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UNITED STATES DEPARTMENT OF THE

GEOLOGY AND BIOLOGY 

NORTH ATLANTIC DEEP-SEA

PART 3. DIATOMACEAE

INTERIOR

OF

CORES

GEOLOGICAL SURVEY PROFESSIONAL PAPER 196-B

UNITED STATES DEPARTMENT OF THE INTERIOR 

Harold L. Ickes, Secretary

GEOLOGICAL SURVEY 

W. C. Mendenhall, Director

Professional Paper 196-B

GEOLOGY AND BIOLOGY OF

NORTH ATLANTIC DEEP-SEA CORES

BETWEEN NEWFOUNDLAND AND IRELAND

PART 3. DIATOMACEAE

BY

K. E. LOHMAN

UNITED STATES

GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1941

For sale by the Superintendent of Documents, Washington, D. C. ....... Price 45 cents

CONTENTS

Outline of the complete report-.-.-______________________________________________________________________________ v

Summary of the complete report._----____---____-_-_-_-_-____-_-_-_-_-_-----____-___-______-_--____----__-._--_. vn

Foreword, by C. S. Piggot_____-_----___-__-_-_--______-____________-_____-_-_--___-_-_-_-_-.-_-__---------__-__ xi

General introduction, by W. H. Bradley.__-_-____-______-_____________-_--_--__---_--_______________-------__--__ xm

Significance of the investigation._____-________„---________________-_--_--_-___-_-_-__--___-____------_.----__ xm

Location of the core stations.___-__-___-____________________________--_______-__-_-____-__-__-_-_-_-----_-__ xiv

Personnel and composition of the report._____-___-___________-______-_____---__---_---_-_-_-___------_---____ xiv

Methods of sampling and examination....__-____-__-______________-_____-___..--_--_-_-_-_-_-____----------__- xiv

Part 3. Diatomaceae, by K. E. Lohman__-_____________________________-_-_---_____-_-_-__________-_-----------__ 55

Introduction ________________________________________________________________________________________________ 55

Collection of samples.._____________________________________________________________________________________ 55

Preparation of material..____________________________________________________________________________________ 56

Method of study__________________________________________________________________________________________ 56

Distribution of diatoms in the cores and their ecologic significance._____________--____---------____--------______ 57

Systematic descriptions.___-_____-_-______-.__________-_________-_-_--___-______-_-----_-_-___-------___--__- 63

Index._______________________________________________________________________________________________________ xvn

ILLUSTRATIONS

PLATE 1. Bathymetric chart of a part of the North Atlantic Ocean showing the location of the core stations. ___________ xiv

2. Longitudinal sections of the air-dried cores.____________________________________________________________ xiv

11. Chart showing distribution and temperature significance of the diatoms in the cores.________________________ 62

12-17. Diatoms from the North Atlantic deep sea core8-_______-_----_-_-__--_-___----_-----_--_-_---_-------_- 87-93

FIGURE 1. Profile across the North Atlantic Ocean bottom along the line of the numbered core stations.________________ xiv

22. Map of the North Atlantic Ocean showing surface currents.______-_______-_--_--_-_-_-_____--_-__._____- 60

TABLES

TABLE 1. Geographic location, length of cores, and depth of the water from which they were taken.._______----_--__-___ xiv

8. Locations and numbers of the diatom samples__________________________________________________________ 55

9. Distribution and relative abundance of diatoms from Lord Kelvin cores, North Atlantic Ocean_______._________ 57

10. Ecologic census of the cores as a whole_______________________-__-___--___-_-___---_-___--__-__-__-_____- 59

11. Ecologic census by cores, percent, weighted according to relative abundance_________________________________ 59

12. Ecology of diatoms west and east of the Faraday Hills_________-____---__-___-__-_----_-_-___-_________-__ 60

13. Distribution of the diatoms according to temperature facies___-_____--_--__-_-_-_------_____--_---__-____ 61

in

OUTLINE OF THE COMPLETE REPORT

Foreword, by C. S. Piggot.

General introduction, by W. H. Bradley.

PART 1. Lithology and geologic interpretations, by M. N. Bramlette and W. H. Bradley.

2. Foraminifera, by Joseph A. Cushman and Lloyd G. Henbest.

3. Diatomaceae, by Kenneth E. Lohman.

4. Ostracoda, by Willis L. Tressler.

5. Mollusca, by Harald A. Rehder.

6. Echinodermata, by Austin H. Clark.

7. Miscellaneous fossils and significance of faunal distribution, by Lloyd G. Henbest.

8. Organic matter content, by Parker D. Trask, H. Whitman Patnode, Jesse LeRoy Stimson, and John R. Gay.

9. Selenium content and chemical analyses, by Glen Edgington and H. G. Byers.

SUMMARY OF THE REPORT

In May and June 1936 Dr. C. S. Piggot of the Geophysical 

Laboratory, Carnegie Institution of Washington, took a series of 

11 deep-sea cores in the North Atlantic Ocean between the 

Newfoundland banks and the banks off the Irish coast. These 

cores were taken from the Western Union Telegraph Co.'s cable 

ship Lord Kelvin with the explosive type of sounding device 

which Dr. Piggot designed. In the fall of that year he invited a 

group of geologists of the United States Geological Survey to 

study the cores and prepare a report. Biologists of the United 

States National Museum, the University of Buffalo, and chemists of the United States Department of Agriculture cooperated 

in the investigation and contributed to the report.

The westernmost core of the series (No. 3) was taken in the 

blue mud zone, but all the others were taken in parts of the ocean 

where the bottom is blanketed with globigerina ooze. The 

shortest cores are No. 8, taken on the mid-Atlantic ridge in 1,280 

meters of water, and No. 11, taken where the core bit struck 

volcanic rock. The cores range in length from 0.34 to 2.93 

meters and average 2.35 meters. They were taken at depths 

ranging from 1,280 to 4,820 meters.

Lithology and geologic interpretations.—In about 20 representative samples from each core the percentages of calcium carbonate, 

clay and silt, and sand were determined and plotted, and the 

relative abundance of Foraminifera, coccoliths, and diatoms was 

estimated. Material between these guide samples was examined 

microscopically, especially in certain critical zones.

Two zones were noted in which silicic volcanic ash (refractive 

index near 1.51) is common. The upper ash zone was found in 

all the cores except No. 11, but the lower one was found only in 

the lower part of cores 4 to 7. In core 3 the upper ash zone is 

represented by shards scattered very sparsely all through the 

core, as this core, despite its length of 2.82 meters, apparently did 

not reach the bottom of the ash zone. The upper ash zone, 

together with other adjacent lithologic zones, serves to correlate 

the cores, and the lower ash zone, found west of the mid-Atlantic 

ridge, helps to confirm the correlation.

Besides the zones of volcanic ash four other zones distinctive in 

lithologic character were found. These zones are characterized 

by a relative abundance of sand and pebbles, by a smaller 

percentage of calcium carbonate, and by a sparsity of Foraminifera and coccoliths. They are distinctive also in texture. The 

pebbles are subrounded to angular and include a wide variety of 

rock types—sandstone, gneiss, soft shale, and limestone—of 

which limestone is the most common. Some of the pebbles are 

as much as 2 centimeters across. These zones are interpreted as 

glacial marine deposits formed during the Pleistocene glacial 

epoch, when continental glaciers were eroding the land. Drift 

ice from the continental glaciers apparently transported consideraable quantities of rock debris far out into the ocean basin.

Between the glacial marine zones found in the North Atlantic 

cores the sediments consist chiefly of foraminiferal ooze or marl, 

much like that which is forming today in the same area.

The uppermost glacial marine zone is represented in all the 

cores except Nos. 3 and 11 and lies just below the upper volcanic 

ash zone. In cores 4 to 7 the glacial zones are relatively thin and 

are spaced at approximately equal intervals; between the third 

and fourth glacial zones (in descending order) is the lower volcanic 

ash. East of the mid-Atlantic ridge only the uppermost glacial

zone has been identified. Other glacial marine deposits are 

recognizable but their correlation is less certain.

Three interpretations are offered as possible explanations of 

the four glacial marine zones. The first is that each glacial 

marine zone represents a distinct glacial stage of the Pleistocene 

and that each zone of foraminiferal marl separating two glacial 

marine zones represents an interglacial stage. This interpretation seems least probable of the three. The second interpretation 

is that the upper two glacial marine zones and the intervening 

sediment may correspond to the bipartite Wisconsin stage, 

whereas the lower two represent distinct glacial stages of the 

Pleistocene separated from each other and from the zone representing the Wisconsin stage by sediments that represent interglacial epochs no greater in length than postglacial time. This 

interpretation seems to imply too short a time for most of the 

Pleistocene epoch. The third interpretation, which is favored 

by the authors, is that each of the four glacial marine zones 

represents only a substage of the Wisconsin stage. This implies 

that the North Atlantic at approximately 50° north latitude for 

comparatively long periods of time alternately contained an 

abundance of drift ice and then was quite, or nearly, free of ice, 

while on land a continental ice sheet persisted, though it alternately waned and grew.

In the four cores in which the postglacial sediments are 

thickest the pelagic Foraminifera, according to Cushman and 

Henbest, reveal an interesting condition. These organisms 

indicate that during the middle part of the postglacial interval 

the temperature of the surface water in that part of the North 

Atlantic was somewhat higher than prevails today.

On the assumptions that the top of the uppermost glacial 

marine zone represents the beginning of the postglacial epoch as 

defined by Antevs, and that this was probably as much as 9,000 

years ago, the postglacial sediment in these cores accumulated 

at a rate of about 1 centimeter in 265 years; but, because the sea 

probably cleared of detritus-laden drift ice long before the land 

in the same latitude was cleared of the retreating continental 

ice sheet, the average rate of accumulation may have been as 

low as 1 centimeter in 500 years.

Coarse-grained sediment on the tops of ridges and fine-grained 

sediment in the deeper basins indicate that currents move across 

these ridges with sufficient velocity to winnow out the finer 

particles and sweep them into deeper basins beyond.

The fact that the glass shards in the volcanic ash zones have 

been reworked and distributed without any gradation in size 

through many centimeters of the overlying sediments leads us 

to believe that mud-feeding animals are continually working over 

these shards and other particles of sand and silt so that they are 

redistributed at successively higher levels. The shards and other 

particles may also be reworked by gentle bottom currents that 

move the material from mounds and ridges on the sea floor and 

drift it about over the adjacent flatter areas.

Several layers in the cores are sharply set off by the coarser 

grain size of the sediment or by a regular gradation in grain size 

from coarsest at the base to fine at the top. These may be a 

result of submarine slumping.

The term globigerina ooze is used loosely in this report to 

designate sediment, half or more than half of which, by weight, 

consists of Foraminifera. This usage accords more closely with

VII
VIII SUMMARY OF THE REPORT

the usage adopted by Correns in the Meteor reports than with 

the usage of Murray and Chumley in the Challenger reports, 

which was based solely on the carbonate content. Limy muds 

containing a lesser but still conspicuous number of Foraminifera 

are referred to as foraminiferal marl. The carbonate content 

of the globigerina ooze in these cores ranges from 46.6 to 90.3 

percent and averages 68.2 percent. In 191 samples representing 

all the lithologic types, the carbonate content ranges from 10.0 

to 90.3 percent and averages 41.3 percent. Coccoliths are 

abundant in many parts of the cores, but by reason of their small 

size they rarely make up as much as 10 percent of the sediment. 

Pteropods are rather numerous in parts of the cores taken on the 

mid-Atlantic ridge and on the continental slope off the Irish 

coast.

Most of the calcium carbonate in these sediments consists of 

the tests and comminuted fragments of calcareous organisms. 

The finest particles of carbonate are of indeterminate origin, but 

their irregular shape and range in size suggest that they are 

largely the finest debris of the comminuted organisms rather 

than a chemical precipitate. Clusters or rosettes of calcium 

carbonate crystals were found in many samples, but they are not 

abundant. They evidently formed in the mud on the sea floor.

No conclusive evidence of an increase in magnesium carbonate 

with depth was found, though some of the data suggest it. The 

magnesium carbonate is somewhat more abundant in the glacial 

marine zones than elsewhere, but its concentration in those zones 

is probably accounted for by the presence of clastic grains and 

pebbles of dolomite.

Diatom frustules, radiolarian skeletons, and sponge spicules 

are the most common siliceous organic remains found in the 

cores, and these generally form less than 1 percent of the sediment. One notable exception is the sediment in the middle part 

of core 9, just east of the mid-Atlantic ridge, which contains 50 

percent or more of diatoms.

Ellipsoidal and elongate or cylindrical pellets that appear to 

be fecal pellets are plentiful in the mud at the tops of cores 10 

and 12, taken in the eastern part of the North Atlantic, but 

were not found elsewhere. No attempt was made to identify 

them further.

The sand-size material showed no marked variation in the 

mineral composition of the clastic grains at different horizons 

within individual cores and no conspicuous lateral variation 

from core to core. The mineral grains in the sand-size portions 

were not separated into light and heavy fractions, but simple 

inspection showed that grains of the heavy minerals are somewhat more common in the glacial marine deposits than elsewhere. Well-rounded sand grains are sparsely scattered through 

all the cores, but they are rather more plentiful in the glacial 

marine zones. These grains, which range in diameter from about 

0.1 to 1.0 millimeter and average 0.5 millimeter, have more or 

less frosted surfaces. They may have been derived from the 

reworking of glacial marine deposits or they may have been 

rafted by seaweeds. Little was done with the clay minerals 

other than to note that most of them have the optical properties 

of the beidellite or hydrous mica groups.

Six samples were tested with a 10-inch spectograph, which 

revealed the presence of appreciable amounts of barium and 

somewhat less of boron in each sample. All the samples gave 

negative tests for antimony, beryllium, bismuth, cadmium, germanium, lead, silver, tin, and zinc.

The original porosity of several samples in core 3 was calculated from the porosity of the dried samples. The original 

porosity plotted against depth in the core seems to indicate that 

fine-grained blue muds buried to a depth of 2 or 3 meters in the 

ocean floor are appreciably compacted.

Partial mechanical analyses of nearly 200 samples were made 

and plotted, but only four complete mechanical analyses were

made. The complete analyses were made by the sedimentation 

method and include four distinctive types of sediment.

Pumiceous fragments and smaller shards of basaltic volcanic 

glass (index of refraction near 1.60) are scattered throughout all 

the cores, but are somewhat more common east of the mid-Atlantic ridge than west of it. Unlike the alkalic volcanic ash it 

shows no conspicuous concentration in zones. Most of the basaltic glass and pumice has a thin surface alteration film of palagonite. The films are thickest on fragments in cores taken from 

ridges where oxygen-bearing waters had free access to the sediments. Two varieties of palagonite are recognized.

Core 11 represents only 34 centimeters of the sea floor because 

the core bit encountered deeply altered olivine basalt. About 

15 centimeters of globigerina ooze rests on and within irregular 

cavities of the upper surface of a mass of clay that is apparently 

altered basalt. This clay is impregnated with manganese and 

contains nodular lumps of altered basalt. Part of the basalt 

near the base of the core is less altered. The clay contains scattered grains of sand and foraminiferal shells in which the original 

calcium carbonate has been replaced by a zeolite resembling phillipsite. This core may have penetrated the upper, deeply altered 

part of a submarine lava flow, but the evidence is not conclusive.

Core 10 contains two rather thick beds of distinctive clayey 

mud. About half of this mud is a beidellite or hydrous mica 

type of clay and the other half is made up of silt-size particles of 

basaltic glass, magnetite, augite, and calcic plagioclase. It 

contains very little common clastic material and exceedingly 

few Foraminifera. The composition and texture suggest that 

this mud was derived largely from a submarine volcanic eruption 

that threw into suspension clay particles perhaps partly from the 

normal sediment and from deeply altered basalt. A complete 

chemical analysis of this mud is given.

Foraminifera.—From these cores 184 samples representing 

every lithologic zone were examined for calcareous fossils. All 

but five samples contained Foraminifera. As in existing oceans 

deeper than several hundred meters, pelagic Foraminifera greatly 

outnumber the bottom-dwelling forms, though in variety of form 

and in number of genera and species the bottom forms greatly 

exceed the pelagic. Several zones of relatively pure globigerina 

ooze were found, and many in which the ooze was clayey or sandy. 

Though variations in temperature were reflected by faunal 

changes, the general bathymetric facies of the faunas appear to be 

rather uniform throughout each core. The bottom faunas are 

least varied and prolific in cores from the deepest water, whereas 

in cores from the shallowest water they are by far the most 

varied and prolific. Cores from intermediate depths contain 

faunas of intermediate bathymetric facies. These relations to 

depth are, in general, characteristic also of faunas in the existing 

oceans. A few scattered specimens of Elphidium or Elphidiella 

were found. These genera thrive in shallow water, but in these 

cores the shells are so rare, so erratically distributed, and in some 

so poorly preserved that it seems probable they were rafted in by 

seaweeds or ice and therefore have no significance as indicators of 

depth. No species peculiar to the Miocene or Pliocene were 

found. It appears, therefore, that all the sediments penetrated 

by the cores are younger than Pliocene. Alternation of faunas 

that are characteristic of the warm and cold climates of the 

present day indicates great climatic changes during the time 

represented by these cores. The foraminiferal facies characteristic of cold and warm climates correlate with the alternating 

sequence of glacial-marine and warmer-water sediments indicated 

by the lithology. This correlation suggests that all the sediments in these cores are of Recent and Late Pleistocene age.

Diatomaceae.—Fifty-two species and varieties of diatoms were 

found in these cores. A large percentage of the species are neritic, 

warm-water forms that are foreign to the region today. Several
SUMMARY OF THE REPORT IX

alternations of warm-water and cold-water diatom floras occur 

in most of the cores, but their position in the cores is not in 

accord with the alternations of temperature inferred from lithology and foraminiferal facies. It is suggested that this disagreement may be due to the much longer settling time of the diatoms 

and that allowance should be made for it. The time equivalent 

of this difference of phase, as calculated from the vertical displacement necessary for the best approximation to agreement 

between the foraminiferal and lithologic data on the one hand 

and the diatom data on the other is of the order of 23,000 years. 

This figure appears absurdly high and a figure of several hundred 

years, based on extrapolation of experimentally timed settling 

in a relatively small vessel, is considered more reasonable. The 

action of cold and warm currents, some surficial and some deep 

seated, is suggested as the possible cause of the apparently erratic 

distribution of the diatoms. The possibility that the phase difference of 23,000 years mentioned above is related to shifts of 

ocean currents caused by advances and recessions of drift ice is 

offered as a speculation. Of 52 species and varieties illustrated, 

2 species and 1 variety are described as new.

Ostracoda.—In preparing a series of samples from the cores for 

the study of the Foraminifera about 175 specimens of Ostracoda 

were found. These belong to 13 genera and 27 species, all living 

forms, though 12 of the species are known also as fossils. Most 

of the ostracodes were found in three cores that were taken in 

the shallowest water (1,280 to 3,230 meters). One of these cores 

(No. 8) was from the top of the mid-Atlantic ridge and the other 

two (Nos. 12 and 13) were from the continental slope southwest 

of Ireland. In the cores from deeper water (3,250 to 4,820 

meters) ostracodes were scattered very sparsely. Like most 

marine ostracodes, all the species found in the cores are bottom 

dwellers. Most of the species are decidedly cold-water forms 

that are found in tropical waters only at great depth, where the 

temperature is near freezing. Northern forms predominate; only 

2 of the species have not previously been known from northern 

waters, and 10 species are definitely Arctic forms. A few species 

that have a wider temperature range live not only in cold waters 

but also in the deep warm water of the Mediterranean.

The predominance of distinctly cold-water ostracodes and the 

prevalence of Arctic forms suggest that the temperature of the 

water in this part of the North Atlantic was formerly somewhat 

lower. But, as might be expected from the fact that all the 

species in these cores are bottom dwellers, their distribution in 

the cores shows no evident relationship to the cold and warm 

zones indicated by the composition and texture of the sediments 

and by the pelagic Foraminifera.

Mollusca.—The mollusks recovered from these cores can be 

divided into two groups, the pteropods and the other gastropods 

and pelecypods. The pteropods are by far the more numerous. 

All the specimens of the pelecypods and gastropods, other than 

pteropods, are representatives of deep-water species that are now 

b'ving in the same boreal or cold-temperate waters. Also, the 

fragments that could not be identified specifically belong to forms 

that have congeners now living in these waters. The fauna of 

these cores, even that taken from the lower parts of the cores, 

shows no appreciable difference from that now living in the same 

localities. Among these mollusks no evidence of shallower or 

considerably deeper water is demonstrable. Molluscan remains, 

other than those of pteropods, are too scarce to attempt to 

differentiate cold- and warm-water facies, as was done with the 

foraminiferal faunas.

The Pteropoda, which are far more abundant in the cores than 

the other mollusks, belong to two genera and three species. One 

of the species is new. The geographic distribution of the pteropods is limited more by the temperature of the surface water 

than by any other factor. Nevertheless, as one species is cosmopolitan, one boreal, and one a new species thought to be the

northern analogue of a more southern species, and as all three 

species occur together, they have no significance for differentiating cold- and warm-water facies. These organisms are pelagic 

and their shells have a rather wide distribution, but, as they are 

found on the sea floor at depths ranging from 247 to 3,750 meters, 

they are of little aid as indicators of depth of the ocean at the 

time these deposits were laid down.

Echinodermata.—The remains of 9 species of Echinodermata 

were found in the cores. These include 1 ophiuroid, 7 echinoids, 

and 1 crinoid. No remains of asteroids were found. All the 

echinoderms found belong to species now living in that part, or 

adjacent parts, of the North Atlantic. Echinoderm remains are 

rather uniformly distributed among the cores, but they are most 

numerous in core 8, which was taken in 1,280 meters of water 

on the crest of the mid-Atlantic ridge. By far the commonest 

species is Pourtalesia miranda, remains of which were found in 

nearly two-thirds of the 82 echinoderm-bearing samples and in 

all the cores except 8 and 11.

Because the association of species in the cores is closely 

similar to the association of living species in that part of the 

North Atlantic and because the association of species within each 

core is independent of the distance below the top of the core it 

appears that neither the distribution nor the composition of the 

echinoderm fauna has changed significantly during the interval 

represented by these cores. No evident relationship was found 

between the distribution of the various species of echinoderms 

and the cold- and warm-water facies of the sediments indicated 

by both the Foraminifera and the lithology.

Miscellaneous fossils and significance of faunal distribution.— 

The principal fossil groups represented in the cores, listed in 

order of abundance, are foraminifers, diatoms, echinoids, siliceous 

sponges, radiolarians, ophiuroids (spines and plates), ostracodes, 

and pteropods. Remains of barnacles, brachiopods, pelecypods, 

holothuroids, bryozoans, gastropods, and teleost fishes (otoliths) 

were also found, but all these are rare. The foraminifers, diatoms, ostracodes, echinoderms, pelecypods, and gastropods were 

studied separately by specialists. The other groups are briefly 

noted and illustrated for the sake of the record. The most 

varied and prolific faunas were found in the three cores that 

were taken from the shallowest water and the least varied and 

least prolific were found in those from the deepest water. The 

bottom-living faunas throughout each core have a broadly similar bathymetric facies, and the bathymetric facies of each core 

appears to correspond to that of the fauna now inhabiting that 

locality. Faunas having the characteristics of very shallowwater marine faunas are either absent or, if present, are so rare 

and erratically distributed that they appear to be foreign in 

origin rather than indigenous. Ostracodes and pteropods are 

locally abundant in the cores from the shallower water, but are 

absent or rare at all horizons in those from the deeper water. 

The distribution and bathymetric facies of the faunas weigh 

heavily against the hypothesis of extreme changes in ocean 

level during the later part of the Pleistocene.

Organic matter content.—The content of organic matter, as 

determined from 123 samples, ranges from 0.1 to 1.0 percent of 

the total weight of the seoiments, and the average is about 0.5 

percent. As in near-shore sediments, it is influenced by the 

configuration of the sea bottom. It is small on ridges and large 

in the deeps. It is particularly large in the sediments at the 

base of the east slopes of ridges, owing in part, probably, to 

material washed from the vicinity of the ridges by eastwardsweeping ocean currents. The organic matter content of the 

upper layers of the sediments in the abyssal deeps is greater 

for a few hundred miles east of the mid-Atlantic ridge than it 

is for a similar distance west of the ridge. The organic content 

does not vary consistently with depth except in core three, 

taken at the foot of the continental slope east of the Grand
SUMMARY OF THE REPORT

Banks, where it seems to decrease about 25 percent in the first 

1.5 meters. The organic matter content of the sediments tends 

to be greater in the warm zones, than in the cold zones, and in 

general it is slightly greater in sediments which, according to 

Cushman's determination of the Forammifera, were probably 

deposited in areas in which the surface water was relatively 

warm. The organic content is rather closely related to the 

texture, and increases with increasing fineness of the sediments. 

The rate of deposition of organic matter is greater east of the 

mid-Atlantic ridge than west of it, presumably owing in part 

to a greater supply of plankton and in part to a slower rate of 

decomposition of the organic matter after it is laid down in the 

sediments. The slower rate of decomposition within the sediments is inferred from the greater state of reduction of the 

sediments, which is indicated by the nitrogen-reduction ratio. 

The nitrogen-reduction ratio suggests a slight increase in state 

of reduction with increasing depth of burial in the upper part 

of the deposits, but indicates no significant change in the lower 

part. The percentage of organic content tends to increase as 

the percentage of Foraminifera in the sediments decreases, but 

it shows no relationship to the calcium-carbonate content.

Selenium content and chemical analyses.—As a part of a comprehensive investigation of the distribution of selenium in marine

sediments and soils derived from them complete fusion analyses 

were made of 20 samples from the suite of 11 cores. These 

samples were taken from the tops of the cores and at intervals of 

approximately 1 and 2 meters below the top. In addition, 1 

core taken on the continental shelf off Ocean City, Md., and 3 

cores from the Bartlett Deep were sampled and analyzed, making 

a total of 31 analyses. The results of the analyses include all 

the normal analytical data obtained in a so-called complete soil 

analysis by the fusion method, and, in addition, determinations 

of organic matter, nitrogen, chlorine (in all but 12 analyses), 

hygroscopic water, and selenium. All the samples were analyzed 

with the entrained sea salts. The core from the continental 

shelf off Ocean City contained the most selenium—at the top 

0.6 part per million, at 1 meter 1.0, and at 2 meters 2.0 parts per 

million. The samples from the North Atlantic cores showed a 

selenium content ranging from 0.06 to 0.8 part per million. Of 

the samples from the Bartlett Deep one contained 0.2 part per 

million of selenium, but all the others contained less than 0.08 

part per million. No evidence was found of a relation between 

the selenium content and volcanic activity.

The silica-sesquioxide and silica-alumina ratios are tabulated 

and their significance as means of comparing the analyses is 

discussed.
FOREWORD

By C. S. PIGGOT '

During the last cruise (1927-29) of the nonmagnetic 

ship Carnegie of the Department of Terrestrial Magnetism of the Carnegie Institution of Washington a 

number of samples of the deep ocean bottom were 

obtained by means of the telegraph snapper. The 

Geophysical Laboratory determined the radium content 

of these samples and found that they contained a concentration of radium 2 as astonishingly high as that 

reported by Joly 3 and Pettersson 4 from similar samples 

taken by the Challenger and Princess Alice II. This 

high radium concentration in the surface layer of the 

ocean bottom, which constitutes 72 percent of the surface of the globe, raises questions of great significance 

to both oceanography and geophysics. An obvious 

question is whether radium in so high a concentration is 

present down through all deep-sea sediments or only 

at the surface.5 If the first hypothesis is correct it 

indicates the presence of uranium throughout the sediments, whereas the second indicates the existence of 

radium itself, presumably separated out from the sea 

water. The study of this question requires samples of a 

type analogous to the cores so extensively used in subsurface exploration on land. Inquiries among oceanographic organizations established the fact that although 

some cores a meter or more in length had been obtained 

from relatively shallow water, many of them were much 

distorted by the tune they reached the laboratory, and 

none as long as 1 meter had been obtained from a depth 

of 4,000 meters or more.6 Those engaged in such research 

emphasized the need of apparatus capable of obtaining 

undistorted cores from great depths. In 1933 the 

Council of the Geological Society of America approved a 

grant for the development of such apparatus.7 Fortunately, cooperation was obtained from several special

' Geophysical Laboratory, Carnegie Institution of Washington.

1 Piggot, C. S., Radium content of ocean-bottom sediments: Am. Jour. Sci., 5th 

ser., vol. 25, pp. 229-238, 1933.

3 Joly, J., On the radium content, of deep-sea sediments: Pbilos. Mag., vol. 16, pp. 

190-197,1908.

« Pettersson, Hans, Teneur en radium des depots de mer profonde: Resultats de 

Campagnes Scientiflques par Albert I " Prince Souverain de Monaco, vol. 81, 1930.

• Piggot, C. S., op. cit., p. 233.

• Since these inquiries were made D. Wolansky has published her review in the 

Geologische Rundschau (Band 24, Heft 6, p. 399,1933), in which she refers to the work 

of A. D. Archanguelsky in the Black Sea (Soc. Naturalistes Moscow Bull., new ser., 

vol. 35, pp. 264-281,1927). Wolansky mentions cores 3 to 4 meters long from depths 

of 2,237 meters. Bee also Wiss. Ergeb. Deutschen Atlantischen Exped. Meteor, 

1925-27, Band 3, Teil 2, Lief. 1, pp. 4-28,1935.

1 Piggot, C. S., Apparatus to secure core samples from the ocean bottom: Geol. 

Soc. America Bull., vol. 47, pp. 675-684,1936.

agencies, particularly the Burnside Laboratory of the 

E. I. du Pont de Nemours, whose ballistics expert, Dr. 

B. H. Mackey, offered fundamental suggestions and 

made many essential calculations and tests; also the 

United States Bureau of Lighthouses, from whose lightship tender, the S. S. Orchid, many experimental soundings were made. Several forms of the apparatus were 

developed and tested, and in August 1936 14 satisfactory 

cores were obtained from the canyons in the continental 

shelf off New Jersey, Delaware, and Maryland, and 

another from the ocean floor below 2,500 meters of 

water.8 This first deep-sea test was made possible by 

the cooperation of the Woods Hole Oceanographic 

Institution and was carried out in connection with an 

investigation of the submarine canyons by H. C. Stetson 

of that institution. This test demonstrated the feasibility of the apparatus as built but suggested some 

minor changes in design. These were incorporated in 

another apparatus, which was put aboard the cable ship 

Lord Kelvin at Halifax, Nova Scotia. Through the 

courtesy of Mr. Newman Carlton, Chairman of the 

Board of Directors of the Western Union Telegraph Co., 

the Carnegie Institution of Washington was invited, to 

have a member of its staff accompany the Lord Kelvin 

while that ship was engaged in making repairs to the 

North Atlantic cables, in order to test the apparatus in 

deep water. This offer was gladly accepted, and in 

May and June of 1936 I was on board the Lord Kelvin 

with the apparatus.

Because of the personal interest and cooperation of 

the commanding officer, Lt. Com dr. Bredin Delap, 

Royal Navy, retired, the undertaking was more successful than had been anticipated, and a suite of 11 

excellent cores was obtained, extending from the Grand 

Banks of Newfoundland to the continental shelf southwest of Ireland.

All but two of these cores (Nos. 8 and 11) are more 

than 2.43 meters (8 feet) long, and all contain ample 

material for study. Of the two short cores, No. 8 was 

taken from the top of the Faraday Hills, as that part 

of the mid-Atlantic ridge is known, where the material 

is closely packed and more sandy and consequently 

more resistant; No. 11 came from a locality where the

8 Cushman, J. A., Henbest, L. G., and Lobman, K. E., Notes on a core sample from 

the Atlantic Ocean bottom southeast of New York City: Geol. Soc. America Bull., 

vol. 48, pp. 1297-1306, 1937.

XI
XII FOREWORD

apparatus apparently landed on volcanic rock that may 

be part of a submarine lava flow. Soundings at the 

localities where the cores were taken show depths ranging from 1,280 meters at the top of the Faraday Hills to 

4,820 meters in the deep water between the mid-Atlantic 

ridge and the continental shelf.

The thorough test made possible by the interested 

cooperation of everyone on board the Lord Kelvin fully 

demonstrated the capacity of the apparatus and produced material from strata of oceanic sediments deeper 

than have ever before been available.

In order that this pioneer material might be examined to the best advantage and an adequate estimate 

made of the potentialities of cores of this type, agroupof 

investigators representing various fields of science was 

invited to examine them. Efforts have been made to 

arrange the sequence of these investigations in such a 

way that the maximum information may be obtained 

with the minimum destruction of the samples.

The cores are now at the Geophysical Laboratory of 

the Carnegie Institution of Washington, where they and 

others that may be obtained by this laboratory will be 

held available for further research.
GENERAL INTRODUCTION

By W. H. BRADLEY

SIGNIFICANCE OF THE INVESTIGATION

The long cores of deep-sea sediment considered in 

this report represent a longer span of the earth's late 

geologic history, as recorded in abyssal sediments, than 

has been heretofore accessible. In a measure, therefore, this study has been exploratory. Because of that exploratory aspect we have not only presented the observations but also have deliberately speculated upon various 

possible interpretations of the features observed in the 

cores and upon their relations with one another. Because the cores are few in number and widely spaced, 

we offer many of the interpretations not as definite 

conclusions but rather as suggestions to be tested by 

whatever coring may be done in the future in that part 

of the North Atlantic.

From this investigation it appears that glacial marine 

deposits may prove to be sensitive indicators of the climatic changes that caused the growth and decay of 

continental ice sheets during the Pleistocene. In particular, it seems that the glacial marine record may 

throw light on the climatic fluctuations that determined substages of the Pleistocene. The marine 

record was the result of a continuously operating series 

of causes such that the deposits of each glacial substage 

were separated from one another by the deposits of the 

intervening warmer substage. The record of each 

substage has remained intact and was not obliterated 

by readvances of the ice. As the equatorward extent 

of the glacial marine deposits implies a corresponding 

expansion of continental ice sheets, the extent of the 

deposits may be used as a measure of the intensity of 

the climatic changes, and their thickness may be used 

as a rough indicator of the duration of glacial substages. 

