Miocene Marine Diatoms from the 

Kirkwood Formation, Atlantic 

County, New J~rsey 

U.S. GEOLOGI 

Miocene Marine Diatoms from the 

Kirkwood Formation, Atlantic 

County, New jersey 

By GEORGE W. ANDREWS 

Early and middle Miocene marine diatom assemblages 

from the northern part of the Atlantic Coastal Plain region 

and their stratigraphic significance 

U.S. GEOLOGICAL SURVEY BULLETIN 1769 
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

UNITED STATES GOVERNMENT PRINTING OFFICE: 1987 

For sale by the Books and Open-File Reports Section, U.S. Geological Survey, 

Federal Center, Box 25425, Denver, CO 80225 

Library of Congress Cataloging in Publication Data 

Andrews, George Willliam, 1929-

Miocene marine diatoms from the Kirkwood Formation, Atlantic County, New 

Jersey. 

(U.S. Geological Survey bulletin ; 1769) 

Bibliography: p. 12 

Supt. of Docs. no.: I 19.3:1769 

1. Diatoms, Fossil. 2. Paleobotany-Miocene. 3. Kirkwood Formation (N.J. 

and Pa.) 4. Paleobotany-New Jersey-Atlantic County. 

I. Title. II. Series. 

QE75.89 no. 1769 557.3 s 86--600397 

[QE955] [561' .93] 
CONTENTS 

Abstract 1 

Introduction 1 

Location of deposit 2 

Stratigraphy of deposit 2 

Previous work 2 

Summary of investigation 5 

Diatom biostratigraphy 5 

Age of diatom assemblages and Miocene strata 7 

Paleoecology 8 

Systematic paleontology 8 

References cited 12 

PLATES 

[Plates follow references cited] 

1. Actinoptychus, Aulacodiscus, Delphineis. 

2. Rhaphoneis. 

3. Sceptroneis, Rhaphoneis, Delphineis. 

FIGURES 

1. Index map showing Atlantic City Girl Scout Camp 4 borehole site, Atlantic County, 

N.J. 3 

2. Chart showing stratigraphic position and depth of samples studied for diatoms in 

the Atlantic City Girl Scout Camp 4 borehole, Atlantic County, N.J. 4 

TABLE 

1. Stratigraphic occurrence of marker diatoms in the Atlantic City Girl Scout Camp 

4 borehole core samples, Atlantic County, N.J. 6 

Contents Ill 

Miocene Marine Diatoms from the Kirkwood 

Formation, Atlantic County, New Jersey 

By George W. Andrews 

Abstract 

Although diatoms have been known from the New 

Jersey Miocene rocks for nearly 100 years, no serious effort 

has been made previously to use diatoms for modern 

biostratigraphic correlation in this region. Samples from a 

core taken on the Atlantic City Girl Scout Camp 4 (ACGSC-4) 

property, about 3.2 miles (5.3 km) northwest of Mays Landing, Atlantic County, New Jersey, have been examined for 

diatoms, and the results are herein reported. 

Diatoms occur in this core in a single sample from a 

depth of 293 feet (89 m) and in an upper interval from a depth 

of 155 to 239 feet (47 to 73 m). The lower sample contains a 

poorly preserved diatom assemblage, but fragments of Actinoptychus heliopelta were present. This diatom suggests the 

correlation of this bed with East Coast Diatom Zone 1 of 

Andrews (1978, Marine diatom sequence in Miocene strata 

of the Chesapeake Bay region, Maryland: Micropaleontology, v. 24, no. 4, p. 371-408, pis. 1-8) and a late Burdigalian 

age (late early Miocene). This bed is equivalent to the oldest 

part of Lithologic Unit 3 of the Calvert Formation in the 

Chesapeake Bay region of Maryland. 

The lower diatomaceous bed is separated from the 

upper diatomaceous interval by a 54-foot (16-m) section that 

is barren of diatoms in the core. The upper interval contains 

marine marker diatoms indicative of East Coast Diatom Zone 

2 of Andrews (ibid.) and a Langhian age (early middle 

Miocene). This interval correlates well with the upper part of 

Lithologic Unit 3 and Units 4 to 9 of the Calvert Formation of 

Maryland. A new marine diatom species having potential 

value as a marker diatom, Rhaphoneis praeparilis, is 

described from this interval. The barren interval between the 

two diatomaceous levels represents approximately 1 million 

years of geologic time. 

The upper diatomaceous interval in the core is found in 

approximately the upper 25 percent of the Kirkwood Formation. The lower diatomaceous bed occurs about 54 feet 

below the upper bed. The remainder of the Kirkwood 

(approximately the lower 60 percent) cannot be dated by 

diatoms, but it must represent an interval of early Miocene 

deposition unknown farther south along the Atlantic Coastal 

Plain. Planktic foraminifera from a depth of 473 feet (144m) 

indicate an age of about 19.0 to 21.8 Ma (Zone N5) near the 

base of the Kirkwood Formation. 

INTRODUCTION 

The sedimentary rocks of the Atlantic Coastal 

Plain of New Jersey were recognized in the 

mid-eighteenth century, and an excellent summary of the 

early stratigraphic investigations and nomenclature is 

given by Spangler and Peterson (1950, p. 7-15). Cook 

(1868, p. 294-298) recognized the occurrence of a 

Miocene fossiliferous deposit in New Jersey in his discussion of the "Shiloh Marl" from Cumberland County. 

The earliest report on Miocene diatoms from New Jersey 

is that published by Kain and Schultze (1889) on the 

diatoms from an artesian well in Atlantic City. 

The older of the two Miocene formations now 

recognized in New Jersey is the Kirkwood Formation, 

originally described by Knapp (1904, p. 81). The Kirkwood Formation crops out in a northeasterly trending 

irregular band from Shiloh in the southwest to Asbury 

Park in the northeast, as shown by Richards and Harbison 

(1942, fig. 1). It dips through the subsurface to the 

southeast and probably reaches its maximum thickness in 

New Jersey near Wildwood and Cape May. The 

Kirkwood Formation contains an extensive molluscan 

fauna, which Richards and Harbison (1942) described. 

They correlated the lower part of the Kirkwood Formation with the Calvert and Chop tank Formations of Maryland and the upper part of the Kirkwood with the St. 

Marys Formation of Maryland. More recently, Isphording (1970) studied the mineralogy and lithology of the 

Kirkwood Formation and subdivided the formation into 

the Alloway Clay Member, Asbury Park Member, and 

Grenloch Sand Member. The delineation of these members seems to be, at least in part, facies related. 

Goldstein (1974) made an extensive palynological 

study of the Kirkwood Formation. He delineated five 

subsurface palynological phases in the Kirkwood Formation, correlating his oldest Phase I with the Tampa 

Formation of Georgia and Florida, his Phase II with the 

Hawthorn Formation of South Carolina and Georgia, his 

Phase III with the Calvert Formation of Maryland, his 

Phase IV with the Choptank Formation of Maryland, and 

his Phase V with the St. Marys Formation of Maryland. 

Introduction 
He further correlated his Phase III palynological 

unit with the Asbury Park and Alloway Clay Members of 

the Kirkwood Formation of Isphording (1970) and with 

the occurrence of the diatom Actinoptychus heliopelta 

from the lower part of the Calvert Formation in Maryland. Relating Goldstein's study of the pollen biostratigraphy precisely to the diatom biostratigraphy of the 

Atlantic City Girl Scout Camp (ACGSC-4) borehole 

core is difficult. The diatomaceous section herein studied 

may be equivalent to palynological Phase III of Goldstein 

(1974), but most ofthis diatomaceous section is distinctly 

younger than the Actinoptychus heliopelta zone. 

This report represents the first attempt to correlate 

the Miocene formations of New Jersey with the East 

Coast Diatom Zones proposed by Andrews (1978) for 

the Chesapeake Bay region of Maryland. Correlation of 

the Kirkwood Formation with the Miocene formations of 

Maryland and Virginia was made in a general way by 

many of the early diatom workers. However, with the 

establishment of a system of diatom zonation, this correlation now should be more precise than has previously 

been possible. 

LOCATION OF DEPOSIT 

The diatoms studied for this report were derived 

from cores taken from a borehole drilled approximately 

3.2 miles (5.3 km) northwest of Mays Landing, Atlantic 

County, N.J. The borehole, which was drilled by the U.S. 

Geological Survey (USGS), was spudded on August 7, 

1984. Samples were collected under the supervision of 

James P. Owens (U.S. Geological Survey, Reston, Va.). 

The borehole was drilled on the property of Atlantic City 

Girl Scout Camp No. 4 and will be referred to as 

ACGSC-4 subsequently in this report. The location of 

the borehole site is approximately 0.6 mile (1.0 km) south 

and 0.7 mile (1.1 km) west of the northeast corner of the 

Dorothy 7¥2-minute quadrangle (U.S. Geological Survey, 

1972). The location of the borehole site is shown on 

figure 1. The borehole was drilled near the upper edge of 

a low escarpment at the margin of the modern flood plain 

of the Great Egg Harbor River, and the altitude of the 

wellhead is approximately 50 feet (15m). The borehole 

has been converted into a water well by the property 

owners (James P. Owens, oral commun., 1985). 

