, and backscatter electron imaging that 

shows higher magnesium areas as darker carbonate and is useful 

for rapid visual identification of mineral distribution. For details 

of analyses, see Nash and Adey (2017a,b).

RESULTS

Genetic Lineages and Evolutionary Relationships

Genetic information was successfully acquired from 98 

specimens. Specimens with identical sequences were used to 

update morphological and distributional data (Appendix Figure A1). The plastid markers used, psbA and rbcL, recovered 

congruent topologies (Figure 1). The identification of specimens 

based on morpho-anatomical features versus identification from 

sequences of type material obtained a 95% success.

Lineages successfully identified by a DNA sequence from 

type material included P. borealis sp. nov., P. calcareum (Pallas) W. H. Adey & D. L. McKibbin (the generitype), P. investiens, P. laevigatum, P. lamii (Me.Lemoine) Y. M. Chamberlain, 

P. lusitanicum V. Peña, P. nantuckensis sp. nov., P. rugulosum, 

and P. squamulosum (Figure 1). Other lineages could not be 

assigned a name (Figure 1). There is no single clade containing 

all Boreal–Subarctic transition zone species. Rather, these and 

Boreal to warm temperate species are mixed in each clade (Figure 1) as follows: a clade of P. lamii, P. lusitanicum, and P. rugulosum is strongly supported by psbA and weakly to strongly by 

rbcL; a clade of P. squamulosum and specimens identified as 

P. lenormandii is fully supported by rbcL and weakly to strongly 

by psbA, as is a clade of P. borealis, P. investiens, and P. laevigatum; a clade only weakly supported by analyses of both markers 

contains P. calcareum and P. nantuckensis.

Phymatolithon Foslie 1898:4 nom. cons.

We present herein an amended generic description updated 

from Adey (1964).

Plants crustose; hypothallium growing subparallel to the 

substrate and arcing upward to form the perithallium, short 

dead-ended filaments turning down to the substrate; epithallium 

thin, 0–2 cell layers (mean ~0.5) and cell walls thinly calcified 

and not armored; below a single layer of intercalary meristem 

cells on average shorter than the first perithallial derivatives; 

perithallial cells gradually lengthening as they are buried; calcified cell walls 2–4 μm thick of two components, an inner wall of 
NUMBER 41 • 1 9

FIGURE 1. Phylograms inferred from maximum likelihood (ML) analyses of psbA (left) and rbcL (right) plastid markers for selected 

species of Phymatolithon, including all North Atlantic Boreal–Subarctic transition zone species. Names in bold indicate either type 

sample DNA or samples producing DNA that matches sequences from type material. Support values at nodes are bootstrap/posterior 

probabilities: only values above 50%/0.5 are shown. Samples indicated by alphanumeric or number codes after taxon names are also 

included in Appendix Figure A1. Dark gray bars on right of phylogram with letters indicate the extent of accepted taxa; unlettered dark 

grey bars are apparent unnamed Phymatolithon species. Figure by author JJHK.
FIGURE 2. A, B. Mean hypothallial cell shape (ratio of cell 

length to cell diameter, L/D) as a function of hypothallial 

thickness for the Phymatolithon species of this paper. Note 

the scale change in hypothallium thickness from A to B. The 

eastern North Atlantic species, P. borealis and P. investiens, 

have considerably thicker hypothallia, although all species as 

populations have significantly different hypothallial dimensions. C. The two thick hypothallium species combined are 

highly significantly different from the combined thin hypothallium species (see text; red data points = thin hypothallia species: P. rugulosum, P. laevigatum, P. squamulosum,

P. nantuckensis; black data points = thick hypothallia species: P. borealis, P. investiens). Figure by author WHA.
NUMBER 41 • 2 1

P. squamulosum and P. nantuckensis, have considerably lower 

meristem CVLs than the remaining species. It seems likely that 

this difference results from a lower rate of cell division in the 

meristem. Deeper in the perithallium, CVL values decrease to 

roughly half their rates nearer the meristem.

The change of cell diameter with depth in the perithallium 

(Figure 5) is much less than it is for cell length (Figure 3); this 

is logical considering that in crust species lateral extension is 

accomplished by hypothallial growth and the number of filaments per unit surface area is essentially fixed. (In Figure 5, we 

see that P. nantuckensis is highly erratic as compared to other 

species, and it seems likely that this results from the limited 

sampling in this case; 2 plants and 10 measurement sets versus 

28–41 plants and 31–52 measurement sets in other species). In 

the following treatment of perithallial development, we do not 

include P. nantuckensis; this matter is treated in the Discussion. 

Statistical analysis of cell diameter, using GLM ANOVA models 

and Scheffé’s tests, shows that mean cell diameter in P. rugulosum is narrower than in other Phymatolithon species, which are 

otherwise all similar to each other. The slopes of P. borealis and 

P. investiens, cells 4–8, are negative, but this is not significant by 

Scheffe’s tests. However, as shown in Figure 5C, the combined 

thin hypothallia species have a highly significant positive slope 

(by p < 0.001). Because this is an expansion of the cell lumina, it 

is likely the result of a loss of inner cell wall carbonate; although 

this might be an artifact of cell fusions, the species with a thick 

hypothallium (P. borealis and P. investiens) both have slightly 

more fusions than the thin hypothallium species (see below) and 

apparently show a slight negative slope with depth.

Variation in cell diameter (Figure 6), following the cessation of cell division, shows roughly the same values as cell length 

(Figure 4). As expected, cell diameter CV is more or less constant 

with depth. However, when the two thick hypothallium species 

are combined, a first-order regression of CV, by GLM regression F test, has a highly significant positive slope. This result 

suggests that the nonsignificant negative slope of cell diameter 

for these species is probably correct. We treat this matter in the 

Discussion.

The ratio of cell length to cell diameter (L/D) with depth 

in the perithallium is shown in Figure 7. The resulting curves 

are similar to the growth curves, as might be expected, because 

change in diameter is minimal; however, the differences in L/D 

between the mature cells of the first three species are highly significant. Although all three have the same basic growth pattern 

with depth, cell shape, a character rarely applied in coralline 

literature, is the most defining feature of species differentiation 

based on cell dimensions in the mature upper perithallium (subelongation zone). Although mature postgrowth cells (cells 4–8) 

appear to have a “drift” in both length and diameter, as we presented earlier and treat in detail in the Discussion, all species 

(except P. nantuckensis, with inadequate data) have mature cells 

with remarkably stable L/D ratios (i.e., cell shape). Phymatolithon rugulosum, P. borealis, and P. investiens all have somewhat elongate cells, with a mature cell ratio of approximately 1.5 

a few cells thick (7–25 μm; mean 18 μm). However, although 

P. rugulosum and P. laevigatum have essentially the same hypothallial thickness, P. rugulosum has significantly more elongate 

cells than P. laevigatum (p < 0.01). All these species have overlapping dimensions (both hypothallium thickness and cell elongation), and only population/statistical testing can provide a cogent 

understanding of species differences.

Because hypothallium development with time is dependent 

upon progression across an irregular and perhaps even changing substrate, the characters of cell size and tissue thickness are 

inherently more variable than those of the perithallium, which 

lacks substrate contact. As we have shown, hypothallial characters can be quite valuable, and in some cases highly definitive, even on individual specimens (for example, differentiating 

P. rugulosum from P. investiens). However, in general, for largerscale use, population/statistical analysis is necessary.

Perithallium

All Phymatolithon species have short, intercalary meristematic cells, ranging from approximately 1 to 8 μm long (mean 

3.5 μm) in the species treated here, depending upon the division cycle. The perithallial cells are cut off at similar length, but 

consequent to subsequent growth, in species treated here, the 

cutoff cells range from approximately 2 to 9 μm (mean 4.6 μm). 

These perithallial cells continue to lengthen as they are buried 

by subsequent divisions of the meristematic cells (Figure 3A–C). 

Figure 3C shows the mean length of meristematic cells and the 

first 8 proximal perithallial cells for the five species with sufficient data to produce smooth curves (see below). A first-order 

curve fit to cells 1–4, by least mean squares, has a slope of 1.068 

with a fit of R2 = 0.983, with both slope and intercept fits, by a 

t test, of p < 0.01. A similar curve fit to cells 4–8 has a slope of 

0.183 with a fit of R2 = 0.908, with slope and intercept fit by a 

t test of p < 0.01. Thus, significant cell elongation is achieved by 

cell number 4, although some small additional elongation with 

depth occurs in most species. This pattern of division and elongation results in increased thickness of the perithallium. Mature 

cell length for cell positions 4–8 for each species is not significantly different from the others by Scheffé’s and Student–Kuels 

tests. However, if the shorter pair (P. rugulosum and P. laevigatum) and separately the longer-celled set of P. nantuckensis, 

P. squamulosum, P. borealis, and P. investiens are combined, fitted first-order curves by t tests have significantly different slopes 

(p = 0.04) and highly significant intercepts (p < 10−4). We return 

to this issue when we treat cell shape.

Figure 4 shows the coefficient of variation in cell length 

(CVL) as a function of cell position. In all Phymatolithon species, 

high levels of variation in cell length occur in the meristematic 

cells and in the first several rapidly growing perithallial cells, 

which is consistent with the independent division of meristematic 

cells and elongation of their derivatives relative to adjacent filaments and those in the species population. The two species with 

the least perithallial growth, giving rise to lesser crust thickness, 
FIGURE 3. Change in mean cell length (pit to pit) of 

perithallial cells in all Phymatolithon species of this paper 

as a function of cell position. A. Thin hypothallium species. B. Thick hypothallium species. C. All species combined except P. nantuckensis (omitted because data were 

not sufficient to produce a smooth curve; see Discussion). 

Number of stations/plants/filaments measured (i.e., for 

each data point) as follows: P. rugulosum, 25/41/52; 

P. laevigatum, 33/44/47; P. squamulosum, 22/27/33; 

P. nantuckensis, 1/2/10; P. investiens, 17/29/31; P. borealis, 18/28/31. Figure by author WHA.
NUMBER 41 • 2 3

FIGURE 4. Coefficient of variation of cell length 

as a function of cell position in all the Phymatolithon species of this paper. A. Thin hypothallium 

species. B. Thick hypothallium species. Number 

of measurements as in Figure 3. Figure by author 

WHA.

(Figure 5). However, at L/D = 1.25 for P. squamulosum, and at 

L/D = 1.03 for P. laevigatum, the remaining species have shorter, 

ovoid, or even round cells in the latter case. This three-way separation is highly significant (p < 0.001) by ANOVA.

When L/D is plotted as a function of cell position in the 

perithallium (Figure 7), but showing the extension to the hypothallium, it is seen that L/D roughly doubles, making hypothallial 

cells generally more elongate than perithallial cells in the same 

species. However, the cell ratios between species are proportionally largely unchanged from the perithallium ratio.

The dissolution of usually narrow channels in cell walls 

between perithallial cells of adjacent filaments (typically 

referred to as fusions) are well known in the genus Phymatolithon (Adey, 1964, 1966a; Irvine and Chamberlain, 1994); 

these develop gradually with depth in the perithallium (Figure 8; Plates 1D, 6D, 8C). The term fusion may be a misnomer, 

as generally such cell connections are formed by dissolution 

of cell wall carbonate in well-defined tunnels of which the 

sides are eventually recalcified. As shown in Figure 8A, fusions 

rarely occur in the meristem, and only occur in less than 10% 
FIGURE 5. Change in mean cell diameter (width midcell lumen) as a function of cell position for the Phymatolithon species of this paper. A. Thin hypothallium 

species. B. Thick hypothallium species. Number of measurements as in Figure 3. C. Combined thin species cell 

diameter as a function of cell position with P. rugulosum

weighted by means (P. nantuckensis not used, see above). 

At R2 = 0.56481, the diameter increase is significant. By 

t test, the slope is highly significant. The negative slope 

of the two thick hypothallium species is not significant 

(however, see Figure 6). Figure by author WHA.
NUMBER 41 • 2 5

referred to them as starch globules; however, these do not appear 

in SEM images and may be membranous oil globules that break 

down on drying. Although not always very abundant, these 

“staining bodies” can usually be located, especially in hypothallial cells, and, in Phymatolithon, only in the species of the 

P. laevigatum–P. borealis–P. investiens subclade, the three most 

closely related Phymatolithon species of this paper. Staining bodies tend to develop rapidly in the growth phase of the perithallium (Figure 9), suggesting that this is also the zone of strongest 

photosynthesis with the formation of storage food. Presumably 

the staining bodies in the hypothallium develop at plant margins 

of cells to a depth of cell 4. From that level deeper, they develop 

rapidly. As shown in Figure 8B, to a large extent growth and 

fusion development are independent; roughly three-quarters 

of fusions develop after significant cell elongation stops. By 

ANOVA, the differences between cells 1–3 and 4–8 are highly 

significant.

Most cold-water corallines produce starch storage globules that are readily visible in SEM mounts. However, as first 

described by Adey (1964) and further discussed by Irvine and 

Chamberlain (1994), some Phymatolithon species have additional globules that stain heavily with hematoxylin. Adey (1964) 

FIGURE 6. Cell diameter coefficient of variation (CV) as 

a function of cell position in all Phymatolithon species of 

this paper. A. Thin hypothallium species. B. Thick hypothallium species. Number of measurements as in Figure 3. 

After cell elongation ceases, the strongly positive slope of 

the thick hypothallium species cell diameter CV suggests 

that the nonsignificant decrease in cell diameter is likely 

real and is caused by addition of carbonate to cell lumen 

walls. Figure by author WHA.
2 6 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

FIGURE 7. Ratio of cell length to cell diameter 

(L/D) as a function of cell position for all the Phymatolithon species of this paper. A. Thin hypothallium species. B. Thick hypothallium species. 

Number of measurements as in Figure 3. Note 

that each hypothallial value (two times perithallium value) is the mean of three cells rather than a 

single cell (e.g., for P. rugulosum the data source 

is 25/41/156). Except for the highly variable 

P. nantuckensis, with 10 measurement sets from 

two plants, L/D in the perithallium is proportional to that in the hypothallium for each species. 

Figure by author WHA.

when the overlying photosynthetic perithallium is thin and photosynthate is being transported to the rapidly growing hypothallium. We have not researched this matter. In any case, in the 

North Atlantic Boreal–Subarctic transition zone, this is a diagnostic character for separating this subgroup from the remaining 

species of the genus.

Tissue Variation and Wall Mineralogy

As Adey et al. (2005, 2013) showed for Arctic–Subarctic Lithothamnion and Clathromorphum spp., and as Nash 

and Adey (2017a,b) show for Arctic Leptophytum, Kvaleya, 

and Boreal–Subarctic transition zone Phymatolithon spp., the 

high-magnesium calcite cell walls have an inner wall (IW, the 

wall) with radial calcite granules (Plates 9–11). Adjacent filaments of cells are separated by a calcitic formation, called interfilament (IF, middle lamella; Plates 9B,D; 10C,D; 11C–F), that is 

distinctive but highly variable in thickness, structure, and magnesium content among genera, among species within a genus, 

and even among the hypothallium, perithallium, and wound 

tissue of an individual crust. Phymatolithon species generally 

have a thin IF layer that probably functions at least partially as 

a glide plane, allowing differential elongation between cells of 

adjacent filaments; however, the variation between tissue subtypes is considerable (Plates 9–11), and this we describe in detail 

below. In the Phymatolithon species presented in this paper, 
NUMBER 41 • 2 7

(in the high-Mg-calcite walls). We discuss cell wall variation in 

greater detail below. There are other subtissues typically present 

in the perithallia of Phymatolithon species, including secondary hypothallia, but we do not examine these in detail in this 

paper. Conceptacles, both bi-tetrasporangial and gametantial, 

also have supporting tissues, including two types of roof growth 

and nurse tissue in the bi-tetrasporangial conceptacles (Adey 

et al., 2013).

crust perithallia typically have a complex of subtissues, mostly 

relating to “injury” caused by grazers or other surface damage 

(Plates 1A; 2C; 4F; 6A,B; 7E); however, this can also result from 

the breakout and regrowth over or within post-mature conceptacles. Typically, such “wound tissue” consists of more rapid cellular growth necessary to repair crustal damage (usually a hole); 

such tissue usually consists of longer, thinner-walled cells, with 

decreased interfilament calcification and increased magnesium 

FIGURE 8. A. Percent of cells with fusions as a 

function of cell position for all the Phymatolithon

species of this paper except P. nantuckensis (see 

text). Number of measurements as in Figure 3. 

B. Mean cell length (of all species, as shown in 

A) at each cell position as a function of the cell 

fusions at that position. Number of measurements 

as in Figure 3. Figure by author WHA.
2 8 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

cycles, with peaks in the winter and early spring; two of the 

newly added species, P. borealis and P. investiens, appear to have 

very similar cycles, never producing bi-tetrasporangial conceptacles in summer. Adey and Adey (1973) developed similar curves 

of reproductive cycles for these species as a combined P. polymorphum; because data for P. investiens were very limited, these 

curves likely represented P. borealis sp. nov. Phymatolithon 

squamulosum apparently remains an exception, with no welldefined yearly cycle. The more distantly related P. nantuckensis

sp. nov. has conceptacles of all types during the summer. We have 

only summer collections for this species, but it would appear 

that, similar to P. squamulosum, it does not have a defined yearly 

reproductive cycle.