Similarly, the thickness and poleward extent of tongues 

of nonglacial sediment—the foraminiferal marl—are 

measures of deglaciation. The areal extent of these 

tongues of sediment can be determined by additional 

cores taken at properly located stations.

When the glacial marine record is more fully known 

it should provide a basis for correlating the Pleistocene 

history of Europe and North America.

Cores taken along the meridians hi series extending 

from the Arctic regions into the tropical parts of the 

Atlantic should make it possible to map the southern 

limits of pack ice in the sea during successive glacial 

maxima, at least for the later part of the Pleistocene.

As the pelagic Foraminifera in these abyssal sediments 

are reliable indicators of surface-water temperatures in 

the Recent and Pleistocene epochs, it should be possible 

to trace southward into the tropics layers or beds of 

foraminiferal ooze that are the time equivalents of 

glacial marine zones. Such layers of foraminiferal ooze 

could then be correlated with the layer of globigerina 

ooze in the tropics that Schott 9 identified as a relatively cold-water deposit that probably represents the 

last glacial epoch of the Pleistocene.

The study of climatology as well as geology may be 

advanced by the information to be derived from long 

sea-bottom cores. Significant evidence bearing on postglacial climatic changes may be obtained from minutely 

detailed study of the Foraminifera in cores taken in 

parts of the ocean where postglacial sedimentation has 

been comparatively rapid, as, for example, near the 

seaward edge of the blue-mud zone. On the assumption that such sediment accumulates at an essentially 

uniform rate, climatic fluctuations may be located approximately in time within the postglacial interval and 

may be correlated from place to place along the ocean 

margins from the Arctic to temperate or even tropical 

latitudes and perhaps also from continent to continent.

Archeology, also, might profit from the knowledge 

of a relatively timed and correlated sequence of climatic changes, for such changes may well have made a 

significant impress on the habits and migrations of 

peoples, particularly those that dwelt in regions where 

small changes in either temperature or rainfall were 

critical. As I have pointed out in an earlier paper, 10 

students of archeology and early history, particularly in 

the Mediterranean region, might profit much from 

detailed studies of long cores of the sediment in the 

deep basins of the Mediterranean. In cores from that 

sea, as elsewhere, changes in the foraminiferal faunas 

would indicate climatic changes, and the sediments 

would yield, in addition, evidence of volcanic eruptions, 

and earthquakes. The tune when the Sahara became 

a desert should also be recorded in the Mediterranean 

sediments by wind-blown sand. Such a change might 

conceivably be integrated with the wealth of archeo-

' Schott, W., Die Foraininiferen in dem aquatorMen Teil des Atlantischen Ozeans: 

Wiss. Ei-geb. Deutschen Atlantischen Exped. Meteor, 1926-27, Band 3, Teil Z, Lief. 1, 

pp. 120-^28,1935.

'• Bradley, W. H., Mediterranean sediments and Pleistocene sea levels: Science 

new serJ, vol. 88, pp. 376-379, 1938.
XIV GENERAL INTRODUCTION

logical records of the region, and the later volcanic 

eruptions and earthquakes might be correlated with 

early history.

Some of the problems sketched so briefly here are 

touched upon in the several chapters of this report, 

but most of them must be left for future investigators. 

Nevertheless, methods by which such problems may 

be attacked are described and discussed at considerable 

length, particularly in the chapters on "Lithology and 

geologic interpretations" and "Foraminifera."

LOCATION OF THE CORE STATIONS

The cores were taken along a slightly irregular line 

between the easternmost part of the Newfoundland 

Banks and the banks off the southwest coast of Ireland, 

as shown in plate 1. Each core obtained by the Piggot 

coring device is numbered to correspond with the station 

number of the cable ship Lord Kel/.in. Stations 1 and 

2 were trial stations at which preliminary tests were 

made to familiarize the crew with the apparatus, and 

no cores were preserved. The 11 cores studied are 

numbered consecutively, 3 to 13. The relation between

M. N. Bramlette, J. A. Cushman, L. G. Henbest, K. E 

Lohman, and P. D. Trask. As the biologic phase of 

the work progressed it became evident that other 

organisms than the foraminifers and diatoms should be 

studied. Accordingly Mr. Henbest invited Dr. Willis 

L. Tressler, of the University of Buffalo, to examine the 

ostracodes, Dr. Austin H. Clark of the United States 

National Msueum, to examine the echinoderms, and 

Dr. Harald A. Rehder, also of the United States 

National Museum, to examine the mollusks.

The organic matter content of the sediments was 

studied by Mr. Trask in collaboration with Messrs. 

H. Whitman Patnode, Jesse LeRoy Stimson, and John 

R. Gay, all members of the American Petroleum 

Institute.

As part of a comprehensive research project on the 

distribution of selenium in marine sediments and the 

soils derived from them Dr. H. G. Byers and Mr. Glen 

Edgington, of the Bureau of Chemistry and Soils, 

United States Department of Agriculture, made complete chemical analyses of 20 samples from these deepsea cores. These analyses, together with analyses of

w.

ST JOHNS 

NEWFOUNDLAND

Meters

MID-ATLANTIC RIDGE 

"FARADAY HILLS" 

789

E.

LANDS END 

ENGLAND

FIGURE 1.—Profile across the North Atlantic Ocean along the line of the numbered core stations shown on plate 1.

the core stations and the submarine topography is 

shown in figure 1, which is a profile along the dashed 

line in plate 1 that connects the stations and extends 

from St. Johns, Newfoundland, to Lands End, England. 11

TABLE 1.—Geographic location, length of the cores, and depth of 

the water from which they were taken

Core number

3......— ............................

4....... ..............................

5........... ..........................

6

7— .——. — — , ——-———-

8............... — ......... ........ ..

9.—. „.„..- — .-..— — -—.--—

iO.... ................................

).!„.— .————_— — — . — —

12...... ...... ..................... ...

13... — ..............................

Depth 

of water 

(meters)

4,700

3,955

4,820

4,125

3,250

1,280

3,745

4,190

4,820

3,230

1,955

Length 

of core 

(meters)

2.81

2.71

2.82

2.90

2.62

1.24

2.76

2.97

.34

2.43

2.21

Lat. N.

46°03'00"

48°29'00"

48°38'00"

49°03'30"

49°32'00"

49°36'00"

49°40'00"

49°45'00"

48°38'00"

49°37'00"

49°38'00"

Long. W.

43°23'00"

35°54'30"

36°01'00"

32°44'30"

29°21'00"

28°54'00"

28°29'00"

23°30'30"

17°09'00"

13°34'00"

13°28'00"

PERSONNEL AND COMPOSITION OF THE REPORT

At the request of Dr. C. S. Piggot, of the Geophysical 

Laboratory of the Carnegie Institution of Washington, 

the following six members of the United States Geological Survey undertook a systematic study of the 11 

deep-sea cores from the North Atlantic: W. H. Bradley,

11 Data for plate 1 and figure 1 were taken from International Hydrographic Bureau, 

Carte Gfinerale Bathyme'trique des Ocfians, 3d ed., sheets A-l and B-l, copies of 

which were furnished by the U. S. Hydrographic Office.

samples from several other deep-sea cores and a discussion of the occurrence of selenium, are included in 

the chapter on "Selenium content and chemical 

analyses."

METHODS OF SAMPLING AND EXAMINATION

The Piggot coring device 12 takes the cores in brass 

sampling tubes that have an inside diameter of 4.9 cm. 

As soon as a core is taken, the tube is cut off at the 

approximate length of the core and sealed. The cores 

here discussed were opened under Dr. Piggot's direction 

at the Geophysical Laboratory of the Carnegie Institution of Washington. A longitudinal cut was made 

along one side of each brass core barrel by means of a 

milling cutter so adjusted that it did not cut quite 

through the wall of the tube. The thin strip remaining 

was then ripped out without letting brass chips get 

into the core. After allowing the mud cores to dry 

somewhat, but not enough to shrink away from the 

tube walls, the cores and core barrels were cut in half 

longitudinally with a metal-cutting band saw. In this 

cutting, the milled slot was held uppermost so that the 

saw cut only the lower wall of the core barrel and 

threw the cuttings downward, away from the core.

" Piggot, C. S., Apparatus to secure core samples from the ocean bottom: Qeol. 

Soc. America Bull., vol., 47, pp. 675-684,1936.
GEOLOGICAL SURVEY

60° (Follows p. XV) 50' 40 20 PROFESSIONAL PAPER 196 FLATS 1 10°

Sea level to 

500 meters

500-2,000 

meters

2,000-4,000 

meters

4,000-6,000+ 

meters

BATHYMETRIC CHART OF A PART OF THE NORTH ATLANTIC OCEAN.

The numbered circles indicate the core stations. The dashed line connecting them is the line of the proBle shown in figure 1. The light dotted line along the coasts is the 200-meter depth contour. The usual limit of drift ice is shown by the heavy dotted line. The small triangles indicate the position of iceberg* reported far beyond their normal range during the period January 1900 to July 1916, according to information compiled by J. T. Jenkins (A Textbook of Oceanography, fig. 14, London, Constable & Co., 1921).

40°

U.S. GOVERNMENT PRINTING OFFICE : 1940 — O-228324

GEOLOGICAL SURVEY PROFESSIONAL PAPER 196 PLATE 2

678

W.

2 J

Meters

9 10 M 12 13

LONGITUDINAL SECTIONS OF THE AIR-DRIED CORES. 

Half of the core barrel was removed from core 11, but the core itself was not cut. Photograph by Geophysical Laboratory, Carnegie Institution of Washington.

GENEEAL INTRODUCTION XV

Each half core then remained undisturbed in its half 

cylinder cradle of brass core barrel. (See pi. 2.)

As several months elapsed between the time the cores 

were opened and the time this investigation began, the 

mud had dried thoroughly when Mr. K. E. Lohman 

took a succession of overlapping photographs of each 

core, about one fifth natural size. These photographs 

were then assembled as a key chart upon which were 

marked the parts from which samples for all phases of 

the investigation were taken. The dried segments of 

mud shifted somewhat from their original places each 

time samples were removed, though care was taken

to see that during sampling the segments kept their 

original order and orientation. By reference to this 

photographic key the findings of all the investigators 

have been correlated.

Most of the material was hard enough to be sawed 

into blocks with a hack saw, but a few of the most 

friable parts were sampled with small channel-shaped 

scoops of sheet metal after the loose material on the 

surface had been brushed away.

Samples for all phases of this investigation were 

taken from only one half of each core, the other half 

being held intact in the Geophysical Laboratory.

GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES 

BETWEEN NEWFOUNDLAND AND IRELAND

PAET 3. DIATOMACEAE

By K. E. LOHMAN

INTRODUCTION

This report is one of a series bearing on different 

phases of the investigation of the deep-sea cores collected 

in the North Atlantic by C. S. Piggot in 1936. (See 

Foreword of this professional paper.) Its scope is 

confined to the diatoms found in the cores. The report 

is divided into two parts. The first part deals1 with 

the distribution of diatoms in the cores, with a discussion of their ecologic and geologic significance; the 

second part gives a systematic description of the diatoms. The geographic location of these cores is shown 

on plate 1 in part 1 of this professional paper.

COLLECTION OF SAMPLES

During the winter of 1936-37, 67 samples were selected from the cores at the Geophysical Laboratory 

in Washington by W. H. Bradley, of the Federal 

Geological Survey, and myself. The location in the 

core of each sample and the location of all samples 

taken by the different investigators studying the material were carefully plotted by Mr. Bradley on a photographic chart that he had prepared. Portions sawed 

from pieces of the core were stored in labeled screwcap bottles for future study. As the' core had dried 

sufficiently, it was possible to get solid pieces, which 

reduced the possibility of contamination from neighboring parts of the core to a minimum. Although 

each sample was examined with a 10 X hand lens as 

it was collected, only the large discoid diatoms could be 

seen and then only when fairly abundant. The large 

amount of fine material present or the abundance of 

Foraminifera generally made it impossible to determine by inspection with a hand lens which sample 

contained diatoms.

Core 5 was sampled first at intervals ranging from 

9 to 40 centimeters. The 14 samples from this core 

were prepared and studied before further sampling 

was done in an attempt to determine the justifiable 

frequency of sampling for the other cores. Diatoms 

were found in only 4 of the 14 samples collected from 

this core, and all were in the upper half.

In the meantime, M. N. Bramlette, who collected 

at short intervals from all the cores for his lithologic

250584—11———2

studies, had looked at the whole lot under the microscope and had noted, among other things, the presence 

or absence of diatoms in each sample. The results of 

Mr. Bramlette's preliminary examination served as an 

excellent guide for sampling the remainder of the cores, 

and acknowledgment is here made to him for the very 

material saving in time effected by his help. Mr. Bramlette reported no diatoms from cores 8 and 11, and 

therefore they were not sampled by me.

The location of the samples collected, the numbers 

assigned to them for use in this report, to which reference will be made frequently, their permanent Federal 

Geological Survey diatom locality numbers, and the 

presence or absence of diatoms is indicated in the following table:

TABI*E 8.—Locations and numbers of the diatom samples

Core No.

3. __-. — .

4- .......

5— ------

6... ......

Location of station

Lat. N.

46°03'00"

48°29'00"

48°38'00"

49°03'30"

Long. W.

43°23'00"

35°54'30"

36°01'00"

32°44'30"

Depth of 

water 

(meters)

4,700

3,955

4,820

4,125

Sample

No.

L-l

L-2

L-3

L-4

L-5

L-6

L-7

L-8

L-9

L-10

L-ll

L-12

L-13

L-14

L-15

L-16

L-17

L-18

L-19

L-20

L-21

L-22

L-23

L-24

L-25

L-26

L-27

L-28

L-29

L-30

L-31

L-32

L-33

L-34

L-35

L-36

L-37

L-38

L-39

Position of 

sample in 

core, in 

centimeters 

below top

5-8

40-48

81-89

130. 5-137

185-187

190-192

233-238

253-257

7. 5-9. 5

29-33

74-79

83-87

132-136

177-179

207-210

264-268. 5

0- 2

21-23

30-32

34-38

46-48.5

58-6i

95-99

111-113

124-126

158-159

203-205

225-228

262-264

277-281

0-4.5

38.5-42

81.5-85

118-122

152-158. 5

183-188

200-203

226-230

244-248

275-281

Diatoms 

present 

(+)or 

absent (-)

+

t

+

+

+

+

+

+

_

—

—

—

+

—

+

+

—

+

—

—

—

—

—

+

+

+

+

+

+

+

U.S.G.S. 

diatom 

locality 

No.

2863

2864

2865

2866

2867

2868

2869

2831

2832

2854

2833

' 2834

2835

2836

2837

2817

2818

2819

2S3J

2820

2821

2822

2823

2824

2825

2826

2827

2828

2829

2838

2839

2840

2841

2842

2892

2843

2893

2844

2894

55
56 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

TABLE 8. — Locations and numbers of the diatom samples — Con.

Core No.

7.........

9........

10.————

12........

13.————

Location of station

Lat. N.

49°32'00"

49°40'00"

49°45'00"

49°37'00" 

49°38'00"

Long. W.

29°21'00"

28°29'00"

23°30'30"

13°34'00" 

13°28'00"

Depth of

water 

(meters)

3,250

3,745

4,190

3,230 

1,955

Sample 

No.

L-40 

L-41

L-42 

L-43 

L-44 

L-45 

L-46 

L-47 L-48

L-49 

L-50 

L-51 

L-52 

L-53 

L-54 

L-55 L-56

L-57 

L58 

L-59 

L-60 L-61

L-62 

L-63 L-64

L-65 

L-66 

L-67

Position of 

sample in 

core, in 

centimeters 

below top

3.5-7 

55-58 

94-96 

119-123 

158-161 

183-187 

190-192. 5 

233-237 

258—262

0-6.5 

47-53 

108-114 

142-151 

178-188 

206-213 

246-250 

267-272

29-33 

80-86 

86-89 

233-237 

258-263

0-5 

30. 5-33 

90. 5-95

0-7 

141-143 

182-187. 5

Diatoms 

present 

(+)or 

absent (-)

+ ++++++++ +++++11+ 

U.S.Q.S. 

diatom 

locality 

No.

2845 

2846 

2847 

2848 

2849 

2850 

2853 

2851 

2852

2855 

2856 

2857 

2858 

2859 

2860 

2861 

2862

2870 

2871 

2872 

2873 

2874

2875 

2876

2877

2878 

2879 

2880

PREPARATION OF MATERIAL

All the samples were given as nearly as possible the 

same treatment in the cleaning and concentrating operations in order that the relative abundance of species 

from the different samples would be comparable. All 

possible precautions were taken to prevent contamination from other samples or from outside sources. 

Briefly, the method used was as follows:

All outside (possibly contaminated) material was removed from each sample with a knife (washed between 

samples), leaving a small block with a volume of about 

2 cc. This was boiled in 1:1 hydrochloric acid for 

about 30 minutes to remove calcareous and other acidsoluble constituents and to disintegrate the material. 

The remaining acid, various chlorides in solution, and 

fine clastic material in suspension were removed by repeated decantations after definitely timed settling periods. The coarse fraction, which had a more rapid 

settling rate than the diatoms, was removed by reversing the process. At this stage in the process the samples were carefully examined for diatoms, merely to 

determine their presence or absence. Several large! 

drops of the concentrated residue were removed with a 

clean pipette and examined under a microscope. Those 

showing no diatoms or diatom fragments were discarded as barren.

Organic matter was removed by boiling the above residue in concentrated sulphuric acid until it was well 

blackened and then adding granular sodium nitrate. 

Another series of timed decantations removed the acid 

and the remaining fine clastic material. In some of the 

samples containing a large percentage of clay, the boiling in sulphuric acid caused a pronounced flocculation,

which was dispersed by adding 20 cc. of concentrated 

sodium hydroxide solution to one of the decantations. 

Contrary to popular belief, diatoms are not visibly affected by standing in cold sodium hydroxide solutions 

of medium strength for more than a year. In the treatment described here the diatoms were exposed to the 

caustic solution for a few hours at the most.

The residue from the above procedure was snow 

white and consisted of diatoms, radiolaria, sponge 

spicules, volcanic ash, and quartz and other resistant 

minerals, all of which were presumably present in the 

original sample. This was separated into a coarse and 

a fine fraction by short-time settling and decantation 

and bottled for study. The fine fraction contained 

most of the diatoms and fine ash particles whereas the 

coar.se fraction contained the heavy minerals, quartz, 

radiolaria, coarse ash particles, and in some fractions 

a few very large diatoms. A drop of 40-percent formaldehyde solution was added to each bottle to prevent the growth of a mold, which, by some strange 

quirk of nature, can prosper on freshly washed diatoms 

and distilled water.

During the preparation described above, every effort was made to arrange the timing of the decantations so that few, if any, small diatoms were lost. 

This necessarily resulted in a final concentrate that 

still contained a little clastic material, but this was 

deemed of much less importance than the preservation 

of the original relative abundance of the diatoms as 

nearly as possible. The "beautifully cleaned material" 

of many diatomists is nearly always obtained at the 

cost of losing some of the smaller diatoms.

METHOD OF STUDY

As a result of the cleaning and concentrating operations described above, 29 samples were discarded 

as barren, leaving 38 samples containing diatoms in 

varying amounts. A total of 66 strewn slides mounted 

in Hyrax were made of the 38 samples, using 18-mm. 

round cover glasses. These were systematically traversed with a mechanical stage under a magnification 

of 350 diameters, and with sufficient overlap so that 

no part of the slide was missed. Diatoms were recorded in terms of the coordinates of the mechanical 

stage. A total of 380,000 separate fields were examined.

In addition, a number of arranged group slides on 

which the diatoms were individually selected and 

mounted under the microscope by means of the mechanical finger were prepared, primarily for convenience 

in making the photomicrographs used to illustrate this 

report.

The frequency of occurrence of each species on a slide

was observed and recorded for each slide and furnished

the basis for the fourfold grouping into abundant,

common, frequent, and rare, indicated on the check list

j of species given in table 9.
PART 3. DIATOMACEAE 57

TABLE 9.—Distribution and relative abundance of diatoms from Lord Kelvin cores, North Atlantic Ocean

[X Now living in North Atlantic Ocean. Ecology: M, Marine; B, brackish water; F, fresh water; N, neritic; O, oceanic; C, cold; T, temperate; W, warm. Relative abundance:

R, Rare; F, frequent; C, common; A, abundant]

sulcata (Ehrenberg) Kiitzing. _ ....... __.__x

oculus-iridis Ehrenberg var. borealis (Bailey)

crenulatus Qrunow var. nodulifer Lohman,

curvatulus var. minor (Ehrenberg) Qrunow _ _

octonarius Ehrenberg (=A. ehrenbergii 

Balfs) — .——-— — — - — — -— — — X

Asteromphalus roperianus Balfs var. atlanticus

campanulifer Schmidt ______ . ___ _____

senarius Ehrenberg (= A. undulatus of authors)-—————...———-——^

Thalassiothrix longissima Cleve and Granow____X 

Eunotia praerapta Ehrenberg var. bidens (W.

smithii (Br6bisson) Cleve.--- ___ ___________

Core no.

Sample no.

Depth below top 

of core (centimeters)

F

M 

M 

M 

M 

B 

M

F

T}

M

M 

M

M

M 

M 

M 

M 

M 

M 

M 

M

M 

M 

M

M 

M 

M M-B

M

M 

M

M 

M

M

M 

M 

M

M 

M 

M 

M M-B 

M

F

M 

F-B 

M M-B

M 

M 

M M-B

M

N 

N 

O

N 

N 

N

O

N

0

N 

N 

N 

? 

N 

?

N

N

N-O

N-O

0 

0

N 

N 

N 

N?

N N-O 

N-O

O

?

N 

O 

0 

0

N 

O

N

N 

N 

N 

N 

N 

N 

N?

T T-C 

T 

W 

C C-T 

T 

T 

W 

W

w 

c 

w 

w c-w

?

c

f

W-T 

W

c 

w

T 

T /p ?

T 

C 

T?

T T-W 

W

T

W?

W-T 

C 

Wc-w 

w 

c

T

W

T

W C-W

c-w

T-W 

W 

T C-W

3

3

3

R

--

R

E 

B

--

E

F

-

E

-

F

2

00

T

3

E

F

E

E 

E

C

F

F

A 

R 

R

R

E

F 

R

F

F

F

R

? h-1

OS

T

00

E 

R

F 

R

B 

B

F

F

A 

E

B

R

F

R

F

H-H

t^

CO

3 

§

R

F 

R

R

F

R

R 

R

F

F

A 

F 

R

R

F 

F

F

C 

F

C

F

A

R

IO±

IN

O>

3

oc

R

--

R

--

R

--

--

F

co 1

CO

83

co 

S3

F

B

R

R

C 

F

R

R

R

F

R

R

r

t^to?CO&

R

--

R

F 

F

R

R

4

<?

*C

2 t^

--

--

R

--

--

R

o~

o> t~i

--

R

F

F

F

B

F

F

F

F

R

F

C

R

R

F

5

to

7

2

R

R

R

--

R 

R

R

R

OS 

TJ

00

2co

R

F

R

R

C

F 

F

R

C

^

10

oc I•*

--

--

F

F

R

-

R 

R

F

9

CO

7

R

R

-

R

--

R

F

6

o

CO

>o 

•* 

1

o

R

F

c

F

--

F 

R

R

F

R

F

F

R

R

F

A

F

3

<M

I

8

R

F

F

R 

F

R

F 

R

R 

F

R

R

F

F

R

R

A

F

IN

CO

>O?•

oc

F

R

R 

R

C

F

F

R

R

C

CO"

g*

J

R

F 

F

R

F

R

F

F 

F

F

*C"

00

oc i

R

--

--

t^

CO1

i

--

c 

c

F

F

F

F

R

F

C

R

R

F

o>

CO

i

k

-

-

R

7

T

t^

co'

R

R

-

•*•^

tc

i

F

-

R

CO

T

*O

8

i

R

R

-

--

9

1

CO

R

R

R 

R

R

R

R

R

R

R

R

§

CO

2•*

R

F

R 

B

F 

R

R

R

F

1j

•*i1-H

R

F

F

F

F

R

R

R

F

F

F

F

R

R

R

F

F

F

R

F

R

C

R

R

R

cs I3

IT.

i

--

R

F

F

R

R

C

R

F

R

A

F

R

R

F

F

R

R

R

R

F

R

F

C

R

S

oc

1-H1

R

R

B

R

•* 

1

CO

s§

--

F 

R

R

B 

B

F

A

C 

B

F

B

F

R

R

R

F

R

C

R

B

o

CM 

^

CN

R

F

R

F 

R

R

R

F

CO"L

IN t^

SCO 

IN

B

R

R

F

F

R 

R

F

F

R

C

10

^

I

--

R

R

R 

R

R

-

0>?

3 i

00

--

F

F

F

C 

R

F 

C 

R

F

F

R

R

R

^

I>-

!

8

F

R 

R

R

B

B

R

R

-

R

1

i 

i

R

R

__

R

R

R

12

IN CO

^

CO

-.2is

F F

F"

F ..

R.. 

F__

R

R..

DISTRIBUTION OF DIATOMS IN THE CORES AND THEIR 

ECOLOGIC SIGNIFICANCE

The distribution of samples in the cores and the 

relative abundance of the diatoms in them are shown 

graphically in plate 11. The diatom occurrences were 

extremely spotty, for which no adequate explanation 

was found as a result of this investigation. In cores 

3, 6, and 9, diatoms were fairly well distributed 

throughout, although in each core they were more 

abundant in the upper parts. Cores 3 and 9 were the 

only ones from which every sample collected contained 

diatoms, and core 9 was the most highly diatomaceous 

of all. Parts of this core are really impure diatomite. 

In addition to the three mentioned above, cores 7 and 

10 contained a few diatoms in the lower part. The 

other cores contained diatoms only in the upper parts.

The barren samples contained Foraminif era in varying 

degrees of abundance, some ostracodes, coccoliths, radiolaria, sponge spicules, and molluscan fragments, 

clastic material ranging from extremely fine clay to 

coarse sand and pebbles, and a considerable amount of 

volcanic ash which was restricted to definite zones. 

As these constituents have been studied by other investigators, they will not be considered here.

The diatom flora from the cores consists of 52 species 

and varieties distributed, with respect to geologic age, 

as follows:

Recent only____________________— 12 

Recent and fossil_________________± 36 

Fossil only (?)____________________ 1 

New species and varieties_____________ 3

52
58 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

The only diatom in the core (aside from the two 

species and one variety here described as new) that is 

not known definitely from floras living today is Ooscinodiscus convewus Schmidt, described originally from 

Miocene rocks on the island of Barbados 1 and also 

reported from middle Miocene rocks in California by 

Hanna.2 Heiden and Kolbe 3 reported this species from 

Observatory Bay, Kerguelen, but did not state whether 

or not the diatom was in a living state when found. It 

was found commonly to rarely in most of the samples 

from core 9, but no geologic significance could be inferred from this occurrence. .The remainder of the 

species are either Recent only or are found both in living 

material and in fossil beds ranging from Cretaceous to 

Pleistocene. Therefore, no geologic age can be assigned 

to any parts of the core purely on the basis of the 

diatoms.

An analysis of the ecologic conditions represented by 

the diatom flora proved much more fruitful.

Of the 52 species and varieties of diatoms found in 

the 38 diatomaceous samples from the cores, only 17, 

or 33 percent, have been reported by Lebour,4 as living 

in the North Atlantic at the present time. These have 

been indicated in the first column of the check list. 

Although it is true that the 67 percent that are missing 

from the cores include many plankton diatoms that are 

only slightly silicified and hence might not have been 

preserved in the sediments, the fact remains that some 

of these slightly silicified plankton diatoms were found. 

Chaetoceros atlanticivm, Cleve, a planktonic diatom of 

this type, was found in an excellent state of preservation 

in the top of core 6 and in a sample taken 142KL51 

centimeters below the top of core 9. Rhizosolenia stylirformis Brightwell, another species of the same type, was 

found at various depths in three cores down to 238 centimeters below the top. Furthermore, many of the species in the missing 67 percent are heavy-walled, massive 

species belonging to the genera BiddulpMa, Triceratiwn, and HemJumjilus, which would have been preserved 

had they been present.

Diatoms, particularly the planktonic species, are necessarily so constructed that they have a very large surface per unit weight and hence are able to float in the 

water. Their settling time in 2 to 3 miles of sea water, 

turbulent in the upper part and having relatively high 

density and viscosity in the lower part, must be very 

long. The large number of variables present, many of 

which are unknown, make any computation of the settling time uncertain, but it must be measured in hun1 Schmidt, Adolf, Atlas der Diatomaceenkunde, pi. 60, fig. 15, 1878.

3 Hanna, G. D., The diatoms of Sharktooth Hill, Kern County, California : California Acad. Sci. Proc., 4th ser., vol. 20, No. 6, p. 179, pi. 6, 

figs. 2, 3 ; pi. 7, fig. 1,1932.

9 Heiden, Heinrich, and Kolbe, R. W., Die marinen Diatomeen, in Von 

"Drygalski, B., Die deutsche Sudpolar-Expedition 1901-1903, Band 8, 

Botanik, Heft 5, p. 497, 1928.

* Lebour, M. V., The planktonic diatoms of northern seas, Ray Soc. Mon. 

116, 244 pp., 1930.

dreds of years. If this is true the difference between 

the flora from the cores and that living in the overlying 

sea today is not so surprising as it appears to be at first 

sight. Apparently many of the species found at present 

in the upper waters of this part of the North Atlantic are 

not deposited on the saa floor directly beneath but are 

carried away by currents and deposited elsewhere.

This idea is greatly strengthened by the fact that a 

very large percentage of the diatoms from the cores are 

warm-water forms that thrive in subtropical and even 

in tropical waters today and were probably introduced 

into the North Atlantic by currents such as the northward-flowing Gulf stream.

In order to obtain some roughly quantitative data that 

would lead to an approximate determination of the 

origin of the diatoms found in the cores, three columns 

giving the ecology have been included in the check list, 

table 9.

In these columns, the second, third, and fourth, an attempt has been made to list the broader subdivisions 

of ecologic conditions into which the living counterparts of the diatoms from the cores are found today. 

The type of water (marine, brackish, or fresh) in which 

the species lives today is indicated in the second column. 

The type of environment with respect to the coast line, 

oceanic (living and reproducing in the open sea) or 

neritic (living and reproducing near the coast), is indicated in the third column. In the fourth column are 

listed the dominant temperature facies for each species 

in a threefold qualitative classification of warm, temperate, and cold. In all three columns species that are 

found living in two or more ecologic subdivisions are so 

indicated; for example, C-W indicates that a species is 

more or less indifferent to considerable temperature 

differences and can prosper in all types of water from 

cold to warm.

The distribution of species with respect to the ecologic facies represented is summarized according to two 

methods of approach in table 10. In the first column 

on the right, the percentage of the total number of 

species and varieties found (52) is given for each classification. In the second column on the right the percentage of the total number of individuals in each 

classification is given. This second column has been 

computed from the data given in the check list, weighting the different diatoms according to their abundance 

as follows: R (rare)=l; F (frequent) =3; C (common) =6; and A (abundant) =10. These figures are 

purely arbitrary but represent the order of magnitude 

of the relative abundance and certainly give a much 

more accurate ecologic census than the unweighted 

figures in the first column.

The high percentage of marine species is to be expected, as the nonmarine forms are obviously accidentally introduced, either by ocean currents carrying 

fresh-water and brackish-water forms out from the 

mouths of rivers or by floating icebergs.
PART 3. DIATOMACEAE 59

TABLE 10.—Ecologic census of the cores as a whole

A. Type of water:

Marine and brackish

Brackish___ _ _ _ ____ _

Fresh______ _____ __ _______

B. Relation to coast: 

Neritic_ _____ ______

Oceanic _____

Indeterminate- _ ______

C. Temperature: 

Warm__ ______ _ ___

Warm-temperate __ _____ ___

Temperate __ _ ______

Temperate-cold _ ____ __

Cold__________.____________

Cold to warm. ___ _

Percent (unweighted, based 

on number of 

species)

82.8

7.7

1.9

3. 8

3.8

100. 0 

52. 0

19. 2

7.7

21. 1

100.0

28.8

7.7

27.0

3.8

15. 4

7.7

9.6

100. 0

Percent (weighted according to 

relative abundance)

96. 8

2. 5

.2

. 2

.3

100. 0 

45. 9

23.0

23.7

7.4

100. 0 

28.6

9.5

14. 6

5.2

32.0

4. 1

6.0

100.0

The relatively high percentage of neritic forms is 

much more significant, as most of the diatoms constituting the present-day plankton of the North Atlantic 

are oceanic forms.

The distribution of different temperature facies for 

the cores as a whole shows a slight predominance of 

cold-water forms, although the percentage of warmwater forms is high for the latitude in which the cores 

were taken.

In order to show the change in the various ecologic 

factors from core to core the percentages of the different classifications were determined for each core, 

weighted according to relative abundance by the 

method used above. The results are shown in table 11.

The presence in core 7 of only five species, represented 

by a very small number of individuals, makes the percentages from this core erratic and misleading. For 

this reason core 7 will not be considered in the discussion 

to follow.

In all the cores the percentage of neritic species is 

much higher than the percentage of oceanic species. 

Furthermore, there is an increase in the percentage of 

neritic species going from core 3 to core 13, that is, 

from west to east. The percentage of oceanic species 

is much less in the eastern cores than in the western 

ones.

The change in temperature indicated by the diatoms 

is equally striking. The percentage of warm-water 

forms increases from west to east, with an even more 

rapid decrease in the percentage of cold-water forms 

in the same direction.