STRATIGRAPHY OF DEPOSIT 

The ACGSC-4 borehole was drilled to a total 

depth of 945 feet (288m), but this report discusses only 

the diatomaceous stratigraphic section of the Miocene 

Kirkwood Formation. The pertinent part of a lithologic 

and gamma ray log for this borehole (adapted from a log 

prepared by James P. Owens, U.S. Geological Survey, 

Reston, Va.) is shown in figure 2. The upper part of the 

hole penetrated sandy surficial materials and the Cohansey Sand of probable Miocene age to a depth of approximately 150 feet (46 m) (James P. Owens, oral commun., 

1985). The Kirkwood Formation, a sequence of alternating clays, sandy clays, and sands, was penetrated to a 

depth of approximately 484 feet (148 m) (James P. 

Owens, oral commun., 1985). Part of this Kirkwood 

section has proven to be diatomaceous. Below 484 feet 

(148m), the borehole penetrated sands of Eocene age. 

These sands were not examined for diatoms because the 

sandy deposits of pre-Miocene age are not known to 

contain diatoms in the Atlantic Coastal Plain. 

PREVIOUS WORK 

The earliest report on the fossil diatoms of New 

Jersey was made by Kain and Schultze (1889) on the 

samples derived from an artesian well at Atlantic City, 

N.J. They published a list of diatom species derived from 

samples taken between 387 and 638 feet (118 and 195m) 

in well depth, and they named and described several new 

diatom species. They noted the similarity of these New 

Jersey diatoms to those in the Miocene deposits of 

Maryland and Virginia, but they did not speculate extensively on any stratigraphic correlation. Their paper is of 

importance to diatom biostratigraphy in that it contains 

the original description of Delphineis novaecaesaraea 

(Kain and Schultze) Andrews, recognized by Andrews 

(1978) as an important Miocene marker diatom. 

Woolman (1891) described more extensively the 

stratigraphic section in the artesian wells at Atlantic City. 

He suggested the correlation of the diatomaceous beds in 

the Atlantic City wells with a similar bed in an artesian 

well at Cambridge, Md. He reported that the diatom 

species were relatively consistent throughout a 275-foot 

(84-m) section, and he recognized Paralia sulcata as one 

of the most frequent diatoms. Woolman (1892) again 

reported the occurrence of a continuously diatomaceous 

section between depths of 382 and 697 feet (116 and 213 

m) in the Atlantic City wells. He also reported the 

occurrence ofActinoptychus heliopelta at depths of 625 to 

675 feet (191 to 206m) at Atlantic City and in outcrops 

near Shiloh, N.J. He made a tentative correlation with the 

deposit cropping out along the Patuxent River near 

Nottingham, Md., but his suggestions of correlation with 

deposits at Bermuda Hundred and Petersburg, Va., are 

no longer tenable. Boyer (1895) reported on a diatom 

assemblage from a well near Wildwood in southern New 

Jersey. However, this was in a shallow deposit dominated 

by freshwater species and probably of Pleistocene or 

Holocene age. 

2 Miocene Marine Diatoms from the Kirkwood Formation, Atlantic County, New Jersey 
DOROTHY QUADRANGLE 

NEW JERSEY 

7.5 MINUTE SERIES (TOPOGRAPHIC) 

WILLIAMSTOWN 18 MI. 

WEYMOUTH 1.9 MI. 