In Table 2, we numerically and pictorially present the essential mean dimensions of bi-tetrasporangial conceptacles for the 

six species in this paper; cross sections are mean dimensions, all 

to the same scale. Although some of these species were treated 

previously in regional publications and there is little change in 

the essential parameters, in this paper these data are derived 

from across the North Atlantic range of each species. Note that 

in Phymatolithon squamulosum (Plate 4D,F) and P. nantuckensis (Plate 3B,C), mature conceptacles have roofs that are raised 

above the surrounding vegetative crust, which derives from two 

factors: the depths of formation of the conceptacle primordia are 

less than those in all the thicker species (generally 4–8 cells as 

compared to 15–25 cells below the surface); however, in addition, upward growth of the surface of these crusts is considerably less pronounced than crusts of the generally thicker species. 

Reproduction

General

The extraordinary adventitious development of Phymatolithon conceptacles, from primordial discs several to tens of cells 

below the intercalary meristem in the perithallium, has been earlier described and occurs in the species newly presented in this 

paper (e.g., Plate 7A,C,D). Adey (1964, 1966a) demonstrated 

this process, both diagrammatically and photographically, for 

the three species in this paper that occur in the Gulf of Maine. 

Here we add the new species, Phymatolithon nantuckensis, 

described from Nantucket Island in the western North Atlantic, 

Phymatolithon borealis sp. nov. (replaces P. polymorphum Foslie; Adey 1970b, 1971; Irvine and Chamberlain, 1994), and Phymatolithon investiens from central and eastern North Atlantic.

Bi-tetrasporangial Plants

In this paper, we use the term bi-tetrasporangial conceptacles instead of asexual conceptacles as in the earlier literature. 

Although bisporangial conceptacles are probably part of an independent asexual loop in a reproductive cycle and are the most 

common conceptacles for most Arctic and Subarctic species, tetrasporangial conceptacles, more common in Boreal to tropical 

corallines, provide the chromosomal reduction division of sexual 

cycles. Many of the Phymatolithon species studied earlier presented quantitatively well-defined yearly asexual reproductive 

FIGURE 9. Mean staining body size (diameter, 

μm) (absence = 0; see text) as a function of cell 

position. Number of measurements as in Figure 3. Phymatolithon species of this paper not 

included do not have staining bodies. All three 

species shown belong to a single clade of the 

larger Phymatolithon tree (see Figure 1). Figure by author WHA.
NUMBER 41 • 2 9

conceptacles and the thicker adherent crust species at maturity 

remain considerably sunken; at p < 0.001 (t = 18.8, df = 50.4, 

N = 35–45), these height differences are highly significant. By 

the same test, the two thick hypothallium species, P. borealis and 

P. investiens, are also significantly different (t = 3.8, df = 20.6, 

N = 6–20, p < 0.01) from each other in cavity diameter. In the 

thick hypothallial species P. borealis (Figure 10B; Plates 5C, 6A), 

conceptacles are sunken at maturity. Although the pore plate is 

not significantly deeper than in P. rugulosum and P. laevigatum

(Figure 10A), the mature conceptacle cavity floors of the latter 

Bi-tetrasporangial conceptacle elevation relative to the crust surface results only in part from internal conceptacle development 

and derives also from the relative growth (or lack of it) in the 

surrounding perithallus (Adey et al., 2013).

In Figure 10, we plot bi-tetrasporangial conceptacle height 

as a function of conceptacle cavity diameter. By the Welch–

Satterthwaite t test, the thin hypothallial species (Figure 10A) are 

all significantly different from each other (t = 6.4, df = 40.1, N = 

14–45, P < 0.001) in the key conceptacle cavity diameter dimension, whereas the thin imbricate species have elevated mature 

(0.24)

148

(0.18)

239

(0.74)

–32

(0.24)

93

(0.26)

82

(0.19)

153

(0.46)

–40

(0.19)

73

200 μm

#stats #plants #concs

Pore Plate

Diam

(CV)

Pore Plate

Elev +–

(CV)

Cavity

Diam

(CV)

Cavity

Height

(CV)

14 16 43

Phymatolithon

laevigatum

(0.23)

150

(0.20)

187

(0.44)

+74

(0.20)

108

12 14 31

Phymatolithon

squamulosum

95 140 +52 88

1 2 10

(0.25)

103

(0.20)

184

(0.46)

–58

(0.18)

125

4 4 16

97 158 –57 102

1 1 6

Phymatolithon

nantuckensis

Phymatolithon

borealis

Phymatolithon

investiens

11 14 43

Phymatolithon

rugulosum

TABLE 2. Mean dimensions (μm) of asexual conceptacles of Phymatolithon species in the 

North Atlantic Boreal–Subarctic transition zone. Drawings by W. H. Adey.
3 0 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

is somewhat uncertain. The larger conceptacle cavity diameters 

are directly and significantly a function of pore plate diameter as 

shown in Figure 11 for P. laevigatum. In agreement with the figures shown in Irvine and Chamberlain (1994), and in contrast to 

the superficially similar Leptophytum laeve, all these species lack 

distinctive pore cells in conceptacle roofs (and, as we present 

below, have short gonimoblast filaments across the conceptacle 

floor in mature carposporangial conceptacles, as compared to 

the laterally placed long gonimoblast filaments of Leptophytum; 

Adey, 1966a).

species are considerably deeper than in P. borealis (Table 2). 

The rapid growth in P. borealis of surrounding perithallial tissue relative to conceptacle development is also reflected in the 

high percentage of conceptacle cavities deeply embedded in the 

crust (Plates 5B, 6F). P. borealis bi-tetrasporangial conceptacles 

are intermediate in conceptacle cavity diameter between P. rugulosum and P. laevigatum. Although P. investiens conceptacles 

are dimensionally similar to those of its sister species, P. borealis

(conceptacle cavities are somewhat smaller), with only six conceptacles from one plant of P. investiens measured, the similarity 

FIGURE 10. Bi-tetrasporangial conceptacle height to crust 

surface (pore plate surface height above or below crust surface) as a function of conceptacle cavity diameter for all 

the Phymatolithon species of this paper. A. Thin hypothallium species. B. Thick hypothallium species. Number of 

stations/plants/conceptacles (each data point from a single 

conceptacle) as follows: P. rugulosum 11/13/52; P. squamulosum 14/16/35; P. nantuckensis 1/2/10; P. laevigatum

14/16/43; P. borealis 5/5/20; P. investiens 1/1/6. (See also 

Table 2.) Figure by author WHA.
NUMBER 41 • 3 1

FIGURE 11. Conceptacle dimensions (ConcCavDiam; ConcCavHgt; RoofTk [roof thickness]; ConcElev) as a function of conceptacle pore plate diameter (PPdiam) for P. laevigatum. Conceptacle cavity 

dimensions have a direct first-order relationship with the conceptacle pore plate diameter (which in 

turn is determined by the conceptacle primordial disc diameter). Other conceptacle dimensions are 

independent of primordial disc diameter. See text for full explanation. Figure by author WHA.

Gametangial Plants

In general, in Phymatolithon, gametangial conceptacles 

are rarer than bi-tetrasporangial conceptacles, and predictable 

annual reproductive cycles have not been reported. In Tables 3 

and 4, we present the mature shape and dimensions of both 

female and carposporangial conceptacles of the Boreal–Subarctic 

transition zone Phymatolithon species (Plates 3D–F; 5E,F; 7C–F). 

Single-pored female (carpogonial) conceptacles are equal to or 

considerably smaller than their bi-tetrasporangial counterparts; 

yet they are either raised or only weakly sunken, even in the 

Phymatolithon species with strongly sunken bi-tetrasporangial 

conceptacles. This situation is the result of two key factors: the 

roof and sporangial filaments of bi-tetrasporangial conceptacles 

in the Melobesioideae stop growing in mid-development, once 

sporangia mother cells are formed, while the roofs of sexual conceptacles continue to grow until either breakout or reimmersion 

into vegetative tissue, if the conceptacle is buried. Except for 

P. rugulosum, the conceptacle roofs are generally twice the thickness of the bi-tetrasporangial conceptacle roofs because of the 

continued overgrowing, hypothallial-like character of their roof 

tissue. Male conceptacles have been found in all these species 

except P. nantuckensis and P. investiens, for which our sample 

number is considerably smaller than for the other species. In 

general, male conceptacles are rare in our collections, perhaps 

because they are short lived and mostly produced in winter. In 

each species in which they have been described, spermatia are 

produced on extensive dendritic arrays on all surfaces of the very 

small conceptacle cavities (Plate 5D). Phymatolithon borealis

routinely buries its conceptacles in older crust (Plates 5B; 6A–F). 

In female crusts, unfertilized, buried, female conceptacles are 

common, suggesting that spermatia frequently do not achieve 

their target, either because of timing, or inadequate production, 

or density of reproductive plants. In P. investiens such conceptacles, although present, are usually replaced with new wound 

tissue (Plate 8E).
3 2 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

In Figure 12 and Plates 3E,F, 5E,F, and 7C–F, we present 

new information on female pre- and postfertilization development from procarps to mature carposporangia as a mosaic of 

P. investiens, P. borealis, and P. nantuckensis. As we discuss later, these patterns are consistent with the previously 

described structures and developmental patterns for P. rugulosum, P. squamulosum (as P. lenormandii), and P. borealis (as 

P. polymorphum) (discussion in Suneson, 1943; Adey, 1964, 

1966a; Irvine and Chamberlain, 1994). Carpogonial branches 

are short (3 or 4 cells including the carpogonium; they bear 

a single carpogonium, sometimes with an additional single 

sterile cell borne on the hypogynous cell (Figure 12). We have 

not observed two carpogonia side by side on a single branch. 

After fertilization, all cells of the carpogonial branch fuse, producing fusion cells that are small and very irregular, including several adjacent, unfertilized, carpogonial branches. Many 

single-celled gonimoblast filaments are then produced across 

the fertile disc, each producing a single large carposporangium. 

As in the bi-tetrasporangial conceptacles, after fertilization the 

developing carposporangia appear to release an acid that dissolves the carbonate walls in cells lateral to and beneath the 

conceptacles (and sometimes the lower parts of the new roof 

tissue). Following cell wall dissolution, the conceptacles considerably enlarge in cavity volume as the carposporangia expand, 

in P. squamulosum, P. nantuckensis, and P. investiens increasing in volume by several fold.

Biogeography and Ecology

Adey and Steneck (2001) used the bottom cover data for 

all crustose coralline species as a “first level proof” for the thermogeographic model (in this paper we only refer to the cover 

data for Phymatolithon spp.). Later, Adey and Hayek (2011) 

1 station

9 conc

outer

conc

dia

(190) 131 (–18) (85) (15)

200 μm

–119

cav

dia

cav

oor

depth

cav

hgt

roof

tk

pore

hgt

P. rugulosum

1 station

4 conc

194 139 17 –112 72 43

(270) 120 68 –56 75 47

P. laevigatum

3 stations

5 conc

P. squamulosum

198 111 44 –84 82 44

1 station

3 conc

P. nantuckensis

245 153 –29 –140 93 58

3 stations

8 conc

P. borealis

318 179 73 –90 89 62

5 stations

15 conc

P. investiens

TABLE 3. Dimensions (μm) of female conceptacles of Phymatolithon species in the 

North Atlantic Boreal–Subarctic transition zone. Drawings by W. H. Adey.
NUMBER 41 • 3 3

would likely support the presence of the indicated species are 

plotted (e.g., stations that only have depths below 3 m are not 

plotted for absence of P. squamulosum [Figure 15], as that species is almost entirely intertidal and uppermost sublittoral in its 

occurrence). Similarly, stations having only an intertidal zone are 

not presented as absent for P. rugulosum (Figure 14) when it is 

not found.

Except for the localized P. nantuckensis species that occurs 

in the large, pebble-bottomed “harbor” of Nantucket Island 

south of Cape Cod in the western Atlantic, and the very leafy 

P. investiens of northernmost Norway (Figure 17), the species 

of this paper are geographically widespread, primarily on rock 

developed a successful “second test” for the western North 

Atlantic, using multivariate statistics, for all macroalgae. It is 

those papers that support the southwest–northeast trending 

Boreal region across the northern North Atlantic around which 

this paper was organized. By restricting our southern limits to 

the Norwegian coast (that is, the colder Boreal), we have avoided 

the complexity of Lusitanean and Mediterranean species of Phymatolithon that enter the flora from the south in the British Isles. 

Here we alternatively present the geographic data for each Phymatolithon species as abundance at each station (Figures 13–17). 

The cover value (% of coralline total cover) for each species at 

each station is also given in Table 1. Note that only stations that 

TABLE 4. Dimensions (μm) of cystocarpic conceptacles of Phymatolithon species in the 

North Atlantic Boreal–Subarctic transition zone. Drawings by W. H. Adey.

183

outer

conc

dia

cav

dia

pore

hgt

conc

oor

cav

hgt

roof

tk

164 18 –118 95 41

200 μm

1 station

4 conc

P. laevigatum

388 240 139 –68 155 49

4 station

8 conc

P. squamulosum

306 184 78 –80 107 30

1 station

10 conc

P. nantuckensis

205 177 –32 –169 122 48

2 station

7 conc

P. borealis

315 223 85 –123 125 65

1 station

1 conc

P. investiens
3 4 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

FIGURE 12. Development of female carpogonium from formation to carpospores after fertilization. The presentation is 

centered on the new species Phymatolithon nantuckensis with the poorly known P. investiens (right) and P. borealis (left) 

as backup. The mature, and early fertilized, carpogonium of P. borealis (left) is presented to back up the fuller presentations by Suneson (1943), as Lithothamnion polymorphum, and Irvine and Chamberlain (1994), as Phymatolithon purpureum (see text for fuller explanation). Drawn by WHA from microtome slides stained with phosphotungstic hematoxylin; 

digital image finished by Alice Tangerini for Smithsonian Institution.
NUMBER 41 • 3 5 FIGURE 13. Distribution of Phymatolithon laevigatum in Boreal–Subarctic Atlantic. Gray dots = stations outside the Boreal– Subarctic Atlantic and not considered in this paper; black dots = species absent; at stations where substrate collections of crustose corallines obtained and within depth range of species, for abundance see legend on figure. The cover value (% of coralline total cover) at each station is given in Table 1. Figure by author WHA.
3 6 

• SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

FIGURE 14. Distribution of Phymatolithon rugulosum in Boreal–Subarctic Atlantic. Gray dots = stations outside the Boreal–Subarctic Atlantic and not considered in this paper; black dots = species absent; at stations where substrate collections of crustose corallines obtained and within depth range of species, for abundance see legend on figure. The cover value (% of coralline totalcover) at each station is given in Table 1. Figure by author WHA.
NUMBER 41 • 3 7 FIGURE 15. Distribution of Phymatolithon squamulosum in Boreal–Subarctic Atlantic. Gray dots = stations outside the Boreal– Subarctic Atlantic and not considered in this paper; black dots = species absent; at stations where substrate collections of crustose corallines obtained and within depth range of species, for abundance see legend on figures. The cover value (% of coralline total cover) for each species at each station is given in Table 1.
3 8 

• SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

FIGURE 16. Distribution of Phymatolithon borealis in Boreal–Subarctic Atlantic. Gray dots = stations in the eastern N. Atlantic outside the Boreal–Subarctic Atlantic and not considered in this paper, also western N. Atlantic where P. borealis was not found at any station; black dots = species absent; at stations where substrate collections of crustose corallines obtained and within depth range of species, for abundance see legend on figure. The cover value (% of coralline total cover) at each station is given in Table 1. Figure by author WHA.
NUMBER 41 • 3 9 FIGURE 17. Distribution of Phymatolithon investiens and P. nantuckensis in Boreal–Subarctic Atlantic. P. nantuckensis found at a single locality in the western N. Atlantic (Nantucket Island). Gray dots = stations outside the Boreal–Subarctic Atlantic and not considered in this paper, also western N. Atlantic where P.investiens was not found at any station; black dots = species absent; at stations where substrate collections of crustose corallines obtained and within depth range of species, for abundance see legend on figure. The cover value (% of coralline total cover) at each station is given in Table 1. Figure by author WHA.
4 0 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

surfaces. Only rarely does P. borealis (Figure 16), and occasionally P. investiens, occur abundantly within rhodolith beds, and 

only P. investiens forms “potato-chip” type rhodoliths. Phymatolithon squamulosum is primarily an intertidal species, and it does 

not compete well with other subtidal corallines, even in intertidal 

pools. However, like many corallines, it also does not withstand 

significant drying at low tide. Thus, unlike other species in this 

flora, it tends to be patchy geographically and dependent on 

extensive fucoid cover (mostly Ascophyllum Stackhouse); some 

rock types (smooth granite) are very inhibitive, whereas porous, 

schistose rock can support the species even when minimal fucoid 

cover is present. Its great abundance from Cape Ann, Massachusetts, northeastward to western Penobscot Bay in the Gulf 

of Maine, followed by a virtual absence from Blue Hill Bay eastward to Passamaquoddy Bay (Figure 15), relates to the change 

from often schistose or layered sedimentary rocks in the more 

western areas and primarily granitic rocks eastward. Further 

northeast, in Nova Scotia, the species again becomes common. 