One of the most striking features on the profile 

across the North Atlantic along the line of the cores 

(see fig. 1) is the sharp mid-Atlantic ridge, which at 

that locality is known as the Faraday Hills. It seems 

reasonable to believe that such a pronounced topographic feature must affect ocean currents, at least in 

the immediate vicinity. To test this hypothesis with 

the data at hand, the percentages of diatoms falling in 

the last two groups (relation to coast and temperature) 

were determined and weighted according to the method

TABLE 11.—Ecologic census by cores, percent, weighted according to relative abundance

A. Type of water: 

Marine- _____ ___

~R|-Q /-Ifl oVl

TTvpfili

B. Relation to coast: 

Neritic- _ _ _ . _

Indeterminate _ - .

C. Temperature: 

Warm. _ _

Temperate-cold

Cold__ _____________________________

Cores

96

3

1

100

45

17

36

2

100 

22

9

13

5

40

9

2

100

Core 4

98

2

100

47

25

18

10

100 

25

15

18

35

7

100

Core 5

92

6

2

100

49

31

18

2

100

24

16

11

6

43

100

Core 6

95

5

100

48

30

16

6

100 

30

10

14

4

35

4

3

100

Core?

75

25

100 

50

12

12

26

100 

25

37

38

100

Core 9

98>£

1

%

100 

39

28

20

13

100 

27

8

15

3

31

3

12

100

Core 10

97

3

100 

54

9

27

10

100 

32

14

14

7

20

2

11

100

Core 12

100

100 

56

22

22

100

44

33

6

17

100

Core 13

98

2

100 

60

8

30

2

100 

62

8

20

8

2

100
60 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

described above and placed in two columns (table 12), 

one containing the percentages of all diatoms occurring 

west of the ridge (cores 3, 4, 5, and 6) and the other 

containing the percentage^ of all diatoms occurring 

east of the ridge (cores 9, 10, 12, and 13). The group 

for the type of water is not included as it does not 

appear to have any significance.

TABLE 12.—Ecology of diatoms west and east of the Faraday Hills

B. Relation to coast: 

Neritic__-_-_ __ _ _ _ __

Oceanic _____ _

Neritic-oceanic_ _ _____

Indeterminate. __ _ __ _ _

C. Temperature: 

Warm _ _ ______

Warm-temperate _ __ _______

Temperate. _ ___ ______

Temperate-cold___ _______

Cold______.____________________

Cold-warm___ _ _ _ _ _ _

Indeterminate. __

Percent, weighted according 

to relative abundance

West of 

Faraday Hills

47 

26 

22 

5

100

25 

13 

14 

4 

38 

3 

3

100

East of 

Faraday Hills

52 

11 

25 

12

100

41 

8 

12 

13 

15 

1 

10

100

The distribution shown in table 12 indicates a marked 

difference in the ecologic significance of the diatom 

floras on each side of the mid-Atlantic ridge.

The flora from the cores east of the ridge contains a 

much larger proportion of neritic species than the one 

from the cores west of the ridge. Still more obvious is 

the marked difference in temperature shown by the two

floras. The eastern flora contains more than twice as 

many warm-water species as the western flora. In figure 

22 the directions of ocean currents according to Schott 

are shown. The cores west of the mid-Atlantic ridge 

lie in the path of contact of the warm Gulf Stream and 

the cold Labrador Current, which means that a large 

percentage of the flora was probably introduced by the 

cold waters from the north. On the east side of the midAtlantic ridge, however, the warmer Gulf Stream is 

the dominant current and has undoubtedly contributed 

a large share of the diatoms found in cores 9 to 13, inclusive. In addition to the warm-water species introduced by the Gulf Stream, the sediments on the east side 

of the ridge probably received many warm-water diatoms brought northward along the European coast by 

a warm deep current from the Mediterranean Sea, 

which, according to Harvey 5 has been found by Nansen 

as far north as Ireland. The proportion of the warmwater species found in the cores east of the mid-Atlantic 

ridge that were introduced by this deeper current is not 

known, but it may be rather high, as the percentage of 

warm-water forms increases rapidly going east from the 

ridge.

Although the mid-Atlantic ridge may not have a pronounced effect on the dominantly surficial currents of 

the sea, such as the Gulf Stream, it appears highly probable that the deep-seated outflow from the Mediterranean would be largely restricted to the eastern basin 

of the North Atlantic by it.

The lithologic studies of Bramlette and Bradley in 

part 1 of this report have shown the existence of two 

zones of volcanic ash and four zones in which sand and

6 Harvey, H. W., Biological chemistry and physics of sea water, p. 116, 

1928.

90" 80" 70" 60° 50° 4O° 3O" 2O° Id" O"

FIGURE 22.—Map of the North Atlantic Ocean showing the location of the core stations, by numbers, and the distribution of the surface currents, 

by arrows. The larger arrows indicate the most rapid currents and the smaller arrows slower currents. The stippled areas represent places 

where tidal currents predominate. (After Schott, Gerhard, Geographie des atlantischen ozeans, 2d ed., pi. 15, 1926.)
PART 3. DIATOMACEAE 61

pebbles are relatively abundant and calcareous organisms are scarce. The zones of sand and pebbles are 

interpreted as glacial marine deposits formed probably 

during the latter part of the Pleistocene. The alternation of warmer and colder zones was substantiated by 

the independent work of Cushman and Henbest, who 

studied the Foraminifera from the cores. (See part 2, 

Foraminifera.)

In order to determine whether or not the evidence 

offered by the diatoms agreed with this determination, 

the distribution of the diatoms in each core was studied 

statistically by the following method, suggested by 

Parker D. Trask, of the Geological Survey, to whom 

acknowledgment is here made.

The diatoms were weighted according to relative 

abundance in a threefold classification of warm, temperate, and cold, for each sample. Species having more 

than one temperature facies represented in the check 

list, such as warm-temperate or temperate-cold, etc., 

were given equal counts for each temperature. The 

warm-water totals were multiplied by +1, the temperate totals by 0 and the cold-water totals by —1. The 

algebraic sum of the totals for the warm-water and 

cold-water columns was then divided by the sum of the 

totals for warm, temperate, and cold forms, and the 

resulting ratio was taken as the mean for each sample. 

The means, obviously, varied between the limits of +1 

and —1 and were used as numerical indicators of the 

temperature facies represented by the diatom flora as 

a whole in each sample. The probable error was computed by the method of least squares in order to give 

some idea of the reliance (from a purely statistical 

point of view) to be placed on each determination.

The results are given in table 13 and are shown graphically on plate 11.

The temperature facies indicated by the diatoms from 

different parts of the cores when plotted by the above 

method bear no apparent relation to those obtained by 

Bramlette and Bradley from the lithologic evidence and 

by Cushman from foraminiferal evidence. In the most 

extreme disagreement, sample L-20 in core 5, the diatoms show an abrupt change to relatively warm conditions during the middle of one of the glacial stages outlined by the above authors. W. H. Bradley 6 has 

suggested that the temperature picture given by the 

diatoms may be correct but out of phase with the lithological and foraminiferal evidence on account of the 

much longer settling time of the diatoms. This appeared to be a promising lead, which was tested by sliding the chart for the lithologic and foraminiferal 

evidence (pi. 4, pt. 1) up and down over plate 11. It 

seems reasonable to believe that, if this hypothesis were 

correct, the difference in phase might be approximately 

the same for all the cores. When the diatom chart was 

superimposed upon the lithologic chart of Bramlette

TAELE 13. — Distribution of the diatoms according to temperature facies

Core 3--- _ _ .__

Core 4.. _________

Core 5 _ . _ _

Core 6___ _______

Core 7_____ _____

Core 9_-_-_______

Core 10_ — ______

Core 12__. _______

Core 13

Sample 

No.

L-1 

L-2 

L-3 

L-4 

L-5 

L-6 

L-7

L-8 

L-10

L-16 

L-19 

L-20 

L-23

L-30 

L-31 

L-32 

L-33 

L-35 

L-37 

L-39

L-40 

L-44 

L-46 

L-49 

L-50 

L-51 

L-52 

L-53 

L-54 

L-55 

L-56

L-58 

L-59 

L-60 

L-61

L-62 

L-63

L-65

Weighted totals

Warm

4 

23 

10 

31 

1 

10 

4

1 

15

1 

10 

8 

2

21' 

14 

12 

12 

0 

21 

0

1 

1 

0 

4 

2 

18 

19 

1 

17 

10 

13

3

16 

5 

1

8 

0

28

Temperate

3

11 

10 

23 

1 

5 

3

1 

12

3 

9 

3

2

8 

13 

11 

10 

1 

7 

1

1 

3 

2 

3 

2 

16 

13 

1 

12 

4 

6

2 

6 

4 

3

3 

3

16

Cold

7 

26 

23 

38 

1 

13 

5

1 

13

4 

13 

3 

5

21 

19 

13 

5 

1 

17 

0

0 

3 

0 

4 

8 

15 

21 

3 

19 

5 

9

1 

8 

3 

2

4 

3

5

Mean

-0. 21 

-.05 

-.30 

-.08 

.00 

-. 11 

-.08

.00 

+.05

-.37 

-.09 

+.36 

-.33

.00 

-. 11 

-.03 

+.26 

Indet. 

+.09 

Indet.

+.50 

-.29 

Indet. 

.00 

-. 50 

+.06 

-.04 

-. 40 

-.04 

+.26 

+.14

+.33

+.27

+.17 

_ ]*j

+.27 -.50

+.47

Probabje 

error

±0. 16 

±.08 

±. 10 

±.05

±. 12 

±.17

±.09

±.24 

±.10 

±.19 

±.23

±. 09 

±.09

±. 12

±. 09

±. 16 

±. 22

±.24 

±.08 

±.08 

±.34 

±.08 

±.16 

±. 12

±.27 

±. 12 

±.17 

±.21

±. 17 

±.29

±. H

8 Oral communication.

and Bradley and displaced downward a distance equal 

to 46 centimeters of the core, a good agreement was obtained in cores 5 and 12, and a fair agreement in cores 

6 and 9. The displacement is in the right direction, but 

the amount of the displacement necessary for a reasonably good agreement seems excessive. W. H. Bradley,7 

in calculating probable rates of deposition for the sediments comprising the deep-sea cores, arrived at a figure 

of approximately 15,000 years per foot of sediment. 

The 46 centimeters difference in phase mentioned above 

would correspond to somei 23,000 years as the difference 

in settling time between the coarse clastic material and 

the diatoms, which does not appear at all reasonable or 

probable.

Attempts to apply Stoke's law concerning the settling 

velocity of spherical particles in a viscous medium to 

the problem of determining the settling time of diatoms

7 Oral communication.
62 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

in sea water were abandoned, owing to the difficulty 

in arriving at an adequate means of correcting for the 

deviation from a sphere in the shape of the diatoms 

and in arriving at an even reasonably accurate figure 

for their effective density. It appeared that a figure 

giving more nearly the correct order of magnitude 

would be obtained by extrapolating an experimentally 

determined rate of settling under known conditions.

Experiments on the settling time of some of the 

diatoms from the cores were, therefore, made in a 

short vertical column 10 centimeters high, and an 

average time of 60 minutes for the .smaller forms 

(10/i to 20/t in diameter) was found to be necessary 

for settling in undisturbed distilled water at 20° C. 

The difference in density between sea water and distilled water was disregarded, but the relatively great 

increase in viscosity with -reduced temperature was 

considered in the calculation. The figures obtained 

were 52 years for distilled water at 5° C. and 64 years 

for distilled water at 0° C. These figures appear to 

be .very small, especially when compared with the 

former figure of 23,000 years, but they are at least 

reasonable, if several factors are taken into account 

whose magnitudes are difficult to estimate even approximately. The figures of 52 years for water at 

5° C. and 64 years for water at 0° C., are probably of 

the right order of magnitude for the conditions stated 

but are only very roughly approximate at best. Furthermore, they are tremendous extrapolations from 

very meager data and even if correct would be so only 

for undisturbed distilled water. The conditions in a 

deep ocean basin, such as the North Atlantic, are so 

much more complex than the ideal conditions under 

which the calculations were made that the figures when 

applied to the ocean basin are no longer even of the 

right order of magnitude. Amid all these uncertainties, however, one thing is certain. The actual 

settling time for the diatoms found in the cores must 

have been much greater than the 64 years computed 

for the hypothetical conditions. A large part of this 

increase is due to the greater density and viscosity of 

sea water. The net effect of turbulence in the surficial 

waters on the settling time is probably zero because 

as many diatoms would be accelerated as retarded, but 

the slow upwelling of deeper waters might locally 

retard settling. A final broad approximation of several hundred years appears to be the order of magnitude of the settling time for the diatoms in the cores 

from the North Atlantic. This order of magnitude, 

although approaching the realm of pure speculation, 

appears at least qualitatively reasonable.

This figure is not sufficiently precise to offer a means 

of adjustment for the discrepancies between the temperature variations plotted on plate 11 and those of 

Bramlette and Bradley, but it does offer a means of investigation of some of the anomalies that have occurred 

in the data presented previously.

Even if the minimum figure of several hundred years 

for the settling time of diatoms in deep ocean basins 

is accepted, it is obvious that any interpretation of 

the ecologic factors involved in the composition of a 

diatom flora found at great depth is greatly complicated 

by other factors. The lack of light at great depths 

rules out the possibility of any diatoms living attached 

to the bottom. The turbulence of the upper waters and 

various ocean currents render it extremely improbable 

that any diatoms living in the surface waters will be 

eventually deposited on the sea floor directly beneath. 

It follows, then, that the path of a diatom from the surface to the bottom is never along a vertical line but 

always along an inclined one, the direction and degree 

of inclination of which may change many times before 

the final landing. The path is further complicated by 

the fact that diatoms are used as food by many marine 

animals, and the f rustules may be transported unknown 

distances before being ejected and allowed to begin new 

paths toward the bottom. Furthermore, according to 

Bramlette and Bradley (pt. 1, Lithology and geologic 

interpretations), the alkalic volcanic glass shards have 

apparently been reworked from the tops of mounds and 

ridges on the sea floor and have been drifted about over 

large areas by bottom currents so that they are now 

distributed through a considerable thickness of sediment 

above the original ash layers. Any such bottom currents would of course also move diatoms about over the 

sea floor and tend further to augment the randomness 

of their ultimate distribution in the sediments. All 

these variable factors affect the final resting place, but, 

unfortunately, few can be evaluated even to the order 

of magnitude.

Thus the discrepancy between the present-day surface diatom flora in the North Atlantic and that found 

in the cores is not surprising and needs no further 

comment.

The large percentage of warm-water species in the 

cores is not surprising as more than sufficient time was 

available for their transportation from warm habitats. 

Some of the diatoms necessarily started for the bottom 

many hundreds or possibly thousands of miles from 

their final resting place. Even if no other agency influenced its course, a diatom might travel many miles 

before it got out of the zone of influence of the Gulf 

Stream alone.

The fact that, even by displacing vertically the 

plotted temperature deviations indicated by the diatoms 

(pi. 11) from those obtained by other means, only partial agreement was obtained is not anomalous when the 

slow settling rate is considered. Although the settling 

rate for diatoms in still water might be nearly the same 

in different parts of the ocean of equal depth, it is 

highly improbable that the various complicating factors operated to produce the same net effect on the settling rates for the diatoms in all of the cores, or even 

for all the samples in any one core. For example, in
GEOLOGICAL StJhVEV

L-6

E 4 ,

•L-8

L-10 

L-ll

L-IS

L-19

L-22

L-23

L-24

L-33

L-39

-0.5

-1.0 Meter

EXPLANATION

Diatomaceous samples

L-50

L-S2

L-53

L-56

Barren samples

I (3

L-58 

L-5Q

CHART SHOWING DISTRIBUTION AND TEMPERATURE SIGNIFICANCE OF THE DIATOMS IN THE CORES.

Each core is represented by a column whose length is indicated by the meter scale below column 8. The samples are indicated by patterned rectangles. At the right of each rectangle 

is the sample number, and at the left is a letter indicating the relative abundance of the diatoms: R, rare; F, frequent; C, common; and A, abundant. The mean temperature 

fades indieated by the diatom flora of each sample is indicated by die position of a dot within the sample rectangle. The distance of the dot from the center line of the column is 

a measure of the warmness or coldness of the diatom enyironment indicated by the assemblage of diatoms in the sample. As a visual aid, these dots in the rectangles are connected 

by dotted lines.

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L-62 C

L-63

L-64

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L-65

L-66

L-67

PART 3. DIATOMACEAE 63

core 8, taken at the top of the mid-Atlantic ridge, the 

absence of diatoms as well as other fine constituents has 

been explained by Bramlette and Bradley as due to the 

winnowing out of the fine material from the top of the 

ridge during deposition by a bottom current apparently 

flowing eastward. This idea is strengthened by the 

unusually high percentage of fine material and diatoms 

found in core 9, taken at the eastern base of the ridge.

The maximum settling time for the diatoms is probably of the order of magnitude of several hundred years, 

based on the extrapolation of the laboratory experiments. This is so different from the very large figure 

of 23,000 years obtained by vertical shifting of the 

plotted temperature deviations (pi. 11) that the larger 

figure appears to have little significance. If this is so, 

the partial agreement in temperature variation between 

the diatom data on the one hand and the foraminiferal 

and lithologic data on the other may be entirely fortuitous. This possibility is strengthened by the fact that 

the agreement was not uniform for all the cores. Dr. 

Roger Revelle, of the Scripps Institution of Oceanography, has suggested 8 that the partial agreement between the two lines of evidence may not be fortuitous 

but may be due to changes in ocean currents caused by 

the advance and recession of the ice during glacial and 

interglacial epochs. At present (see fig. 22) the warm 

Gulf Stream swings in a general northeasterly direction 

along the line of the cores, particularly in the region 

from the mid-Atlantic ridge eastward. It seems highly 

probable that during the maximum southerly advance 

of the drift ice in a glacial epoch the Gulf Stream would 

be deflected southward. Presumably the cold Labrador 

Current would be weaker during a glacial epoch than 

during an interglacial one. Thus, although the Gulf 

Stream bringing the tropical forms northward would 

actually be deflected somewhat to the south, nevertheless 

the slackening of the Labrador Current might result 

in the deposition of a higher percentage of warm-water 

diatoms along .the line of the cores in a glacial epoch 

than in an interglacial epoch. Furthermore, owing to 

probable lobelike extensions on the southern limit of the 

glacial ice in the North Atlantic, the difference in phase 

between diatoms and Foraminifera might be quite different in the different cores.

This idea is included here as a frank speculation, as it 

cannot be proved with the available data. The results 

of subsequent comparisons of temperature f acies based 

on diatom and f oraminiferal data may corroborate! this 

speculation and form one method of approaching the 

almost untouched field of paleo-oceanography.

The most definite generalization that has come out of 

my study of the cores from the North Atlantic is that 

much more caution is needed in making geologic or 

ecologic interpretations of diatom floras from very deep 

ocean basins than from shallow basins where the chances

8 Personal communication.

are much greater that the organism will be deposited in 

nearly the identical geographic location as the one in 

which it lived.

SYSTEMATIC DESCRIPTIONS

The classification of diatoms has occupied the attention and exercised the imagination of many students of 

these organisms during more than a hundred years, 

and has been based primarily, by different authors, upon 

the mode of living, the nature and distribution of the 

endochrome, the presence or absence of a raphe, the 

external shape of the valves, the type of symmetry 

developed by the markings on valves, and upon various 

combinations of the above.

From the point of view of the paleontologist, any 

system of classification that depends, even in part, upon 

the soft (and hence usually unfossilized) parts is not 

satisfactory. Although relatively few of the students 

of diatoms have been geologists or paleontologists, 

nevertheless a great many workers have studied fossil 

diatoms in the eternal search for new and interesting 

species. As a result, only the classifications based on 

the shape, structure, and markings of the "indestructible" siliceous1 shell have survived.

During the last 30 or 40 years the excellent classification proposed by Schiitt in Engler and Prantl's Naturliche Pflanzenfamilien, which was published in 1896, 

has been almost universally followed. In Schiitt's 

scheme the diatoms were divided into two suborders, the 

Centricae, in which the structure and markings were 

related to a central point, and the Pennatae, in which the 

structure and markings were related to a longitudinal 

line. Aside from minor changes in the naming of the 

suborders and slight rearrangement of families, little 

real change and almost no improvement have been introduced during the 40 years following the first appearance 

of Schiitt's classification. In 1937 Hendey 9 proposed a 

new classification based in part on Schiitt's earlier one 

but eliminating the twofold separation into centric and 

pennate forms. As Hendey points out, such genera as 

Biddulphia, Chaetoceros, Rhizosolenia, Anaulus, and 

Triceratiidm do not fall into either of Schiitt's major 

divisions. For convenience Schiitt and all who have 

followed him have included the above genera, as well 

as others equally unfit, in the Centricae. Hendey considers the diatoms as a class of Algae, Bacillariophyceae, 

comprising 1 order, Bacillariales, which is divided into 

10 suborders. The 10 suborders are again divided into 

families and subfamilies in the customary manner. The 

scheme is simple and workable and removes many of the 

anomalies and ambiguities inherent in the older system. 

It is unfortunate that Hendey included in his classification only a few genera outside of those he encountred in 

the material from the southern seas. Although it is

9 Hendey, N. I., The plankton diatoms of the southern seas: Discovery 

Kepts., vol. 16, p. 199, 1937.
64 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

true that other authors will undoubtedly add genera 

with which they happen to be working, it would seem 

better if the one who proposed a new classification 

would make it as complete as possible. In spite of this 

lack it is a most valuable contribution and is the system 

followed in this report.

A synonymy is given for each species, arranged according to standard practice in the Geological Survey. 

The description by the founder of the species is cited 

first; next, references to the species and genus as at 

present accepted, in chronologic order; and last, synonyms and misidentifications, also in chronologic order. 

Complete synonymies have not been attempted, as 

to do so would have lengthened the report out of all 

proportion. For the same reason, descriptions have been 

given only for species that were considered to be new 

or inadequately described elsewhere. All species are 

illustrated, however, and references are given either 

to adequate descriptions or illustrations, or both.

ALGAE

Class BACILLARIOPHYCEAE 

Order BACILLARIALES

Suborder DISCINEAE

Family COSCINODISCACEAE

Subfamily MELOSIROIDEAE

Genus MELOSIRA Agardh, 1824

Melosira granulata (Ehrenberg) Ralfs 

Plate 12, figure 9

Gaillonella granulata Ehrenberg, K. Akad. Wiss. Berlin Abh.,

1841, p. 127, many figures, 1843.

Ehrenberg, Mikrogeologie, pi. 33, group 2, fig. 15,1854. 

Melosira granulata (Ehrenberg) Ralfs, in Pritchard, A., History

of the Infusoria, 4th ed., p. 820, 1861. 

Van Heurck, Synopsis diatome"es Belgique, pi. 87, figs. 10-12,

1882. 

Schmidt, Atlas der Diatomaceenkunde, pi. 181, figs. 51, 08,

1893.

Boyer, Acad. Nat. S'ci Philadelphia Proc., vol. 78, supplement, p. 30, 1926. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und

der Schweiz, Teil 1, p. 248, fig. 104, 1927. 

Hustedt, in Pascher, Die Stisswasser-Mora Mitteleuropas,

Heft. 10, 2d ed., p. 87, fig. 44, 1930.

This fresh-water diatom was found rarely in sample 

L-16 from the top of core 5 and in samples L-46 from 

core 7. It may have been deposited from a melting 

iceberg or may have been carried out to sea from the 

mouth of some river. Its presence in the cores indicates 

the extent of the migration of diatom tests in the open 

sea. The nearest land is the Azores, some 600 to 700 

miles distant.

The spelling of Gaittonella is variable, Gallionell-a, 

Gaillionella, and Gaillonella often occurring in different parts of the same paper. Hustedt,10 noting that 

the word is taken from Gaillon, prefers the form here

10 Hustedt, Friedrich, Die Kieselalgen Deutschlands, Osterreichs, und der 

Schweiz, Teil 1, p. 226, 1930.

given, although in the same work he also used 

GaUionella.

Dimensions of figured specimen (U. S. G. S. diatom 

catalog no. 1928-1) : Length, 20/*; diameter, T/*. From 

sample L-16 (U. S. G. S. diatom locality 2817), 0-2 cm. 

below the top of core 5.

Found rarely in samples L-16, L-40, and L-46.

Melosira sulcata (Ehrenberg) Kiitzing 

Plate 12, figure 1

GiiUoneHa sulcata Ehrenberg, Die Infusionsthierchen als vollkommene Organismen, p. 170, pi. 21, fig. 5, 1838. 

Melosira sulcata (Ehrenberg) Kiitzing, Die kieselschaligen

Bacillarien Oder Diatomeen, p. 55, pi. 2, fig. 7, 1844. 

Van Heurck, Synopsis diatomees Belgique, pi. 91, figs. 15,

16, 1882. 

Schmidt, Atlas der Diatomaceenkunde, pi. 178, figs. 1-5,

7-19, 22-24, 1893. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und

der Schweiz, Teil 1, p. 276, figs. 118, 119, 1928. 

Hendey, Discovery Reports, vol. 16, p. 235, 1937. 

Orthosira marina W. Smith, Synopsis of the British Diatomaceae, vol. 2, p. 59, pi. 53, fig. 338, 1856. 

Paralla sulcata Cleve, K. Svenska Akad. Haiidl., Bihang, Band

1, no. 13, p. 7, 1873. 

Schmidt, Atlas der Diatomaceenkunde, pi. 176, figs. 28,

32-39, 42-44, 46, 1893.

Orthosira sulcata O'Meara, Royal Irish Acad. Sci. Proc., vol. 

2, ser. 2, p. 252, 1876.

This cosmopolitan species was found in nearly every 

sample examined, ranging in abundance from rare to 

frequent. It is fundamentally a littoral form, although sporadically found in plankton. It is fairly 

uniformly distributed throughout most of the cores. 

Melosira sulcata has a long geologic history. It is 

known from the Eocene to the Recent, and Schulz 11 

has recently reported a variety, siberica Grunow, from 

a Cretaceous coral rock in Danzig Bay. In littoral 

deposits of various ages it is usually common to abundant. Hendey 12 has commented on its rarity in the 

Antarctic Ocean.

Diameter of figured specimen (U. S. G. S. diatom 

catalog no. 1983-1), 32 /x. From sample L-63 (U. S. 

G. S. diatom locality 2876), 30.5-33 cm. below the top 

of core 12.

Found rarely in samples L-l, L-2, L-3, L-4, L-5, 

L-16, L-19, L-23, L-30, L-31, L-33, L-35, 1^49, L-50, 

L-51, L-53, L-55, L-56, and L-61 and frequently in 

samples L-6, L-32, L-44, L-60, L-62, L-63, and L-65.

Genus PODOSIRA Ehrenberg, 1840 

Podosira stelliger (Bailey) Mann

Plate 12, figures 5, 6

Hijalodiscus stelliger Bailey, Smithsonian Contr. Knowledge, 

vol. 7, p. 10, 1854.

11 Schulz, Paul, Diatomeen aus senonen Schwamgesteinen der Danziger 

Bucht: Bot. Arclliv. Band 37, p. 393, fig. 3, 1935.

12 Hendey, N. I., The plankton diatoms of the southern seas : Discovery 

Repts., vol. 16. <p. 235, 1937.
PART 3. DIATOMACEAE 65

Podosira stelliger (-Bailey) Mann,, Contr. U. S. Nat. Herbarium,

vol. 10, part 5, p. 242, 1907. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der

Schweiz, Teil 1, p. 286, fig. 128, 1928. 

Hyalodiscus stelUger Bailey. Van Heurck, Synopsis diatomees

Belgique, p. 213, pi. 84, fig. 1, 2, 1882. 

Van Heurck, Treatise on the Diatomaceae, p. 448, fig. 173;

pi. 22, fig. 650, 1896.

Wolle, Diatomaceae of North America, pi. 69, figs. 4-5, 1894. 

Boyer, Acad. Nat. Sci. Philadelphia Proc., vol. 78, Supplement, p. 34, 1926.

Hendey, Discovery Repts., vol. 16, p. 236, 1937. 

Podosira polita Hanna and Grant, California Acad. Sci. Proc., 

4th Ser., vol. 15, p. 164, pi. 20, fig. 5, 1926.

The synonomy of this interesting diatom could be 

continued for some length, but enough is given above 

for the present purpose. Bailey's original description 

(first citation above) follows: "Discoid, bases with a 

broad margin, covered with distinct rectilinear rows of 

dots, arranged in sectoral groups, so as to produce ai 

stellate appearance." The economy of words and ideas 

in this description and the absence of a figure may explain some of the misunderstandings that have arisen 

in regard to it. But the difficulties connected with the 

species pale into insignificance when compared with thej 

much greater ambiguities surrounding the two genera 

into which it has been placed by different authors. An 

excellent review of these difficulties up to 1907 is given 

by Mann,13 who proposed that Podosira and Hyalodiscus be combined under the older name, Podosira. 

He gave a detailed description of the combined genus, 

retaining what he considered to be the most important 

and diagnostic characteristics of each of the former 

genera. Mann, as well as many of his predecessors, was 

so obsessed by the fact that both genera possessed an 

umbilicus that he came to look on this as the most important characteristic of both genera, and hence consistent differences between the two were overlooked. 

Since individuals belonging to both genera grow singly/ 

or in groups of several frustules attached to each other 

by means of short gelatinous stipes, the relative size 

and presence or absence of an umbilicus (caused by this 

method of growth) is of little significance as a specific, 

and even less as a generic character.

Hustedt 14 has recently separated Mann's Podosira 

back into Podosira and Hyalodiscus, disregarding the 

variable and uncertain umbilicus as a generic characteristic. He included in Podosira all species in which 

the markings outside the umbilicus (when present) are 

arranged in definite radial sectors, and in Hyalodiscus 

those in which the outer markings exhibit no sectorial 

arrangement. Other minor generic characters separate 

the two, but the presence or absence of a sectorial arrangement is the most significant. This appears to. be

13 Mann, Albert, Diatoms of the Albatross voyages : U. S. Nat. Herbarium, 

vol. 10, part 5, p. 240, 1907.

84 Hustedt, Friedrich, Die Kieselalgen Deutschlands, Osterreichs, und 

der Schweiz, Teil 1, p. 279 (Podosira), and p. 290 (Hyalodiscus), 1928.

the best solution of the difficulty. Although the number 

of sectors is variable in Podosira and is of little or no 

value as a characteristic, the presence or absence of sectors appears to be significant and provides a definite 

ground for separation.

Diameter of figured specimen (U. S. G. S. diatom 

catalog no. 1984-2), 56^. From sample L-65 (U. S. 

G. S. diatom locality 2878), 0-7 cm. below the top of 

core 13. Two views are given, as it is impossible to 

obtain sufficient magnification and resolution to show 

the finer markings and sufficient depth of focus to show 

the entire diatom sharp at the same time.

Found rarely in samples L-3 and L-46 and frequently 

in sample L-65.

Subfamily SKELETONEMOIDEAE 

Genus ENDICTYA Ehrenberg, 1845

Endictya Ehrenberg, K. Akad. Wiss. Berlin, Ber., p. 76, 1845. 

Dictyopyxis Ehrenberg, in part. 

Melosira Agardh, in part. 

Orthosira Thwaites, in part. 

Coscinodiscus Ehrenberg, in part.

The genus Endictya Ehrenberg has been in a nomenclatorial tangle for many years. Battray 15 included 

Endictya in the already large and unwieldy genus 

Goscinodiscus without observing the true nature of the 

differences between the two. He says, when discussing 

Coscinodiscus concavus (Ehrenberg) Gregory, "Specimens sometimes named Endictya oceanica differ from 

0. concavus only in showing the markings somewhat 

more irregular." 16 Mann 1T doubtfully followed Rattray after clearly stating the differences between the two 

genera. His remarks are worth repeating here:

The most unsatisfactory member of the above combination to 

me is Endictya Ehrenb. The close resemblance of its members 

to the evident Coscinodiscus forms C. ro'bustus Grev. and C. 

marginatus Ehrenb. is responsible for this union. But they are 

also close to some specimens of Stephanopyxis and besides have 

certain peculiarities found in no other Coscinodiscus. The valves 

are not flat or convex disks, but cups; not bounded by a ring-like 

margin, but when viewed from the valval side, encircled by a 

somewhat raised and pointed edge from which the valves turn 

vertically downward to form a band, ornamented like the face 

of the valve with a rugged network; so that the two valves if 

placed together form, without the connecting girdle, a cylindrical 

pill box.

By 1925 Mann 18 formally accepted Ehrenberg's 

Endictya. Hustedt 19 has also recognized the distinctness of Endictya and has published the best description 

to date.

15 Rattray, John, A revision of the genus Goscinodiscus and some allied 

genera : Royal Soc. Edinburgh Proc., vol. 16, p. 450, 1889. 

"Idem, p. 470.

17 Mann, Albert, Diatoms of the Albatross voyages: Contr. U. S. Nat. 

Herbarium, vol. 10, part 5, p. 246,1907.

18 Mann, Albert, Marine diatoms of the Philippine Islands : U. S. Nat. 

Mus. Bull. 100, vol. 6, part 1, p. 75,1925.

w Hustedt, Friedrich, Die Kieselagen Deutschlands, Osterreichs, und 

der Schweiz, Teil 1, p. 296, 1928.
66 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

Endictya oceanica Ehrenberg

Plate 12, figure 3

Endictya, oceanica, Ehrenberg, K. Akad. Wiss. Berlin Ber., p. 76, 

1845.

Ehrenberg, Mikrogeologie, pi. 35A, group 18, figs. 6, 7, 1854. 

Schmidt, Atlas der Diatomaceenkunde, pi. 65, figs. 10,12, 13,

1881. 

Van Heurck, Treatise on the Diatomaceae, p. 445, fig. 169,

1896. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und

der Schweiz, Teil 1, p. 297, fig. 136, 1928. 

Endictya, cribrosa Brebisson, Annals and Mag. Nat. History, Ser.

2, vol. 19, p. 11, pi. 2, flg. 15, 1857. 

Orthosira oceanica, Brightwell, Quart. Jour. Micr. Sci., vol. 8,

p. 96, pi. 6, fig. 14, 1860. 

Coscinodiscus concavus Gregory, in part.