4372 

N~C< JERsv 4370 

QUADRANGLE LOCATION 

5000 6000 7000 FEET 

~~~==~==~==~==~==~==~==~ 

Figure 1. Atlantic City Girl Scout Camp 4 borehole site, Atlantic County, N.J. 

The most comprehensive early report on the stratigraphic occurrence of fossil diatoms in New Jersey was 

made by Woolman (1895, p. 160-172), who discussed 

extensively the diatomaceous clay beds encountered in an 

artesian well at Wildwood, N.J. He reported, however, on 

a stratigraphic section considerably downdip and hence 

stratigraphically thicker than that at the ACGSC-4 site 

studied for this report. Woolman recognized four distinctive diatomaceous deposits in the Wildwood well. The 

uppermost of these he termed "Diatom bed no. 1" and 

reported as occurring from depths of 29 to 46 feet (9 to 

14 m). This bed, which contained a relatively modern 

marine diatom assemblage, probably of Pleistocene or 

Holocene age, was noted as being distinct from the older 

Miocene diatom assemblages. Woolman's "Diatom bed 

no. 2" came from depths of from 78 to 181 feet (24 to 55 

m) and, from the information given, appears to contain a 

mixture of marine and nonmarine diatoms. The species 

list published by Boyer (1895) from these beds was 

reprinted by Woolman (1895, p. 163-165). Evaluating 

this diatomaceous deposit by modern standards is difficult, but the deposit's stratigraphic position suggests that 

it may be of Pleistocene age. 

"Diatom bed no. 3" is also termed the "Great 

400-Foot Marine Miocene Diatomaceous Bed" by Woolman (1895, p. 165-169), and it is reported to occur in 

outcrop at Asbury Park and Shiloh, N.J., and in the 

subsurface at Asbury Park, Barnegat, Beach Haven, 

Atlantic City, Ocean City, Wildwood, Pleasant Mills, 

May's Landing, and Port Norris, N.J. The thickness of 

Previous Work 3 
AGE 

w 

z 

w 

() 

0 

FORMATION 

COHANSEY 

SAND 

KIRKWOOD 

FORMATION 

DEPTH, 

IN FEET LITHOLOGY 

·-------- -·- .. - -· -~-.: ~·::; -:· : . ; _··~ 

:·.~ ... ;.-.::·.:.~ :--:: ·:=:: !.". • • • • • 

1 50- ;: .. ··:.:-=.- :.~·~.=~:~ .. :~ .. r~~~~::: ......... - ----··- -.:_~· -~:.: ·.:•. :::.-. - --=··- .. --·-

1-·"- ···- ···-

...... ,-.... -.. ···-· ·,:·; ·; .·:. .· :: ..... -: .. ·:-;c 

250-?;/Y>:.f. .:·~·:,_:· l .-.. ~ .;·~~: 

·> ·.'- . c. .~, ., ·~ .· ...... ~ · ........ . - -·-- ···- .. =-.::. ··..;-:_··:._-_ •.. 

3 o o- ~:-~."--:;_ -~ :~·:­ : :a·- . ~ .. , ( 

(:~:~:_~_-: 

i_i~ ~:=_~~ ~:-::~-

3 5 o- :-.. :: .:...:;. :::-:;::, :-::-: ------- --- - ···--··--- --.... -···-···- ···- - ···- ···- ···- ------ -------

4 o o- :~~::~JtJ.~~~ --- ~--:. 

~ ::.-:-:: ~:: =-··. :· -···- -··- - -··-- ···- ------- ---- .:: ~ • .::-.::f;.-=-

SAMPLE DEPTHS, USGS DIATOM 

GAMMA RAY LOG IN FEET (METERS) LOCALITIES 

---155 (47)--- --7291 

---175 ~531--- --7292 ---179 55--- --7293 

---199 (61)--- --7294 

---215 (66)--- --7297 

---225 (69)--- --7298 

---235 (72)--- --7299 

---239 (73)--- --7300 

---293 (89)--- --7301 

---295 (90)---

---335 (102)---

---345 ( 1 05)---

---355 (108)---

---360 ( 11 0)---

---370 (113)---

---409 (125)---

---425 ( 130)---

---43 6 ( 1 3 3)---

--455 (139)---

---446 ( 136)---

---466 (142)---

---475 (145)---

---480 ( 146)---

EXPLANATION 

(ZJ Clay liS] . Sand -

~ . Sandy clay I'~ "I Macrofossils 

Figure 2. Stratigraphic position and depth of samples studied for diatoms in the Atlantic City Girl Scout Camp 4 borehole, 

Atlantic County, N.J. 

4 Miocene Marine Diatoms from the Kirkwood Formation, Atlantic County, New Jersey 
bed no. 3 is reported as 290 feet (88 m) at Atlantic City 

and as 423 feet (132 m) downdip at Wildwood, N.J. 

Woolman makes a positive correlation of this bed with 

the deposits along Chesapeake Bay and Popes Creek, 

Md., as well as other localities in Delaware, Maryland, 

and Virginia. Woolman reported that "Diatom bed no. 

4" (1895, p. 169) occurred as a distinct bed in the 

Wildwood well from depths of 1,040 to 1,060 feet (317 to 

323m) and that it is separated from bed no. 3 by a section 

of non diatomaceous strata approximately 247 feet (75 m) 

in thickness. Woolman (1895, p. 170) stated that the 

diatom assemblage of bed no. 4 is similar to that of bed 

no. 3, but that bed no. 4 is characterized by the occurrence ofActinoptychus heliopelta. ConcerningA. heliopelta, he stated (p. 172), "This diatom is especially c~aracteristic of the base, and the base only, of the Mmcene 

diatomaceous clay deposits of the Atlantic coastal plain." 

Following these pioneer diatom studies by Kain, 

Schultze, Boyer, and Woolman, little formal biostratigraphic work was conducted on the fossil diatoms of New 

Jersey. Aside from incidental references to the occurrence of diatom species scattered in the diatom literature, only one significant publication has appeared. 

Patrick (1944) reported on the Miocene diatoms from a 

well boring at Brandywine Lighthouse in Delaware Bay. 

This paper described selected, as well as new, species 

and, as the author stated (p.1 ), ". . .no attempt has been 

made to identify all the species present." The diatoms 

studied and reported on were recognized to be of 

Miocene age. 

SUMMARY OF INVESTIGATION 

Twenty-three samples were examined for diatoms 

from the ACGSC-4 borehole core. These ranged in 

depth from 155 to 480 feet (47 to 146m). The depths of 

individual samples are indicated on figure 2. Those 

samples not found to contain diatoms are shown only by 

their depths, whereas those containing diatoms are shown 

by their depths and the four-digit USGS diatom locality 

numbers. All of the diatomaceous samples were taken 

from the Kirkwood Formation. Those samples taken 

from the upper part of the Kirkwood Formation between 

depths of 155 and 239 feet (47 and 73 m) contained 

reasonably well preserved diatom assemblages. The interval between 239 and 293 feet (73 and 89 m) was not 

sampled because of the sandy nature of the rocks and 

poor core recovery. A sample taken from a depth of 293 

feet (89 m) contained a sparse, fragmentary, and weathered diatom assemblage, distinct from those of the 

overlying strata. Fourteen samples taken from the lower 

part of the section logged as Kirkwood Formation, 

between depths of 295 and 480 feet (90 and 146m), do 

not contain diatoms. 

DIATOM BIOSTRATIGRAPHY 

The uppermost diatomaceous interval in the 

ACGSC-4 borehole at a depth of 155 to 239 feet ( 47 to 

73 m) is apparently the equivalent of "Diatom bed no. 3" 

reported by Woolman (1895, p. 165-199) from an artesian well at Atlantic City, N.J. The samples from this 

upper interval in ACGSC-4 contain a substantial amount 

of diatoms and diatom debris showing fair preservation. 

The assemblages are dominated by the small centric 

species Paralia sulcata (Ehrenberg) Cleve and contain 

common large centric diatom species and small pennate 

diatom species. Most of these forms are shallow-water 

pelagic or benthic species that suggest deposition in 

shallow marine waters. Woolman (1891, 1895) published 

a list of 149 diatom species from his Atlantic City well 

samples. The ACGSC-4 borehole samples probably 

would yield a similar number of diatom taxa if the 

samples were studied exhaustively. However, many of 

these diatom taxa are long ranging (including the abundant Paralia sulcata), from at least Miocene to modern 

ocean environments, and hence are not useful for biostratigraphic correlation. Others are known to be 

restricted to fossil deposits, but their precise stratigraphic 

ranges are not yet well known. I have, therefore, restricted 

my attention to a relatively few diatom taxa that have 

proven to be useful as biostratigraphic markers farther 

south on the Atlantic Coastal Plain-from Maryland 

(Andrews, 1978) to Georgia (Abbott and Andrews, 1979; 

Andrews and Abbott, 1985). 

The occurrence of these selected marker diatom 

species in the ACGSC-4 borehole core samples is shown 

in table 1. The details of occurrence of each taxon will be 

presented in the section on systematic paleontology. In 

general, the marker diatoms correlate these beds well 

with East Coast Diatom Zone 2 as proposed by Andrews 

(1978) for the Miocene rocks of the Chesapeake Bay 

region of Maryland. These diatoms suggest correlation of 

the upper part of the Kirkwood Formation as exposed in 

the ACGSC-4 borehole with the upper part of Lithologic 

Units 3 to 9 of the Calvert Formation in Maryland, these 

lithologic units being equivalent to the "zones" of 

Shattuck (1904). 

This correlation can be defined a little more precisely perhaps by consideration of the occurrence of the 

species of Sceptroneis. Sceptroneis grandis and S. hungarica were observed only in the two uppermost samples of 

the sequence in ACGSC-4, whereas S. caduceus was 

observed in six older samples (loc. nos. 7293-7300). 

Although this change in species is not absolutely clear cut 

in Maryland, it apparently occurs within Lithologic Units 

6 to 8 of the Calvert Formation. The change in Sceptroneis between samples at 155 and 179 feet (47 and 55 m) in 

the ACGSC-4 borehole in the Kirkwood Formation 

Diatom Biostratigraphy 5 
Table 1. Stratigraphic occurrence of marker diatoms in the Atlantic City Girl Scout Camp 4 core samples, Atlantic County, 

N.J. 

DIATOM SPECIES 

Actinoptychus heliopelta 

Actinoptychus splendens sensu lato 

Aulacodiscus rogersii 

Delohineis ovata 

Rhaphoneis fusiform is 

Rhaphoneis margaritata 

Rhaphoneis praepatllis, n. sp. 

Rhaphoneis scalaris 

Sceptroneis caduceus 

Sceptroneis grandis 

Sceptroneis hungarica 