Phymatolithon squamulosum is common in southwestern Iceland and on the entire coast of Norway, being especially abundant in the south.

Phymatolithon laevigatum (Figure 13) tends to be limited 

to the upper half of the subtidal photic zone and occasionally 

occurs in larger tide pools. However, it is conspicuous that P. 

laevigatum has a considerable ability to thrive in lower salinities 

and at higher temperatures. Near the northern end of its range 

in the brackish waters of the Cape Breton Bras D’Or “Lakes,” it 

is abundant and appears to be the only coralline present; similarly, in the estuary of Humber Arm, in western Newfoundland, 

it is relatively abundant. At the other temperature extreme (summer temperatures >20°C), on the western North Atlantic coast, 

ranging from Nantucket Sound to Long Island Sound, it is the 

dominant coralline species. Off northern New Jersey, the most 

southerly known site bearing rock ledges before the 800 km 

sandy coast barrier to corallines extending to south of Cape Hatteras, it is the only coralline present on the scattered rock ledges. 

Although sharply limited in the northern Gulf of St. Lawrence 

and absent in Arctic–Subarctic Labrador, P. laevigatum is abundant in the warm summer waters of the southern Gulf of St. 

Lawrence. Although virtually absent from Icelandic waters, and 

there present only on the warm southwestern coast, this species 

becomes abundant again in southern Norway and becomes the 

dominant species in the Norwegian Skagerrak and Oslofjord. In 

contrast, P. rugulosum (Figure 14) is most strongly developed 

at midphotic depths in the subtidal and does not occur at lower 

salinities and in warmer waters within the western Atlantic 

region. It is locally abundant in southwestern Iceland and at scattered localities on the outer Norwegian coast; as a widespread 

dominant, it is primarily a species of the western North Atlantic.

Neither of the species with a thick hypothallium has been 

found in the western North Atlantic. Phymatolithon borealis

occurs abundantly in southern Iceland and Norway. In Iceland it 

is reduced on the northwestern coast and is absent or rare in the 

colder, Subarctic north and east Iceland. Phymatolithon borealis

is the dominant rock-encrusting coralline on the outer coast of 

southern Norway; it is considerably more limited in the fjords, 

where it is replaced by Subarctic species from Trondheimsfjord 

northward and P. laevigatum further south. Phymatolithon 

investiens is a dominant species on the outer north Norwegian 

coast; on the central outer coast, it co-occurs with P. borealis and 

is sometimes epiphytic on that species or epizoic on barnacles 

and bryozoans. Phymatolithon investiens is moderately abundant as “potato chip” rhodoliths in the sounds of the outer coast 

of northern Norway where strong currents and moderate depths 

favor rhodolith formation. Along with other Phymatolithon species, it is sharply reduced in the inner fjords, being replaced by 

Subarctic species (Adey, 1971).

Species Descriptions

Perithallial cell measurements reported below are based on 

cells 4–7, with 1 being the meristematic cell, 2 the first perithallial cell below, etc. Measurements are gi ven as L47/44 = 2.8–10 μm 

(5.7) [1.1], where L = cell length; 47/44 = 47 cell series measured 

from 44 plants; 2.8–10 μm = minimum–maximum cell length; 

(5.7) = mean cell length; and [1.1] = standard deviation. Perithallial cell length, diameter, ratio, and coefficient of variation (CV) 

with depth are given in Figures 3–7.

Phymatolithon laevigatum (Foslie) Foslie 1898:8

Basionym: Lithothamnion laevigatum Foslie 1895:167.

Heterotypic Synonym: ?Lithothamnion emboloides Heydrich 

1900:74.

Lectotypus: TRH C25-3749, Helgoland, Germany, not dated, 

leg. Kuckuck. Designated by Adey and Lebednik (1967).

Morphology and Habitat: Encrusting, epilithic thalli 

firmly attached, thin, to 1 mm, lightly rugose, often with whitish 

surface swirls; pink when freshly collected; on boulders and bedrock, intertidal pools to 25 m depth; can tolerate warmer waters 

to 22°C and lower salinities to 18 ppt.

Anatomy: Epithallium as for genus (Plate 1C); perithallial 

cells L47/44 = 2.8–10 μm (5.7) [1.1]; D47/44 = 2.2–10 μm (5.5) [1.5] 

(Figures 4–9); hypothallium thin, 13–55 μm thick (mean 27.4, 

SD 11.8; Figure 2; Plate 1A).

Reproduction: Bi-tetrasporangial conceptacles flush with 

surface or sunken, bowl shaped with a distinctive raised rim 

(Table 2; Plate 1E,F); conceptacle cavity diameter (diam)43/16 = 

168–350 (239) [43] μm (Figure 10); roofs (0–120 μm below surrounding surface). Gametangial conceptacles sunken, rare, and 

more poorly known; see Tables 2–4.

Distribution: Widespread in the Boreal–Subarctic transition zone (Figure 13) and south into the Boreal region in the 

North Atlantic.

Comments: Topotype material from Helgoland, Germany 

(Figure A2a) has been sequenced that morpho-anatomically 

matches the lectotype specimen. Among the other North Atlantic Phymatolithon spp., P. laevigatum can only be confused with 

P. rugulosum with which it shares considerable distribution 
NUMBER 41 • 4 1

overlap (see Figures 13, 14). Phymatolithon laevigatum is distinguished by its coarser surface ridges, bi-tetrasporangial conceptacle roofs with a bowl shape and a distinctive raised rim, its less 

elongate perithallial cells, and statistically significantly greater 

mean cell diameter and higher mean bi-tetrasporangial cavity 

diameter compared with P. rugulosum.

Phymatolithon rugulosum W. H. Adey 1964:381

Holotypus: MICH 701752, southwest Merchant Island, East 

Penobscot Bay, Maine, USA, 2.xi.1961, 3–5 m below mean 

low water, leg. W. H. Adey, 61-41A-3.

Isotypus: S-163, US 171023.

Morphology and Habitat: Encrusting, smooth, epilithic 

thalli firmly attached, thin to 4 mm, with fine rugulose surface; 

bluish-pink when freshly collected; on boulders and bedrock, 

depth 0–40 m (peak abundance at ~5–10 m).

Anatomy: Epithallium as for genus; perithallial cells L53/41

= 3–11.4 μm (6.1) [1.5]; D53/41 = 2–8.6 μm (4.1) [1.1] (Figures 

4–9); hypothallium thin, 8–50 μm thick (mean 26.5, SD 9.6) 

(Figure 2).

Reproduction: Small, bi-tetrasporangial conceptacles, 

cavity diam45/13 = 100–220 μm (151) [28] (Figure 10); conceptacle roofs sunken (6–96 μm below surrounding surface) with a 

distinctive lateral shelf (Table 2; Plate 2C–F). Gametangial conceptacles rare, and more poorly known (Tables 3, 4).

Distribution: Widespread in the Boreal–Subarctic transition zone; in the Northwest Atlantic not reported south of Cape 

Cod Bay, Massachusetts, USA, and extending north through 

all but northernmost Newfoundland; absent in Labrador; most 

common on east coast of Iceland, but present throughout; not 

reported east of Vardø, northern Norway (Figure 14), extending 

south in the Boreal region throughout Ireland, Scotland, Wales, 

and England; not confirmed from France (see under comments 

below).

Comments: This species was placed in synonymy under P. 

lamii apparently on the basis of its morphological similarity and 

the apparent overlapping measured features such as cell length 

and diameter, conceptacle diameters, height and cell roof thickness, and tetrasporangial cell lengths and widths (Chamberlain, 

1991: tbl.1). Irvine and Chamberlain (1994) described P. lamii

as lacking a distinctive rim, whereas P. rugulosum has a highly 

distinctive sunken shelf lateral to the pore plate. Unfortunately, 

current available numerical data for P. lamii do not make a statistical comparison possible. DNA sequences, however, indicate 

that these are distinct species, with P. lamii more closely related 

to the recently described P. lusitanicum than to P. rugulosum. At 

present, P. rugulosum and P. lamii are separated biogeographically, with P. rugulosum not reported south of England and P. 

lamii not north of France.

In the Boreal–Subarctic transition zone across the entire 

Atlantic Ocean (Figure 14), vegetative P. rugulosum can only 

be confused with the similarly smooth and closely adherent P. 

laevigatum. But when fresh, and with attention, surface markings and color can distinguish these species. Surface ridges when 

present are finer in P. rugulosum compared to P. laevigatum. 

When reproductive, in winter, P. rugulosum conceptacles are 

smaller and more sunken than in P. laevigatum, and they also 

possess a diagnostic lateral shelf compared to the bowl-shaped 

roof and raised rim of P. laevigatum.

Phymatolithon nantuckensis W. H. Adey, J. J. HernandezKantun & P. W. Gabrielson sp. nov.

Holotypus: US 171011, Nantucket Harbor, Nantucket Island, 

Massachusetts, USA; 41°18′15.51′′N, 70°2′42.60′′W; 

1.viii.1961; shallow to 5 m; leg. W. H. Adey 61-12-1.

Morphology and Habitat: Encrusting, epilithic thalli 

firmly attached, thin and imbricating, to 600 μm thick by multiple self-overgrowth (Plate 3B); abundant on small pebbles 3–10 

cm in diameter at 2–3 m depth; pink when freshly collected.

Anatomy: Epithallium as for genus; perithallial cells L10/2

= 4.9–12.6 μm (7.7) [1.6], D10/2 = 3–9.1 μm (5.3) [1.0] (Figures 

4–9); hypothallium thin (Plate 3A,B) 7–25 μm thick (mean 18 

μm, SD 6.2; Figure 2).

Reproduction: Small, mature bi-tetrasporangial conceptacles, cavity diam10/2 = 120–160 μm (140) [14] (Figure 10); conceptacle roofs raised (32–100 μm), but conceptacle floor 18–86 

μm below crust surface (Table 2); gametangial conceptacles 

(Tables 3, 4; Plate 3E,F).

Distribution: Known only from the type locality, the harbor (lagoon) of Nantucket Island, USA (Figure 17).

Comment: The existence of this entity was known by the 

senior author for 55 years, but it was thought to be perhaps an 

introduced European species, as a result of the extensive use of 

Nantucket Harbor as a major whaling port in the late eighteenth 

and early nineteenth centuries. DNA sequencing has revealed 

this to be a distinct species, not matching with any European 

Phymatolithon species. Whether it is restricted to this area of 

a few square kilometers or is more widely distributed in very 

small numbers in the Northwest Atlantic remains to be determined. The area south of Cape Cod is environmentally isolated 

from both the Gulf of Maine and the more tropical region to the 

south; in addition Nantucket Harbor is large (more a bay created by an extensive sand bar), and the island itself is relatively 

isolated. Thus the possibility of this being a relict species cannot 

be discounted. Whaling ships travelled very widely in the late 

eighteenth and early nineteenth centuries, and a North Pacific 

origin might be considered. However, current DNA-based 

research has failed to locate any Phymatolithon species in the 

North Pacific. Furthermore, based in its distribution, and considerable DNA analysis, Phymatolithon is probably a Tethyan 

genus.

Phymatolithon squamulosum (Foslie) W. H. Adey, J. J. 

Hernandez-Kantun & P. W. Gabrielson comb. nov.

Basionym: Lithothamnion squamulosum Foslie 1895:155, pl. 

19, figs. 24–26.

Homotypic Synonym: Lithothamnion lenormandii (Areschoug) 

W. H. Adey f. squamulosum (Foslie) Foslie.
4 2 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

Holotypus: TRH B5-1962, Stensund [now Steinsund], Sulen 

[now Sula], indre [= inner], Sogn, Norway, vii. 1894; nederst lit. reg, beskyttet [= lowest littoral region, protected], 

leg. Boye (Woelkerling et al., 2005:267).

Isotypus: BM000044670, Box 434; collection data as above.

Morphology and Habitat: Thalli thin, imbricating and 

leafy, smooth when young, becoming squamulose with selfovergrowth and buried conceptacles, to 300 μm thick; violet 

when freshly collected; common on intertidal bedrock to uncommon in uppermost subtidal (<3 m depth), frequently under Ascophyllum or on schistose rock (retains moisture), not in tide pools; 

occurs with Clathromorphum circumscriptum (Strömfelt) Foslie, 

rarely with P. laevigatum.

Anatomy: Epithallium as for genus; perithallial cells L33/27

= 3.5–11.9 μm (7.0) [1.5], D33/27 = 3.5–8.4 μm (5.7) [1.2] (Figures 4–9); hypothallium 15–75 μm thick (mean 40.5, SD 15.4; 

Figure 2).

Reproduction: Mature bi-tetrasporangial conceptacles 

common, cavity diam10/2 = 122–276 μm (190) [38] (Figure 10); 

conceptacle roofs raised (10–135 μm (74) [33]) but with 

conceptacle floor approximately 75 μm below crust surface 

(Table 2). Gametangial conceptacles uncommon (see Tables 3, 

4; Plate 4).

Distribution: Geographically patchy in the Boreal–Subarctic North Atlantic transition zone; from northernmost to 

southernmost Norway; eastern and southern Iceland; uncommon in Newfoundland, absent northern Gulf of St. Lawrence 

and Labrador, patchily abundant Nova Scotia south to Woods 

Hole, Massachusetts, USA (Figure 15). In Boreal waters around 

Ireland and the UK, and confirmed as far south as Trévignon, 

France.

Comments: We sequenced an isotype specimen of Lithothamnion squamulosum (type locality: Sogn, Norway) in BM, 

because a partial rbcL sequence provided by Dr. Viviana Peña 

from an isolectotype specimen of Melobesia lenormandii Areschoug [basionym of Phymatolithon lenormandii (Areschoug) W. 

H. Adey, type locality: Arromanches-les-Bains, Calvados, France] 

in CN, was distinct at the species rank from field-collected material that we had called P. lenormandii. rbcL sequences from our 

field-collected material were identical to the isotype specimen of 

L. squamulosum; thus we made the new combination, P. squamulosum. It was relatively recently that Babbini and Bressan 

(1997) placed L. squamulosum in synonymy under P. lenormandii without comment.

With its primarily intertidal habitat and thin hypothallus, 

P. squamulosum cannot be confused with any other Phymatolithon species in the Boreal–Subarctic transition zone. In the 

Boreal part of its range, we do not know how it differs from 

P. lenormandii, as no one has found field-collected material 

that matches the rbcL sequence obtained for type material of 

P. lenormandii. It is likely that the description in Irvine and 

Chamberlain (1994) includes both species or, perhaps, is solely 

P. squamulosum.

Phymatolithon borealis W. H. Adey, J. J. Hernandez-Kantun & 

P. W. Gabrielson

Holotypus: US 170979, Heimey, Westmanneyjar, Iceland, 17 viii 

1966, leg. W. H. Adey, 66-27, 0-10K.

Morphology and Habitat: Encrusting, smooth, weakly 

leafy, unless overgrowing substrate irregularities, rarely cantilevered, becoming thick (to 5 cm), often with buried postmature 

bi-tetrasporangial conceptacles; violet when freshly collected, 

often becoming greenish-yellow when dry; abundant on bedrock 

0–30 m.

Anatomy: Epithallium as for genus; perithallial cells L124/29

= 3–11 μm (6.9) [1.3], D124/29 = 3–7.5 (4.6) [0.9] (Figures 4–9); 

hypothallium 30–140 μm thick (mean 77, SD 25.2; Figure 2; 

Plate 5).

Reproduction: Mature bi-tetrasporangial conceptacles 

22–100 μm (58) [27]) in diameter, roofs fully sunken with a 

raised rim but without a circumferential shelf (Table 2), cavity 

diam20/5 = 150–288 μm (199) [39] (Figure 10). Gametangial conceptacles (see Tables 3, 4). Postmature conceptacles often buried 

and remaining as yearly layers in the crust (Plates 5B, 6A,F).

Distribution: In the Boreal–Subarctic transition zone, only 

in Iceland and southern Norway (Figure 16). Common in Boreal 

waters around Ireland and the UK.

Comment: Despite its abundance in shallow subtidal (<15 

m) waters in Iceland and southern Norway and its occurrence in 

mid-, but mostly low, intertidal and shallow subtidal habitats in 

Boreal waters, this species appears not to have been named. In 

Boreal–Subarctic transition zone waters, Phymatolithon borealis

can only be confused with the other thick hypothallium species, 

P. investiens, but these two species only overlap in distribution 

along the central coast of Norway, and P. investiens is, in general, a deeper-water species. In European Boreal waters, P. borealis

appears most similar to Phymatolithon purpureum. Type material of P. purpureum has not been sequenced, to our knowledge. 