Individuals from the Atlantic cores assigned to this 

species have a very narrow mantle, usually about 7ju, 

wide, and do not exhibit the secondary structure shown 

by Hustedt (fig. 136c, 5th citation above). Only one 

valve was found that could be photographed, and it is 

not very good. Some of the areolae in the central part 

of the valve have air bubbles entrapped, which makes 

them appear darker than the rest. Parts of the valve 

show evidences of corrosion, probably of a chemical 

rather than a mechanical origin. None of the other 

species present in the sample from which this came 

(L-52, core 9) showed evidence of chemical corrosion, 

and this, taken together with the fact that the species 

was present in no other core, suggests transportation 

for some considerable distance by ocean currents before 

deposition. It is found commonly along the coast of 

southern Europe, in the Black Sea, near the Philippine 

Islands, and generally in warmer waters than occur in 

the North Atlantic.

Diameter of figured specimen (U. S. G. S. diatom 

catalog no. 1970-16), 8V From sample L-52 (U. S. 

G. S. diatom locality 2858), 142-151 cm. below the top 

of core 9.

Found rarely in sample L-52.

Endictya robusta (Greville) Hanna and Grant

Plate 12, figure 4

Coscinodiscus rooustus Greville, London Micr. Soc. Trans., new 

ser., vol. 14, p. 3, pi. 1, fig. 8,1866.

Endictya robustus (Greville) Hanna and Grant, California Acad. 

Sci. Proc., 4th ser., vol. 15, no. 2, p. 144, pi. 16, figs. 2, 3, 

1926.

Coscinodiscus rooustus Greville, Schmidt, Atlas der Diatomaceenkunde, pi. 62, figs. 16,17,1878.

Rattray, Royal Soc. Edinburgh Proc., vol 16, p. 511, 1889. 

Mann, Contr. U. S. Nat. Herbarium, vol. 10, pt. 5, p. 258,

pi. 48, fig. 4, 1907. 

Boyer, Synopsis of North American Diatomaceae, p. 54,1926.

Coscinodiscus subvelatus Grunow. Schmidt, Atlas der Diatomaceenkunde, pi. 65, fig. 9, 1881.

Coscinodiscus kinkerianus Truan and Witt, Die Diatomaceen der 

Polycystinenkreide von J^remie in Hayti, p. 13, pi. 3, fig. 1, 

1888.

This species is frequently confused with Coscinodiscus 

marginatus Ehrenberg, as both are without central space 

or rosette and have similar markings. The principal 

difference between the two is the generic characteristic 

that defines Endictya, namely, that in Endictya the 

areolae do not terminate at the margin as in Cosdnodiscus but turn abruptly and form the mantle. In valve 

view, the areolae forming the mantle in Endictya robusta have much the same appearance as the marginal 

striae in C. marginatus. In Endictya it is possible to 

focus vertically through several rows of areolae in the 

mantle (when seen in valve view), whereas in Coscinodiscus the limit is the depth of the margin. The 

remarkable connecting zone or girdle of E. robusta is 

a feature which immediately distinguishes it when present. Rattray's brief description 20 of this girdle is worth 

repeating here:

In a S'anta Monica form 0.13 mm. in diameter, discovered by 

Dr. Rae, the usual striated border was surrounded by a second 

more sharply defined but narrower band, with a slightly convex 

surface, and bearing delicate striae, 8 to 10 in 0.01 mm.; at 

one place this band is interrupted and somewhat more convex 

on the two sides of the break. This gives it the appearance of 

an elastic spring enveloping the valve.

Brun 21 has also found a specimen of Coscinodiscus 

crassus Bailey with a similar girdle, but there is no 

possibility of confusing Endictya robusta with G. crassus as they are different in many respects.

This cosmopolitan species was found in many samples 

from six of the cores and usually occurred most frequently in the upper part of each core. It is a coolwater diatom most abundant today in the northernhemisphere and has had a wide distribution since the 

middle Tertiary, reaching its heydey in upper Miocene 

time.

Diameter of figured specimen (U. S. G. S. diatom 

catalog, no. 1958-2), 108/t. From sample L-52 (U. S. 

G. S. diatom locality 2858), 142-151 cm. below the 

top of core 9.

Found rarely in samples L-6, L-10, L-16, L-23, L-32, 

L-49, L^53, and L-56, and frequently in samples L-2, 

1^3, L-4, L-19, L-30, L-31, L-50, L-51, and L-59.

Subfamily THALASSIOSIROIDEAE 

Genus THALASSIOSIRA Cleve, 1873

Thalassiosira baltica (Grunow) Ostenfeld

Plate 12, figure 11

Coscinodiscus polyacanthus var. baltica Grunow, K. svenska

vetensk. akad. Handl., Band 17, No. 2, p. 112, 1880. 

Coscinodiscus ~balticm Cleve. Soc. Fauna Flora Fenn. Acta,

Band 8, No. 2, p. 68, 1891. 

Thalassiosira oaltica (Grunow) Ostenfeld, Nyt mag. naturvidensk., Band 39, Heft. 4, p. 290, 1901. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und

der Schweiz, Teil 1, p. 328, fig. 164, 1928.

20 Rattray John, A revision of the genus Coscinodiscus and some allied 

genera : Royal Soc. Edinburgh Proc., vol. 16, p. 512,1889.

21 Brun, Jacques, Diatome'es marines fossiles ou pelagiques: Geneve Soc. 

Physique Histoire Nat. M6m., Tome 31, pt. 2, no. 1, p. 21, pi. 20, flg, 3,1891.
PART 3. DIATOMACEAE 67

The prominent marginal apiculi, which are characteristic of this species, are well exhibited on the 

specimens from the cores but, unfortunately, are extremely difficult to show in a photomicrograph. The 

high magnification required to reproduce this tiny 

specimen on an adequate scale is incompatible with 

the depth of focus needed to show both apiculi and 

areolae in focus simultaneously. In the present instance this difficulty was augmented by the fact that 

the most nearly whole specimen found was slightly 

tilted in mounting.

Lebour 22 gives the following distribution for this 

brackish-water neritic diatom: "Southern part of North 

Sea, Danish seas, Cattegat, Great and Little Belts, Gulf 

of Finland, Gulf of Bothnia, common in the Baltic. 

Also recorded from Gulf of Maine and California."

Diameter of figured specimen (U. S. G. S. diatom 

catalog no. 1965-4), 27/x. From sample L-3 (U. S. 

G. S. diatom locality 2865), 81-89 cm. below the top 

of core 3.

Found rarely in samples L-3 and L-4.

Thalassiosira decipiens (Grunow) Joergensen

Plate 12, figure 8

Coscinodiscus decipiens Grunow, in Van Heurck, Synopsis des

diatomees Belgique, pi. 91, fig. 10, 1882. 

Thalassiosira decipiens (Grunow) Joergensen, Hydrogr. biol.

inv. Norwegian fjords, p. 96, pi. 6, fig. 3', 1905. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der

Schweiz, Teil 1, p. 322, fig. 158, 1928.

Hendey, Discovery Repts., vol. 16, p. 238, pi. 11, fig. 9, 1937. 

Thalassiosira gelatinosa Henson, Komm. Wiss. untersuchung 

deutschen Meere in Kiel Ber., p. 87, 1887.

This species usually has very prominent marginal 

apiculi, but many specimens found in the cores have 

very faint ones. In the specimen photographed, the 

apiculi are present, but in order to show them it would 

have been necessary to focus so far down as to obscure 

the markings over two-thirds of the valve. The small 

excentric nodule that indicates the point of attacliment 

of the gelatinous stipe that connects the frustules together to form a chain is well shown.

This species is neritic along the coast of Europe and 

is occasionally found in oceanic waters. It is fairly 

common in temperate waters in the Northern Hemisphere.

Reinhold 23 has recorded the earliest known geologic 

occurrence of this species from; rocks doubtfully assigned to the lower Eocene near Maastricht, Netherlands.

Diameter of figured specimen (U. S. G. S. diatom 

catalog no. 1970-4), 30/t. From sample L-52 (U. S. 

G. S. diatom locality 2858), 142-151 cm. below and top 

of core 9.

23 Lebour, M. V., The planktonic diatoms of northern seas, p. 61, 1930.

23 Reinhold, Th., Diatoms from rocks, possibly belonging to the Danian 

(or Lower Eocene), near Maastricht, The Netherlands: Nederland Jaarv. 

geologisch Bureau Jaarv., 1930, p. 17, pi. 1, fig. 12, 1931.

Found rarely in samples L-l, L-2, and L-19 and 

frequently in samples L-31 and L-52.

Subfamily COSCINODISCOIDEAE 

Genus STEPHANODISCUS Ehrenberg, 1845

Stephanodiscus astraea (Ehrenberg) Grunow

Plate 12, figure 2

Discoplea astraea Ehrenberg, Berlin Akad. Wiss. Ber., 1844, p.

267, 1844. 

Stephanodiscus astraea (Ehrenberg) Grunow, K. Svenska vetensk. akad. Handl., Band 17, no. 2, p. 114,1880. 

Schmidt, Atlas der Diatomaceenkunde, pi. 226, figs. 1-5,

1901.

Boyer Acad. Nat. Sci. Philadelphia Proc., vol. 78, Supplement, p. 61, 1927.

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der 

Schweiz, Teil 1, p. 368, fig. 193, 1928.

The wide distribution of this fresh-water and brackish-water species and its rare occurrence in a marine 

environment suggest that its occurrence in only one 

sample (L-56), near the bottom of core 9, is the result 

of transportation from shore. Fricke 24 has reported 

it from Flensburg as Kecent marine, but it appears possible that his specimen was also introduced into the sea 

from some stream. It has not been observed actually 

living in a marine environment. Only one specimen 

was found in the core and it was badly worn.

Diameter of figured specimen (U. S. G. S. diatom 

catalog no. 1962-1), 38/t. From sample L-56 (U. S. 

G. S. diatom locality 2862), 267-272 cm. below the top 

of core 9.

Found rarely in sample L-56.

Genus COSCINODISCUS Ehrenberg, 1838 

Section EXCENTRICAE Rattray

Coscinodiscus excentricus Ehrenberg

Plate 12, figure 7; plate 13, figure 8

Coscinodiscus excentricus Ehrenberg, Berlin K. Akad. Wiss.,

Physical Abh., 1839, p. 146, 1841. 

Smith, Synopsis of the British Diatomaceae, vol. 1, p. 23, pi. 3,

fig. 38, 1853.

Ehrenberg, Mikrogeologie, pi. 18, fig. 32; pi. 21, fig. 6, 1854. 

Schmidt, Atlas der Diatomaceenkunde, pi. 58, figs. 46-49,

1878.

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 461,1889. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der

Schweiz, Teil 1, p. 388, fig. 201, 1928. 

Hendey, Discovery Repts., vol. 16, p. 242, 1937. 

Coscinodiscus minor Schmidt, Atlas der Diatomaceenkunde, pi.

113, fig. 9, 1888. 

Coscinodiscus labyrinthus Roper, Quart. Jour. Micr. Sci., vol. 6,

p. 21, pi. 3, fig. 2a-b, 1858.

It is frequently difficult to separate this species from 

Planktoniella sol (Wallich) Schiitt,25 particularly when 

individuals like that shown on plate 13, figure 8 are 

found. This particular individual (U. S. G. S. diatom

24 Fricke, Friedrich, in Schmidt, Atlas der Diatomaceenkunde, pi. 226, 

fig. 5, 1901.

25 Hustedt, Friedrich, Die Kieselalgen Deutschlands, Osterreichs und 

der Schweiz, Teil 1, p. 465, fig. 259,1929.
68 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

catalog no. 2000-3) has very faint apiculi, which do not 

show in the photograph and might easily be taken for 

the center of Planktoniella sol, the slightly silicified 

outer portion of which is rarely found preserved in 

fossils. The normal form with prominent apiculi is 

shown on plate 12, figure 7.

Coscinodiscus excentricus ranges all through the Tertiary, and Schultz 26 has recently reported it from a coral 

rock of probable Cretaceous age in Danzig Bay.

Diameter of figured specimens: U. S. G. S. diatom 

catalog no. 1968-8, from sample L-51 (U. S. G. S. diatom 

locality 285T), core 9, 108-114 cm. below top, 45/*; IT. S. 

G. S. diatom catalog no. 2000-3, from sample L-52 

(U. S. G. S. diatom locality 2858), core 9, 142-151 cm. 

below top, 39^.

Found rarely in samples L-l, L-2, L-3, 1^-4, L-6, 

L-31, L-32, L-40, L-49, L-50, L-53, L-58, 1^60, and 

Lr-61, frequently in L-10, L-20, L-33, L-51, L-52, L-54, 

L-56, and L-65, and commonly in L-37.

Coscinodiscus circumdatus Schmidt

Plate 12, figure 12

Coscinodiscus circumdatutf Schmidt, Atlas der Diatomaceenkunde, pi. 59, fig. 3, 1878. 

Van Heurck, Synopsis diatom<§es Belgique, pi. 131, fig. 4,

1883. 

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 466, 1889.

Valve usually flat but occasionally slightly domed; 

without rosette or central space; diameter, 60-TOju,; covered with polygonal areolae, 7 to 8 in 10/x over center 

three-fourths of valve, 10 to 11 in 10/A near margin; 

arranged in nearly straight to slightly sigmoid decussating rows. Border complex, consisting of narrow 

zone, 2ju, wide, filled with fine decussate markings, 14-16 

in lO//, and crossed by very narrow radial apiculi having 

a length equal to the width of the marginal zone and an 

average spacing of 3jn and with a very narrow margin 

having short radial striae, 11 to 13 in 10/x.

Diameter of figured specimen (U. S. G. S. diatom catalog no. 1941-2), 62,*. From sample L-30 (U. S. G. S. 

diatom locality 2838), 0-4.5 cm. below top of core 6.

Kattray's description (last citation above) of this 

diatom was apparently written from Schmidt's figure 

(first citation above) and not from an actual specimen 

and as a result is very misleading. The border appears 

hyaline under a dry objective but clearly shows the decussate markings when viewed under an oil immersion 

objective. The valve might be mistaken for C. excentricus Ehrenberg, as the markings on G. circumdatus are 

frequently (but not always) arranged so as to resemble 

C'. excentricus. The distinctive border at once sets this 

species apart. A sort of pseudo rosette occurs frequently, consisting of a somewhat indefinite circlet of 

areolae surrounding a central one, all of which are the 

same size.

26 Schulz, Paul, Diatomeen aus senonen Schwamgesteinen der Danziger 

Bucht: Dot. Archiv., Band 37, p. 387,1935.

Although this species has been known for 50 years, it 

has been reported previously only from the original occurrence at Yokohama. No information is available as 

to the source of Schmidt's original specimen, which was 

collected by Griindler. Its second occurrence in the 

North Atlantic core is very interesting, particularly so 

in view of the fact that it was found frequently in one 

sample (L-30) from the top of core 6, and not even a 

recognizable fragment was found in any other sample 

studied.

Section LINEATAE Rattray

Coscinodiscus lineatus Ehrenberg

Plate 12, figure 10

Cosoinodiscus lineatus Ehrenberg, Berlin K. Akad. Wiss., Physical. Abh., 1838, p. 129, 1839.

Ehrenberg, Mikrogeologie, pi. 18, fig. 33; pi. 22, fig. 6; pi. 

35A, group 16, fig. 3; group 17, fig. 7,1856.

Schmidt, Atlas der Diatomaceenkunde, pi. 59, figs. 26-32, 

1878; pi. 114, fig. 13, 1888.

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 472, 1889.

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der 

Schweiz, Teil 1, p. 392, fig. 204, 1928.

Hendey, Discovery Repts., vol. 16, p. 242, 1937. 

Ooscinodiscus ehreribergii O'Meara, Royal Irish Acad. Proc., 2d 

ser., vol. 2, p. 264, pi. 26, fig. 24, 1875.

This cosmopolitan species has a world-wide distribution in the oceanic and neritic plankton of temperate 

and subtropical seas. Its known geological range is 

from Cretaceous 27 to Recent.

Most of the cores contained this diatom at various 

depths and in amounts ranging from rare to common.

Diameter of figured specimen (U. S. G. S. diatom catalog no. 1967-5), 89/x. From sample L-51 (U. S. G. S. 

diatom locality 2857), core 9,108-114 cm. below top.

Found rarely in samples L-l, L-2, L-19, L-32, L-49, 

L-50, L-54, and L-60, frequently in L-4, L-10, L-20, 

L-31, L-33, L-51, L-52, L-55, L-56, L-59, and L-62, 

and commonly in L-30, L-37, and L-65.

Section STELLATAE Rattray 

Coscinodiscus stellaris Roper

Plate 13, figure 2

Coscinodiscus stellaris Roper, Quart. Jour. Micr. Sci., vol. 6,

p. 21, pi. 3, fig. 3, 1858.

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 493, 1889. 

Schmidt, Atlas der Diatomaceenkunde, pi. 164, fig. 4, 1891. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und

der Schweiz, Teil 1, p. 396, fig. 207, 1928. 

Lebour, Planktonic diatoms of northern seas, p. 49, pi. 1,

fig. 4, 1930.

Grunow's Ooscinodiscus symbolophorus 28 differs from 

C. stellat4s in having much coarster structure. I agree 

with the following statement by Mann: 29

27 Schulz, Paul, Diatomeen aus senonen Schwammgesteinen der Danziger 

Burht: Bot. Archiv, Band 37, p. 390,1935.

28 Grunow, Albert, Die Diatomeen von Franz Josefs-Land : Akad. Wiss. 

Wien, Math.-naturwiss. El, Denkschr., Band 48, p. 82, pi. D, figs. 3-6, 

1884.

29 Mann, Albert, Diatoms of the Albatross voyages: Contr. "U. S. Nat. 

Herbarium, vol. 10, part 5. p. 257,1907.
PART 3. DIATOMACEAE 69

I am convinced that there is no reasonable ground for 

Grunow's C. symbolophorus as distinguished from Roper's older 

name C. stellaris. Grunow admits that the difference is one 

of relative fineness of marking—too slight a character for 

creating a new species, especially when this difference is by 

no means striking and many intermediate forms are obtainable.

Mann, however, in his early zeal for strict priority, 

tried to throw the two well-known species, C. stellaris 

and C. synibolophorus, into obscurity by reviving 

Ehrenberg's old name pentas. Apparently his reasoning was as follows: Starting with the defensible contention that there was less than specific difference 

between C. stellaris and G. symbolophorus, he lumped 

both into Grunow's specie^ symbolophorus. Grunow, 

however, had taken his specific name from Ehrenberg's 

old genus Symbolophora, which had as its principal 

differentiating characteristic the central stellate cluster 

of irregular markings. Grunow was in considerable 

doubt as to the validity of his .species, for he said, 

"Diese Art ist so nahe mit C. subtilis verwandt, dass 

es vielleicht besser ware, sie als Varietat derselben zu 

betrachten."

Mann then selected Ehrenberg's specific name pentas 

(from Symbolophora pentas} and combined both C. 

stellaris and C. symbolophorus into Coscinodiscus pentas 

(Ehrenberg) Mann. Although it might be possible to 

justify this obscuring of two well-known names on the 

ground of strict priority, common sense dictates otherwise. He completely ignored Jorgensen's very satisfactory disposition of Grunow's doubtful species, which 

appeared in 1905, 2 years before Mann's paper was published. Jorgensen 30 made C. symbolophorus a variety 

of C. stellaris, thus preserving two useful names that 

have appeared in a great deal of diatom literature for 

over half a century. Boyer,31 in 1927, ignored the whole 

dispute and retained C. stellaris and C. synibolophonjis 

as separate species. Hustedt 32 followed Jorgensen in 

retaining Roper's specific name stellaris and making 

symbolophora a variety of it.

Although an oceanic, cool-water species common in 

both southern and northern seas, it occurred in only two 

samples in one core and then rarely.

Diameter of figured specimen (U. S. G. S. diatom 

catalog no. 1970-14), 62/x. From sample L-52 (U. S. 

G. S. diatom locality 2858), core 9, 142-151 cm. below 

top. Unfortunately the specimen was badly damaged in 

mounting, the central portion being broken and pushed 

below the rest of the valve.

Found rarely in samples Lr-51 and I/-52, core 9.

30 Jorgensen, B., The protist plankton ana the diatoms in bottom samples, Hydrographical and biological investigations in Norwegian fjords; 

Bergens Mus. Skrifter, vol. 7, p. 196,1905.

31 Boyer, C. S., Synopsis of North American Diatomaceae: Acad. Nat. 

Sci. Philadelphia Proc., vol. 78, suppl., pp. 49-50, 1927.

32 Hustedt, Friedrich, Die Kieselalgen Deutschlands, Osterreichs, und 

der Schweiz, Teil 1, p. 396,1928.

Section RADIATAE Rattray 

Coscinodiscus africanus Janisch

Plate 13, figures 4, 7, 10

Coscinodiscus africanus Janisch, in Schmidt, Atlas der Diatomaceenkunde, pi. 59, figs. 24, 25, 1878. 

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 534, 1889. 

Mann, Contr. U. S. Nat. Herbarium, vol. 10, pt. 5, p. 247,1907. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der

Schweiz, Teil 1, p. 428, fig. 231, 1928. 

Heideii and Kolbe, Deutsche Sfidpolar-Expedition, Band 8,

Botanik, Heft 5, p. 496, 1928.

Mann's explanation (see 3d citation above) of the 

spiral border markings in this species is open to considerable question. The spiral markings (see pi. 13, 

fig. 10) are distinctly visible with a 2-mm. oil-immersion 

apochromat (Mann says they are not visible with a 

1/12-in. objective). He thought that the markings were 

illusory and were only seen when both valves of a frustule were in contact, and then only under low powers. 

Schmidt's original figure (4th citation above) is the best 

one published insofar as the border is concerned and 

closely approaches an accurate representation of this 

peculiar diatom. The actual structure appears to be as 

follows: The areolae terminate along an abrupt, irregular edge, which is the inner (toward the center) edge 

of an irregular space between the areolae and the radial 

marginal striae. This space appears hyaline, but careful focusing with a 2-mm. oil-immersion apochromat 

reveals tiny dots in no regular arrangement. The marginal striae are short, about 16//, in 10//,, and rounded, 

usually followed by another annular row of short, 

rounded striae offset from the first, the whole giving the 

appearance of a single ring of bifurcated striae. At 

intervals of 4^ to 5/x along the margin are short apiculi, 

which project outward from the margin into a narrow 

hyaline ring surrounding the valve. The apiculi turn 

abruptly at an angle of about 90° in the hyaline ring 

and bend downwards at an acute angle to the surface of 

the valve, giving the spiral appearance. Mann's idea 

of their illusory nature was probably due to the difficulty experienced in focusing these sloping (toward or 

away from the observer in valve view) apiculi. The 

sloping apiculi also account for the great difficulty experienced in photographing them at high magnifications. The term "apiculi" is here used loosely, as they 

are not apiculi in the ordinary sense but apparently 

markings in the hyaline outer ring.

G. africanus is a warm-water marine species and probably neritic. Its occurrence in the cores again suggests 

transportation for a considerable distance before 

deposition.

Diameter of figured specimen (U. S. G. S. diatom 

catalog no. 1972-1), 41^. From sample L-4 (U. S. G. S. 

diatom locality 2866), 130.5-137 cm. below the top of 

core 3.

Found rarely in samples L-4, L-51, and D-54.
70 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

Coscinodiscus argus Ehrenberg

Plate 13, figures 1, 3

Coscinodiscus argus Ehrenberg, K. Akad. Wiss. Berlin, Physikal.

Abh. 1838, p. 129, 1839.

Ehrenberg, Mikrogeologie, pi. 21, fig. 2, 1854. 

Grunow, Akad. Wiss. Wien, Math.-naturwiss. Kl., Denkschr.,

Band 48, p. 72, 1884.

Schmidt, Atlas der Diatomaceenkunde, pi. 113, fig. 7, 1888. 

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 527, 1889. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der

Schweiz, Teil 1, p. 422, fig. 226, 1928. 

Reinhold, Nederland. Geol. Bur. Jaarv. 1930, p. 15, pi. 1,

figs. 9, 10 (?), and 11, 1931.

Coscinodiscus irradiatus Harting, K. Akad. Wetensch. Amsterdam Verh., No. 2, p. 8, pi. 1, fig. 1, 1864. 

Coscinodiscus heteroporus Ehrenberg, K. Akad. Wiss. Berlin Ber.,

1844, p. 265, 1845.

Schmidt, Atlas der Diatomaceenkunde, pi. 61, figs. 1, 4,1878. 

Coscinodiscus woodwardii Schmidt, Atlas der Diatomaceenkunde, pi. 61, figs. 2, 3, 1878.

Specimens with polygonal areolae (pi. 13, fig. 3) and 

with rounded areolae (pi. 13, fig. 1) that differed in no 

other particular were found in the same sample. Hustedt's figure (see 6th citation above) shows the rounded 

areolae; other authors have usually illustrated the form 

with polygonal areolae. Keinhold's figure 10 (see 7th 

citation above) is here questioned; as the markings are 

definitely fasciculate, there is apparently a central 

space, and what appear to be apiculi can be seen on the 

upper margin. These features definitely remove the 

specimen in question from 0. argus and place it nearer 

to G. fimbriatus Ehrenberg. His figure 11 appears satisfactory, as does his later figure 33 from the upper 

Miocene of Java.

This is another species with a long geologic range. 

It has been found in beds of various ages from lower 

Eocene to the Recent, but the fossil species are much 

more numerous than the Recent. The evidence is at 

least suggestive that the heydey of this species has been 

reached and passed and that it is now declining toward 

extinction. The few Recent occurrences listed in the 

literature indicate that this is a distinctly warm-water 

marine species, although Hustedt 34 says, regarding its 

occurrence and distribution: "In alien Meeren verbreitet, aber vielledcht nur litoral unter anderen Diatomeen."

Diameter of figured specimens, plate 13, figure 3 

(U. S. G. S. diatom catalog no. 1968-3), 77^; plate 13, 

figure 1 (U. S. G. S. diatom catalog no. 1968-2), 71^. 

Both from sample I/-51 (U. S. G. S. diatom locality 

2857), 108-114 cm. below the top of core 9.

Found rarely in samples I/-31 and L-51.

88 Reinhold, Th., Fossil diatoms of the Neogene of Java and their zonal 

distribution : Nederland en Kolonign Geol.-Mijnbouwk. Genootschap Verb., 

Geol. ser., Deel 12, p. 93, pi. 10, fig. 11, 1937.

84 Hustedt, Friedrich, Die Kieselalgen Deutschlands, Osterreichs, und 

der Schweiz, Teil 1, p. 422,1928.

Coscinodiscus asteromphalus Ehrenberg

Plate 13, figure 11

Coscinodiscus asteromphalus Ehrenberg, K. Akad. Wiss. Berlin

Ber. 1844, p. 77, 1845. 

Ehrenberg, Mikrogeologie, pi. 18, fig. 45; pi. 33, group 15,

fig. 7, 1854. 

Grunow, Akad. Wiss. Wien, Math-naturwiss. KL, Denkschr.,

Band 48, p. 78, pi. 3 (C), fig. 9,1884. 

Schmidt, Atlas der Diatomaceenkunde, pi. 63, fig. 12, 1878;

pi. 113, figs. 22, 23, 1888. 

Van Heurck, Synopsis diatome'es Belgique, pi. 128, figs. 1-8,

5, 1883.

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 549, 1889. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der

Schweiz, Teil 1, p. 452, fig. 250, 1928. 

Hendey, Discovery Repts., vol. 16, p. 243,1937. 

Coscinodiscus asteromphalus var. conspicua Grunow, in Van

Heurck, Synopsis diatomees Belgique, pi. 130, figs. 1, 2, 5,

6,1883.

The distribution in the cores of this large and ornate 

diatom was very peculiar. It occurred commonly to 

rarely in the upper half of core 3, rarely in the lower 

third of core 9, and nowhere else. The geologic distribution of this species is equally erratic. It occurs 

commonly in the Calvert formation, of middle Miocene 

age, in Maryland and Virginia, but has not been found 

in the Temblor formation, of the same age, in the Coast 

Ranges in California, although a very large percentage 

of the species in each are common to the two formations.35 By upper Miocene time it had become rare 

on the Atlantic Coast 36 and common on the coast of 

southern California.37 It is also a common species in 

upper Pliocene rocks in the Kettleman Hills, Calif.38 

Diatoms have not been recorded from definitely dated 

Pliocene rocks along the Atlantic Coastal Plain. During the Pleistocene, however, C. asteromphalutf, appears 

to have become more widely distributed, and at present 

it is practically world-wide, although rarely abundant 

at any one locality. According to Hendey,39 it is "a 

neritic diatom, favoring a fairly high salinity."

Diameter of figured specimen (U. S. G. S. diatom 

catalog no. 2004-2), 198/t. From sample 1^-2 (U. S. 

G. S. diatom locality 2864), 40-48 cm. below top of 

core 3.

Found rarely in samples L-4, L-54, L-55, and L-56, 

frequently in sample L-3, and commonly in sample 

L-2.

85 Lohman, K. B., Comparison of the diatom floras from the Calvert 

formation (middle Miocene) of Maryland and Virginia with those from 

the Temblor formation (middle Miocene) of California. (In preparation.)

a'Henbest, L. G., Lohman, K. B., and Mansfield, W. C., Foraminifera, 

diatoms, and mollusks from test wells near Elizabeth City, N. C.: U. S. 

Geol. Survey Prof. Paper 189-G, p. 222,1939.

8T Lohman, K. E., in Hoots, H. W., Geology of the eastern part of the 

Santa Monica Mountains, Los Angeles County, California; U. S. Geol. 

Survey Prof. Paper 165-C, p. 114, 1931.

38 Lohman, K. E., Pliocene diatoms from the Kettleman Hills, California : 

U. S. Geol. Survey Prof. Paper 189-C, p. 82, pi. 21, fig. 3,1938.

89 Hendey, N. I., The plankton diatoms of the southern seas : Discovery 

Repts., vol. 16, p. 244,1937.
PART 3. DIATOMACEAE 71

Coscinodiscus convexus Schmidt

Plate 13, figure 9

Coscinodiscus convexus Schmidt, Atlas der Diatomaceenknnde,

pi. 60, fig. 15, 1878.

Rattray, Royal Soc. Edinburgh Proc. vol. 16, p. 052, 1889. 

Heiden and Kolbe, deutsche Siidpolar-Bxpedition 1901-1903,

Band 8, Botanik, Heft 5, p. 497, 1928. 

Hanna, California Acad. Sci. Proc., 4th ser., A'ol. 20, No. 6,

p. 179, pi. 6, figs. 2, 3 ; pi. 7, fig. 1, 1931.

The specimens found in the cores have coarser areolation than Schmidt's specimens, but the difference is too 

slight to warrant making a new species. The aerolation 

ranged from li/> to 4 in 10/t in two individuals otherwise 

identical. The size and degree of convexity ranged between wide limits also, but, with the large number of 

specimens available, many of which formed gradational 

series, it appears wiser to refer them all to this species. 

One of the least convex specimens was chosen for the 

photomicrograph, as the more convex individuals are 

extremely difficult to focus all over simultaneously.

Schmidt's type came from the Springfield deposit, 

Barbados (probably Eocene in age), and Hanna's material (last citation above) came from the middle Miocene Temblor formation, Sharktooth Hill, Kern County, 

Calif. Heiden and Kolbe (3d citation above) reported 

this species from Observatory Bay, Kerguelen, but did 

not give its abundance nor state whether or not it was 

in the living state when found. It is entirely possible 

and certainly not improbable that this is another extinct 

species, which may have been redeposited from beds of 

Miocene age. It is an exceedingly robust, highly silicified species and would be able to withstand transportation over great distances.

Diameter of figured specimen (U. S. G. S. diatom catalog no. 1970-6), 178/t. From sample L-52 (U. S. G. S. 

diatom locality 2858), 142-151 cm. below the top of 

core 9.

Found rarely in samples L-4, L-5, L-49, L-54, and 

L-56, frequently in samples L-50, L-51, L-59, and L-62, 

and commonly in sample L-52.

Coscinodiscus decrescens Grunow

Plate 13, figure 6

Coscinodiscus decrescens Grunow, in Schmidt, Atlas der Diatomaceenkunde, pi. 61, figs. 8, 9, 10 (?), 1878. 

Grunow, Akad. Wiss. Wien, Math.-naturwiss. KL, Deukschr.,

Band 48, p. 80, 18S4.

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 525, 1889. 

De Toni, Sylloge algarum omnium hucusque cognitarum,

vol. 2, p. 1252, 1894. 

Van Heurck, Expedition Antarctique Beige, Botanique, p.

47, 1909. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der

Schweiz, Teil 1, p. 430, fig. 233, 1928. 

Hendey, Discovery Repts., vol. 16, p. 245, 1937. 

250584—41———3

Keinhold 40 has reported tins species from rocks of 

middle Miocene age in Java. The original type (see 

1st citation above) came from Eocene rocks in Barbados, and 1 41 have found it in the Modelo formation, of 

upper Miocene age, in the Santa Monica mountains, 

Los Angeles County, Calif. It is frequently found in 

European waters both in plankton and in littoral floras. 

Hendey (see last citation above) found it only in the 

plankton off south Georgia at water temperatures averaging 0° C. Although it has not been reported from 

the North Atlantic, it might be indigenous in that 

region.

Diameter of figured specimen (U. S. G. S. diatom 

catalog no. 1947-1), 39/t. From sample L-33 (U. S. 

G. S. diatom locality 2841), 118-122 cm. below the top 

of core 6.

Found rarely in samples L-33 and L-50.

Coscinodiscus kurzii Grunow

Plate 33, figure 5

Coscinodiscus kurzii Grunow, in Schmidt, Atlas der Diatomaceenkunde, pi. 11, fig. 17, 1888.

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 564, 1889. 

Lohman, U. S. Geol. Survey Prof. Paper 1S9-C, pi. 20, fig. 1;

pi. 21, fig. 2, 1938.

This species has not been reported living. Grunow's 

original specimen (see 1st citation above) came from 

Elephant Point, and I have found it occurring commonly in the Etchegoin and San Joaquin formations, 

of upper Pliocene age, in the Kettleman Hills, Calif. 