EAST COAST DIATOM ZONE 

should therefore approximate Lithologic Units 6 to 8 in 

the Calvert Formation. 

The single diatomaceous sample from a depth of 

293 feet (89 m) is separated from the overlying diatomaceous interval by 54 feet (16 m) of sandy sediments in 

DIATOM LOCALITY AND DEPTH IN FEET (METERS) 

""' ""' ~ "" "" "" ,...,. ,...,. ,...,. ,.... (W) l.l) ,.. <0 0) C\1 (W) 0) 

-.::1" LC) l.l) co <0 <0 ,...... ,...... co ""' ""' ""' ""' ""' ""' ~ ~ '-" 

U) LO 0> 0> U) LO 1.0 0) (I) U) ,.... ,.... 0> ,_ C\1 ('f) (") 0) ,_ ,.... ,_ ,_ C\1 C\1 C\1 C"J C\1 I I I .Jt. I I I I I ,_ C\1 (I) ,.... CX) 0) 0 ...... (7) 0) 0> 0) 0> 0) 0) 0 0 

C\1 C\1 C\1 C\1 C\1 C\1 C\1 (W) C? ~ ~ ,.... ,.... ,.... ,.... ,.... ,.... ,...... 

X 

X X X X X X X 

X 

X X X X X X X 

X X X 

X X X X X X X X X 

X X X X X 

X X X X X X X X 

X X X X X X 

X X 

X 

2 1 

which core recovery was poor and which were unlikely to 

contain diatoms. The diatomaceous sample at a depth of 

293 feet (89 m) contains diatom debris of extremely poor 

preservation in which only the fragments of diatoms most 

resistant to dissolution were observed. However, four6 Miocene Marine Diatoms from the Kirkwood Formation, Atlantic County, New Jersey 
and five-pointed star-shaped hyaline centers of Actinoptychus heliopelta suggest that this bed is substantially 

older than the upper diatomaceous sequence observed in 

ACGSC-4. The observed fragments of Actinoptychus 

heliopelta are definitive for that species, for no other 

known Miocene diatom has a central hyaline area having 

four- or fivefold stellate symmetry. Such fragments have 

been observed also in Maryland in connection with more 

complete but weathered specimens of A. heliopelta. Actinoptychus heliopelta is considered to be a marker diatom 

for East Coast Diatom Zone 1 of Andrews (1978), and it 

appears to be separated in Maryland from zone 2 by a 

substantial period of time. The sample from the 293-foot 

(89-m) depth appears to correlate with the lower part of 

Lithologic Unit 3 of the Calvert Formation as exposed 

along the Patuxent River and elsewhere in Maryland. 

Woolman (1895, p. 169-170) indicated that a "Diatom 

bed no. 4," of about 20 feet (6 m) in thickness containing 

A. heliopelta occurs in an artesian well at Atlantic City, 

N.J. The extremely degraded diatom fragments at a 

depth of 293 feet (89 m) in the core probably represent 

the extreme updip limit of preserved zone 1 diatoms in 

the New Jersey Coastal Plain deposits. 

Although the above proposed correlations of the 

New Jersey Miocene strata are reasonably definitive, a 

few minor anomalies cannot be readily resolved at this 

time. The two uppermost samples in the ACGSC-4 

contained rare specimens whose external outlines resemble Rhaphoneis amphiceros (Ehrenberg) Ehrenberg and 

Rhaphoneis scutula Andrews, species not known to occur 

elsewhere in the Atlantic Coastal Plain earlier than in 

East Coast Diatom Zone 6 of Andrews (1978) of middle 

Miocene (Serravallian) age. If these specimens are truly 

conspecific with R. amphiceros and R. scutula, they may 

represent sample contamination from unspecified 

younger strata. Closer examination, however, suggests 

that these specimens resemble Rhaphoneis pwvula 

Andrews, a small and long-ranging species. These forms 

may suggest the evolutionary derivation of R. amphiceros 

and R. scutula from R. pwvula. However, they were far 

too rare in these samples to treat with certainty in this 

report. 

Another interesting feature is the rare to frequent 

occurrence in the upper five samples of the core of a 

small lanceolate fragilarioid diatom herein described as 

Rhaphoneis praeparilis n. sp. Although this diatom is 

similar to Rhaphoneis pari/is from East Coast Diatom 

Zones 3 to 6 in Maryland, it has no recognized analog 

there in diatom zone 2. Rhaphoneis praeparilis is defined 

and distinguished from R. pari/is in the section on systematic paleontology. This diatom occurs too frequently 

in the core to be readily dismissed as a contaminant. The 

seemingly anomalous occurrences of diatoms resembling 

younger forms may reflect somewhat different environmental conditions in the New Jersey Coastal Plain than 

were present farther south. The occurrence of cooler 

Miocene waters in New Jersey is one such possibility. 

However, no definitive statement can be made until more 

stratigraphic sections are studied and evaluated. 

AGE OF DIATOM ASSEMBLAGES AND 

MIOCENE STRATA 

The older of the two diatom assemblages represented in the ACGSC-4 borehole core at a depth of 293 

feet (89 m) appears to be of late Burdigalian age (late 

early Miocene). In Maryland, East Coast Diatom Zone 1 

of Andrews (1978) and Atlantic Margin Siliceous 

Microfossil Zone 1 of Abbott (1978) were reported to 

contain the marker silicoflagellate Naviculopsis quadtata, 

as well as the marker diatom Actinoptychus heliopelta. 

Andrews (unpublished data, 1984) found in several localities in Maryland that the boundary between the Naviculopsis quadrata silicoflagellate zone of Bukry and Foster 

(1974) and the Naviculopsis ponticula silcoflagellate zone 

of Bukry (1981b) falls within theActinoptychus heliopelta 

diatom zone of Andrews (1978) and Abbott (1978). This 

boundary between the Naviculopsis quadrata and N. 

ponticula silicoflagellate zones is correlated by B~kry 

(1981b, p. 434) with that between the Sphenoltthus 

belemnos calcareous nannofossil zone and the overlying 

Helicosphaera ampliaperla calcareous nannofossil zone; 

that is, between nannofossil zones CN3 and CN4 (Bukry, 

1981a, p. 338). The Neogene time scale of Berggren and 

others (1985) indicates an absolute age of about 17.1 Ma 

for this zone boundary. This age falls within the planktic 

foraminifera zone N7 of Blow (1969) and agrees with the 

assessment of Abbott (1978, p. 25), who assigned the 

Actinoptychus heliopelta diatom zone to N6 or N7. Unfortunately, no diagnostic silicoflagellate species was 

observed in the 293-foot (89-m) poorly preserved sample 

from the ASGSC-4 borehole, but the evidence cited 

above suggests a date near 17.1 Ma for this bed, a late 

Burdigalian age (late early Miocene), and a correlation 

with planktic foraminifera zone N7 and with calcareous 

nannofossil zones NN4 and CN3 to CN4. 

The younger of the two diatom assemblages in the 

core, from 155 to 239 feet ( 47 to 73 m) in depth, appears 

to be Langhian (early middle Miocene) in age. In Maryland, East Coast Diatom Zone 2 of Andrews (1978) and 

Atlantic Margin Siliceous Microfossil Zone 2 of Abbott 

(1978), which are approximately equivalent, include the 

upper part of Lithologic Unit 3 and Units 4 through 9 of 

the Calvert Formation. Abbott (1978, p. 25) correlates 

this diatom zone with planktic foraminifera zones N8 to 

N9 of Blow (1969) and calcareous nannofossil zone NN5 

of Martini and Worsley (1970). Following the Neogene 

time scale of Berggren and others (1985), I estimate that 

diatom zone 2 began at about 16.0 Ma and ended at 

about 15.6 Ma and that the upper diatomaceous interval 

Age of Diatom Assemblages and Miocene Strata 7 
in the ACGSC-4 borehole falls within this time constraint. These diatom assemblages are probably of late 

Langhian age, although diatom zone 2 does extend 

upward into the base of the Serravallian. 

The sandy sediments between depths of 239 and 

293 feet (73 and 89 m) have no analog in any known 

Maryland deposits. In Calvert and Anne Arundel Counties, Md., the diatomaceous sediments of diatom zone 2 

rest directly on the weathered surface of diatom zone 1 

(Andrews, unpublished data). These intercalated sandy 

deposits in New Jersey must represent sedimentation 

during some portion of the time between 17.1 and 

16.0 Ma. 

The lower part of the Kirkwood Formation between 

295 and 480 feet (90 and 146m) was extensively sampled 

for diatoms (see fig. 2), but no diatoms or diatom 

fragments were observed. The relatively thin Lithologic 

Units 1 and 2, 7 feet (2.1 m) or less in thickness, assigned 

by Shattuck (1904) to the Calvert Formation in Maryland 

may be in some part equivalent to this 185-foot (56-m) 

section of the core, but there are no diatoms in this 

section to help us. However, a probable early Miocene 

age, based on calcareous nannofossils at a depth of 478.5 

feet (146m) in the core, was suggested by L.M. Bybell 

and R.Z. Poore (U.S. Geological Survey Report on 

Referred Fossils, Jan.18, 1985). An age of early Miocene 

(planktic foraminiferal zone N5) was suggested by contained planktic foraminifera for a sample at a depth of 

473 feet (144m) by R.Z. Poore (U.S. Geological Survey 

Report on Referred Fossils, April 1985). This age suggests that the base of the Kirkwood Formation, as 

represented in the core, may be early Burdigalian (early 

Miocene) in age, approximately 21.8 Ma to 19.0 Ma. 

PALEOECOLOGY 

The diatom assemblages observed in the ACGSC-4 

borehole core are dominated by the small centric marine 

diatom Paralia sulcata (Ehrenberg) Cleve. This diatom, 

although not necessarily confined to shallow marine 

waters, is found most abundantly in marine waters of 

normal salinity in shallow shelf environments. Modern 

blooms of this taxon apparently occur in shallow marine 

waters enriched by nutrient-laden upwelling waters from 

the deeper parts of the ocean basin. Species of Delphine is 

living in modern oceans are thought to be indicators of 

coastal upwelling waters, and, by analogy, Delphineis 

ovata may be considered such an indicator during its 

