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United States. Department of the inteiior. ( U. S. geological survey).

Department of the interior | — | Monograplis | of the I United
States geological survey | Volume XV-text [plates] | [Seal of the
department] |

Washington | government printing office | 1889

Second title : United States geological survey | J. W. Powell,
director | — | The Potomac | or | Younger Mesozoic flora | by |
William Morris Fontaine | [Vignette] |

Washington | government printing office | 1889

4°. 2 V. text xiv, 377 pp ; plates x pp. 180 pi.

Fontaine (William Morris).

United States geological survey | J. W. Powell, director | — |
The Potomac | or | Younger Mesozoic flora | by | William Morris
Fontaine | [Vignette] |

Washington | government printing office | 1889

4°. 2 V. text xiv, 377 pp ; plates x pp. 180 pi.

[United States. Department of tlxe interior. {XT. S. geological survey).
Monograph XVj.

United States geological survey | J. W. Powell, director | — |
The Potomac | or | Younger Mesozoic flora | by | William Morris
Fontaine | [Vignette] |

Washington | government i)rinting office | 1889

4°. 2 V. text xiv, 377 pp; plates x pp. 180 pi.

[United States. Department of the interior. {Tf. S. geoloqical survey).
Moiiograpli XV].

Digitized by the Internet Archive

in 2009 with funding from

Boston Library Consortium IVIember Libraries

http://www.archive.org/details/potomacoryoungerOOfont

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[Monograph XV.]

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51. On Invertebrate Fossils from the Pacific Coast, by Charles Abiathar White. 1889. 8°. 102
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.52. Subaerial Decay of Rocks and Origin of the Red Color of Certain Formations, by Israel Cook
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IV ADVERTISEMENT.

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54. A Report on the Thevnio-Eleotrical Measurement of High Temperatures, by Carl Barus.

55. Report of work done in the Division of Ctiemistry and Plivsics, mainly durina' the fiscal vear
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.56. Fossil Woods and Lignites of the Potomac Formation, by F. H. Kuowlton.

57. Notes on the Geology of Southwestern Kansas, by Robert Hay.

58. On the Glac.al Bonndary, by G. F. Wright.

lu preparation :

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— Mineralogy of tbe Pacific Coast, by W. H. Melville and Waldemar Lindgren.

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— Altitudes between Lake Superior and the Rocky Mountains, by Warren Uphaiu.

— Mesozoic Fossils in the Permian of Texas, by C. A. White.

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— A Late Volcanic Eruption in Northern California and its peculiar lava, by J. S. Diller

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Mineral Resources of the United States [1882], by Albert Williams, jr. 1883. 8°. xvii, 813 pp.
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Mineral Resources of the United States, 1883 and 1884, by Albert Williams, jr. 1885. 8°. xi\',
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Mineral Resources of the United States, 1885. Division of Miuiug Statistics and Technoloo-v
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Mineral Resources of the United States, 1887, by David T. Day. 1888. 8°. vii, 832 pp. Price
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In preparation :

Mineral Resources of the United States, 1888, by David T. Day.

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To TjiE Director of the

United States Geological Survey,

Washington, D. C.
Washington, D. C, Septemher 1, 1889.

DEPARTMENT OF THE INTERIOR

MONOGRAPHS

United States Geological Survey

VOLUME XV-TEXT

WASHINGTON

GOTERNMENT PRINTING OFFICE

1889

UNITED STATES GEOLOGICAL SURVEY

J. W. POWELL, DIRECTOR

THE POTOMAC

TOUNGEE ME80Z0I0 FLOEA

BY

WILLIAM MORRIS FONTAINE

1

li'#

WASHINGTON

GOVERNMENT PRINTING OFFICE

1SS9

CONTENTS

Page.

LETTKR of transmittal XIII

Intkoduction 1

Plant localities 10

Location and geology of the Potomac beds 33

Location of the Potomac beds 33

Geology of the Potomac beds 47

Geological position and origin of the lower Potomac beds - 58

Description oif the species 63

Cryptogams 63

Eqnisetese 63

Filices 66

Phanerogams 166

GymnospermfB 166

Zamiese 166

Coniferas 193

Gyninospermous fruits , 262

Undetermined plants "274

Angiospermae 277

General remarks and conclnsious 320

List of Potomac plants 326

Geological affinities of the Potomac plants 333

Eqniseta 334

Ferns ' 330

Cy cads 34 1

Conifers 343

Angiosperms 346

Tables 349

Index 373

[The plates are bound in a separate volume.]

LLUSTRATIONS,

XII.
XIII.

XIV.
XV.

3. 1-6, 8. Equisetum VirgiDicum.
.7. Equisetum LyeUi.
8. 1-3, 6, 7, 9. Equisetum Virginicum.
gs. 4, 5. Equisetum Lyelli.
g. 8. Rhizome of Equisetum, sp. uiidet.
g. 10. Equisetum Marj'landicum.
g. 11. Cladophlebis constricta.
g. 1. Cladophlebis latifulia.
g. 2. Cladophlebis constricta,
gs. 3-8. Cladophlebis Virginieusls.
gs. 1, 3-6. Cladophlebis Yirginiensis.
g. 2. Cladophlebis deiiticulata.
g. 7. Cladophlebis parva.
g. 8. Cladophlebis falcata.
gs. 1-6. Cladopblebis falcata.

7. Cladopblebis acuta,
gs. 1-3. Cladophlebis parva.

;. 4. Cladophlebis latifolia.

:s. 5, 6, 8-14. Cladopblebis coustricta.

.7. Cladophlebis falcata.

;s. 1, 2. Cladophlebis falcata.
gs. 3-5. Cladophlebis oblongifolia.
,g. 6. Cladophlebis acuta.
g. 7. Cladophlebis denticulata.
gs. 8-11. Angiopteridium auriculatum.

;3. 1-7. Pecopteri.s Virginieusis.

8. 1-6. Pecopteris Viiginiensis.
gs. 7-9 Cladophlebi.s creuata.
gs. 1, 2. Cladophlebis creuata.
gs. 3, 4. Cladophlebis inclinata.
gs. 5, 8. Cladophlebis, sp. uudet.
gs. 6, 7. Cladopblebis acuta.
g.9. Aspleulum dubium.
gs, 1-6. Aspidium Frederickshurgense.
gs. 7, 8. Cladopblebis acuta.
gs. 1-6. Aspidium Frederickshurgense.

1-3. Cladophicbis crenata.
gs. 4, 5. Cladophlebis distans.
gs. 6-8. Pecopteris strictinervis.
gs. 9, 10. .Aspidium ellipticum.
gs. 1-5. Aspidium beterophyllum.
gs. 1-5. Aspidium heterophyllura.
ig. 6. Cladophleois, sp. undet.
g. 7. Aspidium Virginicum.
g. 8. Pecopteris ovatodentata.
gs. 1, 3, 8. Aspidium angustipinnatum.
g. 2. Aspidium cystopteroides.
gs. 4, 5. Polypodium fadyenioides.
g. 6. Aspleniopteris adiantifolia.
g. 7. Acrostichum crassifolium.
g. 9. Aspidium. Frederickshurgense.

XVTII.
XIX. F;

Plate XVII. Fig. 1. Aspidium angustipinnatum.
Aspidium niacrocarpum.
gs. 3-7. Thinnfeldia variabilis.
;. 1-6. Thinnfeldia variabilis.

1. Cladopblebis crenata.

2. Cladophlebis. sp. unrtct.
g. 3. Cladophlebis, sp. undet.
g.4. Aspidium Oerstedi?.
ig. 5. Cladophlebis alata.
gs. 6, 7. Aspidium Fredericksburgensi
;g. 8. Pecopteris microdonta.
g. 9. Pecopteris strictinervis.
g. 10. Aspidium augustipinuatum.
gs. 1,2, 4. Pecopteris constricta.
g. 3. Pecopteris strictinervis.
ga. 5, 11. Pecopteris microdonta.
g. 6. Cladophlebis crenata.
g. 7. Cladophlebis, sp. undet.
g. 8. Cladophlebis inclinata.
gs. 9, 10. Cladophlebis rotuudata.
gs. 1-3. Pecopteris brevipennis.
g.4. Cladopblebis sphenopteroides.
g. .5. Aspidium ohlongifolium.
g. 6. Aspidium parvifolium.
g. 7. Pecopteris socialis.
g. 8. Stenopteris Virginica.
gs. 9, 13. Cladophlebis constricta,
g. 10. Pecopteris anguatipennis.

.11. Gleicbenia Nordenskioldi.
g. 12. Undetermined fern.
g.l4. Aspidium Virginicum.
g. 15. Aspidium pinnatifidura.
gs. 1-3, 6, 7. Aspleniopteris pinnatifida
gs. 4, 5. Polypodium dentalum.
g. 8. Cladophlebis petiolata.
g. 9. Aspidium Dunkeri.
gs. 10, 11. Pecopteris Browuiana.
g. 12. Pecopteris ovatodentata.
g. 13. Pecopteris strictinervis.
g. 1. Pecopteris ovatodentata.
gs. 2-7. Pecopteris Browniana.
g. 1. Thyrsopteris Virginica.
g. 2. Pecopteris Virginiensis.
g. 3. Thyrsopteris elliptica.
gs. 4, 6, 7, 9. Thyrsopteris deutata.
gs. 5, 10. Thyrsopteris brevifolia.
g. 8. As]iidium parvifolium.
gs. 1,2. Thyrsopteris dentafa.
g. 3. Sphenopteris thyrsopteroides.
gs. 4, 5, IG. Thyrsopteris nervosa.
6,7.14,15. Aspidium dentatum.
VII

VIII

ILLUSTEATIONS.

xxxn.

SXXIII.

xxsv.

XXXVI.

[g. 8. Cladoplilebis ina^quiloba.

9. Cladoplilebis pacbypbylla.

10. Asindium parvifolium.
i. 11, 12. Aspidium Duukeri.

13. Osmunda spiieuopteroides.
igs. 1, 14, 16, 17. Aspidium parvifolium.
igs. 2, 8, 9, 18. Aspidium Duukeri.
igs. 3, 13. Pecopteris Browniana.
igs. 4, 5. Pecopteris pacbypbylla.
igs. 6, 7. Thyrsopteris rarinervis.

;8. 10-12. Tbinnfeldia granulata.
Ig. 15. Cladopblebis, sp. undet.
igs. 1-5, 8. Tbinnfeldia granulata.
}. 6, 7. Tbinnfeldia rotundiloba.
10. Sagenopteris latifolia.
igs. 9, 11-17. Sagenopteris elliptica.

;. 1. Angiopteridium auriculatum.

;s. 2, 4, 6. Scleropteris elliptica.

;s. 3, 5. Scleropteris Yirginica.

:. 7. Scleropteris elliptica, var. longifolia,
ig. 1. Scleropteris elliptica.

r. 2. Angiopteridium nervosum.

;. 3. Angiopteridium ellipticum.

ig. 4. Angiopteridium densinervc.

Fig. 5. Angiopteridium pacbypbyllam.

igs. 6, 7. Angiopteridium ovatum.

[3. 8, 9. Angiopteridium strictinerve.

;s. 1, 5. Angiopteridium strictinerve, var.
latlfolium.

'igs. 2, 3. Anomozamites angustifolius.
ig. 4. Anomozamites Virgiuicus.

js. 6, 7. Angiopteridium dentatum.

;. 8. Platypterigium densinerve.

js. 1, 4. Platypterigium densinerve.

;. 2. Platypterigium Rogersianura.

;. 3. Anomozamites Virgiuicus.

13. 1, 2. Platypterigium densinerve.

;. 1. Platypterigium densiaerve.

5.2. Platypterigium Kogerslanura.

J. 1. Platypterigium densinerve.

!;. 2. Platypterigium Ivogersianura.
ig. 3. Tbyrsopteris brevipennis.

5. 4. Spbenopteris acrodentata.

■js. 1, 2. Platypterigium densinerve,

js. 3-5, Spbenopteris latiloba.

;, 1. Cladopblebis brevipennis.

;. 2, Tbyrsopteris brevipennis.

;. 3. Tbyrsopteris alata.
igs. 4-9. Spbenopteris latiloba.
ig. 1. Spbenopteris latiloba.
igs. 2, 4. Tbyrsopteris nervosa,
igs. 3, 9. Tbyrsopteris brevipennis.
igs. 5-8. Thyrsopteris divaricata.

J. 1. Tbyrsopteris brevipennis.

;3. 2-4, 8. Tbyrsopteris Meekiana.

53. 5-7, 9. Tbyrsopteris Meekiana, var. an-

gustiloba.

;s. 1, 2. Tbyrsopteris crenata.

;. 3. Tbyrsopteris densifolia.
ig. 4. Tbyrsopteris insignis.
5. Tbyrsopteris nervosa.

Ig. 1. Thyrsopteris insignis.

;3, 2-5. Tbyrsopteris densifolia.

;. 6. Tbyrsopteris nervosa.

;s. 1-3. Tbyrsopteris crassinervis.
ig. 4. Thyrsopteris brevipennis.

;. 5. Osmunda Bicksonioides.

Plate XLT. Fig. 6. Thyrsopteris insignis.

XLII. Figs. 1,2,4. Thyrsopteris insignis

Fig. 3. Tbyrsopteris insignis, vai

nis.

XLIII. Figs. 1, 3. Tbyrsopteris insignis.

Fig. 2. Thyrsopteris insignis, vai

stipe

Figs. 4-6. Thyrsopteris rariuervis.
Fig. 7. Tbyrsopteris decurrens.
Fig. 8. Thyrsopteris Meekiana. var. auguati-
loba.
XLIV. Figs, 1,2, 5. Thyrsopteris rarinervis.

Fig. 3. Tbyrsopteris Meekiana, var. angusli-

loba.
Fig. 4. Thyrsopteris angustifolia.
XLY. Figs. 1,2,4, 5. Tbyrsopteris microphylla.
Fig. 3, Thyrsopteris angustifolia.
XLVI. Fig. 1. Thyrsopteris elliptica.

Figs, 2, 4. Tbyrsopteris decurrens.
Figs, 3, 5. Tbyrsopteris pacbyracbis.
XLVll. Figs. 1,2. Thyrsopteris pachyracbis.
Fig. 3. Tbyrsopteris distans.
Fig. 4. Thyrsopteris Meekiana, var. augusti-
loba.
CLYIIT. Fig. 1. Thyrsopteris Meekiana, var. augnsti-
loba.
Fig. 2. Thyrsopteris angustifolia.
Figs. 3-5. Thyrsopteris angustiloba.
XLTX. Fig. 1. Tbyrsopteris pacbyracbi.s.
Fig. 2. Thyrsopteris rarinervis.
Figs. 3, 4. Tbyrsopteris angustifolia.
Figs. 5-7. Thyrsopteris decurrens.
L. Figs. 1, 2. Spbenopteris Mantelli.
Fig. 3. Tbyrsopteris pacbypbylla.
Fig. 4. Spbenoptei'is spatulata.
Fig. 5. Spbenopteris pacbypbylla.
Figs. 6, 9. Tbyrsopteris elliptica.
Figs. 7, 8. Tbyrsopteris Meekiana.
LI. Fig. 1. Thyrsopteris pecopteroides.
Fig. 2. Tbyrsopteris pinnatifida.
Fig. 3. Tbyrsopteris Meekiana.
Fig3.4, G, 7. Thyrsopteris elliptica.
Fig. 5. Tbyrsopteris densifolia.
LII. Fig. 1. Tbyrsopteris heteromorpba.
Figs. 2-4. Thyrsopteris varians.
Fig. 5. Thyrsopteris rhombifolia.
LIII. Figa. 1-3. Tbyrsopteris varians.
Fig. 4. Thyrsopteris heteroloba.
Fig. 5. Thyrsopteris bella.
LIV. Fig. 1. Tbyrsopteris rhombifolia.

Figs. 2, 11. Tbyrsopteris Meekiana, var. an-
gustiloba.
Figs. 3, 9. Aspidium Duukeri.
Figs. 4, -5, 7. Thyrsopteris pinnatifida.
Fig. C. Thyrsopteris elliptica.
F.g. 8. Thyrsopteris distans.
Fig. 10. Tbyrsopteris varians.
LV. Fig. 1. Thyrsopteris Meekiana, var. angusti-
loba.
Fig. 2. Tbyrsopteris angustifolia.
Fig, 3. Tbyrsopteris angustiloba.
Fig. 4. Thyrsopteris elliptica.
Fig. 5. Thyrsopteris microloba, var. alata.
Figs. C, 7. Tbyrsopteris bella .
LVI. Figs. 1, 3. Thyrsopteris Meekiana, var. an-
gustiloba.
Figs. 2. 5. Thyrsopteris bella.

ILLUSTEATIONS.

IX

Plate LVI. Figs. 4, 8. Thyrsopteris nana.

Fif^s. 6, 7. Thyrsopteris elliptica.
LVII. Figs. 3, 5. Thyrsopteris bolla.
Fig. 2. Thyrsopteris varians.
Figs. 3, 8. Thyrsopteris inaequiplnnata.
Fig. 4. Thyrsopteris microloha.
Fig. 6. Thyrsopteris elliptica.
Fig. 7. Thyrsopteris pinuatifida.
LVIII. Fig. 1. Thyrsopteris microloha. var. alata.
Fig. 2. Thyrsopteris elliptica.
Fig. 3. Thyrsopteris heterophylla.
Fig. 4. Thyrsopteris bella.
Fig. 5. Sphenopteris thyisopteroides.
Fig. G. Thyrsopteris sphenopteroides.
Figs. 7, 10. Thyrsopteris obtusiloba.
Fig. 8. Thyrsopteris angustifolia.
Fig. 9. Osmunda Dicksouioldes.
LIX. Figs, 1,4, 8.9, 1 1. Osmunda Diclcsonioides.
Figs, 2, 12. Aspidium microcarpura.
Fig. 3, Thyrsopteris squarrosa.
Fig. 5. Fern frond in cii cinate vernation,
Figs. G, 7, Thyrsopteris rhonibiloba.
Fig. 10. Thyrsopteris retusa,
LX. Figs. 1,3. OsmundaDiclisonioides, var.latipen-

Figs. 2, 4, 5, 9. Osmunda Dicksonioides,

Figs. 6, 7, Aspidium raicrocarpum.

Fig. 8, Thyrsopteris rhombiloba,
LXL Figs. 1,2, Osraunda Dicksouioides,

Fig, 3. Osmunda Dicksonioides, var. latipennis.

Figs. 4, .5. Ctenopteris insignis.

Fig. 6, Undetermined plant.

Fig, 7. Zamiopsis pinnatifida.

Fig. 8. Zamiopsis lougipennis.
LXn, Fig. 1. Ctenopteris insignis.

Fig. 2. Ctenopteris integrifolia.

Fig. 3. Zamiopsis insignis.

Fig. 4. Ctenopteris "Virginiensis.

Fig. 5. Zamiopsis pinnatifida.
LXIII, Figs. 1,2, Ctenopteris insignis.

Figs. 3, 4. Scleropteris dentata,
LXIY. Figs. 1,3. Zamiopsis insignis.

Fig. 2. Zamiopsis pinuatifida.
L5V. Fig. 1. Ctenopteris Virginiensis,

Fig, 2. Ctenopteris angustifolia.

Fig. 3. Ctenopteris integrifolia.

Figs. 4-6. Zamiopsis insignis.
LXVI. Figs, 1, 5-8. Zamiopsis laciniata.

Fig. 2. Zamiopsis insignis.

Fig. 3. Zamiopsis petiolata.

Fig. 4. C enopteris Virginiensis.
LXVII. Fig. 1, Zamites tenuinorvis.

Fig. 2. Zamiopsis pinnatifida.

Fig. 3, Ctenopteris minor.

Fig, 4. Ctenopteris angustifolia.

Fig. 5, Ctenopteris longifolia.

Fig. 6. Bioouites Bnchianus, var, angixstifolius.

Fig. 7. Zamiopsis insignis.
LXYTII. Fig,l. Dioonites Bnchianus,

Figs. 2, 3, Ctenophyllum latifolinm.

Fig, 4. Dioonites Bnchianus, var. angustifoliiis.

Fig. 5. Glossozamites distans.

Fig, 6, Podozamites subfalcatus.
LXIX. Figs. 1,3. Dioonites Bnchianus.

Fig. 2, Zamites tenuinervis.
LXIX. Fig. 4. Zamites crassinervig.

Plate LXX. Fig. 1, Zamites tenuinervis.

Figs, 2, 3, Dioonites Buchianus.
Fig. 4. Encephalartopsis nervosa.
LXXI. Fig. 1. Dioonites Buchianus.

Fig. 2, Dioonites Buchianus, var, angustifo-

lius.
Figs, 3, 4. Encephalartopsis nervosa.
LXXH. Figs. 1,2. Dioonites Bnchianus.

Figs. 3, 4. Encephalartopsis nervosa,
LXXirr. Figs. 1-3. Dioonites Buchianus.
LXXIV. Figs. 1-3. Dioonites Buchianus.
LXXy. Fig. 1. Nageiopsis longifolia.
Fig. 2. Nageiopsis rccurvata.
Fig. 3. Zamites tenuinervis,
LXXVI. Fig. 1. Podozamites pedicellatus.
Figs, 2-6, Nageiop.sis longifolia.
Fig. 7. Zamites tenuinervis.
LSXVir, Figs. 1,2, Kageiopsis longifolia.
Fig, 3. Nageiopsis decrescens.
Fig, 4. Nageiopsis ovata.
LXXVIII. Fig?. 1-5. Nageiopsis longifolia.
Fig. 6, Zamites tenuinervis.
Fig, 7. Podozamites pedicellatua.
LXXIX. Figs. 1, 3. Nageiopsis zamioides.
Figs, 2, 6, Nageiopsis crassicaulis.
Fig. 4, Nageiopsis recurvata.
Fig. 5, Podozamites distantinervis.
Fig, 7, Nageiopsis longifolia.
LXXX, Figs. 1, 2, 4. Nageiopsis zamioides.
Fig, 3. Nageiopsis recurvata.
Fig. 5. Nageiopsis ovata.
Fig, 6. Podozamites acutifolius,
LXXXI. Figs, 1-G. Nageiopsis zamioides,
LXXXII. Fig, 1. Nageioi)sis crassicaulis.

Fig. 2, Podozamites grandifolius.
Fig, 3. Nageiopsis latifolia.
Fig. 4. Podozamites distantinervis.
Fig. 5. Podozamites pedicellatus.
LXXXin. Figs. 1, 2, 6, 7. Podozamites distantinervis.
Fig, 3. Zamites crassinervis.
Fig. 4. Zamites distantinervis.
Fig, 5. Podozamites grandifolius.
LXXXTV. Figa, 1, 2. 8, 10,14.15. Podozamites distanti-
nervis.
Figs. 3, 9, 11. Nageiopsis crassicaulis.
Fig. 4. Nageiopsis heterophylla.
Fig. 5. Phyllocladopsis heterophylla.
Fig. C. Nageiopsis microphylla.
Fig. 7, Zamites tenuinervis.
Fig. 12. Zamites ? sp, nndet.
Fig. 13, Zamites suhfalcatus.
LXXXY, Figs, 1, 2, 8, 9, Nageiopsis longifolia.
Fig, 3, Zamites suhfalcatus.
Fig, 4, Zamites ovalis.
Fig. 5. Feildeniopsis crassinervis.
Fig, 6. Nageiopsis in^quilateralis.
Fig, 7, Nageiopsis obtnsifolia.
Figs, 10, 15. Podozamites acutifolius.
Fig, 11, Nageiopsis acuminata.
Figs. 12, 16, Podozamites distantinervis.
Fig. 13. Araucaria obtnsifolia.
Fig. 14. Nageiopsis microphylla,
LXXXYI. Figs. 1-3,5. Nageiopsis microphjila.
Fig. 4. Araucaria podocarpoides.
Figs, 6, 7. Nageiopsis heterophylla,
Figa. 8, 9. Nageiopsis angustifolia.

ILLUSTRATIONS.

Plate LXXXVII. Fi^. 1. Podozamites aoutifolius.

Figa. 2-6. Kageiopsis augustifolia.
LXXXYIII. Figs. 1, 3, 4, 6-8. Nageiopsis an guati folia.
Figs. 2, 5. Nageiopsis heteroph.ylla.
LXXXIX. Figs. 1,3. Baieropsis expansa.
Fig. 2. Nageiopsis angnstifolia.
Fig 4. Baieropsis plnripartita.
XC. Fig. 1. Baieropsis expansa.

Figs. 2-5. Baieropsis plnripartita.
Fig. 6. Baieropsis macropbylla.
XCI. Figs. 1,3,4,7. Baieropsis pluripartita.
Fig. 2. Baieropsis expansa.
Fig. 5. Baieropsis pluripartita, var. rai-

nor.
Fig. 6. Baieropsis longifolia.
XCII. Figp. 1, 2, 6. Baieropsis pluripartita.

Figs. 3, 4. Baieropsis pluripartita, var.

minor.
Fig. 5. Baieropsis expansa
Fig. 7. Baieropsis denticulata. var. an-
gnstifolia.
Figs. 8,9. Baieropsis atlianti folia.
XCIII. Figs. 1-3. Baieropsis adiantifolia.
Figs. 4-6. Baieropsis foliosa.
Fig. 7. Baieropsis denticulata.
XCIV. Fig. 1. Baieropsis adiantifolia, var. mi-
nor.
Figs. 2, 3. Baieropsis adiantifolia.
Fig. 4. Acrostichopteris densifolia.
Figs. 5, 9, 10, 12. Acrosticliopteris par-

vifolia.
Figs. G, 7, 11, 14. Acrostichopteris parcc-

lobata.
Fig. 8. Acrosticliopteris cyclopteroides.
Fig. 13. Baiera multifolia.
XCV. Figs. 1-5. Freuelopsis ramosissima.
XCVI. Figs. 1-3. Frenelopsis ramosissima.
XCVir. Figs. 1-6. Frenelopsis ramosissima.
XCVIII. Figs. 1-G. Freuelopsis ramosissima.
XCtX. Figs. 1-4. Frenelopsis ramosissima.
G. Figs. 1-3. Frenelopsis ramosissima.
Fig. 4. Brachyphyllum crassicaule.
CI. Fig. 1. Frenelopsis ramosissima.
Figs. 2, 3. Leptostrobus longifolius.
Fig. 4. Leptostrobus foliosus.
CII. Figs. 1-4. Leptostrobus longifolius.
Figs. 5, 6. Laricopsis brevifolia.
Figs. 7,8. Laricopsis longifolia.
Figs. 9,10. Laricopsis augustifolia.
cm. Figs. 1,4. Laricopsis angnstifolia.
Figs. 2, 3, Laricopsis longifolia.
Fig. 5. Leptostrobus foliosus.
Figs. 6-12. Leptostrobus longifolius.
CIV. Fig. 1. Leptostrobus foliosus.

Figs. 2, 3. Cepbalotaxopsis ramosus.
Figs. 4, 5. Cepbalotaxopsis magnifolia.
Fig. G. Leptostrobus longifolius.
CV. Figs. 1,2, 4. Cepbalotaxopsis magnifolia.

Fig. 3. Cepbalotaxopsis brevifolia.

CVI. Figs. 1,3. Cepbalotaxopsis magnifolia.

Figs. 2, 4. Cepbalotaxopsis ramosa.

Fig. 5. Cepbalotaxopsis brevifolia.

CVIT. Figs. 1,2, 4. Cepbalotaxopsis magnifolia.

Fig. 3. Cepbalotaxopsis ramosa.

Fig. 5. Cepbalotaxopsis brevifolia.

CVm. Figs. 1,3, 4. Cepbalotaxopsis magnifolia,

Fig. 2. Cepbalotaxopsis ramosa.

Plate CVIII. Fig. 5, Cepbalotaxopsis micropbylla.
CIX. Figs. 1-7. Bracbypbyllum crassicaule.
Fig. 8. Torroya Virgiuica.
Fig. 9. Cepbalotaxopsis micropbylla.
ex. Figs. 1-3. Bracbypbyllum ciassicaule.
Fig. 4. Bracbypbyllum parceramosum.
CXI. Figs. 1-5. Freuelopsis parceramosa.

Figs. 6, 7. Bracbypbyllum crassicaule.
CXII. Figs. 1-5. Frenelopsis parceramosa.

Figs. G-8. Bracbypbyllum crassicaule.
Figs. 9-11. Sequoia cycadopsis.
C5III. Figs. 1-3. Sequoia cycadopsis.
Fig. 4. Torreya i'alcata.
Figs. 5, 6. Atbrotaxopsis expansa.
CXIV. Figs. 1-3. Atbrotaxopsis grandis.

Figs. 4, 5. Atbrotaxopsis tenuicaulis.
CXV. Figs. 1, 3. Atbrotaxopsis pacbypbylla.
Fig. 2. Atbrotaxopsis expansa.
Fig. 4. Atbrotaxopsis tenuicaulis.
CXVI. Figs. 1-4. Atbrotaxopsis grandis.
Fig. 5. Atbrotaxopsis expansa.
Fig. 6. Atbrotaxopsis tenuicaulis.
Ffg 7. Sequoia, sp. undet.
CXVII. Figs. 1.3-5. Atbrotaxopsis pacbypbylla.
Fig. 2. Atbrotaxopsis tenuicaulis.
Fig. 6. Atbrotaxopsis expansa.
Fig. 7. Sequoia aubulata.
Fig. 8. Sequoia Keicbenbacbi, var. longifolia.
CXVIII. Figs. 1,4. Sequoia Keicbenbacbi.
Fig. 2. Sequoia ambigua.
Fig. 3. Sequoia rigida.
Figs. 5, 6. Sequoia subulata.
Fig. 7. SpbenolepidiumSternbergianum, var.
densifolium.
CXIX. Figs. 1-5. Sequoia Keicbenbacbi.
CXX. Figs. 1-6. Sequoia ambigua.

Figs. 7, 8. Sequoia Keicbenbacbi.
Fig. 9. Sequoia, sp. undet.
CXXI. Fig. 1. Araucaria zamioides.
Fig. 2. Sequoia rigida.
Fig. 3. Sequoia delicatula.
Fig. 4. Sequoia densifolia.
Figs. 5, 7, 9. Spbenolepidium Sterubergiannm,

var. densifolium.
Fig. C. Taxodium (Glyptostrobus) Virgini-

cum.
Figs. 8, 10, 11. Spbenolepidium Sternberg-
ianam .
CXXII. Fig. 1. Taxodium (Glyptostrobus) Brookense.

Fig. 2. Sequoia Keicbenbacbi.
CXXIII. Fig. 1. Taxodium (Glyptostrobus) expansum.
Figa. 2, 3. Taxodium (Glyptostrobus) ramo-

CXXIV. Fig. 1. Taxodium (Glyptostrobus) denticula-
tum.
Fig. 2. Taxodium (Glyptostrobus) ramosum.
Figs. 3-9. Taxodium (Glyptostrobus) Brook-
ense.
CSXV". Figs. 1,3. Taxodium (Glyptostrobus) fastigi
atum.
Fig. 2. Spbenolepidium Sternbergiauum, var,

densifolium.
Fig. 4. Spbenolepidium Yirginicum.
CXXVI. Figs. 1, 5, 6. Spbenolepidium Kunianum,
Fig. 2. Sequoia rigida.
Figs. 3, 4. Sequoia gracilis.
CXXVTI. Fig. 1. Taxodium (Glyptostrobus) lamosum.

ILLUSTKATIONS.

XI

recurvifoliuin.

m dentifolium.
arc e ram 0 sum.
Sternbergianuni.
Kurrianum.
a SternbergJanuiD,

Plate CXXVII. Fig. 2. SpheBolepidium recurvifolium.
Figs. 3, -t. Sphcnolepidium dentifolium.
Fig. 5. Sequoia ambigua.
CXXVin. Figs. 1, 7. Spiierolepidinm Kurrianum.
Figs. 2-6. Spbenolepidium dentifolium.
CXXIX. Figs. 1, 2, 4, 6, 8. Spbenolepidium Kurri-
anum.
Fig. 3. Spbenolepidium Sternbergianuni,

Tar. densifolium.
Fig. 5. Spbenolepidium dentifolium.
Fig. 7. Spbenolepidium parceramosum.
CXXX. Fig. 1. Spbeuolepidium Sternbergianum,

Tar. densifolium.
Figs. 2, 7. Sphenolepidiur
Fig. 3. Sequoia rigida.
Figs. 4^6, 10. Spbeuolepidi
Fig. 8. Spbenolepidiun:
Fig. 9. Spheuolepidiui
Fig. 11. Spbenolepidiu
CXXXI. Figs. 1,3. Spbenolepidi

Tar, densifolium.
Fig. 2. Spbenolepidium parceramosum.
Fig. 4. Spbenolepidium Kurrianum.
Fig. 5. Tasodium (Glyptostrobus) Brook-

ense.
Figs. 6, 7. Spbenolepidium pacbypbyllum.
CXXXII. Fig. 1. Taxodium (Glyptostrobus) -ramo-

sum.
Figs. 2, 5, 6. Sequoia, sp. undet.
Fig. 3. Sequoia ambigua.
Fig. 4. Spbenolepidium Stembergianum,

Tar. densifolium.
Fig. 7. Abietites macrocarpns.
Figs. 8, 9. Abietites ellipticus.
Fig. 10. Sequoia, sp. undet.
CXXXIII. Fig.l. Abietites augusticarpus.
Figs. 2-4. Abietites ellipticus.
Figs. 5-7. Williamsouia Virginiensia.
Figs. 8-12. Araucarites Aquiensis.
CXXXIV. Fig.l. Carpolitbns fasciculatus.

Figs. 2-4, 6, 8. Carpolitbus ternatns.
Fig. 5. Carpolitbus agglomeratus.
Fig. 7. Araucarites Virgiuiciis.
Fig. 9. Carpoli tbus conjugatus.
Fig. 10. Carpolitbus geminatus.
Figs. 11-14. Carpolitbus Virginiensis.
CXXXV. Figs. 1,5. Carpolitbus Yirgimensis.
Figs. 2, 4, Carpolitbus Erookensis.
Fig. 3. Carpolitbus latus.
Fig. 6. Leptostrobus.sp. undet.
Fig. 7. Anient of conifer.
Fig. 8. Bracbypbyllum, sp. undet.
Fig. 9. Bracbypbyllum, sp. undet.
Fig. 10. Atbrotaxopsis grandis.
Figs. 11.21. Cycadeospermnm spatulatum.
Fig. 12. Cycadeospermum acutura.
Fig. 13. Cycadeospermum obovatum.
Fig. 14. Capsules, sp. undet.
Figs. 15, 18, 22. Atbrotaxopsis espansa.
Fig. 16. Ament of angiosperm .'.
Fig. 17. Carpolitbus curTatus.
Fig. 19. Cycadeospermum ellipticum.
Fig. 20. Cycadeospermum augustum.
CXXXYI. Fig. 1, Macrospores, sp. undet.

Figs. 2-5, 8. Aments of conifers, sp. undet.
Fig. 6. Carpolitbus Erookensis.
Fig. 7. Pollen sacs, sp. undet.

Plate CXIZXVI.

CXXXVII.

cxxxvni.

CXL.
CSLI.

CXLII.
CSLIII.

CXLVIII.
CXLIX.

Fig. 9. Carpolitbus sessUis.

Figs. 10, 11. Leptostrobus, sp. uodet.

Fig. 12. Cycadeospermum rotundatum.

Figs, 13, 14. Undetermined plants.

Fig. 15. Carpolitbus mucronatus.

Figs. 1-5. Undetermined plants.

Fig. 6. Acaci?epbyllum longifulium.

Figs. 1-3. Acacisepbyllum lougifoliura.

Figs. 4, 6-9. Acaciiepbyllum spatulatum-

Fig. 5. Acacijephyllum raicropbyllum.

Figs. 10-12. Ctenis imbricata.

Fig. 13. Sagenopteris Virginiensis.

Fig. 14. Conospermites ellipticus.

Fig. 1. Sagenopteris Virginiensis.

Fig. 2. Protesephyllura, sp. undet.

Fig. 3. Protecepbyllum reniforrae.

Fig. 4. Proteaspbyllum orbiculare.

Fig. 5. Proteaepbyllum oblougifoliura.

Fig. 6. Rogersia longifolia.

Fig. 7. Sassafras parTifolium.

Figs. 1. 2. Proteasphyllum oblongifuliiiiu.

Fig. 3. Ficopbyllum tenuinerve.

Fig. 1. Protea^pbyllum ovatum.

Fig. 2. Ficopbyllum tenuinerve.

Figs. 1, 2. Protesepbyllum ellipticum.

Figs. 1,3. Ficus Virginiensis.

Fig. 2. Kogersia angustifolia.

Fig. 1. Ficus Virginiensis.

Fig. 2. Rogersia longifolia.

Fig. 3. Ficopbyllum crassinerTe.

Figs. 1,4. Ficopbyllum tenuinerTe.

Fig. 2. Ficopbyllum serratum.

Fig. 3. Ficopbyllum crassinerve.

Fig.l. Ficopbyllum crassinerve.

Figs. 2, 4. Salicipbyllum ellipticum.

Fig. 3. Celastropbyllum arcinerTe.

Fig. 5. Celastropbyllum proteoides.

Fig.l. Sapindopsis cordata.

Fig. 2. Ficopbyllum tenuinerTe.

Fig. 3. Sapindopsis elliptica.

Fig. 4. Ficopbyllum crassinerve.

Figs. 1,2, 4. Ficopbyllum crassinerve.

Figs. 3, 5. Ficus Fredericksburgensls.

Figs. 1, 3, 5. Ficopbyllum tenuinerve.

Fig. 2. Pbyllites pacbypliyllus.

Figs. 4, 8. Rogersia angustifolia.

Figs. 6, 7. Quercopbyllum tenuinerve.

Fig. 9. Ficopbyllum serratum.

Fig. 1. Rogersia longifolia.

Figs. 2-7. Rogersia angustifolia.

Fig. 8. Salicipbyllum ellipticum.

Figs. 9, 10. Vitipbyllum (Cissites) crassi-

folium.
Fig. 11. Myrica Erookensis.
Fig. 12. Salicipbyllum longifolium.
Fig. 13. Proteitpbyllum tenuinerve.
Fig.l. Sapindopsis variabilis.
Figs. 2, 3. Sapindopsis magnifolia.
Fig. 4. Bombax Virginiensis.
Figs. 1, 4. Sapindopsis variabilis.
Figs. 2, 3. Sapindopsis magnifolia.
Fig. 5. Sassafras cretaceum, var. beterolo-

bum.
Fig. 1. Sapindopsis tenuinervis.
Fig. 2. Sapindopsis magnifolia.
Fig. 3. Sapindopsis variabilis.
Fig. 4. Sapindop.sis brevifolia.

xir

Plate CLIV.
CLV.

ILLUSTRATIOl^S.

CLTII

CLVIIL

CLIX.

OLX

CLXI.
CLXII.

cLxin,

CLXIV

CLXV

CLXVI

Figs. 1, 5. Sapindopsis magnifoUa.
Figs. 2-4. Sapindopsis variabilis.
Fig. 6. Sapindopsis parvifoUa.
Figs. 1, 7. Sapindopsis brevifolia.
Figs. 2-5. Sapindopsis variabilis.
Fig. 6. Sapindopsis magnifolia.
Fi". 8. ITlmipbyllum Brookense.
Fi". 9. PopulopbvUum reniforme.
Fi". 1. Ficopbyllum tenuinerve.
Fig. 2. Prote.'epbyllum tenuinerve.
Fig. 3. Populopbyllam reniforme.
Fig. 4. Proteasphyllum reniforme.
Fig. 5. Celaatropbyllnm obtusidens.
Fig. 6. MyTac<epljyllnra dentatam.
Fig. 7. Prote-Tepbylliim dentatum.
Fig. 8. Celastrophyllnm acutidens.
Fi<f. 9. Quercophyllum grossedentatum.
Fig. 10. Myrica Brookensis.
Fig. 11. Aralisepbyllum aceroides.
Fig. 12. Sassafras bilobatum.
Fig. 13. Sapindopsis obtasifolia.
Figs. 1, 7. Aralia dubia.
Fie. 2. Sterculia elegans.
Figs. 3, 5, 6. .TuglaudipbyllnmintegrifoUum.
Fig. 4. Fieopbyllnm crassinerve.
Flo-. 1. Ulmipbyllum tenuinerve.
Figs. 2, 3. Sterculia elegans.
Fig. 4. Populophyllnm crassinerve.
Fi". 5. Platanopbyllnm crassinerve.
Figs. 6, 7. TJlmipbyllum crassinerve.
Fig. 8. Celastropliyllum Brookense.
Figs. 1,2. Eogersia lougifolia.
Figs. 3-6. Sapindopsis obtusifolia.
Fig. 7. Celastropbyllnm Brookense.
Fig. 8. Sassafras cretaceum.var. heterolobum
Figs. 9, 10. Aralisepbyllum magnifolium.
Figs. 1,2. Protesepliyllum reniforme.
Figs. 3-6. Aristolocliiaipliyllum crassinerve.
Fio-s. 1, 2. Menispermites Virginiensis.
Fig. 1. Hederffipbyllum angnlatum.
Fig. 2. Ar.alia;pbyllum aceroides.
Fig. 3. Hefli'i;cpbyl!um ti enulatnm.
Fig. 4. Encalyptophylhim ol.loiigifolinm.
Figs. 1,4. Araliaailiylliim obtn.'iilobnm.^
Fig. 2. Araliajpbyllum acutilobum.
Fig. 3. Sapindopsis brevifolia.
Fig. 5. SalicipbjUum ellipticum.
Fig. 6. Hymenasa "Virginiensis.
Fig. 7. ■Dlmiphyllum Brookense.
Fig. 8. Aceripbyllum aralioides.
Figs. 1,2. Ficopbyllum eucalyptoides.
Fig. 3. Aralifepbyllum obtusilobum.
Fig. 4. Sassafras bilobatum.
Fig. 5. Sassafras cretaceum.var. heterolobum.
. Figs. 1-3. Taxodium ((ilyptostrobus) Brook-
ense.
Fig. 4. Laricopsis longifolia.
Fig. 5. "Williamsonia "Virginiensis.
Fig. 6. Leptostrobusmultiflorus.
Fig. 1. Taxodium (Glyptostrobus) ramosum.
Fig. 2. Salicipbyllum ellipticum.
Fig. 3. Populopliyllum bederaiforme.
Figs. 4,7. Taxodium (Glyptostrobus) Brook

Plate CLX"VI. Fig. 5. Cladopblebis acuta.

Fig. 6. Spbeuolopidium Virginicum.
CLXVn. Fig. 1. Taxodium (Glyptostrobus) Brook-
ense, var. angustifolium.
Fig. 2. SphenolepidiumKurrianum.
Fig. 3. Taxodium (Glyptostrobus) Brook-
ense.
Fig. 4. Pbyllodadopsis beteropbylla.
Fig. 6. Sequoia Eeicbenbaohi.
Fig. 6. Carpolitbus Brookensis.
CLX"VIII. Fig. I. Frenelopsis parceramosa.
Fig. 2. Brachypbyllum, sp. nndet.
Fig. 3. Dioonites Bucbianus, var. obtusi-

folius.
Fig. 4. Nageiopsis subfalcaia.
Figs. 5, 6. Laricopsis lougifolia.
Fig. 7. Carpolitbus Virginiensis.
Fig. 8. Abietites ellipticus.
Fig. 9. Bracbypbyllum crassicaule.
GLXIX. Fig. 1. Tbiniifeldia granulata.
Fig. 2. Cladoplilebis constricta.
Fig. 3. Pecopteris Virginiensis.
Figs. 4, 5, 9. Undetermined stems.
Figs. 6, 7. Tbyrsopteris rarinervis.
Fig. 8. Callitris, sp. undet.
Fig. 10. Celastropbyllum denticulatum.
CLXS. Fig. 1. Tbyrsopteris divaricata.
Fig. 2. Podozamites acutifolius.
Fig. 3. Zamites ovalis.
Fig. 4. Pinus, sp. undet.
Figs. 5, 6. Pecopteris strictinervis.
Fig. 7. Acaciiepbyllum variabile.
Fig. 8. Ebizome of Equisetiira, sp. undet.
Fig. 9. Podoz.amites subfalcatus.
Fig. 10. Acrosticbopteris longipennis.
Fig. 11. Acrosticbopteris densifolia.
CLXXI. Figs. 1, 5, 7. Acrosticbopteris longipennis.
Figs. 2. 6. Acrosticbopteris densifolia.
Figs. 3, 4. Acrosticbopteris parvifolia.
CLXXII. Figs. 1,4. Prote!Epbyllum dentatum.
Fig. 2. Celastropbyllum tenuinerve.
Figs. 3, 6. C. lastropbyllum latifolinm.
Fig. 5. S.alicipbyllum parvifolium.
Fig. 7. Celastropbyllum denticulatum.
Fig. 8. Menispermites teuuinervis.
Figs. 9, 10. Celastropbyllum obovatum.
Figs. 11, 12. VitipbylUim (Cissites) parvifo.

lium.
Fig. 13. Acrosticbopteris densifolia.
Fig. 14. Acrosticbopteris parvifolia.
CLXXIII. Figs. 1-9. Vitipbyllum (Cissites) multifl-

dum.
CLXXIII. Fig. 10. Ficopbyllum crassinerve.
Fig. 11. Undetermined plant.
Figs. 12, 14. Proteajpbylluiu dentatum.
Fig. 13. Celastropbyllum latifolium.
CLXXIV. Tysonia Marylandica.
CLXXV. Tysonia Marylandica.
CLXXVI. Tysonia Marylandica.
CLXXVII. Tysonia Marylandica.
CLSXVIII. Tysonia Marylandica.
CLXXIX. Tysonia Marylandica.
CLXXX. Tysonia Marylandica.

LETTER OF TRANSMITTAL

Department of the Interior,

U. S. Geological Survey,
University of Virginia, Virginia, January 10, 1889.

Sir: I transmit with this the manuscript and plates describing and
iUustrating the flora of the Potomac or Younger Mesozoic formation of Vir-
ginia.

Almost all of the material described in this memoir was obtained in the
State of Virginia. A small portion was collected in Maryland, at Baltimore.

The work of collection occupied several yeai's. A large number of
localities, extending over the belt between Baltimore, Md., and Petersburg,
Va., were carefully examined, and all significant specimens were selected
from a very large amount of material. A number of the localities were
visited several times and new collections made.

The extent of ground over which the fossiliferous exposures occur
and the thorough examination made entitle us to believe that the fossils
described in this monograph give a fair idea of the unique and interesting
vegetation existing in Potomac times. This flora is unique, for it appar-
ently contains the oldest known angiosperms, and exhibits them in con-
siderable numbers associated with numerous Jurassic types, a conjunction
not hitherto known.

Accompanying my manuscript is a series of tables, comparing the
Potomac plants with previously described fossil floras. These tables were

XIV LETTER OF TEANSMITTAL.

prepared by Prof. Lester F. Ward for his own use, but he has kindly con-
sented to permit their pubhcation as an appendix to this memoir. Their
preparation involved an immense amount of research and comparison, and
their comprehensiveness and accuracy will add greatly to the value of my
work.

Respectfully submitted,

Wm. M. Fontaine.

Hon. J. W. Powell,

Director U. S. Geological Survey.

THE POTOMAC OR YOUNGER MESOZOIC FLORA.

By W. M. Fontaine.

INTRODUCTION.

The plants described in this memoir, with very few exceptions, were
collected personally by me.

The formation from which the plants were obtained was for a lOng time
and by most writers included in the so-called Trias of the AtLantic slope.
Prof William B. Rogers, however, in his earliest publications on the geol-
ogy of Virginia, recognized the difference between this group of strata and
most of the Mesozoic of that State. In his first publications he called the
beds Upper Secondary, and expressed the opinion that they are of about
the age of the English Purbeck. Later^ he asserts the possibility that they
may form a group of passage beds, comparable to the Wealden. In his
more recent writings he calls the formation Jurasso-Cretaceous.

Mr. W J McGee, of the U. S. Geological Survey, has proposed the name
"Potomac" for the group, and this name will be used by me.

Nearly all the plants described in this work come from the Potomac
formation in Virginia. The few exceptions were found in Maryland, and
these embrace all the plants not collected by myself They will be more
particularly noticed further on.

With the exception of the Maryland fossils, all the plants which form
the subject of this work were not only collected by me, but were packed,

' Geology of the Virgiuias, p. 712.

2 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

shipped, unpacked, and worked out of the rough material with my own
hands. The specimens have in consequence never passed from under
my direct supervision. The phants were collected at intervals, and
repeated visits were paid to the more important localities in order to
secure new material which might throw light on imperfect specimens pre-
viously obtained. This method of collection causes delay and imposes
much additional labor, but it has many advantages.

In the first place, the exact locality and geological horizon of a specimen
can be fixed, a matter of great importance in determining the diffusion of
species, and in the discovery of connecting links between the local floras.
In the Potomac formation, owing to the peculiar facies of .some of these
floras, connecting links are of unusual importance.

A much greater advantage is obtained in the increased number of sig-
nificant parts of plants selected and in the greater opportunity afforded
for the detection of new species.

When the material is collected by the person who will describe it special
attention is paid to the significant portions of fossils. In the case of plant-
fossils, parts with the greatest structural significance are often not as con-
spicuous as those with less meaning. They may also be poorly preserved.
They would be rejected in such cases by a collector unacquainted with the
science they illustrate, especially if the amount of material were large.

The circumstances attending my collection of these plant-fossils were
most favorable for thoroughness of exploration and selection. The search
for these impressions extended over several years. During the summer
material was obtained from different localities, and in autumn and winter
this was worked over, studied, and drawn, the drawings in all cases being
made by myself.

It often happened in this study that a number of fragments unlike
the rest were found which were too imperfect to be made out, and this led
me in several cases to make repeated visits to the same localit}^, in the
hope of obtaining more complete specimens of the undetermined species.
The renewed search often met with success. It will be easily seen that a
collection made under such circumstances has a completeness and value
not otherwise attainable.

INTEODUCTION, 3

The distance apart of the most remote plant localities and the number
of intervening spots affording specimens give reason to think that the fossils
obtained enable us to form a fair notion of the vegetation of that period.
This is especially fortunate, for the hitherto known flora of the oldest
Cretaceous is exceedingly scanty.

One feature of the Potomac flora at once attracts attention. This is
the large number of plants confined to single localities. In many cases
this number is so great as to give the local floras a peculiar facies, which,
were it not for the connecting links, would induce one to believe that they
differ considerably in age. This localization is perhaps chiefly due to differ-
ences in the conditions attending the entombment and preservation of the
plants. At any rate this feature attests the richness of the flora. The
variety within certain limits and the abundance of the vegetation must
have been great.

The distance from Deep Bottom on James River to White House
Bluff on the Potomac is more than 90 miles. If we include the Maryland
localities, 50 miles must be added. The number and location of the inter-
vening stations will appear in the account of them presently to be given.

When fossils have been collected at given localities it may easily happen
that natural or artificial changes so alter the exposures that the spot yielding
the impressions is soon concealed. The Potomac beds, owing to their want
of coherence and the poverty of exposures in them, are especially liable to
have fossiliferous portions hidden. Then, too, plant-impressions occur in
them with exceeding irregularity, at best sparingly, and in very thin layers.
It seems, then, desirable to describe with some minuteness the spots where
plant-fossils were fouiid.

Before beginning these descriptions it is proper to give some account
of what was formerly known of plant-fossils from this formation. The
belief, before referred to, in the Triassic age of tlie strata now in question
was due in part to the apparent absence of all fossils that could throw light
on the subject and call for a separation of the Potomac from the older
Mesozoic. So far as is known to me, only two persons have published any-
thing concerning the occurrence of fossil plants in the Potomac beds of
Virg'inia.

4 THE POTOMAC OE YOUNGER MESOZOIC FLOEA.

Prof. William B. Rogers, in his annual reports on the geology of Vir-
ginia/ made more than forty years ago, mentions the finding of certain
plant-fossils in the vicinity of Fredericksburg. He does not describe any
of them, but considers them as indicating for the Mesozoic strata at that
town an age not far from that of the Purbeck of England.

Mr. R. C. Taylor^ gives an account of "certain fossil dicotyledonous
plants in the secondary strata of Fredericksburg." He speaks briefly of
some of the features of the Potomac formation in the vicinity of that town,
and mentions rather vaguely the location of the plants. He says that at
his request some of the impressions were furnished to the geological society
by Mr. F. Shepherd. These seem to have been few in number and poorly
preserved. Mr. Taylor gives in his article some figures and imperfect de-
scriptions of these fossils. The delineations are so vague that little can be
learned from an inspection of them. No dicotyledons are indicated. Cer-
tain long stems of succulent plants are mentioned as appearing in the form
of hollow casts. These may be the Frenelopsis ramosissima, so abundant at
Fredericksburg. Some coniferous twigs with acicular leaves and some
ferns are figured, but they can not be specifically determined. His figure 3
is without doubt a Sderopteris, different from the one (^S. eUiptica) found by
me, being a smaller form. I have seen none of the plants mentioned by
Professor Rogers and none of those described by Mr. Taylor, and, notwith-
standing persistent search, I have failed to find the locahty mentioned by
the latter gentleman. It seems, from what he says, to be different from the
one which yielded me so many fossils.

The mention by Professor Rogers of the discovery of plant-fossils in
the Fredericksburg beds and the account given by Mr. Taylor seem to
have attracted very little attention.

Mr. F. B. Meek many years ago made a search for fossils in the clays
lying on the line of the Baltimore and Ohio Railroad between Washington
and Baltimore. He succeeded in finding at Baltimore a few well-preserved
impressions, which are mostly those of ferns. These were subsequently
placed in the collections of Columbia College, New York, where they now
are. Dr. J. S. Newberry kindly loaned them to me for description. An

1 A reprint of Annual Reports on the Geology of the Virginias, 1884, pp. 7, 712.
s^ Trans. Geol. Soc. Pennsylvania, vol. 1, 1835, pp. 314-325, PI. XVIII, XIX.

INTRODUCTION. 5

account of them will be given in the proper place, and they will be noted
as belonging to Meek's collection of Baltimore plants. So far as I know
the only mention made hitherto of these fossils is an incidental reference
made by Dr. Newberry in his article on the Chinese Mesozoic plants col-
lected by Pumpelly.^

Mr. P. Tyson, while State geologist of Maryland, obtained in 1859
two cycad trunks. They were found in the above-mentioned clays extend-
ing from Washington to Baltimore. One of them was found near Contee's
Station, a point on the Baltimore and Ohio Railroad two miles southwest of
the town of Laurel, and the other near Beltsville, a station on the same
railroad a few miles nearer Washington. These trunks, now in the Museum
of the Maryland Academy of Sciences at Baltimore, are described in this
memoir. I think no previous description has been published. They were
photographed by Mr. Tyson, and copies of the photographs were furnished
by him to a number of his correspondents. Various writers have made
reference from time to time to these trunks. Mr. Tyson, Professor Rogers,
and Prof. P. R. Uhler, of Baltimore, have i-egarded them as indicating the
Wealden age of the clays which afforded them. Professor Uhler first
found the plant locality at Fredericksburg from which I collected. He
says that when he discovered the spot he collected several boxes of
specimens and sent them to Prof Louis Agassiz, at the Museum of Com-
parative Zoology, Cambridge, Mass. According to Professor Uhler these
impressions were finer than any found since at this place. I can well
believe this, for I have observed in collecting at the Fredericksburg locality
that the plant-impressions became poorer and fewer as the stratum was
followed in from the outcrop. I have not been able to learn what became
of these specimens.

Professor Uhler placed a number of the plants collected here in the Mu-
seum of the Maryland Academy of Sciences, where they were subsequently
seen by me. They were the first that I ever saw coming from the Potomac
formation. Professor Uhler found at Baltimore also a number of plant-
impressions. They came mainly from Federal Hill. Unfortunately both
these and his Fi-edericksburg collections have been lost. Owing to a mis-

1 Smithsonian Contributions to Knowledge, vol. XV, No. 202, 1867, pp. 119-123, PI. IX.

6 THE POTOMAC OE TOUNGEE MESOZOIO FLOEA.

take, in the absence of the professor, all these specimens were sent to the
World's Exposition at New Orleans. Nothing has been heard of them
since. As the material was very fragile, and probably was badly packed,
it was no doubt ground to powder before reaching its destination.

It is much to be regretted that these impressions were lost before they
had been carefully studied and described. My recollection of them is not
very distinct, but it is sufficient to enable me to say that the Baltimore fos-
sils were chiefly rather delicately incised ferns, with a sphenopterid facies, ■
not unlike the most important plants collected by Meek.

The plants'*found by Professor Uhler at Fredericksburg contained cer-
tain portions of some species that I have never been able to find myself. I
especially remember an impression of the summit of a large leaf, which then
seemed to me to be a Macrokeniopteris. From my own discoveries since, I
am now sure that it was the tip of a large Anomosamites. I have never suc-
ceeded in finding a single specimen showing the termination of the leaves of
this plant. As Professor Uhler was kind enough to offer to place these spec-
imens in my hands for description, I looked forward with much pleasure to
their examination. The cases above mentioned embrace, so far as I know,
all the discoveries of fossil plants hitherto made in the Potomac formation.

When I first began to search for fossils in the Potomac beds I knew
of no discoveries of plant-impressions in them except those mentioned by
Professor Rogers. Judging from the lithology and the stratigraphy of
these beds, I was convinced that Professor Rogers was right in supposing
that they differed in age from most of the Mesozoic of Virginia. His men-
tion of the existence of plants in the formation induced me to undertake a
systematic search for plant localities. In the course of my first reconnais-
sance I paid a visit to Baltimore, and having learned from Professor Uhler
of the existence of Tyson's cycad trunks and of his own collections
obtained at Baltimore, I made with him a hasty examination of these fos-
sils at the Museum of the Maryland Academy of Sciences.

Professor Uhler had not told me of his discovery of plant-impressions
at Fredericksburg, but while at the museum my attention was attracted
by a small collection of fossil plants unlike any that I had ever seen. Pro-
fessor Uhler informed me that he had collected them at Fredei-icksburg, and

INTEODUCTION.

he was kind enough to promise to show me the spot. Under his guidance
I visited this pLant locality and found the exposure in the form of a small
ledge of rock, showing an outcrop only a few feet in length. Here I
made my first collection from the Potomac strata. Among the specimens
found were some that appeared to be certainly dicotyledons. These plants,
and many others new and of great interest found there, induced me to
make thorough search of the spot. The experience gained at Fredericks-
burg taught me how to look for fossils in this formation. In the course of
several years, during which examinations were made, the number of plant
localities found and the amount of material obtained proved to be unex-
pectedly great.

The mode of occurrence of the plants in the Potomac formation de-
serves a brief general description. There is nowhere any continuous
stratum affording plant- impressions. When found at any locality and on a
given horizon it rarely happens that even in the immediate vicinity any
trace of the plant-bearing bed can be found. One can depend upon nothing
except what is seen on the spot to contain plants. Even this material as a
rule, when followed in working, soon gives out, often suddenly and un-
expectedly. In the sandy portions of the formation we find little besides
silicified wood, and even this is very rare.

Lignite is abundant, but it always occurs enveloped in clay. This,
when damp, is, with hardly an exception, dark gray to black. All the
determinable portions of plants occur in clay, which, as a rule, is but little
indurated. It is usually quite plastic and tenacious. In rare cases the
material is somewhat indurated, so as to approach in nature a shale. Two
colors are common in the clay; one is pale reddish brown or chocolate;
the other when damp is dark lead-gray to nearly black. The first is more
commonly the carrier of identifiable plants, but even this clay is by no
means usually fossiliferous. In many cases it is without a trace of vege-
table matter, and in others it contains nothing but small diffused bits of
plants. The gray clay sometimes contains good impressions, but more
commonly only lignite.

Both kinds of clay occur in two forms: (1) They are found.undisturbed
and as originally deposited; (2) they appear disturbed, that is,-torn up from

8 THE POTOMAC OE YOUNGEE MESOZOIC FLOEA.

the original bed and redeposited in an irregular manner. The undisturbed
clay often possesses a somewhat regular structure. It is then either lami-
nated or cleavable, especially if plants are present. This form of the clays
gives almost all of the well-preserved specimens. These undisturbed clays
occur in more or less extended lenticular sheets that finally thin out and
disappear, showing in their course many irregularities. Often they are
found in pockets of limited extent.

The clays are commonly found disturbed. They then appear in the
form of masses or small particles that have been torn up from some pre-
existing clay layer, transported to a greater or less distance, and deposited
either singly enveloped in the sands, or together in irregular pockets and
layers mixed with some sand. If abundant, the redeposited clay particles,
when cemented together by pressure, form layers, at first sight not unlike
the undisturbed clay beds. It is easy to detect these deposits on attempt
ing to work' out plant impressions occurring in them. They lack the lami-
nated structure and cleavage of the undisturbed material. The clay is
much mixed with sand, and is confusedly heaped together, contorted, and
affected by slickensides. The contained fossils are very fragmentary, and
lie at any angle in the material, so that it is rarely possible to extricate them
without destroying the specimens.

In some cases the redeposited masses are large enough to retain the
original comparatively regular structure, especially if they have not been
transported far. In such cases good impressions may be obtained. In
some cases a remnant of the original bed may be found covered by the dis-
turbed clay. There is no essential difference between the plants in the
original beds and those in the redeposited clays, and hence no very long
period of time had elapsed between the deposition of the original bed and
that of the disturbed material. These confused and disturbed clays may
occur at any horizon in the Potomac, and they are common at and near its
top. They are often mixed with coarse sand, and they even contain peb-
bles, sometimes of large size. It is not unusual to find one of these dis-
turbed clays resting on a cobblestone layer.

A common mode of occurrence for the clay of both colors is in the
form of isolated masses and particles imbedded in the sand. In some cases

I]5ITE0DUCTI0K 9

these particles are small, and are intimately mixed with sand ; in others
they take the shape of rolled masses or balls of considerable size. These
have been seen five or six feet in diameter, but more commonly they are
only a foot or less. The balls rarely contain good impressions, for they
have generally been much crushed and contorted. They are often associ-
ated with large cobbles. The presence of these balls, and of the disturbed
clays, may be taken as indicating that some change has occurred which
increased the agitation of the waters and caused erosion to take place for a
short time. Hence they indicate erosion-horizons. It is clear that the
normal deposit of the Potomac of Virginia was sand, and that the clay
layers were formed only in eddies and still portions of the waters. Any
renewal of the more violent movement, continuing the transport and depo-
sition of sand, might erode the lately deposited clay.

Lignite is very abundant in the Potomac formation, and its mode of
occurrence is worthy of notice. As stated before, it occurs always imbedded
in dark gray clay. The usual form in which this material is found is that
of single logs and limbs, or aggregations of these. The single logs, and
some of the aggregations, were plainly drift matei'ial. It is quite a common
thing to find imbedded in the sand, and surrounded immediately by a patch
of clay, logs of lignite which now lie where they quietly settled to the bot-
tom after floating about for a period. These represent entire trees, and the
lignite does not occur in the fragmentary condition in which it is always
found in the so-called " iron-oi'e clays." The logs occasionally have great
length. In the cutting of the Dutch Gap Canal there was removed, as I am
informed, a lignite log forty feet long. An end of this log may still be seen
in the bank of the canal, indicating a tree of the diameter of ten inches.
At least twenty feet in addition to the forty feet have been removed from it.

In several localities we find aggregations of lignite logs which appear
to have been formed by the prostration of forests, the trees falling where
they grew. In these cases the lignite logs occur lying one over the other
and nearly all having the same direction.

No plants that can be identified have been found south of James River.
In the banks of the Appomattox clay occurs that seems favorable for the
preservation of plant-impressions; only small fragments, however, have

10 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

been seen in it. The fossils found in the Petersburg area were all obtained
from the banks of the James River below Richmond.

PLANT LOCALITIES.