(see last citation above). All of the specimens found 

in the cores were broken, and this, together with the fact 

that this species has never been reported definitely as 

living, invites the speculation that the forms found in 

the cores had been reworked from some fossil outcrop 

and redeposited on the ocean floor.

Diameter of figured specimen (U. S. G. S. diatom 

catalog no. 1951-1), 62/i. From sample L-10 (U. S. 

G. S. diatom locality 2854), 74-79 cm. below the top of 

core 4.

Found rarely in sample L-52 and frequently in 

sample L-10.

Coscinodiscus marginatus Ehrenberg

Plate 14, figures 1, 6

Coxcinodisc-ux utarffinatux Ehrenberg, K. Akad. Wiss. Berlin,

Physikal. Abh. 1841, p. 142, 1843. 

I^hrenberg, Mikrogeologie, pi. 18, fig. 44; pi. 33, group 12,

fig. 13; pi. 38B, group 22, fig. 8, 1854. 

Schmidt, Atlas der Diatomaceenkunde, pi. 62, figs. 1-5, 9,11,

12, 1878.

w Reinhold, Th., Fossil diatoms of the Neogene of Java and their zonal 

distribution : Nederland en Kolonien Geol.-Mijnbouwk. Genootschap Verb., 

Oeol. ser., Deel 12, p. 94, pi. 10, fig. 9, 1937.

41 Lohman, K. E., in Hoots., H. W., Geology of the eastern part of the 

Santa Monica Mountains, Los Angeles County, California: II. S. Geol. 

Surv. Prof. Paper 165-C, p. 114, pi. 28, fig. 5, 1931.
72 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 509, 1889. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der

Schweiz, Teil 1, p. 416, fig. 223, 1928. 

Hendey, Discovery Repts., vol. 16, p. 248, 1937. 

Coscinodiscus limbatus Ehrenberg, K. Akad. Wiss. Berlin, Monatsber., 1840, p. 206, 1841. 

Coscinodiscus fimbriatus-limbatus Bhrenberg, Mikrogeologie, pi.

19, fig. 4, 1854.

Coscinodiscus radiatus forma heterosticta Grunow, in Pantocsek, 

Beitrage zur Kenntnis der fossilen Bacillarien Ungarns, 

Teil 1, p. 70, pi. 20, fig. 184, 1886.

Coscinodiscus subconcavus forma major Schmidt, Atlas der Diatomaceenkunde, pi. 62, fig. 7, 1878.

For the differences between this species and Endictya 

robusta (Greville) Hanna and Grant, see discussion under the latter on p. 66 of this report. It is also sometimes confused with C. radiatus Ehrenberg, from which 

it differs in having coarser areolation, longer and coarser 

marginal striae, and much greater convexity. C. radiatus is usually quite flat. The convexity of G. marginatus is not so evident in plate 14, figure 1 (taken with 

a 16-mm. apochromat) but is very well shown in plate 

14, figure 6 (taken with an 8-mm. apochromat).

This species has had a widespread distribution since 

early Miocene time and occurs today in all warm to 

temperate seas. According to Hendey 42 it is "probably 

a bottom form, meroplanktonic, but sometimes observed 

a considerable distance from land." It is one of the 

most common species found in the cores.

Measurements of figured specimens

U. 8. G. 8. 

diatom 

catalog no.

1967-17___- 

1967-19____

Diameter

115/i 

97/i

Areolae 

near center

1H-2 in 10M 

2 in 10/i

Areolap 

near margin

3 in 10/i 

3 l/2 in 10/i

Marginal striae

$% in 10M 

5 in 10/i

Both from sample L-3 (U. S. G. S. diatom locality 

2857, 81-89 cm. below the top of core 3.

Found rarely in samples L-l, L-7, L-8, L-10, L-20, 

L-58, and L-60, frequently in samples L-2, L-3, L-4, 

L-31, L-33, L-51, L-52, L-54, L55, and L-56, and 

commonly in samples L-19, L-32, and L-59.

Coscinodiscus nodulifer Schmidt

Plate 14, figures 3, 5

Coscinodiscus nodulifer Schmidt, Atlas der Diatomaceenkunde, 

pi. 59, figs. 21-23, 1878.

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 520,1889.

De Toni, Sylloge algarum omnium hucusque cognitarum, 

vol. 2, p. 1249, 1894.

Boyer, Acad. Nat. Sci. Philadelphia Proc., vol. 78, supplement, p. 55, 1926.

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und 

der Schweiz, Teil 1, p. 426, fig. 229, 1928.

Schmidt in his original illustration of this distinctive 

species included a form with prominent marginal

42 Hendey, N. I., The plankton diatoms of the southern seas: Discovery 

Repts.. vol. 16, p. 248, 1937.

apiculi,43 which Kattray 4 * subsequently described as 

var. apiculata. Mann * 5 casually and Hustedt 46 definitely disregarded Rattray's variety and included it 

with the species. This does not appear to have been 

the wisest choice for the following reasons: The apiculi 

are shown quite definitely 011 Schmidt's figure and are 

good morphological characters used without question 

elsewhere; the variety apiculata has been recorded from 

only two localities,47 both in warm tropical waters, and 

both occurrences were presumably in a living state. 

The type species has never been recorded from the 

same localities but has been found widely scattered 

over the globe, both living and from fossil deposits 

as old as middle Miocene. It seems possible, therefore, 

that var. apiculata may represent a particular ecologic condition, such as that found in Campeche Bay, 

and may prove useful as an ecologic indicator when 

and if found in sediments.

C. nodulifer has been reported from neritic zones of 

tropical and subtropical seas by various oceanographic 

expeditions but never in latitudes as high as those of the 

cores (lat. 46° to 49° N.), and it may, therefore, be regarded as a warm-water or warm-temperate-water 

species. Hendey 4S found it in only one sample, at 

latitude 38°27'30" S. at a water temperature of 14.8° C. 

The presence of this species in the cores at higher latitude and in much colder water suggests transportation 

by the Gulf Stream.

Diameter of figured specimens, plate 14, figure 5 (U. S. 

G. S. diatom catalog no. 1967-6), 83/*; plate 14, figure 3 

(U. S. G. S. diatom catalog no. 1967-9), 51/*. Both from 

sample L-51 (U. S. G. S. diatom locality 2857), 108-114 

cm. below top of core 9.

Found rarely in samples L-6, L-31, L-52, L-55, L-59, 

and L-65 and frequently in samples L-2, L-4, and L-51.

Coscinodiscus oculus-iridis var. borealis (Bailey) Cleve

Plate 14, figure 2

Coscinodiscus borealis Bailey, Am. Jour. Sci., ser. 2, vol. 22,

p. 3, 1856.

Schmidt, Atlas der Diatomaceenkunde, pi. 63', fig. 11, 1878. 

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 558, 1889. 

Coscinodiscus oculus-iridis var. boreaUs (Bailey) Cleve, VegaExped. vetensk. lakttagelser, Bandet 3, p. 488, 1883. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der 

Schweiz, Teil 1, p. 456, fig. 253, 1928.

The large robust areolae and the raised zone about 

one-fifth the radius in from the margin distinguish this 

variety from G. oculus-iridis Ehrenberg. In the early

"s Schmidt, Adolf, Atlas der Diatomaceenkunde, pi. 59, fig. 20, 1878.

44 Rattray, John, A revision of the genus Coscinodiscus and some allied 

genera : Royal Soc. Edinburgh Proc., vol. 16, p. 520,1889.

45 Mann, Albert, Diatoms of the Albatross voyages: Contr. U. S. Nat. 

Herbarium, vol. 10, part 5, p. 255, 1907.

48 Hustedt, Friedrich, Die Kieselalgen Deutschlands, Osterreichs, und der 

Schweiz, Teil 1, p. 427, 1928.

47 Rattray, op. cit, p. 520.

48 Hendey, N. I., The plankton diatoms of the southern seas: Discovery Repts., vol. 16, p. 248, 1937.
PART 3. DIATOMACEAE 73

stages of the present investigation many individuals 

were tentatively identified as G. oculm-iridis, but, when 

large numbers of the variety borealis were found, the 

ones previously identified as typical were re-examined 

more critically, and all were assigned to the variety. 

Although this variety is very distinct, its close affinity 

to the type make specific separation unwise. Hustedt 

(last citation above) says, "Fur die spezifische Abtrennung dieser Form liegt kein Grund vor."

It occurred in greater abundance than any other 

diatom in cores 3 and 9. Three other cores contained it 

rarely to frequently.

This is a definitely cold-water form and is common 

in most diatom floras from Arctic waters.

Diameter of figured specimen (U. S. G. S. diatom 

catalog no. 1965-1), 214/*. From sample L-3 (U. S. G. 

S. diatom locality 2865), 81-89 cm. below the top of 

core 3.

Found rarely in samples L-16, L-31, L-33, L-49, 

L-58, L-60, and L-62, frequently in samples L-l, L-7, 

L-10, L-19, L-32, L-37, L-51, and L-59, commonly in 

sample L-6, and abundantly in samples L-2, L-3, L-4, 

L-52, and L-54.

Coscinodiscus radiatus Ehrenberg

Plate 14, figures 7, 8

Coscinodiscus radicrtus Ehrenberg, K. Akad. Wiss. Berlin, Physikal. Abh. 1839, p. 148, pi. 3, figs, la-c, 1841. 

Schmidt, Atlas tier Diatomaceenkunde, pi. 60, figs. 5, 6, 9,

10, 1878.

Van Heurck, Synopsis diatomees Belgique, pi. 129, fig. 1,1883. 

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 514, 1889. 

Hustedt, Die Kieselalgen Deutschlands, Osterrichs, und der

S'chweiz, Teil 1, p. 420, fig. 225, 1928. 

Hendey, Discovery Repts., vol. 16, p. 250, 1937. 

Coscinodiscus caspius Ehrenberg, K. Akad. Wiss. Berlin, Physikal. Abh. 1872, p. 394, pi. 12, group 1, fig. 14, 1873. 

Coscinodiscus ~boreMis Ehrenberg, K. Akad. Wiss. Berlin, Monatsber. 1861, p. 294, 1862.

Coscinodiscus fallax Schumann, Konigsberg K. physikal.-o'konomischen Gesell., Schr., Jahrg. 8, p. 62, pi. 3, fig. 76, 1867.

Hustedt 49 has recently included a great many varieties of G. radiatus with the species, and it appears to 

have been a wise course. Most of the varieties have 

been based on minor differences in areolation and size. 

In a variable species such as this, minor differences 

quickly lead to absurdities if new varieties are erected 

for each departure from the norm. In the material 

studied for this report, many variations of this species 

were found, with practically infinitesimal gradations 

between. The two extremes of such a series are here 

illustrated, one (pi. 14, fig. 7) a large form with areolae 

2 to 2!/2 in 10/A, outer quarter of valve convex, and the 

ether a smaller form (pi. 14, fig. 8) less than half the 

diameter of the former, with areolae 4 to 5 in 10/*, and 

flat from center to margin. In general the smaller

49 Hustedt, Friedrich, Die Kieselalgen Deutschlands, Osterreichs, und 

der Schweiz, Teil 1, p. 420, 1928.

forms are flat, and many of those with diameters greater 

tli an 100/A are convex. Although a great many individuals were found, nearly every one was damaged in someway.

This species has a world-wide distribution in warm 

to temperate seas and is probably encountered as often 

as any marine diatom. It is one of the species found 

most frequently in the cores. It has a long geologic 

history and has been found in many marine diatomites 

of Eocene and later ages.

Diameters of figured specimens: Plate 14, figure 7 

(U. S. G. S. diatom catalog no. 1967-2), 158/*; plate 14, 

figure 8 (U. S. G. S. diatom catalog no. 1967-10), 7l/*. 

Both from sample L-51 (U. S. G. S. diatom locality 

2857), 108-114 cm. below top of core 9.

Found rarely in samples L-2, L-3, L-5, L-16, L-23, 

L-44, L-49, L-55, and L-58, frequently in samples L-4, 

L-6, L-7, L-10, IXL9, L-30, L-31, L-32, 1^33, L-37, 

L-52, L-56, L-62, and L-65, and commonly in samples 

1^54 and L-59.

Section FASGICULATAE Rattray 

Coscinodiscus bicurvulatus Lohman, n. sp.

Plate 15, figure 5

Valve circular, flat, without rosette or central space; 

hexagonal areolae in indefinite fasciculi, occasionally 

straight but usually curved in either clockwise or counterclockwise direction; areolae near center, 7 to 8 in 10/*; 

at semi radius, 6 in 10/*; near margin, 8 to 9 in 10/A. 

Margin narrow with short radial striae, 18 in 10/*; stout 

rounded marginal apiculi, 10/x, apart. Diameter 60-80/t.

Holotype: U. S. G. S. diatom catalog no. 1967-12, 

diameter, 67/*. U. S. G. S. diatom locality 2857. Sample L-52, from 108-114 cm. below the top of core 9, taken 

at a depth of 2.050 fathoms in lat. 49°40'00" N., and 

long. 28°29'00" W., by C. S. Piggot, 1936.

Reinhold 50 has recently published a figure of this 

species and confused it with G. normani Gregory. He 

published two figures (pi. 11, figs. 4 and 9), which he 

called G. normani. Figure 4 is not entirely clear, but 

appears to be C. normani, but figure 9, which is an excellent photomicrograph, is clearly not G. normani but 

identical with the present species. In G. normani the 

fasciculi are straight, with the rows of areolae parallel 

to the center row in each fasciculus, and the narrow zone 

between the apiculi and the margin is covered with very 

fine decussate markings. Both these features are exhibited in Reinhold's figure 4 but not in his figure 9.

This species is somewhat similar to G. curvatulus var. 

odontodiscus (Grunow) Hustedt,51 from which it differs 

in having smaller areolae, particularly near the center 

and margin, and in not having the irregular hyaline

50 Reinhold, Th., Fossil diatoms of the Neogene of Java and their zonal 

distribution : Nederland en Kolonie'n Geol.-Mijnbouwk. Genootschap Verb., 

Geol. ser., Deel 12, pi. 11, fig. 9, 1937.

51 Hustedt, Friedrich, Die Kieselalgen Deutschlands, Osterreichs, und 

der Schweiz, Teil 1, p. 408, fig. 215,1928.
74 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

ring at the center. This ring is well shown in Grunow's original figure. 52

More than a dozen individuals were found in the cores, 

all of which were consistent with the description and 

figure here given. No perfect individual was found; 

the holotype has the margin broken away from half of 

the valve but is otherwise intact. In view of the fact 

that many perfect specimens of more fragile diatoms 

were found, it is entirely possible that this species has 

been reworked from older material.

Found rarely in samples L-2, L-4, L-30, L-51, L-52, 

L-54, L-59, and L-60.

Coscinodiscus crenulatus Grunow var. nodulifer Lohman, n. var.

Plate 14, figure 4; plate 15, figure 1

Valve circular, flat, without rosette but occasionally 

with a small, irregular central space; polygonal areolae, 

7 to 8 in 10^. at the semiradius, usually constant over 

the entire valve, but occasionally somewhat closer 

toward the margin; areolae arranged in definite 

fasciculi; initial and longest row of areolae in each fasciculus sometimes radial but more often tangent to an 

imaginary circle at the center of the valve and onetenth to one-twelfth its diameter; initial row usually 

straight but occasionally slightly curved; remaining 

rows in each fasciculus parallel to the initial one. A 

single nodule I/A to 1.5,u, in diameter is always present, 

although not always obvious, and is always slightly excentric and usually surrounded by a narrow irregular 

space. Marginal apiculi 6^ to 9,u. apart with identation at each apiculus giving a crenulate appearance to 

the margin. Marginal striae, short and robust, 14 to 

16 in 10,u,. Diameter of valve, 30/A to 40/A.

Holotype: U. S. G. S. diatom catalog no. 1970-3 (pi. 

15, fig. 1); paratype: U. S. G. S. diatom catalog 1957-11 

(pi. 14, fig. 4). U. S. G. S. diatom locality 2858. Sample L-52, from 142-151 cm. below the top of core 9, 

taken at a depth of 2,050 fathoms in lat. 49°40/00'/ N. 

and long. 28°29'00" W., by C. S. Piggot, 1936.

Measurements of figured specimens

Specimen

Holotype, 1970-3._.__

Paratype, 1957-11___

Diameter

"40

37

Areolae 

in 10 M

7-8

7-8

Marginal 

striae in 10 p.

15-16

14

Apiculi, 

distance 

apart

M

9

6

This variety differs from C. crennlatus Grunow 53 

principally in the presence of the small excentric 

nodule. This nodule is not present in any published 

figures or descriptions of G. crenulatm. In the type,

52 Grunow, Albert, Die Diatomeen von Franz Josefs-Land : Akad. Wiss. 

Wien, Math.-naturwiss. Kl., Denkschr., Band 48, p. 81, pi. 3 (C), fig. 23, 

1884.

53 Idem. p. 83, pi. 4 (D), flg. 17.

the fasciculi are more definitely curved than in the 

variety, and, according to Hustedt/' 4 who has given the 

best description of the species, the marginal striae 

are more closely spaced (20 in 10 /A) in the type than 

in the variety. Eattray's description 55 of G. .crenulatus is very confusing, as, according to Hustedt,56 he 

made his measurements on Schmidt's figure 57 rather 

than on an actual specimen and failed to notice that 

this particular figure w-as drawn at a magnification of 

990 diameters, whereas the magnification for the balance of the plate was 660 diameters. Eattray used the 

smaller enlargement in computing his measurements.

The type is a littoral form from southern seas, and 

it is possible that the habitat of the variety was similar.

Found rarely in samples L-30, L-51, and L-52.

Coscinodiscus curvatulus Grunow

Plate 15, figure 8

Coscinodiscus curvatulus Grunow, in Schmidt, Atlas der diatomaceenkunde, pi. 57, fig. 33, 1878. 

Grunow, Akad. Wiss. Wien, Math-naturwiss. Kl., Denkschr.,

Band 48, p. 82, pi. D, figs. 11-15, 1884.

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 486, 1889. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und

der Schweiz, Teil 1, p. 406, fig. 214, 1928.

In the figured specimen the extreme margin is lacking, and the marginal apiculi so well illustrated by 

Hustedt in the figure cited above are not prominent, but 

careful focusing on the margin reveals them. Schmidt's 

original figure 58 S!IOWT S the apiculi about as strongly 

developed as those in Hustedt's figure. Eattray 59 on the 

other hand, says, "apiculi absent." It is obvious that the 

apiculi represent a variable feature and one not to be 

taken too seriously, at least as far as this species is concerned. Another variable feature is the degree of curvature of the fasciculi. In most published figures of this 

species a pronounced curvature of the fasciculi is shown. 

In the specimens found in the cores, the curvature is real 

and constant as to direction but very slight. Mann eo 

observed the same lack of pronounced curvature in his 

specimens from Bering Sea.

This species is known from the wT hole Tertiary, the 

earliest occurrence being recorded by Eeinhold,61 who 

found it in rocks of probable lower Eocene age near 

Maastricht, Netherlands.

Its present distribution is widespread in oceanic plankton, but is more abundant in cold northern waters.

54 Hustedt, Friedricb, Die Kieselalgen Deutschlands, Osterreichs, und 

der Schweiz, Teil 1, p. 411, fig. 219, 1928.

55 Rattray, John, A revision of the genus Coscinodiscus and some allied 

genera : Royal Soc. Bdinhurgh Proc., vol. 16, p. 489, 1889.

56 Hustedt, Friedrich, op. cit, p. 412.

57 Schmidt, Adolf, Atlas der Diatomaoeenkunde, pi. 57, flg. 38, 1878.

:* Idem, flg. 33.

69 Rattray, John, op. cit, p. 486.

9(1 Mann, Albert, Diatoms of the Albatross voyages : Contr. U. S. Nat. 

Herbarium, vol. 10, part 5, p. 250, 1907.

61 Reinhold, Th., Diatoms from rocks, possibly belonging to the Daman 

(or Lower Eocene), near Maastricht. Netherlands: Nederland. Geol. 

Bur. .Taarv., 1930, p. 15, pi. 1, figs. 2, 4-8, 1931.
PART 3. DIATOMACEAE 75

Diameter of figured specimen (U. S. G. S. diatom 

catalog no. 1960-3), 91/*. From sample L-54 (U. S. G. S. 

diatom locality 2860), 206-213 cm. below top of core 9.

Found rarely in samples L-2 and L-31 and frequently 

in samples L-52 and L-54.

Coscinodiscus curvatulus var. minor (Ehrenberg) Grunow

Plate 15, figure 3

Coscinodiscus minor Ehrenberg, K. Akad. Wiss. Berlin, Physikal. Abh. 1838, p. 129, pi. 4, fig. 12e, 1840.

Coscinodiscus curvatulus var. ? minor (Ehrenberg) Grunow, 

Akad. Wiss. Wien. Math.-naturwiss. Kl., Denkschr., Band 

48, p. 83, pi. 4 (D), figs. 8-10,1884.

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 487, 1889. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der 

Schweiz, Tell 1, p. 409, fig. 217, 1928.

The curved fascicles immediately distinguish this 

small variety from small forms of C' oscin-odiscus excen - 

t-ricus, with which it is frequently confused. Ehrenberg's earliest figure of this diatom (see first citation 

above) left much to be desired. Many subsequent 

authors have combined Ehrenberg's C. minor with C. 

excentricus, whereas Grunow saw the curved fasciculate 

arrangement of the markings and hence realized its relationship to C. curvatulus. The doubtful accuracy of 

the original figure (now 100 years old) and the various 

interpretations that have been placed on it by other 

authors have confused the true position of this tiny 

diatom. Grunow entertained and recorded a doubt as 

to whether or not C. minor should be made a variety of 

G. curvatulus or combined with it. I agree with Rattray and Hustedt (see above synonymy) that the forms 

Grunow figured were certainly related to -G. curvatulus. 

The specimens from the cores are more finely marked 

than the one figured by Hustedt (see last citation 

above) and approach C. divitm Grunow, which, however, is larger and has a zone of very fine decussate 

markings between the apiculi and the margin.

This variety is frequently found with small forms of 

C, excentricus, pelagic in all seas, but is more abundant 

in colder waters.

Diameter of figured specimen (U. S. G. S. diatom catalog no. 1957-1), 29^. From sample L-52 (U. S. G. fc?. 

diatom locality 2858), 142-151 cm. below top of core 9.

Found rarely in sample L-4, and frequently in sample 

L-52.

Coscinodiscus denarius Schmidt

Plate 15, figure 6.

Coscinodiscus denarius Schmidt, Atlas der Diatomaceenkunde,

pi. 57, figs. 19-21, 1878.

Rattray. Royal Soc. Edinburgh Proc., vol. 16, p. 504, 1889. 

Boyer, Acad. Nat. Sci. Philadelphia Proc., vol. 78, supplement,

p. 51, 1926. 

Hustedt, Die Kiesolalgeu Deutschlands, Osterreichs, und der

Schweiz, Teil 1, p. 399, fig. 210, 1928.

Specimens assigned to this species have polygonal 

areolae, 8 in 10^,, which decrease in size very slightly 

toward the margin. In the photomicrograph the reduction in size of the areolae toward the margin is exaggerated on account of the change in focus from center to 

margin caused by the convexity of the valve. The number of rows of areolae in each fasciculus is greater than 

that usually given by various authors, but the difference 

does not appear to warrant specific separation, as the 

size of the fasciculi differs between different valves and 

even in a single valve.

This species is frequently confused with C. subtili* 

Ehrenberg, from which it differs in having coarser 

areolation and more definite fasciculi.

Schmidt's original specimens came from Eocene 

rocks on the island of Barbados,62 and it has since been 

reported from Campeche Bay in the Gulf of Mexico,63 

and from the Antarctic Ocean.64 Hustedt 65 states that 

except for a report by Peragallo of its occurrence living 

in the Bay of Villefranche, it is not known in European 

waters. It occurred in nearly half the samples from the 

cores but never in large numbers. As far as can be 

determined from available data it is not at all critical 

regarding temperature.

Measurements of figured specimen (U. S. G. S. diatom 

catalog no. 1968-4) : Diameter, 76^,; areolae, 8 in 10^,; 

marginal striae, 13 in 10/A. From sample L-51 (U. S. 

G. S. diatom locality 2857), 108-114 cm. below the top 

of core 9.

Found rarely in samples L-2, L-3, L-7, L-16, L-19, 

L-20. L-31, L~32, L-51, L-54, and L-61, and frequently 

in samples L-4, L-33, and L-37.

Coscinodiscus divisus Grunow

Plate 15, figure 7

Coscinodiscus diiisus Grunow, in Schneider, Naturwiss. Beitr.

zur Kenntniss der Kaukasuslander, p. 125, 1878. 

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 499, 1889. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und

der Schweiz, Teil 1, p. 410, fig. 218, 1928.

Coscinodiscus (curvatulus, var.?) divisus Grunow, Akad. Wiss. 

Wien, Math.-naturwiss. Kl., Denkschr., Band 48, p. 83, 

pi. 4 (D), fig. 16, 1884.

On purely morphologic grounds this species is closely 

related to both C'. curvatulm Grunow and C. rotMi 

(Ehrenberg) Grunow, having the curved fascicles 

(with rows of areolae parallel to a marginal row in 

each fascicle) of the former, and the band of fine, 

decussate markings between the apiculi and the margin 

of the latter. If the phylogenie,s of all three species 

were better known, it seems probable that C. divisus 

might be the intermediate form. On ecologic grounds 

the relationship is, perhaps, less evident but at least

62 Schmidt, Adolf, Atlas der Diatomaceeukunde, pi. 57, figs. 19-21, 

1S78.

03 Rattray, John, A revision of the genns Coscinodtecu* and some allied 

genera : Royal Soc. Edinburgh Troc., vol. 16, p. 504, 1889.

** Heiden, Hemrich, and Kolbe, R. W., Die marinen Diatomeen, in Von 

Drygalski, E., Die deutschen Siidpolar-Expedition, 1901-1903, Band 8, 

Botanik, Heft 5, p. 490, 1928.

65 Hustedt, Friedrich, Die Kieselalgen Deutschlands, Osterreichs, und 

der Schweiz, Teil 1, p. 400, 1928.
76 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

not contradictory. According to Hendey,66 G. 

vatulus is "an oceanic species having a wide distribution in temperate .seas." C. divlsus is, according to 

Hustedt,67 "Wahrscheinlich neritisch oder litoral." 

Regarding the occurrence of G. rothii and its varieties, 

the same author 68 states: "Die Art ist in alien Meeren 

verbreitet und meist haufig. Die Varietaten finden 

sich besonders im Brackwasser der Flussmimdungen, 

zum Teil auch in Binnenseen mit reinem Siisswasser." 

Thus, assuming for the moment that the oceanic G. 

curvatulus was the earlier form, the neritic or litoral 

C. divisus the intermediate form and C. rothii var. 

norm am the end product, we have a gradual transition 

from oceanic through littoral to brackish-water and 

even fresh-water conditions. The geologic evidence, 

as far as known, does not bear this out. Both G. curvatulus and G. rothii are known from the Eocene, 

whereas the oldest recorded occurrence for G. divisus 

is from the upper Pliocene of Java.69 It is entirely 

possible, however, that some of the diatoms identified 

as G. curvatulus in earlier rocks were really C. divisus.

This species was well represented in the cores and 

occurred in nearly half of the samples studied.

Diameter of figured specimen (U. S. G. S. diatom 

catalog no. 1970-11), 57/t. From sample L-52 (U. S. 

G. S. diatom locality 2858), 142-151 cm. below top of 

core 9.

Found rarely in samples L-6, L-20, L-49, L-52, L-56, 

and L-60, and frequently in samples. L-4, L-10, L-30, 

L-31, L-33, L-37, L-51, L-54, L-59, and L-65.

Coscinodiscus subtilis Ehrenberg 

plate 15, figure 4

Coscinodiscu's subtilis Ehrenberg, K. Akad. Wiss. Berlin, Physikal. Abh. 1841, p. 412, pi. 1, group 3, fig. 18; pi. 3, group 7,

fig. 4, 1843. 

Schmidt, Atlas der Diatomaceenkunde, pi. 57, figs. 11-16.

1878.

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 494, 1889. 

Mann, Contr. U. S. Nat. Herbarium, vol. 10, pt. 5, p. 259,1907. 

Boyer, Acad. Nat. Sci. Philadelphia Proc., vol. 78, suppl.,

p. 50, 1926. 

Hendey, Discovery Repts., vol. 16, p. 254, 1937.

The diatoms referred to this species agree more closely 

with Ehrenberg's original description than with some 

descriptions published in later years. Most authors 

give from 6 to 10 areolae per 10/*, whereas these have 12 

in 10/A, as did Ehrenberg's. The marginal striae, 16 in 

lO/i, are finer than usual and are of unequal length, giving the appearance of apiculi when viewed under me68 Hendey, N. I., The plankton diatoms from the south seas: Discovery 

Repts., vol. 16, p. 252, 1937.

87 Hustedt, Friedricb, Die Kieselalgen Deutschlands, Osterreichs, und 

der Schweiz, Teil 1, p. 411, 1928.

68 Idem, p. 404.

"Reinhold, Th., Fossil diatoms of the Neogene of Java and their zonal 

distribution : Nederland en KoloniSu Geol.-Mijnbouwk. Genootschap, Verb., 

Geol. ser., Deel 12, p. 94, 1937.

dium magnifications, but none of the specimens found 

exhibit true apiculi.

G. subtilis has become somewhat of a catch-all for 

finely marked coscinodiscoid forms having fasciculi of 

varying degrees of distinctness and, undoubtedly, has 

been most frequently confused with G. denasrius Schmidt 

and G. rothii (Ehrenberg) Grunow. Hustedt 70 has 

recently reviewed the situation and concluded that the 

name C. subtilis Ehrenberg should be abandoned and 

that forms referred to this species should be included 

in the "Formenkreis" of G. rothii. Although Huste'dt's 

conclusion has much in its favor, it appears best to continue to recognize the species G. subtilis until a definite 

and thorough revision is made of the whole group.

This species has an almost universal distribution, 

cccuring in marine, brackish, and fresh waters, and most 

abundantly today in cold subpolar waters, but also 

along the shores of most continents, in the mud of estuaries and in fresh water. Boyer 71 reports it as, "Very 

common in the water supply of Philadelphia and Camden, where the diameter seldom exceeds 40/* and the 

markings on the semiradius are 10 in 10/*." It occurs in 

many marine fossil deposits from Miocene to Eecent,72 

and it is abundant in some Miocene fresh-water diatomites in the Otis Basin, Harney County, Oreg.73

Diameter of figured specimen (U. S. G. S. diatom 

catalog no. 1972-8), 48/*. From sample L-4 ( U. S. G. S. 

diatom locality 2866), 130.5-137 cm. below the top of 

core 3.

Found rarely in samples L-3 and L-6, and frequently 

in sample L-54.

Genus ACTINOCYCLUS Ehrenberg, 1838 

Actinocyclus curvatulus Janisch

Plate 15, figure 2

Actinocyclus curvatulus Janisch, in Schmidt, Atlas der Diatomaceenkunde, pi. 57, fig. 31, 1878. 

Mann, Contr. U. S. Nat. Herbarium, vol. 10, pt. 5, p. 261,

1907. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der

Schweiz, Teil 1, p. 538, 1929.

Coscinodiscus curvatulus var. subocellatus Grunow, Akad. Wiss. 

Wien, Math.-naturwiss Kl., Denkschr., Band 48, p. 83,

pi. 4 (D),fig. 15, 1884.

Rattray, Royal Soc. Edinburgh Proc., vol. 16, p. 488, 1889. 

Actinocyclus subocellatus (Grunow) Rattray, Quekett Micr.

Club. Jour., ser. 2, vol. 4, p. 145, 1890.

Boyer, Acad. Nat. Sci. Philadelphia Proc., vol. 78, supplement, p. 81, 1926.

The indefiniteness of the pseudonodule on this diatom 

has resulted in much confusion. In view of the fact 

that the most fundamental difference between the gen70 Hustedt, Friedrich, Die Kieselalgen Deutschlands, Osterreichs^ und 

der Schweiz, Teil 1, p. 404, 1928.

71 Boyer, C. S., The diatomaceae of Philadelphia and vicinity, p. 22, 1916. 

72 Rattray, John, op. cit.. p. 495.

73 Lohman, K. B., in Moore, B. N., Nonmetallic mineral resources of 

eastern Oregon : U. S. Geol. Survey Bull. 875, p. 105, 1937.
PART 3. DIATOMACEAE 77

era Coscinodiscus and Actinocyclus is the presence of a 

pseudonodule on the latter, the present species must go 

into Actinocyclus, even though the pseudonodule is not 

always obvious. The distinctness of the pseudonodule 

among the members of this species found in the cores 

ranged through wide limits. Most of the individuals 

were damaged, and the one figured represents the only 

whole specimen found. The dark radial streak near the 

top of the figure is due to a fragment of a diatom 

girdle that is firmly attached. The pseudonodule in this 

particular specimen (shown near the margin at the bottom of the figure) is rather faint, but may be seen 

clearly by proper focusing. It has exactly the same 

appearance as the one in the excellent drawing of A. 

curvatulus by Hustedt (3d citation above).

The distribution of this species is very imperfectly 

known, but appears to be fairly widespread, although 

Hustedt 74 notes that it has not been found in European 

seas. Doubtless it has been confused frequently with 

Cvscinodiscus curvatulus.

Diameter of figured specimen (U. S. G. S. diatom catalog no. 1957-2), 66/*. From sample L-52 (U. S. G. S. 

diatom locality 2858), 142-151 cm. below the top of 

core 9.

Found rarely in samples L-30, L-49, L-50, L-52, 

L-58, L-60 and L-65 and frequently in sample L-51.

Actinocyclus octonarius Ehrenberg 

Plate 16, figure 4

Actinocyclus octonarius Ehrenberg, Die Infusionsthierchen als 

vollkommene Organismen, p. 172, pi. 21, fig. 7,1838.