range in early to middle Miocene time. The core samples 

contain richly varied diatom assemblages, and only a few 

significant diatom taxa have been studied in detail for this 

report. I have not personally attempted to identify all of 

the diatom taxa in these core samples because many are 

long ranging and are not biostratigraphically useful. 

However, C.H. Kain (in Woolman, 1895, p. 167-169) 

prepared a floral list of diatoms from an artesian well at 

Atlantic City, N.J., having 149 taxa in 49 genera of 

diatoms. We cannot be certain that all of these taxa are 

still considered to be valid, but the ACGSC-4 samples 

must correlate with at least a part of Woolman's 400-foot 

(122-m) "Diatom bed no. 3." The report of 149 taxa from 

a Miocene diatomaceous unit does not seem unreasonable, considering that samples from many different levels 

probably were examined exhaustively. Scanning this list 

by Kain (in Woolman, 1895, p. 168-169), the preponderance of diatom taxa are easily recognized as marine 

species, and relatively few as nonmarine. The early 

workers undoubtedly worked with cable-tool well cuttings, with which the opportunities for contamination 

were considerable. Nor do we know how careful the 

workers were in their sample preparations. I have not 

observed any significant nonmarine or brackish water 

diatom component in the ACGSC-4 borehole core samples; therefore, I consider that the deposits were laid 

down in a shallow shelf environment, in marine waters of 

normal to near-normal salinity. 

SYSTEMATIC PALEONTOLOGY 

This report deals specifically with the diatom taxa 

in the ACGSC-4 borehole core known to have biostratigraphic value as markers. The genera and species of 

diatoms studied in this report are arranged in alphabetical order to facilitate use by the reader. A systematic 

arrangement has not been made because this paper is 

primarily of interest to the diatom biostratigrapher, to 

whom a suprageneric classification is of little consequence. 

The format of discussion follows that used by the 

writer in earlier reports on fossil marine diatom assemblages of the Eastern United States. The first citation in 

each synonymy is to the basionym of the taxon. The 

second citation is to the name adopted for use in this 

report, with appropriate references in chronological 

order. Subsequent citations include synonyms, misidentifications, and other errata. These synonymies emphasize the reported fossil occurrences in the Eastern United 

States, and they are not designed to be exhaustive. 

Information is given on the known geologic ranges of all 

taxa herein studied because such information is critical to 

the continuing development of diatom biostratigraphy. 

Genus ACTINOPTYCHUS Ehrenberg, 1841 

Actinoptychus heliopelta Grunow 

Plate 1, figures 1, 2 

Actinoptychus heliopelta Grunow, in Van Heurck, 1883, pl. 123, 

fig. 3; Schmidt and others, 1890, pl. 153, fig. 22; Boyer, 

8 Miocene Marine Diatoms from the Kirkwood Formation, Atlantic County, New Jersey 
1904, p. 499, pl. 134, fig. 3; Lohman, 1948, p. 169, pl. 9, 

fig. 3; Andrews, 1978, p. 382, pl. 1, figs. 7, 8, pl. 6, fig. 2; 

Andrews, 1979, p. 79-98, pis. 1-5. 

Heliopelta spp. Ehrenberg, 1845, p. 268; Ralfs, in Pritchard, 

1861, p. 841. 

Discussion.-Fragments of Actinoptychus heliopelta were observed only in the sample examined from 

USGS diatom locality 7301, at a depth of 293 feet (89 m) 

in the ACGSC-4 borehole. These fragments consist of 

the hyaline centers of valves having attached hyaline rays 

that extend into alternate sectors of the valve. These 

star-shaped fragments show both a fourfold (see pl. 1, fig. 

1) and a fivefold (see pl.1, fig. 2) symmetry, which can be 

identified only with Actinoptychus heliopelta. Similar 

fragments have been observed in Miocene rocks of 

Maryland in connection with well-preserved specimens 

of A. heliopelta. The solid hyaline central part of the valve 

is apparently the part most resistant to dissolution. 

Known geologic range.-From East Coast Diatom 

Zone 1 (Actinoptychus heliopelta partial range zone of 

Andrews, 1978, p. 377-378) and upper part of the 

Naviculopsis quadrata silicoflagellate zone of Bukry and 

Foster (1974) into the overlying Naviculopsis ponticula 

silicoflagellate zone of Bukry (1981b ). This silicoflagellate zone boundary occurs at approximately 17.1 Ma in 

the Burdigalian Stage of early Miocene age. The 293-foot 

(89-m) bed in the ACGSC-4 borehole appears to be the 

age equivalent of the older part of Lithologic Unit 3 of 

the Calvert Formation as exposed near Dunkirk and 

elsewhere in Maryland. It is substantially older than the 

other diatomaceous beds found in the ACGSC-4 

borehole. 

Actinoptychus splendens (Shadbolt) Ralfs sensu Jato 

Plate 1 I figures 3-6 

Actinosphaenia splendens Shadbolt, 1854, p. 16. 

Actinoptychus splendens (Shadbolt) Ralfs, in Pritchard, 1861, p. 

840; Hustedt, 1929, p. 478-480; Lohman, 1948, p. 170; 

Hendey, 1964, p. 95, pl. 22, fig. 1. 

Actinoptychus splendens var. nicobarica Grunow, in Van 

Heurck, 1883, pl. 120, fig. 4. 

Actinoptychus nicobaricus (Grunow) Andrews, 1978, p. 383, pl. 

2, fig. 3. 

Actinoptychus australis (Grunow) Andrews, 1978, p. 382, pl. 1, 

fig. 5. 

Discussion.-The diatoms here considered as Actinoptychus splendens (Shadbolt) Ralfs occur rarely 

throughout the section of East Coast Diatom Zone 2 in 

the ACGSC-4 borehole. In Andrews (1978) I identified 

A. australis and A. nicobaricus as occurring in East Coast 

Diatom Zone 2 in Maryland. The identification of these 

taxa in Miocene rocks of this age is no longer tenable. 

The differentiation of A. australis and A. nicobaricus from 

the better known and still living A. splendens appears to 

be based mainly on a single morphologic feature, a very 

thin median hyaline ray bisecting, from central area to 

margin, each externally raised sector. InA. splendens, this 

ray is continuous from the hyaline central area to the 

labiate process near the margin of the valve. In A. 

nicobaricus, the ray extends outward from the center and 

inward from the labiate process, but it is not continuous. 

In A. australis, the ray extends outward from the center 

only part way toward the labiate process. In specimens 

from ACGSC-4, however, I have seen all three of the 

above ray types on different sectors of the same valve. I 

have also observed valves, otherwise morphologically 

indistinguishable, having no discernible hyaline rays on 

any sector. Hence, these forms must represent a variable 

population of a single species, rather than three separate 

species. I therefore propose to assign the forms of 

Actinoptychus in East Coast Diatom Zone 2 having more 

than six sectors to A. splendens, recognizing that they may 

well be precursors to the more distinct modern form of 

the species. 

Actinoptychus nicobaricus has thus been placed in 

synonymy, as has A. australis sensu Andrews (1978). I 

prefer to retain the name A. australis for a similarappearing diatom common in the Eastover Formation of 

Virginia and of late Miocene age. This diatom shows the 

consistent occurrence of a thin hyaline ray extending 

from the hyaline center to about half radius on each 

externally raised sector of the valve. It stands in contrast 

to the inconsistent occurrence of the hyaline ray in 

specimens from ACGSC-4 and the hyaline ray extending 

from center to margin in the modern species. 

Known geologic range.-Forms of this variable species have been observed in East Coast Diatom Zone 2 of 

Andrews (1978) in Maryland from the upper part of 

Lithologic Unit 3 to Lithologic Unit 8 of the Calvert 

Formation. In this study, it has been observed rarely in 

the ACGSC-4 borehole from depths of 155 to 235 feet 

(47 to 72 m). 

Genus AULACODISCUS Ehrenberg, 1844 

Aulacodiscus rogersii (Bailey) Schmidt 

Plate 1 I figure 7 

Podiscus rogersii Bailey, 1844, p. 137, pl. 3, figs. 1, 2. 

Aulacodiscus rogersii (Bailey) Schmidt, 1875, pl. 107, fig. 3; 

Rattray, 1888, p. 372; Boyer, 1904, p. 497-498, pl. 134, 

fig. 5. 

Description.-Valve round, heavily silicified, nearly 

flat from center to about half the radius, then smoothly 

curved to the margin. Diameter of specimen observed, 

110 J.tm. Valve surface covered with a radiating network 

of fine areolae, about six in 10 J.tm, overlain by a coarser, 

heavily siliceous reticulating network on the exterior. 

Systematic Paleontology 9 
Three to seven ocelluslike structures have been reported 

on the shoulder of the valve. 

Discussion.-Fragments of Aulacodiscus rogersii 

were found commonly in the sample examined from 

USGS diatom locality 7301, at a depth of293 feet (89 m) 

in the ACGSC-4 borehole. Numerous fragments of this 

heavily silicified diatom have been preserved, whereas 

most of the other diatoms in this bed have been destroyed 

by dissolution. The fragments of Aulacodiscus rogersii 

resemble specimens assigned to A. argus (Ehrenberg) 

Schmidt by Lohman (1948, p. 171), Andrews (1980, p. 

24-25), and Andrews and Abbott (1985, p. 71-72, pl. 7, 

fig. 1) from younger Miocene deposits in Maryland and 

Virginia. However, the specimens assigned to Aulacodiscus rogersii in this study show the distinctively flattened 

valve center that characterizes A. rogersii, whereas the 

younger forms previously assigned to A. argus appear to 

have a more nearly rounded valve center. Whether those 

specimens identified as ''Aulacodiscus argus" from the 