Deep Bottom is the locality farthest down the James River where
plant-impressions have been found, and here the Potomac disappears from
view. The spot is about four miles below the Dutch Gap Canal, being
located in a sharp bend of the river near a group of huts A small creek
enters here after having cut a deep ravine through all the formations down
to the top of the Potomac. At this spot the river bank is composed of Qua-
ternary, Eocene marl, and Potomac. In places the Quaternary rests on the
Potomac, but usually the Eocene bed intervenes. Just below the mouth
of the small stream above mentioned a thick mass of Quaternary is seen
resting on a confused mixture of materials that have the character of the
Potomac.

The greater portion of the exposure of this latter is of a rather argilla-
ceous gray sand, that shows all the features so common in the disturbed clay
commonly found in the upper part of the Potomac. This material barely
rises above high-tide level. The argillaceous sand seems to be derived from
the erosion of some stratum which has been torn up and had its fragments
confusedly redeposited. It is a structureless mass, made up of particles
of various sizes cemented together by pressure. Embedded in this sandy
matter "we may find some particles more argillaceous than the main mass,
which retain to some extent the structure and cleavage of the original
stratum. These furnish occasionally fragments of dicotyledons and other
plants of the same sort as those found elsewhere in the Potomac. The gray
masses in which the plants are found are of the same general character as
the debris in which they are embedded, being simply more argillaceous.
Associated with these, and inclosed in the confused matrix, we find large
rounded masses three or four feet in diameter, of a dark chocolate tenacious
clay, which is entirely different from the surrounding sandy matter. This
clay has the character of the chocolate clay so common elsewhere in the
Potomac formation. Its masses contain plant-impressions similar to those
of the gray argillaceous sand, but they are more perfectly preserved.

PLANT LOCALITIES. 11

A little farther down the river the top of the Potomac formation shows
itself undisturbed, rising two or three feet above low tide. It is a dark tena-
cious clay, full of small fragments of plants. The Eocene greensand marl
rests upon it. About two hundred yards distant, in the bottom of the ravine
cut by the creek, the Potomac shows itself again undisturbed, but here only
sand appears The spot affording the plant-impressions seems to be one of
the erosion horizons so common in the top of the Potomac. This locality
will be referred to as " Deep Bottom."

The next plant-bearing locality met with in ascending the river is at
the lower entrance of Trent's Reach. Trent's Reach is the great bend in the
James River to avoid which the Dutch Gap Canal was cut. The exposures
of the Potomac strata in this reach ai-e extensive, but none of them are note-
worthy as yielding plants, except a bluff in the river bank diagonally op-
posite the lower end of the canal, and on the south side of the river. The
spot may be located by its showing the first high bank seen on entering
Trent's Reach. At this place a spring branch enters the river near the
ruins of a small wharf Tlie bank immediately at and below the wharf
contains ten to fifteen feet of the chocolate Potomac clay, but this material,
though highly favorable for the preservation of plant-impressions, revealed
none.

The high bank extends thirty or forty yards above the mouth of the
branch, but the material composing it changes considerably, becoming an
irregular mixture of sand and clay. This portion of the bank has such
sudden and irregular changes of structure and material as to defy descrip-
tion. Most of the impressions were found about fifteen yards above the
mouth of the branch. They occur at different horizons in the bluff and so
irregularly that no description can serve as a guide for finding them. They
may be looked for in the highest part of the Potomac, which shows about
fifteen feet of material, and is capped by Quaternary.

The upper portion for the thickness of three or four feet shows occa-
sionally good impressions. The uppermost portion is quite argillaceous, in
a layer four to six inches thick. This has a brownish color and contains an
immense number of fragments of plants, with now and then good impres-
sions. The fragments seem originally to have made up a large part of the

12 THE POTOMAC OE YOUNGER MESOZOIC FLOEA.

material of the layer, but now many of them have weathered out, so that
the clay is very porous and is full of the cavities left by them. Most
of these fragments are coniferous, and many belong to the species of
Frenelopsis which is found only here. This stratum has yielded a number
of interesting plants. We find in it the following, among other less note-
worthy forms: Baieropsis {B. pluripartita minor'), Williamsonia, JDiodnites,
Pachi/phi/Umn, and Frenelopsis parceramosa.

Some portions of the material under this layer show a tendency to
lamination ; and here occurs a different group of plants, but they are scat-
tered so irregularly that one can never tell where they may be found. Here
is the largest form of Baieropsis seen at Dutch Gap, viz., B.phiripartita, and
various coniferous twigs and cones, as well as several ferns. In one part
of the bluff a log was seen silicified in one portion and changed to lignite
in another. The locality will be referred to in the description of species as
"Entrance of Trent's Reach."

Plant-impressions occur in both banks of Dutch Gap Canal. This
canal is only about one hundred yards long. The banks are layers of sand
and clay irregularly intermixed, and varying much in thickness. The clay
is in both forms, the disturbed and the undisturbed; the latter containing
most of the impressions. It has both of the characteristic colors, the gray
and the reddish. In most of tlie bank the clay occurs in masses and pockets
of variable thickness, apparently replacing portions of the sand. In one
portion of the right bank thin layers of dark gray clay and sand are inter-
stratified. These clay layers sometimes contain very large impressions of
Dioonites BucJiianus, which are over a foot in length, indicating that the leaf
must have been in some cases a yard long. This material is so fragile that
it was impossible to get out specimens nearly as large as they showed them-
selves to be as they lay in the clay. When Dioonites Bucliianus is abundant,
as it is here in places, very few other plants are found. The plants occur
irregularly in the sides of the canal and apparently in small pockets in the
clay. The greater portion of the material is entirely free from them.
Dioonites Bucliianus and a few ferns, with some conifers, especially of the
SpJienolepidium and Sequoia types, are the most common forms in the general
mass of the clay.

PLANT LOCALITIES. 13

On the right "bank of the canal and in the thin interstratified layers of
sand and clay a curious mode of occurrence of plants was discovered. In
examining here the clay layers, to procure as large specimens of Dioonites
as possible, a small mass of pale reddish plastic clay was found embedded in
the interstratified sand and dark gray clay. This reddish clay seemed to
be a ball inclosed in the stratified material. It was without bedding, and
was somewhat contorted and affected with slickensides. From this it will
be seen that its lithologic character differed totally from that of the matrix
in which it was inclosed. The fossils found in it showed still greater difter-
ences, for the large impressions of Dioonites BucManus were lacking, and
instead there was a great variety of plants, some of which have not been
found anywhere else. A number of the species occurring in this homoge-
neous clay seem to have been delicate, finely incised ferns, some of which
were beautifulh^ preserved. This mass seems to have been a fragment torn
off from some bed of clay exceptionally rich in plants, which was subse-
quently embedded in the interstratified sand and clay. The number and
beauty of the impressions found in it make special reference to it desirable.
It will be referred to as "Red clay ball, Dutch Gap Canal." This clay mass
was five to six feet in diameter. The locality in general will be character-
ized as "Dutch Gap Canal." By this will be meant that the plants thus
referred were found in the banks of the canal, but not in the red clay
ball.

Above the canal there is a reach of river about one and a half miles
long. The left bank for this distance is mostly high, and composed of Qua-
ternary resting on Potomac. Most of the Potomac material is a gray,
coarse, current-bedded sand, with here and there pebbles and large clay
balls. In places in the sand, nearly at high-tide level, are lenticular layers,
interrupted patches, and irregular masses of both dark gray and reddish
clay, the former predominating. These are undisturbed. Plants are found
in several places, mostly in the lenticular layers and interrupted patches of
gray clay. The clay is very tenacious and plastic, with indistinct cleav-
age. It is difficult to work out good specimens from it, notwithstanding
the undisturbed condition of the matei'ial. The plants, however, are pre-
served in it very perfectly.

14 THE POTOMAC OE YOUNGER MESOZOIO FLOEA.

The most important locality in tliis reach, and the one which has
3^elded the most numerous and best preserved specimens found at Dutch
Gap, is situated a few yards above a spot used by fishermen as a landhig
place for their reel nets, where a small shanty is located. Where the plants
are obtained two layers of dark gray clay occur in the base of the bluff,
a foot or so above high tide. These layers are undulathig in their course
and tend to run together. Where most distant from each otlier, they are
separated by eighteen inches of sand. Plants occur irregularly in both
layers, but in the lower seam there is a portion, only two to three inches
thick, that contains plant-impressions for a considerable distance.

This fossiliferous seam is usuallj'^ found near the center of the clay layer,
but it rises and falls in its course, so that it is sometimes near the top and
sometimes near the bottom. The clay layers are each about twelve inches
thick, but they vary a good deal. The lower layer is much the richer in
impressions. The best specimens of Equisetum found in the Potomac for-
mation occur at this spot, also very fine specimens of Dioonites. Many coni-
fers, especially long-leaved Sequoias, a number of ferns, good impressions
of Baieropsis pliir'qunfita minor, and a number of other plants may here be
obtained. The locality will be referred to as " Fishing hut above Dutch
Gap Canal."

About two hundred yards above this spot there is a pocket of dark
clay in the sand, which stands at so low a level as to be covered by high
tide. This is full of leaves of Biodnites quite well preserved, but, as is
usually the case when the Dioonites is abundant, only few other species
occur. About one and a half miles above the canal a very large spring
discharges into the river, at a place called Sailor's Tavern. The clays and
sand found farther down the stream still continue to show themselves for
about four hundred yards above the spring in the form of an irregular
bluff. About two hundred and fifty yards above the spring a pocket
of gray clay, irregularly mixed with sandy matter, occurs at about high-
tide level. This material, when it was first found, was carefully exam-
ined, and the impression of the posterior part of a fish was obtained from
it. Above this point on the river no good plant-impressions were found.

PLANT LOCALITIES. 15

These localities embrace all that are worthy of mention in the vicinity
of Dutch Gap. The narrow neck of land through which the canal is cut,
and which is known as Dutch Gap, is by river 17 miles below Richmond;
by country roads, 12 miles.

In the interval between Richmond and Fredericksburg no plant-im-
pressions have been found, and in the immediate vicinity of the latter town
only one place has yielded any notable amount of fossils. As was stated
before, this spot was discovered by Professor Uhler.

The plant-bearing layer at Fredericksburg, on being followed in from
the outcrop, proved to be very limited in horizontal extent. The space
from which impressions were obtained was only about fifteen feet square,
and the fossiliferous material seemed to be a lenticular pocket, apparently
formed in an eddy in the waters. On the outcrop the impressions were
more numerous and better preserved than farther in. The particular layer
that most abounded in vegetable matter served as a water-way, and the
long-continued seepage of water through it destroyed much good material.

The locality now in question is situated just below Mr. Phillips's ware-
house and near the boat-house of the Fredericksburg boating club, on
the right-hand side of the road descending to the steamboat landing.
When first seen by me the fossiliferous material was exposed in the form
of a small ledge of rock close to the road. The ledge was mainly com-
posed of a gray, highly ai'gillaceous, and very fine-grained sandstone,
graduating into sandy shale. About four feet of the material contained
vegetable matter. The upper portion for about three feet contained few
recognizable parts of plants, while it had in a layer of considerable thick-
ness so much comminuted plant-matter that it was colored brown and ren-
dered thinly fissile. Nearly all the good impressions occurred towards the
bottom of the mass, near its junction with a bed of cobble-stones, on which
the fossiliferous stratum rested.

Distinct impressions were found mostly in a layer here three to five
inches in thickness. T'his cobble-stone bed is one of the most curious
features of the locality. It thickened up so as to cut out in all directions
the plant-bearing material. The cobbles are composed of Azoic rock, such
as occurs several miles to the west of the spot, mixed with some rounded

16 THE POTOMAC OE YOUNGER MESOZOIC FLORA.

stones of the typical Potomac sand, here having the consistency of a sand-
stone. The cobble-stone bed itself is very local, and is nothing but a
pocket representing a local erosive horizon, Many of the stones are three
to five inches in diameter and some as much as eight to ten inches. Over
the fossiliferous stratum Quaternary deposits come, having large, partly
rounded Azoic masses in their base. On working the plant deposit and
following it in and along the outcrop it was found to thin out to tlie west
and north, while to the south the material continued without essential litho-
logic change, but lost entirely its fossils.

I made repeated visits to this place and collected largely from it. I
was induced to do this because the study of each collection made known
to me fragments that were not otherwise identifiable, while the};" were clearly
different from the better-preserved imprints. Unfortunately the town au-
thorities availed themselves of the excavation I had made to get material
for mending roads, so that no doubt a large amount of good fossiliferous
matter was wasted. The quarrying operations carried on by myself and
the town finally exhausted the deposit, and the place now appears as a rec-
tangular recess, showing in the walls little besides the Quaternary and the
cobble-stone bed. From its present aspect no one would think that any
plant impressions had ever been found there. This locality will be referred
to in the descriptions of species as " Fredericksburg."

I have made repeated and careful search for other plant localities in
the vicinity of this spot, but with no success. I found that on the same
horizon with these fossil impressions, in the immediate vicinity, the material
was totally different. The changes of rock material on the same horizon
were so many and so sudden, that it soon became evident that there was
nothing here like an extensive fossiliferous horizon. Here and there, very
locally and on different horizons, a few obscure impi-essions might be found,
but they in no case ever extended over more than a foot or so of space
taken horizontally, while in thickness the material would be a mere film.

Nortli of Fredericksburg, however, other localities yield plants. It
may be said here that in searching for plant-impressions in the Potomac
formation there is no guide except the presence of undisturbed clay. Any
layer of this kind may contain impressions, and hence before one can saj

PLANT LOCALITIES. 17

that no fossiliferous localities exist in a given region, he must have exam-
ined every clay layer in it. As these occur generally in small patches
which in the poverty of exjDOSures must be often hidden, it will be easily
seen that many fossiliferous spots may exist where none have been found.

Going north, the next plant locality that has been seen is on the farm
of Mr. Powhatan Moncure and in its vicinity. The spot may be best
located as follows: The Teleg'raph road crosses Potomac Run about seven
miles north of Fredericksburg, at the farm of Mr. Moncure. Near the run,
and just south of it, a rather steep hill descends, and here the road is much
washed, producing a deep gully on the right-hand side. The gull}^ exposes
at the foot of the hill an interrupted stratum of gray clay, which rests
upon a gravel bed. The clay is mixed with sand, and was evidently torn
up from some pre-existing layer, the particles being. deposited confusedly,
sometimes in masses of considerable size. Owing to the mixed character
of the material and the very limited amount of it, it was difficult, except
when the fragments were large, to get out good specimens. All the clay
visible was worked out. The spot is interesting for yielding one of the two
species of Sagenopteris found in the Potomac beds and for the occurrence
of several well-marked plants found also at Dutch Gap and Fredericksburg.
This locality may be designated as "Road-side near Potomac Run."

It may be noted here that the tidal portions of the streams entering
the Potomac River from Virginia are known as " creeks," while from the
head of tide up the streams are called "runs."

At the point on the Telegraph road above mentioned an obscure farm
road diverges to enter a field. At a distance of about two hundred and
fifty yards this road deflects to approach a wooded hill. Whei'e the road
passes first along the base of the hill another fossiliferous stratum occurs.
This is found a few yards up the hill and within the woods. This stratum
is composed of gray shale intercalated in the sand. The material is more
indurated than we usually find the clays to be, and it is well laminated.
Lithologically it is strikingly like the fossiliferous gray shale of the Poto-
mac found at Federal Hill, on Covington street, in Baltimore, which will
be noticed further on. The stratum is from two to three feet thick, and has
apparently considerable horizontal extent, although no traces of it appear

MON sv 2

18 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

on the Telegraph road. It is one of the most favorable materials known
to me in the Potomac formation for the preservation of good fossils.

It is of course composed of undisturbed matter, unlike that found on
the road. The impressions in it are numerous and well preserved, but I
was disappointed to find that they all belonged to a few species only. The
plants are nearly all ferns and conifers. The ferns show close affinit}^ to
the most abundant of those collected by Meek at Baltimore, thus confirming
the indications of the lithology. These plants illustrate the curious local-
ization so common in the Potomac plants. Hardly a single species found
here occurs in the spot on the Telegraph road, the nearest affinity being
with certain Baltimore ferns and Dutch Ga]) conifers. This spot will be
referred to as "Hill-side near Potomac Run."

In the woods that contain the last-described locality an interesthig
occurrence of lignite is met with. The lignite is situated on a small stream
about one-fourth of a mile to the southwest of the plant-locality on the
Telegraph road. The stream exposes in its channel the lignite logs em-
bedded in dark gray clay. This clay is a local deposit in the usual Potomac
sand. The lignite clearly was caused by the prostration of a forest in the
place where the trees grew. The trees may be seen for more than one hun-
dred yards along the bed of the run, lying at different levels, and mostly
turned in the same direction. The logs are much flattened, so that a cross-
section presents the form of a much elongated ellipse. Some of the trunks
appear to have been originally fully two feet in diameter.

This lignite, like all that found in the lower Potomac, seems to have
originated from coniferous wood, and at this place one species of conifer
appears to have furnished most if not all of the material. If we may judge
from the macroscopic character of the lignite, this tree grew in forests over
all of the Potomac terrane; for most of the lignite throughout the Potomac
of Virginia and much of that found in Maryland came from the same species
of tree. It seems to have had a. wood of uniform and compact grain, with
numerous thin, closely-placed rings of annual growth.

This lignite shows peculiar features that are characteristic of nearly
all found in the Virginia Potomac. When dr}?, if it be split longitudinally,
the structure of the wood is beautifully shown ; but if a cross-fracture be

PLANT LOCALITIES. 19

ninde, it presents the features of a true jet. The fracture is conchoidal,
resinous, and deep bhxck in color The only leaf-impression seen in the
clay containing this lignite was a well-marked imprint of Scleropteris eUiptlca.

The next locality yielding plant-impressions found in going north is in
the vicinity of Brooke station. The localities on Potomac Run are near
the western edge of the Potomac area. Brooke station is on the eastern
edge. The area in this region is about four miles wide. Brooke station
is on the Atlantic Coast Line Eailroad, nine miles north of Fredericks-
burg. In the vicinity of Brooke the contact of the Eocene with the Poto-
mac may be seen. The cuttings for the railroad give the exposures here of
the plant-bearing beds. Two localities in this vicinity, a short distance
apart, have been found to yield plant-impressions. One of these occurs in
a cut on the railroad at the 72d mile-post from Richmond, and the other
about one-fourth of a mile farther north and near the railroad crossing over
Acquia Creek. The Potomac formation exposed at these two places shows
marked hthologic differences, and a diversity in the plants is also found.

The cut on the railroad which, exposes the fossihferous material begins
at the mile-post and extends for some distance down the railroad to the
north. The Potomac here has resting upon it a thin layer of Eocene, which
in two places thickens up by dipping and cutting out the Potomac below
the level of the track. This thickening takes place in two narrow bands,
which represent two pre-Eocene ravines cut out of the Potomac. They
run in a northwest and southeast direction, very nearly in accordance with
the direction of the present minor streams of the region. The Potomac ma-
terial is very irregular in structure and composition. It is composed in the
main of sand, with the usual varying character and current-bedded struct-
ure, in which is found clay irregularly- arranged. The clay that contains
plant-impressions is mostly disturbed and deposited in pockets and rude
layers which have no dehnite course, and in which the clay is mucli mixed
with sand, affected with slickensides, and confusedly cemented together
by pressure. Most of the plants seem to have been caught between the
particles of clay as they were pressed together, hence it is difficult to get
out good specimens; but in one portion of the side of the cut, on the left
facing north, a thin irregular stratum was formed by the deposition of fine

20 TEE POTOMAC OR YOUNGER MESOZOIC FLORA.

clay. Tliis possessed some regularity of structure and was cleava-ble. It
afforded a number of interesting plants beautifully preserved. Unfortu-
nately the amount was very limited and the stratum was worked out.
As most of the clay here is lumpy and confusedly thrown together in
particles of some size, the plants, although quite numerous in species, are
generally very fragmentar}^ The s])ecimens occur mostly a few yards
north of the mile-post, the best being obtained on the left hand looking
north.

This locality is remarkable for the large number of species of dicoty-
ledons and conifers found, and also for the number of plants occurring
nowhere else. Most of the conifers and dicotyledons have apparently a
more recent character than the predominant plants found at the more south-
ern localities ; but the identity in mode of occurrence, and the number of
connecting links seen in the plants here, indicate that the flora of this locality
is not essentially different in age from that of the rest of the Potomac. This
spot will be designated as " 72d mile-post," near Brooke. The fossils at
this place give us another illustration of the localization of many of the
Potomac plants.

As stated, the number of species occurring here is lai-ge, and several
of these are very abundant. Nearly all are wanting at the locality pres-
ently to be described, while some of the most common of the species at the
latter are wanting near the mile-post.

Going down the railroad about one-fourth of a mile in a northerly
direction, on the right hand side where a creek crosses the road, we find a
considerable area from which the earth has been removed to make a " fill."
This has caused an abrupt bank to be left about fifty yards from the rail-
road. Most of this bank is composed of the current-bedded Potomac sand,
but in the top of the bank is a stratum of gi'ay shale about eight feet thick.
This is undisturbed material, and shows distinct stratification. Portions of
it are sandy and coarse, but a number of thin layers are composed of fine
clay, and abound in plant-impi-essions ; which, however, all belong to a very
few species. Most of the impressions occur near the top. By far the most
abundant of the impressions are those of Sapindojjsis, which also abound at
the 72d mile-post The locality has been very thorouglily explored, and

PLANT LOCALITIES. 21

very few other species have been found. A small Baieropsis occurs next in
abundance. It is not found at the mile-post, but has most resemblance to a
plant occurring at Federal Hill, in Baltimore. The great number of im-
pressions of Sapindopsis is surprising, as is also the fact that so many of the
imprints show the preservation of the same portions ; i. e., the terminal part
of the pinnate leaf

Two or three imprints of bivalve shells were found. These appear to
be small Unios, and they resemble some of the Wealden TJnios figured in
Bunker's "Monograph of the Wealden."^ This spot will be referred to as
"Bank near Brooke." The clay carrying the fossils seems to be a remnant
of an original stratum of considerable extent. It is comparable to the lower
Potomac clay over the sand in Baltimore.

Going north, the next plant locality was seen at Mr. Kankey's farm, on
Neabsco Run. It lies three-fourths of a mile west of the Telegraph road
and nearly opposite the place where the road crosses the run at Mr. Kankey's
house. This is near the western margin of the Potomac area. Only six
or eight feet of Potomac sand and clay can be seen, and the floor of Azoic
slate is visible in several places. The sand is of the usual kind. The clay
that carries the fossils is dark gray and very tenacious, and it is undisturbed;
but it lies in irregular patches of limited extent. Very few species occur
here. Biodnites Buchianus is the only plant of importance. Great numbers
of its leaves occur in some portions of the clay, so that they are matted
together. Here, as at Dutch Gap, this plant, when ver^^ abundant in a clay,
seems to exclude other species. It is noteworthy that in going north from
Dutch Gap this is the first locality where any trace of this plant occurs, and
the great number of the specimens seen at its reappearance is remarkable.

This locality deserves especial notice for the lignite found there. It
occurs precisely as at Potomac Run, evidently originating in the same way;
i. e., by the prostration of a forest of coniferous trees and their subsequent
change to lignite in the place where they grew. The lignite is exposed
along the channel of a small stream for some thirty or forty yards. The
stream has very feeble erosive power, and the deposit of lignite is probably
not fully shown.

' These have been since determined by Dr. Wliite to be Estheria.

22 THE POTOMAC OR YOUXGER MESOZOIC FLORA,

This lignite exhibits exacth^ the same physical character as that on
Potomac Run, having the curious mingling of features of jet and true lig-
nite with woody structure. Some of the trees, which appear to have been
three feet in diameter, are much flattened, having evidently been subjected
to great pressure. As only a few feet of material now covers these trunks,
the Potomac here must have lost largely by erosion. The locality will be
referred to as "Kankey's on Neabsco Run."

Where the Coast Line Railroad crosses Occoquan River a long cut of
considerable depth has been made to form tlie approach on the south side to
the bridge. This cut shows Potomac sand, with fossiliferous reddish and
gray clay in small irregular patches. In some places the floor of Azoic slate
is shown, so that here, as well as at Kankey's, tlie base of the Potomac is all
that remains. The only fossil worth mentioning that occurs here is Dio-
oiiitcs BucJiianus. It is by no means so abundant as at Kankey's, and in
general the plants are very rare and fragmentary. No collection was made.

The next locality which has afibrded specimens is a little south of Tel-
egraph Station. This station is on the Coast Line Railroad, three miles
north of the crossing over Occoquan River. A series of cuts made in the
Potomac sand and clay are found between the station and the river. The
only spot in this region at which plant-impressions have been found is in
a cut about one and a half miles south of the station, and towards the river.
The material exposed is Azoic slate, with Potomac sand and clay resting on
it. The clay containing plants is mostly disturbed and colored gray. This
has poor impressions, but in the left-hand side of the cut looking north is a
pocket of rather sandy, laminated, and reddish clay, which has afforded a
number of well-preserved impressions. The most important of the plants
here is Bioonites Buchianus. This is the farthest point north at which good
specimens of this fossil have been obtained. Fragments of it occur at Fort
Washington and also at Baltimore, but they are few and small. A number
of ferns, conifers, etc., occur here, giving a group of plants much like those
found at Dutch Gap. The locahty will be referred to as " Near Tele-
graph Station."

White House Bluff is the end of a point which terminates on the Po-
tomac about two miles below Mount Vernon. The bluff begins just below

PLANT LOCALITIES. 23

White House wharf, and extends several hundred yards down the river.
The material composing it is almost wholly Potomac, of which it shows
fully eighty feet. This is capped by about fifteen feet of Quaternary. The
lowest portion of the bluff, for fifteen to twenty feet, is a coarse sand, nearly
white in color, and consolidated to a pretty firm rock. Higher the sandy
matter is yellowish gray, or brownish yellow, from oxidation and from the
admixture of some colored clay. Clay layers, balls, and pockets occur on
both horizons. About sixty feet above water level is a pretty well defined
layer two to four feet thick of mixed sand and disturbed clay. Tliis
seems to be almost pure clay in some places, and may be detected by tlie
water that issues from the face of the bluff. In a number of places it con-
tains a good many bits of plants, among which soxiie undeterminable coni-
fers and small fragments of Dioonites Buclvianus may be seen.

At only one place have well-preserved impressions been found, about
seventy-five yards below tlie old wharf Here a large amount of talus
forms a steep slope up to the foot of a perpendicular bank about twenty
feet high. In the base of this bank the bed above described occurs The
material is difficult of access and collecting is dangerous, since the bank
above threatens to come down upon one working at its base. The clay
presents the usual structural features of the disturbed clays ; but its min-
eral character is unusual, and not found in many of the exposures of the
layer in the bluff. It has a light buff" color, and is very fine in texture and
plastic ; the lumps and masses are so mixed with sand in redeposition and
so much contorted that it is not easy to obtain good specimens. The im-
pressions of leaves are numerous, but the species of plants are few. The
dicotyledon Sapindopsis variabilis, with pinnate leaves, so common at the
two localities near Brooke, gives nearly all the imprints. The state of
preservation of these leaves is similar to that of those seen near Brooke,
the parts of the leaf most commonly found there being most numerous
here also. This locality will be referred to as "White House Bluff."

Fragments of plants with some determinable parts occur at Mount
Vernon, on the Potomac River, two miles above White House, and also at
Fort Washington, on the Maryland shore, about three miles east of Mount

24 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

Vernon. No prolonged search has been made at either of these phxces for
plant-impressions, and it is quite possible that good fossils may be found at
both. Mount Vernon is noteworthy for showing on the sand of the lower
Potomac a gray laminated argillaceous material similar to that seen in
Federal Hill, Baltimore. The Fort Washington bluff shows at its base
lower Potomac, consisting of sand with pockets of disturbed clay. Over
this comes upper Potomac, composed of the Variegated Clay, or so-called
"iron-ore clay," so conspicuous in portions of Maryland. Next above we
have Eocene with impressions of marine shells ; and over all, Quaternary.
The disturbed clay in the top of the lower Potomac shows masses and
particles of various sizes embedded in the sand. Some of the larger par-
ticles retain their original lamination, and in these fragments several spe-
cies of plants may be found. Tlie most important of these are Frenelopsis
ramosissima, Dioonites Buchiamis, and an undetermined dicotyledon.

The lower part of the Potomac formation appears at Washington with
the features characterizing it in Virginia. In the clays exposed in the ex-
cavation for the reservoir a few obscure fragments of leaves occur, being
found in pale reddish clay. In the dark-gray clay, which forms pockets
in the sand composing the greater part of the formation here, a good
deal of lignite is found. This seems to be formed by the alteration of
drift-wood which has accumulated in certain places.

In Virginia the Potomac formation is composed of only one group of
beds, the lower one, which is mostly sand or sandstone, with here and
there sandy clay. In these materials come irregularly subordinate strata
of more or less pure clay, containing the plants found in this formation.
In Maryland the case is different, for here we find a series of beds overlying
the lower or sandstone member, and underlying the Eocene, which as yet
cannot be separated from the sandstone or sand member by any clearly
defined universally present features. For this reason this group is retained
in the Potomac formation, forming its upper member.

The Potomac formation extends from Washington to Baltimore, a dis-
tance of forty miles. In this space the lower or sand member is rarely
seen, for it is too deeply buried imder the upper member to be visible,
except in the lowest natural depressions and the deepest artificial excava-

PLANT LOCALITIES. 25

tions. It possesses in Maryland the features which usually distinguish it
in Virginia, except that, so far as seen in Maryland, it is never cemented
together and indurated sufficiently to be called a sandstone. It is an in-
coherent sand of varying character, which has a current-bedded structure,
clay locally replacing the sand in various ways.

In the city of Baltimoi'e, on Covington and Belt streets and in other
places, several feet of laminated gray shale and clay occur, interbedded
with argillaceous sand. This material shows on Covington street, at the
base of Federal Hill, a thickness for the whole mass varying from six to
twelve feet. This small group of strata, which on the whole is decidedly
argillaceous, rests on the typical sand of the lower Potomac, and forms a
member of this lower formation, which, although probably once generally
present, is now in most places removed by erosion. This argillaceous por-
tion of the lower Potomac in several places in the city, and notably on
Covington and Belt streets, has afforded some interesting plants.

On this plant-bearing material, or, in its absence, on the typical sandy
material of the lower Potomac, we find resting everywhere in Maryland the
thick mass of clay and sandy clay above mentioned, which has been called
by Mr. Tyson and Professor Rogers "the Variegated Clays." Owing to tlie
common occurrence of iron ore in this group of strata, it is very commonly
called the "Iron-ore Clay." As stated above, this formation, at least for
the present, must be regarded as forming the upper member of the Poto-
mac formation. It will in this memoir be called the "Variegated Clay
Group."

This group has not been identified in Virginia, but it may possibly be
feebly represented at Mount Vernon and near Alexandria. The southern
limit so far as made out is Fort Washington. It shows itself in great force
in the vicinity of Baltimore, and has been traced by Mr. W J McGee as far
as the head of Chesapeake Bay, where extensive exposures are shown.

How far it extends into Delaware and New Jersey and what relations
it bears to the plastic clays of the latter State remain to be determined.
It is separated from the lower Potomac below by an erosion horizon, and
it is composed certainly in part of the ruins of this group. From the
Eocene also above it is separated by an erosion horizon. So far as the

26 THE POTOMAC OR YOUNGER MBSOZOIC FLORA.

evidence goes, the indications ave that tlie variegated clay group is of the
same age as the plastic clays of New Jersey.

While showing considerable variations in mineral cha,racter and phys-
ical properties, this group, when unweathered, is mainly composed of an
ash-gray to dark lead-gray plastic clay, often mixed with more or less sand.
Quite commonly much of it is a pure highly plastic clay. In the upper,
and especially the exposed portions, the iron diffused in the clay has become
irregularly oxidized, so that spots, patches, streaks, etc , of red and yellow
colors are mingled with the normal gray. From this feature the names
"Variegated Clays" and "Mottled Clays'' have been taken.

This group during a very long period has been worked locally for the
iron present in it. The clay is without bedding or regular structure of
any kind. It is much affected by slickensides, and, in short, has many of
the features seen in the disturbed clays of the lower Potomac formation.
It has a great deal of disseminated lignite, mostly in the form of small
fragments. Sometimes the lignite is intimately mixed with the clay, and
if the particles are very small tlie clay is made black by them. The
lignite, unlike most of that of the lower Potomac, does not seem to have
been formed from the alteration of trees buried during the accumulation
of the clay, but appears to have been already in the form of lignite when
introduced into the clay. When we consider that the amount of lignite
in the lower Potomac is very large, and note that the Variegated Clay
rests on it and is certainly partly at least made up of the ruins of that
formation, the idea is strongly suggested that the comminuted lignite of
these clays comes from the fragments of the lignite logs so common in
the lower Potomac

What has been said above belongs more properly to the geological
portion of this memoir, but it is necessary to anticipate to this extent in
order to render intelligible what will be said about the probable horizon of
the Baltimore and other Maryland plants, whose exact geologic position has
been left doubtful by their discoverers. Owing to the depth at which the
lower Potomac of Maryland usually occurs, the exposures, so far as found,
are few and limited in extent. Detailed search has not been made in it for
plant-impressions and but few have been found.

PLANT LOCALITIES. 27

Between Washington and Baltimore lignite is the most important sub-
stance of organic origin found in it. The amount of this seems to be large,
and it occurs, as in Virginia, in the form of logs changed to hgnite in places
where the trees were entombed. The characteristic mode of occurrence in
such cases is the appearance of the material in the form of entire trunks,
which have lain undisturbed until the present time. This is vei-y different
from the condition in which we find the lignite of the Variegated Clays.
The lignite logs, as in Virginia, are embedded in gray clay. They occur
sometimes scattered in the sand, but each log has its patch of clay sur-
rounding it. The difference between the mode of occurrence of the lignite
of the lower Potomac and that of the Variegated Clays is well shown
near Hanover, a station on the Baltimore and Ohio Railroad about fifteen
miles south of Baltimore.

Near Hanover a thick mass of the Variegated Clay covers the lower
Potomac. It forms the hills around the station, while the latter is barely
exposed in the beds of the largest creeks. Carbonate of iron here, and in
many other places, has for a long time been undergoing concentration in
the Variegated Clay, owing to concretionary processes. The result has
been the formation of nodules and crusts of iron, which for nearly one hun-
dred years have been obtained by open cuts. Around Hanover these pits
are numerous and extensive, disclosing well the character and structure of
the clay. None of them seem to have penetrated through the clay to the
lower Potomac sand below. This clay has all the irregular features of dis-
turbed clay, that is, the material looks as if it were made up of the con-
fusedly deposited debris formed by the erosion of older clay beds. The
lignite, which is abundant in some places, occurs as fragments, large and
small, mixed with the clay. No entire logs remaining in the position in
which the trees were originally entombed have been seen. The material
was probably lignite and not wood when it was buried in the clay.

Near the station there is a considerable creek, which has cut its chan-
nel below the base of the Variegated Clays. In one place the stream has
just cut down to the top of tlie lower Potomac sand, so as to expose a few
feet of it. The Variegated Clay is seen to i"est on the eroded top of this.
A number of isolated logs of lignite are found here also, much flattened by

28 THE POTOMAC OE YOUNGER MESOZOIO FLORA.

pressure and embedded in clay. It is evident that these logs represent
trunks of trees that settled to the bottom in eddies or reaches of water that
remained quiescent just long enough to permit the deposition of a small
amount of clay around the trunks. One of these logs was seen surrounded
by a crust of marcasite about an inch thick, which was partially changed
to limonite. This was interesting as suggesting one way in which the form
-of portions of plants may be retained in limonite. The wood from which
the lignite was produced seems to have been coniferous. Two kinds of
wood may be detected here even by a hasty inspection. One kind is that
which has given rise to nearly all the lignite of the Virginia Potomac ;
the other was seen here for the first time. This has a coarse grain and
open texture. The rings of annual growth are thick and dense; they stand
out prominently and are more durable than the material between them.
The lignite from this kind of wood is the most common form at Hanover.

A recent visit to Baltirriore enabled me to examine the Potomac forma-
tion there under favorable conditions. The gray shale of the lower Poto-
mac, which at Federal Hill shows a thickpess of two or three feet resting on
the sand, was found to contain a number of plant-impressions. These in
some cases are specifically identical with plants from the Virginia Potomac;
in others they are nearly allied to Virginia plants, and in general character
this flora seems to be similar to that of the lower Potomac of Virginia.

Professor Uhler assisted me in collecting plants from this locality, and
he informed me that several of them are specifically identical with some
of those formei'ly collected by him at Baltimore which were sent to New
Orleans. He informed me also that among the fossils sent to the last-named
city were a number that he had collected at Federal Hill, near the locality
now in question, but at a higher level, and that they all differed from the
species obtained by us jointly. This indicates that there are in the vicinity
of Federal Hill at least two fossiliferous horizons.

Unfortunately my investigations in Baltimore do not fix the horizon of
the plants collected by Mr. Meek. None of the recently obtained species
are identical with his, with probably one exception. The rock material of
Meek's specimens differs so much from the shale which furnishes the speci-
mens on Belt and Covinofton streets as to indicate a difference in horizon.

PLANT LOCALITIES. 29

It is quite probable that Meek's specimens come from that higher horizou
whicli yielded fossils to Professor Uhler, from whose description it would
appear that tliey belong to the lower Potomac flora, as is the case with
Meek's plants.

It is probable, then, that all the plant-impressions found at Baltimore
belong to the lower member of the Potomac formation, none coming from
tlie upper one, or the Variegated Clay.

The spot where I oljtained the plants belongs to the southeast slope of
Federal Hill, and is situated on Covington street, east side, seventy-five
feet north of Cross street.

Since my visit additional collections have been made by Professor
Uhler and Prof Lester F. Ward at the Covington-street locality and on
Belt street. They have been placed in my hands for study, and form a por-
tion of the plants described further on.

The Belt-street locality is on that street, next to and directly north of
Ellicott's iron furnace. It is situated two squares southeast of the Coving-
ton-street locality. The fossils at both spots occur in the clay layers im-
mediately above the sand of the lower Potomac, the lowest rock visible.
At the Belt-street locality Professor Uhler obtained the best specimens of
Cclastrophjllum and Achrosticliopteris that were found.

The doubt that exists as to the true horizon of the plants formerly
found in Maryland arises from the fact that no one who collected them was
aware of the existence of the lower Potomac under tlie Variegated Clays
and of the existence of gray clay in the top of the former, or else, if this
fact was known, the difference in the age of the two was not perceived.

All the gray clay along the Baltimore and Ohio Railroad between
Washington and Baltimore and at the latter place was supposed to belong
to the Variegated Clay group. The base of this group seems to be formed
of material derived from the erosion of the argillaceous upper portion of the
lower Potomac. There is, then, no marked difference in the composition
of the uppermost of the lower Potomac and the lowest of the Variegated
Clay system. It follows, then, that fossils attributed by former collectors
to the lower portion of the Variegated Clay may really come from the top
of the lower Potomac.

30 THE POTOMAC OR YOUNGEE MESOZOIC FLOEA.

A great deal of excavation has been carried on in and around Balti-
more, and by this means the character of the formations there has been
well disclosed. Lignite is abundant, showing two very distinct modes of
occurrence. At all horizons in the Variegated Clays, except at what has
been generally supposed to be its base, this material occurs, as at Hanover
station, in fragments mixed irregularly with the clay. But at several
places near the supposed base of the Variegated Clays it has been found in
entire logs, either isolated or aggregated in masses. The material seems to
have been undisturbed since the change of the trees to lignite. I have not
seen these lignites, and hence can not undertake to determine positively the
formation in which they are found; but from what I have seen of the mode
of occurrence of the lignite in the lower Potomac and in the Variegated
Clays, 1 feel sure that the undisturbed logs occur only in the former.

After this discussion, which is largely an anticipation of matter more
proper for the geologic description of the formation, but which is necessary
on account of the doubt attending the true horizon of the first discovered
]\Jaryland plants, we may notice the occurrence of Tyson's cy cad trunks.

Mr. Tyson has fortunately left in his unpublished notes some record
of the finding of his cycad trunks. By Mr. Tyson and by all others they
have been attributed to the Variegated Claj^s, but this reference is probably
not correct. He sa}'s that on May 5, 1859, he went to Latchford's ore
mine (near Contee's) and got fragments of Saurian bones just exhumed.
They occurred, according to him, near a lignite tree about sixty feet long.
From what was said above this would seem to show that the Saurian bones
were found in the lower Potomac clay and not in the Variegated Clay.
He also states that he went to Dr. Jenkins's place and noted .the position
of the cycad trunks to be at or near the base of the lead-colored clays.
This statement is of importance, for the portion called by him " lead-col-
ored clays" forms the base of the Variegated Clays. This position makes
it quite probable that the horizon of the trunks is really the upper part of
the lower Potomac.

It should be noted that the trunks are thoroughly silicified, and it is
possible that they may have been silicified in the lower Potomac sand, and
then on the erosion of this, during the deposition of the clay containing

PLANT LOCALITIES. 31

them, they may have been introduced into the somewhat later material. I
call attention to this possibility because of the almost universal change of
wood to lignite in the lower Potomac clay. Silicified wood is rare in the
Potomac and occurs almost without exception in sandy matter.

According to M)-. Tyson's notes, one of the trunks, but which it is
impossible to say, was obtained from Dr. Jenkins's mine near Contee's sta-
tion, and the other from Mr. Emack. The latter was obtained from his
farm near Beltsville. It does not appear whether this was obtained from
an iron mine or was picked up on the surface. Presumably it was found
occurring like the one obtained from Dr. Jenkins. The use of the plural
by Mr. Tyson seems to imply this, for while both trunks were sent to
him by Dr. Jenkins, only one was found in his mine. The location of
Contee's station and that of Beltsville are given in the previous mention
of these trunks.

In the excavation of the clay for iron various animal fossils have been
found. The ore-pits in the vicinity of Contee's appear to have yielded
more of these than any others, and they would seem worthy of the notice
of collectors. Unfortunately little attention lias been paid to the collec-
tion and preservation of these fossils. Most of the specimens have been
lost, and in the case of the few that have been preserved nothing is known
of the pits yielding them or of the horizon on which they were found.
Some of these fossils are preserved in the Museum of the Maryland
Academy of Sciences. In the main they have not been examined by
scientific experts, and hence, if proved to come from tlie Variegated Clays,
they can not be used in determining its age. The fact noted by Tyson
that some of them occurred near a large undisturbed lignite tree makes
it not altogether certain that they all occur in the true Variegated
Clays/

The amount of material obtained from the different plant localities and
worked over is very considerable. The area over which these localities
are distributed is large enough to yield a fair representation of the flora

'Since this tvas written Protessor Marsh has obtained a larj^e number of Dinosaurian bones from
this Variegaterl Clay group in Mavylantl. He tljinliS they belonjj to Jnrassic types. His discoyeriea
make it plain that the first discovered animal fossils come from the Variegated Clays.

32 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

of the time of the deposition of the Potomac material. The peculiar
localization of the plant-remains causes the aggregate of different species
collected at the various places to be unexpectedly large.

It is perhaps proper to say something concerning the plan I have
adopted in depicting- these plants, for all the drawings were made by
myself The principal figures have been made of natural size, and por-
tions have been given enlarged to show details of nervation and other
significant points. In almost every case the enlargement is two diameters ;
in a very few cases, where the parts of the plant were very minute, three
diameters were required. Owing to the great saving in time and labor I
have drawn the principal figures simply in outline, the details omitted
being shown in the enlarged parts. As a rule, I have not attempted to
give n fac-siraile of all the accidental defects and distortions shown in the
specimens figured, but at the same time care has been taken not to intro-
duce anything hypothetical.

It has sometimes happened that in removing fossils from the rock in
quarrying, impressions were exposed that could not be taken up without
breaking them and diminishing the perfection of the specimen. Then
again, in transporting the material and in attempting to split up the rock
and work out the fossil, parts would be broken off or otherwise destroyed.
This was especially liable to happen in friable and tender material, wliich
at the same time had little or no regular lamination and structure. These
facts justify a partial restoration in drawing some of the impressions, for
the existing specimens do not in all cases fairly represent what has been
seen. In some cases, then, missing portions have been supplied in the
drawings where they have been at one time seen, or where it is clear from
the parts still remaining what was the character of the missing ones.
These figures I designate as slightly restored.

In a few cases, by taking different portions of the same plant, it has
been possible to give a restoration of the entire leaf, which would show
what were its probable shape and dimensions. This has been done in the
case of some of the dicotyledons found at Fredericksburg. These were
found mostly in a ver}^ fragmentary condition, but the fragments were
sometimes numerous enough to show partially all portions of the leaf

LOCATIOX OF POTOMAC BEDS. 33

These are given simply as restorations of tlie probable original character
of the leaf

Many of the ferns of the Potomac formation have features that cause
them to resemble one another, and yet there are differences not easy to
give in words. These differences are perhaps too sliglit to justify their
separation into distinct species, and yet they are constant and give a facies
to the plants that appears to be worthy of delineation. I have for this
reason thouglit it best to give figures of these, although it increases the
number of illustrations. The somewhat peculiar grouping of the plants of
some localities, if the connecting links were neglected, would cause certain
local floras to appear to be different from the normal Potomac vegetation
It seems best in such cases to give "figures of some at least of the widely
diffused plants which occur with the peculiar ones, even when they may
have been figured from other places.

My thanks are due to Prof Lester F. Ward for valuable assistance in
collecting the fossils, in the identification of them, and in facihtating the
preparation of this memoir. I am under obligations to Dr. J. S. Newberry
for the loan of the fossils collected by Mr. Meek at Baltimore, and for per-
mission to describe them. Prof P. R. Uhler has aided me mucli, facilitat-
ing my examinations in Maryland, and affording me the opportunity to
describe Tyson's cycad trunks. To him I am indebted for the discovery
of the plant locality at Fredericksburg, whicli is the most important one
in the Potomac area.

LOCATION AND GEOLOGY OF THE POTOMAC BEDS.

In order to make clearer the occurrence and geologic relations of the
plants described in this work, it is necessary to give some account of the
location and the general geology of the Potomac beds. In this place only
so much will be said as is required for this purpose. A detailed account
of the geology of the formation will be found in a monograph of the U. S.
Geological Survey, shortly to be published.

LOCATION OF THE POTOMAC BEDS.

In Virginia, the Potomac or Younger Mesozoic forms the greater por-
tion of those beds called by Prof William B. Eogei's, in his annual re-

MON XV 3

34 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

ports ou the geology of Virginia, the " Upper Secondary." But Professor
Rogers under this designation included the strata extending in Hanover
County from the North Anna River to the Chickahominy. This series
belongs almost wholly to the Older Mesozoic, or Rhaitic formation. It is
true that in the vicinity of Hanover Junction the Potomac appears in
some places, but it is inconspicuous.

It is -to be understood that in Virginia the Variegated Clays, or upper
member of the Potomac formation, has not been recognized. The Potomac
of this State is the lower member. Only when we cross the Potomac River
going north is a distinction to be made between lower and upper Potomac.

The Potomac strata show themselves in disconnected areas along a
narrow belt which extends from the Nottoway River twenty miles south of
Petersburg in a northerly direction past the cities of Petersburg, Rich-
mond, Fredericksburg, and Alexandria. This formation continues from
Virginia into the District of Columbia and Maryland, including Baltimore.
The direction of this belt is almost due north and south until Fredericks-
burg- is passed. Then it curves around so as to take a northeast course
by Alexandria and Washington to Baltimore. Beyond Baltimore the lower
member has not been identified with certainty, but judging from the char-
acter of the material seen at its last exposures it is not probable that it
ends at that city. The name Potomac was selected for the* formation by
Mr. McGree on account of its comparatively great development and its typi-
cal character along the Potomac River below Washington.

The belt in which the Potomac areas lie is situated just outside or east
of the terrane of crystalline rocks. This, in Virginia and Maryland, extends
to the head of tide in the principal rivers. The Potomac was buried
deeply beneath the more recent deposits which form the coastal and tide-
water region of the Atlantic slope, and hence it appears only where these
have been removed by erosion. We accordingly find the exposures of this
formation near the junction of the post-Potomac formations with the crys-
talline rocks, and for the most part near the head of tide in the largest
rivers.

The exposures of the formation in the belt above mentioned are so
arranged as to indicate the existence of at least four disconnected areas, all

LOCATIOI^ OF POTOMAC BEDS. 35

of small width. There is, however, good reason to think that this isolation
of the areas is rather apparent than real, and that the formation extends
far to the east and seaward under the later deposits.

A general account only can be given here of the location and dimen-
sions of the several Potomac areas. In this account I will begin at the
north and proceed southward.

My examination of the distribution of the formation north of the
Potomac River in Marj'land and the District of Columbia has not been
sufficiently detailed to enable me to do more than indicate approximatel}'
the location of the area in which exposures are found.

I have not made any search for Potomac strata north of Baltimore,
but Ml'. McGee has found the upper member, or the Variegated Clays, as
stated before, in force near the head of Chesapeake Baj^

Prof William B. Rogers^ speaks of the Variegated Clays which occur
between Washington and Baltimore as extending to Wilmington in Dela-
ware, stating that toward Delaware, from the preponderance of ferru-
ginous coloring, they have been called by Professor Booth the "red clay
formation." How far they extend in that direction, and what relation
these incoherent beds bear to the plastic clays of New Jersey, are points
that remain to be determined.

The upper member, the Variegated Clay, is shown greatly developed at
Baltimore and all along the lines of the Baltimore and Ohio and Baltimore
and Potomac Railroads. The eastern limit is to be found several miles east
of these railroads, the formation being covered in that quarter by a varying
thickness of the Tertiary, by the Quaternary, or by the ruins of these for-
mations.

The western limit lies some miles west of the above-mentioned rail-
roads. The farthest point south at which the Variegated Clay member has
been certainly identified is Fort Washington. Possibly it may form a
portion of the hills at Mount Vernon, but this member is certainly absent
beyond this point.

As stated before, the lower Potomac has not been identified north of
Baltimore. Between Baltimore and Washington it is evidently generally

' Geology of the Virginias, p. 712.

36 THE POTOMAC OR YOUNGER MESOZOIG PLOEA.

present under tlie Variegated Clays, but in most cases it is too deeply
buried under the latter to be seen, except in a few spots, where erosion has
been carried deep enough to reach it.

At Baltimore the only exposures seen are within the city limits. Bal-
timore is evidently near the original shore line of the Potomac waters, for
at this place the Potomac abuts against hills composed of crystalline rock,
and the latter sends tongues into the Potomac terrane.

The Potomac at Baltimore has suffered much and unequally from
erosion. In places the Quaternary alone is found above, resting immedi-
ately on the sands of the lower member. In other places the Variegated
Clay forms the surface, resting on this sand ; and in still others, the typical
sand of the lower member has interposed between it and the Variegated
Clays, fossiliferous, argillaceous sand and laminated clay belonging to the
lower member.

Going south towards Washington, the lower Potomac is covered by
a thick mass of the Variegated Claj^s. It is exposed at Relay Station, nine
miles from Baltimore. At Relay ■ Station also the Potomac must be near
its original western limit, for we find a high bluff of crystalline rock
abutting against and rising much above it. The hills of crystalline rock
at Relay Station appear never to have been covered by the Potomac.

From Relay Station to Washington the Baltimore and Washington
turnpike runs parallel to the Baltimore and Ohio Railroad and a mile or
more west of it. No exposures of the lower Potomac were seen on this
pike, for this portion is covered by the Variegated Clays. The margin
must lie to the west of this road. That it is present under this clay is
shown by its occurrence at Hanover, about six miles south of Relay
Station. This point is some distance east of the western limit of the for-
mation. These are the only points between Baltimore and Washington
where exposures of the lower Potomac have been seen. No detailed
search, however, for exposures in this interval has been made.

At Washington, both in the city and near it, the lower member may
be seen in a number of places We may, for the sake of distinction,
call the belt from Baltimore to Washington the Baltimore area. It is,
however, continuous with the Fredericksburg area of Virginia. In the

LOCATION OF POTOMAC BEDS. 37

vicinity of Washington the lower Potomac is covered by the same for-
mations as at Baltimore. Apparently nowhere north of the Potomac River
does the lower Potomac constitute the surface rock; but it is buried more
or less deeply under later formations.

The case is different in Virginia. Here, in a belt extending from
Washington to Fredericksburg, it occupies the surface, being in tlie
vicinity of the Potomac River alone, covered by Quaternary deposits.
This indicates that in going north of the Potomac River the lower
member lies at a lower level, or else it has lost more from erosion.

Passing from the District of Columbia into Virginia, we find a con-
nected area of lower Potomac rock, which forms the surface in a narrow
belt that extends to a point five miles south of Fredericksburg, where
the Massaponax River enters the Rappahannock. This may be called the
Fredericksburg area. It is the only region in which the lower Potomac
comes to the surface over an area of considerable extent. It forms a belt
on an average three or four miles wide, having its western margin near
the Telegraph road and its eastern near the Potomac River. The Tele-
graph road is a dirt road, which runs from Alexandria to Fredericksburg
and beyond, crossing the principal streams which flow into the Potomac
River" near the head of tide in them. The margin of the lower Potomac
keeps, for the most part, about a mile west of this road after Alexandria
is left.

Since the upper or Variegated Clay member of the formation is ab-
sent in Virginia, the prefix loiver may be omitted in giving an account of
the formation in this State ; Potomac formation being here equivalent to
lower Potomac.

Along the Potomac River the principal exposures of the Potomac forma-
tion are to be seen on the Virginia shore and in the high points that make
down to the river between the creeks. Thus we find extensive exposures
at Mount Vernon, White House Point, Freestone Point, Shipping Point,
Cockpit Point, and near the mouth of Acqiiia Creek. In many places,
however, along the Potomac River, where we would expect to find the for-
mation in question, erosion prior to the deposition of tlie Quaternary has
cut it away to below water level, so that we find the banks of the river

38 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

composed of Qiiaternaiy material. In some places tins is wholly com-
posed of the ruins of the Potomac beds, deposited with but little sorting
aiid modification In these places it is sometimes difficult to distinguish
the Quaternary from the Potomac. Tiiis is the case in High Point, near
the mouth of Occoquan River, where for a long distance the banks of the
Potomac River are formed of Quaternary. Professor Rogers, in his annual
reports, makes this material Potomac.

The exposures of Potomac beds on the Maryland shore are much
fewer than on the Virginia side. This shore, lying farther east in the direc-
tion of the declination of the beds, contains them at lower level. The
formation may be seen barely exposed at Fort Washington, while farther
down the river, at Indian Head, diagonally above High Point and on the
opposite side of the river, a thickness of fully eighty feet is shown.

Along the Potomac River on both sides, as everywhere else, the foi'-
mation has lost greatly by erosion, and the amount thus lost is very
unequal in different places. It is impossible to say when this erosion took
place, but it is clear that much of it occurred prior to the deposition of the
Eocene. The result has been to leave the formation with an exceedingly
irregular surface, and to remove it entirely from considerable areas.

Perhaps the greatest thickness of Potomac exposed at a single locality
is to be found on Acquia Creek, about two miles above the point where the
Atlantic Coast Line Railroad crosses it. Here a high hill shows the forma-
tion rising to the height of one hundred and forty feet above the water.
The chai-acter of the material is well exposed by quarries It is mostly a
coarse gritty sand of light color, which is generally consolidated to a pretty
firm sandstone. In some places we find a good many pebbles, and some-
times a curious mixture of these and clay balls with coarse sand. Little
intercalated clay is found here. From Acquia Creek to near Quantico the
Potomac, althougli occurring a little back from the river, is mostly want-
ing in its banks. Quaternary taking its place. At Quantico and Shipping
Point only about twenty feet is to be seen. Cockpit Point, a.bout two
miles north of this last, shows fully sixty feet of very varying material.

At Freestone Point there is a long deep railroad cut, which shows that
here the Potomac is over one hundred feet thick, composed of heteroge-

LOCATION OF POTOMAC BEDS. 39

nous mattei'. Indian Head, a few miles above Indian Point, sliows much
the greatest exposure of the Potomac seen on the Maryland side. The
rock here has the same irregular structure and mixture of materials as is to
be seen in the cut at Freestone, but the proportion of light colored sand is
much smaller. It is covered here by Eocene, and the Variegated Clay is
wanting. Indeed, as stated before, this group has not been seen anywhere
south of Fort Washington. Gunsen's Creek is the estuary of the imited
creeks Pohick and Accotink. On its south and north shores near its
mouth are extensive exposures of tlie Potomac.

On the south side, near Gunsen's Landing, fully seventy-five feet of
sand and clay appear, having the same general character as in Indian
Head. We see here a graduation of the normal sand of the Potomac into
a greenish sandy clay, which is sometimes mottled with red. The same
thing in a more striking form is seen at Cockpit Point. Some fragments
of lignite, but no impressions of plants, were seen at Indian Head and
near Gunsen's Landing.

On the north shore of Gunsen's Creek, White House Point forms a
high bluff, called White House Bluff, immediately on the river. Here we
may see fully eighty feet of Potomac sand and clay, capped by some ten
feet of Quaternary. This material is sufficiently described in the notice
of the occurrence of the plants at this place. It is strikingly different
from the Potomac shown on the south side of the creek only a short dis-
tance away. We find here a good illustration of the unequal erosion to
which the formation has been subjected.

At the upper and lower ends of the exposure of the Potomac, points
not a half a mile apart, the Quaternary forms the river bank to below
water level. It may be seen rising towards the central portion of the bluff
until fully eighty feet of Potomac is exposed beneath it. As no Varie-
gated Clay or Eocene can be detected in this bluff, it would appear that
it was not submerged until Quaternary times, or else these formations
have been removed by erosion.

Two miles above White House the Potomac again appears in the high
shore on which the Mount Vernon mansion is situated. It shows here six
to eight feet of the light-colored grit which forms the lower portion of While

40 THE rOTOMAC OR YOUNGER MESOZOIC FLORA.

House Bluff. Over this lies about twenty feet of laminated sandy gray
shale, which appears to correspond to the similarly placed material at
Federal Hill, Baltimore, which has been mentioned as containing plant-
fossils.

Between White House and Mount Vernon the Quaternary occupies
the river bank for most of the way. Fort Washington, on the Maryland
shore, is a little north of east from Mount Vernon and about four miles
distant. This place is interesting as showing in the same vertical exposure
all the formations associated with the Potomac. For a very limited space
the Lower Potomac sand with its included clays may be seen, showing
only a few feet in thickness. Resting upon this, in the order ascending, we
have the Variegated Clay, the Eocene, and the Quaternary. From this
point to Washington, about fourteen miles, the Potomac is mostly cut
away, and the Quaternary is along the stream the principal visible rock.

It will be seen from this account that the most easterly exposures of
the formation in question are confined to the immediate vicinity of the
Potomac River. It is not to be supposed that the eastern limit of these
beds is to be found anj^where near this river. The character of the mate-
rial shown in the most eastern localities where the formation is exposed
would lead us to suppose that at these places we are still far from the true
eastern margin of the formation. Strangely enough, we find in some of
the most eastern exposures the maximum thickness of the formation, the
greatest amount of coarse material, and the most irregular structure.
Indeed, if we were to judge from the lithologic and structural features
alone, we would be inclined to think that the material came from the east
and not from the west.

In this area, as in all others, no sti'ikes and dips can be made out for
the Potomac beds. It is clear that the formation as a whole declines to
the southeast. As from Washington to the mouth of Acquia Creek the
general course of the Potomac River is southwest, the declination of the
formation is nearly at right angles to its direction, and on the Maryland
side it would be soon carried beneath the plane of erosion. Near the
mouth of Acquia Creek the Potomac River bends due east and enters
more and more deeply the Tertiary terrane. Hence the last exposures of
the Potomac formation on it occur near the mouth of that creek.

LOCATIOJ^T OF POTOMAC BEDS. 41

It is not necessary to give descriptions of the Potomac formation as ex-
posed in the central and western portions of the area The account given
of the strata at the several plant localities will give an idea of its variable
character. It may be stated generally that along the western margin there
is a larger proportion of argillaceous matter than in the eastern outcrops.
The clayey matter shows also a greater tendency to assume various colors,
due to oxide of iron, and much of it is mottled. These features are seen
more especially in the iipper portions of the formation.

At Fredericksburg the western margin is found about two miles west
of the town. It bends around so as to strike the Rappahannock near the
mouth of the Massaponax River. Here the Eocene lies above it, and this
is the southern termination of exposures in the Fredericksburg area.

From the mouth of the Massaponax to the vicinity of Hanover Junc-
tion no Potomac has been seen. Hanover Junction is the point of cross-
ing of the Atlantic Coast Line, and the Chesapeake and Ohio Railroads. It
is situated in the triangle formed by the North Anna and the South Anna
Rivers, near their junction. The material exposed in this interval is mainly
a tliick mass of sands and sandy clays, very variable in composition and
color. The name Appomattox is proposed for it, from its great develop-
ment in typical form in the vicinity of the Appomattox Rivei*. It is
younger than the Miocene, for it rests on the eroded surface of this, but
being without fossils, its exact age can not be fixed. It is probable that no
exposures of the Potomac can be found between the points mentioned
above, because the erosive power of the streams in the belt where out-
crops may be looked for is not sufficient to remove the thick covering of
superjacent material. The only streams of any size are the upper waters
of the Mattapony. None of these cut through the Eocene.

In the vicinity of Hanover Junction the Potomac shows in several
places a few feet of strata. It has evidently lost much by erosion. In the
cuts on the Atlantic Coast Line Railroad, between the Junction and North
Anna River, a thin remnant ma}^ be seen of the usual character, resting on
the eroded surface of the older Mesozoic (Rhgetic), and capped by Qua-
ternary and Appomattox. On the North Anna River, a short distance
above its junction with the South Anna, the Potomac sand may be seen

42 THE POTOMAC OE YOUNGER MESOZOIC FLORA.

sliowing four or five feet under the Eocene. Here, as is commonly the
case in Virginia where the Eocene marine strata rest immediately on the
Potomac sand, a layer of large cobbles is found in the top of the latter.
The area of Potomac here shown may be called the Hanover area.

Between the South Anna River and Richmond is another gap in the
exposures, none being found until Richmond is reached.

Near Ashland, however, on the surfjxce, there is a large quantity of
cobblestone, which seems to be the debris from eroded Potomac. A re-
cent well-boring in Ashland disclosed under the Appomattox, and over the
older Mesozoic, fifty-six feet of material that may belong to the Potomac.
It is highly probable that the formation iinderlies this interval, but too
deeply buried to be reached by the slight excavating power of the
streams.

At Richmond, owing to the deep erosion of James River, the Potomac
is shown again. It is, however, barely exposed away from the imme-
diate bank of the river, being covered by the Tertiary, both Eocene and
Miocene lying above it. Immediately on the river all the Tertiary has
been cut away as far down as Deep Bottom, where it makes its first
appearance in the rivev bank. At Richmond, and down the James to
Deep Bottom, Quaternary alone is found in the river banks above the
Potomac. The same is true along the Appomattox to near Petersburg,
where the Appomattox formation, with the Tertiary underlying it, comes
above the Potomac. Away from these rivers, in the triangular area
between them and between Richmond and Petersburg, where we may
expect to find the Potomac, the surface is mostly composed of the Appo-
mattox formation, showing in a few places small patches of Tertiary
exposed beneath it. This area of Potomac may be called the Petersburg
area. Its west margin may be taken as approximately determined by the
Atlantic Coast Line Railroad, which runs between Richmond and Peters-
burg. Along this margin the Potomac is mostly hidden under its own
ruins and the thick covering of Appomattox material. It is to be seen
exposed only along the James and Appomattox Rivers, and from what
may be seen on these streams the formation is continuous at least as far
south as Petersburg, twenty miles from Richmond.