Based on the descriptions in Woelkerling and Irvine (1986) and 

Irvine and Chamberlain (1994), P. borealis appears distinct from 

P. purpureum, primarily on the basis of bi-tetrasporangial conceptacle characters: slightly sunken to slightly raised in P. purpureum

versus always sunken in P. borealis, conceptacles with wide, raised 

rims to 100 μm wide in P. purpureum versus narrow (30–40 μm) 

and raised in P. borealis and concave conceptacle pore plates in P. 

purpureum versus flat conceptacle pore plates in P. borealis.

Phymatolithon investiens (Foslie) Foslie 1905:81

Basionym: Lithothamnion investiens Foslie 1895:129, pl. 22, 

figs. 2–5.

Lectotypus: TRH C26-3785 in US (fragment), Lyngö, north of 

Tromso, Norway, no date, leg. Foslie.

Morphology and Habitat: Primary thalli on rock, coralline and shell substrate, moderately thick (to 1 mm), but extensively overgrowing by leafy cantilever, forming loose structures 

and breaking off to develop rhodoliths to 10–20 cm in diameter; 

violet when fresh.
NUMBER 41 • 4 3

Anatomy: Epithallium as for genus; perithallial cells L124/28

= 4.5–12 μm (6.9) [1.4], D124/28 = 3–7 μm (4.8) [0, 9] (Figures 

3–9); hypothallium 98–350 μm thick (mean 176, SD 65; Figure 2; Plates 7, 8).

Reproduction: Mature bi-tetrasporangial conceptacles 

small, 55–60 μm (57) [4], with a raised rim but without a circumferential shelf (Table 2; Plates 7A,B, 8D); roofs sunken; 

cavity diameter diam6/1 = 138–188 μm (158) [16] (Figure 10). 

Gametangial conceptacles (Tables 3, 4; Plates 7C–F, 8E,F). Postmature conceptacles rarely buried.

Distribution: Abundant in coastal northern Norway, especially in deeper water (10–30 m) as rhodoliths (Figure 17).

Comments: Both Phymatolithon investiens and its basionym, Lithothamnion investiens, are considered illegitimate 

names, because Lithothamnion investiens is said to be a superfluous name for Lithophyllum zonatum Foslie (1890: 10). This 

argument assumes, however, that Lithophyllum zonatum and 

Lithothamnion investiens are the same species. Foslie (1895) 

believed that they were, as he listed Lithophyllum zonatum

as a synonym under Lithothamnion investiens, but convincing evidence is lacking. We have sequenced the Lithothamnion 

investiens lectotype specimen designated by Adey in Adey and 

Lebednik (1967: 72), and that sequence is an exact match to 

field-collected material. We have not sequenced the holotype of 

Lithophyllum zonatum, and thus we use the name P. investiens.

As noted above under P. borealis, P. investiens can only be 

confused with that species where they co-occur in central Norway, but P. investiens typically occurs in deeper water (10–30 m) 

where it is common, especially as rhodoliths.

DISCUSSION

For the Boreal–Subarctic transition zone Phymatolithon

species treated herein, there is excellent congruence between the 

DNA sequence data and the identity of specimens and species 

delimitations based on previous morpho-anatomical studies by 

the senior author (Adey, 1964, 1965, 1966a), as well as new 

information in this paper. This agreement is in contrast to nearly 

all other coralline geniculate (Gabrielson et al., 2011; Hind and 

Saunders, 2013; Hind et al., 2014a,b, 2015) and non-geniculate 

genera and species (Basso et al., 2015; Hernandez-Kantun et al., 

2014, 2016; Sissini et al., 2014; van der Merwe et al., 2015; 

Hind et al., 2016), wherein type specimens have been matched 

to field-collected material based on DNA sequences. The major 

reasons for this are fourfold with respect to non-geniculate corallines: (1) most coralline morpho-anatomists have relied on 

small sample sets stored in museums, and rarely have population analyses supported by statistical analysis been employed; 

(2) during the past 60 years since scuba has been widely available, few have taken the opportunity to intensively study these 

organisms in their natural habitat; (3) the gross morphology of 

a species can vary widely with substrate characteristics, such as 

local fleshy algal cover, depth, and wave and current action; and 

(4) specimens often are bulky, especially when collected with 

their substrate intact, and are often mosaics of crusts of several 

different species; rarely has enough coralline-covered substrate 

been returned to museum collections to allow the evaluation of 

infra- and interspecific variation in relationship to the original 

environment.

Included in this group of species, where the morphoanatomical and DNA sequence data are not congruent, are the 

Northeast Atlantic Boreal–Lusitanean Phymatolithon species 

(primarily UK, Ireland, France, and Spain). Thus far, we have 

no match in any database, including our unpublished sequences, 

to the sequence from the isolectotype specimen of P. lenormandii nor to the material excluded from the type of Lithophyllum 

hibernicum Foslie (the rhodolith lacking cup-forming terminal 

branches; Hernandez-Kantun et al., 2015: fig. 6A, top-right 

specimen), both of which belong in Phymatolithon. All the 

Phymatolithon species type specimens whose localities are in 

Boreal Europe need to be sequenced, as well as many more fieldcollected specimens, before we can confidently apply names as 

well as understand the ecology and distributions of these species. At present, all reports of P. lenormandii outside the Boreal 

Northeast Atlantic (Guiry and Guiry, 2017) are likely misapplications of this name.

Hypothallia

Hypothallial thickness and cell shape are useful characters 

for separating Boreal–Subarctic transition zone Phymatolithon

species (Figure 2). Hypothallial overgrowth of initially thin 

crusts, including occasional burial and frequent refilling of conceptacle cavities by secondary hypothallia, can only be ascribed 

to P. squamulosum or the geographically and ecologically 

restricted P. nantuckensis. These species occupy unstable substrate where rapid growth over new surfaces, self-overgrowth, 

and constant conceptacle production have more adaptive value 

than building crust thickness.

At the other extreme, P. borealis and P. investiens have 

very thick hypothallia, typically two to five times that of the 

thin hypothallium Phymatolithon crusts (Figure 2); these are 

crusts that are leafy or “rolling” in character, with the thicker 

hypothallus more able to negotiate holes or valleys in the substrate. In P. investiens, with hypothallia mostly more than 100 

μm thick, and sometimes more than 300 μm, crusts can become 

cantilevered over considerable holes and valleys in the substrate. 

When P. investiens crusts break free of the substrate, continued 

marginal growth and overgrowth can produce rhodoliths with a 

“potato chip” morphology.

Phymatolithon investiens is the only crustose Boreal–Subarctic transition zone Phymatolithon species to have significant rhodolith potential. In rhodolith habit it was only found well north 

of the Arctic Circle, although still in Boreal–Subarctic transition 

zone waters (Adey, 1971). In northern Norway land elevations 
4 4 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

are generally lower than in the southern part of the coast. As a 

result, water depths in the sounds between outer fjords are often 

less than 30 m, are within the photic zone, and large areas are 

more or less flat-lying with strong tidal currents providing favorable conditions for extensive rhodolith development.

Although in the individual epilithic crusts of P. investiens

overgrowths are more substantial and less frequent compared to 

P. squamulosum and P. nantuckensis, P. investiens is morphologically similar to these species as compared to the other Boreal–

Subarctic transition zone species that more rarely overgrow their 

own crusts. For P. borealis and P. investiens, the advantages to 

being able to occupy very irregular surfaces with thick marginal 

primary crusts that can function without continuous substrate 

support seem more or less obvious. However, that these should 

be restricted to the warm winter (eastern Atlantic and southwestern Iceland) part of the North Atlantic Boreal–Subarctic transition zone remains more obscure. This locale restriction may 

result from biogeographical history, or possibly from the slow 

growth occasioned by long winters near 0°C on the colder side 

of the North Atlantic.

Intermediate between these two morphologically extreme 

growth forms are P. laevigatum and P. rugulosum. These species 

have moderately thick hypothallia (Figure 2), but are so tightly 

adherent to their typical rock substrate that removal from their 

habitat with hammer and chisel often brings rock fragments 

attached to their bases. They build long-lived crusts (perhaps 

decades in age) in stable environments; however, as we discuss 

below, they occupy rather different environmental niches.

Perithallia

Non-geniculate corallines, in general, do not produce fixedsize cells within their carbonate matrix; intercalary meristematic 

cells divide and the ventrally produced perithallial cells continue 

to elongate and add wall carbonate for at least several cells deep 

in the perithallium. More deeply in the perithallial tissue, cells 

clearly add (and remove) carbonate within the walls. It is standard in coralline taxonomy to provide a set of cell measurements, 

as a range of dimensions, without statistical data and without 

specifying location (other than perithallium); this approach generally provides data having little value in discriminating species 

or in understanding their growth physiology.

Genera in the Hapalidiales present three general types of 

cell elongation in the perithallium below the intercalary meristem (Adey et al., 2005, 2015b). All Phymatolithon species are 

of the “progressive type,” elongating gradually, mostly over the 

first three to four cells below the meristematic cells, with relative stabilization thereafter (Figure 3). Thus, in Phymatolithon, 

typically cells four to seven below the meristem have the least 

variability and provide the best measure for potential species 

identification. In this range, cell elongation (upward crustal 

extension) has been completed and the cell shape changes 

associated with depth in the perithallium have not yet been 

expressed. Although cell lumen diameter changes far less, it 

tends to increase or decrease a small amount below the level of 

length stabilization (Figure 5).

Among the Phymatolithon species treated herein, statistically significant numerical differences in cell length and particularly cell diameter in the stable cell range (cells 5–7) have been 

shown (Figure 5). Except in P. nantuckensis, cell shape (L/D) varies least within species and is consistently diagnostic among species, even when this measure is extended to the generally more 

elongate hypothallial cells (Figure 8). The thin hypothallial species, P. rugulosum, and the thick hypothallial species, P. borealis

and P. investiens, have relatively long and narrow perithallial cell 

lumina, whereas P. laevigatum has spherical cells, and P. squamulosum is intermediate in this respect. Phymatolithon nantuckensis shows considerable perithallial cell elongation below cell 4 

(Figure 4) that may be the result of its very thin crusts (typically 

70–400 μm), the beginning of the transition from the hypothallium and, in large part, fewer sampled specimens. The tendency 

for perithallial cell diameter to increase slightly with depth in 

the thin hypothallium species (Figure 5) could be an artifact of 

the development of cross-filament fusions with depth below cell 

3 (Adey, 1964; also see Figure 8). However, the thick hypothallium species, P. borealis and P. investiens, also have numerous 

cell fusions; they show the opposite trend, and both the positive 

and the negative slopes are statistically significant. CV values for 

perithallial cell diameter remain equivalently low as compared 

to cell length for the shallow cells (Figure 6). However, except 

for the consistently erratic values for P. nantuckensis, all species 

have a strong tendency for CV values to increase with depth, 

further indication of the dynamics of cell wall carbonate with 

depth.

Significant perithallial growth over several years may also 

occur, producing a more regular seasonal pattern of calcified 

walls of longer, thicker-walled cells in summer and shorter, 

thinner-walled cells in winter. This tendency is most pronounced 

in P. borealis, but it also occurs in Clathromorphum species, 

where the IF layer can be thicker than the IW wall, and varies 

seasonally, being typically much thicker in summer (Adey et al., 

2013). In Clathromorphum, the calcite crystals are large, deltoid 

in shape, and typically oriented vertically or diagonally (Adey 

et al., 2013, 2015b). Additional sub-perithallial tissue types 

develop in the conceptacle roofs of both bi-tetrasporangial and 

gametangial conceptacles, although these could be considered 

tissue types of conceptacles.

Perithallium: A Complex of Tissues

Historically, corallines had been considered to have two basic 

tissue constructions: perithallium and hypothallium. In the 1960s, 

Adey (1964, 1965, 1966a), showing a great range of development 

in what had been previously referred to as cover cells (or deckenzellen), introduced a third tissue type, epithallium. These tissues 

vary widely in different genera and species. Herein, and in earlier 

papers (Adey et al., 2005, 2013, 2015b), we have demonstrated 

a pattern of perithallial cell development and modification with 
NUMBER 41 • 4 5

depth. However, there is a higher level of organization within 

perithallial tissue that develops when cells of different shape 

and calcified wall chemical composition form. These anatomical 

changes occur when the normal intercalary meristem and elongating cell patterns are disrupted by more rapid growth relating 

to damage and return to morphological stability (Plates 1B, 2C, 

3B, 4C,F, 6A,F, 8E). The changes are produced by the coordinated action of a local group of filaments and occur in response 

to grazing or when conceptacles break out after spore release. 

Such “wound” tissue results from deep grazing or from conceptacle breakout and produces a localized and coordinated rapid 

regrowth of distinctive and changing cell morphology (Siobhan 

Williams, W. Adey, J. Halfar, A. Kronz, P. Gagnon, D. Belanger, 

and M. Nash, unpublished manuscript [in review], “Effects of 

light and temperature on Mg uptake, growth, and calcification 

in the proxy climate archive Clathromorphum compactum,” Biogeosciences), cell wall microstructure, and Mg content (Nash and 

Adey, 2017a,b). The regrowth continues until the typical crust 

surface is attained. When the morphological anomaly is repaired, 

the cells return to their normal growth rate and shape.

In addition, Phymatolithon species conceptacles have at 

least two supporting tissues, those of conceptacle roofs (both 

bi-tetrasporangial and gametangial) and of nurse tissues, cells 

surrounding developing bi-tetrasporangia and carposporangia 

whose carbonate walls have been dissolved and the cells crushed. 

Transfer of photosynthate from nurse tissue to developing sporangia has not been demonstrated, but the very large size of the 

quickly developed sporangia indicates that photosynthate must 

be transferred from elsewhere, and the surrounding and underlying crushed tissue is a likely source (Adey et al., 2013).

More or less narrow fusion channels formed between adjacent cells by cell wall dissolution can, and probably do, have 

many roles in coralline metabolism. These channels also provide 

one key to understanding the basic process of cell wall calcification. Corallines produce high magnesium calcite of specific but 

varying magnesium content in their complex cell walls, but they 

also have the capacity to dissolve away that calcite, with some 

precision, at other points in their skeleton. As shown in Figure 8, 

calcification and wall dissolution rarely occur in the same cell, or 

the same local area of tissue, at the same time.

Some species of Phymatolithon have structures internal to cells, called staining bodies. The chemical structure of 

these bodies has not been investigated, but in the North Atlantic Boreal–Subarctic zone species they occur only in a single 

clade, that composed of the species P. laevigatum, P. borealis, 

and P. investiens (Figure 1), and can be useful in identification 

when reproductive structures are not present or when too few 

specimens are available for statistical analysis. The only other 

species in the North Atlantic Boreal–Subarctic known to have 

these distinctive staining bodies are Lithothamnion tophiforme

Unger and Lithothamnion sonderi, but the former typically has 

a branching morphology and the latter is a thin, tightly attached 

deep-water species (>20 m) occurring mostly in southern 

Norway and the British Isles. Lithothamnion tophiforme and 

P. investiens do occur together in the outer sounds and fjords 

of northwestern Norway, the former as rhodoliths and the latter as epiphytic crusts on these rhodoliths. Similarly, in deeper 

waters (>20 m) of southern Norway, P. borealis and L. sonderi

can co-occur. Even when this is the case, the highly distinctive 

armored epithallial cells and elongate meristem cells, as seen in 

thin sections and SEM images of both Lithothamnion species, 

should easily serve to separate the species in section. In a hand 

specimen, L. sonderi is not only a very thin crust, but frequently 

has distinctive, raised white conceptacles, or rim remnants of 

conceptacles; it would not likely be confused with a Phymatolithon species.

Reproduction

Adaptations to Grazing

In spite of the calcified thallus, non-geniculate corallines 

are often subject to considerable surface grazing by scraping 

invertebrates, especially chitons, limpets, and sea urchins. Thus, 

many corallines have evolved special adaptations to reduce the 

effects of grazing, particularly on their conceptacles. Phymatolithon species protect their developing conceptacles by initiating their conceptacle primordia adventitiously, more or less 

deeply (30–100 μm) in the perithallium. In nearly all other nongeniculate corallines, conceptacle primordia are produced from 

the intercalary meristem just below the crust surface, and these 

taxa have evolved other protective mechanisms. Clathromorphum species are truly extraordinary as they have developed a 

thick photosynthetic epithallium and have a symbiotic relationship with limpet grazers. When grazing is prevented, epithallial 

cells build up and, along with settled epiphytes, can cause the 

death of a crust (Adey, 1973; Steneck, 1982, 1992; Adey et al., 

2013). Most Lithothamnion species have very thick-walled epithallial cells (presenting an armored effect; Adey et al., 2005) 

as well as branches, the latter having been shown to reduce 

grazing (Steneck, 1982, 1992), whereas others develop sunken 

conceptacles.