younger Miocene strata are truly conspecific with the A. 

argus living in present-day marine waters remains to be 

determined. 

Known geologic range. -Reported by Boyer (1904, 

p. 498) from localities now known to be in East Coast 

Diatom Zone 1 of Andrews (1978) or in the older part of 

Lithologic Unit 3 of the Calvert Formation in Maryland. 

Boyer (1904) also reported this species from localities 

probably as young as Lithologic Unit 10 of the Calvert 

Formation in Maryland. However, I have not observed 

distinctively flattened specimens attributable to Aulacodiscus rogersii in the younger beds of the Calvert Formation, and Boyer may have confused the dome-shaped 

species, which has been called A. argus with the flattened 

speciesA. rogersii.Aulacodiscus rogersii may be a marker 

for East Coast Diatom Zone 1 or for the older part of 

Lithologic Unit 3 of the Calvert Formation and of the late 

Burdigalian Stage in Maryland. 

Genus DELPHINEIS Andrews, 1977 

Delphineis ovata Andrews 

Plate 1, figures 8-14; plate 3, figure 11 

Delphineis ovata Andrews, 1977, p. 252-253, pl. 1, figs. 12-15, 

pl. 2, figs. 25, 26, pl. 4, figs. 33, 34; Andrews, 1978, p. 392, 

394, pl. 5, figs. 12-14; pl. 8, figs. 5, 6. 

Description. -Valve elliptical to linear-elliptical, 

having curved lateral margins terminating in bluntly 

rounded apices. Length of observed specimens, 30 to 96 

#-(.m; width about 8 to 10 #-(.m. Transverse rows of areolae 

about seven in 10 #-(.m, having areolae in the bottom of 

shallow external grooves. Three areolae on each side of 

hyaline axial area at the center of the valve, reducing to 

two on each side near the apices. Transverse rows of 

areolae parallel at center of valve, becoming slightly 

radiate near the apices. Short, fine rows of areolae 

radiate around the apices of the valve. Hyaline axial area 

narrow, about 1 #Lm in width, and pairs of transapical 

rows of areolae are well aligned across the axial area. The 

apical fine structures-two minute pores and single 

labiate processes on each end of the valve (pl. 3, fig. 

11)-were preserved in a few specimens studied for this 

report. 

Discussion.-This species was observed rarely to 

frequently in samples from 155 to 235 feet (47 to 72 m) 

in the ACGSC-4 borehole. Delphineis ovata most nearly 

resembles the younger species Delphineis penelliptica, 

but it lacks the distinct taper toward the apices that is 

characteristic of the latter species. 

Known geologic range.-Reported by Andrews 

(1978, p. 394) to range from the younger portion of 

Lithologic Unit 3 to the top of Lithologic Unit 9 of the 

Calvert Formation in Maryland. Hence, restricted to 

East Coast Diatom Zone 2 of the Calvert Formation of 

Langhian age (early middle Miocene). 

Genus RHAPHONEIS Ehrenberg, 1844 

Rhaphoneis fusiformis Andrews 

Plate 2, figures 1-4 

Rlzaphoneis fusifonnis Andrews, 1978, p. 386, pl. 3, figs. 14-16. 

Description.-Valve lanceolate with protracted apices, which are narrowly rounded to bluntly pointed. 

Length of observed specimens 40 to 56 #Lm; width about 

10 #-(.m. Ends of valve somewhat asymmetrical and often 

slightly bent in relation to the longitudinal axis. About 

five or six transverse rows of relatively large areolae in 10 

#-(.m. Hyaline axial area narrow to narrowly lanceolate, 

and transverse rows of pores not aligned across it. Apical 

fine structures consist of a pseudo cell us of fine pores and 

a single labiate process. 

Discussion. -Rhaphoneis fusiformis occurs rarely 

in samples from 155 to 179 feet (47 to 55 m) in depth in 

the core. 

Known geologic range.-Reported by Andrews 

(1978, p. 386) from East Coast Diatom Zones 2 and 3 

and from the upper part of Lithologic Unit 3 to Unit 11 

in the Calvert Formation of the Chesapeake Bay region 

of Maryland. Langhian in age (early middle Miocene). 

Rhaphoneis margaritata Andrews 

Plate 2, figures 5-12; plate 3, figure 10 

Rhaphoneis margarita/a Andrews, 1978, p. 388, pl. 4, figs. 5-9, 

pl. 7, fig. 1. 

Description.-Valve varies from shorter subrhomboidal specimens having somewhat produced apices to 

10 Miocene Marine Diatoms from the Kirkwood Formation, Atlantic County, New Jersey 
longer lanceolate specimens having protracted attenuate 

apices. Ends narrowly rounded. Length of observed 

specimens 36 to 1681-'m; width about 16 to 281-'m. Three 

to four transverse rows of areolae in 10 I-'m, parallel in 

larger specimens and slightly radiate in smaller specimens. Areolae show a secondary alignment in nearly 

straight longitudinal rows. Hyaline axial area narrow in 

the center of the valve and virtually indiscernible near the 

apices. Transapical rows of areolae not aligned across the 

axial area. Apical pseudocellus composed of fine pores 

radiating toward the end of the valve, and a single labiate 

process occurs in each end of the valve (pl. 3, fig. 10). 

Discussion.-This robust and distinctive species of 

Rhaphoneis is rare to frequent in samples from 155 to 

239 feet (47 to 73 m) in the core. Fragments were 

observed in the substantially older 293-foot (89-m) sample; this occurrence extends the range of the species 

downward into at least a part of East Coast Diatom Zone 

1. 

Known geologic range.-Reported by Andrews 

(1978, p. 388) from East Coast Diatom Zone 2 in the 

Chesapeake Bay region of Maryland. Found there in 

Lithologic Units 3 to 8 of the Calvert Formation; hence, 

Langhian in age (early middle Miocene). 

Rhaphoneis praeparilis Andrews, n. sp. 

Plate 2, figures 13-19; plate 3, figure 12 

Description.-Valve lanceolate, tapering to protracted, narrowly rounded apices. Length of observed 

specimens, 32 to 50 I-'m; width 8 to 111-'m, eight to eight 

and a half transverse rows of areolae in 10 I-'m, mostly 

parallel but slightly radiate in some specimens. Areolae 

show a secondary alignment in nearly straight longitudinal rows. Transverse rows of areolae are well aligned 

across the narrow but distinct hyaline axial area, having 

four or five areolae in each row, on either side of the axial 

area near the center of the valve. Apical pseudocellus 

composed of fine pores without discernible arrangement. 

A single labiate process is located between the pseudocellus and the main part of the valve in both ends of the 

valve (pl. 3, fig. 12). 

Discussion.-The species bears a superficial 

resemblance to Rhaphoneis pari/is Hanna, but it shows 

some distinctive differences in detailed morphology that 

seem to be consistent. The valve of R. praeparilis is a little 

more broadly lanceolate than that of R. pari/is. The 

narrow hyaline axial area of R praeparilis is similar to 

that of R pari/is, rather than so narrow as to be indistinguishable as in R. lancettula. The transverse rows of 

areolae in R praeparilis contain four or five areolae on 

either side of the axial area in the center of the valve, 

whereas R pari/is shows only three areolae in its transverse rows. Occurs rarely to frequently in samples from 

155 to 215 feet (47 to 66 m) in the core. 

Known geologic range.-This form has not been 

described previously or reported from Miocene deposits 

in the Eastern United States. Hence, it may be restricted 

to East Coast Diatom Zone 2 of Andrews (1978) but 

probably restricted to the northern part of the Atlantic 

Coastal Plain. Rhaphoneis praeparilis may be ancestral to 

R. pari/is Hanna, reported by Andrews (1978) from East 

Coast Diatom Zones 3 to 6 and more widely distributed 

in the coastal plain deposits of the Eastern United States. 

Holotype.- USGS diatom catalog no. 4735-7 (pl. 2, 

fig. 19), length 50 /-'m. From USGS diatom locality 7293, 

ACGSC-4 borehole core, depth 179 feet (55 m), Atlantic 

County, N.J. 

Rhaphoneis scalaris Ehrenberg 

Plate 2, figures 20-23; plate 3, figure 9 

Rhaphoneis scalaris Ehrenberg, 1845, p. 271; Grunow, in Van 

Heurck, 1881, pl. 36, fig. 32; Lohman, 1948, p. 183, pl. 11, 

fig. 3; Andrews, 1975, p. 216, pl. 3, figs. 49, 50, pl. 5, figs. 

64, 65; Andrews, 1978, p. 389, pl. 4, figs. 10, 11, pl. 7, fig. 

6. 

Description.-Valve narrowly lanceolate, having 

protracted apices. Length of observed specimens about 

83 to 104 I-'m, width 13 to 15 I-'m, but many specimens are 

incompletely preserved in these samples. Four transverse 

rows of areolae in 10 I-'m, composed of large, irregularly 

sized areolae. Transverse rows of areolae separated by 

strong siliceous transverse ribs, but the areolae themselves are separated by thinner longitudinal septa located 

near the outer surface of the valve. Hyaline axial area 

narrow but distinct, tapering slightly toward the apices. 

The transverse rows of areolae are not aligned across 

axial area. A small apical pseudocellus of fine pores 

occurs on each end of the valve but is usually poorly 

preserved. Apical processes not known. 

Discussion.-This distinctive species is characterized by its delicate lanceolate shape and its peculiar 

elongate and irregular areolae. It occurs as fragments 

and rare whole specimens in samples from 155 to 239 

feet ( 47 to 73 m) in the core. 

Known geologic range.-Reported by Andrews 

(1978, p. 389) from East Coast Diatom Zone 2 in the 

Chesapeake Bay region of Maryland. Found there in 

Lithologic Units 3 to 8 of the Calvert Formation; hence, 

Langhian in age (early middle Miocene). 

Genus SCEPTRONEIS Ehrenberg, 1844 

Sceptroneis caduceus Ehrenberg 

Plate 3, figures 1-5 

Sceptroneis caduceus Ehrenberg, 1845, p. 271; Ehrenberg, 

1854, pl. 33, pt. 17, fig. 15; Van Heurck, 1881, pl. 37, fig. 