LO0ATIO]S^ OF POTOMAC BEDS. 43

Along the James from Richmond to Deep Bottom, twenty-one miles
by river below that city, the Potomac formation shows itself in the base
of most of the bluffs and high banks, rising to various heights and capped
by Quaternaiy. Considering the variability of the material, it is here
surprisingly like that found in the Fredericksburg and Baltimore areas.
On the James its greatest thickness is attained in Drury's Bluff, eiglit
miles below Richmond. Here about sixty feet of it can be seen. In
Chafin's Bluff, a httle below Drur3r's Bluff, for a long distance it shows
a thickness of ten to twenty feet. In the vicinity of Dutch Gap it is
exposed for several miles, reaching its maximum thickness in Trent's
Reach, where forty feet may be seen.

On the Appomattox it may be found at man}^ places up to Peters-
burg. Its greatest thickness on this stream is found at Point of Rocks.
This is four miles above City Point, where the James and the Appomattox
unite. Here fully eighty feet may be seen. It is noteworthy for the
coarseness of the sand which makes up most of the formation, and for the
large size and abundance of the pebbles and cobble-stones found in it.
Some of the latter, composed of Potsdam quartzite,, attain the dimensions
of ten or twelve inches. This point, although one of the most eastern
exposures, shows the formation in the Petersburg area at its maximum
of thickness and of coarseness, which, as on the Potomac River, indicates
that the eastern margin of the formation is still far distant. The eastern
limit of exposures in this area may be fixed by a line drawn from a point
on the Appomattox three miles above City Point, in a direction a little
east of nortli, to Deep Bottom, on the James. Although exposures do not
occur east of this line, there is good reason to think that the formation
extends far eastward under the Tertiary terrane.

In 1869 an artesian well was sunk at Fortress Monroe to the depth of
907 feet. This well passed through the Miocene and Eocene strata, and
at the depth of 835 feet entered a material which differed totally from the
Tertiary, but possessed the peculiar features of the Potomac formation.
The boring was still in this formation when it was stopped, so that at least
seventy-two feet of this may be found here. Professor Rogers had an
opportunity to study the material from different depths in this well and he

44 THE POTOMAC OR YOUNGBE MBSOZOIC FLOEA.

gives a description of it.^ It is surprising to find here, so far to the east,
the heterogeneous composition, coarse character, and indications of the
action of agitated waters so characteristic of the Potomac formation in its
exposures far to the west. Professor Rogers speaks of a conglomerate of
chiy, sand, and pebbles, which reminds us of the features seen in the
erosion horizons of the Potomac He mentions coarse sandy clay with
brownisli or reddish blotches, clay and sand with some coarse pebbles,
reddish mottled clay with quartz pebbles, and other features common in
the Potomac, but found in no other formation under the Eocene of the
Atlantic slope.

Fortress Monroe, at the mouth of James River, is on an air line in the
direction of the declination of the strata, sixty miles distant from the last
exposures seen on the James and the Appomattox. The average declina-
tion of the surface of the Potomac formation is from these data about four-
teen feet to the mile. The strata in this, as in the Fredericksburg area,
sink in a southeast direction. As no regular dip can be determined, we can
note only the depression of the surface of the formation taken as a whole.

South of Petersburg no detailed examination has been made in
search of Potomac outcrops, aiid lience too much stress should not be laid
on the apparent absence of them in given places. South of this town,
along the eastern margin of the Azoic rocks, no Potomac has been seen
until the Nottoway River, twenty miles distant, is reached. In this inter-
val the Potomac, if present, is buried under a thick mass of the Appo-
mattox formation, and there is no stream capable of cutting down through
it. The country or dirt road from Petersburg to Weldon, in North Car-
olina, runs near the margin of the crystalline tei'rane, and hence outcrops
of Potomac, if they exist, would appear near this road. As stated, none
are seen for twenty miles. When we reach the Nottoway the formation
again appears.

At Boiling's Bridge, where the road above mentioned crosses this
stream, a few feet of typical Potomac sand with clay balls may be seen in
the base of the bank. This is capped by a thin stratum of Eocene with
obscure impressions of marine shells. This exposure was apparently not

' Geology of the Viigiuias, p. 735.

LOCATION OF POTOMAC BEDS. 45

seen by Professor Rogers. About four miles higher up the river there is
another outcrop of a few feet of Potomac in the base of the river bank.
This was seen by Professor Rogers. In both phices the material is a coarse
sand of brownish-gray color, which contains many pebbles, some of which
are three inches in diameter. At the bridge occur balls of dark gray clay
of a foot or more in diameter, which, as in the areas farther north, are
embedded in the pebbly sand. The two exposures considered alone indi-
cate here an area only four miles long; but the coarse pebbly character of
the sand, taken with the ftict that only the top is shown, seems to show that
this, which may be called the Nottoway area, is much more extensive.
The river in cutting down has evidently barely reached the top of the for-
mation.

As the Potomac of the Nottoway area in the most important points
possesses exactly the same features as those of the more northern areas,
there can be little doubt that, if we could trace each of the areas eastward,
we should find them uniting to form one continuous terrane extending from
north of Baltimore to the Nottoway. South of the Nottoway unequivocal
Potomac has not been seen. In portions of Greenville County some of
the Appomattox beds are strikingly like the pebbly sand of the Potomac,
and indeed seem to be composed of the debris of Potomac strata but little
modified. This may explain the announcement of the existence of the for-
mation in this part of Virginia made by Professor Rogers in his earliest
reports, but not repeated in his later ones.

Until the Roanoke at Weldon is reached the streams do not seem to
have cut down through the Tertiary, and hence they do not reach the
horizon of the Potomac. The Roanoke, however, at Weldon, in North
Carolina, has cut down to the Azoic rock, but it is difficult to find expos-
ures at the level where the Potomac may be looked for. The river in
flood deposits a large amount of mud on its banks and in the channels of
the creeks emptying into it, and this hides everything. Except immedi-
ately on the river a thick covering of the Appomattox formation liere, as
everywhere south of the Nottoway, conceals even the Eocene and Miocene
beds. At Weldon, near the north end of the railroad bridge, a small
stream, a mere spring branch, flows at a low level into the Roanoke. Over

46 THE rOTOMAC OE YOUNGEE MESOZOIO FLOE A.

a very small space it has stripped tlie floor of gneiss of the covering which
conceals it. In contact with the gneiss a layer a few inches thick is found,
consisting of coarse sand and gravel, showing some of the characteristic
features of the Potomac. It looks like a mere remnant of what was a
formation of some extent, but which in this place has been almost entirely
removed by erosion, and it suggests the idea that the Potomac may be
found as far south as this place. The exposure, however, is too slight to be
taken as anything more than suggestive of probabilities.

If we take the lower Potomac as ending in the vicinity of the Notto-
way, and extending east only as far as Forti-ess Monroe, it will still rank
among the more extensive formations of the Atlantic coast region. Stretch-
ing from Baltimore to the Nottowaj'', its length would be about two hun-
dred miles. This, with an average wddth of sixty miles, would give twelve
thousand square miles as the approximate space occupied by the Potomac.

There is good reason to think that the present westernmost exposures
of the Potomac do not determine the original extension of the formation
in that direction. It seems at one time to have been present considerably
farther west than any of the outcrops now visible. The formation at
various horizons contains deposits of pebbles and cobble-stones. These are
chiefly composed of quartz, but in some portions rounded stones of various
kinds of crystalline Azoic rocks occur. In the vicinity of Washington
some cobbles and pebbles of Potsdani quartzite may be seen. In the
Petersburg area, especially along the James and Appomattox Rivers, the
Potsdam material is noteworthy for its abundance and the large size of the
stones.

On the weathered surface of the lower Potomac and on that of the
formations adjacent to its outcrops a large amount of gravel and cobble-
stones occurs of the same nature as the material found in the Potomac.
It would seem that tlie original home of this surface material was the
lower Potomac, and that the stones were liberated on the erosion of that
formation. Except along the streams which cross from the Potomac into
the Tertiary terrane, these gravels do not pass far into the region occupied
by the Tertiary and later formations. On the rivers they are found
forming the basal portion of the Quaternary, and as this often rests

GEULOGY OF THE POTOMAC BEDS. 47

directly on the Potomac, it is not always easy to distinguish the Potomac
gravels from tlie later ones. In tliis material the Potsdam cobbles are the
most significant, and they are usually easily identified. The Potsdam
gravel is not seen north of Washington, and south of that city it is not
traced farther than Pohick Church, near White House Point. This
distribution indicates that these stones were brought down the Potomac
River, which crosses for the last time outcrops of the Potsdam a little west
of Harper's Ferry. The Potsdam cobbles may be seen throughout the
Petersburg area near the outcrops of the Potomac, and they are found,
as near Washington, over a belt of country extending considerably to
the west of it and within the Azoic terrane. They may be followed also
all along to the west of the Hanover area, and five or six miles to the,
north of its termination. Much rounded quartz material is found with
these stones. In the Azoic terrane they are often found inclosed in Appo-
mattox clays and sands.

The distribution of this coarse, loose material indicates that the
Potomac once extended west of its present exposures over a belt varying
from ten to twenty miles in width.

THE GEOLOGY OF THE POTOMAC BEDS.

So much has been 'said in the preceding pages concerning the geology
of the formation, that the remarks under this head may be much abbre-
viated. It is very difficult in any brief general account to give a clear
idea of the character of this formation. The want of regular structure
and the continual, often abrupt, changes in mineral character and physical
features make it necessary to give a sepai-ate description of each locality.
Sections at the same locality, taken at intervals of a few yards or even feet,
vary generally in most of their features. It is impossible to take the dip
and strike, and no single bed can be traced over any large area. This
arises from the fact that the characteristic mode of arrangement of the
materials is in irregular pockets, or more commonly in interlocking
lenticular layers. The layers may each continue throughout, containing
the same kind of material, dovetailing between layers of a very different
kind. A layer, on being traced horizontally or vertically, may pass

48 THE rUTOMAO OE 10LT^'GEE MESOZOIO FLORA.

graduaily or abruptly into sonietliing quite different. The individual
layers may be variously constituted, and show in their parts on a minor
scale the variable features discerned in the composition and the grouping
of the la^^ers taken as a whole. Then on various horizons matter pre-
viously deposited seems to have been torn up, transpoi'ted to varying
distances, and deposited in a confused manner. These last-named features
mark what, for the sake of distinction, I call erosion horizons. They add
much to the irregularity of the formation. When one has before him any
considerable exposure of the lower Potomac he may well hesitate to
attempt an accurate description of it, feeling' that this would require an
examination of each j^ard of the material.

The layers of sand are often marked by undulating lines across the
direction of their length, forming a marked current bedding. This feature
is conspicuous in the cuts on the narrow-gauge railroad west of Freder-
icksburg. We may often find gravel, coarse sand, and clay pellets
confusedly mixed together. This is to be seen at the top of the quarry
on Acquia Creek on a large scale. W^hile no regular dip could be made
out from the tracing of individual strata, the formation as a whole sinks
gently to the southeast.

Two principal kinds of material make up the lower Potomac beds;
namely, sand and clay. The sand is by far the most abundant. It is the
typical material, while clay occurs in limited local layers, either inclosed in
the sand or replacing portions of it, owing to the graduation of the sand
into it.

The sand may be loose, or cemented into a pretty firm sandstone,
which has been used as a building stone. This is its nature to a consider-
able extent on Acquia Creek and around Stafford Court House. It is
more generally friable and incoherent, especially in outcrops. All the
material near the Potomac River and north of it has this character, but
the larger portion of the sand of all the areas does not form a coherent
rock. The indurated sand or sandstone generally forms irregular masses,
inclosed in the more friable material, or some irregular portion of a friable
stratum may show this induration. The crumbling sandstone or sand is
often quite fine in texture, and has more or less of a light-colored to white

GEOLOGY OF THE POTOMAC BEDS. 49

clay, which serves as a cementing matter, in which the grains of sand are
embedded. There seems to be some connection between the presence of
this clay and the incoherence of the material, but we find loose sand with
little or none of this clay. This is the material which Professor Rogers
has called "feldspathic sand." I have seen no feldspar, fresh or decayed,
in this material, and the clay, although often quite white and pure, is rarely
the direct product of the decay of feldspar. This argillaceous sand gener-
ally lias a white or light gray color.

In some places the amount of the clay thus intimately mixed with the
sand makes up a large proportion of the material, forming from one-fourth
to one-third or more of the bulk. This sort of sand is common around
Fredericksburg, and may also be found in the lower part of the bluff at
White House, as well as in many other places. Strange to say, we may
find this dispersed clay mixed with coarse sand and even with pebbles.
This is the case at White House, for example, and at Point of Rocks near
City Point. The base of the bluff at White House Point to the height of
fifteen or twenty feet is composed of a very coarse white indurated sand,
containing a large amount of diffused white clay, and in places many
quartz pebbles. These are half an inch in diameter and under, and they
are irregidarly scattered through the mass of the rock. At Point of Rocks,
on the Appomattox, seventy feet and more of this material is exposed. It
contains pockets and irregular courses of large cobbles, most of them of
Potsdam quartzite, some of them attaining the diameter of ten to twelve
inches. Here we find, in one place at least, several masses of the pale red-
dish Potomac clay embedded in this coarse mixture. One of these blocks
was two and one-half feet long and subangtilar-prismatic in shape. There
is a large amount of this irregularly mixed coarse material and white clay
in Trent's Reach. In one layer here the cobbles of Potsdam and other
material abound, and many of them are eight to ten inches in diameter.

These characters in the sand indicate that it was laid down in agitated
and probably shallow waters, in which tliere was little or no sorting of the
materials.

Mica is comparatively rare in all parts of the formation, and is hardly

ever seen in any of the beds of the Fredericksburg area. It is more com-
MON XV 4

50 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

mon in some of the gray clays of the Petersburg area, but it is not there
abundant. This is not what we would expect if we attribute the origin of
the material to the crystalline rocks lying to the west of the Potomac. In
most of these mica forms a large proportion of the rock, as in the granite,
gneiss, mica-schist, hornblende-schist, etc. The sandy matter of the Poto-
mac is b}^ most persons called a sandstone, but it is more properly a sand
in most cases. The gradation in the fineness of the material and the
change in the proportion of clay and sand, as has already been stated, are
not what we should expect if the sediment came from the west, the mate-
rials being coarser and having more sand in the exposures farthest east.

The color of the sand, especially of the lower beds, when they con-
tain much diifused clay, is light gray or white ; but this material, owing
apparently to the oxidation of diffused pyrite, is sometimes colored yellow-
ish, reddish-brown, etc., the colors being in irregular patches and seams.
This coloration often follows, and makes much more distinct the planes of
current-bedding.

Towards the ujjper part of the formation there is a considerable ad-
mixture of colored and impure clays with the sand, which then tends to
assume brownish-gray, yellowish-gray, and other kindred colors. The
colors are in such cases often arranged so as to produce a mottling on a
small scale of gray with other colors, or a blotching on a large scale.
Towards the western margin of the Fredericksburg area, and especially
between Acquia Creek and Occoquan, there is a large proportion of sandy
clays of various colors — gray, reddish, yellowish, etc. The colors here are
often arranged irregularly, producing mottling and blotching. These
colored impure clays are in considerable force along the route of the
Atlantic Coast Line Railroad between Alexandria and Telegraph Station.
Possibly some of the Variegated Clay members may be found with these
clays.

Pebbles and cobbles, as will appear from what has alreadj^ been said,
are not uncommon in the. lower Potomac. They occur at different hori-
zons within the beds and are common towards the top. Very generally in
Virginia, where the Eocene rests on the Potomac sand, the upper portion of
the latter is a layer of cobbles packed in sand. This is the case at Rich-

GEOLOGY OF THE POTOMAC BEDS. 51

mond, where a well dug through the Eocene to the top of the Potomac
disclosed a layer of large cobbles, many of them composed of Potsdam
quartzite, and some ten inches in diameter. The same thing may be seen
at Deep Bottom and near Hanover Junction. Indeed, so common is this
feature, that Professor Rogers, in his earliest publications on the geology
of Virginia, called attention to the trenched and eroded character of the
lower Potomac surface upon which the Eocene rested, and to the accumu-
lation of large stones in places on this surface.

These stones are to be found also generally where the Quaternary
rests on the Potomac, and then they attain their maximum in abundance
and size, deserving sometimes to be called bowlders, since some of the
Potsdam stones are two feet in diameter, while the Azoic masses are occa-
sionally much larger.

The stones within the Potomac beds are generally small, being two to
three inches and under in diameter, but sometimes they attain the diam-
eter of five to six inches and more. They occur sometimes aggregated
into irregular beds and pockets, then attaining their largest size. The
smaller pebbles are often very abundant, scattered through the general
mass of the rock, and showing no particular relation to the inclosing mate-
rial. This may be sand, coarse or fine, or it may be clay. This shows
that there was little sorting action in the waters.

As stated before, Potsdam material is not seen in the northern areas
except in the vicinity of Washington, for in the areas north of Fredericks-
burg the inclosed stones are usually quartz or Azoic. In the Peters-
burg area, as before stated, these are accompanied by an abundance of
Potsdam cobbles. No Potsdam stones were seen in the Nottoway area.
The Nottoway River does not cross the Blue Ridge and touch the Pots-
dam terrane, as do the James and the Potomac. The Potsdam quartzite
is found in place oh the western flanks of the Blue Ridge, but not east
of it.

We find these stones in the top of the lower Potomac where the
Variegated Clays rest on the sand, but sufficient exposures of this contact
have not been seen to enable one to say what is generally the • case at such
a junction. It is not an uncommon thing to find plant-impressions in the

52 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

disturbed clay which is frequently associated with these deposits of stones.
The rich j^lant-layer at Fredericksburg rested on a mass of cobbles. The
plants found on the Telegraph road near Potomac Run, and those on the
railroad near Brooke, as well as the richest deposit of clay at Dutch Gap,
are all associated with pebbles.

It is worthy of mention that Professor Rogers, noticing the abundance
and large size of the Potsdam cobbles at Point of Rocks, and knowing
that they must have been brought from the Blue Ridge, speaks of them as
marking a diluvial era of ancient times. At that period many geologists,
and Professor Rogers among them, were disposed to explain the phenom-
ena of the drift of the glacial period by assuming the existence of a
diluvial rush of waters.

The clays found in the lower Potomac are, as has already been
stated, merely subordinate masses occurring occasionally in the sand.
They are important simply from the ftvct that they contain all the plant-
impressions and nearly all of the undisturbed lignite. Their char-
acter and mode of occurrence have already been given. The original
isolated pure clay layers are usually thin, being one or two feet thick,
but they may suddenly swell up to considerable dimensions, as at the
lower entrance of Trent's Reach. They may split up and be lost in the
sand, and they generally disappear by thinning out and dovetailing
between sand layers.

The sandy mottled clays formed by the graduation horizontally of a
sand into clay are more considerable in amount. This material may be
greenish or grayish in color, and when traced horizontally it may assume
reddish colors in large masses ; or, again, the colors may be intermixed so
as to I'eserable mottled castile soap. In the vicinity of Fredericksburg
this kind of material replaces large portions of the normal sands, and it
sometimes extends over considerable areas, but without any regularity of
occun-ence. As illustrating its occurrence, we may take the condition
of things seen at Cockpit Point. Here the lowest exposed material is a
greenish, gray ai-gillaceous sand. If we follow it, we see it in places be-
coming more nearly a pure clay, but it then soon becomes again sandy,
and is now marked in huge blotches with a brilliant red color. In places

GEOLOGY OP THE POTOMAC BEDS. 53

the entire mass is red. Still fartlier on it changes to a light gray sand,
which is totally unlike the material in other places. This sort of change
is common in the Fredericksburg area, but was not seen in the Peters-
burg district.

A beautifully white, pure, pla-stic clay is sometimes found in the form
of balls, embedded in the sand. It was seen, for example, in the lower
part of White House Bluff. It has never been seen in the original or
undisturbed beds.

The layers of isolated plastic clay in their original position some-
times show peculiar features in their arrangement, and illustrate the
ii regularity of the lower Potomac formation. Sometimes, as at Dutch
Gap, we ma)^ see in the same vertical exposure several of these layers.
They may be found in the sand inclined at different angles to one another,
and in one case several were seen diverging from a common point like
the outspread fingers of a hand. Of course such layers must be deposited
upon a shifting surface. These layers are sometimes cut off at one end
by coarse sand and gravel. When partially cut away they are frequently
associated with clay balls which have been torn from them.

The isolated clay balls and masses often show peculiar features.
They occasionally are seen where no trace is left of the bed which fur-
nished them. Some clay masses, four or five feet in diameter, embedded
in coarse sand, may be seen at the plant locality on the railroad near
Acquia Creek, the dark gray clay contrasting strongly with the light
colored sand. In Trent's Reach, where considerable cliffs of nearly white
sand occur, we may see a number of large balls of gray clay embedded
in the sand, and displayed on the same horizon for a considerable distance
in the face of the bluff.

The embedding of clay balls in coarse sand is one of the most con-
stant and charactei'istic features of the lower Potomac. Clay balls thus
inclosed may be seen at all exposures of the formation from Baltimore
to the Nottoway Piver, and the clay is strikingly similar in all cases.
Clay balls and irregular deposits of disturbed clay are common in the top
of the lower Potomac sand, associated with the pebbles and cobbles of
that horizon. This clav seems to point to the former existence of an

54 THE POTOMAC OE YOUNGER MESOZOIO FLORA.

argillaceous member in the top of the lower Potomac, like that seen at
Federal Hill, Baltimore, resting on the sand and apparently extending
over a wide area. As this member, from its position, was the portion of
the lower Potomac most exposed to erosion, and as it was soft and easily
destroyed, we might expect to find it preserved less commonly than the
nnderh-ing sand. If the lower Potomac has lost much from erosion, this
member, if it existed, would suffer most. There is good reason to think
that in the long period of time that has elapsed since the deposition of the
lower Potomac it has lost much of its thickness. Allusion has already
been made to the trenched and eroded condition of its surface where, as
in Virginia, it is covered by the Eocene. In Virginia the outcrops of the
Potomac occur at very different altitudes, so that it may in some places
stand much higher than the Eocene and 5^ounger formations, even when
found in the immediate vicinity. An example of this may be seen at
Point of Rocks, on the Appomattox. Here the Eocene occurs only a mile
away. It is exposed in a ravine much below the level of the surface of
the Potomac at that point. The two pre-Eocene ravines near Brooke
have been mentioned. They give another example of a worn surface.
In Maryland, between Relay and Baltimore, where the Variegated Clay
rests on the lower Potomac, much irregularity is shown in the height
of the top of the latter formation. Of course, where the Quaternary
rests on the lower Potomac the greatest variation is shown in the height
of its surface. A striking case is at White House Bluff, where eighty
feet of the formation seen in the point shows on each side Quaternary to
the level of the water. Many other localities on the Potomac River and
elsewhere might be mentioned where the lower Potomac rises high above
the surrounding Quaternary.

While from this extensive erosion of the lower Potomac we would
expect to find the former uppermost portions of it generally missing, we
find in some places remnants which appear to represent it. These have
been already mentioned, being the clay bed near the railroad in the
vicinity of Brooke, the upper argillaceous portion of the lower Potomac
at Mount Vernon, and the plant-bearing argillaceous material occurring
in the top of the formation at Federal Hill. This latter may, I think, be

GEOLOGY OF THE POTOMAC BEDS. 55

considered typical of this portion of the lower Potomac, and for this reason
the section at Baltimore will be given fnrtlier on. We may, then, with
some probability conclude that the original uppermost portion of the lower
Potomac in most of the areas was more argillaceous tlian the typical sand
now representing most commonly the formation.

I am thus particular in speaking of this possible uppermost member
for several reasons. It seems that, if we can assume its existence, it may
explain tlie difference seen in tlie facies of the flora found at certain points
It has already been stated that the most noteworthy plants found in the
embedded bowlders at Deep Bottom, also those in the disturbed clay at
the 72d mile-post near Brooke, and in the bank near the railroad in the
vicinity of the last locality, are dicotyledons ; and that these in many
cases have a younger aspect than the plants found elsewhere, as at Fred-
ericksburg and at Dutch Gap.

At the same time, in the places first named, the dicotjdedons out-
number the ferns, c3-cads, and conifers, which is not the case at most of the
Potomac plant localities. The material at Deep Bottom containing these
plants, as well as that at the 72d mile-post, looks as if it were the ruins of
this argillaceous upper member. The clay layer in the bank near the
mile-post, but farther down the railroad, looks like an uneroded remnant
of such a member, and tliis is true of the plant-layer at Baltimore. This
latter contains some dicotyledons similar to some of those found near
Brooke. It might, then, be supposed that the younger aspect of the
dicotyledonous plants at these places is due to the fact that they belong to
a flora distinct from that typical of the lower Potomac, and that this
occurs in an independent younger group of beds.

But there are many difficulties in the way of this supposition. The
connecting links are too numerous. Too many plants found in the local
floras having an older facies occur with these. The stratum in White
House Bluff, which contains numerous dicotyledons like those occurring
near Brooke, is not found so placed that we can admit that it belongs to
a group of beds distinct from and younger than the nomnal lower Poto-
mac sand. It has twenty to thirty feet of this coarse sandy matter above
it, and it is clearly a member of the typical lower Potomac. In all the

56 THE POTOMAC OR YOUNGER MBSOZOIO FLORA.

other eases it is impossible to separate the material carrying' these dicoty-
ledonous plants from that containing the seemingly older ones. There is
no break between the beds, and the general geological features are- the
same in all. An attempt will be made in another connection to give the
significance of these apparently younger elements. If any more argilla-
ceous upper member was ever generally present in the lower Potomac
it is synchronous with it, and the two form one unbroken series

A good type of the upper member, whose probable wide extent has
been noticed above, may be found in the southeast slope of Federal Hill,
Baltimore. The spot is located on Covington street, near Ellicott's iron
furnace. The exposures seen at the time of my visit (August, 1886) wei'e
necessarily temporary, as they were made in the grading of a street and
in slight excavations formed for the purpose of obtaining sand from the
sandy member of the lower Potomac. Professor Uhler writes that the
aspect of the place has since been totally changed. The hill has been dug
away and the pits have been filled up.

I was informed by intelligent persons who had much experience in
excavating the Potomac beds at Baltimore, and whose business compelled
them to make a close study of the different kinds of rocks found there,
that the features seen in the section given below might be seen at a num-
ber of other points in and near the city. In the descending order we
have :

(4) Variegated Clay to the top of the hill Upper Potomac.

(3) luterbedded argillaceous saud aud plastic lead-gray clay 6 ]

to 8 feet I Lower

(2) Layer of ferrugiuous sand aud ocher 4 to 6 iuches j Potomac.

(1) Curreut-bedded sand, maximum thickness shown 8 feet \

The Variegated Clay (No. 4) has already been described in its gen-
eral character. It descends from the top of the hill to near its base. It
is mostly a tenacious gray clay, quite plastic towards the base, and when
obtained from that horizon it is used for making tiles, etc. It has no bed-
ding and no cleavage, is much contorted and affected with slickensides,
contrasting strongly in these points with the clay of No. 3. While gray
is the normal color, it is in places variegated in large blotclies with red

GEOLOGY OF THE POTOMAC BEDS. 57

and other colors, due to iron oxide. Irregular masses of it are sometimes
sandy. It has often small bits of plants and fragments of lignite, but no
lignitic entire trunks were seen. The bottom of this clay is easily distin-
guished from the top of No. 3 by its peculiar structure. At the same
time the clay of No. 3 is rather more sandy.

No. 3 consists of alternations of gray clay and argillaceous sand,
showing a distinctly bedded arrangement, but much irregularity in the
thickness and other features of the constituent beds. The lower portion
has a predominance of sandy matter, but the clay increases as we ascend,
and in the top it exceeds the sand in amount. The sandy layers of No. 3
are gray in color and more argillaceous than No. 1. They have many
blotches and streaks of yellowish-brown and reddish colors mingled with
the dingy gray, which is the principal color, and the layers swell up and
thin away in the most irregular manner. At the base of No. 3 and resting
on No. 2 we find in several places two or three feet of a tender ash-gray
shale, with patches and irregular lenticular thin partings of fine sandy-
matter. This is the portion that contains the recognizable plant-impres-
sions. This portion, and indeed all the clay of No. 3, is easily distin-
guished from the Variegated Clay by most of the workers in the Baltimore
clays, and the plant-bearing part is called "shelly or slaty clay."

No. 2 seems to be simply the upper part of No. 1, which has been
impregnated with iron. It is not universally present, being generally
wanting when formations younger than the Variegated Clay rest on No. 1.
No. 1, at Federal Hill, has clay balls with some pebbles, and it is
stained reddish in some irregularly shaped portions by iron oxide. It is
here very friable, appearing as an incoherent sand. It has very little
diffused white clay or so-called kaohn. It is sought for on account of
the comparatively pure sand that it yields.

The Variegated Clay" seems to be a northern formation. As stated
before, the point farthest south at which it has been seen with its charac-
teristic features is Fort Washington. Here it is much thinner tlian between
Washington and Baltimore. If it appears in Virginia, it occurs without
the features which are so conspicuous farther north. It has not been
recognized in that State.

58 THE POTOMAC OE YOUNGER MESOZOIC FLORA,

This group of clays appears to be greatly developed northeast of
Baltimore, and from the statement of Professor Rogers, previously quoted,
it extends into Delaware.

Mr. McGee has found in this clay formation at the head of Chesa-
peake Bay some poorly preserved plant-impressions, which are nearly all
dicotyledons. These impressions are too few in number and too imperfect
to throw any clear light on the question of the age of the formation. In
the absence of any evidence that shows the Variegated Clay group to be
distinct from and decidedly younger than the lower Potomac formation,
its close association with the latter and the difficulty of separating the
two make it necessary to group them together as forming one series of
beds.

As the Variegated Clay group furnishes none of the plants described
in this memoir, no further description of it is called for.

GEOLOGICAL POSITION AND ORIGIN OF THE LOWEE POTOMAC BEDS.

In what will be said under this head the evidence of the fossil plants
will not be used, but the horizon of the lower Potomac will be fixed so
far as it can be done on evidence independent of them.

Throughout most of the ai-ea occupied by the lower Potomac the
base when seen has been found to be composed of the crystalline rocks,
whose age must be placed so far back that they give us no aid in deter-
mining the lower limit of the horizon of the Potomac. But in the vicinity
of Hanover Junction this formation may be seen resting on the eroded
surface of the older Mesozoic, with evidence of a decided break between
them. This older Mesozoic in this part of Virginia, as I have shown in
Monograph U. S. Greological Survey, No. VI,^ is Rha?tic in age ; at least
the plant-bearing portion of it. If the strata of this formation overlying
the plant-bearing part differ from the rest in age, they are of course
younger.

The striking differences generally found in the lithologic and struct-
ural features of the two formations indicate that the difference in their
ages is considerable, the Potomac being decidedly the younger. Time

' Cout. to the Knowledge of the Older Mesozoic Flora of Virginia.

GEOLOGICAL POSITIdsT OF THE LOWER POTOMAC BEDS. 59

enough must have elapsed to permit an almost total change in the geo-
logic conditions under which the two formations were laid down. The
inland bodies of water, in which the older Mesozoic was for the most part
deposited, had been drained off, so that deposition in Potomac times took
place only outside of the crystalline terrane, within which nearly all of the
older Mesozoic is to be found. The older Mesozoic areas and the crystal-
hne rocks adjoining them are cut by numerous trap dikes. Not a trace of
these traps can be found in the Potomac beds. The period of igneous
activity which has left so many traces, probably at the end of the Older
Mesozoic time, must have then been over when the Potomac sediments
were accumulating. These facts do not enable us to fix the lower limit of
the Potomac horizon very definitely, but at least we can say that the forma-
tion is considerably younger than the Rhsetic.

The upper limit in age can be fixed more nearly. The marine Cre-
taceous of New Jersey and Maryland is wanting in Virginia, as is the
Variegated Clay formation. In this State the oldest formation whicli rests
. upon the Potomac, and whose age is fixed, is the Eocene. Well-exposed
contacts of the Eocene with tlie older formation may be seen in a number
of places. The greensand marl bed is the oldest portion of the Eocene that
contains any considerable number of fossils. This bed contains, among
others, such shells as Ostrea, TiirriteUa, Peden, Ct/therea, CucuUea. This bed
in all of the area south of Fredericksburg, and at tliis place also, rests
directly upon the typical sand of the lower Potomac. This latter, in all
such cases, gives evidence of having lost much from erosion, and its upper-
most portion nearlj^ always contains large cobbles. Towards the northern
part of the State we find under the greensand bed, it is true, a variable
thickness, amounting in some cases to from seventy to ninety feet, of non-
fossiliferous sandy matter. This, however, from the glauconite that it con-
tains and other features, belongs to the Eocene formation. Under it the
lower Potomac still shows marks of great erosion.

The Eocene is a true marine formation, laid down under very different
conditions from those attending the deposition of the lower Potomac. The
eastern margin of the continent must have become depressed enough to
permit the sea to occupy portions that in lower Potomac times showed

60 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

only shallow agitated waters, and an abundant marine fauna flourislied
where hitherto no trace of marine organisms has been found.

Judging, then, from the condition of things in Virginia, we must con-
clude that the Potomac is considerably older than the oldest Tertiary. In
the District of Columbia and in Maryland we have the Variegated Clays
superposed on the lower Potomac. At Relay Station, where tlie clays rest
on the lower Potomac sands, these last show the same marks of erosion and
the same pebble-bed as in Virginia, where the marine Eocene occupies a
similar place. At Federal Hill, where we find the Variegated Clays rest-
ing on an argillaceous member interposed between them and the sands,
the indications of a lost interval are not so decided, but still they may be
seen. We may then conclude with some degree of assurance that these
Variegated Clays are younger than the lower Potomac, although not yet
clearly sepai-able as a distinct formation. So far as the evidence goes, it
indicates that the Variegated Clays probably are of the same age as the
plant-bearing South Amboy clays of New Jersey. These have been held
to be nearly of the age of the Cenomanian of Europe. If this is correct,
then from the stratigraphy and general geologic features the lower Poto-
mac beds nuist be regarded as considerably younger than the Rhsetic and
somewhat older than the Cenomanian. There is, at least in the evidence
above given, nothing which opposes the assumption that the age of these
beds is Neocomian.

It is proper, in this connection to say something as to the origin of the
lower Potomac beds, or the conditions under which they were laid down ;
because, as it happens, they appear to be similar to those attending the
accumulation of a formation which in Europe has a number of plants
closely allied to those of the lower Potomac. In order that the reader
may appreciate the peculiarly irregular character of this formation, it may
be well to repeat in a summary the leading features that ma}^ be seen in it.
If the exposure of the beds at any locality is considerable, all of these
features might be seen there.

The lower Potomac is usually a mass of sandy matter of varying
coarseness, generally incoherent, and having some light-colored interstitial
clay. It has usually a light gray to white color, but this is very often

GEOLOGICAL POSITION OF THE LOWEE POTOMAC BEDS. Q[

marked irregularly Avith colors due to oxide of iron. No regular bedding
or structure is found, but we have a series of interlocking lenticular layers,
showing extreme variableness in composition, texture, and structure. The
arrangement shows mostly current-bedding, and not uncommonly beach-
structure. Dispersed pebbles and clay balls, also nests and pockets of
pebbles and cobbles and disturbed clay, are frequent. Lenticular sheets,
occasionally partially cut away and sometimes containing plant-remains,
are often met with. These are intercalated in the sand in the most irreg-
ular manner, and occur at no fixed horizon, lying sometimes inclined to
one another, as if deposited on a shifting surface. '

These features mark the lower Potomac at all its exposures from the
Nottoway River to Baltimore, and, so far as they can be shown in borings,
they appear to be present as far east as Fortress Monroe. Such charac-
ters could be produced only in deposits accumulating in unquiet and
comparatively shallow shore waters, or in the estuary of a great river.

The entire absence of all marine life shows that the waters must have
been fresh, or at most brackish.

That the deposits accumulated near land, and probably in part at
least in estuary waters, is strongly indicated by the nature and distribu-
tion of the plant-remains. The great quantity of dispersed lignite in the
form of isolated logs and limbs seems to show that the amount of drift
timber must have been large. These trees were probably floated down in
the larger streams.

The areas showing thickly placed logs of Hgnite, appearing to be
formed out of trees which fell where they grew, seem to point to portions
of the shore or to islands in the estuary which were suddenly submerged.
The delicate ferns and other plants, often preserved in great perfection,
could not have been drifted far or floated long in the agitated waters with-
out being destroyed. They probably grew on islands.

It seems probable that the James and Potomac Rivers had their
representatives in lower Potomac times in two streams, which in their
course may not have differed essentially from the present rivers.

If we ai-e permitted to assume that at the time of the accumulation of
the lower Potomac sediment two such rivers existed, and, further, that

62 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

they were mucli larg-er than their representatives and united to form a
great estuary whose waters extended at least from Petersburg to Balti-
more, we could explain the origin of many of the features of the formation
now in question.

The character and distribution of these beds seem to indicate that the
margin of the continent covered by these estuary waters was subjected to
oscillations of level, so that the shore-line retreated and advanced. If we
assume that this margin was first rapidly depi'essed and then elevated
without pause, unquiet conditions would prevail throughout the epoch, and
marine life could not be established in the area affected.

The tendency of the action of the waves and river currents would be
to work over deposits recently made and to produce the peculiar effects
due to alternating erosion and sedimentation which are so conspicuous in
the lower Potomac beds. The tendency would also be to work the
deposited matter seawards and to give in that quarter thicker accumula-
tions than those found on the western margin, for this would be submerged
only temporarily.

If these assumptions be correct, there would be a noteworthy simi-
larity in the conditions attending the formation of the lower Potomac
strata and those of the Wealden of Europe, and it is interesting to note
thai in the plant remains of the lower Potomac there is an important ele-
ment which finds its nearest relations in that formation.

DESCRIPTION OF THE SPECIES.

CRYPTOGAMS.

EQUISETE./E.

EQUISETUM L.

None of tlie Equisetece except Equisetum have been found in the flora
of the lower Potomac. Neither of the species of Schisoneura, which occur
in the flora of the older Mesozoic, or Rheetic of the Richmond Coal Field,
appears. As compared with the species of Equisehmi of the older Meso-
zoic. those of the Potomac formation show a marked change. In the older
Mesozoic the variety of forms, it is true, is small, but the number of indi-
viduals of Equisetum Bogersi is very great, and the specimens are often to
be found filling certain strata in such numbers as to show that the plants
must have grown thickly over large areas, and must have formed the
greater part of the vegetation of the marsh. The great size attained by all
of these individuals and the rarity of their branching show that they
belong to the Triassic and older Jurassic type.

The species of the Potomac strata show decidedly more modern
aspects, and clearly belong in type to the younger Jurassic and Wealden,
showing marked affinity with the species of these periods, especially the
latter. Specimens are rare, and they occur singly, scattered very sparingly
in certain strata. The plants were small and mostly much branched. In
these points they resemble living forms.

Equisetum Vieginicum, sp. nov.

Plate I, Figs. 1-6, 8; Plate II, Figs. 1-3, 6, 7, 9.

Stems and branches branch copiously ; the diameter ranges from 3"°"
to 8"", the average being 4'^"; length of internodes, S""" to 22'"'"; sheaths

64 THE POTOMAC OK YOUIS^GER MESOZOIC FLORA..

closely appressed, 5'"" to lO"'" long; teeth visible on the upper surface of
stems and branches, 5 to 6. Tiiey are usually linear, lanceolate, acute,
rarely somewhat obtuse, and approximate.

Locality: Fishing hut above Dutch Gap Canal.

This pretty little Eqiiisetimi has not been found anywhere except at
the single locality given above. At this place it is rare. This species in
general appearance much more nearly approaches living forms than E.
Boffersi, which is its last predecessor in this region. It is very close to
jE". Burchanlti Schimper, from the Wealden of Germany, and perhaps
should be identified with that species. It does not, however, show the
swollen sheaths and the wide divergence of the teeth seen in tlie Wealden
species. Still, something of both of these features may sometimes be seen.

The most noteworthy features of the Potomac species are the copious
branching and the slight diminution in the size of the successively formed
branches. In many cases there is little or no difference in the size of the
stem and the branch which it sends off. The mode of branching seems
to be quite often dichotomous, but this may possibly be the effect of
compression. The specimens are often partially or wholly decorticated
so as to show no teetli, and in most of the specimens the teeth appear,
from maceration, to be narrower and farther apart than they were
originally.

The unusual forms shown in PL II, Figs. 1-3, appear to be portions
of the main stem, or at least of the primary branches They show six
teeth, while the smaller and much more common forms show five. The
enlarged portion, PI. I, Fig. I'', gives what seems to be the normal original
form of the teeth. They are closely approximate, and have a short acute
tip. PL I, Fig. l*", sliows a slightly different form of teeth. They are
blunter and farther apart at the tips. This is perhaps due to distortion
from pressure and partial maceration.

This plant must have attained a considerable height. It has much
resemblance to the genus Casuarina in the mode of branching, its copious-
ness, the great length of the branches, and their woody character.

DESOEIPTION OP THE SPECIES. 65

Equisetum Lyelli Mantell.

Plate I, Fig. 7; Plate II, Figs. 4, 5.

Schenk^ says of E. Lyelli, from the Wealden of England: "It has a
branching stem, with internodes f long, and is 10"° to 13'°'" in diameter.
The branches are 5'°'" in diameter. The sheaths are 1'^'" long, and the teeth
are linear and acuminate."

The Potomac plant in most of these features agrees closely with E.
Lyelli. The form given in PI. II, Fig. 4, and the smaller stem in Fig. 5 of
the same plate, are probably branches. The resemblance is especially
close in the long, nai-row, and remotely placed teeth. This plant has also
a marked likeness to E. Lusitanicum Heer, from the Jurassic of Portugal.^

Localities: The form given in PI. I, Fig. 7, comes from Fredericks-
burg, and the others from the fishing hut above Dutch Gap Canal.

Rhizome of Equisetum, sp.?

Plate II, Fig. 8.

Plate II, Fig. 8, depicts a fossil which appears to be the rhizome of an
eq^uisetum. It shows no sheaths, is jointed at unequal intervals, and has
on the upper surface three or four narrow prominent ridges. It seems to
be decorticated, and is probably the rhizome of E. Lyelli.

Locality: Fredericksburg; only one specimen was found.

Equisetum Maeylandicum, sp. nov.

Plate II, Fig. 10.

Stems branching copiously; branches long and slender; surface
smooth; branches 1.5'°' and less in diameter; internodes 15"™ or a little
more in length; sheaths slightly swollen, 2'°'° long; teeth visible on the
branches, three to four in number, very short, oval in shape, and termina-
ting in short acute tips.

Localities: Not rai-e on Belt and Covington streets, Baltimore.

Specimens of this little Equisetum may be found occasionally in the
shale, especially of Covington street. They are mostly in the form of

> Die foss. Flor. d. norclwestdeutsch. Wealdenforiiiation, Cassel, 1871, p. 5.
^Compare Heer'a Coutrib. Fl. Fos3. Portugal, Lisboune, 1881, PI. VIII, Figs. 1-6.
MON XV 5

66 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

slender decorticated branches, often attached to stems but sHghtly larger
than the branches, in such a manner as to indicate that the branching was
copious ; in this respect reminding one of E. Virginicum. The branches
average in diameter 1°" and under. Considering their slenderness, they
have a remarkably rigid and woody aspect. The length that many of
these impressions attain and their stiff character remind one of Casmrina.

Rhizome of Equisetum, sp.f

Plate CLXX, Fig. 8.

PI. CLXX, Fig. 8, gives a specimen found at Covington street, Balti-
more. It seems to be the decorticated rhizome of some Equisetum, show-
ing two tubercles. Only one specimen was found. As E. Marylandicum
occurs at this spot, it is probable that this rhizome belongs to it.

FILICES.

The ferns form a very important element in the Potomac flora. Not-
withstanding the great variety of forms, with ygvj few exceptions speci-
mens of ferns are rare at all the localities. This comparative scarcity of
individual preserved fossils is no doubt due to the conditions attending the
fossilization, which favored the preservation of other plants in larger pro-
portion. The large number of species, although represented by compara-
tively few individuals, shows that ferns abounded. There is a curious
mingling of older and more recent aspects in the fern-flora. Taken as a
whole, Jurassic and Wealden types decidedly predominate. The very
large proportion of species belonging to the OladojMebis and Thyrsopteris
forms gives a marked Jurassic facies to the flora. Many forms are closely
allied to Sphcnoptcyis Mantelli and other Wealden species, so that the Weal-
den element is a large one. But the numerous species of As})idium give
modern features a strong representation.

In the ferns, as in most of the other plants of the Potomac, we find
much isolation of the species, forms occurring at a given locality being
commonly restricted to it. In some of the species of CladopMebis we find
some of the closest approximations made by Potomac forms to those of the
older Mesozoic or Rhaetic flora of the Richmond Coal Felds. This latter

UESGEIPTION OF THE SPECIES. 67

flora is in the Potomac terraue, the one which came next to the Potomac
flora among- its predecessors.

Cladophlebis Brong., ex parte.

Saporta^ first defined the character of the genus Cladophlebis. He
gives the following description: "Frond pinnately divided; pinnules sep-
arate from one another, or slightly united, attached to the rachis by the
entire base." Schimper^ gives a much fuller analysis of the generic char-
acter. He says: "Fronds pinnately divided; pinnae spreading; lobes or
pinnules attached by the entii'e base, sometimes confluent, rarely slightly
auriculate, acuminate, or obtuse, occasionally dentate, especially at the
apex, not rarely subfalcately curved upwards ; midnerves pretty strong;
secondary nerves departing at a more or less acute angle, dichotomous
a little above the base, and repeatedly dichotomous : slender to very
slender."

In his later work, however, for Zittel's Handbuch der Palseontologie,
he makes no mention of this genus. If we modify Schimper's descrip-
tion so as to make it read, midnerve strong at base, and towards the sum-
mit dissolving into branches, we have a very accurate description of a
group of ferns that is strongly characteristic of the Jurassic, and which is
fully as much entitled to be called a genus as is Splienopteris or Pecop-
teris. In my opinion it is necessary to retain the name CladopMebls for
all fossil plants with the above-described character, and which have no
fructification by which they can be placed in other genera. It does not
seem proper, as some have done, to group under this specific name all
the Jurassic plants of the Cladophlebis type, which have more or less
resemblance to the Pecopteris Whitbiensis of Lindley and Hutton and the
different plant given the same name by Brongniart. Pecopteris Whitbien-
sis, used by Heer as a specific name for plants widely diffused over the
world in the Jurassic period, is nearly equivalent to the generic name
Cladophlebis. Again, because certain Jurassic plants of the Cladophlebis
type have in their foliage some of the features of ferns possessing the fruc-
tification of Asplenium, Dicksonia, etc., it does not seem proper to group

1 Pal. Frauc, 2d series, Veg^taus, PI. Jurass., vol. 1, pp. 293, 299. = Traits de Pal. Veg., vol. 3, p. 503.

68 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

them as Asplenium, Dicksonia, etc., when they have no fructification and
are found in countries far remote from the supposed fructified forms. For
the reasons given above, the generic name CladopMehis is retained for Meso-
zoic fossil ferns which possess the character given by Schimper, amended
as suggested.

Cladophlebis constricta, sp. nov.

Plate II, Fig. 11 ; Plate III, Fig. 2 ; Plate VI, Figs. 5, 6, 8-14 ; Plate XXI, Figs. 9, 13 ; Plate CLXIX, Fig. 2.

Frond bipinnate or tripinnate, arborescent; principal rachis slender;
primary pinnae remotely placed, very rapidly becoming shorter in ascend-
ing; ultimate pinnna very remotely placed, alternate, in the lower part of
the frond pinnately lobed; in ascending on the frond abruptly passing
first into pinnules with undulate margins and then into those with entire
margins; pinnules mostly very remotely placed, thick and leathery, alter-
nate, at their tips subacute or obtusely rounded, often constricted at base ;
in shape oblong to ovate; the midnerves of the pinnules towards their
summits split np into branches. The lower lateral nerves are once or
twice forked, the upper ones once forked.

Localities: Fredericksburg; 72d mile-post, near Brooke: Deep Bot-
tom; Covington street, Baltimore. In all these places rare.

I have united in this species a number of forms which differ some-
what in facies, but not enough to form the basis of specific separation.
In PI. XXI, Figs. 9, 13, are given two small fragments coming from Deep
Bottom, being the only specimens found there. They are thick and
leathery in character, and difi^er considerably from the fine specimen
given in PI. II, Fig. 11, which comes from Fredericksburg. The small
fragment depicted in PI. CLXIX, Fig. 2, comes from Covington street,
Baltimore. This also is leathery in character, and is much smaller than
most of the normal forms. The forms given in PI. VI, Figs. 3, 12-14, come
from the 72d mile-post, near Brooke. Their texture is very leathery and
thick, and the general character of the pinnules is not exactly that of the
type form, which may be considered as given in PI; II, Fig. 11. PI. VI,
Fig. 9, gives a small fragment from Fredericksburg which in facies is
much like a Gleichenia, and is quite aberrant.

DBSCEIPTION OF THE SPECIES. 69

The smaller forms of this species are somewliat like Pecopteris horealis
Brong., which, as Hear has shown, occurs in Korae, Greenland. Fecopteris
lihcrata Heer in the Jurassic flora of Cape Boheman,^ has the pinnules
constricted at base, and is a good deal like some of those found in this
species. But neither one of these species is near enougli to the Potomac
plant to be identified without hesitation with it.

The leaf substance of all the specimens of this plant must have been
thick and leathery, for the pinnules and lobes make deep impressions in
the shale, and some of the rounded small pinnules and lobes leave round
pits. The epidermis of the pinnules seems to have been thick and durable,
for the specimens often have a dark brown sinning surface. I have, with
a good deal of hesitation, placed in this species some of the specimens
given in- the figures named

Among described fossils, Schenk's Alethopteris cycadina stands nearest
to the plant now in question. The resemblance is considerable between
the form given in PI. VI, Fig. 2, and Schenk's Foss. Flor. d. nordwest-
deutsch. Wealdenformation, PI. X, Fig. 2.

Cladophlebis latifolia, sp. nov.

Plate III, Fig. 1 ; Plate VI, Fig. 4.

Frond bipinnate or tripinnate; principal rachis slender, with a keel in
the middle; pinnas quite remotely placed; pinnules broad, very obtuse,
with undulate margins; alternate, subauriculate, and rounded olf at base,
attached by the middle of the base, separate and rather remote ; midnerve,
as in the genus generally, strong at base, and towards the summit splitting
up into veins; lower lateral nerves forming copiously branched groups;
those higher are bifurcate, and simply forked, slender, but very distinctly
defined; leaf-substance thin.

Locality : Fredericksburg.

This beautiful species was found only at Fredericksburg, and but two
specimens were obtained.

The dimensions and character shown indicate that the plant was prob-
ably arborescent. It is nearly allied to no fossil known to me. It is more

1 Flor. Foss. Arctica, vol.4, Ziii-ioh, 1877, No. 1, p. 30, PI. VI, Fig. 2.

70 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

like Pecopteris Saiburnensis, L. and H., from the Oolitic formation of Hai-
burn Wyke, Yorkshire, England, than any other previously described
plant, but is quite distinct from this. It has some resemblance to Neiirop-
teris undulata, L. and H., Foss. Flor., vol. 2, PL LXXXIII.

Cladophlebis Vieginiensis, sp. nov.

Plate III, Figs. 3-8 ; Plate IV, Fig. 1, 3-6.

Frond bipinnate or tripinnate, arborescent ; principal rachis very
stout and woody ; rachises of the penultimate and ultimate pinnte stout,
rigid, on the under side rounded and prominent, on the upper side ridged
on each margin ; ultimate pinna? very long, rather remote, subopposite ;
pinnules alternate to subopposite, at the tips varying froui acute to obtuse,
with margins usually very entire, rarely crenulate to subdentate, in shape
ovate to lanceolate and subfalcate, attached by the greatly -widened base,
mostly separate to the base ; midnerve stout at base, but soon becoming
attenuated, and some distance below the summit splitting np into veins ;
lateral nerves at the base of the pinnules branched several times, in some
cases forming nerve-bundles, in ascending towards the tips of the pinnules
less and less subdivided, finally simply furcate and unbranched.

Locality: Fredericksburg.

This splendid plant is perhaps the most common fern at Fredericks-
burg, but it is not abundant there. The specimens are usually quite frag-
mentary, as if they had been transported some distance. From the size
of the rachis shown in PI. Ill, Fig. 3, the plant must have been arbor-
escent. The rachis of the pinnse in all the specimens is strong and rigid.
The under side of the rachis is usually i-ounded and prominent. On its
upper surface a strong ridge is often seen on each margin, and to this the
pinnae and pinnules are attached. The pinnules of PI. Ill, Fig. 3, may be
taken as typical for form and dimensions. Sometimes, however, pinnules
may be seen which are quite obtuse at their tips, and in some cases they
occur with margins showing incipient lobing. These come probably from
lower portions of the frond. Possibly in PI. IV, Figs. 1, 3, may be de-
noted a smaller species of this type.

DESCEIPTION OF THE SPECIES. 71

This plant is plainly Jurassic in type, and may be regarded as a sur-
vivor of the Jurassic flora. It is so much like the sterile forms of the plant
from the older Mesozoic or Rhsetic flora of Virginia, first made known by
Bunbury and described by me in Contributions to the Knowledge of the
Older Mesozoic Flora of Virginia,^ under the name Acrostichides linnce-
cefolius, that one is tempted to consider it as a descendant of the latter.
Comparison may be made with PI. VII, Fig. 1, and PI. VIII, Fig. 1, of
the work cited. It is also in some points much like Acrostichides rhomhi-
foliiis, described in the same monograph.

The Potomac plant is strikingly like Brongniart's Pecopteris Whit-
hiensis, and P. tenuis, and one may well hesitate to separate them. Heer,
in Flor. Foss. Arctica, vol 4, under the name Aspleniam, has described
some forms that are very close to the plant now in question. It does not,
however, seem proper to make the Potomac plant an Asplenium so long as
it shows no fructification.

Cladophlebis denticulata, sp. nov.

Plate IV, Fig. 2; Plate VII, Fig. 7.

Frond bipinnate or tripinnate ; rachis of the pinnfB rather slender ;
pinnules opposite to alternate, attached by the entire base, oblong to lance-
olate, subfalcate, minutely dentate toward their tips, those in the upper
part of the frond entire ; midnerve as in the genus ; lateral nerves bifur-
cate or simply forked, and rather slender.

Localities: Fredericksburg; road-side near Potomac Run; very rare.

I have with much hesitation united the plant given in PI. IV, Fig.
2, which comes from Fredericksburg, and that depicted in PI. VII, Fig.
7, wliich was found on the road-side near Potomac Run. The latter dif-
fers from the former in having the pinnules more erect, oblong in shape,
and separate to the base. Then, too, they have their nerves simply forked,
and more Pecopteris-like. The very fragmentary nature -of the specimens
does not permit the true nature of the species to be fully made out.

The form given in PI. VII, Fig. 7, may be compared with Pecopteris
denticulata, Heer, as given in Flor. Foss. Arctica, vol. 3, Die Kreideflora

' U. S. Geol. Survey, Mou. No. 6, 1883.

72 THE POTOMAC OR YOUNGER MBSOZOIC FLORA.

des Arctisclien Zone, PI. XXVI, Fig. 7. The Potomac plant resembles
this a good deal. The form from Fredericksburg given in PI. IV, Fig.
2, is much like Nct(ro2)teris Ugata,^ L. and H., but the nerves are more
copiously branched and the pinnules are broader. The Potomac plant is
no doubt nearer this latter than any other described form.

Cladophlebis falcata, sp. nov.

Plate IV, Fig. 8; Plate V, Figs. 1-6 ; Plate VI, Fig. 7; Plate VII, Figs. 1,2.

Frond bipinnate or tripinnate, arborescent; rachis of the primary-
pinnae or of the frond stout and rigid ; pinnse opposite, with a moderately
strong rigid rachis ; pinnules mostly opposite, sometimes alternate, falcate,
acute to obtuse, separate to the base, and slightly rounded off on the upper
side, with margins mostly entire, rarely slightly lobed, attached by the
whole of the broad base, varying in size according to position on the frond.
The pinnae of ultimate order, in ascending on the frond, pass through pin-
nules that are long and falcate with slightly lobed margins, into those of
smaller size with entire margins ; midnerve rigid and continued to near
the summit, with comparatively little diminution in size. The lateral
nerves are bifurcate and go off at an acute angle, and curve outwards to
meet the margin.

Locality : Fredericksburg ; not very rare.

This fine plant is one of the most common ferns at Fredericksburg.
It has, more than is usual in the Cladophlebids, the aspect of an Alethop-
teris, and although a good deal larger, is something like the Pecopteris JVhit-
biensis of Lindley and Hutton. The Jurassic ferns that have some resem-
blance to this species are numerous, and it is hardly worth while to refer
to all of them, as none of them can with much probability be identified
with it. The forms with larger pinnules may be compared with Pecopteris
insignis, L. and H ,' but, besides other points of difference, the nervation is
essentially distitict.

Heer's Asplenium sj^ectabile, Flor. Foss. Arctica, Jura. Flor. Ost. Sib.,
vol. 4, PL XXI, Figs. 1, 2, has the nervation of this plant. The Potomac
specimens, with smaller pinnules, resemble more or less a number of

' Foss. Flora of Great Britain, PI. LXIX. = Ibid., PI. CVI.

DESCEIPTION OF THE SPECIES. 73

Jurassic ferns from widely separated portions of the globe. Among these
we have Neuropteris recentior, L. and H., Foss. Flor. of Great Britain, PL
LXVIII, and several of the fossils united by Heer with Asplenium Wh'dhi-
ensis, in his article on the Jura. Flor. Qst. Sib., Flor. Foss. Arctica, vol. 4,
No. 2, p. 94, Pecopteris Indica of Oldham and Morris, and Nathorst's figures
of CladopUebis nehhensis from the Rliastic of Sweden, resemble in some
points the smaller forms of the Potomac plant. Some of the pinnules of
C. nehhensis show a fine toothing similar to that found on CladopUebis
denticulata.

I have with some hesitation grouped under the species C. falcata sev-
eral forms that do not resemble in all respects the more common and typ-
ical specimens of that species, which may be taken as represented in PL V,
Figs. 1, 2. The bluntly terminated pinnules in PL V, Figs. 3, .5, also the
very slightly fsxlcate pinnules and the nerves of PL VII, Fig. 2, show a
departure from the normal form.

Cladophlebis paeva, sp. uov.

Plate IV, Fig. 7; Plate VI, Figs. 1-3.

Frond bipinnate or tripinnate; principal rachis proportionally very
stout and rigid; pinnse short, alternate to subopposite; pinnules alternate,
ovate, subfalcate, acute, except in the upper part of the frond, separate to
the base; midnerve as in the genus; lateral nerves mostly once forked;
leaf-substance thick.

Locality: Fredericksburg; rare.

In the shape of its pinnules it belongs to the same type as C. Virgini-
ensis, but the nerves are not so copiously branched towards the base of the
pinnules, and do not diminish in the number of branches so rapidly towards
the summit of the pinnules. It is much like Cladophlebis pseudoivliit-
hiensis,^ but is a smaller plant. It resembles also the upper part of Pecop-
feris dentata, given by Lindley and Hutton in Foss. Flor. of Great Britain,
PL CLXIX. The nerves, however, do not agree with those of that plant.

This small fern is probably another, survivor of the Jurassic, or rather
Rhsetic, flora of Virginia.

' Coutributions to the Knowledge of the Older Mesozoic Flora of Virgiuia: U. S. Geol. Survey,
Mou. No. 6, 1883, p. 52, PI. XXVII, Fig. 4.

74 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

Cladophlebis acuta, sp. nov.

Plate V, Fig. 7; Plate VII, Fig. (j; Plate X, Figs. 6,7; Plate XI, Figs. 7,8; Plate CLXVI, Fig. 5.

Frond bipinnate or tripinnate, arborescent; principal rachis stout and
rigid; pinnaj with stout rigid rachises go off at an angle of 45° and curve
upwards; pinnules alternate, united at base, falcate, ovate to oblong,
acuminate; midnerve rather stout and rigid, prolonged to near the summit
of the pinnules; lateral nerves furcate, with branches subparallel.

Localities: Hill-side near Potomac Run, rather common; rare at
fishing hut above Dutch Gap Canal.

This plant has some of the features of the Pecopteris type combined
with those of CladoiMehis. The pinnules show sometimes an inclination
forward along the i-achis. In the typical forms, such as PI. XI, Fig. 8, the
pinnules are united at base and decidedly falcate. PI. XI, Fig. 7, and
PI. V, Fig. 7, give forms with unusually long and slender pinnules. They
probably represent ultimate pinnae changed in the upper part of tlie frond
to pinnules. PI. X, Fig. 6, differs from the normal foi'ms a good deal, and
hesitatingly I unite it with the species now in question.

Cladophlebis acuta is more like Bunker's Neuropteris Alberts ii from the
Wealden of Germany than any other previously described fossil, and is no
doubt quite near the Wealden species. Schenk, in Foss. Flor. nordwest-
deutsch. Wealdenformation, PI. VI, Fig. 4, gives a form Avith the name
Alethopteris Albertsii, which resembles our plant more than do the figures
of Dunker. Heer, in Flor. Foss. Arctica, vol. 6, Pt. 2, Pis. XVI, XXVIII,
XLVI, has given a number of figures of a plant which he identifies with
Bunker's species, but which he calls Pteris Albertsii, making it a Pteris
without any evidence from fructification. The Potomac fossil is very close
in form to the figure he gives from Unter Atanekerdluk, PI. XVI, Fig. 6.

Cladophlebis oblongifolia, sp. nov.

Plate VII, Figs. 3-5.

Frond bipinnate or tripinnate; arboi-escent ; ultimate pinnae long and
linear, with rigid and comparatively stout rachises; pinnules alternate,
oblong, very slightly falcate, in the upper part of the frond with entire

DESCEIPTION OF THE SPECIES. 75

margins, in the lower portions of the plant with crenate margins; mid-
nerve pecopteris-like, rigid, and prolonged to near the summit of the
pinnules; lateral nerves very regularly once forked, with branches sub-
parallel; leaf-substance thick and leathery.

Localities: Fredericksburg, very rare; more common but still rare at
fishing hut above Dutch Grap Canal; found also in the banks of Dutch
Gap Canal, and in the red clay ball occurring in these banks.

This plant is rare at all the localities where it occurs. It is found in
fragments that are too small to give a good idea of the character of the
frond. That represented in Fig. 5 was found in the red clay ball which
occurs in the right-hand bank of Dutch Gap Canal. To judge from the
size of the rachis in Fig. 5 the plant must have attained very considerable
dimensions. This -specimen shows a ridge on each side of the rachis.
This is one of the forms that possess some of the features of Pecopteris
and Aletliopteris. It does not bear much resemblance to any previously
described fossil known to me. It seems to be nearest to Pecopteris Whit-
hiensis of Lindley and Hutton. It appears also to be like CladopMebis
Virginiensis of this work, but can not be united with it by transitional
foi'ms.

Cladophlebis ckenata, sp. nov.

Plate IX, Figs. 7-9 ; Plate X, Figs. 1, 2 ; Plate XIII, Figs. 1-3 ; Plate XIX, Fig. 1 ; Plate XX, Fig. 6.

Frond bipinnate or tripinnate; rachis of the primary and secondary
pinnse strong and rigid; pinnse mostly alternate, rarely opposite, going off
at an angle of 45°, and closely placed; pinnules alternate, obliquely
rounded at base above, and slightly decurrent on the lower side; in shape
ovate-acuminate and falcate ; margins with distinct crenate toothing ;
midnerve as in genus; lateral nerves of the basal lobes of the pinnules
fasciculate and palmately diverging, those of the upper lobes once or
twice forked.

Localities: Fredericksburg, most common; 72d mile-post, near Brooke;
hill-side near Potomac Run; rare.

The crenate lobing of the pinnules seems to be a constant feature,
and there does not appear to be any tendency to pass into entire pinnules.