Hendey, Discovery Repts., vol. 16, p. 262, 1937. 

Actinocyclus ehrenbergii Ralfs, in Pritchard, A history of Infusoria, 4th ed. p. 834, 1861.

Van Heurck, Synopsis diatomees Belgique, pi. 123, fig. 7, 

1883; p. 215, 1885.

Rattray, Quekett Micr. Club Jour., ser. 2, vol. 4, p. 171, 18^0.

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der 

Schweiz, Teil 1, p. 525, fig. 298, 1929.

Hanna, California Acad. Sci. Proc., 4th ser., vol. 20, p. 168, 

pi. 2, figs. 1, 2, 3, 1932.

Lohman, U. S. Geol. Survey Prof. Paper 189-C, p. 83, pi. 22, 

fig. 1, 1938.

The synonymy of this well-known species could be 

extended almost indefinitely, but this has already been 

done so often that nothing would be gained here by 

repeating it.

Hendey (see 2d citation above), has invoked the rule 

of strict priority and thus revived Ehrenberg's hundredyear-old original name from oblivion. Although Ralfs' 

name has been hallowed by long usage, it is, as Hendey 

has ably demonstrated, invalid. Ralfs, possibly thinking to appease Ehrenberg's displeasure, caused by 

throwing 118 of his names into synonymy, named the 

whole group Actinocyclus ehreribergii instead of using 

octonarius, the earliest name. It is with some misgiving

74 Hustedt, Friedrich, Die Kieselalgen Deutschlands, Osterreichs, und 

der Schweiz, Teil 1, p. 539, 1929.

that I agree with Hendey in this matter, as common 

sense would appear to dictate that Ralfs name be retained, even though invalid, on the grounds of long 

and universal usage. However, the plea of "commonsense usage" might better be reserved for doubtful cases 

and not be applied in such clearly unequivocal ones as 

the present. It seems necessary, therefore, to follow 

Hendey and return to Ehrenberg's original name, although those who are inclined to use the common-sense 

plea in all cases may call it sheer pedantry.

The specimens found in the cores are all smaller than 

typical ones but differ in no other respect. They range 

from 34^ to 50/A in diameter, but the radial beads on 

each specimen are but 7 in 10/*, the mean for the type.

At the present time this neritic diatom has a worldwide distribution in temperate seas. Its known geologic 

range is middle Miocene 75 to Recent.

Measurements of figured specimen (U. S. G. S. diatom 

catalog no. 1971-1) : diameter, 35jtt; radial beads, 7 in 

10/A. From sample L-3 (U. S. G. S. diatom locality 

2865), 81-89 cm. below the top of core 3.

Found rarely in samples L-54 and L-66, frequently in 

L-2, L-3, L-10, and L-51, and commonly in L-4.

Genus ROPERIA Grunow, 1883 

Roperia tessellata (Roper) Grunow

Plate 16, figure 3

Eupodiscus tessellatus Roper, Quart. Jour. Micr. Sci., vol. 6,

p. 19, pi. 3, fig. 1, 1858. 

Roperia tessallata (Roper) Grunow, in Van Heurck, Synopsis

diatomees Belgique, pi. 118, figs. 6, 7, 1883. 

Rattray, Royal Micr. Soc. Jour., vol. 8, p. 917, 1888. 

Boyer, Acad. Nat. Sci. Philadelphia Proc., vol. 78, supplement, p. 88, 1926. 

Heiden and Kolbe, Deutsche Siidpolar Expedition 1901-1903,

Band 8, Botanik, Heft 5, p. 507, 1928. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und

der Schweiz, Teil 1, p. 523, fig. 297, 1929. 

Actinocyclus tessellatus Ralfs, in Pritchard, History of the

Infusoria, 4th Ed., p. 835, 1861. 

Mann, U. S. Nat. Herbarium Contr., vol. 10, pt. 5, p. 264,

1907.

This pelagic diatom is found frequently in the central Pacific Ocean, off Rio de Janeiro, and along the 

coast of Europe. It is apparently a temperate to warm 

water form and may have been brought to the North 

Atlantic by the Gulf Stream. Lebour 76 has recorded 

it from (presumably) the North Atlantic but gives no 

information regarding locality or relative abundance.

Diameter of figured specimen (U. S. G. S. diatom 

catalog no. 1967-7), 62 ^ From sample L-51 (U. S. 

G. S. diatom locality 2857), 108-114 cm. below the 

top of core 9.

Found rarely in samples L-2, L-6, L-10, L-51, and 

L-52 and frequently in samples L-4, L-3Q, and L-65.

75 Hanna, G. D., The diatoms of Sharktooth Hill, Kern County, California : California Acad. Sci. Proc., 4th ser., vol. 20, No. 6, p. 168, 1932. 

"6 Lebour, M. V., The planktonic diatoms of northern seas, p. 55, 1930.
78 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

Family HEMIDISCACEAE

Subfamily HEMIDISCOIDEAE

Genus HEMIDISCUS Wallich, 1860

Hemidiscus cuneiformis Wallich, s. I.

Plate 16, figures 1, 2, 0

Hemidiscus cuneifoi'tnis Wallich, London Micr. Soc. Trans., new

ser., vol. 8, p. 42, pi. 2, figs. 3, 4, 1860. 

Ralfs, in Pritchard, History of the Infusoria, 41h ed., p. 8-13,

pi. 6, fig. 14, 1861.

Mann, Contr. U. S'. Nat. Herbarium, vol. 10, pt. 5, p. 316, 1907. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der

Schweiz, Teil 1, p. 904, fig. 542, 1930. 

Hendey, Discovery Repts., vol. 16, p. 264, 1937. 

Kuodia gibla Bailey. Ralfs, in Pritchard, History of the Infusoria, 4th ed, p. 852, pi. 8, fig. 22, 1861. 

Boyer, Acad. Nat. Sci. Philadelphia Proc., vol. 78, supplement, p. 87, 1926.

Euodia cuneiformis (Wallich) Schiitt, in Bngler and Prautl, 

Naturliche Pflanzenfamilien, Teil 1, Abteilung 16, p. 100, 

1896.

Gran, Nordisches Plankton, Lief. 3, p. 45, 1905. 

Euodia inornata Castracane, Challenger Repts., Botany, vol. 2, 

p. 149, pi. 12, fig. 1, 1886.

Different authors have expressed very decided and 

diverse views regarding the disposition of this species 

and its varieties. Mann (3d citation above) could see 

no reason for making certain "species" such as HemidisciitS rectm (Castracane) Mann and H. ventrtcosa 

(Castracane) Mann varieties of H. cuneifo-rmis. With 

considerable justification he says, "On the other hand, 

it should be here noted that the striking build of the O

members of this genus leads to the too easy conclusion 

that all cuneiform frustules bearing a reasonably close 

resemblance to the original species, Hemidiscus cuneiformis Wall, must be mere varieties of it." Hustedt 

(4th citation above), on the other hand, after a careful 

study of the situation, recognized four varieties of H. 

cun-eifonnix, namely, gib~ba, recta, ventricoxa, and orbicufam, all as members of a closely related group or 

"formenkreift."

Hendey (5th citation above), finding himself unable 

to accept either of these alternatives, referred all his 

forms to II. cwneifotmJx. He says :

Much variation in outline has been observed, and many 

species and varieties have been created upon such variable 

characters as the ratio between the apical and transapical axes, 

the degree of gibbosity displayed upon the ventral side, the 

convexity of the dorsal side, and the development of the marginal 

spinulae and pseudo-ocellus. From the vast amount of material examined from such widespread areas as the waters 

around the Cape of Good Hope, the west coast of Africa, the midAtlantic, and the Humbolt current in the Pacific, specimens were 

obtained forming a series of intermediate forms that made it 

impossible to recognize the value of the nomenclatorial species 

and varieties. All of the specimens observed have been referred 

to H. mineifonnis Wallich.

My own experience in dealing with a fairly large 

number of forms from the cores has caused me to agree 

with Hendey, although I believe it safer to add sensu 

lato to the name when so used.

The forms found in the cores and referred to this 

species were quite variable in size and shape, but the two 

figured forms were the most common. My figures 1 and 

5 would be Hustedt's variety ventricosa, and figure 2 

would be near his variety orbicularis.

This is an oceanic species with a wide distribution in 

tropical and subtropical seas, although it is occasionally 

found in the North Atlantic as an introduced species.77

Dimensions of figured specimens

Figure

l

2

U. S. G. S.

diatom 

catalog

number

1970-2

1967-15

1970-13

U. S. G. S.

diatom 

locality

number

2858

2857

2858

Sample 

number

L-52

L-51

L-52

Length

114

49

69

Width

"74

43

51

Found rarely in samples L-l, L-49, L-52, and L-54, 

frequently in samples L-2, L-6, L-30, L-51, and L-59, 

and commonly in samples L-4 and L-65.

Family ACTINODISCEAE

Subfamily ASTEROLAMPROIDEAE

Genus ASTEROMPHALUS Ehrenberg, 1844

Asteromphalus roperianus var. atlanticus Castracane

Plate 16, figure 6

Asteromphalus ro/jerianus var. atlanticus Castracane, Challenger

Repts., Botany, vol. 2, p. 133, pi. 5, fig. 3, 1886. 

De Toni, Sylloge algarum omnium hucusque cognitarum, 

vol. 2, p. 1411, 1894.

Castracane's original figure of this diatom is drawn 

with more geometric precision than similitude; otherwise the specimen found in the core agrees perfectly. 

The two characteristics which Castracane used in his 

description to differentiate his variety from the species, 

the straight inner edge of the sectors and the failure of 

the hyaline rays to reach the margin, are well exhibited 

in the present specimen. Unfortunately, the convexity 

of the valve is so great that the margin is out of focus 

in my photomicrograph and the latter characteristic is 

not shown clearly. The validity of the variety depends 

on the constancy of these characteristics, but this could 

not be tested in the present case, as only one specimen 

was found. Rattray 78 says in his description of A.

ropencvnus. the intervals broad, their edges

parallel, the outer ends sometimes slightly expanded, 

not reaching the border." On the other hand, Hendey,79 who had a great many specimens of A. roperianus 

at his disposal says in his excellent description, "Hyaline rays proceed from the central area to the periphery." If Hendey's diagnosis of the species is correct, 

and I feel sure that it is, then Castracane's variety is a

77 Lebour, M. V., Tho plank tonic diatoms of northern seas, p. 56, 1980.

78 Itattray, John, A revision of the genus Coscinodiscus and some allied 

genera : Royal Soc. Edinburgh Proc., vol. 16, p. 657. 1889.

79 Hendey. N. I., The plankton diatoms of the southern seas : Discovery 

Repts., vol. 16, p. 270, 1937.
PAR.T 3. DIATOMACEAE 79

valid one. In my specimen the margin is very narrow 

and the hyaline rays stop 2 to 3/u from the periphery. 

Hexagonal areolae continuous with those on each sector 

fill the space between the end of the ray and the 

periphery.

Diameter of figured specimen (U. S. G. S. diatom catalog no. 1960-1), 7l/i. From sample L-54 (U. S. G. S. 

diatom locality 2860), 206-213 cm. below the top of 

core 9.

Found rarely in sample L-54.

Subfamily ACTINOPTYCHOIDEAE 

Genus ACTINOPTYCHTJS Ehrenberg, 1843

Actinoptychus bipunctatus Lohman n. sp.

Plate 16, figures 7, 10-12

Valve discoid, divided into 10 sectors, alternately 

raised or depressed. Central area indefinite in outline, 

sometimes hyaline, but usually covered with fine, scattered punctae in no definite arrangement. Raised 80 sectors covered with large rounded polygonal markings, 7 

to 8 in 10/A, which appear round under medium or low 

magnification. Depressed sectors covered with similar 

markings overlain by fine puncta, 19 to 20 in lOju, arranged in rows parallel to the center, radial row in each 

sector. Narrow, hyaline space occasionally across outer 

ends of raised sectors only. Marginal apiculi usually 

opposite the center of all sectors, occasionally only in 

depressed (bipunctate) sectors. Occasional valves have 

one to three apiculi perpendicular to the plane of the 

valve and in the sectors about one-fifth to one-fourth 

of the radius away from the margin. Margin narrow, 

0.7 to 1.0/A wide, covered with fine decussate puncta, 20 

to 22 in 10/x. Diameter, 25 to 35^.

Holotype: U. S. G. S. diatom catalog no. 2000-1 (figs. 

10-12), diameter, 34^. Paratype: IT. S. G. S. diatom 

catalog no. 1970-10 (fig. 7), diameter 26/x. Both from 

U. S. G. S. diatom locality 2858. Sample L-52 from 

142-151 cm. below the" top of core 9, taken at a depth 

of 2,050 fathoms in lat. 49°40'00" N. and long. 28°29'00" 

W. by C. S. Piggot, 1936.

The fine puncta on the depressed sectors can be seen 

with difficulty with a 4-mm. apochromat used at nearly 

full aperture and are quite obvious under a 2-mm. oil 

immersion apochromat. When a dry objective is used 

with an effective numerical aperture of around 0.50, the 

fine puncta 011 the depressed sectors are not visible, and 

the diatom somewhat resembles A. par v us Mann.81 

Mann's species, however, in addition to having identical 

markings on all sectors, is much less undulate and never 

has a hyaline space across the outer ends of any sectors. 

In the present species, the narrow hyaline space across 

the outer ends of the raised sectors is definitely seen with 

some difficulty and is never present across the ends of the

80 The terms "raised"' and "depressed" may be interchanged if the 

valve is viewed from the opposite side.

81 Mann, Albert, Marine diatoms of the Philippine Islands : U. S. Nat. 

Mus. Bull. 100, vol. 6, part 1, p. 15, pi. 1, fig. 8, 1925.

depressed bipunctate sectors. The fine puncta in the 

bipunctate depressed sectors extend into and become 

continuous with the marginal puncta, but the coarser 

markings in the same sectors stop about I/A short of the 

margin, giving the appearance of a hyaline space when 

viewed with objectives of insufficient aperture to resolve 

the finer puncta. These obviously illusory spaces in the 

depressed sectors are more visible under low and medium 

magnifications than the real spaces in the raised sectors.

Hanna and Grant 82 have figured a 10-sectored specimen of A. maculatus Grove and Sturt, of about the same 

size as the present species which might be confused with 

it. A. bipunctatus has a narrower margin with the same 

type of markings throughout, whereas A. maculatus 83 

has the symmetrical group of coarse marginal puncta 

opposite each bipunctate sector, has coarse markings 

(maculations) in alternate sectors and fine markings 

throughout (the reverse is true in the present species), 

and has a prominent hyaline space opposite the sectors 

with fine markings only.

A large number of individuals of this species were 

found in the cores, and the characters as given above 

were remarkably constant, with the following exceptions : The scattered puncta in the central area ranged 

from prominent in most specimens to absent in a few; 

the marginal apiculi were present on all sectors in most 

cases and on alternate sectors in a few specimens. The 

number of sectors, usually considered to be a feature 

of minor importance in this genus, was uniformly 10 in 

all specimens observed.

Found rarely in samples L-30, L-50, L-51, and 1^-59, 

and frequently in samples L-31, Lr-52, and L-54.

Actinoptychus campanulifer Schmidt

Plate 16, figure 8

Acti-noptycJius Cftmpanulifer Schmidt, Atlas der Diatomaceenkunde, pi. 29, figs. 13-15, 1875.

The occurrence of this diatom in the cores is the 

first known to me since its original discovery by 

Schmidt from Rio Brasil in 1875. The broad hyaline 

submarginal space on alternate sectors, with pronounced marginal apiculi on intervening sectors, are 

distinguishing features that are constant among the 

specimens studied.

The specimen figured is the best one found, and unfortunately it was tilted somewhat- in mounting, so 

that only half of the valve is in focus.

Diameter of figured specimen (U. S. G. S. diatom 

catalog no. 1984-5), 33^. From sample 1^65 (U. S. 

G. S. diatom locality 2878), 0-7 cm. below the top of 

core 13.

Found rarely in samples L-62 and L-65.

82 Hanna, G. 1)., and Grant, W. M., Miocene marine diatoms from Maria 

Madre Island, Mexico: California A cad. Sci., 4th ser., vol. 15, no. 2, 

p. 122, pi. 11, figs. 8, 9, 1926.

83 Grove, Edmund, and Sturt, Gerald, On a fossil marine diatomaceous 

deposit from Oamaru. Otago, New Zealand : Quekett Micr. Club Jour., ser. 

2, vol. 3, p. 64, pi. 5, fig. 5, 1887.
80 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

Actinoptychus senarius (Ehrenberg) Ehrenberg

Plate 16, figure 9

Actinocyclus senarius Ehrenberg, Die Infusionsthierchen als 

vollkommene Organismen, p. 172, pi. 21, fig. 6,1838.

Actinoptychus senarius (Ehrenberg) Ehrenberg, Berlin K. Akad.

Wiss. Physikal. abh., 1841, p. 400, pi. 1, fig. 27, 1843. 

Hendey, Discovery Repts., vol. 16, p. 271, 1937.

Actinocyclus sp. Bailey, Am. Jour. Sci., 1st ser. vol. 42, pi. 2, 

fig. 11, 1842.

Actinocyclus undulatus Kiitzing, Die kieselchaligen Bacillarien 

oder Diatomeen, p. 132, pi. 1, fig. 44, 1844.

Omphalopelta areolata Ehrenberg, K. akad. Wiss. Berlin, Ber.

1844, p. 270, 1845.

Ehrenberg, Mikrogeologie, pi. 33, group 13, fig. 17; pi. 35A, 

group 18, fig. 2, 1854.

Actinoptychus undulatus (Kiitzing) Ralfs, in Pritchard, A 

history of Infusoria, 4th ed., p. 839, pi. 5, fig. 88, 1861.

Actinoptychus omphalopelta Grunow, in Fenzl, Reise der Osterreichischen Fregatte Novara um die Erde in Jahren 1857, 

1858, 1859, Bot. Theil, Band 1, p. 25, 1870.

Actinoptychus undulatus Kiitzing. Grunow, idem, p. 25, 1870.

Actinoptychus undulatus var. senarius Grunow, idem, p. 25,1870.

Actinoptychus undulatus Ehrenberg. Schmidt, Koinm. zur 

Untersuchung der deutschen Meer in Kiel, p. 94, pi. 3, 

figs. 29, 30, 1874. 

Schmidt, Atlas der Diatomaceenkunde, pi. 1, figs. 1-4, 1875;

pi. 109, fig. 1, 1886; pi. 132, fig. 16, 1888. ' 

Van Heurck, Synopsis diatomees Belgique, pi. 22B, fig. 14, 

1880; pi. 122, figs. 1, 3,1883; p. 210,1885.

Actinoptychus undulatus var. microsticta Grunow, in Van 

Heurck, Synopsis diatomges Belgique, pi. 122, figs. 2, 4, 

1883.

Actinoptychus undulatus Ehrenberg. Van Heurck, Treatise on 

the Diatomaceae, p. 493, fig. 232; p. 494, fig. 234; p. 496, 

pi. 22, fig. 648, 1896.

Actinoptychus undulatus (Bailey) Ralfs. Mann, Contr. U. S. 

Nat. Herbarium, vol. 10, pt. 5, p. 272, 1907.

Actinoptychus undulatus (Kiitzing) Ralfs. Boyer, The Diatomaceae of Philadelphia and vicinity, p. 24, pi. 4, figs. 1, 2, 

4, 6, 1916.

Actinoptychus undulatus (Bailey?) Ralfs. Boyer, Acad. Nat. 

Sci. Philadelphia Proc., vol. 78, supplement, p. 64, 1926.

Actinoptychus undulatus (Bailey). Hanna and Grant, California Acad. Sci. Proc., 4th ser., vol. 15, no. 2, p. 124, pi. 12, 

fig. 4, 1926.

Actinoptychus undulatus Ehrenberg. Hanna, Jour. Paleontology, vol. 1, no. 2, p. 108, 1927.

Actinoptychus undulatus Ralfs. Karsten, in Engler, Die naturlichen Pflanzenfamilien, Band 2, Bacillariophyta, p. 219, 

fig. 236, a, b, 1928. 

Coupin, Album general des Diatomees, pi. 294, fig. H, 1930.

Actinoptychus undulatus (Bailey) Ralfs. Hustedt, Kieselalgen 

Deutschlands, Osterreichs, und der Schweiz, Teil 1, p. 475, 

fig. 264, 1929. 

Hanna, Califomia Acad. Sci. Proc. 4th ser., vol. 20, No. 6,

p. 172, 1932.

Mills, An Index to the Genera and Species of the Diatomaceae, vol. 1, p. 117, 1933.

Actinoptychus undulatus Ehrenberg. Lohman, U. S. Geol. Survey Prof. Paper 189-C, p. 82, pi. 20, fig. 8; pi. 22, fig. 3,1938.

Although the above list may seem unnecessarily long 

and detailed, it is only a fragment of the available 

synonymy of this species. The present synonymy has 

been given in considerable detail to show the uncertainty with which the name Actinoptychus undulatus

has been used in the past by different authors, and to 

justify Hendey''s action 84 in invoking the rule of strict 

priority by returning to Ehrenberg's original name, 

Actinoptychus senwrius. In each of the citations the 

authorship of the species is given, exactly as it appears 

in the paper cited. The synonymy itself presents such 

a graphic picture of the uncertainty with which the 

name Actinoptychus undulatus has been used by different authors (occasionally even by the same author in 

different works1 ) that the point hardly needs elaboration 

here.

As Hendey's excellent volume on the planktonic diatoms of the southern seas may not be available to many, 

his argument for changing the name of this well-known 

diatom deserves to be repeated here. He says: 85

It has been often said that there existed in the minds of early 

diatomists a confusion between Actinoptychus and Actinocyclus. 

Although this has now been settled, the following notes are included in order to make clear the reasons which have led to 

changes being made in the names of some well-known species. 

Ehrenberg (1838, p. 171) M established the genus Actinocyclus. 

Two species were described and figured, A. senarius and A. octonarius. Later, other forms were added, and Ehrenberg, realizing 

that the genus contained more than one group, desired to make a 

separation. Ehrenberg (1840a) 87 introduced a subgenus in the 

following manner:

"Actinocyclus (Actinoptychus) senarius, synonym Actinocyclus senarius 1838." Later Ehrenberg ((1841) 1843, p. 400) 8' 

established the genus Actinoptychus. On a previous page (p. 

328), and in the description of the plates, the combination 

Actinoptychus senarius was used, and there is reason to believe 

from the similarity of the figures provided that Actinoptychus 

senarius Ehrenberg was based on Actinocyclus senarius (1838). 

Ehrenberg (1843, p. 400) explained that the separation was 

necessary on account of structural differences that existed in 

Actinocyclus (1838) and continued at some length to explain 

the differences upon which the separation was made. Actinocyclus octonarius (1838) was retained as the type species of 

Actinocyclus. The species Actinoptychus senarius is often 

attributed to Bailey in the following manner: "Actinoptychus 

undulatus Bailey," but there appear to be no grounds for this. 

Bailey (1842) 89 mentioned the occurrence of a number of 

species of Actinocyclus in fossil material from Richmond, Virginia, and provided figures which undoubtedly represented the 

species under consideration here, but the figures were unnamed, 

Ehrenberg (1843, p. 328) accepted Bailey's figure as being 

equal to his Actinoptychus senarius. Kiitzing (1844) 90 took 

Bailey's illustration as a type illustration and described 

Actinocyclus undulatus. Ralfs (1861J 81 placed this species in

84 Hendey, N. I., The plankton diatoms of the southern seas: Discovery 

Repts., vol. 16, p. 271, 1937.

& Hendey, N. I., Idem., p. 271.

so Ehrenberg. C. G., Die Infusionsthierchen als volkommene Organismen, 

p. 171, 1838.

87 Ehrenberg, C. G., Uber noch jetzt zahlreich lebende Thierarten der 

Kreidebildung und den Organismus der Polythalmien: K. Akad. Wiss. 

Berlin. Physikal. Abh. 1839, p. 137, pi. 4, fig. la-e, 1841.

88 Ehrenberg, C. G., Verbreitung und Einfluss des mikroskopischen 

Lebens in Sud- und Nord-Amerika: Berlin K. Akad. Wiss. Physikal. Abh., 

1841. p. 400, 1843.

^Bailey. J. W.. A sketch of the infusoria of the family Bacillaria, with 

some account of the most interesting species which have been found in a 

recent or fossil state in the United States: Am. Jour. Sci., vol. 42, p. 93, 

pi. 2, fig. 11, 1842.

90 Kiitzing, F. T., Die kieselschaligen Bacillarien oder Diatomeen, p. 132, 

pi. 1, fig. 44, 1844.

91 Ralfs, John, in Pritchard, Andrew, A history of Infusoria, 4th ed., p. 

839. pi. 5, fig. 88, 1861.
PART 3. DIATOMACEAE 81

the genus Actinoptychus, but accepted Ktitzing's epithet. 

Ehrenberg's epithet is used here to satisfy claims of priority.

This is another case (see Actinoctyclus octonarius 

Ehrenberg, p. 77) where there is no choice between the 

claims of strict priority and the "common sense" view 

of allowing a well-established name to stand.

This neritic species is common in subtropical seas, and 

Lebouri92 has reported it from "all parts of the North 

Sea, Norwegian Seas, Danish Seas, Skaggerak, Baltic, 

North Atlantic, Finland, English Channel, West Coast 

of France, Mediterranean, Atlantic and Pacific American coasts." Its geologic range is Eocene 93 to Recent.

Diameter of figured specimen (IT. S. G. S. diatom 

catalog no. 1958-1): 39^. From sample L-52 (IT. S. 

G. S. diatom locality 2858), 142-151 cm. below the top 

of core 9.

Found rarely in samples L-23, L-31, L-32, L-37, and 

L-52 and frequently in sample L-10.

Suborder BIDDULPHINEAE

Family CHAETOCERACEAE

Subfamily CHAETOCEBOIDEAE

Genus CHAETOCEROS Ehrenberg, 1844

Subgenus PHAEOCEROS Gran, 1897

Chaetoceros atlanticum Cleve

Plate 17, figure 1

Chaeloceros atlanticum Cleve, K. svenska vetensk. akad. Handl.,

Band 1, no. 13, p. 11, pi. 2, fig. 8, 1873. 

Gran, Nordisches Plankton, Lief. 3, p. 64, fig. 74, 1905. 

Hustedt, in Schmidt, Atlas der Diatomaceenkunde, pi. 337,

fig. 1, 2, 1921. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der

Schweiz, Teil 1, p. 641, fig. 363, 1930. 

Hendey, Discovery Repts., vol. 16, p. 290, 1937. 

Chaetoceros dispar Castracane, Challenger Repts., Botany, vol.

2, p. 76, pi. 8, fig. 6, 1886. 

Chaetoceros auda® Schiitt, Deutsche bot. GeselL Ber., Band 13,

p. 47, pi. 5, fig. 25, 1895.

Chaetoceros polyaonum Schiitt, Deutsche bot. Gesell. Ber., Band 

13, p. 46, pi. 5, fig. 24, 1895.

This oceanic species is common in north polar and 

North Atlantic waters and is frequently found in European seas farther south. Hendey (5th citation above) 

notes that it prefers a high salinity and although common in south temperature seas is seldom found in Antarctic waters.

Major axis of valve in specimen figured (IT. S. G. S. 

diatom catalog no. 1957-4), 27^. From sample L-52 

(U. S. G. S. diatom locality 2858), 142-151 cm. below 

the top of core 9.

Found rarely in sample L-30 and frequently in 

sample L-52.

92 Lebour, M, V., The planktonic diatoms of northern seas, p. 51, fig. 27, 

1930.

93 Hanna, G. D., The lowest known tertiary diatoms in California : 

Jour. Paleontology, vol. 1, no. 2, p. 108, 1927. (From Kreyenhagen 

shale in Phoenix Canyon, Fresno County, California, then considered by 

Hanna to be Lower Miocene in age, but now thought to be Upper Eocene.)

Suborder SOLENIINEAE

Family RHIZOSOLENIACEAE

Subfamily RHIZOSOLENIOIDEAE

Genus RHIZOSOLENIA Ehrenberg, 1843, emend. Brightwell, 1858

Rhizosolenia bergonii H. Peragallo

Plate 17, figure 2

Rhizosolenia bergonii H. Peragallo, Le Diatomiste, vol. 1, p. 110,

pi. 15, fig. 5, 1892.

Gran, Nordisches Plankton, Lief. 3, p. 51, fig. 60, 1905. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der

Schweiz, Teil 1, p. 575, fig. 327,1929. 

Lebour, The planktonic diatoms of northern seas, p. 102, fig.

74b, 1930. 

Rhizosolenia amputata Ostenfeld, in Schmidt, Bot. Tidsskrift,

Band 25, p. 227, fig. 4, 1902. 

Hustedt, in Schmidt, Atlas der Diatomaceenkunde, pi. 318,

fig. 1-3, 1920.

Only the spines of this oceanic species were found 

and these rarely. The characteristic canal, cup-shaped 

at the apex and inflated at the base, and the fine markings on the shoulder serve to identify these fragments.

It is usually found in tropical and subtropical seas. 

Lebour (4th citation above) gives the northerly limit 

of this species as lat. 48° N.

Length of fragment figured (U. S. G. S. diatom catalog no. 1961-1), 8fyu From sample L-55 (U. S. G. S. 

diatom locality 2861), 246-250 cm. below the top of 

core 9.

Found rarely in sample L-55.

Rhizosolenia styliformis Brightwell

9 Plate 17, figures 3, 4

Rhizosolenia styliformis Brightwell, Quart. Jour. Micr. Sci., vol.

6, p. 95, pi. 5, fig. 5, 1858.

Peragallo, H., Le Diatomiste, vol. 1, p. Ill, pi. 17, fig. 5, 1892. 

Van Heurck, Treatise on the Diatomaceae, p. 415, fig. 133;

pi. 17, fig. 601, 1896.

Gran, Nordisches Plankton, Lief. 3, p. 54, 1905. 

Hustedt, in Schmidt, Atlas der Diatomaceenkunde, pi. 316,

figs. 1-4, 8-11, 1914. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der

Schweiz, Teil 1, p. 584, fig. 333, 1929. 

Hendey, Discovery Repts., vol. 16, p. 320, pi. 11, figs. 15-17,

1937.

Kain and Schultze 94 have reported this species from 

beds that are probably equivalent to the Calvert formation (middle Miocene) of Maryland, from a depth of 

387-638 feet in a well at Atlantic City, N. J. Brun and 

Tempere^5 also reported this species as abundant in 

a calcareous shale of probable upper Miocene age in 

Sendai, Japan. Its occurrence in these older rocks is 

particularly interesting, as the cell wall in this species 

is usually much less highly silicified than in other diatoms. Many specimens were found in the cores, but

04 Kain, C. H., and Schultze, E. A., On a fossil marine diatomaceous deposit from Atlantic City, N. J.: Torrey Bot. Club Bull., vol. 16, p. 76, 

1889.

95 Brun, 3., and Tempere, J., Diatomges fossiles du Japon : GenSve Soc. 

Phys. Hist. Nat. M6m., tome 30, No. 9, p. 73, 1889.
82 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

in each case only the apical spines and small portions 

of the valve were preserved. The winglike projections 

near the base of the spine are clearly shown in figure 3. 

This is an oceanic species of world-wide distribution, 

common in both tropical seas and in the colder subArctic and sub-Antarctic waters.

Over-all lengths of fragments figured

Figure

4

3

U. S. G. S. 

diatom catalog number

1960-2

1964-5

U S. G. S. 

diatom locality number

2860

2864

Sample 

number

L-54

L-2

Length 

in M

92

75

Found rarely in samples L-3, L-6, L-31, and L-54 

and frequently in samples L-2, L-4, L-30, and L-37.

Suborder ARAPHIDINEAE

Family FRAGILARIACEAE

Subfamily FRAGILARIOIDEAE

Genus RHAPHONEIS Ehrenberg, 1844

Rhaphoneis surirella (Ehrenberg) Grunow 

Plate 17, figure 6

Zygoceros surirella Elirenberg, K. Akad. Wiss. Berlin Abh., pi. 4,

fig. 12, 1840.96 

Ralfs, in Pritchard, History of the Infusoria, 4th ed., p. 850,

pi. 11, figs. 50, 51, 1861.

Rhaphoneis surirella (Ehrenberg) Griuiow, in Van Heurck, Synopsis diatomees Belgique, pi. 36, fig. 26, 27a, 1881. 

De Toni, Sylloge algarum omnium hucusque cogiiitarum,

vol. 2. p. 712, 1892. 

Hustedt, Die Kieselalgeu Deutschlands, Osterreichs, und der

Schweiz, Teil 2, p. 173, fig. 679 a-c, 1931. 

Dimcroffrattima stirircUa Grunow, K. svenska vetensk. »akad.

Handl.. Band 5, no. 8, p. 11, 1878. 

Fruffilaria surirella Schonfeldt, Die dentsclien Diatomeen des

Siisswassers und des Brackwassers, p. 103, 1907. 

Rhaphoneis surireUa Ehreuberg. Hustedt, in Schmidt, Atlas 

der Diatomaceenkuiide, pi. 267, figs. 47—49, 1911.

The pseudoraphe in this species is frequently expanded near the apices. In the specimen found in the 

core, the pseudoraphe was parallel-sided throughout its 

length. Hustedt (5th citation above) has figured both 

forms.

This species lives in brackish and salt water and is 

frequently found in brackish estuaries and along the 

coast of southern Europe.

Length of figured specimen (U. S. G. S. diatom catalog no. 1984-4), 36,.*. From sample L-66 (U. S. G. S. 

diatom locality 2878), 0-7 cm. below the top of core 13.

Found rarely in sample L-66.

Genus THALASSIOTHRIX Cleve and Grunow, 1880 

Thalassiothrix longissima Cleve and Grunow

Plate 17, figure 5

lltuhtxKiothriae Cleve, K. svoiiska vetensk. akad. Handl., 

Bihang, Band 1, 110. 13, p. 22, pi. 4, fig. 24, 1873.