Many corallines in the Subarctic and the Boreal–Subarctic 

transition zone, including most Phymatolithon species (Adey, 

1964), produce their bi-tetrasporangial conceptacles in winter, 

when grazer activity is minimal. Phymatolithon species that 

are not restricted to winter reproduction occupy environments 

which are largely grazer reduced. Phenological data and grazing 

experiments from cold-water anti-Boreal and Antarctic crustose 

corallines would be an interesting comparison. Recently, while 

carrying out laboratory experiments with C. compactum, we 

learned that if temperatures are raised while the conceptacles are 

maturing, chitons that are present in the experimental system, 

which would normally graze just the epithallium, gouge deeply 

into the conceptacles, removing sporangia as well as surface 

crust, a behavior never seen in situ (Williams et al., unpublished). 

Thus, grazer and coralline crust interactions are complex and 

can be significant (see also Steneck, 1982, 1992).
4 6 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

Bi-tetrasporangial Conceptacles

For all non-geniculate coralline taxa in Subarctic and 

Boreal–Subarctic transition zone waters, bi-tetrasporangial 

conceptacles are far more common than gametangial conceptacles (Adey, 1964, 1965, 1966; Adey and Adey, 1973); in most 

cases, they are initiated in autumn and produced in winter. As 

we have shown with population/statistical techniques, conceptacle dimensions are generally a reliable character for separating 

congeneric species within these regions, and this distinction has 

been widely accepted in the field over the past century. However, 

not all species are separated by conceptacle dimensions, and in 

some cases one has to rely on multivariate analysis for confident 

species differentiation (Figure 10). Perhaps more importantly, in 

spite of the high levels of statistical confidence for conceptacle 

parameters, all the Boreal–Subarctic transition zone Phymatolithon species have overlapping dimensions. Although this characteristic had been demonstrated for many genera in some earlier 

studies (e.g., Adey, 1964, 1965, 1966a; Adey and Adey, 1973), 

it has been routine in other coralline studies to utilize dimensional ranges for all characters. Rarely will this approach supply 

confident differentiation of species, especially when comparing 

species from different biogeographical regions.

The shapes and sizes of Phymatolithon bi-tetrasporangial 

conceptacles are statistically species specific (Table 2; Figure 10). 

However, there is also considerable overlap in dimensions for 

some species in all characters (Figure 10); although the measurements of a few conceptacles to distinguish P. laevigatum from 

P. nantuckensis would suffice, either numerous measurements 

or the use of a multi-character display (Adey, 1964) would be 

required to numerically separate P. laevigatum from P. rugulosum. On the other hand, the raised rim of the former species, as 

compared to the inner shelf of the latter, are highly diagnostic 

characters. The well-sunken conceptacles of the P. borealis and 

P. investiens clade, with their distinctive upper rim, is diagnostic, as is the rounded “bowl” shape of the large conceptacles of 

P. laevigatum. The conceptacle of P. investiens is smaller than 

P. borealis, and the tiny, sunken conceptacle of P. rugulosum

bears the equivalent of the raised rim of the P. borealis clade; 

however, it occurs as a quite diagnostic sunken shelf.

In Table 2, for each species for which we have large data 

sets, we have given CV values for each conceptacle dimension. 

Most parameters have characteristically low CV values (0.19%–

0.26%), but the height (or depth) of the pore plate, above or 

below the vegetative surface, has a large CV (0.44%–0.74%). 

[Note: we have not shown conceptacle roof values in the table 

to reduce complexity, but roof CV values for all species are also 

low (0.19%–0.24%)]. As has been demonstrated for many Phymatolithon species, the diameter of the conceptacle pore plate is 

species specific, and is essential the same diameter as the primordial disc. Also, the conceptacle cavity diameter, although larger, 

is directly and significantly a function of pore plate diameter 

(Adey, 1964), as shown in Figure 11 for P. laevigatum. However, 

the remaining conceptacle vertical characters (conceptacle cavity height, roof thickness, and conceptacle elevation) are independent of the horizontal characters. The horizontal character 

dimensions are determined by primordial disc diameter, whereas 

the vertical dimensions are controlled primarily by rate of development of conceptacle maturation relative to the growth of the 

vegetative surface. The remaining species have very similar plots 

for all parameters and are not presented.

Pore plate diameter and cavity diameter of the bitetrasporangial conceptacles are tightly linked (as derived from 

the primordial disc; Figure 11; Table 2) and are clearly genetically controlled. Conceptacle cavity height and roof thickness 

are independent variables; as they have low variability (Table 2), 

it is likely that they are separately genetically controlled, probably as sporangium dimensions. On the other hand, conceptacle 

elevation is independent of the lateral conceptacle dimensions 

(pore plate/cavity diameter) and has a high level of variability 

that relates not only to the rate of sporangial development but 

also to the rate of growth of the surrounding vegetative perithallium. After sporangial mother cells have fully formed, vertical 

elongation of sporangia, including their thick cap wall with 

the surrounding structural filaments of the roof, ceases. The 

sporangia now induce a dissolution of surrounding, and to a 

lesser extent underlying, cellular carbonate; their division and 

expansion crushing the cells, now without their carbonate walls. 

Although we have insufficient data to securely link the depth of 

the primordial disc to mature roof height (depth), casual observation suggests that such a link is only partly responsible for 

mature conceptacle elevation; perithallial growth during conceptacle development and maturation is a key factor (Adey et al., 

2013). As we noted previously in our treatment of perithallium, 

conceptacle nurse and roof tissues form part of the diversity of 

tissues in these crusts.

This link of surrounding perithallial growth to conceptacle 

development and height was shown diagrammatically for Clathromorphum compactum by Adey et al. (2013). In P. rugulosum

and P. laevigatum, for which we have abundant primordial disc 

data, approximately half the ultimate conceptacle cavity height 

is accommodated by upward perithallial growth and half by 

the crushing of perithallial cells beneath the sporangia (Plates 

2, 3, 5) However, these are moderately thin crusts, with minimum upward growth, so the 5–10 μm increase in crust thickness 

during the 6 months while the conceptacles are developing is 

considerably less than the approximately 100 μm produced by 

the Subarctic Clathromorphum crust during 9 months of development. In the thin crust species, P. squamulosum and P. nantuckensis, conceptacles become raised at maturity, which derives 

from two factors: the depths of formation of the conceptacle primordia are less than those in all the thicker species (generally 4–8 

cells as compared to 15–25 cells below the surface); in addition, 

upward growth of the surface of these crusts is considerably less 

than crusts of the generally thicker species. Bi-tetrasporangial 

conceptacle elevation relative to the crust surface results only in 
NUMBER 41 • 4 7

part from internal conceptacle development; it derives also from 

the relative growth of the surrounding perithallus (Adey et al., 

2013). The key element relevant to taxonomic characters is that 

the depth of conceptacle primordial formation is genetically controlled. The height of mature conceptacles, however, is far more 

complex, controlled in part by perithallial growth, in part by different genes, and in part by environmental conditions.

In the thick hypothallial species, P. borealis (Figure 10B), 

conceptacles are sunken at maturity; although the pore plates 

are somewhat deeper than in P. rugulosum and P. laevigatum

(see Table 2), the mature conceptacle cavity floors are considerably deeper than in the former species (Table 2). The rapid 

growth in P. borealis of surrounding perithallial tissue relative to 

conceptacle development is also reflected in the high percentage 

of conceptacle cavities deeply embedded in the crust. P. borealis

bi-tetrasporangial conceptacles are intermediate in conceptacle 

cavity diameter compared to P. rugulosum and P. laevigatum. 

Although P. investiens conceptacles appear dimensionally close 

to those of its sister species, P. borealis, with the conceptacle 

cavity appearing somewhat smaller, with only six conceptacles 

observed from one plant of P. investiens the correct relationship remains somewhat uncertain. In agreement with the figures 

shown in Irvine and Chamberlain (1994), and dissimilar to Leptophytum leave, all these species lack distinctive pore cells in the 

bi-tetrasporangial conceptacle roofs.

Among Clathromorphum species in the western Atlantic 

Subarctic, conceptacle shape and placement are indistinguishable, but patterns of degeneration and breakout, or lack thereof, 

are sometimes highly distinctive (Adey, 1964; Adey et al., 2013). 

Clathromorphum circumscriptum occupies the high-energy and 

extremely disruptive intertidal tide pools and shallow subtidal 

zones. Spore release occurs each spring with the breakout of 

fields of conceptacles, with the resulting loss of considerable 

crust; sometimes this process extends far below the intercalary 

meristem, and crusts die in the process. However, this species 

occupies an unstable environment where new, unoccupied substrate is often available and long-term space competition has 

minimum value. The massive and certain release of all produced 

spores provides the greatest opportunity to settle the abundant 

rock surface newly available each year. In deeper water, its sister 

species C. compactum maintains its conceptacles year after year, 

the conceptacles being buried, and often spores remain and are 

lost to reproductive potential. There is rarely a die-off, and the 

individual plants continuously occupy rock space for extended 

periods (typically to hundreds of years, but known to 1900 years; 

Adey et al., 2015a). Clathromorphum compactum occurs in a 

more stable environment, where competition for space by a host 

of encrusting invertebrates is extreme; once cover is established, 

it is more important to maintain that cover than to provide new 

spores, most of which will find few opportunities to settle. Nevertheless, as Adey (1965) demonstrated, when new artificial substrate is placed in the C. compactum environment in midwinter 

when grazers are largely inactive, rapid settlement occurs and 

the sporelings are rarely grazed. Phymatolithon borealis, alone 

among the Phymatolithon species treated herein, reliably buries 

its conceptacles in the perithallia. This structure allows differentiation with its close relative P. investiens, but equally important, 

because it is characteristic of broad bedrock surfaces where space 

competition is extensive, as in the Clathromorphum species cited 

above, it indicates the importance of long occupation of these 

surfaces once successful attachment is achieved. This Clathromorphum example, along with our previous discussion for Phymatolithon spp., also shows that many reproductive adaptive 

factors are in play in addition to conceptacle size and shape.

The shape and elevation of Phymatolithon conceptacles 

relative to the crust surface demonstrates considerable niche specialization. Species in harsher environments (the non-tide-pool 

intertidal environment for P. squamulosum and unstable substrate for P. nantuckensis and P. investiens), where invertebrate 

grazers are at a disadvantage, have elevated conceptacles (only 

female/carposporangial conceptacles for P. investiens). Here, 

the production of excess crust with carbonate structure requires 

energy and time, produces excess weight, and is a disadvantage 

from burial in pebbles or finer sediment or drying or freezing on 

a long tidal cycle at an inopportune time. Species with tightly 

adherent, relatively thick crusts, in more stable environments, 

where grazers (limpets, chitons, and sea urchins) have an advantage, produce deeply sunken conceptacles.

Gametangial Conceptacles

These conceptacles are less reliable as species indicators, 

probably in large part because they are far more rare. Presently, 

we do not have enough information to pursue how gametangial 

conceptacles relate to strategies for survival. The available data 

are presented in Tables 3 and 4, primarily to indicate genetic 

affinities in support of DNA sequence data. In Phymatolithon

gametangial conceptacles, where the roof is produced by a 

hypothallium-like overgrowth (rather than the nonreproductive 

ephemeral filaments between the developing carpogonia or the 

highly productive spermatial filaments), the link between conceptacle primordial depth and mature conceptacle height is reduced. 

In P. investiens, P. squamulosum, and P. nantuckensis, in which 

perithallial growth is more limited, the result is elevated sexual 

conceptacles, even though the original primordia were sunken 

in the perithallium. Simple use of the terms raised or sunken 

conceptacles is likely inadequate in most cases as a taxonomic 

character, with greater biological understanding being needed 

for accurate utilization.

Ecology

In this section we bring together our ecological analyses for 

Phymatolithon species across the entire North Atlantic Boreal–

Subarctic transition zone; we also offer testable hypotheses for 

the environmentally controlling factors.
4 8 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

Across the Boreal–Subarctic transition zone, the six Phymatolithon species occur largely in different environmental 

niches. Leaving aside the localized P. nantuckensis (which is 

monotypic at its type locality), the remaining species have overlapping distributions, but intraspecific competition is clearly limited to those in overlapping habitats. It is difficult to identify a 

morphological characteristic that affords near-total dominance 

to P. laevigatum in warmer, polyhaline, brackish waters; indeed, 

it may be entirely physiological. On the other hand, the highly 

imbricate structure of P. squamulosum allows water retention, 

and in its intertidal habitat it is typically the only coralline present. Also, the presence of overlying rockweed or a porous rock 

surface allows the plant to become highly abundant locally. Neither P. borealis nor P. investiens has crossed to the western North 

Atlantic, most likely because of low winter temperatures (neither 

species has a significant presence in the inner Norwegian fjords, 

which often freeze over in winter (Adey, 1971; Adey and Hayek, 

2011). This restriction provides a niche for P. rugulosum, which 

although not competitive with Subarctic species further north 

in Labrador, becomes a dominant in the coastal Gulf of Maine, 

with its cold winters (0°–2°C). In Iceland, where winter water 

temperature grades strongly, from cold (near 0°C) in the north 

and east to quite warm (6°C) on the southern coast, P. rugulosum becomes abundant in the transition zone of the west coast. 

It occurs only at scattered localities on the Norwegian outer 

coast. It seems likely that a finer meshwork of stations along 

central Norwegian fjords would show that it is most abundant 

in mid-fjord regions, with P. borealis replacing it seaward and 

Clathromorphum circumscriptum replacing it landward.

Biogeography

The North Atlantic marine biota, including seaweeds and 

corallines, was biogeographically derived from two very different source regions following the opening of the North Pacific Bering Strait in the late Pliocene. The Arctic and Subarctic coralline 

flora is primarily North Pacific (especially the Okhotsk to Bering 

Sea regions) in origin, whereas the Atlantic Boreal, Lusitanean, 

and Mediterranean coralline floras are primarily Tethyan (preMediterranean) in origin (Adey and Steneck, 2001; Adey and 

Hayek, 2005, 2011; Adey et al., 2013). Even considering the 

north–south movement of biota during Pleistocene climate fluctuations, warm-water (tropical western Atlantic/Caribbean and 

Carolinean) corallines were not able to cross the long sandy and 

muddy coast that is continuous from roughly Cape Hatteras to 

Long Island in the western North Atlantic. The shallow waters 

of the eastern North American coast south to Florida further 

inhibited the development of a significant hard bottom coralline flora, further preventing the entry of warm-water corallines 

from the tropical and subtropical western North Atlantic into 

the Boreal coralline flora of New England. Thus, Boreal corallines from the eastern North Atlantic, mostly in shallower water, 

mix with Subarctic corallines from Rhode Island to the southern 

Gulf of St. Lawrence. Phymatolithon laevigatum on highly scattered patches of hard bottom reaches to the northern New Jersey 

coast. From Newfoundland north, Subarctic and Arctic species 

form the coralline flora.

In the eastern North Atlantic, Phymatolithon species dominate the cold-water Boreal coralline flora because of the influence 

of the Gulf Stream (and continuing Norwegian and Irminger 

Currents). The Subarctic coralline flora only reaches northern 

and eastern Iceland and the more northern inner fjords of Norway, where the continental influence provides cold winters and 

ice-bound waters (Adey, 1968, 1971: Adey and Adey, 1973). 

Further south on the warmer western European coasts, several 

additional Phymatolithon species, along with many Lithophyllum species, dominate the warmer Boreal and Lusitanean floras 

(Irvine and Chamberlain, 1994). However, to the north and 

northeast, the Boreal boundary rather sharply, but complexly, 

interdigitates with the Subarctic coralline flora dominated by 

Lithothamnion, Clathromorphum, and Leptophytum species. 

As we discussed earlier, in the cold-water Boreal, Phymatolithon

species are largely ecologically and biogeographically partitioned 

so that there is little interspecific competition.

Phymatolithon laevigatum occurs across the entire region, 

although it is rare in Iceland; it occurs abundantly primarily in 

warmer waters, where temperatures reach more than 15°C in 

summer, and especially in waters of lower salinity (to 15 ppt). 

It is highly abundant in the warmer, lower-saline waters of the 

southern Norwegian coast and in the Skagerrak, and the holotype derives from Helgoland. It would be particularly interesting to examine the genetics of P. laevigatum populations from 

the eastern and western North Atlantic, to determine when the 

cross-ocean transit took place, as has been done with the rockweed Fucus serratus (Johnson et al., 2012). Phymatolithon rugulosum occurs in deeper and colder full coastal salinity waters 

where summer temperatures generally do not exceed 15°C; it is 

abundant only in southwestern Iceland and the central western 

North Atlantic.