76 THE POTOMAC OR YOUNGER MESOZOIO FLORA.

Most of the specimens figured come from Fi-edericksburg. PI. IX,
Fig. 2, a form with opposite pinnaj, comes from the 72d mile-post, near
Brooke. PI. XIII, Fig. 3, comes from the hill-side near Potomac Run.
It has the lobes more rounded than usual. The pinnules are often decur-
rent some distance on the rachis.

This plant is not very near any described fossil known to me. It
may be compared with Cyathea Tchihatclicwi, Schmalhausen,^ but shows
obvious differences. In the shape of the pinnules the species is nearest to
Pecopteris horeaUs, Brong., as figured by Heer," from the Kome beds, but
this latter has the nerves single.

Cladophlebis, sp.? sp. nov.

Plate X, Figs. 5, 8 ; Plate XX, Fig. 7.

Nature of frond and pinnre unknown; pinnules alternate, oblong,
acute, slightly falcate, attached by a widened base under a large angle;
midnerve vanishing before attaining the tip of the pinnule; lateral nerves
not seen; leaf-substance thick.

Localities: Fredericksburg; hill-side near Potomac Run; at both
places very rare.

Cladophlebis inclinata, sp. nov.

Plate X, Figs. 3, 4 ; Plate XX, Pig. 8.

Frond bipinnate or tripinnate, arborescent (1); pinnse of ultimate order,
opposite, short; pinnules, ovate-lanceolate, acute, inclined forward, alter-
nate, attached by the whole of the widened base, separate to the base,
slightly falcate ; midnerve of pinnules slender above the base, but con-
tinued to near the apex of the pinnules ; lateral nerves once forked.

Locality: Near Telegraph Station; not uncommon.

This plant is a good deal like some of the forms of C. acuta, as given
in PI. X, Fig. 6, but the pinnules are smaller and not united at the base,
and none of the lateral nerves are more than once forked. It is so much
like Pteris AlbertsiP Heer, found in the flora of the Atan^ beds, that it is

' Beitr. Jura Flora Russland's, PI. Ill, Fig. 3. St. Petersburgb, 1879
2Flor. Foss. Arc, vol. 6, Pt. 2, PI. II, Figs. 9% 10.
IbifL, PI. XVI, Figs. 5, 6; PI. XXVIII, Figs. 1-3 ; PI. XL VI, Pigs. 22-24.

DESOEIPTION OP THE SPECIES. 77

with mucli hesitation that I separate them. Heer thinks that this plant is
Bunker's Neuropteris Albertsii, but it seems to be quite different from the
forms figured by either Dunker or Schenk.

Cladopht.ebis distans, sp. nov.

Plate XIII, Figs. 4, 5.

Frond bipinnate or tripinnate; principal rachis stout and rigid; pinnee
alternate, linear elongate, witli rigid strong rachises ; pinnules oblong or
ovate, very obtuse, distant; leaf-substance thick and leathery, slightly fal-
cate, alternate, attached by the entire base ; midnerve peeopteris-like ; lat-
eral nerves once forked and strong.

Locality : Not very rare in the banks of Dutch Gap Canal ; rare at
fishing hut above the canal.

This small fern seems to be quite restricted in its distribution. It is
well characterized by its pinnules, which are small in size, of leathery
texture, and remotely placed.

Cladophlebis, sp. ? sp. nov.

Plate XV, Fig. 6 ; Plate XIX, Fig. 3.

Frond and pinnae unknown; pinnules subopposite, ovate to ovate-
oblong, obtuse, united at the widened base, going off nearly at a right
angle; midnerve as in the genus; lateral nerves once forked, or with one
branch of the basal pair forking again.

Localities: Hill-side near Potomac Run; bank near Brooke; very
rare at both places.

This plant is too rare and found in fragments too small to permit its
character to be made out. It seems, however, to be quite distinct from
any other fern described coming from the Potomac formation.

Cladophlebis alata, sp. nov.

Plate XIX, Fig. 5.

Frond tripinnatifid, arborescent; principal rachis stout and rigid;
pinnae alternate, curving upwards, with strong rigid rachises; pinnules
with thick leaf-substance, opposite or subopposite, in shape Hnear-lance-

78 THE POTOMAC OE YOUNGER MESOZOIC FLOEA.

olate, acute, aud falcate, narrowed at the base and decurrent, forming a
strong wing on the rachis, margins cut more or less deeply into ovate-
acute teeth ; midnerve slender, prolonged to near the summit of the pin-
nules; lateral nerves fasciculate in each tooth or lobe, forming nerve-
bundles, with mostly four branches.

Locality : Fredericksburg ; very rare.

This fine, well characterized plant is very rare, and, so far as known,
occurs only at Fredericksburg. It seems to have been a fern of large
size, and was probably arborescent. Some of the Potomac ferns else-
where described, such as Cladoplilchis crenata and Asjndium FredericJcs-
biirgense, look a good deal like this plant, but the decided narrowing of the
pinnules on both sides at the base and the distinct wing in CladojjJileUs
data serve to distinguish it.

Geyler gives a figure^ of his Pecopteris exiliformis, which in general
form looks something like the Potomac species, but the differences are
marked.

Cladophlebis, sp. ! sp. nov.

Plate XIX, Fig. 2.

Frond and pinnge unknow^n; pinnules linear-lanceolate, acute, with
margins cut into ovate-acute lobes and teeth; midnerve as in the genus;
lateral nerves in each lobe or tooth having a midnerve, which sends off on
each side alternately branches that are mostly single, and curve upwards
towards the summit of the tooth.

Locality: Near Telegraph Station.

This plant is too fragmentary to make out its character. It may be
merely a portion of the upper part of the frond of some of the species
described under another name. The so-called pinnules look like pinnai
reduced to pinnules.

Cladophlebis rotundata, sp. nov.

Plate XX, Pigs. 9, 10.

Frond bipinnate or tripinnate, arborescent (?) ; principal rachis stout,
rounded, and prominent; pinnae short, with a strong rigid rachis; ultimate

' Foss. Pflauzen Juraformation Japans, Palseoutograpbica, vol. 24, lcJ77, PI. XXX, Fig, l^

DESCKIPTION OP THE SPECIES. 79

pinnae, from the lower part of the frond, with alternate, short, broadly
ovate, very obtuse, round-lobed pinnules, those of the upper part of the
frond having the lowest pinnules distinct and more or less round-lobed,
and towards the summit with pinnules passing through such forms as
rotundate, subrhombic, and decurrent to entire and rounded, the latter hav-
ing the tips round-lobed and very obtuse; nerves varying according to the
position and shape of the pinnules, those of the round-lobed pinnules and
of the pinnae reduced to pinnules flabellately diverging in each lobe, the
branches being either forked or simple. The nerves of the subrliombic
pinnules have a midnerve, which sends off alternately on each side forked
or simple brandies. All the nerves are very strongly marked and stout.
The leaf-substance is thick and leathery.

Locality: Fredericksburg; rare.

This plant is well characterized by its very strong prominent nerves
and by the varying pinnules, which show some of the features oi Splienop-
teris, of Tliyrsopteris, and of Cladophlebis, respectively. It seems to be
unique.

Cladophlebis sphenopteroides, sp. nov.

Plate XXI, Fig. 4.

Frond bipinnatifid or tripinnatifid ; pinnules or uppermost pinnae
ovate-lanceolate, obtuse, narrowed much at base and attached by the nar-
rowly winged base of the rachis or midnerve, lower ones deeply and
obliquely cut into oblong lobes, which are very obtuse and rounded at
their tips, upper ones cut less deeply and into fewer lobes, at the summit
united and forming a termination similar to the lower pinnules or pinnee ;
nerves flabellately diverging in each lobe, branching several times, very
fine and closely placed, but very distinct.

Locality: Fishing hut above Dutch Gap Canal; very rare.

This plant, although found in small fragments only and very rarely,
is still evidently a distinct species. It should, perhaps, be placed rather in
the Splienopteris than in the CladopMebis group of ferns. It is something
like Tliyrsopteris prisca,^ Eichw., as figured by Heer, but the nerves are

1 Flor. Foss, Aretica, voL 4, No. 2, Beitriige zur Flor. Ost. Sib., PI. XVIII, Fig. 8.

80 THE POTOMAC OE YOUNGER MESOZOIO FLORA.

more numerously divided and much finer, and the pinnules are longer and
proportionately more slender in the Potomac plant.

Cladophlebis petiolata, sp. nov.

Plate XXII, Fig. 8.

Frond bipinnate or tripinnate ; rachis of primary pinnae comparatively
stout and rigid; pinnules, or reduced ultimate pinnre, alternate, oblong,
acute, somewhat falcate, narrowed to the base into a winged petiole, cut
into ovate subacute teeth; lateral nerves in each tooth composed of a
slender midnerve, wliich sends out alternately on each side simple nerves.

Locality: Red clay ball in the banks of Dutch Gap Canal; very rare.

This plant is in form a good deal like Thinnfeldia variahilis, from the
72d mile-post, near Brooke. The nerves, however, are fewer, coarser,
and more remote. It seems to be a distinct new species.

Cladophlebis in-.equiloba, sp. nov.

Plate XXV, Fig. 8.

Frond bipinnate or tripinnate; primary rachis slender; pinnules or
reduced pinnae petiolate, lanceolate-acute, alternate; leaf-substance thick;
basal lobe on the upper side of the pinnules or pinnae ovate-obtuse, erect,
and much larger than the other lobes or teeth; the other lobes or teeth of
the pinnules ovate-acute, and directed towards the tip of the pinnules;
pinnules towards the summit of the primary pinnse sparingly and acutely
toothed; nerves of the lobes and teeth not seen.

Locality: Fredericksburg; very rare.

This small plant seems to show the upper portion of a primary pinna
in which the ultimate pinnae are reduced to lobes and teeth. It seems to
be a distinct species.

Cladophlebis pachyphylla, sp. nov.

Plate XXV, Fig. 9.

Ultimate pinnae, linear, with a comparatively stout rachis; pinnules
subopposite, with a dense leathery leaf-substance, ovate-falcate, acute,
remotely placed, separate to the base, free on the upper side, and cut

DESCRIPTION OF THE SPECIES. 81

away to form a sort of petiole, attached only by the lower portion of the
base; midnerves strong; lateral nerves not seen.

Locality: Fredericksburg; very rare.

This' seems to be a very distinct species. It belongs to tlie Jurassic
type of Cladoplilebis. It is something like Pecopteris WiUiamsoni, Brong.,
but is a much smaller form.

Cladophlebis, species 1 sp. nov.

Plate XXVI, Fig. 15.

Pinnules subfalcate, thick and leathery, sejjarate to the base, attached
by the whole of the widened base; in shape ovate-acute; nerves not seen.

Locality: Fredericksburg.

The small specimen figured was the only one found. It seems to be
a distinct species.

Cladophlebis brevipennis, sp. nov.

Plate XXXVI, Fig. 1.

Frond, ? ultimate pinnae very short, subopposite, cut to varying depths
into rounded, oval, or elliptical pinnules and lobes ; pinnules rounded at
base; nerves strong, rather distant, composed of a midnerve dissolved a
short distance above its base into branches, which are once or twice forked,
and curve strongly outwards to meet the margin of the pinnules and
lobes ; leaf-substance thick.

Locality : Fishing hut above Dutch Gap Canal ; very rare.

This plant is something like ClachpMebis constricfa ; the nerves, how-
ever, curve outward more strongly, and are more copiously branched, and
the ultimate pinnpe are much shorter. It is also something like Bunker's
Pecopteris Murchisoni, but the pinnules are rounded and narrowed at base,
and the nerves are more flabellate and spreading.

PECOPTERIS, Brong.

Fronds once or several times pinnate ; pinnules mostly entire,
attached by the whole of the base, which is rarely narrowed ; midnerves
extending to the tips of the pinnules ; lateral nerves g'oing off on each side
MON XV 6

82 THE POTOMAC OE YOUNGER MESOZOIC FLORA.

of the midnerve in a pinnate manner, and at a varying angle, simple, or
several times forked, not anastomosing.

The genus Pecoptois, based mainly on the nervation and probably
containing many species of distinct ferns, serves simply as a convenient
oroui)ing of plants having a particular f;xcies, and whose generic character
can not be otherwise fixed. There are a number of forms in the Potomac
flora which have the character given above for Pecopteris, and which is
taken from Schimper's description of the genus. The number of ferns,
however, found in the Potomac flora which could be placed in the genus
Pecopteris is far less than that of those which possess the characters of
CladophleWs and Tliyrsopteris. This type is rather feebly represented in the
Potomac flora,

Pecopteris Vieginiensis, sp. nov.

Plate VIII, Figs. 1-7 ; Plate IX, Figs. 1-6 ; Plate XXIV, Fig. 2 ; Plate CLXIX, Fig. 3.

Frond bipinnate or tripinnate, arborescent; pinnae alternate, very
long ; leaf-substance thick and durable ; the principal rachis and that of
the ultimate pinnse stout, rigid, with the margins on the upper face raised in
the form of a cord ; pinnules elongate-oblong to narrowly linear, opposite
to alternate, much narrowed at the base and separate to the base, cut
away obliquely on the upper side and decui-rent slightly on the lower one,
or else united at base to form a wing along the rachis of the pinn^; mar-
gins denticulate to distinctly dentate, straight or more commonly slightly
falcate ; midnerve prolonged to near the tips of the pinnules, often rather
slender but distinct; lateral nerves once forked, one of the branches
usually ending in the tip of the tooth on the margin.

Localities : Red clay ball in the banks of Dutch Gap Canal ; fishing
hut above Dutch Gap Canal; Fredericksburg; road-side near Potomac
Pun ; 72d mile-post, near Brooke ; near Telegraph Station ; Covington
street, Baltimore.

This is perhaps the most widely diffused of the Potomac plants. At
the locality on the road-side near Potomac Run the fragments are among
the most common. They occur in such a way in the irregularly deposited
clay as to suggest that the dimensions attained by this fern were great.
The clay was of sucli a nature at this locality as to render it impossible

DBSOEIPTION OF THE SPECIES. 83

to take out the specimens witliout reducing their size very considerably.
In PL VIII, Fig. 2, is shown a fragment of what was formerly a portion
of the frond a foot wide and more -than a foot long. At all the other
localities it is rare. It is a singular fact that not a trace of this plant is
found at the locality on the hill-side, which is not more than one hundred
and fifty yards distant from that on the road-side. This is true, although
ferns are the most common fossils at the first-named place.

This fern is so well characterized, that there is no difficulty in identify-
ing it. Indeed it can usually be detected at a glance. The plant shows
some variation. Some of the pinnules, especially in those specimens found
at the fishing hut above Dutch Gap Canal and at Baltimore, are very
narrow, elongate, and slightly toothed. We may take PI. VIII, Fig. 6, as
a"t5rpical specimen, the teeth being acute; but in Fig. 1 of the same plate
we have a plant from Fredericksburg which has the teeth less deeply cut
and more obtuse. This form somewhat resembles Cladophlehis dblonga.

In most cases, and in typical forms, the pinnules are narrowed at
base, strongly decurrent, and united to form a wing, as in PI. VIII, Fig. 4,
from Fredericksburg, and Figs. 2, 6 ,7 of the same plate, coming from the
road-side near Potomac Run. In such forms, however, as PI. VIII, Fig. 3;
PI. IX, Fig. 1, from Fredericksburg, and Fig. 5 of the same plate, from
the 72d mile-post, as well as PL IX, Fig. 2, from the fishing hut above
Dutch Gap Canal, the pinnules are separate, not decurrent at base, less
linear, and nari-ow in form, and less inclined forward. These points may
be due to the fact that the parts which show them come from a portion of
the frond different from that affording the normal forms, or they may be
of sufficient importance to denote a variety of the species.

The form, PL VIII, Fig. 5, from the locality at the 72d mile-post, is
the only specimen which gives the summit of a compound pinna. The
corded margins of the racliis appear only on the upper surface, as in
PL VIII, Fig. 2, while the lower face is rounded and prominent, as in
Figs. 1, 4, 6 of the same plate. The lateral nerves are typically once
forked only, as in PL VIII, Figs. 2% 2^ but in PL VIII, Fig. 3, and PL
IX, Fig. 1, they in the lower teeth form nerve-groups, composed of lateral
nerves which go off alternately from a midnerve.

84 THE POTOMAC OR YOUNGER MESOZOIG FLORA.

This plant is more like Pecopteris denticulata,^ Brong., than any other.
The only difference is found in the more slender and elongated pinnules
of the Potomac fossil and in their greater thinness. Pteris frigida,^ Heer,
from the Atane beds, resembles the Potomac plant, but it lacks the distinct
toothing- found in the latter.

Pecopteris Strictinervis, sp. nov.

Plate XIII, Figs. 6-8 ; Plate XIX, Fig. 9; Plate XX, Fig. 3 ; Plate XXII, Fig. 13; Plate CLXX, Figs. 5, 6.

Frond bipinnatifid or tripinnatifid ; rachises slender; pinnae suboppo-
site to alternate, linear; pinnules united for a considerable distance above
their bases, oblong, usually obtuse and inclined forward, slightly falcate,
those of the lower part of the frond denticulate, of the upper part entire;
leaf-substance thick and obscuring the nerves, which are slender and im-
mersed in it; lateral nerves of the lower pinnules furcate, with the lower
branch ending in the teeth ; lateral nerves of the upper pinnules mostly
forked only in the basal ones, most of them simple, all usually parallel
and straight, or nearly so.

Localities: Fredericksburg; Covington street, Baltimore; rare.

This elegant little plant occurs more abundantly at Fredericksburg
than at Baltimore. All the specimens figured, except PI. CLXX, Figs. 5,
6, come from the former place. Still it is not an abundant plant even
there. PI. XIII, Fig. 6, seems to be an abnormal form, which has the
pinnules united higher up than usual and the lateral nerves more commonly
forked and more curving than is usual in the pinnules of this fern, which
have entire margins. Perhaps it would be better to separate this as a
variety with the name var. imita. PI. XIII, Fig. 7, gives a normal form
for the pinnge and pinnules coming from the middle part of the frond.
Fig. 8 of the same plate seems to come from down lower on the frond,
where the toothing is more distinct and the nervation is all forked. PI.
XIX, Fig. 9, is a normal form for the parts belonging to the upper portion
of the frond.

This plant is very much like Pecopteris Browniana, Dunker, of the
Wealden of Germany, as figured by Schenk in Foss. Flor. Nordw. Weald-

iHist. V^g.,Pl. XCVIII, Figs. 1, 2. '^Flor. Foss. Arc, vol. 6, PI. X, Figs. 1-4; PI. XI, etc.

DBSCEIPTION OF THE SPECIES. 85

enformation, Plate V, Fig. 2. The Potomac plant is, however, a stronger
form, and the nerves are more commonly single, straight, and parallel than
in the Wealden fern.

Pecopteris Ovatodentata, sp. nov.

Plate XV, Fig. 8; Plate XSII, Fig. 12; Plate XXIII, Fig. 1.

Frond bipinnate or tripinnate, arborescent; pinnules or reduced pinnae
subopposite, linear acute, separate to the narrowed base, slightly decur-
rent, margins cut distinctly into ovate-subacute teeth; midnerve continued
to the summit of the pinnules or pinnse; lateral nerves furcate.

Localities: Fredericksburg; entrance to Trent's Reach; fishing hut
above Dutch Gap Canal; rare at all localities.

This plant is more common at tlie Dutch Grap localities than at Fred-
ericksburg, but is nowhere abundant. This fossil is found in fragments
too small, and occurs too rarely to permit its true character to be made
out. It is not close to any previously described fossil known to me.

Pecopteris Microdonta, sp. nov.

Plate XIX, Fig. 8 ; Plate XX, Figs. 5, 11.

Frond bipirmate or tripinnate, arborescent?; principal rachis strong
and woody; pinnae of the ultimate order opposite, with a rigid rachis; pin-
nules lanceolate-acute, somewhat falcate, slightly narrowed and decurrent
at base, attached by the lower portion of the base; distinct, with margins
cut into small ovate-acute teeth; midnerve strong at base, lateral nerves
in each tooth simply forked, or in the lowest teeth with the upper branch
again forked.

Localities: Fredericksburg; entrance to Trent's Reach; near Dutch
Gap Canal; at each place rare.

The specimen from the Dutch Gap locality, PI. XX, Fig. 11, has a
somewhat different facies from the Fredericksburg form, PI. XIX, Fig. 8,
the pinnules being longer and proportionally narrower. The specimens
found indicate that the plant was large and probably arborescent.

86 THE POTOMAC OE YOUNGER MESOZOIO FLORA.

Pecopteeis consteicta, sp. nov.

Plate XX, Fiss. 1,2,-:.

Frond bipinnate or tripinnate, arborescent ?; rachis of the primary pin-
nse or of the frond stout and rigid ; pinnae alternate, with comparatively
stout and straight rachises ; pinnules with a thick and dui-able leaf- sub-
stance, opposite to alternate, narrowed at the base, and attached by the
central portions, those of the lower part of the frond cut deeply into ovate
acute lobes that are directed slightly forward, subfalcate, those of the mid-
dle portion of the frond oblong, acute, subfalcate, with ovate acute teeth,
the basal lower one being inserted in the angle betweeii the main and sec-
ondary rachises ; midnerve distinct but slender, extending to the summit of
the pinnules ; upper pinnae narrowly linear, with ovate subfalcate pin-
nules united more or less at base ; lateral nerves in each lobe or tooth
composed of a midnerve, which sends off alternately on each side branches,
the lowest one of which on each side is forked ; the others are simple.
All the lateral nerves are very strong and prominent.

Localit}^ : Fredericksburg ; not uncommon.

This handsome fei'n is very much like Bunker's Pecopteris Browniana,
and it is even more like Pecopteris strictinervis, it being so close to the
latter that I have hesitated to separate them. The specimen shown in
Fio-. 4 seems to be a portion of a compound pinna which comes from the
upper part of a frond where the pinnje have become greatly reduced, and
the large pinnules shown in Fig. 1, coming from the lower portion of the
frond, and in Fig. 2 from the middle part, are reduced to small ovate pin-
nules united at the base, and to ovate teeth. The lateral nerves in the
pinnules and lobes of this specimen are so distinct, that they look like
threads on the surface of the plant.

Pecopteeis brevipennis, sp. nov.

Plate XXI, Figs. 1-3.

Frond bipinnate or tripinnate, arborescent I ; principal rachis stout
and rigid ; pinnules, or pinnse reduced to pinnules, subopposite to alternate,
oblong, acute to obtuse at the tips, short, very uniform in length, cut into

DESCEIPTION OF THE SPECIES. 87

ovate or rounded oblong teeth wliich are subacute to very obtuse ; nerves
in each lobe or tooth composed of a midnerve which sends off on each
side alternately branches which are single and arch upwards towards the
the summits of the lobes.

Localities: Hill-side near Potomac Run ; fishing hut, above Dutch Gap
Canal ; rare at both localities.

As this plant is found only rarely and in fragments, it is possible that
it may be identical with some other of the species described from the Poto-
mac formation.

Pecopteris socialis, Heer.

Plate XXI,/Fig. 7.

Leaf-substance thick and leathery ; principal rachis strong ; pinnules,
or pinnae reduced to pinnules, subopposite to alternate, narrowed at the
base, and cut more or less deeply into ovate-acute to obtuse teeth; mid-
nerve of the pinnules, or reduced pinnse, distinct ; no lateral nerves in the
lobes and teeth visible, only a midnerve.

Locality : Bank near Brooke ; rare.

This plant is found rarely and in small fragments. Fig. 7 gives the
largest specimen found. The detached ultimate pinnae given in this figure
agree quite well with the form given by Heer.^ The only difference is the
fact that in Heer's plant the pinnules, or reduced pinnae, are opposite.
This may well be the case with the Potomac plant, for the specimens
found belong to the uppermost and variable portions of the frond, which
often differ from the normal forms.

Pecoptekis angustipennis, sp. nov.

Plate XXI, Fig. 10.

Frond and primary pinnae unknown; pinnules, or reduced pinnae,
narrowly linear acute, cut obliquely into oblong or ovate-obtuse lobes or
pinnules; the pinnules or lobes containing each a midnerve, sending off on
each side alternately straight, simple branches.

Locality: Fishing hut above Dutch Gap Canal ; very rare.

1 Flor. Foss. Arc, vol. 6, Pt. II, PI. VII, Fig. 4.

88 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

The true character of this plant can not be made out until more and
better specimens are found. It has some resemblance to Pecopteris ovato-
dentata, and may possibly be tlie same with that fern.

Pecopteris Beowniana, Dunker.

Plate XXII, Figs. 10, U ; Plate XXIII, Figs. 2-7; Plate XXVI, Figs. 3, 13.

Pecopteris Browniana, Diinker, Monograph, PI. "VIII, Fig. 7.

AleUiopleris Bronniana, Scbimper, Traite, III, p. 503.

Pveopitris Brou-niana, Scheuk, Foss. Flor. Nordw. Weald., PI. V, Figs. 2, 2".

AUthopteria Browniana, Scbenk, Foss. Flor. Nordw. Weald., PI. XXVI, Figs. 3-5.

Frond tripinnate, arborescent ; the rachises of different orders are
comparatively stout and rigid; ultimate pinnae short, subopposite or oppo-
site, linear, acute; pinnules varying considerably in different parts of the
frond, usually quite small, in shape oblong-obtuse to subacute; separate at
base in the lower portions of the frond, united slightly in the upper por-
tions, generally separate; in the upper part of the frond the pinnae reduced
to pinnules, either toothed or with entire margins, the former much nar-
rowed at base, forming a sort of petiole.

Localities : Fredericksburg ; Baltimore, among the plants collected by
Meek, and at Covi-ngton street ; red clay ball in the banks of Dutch Gap
Canal; hill-side near Potomac River; 72d 7xiile-post, near Brooke.

This elegant little plant is one of the most widely diffused ferns of the
Potomac formation. It is at the same time quite well preserved in the
specimens found, hence the different parts can be made out pretty well.
It being thus fully represented, some of the specimens differ somewhat
from the European forms of the Wealden. The drawing, PI. XXII, Fig.
11, is from a specimen collected by Mr. Meek. The nerves of this species,
although not strong, are very distinct.

Pecopteris pachyphylla, sp. nov.

Plate XXVI, Figs. 4, 5.

Frond bipinnate or tripinnate ; racliis in pinnae of all orders, com-
paratively stout and rigid; ultimate pinnae in the lower part of the frond
linear, in the upper part oblong-lanceolate; all alternate; pinnules very
small, oblong, very obtuse, subopposite, slightly falcate, united at base to

DESCRIPTION OP THE SPECIES. 89

form awing, with margins undulate or crenate; leaf-substance very thick
and leathery ; nerves composed in each pinnule of a midrib, which extends
to the tip, and sends off alternately on each side into the teeth simple
branches, all sharply defined.

Locality: Fredericksburg; not uncommon.

This little fern, although found only in small fragments, seems to be
very well characterized. It has some of the features of a Thyrsopteris, and
perhaps should be placed in that genus rather than in Pecoj^teris. It is not
closely allied to any described plant known to me.

SPHENOPTERIS, Brongn.

Herbaceous plants, with fronds ranging from pinnate to tripinnatifid ;
jDinnules cuneate or lobed, lobes dentate or subdivided ; primary nerve
slender, towards the summit often bifid or dissolved into branches ; second-
ary nerves diverging towards their extremities, or prolonged into the lobes
or teeth.

This genus is another of the heterogeneous groups which serve to col-
lect together ferns which may belong to quite distinct genera and species,
but which have in common cei'tain features not dependent upon the fructi-
fication, and are not otherwise characterized. The number of ferns of the
8x}henopteris type found in the Potomac flora is small. I place provision-
ally in this genus a small number of forms. There are a number of plants
in the Potomac flora, especially those of the t3'pe of Sphenopteris ManteUi
Brongn., which have predominantly the character of Thyrsopteris. These I
have placed under this latter genus.

Sphenopteeis thyesopteroides, sp. nov.

Plate XXV, Fig. 3 ; Pl.ate LVIII, Fig. 5.

Frond unknown ; rachis of the principal pinnae winged, ultimate pin-
nae opposite or alternate, short, and terminating in incised and lobed seg-
ments with acute tips, broadly winged; pinnules narrowed at the base,
incised into oblong acutely dentate lobes, or cut into oblong acute teeth;
leaf-substance thin ; nerves few and distinct ; nerves in each pinnule com-

90 THE POTOMAC OE YOUNGER MESOZOIO FLORA.

posed of a midnerve, wliich sends off very obliquelj alternate forked or
simple nerves that go into the lobes and teeth. In each segment there
are several nerves, which diverge flabellately into the teeth.

Localities : Fredericksburg ; fishing hut above Dutch Gap Canal ;
rare.

This small plant has a well-mai'ked Sphenopteris facies. It is some-
thing like Sphenopteris Williamsonis Brongu. and also resembles somewhat
S. denticulata Brongn., of the Oolite of England, but seems to be distinct
from both of these and a well marked new species.

Sphenopteris acrodentata, sp. nov.

Plate XXXIV, Fig. 4.

Frond tripinnatifid ; secondar}' pinna; opposite, very short, terminat-
ing in a round-lobed segment which is cnneate at base ; ultimate pinnte or
pinnules subopposite, the lower ones cut obliquely in broadly elliptical
lobes or pinnules nearly down to the midrib, lobes and pinnules narrowed
towards their bases, the upper ones reduced to pinnules which are first
lobed and then simple ; pinnules and lobes at their summits rounded, very
obtuse, and furnished with very minute teeth; nerves of the rounded lower
pinnules and of the lobes, several times forked and diverging flabellately,
the ultimate branches ending in the teeth.

Localities : Fishing hut above Dutch Gap Canal ; Baltimore, on Cov-
ington street ; very rare at both localities.

The specimens figured come from the Dutch Gap locality. The plant
is more common here than at Baltimore. A small fragment only was
found at the latter place.

Sphenopteris latiloba, sp. nov.

Plate XXXV, Figs. 3-5 ; Plate XXXVI, Figs. 4-9 ; Plate XXXVII, Fig. 1.

Frond tripinnate, arborescent; principal rachis very stout; leaf- sub-
stance thick and coriaceous ; primary pinnse opjDOsite, and having a stout,
rigid rachis, which is often somewhat flexuous; ultimate pinnse remotely
placed, very short, passing towards the summit of the principal pinna or
of the frond through lobed pinnules into entire ones ; pinnules remotely

DESCRIPTIOiSr OF THE SPECIES. 91

placed, cuneate at base, those in the lowei' part of the frond cut more or
less deeply into oblong acute to obtuse lobes, passing towards the tips of
the ultimate pinnse into lobed pinnules like those of the upper part of the
frond, and at the tips into ovate or oblong lobes and teeth. In the upper
part of the frond they are elliptical, three lobed, or entire; all the pinnules
and segments are broad. The ultimate pinnae and the pinnules of the
lower part of the frond usually terminate in three lobed segments or in
broad elliptical pinnules. The nerves are copiously branched, diverge
flabellately into the lobes and teeth, and are very distinct and strong.

Localities: Fishing hut above Dutch Gap Canal, rather common;
Fredericksburg ; Deep Bottom ; near Telegraph Station ; at all except the
first rare.

This is the most common fern at the fishing hut above Dutch Gap
Canal, and a number of good specimens were found there, although none
of them are of large size. PI. XXXV, Fig. 4, is somewhat diff"erent from
the normal forms in showing a keeled principal rachis, and in the narrower
segments of the pinnules. It resembles PL XXXVII, Fig. 1, the only
specimen found at Deep Bottom. In PI. XXXVI, Figs. 5-8, are given the
normal forms which are most common at the fishing hut locaKty. None
of the specimens show apparently anything more than fragments of a com-
pound pinna, which, in the case of the stoutest forms, may be a primary
pinna. The rachises of the compound penultimate pinnae are sometimes
swollen at the insertion of the ultimate pinnte. The plant is a very well
characterized one, and can usually be distinguished at a glance. It is one
of the more widely diff"used ferns of the Potomac flora. It is not nearly
allied to any previously described plant known to me.

Sphenopteris Mantelli Brongn.

Plate L, Figs. 1,2.

Frond bipinnate or tripinnate ; primary pinnae in outline ovate-lance-
olate, acuminate ; secondary pinnae alternate, approximate, erect, fasti-
giate ; pinnules alternate and opposite, straight, linear, or linear-cuneate,
at base adnata and decurfent, at the apex acuminate, very entire, the
lower ones often dentate or pinnatifid.

92 THE POTOMAC OR YOUNGER MESOZOIO FLORA.

This is Heer's^ description. To tins he adds that the upper pinnules
have only a midnerve, while the lower ones have from one to three secon-
dary nerves, which detach themselves at a very acute ang-le.

The species S. MantelU seems to be quite polymorphous, and different
authorities on fossil plants have nnited with this species a large number of
plants which vary considerably and come from widely separated regions.
There is quite a large number -of closely allied plants in the Potomac
flora which have more or less of the characters of S. MantelU. These may
be noted as belonging to the type of this species, but it does not seem
advisable to combine them under one species. Most of them have the
chai-acters of Tlujrsopteris, and I have described them as belonging to that
genus. It is a fact worthy of mention that there are in the Potomac flora
several types which resemble described fossils, and under which a number
of allied species may be grouped. Thus we find the type of Splienopteris
MantelU, of Neuroptefis Alhertsii Dunkr., of Pecopteris Broioniana, of Cla-
dopMehis (Pecopteris) Whitbiensis, etc.

In using the name Sphenopteris MantelU., I have i-estricted its applica-
tion to the forms given on PI. L, Figs. 1, 2, which have clearly the char-
acter of the original species. These specimens come from Baltimore, and
are found among the specimens collected by Meek at that place. These
specimens do not have their locality fixed exactly, but it appears probable
that they were obtained from Fe deral Hill near or on Covington street.
The fragments supposed to be S. MantelU have the principal rachis com-
paratively veiy stout, with alternate pinnules, which are cut into narrow
linear incurved lobes and teeth, each having a simple slender nerve.
Among Meek's specimens there is one form given in Fig. 2, which is
smaller than the normal one represented in Fig. 1. In this smaller form
the principal pinnae ai-e opposite, and the lobes of the pinnules much more
minute than in the fossil depicted in Fig 1. Probably this plant, with the
more slender pinnules and lobes, simply represents a different part of the
frond from that given in Fig. 1, and hence the difference in dimensions.
The plant is evidently rare at Baltimore, at least on the horizon of the beds
yielding the specimens found on Belt and Covington streets, for no spec-

' Flor. Foss. (In Portugal, p. 12.

DESCRIPTIOJSr OF THE SPECIES. 93

imens have been found at these locaHties. It is probable that Meek's spec-
imens come from a hig'her level, as the horizon of the Belt and Covington
streets plants is not often exposed, and is shown only in excavations made
near the level of these streets.

Sphenopteeis spatulata, sp. nov.

Plate L, Fig. 4.

Frond unknown ; pinnse small, short, alternate, terminated with a
denticulate segment like the uppermost lobes or pinnules ; pinnules
minute, lower ones spatulate and triple-toothed, upper ones spatulate and
obscurely toothed ; leaf-substance thick and leather3', nerves not seen.

Locality : Entrance to Trent's Reach ; very rare.

The plant is so rare and fragmentary, that its full character can not be
made out. It seems to be a new species, characterized by its thick leaf-
substance and very minute size.

Sphenopteris pachyphylla, sp. nov.

Plate L, Fig. 5.

Frond unknown ; rachis of the penultimate pinnae very thick in pro-
portion to the other dimensions, apparently succulent ; ultimate pinnae or
pinnules very short ; pinnules or lobes broadly elliptical in outline, cut
obliquely into oblong minutely dentate lobes ; leaf-substance thick and
leathery ; nerves not seen.

Locality : Entrance to Trent's Reach ; very rare.

Although this plant is very rare and fragmentary, it differs from all
others known to me in the very thick main rachis and the very small seg-
ments into which the pinnules are cut.

ASPIDIUM, Swartz.

The genus Aspidium seems to be largely represented in the Potomac
flora. The number of species is considerable, and the large number of
individuals belonging to each species seems to indicate that ferns of this
group were among the most common ones. The plants are quite commonly
friTctified, the fructification being often very well preserved. The large

94 THE POTOMAC OR YOUNGER MESOZOIO FLORA.

development of this genus introduces a strong modern element into the
flora, and it is a noteworthy feature that so many well-chai-acterized species
of this genus occur with numerous forms belonging in type to the Jurassic
flora.

The tribe of the Aspidie?e is represented in the Potomac flora by
forms that belong to the generic types of both Asiridium proper and
Didymoclilcena. As with these imperfect specimens the identification can
not be certainly made with the one genus or tlie other, it seems best to
place them all provisionally under the principal genus Asjndnim. It
should be noted, however, that some of these species may belong not to
the tribe of Aspkllece, but to that of the DavaUiece.

AspiDiUM Feedericksburgense, sp. nov.

Plate XI, Figs. 1-6 ; Plate XII, Figs. 1-6 ; Plate XVI, Fig. 9 ; Plate XIX, Figs. 6, 7.

Frond bipinnate or tripinnate, arborescent; rachis of the penultimate
pinnpe very stout and rigid ; pinnre of tlie ultimate order mostly alternate,
rarely opposite or subopposite, with rigid and proportionally rather slen-
der rachises, very long, linear ; pinnules alternate, oblong or ovate, obtuse,
slightly falcate, and usually somewhat rounded and narrowed at the
attachment to the rachis, separate, those of the lower pinnae with crenate
margins, those of the upper ones entire, passing in tlie middle part of
the frond through pinnules with undulate margins; leaf-substance thick
and leathery ; midnerve similar to that of Cladophlehis, that is, strong at
base and dissolving into branches at the summit ; lateral nerves of the cre-
nate and undulate pinnules in groups in each tooth, composed of a mid-
nerve which sends of£ alternate simple branches, or else of forked nerves
with one of the branches forking again ; those of the pinnules with
entire margins usually once forked, all quite distinct; sori very large, reni-
form in shape, and distributed in two rows, one on each side of the mid-
nerve, attached to the summit of the upper branch of a furcate nerve.

Localities : Fredericksburg ; and near Telegraph Station.

This plant is one of the most common ferns at Fredericksburg. All
the specimens figured come from this place, except that in PI. XI, Fig. 1,
which comes from near Telegraph Station, where the plant is not rare.

DESCRIPTION OF THE SPEOIES. 95

Its relative abundance at Fredericksburg may be due to the fitness of the
phmt for preservation, since it has a leathery durable leaf-substance. To
judge from the specimen given in PI. XII, Fig. 1, the plant must have
attained a very large size, for this specimen is probably merely a com-
pound pinna not of primary rank. Fig. 3 of the same plate probably
represents a similar part of the frond, but down lower, where the pinnules
show incipient toothing. Fig. 5 of this plate shows pinnules wider than
usual, with slightly undulate margins. Fig. 6, same plate, probably comes
from the uppermost part of the frond, where the ultimate pinnte are
reduced to lobed pinnules.

The ultimate pinnae of the lower part of the frond, as shown in PI. XL,
Fig. 3, must have been very long. Fig. 6 of the same plate may possibly
belong to a different species, but more probably represents a somewliat
abnormal form coming from high up on the frond. PI. XIX, Fig. 7, gives
opposite ultimate pinnae, a rare occurrence. The sori in this fern are
proportionally very large.

The plant has no close affinity with any described fossil known to me.
It is nearer As])idium Oerstedi^ Heer, than any other.

ASPIDIUM ELLIPTICUM, sp. UOV.
Plate XIII, Figs. 9, 10.

Frond bipinnate or tripinnate, arborescent; rachis of the principal
pinna stout and rigid; ultimate pinn« alternate, short, oblong-lanceolate,
terminating in an elliptical obtuse pinnule or lobe, which is similar to the
pinnules lower down on the pinna; lower pinnules distant, elliptical in
shape, obtuse, attached by the middle of the much narrowed base, or by
the midnerve alone; upper pinnules attached by the entire widened base;
uppermost ones united towards the tip of the pinnae; all very thick and
leathery in texture; lateral nerves not distinct, but apparently simple, and
bearing the sori on their summits; sori pear-shaped or truncate-elliptical,
in two rows, one on each side of the midnerve; sterile forms not seen.

Localities: Hill-side near Potomac Run; bank near Brooke ; rare.

1 Compare Flor. Foss. Arc, vol. 6, part 2, Fos8. Flor. Gronlands, PI. XXXIV.

96 THE POTOMAC OE YOUNGER MESOZOIC FLOEA.

Only the fructified form of this feru was seen. The dehiscence of
the sori seems to be marginal, and there are indications of the escaping
sporangia, as shown in PI. XIII, Fig. 9°, which represents a greatly
enlarged sorus. The plant seems to be a distinct new species.

ASPIDIUM HETEROPHYLLUM, Sp. nOV.
Plate XIV, Figs. 1-5; Plate XV, Figs. 1-5.

Frond tripinnate, arborescent ; rachises of the pinnse of various orders,
strong and rigid; principal pinnse very large, spreading widely; penulti-
mate pinnse alternate, in outline elongate-oblong or elliptical, acuminate,
abruptly and greatly narrowed towards the summit, slightly so towards the
base ; ultimate pinnse linear, acute, quite short, being longest towards
the middle of the penultimate pinna?, at first rapidly shortened towards the
upper part and then gradually giving the acuminate terminations of
the penultimate pinna\ The basal ultimate pinna on the lower side of the
penultimate pinnae is usually abnormally short and broad, being inserted
in the angle made by the junction of the penultimate pinna with the prin-
cipal rachis.

Towards the summit of the penultimate pinnse the ultimate ones pass
through pinna? reduced to toothed pinnules into those which finally
become simple pinnules; pinnules varying according to position on the
frond, usually alternate, short, acute to obtuse, slightly falcate ovate,
attached by a widened base; those from the lower part of the frond with
dentate or undulate margins, those from the middle portions with entire
margins, those from the summit of the pinnse of the various orders united
to form teeth. The basal pinnule on the lower side of the ultimate pinnse,
inserted in the angle between the ultimate and penultimate rachises and
partly on the latter, differs from the normal pinnules in shape and size,
being heteromorphous and larger than the normal one. It is furnished with
a lobe or tooth on the lower side. In the sterile forms the character of the
pinnules and of the nervation is that of CladojMehis. The pinnules have
each a midnerve sending off alternately on each side slender but distinct
lateral nerves, simple or once forked. Fructified forms have the pinnules
mostly obtuse, while those in the sterile portions are acute; the soi'i are

DESCRIPTIOX OF THE SPECIES. 97

placed on the lower portion of the pinnules in a row on each side of the
midnerve, and extend nearly to the summits of the pinnules. They are
reniform, proportionally large, and inserted in the end of the upper branch
of a forking nerve.

Locality: Fredericksbui-g.

This beautiful fern is not very rare at Fredericksburg. It has afforded
the most perfect specimens found of the ferns of the Potomac flora, and a
sufficient number of them has been obtained to give a pretty good idea of
the character of the plant. From the size of some of the specimens we
may conclude that it attained the dimensions of a tree, for all the speci-
mens seem to be fragments of compound pinnae, which were probably not
of primary rank. PI. XIV, Fig. 1, seems to show a portion of the upper
part of a compound pinna, and Fig. 2 to represent a portion of a penultimate
pinna coming from a part of the frond lower than Fig. 1, and hence
larger. Fig. 3 seems to show the summit of a compound pinna like Fig. 1,
and the same may be said of PI. XV, Fig. 2. Portions like PI. XIV, Fig.
5, and PI. XV, Fig. 4, appear to belong to the lower part of the frond,
where the pinnules begin to show division into teeth.

This plant is not very near any described fern. The sterile portion
reminds one of Cladophlehis parva for this part of the fern belongs to
the type of Cladophlehis. The plant is a little like Aspidium Oerstedi Heer,
but caa not be identified with that species.

Aspidium Virginicum, sp. nov.

Plate XV, Fig. 7 ; Plate XXI, Fig. 14.

Frond bipinnate or tripinnate ; arborescent ? ; rachis of the principal
pinna stout and rigid ; pinnae of ultimate order reduced to pinnules in the
terminal portions of the penultimate pinnae, alternate, linear lanceolate,
■passing through pinnately lobed pinnae into pinniiles with entire margins;
leaf-substance thick and leathery ; nerves slender, immersed in the leaf-
substance, and seen with difficulty ; pinnules of the lower pinnae opposite,
separate to the base ; attached by the entire base, elongate oblong, sub-
acute, with denticulate margins ; sterile form of the frond not seen ; sori
comparatively small, reniform, in two rows, one on each side of the mid-

MON XV 7

98 THE roroMA.0 or younger mesozoic flora.

nerve of the pinnules, and placed at the summit of the upper branch of a
forking nerve.

Localities : Road-side near Potomac Run ; 72d mile-post, near
Brooke ; rare.

This fern is somathing like the living species Neplirodimn acutum
Hook, atid has no near affinity with any described fossil. As its sterile
form has not been found, its full character can not be made out.

ASPIDIUM ANGUSTIPINNATUM, sp. nOV.
Plate XVI, Figs. 1,3,8; Plate XVII, Fig. 1 ; Plate XIX, Fig. 10.

Frond bipinnate or tripinnate, arborescent ; in the sterile forms the
principal rachis is stout, straight, and rigid ; the ultimate pinnre alternate,
with a strong stiff rachis, linear-lanceolate, comparatively short ; pinnules
in sterile and fertile forms Pecopteris-like, closely-placed, separate to the
base, opposite, rarely subopposite, linear, slightly falcate; leaf-substance
thick ; sterile leaves in the lower part of the frond denticulate, towards
the summit of the compound ultimate pinnae united and passing into
lobes ; midnerve of sterile and fertile pinnules continuing to the summit
of the pinnules ; lateral nerves of the sterile pinnules of the lower and
middle portions of the penultimate pinnse furcate towards the base of the
pinnules and simple towards their tips ; in the upper pinnules mostly sim-
ple, in the fertile pinnules furcate, and bearing the sori on the end of the
upper branches.

In the fertile forms the principal rachis is comparatively slender, the
ultimate pinnae are opposite and widest towards their middle, and quite
long; the sori are placed on the margin of the pinnules, unlike those of the
preceding species, which have them within the margin. The sori are com-
paratively large, reniform in shape, placed in a row on each side of the
midnerve, and in no case extend to the tips of the pinnules. They diminish
in numbers in passing from the pinnules of the lower part of the ultimate
pinnse to those of the upper portion, and disappear a little beyond the mid-
dle portion of the pinnse.

Localities: Entrance to Trent's Reach; fishing hut above Dutch Grap
Canal; Fredericksburg; hill-side near Potomac Run.

DESOKIPTION OF THE SPECIES. 99

The fine specimens deiDicted in PI. XVII, Fig. 1, and PI. XVI, Fig. 3,
come from the entrance to Trent's Reach. The latter seems to be the
upper part of a compound pinna. The sori are comparatively large.
Nerves occur on all of the pinnules. They are most numerous on the
pinnules near the base of the ultimate pinnaj, and are not present at all on
the pinnules towards the end of these pinnse. A noteworthy feature of
the fructified pinnules is the fact that the basal ones are shorter and smaller
than those towards the middle of the ultimate pinnae. In this feature,
and in tbe opposition of the ultimate pinnse, the fertile form differs from
the sterile one. The plant seems to be not near any described form. It is
more like Aspidium Jenseni Heer, than any other.

ASPIDIUM CYSTOPTEROIDES, Sp. nOV.
Plate XVI, Fig. 2.

Sterile fronds not seen; rachis of ultimate pinnse sleiider; pinnules
alternate, attached by the middle portion of the base, crenately toothed,
obtuse; sori rather large, in two rows, one on each side of the midrib,
placed near the margin, on the summit of the uppermost branch of the
nerves; subglobose in shape, similar to tliose of Cystopteris, with an inflated
indusium at base ; nerves branching palmately in each tooth.

Locality: Fredericksburg.

This pretty fern is very rare at Fredericksburg. It is much like the
genus Cijstopteris of the Aspidece. It does not seem to be nearly allied to
any described fossil.

Aspidium Oeestedi? Heer.

Plate XIS, Fig. 4.
(See Heer, Flor. Foss. Arctica, vol. 6, Part 2, Foss. Flor. Gronlands, p. 30; vol. 7, i). 2.)

Pinnules narrowly linear, acute, with minute teeth directed forwards;
nerves simple, parallel and ending in the teeth.

Locality : Near Telegraph Station.

This plant, although found in only one small fragment, is quite distinct
from all others of the Potomac flora. I unite it with Heer's plant provision-
ally and with doubt, as tlie fragliaent is too small to give the full character

100 THE POTOMAC OR YOUNGER MBSOZOIO FLORA.

of the feni. It may be compared with that shown in Vol. VII of Heer's
work just cited, PI. XLVIII, Fig. 11.

ASPIDIUM OBLONGIFOLIUM, Sp. nOV. 1
Plate XXI, Fig. 5.

Pinnules oblong, slightly falcate, acute, dentate; sori in a row on
each side of the midnerve, on the summits of the single lateral nerves,
round to broadly elliptical in shape, comparatively large.

Locality: Road side near Potomac Run ; very rare.

This is an Aspidium of the Didymochloena type. It may belong to
some of the elsewhere described Potomac forms.

Aspidium parvifolium, sp. nov.

Plate XXI, Fig. 6 ; Plate XXIV, Fig. 8 ; Plate XXV, Fig. 10; Plate XXVI, Figs. 1, 14, 16, 17.

.Frond bipinnate to tripinnate; ultimate pinnse alternate; pinnules, or
reduced pinnse alternate to opposite, in the sterile portions small, o])long-
lanceolate, acute, with winged rachises, pinnules or reduced pinnse of the
lower pinnfe cut into ovate small lobes, the lowest ones being minutely
toothed, the upper pinnules also minutely toothed ; nerves of the lowest
lobes or teeth composed of a midrib, which sends off on each side, alter-
nately, simple nerves; in the upper lobes and teeth they are furcate; leaf-
substance thin, and usually decurrent ; in the fertile portions the pinnules
or reduced pinnse are ovate-oblong, obtuse, with ovate-acute lobes, the two
lower being slightly dentate ; nerves in the lower lobes simple, and alter-
nately given off on each side of a slender midrib, those in the middle and
upper lobes several times or simply forked ; in the sterile forms the basal
upper lobe of the pinnules or reduced pinnse usually larger than the others
and directed upwards parallel with the penultimate rachis ; sori subglobose
in the two basal lobes and situated on the summit of the midrib and of all
the lateral nerves, but in the higher lobes mostly single in each lobe, and
placed on the summit of the upper branch of the lateral nerves.

Localities: Fredericksburg; red clay ball in the banks of the Dutch
Grap Canal ; fishing hut above this canal ; rather rare at all places.

This is an Aspidium of the Polystichum type. It does not seem to
be near any described plant.

DESCRIPTION OF THE SPECIES. 101

ASPIDIUM PINNATIFIDUM, Sp. DOV.
Plate XXI, Fig. 15.

Frond unknown; probably bipinnatitid; reduced pinnge or pinnules,
linear, cut pinnately nearly to the rachis into ovate-falcate obtuse lobes or
pinnules; leaf-substance thick and leathery; sori in a row on each side of
the midrib, elliptical in shape and small, placed on the simple lateral
nerves within the margin of the lobes.

Locality : Bank near Brooke ; very rare.

This is another of the Aspidiese of the Didymochloena type. It is not
nearly like any described fossil.

AsPiDiUM DuNKEEi Schimper, sp.

Plate XXII, Fig. 9; Plate XXV, Figs. 11, 12; Plate XXVI, Figs. 2, 8, 9, 18; Plate LIV, Figs. 3, 9.

Pecopteris Dunlieri, Schimper, Traitfe, vol. I, p. 539.

Pecopteris 2>olymorplia, Duuker, Mou., PI. VII, Fig. 5.

Pecopteris Uiigeri, Dunker, Mon., PI. IX, Fig. 10.

Pecopteris Dttnkeri, Schenk, Foss. Flor., PI. V, Figs. 1", l''; PI. X, Fig. 1.

Frond bipinnate or tripinnate, arborescent; principal rachis stout and
rigid; ultimate pinnse alternate, short, linear-lanceolate; pinnules alternate
or subopposite, short, closely placed, narrowed at the base, cut more or less
deeply into lobes or teeth which are ovate or oblong, obtuse or subacute,
very small, those of the fertile portions of the frond standing nearly per-
pendicular to the rachis and having in each lobe or pinnnle a simple
lateral nerve which bears a sorus on its summit, those of the sterile and
more common portions more obliquely placed, mostly subacute, with
nerves in each lobe that fork sim^^ly in the upper ones, and in the lower
ones are composed of a midnerve with alternate simple branches; leaf-
substance thick ; sori very minute, club-shaped or elliptical, visible dis-
tinctly only with the help of a lens, and present only in the pinnules of
the lower part of the pinnse, and mostly found on the lobes towards the
base of these.

Localities : Near Telegraph Station ; red clay ball in the banks of
Dutch Gap Canal; Fredericksburg; entrance to Trent's Reach; fishing
hut above Dutch Gap Canal; rather rare at all localities.

102 THE POTOMAC C)E YOUNGEE MESOZOIG FLOEA.

This very finely cut fern is found most abundantly at tlie fishing hut
above Dutch Grap Canal, but is not very common even there. The sori
are so small and the fertile pinnules so leathery that they can be seen
only when the lower surface is uppermost. In PI. XXII, Fig. 9% is given
a magnified pinnule with its lower surface uppermost; in Fig. 9^ a similar
pinnule with its upper surface uppermost, and showing no sign of sori.
This latter is the common aspect of the plant. This may explain why the
sori were not seen by Dunker and Schenk. It seems to be certainly
Dunker's species. The lobes in most of the specimens seem to be more
closely placed than in Banker's plant. It is one of the most widely
diffused ferns of the Potomac flora.

ASPIDIUM DENTATUM, sp. UOV.
Plate XXV, Figs. 6, 7, 14, 15.

Frond tripinnate ; principal rachis comparatively stout and rigid; ulti-
mate pinnse alternate, very short, linear-lanceolate ; pinnules membrana-
ceous, alternate, lower ones separate to the base, upper ones united and
reduced to lobes ; lower pinnules broadly ovate, acute, narrowed to the
base, and subpetiolate, cut nearly to the midnerve into ovate, acute teeth,
reduced in the upper part of the compound pinnte to ovate, obtuse lobes
and teeth ; sori very small, subreniform or globose, placed within the mar-
gin on the summit of the alternate simple lateral nerves ; nerves in each
of the pinnules and lobes, composed of a midnerve, with simple alternate
lateral ones on each side; in the uppermost lobes. the nerves become one
or more times forked, without a midnerve.

Localities: Red clay ball in banks of Dutch Gap Canal; hill-side near
Potomac Run; near Telegraph Station; rare in most of the locahties.

This pretty little plant is rather abundant at the locality on the hill-
side near Potomac Run. Forms such as Fig. 15 are quite common here,
but as a rule show no fructification. The fructified specimen, Fig. 14, was
found in the red clay ball in the banks of Dutch Gap Canal. Fig. 15 is a
good deal like the smaller forms of Thyrsopteris Murray ana (Brongn. sp.)
Heer, but is no doubt a distinct species.

DESCEIPTION OF THE SPECIES. 103

ASPIDIUM MACEOCARPUM, Sp. nOV.
Plate XVII, Fig. 2.

Sterile frond not seen; fertile frond showing only a skeleton imprint ;
principal rachis stout and rigid ; plant most probably arborescent ; rachis
of the ultimate pinnpe stout and rigid ; shape and dimensions of the pin-
nules not disclosed; apparently large, elongate-oblong, attached by the
entire base, alternate ; midnerve rather slender, straight ; lateral nerves
simple, and bearing at their summits the sori arranged in a row on each
side of the midrib. The sori are very large, reniform in sliape, and seem
to have been situated near the margin of the pinnules. Under a good lens
the sporangia may be seen arranged often in a band near the margin of
the sori.

Locality: Red clay ball in the banks of Dutch Grap Canal; rare.

This plant seems to have been a fine large fern. It is seen only as an
imprint on the surface of the fine clay, giving a skeleton of the more dura-
ble parts. The imprints of the sori are very distinct. The sterile form was
not seen. This seems to be a species distinct from all described ones.

ASPIDIUM MICEOCARPUM, Sp. nOV.
Plate LIX, Figs. 2, 12 ; Plate LX, Figs. 6, 7.

Frond tripinnate; sterile forms have the pinna? of ultimate order
short, subopposite, with pinnules towards the base separate and rather
remote, slightly decurrent, obtuse, oblong and subopposite, but towards the
tips graduating into lobes and teeth which are ovate-obtuse ; leaf-sub-
stance thick ; lateral nerves in each pinnule or lobe composed of a mid-
nerve, which-on each side sends off alternately branches which fork or are
simple. Fertile portions of the frond have sometimes sterile and fructified
pinnules on the same pinna, but usually the fructified pinnules are on
distinct parts of the frond, and then the specimens found show only the
skeletons of the sori and nerves, the sori by their arrangement giving the
outlines of the pinnules ; sori very minute, visible distinctly only with the
help of a strong lens ; rounded in shape, and arranged in a row on each
side of the midnerve, placed at the summit of a simple lateral nerve.

104 THE POTOMAC OR YOUNGER MESOZOIO FLORA.

They extend from the base to the summit of the pinnules. The arrange-
ment of the sori indicates that the fructified pinnules in the lower pinn.ie
are toothed or lobed, and that towards the summit of the compound pinnaj
they graduate into lobes and teeth.

Locahty: Hill-side near Potomac Run ; very abundant.

The fructified forms are the common ones, sterile forms are very rare.
Numerous specimens, such as are depicted in PI. LIX, Fig. 12, and PL
LX, Fig. 7, and smaller ones, jnay be found here, the pinnules being
reduced to imprints of the sori and principal nerves. The plant seems to
be a very well marked new species.

POLYPODIUM, L.

The genus Polypodium, if it exists in the Potomac flora, is not repre-
sented by many species. The imperfect preservation of the specimens
does not permit the certain determination of the genus, but there are two
species which agree better with this genus than any other, and for this
reason I place them provisionally in it.

Polypodium fadyenioide, sp. nov.

Plate XVI, Figs. 4, 5.

Pinnules narrow and linear, obtuse; fragments of the fertile ones
alone were seen ; leaf-substance very thick and leathery ; sori very large,
globose in shape, placed on the ends of strong simple lateral nerves,
which are at their summits expanded into club-shaped receptacles arranged
in a row on each side of the midnerve of the pinnules, a little within the
margin, and extending nearly from the midnerve to the margin.

Locality : Road-side near Potomac Run ; very rare.

The pinnules of this plant seem to have been narrow and long, very
thick and leathery. The club-shaped summits of the nerves which sup-
ported the sori appear, when the upper surface of the pinnules is presented
upwards, showing through the leaf-substance as elliptical elevations, look-
ing like sori, as shown in Fig. 5. Figure 4 represents, slightly enlarged, a
fragment of a much longer pinnule with the lower side uppermost, showing
the character of the very large sori. A granulation is seen with the help

DESCRIPTION OF THE SPECIES. 105

ot a lens over the surface of the sori, as if caused by the sporangia. No
indusium appears.

This fossil is a good deal like the living Fadyenia itroUfera, and the
specific name is chosen from this resemblance. It is a little like Nathorstia
angustifolia Heer/ but is distinct from that plant.

POLYPODIUM DENTATUM, Sp. nOV.
Plate XXir, Figs. 4, 5.

Frond bipinnatifid; pinnae in the sterile forms of ultimate order, or
pinnules linear-elongate, cut more or less deeply into broad, ovate, slightly
falcate, acute lobes or pinnules; midnerve of the pinnse strong and rigid;
nerves of the lobes or pinnse composed of a nerve-bundle formed by a
parent nerve which goes off obliquely and curves outward towards the
outer edge of the lobes, sending off branches only from the upper side;
the branches curved strongl}^ outward, and each twice forked, except the
upper one, which is once forked; fertile pinna? or pinnules serrate,
narrowly linear; nerve-bundles in each tooth branching and diverging
flabellately from the insertion, the lower branch forking several times, the
upper one simple and directed obliquely upwards, bearing on its summit
in each tooth an obovate sorus.

Locality: Fredericksburg; very rare.

This seems to be a very distinct species. The lens shows a granula-
tion over the surface of the club-shaped sori which seems to be caused by

the sporangia.

ACROSTICHUM, L.

The genus Acrosticlmm seems to be represented in the Potomac flora
by the small fragment described below. It also has near allies in the new
genus Acrostichopteris, so abundant at Baltimore.

ACROSTICHUM CRASSIFOTJUM, sp. nov.
Plate XVI, Fig. 7.

Frond and pinnpe not seen ; pinnules very obtuse, thick and leathery
in texture; nerves not seen distinctly; sori small, in three double rows,
each row separated from its fellow by a pretty distinct line, which is

■Flor. Foss. Arc, vol. 6, part 1, No. 2, PI. I, Figs. 1-6.

106 THE POTOMAC OE YOUNGBli MESOZOIC FLOEA.

apparently a nerve. The entire under surface of the pinnule is covered
by the sori.

Locality: Fredericksburg.

Only a small frao-meiit of this curious fern was found, and conse-
quently little can be made out as to its true nature. It seems to be quite
different from all previously described fossils.

ACROSTICHOPTERIS, gen. nov.

Fronds probably creeping, with veiy long, often tlexuous rachises,
which seem to have been more or less succulent; pinnae going off obliquely,
long and apparently slender; ultimate pinnae or pinnules subopposite to
alternate, comparatively short, and cut down nearly to the rachis into more
or less cuneate-flabellate pinnules or primary segments. These are divided
generally into cuneate-flabellate segments, which in turn are separated
into oblong segments ending in oblong, or ovate-obtuse, or acute teeth;
pinnules decurrent and forming a wing; nerves slender but distinct,
flabellately diverging, forking dichotomously, and ending in the teeth;
fructification occurring on the basal segments of the pinnules, in the upper
portions of the frond on the upper one alone, in the lower portions on
the upper and lower ones, the fructified segments close appressed to the
principal rachis. The fructified segments are so modified as to take the
form of leathery, rounded, or elliptical segments, which on the lower side
are covered by the naked sori, and seen frooi the upper side, especially
when compressed on the clay, look like pods.

This curious genus of ferns seems to be of a composite character
The sterile forms look so much like Baieropsis that before the fructified
forms were found, which occur only at Baltimore, they were taken to be
small forms of that genus.

The genus in the naked sori is like Polypod'mm, but in most features
stands nearest to Acrostichum, much resembling tlie section Bhipidopicris.
In this latter, however, the fructification is borne on separate pinnules. If
we place the fructified pinnules of Bhipidopteris as basal segments on the
sterile ones, we have a form strikingly like Acrosticliopteris. This genus
has also some resemblance to Marsilea.

DESCEIPTION OP THE SPECIES. 107

ACROSTICHOPTERIS LONGIPENNIS, sp. nov.
Plate CLXX, Fig. 10 ; Plate CLXXl, Figs. 1, 5, 7.

Fronds with very long-, more or less flexuous pinnse, apparently creep-
ing; ultimate pinnae or pinnules subopposite to alternate, going off at a
large angle and arching slightly away from the principal rachis, ending in
one or two oblong lobes which have oblong blunt teeth. At base they are
cut into pinnules or segments which are cuneate, fan-shaped, and these in
turn are cut into oblong segments, which end in oblong or ovate-subacute
teeth; the pinnules or segments, in ascending from the base of the ultimate
pinnae towards their summits, diminish in the number of segments; nerves
slender but distinct, flabellately diverging and forking dichotomously, the
ultimate branches ending in the teeth; fructification as in the genus, and
occurring On the basal upper lobe in the upper part of the frond. In the
lower parts of the same they are found on the upper and lower basal lobes;
the fructified lobes rounded or elliptical, and close appressed to the prin-
cipal rachis.