Systematic Paleontology 11 
5; Boyer, 1904, p. 489, pl. 135, fig. 12; Hustedt, 1931, pl. 

130, fig. 651; Lohman, 1948, p. 183-184, pl. 11, fig. 7; 

Andrews, 1978, p. 396-397, pl. 5, figs. 18-20, pl. 8, figs. 9, 

10. 

Description.-Valve slender, elongate, clavate, having a larger broadly rounded capitate head-pole and a 

distinctly smaller sharply rounded foot-pole. Many specimens show a slight to moderate central swelling of the 

valve. Some specimens slightly curved longitudinally, and 

others somewhat twisted around the longitudinal axis. 

The species is highly variable in length and shape. Whole 

specimens are extremely rare in the samples studied for 

this report. Andrews (1978) reported a length range of 57 

to > 269 J.tm. Valves generally narrow, about 8 to 10 J.tm 

in width. Transverse rows of areolae about five in 10 J.tm, 

short and parallel, not aligned across axial area. Hyaline 

axial area narrow, but distinct. Both ends show a single 

centrally located labiate process forming the focal point 

of fine pores of the pseudocellus radiating to the tip of 

the valve. 

Discussion. -Sceptroneis caduceus is readily distinguishable from S. grandis and S. hungarica by its much 

more delicately silicified valves and by the strikingly 

expanded head-pole in which the pseudocellus is readily 

resolved by the light microscope. Fragments of S. 

caduceus are frequent to common in the core from 

depths of 179 to 239 feet (55 to 73 m). 

Known geologic range.-Reported by Andrews 

(1978) from rocks of late Burdigalian age (late early 

Miocene) to Langhian age (early middle Miocene). From 

East Coast Diatom Zones 1 and 2 of Andrews (1978), 

but apparently ranging only as high as Lithologic Unit 8 

of the Calvert Formation in the Chesapeake Bay region 

and hence extinct below the top of Diatom Zone 2. 

Sceptroneis grandis Abbott 

Plate 3, figures 6, 7 

Sceptroneis grandis Abbott, in Abbott and Ernissee, 1983, p. 

302-303, pl. 11, fig. 7, pl. 12, fig. 1. 

Sceptroneis caduceus Hanna, 1932 (non Ehrenberg, 1845), p. 

216-217, pl. 16, figs. 5-7. 

Description. -Valve heavily silicified, clavate, lanceolate, having a bluntly rounded head-pole and a more 

narrowly rounded foot-pole. Length of observed specimens, 114 to 120 J.tm, but range in length is much greater 

than this. Width about 15 J.tm. About three and a half 

transverse rows of areolae in 10 J.tm, short and parallel, 

having large, well-defined areolae. The transverse rows 

of areolae are not aligned across the axial area. Hyaline 

axial area very narrow, in some specimens distinct, but in 

others distinguishable only by the misalignment of the 

areolae on either side. Both ends show a pseudocellus 

composed of fine pores radiating toward the tip of the 

valve. Presumably the focal point of the pores of the 

pseudocellus is a single labiate process, but this structure 

is not readily discerned under the light microscope. 

Discussion. -Sceptroneis grandis is distinct from S. 

caduceus because of its heavier silicification, more massive construction, and coarser areolation. It occurs rarely 

in the core from depths of 155 and 175 feet ( 47 and 53 

m), the two uppermost diatomaceous samples studied for 

this report. 

Known geologic range.-Reported by Abbott, in 

Abbott and Ernissee (1983) from planktic foraminiferal 

zones N8 to N9 in the Pungo River Formation of North 

Carolina; hence, Langhian (early middle Miocene) in 

age. 

Sceptroneis hungarica (Pantocsek) Andrews 

Plate 3, figure 8 

Rhaphoneis hungarica Pantocsek, 1886, pt. 1, p. 34, pl. 3, fig. 30, 

pl. 25, fig. 224. 

Sceptroneis hungarica (Pantocsek) Andrews, 1978, p. 398, 400, 

pl. 5, figs. 21, 22. 

Description.-Valve broadly lanceolate, having 

only slight longitudinal asymmetry, and ends slightly 

produced. Head-pole bluntly rounded, and foot-pole 

slightly more sharply rounded. Length of observed specimen about 48 J.tm, and width about 15 J.tm, somewhat 

smaller than reported by Andrews (1978) for this species. 

Three to three and a half transverse rows of areolae in 10 

J.tm, composed of few large, round areolae. Axial area 

very narrow, only the dividing line between nonaligned 

rows of areolae on either side of the valve. Apical fine 

structures not observed. 

Discussion.-The relatively short valve of S. hungarica, and its blunt and noncapitate apices, distinguishes 

this species morphologically from S. grandis. The species 

was rare in the uppermost diatomaceous sample examined from the core, at 155 feet ( 4 7 m). 

Known geologic range.-Reported by Andrews 

(1978) in East Coast Diatom Zone 2 from about the 

middle of undifferentiated Lithologic Units 4 to 8 and in 

Unit 9 of the Calvert Formation in the Chesapeake Bay 

region. Langhian (early middle Miocene) in age. 

REFERENCES CITED 

Abbott, W.H., 1978, Correlation and zonation of Miocene 

strata along the Atlantic margin of North America using 

diatoms and silicoflagellates: Marine Micropaleontology, 

v. 3, p. 15-34, pis. 1, 2. 

Abbott, W.H., and Andrews, G.W., 1979, Middle Miocene 

marine diatoms from the Hawthorn Formation within the 

Ridgeland Trough, South Carolina and Georgia: 

Micropaleontology, v. 25, no. 3, p. 225-271, pis. 1-8. 

Abbott, W.H., and Ernissee, J.J., 1983, Biostratigraphy and 

paleoecology of a diatomaceous clay unit in the Miocene 

12 Miocene Marine Diatoms from the Kirkwood Formation, Atlantic County, New Jersey 
Pungo River Formation of Beaufort County, North Carolina: Smithsonian Contributions to Paleobiology, no. 53, p. 

287-353, pis. 1-26. 

Andrews, G.W., 1975, Taxonomy and stratigraphic occurrence 

of the marine diatom genus Rhaphoneis: Nova Hedwigia, 

no. 53, p. 193-222, pis. 1-5. 

---1977, Morphology and stratigraphic significance of 

Delphineis, a new marine diatom genus: Nova Hedwigia, 

no. 54, p. 243-260, pis. 1-8. 

---1978, Marine diatom sequence in Miocene strata of the 

Chesapeake Bay region, Maryland: Micropaleontology, v. 

24, no. 4, p. 371-408, pis. 1-8. 

---1979, Morphologic variations in the Miocene diatom 

Actinoptychus heliopelta Grunow: Nova Hedwigia, no. 64, 

p. 79-98, pis. 1-5. 

---1980, Neogene diatoms from Petersburg, Virginia: 

Micropaleontology, v. 26, no. 1, p. 17-48, pis. 1-6. 

Andrews, G.W., and Abbott, W.H., 1985, Miocene diatoms 

from the Hawthorn Formation, Thomas County, Georgia: 

Bulletins of American Paleontology, v. 87, no. 321, p. 

53-109, pis. 6-13. 

Bailey, J.W., 1844, Account of some new infusorial forms 

discovered in the fossil Infusoria from Petersburg, Virginia, and Piscataway, Maryland: American Journal of 

Science, v. 46, p. 131-141, pl. 3. 

Berggren, W.A., Kent, D.V., Flynn, J.J., and Van Couvering, 

J.A., 1985, Cenozoic geochronology: Geological Society of 

America Bulletin, v. 96, no. 11, p. 1407-1427. 

Blow, W.H., 1969, Late Middle Eocene to Recent planktonic 

foraminiferal biostratigraphy, biochronology and paleoclimatology: First International Conference on Planktonic 

Microfossils, Geneva, Switzerland, 1967, Proceedings, v. 1, 

p. 199-422, pis. 1-54. text figs. 1-43. 

Boyer, C.S., 1895, A diatomaceous deposit from an artesian 

well at Wildwood, N.J.: Bulletin of the Torrey Botanical 

Club, v. 22, no. 6, p. 260-266. 

---1904, Thallophyta-Diatomacea, in Systematic paleontology of the Miocene deposits of. Maryland: Maryland 

Geological Survey, Miocene, p. 487-507, pls. 134, 135. 

Bukry, D., 1981a, Cenozoic coccoliths from the Deep Sea 

Drilling Project: Society of Economic Paleontologists and 

Mineralogists, Special Publication 32, p. 335-353. 

---1981b, Synthesis of silicoflagellate stratigraphy for Maestrichtian to Quaternary marine sediment: Society of Economic Paleontologists and Mineralogists, Special Publication 32, p. 433-444. 

Bukry, D., and Foster, J.H., 1974, Silicoflagellate zonation of 

Upper Cretaceous to lower Miocene deep-sea sediment: 

U.S. Geological Survey Journal of Research, v. 2, no. 3, p. 

303-310. 

Cook, G.H., 1868, Geology of New Jersey: New Jersey Geological Survey publication, 900 p. 

Ehrenberg, C.G., 1845, Untersuchungen tiber die kleinsten 

Lebens formen im Quellenlande des Euphrats und Araxes, 

so wie tiber eine an neuen Formen sehr reiche marine 

Tripelbildung von den Bermuda-Inseln: Koniglichen 

preussischen Akademie der Wissenschaften zu Berlin, 

Bericht 1844, p. 253-275. 

---1854, Mikrogeologie: Leipzig, L. Voss, p. 1-374, pis. 

1-41. 

Goldstein, F.R., 1974, Paleoenvironmental analyses of the 

Kirk-wood Formation: Rutgers University, unpublished 

Ph.D. dissertation, 70 p. 

Hanna, G.D., 1932, The diatoms of Sharktooth Hill, Kern 

County, California: California Academy of Sciences, Proceedings, ser. 4, v. 20, no. 6, p. 161-263, pls. 2-18. 

Hendey, N.I., 1964, An introductory account of the smaller 

algae of British coastal waters, pt. V, Bacillariophyceae 

(Diatoms): London, Ministry of Agriculture, Fisheries, 

and Food, Fishery Investigations Series 4, p. 1-317, pis~ 

1-45. 

Hustedt, Friedrich, 1927-1966, Die Kieselalgen Deutschlands, 

Osterreichs und der Schweiz: Band 7 of Rabenhorst, G .L., 

Kryptogamenflora * * *: Leipzig, Akademische Verlagsgesellschaft, pt. 1, p. 1-920, figs. 1-542, 1927-1930; pt. 2, p. 

1-845, figs. 543-1179, 1931-1959; pt. 3, p. 1-816, figs. 

1180-1788, 1962-1966. 

Isphording, W.C., 1970, Petrology, stratigraphy and 

re-definition of the Kirk-wood Formation (Miocene) of 

New Jersey: Journal of Sedimentary Petrology, v. 40, no. 3, 

p. 986-997. 

Kain, C.H., and Schultze, E.A., 1889, On a fossil marine 