Phymatolithon borealis occurs abundantly on hard rock 

substrate in southern Iceland and the North Sea outer coast 

of southwestern Norway, where winter temperatures do not 

drop below about 3°C; it is mostly replaced by P. laevigatum

when entering southern and Skagerrak waters where salinities are lower and winter temperatures, especially in fjords and 

other inshore waters, can drop below 0°C. Its sister species, 

P. investiens, is primarily an outer coast northern Norwegian species, where in spite of the high latitude, winter temperatures are 

above 3°C. Phymatolithon investiens, with its expansive leafy 

habit, often occurs as an epizoic on calcified invertebrates and 

epiphytically on other corallines; it occupies mostly looser substrate, sometimes occurring in rhodolith beds, which, because of 

the change in topography and shallower inter-fjord and sound 

waters, are more abundant in northern Norway. The two species 

overlap on the outer central Norwegian coast, primarily between 

Bodø and Tromsø.
NUMBER 41 • 4 9

Calcification

Currently, we do not have a definitive understanding of the 

biophysical and chemical process of calcification in corallines. 

However, we do have a considerable amount of structural and 

physiological information that provides boundaries to the process. In the following, we assume that all corallines, and certainly 

those of the colder Boreal–Subarctic regions, have the same basic 

calcification process. Because many tropical genera of crustose 

corallines (Mastophoroideae and Lithophylloideae included) 

have meristem/growth patterns similar to that of Lithothamnion

(Adey, 2005, 2015b; Nash and Adey, 2017a,b), it is likely that 

the patterns we describe are universal. Most critically, we know, 

from experimental and field studies (Adey et al., 2013), that 

Clathromorphum does not require light to calcify, although ultimately stored energy from photosynthesis is required. Also, there 

are non-photosynthetic coralline parasites, such as Kvaleya in the 

North Atlantic and Arctic (Adey and Sperapani, 1971; also Ezo

on Lithophyllum; Adey et al., 1974) that show the same basic 

calcified wall structure as free-living corallines; in these cases the 

calcified walls are developed using photosynthate derived from 

their hosts (Nash and Adey, 2017a). Thus, calcification is almost 

certainly metabolically driven (Adey, 1998) rather than supported by pH elevation during photosynthesis.

All crustose corallines (ranging from Arctic to tropical) that we have examined with high-magnification SEM 

(5,000–100,000×), have two distinct types of cell wall calcification: inner wall (IW) and interfilament (IF) (Plates 9–11). 

IW calcification occurs broadly across the Corallinophycideae 

as short, narrow, radial crystals (approximately 0.1 μm in section; Plates 9B–D; 10A,B; 11B,C). At magnifications exceeding 10,000×, these crystals can be seen to be multi-lobed and 

0.5–1.0 μm long, oriented more or less perpendicular to the 

cell lumen (Plate 9B–E). In contrast to Clathromorphum, in 

which all perithallial (and epithallial) calcification occurs in a 

very narrow band roughly in the middle of meristem cells (the 

meristem split; Adey, 1965; Adey et al., 2015b), Phymatolithon

calcification is diffuse along the side walls of both the meristem 

cell and perithallial cells 2–4, where elongation occurs. IF calcification can be highly developed (as in Clathromorphum; Adey 

et al., 2013, 2015b), but in most progressive growth corallines 

(particularly all Phymatolithon spp.) the IF calcite consists of 

a few layers of more or less tabular crystals that are approximately 0.1 μm square and 0.5–1.0 μm long; typically, they are 

randomly oriented, but generally lying parallel to the cell lumen 

wall (Plates 9B,C,E; 10A–F; 11B–F). As differential elongation 

occurs in cells on both sides of the IF, we call these surfaces glide 

planes; in most progressive growth species, these glide planes can 

strikingly present visually in vertical fractures as extensive vertical surfaces the width of the cells. Of the species we treat in this 

paper, P. rugulosum has an unusually well-developed IF (Plate 

11), and for the species treated in this paper this species also 

appears in a separate subclade (Figure 1).

Corallines routinely both calcify and de-calcify metabolically in the same plant, at the same time, but probably not in 

the same cell (or perhaps even the same cell grouping). Both processes occur in the vegetative perithallium and hypothallium and 

in reproductive tissues (conceptacles). The dissolution of usually 

narrow channels in walls between perithallial cells of adjacent 

filaments (typically referred to as fusions) is well known in Phymatolithon. The term fusion, although a misnomer as applied 

to the process in corallines (the fusion channels are typically 

quite narrow, more like tunnels), is nevertheless a widely applied 

shorthand term that we continue to use. These fusions develop 

progressively with depth in the perithallium, but mostly after cell 

elongation ceases (Figure 8B; Adey, 1964, 1966a). On average, 

roughly 75% of fusion cell formation occurs shortly after cell 

elongation (with IW calcification) stops (Figure 8).

In the strongly attached crusts of P. rugulosum and P. laevigatum, the cell lumina expand in diameter with depth. Because in 

most cases such expansion must be accompanied by removal of 

carbonate cell wall, we are currently exploring whether the carbonate metabolites are transferred to the actively growing surface. However, it is conspicuous that the two species with thick 

hypothallia (P. borealis and P. investiens), and in the latter case a 

larger-scale leafy habit, develop significantly smaller cell lumina 

with depth. As this development must result from thickening of 

carbonate cell walls, perhaps with a stronger development of 

IF, this would enhance crust strength to allow the cantilevered 

growth achieved by these plants. Such changes in density, tied 

to the production of interfilament carbonate, have been demonstrated for Clathromorphum compactum (Chan et al., 2017), 

and it would be valuable to perform such studies in the species 

presented here.

In general, growth and calcification in cold-water corallines 

is dependent on temperature and light (Adey, 1970c; Adey and 

McKibbin, 1970; Williams et al., unpublished). However, each 

species, and to some extent each genus, has its own patterns of 

dependency. There are coralline species that grow, calcify, and 

reproduce with seawater temperatures never exceeding 3°C and 

with a half year of no sunlight. Other species, with the same 

basic wall structure, but a somewhat different carbonate chemistry, never see seawater temperatures below 20°C, and probably 

reach 40°C and succeed with exposure to full tropical sunlight, 

although likely always wetted by wave-breaking spray.

Magnesium Content

As we have shown, in the perithallium of the Phymatolithon species (Nash and Adey, 2017b), IF calcite has the lowest 

Mg (8.9%), whereas the cell walls have significantly higher Mg 

(13.4%); the carbonate of hypothallial cells has even higher Mg 

content (17.1%). The cell walls in the tissues that regrew from 

broken-out conceptacles as wound tissue also had high Mg content (18.6%), not significantly different from hypothallial cells. 

As wound tissue has cells that are morphologically similar in size 
5 0 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

and cell wall structure to hypothallial cells, and clearly result 

from growth that is more rapid than the surrounding perithallium, with equivalently higher Mg content, it is suggestive that 

Mg content in specific cells and tissues is related to growth rate. 

Nevertheless, within specific tissues Mg content is clearly dependent upon temperature (Nash and Adey, 2017a,b).

Finally, especially in hypothallial cells of tropical coralline 

crusts, very high magnesium content can occur, exceeding 40%; 

in this context we note that the level of a shift from high magnesium calcite to the crystal dolomite has been described (Nash 

et al., 2012). Although this may not generally be applicable to 

cold-water corallines, dolomite has been described in a Clathromorphum crust from Greenland (Nash and Adey, 2017b). These 

Mg variations are in agreement with the Mg offsets obtained 

for the cell wall, IF, and hypothallial cells in Leptophytum laeve

and Kvaleya epilaeve from Arctic Labrador (Nash and Adey, 

2017a). The elevated Mg in perithallial cell walls compared to 

IF (called interstitial) has also been noted for Lithothamnion 

glaciale (Ragazzola et al., 2016). Climate archiving, using Mg 

concentration (and other wall chemistry) as a proxy for seawater 

temperature (and other variables) at the time of wall formation 

has become an important tool in paleoclimatology (e.g., Halfar 

et al., 2013). Greater precision can likely be achieved in coralline 

climate archiving by considering these tissue and cellular variations in Mg content. Most Phymatolithon species have too little 

vertical growth to be climate archives, although yearly layers are 

often seen in P. borealis, and this species could have limited use 

in paleoclimatology.

CONCLUSIONS

As we describe in the Introduction, many nineteenth and 

twentieth century coralline identifications by a wide range of 

phycologists, based on classical coralline systematic studies, 

have often not been confirmed in the DNA sequence analyses 

of the past decade. Here, however, we have demonstrated a very 

high degree of conformity between sequence analyses and morphological and reproductive analyses when large geographically 

extensive collections and population-level analyses, supported 

by statistical treatments, are utilized.

In the classical literature, coralline crusts were presented 

as composed of two tissues, perithallium and hypothallium, 

with little recognition of the underlying carbonate wall structure. However, as we briefly review in the Introduction, recent 

literature has tended to describe corallines as a cushion of independent calcified filaments, lacking tissue level or carbonate wall 

differentiation. Here we have shown a high diversity in both tissue type and high magnesium carbonate wall structure. Similarly, 

in the past, conceptacles (the reproductive structures) have been 

treated as entities largely independent of vegetative construction. 

Here, analyses of conceptacle development in Phymatolithon

have demonstrated the linkage between genetic control and vegetative growth, parameters that interact to produce considerable 

variation in some characters of final gross morphology but not 

in others.

As demonstrated in an earlier publication on the unrelated 

Arctic and Subarctic genus Clathromorphum (Adey et al., 2013), 

we have also shown in species of Phymatolithon a dynamism in 

the development of vegetative anatomy, carbonate structure, and 

reproductive features, with a complex of tissues and interacting 

modes of formation. This depiction belies a simplistic model for 

this geographically and ecologically important subclass (Floridiophyceae) of red algae. With this study, augmenting earlier analyses that included the other dominant genera (Clathromorphum, 

Lithothamnion, Leptophytum), the colder waters of the North 

Atlantic (biogeographical regions Arctic, Subarctic, and Boreal) 

provide the only geographically extensive coralline flora to be 

fully analyzed for linkage between morphology, physiology, ecology, and biogeography supported by DNA sequence analyses. 

Similar analyses of Lithophyllum (Pseudolithophyllum) orbiculatum, an additional important species of the Boreal fringe, 

are presently being undertaken by two of the current authors 

(WHA, PWG).
NOTES FOR SPECIMEN DESIGNATIONS IN PLATES

Specimen designations may include the following data: type of specimen, sample 

number, DNA analysis sample number, herbarium abbreviation, official specimen number, and origin of specimen. See Adey and Lebednik (1967) for details on origin data. 

Examples defined as follows:

Foslie Isotype, no. 234 Sample extracted from Holotype, numbered and 

deposited in Foslie Collection of Coralline Collection, 

Herbarium US

DNA S186 DNA extracted from this sample and numbered for 

analysis

US 171025 Official specimen number, Herbarium US (U.S. 

National Herbarium)

61-14; 61-43 Specimen numbers in Coralline Collection, Herbarium US (see Table 1 for details).

Plates 1–8 are by W. H. Adey; plates 9–11 are by M. C. Nash. The SEM images 

showing sections in plates 1–8 are of vertical fractures made with a razor blade or fine 

wire cutters; sections were then mounted and coated with carbon. The procedures for 

plates 9–11 are described in “Materials and Methods.”

Plates
5 2 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

PLATE 1. (Opposite page) Phymatolithon laevigatum: scanning electron microscopy (SEM) 

images.

A. Hypothallium (mid image) and lower perithallium (above); plant tightly attached to granite (crystals below hypothallium). Interfilament “stripe” (arrows in transition zone in lower 

perithallium). Foslie Isotype, no. 234; DNA S186; US 171025; Helgoland, Germany.

B. Perithallium with wound tissue (right) in broken-out conceptacle. Much of the vertical 

fracture in this specimen occurs along the perithallium interfilament and presents as numerous vertical stripes. The wound tissue typically consists of large, thin-walled cells, superficially 

similar to hypothallium and possessing high Mg content, as does the hypothallium. 64-14; 

Pictou, Nova Scotia, Canada.

C. Surface view of epithallium. Roofs of most epithallial cells have sloughed; lateral walls 

remain, with scattered epithallial cell roof fragments (arrows). 61-43; DNA S179; US 171009; 

Woods Hole, Massachusetts, USA.

D. Vertical fracture with perithallial cell walls (mostly inner wall, IW) having many fusions. 

Arrows indicate fusions perpendicular to the plane of the fracture. Above the leftmost fusion, 

IW has reformed and is perpendicular to the fusion axis. Numbering and locality as in A.

E. Surface view of crust with several of the bowl-shaped bi-tetrasporangial conceptacles diagnostic for this species; each conceptacle has a strongly raised rim. Numbering and locality as 

in A.

F. Mature bi-tetrasporangial conceptacle in section, showing bowl shape of both cavity and 

roof, as well as the raised rim. Numbering and locality as in A.
NUMBER 41 • 5 3
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PLATE 2. (Opposite page) Phymatolithon rugulosum: SEM images.

A. Perithallium with vertical fractures both axially, along filaments, and along interfilament 

(IF) carbonate band, creating “stripes.” Holotype; 61-41A-3; DNA S163; US 171023; Maine, 

USA.

B. Surface view at conceptacle margin with pores from broken-out sporangial plugs (right 

arrow) and epithallial cells with partially intact calcified roofs and interfilament ring (left 

arrow). 61-35; DNA S170; US 171012; Maine, USA.

C. Immature conceptacle with lateral shelf being built by conceptacle wall tissue with the 

characteristic of “wound” tissue, typical of rapid growth areas in perithallium. The lower 

part of this tissue will later be crushed by sporangial lateral expansion (see E). Numbering 

and locale as in B.

D. Abundant mature, sunken bi-tetrasporangial conceptacles with the distinctive partly 

sunken lateral “shelves” characteristic of this species. Numbering and locale as in A.

E. Mature bi-tetrasporangial conceptacles with lateral crushing by sporangia removing lower 

shelf wound tissue as well as lateral and basal vegetative tissue. These crushed cells likely serve 

as nurse tissue. Numbering and locale as in A.

F. Surface view of conceptacle at higher magnification showing distinctive shelf and sporangial 

pores. Numbering and locale as in A.
NUMBER 41 • 5 5
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PLATE 3. (Opposite page) Phymatolithon nantuckensis: stained microtome sections.

A. Young crust with thin hypothallium (bottom arrow), perithallium (middle arrow), and 

epithallium (top arrow). In contrast to most Phymatolithon species, in which epithallial cells 

are present on less than 30% of filaments, 3⁄4 of the measured filaments in this species bore 

epithallial cells. 61-12; DNA S283; US 171021; Nantucket, Massachusetts, USA.

B. Multiple, thin, overgrowing crusts, partly filling broken-out conceptacles, creating the 

complex morphology characteristic of this species. Typical lightly raised tetrasporangial conceptacles. Numbering and locale as in A.

C. Mature bi-tetrasporangial conceptacle with tetrasporangia, an undivided sporangium, and 

sporangial plugs. Numbering and locale as in A.

D. Mature fertilized carpogonial conceptacle. Single carposporangium forming in the center 

of conceptacle and dendritic fusion cells (below). Numbering and locale as in A.

E. Mature carposporangial conceptacle with carposporangia (horizontal arrow) and single 

gonimoblast cells (vertical arrow). Numbering and locale as in A.

F. Base of carposporangial conceptacle showing developing carposporangium (horizontal 

arrow), single gonimoblast cell (right vertical arrow), and fusion cell (left vertical arrow). 

Numbering and locale as in A.
NUMBER 41 • 5 7
5 8 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

PLATE 4. (Opposite page) Phymatolithon squamulosum: SEM images.

A. Perithallium and hypothallium in crust growing over fragment of barnacle shell. 67-2, 

0-10F, DNA S212. US170995. Trondheimsfjord, Norway.

B. Two P. squamulosum crusts meeting. Left: crust developing fast-growing perithallium with 

large thin-walled cells characteristic of wound tissue, likely precedent to overgrowing crust on 

right (see Figure 3). 66-14; DNA S227; US171020; Kolgrafafjord, Iceland.

C. Crust overgrowing itself and developing a bi-tetrasporangial conceptacle. Note fastgrowing (thin-walled) cells that form conceptacle sides; these fast-growing perithallial tissues 

resemble hypothallial cells, with their thin walls and high magnesium (Mg) levels, but unlike 

most hypothallium consist mostly of IW wall (see text and F). Numbering and locale as in B.

D. Typical dense aggregation of raised bi-tetrasporangial conceptacles with detritus collecting 

between the conceptacles (see E). Numbering and locale as in B.

E. Typical raised flat-topped bi-tetrasporangial conceptacle without a raised rim. Striations 

are caused by mollusk grazers. Numbering and locale as in A.

F. Mature bi-tetrasporangial conceptacle showing fast-growing, thin-walled cells that form 

the sides; crushing by developing sporangia initiated. Numbering and locale as in B.
NUMBER 41 • 5 9
6 0 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

PLATE 5. (Opposite page) Phymatolithon borealis: stained microtome images.

A. Moderately thick crust, likely several years old (note banding), with single basal hypothallium and without overgrowing hypothallium. 66-43, 0-10C; DNA S223; US 170999; Trondheimsfjord, Norway.