Localities: Abundant at Belt and Covington streets, Baltimore; most
common at the first-named locality.

PI. CLXXI, Fig. 1, seems to represent a sterile form. This comes
from Belt street. Figure 7 of the same plate has both of the basal lobes
fructified. This comes from Covington street. Figure 5 of the same
plate has only the fructified lobes retained on the piincipal rachis.

ACEOSTIOHOPTERIS DENSIFOLIA, Sp. nOV.
Plate XCIV, Fig. 4; Plate CLXX, Fig. 11; Pliite CLXXI, Figs. 2, 6; Plate CLXXII, Fig. 13.

Principal rachis slender ; ultimate pinna3 or pinnules densely crowded,
often overlapping, very broad in proportion to their length, lower ones
sometimes abnormally short and wide as compared with those higher up,
being broad, fan-shaped in outline; primary segments or pinnules dimin-
ishing towards the ends of the ultimate pinnae in the number of segments ;
lower pinnules or segments cut into two or three main lobes, narrowly
oblong or ovate, ending in minute teeth; nerves as in generic description;
fructification on the lower basal lobe or on both; fructified lobes elliptical
in shape and proportionally very large.

108 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

Localities : It is common on both Belt and Covington streets, Balti-
more, and is rare at the fishing hnt above Dutch Gap Canal.

Only the sterile form, PI. XCIV, Fig. 4, was found at the last-named
locality. Fructified forms are the most common ones at Baltimore, and
the same is true of the preceding species, A. longipennis.

ACROSTICHOPTERIS PAEVIPOLIA, Sp. nOV.
Pl.ate XCn^ Figs. 5, 9, 10, 12 ; Plate CLXXI, Figs. 3, 4 ; PUite CLXXII, Fig. 14.

Principal rachis comparatively very stout and rigid ; ultimate pinnae
or pinnules short, remote, small ; pinnules or segments of the first order
cut normally into two lateral lobes and one terminal one, the latter largest,
minute ; the principal lobes diverge flabellately, each being cut normally
into two oblong lobes, which end either in very short acute triangular teeth,
or in oblong or ovate-obtuse to acute ones ; nerves forking dichotomously,
flabellately diverging, the ultimate branches ending in the teeth.

Localities : Belt and Covington sti-eets, Baltimore ; although rare there,
the most abundant species of the genus at the fishing hut above Dutch
Gap Canal ; rare at the entrance to Trent's Reach.

ACROSTICHOPTERIS PARCELOBATA, sp. nOV.
Plate XCIV, Figs. 6, 7, 11, 14.

Ultimate pinn-ae or pinnules very sliort, terminating in a three-lobed
segment or pinnule ; principal segments or pinnules rapidly diminishing in
ascending in the number of segments or lobes ; the lowest pinnules or
principal segments narrow and cuneate at base, as are all, mostly cut
deeply into two unequal lobes, the vipper ones being the smaller, both sub-
divided one or more times into strap-shaped lacinite, whicli end in nar-
rowly oblong obtuse teeth; nerves forking repeatedly in a dicliotomous
manner, so that the ultimate branches end in the teeth; fructified forms not
seen.

Localities: Fishing hut above Dutch Gap Canal; road-side near Poto-
mac Run ; rare.

The one shown in Fig. 11 from the Dutch Gap locality differs some-
what from that in Fig. 6 from the same locality and from that in Fig. 7

DESCfilPTION OP THE SPECIES. 109

from near Potomac Run, but the difference is not sufficient to separate
them. Figure 14 gives, magnified, a complete leaf corresponding to those
of Fig. 7, but more complete than any found on that specimen.

ACROSTICHOPTERIS CYC'LOPTEEOIDES, Sp. nOV.
Plate XCIV, Fig. 8.

Pinnules rounded, fan- shaped, cyclopteris-like in form, divided to the
base into three principal laciniee, which in turn are subdivided at different
distances from the base into subordinate lobes ; lacinise all oblong, diverg-
ing flabellately, the principal ones cuneate at base; they end in obtuse
oblong teeth, which are quite narrow ; nerves obscure, but, as in the gen-
eric description, dividing repeatedly in a dichotomous manner from the
base and diverging flabellately, so that the ultimate branches end in the
teeth; fertile forms not seen.

Locality : Fishing hut above Dutch Gap Canal ; rare.

Several specimens of this plant were found, but they appear only in
the form of detached pinnules, one of the largest of which I have figured.
It has a small bit of the rachis still attached. This i^lant shows a number
of detached pinnules lying as if they had fallen from the same plant. It
is more like Baieropsis than any of the species of Acro€tichopteris^ and in its
fragmentary state, with fructification not shown, it may belong to that
genus of conifers.

ASPLENIUM L."

The genus Asplenium found by Heer so abundant in the Jurassic flora
of Siberia is not determined positively in the Potomac flora. The species
described below — A. duhium — quite possibly may belong to the tribe of
the Aspidiece, being found in the section with oblong sori as in Fadyenia.

Asplenium dubium, sp. nov.

Plate X, Fig. 9.

Frond bipinnate or tripinnate ; pinnules oblong, subacute, separate to
the base, alternate, nearly at right angles with the rachis ; nerves furcate,
bearing the sori on the end of the upper branch, sori elliptical, in a row

110 THE POTOMAC OR YOUNGER MESOZOIO FLORA.

on eacli side of the miduerve, and not extending to the tips of the pin-
nules.

Locality : Fredericksburg ; only one specimen found.

This plant is in too fragnientary a condition to make out its true char-
acter. The shape of the pinnules is something like that of those of Bun-
ker's JSfeitroptens Alhertsii. The plant 4s quite near to Asplenium argiitulum
Heer.i

THINNFELDIA Ett. (ex parte).

Fronds bipinnate or tripinnate ; pinnules varying much in size and
shape, mostly oblong-, ovate-lanceolate, or oblong-obovate, (iecurrent and
mostly confluent at base, coriaceous; primary nerve of the pinnules dis-
solved before attaining the apex into many dichotomous nerves ; secondary
nerves going off at a very acute angle, diverging in ascending, several
times dichotomous.

The description given above for the genus is very nearly that given
by Schimper. There are several species of ferns in the Potomac flora
which would come under the group having these characters. The plants,
however, are not common, except at the 7"2d mile-post, near Brooke, where
Thinnfeldia variabilis is the most common fern.

Thinnfeldia Variabilis, sp. nov.

Plate XVII, Figs. 3-7; Plate XVIII, Figs. 1-6.

Frond bipinnate or tripinnate ; rachises of the pinnsB stout, arbores-
cent ; pinnules lobed or toothed, with mostly ovate-obtuse lobes or teeth,
short, varying much in size and nature according to position on the frond,
passing in ascending, in the upper part of the pinnae, through toothed and
undulate pinnules into entire ones ; lower pinnules attached by the rachis
alone, and deeply cut into broadly ovate-obtuse lobes ; up higher in the
pinnae and on the frond they have ovate teeth and are attached by the
middle of the much-narrowed base, and are slightly decurrent ; towards
the- top the ultimate pinnae pass into crenately lobed segments and these
into lobed and toothed pinnules, like those lower down ; all are acute ;

iFlor. Foss. Arc, vol. 4, pt. 2, Beitrage zur Flor. Ostsib., PI. Ill, Fig. 7 ; PI. XIX, Figs. 1-4.

DESCEIPTION OF THE SPECIES. 1 1 1

leaf-substance thick and leathery ; midnerve neurojDteris-like, and vanish-
ing before attaining the apex of the pinnules; lateral nerves occur in the
lower portions of the pinnules mostly in nerve groups ; all go off very
obliquely and fork usually several times, very fine and closely placed, but
distinct.

Localities : 72d mile-post, near Brooke, common, and the most abun-
dant fern; road-side near Potomac Run; rare.

All the specimens figured, except that in PI. XVIII, Fig. 6, come from
the 72d mile-post, near Brooke. Strange to say, while the plant is abun-
dant at the 72d mile-post, not a trace of it can be seen at the "bank" near by,
This is a striking illustration of the localization of the species in this flora.

Taken as a whole 'this Thinnfeldia is unlike any described fossil.

Some of the pinnules in shape remind one of T. rhomloidalis Ett., given

by Schenk.^

Thinnfeldia geanulata, sp. nov.

Plate XXVI, Figs. 10-12; Plate XXVII, Figs. 1-5, 8; Plate CLXIX, Fig. 1.

Frond bipinnate or tripinnate ; rachises comparatively stout ; leaf-
substance thick; pinnules varying in size and shape with their position on
tlie pinnge and frond ; in shape they are ovate-elliptical to subrhombic, the
lower ones irregularly cut into oblong to elliptical lobes ; the lower surface
of the pinnules has a very fine granulation between the nerves, Avhich can
be seen distinctly only by the help of a lens ; nerves closely placed, very
fine but distinct on the under surface of the pinnules, repeatedly branching
and diverging flabellately.

Localities : Fishing hut above Dutch Gap Canal, and road-side near
Potomac Run ; rare.

The plant occurs more commonly at the former locality, where several
specimens were found. It is very rare at the locality near Potomac Run.

Thinnfeldia rotundiloba, sp. nov.

Plate XXVII, Figs. 6, 7.

Frond bipinnate or tripinnate ; principal rachis rather stout; pinnules
with thick texture, alternate, broadly ovate in outline, obtuse, cut more or

'Foss. Flur. der Greuzschicliten, PI. XXVII, Figs. 4, 5.

112 THE POTOMAC OE YOUJSTOBE MESOZOIG FLOEA.

less deeply into subrhombic or broadly elliptical and rounded lobes ;
nerves numerous, closely placed, slender but distinct, repeatedly branching
in the lower lobes, and diverging flabellately ; midnerve in the terminal
lobe dissolving in branches some distance below the summit, and in its
lower portion sending off very obliquely nerve bundles or branches which
fork one or more times.

Localities : Fredericksburg ; road-side near Potomac Run ; very rare.

This plant in some of its forms is something like T. granulata, but it
shows none of the granulations and the pinnules are more obtuse.

Stenopteris Saporta.

Frond large, bipinnatifid ; rachis slender and narrowly winged ;
pinnse subopposite ; segments of the pinnae long, linear, bluntly termi-
nated, showing the same width and structure as the parts to which they
are attached; that is, a slender, narrowly winged midnerve, segments some-
times forked at their tips. This descripti:tu given by Schimper^ agrees
well with one of the Potomac species, and for this reason I place it pro-
visionally in Saporta's genus.

Stenopteris Virginica, sp. nov.

Plate XXI, Fig. 8.

Frond unknown ; lobes of the pinnules or pinnge of ultimate order,
forking at the ends or simple ; pinnules and lobes coriaceous, strap-shaped,
subacute, having a single slender nerve.

Locality: 72d mile-post, near Brooke; rare.

This plant agrees with Saporta's genus Stenopteris, which contains, as
far as certainly made out, only the single species S. desmomera. The
description, however, which makes the midnerve narrowly winged does not
apply, as the laminae on each side of that nerve in the Potomac plant are
comparatively wide. Only a single specimen was found at the Brooke
locality.

' Zittel's Handbuch tier Palseontologie, vol. 2, i>. 111.

DESCEIPTIOH OF THE SPECIES. 113

Angiopteridium, Schimper.

Frond simply pinnate ; pinnules long, linear, more or less narrowed
towards their ends, rounded at the base or nearly heart-shaped, attached
to the principal rachis by the midnerve alone, which sometimes forms a
disarticulating short pedicel; midnerve strong, lateral nerves going off
obliquely and abruptly, taking a horizontal position or bent somewhat
obliquely upwards, simple and forked.

This description given by Schimper^ agrees exactly with a number of
species found in the Potomac flora. Angiopteridimn is a characteristic
Jurassic type, and the number of species of this genus occurring in the
Potomac flora adds decidedly to the Jurassic element otherwise so strongly
represented in this flora.

Angioptekidium auriculatum, sp. nov.

Plate VII, Figs. 8-11;. Plate XXVIII, Fig. 1.

Frond pinnate ; pinnules thick and leathery, long linear, subacute,
remotely placed, free to the base, auriculate at base, attached by the mid-
rib alone ; auricles of the' bases of the pinnules overlapping the upper sur-
face more or less ; midrib of pinnules rather stout and rigid; lateral nerves
often obscurely shown, fasciculate or bifurcate, and towards the tips simply
forked.

Localities: Fredericksburg; road-side near Potomac Run ; rare.

The plant is rare at each locality, but is most common at Fredericks
burg. It is something like Pteris longipennis Heer,^ but there is no reason
to think that it is a Pteris. It resembles Pecopteris salicifoUa,^ Oldham and
Morris. The forms figured in Figs. 8, 9, '11 occur at Fredericksburg;
Fig. 1 0 occurs at the locality near Potomac Run. This is different from
the others in the great length of the pinnules and in the fasciculate nerves,
which are bifurcate, with the branches again forking near their tips. The
nerves are obscure on the upper surface of the pinnules. The main rachis
is stout and keeled on the under surface, as is shown in Fig. 9. On the

' Zittel's Hand-book, vol. 2, p. 134.

^Foss. Flor. Arc, toI. 6, pt. 2, PI. X, Figs. 5-13.

'Foss. Flora of the Rajmahal series, PI. XXVII, Fig. 2.

MON XV 8

114 THE POTOMAC OR YOUNGER MESOZOIO FLORA.

upper surface the auricles at the base of the pinnules overlap more or less
the sui'face of the main rachis.

Angiopteridium nervosum, sp. nov.

Plate XXIX, Fig. 2.

Frond unknown ; pinnules seen only in fragments, but apparently
long, 3.5"'" wide; midnerve comparatively very slender; leaf-substance
comparatively thin; lateral nerves slender but distinct, going off at an
angle of over 45", arched backwards slightly for a short distance from tlie
midrib, and then inclined forward towards the tip of the pinnules ; simple
or forking at various distances between the midrib and margin.

Locality: Fredericksburg; rare.

This plant was found in only a few small fragments. The nerves on
the right-hand half of the figure are distorted by pressure. They are
shown in their normal position in the left-hand half It is something like
Tceniopteris Stenoneura Schenk,' and also Tceniopteris tenuinervis Brauns,
as given in Figs. 3, 4, of the same plate, but it is larger than either, and
has the nei'ves more dichotomous than the last. It is also a little like
Tceniopteris vittata Brongn. It has nearly the nervation of Angiopteridium
McClellandi of the Indian flora.

Angiopteridium ellipticum, sp. nov.

Plate XXIX, Fig. 3.

Frond unknown ; pinnules elliptical, length, 37°"", maximum width
15°"°; leaf-substance membranaceous; midnerve comparatively very stout ;
lateral nerves slender but very distinct, going off at an acute angle and
then obliquely ascending to the margin, mostly forked at or near the base,
branches simple and nearly parallel.

Locality: Fredericksburg; only one specimen found.

This is a very distinct but unusually small plant. It seems to be
nearer to Stangerites ensis Oldham and Morris, than any other. This has
been made an Angiopterklium by Schimper. Possibly this ma}^ be a young
leaf of some of the species described under another name in the Potomac
flora.

'Foss. Flor. der Grenzschiohten, PI. XXV, Fig. 5.

DESOEIPTION OP THE SPECIES. 115

Angiopteeidium densinerve, sp. nov.

Plate XXIX, Fig. 4.

Only a small fragment, of a pinnule seen ; midnerve slender ; lateral
nerves slender, closely placed, going off at an acute angle and maintaining
the same direction to the margin, nearly parallel, forked at the base or
above.

Locality : Fredericksburg.

Only one fragment was found, but this seems to indicate a well-
marked species.

Angiopteeidium pachyphyllum, sp. nov.

Plate XXIX, Fig. 5.

Frond unknown ; pinnules apparently long and proportionally quite
narrow ; midrib stout and prominent ; leaf-substance thick, shining, and
leathery, hiding the lateral nerves on the upper side.

Locality : Fredericksburg.

Only a fragment of a pinnule was found, so that its length could not
be made out. The specimen probably presents the upper surface of the
leaf uppermost.

Angiopteeidium ovatum, sp. nov.

Plate XXIX, Figs. 6, 7.

Frond unknown ; pinnules ovate, broad and rounded at base, truncate
and serrately toothed at the tip; maximum width, 36"""; length, 8'^'";
midnerve stout at base and split up into branches at the summit ; leaf-
substance membranaceous ; lateral nerves slender but very sharply defined,
remote, going off at an acute angle, arched backward near the base and
forward higher up, forked near the base or above, branches slightly di-
verging, mostly simple, very rarely forked near the margin.

Locality : Fredericksburg.

This is a very rare plant, but a distinctly defined one. The two
specimens figured were so placed as to indicate that they belonged to the
same pinnule, Fig. 7, representing the tip, corresponding to Fig\ 6.

116 THE POTOMAC OE TOUNGEE MBSOZOIC FLOEA.

This plant is luore like Macrotcenioptcris ovata Schimper, Tceniopteris
ovalis Oldham and Morris, from Bindrabun, India, than any other described
fossil. The apparent stipe in the plant of Oldham and Morris seems to
be simply a portion of the midnerve stripped of the lamina of the pinnule.

Angiopteridium strictinerve, sp. nov.

Plate XXIX, Figs. 8, 9.

Frond pinnate ; principal rachis stout and rigid ; pinnules elongate-
lanceolate ; midnerves strong, rounded, and prominent ; leaf- substance
thick ; lateral nerves closely placed, forked mostly at their insertion,
rarely higher up, sometimes simple, branches simple and parallel, arched
near the base strongly backward and above curved slightly forward, thin
but distinct.

Locality : Fredericksburg ; rare.

Although rare, this is the most common species of the genus at
Fredericksburg. In the shape of the pinnules and in the course of the
lateral nerves it is something like Oleandridium ienuinerve Schimper,
Tceuiopteris tenuinervis Brauns, as figured by Schenk,^ but that is a simple
frond.

Angiopteeidium strictinerve, var. latipolium. sp. nov.

Plate XXX, Figs. 1, 5.

Frond unknown; pinnules larger than in the normal A. strictinerve,
in some cases, as in Fig. 5, attaining the width of 44°""; midrib com-
paratively stout ; lateral nerves fine but distinct and sharply defined, often
simple, forking at the base or higher up, branches simple and parallel,
arched backward in the lower portion of the lateral nerves and then
inclined forward.

Locality: Fredericksburg; rare.

This plant is in some points similar to Angiopteridium nervosum,
described elsewhere, but the nerves are finer and more closely placed. In
Fig. 1 there are two fragments of pinnules so placed as to indicate that
they belong to the same frond, coining off pinnately from a common
rachis.

' Foss. Flor. der Grenzschicliten., PI. XXV, Fig. 3.

DESCEIPTION OP THE SPECIES. 117

Angiopteeidium dentatum, sp. nov.

Plate XXX, Figs. 6, 7.

Frond pinnate ; leaf-substance thin ; pinnules oblong-ovate, abruptly
narrowed at tlieir tips, margins finely serrate, sometinaes with double teeth;
midnerves strong towards their bases and attenuate towards their suramits,
and near the apex splitting up into branches ; lateral nerves going off at a
very oblique angle and curving out to meet the margin, simply forked or
several times forking, slender but distinct.

Locality : Fredericksburg ; rare.

This plant in the general shape of the pinnules and the nervation is
much like the Neuropterids of the Carboniferous era, and is peculiar in
the fine toothing of the margin. I place it provisionally in the genus
Angiopteridntm, but possibly this and A. ovatnm should be made a new genus.
This plant seems to be a type between Thinnfeldia and Angiopteridium.

ASPLENIOPTERIS, gen. nov.

Frond bipiunate or tripinnatifid; pinnules linear-lanceolate, or oblong,
acute to obtuse, lobed or toothed, sori proportionally very large, elongate
to narrowly elliptical, in a row on each side of the midrib, one in each lobe
or tooth, inserted on thick supports or segments, which represent the trans-
formed segments or lobes, placed on the anterior margin of these, and run-
ning down nearly their entire length. Type, Aspleniopteris pinnatifida.

This curious type of fern difi'ers in some respects from all described
fossils. The most noteworthy feature is the contraction of the lobes or
teeth of the pinnules into thick leathery supports which bear the long nar-
row sori on their anterior margins, the general shape and position of the
sori resembling those features in Aspleniiim. Aspleniopteris pinnatifida may
be taken as the type, that being pretty fully represented in the parts found.
The genus may be compared with Bichsonia clavipes, Heer,-^ but, unlike
that plant, the sori are long, naiTow, and not borne always on the summit
of the modified lobes. The genus seems to be a composite type, uniting
the features of Pteris, Aspleiiiuin, and Osmimda, resembling the latter in

> Flor. Foss. Arc, vol. 4, pt. 2, PI. II, Fig. 7.

118 THE rOTOMAG OR YOUNGER MESO^OIO FLORA.

the reduction of the lobes to mere supports for the sori. The singleness of
the sori in the lobes, their great size, and anterior position form peculiar
features.

ASPLENIOPTERIS PINNATIFIDA, Sp. nOV.
Plate XXII, Figs. 1-3, G, 7.

Frond tripinnatifid ; rachis of the primary pinna or of the frond very
stout, rigid, and straight; pinn?e or pinnules alternate, var^'ing much in
length according to position, with strong rigid rachises ; sterile pinnules
linear-lanceolate, subacute, lower ones very long, much diminished in
length in ascending, cut more or less deeply into crenate and rounded
teeth and lobes; lateral nerves in each lobe flabellate diverging, with the
branches forked or simple, nerves very strong and distinct; fertile pinnae or
pinnules very long, with strong rigid rachises, linear, subacute ; lobes or
teeth reduced to thick leathery supports, which bear the narrowly elliptical
sori on the anterior face ; the sori very long, almost as long as the lobes,
standing one in each lobe, appai-ently included between the two branches
of a nerve that forks at the insertion.

Localit}' : Fredericksburg.

This remarkable plant is rare. I can not feel sure. that the sterile
forms, Figs. 1-3, with rounded lobes belong to the same species with the
form depicted in Figs. 6, 7, possessing narrow subacute fructified lobes,
but the nervation and general character of the segments of the pinnse
indicate that they belong to the same species. The partially fructified
form PI. XXII, Fig. 7, has the lobes on the upper side mostly sterile, indi-
cating how they are modified in the development of the sori.

ASPLENIOPTEEIS ADIANTIFOLIA, Sp. nOV.
Plate XVI, Fig. G.

Sterile frond not seen ; fertile frond bipinnate or bipinnatifid ; pin-
nules or lobes reduced to leathery thick pedicels or supports, which bear
on their anterior or upper margin narrowly elliptical or oblong sori ; sori
proportionally very large.

Locality : Fredericksburg ; very rare.

DESCRIPTION OF THE SPECIES. 119

This small plant was found in too fragmentary a condition to permit
its full character to be made out. It has some features that resemble those
of Adiantum, especially the terminal position of the elongate sori on the
basal upper lobes and the two terminal segments. The basal upj^er seg-
ment is much larger than the others, and, unlike them, is subdivided into
several segments, which bear the soi'i on the tips of the lobes.

GLEICHENIA Swartz.

The genus Gleichenia seems, if present at all in the Potomac flora, to
be very feebly represented. In this respect the Potomac flora diff"ers
greatly from that of nearly the same age described by Heer as coming
from Kome, Greenland.

Gleichenia Noedenskioldi ? Heer.

Plate XXI, Fig. 11.

Frond unknown; pinnae linear, narrow; pinnules in the lower part of
the pinnae separate to the base, in the upper portion united at base, oblong-
obtuse, minute ; nerves of the pinnules distinct, consisting of a midnerve
which sends off alternately lateral nerves, which in the lower part of the
pinnules are forked, but in the upper portion are simple.

Locality : -Fishing hut above Dutch Gap Canal ; very rare.

This plant is found only in small fragments. In the absence of fruc-
tification its identification with Gleichenia is not certain. It is very much
like G. Nordenskidldi Heer.^

Undetermined fern, sp. nov.

Plate XXI, Pig. 12.

This small fragment is too incomplete to justify a description. It
reminds one of Asplenmm Dicksonianwn Heer.^

Occurs very rarely at the fishing hut above Dutch Gap Canal.

THYRSOPTERIS Kunze.
Sterile and fertile pinnules dimorphous ; sterile frond decompound ;
pinnules constricted at base, cut into lobes or teeth ; nerves, lateral ones,

' Compare Flor. Foss. Arc, vol. 3, pt. 2, PI. IX, Figs. 6, 12.
2 Compare Flor. Foss. Arc., vol. 3, pt. 2, PI. I, Fig. 1.

120 THE POTOMAC OJtl rOUNGER MESOZOIC FLORA.

going off obliquely or under an acute angle ; fertile pinnae contracted ;
sori globose, paniculate or racemose, inserted on a pediceled involucre.

This description, given by Heer^ for the genus Thyrsopteris, so far as
the portion pertaining to the sterile frond is concerned, agrees well witli a
large number of species in the Potomac flora. These I place provisionally
in the genus Thyrsopteris, on account of the great resemblance that the
shape of the pinnules, the lobing, and the nervation show to the sterile
forms of various species determined to be Thyrsopteris by their fructifica-
tion. As, however, no fructification is found in the Potomac species, the
placing of these plants in the genus must be regarded as provisional. It is
quite possible that some of them belong to Aspidiiim and Dicksonia. The
genus Thyrsopteris seems to be eminently a Jurassic type of fern. How-
ever it may prove to be with the fructification of the various species
assigned in this memoir to this genus, it is probable that they are at least
distinct and true species. The great variety and comparative abundance
of these forms show that this type was developed in the Potomac flora to
an unusual degree. They surpass all other types, even that of Cladophle-
bis, and give a decided Jurassic facies to the assemblage of ferns found
in this flora. Even if we can not by fructification determine the affinities
of fossils with living plants, the large development of sterile forms of well-
marked types is of importance in fixing the character of a flora.

It should be noted that a number of the species of Thyrsopteris
described in the following pages show a good many features similar to
those of Sphenopteris Mantelli, as described by Schenk and Heer.

Thyrsopteris Virginica, sp nov.

Plate XXIV, Fig. 1.

Frond not seen; pinnse of ultimate order, linear-lanceolate, acute, nar-
rowed to a petioled base, and cut very obliquely into oblong lobes, the
lower of which are obtusely dentate; rachis of ultimate pinnules very
slender ; lateral nerves in each lobe flabellate, sending off branches which
in the lower lobes are once or twice divided, in the upper ones forked or
simple, rather remote, very distinct and strong.

' Plor. Foss. Arc, vol. 4, pt. 2, p. 28.

DESCEIPTION OF THE SPECIES. 121

Locality : Hill-side near Potomac Run ; very rare.

This plant is not unlike the undetermined plant PI. XXI, Fig. 12, and
may be the same. The fragments found are too small and rare to permit
its true nature to be made out. It is a little like Heer's plants, Adiantites
Nynvpharmn, and JDicksonia {Asplenium) Johnstriqn.

Thyrsopteris brevifolia, sp. nov.

Plate XXIV, Figs. 5, 10.

Frond bipinnate or tripinnate ; rachises slender ; ultimate pinnse long,
going off at a large angle and slightly curved upwards, linear, alternate;
pinnules all very short in proportion to their width, lower ones separate to
the base, upper ones united to form a narrow wing ; pinnules much nar-
rowed at base, cut obliquely more or less deeply into lobes or teeth accord-
ing to position on the frond ; lobes of the lower pinnules cuneiform or nar-
rowed at base, very obtuse, fan-shaped and emarginate; of the upper ones,
oblong or ovate, very obtuse, towards the ends of the pinnae reduced to
oblong or ovate blunt teeth or lobes; nerves in the lower lobes of the
lower pinnules flabellate, remote, forking once or twice in the upper lobes
of the lower pinnules, and in the upper pinnules single, all quite distinct.

Locality: Red clay ball in the banks of Dutch Gap Canal ; rare.

This well characterized and elegant little plant is near to Splienopteris
dissocialis Phillips. It reminds one also of Splienopteris hymenoplnjlloides
Brongn.

Thyrsopteris dentata, sp. nov.

Plate XXIV, Figs. 4, 6, 7, 9 ; Plate XXV, Figs. 1, 2.

Frond bipinnate or tripinnate, arborescent ? ; leaf-substance thick ;
rachises narrowly winged; compound pinnaj terminating in a lobed acute
segment ; ultimate pinnae or pinnules opposite or subopposite, reduced
towards the ends of the compound pinnre to dentate pinnules, and at the
summit to united lobes ; united at base to form a narrow wing, those of
the lower part of the frond cut deeply into oblong or subquadrate spiny-
toothed lobes or pinnules ; those higher up have obliquely cut lobes and

122 THE POTOMAC OR TOUNGEE MESOZOIC FLOEA.

teeth of varying depth, the basal ones subquadrate or ovate and spiny-
toothed ; the ultimate pinnae or pinnules gradually diminish towards the
ends of the compound pinnje ; the nervation in the pinnules and lobes
rather variable according to the position of the part, remote, very distinct
and strong ; the lower pinnules and lobes have a midnerve sending off on
each side alternate branches either forked or simple, in the upper ones
either once forked or simple.

Localities: Fredericksburg; hill-side near Potomac Run; red clay ball
in banks of Dutch Gap Canal ; rare.

This handsome plant is characterized bv its subquadrate, acutely den-
tate lobes and pinnules, and by the remoteness and strength of the nerves
in theui. It is not common at the localities where it is found. It is near
to Phillips's S^jhenoj^teris affinis.

Thyesopteris nervosa, sp. nov.

Plate XXV, Figs. 4, 5, 16 ; Plate XXXVII, Figs. 2, 4 ; Plate XXXIX, Fig. 5 ; Plate XL, Fig. 6.

Frond bipinnate or tripinnate, arborescent; principal rachis flexuous,
rather slender; ultimate pinnae alternate, remote; pinnules alternate ; leaf-
substance thick, very obliquely inserted on the rachis, in shape oblong-
acute, in the lower ones cut rather deeply into subrhombic basal lobes,
which toward the tips of the pinnules pass into ovate or elliptical lobes and
teeth, in the upper ones cut into elliptical acute lobes and teeth ; the pin-
nules narrowed at base nearly or quite into a petiole ; nerves very distinct,
slender, closely placed, going off from the midnerve very obliquely, diverg-
ing flabellately into each lobe and tooth, deeply forked, forking repeat-
edly, the branches subparallel.

Localities : Fredericksburg ; hill-side near Potomac Run ; not very
rare.

This is a very fine fern, and although the fragments found are not
large, they evidently belong to plants that must have attained very consid-
erable dimensions. It has some similarity to Thjrsopteris xmsca Heer.
The fragment shown in PI. XXV, Fig. 16, has longer and narrower lobes
than the normal forms and may be different.

DESCEIPTION OP THE SPECIES. 123

Thyesopteris earinervis, sp. nov.

Plate XXVI, Figs. 6, 7 ; Plate XLIII, Figs. 4-6 ; Plate XLIV, Figs. 1, 2, 5 ; Plate XLIX, Fig. 2 ; Plate

CLXIX, Figs. 6, 7.

Frond tripinnate, arborescent ; principal rachis and tliat of the penul-
timate pinnae strong-, rigid, straight ; that of the ultimate pinnae rather
slender; penultimate and ultimate pinnae alternate ; ultimate pinnse more
or less distinctly petioled, linear-lanceolate, acute ; pinnules diminishing
in size from the base to the tips of the ultimate pinnae, passing from
toothed pinnules separate nearly to the base, through entire pinnules more
fully united, to lobes at the summit of the pinnte ; pinnules linear to
narrowly elliptical, acute, obliquely placed, decurrent, and united at base
to form a wing of varying width, thick and leathery, narrowed at base,
those of the lower portion of the frond and of the pinnse minutely dentate;
towards the summit of the compound pinnse the ultimate pinnse reduced
to lobed and toothed pinnules ; nerves of the pinnules of the normal kind,
composed of a distinct midnerve, which sends off alternately into each lobe
or tooth a single nerve.

Localities: Fredericksburg; 72d mile-post, near Brooke ; White House
Bluff; enti-ance to Trent's Reach.

This fine plant is pretty widely distributed, and at White House Bluff
it is by far the most common fern. The forms depicted in PI. CLXIX,
Figs. 6, 7, come from this place, and are plainly but small portions of
what were once large fragments. The plant is not common at the entrance
to Trent's Reach. PI. XLIV, Fig. 2, gives, slightly restored, a fine speci-
men found here. Fig. 1 of the same plate, and PI. XLIX, Fig. 2, give
two very good specimens which come from Fredericksburg. The first
named seems to be the upper part of the compound pinna depicted in the
last-named figure. The principal rachis seems to have been keeled or
ridged on the under side.

This plant is one of the Sphenopteris ManteUi type, and perhaps by
some would be united with that species, but it is more robust, and the
pinnules are more like those of the Tliyrsopteris type. It looks in some
points a good deal like Sphenopiteris longifoUa, Dunker (Mon. Weald., PI VIII,
Fig. 4), which Schenk unites with S. Goepperti. It however differs from S.

124 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

Gospperfi in the leathery texture of the pinnules and in other points. In
the cutting of some of the pinnules there is a good deal of likeness to
T. elegans, Kunze, the living species and the sole survivor. It may also be
compared with Asplenium JDkhsonianum Heer.^ It resembles more than
any other described fossil Thyrsopteris elongata Geyler.^

Thyrsoptekis brevipennis, sp. nov.

Plate XXXIV, Fig. 3 ; Plate XXXVI, Fig. 2 ; Plate XXXVII, Figs. 3, 9 ; Plate XXXVIII, Fig. 1 ;

Plate XLl, Fig. 4.

Frond tripinnate ; leaf- substance thin ; penultimate pinnte mostly
opposite, short ; rachises slender, terminated l)y an obtusely lobed seg-
ment; lovsrer ultimate pinnae pinnate, with basal pinnules three lobed,
passing towards their tips abruptly thi'ough entire pinnules into lobes more
or less united, short ; towards the upper part of the frond and compound
pinnae the ultimate pinnse pass rapidly into pinnules and lobes that are
more or less united ; nerves departing in groups or nerve-bundles into
each lobe or tooth, flabellately diverging, and branching several times,
slender but rather distinct.

Localities : Red clay ball in banks of Dutcli Gap Canal ; fisliing hut
above Dutch Gap Canal ; Baltimore, collected by Meek ; Deep Bottom.

This plant in facies is more like a Spheyiopteris than any of the species
united under Thyrsopteris, and this feature is dependent in part on the
shoi'tness of the ultimate pinnae and tlie abrupt passage from lobed pinnules
to united lobes. It is comparatively abundant among the plants collected
'by Meek at Baltimore, but is rare at the other localities. There are a
number of these species with Sphenopteris facies found in the Potomac
flora which differ sufficiently to forbid their union in one species. They
may be noted as Thyrsoptericls with a Sphenopteris facies.

Thyrsopteris alata, sp. nov.

Plate XXXVI, Fig. 3.

Frond unknown, probably tripinnate ; principal rachis narrowly
winged, very slender, somewhat flexuous ; ultimate pinnae alternate, short,

iFlor. Foss. Arc, vol. 3, No. 2, PI. I, Figs. 1-.5.

^Foss. Pfl. Juraform. Japans Palajontographica, vol. 24, 1877, PI. XXX, Fig. 5 ; PI. XXXI, Figs. 4, 5.

DESGEIPTION OF THE SPECIES. 125

with a winged rachis ; lower pinnules with oblong lobes rounded at the
ends, cut very obliquely and more or less deeply, passing towards the
tips of the ultimate pinnae into oblong- obtuse lobes all minutely toothed
on the summits or terminal margins ; nerves distinct, diverging flabellately
in each lobe and forking several times; the midnerve of tlie pinnules
splitting up towards its summit.

Locality : Hill-side near Potomac Run ; rare.

This plant in the position of the toothing resembles Sphenopteris
acrodentata, but the lobes are narrower and the rachises winged, characters
not found in that species.

Thyrsopteris divaricata, sp. nov.

Plate XXXVII, Figs. 5-8; Plate CLXX, Fig. 1.

Frond tripinnate ; principal rachis slender, slightly flexuous ; ultimate
pinu^ remote, alternate, short ; penultimate pinnaj terminating usually in
a three-lobed segment ; pinnules of the lower part of the frond and com-
pound pinnas cut more or less deeply and quite obliquely into oblong or
ovate lobes, the two basal lobes being cut down nearly to the midnerve,
often with three teeth, diverging more or less widely. Towards the tip of
the ultimate pinnae and the summit of the frond the pinnules pass through
toothed elliptical pinnules into simple pinnules and lobes ; midnerve of the
pinnules splits up at the tip into branches ; nerves go off obliquely into
each lobe or tooth, composed in the lower ones of a midnerve, whicli sends
off alternately on each side branches forked or simple, composed in the
upper ones of forking and simple nerves.

Localities : Fishing hut above Dutch Gap Canal ; Fredericksburg ;
red clay ball in banks of Dutch Gap Canal ; rather rare.

This plant is noteworthy for the peculiar divergence of the two lowest
lobes in the pinnules and the extreme slenderness of the primary rachis. It
is not common, and appears not to be nearly allied to any described fossil.

Thyrsopteris Meekiana, sp. nov.

Plate XXXVIII, Figs. 2-4, 8 ; Plate L, Figs. 7, 8 ; Plate LI, Fig. 3.

Frond tripinnate, arborescent; pinnse and pinnules much crowded ;
rachises, especially the principal ones, as a rule, very stout; ultimate

126 THE POTOMAC OE YOUKGBR MESOZOIC FLOEA.

piniiEe alternate or subopposite, short, and in the lower poi'tion of the frond
spreading ; pinnules in the basal portion of the ultimate pinnaj, in the
lower part of the frond, cut deeply and obliquely into subacute, elliptical,
or subrhombic lobes, passing in the upper part of the ultimate pinnse and
of the frond through round-lobed pinnules into entire elliptical and acute
ones, and finally into lobes of the same shape ; nerves in each lobe flab-
ellately diverging, composed of a midnerve which sends off alternately on
each side branches either forked or simple.

Localities: Baltimore, collected by Professor Meek; Fredericksburg;
fishing hut above Dutch Gap Canal ; one small fragment from Covington
street, Baltimore ; rare at most localities, but one of the most common
ferns in Meek's collection made at Baltimore.

This is a Potomac Thyrsopterid of the Splienopteris type. In some
features it is like certain Potomac plants described under other names.
In lobing it is somewhat like Thyrsopteris hrevipennis, but the facies is
quite different, the rachis is stouter, the lobes and pinnse are more acute,
elongate, and crowded.

Thyrsopteeis Meekiana, vai-. angustiloba, sp. nov.

Plate XXXVIII, Figs. 5-7, 9; Plate XLIII, Fig. 8; Plate XLIV, Fig. 3; Plate XLVII, Fig. 4; Plate
XLVIII, Fig. 1; Plate LIV, Figs. 2, 11 ; Plate LV, Fig. 1 , Plato LVI, Figs. 1, 3.

Frond tripinnatifid, arborescent ? ; rachises comparatively slender ;
pinnse and pinnules subopposite to alternate ; pinnules of the lower parts
of the compound pinnse cut deeply and very obliquely into narrowly ellip-
tical acute lobes or teeth ; pinnules of the upper portions passing through
those with elliptical or ovate teeth into entire ones; nerves as in T. Meehi-
ana, but less spreading and not so copiously branched.

Localities: Baltimore, common in the plants collected by Meek,
occurring on tlie same pieces of shale with T. Meekiana, and almost as
abundant as that species; fishing hut above Dutch Gap Canal; Fredericks-
burg; 72d mile-post, near Brooke.

This plant has the same general character as T. Meekiana, bnt is
more slender than that and has the pinnules and pinnee less crowded. As
these features appear to be constant, this form seems entitled to l)e considered
as a variety.

DESCEIPTION OF THE SPECIES. 127

Thyksopteeis crenata, sp. nov.

Plate XXXIX, Figs. 1, 2.

Frond tripinnate, arborescent ; pinnae and pinnules opposite ; lower
penultimate pinnee without pinnules or pinnas near the insertion on the
main rachis ; leaf-substance of the pinnules thick and leathery ; pinnae of
the lower portion of the compound pinnae passing towards the summit of
the compound pinnae into crenately toothed and finally into entire pin-
nules; lower and basal pinnules crenately toothed, oblong to subquadrate
in form, separate to the much narrowed base ; upper pinnules entire, ellip-
tical to subrhombic, sUghtly decurrent, united more and more in ascend-
ing; nerves of the crenately toothed pinnules composed of a midnerve
which dissolves into branches towards its summit, sending off very
obliquely and alternately on each side nerve-bundles curving strongly
outwards to enter the teeth, and several times subdivided, in the upper
entire pinnules composed of a midnerve sending off obliquely' and alter-
nately lateral branches curved outwards and forked one or more times,
or simple towards the tips of the pinnules; all lateral nerves strong.

Locality: Fredericksburg; rather rare.

This fine plant seems to have no near affinity with any described
fossil. The rachises are strong, rounded, and prominent.

Thyksopteeis insignis, sp. nov.

Plate XXXIX, Fig. 4 ; Plate XL, Fig. 1 ; Plate XLI, Fig. 6; Plate XLII, Figs. 1, 2, 4; Plate XLIII,

Figs. 1, 3.

Frond tripinnate, very large, arborescent ; leaf-substance of the pin-
nules thick and coriaceous ; rachises strongly winged, sometimes a little
flexuous; pinnae of the first order very long and spreading; ultimate
pinnje in the lower part of the frond very remote, subopposite to alter-
nate; pinnules quite variable, according to position on the frond and com-
pound pinnae, and always rather remotely and very obliquely placed,
alternate to opposite, and decurrent ; in the lower part of the frond as in
PI. XXXIX, Fig. 4, and PI. XL, Fig. 1, oblong-lanceolate to narrowly
elliptical, acute, cut more or less deeply in the basal pinnules and very
obliquely into oblong or ovate acute lobes, those towards the tips of the

128 THE POTOjMAG OR YOUNGER MESOZOIC FLORA.

ultimate pinnne becoming' entire and narrowly elliptical. In tliis portion of
the frond there is a distinct midnerve in each pinnule, which at its summit
splits into branches, while it sends off alternately and obliquely on each
side lateral nerves into the lobes. These in the basal lobes have a mid-
nerve which sends off alternately on each side simple nerves, and in those
up higher they fork once or twice ; pinnules of the middle portion of the
frond and compound pinnae (see PI. XLII, Fig. 2) are remote, linear, acute,
and decurrent to form a wing, cut into acute short teeth; midnerve and
lateral nerves of these rather slender but distinct; lateral nerves of each
tooth forking deeply, one branch ending in the tip of the teeth; pinnules of
the upper part of the frond and compound pinnae (see PI. XLII, Figs. 1,
4) reduced to narrowly oblong lobes and teeth. The ultimate pinnse also,
in passing- to the upper portions or tips of the compound pinnae, pass into
lobed and toothed pinnules similar to those down lower. The compound
pinnae most probably end abruptly with a terminal pinnule like those
lower down. (See PL XLIII, Fig. 1.)

Localities: Fi'edericksburg ; road-side near Potomac Run; rather
abundant at the former place, rare at the latter.

Tlie variability of this splendid plant causes it in one or another of
its forms to approach several that are described under other names. It
belongs to the Sphenopteris IlaiitelU type of Thijrsopteris, but the thick
leaf-substance, remoteness of the pinnae and pinnules, the strong wing,
and the once forking lateral nerves distinguish it. In PI. XLIII, Fig. 1,
the tip of a compound pinna is shown, and it has abruptly terminating it
a pinnule similar to those lower down. It is a good deal like T. insignis,
var. angustipennis, as shown in PL XLIII, Fig. 3, but this latter does not
have the rachises winged. Among described fossils we find AsjncUuin
Jolmstrupi, Heer,^ something like the plant now in question.

Thyrsopteeis insignis, var. angustipennis, sp. nov.

Plate XLII, Fig. 3; Plate XLIII, Fig. 2.

Frond bipinnate or tripinnate, arborescent ; rachises stout and promi-
nent ; leaf-substance thick and leathery ; ultimate pinnae alternate ; pinnules

■ Compare Flor. Foss. Arc, vol. 3, No. 2, PI. I, Figs. 6, 7.

DESCEIPTION OP THE SPECIES. 129

alternate, linear, acnte, narrowed to a long, slender, wedge-shaped base, and
attached by tlie midnerve alone; phmules cut more or less deeply and
obliquely into oblong or narrowly ovate, acute, diverging teeth ; midnerve
slender ; lateral nerves simple, one in each lobe or tooth, slender.

Locality : Fredericksburg ; rare.

This plant belongs to the Splienopteris Mantelli type, and is strikingly
like T. insignis. The rachis, however, is not winged, and the pinnules are
narrowed to a longer and more slender base. This plant is not uncommon
at Fredericksburg, and is sometimes found with pinnules even more slender
than those depicted. They cover with a confused heap some fragments of
the rock.

Thyrsopteris densipolia, sp. nov.

Plate XXXIX, Fig. 3 ; Plato XL, Figa. 2-5 ; Plate LI, Fig. 5.

Frond tripinnate, arborescent ; leaf-substance thick and coriaceous ;
principal rachis strong, keeled on the under side ; pinnae of ultimate order
alternate^ short, linear-lanceolate, acute; pinnules crowded, obliquely
placed, short, subacute to obtuse, much narrowed at base, and decurrent
in the basal ones to form a partial wing, those higher up united more and
more, and passing through entire pinnules into more or less united lobes :
lower or basal pinnules cut very obHquely more or less deeply into sub-
acute to obtuse teeth ; nerves very slender and seen with difficulty, com-
posed in the pinnules of a midnerve which sends off obliquely and alter-
nately into the teeth lateral nerves, which are once or twice forked and
curve outward.

Localities : Fredericksburg ; 72d mile-post, near Brooke ; not un-
common.

This plant is near Thyrsopteris insignis, but the pinnules do not form
a continuous wing, and they are, as a rule, shorter and broader than those
of the latter. The pinnules are more crowded, and the nerves differ much.
This plant has some resemblance to the Wealden fossil Splienoxiteris
Gcepperfi Dunker.

MON XV 9

130 THE POTOMAC OE YOUNGER MESOZOIC FLORA.

ThYRSOPTEKIS CRASSINERVIS, Sp. IIOV,
Plate XLI, Figs. 1-3.

Frond bipinnate or tripinnate ; rachises all slender ; ixltimate pinnae
opposite or subopposite, short, subacute; penultimate pinnse very long;
upper basal pinnule of the ultimate pinnpe heteromorphous, much larger
than the others, cut more or less deeply into three obtuse lobes or teeth ;
pinnules mostly elliptical or subrhombic, lower ones separate to the base,
upper ones more and moi'e u^nited and passing into ovate lobes ; leaf-
substance thick ; nerves very strong, standing out like threads ; midnerve
of the pinnules splitting up into branches at the summit, sending off alter-
nately on each side lateral nerves which branch once or twice, and in the
lobes of the heteromorphous pinnule sending off a flabellately diverging
nerve-bundle, the branches of which mostly fork near their ends.

Locality : Fredericksburg ; rather rare.

This belongs to the Splienopteris type of Thyrsopteris^ and resembles
in some respects several of that type, but. it is distinguished by its strong
nerves and heteromorphous upper basal pinnule.

Thyrsopteris decurrens, sp. nov.

Plate XLIII, Fig. 7 ; Plate XLVI, Figs. 2, 4 ; Plate XLIX, Figs. 5-7.

Frond tripinnate, arborescent, of large size!; principal rachis some-
what flexuous ; rachises of all orders winged ; pinnules decurrent, rather
remote, varying in shape according to position and consequent lobing
from oblong to linear-acute, diminishing much in size and depth of lobing
in ascending towards the summits of the compound pinnae, much narrowed
at base and going off obliquely ; the lower pinnules deeply and obliquely
cut into narrow, oblong, obtuse lobes, upper ones narrowly oblong to
linear, with acute, elliptical, shallow teeth ; nerves in each lobe or tooth
distinct, in those of the lower parts of the pinnae deeply forked, in those
of the upper parts simple, all very oblique and approximately parallel.

Localities : Red clay ball in banks of Dutch Gap Canal ; Fredericks-
burg; 72d mile-post, near Brooke; hill-side near Potomac Run; fishing-
hut above Dutch Grap Canal ; in all places rather rare.

DESCEIPTION OF THE SPECIES. 131

This is one of the most widely difFused of the Potomac ferns. In
that respect it differs from most of the ferns of this formation, for they are
usually much isolated in occurrence. It does not seem to be nearly allied
to any known fossil.

TnYESOPTERlS ANGUSTIFOLIA, sp. nOV.

Plate XLIV, Fig. 4; Plate XLV, Fig. 3; Plate XLVIII, Fig. 2; Plate XLIX, Figs. 3, 4; Plate LV,
Fig. 2; Plate LVIII, Fig. 8.

Frond tripinnate, arborescent ; pinnules and lobes narrowly oblong to
acute ; pinnae and pinnules usually much crowded ; ultimate pinnae and
pinnules alternate, diminishing in passing towards the ends of the com-
pound pinnae into pinnules and lobes ; pinnules and lobes narrow, obliquely
cut, in shape narrowly oblong to linear, lower pinnules separate to base,
and furnished with narrowly elliptical acute lobes and acute teeth, passing
in ascending into more and more fully united narrowly elliptical teeth ;
nerves in each lobe of the upper pinnules forked, with the upper branch
forking again or single in some cases. In the lower pinnules the lobes have
a midrib with alternate simple branches going off on each side ; midrib and
lateral nerves of the pinnules all slender.

Localities: Entrance to Trent's Reach ; fishing-hut above Dutch Gap
Canal ; 72d mile-post, near Brooke ; hill-side near Potomac Run ; not
common anywhere.

This is a widely diffused fern. It is distinguished by the narrowness
of its lobes and pinnules and the absence of a wing on the rachises. It
belongs to the Sphenopteris Gcepperti type of Thyrsopteris. Some of the
specimens sent from Professor Uhler's collection, gotten at Baltimore, to
New Orleans, and thus lost, were similar to this plant, and hence it
probably occurs at Baltimore.

Thyrsopteris microphylla, sp. nov.

Plate XLV, Figs. 1, 2, 4, 5.

Frond tripinnate, large, arborescent; principal rachis strong; penult-
imate pinnae alternate, with strong rigid rachises comparatively short, ter-
minated abruptly by an ultimate pinna similar to those lower down on the

132 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

compound pinna ; ultimate pinnse of the upper part of tlie frond (see Fig.
2) reduced to acute, elongate, elliptical lobes and teeth; the ultimate pinnse
subopposite to alternate, obliquely placed, linear-lanceolate, subacute, with
slender midribs terminated by an elliptical subacute lobe, attached to the
principal rachis by a much narrowed base, composed of the midnerve with
a narrow wing ; pinnules small, linear-oblong to elongate-elliptical, acute
to obtuse, basal ones separate nearly to the midnerve, those of the ultimate
pinnse slightly notched into acute teeth; pinnules towards the tip of the
ultimate pinnae and higher on the frond without the teeth and more united
at base; nerves in the basal pinnules composed each of a slender midnerve,
which sends off on each side alternate simple nerves which go one to each
tooth ; in the lobes and simple pinnules higher on the frond, the nerves once
or twice forked or simple ; usually the second forking occurs in the upper
branch of the forking nerves and is found in the lower pinnules of the frond
on the ultimate pinnse.

Localities : Fredericksburg, not uncommon ; hill- side near Potomac
Run ; rare.

This fine plant belongs to the Sphenopteris ManteUi type of Thyrsop-
teris, and is in some of its forms like T. rarinervis and T. angiistifoUa. It
is not winged, however. All the specimens figured except the small one
(Fig. ,5) come from Fredericksburg.

Thyesopteris pachyrachis, sp. nov.

Plate XLVI, Figs. 3, 5; Plate XLVII, Figs. 1, 2 ; Plate XLIX, Fig. 1.

Frond tripinnate, large, arborescent; pinnse and pinnules usually
crowded; rachises very stout, round, an-d prominent; ultimate pinnae op-
posite to alternate, lanceolate in outline, rather short: pinnules passing
rapidly into lobes and teeth towards the upper part of the frond and
compound pinnae ; lower pinnules narrowed to the base, oblong or sub-
quadrate, acute, cut more or less deeply and very obliquely into narrowly
elliptic acute teeth. In the upper parts the pinnules become narrowly
elliptic, toothed, and united by decurrent bases, or pass into very obliquely
placed teeth of the same shape. The ultimate pinnae pass into pinnules

DESCRIPTION OF THE SPECIES. 133

in the upper part of the compound pinnse. The nerves are fine but dis-
tinct, closely placed, deeply forked, flabellately diverging in each lobe and
tooth, consisting of a slender midnerve, which sends off very obliquely
deeply forked or simple branches.

Localities: Fredericksburg; road-side near Potomac Run; near Tel-
egraph Station; fishing-hut above Dutch Gap Canal ; rare everywhere.

This fine plant belongs to the Sphenopteris longifoUa type of Wealden
ferns. Its facies is one highly characteristic of the Potomac ferns, includ-
ing more forms than any other. It is not closely allied to any described
fossil known to me.

Thyesopteeis elliptica, sp. nov.

Plate XXIV, Fig. 3 ; Plate XL VI, Fig. I ; Plate L, Figs. 6, 9 ; Plate LI, Figs. 4, 6, 7 ; Plate LIV, Fig.
6 ; Plate LV, Fig. 4 ; Plate LVI, Figs. 6, 7 ; Plate LVII, Fig. 6 ; Plate LVIII, Fig. 2.

Frond quadripinnate, large, spreading, and arborescent ; rachises
strongly winged, keeled on the under side ; principal rachis very stout, and
often more or less flexuous; leaf-subtance of the pinnules thick; arrange-
ment of the ultimate pinnae various. The plant shows a tendency to a pal-
mate mode of subdivision of the principal rachis (see PI. LVI, Fig. 6);
compound pinnae abruptly terminated by penultimate pinna; like those
down lower (see PL LI, Fig. 6); ultimate pinnae crowded, quite short;
lower pinnules of the ultimate pinnae, in the lower part of the frond cut
more or less deeply and obliquely into narrowly oblong to elliptical
obtuse lobes or rounded teeth, separate to the wing of the rachis, obliquely
placed, much narrowed at the base, elliptical or ovate in shape ; pianules
in ascending towards the summit of the frond and ends of the compound
pinnae pass into entire elliptical pinnules, and these, united more and more,
pass into lobes and teeth ; midnerve of the lobed pinnules splitting at the
summit and sending off down lower alternately into the lobes branches
which fork once or twice ; branches in the upper pinnules either once
forked or simple.

Localities: Fredericksburg, not uncommon; red clay ball in banks
of Dutch Gap Canal ; rare.

This plant is not very close to any previously described fossil.

134 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

Thyesopteris distans, sp. nov.

Plato XL VII, Fig. 3 ; Plate LIV, Fig. 8.

Frond tripinnate, large, arborescent ; rachises strong, narrowly winged;
pinnte and pinnules very remotely placed ; penultimate pinna3 subopposite,
with ultimate pinnge abruptly and irregularly diminished in length and
size ; ultimate pinnae linear-lanceolate, passing above into lobed, toothed,
or entire pinnules ; basal pinnules of the lowermost ultimate pinnae nar-
rowly oblong, acute, denticulate, passing towards the tips of the ultimate
pinnte rapidly into narrowly oblong, acute lobes and teeth; nerves in the
pinnules and lobes, composed of a midnerve which sends off obliquely
and alternately on each side branches, which are forked in the lo\yer ones,
simple above, fine, closely placed, but distinct.

Locality : 72d mile-post, near Brooke ; not uncommon.

This plant belongs to the 8i)lienoptens Gcepperti type. The principal
rachis is very strong. It is probable that in this and all the specimens of
Thyrsopteris, Cladophlehis, Pecopteris, etc., the principal rachises are portions
simply of compound pinnae. In the descriptions, when plants are given as
bipinuate, tripinnate, etc., it is meant that the frond is probably at least
divided to the extent named. This plant seems to be not very near any
other described fossil.

Thyesopteris angustiloba, sp. nov.

Plate XLVIII, Figs. 3-5; Plate LV, Fig. 3.

Frond tripinnate; rachises distinctly winged; pinnules and lobes,
especially the latter, very narrow ; penultimate pinnae alternate, rapidly
diminished in ascending towards the summit of the compound pinnae into
ultimate pinnae and pinnules, and finally into lobes ; ultimate pinnae sub-
opposite, closely placed, decurrent to form a wing, the lower ones cut
obhquely and more or less deeply into narrowly oblong or eUiptical
pinnules towards their bases, but towards their ends these pass into lobes
and teeth of the same form, narrowed to a subpetiolate base ; higher on
the compound pinna they change rapidly through toothed pinnules into

DESCRIPTION OF THE SPECIES. 135

entire ones, and finally into lobes and teeth ; nerves in the pinnules and
lobes, forked deeply in the basal ones, in the upper ones simple, all very
oblique, fine, but distinct.

Localities: Fredericksburg; fishing-hut above Dutch Gap Canal;
entrance to Trent's Reach ; White House Blufi".

This plant is quite widely difi'used. It is comparatively abundant at
White House Bluff', where a number of poorly preserved specimens occur,
evidently in some cases being fragments of large portions of the frond.
It is also not very rare at the entrance to Trent's Reach. In other places
it is very uncommon. The general aspect of this plant is much like that
of Thy y softer is angustifoUa, but the distinctly winged rachis compels me to
separate them. It belongs to the Splienopteris Mantelli type.

Thyrsopteeis pachyphylla, sp. nov.

Plate L, Fig. 3.

Frond and pinnas unknown ; ultimate pinnae terminated by a broadly
fan-shaped pinnule, which is toothed on the terminal margin ; pinnules not
fully shown, only those near the tip of the ultimate pinnae seen, alternate,
elliptical, acute, furnished with ovate teeth ; leaf-substance thick ; nerves
not seen.

Locality : Road-side near Potomac Run.

Only one small specimen was found, but the plant seems to be a
distinct new species, not near to any described fossil.

Thyrsopteeis pecopteroides, sp. nov.

Plate LI, Fig. 1.

Rachis of the penultimate pinnse stout ; ultimate pinnse closely placed,
opposite or subopposite, short, linear-acute ; pinnules minute, passing to
lobes towards the ends of the ultimate pinnse, subrhombic to ovate, decur-
rent to form a wing, lower ones slightly toothed ; leaf-substance thick ;
nerves in the pinnules composed of a midnerve, which goes off obliquely
and is turned strongly outward, and sends off alternately on each side
branches which are forked or simple.

Locality : Fredericksburg ; rare.

136 THE POTOMAC OE YOUNGBE MESOZOIC FLOEA.

This, although found only in one or two small fragments, seems to be
quite a distinct new species. It looks more like some of the Gleicheuice
from the Lower Cretaceous of Greenland than any other plant.

Thyrsoptkris pinnatifida, sp. nov.

Plate LI, I'ig. 2; Plate LIV, Figs. 4, 5, 7; Plate LVII, Fig. 7.

Frond triijinnatifid, arborescent; rachises slender; ultimate pinnae
alternate; primary pinnse towards the summit suddenly changing from
penultimate pinna3 to ultimate ones (see PI. LVII, Fig. 7); ultimate pinnae
short, closely placed, terminating in acute oval lobes, obliquely inserted,
alternate, changing in passing to the summits of the principal pinnae and of
the penultimate ones into lobed pinnules and finally into entire pinnules,
much narrowed at base, and attached by the narrowly winged midnerve,
cut down nearly to the midnerve in their basal portions into narrowly
oblong or elliptic-acute pinnules ; towards their ends and higher on the
compound pinnae the pinnules graduate into lobes and teeth ; pinnules and
lobes minute ; nerves in tlie pinnules of the lower parts forked deeply,
with the upper branch forking again ; in the lobes higher simply forked.

Locality : Fredericksburg.

This elegant little plant is not very rare at Fredericksburg. It is
notewortliy for the very regular and elegant shape of the pinnules and
lobes and for their minute size.

Thyrsopteris heteromorpha, sp. nov.

Plate LII, Fig. 1.

Frond apparently palmately branching, with the primary pinnae radi-
ating from the top of the common stipe ; ultimate pinnae of the central
compound pinnae passing abruptly in ascending into obtusely lobed pinnules,
and at the top changing into entire elliptical pinnules ; ultimate pinna?-
closely crowded, short, and obliquely inserted, passing in ascending into
lobed and finally into entire pinnules, those of the upper side of the penult-
imate pinnae larger and more deeply cut than those of the lower side, those
towards the base of the penultimate pinnae cut into elliptical subacute
pinnules and lobes, which are narrowed at base and obliquely placed, the
pinnules of the upper side being sometimes crenately toothed; leaf-sub-

DESCRIPTION OF THE SPECIES. 137

stance leathery and thick ; nerves very strong, causing the leaflets some-
times to look as if they were corded. In the crenate pinnules (Fig. I'') the
nerves consist of a midnerve which splits up towards the summit and sends
ofi" at base two nerve-bundles ; these diverge flabellately into the teeth, with
the branches simple and forked ; higher the lateral nerves fork deeply,
with the upper branch forking again ; the entire pinnules (Fig. 1^) have
branches diverging alternately from a midnerve, curving outward and once
or twice forked.

Locality : Fredericksburg ; rather rare.

This plant belongs to the Sphenopteris Gmpperti type. It seems to be
a well-characterized new species of a strongly defined Wealden type.

Thyrsopteeis varians, sp. nov.

Plate LII, Figs. 2-4 ; Plate LIII, Figs. 1-3; Plate LIV, Fig. 10; Plate LVU, Fig. 2.

Frond tripinnate or quadripiimate, large and spreading; leaf-substance
thick and leathery ; rachises of the penultimate pinna? often partially or
fully winged ; ultimate pinnae vaiying in size and shape with their posi-
tion on the frond, tending to pass in ascending towards the ends of the
penultimate pinnae rapidly through lobed into entire pinnules. Principal
rachis generally stout and prominent, often flexuous; ultimate pinnaj on
the upper side of the penultimate pinna sometimes much larger than those
on the lower side, especially the basal upper one ; ultimate pinnse of the
lower part of the frond and compound pinnae furnished with remote, ellip-
tical, oblong, or subrhombic pinnules, which pass in ascending into lobes
and teeth of the same nature. In the pinnules of the lowest portions the
nerves are composed of a midnerve which sends off flabellately diverging
branches, which are forked or simple ; in the lobes and teeth of the upper
portions they consist of a midnerve which branches- several times, begin-
ning near the base, the branches diverging flabellately, or of a lateral nerve
in each lobe which forks once or twice.

Locality: Fredericksburg; not rare.

A number of good specimens of this plant were obtained. I have,
with a good deal of hesitation, united under this species a number of forms
which differ somewhat in aspect, but there seems to be such a transition

138 THE POTOMAC OE YOUNGER MBSOZOIO FLORA.

from one to the other as to forbid their separation. Plate LII, Fig. 2,
shows no wing on the raehis of the uUimate pinna, hut shows a feature
cotomon in this species, viz: the uhimate pinnae on the upper side of the
penultimate rachis are larger than those on the lower side. In Fig. 3, of
the same plate, the rachis is not winged, and the ultimate pinnae do not
show the marked disparity in size often seen ; Fig. 4^ of the same plate,
shows the ultimate pinnre or pinnules decurrent, and forming a partial
wing to the rachis. The nerves in the lobes or pinnules of tliis form are
more numerous and deeply forked than in Fig. 2. In PI. LIII, Fig. 1, the
penultimate rachis is winged, and the pinnules, here reduced to lobes,
have remote, sparingly branched, strong nerves. The ultimate pinnas do
not differ mvich in size. In Fig. 2, of the same plate, we have a surprising
difference in the size of the ultimate pinnae on opposite sides of the penulti-
mate rachis. In Fig. 3, of this plate, the usual disparity of the ultimate
pinnae is seen, and the pinnules differ from the normal ones markedly
in the nerves, which are fine, closely placed, deeply forked, and com-
paratively numerous. In PI. LIV, Fig. 10, the basal upper pinnule is
decidedly longer than the rest, and directed upwards parallel with the
penultimate rachis, which is strongly winged. This is probably the upper
portion of a compound pinna. This fern seems to be not closely allied to
any described fossil, and to have been a large plant.