Thalassiothrix longissima Cleve and Grunow, K. svenska vetensk.

akad. Handl., Band 17, no. 2, p. 108, 1880. 

Heiden and Kolbe, Deutsche S'iidpolar-Expedition, Band 8,

Botanik, Heft 5, p. 565, pi. 6, fig. 123, 1928. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der

Schweiz, Teil 2, p. 247, fig. 726, 1932. 

Hendey, Discovery Repts., vol. 16, p. 336, 1937.

This diatom, the longest known, attains a length of 

4 mm. with an average width of only 3 to 4/u,. As only 

fragments of varying length are found in anything but 

recent material, it is easily confused with Thalass-lonema 

nitzschioides (Grunow) Hustedt, which has somewhat 

similar markings. The latter species, however, grows 

in stellate or zigzag clusters, and individual frustules 

rarely attain a length of lOOju.

It occurs commonly to frequently in middle Miocene 9T 

and later rocks in California. In general the forms 

assigned to this species from the cores are somewhat 

heavier-walled that the California forms; otherwise they 

are identical. In the Upper Miocene Monterey formation in California, concentrations of this diatom occur in 

the form of thin partings in shale up to beds several 

inches thick, in which it forms a very large percentage of 

the material present. No such concentrations were 

observed in the cores.

Brim and Tempere 98 found it in considerable abundance in Japan in what are now considered to be upper 

Miocene rocks. In my report on the Pliocene diatoms 

from the Kettleman Hills, Calif.,99 I erroneously assigned this diatom to Thalassw'iiema nitzschioid,ex 

Grunow.

It is a true pelagic marine cold-water diatom and 

is very common in the Arctic seas, the North Atlantic, 

along the European coasts, and in the South Atlantic 

and South Pacific.

Although one of the most abundant species found in 

the cores, no whole specimens were found. The fragments ranged from 3/A to 6/u, in width, and 30^ to 165^ in 

length.

Dimensions of figured specimen (fragment) (U. S. 

G. S. diatom catalog no. 1957-9) : Length, 165ju; maximum width, 6|U,. From sample L-52 (U. S. G. S. diatom 

locality 2858), 142-151 cm. below the top of core 9.

Found rarely in sample L-6, L-7, L-8, L-16, L-49, 

L-53, L-59, and L-61, frequently in samples L-l, L-2, 

L-3, L-20, L-23, L-33, L-50, and L-55, commonly in 

samples L-10, L-19, L-32, L-37, L-51, 1^52, L-54, and 

L-56, and abundantly in samples L-4, L-30 and L-31.

96 This citation is doubtful, as I have been unable to find the original. 

Reference here taken from Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der Schweiz, Teil 2, p. 173, 1931.

97 Lohman, K. E., Comparison of the diatom floras from the Temblor 

formation (middle Miocene) in California with those from the Calvert 

(middle Miocene) in Maryland and Virginia : MS. (Report in preparation).

98 Brun, Jacques and Tempere, J., Diatoniees fossiles du Japon. Especes 

marines et nouvelles des calcaires argileux de Sendai et de Yedo : Geneve 

Soc. Physique Hist. Nat. Me"m., tome 30, no. 9, p. 74, 1889.

99 Lohman, K. E.. Pliocene diatoms from the Kettleman Hills, California : 

U. S. Geol. Survey Prof. Paper 189-C, p. 83, 1937.
PART 3. DIATOMACEAE 83

Suborder RAPHIDIOIDINEAE

Family EUNOTIACEAE 

Genus EUNOTIA Ehrenberg, 1837

Eunotia praerupta Ehrenberg var. bidens (W. Smith) Grunow

Plate 17, figure 7

Hirnantidium bidens Ehrenberg. W. Smith, Synopsis of the

British Diatomaoeae, vol. 2, p. 13, pi. 33, fig. 284. 1854. 

Eunotia praerupta Ehrenberg var. bidens (W. Smith) Grunow, 

in Van Heurck, Synopsis diatomees Belgique, pi. 34, figs. 

20, 21, 1881. 

Grunow, Akad. Wiss. Wien, Math.-naturwiss. Kl., Denkschr.,

Band 48, p. 48, pi. 2 (B), fig. 12, 1884. 

Hustedt, in Schmidt, Atlas der Diatomaceenkunde, pi. 273,

figs. 26-28, 32, 33, 1911. 

Hustedt, in Pascher, Die Susswasser-flora Mitteleuropas,

Heft 10, p. 174, fig. 213, 1930. . 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und

der Schweiz, Teil 2, p. 281, figs. 747A, i-m, 1932. 

Eunotia, bigibba Gregory (not Kiitzing), Quart. Jour. Micr. 

Sci., 1854, p. 95, pi. 4, fig. 3.

William Smith, in his original (?) description of 

Himantidium bidens cited Ehrenberg as the author, 

but no one has since been able to discover where or 

when Ehrenberg described it. The authority is, 

therefore, attributed to Smith.

This is another fresh-water diatom that must have 

been transported many miles to be deposited on a midAtlantic sea bottom.

Length of figured specimen (U. S. G. S. diatom catalog no. 1987-1), 69/i. From sample L-39 (U. S. G. S. 

diatom locality 2894), 275-281 cm. below the top of 

core 6.

Found rarely in sample no. L-39.

Genus PSEUDOEUNOTIA Grunow, 1881 

Pseudoeunotia doliolus (Wallich) Grunow

Plate 17, figure 12, 13

Synedra doliohis Wallich, Micr. Soc. London Traus., new ser.,

vol. 8, p. 48, pi. 2, fig. 19, 1860. 

PscudocHtwtia doUolus (Wallich) Grunow, in Van Heurck,

Synopsis diatomees Belgique, pi. 35, fig. 22, 1881. 

Mann, U. S. Nat. Mus. Bull. 100, vol. 6, pt. 1, p. 140, pi. 30,

figs. 7-8, 1925. 

Heiden and Kolbe, Deutsche Sudpolar-Expeditkm 1901-11)03,

Band 8, Botanik, Heft 5, p. 558, 1928. 

Hustedt, Die Kieselalgen Deutschlands, Osterreichs, und der

Schweiz, Teil 2, p. 259, fig. 737, 1932.

Himantidium? doliolus Grunow, Zool.-bot. Gesell. Wien Verh., 

Band 12, p. 342, 1862.

Hustedt's figure (5th citation above) is somewhat misleading, as he does not show the heavy, double-beaded 

margin that is clearly shown in Grunow's figures (2d citation above) and in Mann's figures (3d citation above). 

It is very prominent on the forms found in the cores. 

My specimens have the same slender, produced apices 

shown in Mann's figures, and not the broader apices 

shown by Hustedt.

This is a littoral, warm-water species found along the 

coast of southern Europe and around the Philippine

Islands. It has never been reported from the North or 

West Atlantic, and its presence in the cores suggests long 

travel before deposition.

Dimensions of figured specimen (U. S. G. S. diatom 

catalog no. 2000-2) : Length, 75/u,; width, 8^. From 

sample 1^52 (U. S. G. S. diatom locality 2858), 142-151 

cm. below top of core 9.

Found rarely in samples L-10, L-37, L-51, and L-52.

Suborder MONORAPHIDINEAE

Family ACHNANTHACEAE

Subfamily ACHNANTHOIDEAE

Genus RHOICOSPHENIA Grunow, 1860

Rhoicosphenia curvata (Kiitzing) Grunow

Plate 17, figure 8

Gomphonema citrvatum Kiitzing, Linnaea, vol. 8, p. 567, pi. 16,

fig. 51, 1833.

Rhoicosphenia curvata, (Kiitzing) Grunow, in Fenzl, Reise der 

Osterreichischen Fregatte Novara urn die Erde, Bot. 

Theil, Band 1, Algen, p. 8, 1870. 

Van Heurck, Synopsis diatomees Belgique, p. 127 (1885),

pi. 26, fig. 1-3, 1880. 

Schmidt, Atlas der Diatomaceenkunde, pi. 213, figs. 1-5,

1899. 

Pantocsek, Die Kieselalgen oder Bacillarien des Balaton,

p. 60, pi. 7, figs. 155, 156, 1901. 

Buyer, Diatomaceae of Philadelphia and vicinity, p. 56, pi.

19, figs. 25-27, 1916. 

Hustedt, in Pascher, Die Susswasser-flora Mitteleuropas,

Heft 10, p. 211, fig. 311, 1930. 

Hustedt, Die Kieselalgen, Deutschlands, Osterreichs, und

der Schweiz, Teil 2, p. 431, fig. 879, 1933. 

Gomphonema fractum Schumann, Konigsberg physikal.-okonomische Gesell. Schr., Band 3, p. 187, pi. 9, fig. 32, 1863, 

Rhoirosphenia fracta Rabenhorst, Flora Europaea algarmn, p.

292, 1864. 

Rhoicosphenia curvata var. fracta Cleve, K. svenska vetensk.

akad. Handl., Band 27, no. 3, p. 166, 1895.

Rhoicospherma linearis Ostrup, Danske Diatomeer, p. 120, pi. 3, 

fig. 74, 1910.

This widely distributed fresh-water and brackishwater form was probably introduced into the basin of 

deposition by currents.

Dimensions of specimen figured (U. S. G. S. diatom 

catalog no. 1951-2) : Length (as shown), 68^; maximum width, 14|U,. From sample L-10 (U. S. G. S. diatom locality 2854), 74-79 cm. below the top of core 4.

Found rarely in sample L-10.

Suborder BIRAPHIDINEAE

Family NAVICULACEAE 

Subfamily NAVICULOIDEAE 

Genus NAVICULA Bory, 1822

Navicula pennata Schmidt

Plate 17, figure 14

NaviciiJa pennata, Schmidt, Atlas der Diatomaceenkunde, pi. 48.

fig. 41-43, 1876. 

Cleve, K. svenska vetensk. akad. Handl., Band 27, no. 3.

p. 32, 1895. 

Mann, Contr. U. S. Nat. Herbarium, vol. 10, pt. 5, p. 349,

1907.
84 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

Boyer, Diatomaceae of Philadelphia and vicinity, p. 96, pi.

27, fig. 22, 1916. 

Lohman, U. S. Geol. Survey Prof. Paper 189-C, p. 84, pi. 22,

fig. 16, 1938.

Mann (see 3d citation above) has listed as synonyms 

of this species, N. Mnkeri Pantocsek,1 N. pinnata Pantocsek,2 and Scoliopleura szakalensis Pantocsek,3 which 

for several reasons does not appear to have been a wise 

choice. The type of N. pennata Schmidt came from 

the Mediterranean Sea and has since been found living 

in several other localities. Neither N. Mnkeri or N. 

pinnata have been found living and hence may be of 

value in stratigraphy if kept separate from N. pennata. 

Cleve * combined Scoliopleura szdkalensis and Navicula 

Mnkeri as Navicula pennata var. Mnkeri, which appears to be a satisfactory solution of the difficulty. 

Cleve retained N. pinnata, Pantocsek as a separate 

species, and several other authors have followed.5

This is a warm-water species of wide distribution at 

present and is known from the Pliocene 6 to the Recent.

Dimensions of figured specimen (fragment) (U. S. 

G. S. diatom catalog no. 1964r-l) : Length, 75/*; width, 

17/*; costae, 4-5 in 10^. From sample L-2 (U. S. G. S. 

diatom locality 2864), 40-48 cm. below the top of core 3.

Found rarely in samples L-2 and L-66.

Genus DIPLONEIS Ehrenberg, 1844 

Diploneis interrupts (Kiitzing) Cleve

Plate 17, figure 15

Navicula interrupt® Kiitzing, Die kieselschaligen Bacillarien

Oder Diatomeen, p. 100, pi. 29, fig. 93, 1844. 

Diploneis interrupts (Kiitzing) Cleve, K. svenska vetensk.

akad. Handl., Band 26, no. 2, p. 84, 1894. 

Boyer, Acad. Nat. Sci. Philadelphia Proc., vol. 79 5 supplement, p. 348, 1927. 

Hustedt, in Pascher, Siisswasser-flora Mitteleuropas, Heft

10, p. 252, fig. 400, 1930. 

Navicula interrupta Kiitzing. Donkin, The natural history of

the British Diatomaceae, pt. 1, p. 47, pi. 7, fig. 2, 1870. 

Schmidt, Atlas der Diatomaceenkunde, pi. 12, figs. 3-11,

1875; pi. 69, fig. 24, 1881. 

Van Heurck, Synopsis diatomdes Belgique, p. 89, 1885;

pi. 9, figs. 7, 8, 1880. 

Navicula interrupts var. novae-seel undiae Schmidt, Atlas der

Diatomaceenkunde, pi. 12, fig. 12, 1875. 

Diploneis didyma Ehrenberg, K. Akad. Wiss. Berlin, Physikal.

Abh., 1870, pi. 2, fig. 13, 1871. 

Navicula puclla Schmidt, Atlas der Diatomaceenkunde, pi. 69,

fig. 25, 1881.

This brackish-water and marine species is one of 

the most tolerant diatoms known. It occurs in brack1 Pantocsek, Josef, Beitrage zur Kenntnis der fossilen Bacillarien Ungarns, Teil 2, p. 50, pi. 9, fig. 169,1889.

a Idem, Tell 2, p. 54, pi. 20, fig. 308.

3 Idem, Teil 2, p. 57, pi. 8, fig. 154.

* Cleve, P. T., A synopsis of the naviculoid diatoms, part 2 : K. svenska 

vetensk. akad. Handl., Band 27, no. 3, p. 33,1895.

5 Mills, F. W., An index to the genera and species of the Diatomaceae, 

part 15, p. 1120, 1934.

9 Lohman, K. B., Pliocene diatoms from Kettleman Hills, California: 

U. S. Geol. Survey Prof. Paper 189-C, p. 84, pi. 22, fig. 16,1938.

ish to almost fresh water, under truly marine conditions, and under an equally wide variety of temperatures. Cleve 7 listed the following habitats for this 

diatom:

Spitzbergen, Beeren Biland (Lagst), Kara, Finmark, North 

Sea, Baltic (Tornea to Riigen), Mediterranean Sea, Red Sea 

(Grun.), Java, Samoa, Australia, Aukland (Grun.), Cape Good 

Hope (Atl.), Atlantic Coast of America, Greenland, Arctic 

America, Franzenbad, Halle, Great Salt Lake.

The reference to Great Salt Lake above is misleading, as it implies that Diploneis interrupta is living.in 

the highly saline water of the Great Salt Lake. In 

1870 Ehrenberg 8 published a paper on diatoms from 

California in which he lists D. didyma (— D. interrupta) from three samples of "Sehr weisse, mehlartige, 

leichte Erde" cataloged as "Salt Lake Nr. 6550, Nr. 

6551, and Nr. 6559," on pages 14, 15, and 16 respectively. In his checklist, facing page 68, the same samples are again listed by "Salt Lake Nr. 6550" etc., but 

without the lithologic description given in the text. 

It appears that Cleve, in making his list of habitats, 

used the checklist and thought that Ehrenberg's material from Salt Lake was living in the lake water. 

Patrick,8 who studied the diatoms in mud samples 

around the shores of the Great Salt Lake, says, "No 

diatom flora is found living in the lake proper today."

Dimensions of figured specimen (U. S. G. S. diatom 

catalog no. 1986-1) : Length, 33ju,; maximum width, 

13/A; width at constriction, 7/u,; costae, 11 in 10/x. From 

sample L-37 (U. S. G. S. diatom locality 2893), 226- 

230 cm. below the top of core 6.

Found rarely in sample L-37.

Diploneis smithii (Brebisson) Cleve

Plate 17, figure 18

Navicula smithii Brebisson, in Smith, Wm., Synopsis of the

British Diatomaceae, vol. 2, p. 92, 1856.

Diploneis smithii (Brebisson) Cleve, K. svenska vetensk. akad. 

Handl., Band 26, N'o. 2, p. 96, 1894.

Boyer, Acad. Nat. Sci. Philadelphia Proc., vol. 79, supplement, p. 354, 1927.

Hustedt, in Pascher, Die Siisswasser-fiora Mitteleuropas, 

Heft 10, p. 253, fig. 402, 1930.

Lohman, U. S. Geol. Survey Prof. Paper 189-C, p. 84, pi. 23,

fig. 10, 1938.

Navicula smithii Br6bisson. Schmidt, Atlas der Diatomaceenkunde, pi. 7, figs. 14-20, 1875.

Van Heurck, Synopsis diatome"es Belgique, p. 91, 1885; 

pi. 9, fig. 12, 1880; supplement, pi. B, fig. 23, 1884.

Mann, Contr. U. S. Nat. Herbarium, vol. 10, pt. 5, p. 354, 

1907.

Hanna and Grant, California Acad. Sci. Proc., ser. 4, vol. 15, 

No. 2, p. 155, pi. 19, fig. 1, 1926.

7 Cleve, P. T., Synopsis of the naviculoid diatoms: K. svenska. vetensk. 

akad. Handl., Band 26, no. 2, p. 84,1894.

8 Ehrenberg, C. G., Uber die wachsende Kenntniss des vmsichtbaren 

Lebens als felsbildende Bacillarien in Californien: K. Akad. Wiss. 

Berlin Physikal. Abh. 1870, No. 1, pp. 1-74, pis. 1-3, 1871.

9 Patrick, Ruth, Some diatoms of Great Salt Lake: Torrey Bot. Club 

Bull., vol. 63, p. 165, 1936.
PART 3. DIATOMACEAE 85

Hanna and Grant, Jour, Paleontology, vol. 3, no. 1, p. 98,

pi. 13, fig. 5, 1929. 

Navicula elliptica W. Smith, Synopsis of the British Diatomaceae, vol. 1, p. 48, pi. 17, fig. 152a, 1853. 

Navicula doczyi Pantocsek, Beitrage zur Kenntniss der fossilen

Bacillarien Ungarns, Teil 2, p. 45, pi. 14, fig. 247, 1889. 

Navicula (Diploneis) smitMi (Brebisson) Cleve. Reinhold,

Nederland en Kolonien Geol.-Mijnbouwk. Genootschap,

Verh., geol. ser., Deel 12, p. 112, pi. 14, fig. 11, 1937.

This diatom has a world-wide distribution in marine 

and brackish waters in warm, temperate, and cold 

zones. The specimen figured is an elongate, elliptical 

form, but others in the same sample were somewhat 

more angular, approaching the one illustrated in plate 

7, figure 18, of Schmidt's Atlas.

Dimensions of figured specimen (U. S. G. S. diatom 

catalog no. 1981-1) : Length, 81 p" width, 39/t. From 

sample L-60 (U. S. G. S. diatom locality 2873), 233- 

237 cm. below the top of core 10.

Found rarely in samples L-51 and L-60.

Diploneis weissflogii (Schmidt) Cleve 

Plate 17, figure 16

Navicula weissflogii Schmidt, Gesell. Naturwiss. Zeitschr.,

Band 41, p. 406, pi. 6, figs. 3, 4, 1873. 

Diploneis weissflogii (Schmidt) Cleve, K. svenska vetensk.

akad. Handl., Band 26, No. 2, p. 91, 1894. 

Boyer, Acad. Nat. Sci. Philadelphia Proc., vol. 79, supplement, p. 351, 1927. 

Navicula weissflogii Schmidt. Van Heurck, Synopsis diatomees

Belgique, p. 90, supplement, pi. A, fig. 21, 1885. 

Van Heurck, Treatise on the Diatomaceae, p. 194, pi. 3,

fig. 148, 1896.

Reinhold, Nederland en Kolonien, Geol.-Mijnbouwk, Genootschap, Verb., geol. ser., Deel 12, p. 112, pi. 13, fig. 7, 

1937.

Cleve 10 has included Navicula diversa Greville u in 

the synonymy of this species with a query. If Greville's description and figure are accurate, the query 

should stand, as his species is much less constricted, 

the central transverse bars have the small nodules at 

the outer ends rather than towards the center, and the 

markings are much finer, with a stauriform central 

space. Greville's species should, therefore, not be combined with Diplortieis weissflogii, although Peragallo 12 

and Mills 13 (possibly ignoring Cleve's query) have 

done so.

This is a temperate to warm water species with a 

known geologic range of upper Miocene 14 to Recent.

Dimensions of figured specimen (U. S. G. S. diatom 

catalog no. 1972-3): Length, 36/u,; maximum width, 

16/x; width at constriction, llju,. From sample L-4

>• Cleve, P. T., Synopsis of the naviculoid diatoms, part 1: K. svenska 

vetensk. akad. Handl., Band 26, no. 2, p. 91, 1894.

11 Greville, R. K., Descriptions of new genera and species of diatoms 

from the South Pacific : Edinburgh New Philos. Jour., new ser., vol. 18, 

p. 186, pi. 4, fig. 14, 1863.

12 Peragallo, M., Catalogue general des Diatome'es, p. 313, 1897.

18 Mills, F. W., An index to the genera and species of the Diatomaceae, 

part 9, p. 628, 1934.

14 Reinhold, Th., Nederland en Kolonien, Geol.-Mijnbouwk. Genootschap, 

Verh., geol. ser., Deel 12, p. 72, 1937.

(U. S. G. S. diatom locality 2866), 130-137 cm. below 

top of core 3.

Found rarely in sample L-4.

Genus PLETTROSIGMA Wm. Smith, 1852 

Pleurosigma naviculaceum Brebisson

Plate 17, figure 17

Pleurosigma naviculaceum Brebisson, Cherbourg Soc. Sci. Nat.

Mem., tome 2, p. 17, fig. 7, 1854. 

Cleve and Grunow, K. svenska vetensk. akad. Handl., Band

17, no. 2, p. 51, 1880.

Van Heurck, Synopsis diatomees Belgique, p. 116, supplement, pi. C, fig. 35, 1885.

Peragallo, Le Diatomiste, vol. 1, p. 11, pi. 4, figs. 19, 23,1891. 

Cleve, K. svenska vetensk. akad. Handl., Band 26, No. 2,

p. 36, 1894. 

Boyer, Diatomaceae of Philadelphia and vicinity, p. 74,

pi. 22, fig. 6, 1916. 

Pleurosigma transversale W. Smith, Synopsis of the British

Diatomaceae, vol. 2, p. 96, 1856. 

Pleurosigma japonicum Castracane, Challenger Repts., Botany,

vol. 2, p. 38, pi. 29, fig. 14, 1886.

This species is most frequently found in tropical 

waters, although Cleve 15 has reported it from the 

North Sea and Boyer 16 has reported it from Long 

Island Sound. In the material studied for this report 

it was found only in the two easternmost cores.

Dimensions of figured specimen (U. S. G. S. diatom 

catalog no. 1984-1) : Length, 87/t; width, 21^. From 

sample L-66 (U. S. G. S. diatom locality 2878), 0-7 cm. 

below the top of core 13.

Found rarely in sample L-62 and frequently in 

sample L-66.

Family BACILLARIACEAE

Subfamily NITZSCHIOIDEAE

Genus NITZSCHIA Hassall, 1845

Nitzschia marina Grunow

Plate 17, figure 10, 11

Nitsschia marina Grunow, hi Cleve and Grunow, K. svenska 

vetensk akad. Handl., Band 17, No. 2, p. 70, 1880.

Grunow, in Van Heurck, Synopsis diatomees Belgique, pi. 

57, fig. 26-27, 1881.

De Toni, Sylloge alg&rum omnium hucusque cognitarum, 

vol. 2, Bacillarieae, p. 500, 1891.

Mann 17 erroneously combined this species with Nitzschia angustata (Wm. Smith) Grunow. The differences between the two are as follows:

Length

2V. angustata 

. __________ 25-110/u

____ T ______ 5-10M

Length- width ratio _____ 5-11

Longitudinal fold. _____ Usually present

Transverse striae __ ___ 8-13 in 10/,

Puncta in transverse 18-20 in lOju

striae.

Arrangement of puncta Single rows 

in transverse striae.

N. marina

95-165/Lt

8-9. 5/u

12-17

Never present 

12 in 10/i 

19 in 10/«

Double, staggered 

rows.

15 Cleve, P. T., Synopsis of the naviculoid diatoms, part 1: K. svenska 

vetensk. akad. Handl., Band 26, no. 2, p. 36, 1894.

19 Boyer, C. S., The Diatomaceae of Philadelphia and vicinity, p. 74,1916.

17 Mann, Albert, Diatoms of the Albatross voyages: Contr. U. S. Nat. 

Herbarium, vol. 10, part 5, p. 379.1907.
86 GEOLOGY AND BIOLOGY OF NORTH ATLANTIC DEEP-SEA CORES

The most significant difference is the last one in the 

table, namely the arrangement of the puncta in the 

transverse striae. In N. angustata the puncta are arranged in single rows; in N. marina the puncta are 

arranged in double rows, with the puncta in any one 

row opposite the space between puncta in the adjacent 

row. Furthermore, the puncta in each pair are closer 

together than those in adjacent pairs, which is very 

well shown on the lower part of plate 17, figure 11. 

When viewed with a high-power dry objective the 

doubling is extremely difficult to see, and the transverse 

striae appear to be composed of a single row of pucta. 

Under the increased resolving power of an oil-immersion objective of N. A. 1.30, however, the staggered 

double rows are very easily observed. The much 

greater length-width ratio of N. marina is another consistent difference.

This species has a wide geographic distribution, 

from the Mediterranean Sea to the North Atlantic, 

O'ff Lower California, and in the Arctic Ocean. It 

has not been reported as abundant in any locality, and 

the ecologic data in the literature is very sketchy. 

After a careful review of the literature the most reasonable conclusion appears to be that it is a marine 

neritic species inhabiting cold to warm waters, with 

a preferance for cold waters. For the purpose of computing the distribution of the temperature facies of 

the diatoms from the cores (see table 13 and plate 11) 

this species has been considered to be a cold-water, 

neritic one.

Dimensions of figured specimen (U. S. G. S. diatom 

catalog no. 1942-1): Length, 139ju; maximum width, 

9.5/x; transverse striae, 12 in 10/u,; puncta, 19 in lOju. 

From sample L-30 (U. S. G. S. diatom locality 2838), 

0-4.5 cm. below the top of core 6.

Found rarely in samples L-51, L-54, L-59, and L-65 

and frequently in samples L-10, L-30, L-31, and L-37.

Nitzschia panduriformis Gregory

Plate 17, figure 9

NitzscMa panduriformis Gregory, Royal Soe. Edinburg Trans.,

vol. 21, p. 529, pi. 14, fig. 102, 1857. 

Van Heurck, Synopsis diatomees Belgique, p. 172, 1885;

pi. 58, figs. 1-4, 1881. 

Wolle, Diatomaceae of North America, pi. 44, figs. 3, 4,

9, 1894. 

Mann, Contr. U. S. Nat. Herbarium, vol. 10, pt. 5, p. 380,

1907.

Husteclt, in Schmidt, Atlas der Diatomaceenkunde, pi. 331,

figs. 19-21, 1921.

Boyer, Ac&d. Nat. Sci. Philadelphia Proc., vol. 79, supplement, p. 497, 1927. 

Nitzschia latestriata var. panduriformis Rabenhorst, Flora

Europaea algarum, Sectio I, p. 154, 1864.

Tryblionella pandurifoi'mis (Gregory) Pelletan, Les diatomees, 

histoire naturelle, D. 29, fig. 284, 1891.

My specimens agree in shape and structure with the 

form figured by Hustedt in Schmidt's Atlas, plate 331, 

figure 20, but are somewhat smaller. Hustedt's specimen is 126/u, long and 31ju, wide, wT hereas the one here 

figured is 89/u. long and 20/u, wide; in both the transverse rows of dots are 15 in lOju, and the other features 

are similar. Hustedt labeled his figure NitzscMa panduriformis Gregory, which is here considered correct. 

Mills 18 has referred Hustedt's figure 20 (only) to 

N. panduriformis var. lata (Witt) Grunow, which 

must have been a mistake. Grunow 19 in defining his 

variety lata, says:

Schaale breiter mit mehr abgerunden Enden, sonst ganz ahnlich und durch zahlreiche Mittelformen welche grosser Oder 

kleiner und in der Mitte mehr oder weniger eingeschnurt sind, 

mit der Hauptart zusammenhangend. Querstreifen 13-18 in 

0.01 mm. (Tryblionella lata O. Witt).

Grunow's description, obviously does not agree with 

Hustedt's figure 20, which differs from the type only 

in having a slightly higher length-width ratio. This 

ratio is not constant in N. pandwif'arm-is and varies 

materially in the specimens from the core. I have 

referred my specimens to Gregory's species as interpreted by Hustedt.

This marine and brackish-water species is found 

along both the Atlantic and Pacific coasts, usually in 

temperate waters.

Dimensions of figured specimen (U. S. G. S. diatom 

catalog no. 1982-3) : Length, 89/x; maximum width, 

20/x; width at constriction, 17/u,; transverse and oblique 

rows of dots, 15 in 10^; keel puncta, 6 in 10/M. From 

sample L-61 (U. S. G. S. diatom locality 2874), 258- 

263 cm. below the top of core no. 10.

Found rarely in sample L-61.

18 Mills, F. W., An index to the genera and species of the Diatomaceae, 

part 16, p. 1225, 1934.

19 Grunow, Albert, in Cleve, P. T., and Grunow, Albert, Beitrage zur 

Kenntniss der arctischen Diatomeen : K. svenska vetensk. akad. Handl., 

Band 17, no. 2, p. 71, 1880.
PLATES 12-17

87

250584—41———*
PLATE 12

FIGURE 1. Melosira sulcata (Ehrenberg) Ktitzing. U. S. G. S. diatom catalog no. 1983-1, locality 2876. Diameter, 32/u. X 1600.

2. Stephanodiscus astraea (Ehrenberg) Grunow. U. S. G. S. diatom catalog no. 1962-1, locality 2862. Diameter, 38ft. 

X 1000.

3. Endictya oceanica Ehrenberg. U. S. G. S. diatom catalog no. 1970-16, locality 2858. Diameter, 84j*. X 700.

4. Endictya rdbusta (Greville) Hanna and Grant. U. S. G. S. diatom catalog no. 1958-2, locality 2858. Diameter, 108/u. 

X 475.

5. Podosira stelliger (Bailey) Mann. U. S. G. S. diatom catalog no. 1984-2, locality 2878. Diameter, 56**. X 770. Focused 

on margin.

6. Podosira stelliger (Bailey) Mann. U. S. G. S. diatom catalog no. 1984-2, locality 2878. Diameter, 56**. X 770. Focused on central portion.

7. Coscinodiscus excentricus Ehrenberg. U. S. G. S. diatom catalog no. 1968-8, locality 2857. Diameter, 45/*. X 980.

8. Thalassiosira decipiens (Grunow) Joergensen. U. S. G. S. diatom catalog no. 1970-4, locality 2858. Diameter, 30** 

X 1370.

9. Melosira granulata (Ehrenberg) Ralfs. U. S. G. S. diatom catalog no. 1928-1, locality 2817. Length, 20/*; diameter, 

7/u. X 1280.

10. Coscinodiscus lineatus Ehrenberg. U. S. G. S. diatom catalog no. 1967-5. locality 2857. Diameter, 89*t. X 670.

11. Thalassiosira baltica (Grunow) Ostenfeld. U. S. G. S. diatom catalog no. 1965-4, locality 2865. Diameter, 27ju. X 1000.

12. Coscinodiscus circumdatus Schmidt. U. S. G. S. diatom catalog no. 1941-2, locality 2838. Diameter, 62j*. X 970.
GEOLOGICAL SURVEY PBOPESSIONAL PAPER 196 PLATE 12

11

DIATOMS FROM THE NORTH ATLANTIC DEEP SEA CORES.
GEOLOGICAL SURVEY PBOFESSIONAL PAPER 196 PLATE 13
GEOLOGICAL SURVEY PROFESSIONAL PAPER 196 PLATE 12

>•'•*.<»» *-£yx'

11

DIATOMS FROM THE NORTH ATLANTIC DEEP SEA CORES.


GEOLOGICAL SURVEY PROFESSIONAL PAPER 196 PLATE

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9 ifc 10

DIATOMS FROM THE NORTH ATLANTIC DEEP SEA CORES.
PLATE 13

FIGUEE 1. Coscinodiscus argus Ehrenberg. U. S. G. S. diatom catalog no. 1968-2, locality 2857. Diameter, 71/t. X 780.

2. Coscinodiscus stellaris Roper. U. S. G. S. diatom catalog no. 1970-14, locality 2858. Diameter, 62/u. X 640.

3. Coscinodiscus argus Ehrenberg. U. S. G. S. diatom catalog no. 1968-3, locality 2857. Diameter, 77/u. X 760.

4. Coscinodiscus africanus Janisch. U. S. G. S. diatom catalog no. 1972-1, locality 2866. Diameter, 41/u. X 1230.

5. Coscinodiscus kurzii Grunow. U. S. G. S. diatom catalog no. 1951-1, locality 2854. Diameter, 62/u. X 750.

6. Coscinodiscus decrescens Grunow. U. S. G. S. diatom catalog no. 1947-1, locality 2841. Diameter, 39/u. X 930.

7. Coscinodiscus africanus Janisch. U. S. G. S. diatom catalog no. 1972-1, locality 2866. Diameter, 41ju. X 1050.

8. Coscinodiscus excentricus Ehrenberg. U. S. G. S. diatom catalog no. 2000-3, locality 2858. Diameter, 39/u. X 900.

9. Coscinodiscus convexus Schmidt. U. S. G. S. diatom catalog no. 1970-6, locality 2858. Diameter, 178/u. X 295.

10. Coscinodiscus africanus Janisch. U. S. G. S. diatom catalog no. 1972-1, locality 2866. Diameter, 41/u. X 1900. 

11. Coscinodiscus asteromphalus Ehrenberg. U. S. G. S. diatom catalog no. 2004-2, locality 2864. Diameter, 198ju. X 293.

89
PLATE 14

FIGURE 1. Coscinodiscus marginatus Ehrenberg. U. S. G. S. diatom catalog no. 1967-17, locality 2857. Diameter, 115/*. X 474.

2. Coscinodiscus oculus-iridis Ehrenberg var. borealis (Bailey) Cleve. U. S. G. S. diatom catalog no. 1965-1, locality 2865. 