B. Thick crust with several years of buried bi-tetrasporangial conceptacles typical of the species. 66-26-4; DNA S136; US 170980; Grindavik, S. Iceland.

C. Young crust with mature tetrasporic conceptacle. Conceptacle fully sunken with a raised 

rim. Numbering and locale as in A.

D. Mature male conceptacle. Walls clothed with dense dendroid branches bearing spermatangial mother cells. 66-42-1; DNA S224; US 171000; Trondheimsfjord, Norway.

E. Fully sunken, mature carpogonial conceptacle with numerous trichogynes. Roof formed 

from lateral in-growing. 67-1; Trondheimsfjord, Norway.

F. Sunken carposporangial conceptacle with one-celled gonimoblasts (small arrows) and carposporangia (large arrows). Left pair rotated by sectioning. 67-1; Trondheimsfjord, Norway.
NUMBER 41 • 6 1
6 2 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

PLATE 6. (Opposite page) Phymatolithon borealis: SEM images.

A. Two-year-old crust growing over older crust (below). Center conceptacle buried; a year 

older with overlying wound repair. 66-17-13; 90-120A; DNA S139; US 171018; Kollafjord, 

W. Iceland.

B. Perithallium with overlying halite crystals (caused by specimen drying from seawater). 

Meristem (upper right arrow), interfilament, as stripe (mid-right arrow). Fusions (left and 

bottom right arrows). 66-26-40-10; DNA S136; US 170980; Grindavik, S. Iceland.

C. Surface extension of upper cell walls (IW) and interfilament (IF) around meristem cells (top 

arrow). Epithallial cell with partial calcite upper wall roof (lower arrow). Numbering and 

locale as in B.

D. Perithallial cells with 1–2 μm thick calcitic walls (IW) and very thin layer of interfilament 

(IF) calcite granules between the cells. Abundant fusions. Numbering and locale as in A.

E. Crust with small bi-tetrasporangial conceptacles bearing a slightly raised rim (not an inner 

shelf); also not bowl shaped (see A). Numbering and locale as in A.

F. Thick crust with layers of buried conceptacle cavities. Conceptacle grown out with wound 

tissue (mid right). 66-27 0-10K; DNA S116; US 171979; Heimey, Westmanneyjar, S. Iceland.
NUMBER 41 • 6 3
6 4 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

PLATE 7. (Opposite page) Phymatolithon investiens: stained microtome sections.

A. Developing bi-tetrasporangial conceptacle formed deep in perithallium, with overlying 

plug being shed. Sporangial mother cells bearing thick cap walls. 66-42-5B; Trondheimsfjord, 

Norway.

B. Young bi-tetrasporangial conceptacle with sporangial mother cells having fully developed 

cap walls (pore plugs). Numbering and locale as in A.

C. Young female conceptacle with overlying plug of perithallial tissue being shed; roof being 

formed from overgrowing perithallium (roof tissue). 68-29-1; Leirviken, Ranfjorden, northwestern Norway.

D. As in C. Numbering and locale as in C.

E. Young female conceptacle with carpogonial filaments maturing and initiating trichogynes. 

Roof overgrowing. 68-34-11; Tromsøy, off Biological Station, northern Norway.

F. Raised female conceptacles with mature and partially fertilized carpogonia. Roof overgrowth nearly complete. Numbering and locale as in E.
NUMBER 41 • 6 5
6 6 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

PLATE 8. (Opposite page) Phymatolithon investiens: SEM images.

A. Crust of thick hypothallium and perithallium. Arrows show fractures along interfilament 

as frequent vertical stripes. The large-lumen, thin-walled hypothallial cells are indicative of 

minimum IW wall with high magnesium content (see text). 68-30-3; Lofoten Islands, northern 

Norway.

B. Surface of mostly meristem cells with projecting interfilament margins. Arrows indicate 

scattered epithallial cells with partially calcified roofs partially broken out. Numbering and 

locale as in A.

C. Vertical fracture in upper perithallium. Upper arrow, meristem cell. Middle arrow, interfilament in section. Lower arrow, fracture along interfilament surface. Numbering and locale as 

in A.

D. Sunken pore plate of mature bi-tetrasporangial conceptacle. Arrow indicates raised rim. 

69-2-6; DNA S222; US 171006; Tromsøy, northern Norway.

E. Double crust formed by upper overgrowing older crust, with mature carposporangial conceptacle (left) and unfertilized, degenerating female conceptacle with wound repair tissue filling cavity below (arrows). Numbering and locale as in D.

F. Raised mature carposporangial conceptacle. Some of the underside of the roof, as well as 

laterally and below conceptacle cavity, shows crushing of vegetative cells (nurse tissue) to 

form space for developing carposporangia (blot over left side of roof is mounting cement). 

Numbering and locale as in D.
NUMBER 41 • 6 7
6 8 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

PLATE 9. (Opposite page) Phymatolithon spp.: magnesium calcite cell walls.

A, B. P. borealis.

C. P. laevigatum.

D. P. investiens. (See white box in E; black box in Plate 10E.) In all three species above, radial 

magnesium calcite grains of the inner cell walls (IW) provide most of the carbonate structure, 

as well as tops and bottoms of the cell walls which are filled to the corners. Interfilament (IF) 

is 1–2 grains thick.

E. P. investiens. Radial grains are composed of multiple short shorter grains (black arrows) 

with radial alignment.

F. P. rugulosum. Inner cell walls are radial as in other species, but interfilament is thicker (to 

1 μm; see Plate 11.)
NUMBER 41 • 6 9
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PLATE 10. (Opposite page) Phymatolithon spp.: magnesium calcite wall details, inner wall 

(CW), and interfilament (IF).

A. P. borealis with interfilament grains (IF) approximately 200–400 nm in length coating the 

external wall of the adjacent cell. Grains are aligned vertically (against cell wall, CW) and 

roughly parallel to filament axis.

B. P. investiens with interfilament (IF) grains aligned similarly to those in P. borealis.

C, D. P. laevigatum sample has fractured along the interfilament planes, exposing intact cell 

walls coated in interfilament grains. Interfilament grains are comparable to those in both P. 

borealis and P. investiens. Cell fusions (CF).

E. Plan view: P. rugulosum differs with a wider thickness of interfilament; grains do not 

exhibit any particular orientation.

F. P. rugulosum interfilament has secondary mineralization to blocky magnesium calcite 

(white arrows); original grains are elongate (black arrows).
NUMBER 41 • 7 1
7 2 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

PLATE 11. (Opposite page) Phymatolithon rugulosum: magnesium calcite walls.

A. Surface of P. rugulosum. Epithallus is not present, exposing the meristem cells in plan view 

cross section.

B. Perithallial cells below broken-out meristem in plan view. Cell walls with radial magnesium 

calcite (black arrows); gaps in interfilament (white arrow).

C. Interfilament grains aligned to plane of nearest cell wall (black arrows).

D. Meristem cells in surface view without epithallium; interfilament grains reach to surface. 

Gaps in interfilament at cell corner junctions. White box magnified in E.

E. Interfilament bends through corners, and clearly there must have been organic material 

constraining growth to this shape.

F. Interfilament of E at greater magnification (black arrows).
NUMBER 41 • 7 3

Appendix: Supplementary Materials
7 6 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

FIGURE A1. Phymatolithon (P.) tree of all utilized samples: combined rbcL and psbA data sets with identical sequences by using 

unpaired group method with arithmetic mean (UPGMA) with uncorrected p-distances (proportion [p] of nucleotide sites at which two 

sequences being compared are different) and 1,000 resamplings for statistical support (see text). Tree was split to fit on the page; upper 

portion is on left and bottom extension is to the right. Basic locality information is included. Expanded subsets allowing locality and 

station identification are given in Appendix Figures A2a, A2b, and A2c. See Table 1 in main text for station latitude and longitude as 

well as site ecological data. Figure by J. Hernandez-Kantun.
NUMBER 41 • 7 7

FIGURE A2a. Station locality information for Phymatolithon laevigatum keyed to tree of Figure A1. 

Figure by J. Hernandez-Kantun.
7 8 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

FIGURE A2b. Station locality information for Phymatolithon rugulosum, P. squamulosum, 

and P. nantuckensis keyed to tree of Figure A1. Figure by J. Hernandez-Kantun.
NUMBER 41 • 7 9

FIGURE A2c. Station locality information for Phymatolithon borealis and P. investiens keyed to tree of 

Figure A1. Figure by J. Hernandez-Kantun.
8 0 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

TABLE A1. Information on DNA specimens with station locality data and museum/herbarium acquisition code numbers. Abbreviations: PCR, polymerase chain reaction; USNH, United States National Herbarium (US). Collection data presented are as follows: collection locality; collection date; site information if known; authority. A dash (–) indicates data are not available/not known. Samples in 

bold are type specimens. See Table 1 in main text for station latitude and longitude information as well as site ecological data.

Name of sample PCR code

Herbarium code; 

collection code Collection data

USNH Algal 

Collection number

Phymatolithon 

borealis sp. nov.

S116 US 170979; 

66-27, 0-10 K

Westmanneyjar, Iceland; 17 Aug 1966; leg. W. 

H. Adey

170979

Phymatolithon borealis S136 US 170980; 

66-26-4, 0-10

West Grindavik, southwest Iceland; 11 Aug 

1966; leg. W. H. Adey

170980

S139 US 171017; 

66-17-13, 90-120 A

Hunafloi, northwest Iceland; 28 Jun 1966; leg.

W. H. Adey

171017

S218 US 170981; 

66-26, 30-50 F

West Grindavik, southwest Iceland; 11 Aug 

1966; leg. W. H. Adey

170981

S223 US 170999; 

66-43-1, 0-10 C

Digertmulen, Trondheimsfjord, Norway; 27 Dec 

1966; leg. W. H. Adey

170999

S224 US 171000; 

66-42-1, 0-10 F

Digertmulen, Trondheimsfjord, Norway; 23 Nov 

1966; leg. W. H. Adey

171000

S277 US 171001; 

66-36-3, 0–3 m

Landegodefjord, north Norway; 17 Sep 1966; 

leg. W. H. Adey

171001

L55 BM000657777; Sample 

83/497; Box 1933

Wembury, south Hams District, England; 5 Dec 

1983; on rock; leg. Y. M. Chamberlain

–

L60 BM000657702; Sample 

83/180; Box 1896

Fanore, County Clare, Ireland; 1 Mar 1983; on 

rock, low intertidal; leg. Y. M. Chamberlain

–

L63 BM000712102; Sample 

LI760825/1; Box 2545

Fanore, south of Black Head, Ireland; 25 Aug 

1976; on pebbles used to cover Paracentrotus; 

leg. L. M. Irvine

–

L64 BM000657730; Sample 

83/307; Box 1910

Fanore, County Clare, Ireland; 12 Jul 1983; leg.

P. J. Cooke

–

L65 BM000530600; Box 1110 Bellacragher Bay, Connacht, Ireland; May 1911; 

leg. A. D. Cotton

–

L74 BM000657996; Sample 

88/121; Box 2058

South Devon, Wembury, England; 24 Nov 1988; 

mid- and low-tide rocks; leg. Y. M. Chamberlain

–

L78 BM000712357; Box 2637 South Haven, Pembrokeshire, Wales; Aug 1983; 

pool in cave; leg. S. Hescock

–

L80 BM000712417; Box 2660 Kimmeridge, Dorset; England; 25 May 1982; 

lagoons and reef

–

L82 BM000712507; Box 2688 Wembury, south Hams District, England; 28 

Mar 1987; mud and silt cover after storm; leg.

unknown

–

L83 BM000711754; Sample 

LI100207/1; Box 2879

Plockton, Scotland; 7 Feb 1970; leg. L. Irvine –

L86 BM001032134; Box 3861 East Cornwall, Hannafore Point, Looe, England; 

50°20′42′′N, 4°27′6′′W; 2 Feb 2010; leg. J. 

Wilbraham

–

E22.6IX12all – – –

Phymatolithon 

calcareum

E246 – – –
NUMBER 41 • 8 1

Name of sample PCR code

Herbarium code; 

collection code Collection data

USNH Algal 

Collection number

Phymatolithon investiens (type)

S273 US 171024; F.T. 233 As Lithothamnion investiens, Lyngo, north 

Tromso, Norway; 15 Jun 1892; isotype from the 

Foslie Collection

171024

Phymatolithon 

investiens

L70 BM000530363; Box 904 As Phymatolithon polymorphum f. intermedia; 

locality and leg. unknown

–

S114 US 170997; 

69-9, 10-30 C

Hjelmsoy, Akkarfjord, north Norway; 25 Jun 

1969; leg. W. H. Adey

170997

S135 US 171002; 

69-10, 35–45 m

Gjesvaer, north Norway; 25 Jun 1969; leg. W. 

H. Adey

171002

S137 US 171004; 

69-10

Gjesvaer, north Norway; 25 Jun 1969; intertidal; 

leg. W. H. Adey

171004

S138 US 171003; 

66-28-3, intertidal

Northwest corner of Kvaloy, north Norway; 29 

Aug 1966; leg. W. H. Adey

171003

S221 US 171006; 

69-8 (2), 40–45 m

Rolfroysund, north Norway; 24 Jun 1969; leg.

W. H. Adey

171006

S222 US 171005; 

69-2-6, 70-90

Off Biological Station, Tromso, north Norway; 

14 Apr 1969; leg. W. H. Adey

171005

S279 US 171026; 

69-8 (2), 40–45 m

Revabotn, Rolfroysund, north Norway; 24 Jun 

1969; leg. W. H. Adey

171026

S280 US 171007; 

69-8 (2), 40–45 m

Revabotn, Rolfroysund, north Norway; 24 Jun 

1969; 40–45 m; leg. W. H. Adey

171007

Phymatolithon laevigatum (type)

S186 US 171025; 

F.T. 234

Helgoland, Germany; isotype from Foslie 

Collection

171025

Phymatolithon 

laevigatum

S155 US168008; 

64-1, 0-10 D

Harding Point, Port Hebert, Nova Scotia, 

Canada, 6 Jun, 1964; leg. W. H. Adey

168008

S157 US 170984; 

66-39, 0-10 C

Beitstadfjord, Trondheimsfjord, south Norway; 

13 Oct 1966; leg. W. H. Adey

170984

S158 US 168113; 

64-5, 0-30 D

Bras D’Or Lakes, Nova Scotia, Canada; 11 Jul 

1964; leg. W. H. Adey

168113

S159 US 168045; 

64-2, 0-10 B

Southeast side of Shannon Island, Nova Scotia, 

Canada; 8 Jun 1964; leg. W. H. Adey

168045

S160 US 168447; 

64-12, 30-50 C

Beaton Point, Mabou, Cape Breton, Nova Scotia, Canada; 25 Jun 1964; leg. W. H. Adey168447

S161 US 170985; 

67-11, 10-30 C

Hardangerfjord, south Norway; 31 Jul 1967; 

leg. W. H. Adey

170985

S174 US 171008; 

62-19-7, 1–2 m

Eagle Island, Penobscot Bay, Maine, USA; 28 

Apr 1962; leg. W. H. Adey

171008

S175 US 170986; 

64-26-1C, 0–3 m

Humber Arm, west coast of Newfoundland, 

Canada; 21 Jul 1964; leg. W. H. Adey

170986

S176 US 170987; 

64-5, 0–6 m

Bras D’Or Lakes, Nova Scotia, Canada; 11 Jul 

1964; leg. W. H. Adey

170987

S177 US 168001; 

64-1-1, intertidal

Port Hebert, Nova Scotia, Canada; 6 Jun 1964; 

leg. W. H. Adey

168001

S179 US 171009; 

61-43-1, 0–6 m

Woods Hole, south of Cape Cod, Massachusetts, 

USA; 17 Nov 1961; leg. W. H. Adey

171009

TABLE A1. (Continued)
8 2 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

Name of sample PCR code

Herbarium code; 

collection code Collection data

USNH Algal 

Collection number

Phymatolithon laevigatum (continued)S213 US 171010; 

61-10-1, 20-25

Martha’s Vineyard, Vineyard Sound, south of 

Cape Cod, Massachusetts, USA; 27 Jul 1961; 

leg. W. H. Adey

171010

S214 US 170988; 

66-42, 0-10A

Digertmulen, Trondheimsfjord, Norway; 23 Nov 

1966; leg. W. H. Adey

170988

S215 US 170989; 

67-2, 0-10 R

Prestvaagen, Vaerra Botnen, Trondheimsfjord, 

Norway; 3 Feb 1967; leg. W. H. Adey

170989

S216 US 170990; 

67-9-1, intertidal

Tobehl, Indre Solen, Lagoyfjord, south Norway; 

26 Jul 1967; leg. W. H. Adey

170990

L44 BM000569182; Sample 

1401; Box 1660b

Helligsø, north Denmark; 13 Aug 1985; sublittoral 1–2 m; scattered stones on sandy seashore; 

leg. Ian Tittley

–

L46 BM000569181; Sample 

1401; Box 1660a

Helligsø, north Denmark; 13 Aug 1985; sublittoral 1–2 m; scattered stones on sandy seashore; 

leg. Ian Tittley

–

L47 BM000569300; Sample 

1400; Box 1659

Jylland, Oddesund, north Denmark; 13 Aug 

1985; inner sheltered areas, scattered stones 

on sandy seafloor; sublittoral 1–2 m; leg. Ian 

Tittley

–

L48 BM000569299; Sample 

1400; Box 1659

Jylland, Oddesund, north Denmark; 13 Aug 

1985; inner sheltered areas, scattered stones 

on sandy seafloor; sublittoral 1–2 m; leg. Ian 

Tittley

–

L58 BM000659096; Box 729 Foslie Herbario, Helgoland, Germany; 29 Jan 

1894; leg. Dr. Kuckuck

–

E242 – – –

E270 – – –

36 – – –

Phymatolithon nantuckensis sp. nov.