Thyesopteeis ehombifolia, sp. nov.

Plate LII, Fig. 5 ; Plate LIV, Fig. 1.

Frond apparently palmately divided; plant slender; principal rachises
slender, rounded, and prominent ; ultimate pinnae short, distant, opposite,
pinnules remote ; leaf-substance thick, upper basal pinnule larger than the
rest, more copiously and deeply lobed; pinnules subrhombic to rhombic in
shape, slightly curved forward, acute, rarely obtuse ; nerves very distinct,
composed in the pinnules of a midnerve which sends off alternately and
very obliquely on each side forked or simple nerves, and which at its sum-
mit dissolves into bi-anches. In the heteromorphous basal upper pinnule a
nerve-bundle goes off flabellately diverging into the basal lobes, -the
branches of which are simple.

DESCEIPTION OP THE SPECIES. 139

Localities: Fredericksburg; fisliing'-liut above Dutch Gap Canal;
rare.

Plate LIV, Fig. 1, depicting a specimen from the last-mentioned local-
ity, differs from the more common Fredericksburg forms in having the
penultimate rachis keeled, perhaps because the under side is shown. It
gives the summit of a primary pinna.

This pretty little fern seems to form a well-marked new species.

Thyesopteeis heteeoloba, sp. nov.

Plate LIU, Fig. 4.

Frond tripinnate; rachises strongly winged; principal rachis flex-
uous; penultimate pinnse alternate, with a strong rigid rachis; ultimate pin-
nae alternate, short, attached by the narrowly winged rachis which forms a
sort of petiole, cut obliquely into oblong, obtuse, or spatulate pinnules or
lobes to varying depth, according to the position on the pinnae ; upper
basal pinnules always larger than the lower pinnules, furnished with three
shallow, very obtuse lobes ; towards the summit of the ultimate joinnai and
of the frond the pinnules pass to obtuse lobes ; nerves in each pinnule and
lobe fine, closely placed, flabellately diverging, with simple or forking
branches.

Locality : Fredericksburg ; rare.

This seems to be a very distinct new species, and it is very rare. It
is somewhat like T. varians.

Thyesopteeis bel^a, sp. nov.

Plate LIII, Fig. 5; Plate LV, Figs. 6, 7; Plate LVI, Figs. 2, 5; Plate LVII, Figs. 1, 5; Plate LVIII,

Fig. 4.

Frond quadripinnate, spreading, arborescent 1 ; rachises comparatively
very slender ; primary rachis somewhat flexuous ; penultiuiate pinnae
alternate or opposite, long, closely placed, passing towards the summit of
the principal pinnae into ultimate pinnae ; ultimate pinnae, short, opposite
to alternate, terminating in a three-lobed segment, usually closely placed,
oblong-lanceolate in form, passing above into lobed and simple pinnules ;
pinnules passing in ascending into simple ones, and finally into lobes,

140 THE POTOMAC OK YOUNGER MESOZOIC FLORA.

lower ones cut obliquely into oblong or elliptical lobes or teeth, basal ones
sometimes blunt-lobed, greatly narrowed at base, all minute ; leaf-substance
thin ; nerves in the lobes or teeth slender but distinct, composed in the
pinnules of a midnerve with obliquely placed, alternate forking or simple
branches on each side, and in the lobes and teeth of lateral nerves, which
fork once or twice and go off very obliquely.

Localities : Fredericksburg ; entrance to Trent's Reach ; White House
Bluff; fishing-hut above Dutch Gap Canal; rare.

This elegant little plant is one of the more widely diffused ferns. It
is noteworthy for the minuteness of the pinnules and lobes. It seems to
be a well-marked new species.

Thyrsopteeis microloba, sp. nov.

Plate LVII, Fig. 4.

Frond arborescent, tripinnate ; ' principal rachis proportionally very
stout, rigid, and prominent; penultimate pinnse alternate, closely placed,
much narrowed at the base, decurrent; lower pinnules of the ultimate
pinnae elliptical, narrowed at base, slightly and obtusely toothed, minute,
the upper basal pinnule larger than the rest and more deeply toothed ;
pinnules on the upper side generally larger than those on the lower, and
showing a toothing up higher towards the tips of the ultimate pinnas ;
pinnules towards the ends of the ultimate pinnaj passing into lobes and
teeth ; leaf-substance rather thick ; nerves in the lower pinnules pinnate
from a midnerve, with branches forked and simple, those of the lobes up
higher forked or simple.

Locality : Fishing-hut above Dutch Gap Canal ; rare.

This is a plant with very minute pinnules and lobes, which has the
penultimate rachises not winged, and which thus differs from the variety
alata.

Thyrsopteeis microloba, var. alata, sp. nov.

Plate LV, Fig. 5; Plate LVIII, Fig. 1.

This differs from T. microloba mainly in the presence of a wing on
the rachises of the penultimate pinnse, the smaller size of the principal

DESCEIPTION OF THE SPECIES. 141

rachis, and in the proportionally larger size of the pinnules and lobes.
PI. LV, Fig. 5, appears to represent the upper portion of a compound
pinna, corresponding to the upper portion of the fragment represented in
PI. LVII, Fig. 4, where the pinnules are reduced to lobes and the ultimate
pinna; to pinnules.

Localities : Fredericksburg ; above Dutch Gap Canal, near the fish-
ing-hut.

The plant is not common anywhere, but is most abundant in thin
shale partings in the bank a little above the spot at the fisliing-hut, where
so many plants were collected. It does not occur, strange to say, at this
last-named spot, which is only a few yards distant. The fine specimen,
PI. LV, Fig. 5, was found at the Dutch Gap locality.

Thyrsopteris nana, sp. nov.

Plate LVI, Figs. 4, 8.

Frond very small, tripinnate; rachises slender; ultimate lower pinnge
or pinnules very minute, short, rather remotely placed, much narrowed at
the base, subrhombic in shape, cut very obliquely nearly to the midnerve
into very small elliptical or oblong pinnules or lobes, which are mostly
obtusely rounded at the ends, rarely subacute, the lower ones diverging
considerably ; the ultimate pinmie terminate in a three-lobed segment ; the
ultimate pinnse pass towards the ends of the penultimate pinnae and of
the principal pinnte into pinnules, which have a wedge-shaped base, and
are cut deeply into three lobes, the lower pair diverging strongly ; nerves
of the pinnules and lobes fine but distinct, closely placed, those of the
pinnules in the louver portion of the pinnae flabellately diverging from a
short basal nerve, mostly simple in the lobes, once or twice forking, and
without the basal nerve.

Localities : Fredericksburg ; fishing-hut above Dutch Gap Canal ;
quite rare.

This is a very small plant, which seems quite distinct from all other
described fossils.

142 THE POTOMAC OK YOUNGER MESOZOIG FLOEA.

ThYRSOPTEEIS INiEQUIPINNATA, sp. nOV.
Plate LVII, Figs. 3, 8.

Frond tripinnatifid ; racliises slender ; ultimate pinna? opposite or sub-
opposite, of unequal length on opposite sides of the penultimate rachis,
rather remote, graduating' above through lobed and dentate into entire pin-
nules, the latter being at the sunnuit of the compound rachis and becoming
more remote in the upper part ; pinnules opposite, elliptical, much narrowed
at the base, passing towards the summit of the ultimate and primary
pinna^ into entire ones, the lower ones cut into shallow, elliptical, subacute
teeth ; nerves fine, in the pinnules composed of a midnerve which in the
toothed lower pinnules sends off very obliquely and alternately flabellate
nerve-bundles with forking or simple branches, and splits up into branches
at its summit ; in the entire pinnules it gives off in like manner lateral
nerves that are forked or simple.

Locality : Fishing-hut above Dutch Gap Canal ; rare.

The marked inequality in the length of the ultimate pinna? on opposite
sides of the principal rachis is the most noteworthy feature of this small
plant. It seems to be unique.

TnYRSOPTEEIS HETEROPHYLLA, sp. nOV.
Plate LVIII, Fig. 3.

Frond probably tripinnate ; rachises slender; penultimate pinnte alter-
nate, short, closely placed, terminating in a three-lobed segment, with
broadly winged rachis ; pinnules remote, those on the upper side larger
and less obliquely placed than those on the lower side, much narrowed at
base, and decurrent to form a broad wing, cut more or less deeply into
ovate teeth, elliptical to subrhombic in shape; leaf-substance thick; nerves
distinct, pinnately departing from a slender midnerve, simple, one in each
tooth.

Locality: Fredericksburg; very rare.

Although only a small fragment was found, this plant seems to be a
distinct species. It is much like Thyrsopteris Maa'kiana'^ Heer.

' Compare Flor. Foss. Arc., vol. 4, Part II, Beitrage ziir Jura Flor., etc., PI. I, Fig. 1».

DESCRIPTION OF THE SPECIES. 143

Thyesopteeis obtusiloba, sp. nov

Plate LVIII, Figs. 7, 10.

Frond tripinnatifid ; pinnae of ultimate order and pinnules subopposite,
remotely placed, short ; pinnules narrowly oblong, obtuse, passing above
into entire ones, lower ones cut to varying depths into oblong, very obtuse
lobes ; lateral nerves very strong, in the lower lobes given off pinnately
on each side of a midnerve which splits up at the summit ; the lateral
nerves forked or simple, in the upper lobes flabellate and forking once or
twice.

Localities : Red clay ball in the banks of Dutch Gap Canal ; hill-side
near Potomac Run ; rare.

This plant has the facies of a CladoiMebis. It seems to be a distinct
new species.

Thyesopteeis sphenopteeoides, sp. nov.

Plate LVIII, Fig. 6.

Frond bipinnate or tripinnate ; ultimate pinnse winged; leaf-substance
thick; pinnules small, much narrowed at base, almost petioled, distant,
elliptical or subrhombic in shape, acute; lower ones cut into diverging
ovate-acute lobes, upper ones entire; nerves strong, composed in each pin-
nule of a midnerve which splits up towards the summit and sends off pin-
nately into the lobes and teeth lateral nerves which fork usually once.

Locality: Hill-side near Potomac Run ; very rare.

This seems to be nearly allied to no previously described species.

Thyesopteeis squaeeosa, sp. nov.

Plate LIX, Fig. 3.

Frond tripinnatifid ; primary rachis stout, somewhat flexuous ; ulti-
mate pinnae alternate, winged, closely placed ; pinnules crowded, much
narrowed at base, short in outline, triangular, cut more or less deeply into
lobes which spread widely from the midnerve, standing almost at right
angles with it, the lobes more or less club-shaped or spatulate in form, the
basal ones being obtusely three-lobed ; the pinnules are broadest at base,
and stand nearly at right angles witli the midrib ; nerves strong, com-

144 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

posed in the lower lobes of a flabellately diverging nerve-bundle, the
branches of which are forked or simple ; in the upper ones composed of
forking nerves.

Localities : Hill-side near Potomac Run ; near Telegraph Station ;
quite rare.

This seems to be a well-marked distinct species with a Sphenopteris
facies.

Thyrsopteeis ehombiloba, sp. nov.

Plate LIX, Figs. 6, 7 ; Plato LX, Fig. 8.

Frond tripinnate, arborescent ; principal rachis stout ; ultimate pinna3
alternate, linear-lanceolate in outline, terminating in an acute lobed seg-
ment ; pinnules closely placed, alternate, oblong or subrliombic, acute,
passing above into united lobes, cut more or less deeply into subrhombic
lobes, much narrowed at base, decurrent to form a wing on the penultimate
rachis; nerves of the pinnules composed of a midnerve which, splits up at
the top and sends off pinnately into the lower iobes nerve-bundles which
diverge flabellately in the lobes, the branches being simple, or forked in
the lower lobes ; in the upper lobes the lateral nerves fork once or twice.

Locality : Hill-side near Potomac Run ; not uncommon.

The penultimate pinnae of this plant in the upper parts of the com-
pound pinnse are reduced to pinnules, as is shown in PI. LX, Fig. 8, and
in the lower portions of the frond, as in PI. LIX, Fig. 6, they seem to pass
into tiltimate pinnae. These do not have the rachis to which they are
attached winged. The plant seems to be a distinct new species.

Thyesopteris retusa, sp. nov.

Plate LIX, Fig. 10.

Frond tripinnate; principal rachis stout; pinnae alternate; ultimate
pinnae short, lanceolate in shape, rachis winged, terminating in a lobed
segment formed of united and reduced pinnules; pinnules towards the ends
of the ultimate pinnae passing into lobes and teeth ; those of the lower por-
tion of the ultimate pinnae much narrowed at base, united by decurrence
to form a wing, oblong, terminating in three acute teeth, cut into retuse

DESCRIPTION OF THE SPECIES. 145

lobes ; lateral nerves of the pinnules few and remote, going pinnately on
each side of the midrib into the lobes, and forking once or twice, all
strong.

Locality : Hill-side near Potomac Run ; rai-e.

This small plant reminds one of Thyrsopteris squarrosa, but appears to
be a well-marked distinct species, not nearly allied to any described fossil.

Undetermined Fern in circinate vernation, sp. ?

Plate LIX, Fig. 5.

Small, circinate fern fronds, similar to the form depicted in Fig. 5, are
quite common in the shale on the hill-side near Potomac Run. They
occur mostly in the form of small fragments. This locality is noteworthy
for the great number of specimens of a comparatively small number of
species of ferns that it affords. It is eminently a fern locality, being the
only place where the specimens of that family surpass in numbers all
others put together.

OSMUNDA, L.

The genus Osmunda is not represented in the Potomac by many spe-
cies, but the number of individuals, of at least one of the species, is con-
siderable.

Osmunda sphengpteroides, sp. nov.

Plate XXV, Fig. 13.

Frond most probably bipinnatifid, spreading; rachises slender; sterile
and fertile pinnules on the same pinna ; lower pinnules of the ultimate
pinnae fertile, the upper ones sterile, occasionally some of the basal lobes
of the upper pinnules fructified ; pinnules alternate, remote, especially the
fertile ones ; fertile pinnules much reduced in siae, oblong in form, with
bluntly rounded lobes, which are covered with sori ; sterile pinnules short,
cut more or less deeply into oblong, elliptical, subacute lobes, obliquely
placed, narrowed at base to a sort of petiole ; nerves fine, but distinct,
branching fiabellately in each lobe or tooth, departing from a more or less
pronounced midnerve, the branches sometimes forked, but more commonly
simple.

MON XV 10

146 THE POTOMAC OE YOUNGER MESOZOIO FLOKA.

Locality: Red clay ball in the banks of Dutch Gap Canal; rare.

This is a well marked species. Its rarity may be only apparent. The
plants found in the red clay ball form a peculiar assemblage, a number of
them, as in this case, being- found nowhere else. The amount of material
in this ball was small, and owing to this, we can not say whether or not
the plants found in it were actually rare in the stratuui represented by this
ball, and from which it was torn. It would seem that this ball belonged to
a fossiliferous layer, not now to be seen in place in the exposures about
Dutch Gap. No doubt many originally rich fossiliferous layers have been
destroyed in the local erosions to which the formation was from time to
time in the course of its deposition subjected.

The plant is possibly composite in nature, and not a sharply differen-
tiated Osmimda, but as it contains more of the features of this genus tlian
any other, I have placed it there. The sori are very small, being fine dots.
The exact details of their structure could not be made out.

OSMUNDA DiCKSONIOIDES, Sp. nOV.

Plate XLI, Fig. 5 ; Plate LVIII, Fig. 9; Plate LIX, Figs. 1, 4, 8, 9, 11; Plate LX, Figs. 2, 4, 5, 9;

Plate LXI, Figs. 1, 2.

Sterile frond large, arborescent, tripinnate ; rachises stout, especially
the principal ones; ultimate pinnte subopposite to alternate, closely placed,
linear-lanceolate, acute, ending with pinnules reduced to united teeth and
passing towards the summits of the compound pinnse into pinnules; pin-
nules or reduced pinnae alternate, closely placed, oblong to ovate, passing
above towards the tips of the compound and ultimate pinnae through oblong
or ovate lobed or toothed pinnules into entire ones, and finally into united
teeth, ovate-acute in form. The lower pinnules or reduced pinnae are much
narrowed at base, cut more or less deeply into ovate, elliptical, subquad-
rate, acute lobes and teeth, the lobes, especially the basal ones, being often
toothed ; the nerves in each lobe composed of a midnerve sending off
obliquely and alternately branches either forked or simple ; reduced in the
teeth of the upper pinnules and of the terminal portions of the lower ones
to forked or simple lateral nerves in each lobe or tooth; the fertile frond
distinct from the sterile one ; the pinnules of the former much reduced in

DESCEIPTION OF THE SPEOIES. 147

size, very thick and leathery, apparently consisting of a midrib, which has
on each side a narrow thickened lamina, bearing on the margins large fruit-
masses rounded in form.

Locality : Hill-side near Potomac Run.

The fertile forms are very rare at this locality, but the sterile ones are
very abundant, and much the most common of the specimens found here.
The form depicted in PL LX, Fig. 5, I regard as the fructified form of the
fern which is described above, and which shows so many well-preserved
sterile specimens. As, however, the sterile and the fructified forms were
not found connected together, the union can not be taken as certainly
authorized. Unfortunately the fructification is not well enough preserved
to render its details clear. Fig. 5 gives the appearance as seen in natural
size with the unaided eye. Fig. 5^ gives the appearance under a lens.
The apparent fruit-masses look like rounded masses of naked sori or
sporangia. The entire fructified pinnules are so much thickened and so
poorly preserved, that nothing but the rounded shape and granular appear-
ance of the fruit- masses can be made out. Each mass of fruit seems to
represent a contracted and modified pinnule or lobe. The metamorphosis
of the pinnules reminds one of Osmunda more than of anv other living
genus, aiad I place the plant provisionally in this genus. Possibly this
may be a new genus, composite in character, which has . some of the
features of Tki/rsopteris and Osmunda, for there is an indication of a cup-
shaped grouping in the fruit dots. It is strange that no specimen of this
plant was found on the road-side near by.

Osmunda Dicksonioides, var. latipennis, sp. nov.

Plate LX, Figs. 1, 3 ; Plate LXI, Fig. 3.

Frond tripinnatifid, large, arborescent; rachises proportionally slender;
pinnae and pinnules alternate ; rachises of the ultimate pinnae narrowly
winged ; pinnules with membranaceous leaf-substance, short, oblong in
shape, and acute, attached by the middle point of the narrowed base, cut
more or less deeply into rounded, subquadrate, or broadly oval lobes, the
lower ones of which have shallow, subacute teeth ; fructified form not
seen. Nerves in each lobe remote, strong, composed of a nerve-bundle

148 THE POTOMAC OR YOCJJSTGER MESOZOIC FLORA.

which diverges flabe]lately from a more or less pronounced midnerve, the
branches usually once forked, rarely bifurcate.

Locality : Hill-side near Potomac Run ; comparatively rare.

This plant is much more- rare than the- type species, and, although
evidently nearly allied to it, has the nerves more widely diverging and
remote, a more regular dentation, a winged rachis in tlie ultimate pinnse,
and wider, more rounded lobes. The pinnules also are decidedly broader
in proportion to their length.

SAGENOPTERIS, Pr.

The Jurassic genus Sagenopteris is represented in tlie Potomac flora
by several well-characterized species. None of these, however, seem to
be very- abundant, and the genus furnishes a very small element to the
flora.

Sagenopteeis latipolia, sp. nov.

Plate XXVII, Fig. 10.

Frond unknown ; pinnules apparently subquadrilateral, narrowed
gradually to the base and rapidly to the summit ; midnerve in the lower
part of the pinnule strong, in the upper part dissolving into branches ;
lateral nerves going off very obliquely, branching near the midrib, turning
outward, and then by repeated branching and anastomosis forming long,
rather regular, elliptical to rhombic meshes, which fill the lamina.

Locality : Near Telegraph Station.

Only two fragments of this plant were found. As, however, no
detailed exhaustive searcb was made at this locality, and the amount of
material was small, the rarity may be apparent rather than real. The
shape of the pinnules is nearer that of S. rJioifoUa of the Ehetic than that
of any other species of the genus known, but the anastomosis is more
copious than that of the Rhetic species. In copiousness of anastomosis
and in the shape of the meshes it is nearer S. MantelU Schenk, of the
Wealden. It seems to lie between these two species. In the figure the
margin on the right-hand side appears to represent the original border of
the leaf, but the other parts have been torn away.

DESCKIPTION OF THE SPECIES. 149

Sagenopteris elliptica, sp. nov.

Plate XXVII, Figs. i>, 11-17.

Frond with five pinnules at the summit of a strong stipe, the right and
left outermost pinnules smaller than the inner ones; pinnules narrowed
gradually to a slender wedge-shaped base, and attached by a short petiole,
elongate-elliptical in outline and acute to acuminate at the tips, rarely sub-
quadrate in outline ; midnerve strong at base, dissolving towards the
summit into branches ; lateral nerves leaving at an acute angle, curving
out to meet the margin, repeatedly branching and anastomosing-, so as to
form meshes, which are quite irregular in size and shape ; meshes elongate-
oblong or irregular subrhombic, some much larger than the others ; between
the nerves on the lower side of most of the pinnules numerous rounded
or oblong minute elevations or dots occur, which can be seen distinctly
only with the help of a lens ; these appear to be the fructification.

Localities: Road-side near Potomac Run; Kankey's; Covington
street, Baltimore.

At each of the two last-named localities a small fragment only was
found. It is most abundant at the Rotomac Run locality, from which all the
specimens figured come, but it is not very common even here. No speci-
men was found at the other or hill-side locality, only a few hundred feet
away. The dots look much like fructification, and I have no doubt that
this is their character. This would place the plant in the Dktijopteris
group of Polypodium. It would seem from this that Sagenopteris is a fern
and not a rhizocarp, as Schimper finally held it to be. Although this
species has five pinnules at the summit of the stipe, it seems to be clearly
a Sagenopteris.

This plant, in the general shape of the pinnules and the character of the
midnerve, reminds one strongly of the Neuropterids of the Coal Measures.
The shape of some of the pinnules, as in Fig. 16, is strikingly like that
given by Brongniart in his Histoire for Glossopteris PMllipsii (PI. LXI his,
Fig. 5), which he makes a Sagenopteris. The pinnules in some specimens
are much like those of Sagenopteris rhoifolia} The plant is decidedly

'Compare Scheak: Foas. Flor. der Greazschiohten, PI. XII, Fig. 4.

150 THE POXOMAO OR YOUNGER MESOZOIC FLORA.

Jurassic in type. In Fig. 14, the lowest pinnule on the right-hand side
belongs to the left hand, and forms the outermost one on that side. It has,
by displacement and pressure, been turned to one side and doubled back
under the summit of the stipe, so as to lie alongside of the outermost one of
the right-hand side of that frond.

c

Sagenopteris Virginiensis, sp. nov.

Plate CXXXVIII, Fig. 13 ; Plate CXSXIX, Fig. 1.

Frond unknown; shape of pinnules not seen, probably broadly ellip-
tical or oval; stipe or petiole of pinnules apparently long; midnerve toward
tlie base very strong, dissolving in branches towards the apex ; areolation
very distinct, formed by lateral nerves which go off obliquely and curve
outwards to meet the margin, forking repeatedly, and anastomosing to form
meshes that ai'e irregular in size and shape, being mostly elongate, oblong,
or subrhombic.

Locality: Fredericksburg; very rare.

Plate CXXXVIII, Fig. 13, seems to represent the upper part of the
specimen figured in PI. CXXXIX, Fig. 1. The lamina of the leaf in the
lower part of this specimen has been torn away, leaving the midrib bare.
This appears to be a very large species of the genus.

SCLEROPTERIS, Saporta.

Frond bipinnate or tripinnate, coriaceous ; pinnse pinnately parted,
pinnules or segments more or less constricted at base, decurrent on the
lower side, and forming a narrow wing to the rachis, entire, or incised and
lobed on the anterior margin ; nervation immersed, formed of a few nerves
branching flabellately from a common nerve at the base, diverging flabel-
lately by repeated branching to fill the limb.

The above is very nearly Saporta's diagnosis of the genus Sderopteris
established by him. I modify the nervation only so as to include the
forms described in the next following pages, which clearly belong to this
genus. As to the nervation, Saporta says, in Paleontologie Fran9aise,
Plantes Jiirassiques, vol. 1, page 365, that the nerves come out obliquely
from the back side of the pinnules. This is not the case in all specimens,

DESCEIPTION OP THE SPEOIES. 151

even of those placed by him in the genus, as in PI. XLV, Fig. 2, given
by him of PhiUips's Splienopteris lanceolata, which he makes Scleropteris
Pliillipsii. Sapovta shows quite satisfactorily that Brongniart's genus
Pachi/pteris, which has for its type P. ovata, was established under the
mistaken idea that the specimen furnishing the type had in the pinnules
only a midnerve. It is identical with Phillips's Neuropteris kevigata. This
Saporta makes a Sderopteris with the name S. Icevigata.

Zigno, however, takes this plant as belonging to his genus Dicliopteris,
because it appears to have the nerves, several in number and parallel, pro-
ceeding obliquely from the rachis. But an inspection of Zigno's figure
shows that this idea of the nervation arises from the fact that he has not
draw.n the true point of insertion of the lateral nerves, which is farther
within the apparent rachis, and at this point the nerves most probably
unite. Zigno has taken the margin of the wing for that of the rachis.
According to this, Pachypteris ought not to be considered as a genus.
Brongniart's Pachypteris ovata would be Scleropteris Icevigata Sap., while
Saporta makes Brongniart's Pachypteris lanceolata, and Phillips's Sphenopte-
ris lanceolata, Scleropteris PMUipsii.

Scleropteris elliptica, sp. nov.

Plate XXVIII, Figs. 2, 4, 6; Plate XXIX, Fig. 1.

Frond bipinnate or tripinnate, arborescent; principal rachis stout and
woody; ultimate rachises rather slender, straight, and winged; ultimate
pinnse alternate, linear, terminating abruptly in a pinnule like those lower
on tlie pinnpe; pinnules or segments thick and leathery, narrowly elliptical,
acute, opposite, narrowed at base into a sort of petiole, decurrent to form a
narrow wing; nerves immersed in the thick leaf-substance, inconspicuous,
diverging flabellately from a short common or mother nerve which does
not extend beyond the base of the pinnules, branches once or twice forked
or simple.

Localities: Fredericksburg; lignite deposit near Potomac Run; fish-
ing-hut above Dutch Gap Canal; Kankey's ; near Telegraph Station.

The plant is not very rare at Fredericksburg. The two fine specimens
figured in PI. XXIX, Fig. 1, and PI. XXVIII, Fig. 6, come from that

152 THE POTOMAC OR YOUNGER MESOZOIO FLORA.

locality. The leaf-substance of this plant is so thick and the epidermis so
well preserved that on drying the leaves curl up and peel off from the
stone like paper, so that it is difficult to preserve the specimens. The
nerves are seen with difficulty, but still they were clearly made out. Plate
XXVIII, Fig. 6, gives a portion lower on the frond than the part figured
in PI. XXIX, Fig. 1. Plate XXVIII, Fig. 2, gives a small form from
Fredericksburg with unusually remote pinnules.

All the features of this plant, except the nerves, agree exactly with
those given by Brongniart for Pacliypterls lanceolata, and the resemblance to
Phillips's Sphenopieris lanceolata is striking.

This Potomac plant was evidently a large one. In this and the other
species of the genus found in the Potomac beds there is no tendency to
the lobing of the pinnules given by Saporta as existing on the anterior
margin of some species.

SCLEROPTEEIS ELLIPTICA, var. LONGIFOLIA, Sp. UOV.
Plate XXVIII, Fig. 7.

Frond and pinnaj not seen; pinnules linear-elliptical, alternate or
opposite, oblong-subacute, gradually narrowed towards the base, very
long, decurrent, forming a narrow wing ; leaf-substance leathery ; nerves
comparatively fine, closely placed, forking from a common nerve at the
base, diverging slightly, branches deeply once or twice forked, with the
ultimate branches parallel.

Locality : Fredericksburg ; very rare.

This is probably only a variety of Scleropteris elliptica, but the differ-
ences are considerable. The figure gives the summit of an ultimate pinna,
which ends in a pinnule larger than those immediately below it on the
pinna. It is noteworthy that the pinnules diminish very rapidly in passing
towards the tip of the pinna.

Scleropteris Vieginica, sp. nov.

Plate XXVIII, Figs. 3, 5.

Frond bipinnate or tripinnate ; rachises comparatively stout ; primary
pinnae or those of the frond terminated by an ultimate pinnule like those

DESCEIPTION OF THE SrECIES. 153

immeaiately below it on the principal racliis ; iiltimate pinnje opposite,
terminated by a lobed tip, the pinnules of the lower portion having here
passed into more or less united lobes; pinnules small, opposite, thick, and
leathery, elongate -elliptical, acute, narrowed gradually to the base and
inserted by a sort of petiole, decurrent to form a narrow wing ; nerves
inconspicuous from immersion, branching from a connnon point or a very
short nerve at the base of the petiole, diverging slightly, the secondary
branches forking once or twice.

Locality : Red clay ball in banks of Dutch Gap Canal ; rare.

This is a much smaller form than S. eUijMca, and more like S. Pomeli
Saporta, being, however, somewhat larger than that.

SCLEEOPTEEIS DENTATA, sp. nOV.
Plate LSIII, Figs. 3, 4.

Frond bipinnate ? ; rachises slender, those of the ultimate pinnae
winged ; pinnules with leathery leaf-substance, oblong to elliptical, acute,
greatly narrowed at base, and decurrent to form a wing; lower pin-
nules cut very obliquely into ovate-acute lobes, which pass in the pin-
nules higher on the frond and towards the tips of the ultimate pinnge into
triangular and shallow acute teeth; the ultimate pinnse (Fig. 3) terminate
with an oblong pinnule, which has at its summit three teeth ; nerves of
the pinnules composed of a slender midnerve, which sends off alternately
into each lobe or tooth a deeply forked lateral nerve, sometimes having
one of the branches forking again.

Locality : Fredericksburg ; quite rare.

This fern shows a curious blending of the features of Sclei-opteris and
Cteno])teris, standing midway between them. Perhaps it would be better
to make it a new genus.

CTENOPTERIS, Brong.

Frond bipinnate or tripinnate ; pinnae broadly lineaiwlanceolate, pin-
nate, and pinnatifid ; pinnules attached by the entire base, slightly decur-
rent, lower ones separate, upper ones slightly united at base, slightly curved

154 THE POTOMAC OR YOUNGER MESOZOIO FLORA.

forward; leaf-substance thick, margins entire or with spinous teeth; nerves
several, arising- from the rachis either separately, or from a common point,
or from a short parent nerve, branching one or more times, branches turned
slightly outward, or with a central nerve that sends off on each side
branches that diverge flabellately.

The forms from the Potomac flora that I have placed in the genus
Ctenopteris, with the amended description given above, differ somewhat from
the typical form on which Brongniart founded the genus, viz, Ctenopteris
cycadea Brong., and the species of Saporta, C. grandis, but stand very
near to the latter.

These Potomac species apparently are composite in type and unite
some of the features proper to several genera of ferns. They have, how-
ever, so many of the characters of Gtenopteris that it seems proper to place
them in that genus.

Perhaps the difterences shown when they are compared with the
typical ctenopterids are due to modifications produced in the genus as time
passed, for we must remember that Ctcnoptcris cycadea and C. grandis are
Liassic fossils, while the Potomac forms are much } ounger. The diverg-
ences are of such a nature as to suggest this relationship, for the chief
ones consist of a greater complexity produced by the differentiation of the
nerves, which tends to produce a midnerve, and by the development of
teeth on the margins of the pinnules or segments

Although from the general character of these plants I regard them as
ferns, still, so long as they show no fructification, it is quite possible that
they may be cycads. Schimper^ well says that the tripinnate character of
the leaf of the genus does not necessarily exclude it from the cycads, for
the cycad genus Bowenia has bipinnate leaves. Bowcnia resembles the
Potomac plants more strongly than the forms on which Brongniart founded
the genus, for this cycad has leaflets cut away obliquely in front and
nerves which diverge from a common point at the base of the pinnules,
features found in the Potomac plants; and, what is more significnnt, some
of the pinnules of Bowenia have at least one spinous tooth, much like
those of the Potomac plants.

'Zittel's Handbuch der Palieoutol., vol. 2, Liferung I, p. 123.

DESCRIPTION OP THE SPECIES. 155

Saporta calls attention to the resemblance of the Jurassic ctenopterids
to the odontopterids of the Carboniferous, and says that there is much
difficulty in giving any good distinction between Ctenopteris and Zigno's
genus Bicliopteris from the Oolite. He thinks it possible that Dichopteris
may represent Ctenopteris in the Oolite, the main difference being that
Dichopteris has its pinnules narrowed at base. Saporta also remarks that
Scleropteris is near to Ctenopteris. The Potomac plants bring these genera
still nearer, supplying connecting links, for we find some with the charac-
ters of each of these genera predominating, and they graduate into one
another. They show that the features relied upon to distinguish Sclerop-
teris, Ctenopteris, and Dichopteris have in the main but little value.
Scleropteris may remain a distinct genus, but, as has been suggested, there
seems to be no good reason why Dichopteris should not be united to
Ctenopteris; for, as Saporta says, the bifurcation of the frond of the former
may have been accidental. If we omit the slight union of the pinnules
at base and the absence of teeth, the resemblance between the nervation
of Dichopteris Visianica,^ its shape, and the attachment of the pinnules, and
these features in some of the Potomac ctenopterids is most striking. We
have the same slight forward curvature of the pinnules, the oblique cutting
away in front, the slight decurrence below, and the same mode of insertion
of the nerves. The nerves differ only in the more copious branching of
the centi'al ones of the Potomac plants.

Heer^ gives figures of plants wliich he places in his cycadean genus
Ctenidium. These, and more especially the species C. dentatum, resemble
in some points the Potomac plants; but in Heer's plants the cycadean feat-
ures predominate, and they certainly belong to a geaiis distinct from that
of the Potomac fossils. Phillips's Odontopteris Leckenhyi Zigno (Geol. of
Yorkshire, p. 218) may also be compared with these plants. The species
Ctetiopteris Itieri^ Sap. seems to belong to a type quite different from C.
grandis and C. cycadea, having the nervation only in common. C. Itieri
is much more fern-like than the two latter.

'Zigno: Flor. Foss. Form. OoUtice., PI. Xll.

^Flor. Foss. flu Portugal, PL XVI.

'Pal. Fraufaise, Plantes Jur., vol. 1, Atlas, PI. XLIV, Figs. 1, 3.

1 56 THE POTOMAC OE YOUNGER MESOZOIO FLORA.

The Potomac fossils give more of the frond than the species hitherto
known, and thus add a good deal to our knowledge of this curious genus.
Unfortunately no trace of fructification was seen.

Ctenopteris insignis, sp. nov.

Plate LXr, Figs. 4, r> ; Plate LXII, Fig. 1 ; Plate LXIII, Figs. 1, 2.

Frond large, arborescent, bipinnate or tripinnate ; principal rachis
very strong, striate; ultimate pinnoe with strong rigid rachises, alternate,
terminating in a lobed segment, the pinnules passing into lobes more or
less united towards the ends of the ultimate pinna?.; pinnules thick and
leathery, those of the lower and middle portions of the pinn?e. attached by
the entire base, slightly decurrent, separate, cut away obliquely above,
alternate to subopposite, gradually diminishing towards the summit of the
pinnte in size and depth of toothing, not sensibly narrowed at base, oblong-
acute, curved slightly forward, terminating in a large ovate to subtriangu-
lar acute tooth. The pinnules usually show two acute or spinous teeth on
each side, a couple near the base, and a second couple near or at the sum-
mit of the pinnule, the associated members of the couples being opposite
or subopposite. Sometimes there is an additional tooth on the posterior
margin below the upper one, and sometimes the terminal tooth is enlarged
to an oblong lobe (see PI. LXI, Fig. 4), which is slightly notched; nerves
several, departing separately from the principal racliis along the entire
width of the base of the pinnule, the outermost ones once forking and
curving outwards, the inner ones forking deeply several times and slightly
diverging flabellately, the ultimate branches nearly or quite parallel, long,
and slender.

Localities: Fredericksburg; road-side near Potomac Run.

This splendid plant is not uncommon at the first-named locality, and
is found in small bits only at Potomac Run. All the specimens figured
come from Fredericksburg. The specimens show a black, glossy plant-
matter, which peels off like paper from the stone, and indicates that the epi-
dermis was dense and durable. A thick coriaceous epidermis covered the
main rachis and all parts of the plant. The nerves are not usually dis-
tinctly seen, being obscured by the thick epidermis. The form given, in

DESCEIPTION OF THE SPECIES. 157

PI. LXI, Fig. 4, differs from the typical forms in having the termination of
the pinnules an oblong lobe, which is slightly notched or toothed. Figure
5 of the same plate appears to be the summit of an ultimate pinna, differing
in the trilobate terminal pinnule from the normal termination, as shown in
PI. LXIII, Fig. 1, where the lobes gradually diminish in size towards the

summit.

Ctenopteris virginiensis, sp. nov.

Plate LXII, Fig. 4 ; Plate LXV, Pig. 1 ; Plate CXVI, Fig. 4.

Frond bipinnate or tripinnate, probably, arborescent ; rachises stout,
strongly ridged or keeled; ultimate pin use subopposite; leaf-substance
thick ; pinnules comparatively short and broad in proportion to their
length, opposite or alternate, slightly decurrent, distinct to the base or
slightly united, attached by the entire base, rounded obliquely on the
upper side at base, slightly curved forwards, posterior margin nearly
always free from teeth, terminating in a triangular tooth, with an acute
tooth on each side of this at the summit of the pinnule, and with an acute
or spinous tooth about midway on the anterior margin ; nerves proceeding
from a common point on the rachis of the ultimate pinnse, branching sev-
eral times and diverging slightly, the ultimate branches long and nearly
parallel.

Locality: Fredericksburg; rather rare.

This plant has a very stout principal rachis, but the species is decid-
edly smaller than C. insignis, and shows some important points of differ-
ence from it. On nearly all the pinnules there are no teeth on the poste-
rior margin of the pinnules, and only one on the anterior margin. The
most important difference is in the nerves. They form two principal
nerve-bundles, which depart from a common point and not from the entire
base of the pinnule. Thus they show a tendency to form a midnerve with-
out actually developing one. In this feature there is an approach to the

Sderopteris type.

Ctenopteris minor, sp. nov.

Plate LXVII, Fig. 3.

Fronds small, arborescent, bipinnate or tripinnate ; principal rachis
strong, rigid ; ultimate pinnse with rachises strong towards the base and

158 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

much attenuated towards the su.mmit, alternate to subopposite, and termi-
nating in a slender toothed or lobed segment ; pumules small, separate in
the lower part of the ultimate pinn;ie, but united at base in the upper part
of the same, attached by a base slightly narrowed and decurrent, cut away
obhquely on the upper side of the base, inclined forwards, alternate to
opposite. Towards the summit of the ultimate pinnjij the pinnules diminish
in size and in the number and depth of the teeth, the uppermost ones
being entire and elongate-oblong in shape. The lower and middle pinnules
of the ultimate pinna' are generally subrhombic in form and vary somewhat
in the number and form of the teeth; they terminate in a comparatively large
triangular or ovate tooth or lobe, which is generally entire and rarely
slio-htly dentate, and generally show two more or less acute teeth on each
side and in pairs, a pair near the base and one near the summit, the mem-
bers of the pairs being opposite or subopposite. Sometimes additional teeth
appear, generally on the posterior margin of the pinnules; principal nerves
several, departing separately from the rachis of the ultimate pinnse so as to
fill the central jwrtion of the base of the pinnules. The outermost ones fork
once and cmwe outwards, the inner ones fork several times and diverge
slightly in a flabellate manner; the ultimate branches are short and diverge
strongly; all the nerves strong.

Locality: Fredericksburg ; rare.

Tliis plant is in many features like Ctenojiteris iitsignis. It differs from
this mainly in the small size of the pinnules, the greater variability of the
teeth, and in the character of the ultimate forking of the nerves. In C.
insignis the ultimate branches of the nerves are long, slender, and nearly
parallel. Perhaps this is merely a small variety of that plant.

Ctenopteris integkifolia, sp. nov.

Plato LXII, Fig. 2; Plate LXV, Fig. 3.

Frond unknown ; pinnules oblong to subelliptical, slightly curved for-
wards, subacute, obhquely cut away on the anterior margin at base,
decurrent on the lower side, separate to the base in the lower portions of
the ultimate pinnae, united slightly in the upper ones, which are much
diminished in size ; nerves several and distinct, departing from the rachis

DBSCEIPTION OP THE SPECIES. 159

at several points, the outer ones once or twice forking and turned out-
wards, the central nerve branching several times, branches flabellately
diverging ; all the ultimate branches from deep forking are long.

Localities: Road-side near Potomac Run; Fredericksburg; very rare.

This plant makes a close approach to Zign.o's Dicliopteris Visianica, the
main difference being the more copious brandling of the central nerve, as
shown in the pinnules of PI. LXV, Fig. 3, magnified in Fig. 3^ In that
shown in PI. LXII, Fig. 2, from Fredericksburg, the pinnules are some-
what falcate, and are united at base. It is apparently a fragment of the
terminal portion of a pinna.

Ctenopteris angustifolia, sp. nov.

Plate LXV, Fig. 2 ; Plate LXVII, Fig. 4.

Frond unknown; ultimate pinnae long, with rather stout rachises, pin-
nules linear or narrowly oblong, in proportion to width quite long, slightly
curved forwards, separate to tlie base, or united to form a wing on the
rachis of the pinnse, cut away obliquely on the upper side at base, and
slightly decurrent on the lower side, attached by the entire base, termi-
nated by from one to three acute or spinous teeth, and having a varying
number of the same placed irregularly on both margins. The nerves
proceed from the rachis at different points along the entire base of the pin-
nules; the outer ones simple or forking once, the central ones forking sev-
eral times, the ultimate branches being long, slender, and slightly diverging.

Locality : Road-side near Potomac Run ; rare.

There is some difference in the two specimens figured, which, how-
ever, may be due to different positions on the frond.

Ctenopteeis longipolia, sp. nov.

Plate LXVII, Fig. 5.

Frond unknown ; rachis of the ultimate pinnaj very broad but not
apparentl}^ very woody ; pinnules placed very remotely, opposite, going
off obliquely, very long, linear, narrowed gradually and sHghtly towards
the base and slightly decurrent, tips not seen ; nerves not well made out,
but apparently as shown in Fig. 5'"; that is, several, departing independ-

160 THE POTOMAC OK YOUNGER MESOZOIG FLORA.

entlv from tlie racliis and forking near the base ; the branches, so far as
seen, simple, and nearly parallel.

Locality : Fredericksbnrg ; only one specimen found.

This is another of those curio us forms which, as they stand nearest to
Ctciioptcrls, are placed provisionally in this genus. The obscurity about
the nerves is wholly contined to their character at the attachment of the
pinnules. They were not distinctly seen at this point, and may be not
forking there but separate. The plant is very much like the genus
JEncephalartos, and especially resembles E. tridentatus Lehm. It may really
belong to this genus.

ZAMIOPSIS, gen. nov.

Fronds large, bipinnate to tripinnatifid ; leaf-substance leathery and
thick, covered with a dense durable epidermis ; rachises strong, rigid, and
keeled on the lower surface, often with ridged or raised margins on the
upper surface ; penultimate pinnse very long, viltimate pinnae or pinnules
usually closely placed, narrowed to the base, mostly linear-lanceolate or
oblong-lanceolate, the lower ones generally cut obliquely into pinnules
which are denticulate, but pass above into denticulate or spinous teeth and
terminate in two or more spinous teetli ; nerves of the pinnules and lobes
mostly composed of a midnerve which goes off- very obliquely and curves
strongly outwards, sending off obliquely and alternately lateral branches,
which are forked or simple and curve upwards towards the summit of the
segment ; in the lobes and teeth the lateral nerves go off very obliquely
and fork once or twice, having very long ultimate branches ; nerves,
although fine, very distinct.

This curious type of ferns, if ferns they are, reminds one of the
cycadean genus Stanyeria in some respects, but in the nature of the lobes
and teetli they differ from Stangena. In most species the nerves towards
the upper portion of tlie ultimate pinufe or pinnules are very oblique and
have long slender branches, while in the lower or basal portions they form
nerve-bundles that curve more or less strongly outwards to meet the mar-
gin of the pinnule or reduced pinna. The plants show a curious blending
of the features of cycads and ferns, with a predominance of the latter.

DESCEIPTION OF THE SPECIES. 161

In the branching of the I'achis we have the fern rather than cycadean
character, although Boivenia shows that this is not necessarily solely a
fern feature. We can hardly assume that Boivenia is the only branching
cycad that ever existed. It is more natural to suppose that it is a survivor
of a group of branching cycads that once possessed numerous forms.
The nervation of the lower portions of the pinnules is rather that of ferns
than of cycads, but Stangeria shows that similar nerves may exist in
cycads. The very long, slender, deeply forking nerves in the summits of
the pinnules are similar to those of cycads. The peculiar spiny teeth are
decidedly like those of cj^cads, but the teeth pass below on the frond into
lobes, and these lower down graduate into segments that we may call
pinnules, and this feature is clearly fern-like. The nerves are immersed
in the dense leaf-substance, so that they are often obscured.

The singular plant Zamioj^sis lac'miata, given on PI, LXVI, has so
many features that cause it to differ from the typical forms of Zamioims,
that it may well be questioned whether or not it should be made a new
genus; but as it has some features allying it to the typical Zamiopsis, I
place it with a good deal of hesitation in that genus. So long as no
fructification is found with these plants their true position can not be
positively determined; meantime they may be placed provisioiially among
the ferns. This, type forms quite an important element in the Potomac
flora.

Zamiopsis pinnatipida, sp. nov.

Plate LXI, Fig. 7 ; Plate LXII, Fig. 5; Plate LXIV, Fig. 2; Plate LXVII, Fig. 2.

Frond large, arborescent 1 ; principal rachis keeled on the under side,
strongly ridged on the upper margins, probably tripinnate ; pinnules or
reduced pinnne alternate, attached by the middle of the narrowed base,
oblong, terminated by usually two acute shallow teeth in the basal por-
tions, cut down nearly to the midrib into ovate denticulate lobes or pin-
nules; up higher on the pinnules or reduced pinnae these pass into ovate
teeth, which become more and more shallow. On the basal lobes or
pinnules there are on each margin two or three shallow spinous teeth ;
midnerve of the ultimate pinnpe or pinnules strong at base, rapidly atten-

MON XV 11

162 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

uated towards the summit, and dissolving into branches near the tips;
Literal nerves of the basal toothed pinnules or lobes composed of a nerve-
bundle which goes off very obHquely from the lower portion of the lobe
or below it, branching several times, curving strongly away from the
midnerve of the pinnule or reduced pinna, slightly diverging, the ultimate
branches going into the teeth, and mostly simple. In the lobes towards the
upper end of the pinnules the nerves become less and less copiously
branched, being finally reduced to nerves forking only once or twice.

Locality : Fredericksburg ; rather rare.

This plant must have been a very large one. Plate LXI, Fig. 7, and
PI. LXIV, Fig. 2, give probably fragments of compound pinnae. The
pinnules cut into lobes are most probably reduced ultimate pinnse, the
lobes representing what are, in portions lower down, pinnules separate to
the base; possibly these fossils may be a variety of the next following,
Zantiopsis insignis, but there seem to be no forms establishing a passage
into that species.

Zamiopsis insignis, sp. nov.

Plate LXII, Fig. 3; Plate LXIV, Figs. 1, 3; Plate LXV, Figs. 4-6; Plate LXVI, Fig. 2; Plate

LXVII, Fig. 7.

Frond very large and spreading, probably tripinnate; leaf-substance
of the pinnules thick and leathery; epidermis, covering the principal rachis,
as well as the other portions of the plant, thick and durable ; principal
pinna; going off at very nearly a right angle, very long, with a very stout,
rigid rachis, keeled on the lower side, with marginal ridges on the upper
side. The ultimate reduced pinnte or pinnules pass towards the summit of
the penultimate pinnse into much reduced toothed pinnules, united at base
and decurrent; ultimate pinnae or pinnules oblong, much narrowed at base
in the lower ones, and attached by the middle of the base, alternate, vary-
ing in size, extent of toothing, and remoteness with tlieir position on the
frond, lower ones cut deeply and obliquely into oblong- or subquadrangu-
lar lobes or pinnules, which usually have near the tips on each side shal-
low spinous teeth, and end in a comparatively large ovate-acute tooth.
Sometimes only one tooth is found on the lobes, and that occurs on the

DESCRIPTION OF THE SPECIES. 163

upper margin ; tliis varies with tlie position of the lobes on the pinnje and
the frond ; on the lower lobes and pinnse it is broadly triangular, rather
deeply cut, and directed outwards ; in the upper pinnse and lobes it is
minute, shallow, and spinous; in the upper portions of the frond the lobes
end in or graduate into spine-like teeth, which are sometimes much prolonged
and quite slender, these teeth directed forwards or outwards are single or
double. The reduced ultimate pinnse or pinnules end variously, either in
two or more acute teeth or in an ovate-denticulate lobe ; miduerve of the
ultimate pinnaj or pinnules strong towards the base, rapidly much atten-
uated higher, and at the summit dissolving into branches ; nerves of each
lobe or pinnule of the basal portions of the lower pinnse or pinnules
composed of a nerve-bundle which goes off very obliquely from the
rachis below the base of the lobe or pinnule, curving strongly outwards,
forking near the base, with each branch forking deeply once or twice again.
Towards the summit of the ultimate pinnse the lateral nerves become very
oblique, do not curve so .suddenly and strongly outwards, but continue for
a long distance, more or less in the direction of the axis of the pinna, are
forked several times with long branches, forming indeed the branches into
which the midnerve splits up. In the upper toothed pinnse the midnerve
(see PI. LXIV, Figs. 1", 1^) continues only a little more than one-third of
the length of the pinna. It is spht up into very obhquely placed, shghtly
diverging, and very deeply forking branches, which fork once or twice, and
have very long, slender, ultimate branches. The lateral nerves from the
lower portions of these pinnse, go oif very obliquely, fork once or twice,
and have very long, slender, ultimate branches.

Locality r Fredericksburg ; rather common.

Tlie specimens obtained of this plant show that it must have attained
a very large size. The fragment figured in PI. LXIV, Fig. 1, is probably
a portion of a compound pinna of large dimensions. The specimen given
in PI. LXV, Fig. 4, which is a portion of probably a penultimate pinna,
shows that these must have been in some cases very long. The epidermis
over the pinnules and rachises of PL LXIV, Fig. 1, was so thick and dur-
able, that it could be peeled off like paper. Plate LXIV, Fig. 3, seems to
show a fragment of a penultimate pinna, forming the lower portion of one

1 64 THE POTOMAC OE YOUNGER MESOZOIC PLOEA.

corresponding- to that depicted in PI. LXV, Fig-. 4. Plate LXIV, Fig. 3,
shows some irregularity in the spacing of the penultimate pinnre or pin-
nules, the central ones on the left-hand side showing an abnormal crowd-
ing-. Plate LXVII, Fig. 1. appears to be an ultimate pinna or pinnule
from still lower on the frond than an}^ of the others, and the lobing- is
irregular, two of the lobes from the middle of the specimen on the right-
hand side being cut deeply into falcate, narrowly oblong, or ovate lobes.
While the general plan of the lobes and teeth is the same throughout, some
variation is shown in the number, arrangement, and shape of the teeth.
Thus we have in PI LXV, Fig. 5, the lobes or incipient pinnules sub-
quadrangular, curved forward, with a terminal ovate tip, and on the exte-
rior margin near the tip a broadly triangular tooth directed outwards.

Zamiopsis longipennis, sp. nov.

Plate LXI, Fig. 8.

Frond unknown; ultimate pinnae or pinnules very long, ensiform,
slightly falcate, acuminate ; margins of the pinnules cut into shallow, nar-
rowly ovate single or double teeth, midnerve strong towards the base and
vanishing towards the ends of the pinnules, splitting up into branches, in
the upper portion not placed centrally in the pinnules ; lateral nerves dis-
tinct, going off very obliquely, curving outwards and forked once or twice,
with the ultimate branches long and slender.

Locality : Fredericksburg ; only one specimen found.

This may possibly be the summit of a pinnule of Zamiopsis insignis,
but it has features not seen in that species, and the pinnule was evidently
much longer than any seen on it. The eccentric position of the midnerve
and the convex expansion of the lower margin near the summit of the pin-
nules are peculiar features.

Zamiopsis laciniata, sp. nov.

Plate LXVI, Fig. 1, 5-8.

Frond very large and wide-spreading, probably arborescent ; ultimate
pinnae alternate, the lower ones very long, rapidly diminishing in length

i

DESCRIPTION OF THE SPECIES. 165

and size ii. ascending towards tlie summit of the principal pinnre, having a
distinctly winged rachis, and terminating in a variously shaped segment
formed of united pinnules or lobes, usually three in number; j)innules very
variable in size and shape, mostly long, ribbon-shaped, slightly narrowed to
the base and attached by the entire base, decurrent, and united to form a
wing, cut very obliquely into a few lobes of varying depth, which are
elongate-oblong or narrowly ovate in shape, and nearly always placed on
the posterior margin of the pinnule. The lobes toward the summit of the
pinnules pass sometimes into acute triangular teeth, which are turned out-
wards. The pinnules at the summit of the ultimate pinnae, pass into more or
less united lobes, which vary a good deal in shape, being sometimes much
narrowed and even wedge-shaped at base, and incised into a varying num-
ber of irregularly shaped teeth ; nerves of the pinnules departing- from a
short mother nerve at the base of the pinnules, forming three branches,
these diverging slightly in a flabellate manner; branches very long, slender,
but distinct, outer branches simple or once or twice forked, the inner one
forking several times and approaching the character of a midnerve ; leaf-
substance thick and leathery.

Locality : Fredericksburg ; rare.

This splendid but very peculiar fossil unites some of the features of
Zamiopsis with some of those of Ctenopteris. It really stands intermediate
to typical forms of these two genera. It also shows some of the features
oi Scleropteris, and it hence belongs to quite a comprehensive type of plants.
As the nervation is not essentially different from that of Zamiopsis, it seems
best to place it provisionally in that genus.

The plant is a remarkable one. In its pinnules and longer lobes, so
far as the shape goes, it reminds one of Saporta's Stenopteris desmomera, but
the nervation is very different. Some of the pinnules towards the tips of
the lower ultimate pinnte are narrowly strap-shaped, and show a very con-
siderable length without any lobing or toothing. But as the tips of these
are wanting, it is possible that they may possess teeth up higher. Figure
6, the upper portion of an ultimate pinna, and also Figs. 5, 7, show how
irregular the toothing and shape of the pinnules, here reduced to lobes,
become in the terminal portions of the ultimate pinnae.

166 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

Zamiopsis petiolata, sp. nov.

Plate LXVI, Fig. ;?.

Frond bipinnate or tripiunate ; principal racliis with a strong wing ;
primary pinna terminating abruptly in a large incised pinnule similar to those
lower down ; pinnules petiolate, attached by the midnerve, prolonged into
a stout petiole, alternate, cut obliquely into oblong or subelliptical obtuse
pinnules, in the lower part of the ultimate pinnae turned outwards. These
graduate in the upper parts of the same into lobes and teeth of the same
general character. The summit of the ultimate pinna is a broad oblong
segment ending in several shallow subacute teeth formed by the union of
the lobes at the summit ; the ultimate pinnae in passing towards the sum-
mit of the penultimate ones diminish much in size, the pinnules and lobes
passing finally into teeth ; lateral nerves in each pinnule and lobe consist-
ing of a nerve-bundle which goes off very obliquely from a point near the
lower end of the pinnule or lobe, branching near the insertion, and curv-
ing out to enter the pinnule or lobe, the branches forking again once or
twice, with the ultimate nerves very long* and slender, owing to their deep
forking.

Locality : Fredericksburg ; very rare.

This is another of the peculiar cycad-like ferns which form such a
striking feature in the Potomac flora. Possibly it is a new genus, and I
place it with doubt provisionally in the genus Zamiopsis. The principal
rachis has on each side a strong succulent wing or margin (see Fig. 3"').
The nerves agree fully with those of Zamiopsis.

PHANEROGAMS.
GYMNOSPERM^^E.

The cycads of the Potomac flora, although presenting a considerable
number of species, by no means equal the Goniferre in that respect, but it
is especially in the number of individuals that this group contrasts with
the Coiiiferce. With the exception of Dioonites the species, when found,
are among the great rarities at the different localities. As the specimens

DESCEIPTION OF THE SPECIES. 167

are generally very fragmentary and apparently injured by- transport, it is
quite possible that the comparative rarity of cycads is apparent rather
than real, being due to the accidents of preservation, which were not
favorable to these plants. Although not equaling the ferns and conifers,
the cycads are present with a development sufficient to form an important
element in the flora and to add greatly to the Mesozoic aspect of the
vegetation.

ANOMOZAMITES Schimper.

Leaves comparatively small, linear or ribbon shaped, sometimes (the
younger?) entire, mostly cut into irregular segments; lamina of the leaf
attached laterally, sometimes undivided or only partially divided, but
most often divided into rectangular lobes unequal in size, which, especially
in the lower ones, are rounded; nerves going off at right angles, simple,
and parallel. The segments have sometimes a corded border.

This description, which is very nearly that given by Schimper^ for
Ammosamites proper, typified in Anomosamites inconstans Goppert, fits
exactly a few of the smaller Tseniopteris-like cycads of the Potomac flora.
The forms thus limited range, according to Schimper, from the Rhfetic to
the Wealden. From the genus proper, having the above description,
certain large leaves are excluded by Schimper in the work above quoted,
and placed in a subgenus, Platypterigium. These will be noticed further
on. In the genus proper of Anomozamites there are two species in the
Potomac flora.

Anomozamites angustifolius, sp. nov.

Plate XXX, Figs. 2, 3.

Leaves comparatively narrow, 4™ wide, ribbon-shaped at the tip,
narrowed rapidly; leaf-substance thin, lower portions of leaf not seen;
midnerve moderately strong; lateral nerves going off nearly at right angles,
simple, parallel, arched slightly forward, towards the tip of the leaflet going
oif more obliquely and arched forward more strongly, slender, but distinct.

Localities : Fredericksburg ; Baltimore ; in Meek's collection ; rare.

' Zittel's Handbuch der Palgeout., vol. 2, Lief. 9, ^. 224.

168 THE POTOMAC OR TOUNGBR MESOZOIC FLORA.

The small fragment (Fig. 2) occurs in the plants collected by Meek at

Baltimore, probably at Federal Hill. It is the smallest of the Potomac

Anomosamites and may be a young form of some of those found in the

Platypterigium subgenus, for it shows no tendency to subdivision of the

lamina.

Anomozamites vikginicus, sp. nov.

Plate XXX, Fig. 4 ; Plate XXXI, Fig. 3.

Leaves proportionally very long, of medium width, 37™" wide, no
segmentation visible; the nerves are simple and go off nearly at riglit
angles, and near the margin curve slightly forward, thin, but distinct; leaf-
substance thin ; midnerve strong. ,

Localities: Road-side near Potomac Run; near Telegraph Station; rare.

The leaves of this plant are considerably larger than those of A. an-
gustifoUus. No tendency to segmentation is shown, and it may be a young-
form of one of the large Platypterigia.

ANOMOZAMITES, subgenus PLATYPTERIGIUM, Schimper.

Leaves large, up to two feet and more in length, and half a foot wide ;
lamina of the leaf thin, divided into segments of unequal size, that are
rounded or obtusely rhombic in shape ; nerves parallel, simple, and
forked; forms are Pteropliyllum Braimsii Schenk., P. princeps Oldham and
Morris, etc.

This description of Schimper for the subgenus agrees well with cer-
tain large leaves that are rather common at Fredericksburg. Schimper
says that these leaves may be compared with the split leaves of Macroke-
niopteris, and such I for some time took them to be, but was finally com-
pelled to think that the segmentation was not the result of accidental
Assuring. The individuals of the species of this genus are very much
more abundant than those of the species of Anomosamites proper. It is
peculiar that I could find no specimen showing the ends of the leaves, and
the base of the leaf also was never found. Parts of the middle portions of
the leaves were by far the most common. The plants collected by Pro-
fessor Uhler at Fredericksburg, and which were lost in transmittal to New
Orleans, contained a fine tip of one of these leaves.

DESCRIPTION OF THE SPECIES. 169

These Platypterigia must have attained a great size, rivaling that of
Macrotceniopferls magnifolia of the Virginia Rhsetic. For some time, vrhen
onl}^ very imperfect specimens had been found, I thought that these were
fissured leaves of that or a nearly allied plant.

My recollection of the lost tip of the leaf in Professor Uhler's collec-
tion is not definite enough to enable me to describe it accurately, for I
examined it only casually, expecting to be able later to critically study it.
The leaf tapered gradually to a subacute point, much as do some of those
of M. magnifolia.

The larger specimens of this subgenus probably formed portions of
leaves that must have been over two feet long (60''") and a half foot wide
(15™). The rachis is very stout and wide, with a ridge or cord running in
the middle on the lower side. The upper side is smooth, or with a marginal
ridge on each side. Fragments of leaves 25™ long, and without sensible
>:^ diminution in their width, have been obtained, and some specimens 14"'°

wide were seen. Midribs with a width of 9°"° have been found, and a por-
tion of a petiole showed the width of 13"". The nerves towards the base,
as shown in PL XXXI, Fig. 2, are more oblique in their course than in the
middle of the leaf The ridge in the center of the midnerve on the under
side seems to be due to the woody bundle of the true midnerve, showing
by pressure through the thick epidermis. This epidermis on the midnerve
is striated parallel with the length of the leaf None of the lateral nerves
are furcate even at base.

Platypterigium densinerve, sp. nov.

Plato XXX, Fig. 8; Plate XXXr, Figs. 1, 4; Plate XXXII, Figs. 1, 2; Plate XXXIII, Fig. 1; Plate
XXXIV, Fig. 1 ; Plate XXXV, Figs. 1, 2.

Leaves very large, pi'obably 60"" and more in length, and as much as
20"" in width ; leaf-substance very thick and membranaceous ; midnerve
moderately strong, covered with a thick, dense epidermis, which is striated
parallel with the length of the leaf, and which makes the midnerve appear
wider than it really is, on the lower surface sometimes appearing ridged
in the middle, on the upper side smooth or corded on each margin at the
attachment of the lamina of the leaf; laminae entire, or more commonly cut

170 THE POTOMAC OR TOUNGEE MESOZOIG FLORA.

into segments of varying width, that are rectangular, irregularly quadrilat-
eral, or subrhombic in shape, and have often the posterior or outer mar-
gins obliquely rounded off; nerves very fine and placed very closely
together, so that two or three occur iir the space of 1"", going off nearly at
right angles, curving very slightly forward, parallel.

Locality: Fredericksburg; not uncommon.

This splendid plant "has yielded a number of specimens, but all of
them, no doubt owing to the great size and to the fragility of the leaf,
show only small portions of the plant. The base and tip of the leaf were
in no case found, although carefully sought for. The specimen men-
tioned as 25""" long, with no sensible diminution in width, belonged to this
plant. One specimen showing only half the lamina of the leaf was 9*="
wide (see PI. XXXV, Fig. 2). This indicates a leaf 20^" wide. The tip
seen in Professor Uhler's collection seems to have belonged to this species.
This plant has the same kind of vaguely defined midnerve that was
described in Contributions to the Knowledge of the Older Mesozoic Flora of
Virginia, Mon. U. S. Geol. Survey, vol. 6, as belonging to 3Iacrotceniopteris
magnifolia Rogers, of the Older Mesozoic or Rhgetic flora of Virginia. It
is due to the dense epidermis and leaf-substance at the junction of the lam-
ina of the leaf and the midnerve, which hides the insertion of the nerves
and widens the apparent midnerve.