diatomaceous deposit from Atlantic City, N.J.: Bulletin of 

the Torrey Botanical Club, v. 6, p. 71-76, 207-210, pis. 89, 

92, 93. 

Knapp, G.N., 1904, Underground waters of New Jersey; wells 

drilled in 1903: New Jersey Geological Survey, Annual 

Report for 1903, part 4, p. 73-93. 

Lohman, K.E., 1948, Middle Miocene diatoms from the Hammond well, in Cretaceous and Tertiary subsurface geology: 

Maryland Department of Geology, Mines and Water 

Resources, Bulletin 2, p. 151-187,331-333, pls. 5-11. 

Martini, E., and Worsley, T., 1970, Standard Neogene calcareous nannoplankton zonation: Nature, v. 225, p. 289-290. 

Pantocsek, Josef, 1886, Beitrage zur Kenntniss der fossilen 

Bacillarien Ungarns: Nagy-Tapolcsany, Julius Platzko, pt. 

1, p. 1-75, pis. 1-30. 

Patrick, Ruth, 1944, Well-boring at Brandywine lighthouse in 

Delaware Bay, pt. 2, Miocene diatoms: Academy of Natural Sciences of Philadelphia, Notulae Naturae, no. 133, 13 

p., 1 pl. 

Pritchard, Andrew, 1861, A history of Infusoria, 4th ed.; 

London, Whittaker and Co., p. 1-968, pis. 1-40. 

Rattray, John, 1888, A revision of the genus Aulacodiscus 

Ehrb.: Royal Microscopical Society Journal 1888, p. 

337-382, pis. 5-7. 

Richards, H.G., and Harbison, Anne, 1942, Miocene invertebrate fauna of New Jersey: Academy of Natural Sciences 

of Philadelphia, v. 44, p. 167-250, pis. 7-22. 

Schmidt, Adolf, and others, 1874-1959, Atlas der Diatomaceenkunde: Leipzig, O.R. Reisland, pis. 1-480. 

Shad bolt, George, 1854, A short description of some new forms 

of Diatomaceae from Port Natal: Transactions of the 

Microscopical Society of London, new series, v. 2, pt. 1, p. 

13-18,pl. 1. 

Shattuck, G.B., 1904, The Miocene deposits of Maryland: 

Geological and paleontological relations, with a review of 

earlier investigations: Maryland Geological Survey, 

Miocene, p. 33-137. 

References Cited 13 
Spangler, W.B., and Peterson, J.J., 1950, Geology of Atlantic 

Coastal Plain in New Jersey, Delaware, Maryland, and 

Virginia: American Association of Petroleum Geologists 

Bulletin, v. 34, no. 1, p. 1-99. 

U.S. Geological Survey, 1972, Dorothy quadrangle, New Jersey: 

U.S. Geological Survey 7Y2-minute topographic map, lat 

39°22.5' N, long 74°45' W, scale 1:24,000. 

Van Heurck, Henri, 1880-1885, Synopsis des diatomees de 

Belgique: Anvers, p. 1-235, pis. 1-132, A-C. 

Woolman, Lewis, 1891, Geology of artesian wells at Atlantic 

City, N.J.: Academy of Natural Sciences of Philadelphia, 

Proceedings, 1890, v. 42, p. 132-144. 

---1892 Review of artesian-well horizons in southern New 

Jersey: 'New Jersey Geological Survey, Annual Report of 

the State Geologist for 1891, p. 223-232. 

---1895, Report on artesian wells in southern New Jersey: 

New Jersey Geological Survey, Annual Report of the State 

Geologist for 1894, pt. 2, p. 151-304. 

14 Miocene Marine Diatoms from the Kirkwood Formation, Atlantic County, New Jersey 
PLATES 1-3 

Contact photographs of the plates in this report are available, at cost, from the U.S. Geological Survey 

Library, Federal Center, Denver, CO 80225. 
PLATE 1 

Figure 1, 2. Actinoptychus heliopelta Grunow (p. 8). 

1. USGS diatom cat. no. 4743-3, x 1,000, eroded hyaline central area from 

eight-sectored specimen. From USGS diatom locality 7301. 

2. USGS diatom cat. no. 4743-2, x 1,000, eroded hyaline central area from 

ten-sectored specimen. From USGS diatom locality 7301. 

3-6. Actinoptychus splendens (Shadbolt) Ralfs sensu lata (p. 9). 

3. USGS diatom cat. no. 4736-5, x 500, diameter 126 .urn. Thin hyaline rays 

continuous from center to margin in some sectors, discontinuous in 

others. From USGS diatom locality 7294. 

4. USGS diatom cat. no. 4735-11, x 500, diameter 91 .urn. From USGS 

diatom locality 7293. 

5. USGS diatom cat. no. 4735-8, x 500, diameter 73 .urn. Thin hyaline rays 

extend part way from central area to margin. From USGS diatom locality 

7293. 

6. Scanning electron microscope photograph, X 1,100, diameter of fragment 84 .urn, inside view, thin hyaline rays extend part way from central 

area to margin. From USGS diatom locality 7297. 

7. Aulacodiscus rogersii (Bailey) Schmidt (p. 9). USGS diatom cat. no. 4743-4, 

x 500, diameter about 120 .urn. Oblique view of large fragment. From USGS 

diatom locality 7301. 

8-14. Delphineis ovata Andrews (p. 10). 

8. USGS diatom cat. no. 4733-8, x 1,000, length 32 .urn. From USGS 

diatom locality 7291. 

9. USGS diatom cat. no. 4736-7, x 1,000, length 30 .urn. From USGS 

diatom locality 7294. 

10. USGS diatom cat. no. 4735-9, x 1,000, length 35 .urn. From USGS 

diatom locality 7293. 

11. USGS diatom cat. no. 4739-1, x 1 ,000, length 76 .urn. From USGS 

diatom locality 7297. 

12. Scanning electron microscope photograph, x 1 ,500, length about 69 .urn. 

From USGS diatom locality 7297. 

13. Scanning electron microscope photograph, x 2,500, length 40 .urn. From 

USGS diatom locality 7297. 

14. Scanning electron microscope photograph, x 2,600, length 33 .urn. From 

USGS diatom locality 7293. 
U.S. GEOLOGICAL SURVEY BULLETIN 1769-PLATE 1 

6 

7 

ACTINOPTYCHUS, AULACODISCUS, AND DELPHINEIS 
PLATE 2 

Figure 1-4. Rhaphoneis fusiformis Andrews (p. 10). 

1. USGS diatom cat. no. 4733-10, x 1,000, length about 51 ~m. From 

USGS diatom locality 7291. 

2. USGS diatom cat. no. 4733-14, x 1 ,000, length 39 ,am. From USGS 

diatom locality 7291. 

3. Scanning electron microscope photograph, x 2,400, length 44 ~m. From 

USGS diatom locality 7293. 

4. Scanning electron microscope photograph, x 2,000, length 45 ~m. From 

USGS diatom locality 7293. 

5-12. Rhaphoneis margaritata Andrews (p. 10). 

5. USGS diatom cat. no. 4734-3, x 500, length 36 ~m. From USGS diatom 

locality 7292. 

6. USGS diatom cat. no. 4735-5, x 500, length 78 ~m. From USGS diatom 

locality 7293. 

7. USGS diatom cat. no. 4739-12, x 500, length 102 ,am. From USGS 

diatom locality 7297. 

8. USGS diatom cat. no. 4739-15, x 500, length 120 ,am. From USGS 

diatom locality 7297. 

9. USGS diatom cat. no. 4739-7, x 500, length 140 ~m. From USGS diatom 

locality 7297. 

10. USGS diatom cat. no. 4736-6, x 500, length 170 ~m. From USGS diatom 

locality 7294. 

11. Scanning electron microscope photograph, x 800, length 147 ~m. From 

USGS diatom locality 7297. 

12. Scanning electron microscope photograph, x 1 ,000, length 115 ,am. 

From USGS diatom locality 7297. 

13-19. Rhaphoneis praeparilis Andrews, n. sp. (p. 11). 

13. Scanning electron microscope photograph, x 2,400, length 42 ,am. 

Transverse rows of areolae poorly ordered in center of valve. USGS 

diatom locality 7293. 

14. Scanning electron microscope photograph, x 2,400, length 38 ,am. 

USGS diatom locality 7293. 

15. Scanning electron microscope photograph, x 1 ,500, length 55 ,am. 

USGS diatom locality 7293. 

16. USGS diatom cat. no. 4739-14, x 1,000, length 34 ~m. USGS diatom 

locality 7297. 

17. USGS diatom cat. no. 4736-3, x 1 ,000, length 41 ~m. USGS diatom 

locality 7294. 

18. USGS diatom cat. no. 4739-8, x 1 ,000, length 46 ~m. USGS diatom 

locality 7297. 

19. Holotype, USGS diatom cat. no. 4735-7, x 1 ,000, length 50 ~m. USGS 

diatom locality 7293. 

20-23. Rhaphoneis scalaris Ehrenberg (p. 11). 

20. Scanning electron microscope photograph, x 1 ,300, length of fragment 

76 ,am. From USGS diatom locality 7293. 

21. USGS diatom cat. no. 4742-4, x 1 ,000, length of fragment about 80 ,am. 

From USGS diatom locality 7300. 

22. USGS diatom cat. no. 4740-13, x 1 ,000, length of fragment 78 ~m. From 

USGS diatom locality 7298. 

23. USGS diatom cat. no. 4741-7, x 1 ,000, length of fragment 76 ~m. From 

USGS diatom locality 7298. 
U.S. GEOLOGICAL SURVEY BULLETIN 1769-PLATE 2 

2 

13 15 

22 23 

RHAPHONEIS 
PLATE 3 

Figure 1-5. Sceptroneis caduceus Ehrenberg (p. 11). 

1. USGS diatom cat. no. 4741-2, X 1 ,000, length of head-pole fragment 109 

p.m. From USGS diatom locality 7299. 

2. USGS diatom cat. no. 4735-10, x 1,000, length of head-pole fragment 

105 ,um. From USGS diatom locality 7293. 

3. USGS diatom cat. no. 474Q-8, X 1 ,000, length of head-pole fragment 63 

p.m. From USGS diatom locality 7298. 

4. Scanning electron microscope photograph, x 1 ,700, length of foot-pole 

fragment 67 ,um. From USGS diatom locality 7297. 

5. Scanning electron microscope photograph, x 1 ,500, length of foot-pole 

fragment 46 ,um. From USGS diatom locality 7297. 

6, 7. Sceptroneis grandis Abbott ( p. 12). 

6. USGS diatom cat. no. 4734-13, x 1 ,000, length 120 ~tm. From USGS 

diatom locality 7292. 

7. USGS diatom cat. no. 4733-3, x 1 ,000, length 114 ,um. From USGS 

diatom locality 7291. 

8. Sceptroneis hungarica (Pantocsek) Andrews (p. 12). USGS diatom cat. no. 

4733-16, x 1 ,000, length of fragment 45 ,um. From USGS diatom locality 

7291. 

9. Rhaphoneis scalaris Ehrenberg (p. 11). Scanning electron microscope 

photograph, inside of valve, x 2,500, length of fragment 39 ~tm. From USGS 

diatom locality 7297. 

10. Rhaphoneis margaritata Andrews (p. 10). Scanning electron microscope 

photograph, inside of end of valve, X 13,000. From USGS diatom locality 

7293. 

11. Delphineis ovata Andrews (p. 1 0). Scanning electron microscope photograph, inside of end of valve, x 15,000. From USGS diatom locality 7293. 

12. Rhaphoneis praeparilis Andrews, n. sp. (p. 11). Scanning electron microscope photograph, inside of end of valve, X 15,000. From USGS diatom 

locality 7293. 
U.S. GEOLOGICAL SURVEY BULLETIN 1769-PLATE 3 

8 

2 

4 

7 

SCEPTRONEIS, RHAPHONEIS, AND DELPHINEIS 




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