S168 US 171011; 

61-12-1, 5 m

Nantucket Harbor, Massachusetts, USA; 1 Aug 

1961; leg. W. H. Adey

171011

Phymatolithon 

nantuckensis

S283 US 171021; 

61-12, 5 m

Nantucket Harbor, Massachusetts, USA; 1 Aug 

1961; leg. W. H. Adey

171021

S284 US 171022; 

61-12, 5 m

Nantucket Harbor, Massachusetts, USA; 1 Aug 

1961; leg. W. H. Adey

171022

Phymatolithon rugulosum (type)

S163 US 171023; 

61-41, A-3

Merchant Island, Maine, USA; 2 Nov. 1961; leg.

W. H. Adey

171023

Phymatolithon 

rugulosum

S154 US 170991; 

66-26, 50-70 H

Stadhur, Grindavík, southwest Iceland; 11 Aug 

1966; leg. W. H. Adey

170991

S156 US 168021; 

64-1, 10-30 B

Port Hebert, Nova Scotia, Canada; 6 Jun 1964; 

leg. W. H. Adey

168021

S170 US 171012; 

61-35-5A, 5 m

Merchant Island, Maine, USA; 30 Sep 1961; leg.

W. H. Adey

171012

S207 US 170992; 

66-12, 30-50 G

Hofsvik, Kollafjord, north Iceland; 10 Jun 1966; 

leg. W. H. Adey

170992

S208 US 170993; 

66-27, 30-50 C

Heimaey, Westmanneyjar, south Iceland; 17 Aug 

1966; leg. W. H. Adey

170993

TABLE A1. (Continued)
NUMBER 41 • 8 3

Name of sample PCR code

Herbarium code; 

collection code Collection data

USNH Algal 

Collection number

Phymatolithon rugulosum (continued)S229 US 170994; 

69-14, 50-70 V

Veidnesodden, Syltefjord, north Norway; 2 Jul 

1969; leg. W. H. Adey

170994

L57 BM000659095;

Sample 21, p. 139; 

Box 430

Foslie Herbarium, Helgoland, Germany; 1893; 

leg. Dr. Kuckuck

–

L62 BM000657696; Sample 

83/170; Box 1892

Carrickadda, County Clare, Ireland; 28 Feb 

1983; leg. Y. M. Chamberlain

–

L76 BM000711982; Box 2496 Shetland Islands, Marki Ness, Sullom Voe, Scotland; Aug 1973; depth 4.5 m, overgrowing on a 

mussel shell; leg. D. Irvine and divers

–

Phymatolithon squamulosum (type)

L68 BM000044670; Box 434 As Lithothamnion squamulosum isotype; Stensund [now Steinsund], Sulen [now Sula], indre 

[= inner], Sogn, Norway (Woelkerling et al., 

2005:267). Jul 1894; ‘nederst lit. reg, beskyttet 

[= lowest littoral region, protected].’ (Woelkerling et al., 2005: 265); leg. Boye

–

Phymatolithon 

squamulosum

S106 US 171013; 

67-10, intertidal

Kvindherredsfjord, Hardangerfjord, south Norway; 30 Jul 1967; leg. W. H. Adey171013

S107 US 170995; 

67-2, 0-10 F

Prestvaagen, Trondheimsfjord, south Norway; 3 

Feb 1967; leg. W. H. Adey

170995

S164 US 171014; 

62-78, intertidal

North of Rockland Breakwater, west Penobscot 

Bay, Gulf of Maine, USA; 24 Aug 1962; leg.

W. H. Adey

171014

S165 US 171015; 

62-60-1, intertidal

Eggemoggin Reach, Maine, USA; 31 Jul 1962; 

leg. W. H. Adey

171015

S166 US 171016; 

62-1, intertidal

Dunham Point, Deer Isle, Maine, USA; 3 Jan 

1962; leg. W. H. Adey

171016

S167 US 170996; 

64-24-1, intertidal

Guernsay Island, Bay of Islands, Newfoundland, 

Canada; 15 Jul 1964; leg. W. H. Adey

170996

S169 US 168002; 

64-1-2, intertidal

Port Hebert, Nova Scotia, Canada; 6 Jun 1964; 

leg. W. H. Adey

168002

S209 US 170964; 

66-12-1, 0-10A

Hofsvik, Kollafjord, north Iceland; 10 Jun 1966; 

leg. W. H. Adey

170964

S210 US 171018; 

66-26, intertidal

Stadhur, Grindavik, south Iceland; 11 Aug 1966; 

leg. W. H. Adey

171018

S211 US 171019; 

66-27, intertidal

Heimey, Westmanneyjar, south Iceland; 17 Aug 

1966; leg. W. H. Adey

171019

S227 US 171020; 

66-14, intertidal

Kolgrafafjord, Iceland; 19 Jun 1966; leg. W. H. 

Adey

171020

S228 US 170998; 

66-39, intertidal

Inderoen, Beitstadfjord, Trondheimsfjord, Norway; 13 Oct 1966; leg. W. H. Adey170998

L11 BM000044805; Box 565 As Lithothamnion sonderi, Helgoland, Germany; 1893; leg. Hauck–

L50 BM000044392; Specimen 

87/22; Box 1779

As Phymatolithon brunneum holotype, 

Lulworth, Dorset, England; 17 Feb 1987; on 

rocks together with Phymatolithon lenormandii

and occurring immediately above the P. purpureum zone; leg. Y. M. Chamberlain

–

TABLE A1. (Continued)
8 4 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

Name of sample PCR code

Herbarium code; 

collection code Collection data

USNH Algal 

Collection number

Phymatolithon squamulosum (continued)L51 BM000044392; Specimen 

87/22; Box 1779

As Phymatolithon lenormandii, Lulworth, 

Dorset, England; 17 Feb 1987; on rocks and 

occurring immediately above the P. purpureum

zone; leg. Y. M. Chamberlain

–

L56 BM000657936; Specimen 

86/60; Box 2010

Trévignon, Trégunc, France; 24 Apr 1986; 

common from tide line downward; leg. Y. M. 

Chamberlain

–

L61 BM000657694; Sample 

83/186; Box 1890

Carrickadda, County Clare, Ireland; 28 Feb 

1983; sandy channel near laboratory; leg. Y. 

Chamberlain

–

L72 BM000657787; Sample 

84/39; Box 1940

West Angle, Pembrokeshire, England; 18 Feb 

1984; on exposed rock at extreme low water 

spring tides; leg. Y. M. Chamberlain

–

L81 BM000712504; Box 2687 Peacehaven, East Sussex, England; 26 Jan 2003; 

chalk platform; leg. K. Sheppard

–

L84 BM001032132; Box 3849 Applecross, Scotland; 57°26′02′′N, 05°48′50′′W; 

16 Oct 2009; leg. J. Brodie and J. Wilbraham

–

L85 BM001032117; Box 3851 Badnaban, northwest Scotland; 58°08′13′′N, 

05°16′16′′W; 18 Oct 2009; leg. J. Brodie and J. 

Wilbraham

–

TABLE A1. (Continued)
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Index

Letters following page references: t refers to tables, f refers to figures, p refers to plates.

Ascophyllum, 40, 42

bi-tetrasporangial conceptacle, 3, 18, 27–32, 

44–47; in P. borealis, 42, 60, 62; in 

P. investiens, 43, 64, 66; in P. laevigatum,

40–41, 52; in P. nantuckensis, 41, 56; 

in P. rugulosum, 41, 54; in 

P. squamulosum, 41–42, 58

Boreal–Subarctic transition zone, 2, 4t, 18, 

19f, 26, 29t, 31, 32t, 33t, 40–48

calcification, 18, 23, 27, 44, 45, 49

carbonate wall: dissolved, 32, 45, 46; 

structure of, 3, 18, 50

carpogonium, 18, 31, 32, 34f, 45, 47; in 

P. borealis, 60, 66; in P. investiens, 64; in 

P. nantuckensis, 56

carposporangium, 18, 30–32, 34f, 45, 47, 56

Clathromorphum, 1–2, 26, 44, 45, 47–50

Clathromorphum circumscriptum, 42, 47, 48

Clathromorphum compactum, 45, 47, 49

conceptacle, 33t. See also bi-tetrasporangial 

conceptacle; asexual, 29t; development 

of, 50; gametangial, 27, 31–32, 44–47

Corallinophycideae, 49

DNA, 2, 3, 18, 80–84t

epithallium, 18, 44, 45, 49; in P. borealis,

42, 62; in P. investiens, 43, 66; in 

P. laevigatum, 52; in P. nantuckensis,

41, 56; in P. rugulosum, 41, 54; in 

P. squamulosum, 42

hypothallium, 18, 23, 26, 27, 49–50; in 

P. borealis, 42, 60; in P. investiens,

43, 66; in P. laevigatum, 40, 52; in 

P. nantuckensis, 41, 56; in P. rugulosum,

41; in P. squamulosum, 42, 58; thickness 

of, 20f, 21, 22f–24f, 26f, 29, 30f, 40, 

43–44

Kvaleya, 26, 49

Kvaleya epilaeve, 50

Leptophytum, 26, 48, 50

Leptophytum laeve, 30, 47, 50

Lithophylloideae, 49

Lithophyllum, 48

Lithophyllum hibernicum, 43

Lithophyllum orbiculatum, 2

Lithophyllum zonatum, 43

Lithothamnion, 1–3, 26, 45, 48–50

Lithothamnion glaciale, 50

Lithothamnion investiens, 43

Lithothamnion polymorphum, 34f

Lithothamnion sonderi, 2, 45

Lithothamnion squamulosum, 42

Lithothamnion tophiforme, 45

magnesium, 3; level of, 18, 26, 27, 45, 49–50

magnesium calcite, 3, 68, 69p, 70, 71p, 72, 

73p; level of, 26, 45, 50

Mastophoroideae, 49

Melobesia lenormandii, 42

nurse tissue, 27, 45, 54, 66

perithallium, 18, 25, 26, 44–47, 49, 50; 

and cell size, 21, 22f, 23, 40; in P. 

borealis, 42, 62; in P. investiens, 43, 64, 

66; in P. laevigatum, 40–41, 52; in 

P. nantuckensis, 41, 56; in P. rugulosum,

41, 54, 72; in P. squamulosum, 42, 58

Phymatolithon, 3; distribution of, 4–17t, 

18; magnesium calcite cell wall of, 68, 

69p, 70, 71p; phylogram of, 19f, 76f; 

taxonomy of, 1–2
9 0 • SMITHSONIAN CONTRIBUTIONS TO THE MARINE SCIENCES

Phymatolithon borealis, 3, 

18, 42; asexual conceptacle 

of, 29t; bi-tetrasporangial 

conceptacle of, 29–30, 30f, 

46, 47; and calcification, 

49; carpogonium of, 34f; 

and cell fusion, 27f; cell 

size of, 23f–26f; as climate 

archivist, 50; conceptacle 

of, 31, 32t, 33t; confused 

with P. investiens, 43; 

distribution of, 38f, 40, 48; 

DNA information on, 80t; 

hypothallium of, 20f, 21, 

43; perithallium of, 21, 22f, 

25, 44; and reproduction, 

28, 32; SEM images of, 62, 

63p; stained microtome 

images of, 60, 61p; staining 

bodies of, 28f, 45; station 

locality information for, 79f

Phymatolithon calcareum,

18, 80t

Phymatolithon investiens, 3, 18, 

42–43; asexual conceptacle 

of, 29t; bi-tetrasporangial 

conceptacle of, 29, 30, 46, 

47; and calcification, 49; 

carpogonium of, 34f; and 

cell fusion, 27f; cell size of, 

23f–26f; conceptacle of, 

31, 32, 32t; confused with 

P. borealis, 42; distribution 

of, 33, 39f, 40, 43–44, 

48; DNA information on, 

81t; hypothallium of, 18, 

20f, 21, 43; perithallium 

of, 21, 22f, 25, 44; and 

reproduction, 28, 32; SEM 

images of, 66, 67p; stained 

microtome sections of, 64, 

65p; staining bodies of, 

28f, 45; station locality 

information for, 79f

Phymatolithon laevigatum,

2, 3, 18, 40–41; asexual 

conceptacle of, 29t; 

bi-tetrasporangial 

conceptacle of, 29–30, 30f, 

46, 47; and calcification, 

49; and cell fusion, 27f; 

cell size of, 24f–26f; 

conceptacle of, 31f, 32t, 

33t; confused with 

P. rugulosum, 41; 

distribution of, 36f, 40, 

48; DNA information 

on, 81–82t; hypothallium 

of, 18, 20f, 21, 44; 

perithallium of, 21, 22f, 

23, 25, 44; SEM images of, 

52, 53p; staining bodies 

of, 28f, 45; station locality 

information for, 77f; 

thallus, 18

Phymatolithon lamii, 18, 41

Phymatolithon lenormandii, 18, 

32, 42, 43

Phymatolithon lusitanicum, 18, 

41, 82t

Phymatolithon nantuckensis, 3, 

18, 41; bi-tetrasporangial 

conceptacle of, 30f, 

46–47; carpogonium of, 

34f; cell size of, 24f–26f; 

conceptacle of, 31, 32, 32t, 

33t; distribution of, 33, 

39f, 48; DNA information 

on, 82t; hypothallium 

of, 18, 20f, 21, 44; 

perithallium of, 21, 22f, 44; 

and reproduction, 28, 32; 

stained microtome sections 

of, 56, 57p; station locality 

information for, 78f; thallus 

of, 18

Phymatolithon polymorphum,

28, 32

Phymatolithon purpureum,

34f, 42

Phymatolithon rugulosum, 2, 3, 

18, 41; asexual conceptacle 

of, 29t; bi-tetrasporangial 

conceptacle of, 29, 

30, 30f, 46, 47; and 

calcification, 49; and cell 

fusion, 27f; cell size of, 

24f–26f; conceptacle 

of, 31, 32t; confused 

with P. laevigatum, 40; 

distribution of, 33, 35f, 40, 

48; DNA information on, 

82–83t; hypothallium of, 

18, 20f, 21, 44; magnesium 

calcite wall of, 72, 73p; 

perithallium of, 21, 22f, 44; 

and reproduction, 32; SEM 

images of, 54, 55p; station 

locality information for, 

78f; thallus of, 18

Phymatolithon squamulosum,

3, 18, 41–42; asexual 

conceptacle of, 29t; 

bi-tetrasporangial 

conceptacle of, 30f, 

46–47; and cell fusion, 

27f; cell size of, 24f–26f; 

conceptacle of, 32, 32t, 33t; 

distribution of, 33, 37f, 

40, 48; DNA information 

on, 83–84t; hypothallium 

of, 18, 20f, 43, 44; 

perithallium of, 21, 22f, 

23, 44; and reproduction, 

28, 32; SEM images of, 

58, 59p; station locality 

information for, 78f; thallus 

of, 18

reproduction, 28–30, 32

Sporolitihon tenue, 3

staining bodies, 28, 45

thallus, 18

tissue variation, 26–27

wall mineralogy, 26–27

wall structure, 49, 50

wound tissue, 26–27, 45, 

49–50; P. borealis,

62; P. investiens, 31, 

66; P. laevigatum,

52; P. rugulosum, 54; 

P. squamulosum, 58
SUMMARY OF REQUIREMENTS FOR SMITHSONIAN CONTRIBUTIONS SERIES

For comprehensive guidelines and specifications, visit https://scholarlypress.si.edu.

ABSTRACTS must not exceed 300 words.

TEXT must be prepared in a recent version of Microsoft Word; use a Times font in 12 point for regular text; 

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should be requested only if required.

TAXONOMIC KEYS in natural history manuscripts should use the aligned-couplet form for zoology. If cross 

referencing is required between key and text, do not include page references within the key, but number the 

keyed-out taxa, using the same numbers with their corresponding heads in the text.

SYNONYMY IN ZOOLOGY must use the short form (taxon, author, year:page), with full reference at the 

end of the manuscript under “References.”

REFERENCES should be in alphabetical order, and in chronological order for same-author entries. Each reference should be 

cited at least once in main text. Complete bibliographic information must be included in all citations. Examples of the most 

common types of citations can be found at SISP’s website under Resources/Guidelines.