The nerves, although exceedingly slender and closely placed, are
sharply defined and have only one woody bundle, differing in this point
from those of the Rhsetic fern. They are usually one- half millimeter
apart, although sometimes only one-third of this. Fragments of the petiole
were very rarely seen.

This plant may be compared with. Nilssonia JoJmstriqn, Heer^ It is
very much like PterophyUum princeps Oldham and Morris,^ and also
strongly resembles PterophyUum Braunsii Schenk. Both of these are
Rhsetic plants, and both are placed by Schimper in his subgenus Platyp-
teriyium. Nilssonia JoJmstrupi seems to be a Platypterigiiim surviving into
the Middle Cretaceous.

' Flor. Foss. Arc, vol. 6, Part II, PL VI, Figs. 1-ii.

2 Pal. indica, Foss. Flor. Rajmahal, Series II, vol. 1, PI. XII., Fig. 1.

DESCRIPTION OF THE SPECIES. 171

Platypterigium Rogersianum, sp. nov.

Plate XXXI, Fig. 2 ; Plate XXXIII, Fig. 2 ; Plate XXXIV, Fig. 2.

Leaf large, rivaling- the dimensions of P. densinerve ; leaf-substance
thicker and more coriaceous than that of P. densinerve. It is comparativel)^
strong and coriaceous ; midrib well defined, rounded, and prominent,
rigid, and without apparent dense epidermis ; nerves comparatively strong,
towards the base of the leaf going off more obliquely, higher and towards
the middle of the leaf going off at a right angle, simple, straight, and par-
allel, more remote than those of P. densinerve, being 1™™ apart.

Locality : Fredericksburg ; rare.

This fine plant is much rarer than P. densinerve. It is a more robust
species than the latter. It is not so pi'one to segmentation as that species,
possibly from its denser and stronger leaf-substance. One specimen was seen
11 cm vvide, and in a length of 12°" showed no division into segments. I
have named the plant in honor of Prof William B. Rogers, who first studied
the geology of the Potomac formation and called attention to its plants.

ZAMITES, Brong., emend.

Leaves small or of medium size, in growing old becoming detached ;
leaflets attached to the upper side of the rachis by a callosity, somewhat
contracted or rounded at base, almost cordate there, linear or ovate-
lanceolate, acute or obtuse, mai'gins entire, of firm consistency ; nerves
simple or forked, the middle ones parallel, diverging only towards the
summit, the lateral ones ending in the margin.

This description, which is essentially that given by Schimper,^ applies
to some detached leaflets found in the Potomac flora. They are always
among the rarest of fossils in this flora, appearing only, in .sparingly dis-
persed fragments. They form a very inconsiderable element in the Poto-
mac flora, being found mostly at Fredericksburg.

Zamites tenuineevis, sp. nov.

Plate LXVII, Fig. 1; Plate LXIX, Fig. 2; Plate LXX, Fig. 1; Plate LXXV, Fig. 3; Plate LXXVI,
Fig. 7; Plalo LXXVIII, Fig. 6; Plate LXXXIV, Fig. 7.

Leaflets very long, attaining the length of 20.5'''° and a width of
24'°", at base abruptly subcordate, in shape ensiform, sometimes curved,

'Zittel's Handbuch der Paloeont., vol. 2, Lief. 2, p. 218.

1 72 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

acute ; nerves veiy numerous and closely placed, fine but distinct, forked
at base or simple, occasionally forked a little higher, parallel after forking.

Localities : Fredericksburg ; Kankey's ; banks of Dutch Gap Canal ;
fishing-hut above the canal ; near Telegraph Station.

This fine plant is the most common cycad at Fredericksburg, where
it is not very i-are. PI. LXX, Fig. 1, is the most complete specimen seen,
but in this the nerves unfortunately were obscure. It is almost always
found in the form of detached fragments of the basal portions of leaves,
showing that the}^ were very deciduous and disarticulated, so as to leave
the detached base more or less heart-shaped. They were apparently
attached by a callosity. In PI. LXXVI, Fig. 7, a small bit of the rachis
may still be seen attached to the base of the leaf When the leaves have
been detached from the callosity by which they were attached, their bases
have a cordate sinus. The plant does not seem to be nearly allied to any
described fossil.

Zamites ceassinekvjs, sp. nov.

Plate LXIX, Fig. 4 ; Plate LXXXIII, Fig. 3.

Leaves broadly elliptical, short, acute, abruptly nan-owed at base and
attached by a callosity ; nerves simple or forking at the very base, very
strong, distant, parallel to near the apex, where they are more crowded.

Locality: Fredericksburg; rare..

This is a well-marked form of a type a good deal like some of the

species of Nar/eiopsis, to be described later, but the leaves seem to have

been very deciduous, unlike Nageiopsis, and are at base, when detached,

somewhat heart-shaped.

«

Zamites distantinervis, sp. nov.

Plate LXXXIII, Fig. 4.

Leaves long, slender, slightly narrowed towards the base, which was
not seen, and gradually so towards the tip, which is lancet-shaped and sub-
acute, almost acuminate, slightly curved and subfalcate ; nerves strong,
proportionally very remote, parallel, not forking in the parts seen.

Locality: Fredericksburg; very rare.

DESCRIPTION OF THE SPECIES. 173

The base of this leaf was not seen, and the nerves towards the tip
were too obscure to be made out. The plant may be Nageiopsis or Podo-
zamites, but the flexuous character of the leaf indicates that it is a Zamites,
and here I place it provisionally.

Zajmites ovalis, sp. nov.

Plate LXXXV, Fig. 4; Plate CLXX, Fig. 3.

Leaves short, oval, acute, abruptly rounded ofi' at base, and showing,
when detached, a heart-shaped sinus, almost as broad at base as elsewhere;
nerves not seen.

Localities: Banks of Dutch Gap Canal; tishing-hut above the canal;
road-side near Potomac Run ; near Telegraph Station : rare.

This plant can be placed among the Zamites only with doubt.

Zamites subfalcatus, sp. nov.

Plate LXXXIV, Fig. 13; Plate LXXXV, Fig. 3. .

Leaves long, proportionally narrow, subfalcate, acute, widest near the
base, abruptly rounded off at base, attachment not seen ; nerves not seen.

Locality : Kankey's ; very rare.

This is another of the doubtful species of Zamites. The epidermis
was so thick that the nerves could not be made out. Only a slight
striation can be seen. The plant specimen given in PI. LXXXIV, Fig. 13,
seems to be a tip of a leaf whose base is probably the specimen figured in
PI. LXXXV, Fig. 3. The amount of material obtained from Kaukej^'s
place 'is so small and the impressions are so poorly preserved, that the
number of specimens of any given plant obtained there can not be taken
as indicating its actual abundance or scarcity.

Zamites, sp. '?

Plate LXXXIV, Fig. 12.

A single fragment of a thick leaf was found at Kankey's place. The
nerves were not seen. It is apparently a portion of a leaf of Zamites too
imperfectly preserved to permit the species to be determined.

174 THE POTOMAC OE YOUJ^TGER MESOZOIO FLOEA.

ENCEPHALARTOPSIS, gen. nov.

Leaves pinnate, leaflets oblong, linear-elliptical, obtuse, terminated by
several spinous teeth, margins having irregularly placed, shallow, spinous
teeth ; nerves numerous, closely placed, forking one* or more times and at
varying intervals, slightly diverging, and mostly ending in the teeth, anas-
tomosing occasionally by branches sent off" abruptly from one nerve to
another.

This curious genus has been found as yet with only one species. It
combines the features of Encephalartos with the anastomosing nerves of
Ctenis. It is so close to Enceplialartos that, were it not for the occasional
anastomosis of the nerves, one would have no hesitation in placing it in
that genus. It probably should be regarded as the prototype of that
genus.

Encephalartopsis nervosa, sp. nov.

Plate LXX, Fig. 4 ; Plate LXXI, Figs. 3, 4 ; Plate LXXII, Figs. 3, 4.

Leaves and leaflets with the character given for the genus ; the shal-
low, spinous teeth on the margins vary in shape, and tend to pass to rec-
tangular notches ; the teeth do not appear on the basal portions of the leaf-
lets ; the base or attachment of the leaflets was not seen ; the nerves are
numerous, closely placed, fine but distinct ; they slightly diverge, fork at
long intervals and at varying heights throughout the length of the leaf, and
are approximately parallel; they anastomose rarely by abruptly sending
off branches to unite with the adjacent nerve ; the anastomosing branches
make comparatively large angles with the parent nerve.

Locality: Fredericksburg; rare.

This plant evidently varied a good deal in the size of its leaves, for
the fragment PL LXXII, Fig. 4, is much laj-ger than that given in PI.
LXX, Fig. 4. In PL LXXI, Fig. 3, the position of the two leaflets indi-
cates that they were disposed in a pinnate manner.

CTENOPHYLLUM, Schimper.

Leaflets variable in size, mostly small, long, linear, comparatively
narrow and ribbon-shaped, gradually narrowed towards the ends, attached

DESCRIPTION OF THE SPECIES. ] 75

to the rachis on the upper side and touching each other, or united at base,
attached by the entire base, nerves in part forking.

This genus is represented in the Potomac flora doubtfully by one spe-
cies, which has in some respects a different character from the typical
forms, such as CienopJiyUum Braimianum Schimper.

Ctenophyllum LATipoLiUM, sp. nov.

Plato LXVIir, Figs. 2, 3. .

' Leaf very large and wide-spreading ; length of leaflets not -disclosed,
width in the same portion of the leaf variable, ranging from 27"" to 35"";
leaflets alternate, going off in the lower part of the leaf at a large angle,
in the upper portion much more oblique, attached by the entire width of
the widened base, which is decurrent and meets the expanded base of the
adjacent ones, forming a broad rounded sinus, those of the upper portion of
the leaf united more and more, all curved slightly upwards towards the
summit of the leaf ; tips of the leaflets not seen ; nerves very strong,
going off obhquely at their insertion in the lower and middle portions of
the lower leaflets, but nearly at right angles in the upper portions, and all
turning strongly outwards to enter the leaflets ; nerves of the uppermost
leaflets all oblique ; the nerves fork at the insertion or are simple and par-
allel ; occasionally but rarely those simple at base fork somewhere higher ;
under a strong lens the nerves are seen to be composed of two closely
placed nerve-strands which form a flat nerve-bundle.

Locality : Fredericksburg.

This splendid plant is very rare; only one specimen was seen. As
found in the rock, it was as is depicted in Fig. 2, and probably the speci-
men depicted in Fig. 3 was attached to the top of it, for it is clearly the
summit of the specimen given in Fig. 2. But in loosening the imprint in
the quany it was much broken up. The leaf originally must have been
of huge dimensions, for the parts seen are clearly but a small portion of it.
The plant shows an irregularity in the size of the leaflets, for in Fig. 2 the
right-hand lower leaflet is much wider than the adjacent ones. The mid-
nerve is stout and rounded. The leaf must have been over a meter in
length. This species is strikingly like the large Ctenopliijlla of the Rhsetic

176 THE POTOMAC OE YOUKGEE MESOZOIG FLOE A.

flora of Virginia (see Contributions to the Knowledge of the Older Mesozoic
Flora of Virginia, Mon. U. S. Geol. Survey, vol. 6, PI. XXXIX, Figs. 1-3,
to PI. XLII, Fig. 1). It may possibly be a descendant of some such plant
as C. grandifoVmm. Its extreme rarity indicates that this form of cycad
Avas nearly extinct in this region.

GLOSSOZAMITES, Schimper.

Leaves pinnate, with leaflets Ungulate or elliptical in shape, obtuse at
the summit, inserted on the upper face of tlie midrib by a contracted base,
equilateral ; nerves fine, branching dichotomously, diverging slightly from
the point of attachment towards the borders of the leaflets, which are
always entire.

This description of the genus given by Saporta coincides exactly with
the character of a fossil found in the Potomac flora. Only one species
of the genus was found. The genus is characteristic of the Lower Cre-
taceous, and seems to play a very unimportant part in the Potomac flora.

Glossozamites distans, sp. nov.

Plate LXVIII, Fig. 5.

Leaf pinnate, midrib slender ; leaflets alternate, diminishing in size in
ascending, distant, oblong, linguiform, slightly curved upwards, attached
to the upper surface of the midrib by a rounded, abruptly narrowed base,
which in the lower ones is slightly auriculate, obtuse ; nerves fine, numer-
ous, closely placed, diverging slightly from the point of attachment, and
ending, except the central ones, in the entire margin ; outer nerves simple
or deeply furcate ; inner ones repeatedly forked, with the ultimate branches
of all very long and approximately parallel.

Locality: Fredericksburg; very rare.

Only one specimen of this very fine plant was found, and that in a
fragmentary condition. The leaflets of the lower portion have a base
which indicates that they were attached by a callosity. The nerves when
forked have very long branches, owing to the distance from their ends at
which the forking takes place. It is very much like Schenk's Podozamites

DESCEIPTIUN OF THE SPECIES. 177

Zitteli (Glossozamites Zlttdl Schimper)/ but the leaflets are not so obtuse and
are farther apart, while the nerves are more branched.

CTENIS (Lindley and Hutton), Zigno emend."

Leaf profoundly pinnatifid ; rachis thick, striated, and farrowed ; leaf-
lets or lacinipe approximate, linear-elongate, entire, enlarged at base,
separated by an acute sinus ; nerves equal, thick, arising from the rachis,
diverging towards the base, then approximate, parallel, forked, branches
uniting to form areolpe that are obliquely elongate, rhomboidal in shape.

The above is Zigno's description of Ctenis, being an amendment of
that of Lindley and Hutton. If we alter this so as to read "leaves pin-
nate," and omit the items "enlarged at base, separated by an acute sinus,"
it will apply to a very noteworthy form found in the Potomac flora. This
is without doubt either a true Ctenis, or so closely allied to it that, in the
absence of more definite characters, it may be placed in that genus.

Ctenis imbeicata, sp. nov.

Plate CXXXVIII, Figs. 10-12.

Leaf very large, pinnate ; leaflets attached by the entire base, which
is narrowed and rounded off on both sides, to the upper face of the midrib
or stem, obtuse at their, tips and rounded, with broad, shallow, seeming
lobes on the under side, imbricated some distance above the base, each
leaflet expanding at that point and partly overlapping the next one; nerves
strong and distinct, wide apart, forking at or near the base or a short
distance higher up ; branches, so for as seen, parallel, anastomosing at
long intervals by a few inosculating branches, so as to form long irregular
or subrhombic meshes, uppermost leaflets united; leaf terminating in a
leaflet in which the midnerve seems to split up into two branches ; at the
tips of the leaflets the anastomosis is more copious and the nerves are finer
and more closely placed.

Locality : Fredericksburg ; very rare.

This remarkable plant agrees quite well with the subgenus Ctenis, and
in some points it is like the figures of Ctenis falcata,^ Lindley and Hutton,

' Sclieuk, Foas. Pflaiiz. tier AVernsdorf. Schichten, 1S71, PI. I, Fig. 8.
^ZigDo, Flor. Foss. Form. Oolitic, vol. 1, 18.5(>-'68, PI. XXIV, Figs. 1-3.
MON XV 12

178 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

given by Zigno. It has the same mode of insertion of the nerves, which
are irregular, forking, and anastomosing, but in Ctenis falcata the leaflets
are decurrent, and become much widened at their insertions. The Potomac
plant is more like Nathorst's plant from the Rhaetic of Sweden, which he
first named Antliropliyopsis Nilssoni, and afterwards called Ctenis fallax
The termination, especially of the leaflets in the two plants, shows a resem-
blance. PI. CXXXVIII, Fig. 12, gives what seems to be the middle of a
leaf of large size. Fig. 11 gives the upper portion of a leaf that seems to
have been much larger than that depicted in Fig. 12, as is shown in the
much greater width of the midrib. This specimen is a good deal distorted
by pressure, so that its true character may be disguised. The wide midrib
seems to be split into two branches, which are connected by smaller nerves.
The fragment of a leaflet visible on its left-hand side seems to have had its
base pressed over upon the upper surface of the midrib, wliile the lower
half of that on the right hand seems to have been torn away by the
splitting off and detaching of a portion of the midrib. The specimen
given in Fig. 10 seems to be the tip of a leaflet, perhaps corresponding to
the basal portions shown in Fig. 12.

PODOZAMITES Fr. Braun (emend.).

Leaves small, with a slender rachis, pinnate ; leaflets alternate, remote,
directed more or less upward, with a gradually narrowed base, often fur-
nislied with a short petiole, ovate-elliptical, elongate, lancet-shaped, or
linear, sometimes somewhat curved, detaching themselves from the rachis,
and usually found isolated ; nerves forked at the base, often very fine and
closely placed, parallel with the margin to near tlie tips of the leaflets,
where they converge.

The genus Podozamites is represented in the Potomac flora apparently
by a considerable number of species ; but as the specimens appear usually
in the form of fragmentary and detached leaves, they do not generally
admit of a full characterization and positive determination. The leaflets
having the character of Poiosamiies are quite rare, and the genus con-
tributes no important element to the flora. They give one the impression
nf a type in decadence Most of them are in form strikingly like the

DESCEIPTION OF THE SPECIES. 179

leaves of Nageiopsis, a genus of conifers described in this work, but they
differ from tliis in the very deciduous nature of the leaflets, and above all
in the convergence of the nerves at their summit.

PODOZAMITES SUBFALCATUS, Sp. nOV.
Plate LXVIII, Fig. 6; Piate CLXX, Fig. 9.

Leaves unknown; leaflets subfalcate, narrowly ellijitical to strap-shaped,
obtuse or subacute, gradually narrowed to the base so as to form a broad,
short pedicel, thick and leatherv; nerves slender, and not well disclosed,
forking near the base, then nearly parallel to near the tips, where they con-
verge.

Locality: 72d mile-post near Brooke ; rare.

Only detached fragments of leaflets were found. The leaflets must
have varied a good deal in size, as PI. LXVIIT, Eig. 6, represents a nearly
complete leaf, which is much smaller than that of whicli PI. CLXX, Fig. 9,
represents a fragment. The shorter form, PI. LXVIII, Fig. 6, is a good
deal like Zamites ovatiis, and Z. affinis Schenk,^ forms which Schimper makes
Podnzamites. The longer leaflet on the other hand is somewhat like Z.
nervosus Schenk, same plate. Fig. 10.

PODOZAMITES DISTANTINERVIS, sp. nOV.

Plate LXXrX, Fig. 5; Plate LXXXII, Fig. 4; Plate LXXXIII, Figs. 1, 2, 6, 7 ; Plate LXXXIV, Fig.s.
1, 2, 8, 10, 14, 15 ; Plate LXXXV, Figs. 12, 16.

Leaves comparatively large, pinnate ; leaflets large, elongate-elliptical
in form, varying a good deal in size, maximum width varying from 27™"" to
40'"", usually comparatively broad, full length not seen, but ranging from
11"" to over 14''", obtuse or subacute at tip, usually somewhat narrowed
toward the base, and at the base rather abruptly rounded off into a short
pedicel ; nerves strong, quite remote, forking at or near the base, and then
parallel to near the tip, where they converge and connive more or less.

Localities: Road-side near Potomac Run; Fredericksburg; near Tele-
graph Station ; rare.

This is the most common Podozamites, but still it is not abundant.
More specimens were found at Fredericksburg than anywhere else, prob-

' Scbenk, Foss. Pflanz. der Wensdoif. Schichteu, lo71, PI. Ill, Fig.s. 7, 8,

180 THE POTOMAC OE YOUNGER MESOZOIC PLOEA.

ably because more material was obtained there than at most places. PI.
LXXXIIT, Fig. 1, gives the upper portion of an unusually large leaflet, in
which the nerves are obscure, but may be seen to converge at the summit.
Fig. 2 of the same plate shows two leaves of medium size in a position as
if coming off from a common stem. PI. LXXXIV, Fig. 10, gives three
leaflets detached, and from displacements overlapping one another. Figs.
14 and 15 of the same plate give the base and the tip of the leaf fragments
slightly enlarged, to show the nervation. The base given in Fig. 14 is
more abruptly rounded off than usual, but little narrowing toward the base
having taken place ; possibly such leaflets, with those such as given in Fig.
8 of the same plate, may belong to a different species.

This Podozamites does not seem to be near any of the heretofore de-
scribed species.

Podozamites pedicellatus, sp. nov.

Plate LXXVI, Fig. 1 ; Plate LXXVIII, Pig. 7; Plate LXXXII, Fig. 5.

Leaves not seen ; leaflets large and long, length not fully disclosed
maximum width varying from 26"°' to 35""° ; shape probably oblong to elon-
gate-elliptical, gradually narrowed to the base, and elliptically shaped there,
furnished with a long, broad pedicel, curved to one side, deciduous ; nerves,
forking near the base, then nearly parallel, tips of leaflets not seen.

Locality : Fredericksburg ; rare.

This possibly may be a Nageiopsis, as the nerves at the tips of the
leaflets were not seen, but the deciduous nature of the leaflets indicates
that they belong to Podozamites.

Podozamites geandifolius, sp. nov.

Plate LXXXII, Fig. 2; Plate LXXXIII, Fig. 5.

Leaflets very large, 4.5"° wide and over 20<=" long; shape not seen,
probably elongate-eUiptical, with stout pedicel at base ; nerves where seen
strong, parallel, remote, composed of two nerve-strands which are closely
placed, and form a flat nerve-bundle.

Localities : Fredericksburg ; road-side near Potomac Run ; rare.

This plant is quite rare, and, owing to their great size, the leaflets were
found only in a fragmentary condition; hence their shape could not be made

DESCRIPTION OF THE SPECIES. 181

out exactly. PI. LXXXIII, Fig. 5, from the Potomac Run locality, indi-
cates that it had at the base of the leaflets a stout pedicel. PI. LXXXII,
Fig. 2, from Fredericksburg, is a fragment of what must have been a very
large leaf. The lower or posterior margin of this leaf is nowhere shown.

PODOZAMITES ACUTIFOLIUS, Sp. nOV.
Plate LXXX, Fig. 6; Plate LXXXV, Figs. 10, 15; Plate LXXXVII, Fig. 1 ; Plate CLXX, Fig. 2.

Leaves very deciduous, varying in length, oblong, subacuminate, main-
taining the maximum width to near the base, and then suddenly rounded
off and attached by a short pedicel ; nerves branching near the base, and
one branch sometimes forking again higher up ; at the tips of the leaflets
the nerves converge to a common point, quite distinct.

Locahties : Fishing-hut above Dutch Gap Canal ; Deep Bottom ; near
Telegraph Station ; road-side near Potomac Run ; bank near Brooke ; rare.

The leaves of this plant are much like those of Podozamites lanceolatus
Schimper, and the larger leaves resemble Podozamites Emmonsi Newberry.
The smaller ones resemble P. tenuinervis-.

I take this opportunity to correct an oversight made in Contributions
to the Knowledge of the Older Mesozoic Flora of Virginia (Mon. U. S. Geol.
Survey, vol. 6) with reference to the employment of the name Podozamites
Emmonsi. This name I used for a Podozamites found by Emmons in the
Rhtetic of North Carolina, overlooking the fact that Professor Newberry
had already used this name for the same plant in his article on the Chinese
Mesozoic plants in Smithsonian Contributions to Knowledge.

DIOONITES Bornemann.

Leaves quite large, with strong rachis ; leaflets attached on the upper
side of this by the whole width of the base, sometimes expanded at base so
as to extend up and down the rachis, linear-lanceolate or elongate -linear,
acute at tips, of firm leathery consistency ; nerves simple and parallel.

This description of Schimper given to the genus agrees exactly with
certain forms that are very common in the Potomac flora. The plants
placed in the genus Dioonites are by far the most abundant cycads in the

182 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

Potomac strata, and these alone give to tliis group of plants the considera-
ble importance that they possess in this flora.

DiooNiTES BucHiANUS Schimper.

Pterophi/llim Buchianum, Ettingshausen, Beitriige z. Fl. der WBaldenperiode, p. 91, PI. T, Fig. 1.
PleiophyUum Saxonicum, Reich., Ettingsliausou, ICreidetiora voq NiedersohoBaa, PI. I, Figs. 11, 12.
Dioonites Saxoniciis, Schimper, Traits de Pal^out., vol. 2, p. 211.

Plate LXVIII, Fig. 1; Plate LXIX, Figs. 1, 3; Plate LXX, Figs. 2, 3; Plate LXXI, Fig. 1; Plate
LXXII, Figs. 1, 2; Plate LXXIII, Figs. 1-3; Plate LXXIV, Figs. 1-3.

Leaves ver}^ large, attaining probably the length of a meter and over;
maximum width, 30™ and over; rachis stout, showing a keel on the under
side ; epidermis over the rachis and leaflets thick and durable ; leaves thick
and leathery ; leaflets varying much in dimensions, distance, shape, and
termination ; leaflets linear-acute, sometimes closely placed, sometimes
remote, those in the middle part of the leaf the mos't commonly found,
these going off at an angle of 45°, those of the upper part more and more
oblique, until at the summit they occur in the prolongation of the mid-
rib, and the leaf is terminated by a leaflet, the terminal leaflets much
shorter and narrower than those lower down ; length varying, attaining in
some cases 2.'^™'; the leaflets slightly narrowed to the base and attached by
the whole width of the base, obliquely set on and decurrent; epidermis
sometimes showing a granulation or a line of dots between the nerves ;
nerves fine, very closely placed, forking at the base, parallel, and terminat-
ing without convergence in the summits of tlie leaflets, some of the outer
ones ending in the margins a little below the summit.

Localities : All points on James River that yield plants, except Deep
Bottom ; especially abundant at entrance to Trent's Reach, in banks of
Dutch Gap Canal, and at fishing-hut above the canal ; very abundant at
Kankey's ; found also at all plant localities north of Kankey's to Fort
Washington, Init not abundant beyond Telegraph Station.

This splendid plaut is one of the most widely diifused and character-
istic fossils of the Potomac flora. At the entrance to Trent's Reach, in the
thin plant-bearing layer near the top of the bluff", the imprints are in places
veiT numerous, and much of the plant-substance is still retained, the relics
being matted together. Here it is found in company with Baieropsis

DESCEIPTIOJSr OF THE SPEOIES. 183

fluripartita, Brachyphyllum, Frenelopsis parceramosa, etc. In the right bank
of Dutch Gap Canal, in the thin partings of dark gray clay, interstratified
with sandy layers, very large impressions occur and the fossils are very
numerous. They seem to occur irregularly distributed and in pockets.
Some of the imprints seen lying in the clay were 12 to 18 inches long and
as wide, but owing to the brittleness of the rock they were much broken
in taking them out. At a spot about 200 yards above the fishing-hut at
Dutch Gap, where hardly any other fossil occurs, the leaves of this plant
are so abundant as to fill the clay for the thickness of a foot or more. It
is a curious fact that at this point, and at several localities north of Fred-
ericksburg, if the remains of this plant occur in great numbers in the
clay, they seem to exclude others. The distribution is apparently some-
what peculiar. On leaving James River not a trace of the plant is to be
seen until Kankey's place is reached. Here immense numbers of the
leaves occur in the dark clay with hardly any other plants. None were
found at Fredericksburg, and as the amount of material obtained there
was large, we may safely assume that it did not exist at that locality. It
occurs as the principal fossil in the ciit where the railroad crosses the
Occoquan. It is abundant near Telegraph Station, but only fragments
occur at White House and at Fort Washington. It has not been cer-
tainly identified north of Fort Washington. Some small bits of leaves
found at Baltimore, on Belt and Covington streets, seem to belong to this
species, but they can not be certainly identified. It was indicated by
fragments found in the excavation for the reservoir at Washington.

Ettingshausen, in his Beitrag zur Flora der Wealden Periode, de-
scribed this plant under the name Pteropliyllum Buchianum, as occurring
in the Wernsdorf strata of the northern Carpathians, considering these
as of AVealden age. He gives a figure of a fragment belonging, as he
thought, to a cycad leaf three or four feet long. Schenk (Die foss. Pflan-
zen der Wernsdorf-Schichten) shows that these strata, according to the
investigations of Hohenegger and Zittel, are not Wealden but Urgonian
in age, younger than the oldest Neocomian, and older than the Gault. It
is very fortunate that the Potomac formation has yielded so many fine
specimens of this plant, as they add a good deal to our knowledge of it.

184 THE POTOMAC Oil YOUNGER MESOZOIG rLORA.

All the parts are shown except the base of the leaves. Among the hun- .
dreds of specimens seen, it is singular that in no case was any portion of
the base found.

The leaves appear to have been thick and durable, for in a number of
cases the leaf-substance may be stripped from the stone, retaining the shape
of the leaflets. The epidermis seems to be especially thick over the mid-
rib. The nerves are immersed in the leaf-substance and are usually
obscured.

In Ettingshausen's figure the specimen is somewhat distorted by press-
ure. The leaflets on the right-hand side have been crushed over at base
so as to appear to be attached to the upper face of the midrib and partly
within its margin, whereas they are really attached to the margin and lie
usually in one plane.

This plant seems not to have been confined strictly to the Urgonian,
but to have survived to a later period, while its narrower form at least
began in the Wealden. Ettingshausen ^ gives figures of Pterophyllwn Sax-
onicum Reich., which certainly represent portions of D. Buchianus. In
these figures some of the leaflets go ofl" at a more open angle than is usual
in D. Buchianus^ but this is due to distortion from pressure, for this mode of
departure can be duplicated in many of the Potomac plants. Ettingshau-
sen says that the surface of the Niederschoena plant is covered with fine
dots arranged in rows between the nerves. In the Potomac plants they
are closer than Ettuigshausen's figure represents them to be. Hosius and
Von der Marck^ represent a fragment which they identify correctly with
Pterophijllum Saxonicum, coming from the Neocomian sandstone of the Teu-
terburger Wald. This is evidently a portion of the midrib and the bases
of two leaflets of Dioonites Buchianus. The leaflets ai'e by distortion from
pressure made to go off nearly at right angles.

Dioonites Buchianus, var. obtusifolius.

Plate CLXVIII, Fig. 3.

Leaves long and wide, with a stout midrib ; leaflets subopposite,
inserted on the upper face of the midrib and considerably within its mar-

' Kreideflora vou Niederschojaa in Saohsen, PI. I, Figs. 11, 12.
2 Flor. der Westfal. Kreideformatioa. PI. XLIV, Fig. 198.

DESCEIPTION OF THE SPECIES. 185

gin, very remote, obtusely rounded off at the tips, comparatively short,
bases of the leaflets thickened and callous when torn off, and when the
midrib is compressed, leaving a depressed scar.

Locality: Left bank of Dutch Gap Canal; rare.

The figure gives a portion only of the large specimen found. The
specimen is 20"" long, and shows no decided diminution in the size of the
midrib or in the lengths of the leaflets ; but the leaflets at the summit of
the stem are only half as far apart as those at bottom ; seventeen leaflets
occurred on the portion found.

DiOONITES BUCHIANUS, var. ANGUSTIFOLIUS.

Pterophiillum aUetinum Gopp., Duaker. Mon. der norddeutsch. Wealdenbild., PI. VII, Fig. 2.
Dioonites abietiniis Miquel, Scheuk. Flor. der nordwestdeutsch. Wealdeufoi-m.,'pi. XVI, Fig. 1.

Plate LXVII, Fig. 6; Plate LXVIII, Fig. 4 ; Plate LXXI, Fig. 2.

Leaflets and nerves as in the normal form D. Btichiamts, except that
they are much narrower in the lower parts of the leaves.

Localities: Dutch Gap, especially at the tishing-hut above the canal:
Kankey's ; crossing of the Occoquan ; near Telegraph Station.

These leaflets, as those of the normal species, vary a good deal in the
distances apart at which they are placed. In PI. LXVII, Fig. 6, they are
very remote; in PL LXXI, Fig. 2, they are very close together. The
forms that are placed in this variety show throughout the leaf narrow leaf-
lets, and they do not seem to be mere accidentally narrow forms of the
typical plant. They never graduate into the wider leaf forms.

This narrow leaf variety seems to be the same with the Wealden plant
figured by Schenk as Dioonites abietinus Miquel, in his Wealden flora, PI.
XVI, Fig. 1. It appears also to be identical with the fossil given by Dun-
ker as Pterophyllum ahietinim Gopp. Hosius and Von der Marck^ give a
figure of what they call R abietinus, which is exactly like some of the
specimens of this Potomac fossil. The figure of the Westphalian fossil
represents a plant distorted by pressure. It comes from the Neocomian
sandstone of the Teuterburger Wald.

1 Flor. der Westfal. Kreideformation, PI. XLIV, Fig. 199.

186 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

The speciiiieus of this variety are much rarer than those of the normal
species B. Buchianus.

This form, if identical with the European fossils named above, begins
in the Wealden and survives into the Neocomian.

TYSONIA, gen. nov.

Trunks varying considerably in shape and in dimensions, petrified with
silica, more or less flattened, seen with the broader side in front, they are
oblong-ovate and truncate ; in cross-section they are broadly subelliptical ;
medulla proportionally small ; woody cylinder comparatively thick ; cor-
tical exterior layer, with the permanent bases of the petioles very thick ;
bases of the petioles in cross-section normally subrhombic or subtriangulai',
with the lower angle very obtuse, the outer angles acute and prolonged, the
superior side forming a curved line bent upwards or forming an obtuse
angle, but often from pressure distorted into irregular, rliombic, or trian-
gular forms; trunks each with a large eccentric terminal leaf-bud or growing
bud ; some of the trunks, probably of female plants, have numerous lateral
buds ; others, probably male plants, are without lateral buds ; bases of the
petioles of the leaves represented by open casts of the petioles, which from
the points of insertion of the petioles pass upwards and outwards, so that
their direction at their exit from the cortical investment is nearly horizontal.

These trunks have some of the characters of Carruthers's genus Bennett-
ifes and of ManteUia Brongn., being apparently an intermediate type. I
have named the genus in honor of Mr. Tyson, who first called attention
to these plants. Carruthers^ says: "Through the kindness of Principal
Dawson I have seen a photograph of one of the cycadean stems found by
P. Tvson, esq., in Maryland. * * * It is obviously a species of
Bemiettites, with smaller leaf-scars than those in B. SaxbyanusP

It seems from liis description of the plant that Carruthers saw a
photograph of trunk No. 1. He does not seem to have had a photograph
of trunk No. 2, which differs in important points from No. 1. Carruthers
thinks that the apparent buds on his Bennettites are not leaf-buds, but
organs of reproduction. There is nothing in the Potomac plants to show

' Fossil cycadean sterna from the secondary rocks of Britain, Trans. Linn. Soc. Loudon, vol. 2('>, I ?rri,

postscript, p. 708.

DESCEIPTIOK OF THE SPECIES. 187

what the nature of the buds was. Carruthers's description of the cross-
section of the bases of the petiole of Bennettites agrees well with the cross-
sections in Tysonia. He explains the exterior aspect of the trunks, which
shows a series of hollow imprints left by the bases of the petioles separated
by plates, as caused by certain processes which seem to have taken place in
the Potomac plant also. He says the trunk, when living, was surrounded
by the permanent bases of the petioles, and the base of each petiole was
clothed with a dense ramentum, which was developed to such an extent as
to separate very considerably each petiole from its neighbor. The silica
forming the petrifying material having found speedy access to the delicate
scales of the ramentum has preserved them in a remarkably perfect manner-
In some of the English specimens the petrified ramentum stands out as a
net-work of ridges, while the originally more durable petioles have decayed
and left rhomboidal cavities representing their original form. Carruthers
states also that the leaf disarticulated at a point some distance from the
cortex, leaving a considerable portion of the bases of the petioles perma-
nently surrounding the stem. This explanation given for the English
Bennetites no doubt applies to the similar features seen in the Potomac
Tysonia. In this latter, now thoroughly silicified in all the specimens seen,
it is clear that the material surrounding the bases of the petioles was silicified
before the bases, and that these subsequently decayed, leaving perfect
hollow casts of their form.

No microscopic examination of the ti'unks of Tysonia has been made,
and I am compelled to confine the description to macroscopic characters.

There are two kinds of trunks, diffei'ing mainly in the presence or
absence of axillary buds There are two kinds of axillary buds on the
same trunk, a feature which, according to Carruthers, appears in Mantellia
but not in Bennettites. In would seem that in the buds on Tysonia, which
resemble those of Bennettites, there was a woody axis of varjnng size,
surrounded by scars of leaves much smaller than the normal ones, or of
bracts. This woody axis certainly protruded beyond the bases of the
petioles. Some of them are larger than others and some are hollow, the
hollows being no doubt due to decay before siHfication. No indication of
fructification has been seen in connection with the Potomac stems.

188 THE POTOMAC OK YOUNGER MESOZOIC FLOKA.

These stems have a number of features in common with Bennetfites, but
do not fullv agree with that genus. Compared with Mnnidlia Brongn.,
Cycadeoklea, Buckhxnd, they show some points of resemblance, Carruthers
says of JSIantclUa trunks that they are cyhndrical, covered with the long
permanent bases of the petioles, and have the fruits borne on secondary
axes which generally protrude beyond the bases of the petioles. In this
feature these secondary axes resemble Tysonia, and not, according to
Carruthers, Bennettites. The axillary branches in MantelUa, like those of
Tysonia, are broken off at the point where they leave the bases of the
petioles. Carruthers says that some of the branches in Mcuitellia are
undeveloped and still exist as unexpanded leaf-buds ; and this seems to be
the case with some of those of Tysonia, those that have little or no woody
axis. Some of the stems of MantelUa have no lateral buds, and they may,
as Carruthers says, be male stems, their staminal flowers being on cones
borne on the termination of the main axis. The Potomac stem No. 2 has
no axillary buds, and shows indications of having borne a terminal ap-
pendage (bud!) by the side of the terminal growing leaf-bud. Carruthers
says that the ManteMia trunks were cylindrical, their flattened condition
being due to pressure.

From this it will be seen that the stems of Tysonia have a number
of points in common with MantelUa. They stand nearer to this than to
Bennettites. The shape of the trunk is more that of Bennettites, but in the
shape of the bases of the petioles and in other features Tysonia more
closely resembles MantelUa.

In describing the new species Tysonia Marylandica, it is best to notice
the two nearly complete stems separatel)^, as they are typical and show
some important points of difference. I will describe them as trunk No. 1
and trunk No. 2. One of these was found, as stated before, near Contee's
station, in an iron-ore pit near the base of the Variegated Clay formation,
and one was found on a farm near Beltsville, a locality a few miles -south
of Contee's. A fragment like trunk No. 1 was found with this trunk, and
another fragment like trunk No. 2 was found on the surface of the Varie-
gated Clay group at a locality (Spring Garden) in the outskirts of Balti-
more. It is impossible now to tell which of the trunks was found near

DESGEIPTION OF THE SPECIES. 189

Contee's. The fragments in all respects resemble the trunks. This would
indicate that the differences seen in the trunks are constant and not merely
accidental, and hence have an important meaning.

Trunk No. 1.

Plates CLXXIV to CLXXVIII.

This trunk is siUcified, of an ash-gray color, and is free from ferru-
ginous matter. It is oblong-elliptical in shape, with a cross-section
roughly elliptical in form, as shown in PL CLXXVIII, which gives a photo-
graph of its top. The flattening may be due to compression. From one
side near the base a considerable portion has been broken off, as is shown
in PL CLXXVI. The maximum height of the trunk, measured on the
the perfect side, seen in PL CLXXIV, is Si"'", and the greatest dimension
at base is 30''"'. Its thickness there is 26'°'. The length of the longest
dimension at top is 19""", and the maximum width there is 12'"°.

At the top a portion is broken away so as to produce a depression
slanting downwards, well shown in PL CLXXVI. This looks a good deal
like the scar that would be left by the tearing away of a terminal stem-like
appendage. This depression occurs on one side of the summit of the
trunk. What was probably the terminal bud of growth is distinct from
this, and is seen in the center of the top on PL CLXXVIII as a rather
faintly marked depression. On the summit, and to the left of the central
bud, is another large depression, which appears to correspond to a terminal
growth or bud of some kind. Plate CLXXV gives a photograph view of
the perfect narrow side of the trunk in question, giving an idea of its thick-
ness. Plate CLXXVII gives a view of the base of the stem, showing the
small central medulla surrounded by a comparatively thick woody zone, a
vaguely defined cortical layer, and outside of all the very thick mass, com-
posed of the bases of the petioles and the material which enveloped them
This last portion makes up much the larger part of the trunk.

On the surface of the trunk, well shown on PI CLXXIV, are several
large, doep, irregularly shaped pits, due no doubt to the decay of several
adjacent bases of petioles before the silicification took place.

190 THE POTOMAC OE YOUNGER MESOZOIC FLORA.

The bud-scars are of two kinds, wliicli are well shown on the plate
last mentioned. The large scars stand out somewhat from the surface of
the trunk, and have a woody axis of varying thickness, surrounded by one
or more concentric circles of small leaf-scars. These leaf-scars are about
one-third the size of the imprints left by the bases of the petioles. The
woody axis within these encircling small leaf-scars varies a good deal in
size, and some of them, as Carruthers pointed out, are more or less hollow,
no doubt being caused by the decay of the axis before silicificatlon took
place. These axes probably bore sonie kind of fructification.

The small leaf scars surrounding these axes were probably caused by
leaves of small size or bracts, whose bases, like those of the larger leaves,
persisted until after the silicification of the material which surrounded them
took place and then decayed The smaller bud-scars are quite different
from those just described. These too may be seen on PI. CLXXIV.
They are considerably smaller than those with the woody axes, and con-
sist simply of concentric circles of small leaf-scars like those around the
woody cores of the larger scars. They have no woody axis, and appear
to be undeveloped buds composed of small leaves or bracts. There is
nothing to show what is the functional meaning of these numerous scars of
buds, but it is quite possible that the larger ones may have borne the
female inflorescence, and hence trunks such as No. 1 would belong to the
female plants. The open pits left by the decay of the bases of the petioles
of the pi'incipal leaves of the trunks are exact casts of these bases. They
seem to have had normally in cross-section a shape that is accurately rep-
resented b}' a bow with the string bent into an acute angle caused by
drawing an arrow to its head, the curving bow representing the upper side
of the hollow cast. Owing to distortion they assume sometimes rhombic
or elongated triangular shapes. They are smaller towards the top of the
stem than towards the bottom, and have an average size towards the bot-
tom of the trunks of 18"™ by 8"™, towards the top of 10™'" by 5""".

Fragment No. 1.

Between Washington and Baltimore was found a large fi'agment
exactl}- resembling trunk No. 1, but not broken off from that. This resem-

DESCEIPTION OF THE SPECIES. 191

blance may indicate that trunk No. 1 came from the same locality. It is
silicified in the same way and has the same kinds of scars. The casts of
the petioles in this fragment are rather larger than those of trunk No. 1,
being 22™" by 12"" in cross-section. This fragment is shaped like an
irregular disk or quoit, having the dimensions 26°"° by 19*"°.

Trunk Ko. 2.

Plates CLXXIX, CLXXX.

This was probably obtained from near Beltsville, being picked up on
the surface of the ground on Mr. Emack's farm. It is exactly like the frag-
ment found at Spring Grarden, Baltimore, being even silicified in the same
way. The silica, replacing the vegetable matter of this trunk, contains a
large amount of iron, so that in proportion to bulk it is much heavier than
trunk No. 1. Curiously enough, both this trunk and the ferruginous frag-
ment found at Spring Garden show a projecting seam of ferruginous silica.
This is shown on the narrower side of the trunk on PI. CLXXX, and
less distinctly on the front left-hand side, on PI. CLXXIX. This seam
appears to be due to a crack in the trunk, which was filled with infil-
trated silica in the form of a vein. This silica in the projecting plate or
vein seems to be in part at least due to a partial filling of the crack by
sand, for grains of sand are mixed with the silica deposited from solution.
On one side of the trunk near the top and close to the projecting silicious
plate, soldered to it and the trunk, are a number of small pebbles coated
with iron. The sand and pebbles indicate that the original place of the
trunk was in sand&tone, not clay, and this would cause us to infer that the
trunk was silicified in the lower Potomac sand. It would then come into
the upper Potomac or clay member only after the destruction of the sand-
stone or sand originally holding it. Trunk No. 2 is ovate in shape, and
decidedly narrowed towards the top. It is not so much flattened as No.
1, as is indicated in the view of the narrow side given in PI. CLXXX. A
small piece is broken away from one side at the top, but still this trunk
is more complete than No. 1. On the broader side, PI. CLXXIX, the
maximum height is 41™, the greatest dimensions at base SS''", the shorter
dimension there 34''"'. The dimensions at the top before the breaking off of

192 THE POTOMAC OE YOUNGER MESOZOIC FLORA.

the fragment were 14™ by 12"". The tapering to the top is caused mainly
by a slope of one face of the trunk, viz, that shown on the right-hand
side on PI. CLXXIX, and hence the terminal bud, or that of growth, is
tin-own much to on*e side of the axis of the trunk. A large terminal bud
may be seen on the highest part of the trunk, and on one side of this is
the break spoken of, which slopes down the trunk just as if the base of a
stem had been torn off. It is quite possible that this may have been a
stalk bearing the male inflorescence. If so, the trunk would be that of the
male plant, and the structural differences from those of No. 1 would be
accounted for by the sexual distinction.

In both No. 1 and No. 2 the growth seems to have been maintained
by the development of successive circles of leaves at the summit of the
trunk which unfolded from a biid composed of undeveloped leaves, and
not from a terminal bud inclosed by bud scales, as Saporta holds to be the
case with his genus Clathropodium. The fracture may be seen on PI.
CLXXIX, near the top of the trunk on the left hand, and very distinctly
on PI. CLXXX in front near the top. Trunk No. 2 shows none of the
larger lateral or axillary growths or buds such as are so common in No. 1.
Near the top are faint indications of what may have been two small unde-
veloped leaf-buds without woody axis, but they are too obscure for us to
conclude positively that they are buds of any kind. They are composed
of circles of very minute apparent leaf-scars, which are much smaller than
those similarly placed in No. 1 and not near so distinct as these.

The hollow casts left by the bases of the petioles indicate that these
had normally, in cross -section, the same shape as those of trunk No. 1.
But there is a greater tendency than in No. 1 for the upper side to be bent
in the form of an angle and thus give the cross-section a rhombic shape.
Some of the imprints are a good deal larger than the others, but the varia-
tions are due to distortions from pressure. The average dimensions of the
cross -sections are 22'"'" by 12'"'".

Feagment No. 2.

This specimen, foixnd at Spring Garden, measures in its greatest length
27'"", and in its greatest width 23'", being in the shape of an irregular prism

DESCEIPTION OF THE SPECIES. 193

It seems to have been split off longitudinally from a trunk so as not to
show any portion of the terminal bud. It has no axillary buds. The
cross-sections of the bases of the petioles resemble those of No. 2, but
are somewhat higher proportionally, being 14"° in height, against only
20™™ in length.

We may from the above detailed account sum up the description of
the species as follows :

Tysonia Maeylandica, sp. nov.

Plates CLXXIV-CLXXX.

Stems ovate or oblong, more or less flattened, medulla comparatively
small ; woody zone large, external integument, with the bases of the
petioles, very thick ; male inflorescence probably borne on a stalk on the
summit of the trunk by the side of the bud of growth of the trunk, and
carried on a trunk without axillary buds ; female inflorescence on axillary
growths; growth of the trunk maintained by a terminal bud, which un-
folded successive circles of leaves.

Localities all in Marjdand, viz: Spring Garden, at Baltimore; near
Contee's station ; near Beltsville.

CONIFER^E.

The conifers form the most important element in the Potomac flora.
Taken as a whole they lend a decidedly ancient asjoect to this flora A
number of the most important of these conifers have passed entirely
away, leaving no living species. The genera still surviving and most
nearly allied to these more important Potomac forms appear now very
locally distributed and contain few species. Indeed we may regard them
as in process of extinction. Such of them as have hitherto been found in
other parts of the world are here much more abundantly represented.

The conifers are largely developed in variety of types and in the
number of individuals belonging to the different types, as well as in the
very general diffusion of the forms. In the number of different species
the conifers are inferior to the ferns, but they far surpass the ferns in the
number of individuals belonging to each species. They are much more

MON XV 13

194 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

generally diffased tiian are most of the species of ferns. When a species
of fern is found it is always, except on Potomac Run, among the rarest of
the plants. At the same time the different species of ferns are usually
very restricted in occurrence. The conifers form the most widely diffused
of the Potomac plants, and when they occur they are generally the most
abundant plants at the locality. One or two examples may be given to
illustrate the abundance of individuals. At the entrance of Trent's Reach,
in one layer six to eight inches thick, fragments of the branchlets of
Fenelopsis ■parceramosa were so abundant, that they formed a considerable
portion of the mass of the stratum. With these immense numbers of
fragments of Baieropsis pleuripartUa were found. Fenelopsis ramosissima is
by far the most common plant at Fredericksburg.

The abundance of imprints of the leaves of conifers is not the only
evidence of the great development of conifers in the Potomac. It is shown
in the immense amount of lignite formed from coniferous wood. This
lignite occurs both in the form of isolated logs and fragments, and in tiers
of logs piled one over the other, as if caused by prostrate forests, indi-
cating that some, at least, of the conifers of that day grew massed in forests
as now.

Certain peculiar genera, now extinct, seem to have been very largely
developed in the Potomac vegetation, and if we are to judge from their
predominance in the fossils of localities where they occur, they must have
formed the leading and most characteristic types. These will be noticed
further on under proper heads. The archaic character of many conifers
as well as ferns does not prepare us to expect to find angiosperms asso-
ciated with these two elements.

NAGEIOPSIS, gen. nov.

Trees or shrubs with leaves and branches spreading in one plane ;
leaves varying much in size and shape, those towards the base of the twigs
sometimes smaller than those higher up, distichous mostly, or rarely sub-
distichous, opposite and persistent, attached by a short slightly twisted
footstalk, usually to the side of the twig, more rarely slightly within the

DESOEIPTIOF OF THE SPECIES. 195

margin on tlie upper or under surface of the stem, either attenuated
towards the base or abruptly rounded off there, at their ends acute or
subacute ; nerves several, coalescing at base to form a footstalk, forking-
immediately at the base or a short distance above, then approximately
parallel to near the tips of the leaves, where they are somewhat crowded
together, but do not converge to a union, ending in or near the extremity.

This fine genus is one of the most largely developed and characteristic
forms of the Potomac flora, furnishing a very important and widely diffused
type. The single leaves and unbranched leafy twigs are so much like the
cycad genus Podozamites, that when they were first found I took them to
be forms of that genus, but later so many specimens were found showing
unquestionable coniferous characters, that I found myself, contrary to my
preconceived notions, compelled to regard the plants as coniferous.

This genus is so much like the Nageia section of Podocarpus, that I have
felt considerable hesitation in making it a distinct genus. It may be a
question whether or not some of the species hitherto described as Podo-
zamites in other formations besides the Potomac should be regarded as be-
longing to Nageio2)sis. In the absence of branching twigs it is not always
easy to distinguish these plants from Podozamites. In the leaves of this
plant, however, the nerves do not converge and unite in the tips as in Podo-
zamites. This is the only feature which will distinguish detached leaves
of the two genera.

I am strongly inclined to think that Podozamites Emmonsi, Newberry,
from the Rhsetic of North Carolina and Virginia, as well as Podozamites
tenuistriatus, from the same formation, belong to Nageiopsis.

Nageiopsis longifolia, sp. nov.

Plate LXXV, Fig. 1; Plate LXXVI, Figs. 2-0; Plate LXXVII, Figs. 1, 2 ; Plate LXXVIII, Figs. 1-5;
Plate LXXIX, Fig. 7 ; Plate LXXXV, Figs. 1, 2, 8, i).

Leafy twigs very large, with stout woody stems sometimes 1*^™ and
over thick ; leaves strap-shaped, narrowed at the base, attached b}^ a short,
slightly twisted petiole most commonly to the margin of the stem, rarely
within it on the upper and lower face, acute or subacute, and gradually
naiTOwed towards the tips, varying in width and length ; maximum lengtli

196 THE POTOMAC OE YOUNGER MESOZOIC ELOKA.

seen 18""" and over, maxinuim width 1™ and over, usually remotely placed,
generally opposite, rarely subopposite, going oflf normally at an angle of
about 45°, but often from pressure distorted in position; nerves compara-
tively few, forking at or near the base, parallel to near the apex, where
they are slightly crowded.

Localities : Fredericksburg ; Kanke3''s ; near Telegraph Station ; 72d
mile-post, near Brooke ; Deep Bottom ; red-clay ball in banks of Dutch
Gap Canal ; fishing hut above Dutch Gap Canal.

This splendid ])lant is quite widely diffused, but it is rare at all points

except Fredericksburg, where it is not uncommon ; all the larger specimens

figured come from this latter locality. PI. LXXV, Fig. 1, slightly restored,

shows that the leafy twigs must have attained great dimensions, for this is

evidently but a small portion of the twig. PI. LXXVIII, Figs. 1, 4, must

form portions of still larger twigs. Fig. 3 of this plate shows a sort of keel

on the stem, probably due to shrinking. On this the leaves are not strictly

distichous PI. LXXVII, Fig. 1,. shows leaves of the greatest width. In

Fig. 2 of the same plate the position of the leaves is due to distortion from

pressure acting downwards. PL LXXVI, Fig. 4, gives leaves of unusual

width On Fig. 5 of the same plate we see the scars left by the bud-scales

of a terminal bud. PL LXXVI, Fig. 'i^, shows at the top of the stem the

bases of two lateral branches. It seems that this plant often continued the

growth of its leafy branches by means of a terminal bud flanked by two

lateral buds. On Fig. 5 there are indications at the place marked by the

scars of the bud-scales that two lateral branches had been torn away.

Before I saw the specimen depicted in Fig. 3 I supposed that the plant

was a Podosamites close to Zamites Gcepperti Schenk.-' In the character of

the leaves it is much like this plant ; Schenk's plant is evidentl}'' much

mutilated.

Nageiopsis zamioides, sp. nov.

Plate LXXIX, Figs. 1, 3 ; Plate LXXX, Figs. 1, 2, 4 ; Plate LXXXI, Figs. 1-6.

Leafy twigs wide-spreading, copiously branching ; leaflets varying a
good deal in length and width according to position, those at the base of
the branches sometimes unequal and much smaller than those up higher.

'FosB. Pflauzen der Wernsdorf. Schichten, PI. Ill, Fig. 6.

DESCRIPTION OP THE SPECIES. 197

The leaflets attain a maximum width of 2"™ and a length of 7"™. They are
widest near the base, and tapei" gradually to an acute tip, are abruptly nar-
rowed at base and rounded oflf, attached by a very short, slightly twisted
foot-stalk mostly to the sides of the stem, usually distichous, varying in
shape from narrowly ovate to linear-lanceolate, opposite nearly always ;
nerves remote and distinct, forking at or near the insertion of the leaves,
diverging strongly on entering the leaf, and almost parallel to near the
summit, where they are more crowded together, the outer ones terminating
in the margins below.

Localities : Fredericksburg ; banks of Dutch Gap Canal ; fishing hut
above Dutch Gap Canal.

This fine plant is abundant at Fredericksburg, but it is quite rare at
other localities, only a few imperfect specimens being found, as, for ex-
ample, at Dutch Gap. As will be seen from the figures, the leaves vary a
good deal in size, shape, and distance apart; the smaller are often more
crowded than the larger ones. The fine specimen given in PI. LXXIX, Fig.
1, apparently branched sevei-al times. In PI. LXXX, Fig. 1, a thick strong
stem is shown, and the leafy twig had evidently considerable length, the
leaves being comparatively remote from each other. Fig. 4 of the same
plate gives fragments of a copiously branching stem, the junction of one
terminal and two lateral twigs being shown radiating from a common point,
which seems to be a usual mode of branching in the plants of this genus.
The two lower left-hand twigs seem to come off in a similar manner from
down lower on the stem. The leaves on this specimen are much crowded.
In PI. LXXXI, Fig. 1, we have apparently the same mode of branching.

This plant, in the nerves and shape of the leaflets, is so much like a
Zamites, ihat for some time I held it to be a cycad. It is the most abundant
species of Nageiopsis found at Fredericksburg. Unlike the leaves of
Zamites and Fodozamites, those of this and the other species of Nageioims
seem to be quite persistent, for they are usually found attached to the stem.

Nageiopsis recuevata, sp nov.

Plate LXXV, Fig. 2; Plate LXXIX, Fig. 4; Plate LXXX, Fig. 3.

Stems stout, leaves remote, recurved, subacute to obtuse, gradually
narrowed to the base, and attached to the margin of the stem, or slightly

198 THE POTOMAC OE YOUNGER MESOZOIC FLOEA.

within it, by a comparatively broad flat pedicel, in shape elongate-elliptical
to oblong, length reaching 8"" and width 15"™. Nerves fine, numerous,
closely placed, forking near the base, and parallel to near the summit, where
they are a little more crowded; the outer nerves on the upper margin end
in the margin of the leaves some distance below the summit.

Localities: Fredericksburg; banks of Dutch Gap Canal ; fishing-hut
above Dutch Gap Canal. It is most common at Fredericksburg, but is rare
everywhere.

Nagieopsis crassicaulis, sp. nov.

Plate LSXIX, Figs. 2, 6; Plate LXXXII, Fig. 1; Plate LXXXIV, Figs. 3, 9, 11.

Leaves with very thick stems even at the summits of the leafy twigs ;
leaflets attaining very considerable dimensions; length not made out, width
up to 27°™ and over, gradually narrowed to the base and tijj; elongate-
elliptical in shape, attached by a short slightly twisted pedicel to the margin
of the stem, or slightly within it; nerves at the base and summit of the
leaves, so far as seen, indistinct and not well made out, fine and rather
remote.

Localities: Road-side near Potomac Run; Fredericksburg; Kankey's ;
72d mile-post, near Brooke; banks of Dutch Gap Canal; fishing-hut above
the canal.

The plant is rare, and having long narrow leaves, with a thin leaf-sub-
stance, the leaves are usually found detached and in fragments; in this re-
spect it is more like Zamites than most of the species of Nageiopsis. The
nerves are usually so fine and the leaf-substance so thick, that they can not
be clearly made out. It is not certain that some of the specimens placed
in this species are not Zamites.

Nageiopsis latifolia, sp. nov.

Plate LXXXII, Fig. 3.

Leaves very broad and short, base and apex not seen; leaf-substance
thin ; shape of leaves probably broadly elliptical ; nerves not fully disclosed,
but probably branching near the base; they are then approximately parallel
to near the apex, following the margins, and parallel.

DESCRIPTION OF THE SPECIE8. 199

Localities : Fishing-hut above Dutch Gap Caual ; road-side near Poto-
mac Run ; very rare.

Several detached leaves of this plant were found at the fishing-hut
above Dutch Gap Canal. They occurred together, as if coming from the
same plant, but were detached so as to give no intimation of the mode of
attachment, kind of stem, etc. The most complete of these leaves is given
in the figure. Fragments indicating even greater width than that of the one
figured were seen. The maximum dimensions indicated were 12™ by 5"™.
It is possible that this plant is a broad-leaved Podosamites, similar to the
broad-leaved forms such as Podosamites JReinii Geyler, described by Geyler
from the Jiirassic formation of Japan. (Ueber Foss. Pflanzen aus der
Juraform. Japans, PI. XXXIV, Fig. 2.)

Nageiopsis deceescens, sp. nov.

Plate LXXVII, Fig. 3.

Leaves, so far as seen, small, closely placed, narrowed at the base and
apex, diminished greatly and abruptly in ascending on the leafy twigs, in
shape narrowly oblong to linear ; nerves forking at base, parallel to near
the apex, the outer ones ending in the margins just below the apex.

Locality : Road-side near Potomac Run.

Only one specimen of this plant was found. It shows the peculiarity
of a sudden diminution of the leaves in ascending. As a rule the leaves
of the species of this genus diminish towards the lower portions of the
leafy branches if there is any inequality in them.

Nageiopsis ovata, sp. nov.

Plate LXXVII, Fig. 4 ; Plate LXXX, Fig. 5.

Stems comparatively veiy stout ; leaves opposite, going off nearly at
right angles from the stem, closely placed, lower ones smaller but gradually
increasing in ascending, broadest near the base and abru^Dtly rounded off
there, attached by an extremely short slightly twisted pedicel, narrowing
to an acute tip, oblong to elongate-elliptical in shape ; nerves indistinct,
but forking at base, diverging on entering the base of the leaf, then nearly

200 THE POTOMAC OE YOUNGER MESOZOIG FLORA.

parallel to the tip, where they are somewhat crowded, the outer ones end-
ing in the margin below the apex.

Locality : Fredericksburg.

The specimens of this pretty plant are quite rare. The lower leaflets
are markedly smaller than those higher on the leafy twigs, but this is a
feature not uncommon in plants of this genus.

Nageiopsis obtusifolia, sp. nov.

Pliite LXXXV, Fig. 7.

Leaves short in proportion to width, very obtuse, attached by a short
slightly twisted pedicel, broadly elliptical or oblong in shape, broadest
near the base, slightly inequilateral at base ; nerves forking once or twice
near the base and then parallel to near the summit, where they are a little
crowded together, the outer ones ending in the margins a little below the
apex.

Locality : Road-side near Potomac Run.

This plant was evidently very rare. It shows the unusual feature of
having the margin of the base on the lower side more convex and broader
than on -the upper side, which latter is cut away in a concave mannei'.
The nerves also tend to go off in bundles, branching more than once at
the base of the leaves. It is very rare.

Nageiopsis in^equilateralis, sp. nov.

Plate LXXXV, Fig. 6.

Leaves snort and broad in proportion to length, slightly inequilateral
at base, obtuse, elliptical, broadest near base, abruptly narrowed on the
lower side at base, and more gradually rounded off on the upper side ;
leaf-substance very thick, epidermis dense and shining; nerves not dis-
tinctly seen, but parallel towards the upper part, and slightly crowded at
the summit of the leaflets.

Locality : Kankey's.

Only one specimen of this plant was found. The thick epidermis
obscures the nerves.

DESGEIPTION OF THE SPECIES. 201

Nageiopsis acuminata, sp. uov.

Plate LXXXV, Fig. 11.

Leaves narrowly ovate, widest at base and slightly acuminate, abruptly
rounded off at base and attached by a short strong pedicel, gradually nar-
rowed towards tips ; nerves not seen.
• Locality : Near Telegraph Station ; very rare.

Only one good specimen seen. It shows a small bit of the stem still
attached. As no large amount of material was obtained at this place the
rarity of the plant may be apparent rather than real. It is possible that
the plant may be a Zamites.

Nageiopsis heterophylla, sp. nov.

Plate LXXXIV, Fig. 4; Plate LXXXVI, Figs. 6, 7; Plate LXXXVIII, Figs. 2, .5.

Stems large, branching freely ; leaves small, narrowly ovate to oblong-
linear, widest near the base and usually rather abruptly rounded off there,
attached by a very short slightly twisted pedicel, gradually narrowed to
acute tips ; leaves sometimes varying irregularly in size, larger and smaller
ones being intermingled or placed on opposite sides of the stem ; leafy
branches terminating in a leaf similar to the lower ones ; nerves forking
once or twice near the base of the leaves, then parallel to near the sum-
mit, where they are more approximate, the outer ones ending in the mar-
gins below the summit.

Localities : Fredericksburg ; fishing hut above Dutch Gap Canal.

This pretty little plant is not uncommon at Fredericksburg. It shows
the peculiar feature (as in PL LXXXVI, Fig. 7, and PI. LXXXVIII,
Fig. 2) of having the leaves at the bases of the twigs very unequal on
opposite sides, and also, as in the first-named figure, the peculiarity of hav-
ing small leaves intermingled with large ones. In PI. LXXXIV, Fig. 4,
the tips of the leaves have been removed by accidents of preservation.