Diameter, 214. X 295.

3. Coscinodiscus nodulifer Schmidt. U. S. G. S. diatom catalog no. 1967-9, locality 2857. Diameter, 51j*. X 1050.

4. Coscinodiscus crenulatus Grunow var. nodulifer Lohman, n. var. Paratype. U. S. G. S. diatom catalog no. 1957-11, 

locality 2858. Diameter, 37/u. X 1320.

5. Coscinodiscus nodulifer Schmidt. U. S. G. S. diatom catalog no. 1967-6, locality 2857. Diameter, 83/tt. X 660.

6. Coscinodiscus marginatus Ehrenberg. U. S. G. S. diatom catalog no. 1967-19, locality 2857. Diameter, 97/u. X 485.

7. Coscinodiscus radiatus Ehrenberg. U. S. G. S. diatom catalog no. 1967-2, locality 2857. Diameter, 158/u. X 425.

8. Coscinodiscus radiatus Ehrenberg. U. S. G. S. diatom catalog no. 1967-10, locality 2857. Diameter, 71jt. X 880. 

00
GEOLOGICAL SURVEY PROFESSIONAL PAPER 196 PLATE 14

DIATOMS FROM THE NORTH ATLANTIC DEEP SEA CORES.


GEOLOGICAL SURVEY

PROFESSIONAL PAPER 196 PLATE 15

7 8 

DIATOMS FROM THE NORTH ATLANTIC DEEP SEA CORES.
PLATE 15

FIGUEE 1. Coscinodiscus crenulatus Grunow var. nodulifer Lohman, n. var. Holotype. U. S. G. S. diatom catalog no. 1970-3, 

locality 2858. Diameter, 40ju. X1410.

2. Actinocyclus curvatulus Janisch. U. S. G. S. diatom catalog no. 1957-2, locality 2858. Diameter, 66/u. X 930.

3. Coscinodiscus curvatulus Grunow var. minor (Ehrenberg) Grunow. U. S. G. S. diatom catalog no. 1957-1, locality 2858. 

Diameter, 29/u. X 1000.

4. Coscinodiscus subtilis Ehrenberg. U. S. G. S. diatom catalog no. 1972-8, locality 2866. Diameter, 48/u. X 1110.

5. Coscinoditcus bicurvatulus Lohman, n. sp. Holotype. U. S. G. S. diatom catalog no. 1967-12, locality 2857. Diameter, 

67/u. X 780.

6. Coscinodiscus denarius Schmidt. U. S. G. S. diatom catalog no. 1968-4, locality 2857. Diameter, 76/u. X 790.

7. Coscinodiscus divisus Grunow. U. S. G. S. diatom catalog no. 1970-11, locality 2858. Diameter, 57/u. X 1150.

8. Coscinodiscus curvatulus Grunow. U. S. G. S. diatom catalog no. 1960-3, locality 2860. Diameter, 91p. X 780.

91
PLATE 16

FIGURE 1. Hemidiscus cuneiformis Wallich, s. 1. U. S. G. S. diatom catalog no. 1970-2, locality 2858. Length, 114/*; width, 74ju. 

X 635.

2. Hemidiscus cuneiformis Wallich, s. 1. U. S. G. S. diatom catalog no. 1967-15, locality 2857. Length, 49;*; width, 43/u. 

X 1000.

3. Roperia tessellata (Koper) Grunow. U. S. G. S. diatom catalog no. 1967-7, locality 2857. Diameter, 62/u. X 940.

4. Actinocyclus octonarius Ehrenberg (=A. ehrenbergii Ralfs). U. S. G. S. diatom catalog no. 1971-1, locality 2865. Diameter, 35/u. X 915.

5. Hemidiscus cuneiformis Wallich, s. 1. U. S. G. S. diatom catalog no. 1970-13, locality 2858. Length, 69/u; width, 51/u. 

X 697.

6. Asteromphalus roperianus var. atlanticus Castracane. U. S. G. S. diatom catalog no. 1960-1, locality 2860. Diameter, 

71/u. X 715.

7. Actinoptychus bipunctatus Lohman, n. sp. Paratype. U. S. G. S. diatom catalog no. 1970-10, locality 2858. Diameter 

26/u. X 1770.

8. Actinoptychus campanulifer Schmidt. U. S. G. S. diatom catalog no. 1984-5, locality 2878. Diameter, 33/u. X 1030.

9. Actinoptychus senarius Ehrenberg (—A. undulatus of authors). U. S. G. S. diatom catalog no. 1958-1, locality 2858. 

Diameter, 39/u. X 1020.

10. Actinoptychus bipunctatus Lohman, n. sp. Holotype. U. S. G. S. diatom catalog no. 2000-1, locality 2858. Diameter, 

34ju. X 1530.

11. Actinoptychus bipunctatus Lohman, n. sp. Holotype. U. S. G. S. diatom catalog no. 2000-1, locality 2858. Diameter, 

34/u. X 1530.

12. Actinoptychus bipunctatus Lohman, n. sp. Holotype. U. S. G. S. diatom catalog no. 2000-1, locality 2858. Diameter,

34;*. X 1530. 

92
GEOLOGICAL SURVEY PROFESSIONAL PAPER 190 PLATE 10

10 —-— 11 12 

DIATOMS FROM THE NORTH ATLANTIC DEEP SEA CORES.


GEOLOGICAL SURVEY PROFESSIONAL PAPER 196 PLATE 17

10

12 14 17

DIATOMS FROM THE NORTH ATLANTIC DEEP SEA CORES.
PLATE 17

FIGURE 1. Ckaetoceros atlanticum Cleve. U. S. G. S. diatom catalog no. 1957-4, locality 2858. Major axis, 27ft. X 1000.

2. Rhizosolenia bergonii H. Peragallo. U. S. G. S. diatom catalog no. 1961-1, locality 2861. Length of fragment, 88/u. 

X 670.

3. Rhizosolenia styliformis BrightwelL U. S. G. S. diatom catalog no. 1964-5, locality 2864. Length of fragment, 75/u. 

X 1000.

4. Rhizosolenia styliformis Brightwell. U. S. G. S. diatom catalog no. 1960-2, locality 2860. Length of fragment, 92At. 

X 784.

5. Thalassiothrix longissima Cleve and Grunow. U. S. G. S. diatom catalog no. 1957-9, locality 2858. Length of fragment, 

165ji. X 520.

6. Rhaphoneis surirella (Ehrenberg) Grunow. U. S. G. S. diatom catalog no. 1984-4, locality 2878. Length, 36/*- X 1020.

7. Eunotia praerupta Ehrenberg var. bidens (W. Smith) Grunow. U. S. G. S. diatom catalog no. 1987-1, locality 2894. 

Length, 69ju. X 790.

8. Rhoicosphenia curvata (Kiitzing) Grunow. U. S. G. S. diatom catalog no. 1951-2, locality 2854. Length of fragment, 

68/u; width (max.), 14ju. X 760.

9. Nitzschia panduriformis Gregory. U. S. G. S. diatom catalog no. 1982-3, locality 2874. Length, 89/u. X 590.

10. Nitzschia marina Grunow. U. S. G. S. diatom catalog no. 1942-1, locality 2838. Length, 139ju; width, 9.5At. X 545.

11. Nitzschia marina Grunow. U. S. G. S. diatom catalog no. 1942-1, locality 2838. Central portion only. X 1480.

12. Pseudoeunotia doliolus (Wallich) Grunow. U. S. G. S. diatom catalog no. 2000-2, locality 2858. Length, 75ft. X 1060.

13. Pseudoeunotia doliolus (Wallich) Grunow. U. S. G. S. diatom catalog no. 2000-2, locality 2858. Enlarged to show 

structure. X 1830.

14. Navicula pennata Schmidt. U. S. G. S. diatom catalog no. 1964-1, locality 2864. Length of frgament, 75n. X 1000.

15. Diploneis interrupta (Kutzing) Cleve. U. S. G. S. diatom catalog no. 1986-1, locality 2893. Length, 33/Lt. X 970.

16. Diploneis weissflogii (Schmidt) Cleve. U. S. G. S. diatom catalog no. 1972-3, locality 2866. Length, 36/*. X 850.

17. Pleurosigma naviculaceum Brebisson. U. S. G. S. diatom catalog no. 1984-1, locality 2878. Length, 87/u. X 1030.

18. Diploneis smithii (Brebisson) Cleve. U. S. G. S. diatom catalog no. 1981-1, locality 2873. Length, 81ju. X 716.

93

INDEX

Page

Achnanthaceae_______________________________ 83 

Actmanthoideae______________________________ 83 

Acknowledgments for aid________________________ XI, XIV 

Actinocyclus_______________________________ 76-77, 88 

curvatulus-—___________________________ 76-77, pi. 15

ehrenbergii_______________________________ 77 

octonarius——_______________________ 77, 80, 81, pi. 16

senarlus——. 

subocellatus. 

tessellatus_. 

undulatus 

sp——————.

80

76

77 

80 

80

(Actinoptychus) senarius____________________—— 80 

Actinodisceae——_____________________________—— 78-81

Actinoptychoideae_____________________________- 79-81 

Actinoptychus__________________________________ 79-81

bipunctatus____________________________ 79, pi. 16 

campanulifer____________________________ 79, pi. 16 

maculatus____—______________________—— 79 

omphalopelta ____________________________—— 80

senarius______________________________80-81, pi. 16

undulatus———_——______________________—— 80

microsticta____________________________ 80

senarius______________________________ 80

africanus, Coscinodiscus_______________________ 69, pi. 13

Age of sediments-—__—__________________——_____——— VIII

Algae__——_____________________________ 63, 64-86

amputata, Rhizosolenia-__________________________ 81

Analyses, chemical___——_____________—_______ X

mechanical.—___——_——__________________________ VIII

Anaulus—————__—____________________________ 63

angustata, Nitzschia-——__________________——___—— 85

apiculata, Coscinodiscus nodulifer____________________ 72 

Araphidineae _——_—____________________________ 82 

Archeology, significance of core study for_____——____— XIII-XIV

areolata, Omphalopelta—_________________________ 80 

argus, Coscinodiscus————______——_____________ 70, pi. 13

Ash, volcanic, composition and distribution______________ VII

Asterolamproideae___—______——_________________ 78-79

Asteromphalus ————-—————————______——____—— 78-79

roperianus_____________________________ 78

atlanticus__——__——__________________78-79, pi. 16

asteromphalus, Coscinodiscus____________________ 70, pi. 13 

astraea, Discoplea__________________,_________ 67

Stephanodiscus-————————_——________________ 67, pi. 12

atlanticum, Chaetoceros_____________________ 58, 81, pi. 17 

atlanticus, Asteromphalus roperianus_____________ 78-79, pi. 17 

audax, Chaetoceros-—————__________—______—_ 81

Bacillariaceae_________________________________ 85-86 

Bacillariales-______________________________ 63, 64-86 

Bacillariophyceae-____________________________ 63, 64-86 

baltica, Coscinodiscus polyacanthus___________________ 66

Thalassiosira—————____________________ 66-67, pi. 12 

balticus, Coscinodiscus-———______________________ 66 

Barium, In sediments———————_————„______________ VIII 

Basaltic glass, occurrence and character of______________ VIII 

bergonii, Rhizosolenia——————————————__——_______ 81, pi. 17 

bicurvulatus, Coscinodiscus-__________________ 73-74, pi. 15 

Biddulphia——_————_——__—_____________________ 58, 63 

Biddulphineae________________________________ 81 

bidens, Eunotia praerupta——___—_—______—____ 83, pi. 17

Himantidium __——_——______________________ 83

bigibba, Bunotia___———___—_——________________ 83 

bipunctatus, Actinoptychus-—_——_——______—_—___ 79, pi. 16 

Biraphidineae-——______—________________________ 83-86

Page

borealis, Coscinodiscus__——————__—.——————————————— 72, 73 

Coscinodiscus oculus-iridis_______—_—_—_——— 72-73, pi. 14 

Boron, in sediments.—_———____—_———————————————— VIII 

Bottom currents, evidence of————_—————————————————— VII 

Bradley, W. H., introduction by_____________—____ XIII-XV

campanulifer, Actinoptychus__—_—————__——————— 79, pi. 16 

Carbonate, in sediments-——————_————————————————— VIII 

Carnegie Institution of Washington, work on deep-sea cores

by___________________________ VII, XI, XIV

caspius, Coscinodiscus__________________——_——-— 73 

Centricae____________________________—_____ 63

Chaetoceraceae_—_____—_______——_————————————— 81

Chaetoceroideae_____________———__——_———_———— 81

Chaetoceros________________-_______——_-___ 63, 81

atlanticum___________________________ 58, 81, pi. 17

audax_—_—_______—_—__——___——_——————_— 81

dispar————_———__——_———————————————————— 81 

polygonum_—__————__————_————————_— 81 

circumdatus, Coscinodiscus-————————————————————— 68, pi. 12 

Climate, relation of sediments to_————____- VII, VIII, X, XIII 

concavus, Coscinodiscus————___———————————————-— 65, 66 

conspicua, Coscinodiscus asteromphalus-———————__———__ 70 

convexus, Coscinodiscus—————————————————————— 58, 71, pi. 13 

Core samples, methods used in obtaining——_—_—————__ XIV-XV 

Core stations, location of——————_—————————————_—_— XIV 

Correlation of zones represented in the cores_____________ VIII 

Coscinodiscaceae-—-—_—————_—_——__————____— 64-77 

Coscinodiscoideae_————————————————————————————— 67-77 

Coscinodiscus___________________________ 65, 66, 67-76

africanus——————___————__————_______________ 69, pi. 13

argus_———_———_——_———————————__——————— 70, pi. 13 

asteromphalus-————————————————————————— 70, pi. 13 

conspicua ———————————————————————————— 70 

balticus ——___———————————____———_____ 66 

bicurvulatus__—_——_——______——_________ 73-74, pi. 15

borealis_______————____________________ 72, 73

caspius—___——_——————————————————————————— 73 

circumdatus-______———____———_—__—_—____ 68, pi. 12

concavus——————————_———————____———_—___ 65, 66 

. convexus_________________—____—__ 58, 71, pi. 13

crassus—-————_—————————————————————————— 66

crenulatus nodulifer————____-___________ 74, pis. 14, 15

curvatulus______________——_____ 74-75, 76, 77, pi. 15

minor______—_—______________——__ 75, pi. 15

odontodiscus__—————____——_____——————_— 73

subocellatus_——_____________________ 76

decipiens——_——__———————__________________ 67

decrescens_______————_—_————_————————_ 71, pi. 13

denarius———————————————————————————— 75, 76, pi. 15 

dlvisus—————————————————————————————— 75-76, pi. 15 

ehrenbergii——_———————————————————————————— 68 

excentricus_____________________ 67-68, 75, pis. 12, 13 

fallax__________——_____—________________ 73 

fimbriatus———————————————————————————————— 70 

flmbriatus-limbatus—————————————————————————— 72 

heteroporus——_———————————————————————————— 70 

irradiatus_______————_____——__————————— 70 

kinkerianus_______———__—-——_—-—————————— 66 

kurzii________..——____———____————_____ 71, pi. 13

labyrinthus________————____————————————.1———— 67

limbatus————————————————————————————————— 72 

lineatus__________—___——————————————— 68, pi. 12 

marginatus——__—————————————————— 65, 66, 71-72, pi. 14 

minor_________________———______————————— 67, 75

nodulifer________________————________ 72, pi. 14 

apiculata___________————————————————— 72

250584—41 XVII
xvm

Page 

Coscinodiscus—Continued.

normani——————————________________________ 73

oculus-iridis——————————_———______—______ 72

borealis_________________________ 72-73, pi. 14

pentas————————————____________________ 69

polyacanthus baltica________________________ 66

radiatus____________________________ 72, 73, pi. 14

heterosticta ____________________________ 72 

robustus——————_————______________________ 65, 66 

rothii___________________________________ 75, 76 

normani——_——————_____________________ 76 

stellaris_____________________________ 68-69, pi. 13 

subconcavus major____—____—————_——————————— 72

subtilis____________________________ 69, 75, 76, pi. 15 

subvelatus ____—_—____—————————————————— 66

symbolophorus____________________________ 68, 69

woodwardil____—______—————_—__——————__ 70

crassus, Cosdnodiscus—_—__——————__———————_ 66

crenulatus, Coscinodiscus——_——_——————————————————' 74, pi. 15

cuneiformis, Euodia _—_____—_————__________——————— 78

Crinoids, in sediments——————————————————————————— IX 

cuneiformis, Euodia___________________—--_——_ 78 

Hemidiscus____________________________ 78, pi. 16 

Currents, bottom, evidence of__-_——_——____—__—_ VII 

curvata, Rhoicosphenia———————_—________—————— 83, pi. 17

curvatulus, Actinocyclus________———__________ 76-77, pi. 15

Coscinodiscus__________________ 73, 74-75, 76, 77, pi. 15 

curvatum, Gomphonema___—___——_————_————_ 83

D

deciplens, Coscinodiscus ————————_—_—————-——__ 67 

Thalassiosira _________——__—————______————— 67, pi. 12

decrescens, Coscinodiscus——————————_____—_——__ 71, pi. 13

denarius, Coscinodiscus______________________ 75-76, pi. 15

Diatomaceae ———————————————________—_____ VIII-IX

Diatoms, classification of-———————————_———_———————__ 63-64

distribution and ecologic significance of———— VIII-IX, 57-63, pi. 11

samples containing, collection and preparation of—————— 55-56

method of study of————_————__—————————— 56

systematic descriptions of—__————__—_________ 63-86

didyma, Diploneis—_————————————_—————————————— 84

Dimerogramma surirella—————__——_———___________ 82

Diploneis ——_____———______————__——__________ 84-85

didyma ———_————__—____________________ 84

interrupta ____—____—________________ 84, pi. 17

smithii ______________________________ 84-85, pi. 17

weissflogii _____——_______________________ 85, pi. 17

Discineae ——________________________________ 64-81

Discoplea astraea_————___——_—_________———_ 67

dispar, Chaetoceros_——_______—________________ 81

diversa, Navicula-____________________-______ 85 

divisus, Coscinodiscus—————_______————_______ 75-76, pi. 15

Coscinodiscus (curvatulus var. ?)_________________ 75

doczyi, Navicula-__——______—________________ 85

doliolus, Himantidium_________—________________ 83

Pseudoeunotia —————————_—————_______——__— 83, pi. 17

Synedra——————:——————_—________________ 83

E

Echinodermata——________

Echinoids, association of_

ehrenbergii, Actinocyclus—

Coscinodiscus _______

elliptica, Navicula__——-

____________________ IX 

_____________________ IX

_______________________ 77

-_____________________ 68

———__——______________ 85 

Elphidiella _________________________________ VIII 

Elphidium ———_—————____————__—__——__ VIII 

Endictya _——___________—______________________ 65-66

cribrosa __——____________________________ 66

oceanlca ——_————————————————__________ 65, 66, pi. 12

robusta————___—___________________ 66, 72, pi. 12

robustus ——————_———————_————______—__ 68

Eunotia ___________—_____________________ 83

bigibba———__——_______________________ 83 

praerupta bidens ———————_——_——__________83, pi. 17

Ennotiaceae ——____________________________ 83 

Euodia cuneiformis ___________________________ 78

gibba ————___———______—_______________ 78

inornata __—___________—_______________ 78 

Eupodiscus tessellatus ___________________________ 77 

Excentricae ——————————_______________________ 67-68

excentricus, Coscinodiscus _______________67-68. 75, pis. 12-13

P

Page

fallax, Coscinodiscus ———————————————————————————— 73 

Farraday Hills, features of____——_——————————————— XIV 

Fasciculatae ___————————————————————————————— 73-76 

Faunas, distribution of-—_——————————————————————— IX 

Fecal pellets, evidence of, in sediments-____———————————— VIII 

flmbriatus, Coscinodiscus ————————————————————————— 70 

fimbriatus-limbatus, Coscinodiscus —————————————————— 72 

Foraminifera, age and correlation of_—————_—————————— VIII

distribution and environmental significance of——————— VI-VIII 

Foraminiferal marl, meaning of term————————————————VII-VIII 

Fossils, miscellaneous, distribution of—————__———_—_—— IX 

fracta Rhoicosphenia —————_——-—-—————————————— 83

Rhoicosphenia curvata ——————————————————————— 83 

fractum, Gomphonema —_____————____—————__—__ 83 

Fragilaria surirella ——_______——————————————————— 82 

Fragilariaceae __—————____————————-————————— 82 

Fragilarioideae —————————_———————————————————— 82

Gaillonella ___________

grannlata __-_-___ 

sulcata —__————.

Gastropods, environment of_.

gelatinosa, Thalassiosira _

gibba, Euodia __———___ 

Hemidiscus cuneiformis

64 

64 

64 

IX

67

78

78

Glacial marine deposits, age and features of___——______ VII 

Glass shards, occurrence and character of __————————————— VIII 

Globigerina ooze, meaning of term_______________—_VII-VIII 

Gomphonema curvatum ——_____________—————_——— 83

fractum ———————_________________—————____ 83

Grain size of sediments________________—________ VIII

granulata, Gaillonella _______—_—_________—___ 64

Melosira —————_——______——___—————____64, pi. 12 

Grunow, Albert, quoted —————__—____—_———————__— 86

H

Hemiaulus ___ 

Hemidiscaceae _ 

Hemidiscoideae 

Hemidiscus —

.____________________________ 58

.____________________________ 78

-___-__________________________ 78

______________________________ 78

cuneiformis _____________________________78, pi. 16

gibba _______________________________ 78

orbicularis ____________________________ 78

recta __-___________________________ 78

ventricosa_____________________________ 78

rectus _——————__________________________ 78

ventricosa________________________________ 78 

Hendey, N. I., quoted——_______________________ 78, 80-81

heteroporus, Coscinodiscus-—______——___——_—____ 70

heterosticta, Coscinodiscus radiatus___________________ 72

Himantidium bidens—_—_—______________________ 83

doliolus——-_______________________________ 83

Hyalodiscus_____———__________________________ 65

stelliger————————————__————_——___—————_____ 64, 65

inornata, Euodia__—_—____—______________—_.. 78 

interrupta, Diploneis————————————_—___———_—___ 84, pi. 17 

Navicula-—————————_—_—_______—________ 84 

Introduction to complete report-————————————————_— XIII-XV 

irradiatus, Coscinodiscus———___——_————————————_—_—— 70

japonicum, Pleurosigma. 85

K

kinkeri, Navicula————_____——_______——————_———— 84

Navicula pennata———————————————_——————————__ 84 

kinkerianus, Coscinodiscus—————————___———————————— 66 

kurzii, Coscinodiscus_————____—____—_—————_— 71, pi. 13

labyrinthus, Coscinodiscus__

lata, Nitzschia panduriformisTryblionella __-________

latestriata, Nitzschia————__.

67

86

86

86
XIX

Page 

limbatns, Coscinodiscus___________________________ 72

linearis, Rhoicosphenia—__———_—_______—_________ 83

Lineatae __________________________________ 68

lineatus, Coscinodiscus-——_——__________________ 68, pi. 12 

Lithologic zones in cores, correlation of_______—_______— VII

Lithology and geologic interpretations-_________-____ VII-VIII 

Location of region studied———--_______—_'_________ VII, XI 

longissima, Thalassiothrix_______________________ 82, pi. 17

M

maculatus, Actinoptychus__-_____________________ 79 

major, Coscinodiscus subconcavus—__——___________—— 72 

Mann, Albert, quoted——_________________________ 65, 69 

marginatus, Coscinodiscus—————___—______ 65, 66, 71-72, pi. 14 

marina, Nitzschia_—______________________ 85-86, pi. 17

Orthosira———_——_————_____________—_____ 64

Marl, foraminiferal, meaning of term________________ VII-VIII 

Mediterranean Sea, sediments in, significance of________ XIII-XIV 

Melosira.————__——______________________.__ 64

granulata——————_——__———______________ 64, pi. 12

sulcata—————————————_————_______—__ 64, pi. 12

siberica-_—__——____________________ 64

Melosiroideae—————————————__——_____—______—— 64-65

microsticta, Actinoptychus undulatus_________________ 80

minor, Coscinodiscus————_——_—________________ 67, 75

Coscinodiscus curvatulus__——___________——_ 75, pi. 15 

miranda, Pourtalesia—___——____________________ IX 

Mollusca———————————————__________________ IX 

Monoraphidineae __———_________________________ 83 

Mud-feeding organisms, roles of-_—_______________ VII

N

Navicula____________________________________ 83-84 

diversa—_______________________________ 85 

doczyi __________________________________ 85 

elliptica_________________________________ 85 

interrupta-_______________________________ 84 

novae-seelandiae_________________________ 84 

kinkeri—______________________________ 84

pennata———————————————_—____—______ 83-84, pi. 17

kinkeri_______________________________ 84 

pinnata-_______________________________ 84 

puella-—________________________________ 84 

smithii——_______________________________ 84 

weissflogii ________________________________ 85 

(Diploneis) smithii__________________________ 85 

Naviculaceae_________________________________ 83-85

naviculaceum, Pleurosigma______________________ 85, pi. 17

Naviculoideae ________________________________ 83-85

Nitzschia___________________________________ 85-86

augustata __——————_——_____________________ 85

latestriata panduriformis——____________________ 86 

marina———————————————_____________ 85-86, pi. 17 

panduriformis-_—________________________ 86, pi. 17

lata _________________________________ 86 

Nitzschioideae________________________________ 85-86 

nitzschioides, Thalassionema————__—_______________ 82 

nodulifer, Coscinodiscus_________________________ 72, pi. 14

Coscinodiscus crenulatus——__________________ 74, pi. 15

normanl, Coscinodiscus__________________________ 73

Coscinodiscus rothii__—______________________ 76

novae-seelandiae, Navicula interrupta_________________ 84

O

oceanica, Endictya___________________________ 65, 66, pi. 12

Orthosira _______________________________ 66

octonarius, Actinocyclus_____________________ 77, 80, 81, pi. 16

oculus-iridis, Coscinodiscus_____________________72-73, pi. 14

odontodiscus, Coscinodiscus curvatulus

omphalopelta, Actinoptychus ___________

areolata-____________________________

Ophiurolds, association of___-

orbicularis, Hemidiscus cuneiformis

______________ 73 

-_____________ 80 

______________ 80 

_____________ IX

.______________ 78 

Organic content of sediments—____________________ IX-X 

Orthosira marina_—_________________________

oceanica ______________________:____________

sulcata ______________________________________________

Ostracoda________________________________________________

Outline of complete report_____________________.

64 

66 

64 

IX 

V

Page

Palagonite, character and occurrence of——————————————— VIII 

panduriformis, Nitzschia_____——_———————————————— 86, pi. 17

Nitzschia latestriata——_——_——————————————————— 86 

Tryblionella_____________——_____——————————— 86

Paralia sulcata——————————————————————————————— 64 

Pelecypods, environment of——————————————————————— IX 

pennata, Navicula__-______——————__————-—— 83-84, pi. 17 

Pennatae _——————————————————————————————— 63

pentas, Coscinodiscus-——————————————————————————— 69

Symbolophora ———_————————————————————————— 69

Phaeoceros _—_—_—_———————————-—————————— 81

Piggot, C. S., coring device designed by——————————— VII, XIV-XV

foreword by—_—_———————————————————————— XI-XIl

pinnata, Navicula—————————————————————————————— 84

Plankton, relation of, to organic content——————————————— X

Planktoniella sol__________————————————_____—————— 67, 68

Pleurosigma ________________————————————————— 85

japonicum ___——————————————————————————— 85

naviculaceum __—_________——___————————— 85, pi. 17

transversale __———————————————————————————— 85

Podosira _-. _____————_—__________——-—————— 64-65

polita ____——————————————————————————— 65

stelliger ___________________—_____— 64-65, pi. 12 

polita, Podosira—————————————.———————————————— . 65 

polyacanthus, Coscinodiscus___—_____—_——————————— 66

polygonum, Chaetoceros———_————————————————- ———— - 81 

Porosity of the sediments—_————————————————————— VIII 

Pourtalesia miranda—____—_-_——_——————————— IX 

praerupta, Eunotia_————_———————————————————— 83, pi. 17 

Pseudoeunotia ——————————————————————————————— 83 

doliolus_______________________________ 83, pi. 17 

Pteropod shells, distribution of____——————-—————— VIII, IX 

puella, Navicula——_—————————-——————————————— 84

R

Radiatae ____________——-——————————————————— 69-73 

radiatus, Coscinodiscus—————————————————————— 72, 73, pi. 14 

Radium, concentration of, on ocean bottom———————————— XI 

Raphidioidineae ———————_—————————————————————— 83 

Rare elements, spectroscopic tests for———————————————— VIII 

Rattray, John, quoted——————————————————————————— 66 

recta, Hemidiscus cuneiformis—————————————————————— 78 

rectus, Hemidiscus————————————————————————————— 78 

Region sampled, extent of__——————————_—————————— VII, XI 

Rhaphoneis ——-————————————————————————————— 82 

surirella_____-_____—____——————————— 82, pi. 17

RWzosolenia-——————-—————————————————————— 63, 81-82

amputata —__—————_————————————————————— 81 

bergonii—_—______—————_—————————————— 81, pi. 17

styliformis ______________————__——__ 58, 81-82, pi. 17

Rhizosoleniaceae _—————___———__———————————————— 81-82

Rhizosolenioideae ______—_——__——_______————__ 81-82

Rhoicosphenia —————————————-—————————————————— 83

curvata——____—————————————————————— 83, pi. 17

fracta ————-————————————————————————— 83 

fracta _____________-_________________———_ 83

linearis -__————__————————__————————— 83

robusta, Endictya__——__——————————_—————— 66, 72, pi. 12

robustus, Coscinodiscus ____——___———_——_—————__ 65,66

Endictya __——___——_____________________ 66

Roperia __—————_—————————————————————————— 77 

tessallata ————————————————————————————— - 77 

tessellata_____—__——_____—___________—— 77, pi. 1R

roperianus, Asteromphalus ———————————————————— 78-79, pi. 16 

rothii, Coscinodiscus —____——_____——__————_————__ 75, 76

S

Sampling and examination of cores, method of—_______ XIV-XV 

Scoliopleura szakalensis ___————_—————_——__——__ 84 

Sediments, age and correlation of_____________________ VIII

grain size of___———_—____—_-__————__ VIII 

organic content of-———_——_——_____—___————_ IX—X

Selenium content of sediments-——————____——___—__ X

senarius, Actinocyclus ————————_————_—_——————— 80

Actinocyclus (Actinoptychus) __—____—_—_______ 80

Actinoptychus ________________________ 80-81, pi. 16

Actinoptychus undulatus ———————————————_—————— 80 

siberica, Melosira sulcata———————————————————————— 64 

Skeletonemoideae __——_______—____—__——_—_ 65-66
XX

Page

smithil, Diploneis__________________________ 84-85, pi. 17

Navlcula _______________________________ 84

(Diploneis) ___________________________ 85

sol. Planktoniella———_________________________ 67, 68

Soleniineae _____________ ___________________ 81-82

Spectroscopic tests of sediments____-_-_____________ VIII

stellaris, Coscinodiscus_________———________ 68-69, pi. 13

Stellatae ————_______________________________ 68-69

stelliger, Hyalodiscus___________________________ 64, 65

Podosira ____________________________ 64-65, pi. 12

Stephanodiscus _______________________________ 67

astraea ___—__________________________67, pi. 12

styliformis, Rhizosolenia__________________ 58, 81-82, pi. 17

subconcavus, Coscinodiscus________________________ 72

subocellatus, Actinocyclus ________________________ 76

Coscinodiscus curvatulus______________________ 76

subtilis, Coscinodiscus—___________________ 69, 75, 76, pi. 15

subvelatus, Coscinodiscus___________——__________ 66

sulcata, Gaillonella____________________________ 64

Melosira _________________ ____________ 64, pi. 12

Orthosira ________________________________ 64

Paralia ________________________________ 64

Summary of complete report______________________ VIII-X

surirella, Dimerogramma_______________________ S2

Fragilaria __________•_____________________ 82

Rhaphoneis ____________________________ 82, pi. 17

Zygoceros __—__________________________ 82

Symbolophora ________________________________ 69

pentas __________________________________ 69

symbolophorus, Coscinodiscus______________________ 68, 69

Synedra doliolus—_____________________________ 83

thalassiothrix______________________________ 82

szakalensis, Scoliopleura___________________________ 84

T

Temperature, relation of type of sediment to________ VII, VIII, X 

tessallata, Roperia_____________________________ 77 

tessellata, Roperia____________________________ 77, pi. 16

tessellatus, Actinocyclus __————————————————————— 77

Eupodiscus ________——:-——-———__———————— 77

Texture of sediments, relation of, to organic content———————— X

Thalassionema nitzschioides _—————————————————————— 82

Thalassiosira ———————————————————————————————— 66-67

baltica _____________________________ 66-67, pi. 12

deci'piens __________——_———______———-———— 67, pi. 12

gelatinosa _—————_—————————————————————— 67

Thalassiosiroideae ————————————————————————————— 66-67

Thalassiothrix ———__—————————————————————————— 82

longissima ————————————————————————————— 82, pi. 17

Synedra _________——___________________ 82

Tidal currents, evidence of———————————————————————— VII

transversale, Pleurosigma———-—-—_—__——_______ 85

Triceratium _____________—————————__————______ 58, 63

Tryblionella lata__——____——————————————————__—— 86

panduriformis _————_———————————————————_— 86

U

undulatus, Actinocyclus————

Actinoptychus ____-

Uranium, in ocean sediments80 

80 

XI

ventricosa, Hemidiscus____ —-————————————___—__ 78

Hemidiscus cuneiformis_-_————————_—_—_______— 78

Volcanic ash, composition and distribution of—_—________ VII

Volcanic glass, occurrence and character of—_____________ VIII

W

weissflogii, Diploneis_________________________ 85, pi. 17

Navicula __—___________________________ 85

woodwardii, Coscinodiscus——————————————————___—__ 70

Zones represented in the cores, correlation of______—____ VIII 

Zygoceros surirella_______________—————————————— 82

o
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