Nageiopsis microphylla, sp. nov.

Plate LXXXIV, Fig. G ; Plate LXXXV, Fig. 14 ; Plate LXXXVI, Figs. 1-3, 5.

Leafy twigs pinnately arranged, terminating in a leaf larger than
those lower down ; leaves very small, naiTowed to the base and apex, ellijD-

202 THE POTOMAC OR YOUNGER MBSOZOIC FLORA.

tical or oblong, acute to acuminate, attached by a very short pedicel ;
nerves forking near the base, then parallel to near the tips, where they are
more crowded.

Localities : Fredericksburg ; road-side near Potomac Run ; fishing
hut above Dutch Gap Canal.

The plant is not uncommon at the Dutch Gap locality, but is com-
paratively rare elsewhere. The best specimens (as PI. LXXXVI, Fig. 5)
come from Fredericksburg. Fig. 3 of the same plate, having its leaves
widest at base and abruptly rounded off there, comes from the Potomac
Run locality, and is possibly a different species. PI. LXXXV, Fig. 14,
shows a stem of unusual thickness.

Nageiopsis angustifolia, sp. nov.

Plate LXXXVI, Figs. 8, 9 ; Plate LXXXVII, Figs. 2-fi ; Plate LXXXVIII, Figs. 1, 3, 4, 6-8 ; Plate

LXXXIX, Fig. 2.

Leafy stems large, branching copiously and wide-spreading ; branches
often opposite, swollen at their attachments to the main stem, and marked
with scars left by the bud-scales; the leafy stems often subdivided towards
their ends into smaller branches on which the leaves are much diminished ;
leaves varying much in size, very long in proportion to width, narrowly
linear-acute to acuminate, generally very remotely placed, narrowed grad-
ually to apex and base, attached by a short twisted pedicel generally to the
sides, sometimes to the upper and lower surfaces of the stems slightly
within the margin ; nerves forking near the base and tlien parallel to the
summit, the outer ones terminating in the margin below the summit of
the leaves, quite strong.

Localities: Fishing hut above Dutch Gap Canal; road-side near Poto-
mac Run; 72d mile-post ; bank near Brooke; Fredericksburg; near Tel-
egraph Station ; Fort Washington.

This fine species is one of the most widely diffused of the Potomac
plants, and is the most generally distributed species of Nageiopsis. It is
not very rare at the Dutch Gap locality, but is most common at Freder-
icksburg, where the plants given in PI. LXXXVI, Figs. 8, 9, and PI.
LXXXVII, Fig. 2, occur. It is one of the most noteworthy connecting

DESCRIPTION OF THE SPECIES. 203

links between the plants of the various localities which, as has been stated,
show so much tendency to isolation and local distribution. It is found
with the numerous Angiosperms of the two localities near Brooke, and con-
nects these with the plants of Dutch Gap and of Fredericksburg. Some
of the leafy stems must have been very large and wide-spreading.

On some of the branches at their bases there are very distinct scars left
by the scales which invested the terminal buds. The branches seem com-
monly to have formed at their extremities a terminal and two opposite lat-
eral buds with which to continue the growth in the next season. The for-
mation of such buds on these plants and on Cephalotaxopsis indicates that
there were well-defined pauses in the growth of the branches. The leaves
seem to have been very persistent, as they are usually attached to the
stems.

The specimen given in PI. LXXXVI, Fig. 9, indicates well the
copiousness of the branching of this plant. It shows on the left hand at
base what seems to be a portion split off from a large stem, and attached
to this is a lateral twig, which has at base the marks of bud-scales. Near
its summit this in turn sends off two opposite lateral twigs. This specimen
and also that of PL LXXXVIII, Fig. 8, show that the leaves tend to dimin-
ish in size when the twigs split up into subordinate branches. This plant
in its mode of branching and in the shape of its leaves, as well as in the
arrangement of the scars of the bud-scales, is much like Cepliahtaxopsis, but
it has several nerves in the leaves.

Nagsiopsis subfalcata, sp. nov.

Plate CLXVIII, Fig. 4.

Stems comparatively very stout ; leaves narrowed graduall}^ to the
base and apex, subacute, subfalcate, attached by a short slightl}^ twisted
foot-stalk; leaf-substance thick and leathery, nerves not seen, but appar-
ently several, and as in Nageiopsis.

Locality: Fishing hiit above Dutch Grap Canal.

Only one specimen of this plant was found. Its position is doubtful,
and it may be a Sequoia, for the foot-stalks seem to be decurrent. They
leave imprints on the stem resembling those of Sequoia.

204 THE POTOMAC OK YOUNGER MESOZOIG FLOEA.

PHYLLOCLADOPSIS, gen. nov.

Leafy stems branching copiously and irregularly ; leaves small, oppo-
site, very thick, of varying sizes on the same branch, varying a good deal
in shape, broadly ovate, broadly elliptical or orbicular, broadest at base,
abruptly narrowed into a short slightly twisted pedicel, obtuse to sub-
acute, terminal leaflet of the twigs like those lower down ; nerves usually not
distinct, being immersed in the thick leaf-substance, radiating pahnateb'
from a common point at base, and forking once or twice.

This genus is quite rare in the Potomac flora, and as yet shows only
one species. Its character and place can not be fixed positively from the
small amount of material found. It is strikingly like Phyllocladus in many
respects. In some features it resembles Nageiopsis^ but the nerves have a
different character. The genus is provisionally formed and named from
the resemblance to Phyllocladus.

Phyllocladopsis heteeophylla, sp. nov.

Plate LXXXIV, Fig. 5 ; Plate CLXVII, Fig. 4.

Plant with the generic character, liaving the terminal leaflet of the
twigs much larger than those next below, and in shape ovate-obtuse ; leafy
branches keeled.

Locality : Fishing hut above Dutch Gap Canal ; rare.

. FEILDENIOPSIS, gen. nov.

Leaves linear-oblong, subspatulate, tapering gradually below to a
broad petiole-like base, mode of attachment not seen ; leaf-substance thick
and glossy, at summit rounded and very obtuse ; nerves distinct and prom-
inent, single and parallel for a short distance above the lowest visible
portion of base, then forking all nearly at the same height, with branches
parallel to near the summit ; at summit curving round to meet one another,
with a strong nerve uniting the abutting nerves. This peculiar plant is
much like Heer's genus Feildenia, from the Miocene of Greenland.

DBSOmPTION OP THE SPECIES. 205

Feildeniopsis crassinervis, sp. nov.

Plate LXXXV, Fig. 5.

Plant with the generic character, having very strong broad nerves,
which are sharply defined like threads in the dense leaves, the latter having
a glossy look, and seeming to narrow so as to form a sheathing or clasping
base. The nerves of this species are quite like those of Heer's species Feil-
denia Mossiana,^ curving around to abut at the summits of the leaves, and the
points of meeting are connected by a strong nerve, which descends and
seems to split up to form the central pair of nerves.

Locality : The olant occurs only at Kankey's and is very rare.

BAIEROPSIS, gen. nov.

Leaves borne towards the ends of the branches ? ; leafy branches pin-
nately arranged, opposite or subopposite, in the same plane with the leaves,
diminishing in ascending in the size and number of the leaves ; towards the
summit of the leafy stem the leafy branches reduced to simple leaves ; the
leaf)' stem terminated by a simple leaf similar to those of the branches and
stem lower down ; leaves on the lower branches pinnately arranged, subop-
posite or alternate ; lower leafy branches terminating, as does the main stem,
by a single leaf; leaves attached pinnately to the branches by short pedi-
cels, in shape like a fan, with wedge-shaped bases, divided nearly to the base
into several principal segments or lacinise, usually two or three in number,
these in turn divided into a varying number of subordinate segments, and
the latter divided into a number of ultimate lacinise, which are strap-shaped,
of varying width and length, and end in teeth ; the lacinise of various orders
subdivided dichotomously, diverging slightly ; the nerves branch repeatedly
in a dichotomous manner, beginning in the pedicel, the branching taking
place at varying- heights ; the nerves diverge in a flabellate manner, and
one or two of the ultimate branches end in the teeth terminating the ulti-
mate lacinise ; they are slender but distinct ; fructification not positively
made out, but apparently in the form of very small rounded or elliptical

' Flor. Foss, Arctica, vol. 5, Pt. 1, Die Mioc. Flor. des Grinnell-Landes, PI. Ill, Figs. 2-5,

206 THE POTOMAC OR YOUNGER MBSOZOIC FLORA.

nut-like seed, that are borne on sliort pedicels on each side of slender stems,
which spring from the main stem like the leaves, and appear to represent
metamorphosed leaves.

This curious group of plants has its single leaves in shape and ner-
vation strikingly like those of JeanpmUia, and in some cases they are
much like those of Baiera. Before the more complete specimens were
found, showing the mode of attachment of the leaves, I thought that the
plants belonged to the genus Baiera. Heer united the plants formerly
called JeanpauHa with Baiera ; but there would seem to be a very consid-
erable difference between such a plant as Jeanpaulia 3£imsteriana, given by
Schenk,^ and Heer's Baiera longifolia. The leaves of Schenk's plant appear
to be compound, composed of pinnately arranged segments with a terminal
segment. The plan of this leaf is much like that of the leafy branches of
Baieropsis, and it may be a question whether or not this Rh?etic supposed
leaf is really a leafy branch. There is also some resemblance between the
mode of segmentation of Baieropsis and that of the plants which Heer^
called Jeanpaulia borealis, and J. lepida, and which in the fourth volume of
the same work he was inclined to think might be ferns. But these two
plants have much shorter and proportionally broader lobes than those of
Baieropsis. Baieropsis in some points is like Saporta's genus Ginhgopliyllmn.
In this latter, however, the leaves are flabellately divided only towards their
summits and very sparingly segmented, while the greater portion of their
length in their lower portions is strap-shaped, and these long strap shaped
basal portions unite at their insertions to form a wing along the midrib.
Some of the leaves of Baieropsis are in shape much like those of some
forms of Adiantum. These might be regarded as Ginkgos, were it not for
the pinnate arrangement of the leaves.

These forms, which I have united under tne generic name Baieropsis,
seem to have more of the characters of the Ginkgo section of broad-leaved
conifers. They are most probably nearly allied to Ginkgopliyllum and
Baiera, but still in some of the forms fern characters are to some extent
present, and so long as the fructification is not clearly made out, the true
place of the group can noi be positively determined.

'Foss. Flor. d. Greozschichten, PI. IX, Fig. 9.

2Fos8. Flor. Arctica, vol. 3, Pt. 2, pp. .W, 58, PI. 11, Fig. 1-15.

DBSCEIPTION OF THE SPECIES. 207

The nature of the apparent fructification is obscure from the poor

preservation of the specimens, and from the fact that the precise connection

of the seed-hke bodies with the leaves is not seen. The seeds are about

2™™ in diameter, are sessile or attached l)y very short pedicels to slender

naked stems, being opposite or subopposite, and on both sides of them.

The stems with their seeds seem to represent metamorphosed leafy

branches or leaves, taking the place of the ordinary leaves, which appear

higher. The general character of these seeds and their apparent mode of

attachment remind one of the supposed seed of Baiera Miinsteriana from

the Rhgetic of Baireuth, which represent metamorphosed leaves of that

plant.

Baieropsis expansa, sp. nov.

Plate LXXXIX, Figs. 1, 3; Plate XC, Fig 1. ; Plate XCI, Fig. 2 ; Plate XCII, Fig. 5.

Leaves very large, having probably the width of 12'"°, and the length
of over 15"", attached by slender pedicels, and apparently distributed as
given in the generic description — i. e., pinnately on leafy twigs, which
themselves are arranged pinnately on a principal stem, the main stem and
branches ending in leaves of the normal kind; leaves divided to near
their bases into several principal lacinige, which in turn are subdivided at
varying heights into subordinate laminae, and these into ultimate ones that
are long and narrow, ribbon-like, with the ends not seen ; all subdivide
dichotomously and diverge so as to give the leaf a fan shape; the ultimate
laciniae 1.5"" wide and under; the nerves distinct, although slender. They
fork at the base in the primary lacinise, and then repeatedly subdivide dich-
otomously in the lacinise at varying intervals, the branches being more or
less parallel.

Localities : Fredericksburg ; red clay ball in the banks of Dutch Gap
Canal ; fishing hut above the canal ; entrance to Trent's Reach.

In some specimens the apparent simple strong nerves under a good
lens seem to run in pairs, the membei's of which are so closely placed that
they seem to the unaided eye to be simple nerves. This fine plant is not
very rare at Fredericksburg in pretty good specimens. At the other local-
ities the great size of the leaves caused them to be preserved in a very
fragmentary state.

208 THE POTOMAC OK YOONGEK MESOZOIC FLOEA.

There is a strong resemblance between the fragments of some of these
leaves and Baiera cretosa^ Schenk, but Scheuk's figure indicates a larger
and coarser leaf

BaIEKOPSIS PLURIPAETITA, Sp. nOV.
Plate LXXXIX, Fig. 4 ; Plate XC, Figs. 2-5 ; Plate XCT, Figs. 1, 3, 4, 7 ; Plate XCII, Figs. 1, 2, 6.

Leafy branches with the character of the genus; stems slender, leaves
bi'oadly fan-shaped, opposite or subopposite, attached by short pedicels,
usually di-\aded down to near the base into three principal segments; these
by repeated dichotomous subdivision give rise finally to long, slender, ulti-
mate segments, that are strap-shaped and about 1""" wide, their length not
being made out, as their tips were not in any case seen, but in the largest
leaves probably attaining the length of 4°" and more from the last point of
subdivision; the nerves slender but distinct, forking at the base to enter the
principal lacinise, and then forking repeatedly and dichotomously at long
intervals, with the branches nearly parallel, one or two being found in the
ultimate lacinise. The apparent fructification (see PI. XC, Fig. A) is as given
in the generic description.

Localities: Entrance of Trent's Reach; banks of Dutch Gap Canal;
red clay ball; fishing hut above the canal.

The plant is not uncommon at the first and last named localities. It is
usually associated in its occurrence with Dioouites BucJiianus. There is a
considerable variation in the size of the leaves and in the number of their
segments, apparently depending on the position of the leaves on the leafy
twigs, those towards the summits being smaller and with fewer segments.
The largest and most perfectly preserved forms were found at the entrance
to Trent's Reach. The leaves were usually found in a very fragmentary
state, and in no case were their tips seen.

Baieeopsis PLURrPARTiTA, var. MINOR, sp. nov.

Plate XCI, Fig. 5 ; Plate XCII, Figs. 3, 4.

Twigs and leaves as in B. pluripartita, but much smaller and constantl}^
so, without gradations into the larger form ; the ultimate lacinise very nu-

1 Die Foss. Ptlanz. der Wernsdorf. Schichteu, PI. I, Fig. 7.

DESCRIPTION OF THE SPECIES. 209

merousand narrow, being under l'"™in width; the leaves attain a maximum
length of 4*"", but mostly are under that, and have a maximum width of
3.5"™, but generally are narrower; nerves as in B. pluripartita, but more
subdivided, closer, and more delicate.

Localities the same as for B. pluripartita.

The specimens of this plant are much more numerous than those of B.
pluripartita, but they are mostly very fragmentary. This is the most com-
mon Baieropsis at Dutch Gap, and it is the most common plant in the red
clay ball. which occurs in the banks of the canal. It appears in numerous
fragments poorly preserved at the entrance to Trent's Reach, being found
in the same layer with Frenelopsis parceramosa, and Dioonites BucUanus.
The lower right-hand leaf in PI. XCII, Fig. 3, is nearly a complete one,
wanting only the tips of the ultimate laciniae, which no doubt, as in B.pluri-
partita, terminated in teeth. The above-mentioned leaf is one of the largest
found in this plant.

Baieropsis foliosa, sp. nov.

Plate XCIII, Figs. 4-6.

Leafy branches abruptly changed to leaves in ascending (Fig. 4) ; lower
leafy branches of the main stems having on the upper side simple leaves, but
on the lower side, towards the base, possessing leafy branches of the normal
type in place of the simple leaves of the upper side; leaves and leafy
branches closely placed; leaves quite small, fan-shaped, short, mostly di-
vided nearly to the base into two principal laminse, both of which are sub-
divided a little above the base into lacinias ; these in turn, by dichotomous
subdivision, give short strap-shaped lobes, which end in two shallow acute
or narrowly elliptical teeth, or else in two narrowly oblong subacute teeth;
nerves forking at base and then repeatedly forking in a dichotomous man-
ner, so that the branches from the last forking end in the teeth.

Localities: Bank near Brooke; White House Bluff.

At the last-named place the plant is very rare, but it is abundant at the
bank near the railroad in the vicinity of Brooke. Here it is, with the ex-
ception of the angiosperm leaves, the most common fossil. There is some
variation in the size of the leaves and in the number of subdivisions, some
MON XV 14

210 THE POTOMAC OR YOUNGER MESOZOIO FLOEA.

of the leaves, as in Figs. 5, 6, being I'xrger than others, as in Fig. 4.
Strange to say, these leaves, although so abundant at the bank near Brooke,
show not a single specimen at the 72d mile-post, only a few hundred feet
distant.

BaIEROPSIS DENTICULATA, sp. UOV.
Plate XCm, Fig. 7.

Stems of the leafy branches proportionally stout ; leafy branches and
leaves alternate ; leaves fan-shaped and wide in proportion to length,
divided to near the base into two principal laminje, and those a little liigher
subdivided into two subordinate lacinise which repeatedly subdivide until
the ultimate lacinia; end in two linear subacute teeth of comparatively
great length; nerves repeatedly forking flabellately, so that the ultimate
branches end in the teeth.

Locality : Fishing hut above Dutch Gap Canal.

This plant is quite rare, and usually occurs in small fragments.

BaIEROPSIS DENTICULATA, var. ANGUSTIFOLIA, sp. nOV.
Plate XCII, Fig. 7.

Leaves subopposite, narrowly fan-shaped to wedge-shaped, quite nar-
row in proportion to their width ; leaves attached more obliquely than in
B. denticulata, but with the laciniee and nerves as in that species, the
lacinise being fewer in number.

Locality : Bank near Brooke ; very rare.

The facies of this plant is different from that of Baieropsis dentiadata.

BaiEROPSIS LONGIFOLIA, sp. IIOV.
Plate XCI, Fig. 6.

Leaves very long in proportion to their width, deeply cut into very
long and slender principal lacinise, which are two in number and diverge
slightly ; these are subdivided several times into long and slender lacinise,
finally giving long narrowly strap-shaped ultimate lacinise which are l""
and under in width, the tips not seen ; arrangement of the leaves as given
in the generic character; nerves rather indistinct, but as in B . pluripartita ;
the main stem quite slender.

DESCRIPTION OF THE SPECIES. 211

Locality : Near Telegraph Station.

This plant has a decided facies of its own, due to the slenderness and
the length of the lacinise. The subdivisions of the leaves are much fewer
than in B. expansa and B. pluripartita, and take the form of pairs. It is
quite rare.

Baieropsis adiantifolia, sp. nov.

Plate XCir, Figs. 8, 9 ; Plate XCIII, Figs. 1-3 ; Plate XCIV, Figs. 2, 3.

Stems moderately strong; leaves subopposite to opposite, closely
placed, often imbricated, subquadrilateral to flabellate fan-shaped, nar-
rowed to a wedge-shaped base, and attached by a short pedicel which
springs from the lower corner of the leaf, so that the inner margin of the
leaves runs close to the main stem, parallel with it, and often overlapping
it, while the lower margin of the leaves stands nearly at right angles with
the main stem ; leaves cut down to near the base into two principal lacinise,
and those higher cut into two or more minor lacinise ; ultimate laciniaj very
shallow and strap-shaped, ending in acute very short teeth, or rarely in
narrowly elliptical and subacute ones ; all the laciniae turned outwards or
upwards, the lower margins of the leaves being entire or having sometimes
an acute tooth ; leaves in ascending towards the tips of the leafy branches
have their lower margins directed more and more upwards, become smaller,
assume more of an elliptical or a wedge shape, have the lacinige only on
the upper margin, and finally coalesce to form a terminal leaflet, which at
base shows three segments, but whose terminal portions are not seen;
nerves fine but distinct, branching at base from a mother nerve and then
dividing repeatedly in a dichotomous manner so as to fill the laminte, and
have the branches ending in the teeth.

Localities : Fredericksburg ; road-side near Potomac Run ; near Tele-
graph Station.

The plant is most frequent at Fredericksburg but is not abundant
there, and is usually in a very fragmentary state. If we look to the shape
of the leaves alone this curious plant is much Hke a fern of the type of
Adiantimi, but the gradations through difi"erent forms connect the speci-
mens so closely with the flabellate leaves of Baieropsis that they can not

212 TUB rOTOMAC OE YOLTNGER MESOZOIC FLORA.

be separated by any good distinctions. The principal difference from the
more common and typical forms of Baieropsis is found in the greater pro-
portional width of the leaves and tlie smaller depth of the subdivision.

Baieeopsis adiantifolia, var. minor, sp. nov.

Plate XCIV, Fig. 1.

Leaves nearly in shape as those of B. adiantifolia, but much smaller,
alternate, with their lower margins making an angle of 45°, with the stems
divided above the base into two lacinia?, one smaller, directed upwards,
and divided near the summit into short strap-shaped lacinije that end in
teeth, and one larger, directed outwards, also subdivided into strap-shaped
lacinias ; nerves as in B. adiantifolia.

Locality : Fredericksburg.

This may be only the upper part of a small branch of B. adiantifolia.

It is very rare.

Baieeopsis maceophylla, sp. nov.

Plate XC, Fig. 6.

Leaves very large, dividing repeatedly into laciniee and diverging
flabellately; form and dimensions of the leaves not made out; ultimate
lacinise, so far as seen, 4°*°' wide ; nerves forking at long intervals, with the
branches parallel.

Locality : Fredericksburg.

Only a few specimens were found. The leaf was probably very
large, the fragments indicating a maximum length of about 20"", with a
nearly equal width. The great size of the leaves caused them to be pre-
served only in fragments. It is possibly a Baiera. The plant has on the
w'ider basal portions of the lacinise a number of peculiar elliptical pro-
tuberances, which seem to spring from off-shoots of the nerves. The exact
nature of these could not be made out, but they seem to be rather a
fungoid growth than fructification.

BAIERA, F. Bi-aun, emend.

Leaves leathery, gradually narrowed into the longer or shorter pedicel,
fan-shaped, with repeated dichotomous subdivision, segments linear, some-

DBSCEIPTION OF THE SPECIES. 213

times ribbon-shaped, incised at the tips or entire, inserted on short branches;
nerve-bundle issuing from the base of the leaf and repeatedly forking.

This description, which is that given by Schimper on page 261 of the
second volume of Zittel's Handbook, applies to only one of the forms of
the Potomac. The essential point is the insertion of the leaves in tufts on
the summit of short branches which form annually. This is a very
different arrangement of the leaves from that in Baieropsis, where they are
all in one plane, arranged pinnately on the sides and at the tips of leafy
twigs.

Baiera foliosa, sp. nov.

Plate XCIV, Fig. 13.

Leaves numerous, grouped in bundles or tufts at the summit of short,
stout, annual growths, having their basal portions long, slender, and grad-
ually narrowing into a pedicel ; their upper portions dichotomously divided
into a small number of strap-shaped lacinitE, the ultimate ones being a little
over 1°"° wide; nerves slender, forking at long intervals, with branches
parallel.

Locality : Fishing hut above Dutch Gap Canal.

This plant, evidently a true Baiera, is very rare, the specimens, few in
number, being, with the exception of the one figured, found in small frag-
ments. The leaves at the summit of the short twigs seem to have been
very numerous and more slender than in the Jurassic Baieras.

FRENELOPSIS, Schenk.

Trees or shrubs ; stems seen in thickness up to 5"" and more ; stems
and branches cylindrical, jointed, branches alternate or whorled, radiating
from the same zone on the principal stems and curving upwards ; epider-
mis dense and durable, cortical tissue thick, and apparently succulent;
leaves on the joints very short, varying somewhat in shape, normally more
or less triangular in form, acute, close appressed, not decurrent, minute and
scale-like, one to three in number, alternating in position on the successive
joints ; epidermis marked with minute tubercles arranged in rows, which
to the unaided eye appear as fine striae running longitudinally on the stem

214 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

and parallel to one another; woody axis of the larger branches and stems
comparatively small, in the ultimate smaller branches apparently wanting,
these being composed seemingly of a succulent material, which was cov-
ered by a dense, durable epidermis ; fruit not seen.

The stems and branches of this plant, originally cylindrical, are now
from pressure always found flat. The stems and larger branches are gen-
erally found decorticated or deprived of their epidermis. The removal of
the epidermis carries away the scale-like leaves, and on the smallest ulti-
mate twigs they in such cases leave no scars But when the Kstems and
largest branches are deprived of their epidermis and not decorticated,
rhombic or triangular scars mark the place of the leaves on the joints.
The larger twigs quite often are arranged on the main stems in an umbel-
late manner. In other cases the branches are arranged in the same plane
and go off alternately

The genus Frenelopsis, as hitherto known, is composed of only two
species, viz, F. Holieneggeri Schenk, and F. occidentaUs Heer. The former
is, according to Schenk, the most abundant plant in those beds in which it
occurs. He gives in Die Foss. Pflanzen der Werusdorf Schichten, the most
complete description and delineation of this species known. We may then,
in our comparative study of this Potomac species, confine ourselves to
Schenk's figures and description. Schenk, in his description of the leaves,
says (page 13) that they occur in pairs opposite to each other, the succeed-
ing pairs being decussate. The leaves of one of the Potomac species cer-
tainly occur in whorls of three, and, judging from the figures given by
Schenk, I am inclined to think that the leaves on F. Holieneggeri occur also in
threes on the joints. In PI. VI, Fig. 6, in Schenk's work, the pair of leaves in
the middle of the stem seem to present on the front aspect of the twig the
greater portion of their width, and by their position strongly suggest that
they are opposed behind by a single leaf, which belongs to the same whorl.
The lower leaf on this twig, by its eccentric position, indicates that it is
opposed behind by two leaves. The position of the pair above mentioned
is quite similar to that seen in some specimens of the Potomac plant F.
ramosissima, where the pair is opposed by a single leaf. If this be the
true character of the arrangement of the leaves, then Schenk's opinion, ex-

DESCRIPTION OP THE SPECIES. 215

pressed on page 15 of the above-named work, is correct, and the plant is
nearly allied to Frenela It is perhaps the ancestral form of the living
Frenela, not yet fully differentiated, for the Potomac plant F. parceramosa
has onl}^ one leaf on each joint.

Heer's F. occidentalis from Valle de Lobos, Portugal, does not afford
specimens well enough preserved to add to our knowledge of the genus.
In his Contributions a la Flor. Foss. du Portugal, PI. XII, Fig. 4, is a good
deal like some of the specimens of F. ramosissima.

The striking resemblance of the Potomac forms, and especially of F.
ramosissima, to Frenela confirms Schenk's original conclusions, and there
seems to be little doubt that Frenelopsis is more nearly allied fo that genus
than to Ephedra, as Heer thought. If the leaves of F. Hoheneggeri are
really in pairs, then the generic description must read: Leaves one to three
on the joints. This would not be incompatible with a relationship to Fre-
nela, for in that genus the leaves are not always in threes, but occur occa-
sionally in fours, or even scattered singly, as sometimes is the case in Fre-
nela australis Hooker. Leaves in fours occur also in F. subiimhellata Par-
latore.

Schenk' very correctly calls attention to the resemblance between F.
Hoheneggeri and Massalongo's Aularthrophyton, depicted in Flor. Foss. del
Monte CoUe, etc. There is so strong a resemblance that it is difficult to
believe that they belong to different genera.

F. ramosissima is probably a better differentiated form in the direction
of Frenela than F. parceramosa and F. Hoheneggeri.

Fkenelopsis ramosissima, sp. nov.

Plates XCV-XCIX ; Plate C, Figs. 1-3 ; Plate CI, Pig. 1.

Tree or large shrub ; stems seen up to a diameter of 5""° ; stems and
branches originally cylindrical, now from pressure always flat, apparently
with a large pith, often appearing to have been hollow; the larger branches
sometimes scattered and alternate, but more commonly in umbel-like
whorls containing three to five branches, usually in the larger branches
curving upwards; stems and branches jointed, with joints usually very

'Die Foss. Pflauzeu der Wernsdorf. Schiohten, p. 15.

216 THE POTOMAO OR YOUNGER MESOZOIO FLOEA.

short, the jointing most conspicuous on those parts which retain the cortical
layer and epidermis, especially distinct in the smallest ultimate branches,
the jointing on the larger decorticated stems often not visible; wood}^ axis
proportionally very small, apparently surrounded originally by a thick suc-
culent cortical layer, which was covered by a firm, parchmeiit-like, very
durable epidermis ; this latter marked by very fine longitudinal lines
formed "of rows of small tubercles or dot-like elevations; in the smallest or
ultimate branches the woody matter seems to have been almost or wholly
wanting, the material composing the branch being succulent and covered
with a firm epidermis; leaves in whorls of threes, leaves of successive
whorls alternating; on the youngest branches the leaves are often retained
uninjured in the form of minute, closely appressed scales, mostly broadly
triangular in form, acute, often acuminate, sometimes mucronate, united at
base ; on the older branches often convex in form, and under a lens show-
ing towards their tips a prominent line forming a sort of keel ; on these
branches, when deprived of epidermis, the leaves leave scars, rhomboidal
in shape, and slightly elongated in the direction of the length of the stems.
The shape of the older leaves varies more than that of the younger ones,
being broadly triangular, with very short acute tips or mucronate, some-
times dome-shaped to broadly conical, with tips prolonged to various
lengths, often acuminate and sometimes mucronate ; the ultimate succulent
branches, seeming to have performed the work of leaves and always short,
go off from the joints in the axes of the scale-like leaves, generally curve
upwards, and apparently lie in the same plane. The subordinate twigs
always end with a branch like those sent off lower down ; ultimate
branches in length, stoutness, number of branches on the penultimate twigs,
and degree of crowding show considerable variation ; in some cases the
ultimate branches are very closely placed, three or four on a side, with a
terminal one short and stout, in other cases they are remotely placed, stout
and long; again, the plants have sometimes on the penultimate twigs a
few remote, very short branches, hardly more than buds ; buds sometimes
found on short twigs, arranged as are the branches, forming club-shaped
growths, in which a number of internodes with partially formed leaves are
shown.

DESCRIPTION OF TOE SPECIES. 217

Localities: Fredericksburg; Baltimore, at Federal Hill.

The plant is verj^ rare at Baltimore, but abounds at Fredericksburg,
where it is by far the most common fossil. The great number of specimens
of this plant at the latter locality indicates that a forest of it must have
grown near by. The existence of well-defined buds shows that the growth
of the plant was not continuous, but that periods of repose occurred. In
many cases the epidermis of the ultimate twigs is so well preserved that it
shows the entire shape and dimensions of the twigs, and may be stripped
off from the stone. In such cases there is no trace shown of woody fiber
and only a faint imprint is left. The entire material of the smaller twigs
was evidently pulpy and succulent. Only in the older and larger stems is
a small woody axis shown. In all cases the removal of the epidermis car-
ried away the leaves, and these leave no scars except on the older
twigs. It is quite common to find the shrunken remains of the twigs
lying in molds which are now considerably larger than themselves, and
which they evidently once filled. In twigs l"^"" and under in diameter we
may often find the parchment like epidermis perfectly preserved, wrinkled
transversely, filled with a brown dust, but showing no woody matter. When
woody matter existed it has always been changed to jet, involving the total
destruction of the tissue, so that its structure can not be made out. The
woody axis, when present in the form of jet, is always much smaller than
the tube of epidermis which incloses it. It is a peculiar fact that the woody
matter of this plant was never found preserving the structure of the tissues.
This results, perhaps, from the succulent nature of the material. This de-
struction of tissue and softening of the material of the plant may account
for some peculiar differences seen in parts which evidently once belonged
to the same plant. On some of the older stems, if some of the succulent
cortical zone remains, or if the epidermis is preserved, the jointing is plainly
shown. (See PI. XCIX, Figs. 2, 3; PI. XCVI, Fig. 3, etc)

In other cases, where only the woody axis is preserved or nothing but
an imprint is left, no indications of jointing can be seen, although on ulti-
mate twigs of the same specimen which retain the epidermis the jointing
is plain. In the decorticated specimens figured on PI. XCVII, Figs 1, 2;
PI. XCVIII, Fig. 2; Plate XCVI, there is no trace of jointing, the softening

218 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

of the tissues and the pressure to which it has been subjected, obliterating,
the evidences of it. In PI. XCVI, Fig. 1, the main stem shows no jointing,
while the ultimate and not fully decorticated twigs do show jointing ; PI.
XCV, Figs. 1, 2, 3, 5, retaining epidermis, show good jointing.

The specimens with buds, as in PI. XCIX, Fig. 1, had thick fleshy
stems, with a comparatively small wood}^ axis, surrounded by a very thick
succulent cortical layer. It looks as if this material was provided to sustain
the growth of the buds. PI. C, Fig. 1, gives a restoration of what was the
probable appearance of one of the smaller twigs. The smaller branches
seem always to have been spread out in one plane and to have gone off
alternately. The tubercles seem to have been borne on the surface of the
epidermis. They are never conspicuous on this species, and are seen best
on the youngest ultimate twigs, requiring the help of a lens to make them
out distinctly.

The most conspicuous features of this species are the copiousness with
which the branching takes place and the shortness and smallness of the
branches. The ultimate branches of F. Holieneggeri form usually very long
cylinders, which feature is never seen in this species.

Considering the great number of specimens found at Fredericksburg,
it is most surprising that no trace of it has been found at any other Vir-
ginia locality. This gives us a striking instance of the localization of the
Potomac plants. This fossil forms a type of Frenelopsis very near to Frenela,
and different in many respects from the other known species.

Frenelopsis paeceeamosa, sp. no v.

Plate CXI, Figs. 1-5; Plate CXII, Figs. 1-5; Plate CLXVIII, Fig. 1.

Tree or shrub; stems and branches originally cylindrical, now found
flat from pressure ; primary and subordinate branches very succulent,
jointed, with very short nodes, usually found in a very fragmentary con-
dition ; epidermis parchment-like and very durable, having rows of minute
tubercles, which form distinctly visible longitudinal lines on tlie stem ;
ultimate branches very long with, in the visible portions, but little diminu-
tion in the width, from pressure appearing as very narrow, strap-shaped
twigs, arranged either in an umbellate manner or alternately in one plane,

DBSCEIPTION OF THE SPECIES. 219

remote or closely placed, varying much in width, viz, from 1™" to 12°"" ;
the maximum length of the largest ultimate branches seen, 13'^": very
prone to break into fragments at the joints and very deciduous ; leaves
very short and closely appressed, very broadly triangular generally, and
but little prolonged above the joint, often seemingly entirely undeveloped,
one on each joint, those of the adjacent joints alternating in position;
branches originally succulent and containing but little woody matter ; in
the ultimate twigs no woody matter is visible, and they appear to have
been composed of a durable epidermis surrounding a fleshy internal portion;
the ultimate twigs unbranched, and seeming to have been very long and
comparatively thick.

Locality : Found only at the entrance of Trent's Reach, and there
almost wholl}^ in a layer G to 9 inches thick near the top of the Potomac
beds.

This remarkable plant is more like Frenelopsis Hoheneggeri Schenk,
than is F. ramosissima. It has larger epidermal tubercles than this latter
fossil, and they make lines in the direction of the length of the stems that
are plainly visible to the unassisted eye. This plant has the same long,
cylindrical, jointed, ultimate twigs as those of Schenk's plant, but the
internodes are much shorter. The leaves when seen are always very
slightly prolonged above the joints, one being on each joint. But in some
twigs on many of the joints no leaves appear, as on the main stem in PL
CXI, Fig. 2, and on many of the joints of PI. CXII, Fig. 5 ; when present
they are often barely visible. The joints are generally marked by strong
constrictions, and many of them simply show a deeply sunken line, which
runs across the stem more or less obliquely, generally with a downward
bend towards the middle. It is evident that the ultimate twigs played the
part of leaves. Only in the older and larger stems do we see any woody
axis, and this is always proportionally very small considering the diameter
of the twigs. The joints are placed very close together, differing in this
point markedly from F. Hoheneggeri. The epidermis is very dense and
strong, and it is owing to it that the twigs are often found well pi'eserved.

The ultimate twigs were deciduous, and it is a rare thing to find any
of them attached to stems. They usually appear as detached fragments.

220 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

Multitudes of these fragments occur in the hxyer mentioned before, and
they formed a considerable portion originally of the stratum They occur
liere with Dioonites BiicJiianus, BracliypliyUum crassicaitle, WUllamsonia Vir-
ginkiisis, Baleropsls i^luripartita, etc. Here again we find a remarkable case
of isolation.

BRACHYPHYLLUM (Brongniart, ex parte), Schimper.

Trees or shrubs, with limbs and twigs l^ranching in an irregularly
pinnate manner ; leaves very short, sj^irally arranged, densely crowded,
and touching by their broadened bases; when living probably fleshy and
pyramidal, curved upwards, or by mutual pressure acquiring a pentagonal
or hexagonal form, and projecting in the form of a very short nipple-
shaped boss, persisting for a long time ; when old and on thickened
branches dilated into a shield-shaped form ; scars left by the fall of the
leaves erect, rhombic in form, contiguous, and mai'ked in the middle by a
vascular cicatrix.

The above is the description of the genus given by Schimper, exclud-
ing the form of Pachyphyllum Saporta, Pagiophyllum Heer, formerl)^ in-
cluded in the genus by Brongniart. He goes on to say that the leaves are
very short, flesh}^, and shaped like a nipple, which may be either straight
or curved upwards, being enlarged and touching the adjacent ones at base.
With age, and in consequence of its dilation, the nipple-shaped jDrojection
disappears almost wholly, and the leaves resemble pentagonal or hexagonal
cushions, which surround the branch like a cuirass. After the fall of
these singular leaves the branches are covered with rhomboidal scars like
those of Lepidodendron.

This description in its essential points agrees better with certain of
the Potomac plants than that of any other known fossils. The Potomac
fossils show mostly only the scars left after the fall of the leaves, and they
do not have the vascular cicatrix in their center, but in all other respects
these scars are exactl)^ like those of Bracliyphylliim. The peculiar mode of
branching of this genus is well shown in the fossils now in question. In
the shape of the leaf-scars and in the arrangement of the branches, as well
as in their form, some of the Potomac fossils are much like Schimper's

DBSCEIPTION OP THE SPECIES. 221

genus Echinostrobus. Again, in many points tliey are a good deal like
Saporta's genus Palceocyparis, but in this latter the leaves are decnssate,
while in the Potomac plants they are more numerous and spirally arranged.
It is possible that the Potomac fossils belong to a generalized type allied
to Ecliimstrobus and Palceoct/paris, but standing nearest to Brachypliyllum
It seems best to place them provisionally in this last genus.

Beachyphyllum crassicaule, sp. nov.

Plate C, Fig. 4; Plate CIX, Figs. 1-7; Plate CX, Figs. 1-3; Plate CXI, Figs. 6, 7; Plate CXII, Figs.
6-8; Plate CLXVIII, Fig. 9.

Trees with large branches, irregularly pinnate ; on the penultimate
twigs the ultimate branches lower and next to the main branch subdivide
pinnately into branches ; those higher are unbranched and simple ; ultimate
branches vary in numbers and closeness, sometimes few and remote, and
again crowded, contiguous, almost touching ; towards the summit of the
penultimate branches the ultimate ones become much crowded and grow
gradually shorter, are cylindrical, and taper gradually to an obtuse point ;
leaf-scars of young leaves elliptical in shape, slightly prolonged in the
direction of the axes of the stems, and such leaves seem to have been
fleshy, slightly convex, and with a free tip slightly keeled in the upper
half; with age the leaves become broader and more convex, being broadly
eUiptical, almost circular, and they leave similar scars after their fall ;
when crowded and dilated with age the leaves and leaf-scars are sub-
rhombic or rhombic in shape ; the surface of the leaves, which is very rarely
preserved, shows fine tubercles or dots, arranged in curving lines parallel
to their margins and converging towards their tips ; cones small, globular,
or subelliptical in shape, attached laterally to the penultimate twigs, taking
the place of ultimate branches ; scales numerous, spirally arranged, touch-
ing, shape not made out, but probably with age rhombic and polygonal.

Localities : Entrance to Trent's Reach ; 72d inile-post, near Brooke ;
fishing hut above Dutch Gap Canal.

Fragments of this plant are abundant at the first-named locality in the
same stratum with Frenelopsis parceramosa, etc., and are rather rare at the
other locahties. Most of the specimens showing scars of leaves occur here.

222 THE POTOMAC OR YOUI^GEE MESOZOIO FLOEA.

PI. CX gives a large imprint of a decorticated branch found at the fishing
hut above the canal. The specimen appears to have been much macerated
before entombment, so that the stone shows only the outline of the twigs,
all traces of leaves and their scars having been removed. The imprint of
the comparatively small woody axes and of the apparently succulent mat-
ter surrounding them is all that is shown. The most common specimens
found at the entrance to Trent's Reach are the terminal portions of the
penultimate twigs. Several good specimens were obtained at the 72d mile-
post. The specimens given in PI. CXII, Figs. 6-8, occur here. This is
another of the connecting links between the floras of the 72d mile-post and
Dutch Gap.

The views of Heer and Saporta differ mucn as to the character of the
cones of Bi-aclwphyllum. Heer ^ depicts a twig of what he calls Brachy-
pjiyllum insigne. This bears two cones. These he describes as subglobose,
with numerous spirally arranged, approximate, woody hexagonal peltate
scales, with a round depression in the center, This description applies
partly to the macerated cone of B. crassicaule, given in PI GIX, Fig. 6, but
the obscure rounded markings on this appear to be not scales but the scars
left by them. This, the only cone found attached to twigs with tlie charac-
ter of BracJiyphylliim, is unfortunately too poorly preserved to throw any light
on the character of the cones of this group. Tliis cone seems to be attached
by a short branch to the under side of the twig, and hence it is partly over-
lapped by this.

Saporta ^ gives figures and descriptions of numerous specimens of
Bracliyphyllam found in France. On page 319, after noticing Heer's conclu-
sions, he says that tlae forms of Brachyphyllum presented at the upper ex-
tremities of their branchlets small or medium-sized ovoid or oblong cones, that
were, according to the sjjecies, persistent or caducous. The cones were com-
posed of numerous scales, arranged spirally, closely imbricated and ap-
pressed, terminated by an apophysial prolongation, lanceolate in shape,
thickened, keeled on the back, and more rarely by means of an apophysis
dilated into a rhomboidal more or less developed cushion. He thinks that

' Flor. Foss. Arctica, vol. 4, pt. 2, Beitriige ziir Jura-Flora Ostslb., etc., PI. XIII, Fig. 9.
- Paleont. Franpaise, 2= S6r. V(5g6taus, vol. 3, 1878, pp. 313-321.

DESCRIPTION OF THE SPECIES. 223

Heer's plant was not Braclujphyllum, but one resembling it, and that the
specimen was too imperfect to decide the matter. At the entrance of
Trent's Reach a number of specimens of well-preserved cones are found
with the twigs of BrachypJujllum. These agree closely with those assigned
by Saporta to Braclujphyllum, and will be described further on. On the
whole, the evidence seems to indicate that Saporta's description of the cones
of this genus is the more nearly correct one.

Bracliyphyllum crassicaule is a good deal like B. Moreauanum, Brongn.,
at least in some of its forms. (See Pal. Francjaise, Vegetaux, vol. 3, PI.
CLXVI, Fig. 1 ; PL CLXVII, Fig. 1.)

Bkachyphyllum paeceramosum, sp. nov.

Plate CX, Fig. 4.

Twigs branching sparingly and dichotomously ; leaves and leaf-scars
elliptical to subrhombic, with the longer dimensions in the direction of the
lengtli of the twigs; leaves convex, spirally arranged, showing a keel in
their upper portions, closely appressed, contiguous, prolonged very slightly
at the tips, branches cylindrical, of the same thickness throughout ; so far
as can be seen about 4°"° in diameter.

Locality: Near Telegraph Station.

This plant, found sparingly near Telegraph Station, differs from B.
crassicaule in the comparatively slender, strictly cylindrical branches,
which show no tapering, subdivide very rarely, and then in a dichotomous
manner, and also in the regular shape of the leaves. In its general aspect
this fossil is a good deal like Cyparissidium. It is also a good deal like
some of the forms of Brachyphyllum gracile. (See Pal. Fran9aise, V^gdtaux,
vol. 3, PI. CLXVI II, Fig. 2 ; PI. CLXX, Figs. 4, 5.)

Bkachyphyllum, sp. ! (Cone.)

Plate CXXXV, Fig. 8.

Cone broadly oblong, widest near the top, length 20"", maximum
width 15"", attached to the summit of a short branch, nari'owed slightly
and gradually toward the base, showing at the summit a slight nipple or
boss-like projection ; scales numerous, spirally arranged, closely appressed,

224 THE POTOMAC OK YOUNGER MESOZOIC FLORA.

and partly imbi'icated, convex, broadly elliptical to subrliombic, and
slightly prolonged at their summits into acute tips.

Locality: Entrance to Trent's Reach ; rare.

These cones are found associated with the branches of Brachijpliyllum
crassicaule. They may belong to this species, or to some other conifer.
They agree pretty well in shape with the macerated cone given in PI.
CIX, Fig. 6. It is obviously a cone of the same type with those described
by Saporta as associated with the French specimens of Brachypliyllum. It
agrees best with the cones of B. gracile^ Brongniart, but does not seem to
be identical with them.

Brachyphyllum, sp. ! (Cone.)

Plate CXXXV, Fig. 9.

Cone small, broadly oblong ! , length not made out, as the basal por-
tion is wanting, width 10"""; scales numerous, closely appressed, partly
imbricated, spirally arranged, tliick and convex, in shape broadly elliptical
to subrliombic, acute at the tips.

Locality : Entrance to Trent's Reach.

These cones occur with those of the preceding species and are more
common than the latter. They seem to belong to a distinct species. In
the rounded shape and in the size they come nearer than any of tlie pre-
viously described ones to what Sapoi'ta thought was the male ament of B.
gracile Brong. It resembles in some points tliat shown in Pal. Fran^aise,
Vegetaux, vol. 3, PI. CLXXI, Fig. 9. It may be the male ament of B. cras-
sicaule, although apparently rather large for that.

Brachyphyllum, sp.f (Cone.)

Plate CLXVIII, Fig. 2.

This is a small fragment of a cone found at the entrance to Trent's
Reach with the two last-described species. It is too imperfect to admit of
description, the margins being in no place preserved, and the surface show-
ing only subrhombic scars with depressed points in the center. These
scars seem to be those left by the scales of the cones.

' Pal. Frau5aise, V6g6taux, vol. 3, 1878, PI. CLXXI, Fig. 7.

DBSCEIPTION OP THE SPECIES. 225

A number of aments of conifei's were found at the 72d mile-post, near
Brooke, and elsewhere, whose species can not be determined. They
appear to be male aments, possibly in some cases of Bracliyiiliyllum, but
certainly of some conifer. They usually occur together in large numbers,
as if coming from plants near by. These will be designated as (a), (&),
(c), etc. These aments resemble somewhat Heer's genus Elatkles.

Ament op Conifer (a), sp."?

Plate CXXXVI, Fig. 2.

Male (!) aments ovate to oblong in shape, small, subacute at their tips ;
scales numerous, broadly elliptical, prolonged slightly into an acute tip,
spirally arranged, thin, close appressed, slightly imbricated, forming a thin
flat ament that leaves only a slight imprint ; length of ament about 9"",
and width about 4°"".

Locality : Near Brooke, at 72d mile-post.

Some fragments of shale for the space of several inches are covered
more or less thickly with these aments, which evidently fell from plants
not far distant. The shape and size of the scales and aments of this
species agree pretty well with some of the strobiles supposed by Saporta
to be male aments of species of Bracliyphyllmn}

Ament op Conifer (6), sp. ?

Plate CXXXVI, Fig. 3.

Aments very small, broadly ovate, obtuse or acute at summit, some-
times attached to shoj't pedicels ; size about three by six millimeters ; scales
very thin, close appressed, slightly imbricated, numerous, spirally arranged,
in shape broadly elliptical to subrhombic, with a slight prolongation into
acute tips.

Locality: 72d mile-post, near Brooke.

The imprints are quite thickly scattered on some few fragments of
shale, but are not so numerous as those of species (a). The cones are
smaller than those of {a).

' Compare Pal. Fran^aise, V^g^taux, vol. 3, PI. CLXVII, Fig. 3, of the strobile of B. Moreauaniim
Biongn.

MON XV 15

226 THE POTOMAC OR YOUNGEE MESOZOIO FLOEA,

Ament of Conifer (c), sp. ?

Plate CXXXVI, Fig. 4.

Aments globose or broadly oblong, very small and varying in size,
the largest being five by three millimeters ; scales arranged as in species («)
and (h), thin, subacute at their tips, closely appressed, minute, narfowly
elliptical in shape, numerous, and spirally arranged, somewhat imbricated.

Locality : 72d mile-post, near Brooke.

They occur on a few pieces of shale in considerable numbers crowded
together ; seem to be different from species (a) and (&) in the smaller and
more variable size and the more rounded form and in the narrowly elliptic
shape of the scales.

Ament of Conifer {d), sp. ?

Plate CXXXVI, Fig. 5.

Aments mostly ovate, sometimes elliptical, varying somewhat in size,
averaging five by three millimeters, broadest at base and narrowed above to
an acute tip ; scales in number and arrangement as in the preceding species,
in shape broadly elliptical to ovate, prolonged at the summit to a very
short acute tip.

Locality: On the railroad near Cherry Hill Station.

This station is on the Alexandria and Fredericksburg portion of the
Atlantic Coast Line Railroad, midway between Quantico and Powell's
Creeks. The aments are found in the shale in a cut a little north of the
station. They occur crowded in considerable numbers on the surface of a
few specimens of the rock. No prolonged search was made here, as there
did not seem to be any prospect of finding good material. With these
were found a few obscure imprints of some conifer with acicular leaves.

Ament of conifer (e), sp.?

Plate CXXXV, Fig. 7.

An ament, elongate-oblong in form, very narrow in proportion to its
length, with numerous chafi'y scales imbricated on a slender axis, in-
curved and spoon-shaped.

DESCRIPTION OP THE SPECIES. 227

Locality : 72d mile-post, near Brooke.

Only one specimen of this fossil was found. It seems to be the male
ament of some conifer, possibly of some one described under another
name. Fig. 1^ represents one of the scales flattened out by pressure on
the surface of the clay. Fig. T" represents the shape of the enlarged scales
as they were attached to the axis.

Ament of conifer, (/) sp. ?

Plate CXXXVI, Fig. 8.

Fig. 8 represents small catkins, that occur rarely, grouped together in
large numbers on the surface of some portions of the clay at the 72d mile-
post. Where found they cover the surface confusedly, as if they had
floated in numbers on the surface of the water. They occur only in small
bits, none showing the entire length. They were linear in shape. No
conjecture can be made as to the species of tree from which they come.

LEPTOSTROBUS Hear.

"Strobile stipitate, very long, with scales that are loosely imbricated,
narrowed at base, and have the upper margin crenulate • * * * leaves
needle-shaped, fasciculated on shortened branches." This is Heer's descrip-
tion of the genus formed to contain peculiar Jurassic plants from eastern
Siberia. He says of Leptostrohus rigida^ that the leaves are 2°"" wide, very
long, with two very distinct nerves, which sometimes show between them-
selves some very fine striae (see PI. VII, Fig. 11"). Some of the fragments
of leaves that he saw were 10.5"" long with the ends not present. If we
modify Heer's description so as to make it read: leaves needle-shaped, very
long, 2""° and under in width, scattered on the larger or principal stems
and grouped in bundles on the ends of short twigs, attached directly to the
stems, nerves slender and parallel, we shall be able to include in this genus
certain remarkable conifers found in the Potomac strata. These Potomac
fossils are a good deal like Schizolepis Fr. Braun, but the leaf of this lat-
ter had only one nerve.

' Flor. Poss. Arctica, vol. 6, pt. 1, Naohtriige zur. Jura-Flora Siberiens, p. 25.

228 THE POTOMAC OE YOUNGER MESOZOIG FLORA.

Leptostrobus longifolius, sp. nov.

Plate CI, Figs. 2, 3; Plate CII, Figs. 1-4; Plate CIII, Figs. 6-12; Plate CIV, Fig.C.

Trees or shrubs with stout and long primary leafy branches, Aviiich
contain the leaves attached singly and scattered along the stem, as now
seen attached to the under surface or to the sides of the stems, but most
probably originally found spirally arranged and attached to the stems on
all sides. The primary leafy branches have lateral and terminal short shoots,
on the ends of which the leaves are arranged in tufts; leaves very long
and narrowly linear or needle-shaped, with their extremities in no case
seen, attached by the entire bases, not narrowed; nerves several, parallel,
slender, and obscure.

Localities: Fishing hut above Dutch Gap Canal; Fredericksburg;
72d mile-post and bank near Brooke; hill-side near Potomac Run.

The plant is not uncommon at any of the localities. It is most abun-
dant at the fishing hut above Dutch Gap Canal, where all the forms
depicted on PL CII occur. The leaves oociir, as elsewhere, most com-
monly detached. They seem to be quite deciduous, especially on the
older and larger stems. All the specimens found have suffered from mac-
eration and transportation in water, and hence the present mode of arrange-
ment of the leaves in the comparatively few cases where they are found
attached does not give an accurate picture of their original condition.
The leaves in tufts at the ends of the short shoots may represent all that
were originally present, or they may be only the younger last-formed ones,
the older ones lower on the twigs having fallen off.

This latter is probably the true state of the case. At any rate, these
short shoots seem to be growths from lateral buds, perhaps annually formed.
Neither on these nor on the longer main stems are any scars left by fallen
leaves to be seen, but this does not' prove that they were not present, for
in all cases the naked portions have lost their epidermis and suffered a
good deal from maceration. They are decorticated and reduced to the
woody fiber, or show only imprints of this. The leaves as now seen on the
older and larger stems seem to be all attached laterally, or to the ends of
the stems or to the under surface. This is probably due to the accidents

DESCRIPTION OF THE SPECIES. 229

of preservation. The leaves on the upper surface, after the settling of the
twig on the bottom, were most exposed to the action of the water and were
removed, while those that were attached to the under surface, being held
in place by the pressure of the superincumbent stem, were retained. Most
of the leaves that appear to be attached to the sides of the stems no doubt
are really attached to their under surface. This seems to be the case in
PI. CI, Fig. 2, and PI. CII, Fig. 3. The ends of the large stems in these
figures are broken off. It is, then, most probable that the leaves were scat-
tered spirally around the larger stems. The leaves seem to have been
attached by their entire unnarrowed bases and to have been directed
upwards towards the summits of the stems. Hence we find them some-
times curved at base as Heer^ has depicted, but I have seen none so much
bent or so regularly, as those of Heer.

The nerves are very obscui-e, and the leaves, even the best preserved,
rarely show any traces of them, for they seem to have been slender and
immersed in the leaf-substance. Generally only fine striae are visible on
them, even with the help of a lens. They seem to be about four in number
and parallel. No difference in strength was noted, as Heer intimated. The
length of some of the leaves must have been very considerable, for some
fragments, with botli the base and summit missing, were as much as IS*""
long. In PI. cm. Figs. 6, 8, 9, are given some fragments of leaves from
the 72d mile-post near Brooke, where detached leaves occur on some por-
tions of the shale in considerable numbers, crowded together or overlying
one another. In some cases, as in 8"" and G'"", they show four very fine
nerves. In others, as 6^, no nerves are seen, but the leaves appear smooth
and convex from pressure. Again, in some cases, as in 6", only one nerve
is visible. Sometimes, as in 6^ and 6°, the nerves vary in strength and are
vaguely shown. These differences are no doubt due to the accidents of
preservation. Sometimes it seems that apparent nerves are longitudinal
wrinkles or folds in the leaves caused by pressure. This seems to be the
case in 6" and 6®.

On the hill-side near Potomac Run a good many detached fragments
of long and veiy narrow leaves with four very fine nerves occur scattered

>Flor. Foss. Arctica, vol. 6, pt. I, PI. VII, Figs. 10-lvJ.

230 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

on some portions of the shale. They are shown partly in PI GUI, Figs.
10-12, and PI. CIV, Fig. 6. These were never seen certainly attached to
any stem, but their bases are sometimes well shown, looking as if they
had been attached in a clasping manner by a widened base, and in PI, CIV,
Fig. 6, the base may be seen attached to what seems to be a portion of the
stem. In PI. CIII, Fig. 12, two bases seem to be put together, possibly by
accident. These leaves may belong to a different species, but I place them
provisionally in the species now being described.

Leptostkobus foliosus, sp. nov.

Plate CI, Fig. 4 ; Plate CIII, Fig. 5; Plate CIV, Fig. 1.

Leaves long and very slender, about 1"°™ in width, length not made out,
densely crowded on the principal and longer shoots throughout their length,
grouped in bundles at the ends of the shorter lateral shoots : nerves very
slender, not well made out, apparently three in number.

Localities: Fishing hut above Dutch* Gap Canal; red clay ball in the
banks of Dutch Gap Canal.

This is clearly a different species from the preceding, and it is not so
common. The nerves could be seen on only one specimen and that vaguely,
so that their number is not positively determined. They appear to be three,
but this may be due to the state of preservation, and the number visible
may vary according to the condition of the fossil. It is quite possible that
the true number may be four. The leaves are almost always seen detached
and crowded together, as if derived from the same specimen.

LePTOSTROBUS 1 MULTIFLORUS, Sp. nOV.
Plate CLXV, Fig. 6.

Strobile stipitate, with a very thick axis of inflorescence, covered by
numerous small spatulate-shaped scales, that are loosely imbricated and
arranged in a spiral manner.

Locality: 72d mile-post, near Brooke.

Only one specimen of this curious inflorescence was found, and it was
too imperfect to make out clearly its character, since the rock on which the
imprint was made is a rather coarse sandstone. The specimen was evi-

DESCRIPTION OF THE SPECIES. 231

dently much injured by maceration before it was entombed. The lower
portion of the axis has lost most of its scales, while the upper portion still
retains them. These scales, although smaller than those given by Heer for
the species examined by him, appear to more nearly resemble those of Zep-
tostrohus than those of any other plant. I place it with doubt in this genus.
The cone somewhat resembles those of Heer,^ but the scales are smaller,
more numerous, and more closely placed.

The following seed have the character of the seeds described by Heer
as Samarojms, from the Jurassic of Ust-Balei, in eastern Siberia.^ These
seeds Heer,^ in subsequent remarks on Lejdostrohus, takes to be those of
that plant. The Potomac seed throw no additional hght on the subject.
It is at least significant that they occur with leafy branches that have the
character of Leptostrobus. It will perhaps be best to distinguish these
Potomac fossil seed as Leptostrobus (a), (ft), etc.

Seed of Leptostrobus '? [a), sp.?

Plate CXXXV, Fig. 6.

Seed smooth, obovate in shape, obtusely rounded at one end, and nar-
rowed at the other into a sort of neck ; winged, with wings of the same
width, except towards the neck, where it is sHghtly narrowed.

Locality: Fishing hut above Dutch Grap Canal.

Seeds of this nature are sparingly found at this locality. They may
be seed of one of the species of Leptostrobus found at Dutch Grap.

Seed of Leptostrobus "? (6), sp.?

Plate CXXXVI, Fig. 10.

Seed broadly elhptical, winged; wing proportionally small and pro-
longed at one end into a slight point, widest in the middle, and narrowed
slightly towards the extremities of the seed.

Locality : Fishing hut above Dutch Gap Canal.

Winged seed of this nature are found sparingly here. They may be
seed of Leptostrobus.

iFlor. Foss. Arctlca, vol. 6, pt. 1, PI. VII, Fig. 7; PI. VIII, Fig3. 1-3.

^Flor. Foss. Arctioa, vol. 4, pt. 2, Beitrage znr Jura-Flora Ostsib. etc., p. 80, et seq.

^Ibid., Nachtrag znr Jura-Flora Sibirieus, vol. 6, pt I, p. 23.

232 THE POTOMAC OR YOLTNGER MESOZOIO FLORA.

Seed of Leptostrobus °! (c), sp.?

Plate CXSXVI, Fig. 11.

Seed oblong-elliptical, with a slight acute tip at one end and a very
short stem-like prolongation at the other. Smooth, winged ; wing very
large in proportion to the seed, widest in the middle and flared out there,
narrowed towards the apex and base, prolonged to a short subacute point,
and ending below in what seems to be a point of attachment to a pedicel.

Locahty: Kaukey's; only one specimen found.

This seed differs from the others in its greater size as well as that of
the wing, and in the greater proportional size of the wing as compared
with the seed, also in the flaring out of the wing in its middle portion. It
is a little like Heer's Saniaropsis rottmdata. It is possible that these seed
do not belong to Leptostrohus, but to the genus next to be described, viz,
Laricoims, for Larix has samara-like seed.

LARICOPSIS, gen. nov.

Trees or shrubs, with the penultimate twigs sending off alternately in
the same plane ultimate branches ; leaves thin, narrow, and thread-like,
attached by the entire base either in bundles at the same point on the
stem or scattered singly on its surface, both on the same stem, very
deciduous, the leaf-bundles leaving small scars Nerves not made out
with certainty, but apparently one for each leaf

This genus is nearer to Larix than to any other known plant, and the
resemblance is sufficiently great to render it possible that it may be the
ancestor of this genus. It should be noted that the young shoots of Larix
often have the leaves scattered singly as they occur in this genus, and it is
probable that the immature portions of Larix approach the ancestral forms
more nearly than the mature portions do. In these specimens also the
leaves appear most often to be attached laterally to the stems as now pre-
served, while no doubt they were originally scattered around the stem.
This appearance, as in the case of Leptostrobus, is doubtless due to the
accidents of preservation. No nerves could be made out with certainty.
The leaves are very narrow, being sometimes like hairs.

DESCEIPTION OF TEE SPECIES. 233

LaEICOPSIS LONGIFOLIA, sp. nOV.
Plate CII, Figa. 7, 8; Plate GUI, Figs. 2, 3; Plate CLXV, Fig. 4; Plate CLXVIII, Figs. 5,6.

Leafy stems comparatively very stout, branching rarely, with the
ultimate branches in the same plane and alternate ; leaves narrow, about
.5°"" or under in width, very long in proportion ; portions seen are over
3°" long and not entire, grouped occasionally in bundles as in Larix, more
commonly scattered singly and attached by the unnarrowed bases, flat and
thin, deciduous on the older branches ; nerves not certainly made out,
apparently one for each leaf

Locality : Fishing hut above Dutch Gap Canal.

The plant is rather rare, and is generally found in a very fragmentary
state or in the form of detached leaves. The removal of the leaf-bundles
leaves sometimes quite distinct dot-like scars on the upper surface of the
stems. Considering the narrowness of the leaves the stems are remarkably
thick. Owing to the crossing of the leaves in superposition they often
look as if they split into branches, and then they remind one strongly of
Heer's geuus Phosnicopsis, but they certainly never fork.

Laricofsis angustifolia, sp. nov.

Plate CII, Figs. 9, 10; Plate GUI, Figs. 1,4.

Twigs slender, branching sparingly; leaves exceedingly narrow and
hair-like, entire length not seen, but certainly equaling 3°", thin, flat,
scattered over the surface of the stems or grouped in bundles ; nerves not
seen.

Localities : Fishing hut above Dutch Gap Canal ; entrance to Trent's
Reach; rare.

These leaves often do not surpass .2°"" in width. As in the case of
the preceding species, they are always broken off towards the tips, so that
their true length can not be made out. The leaves as now seen are all
attached to the sides of the stems apparently, but this is no doubt due to
the fact that they, in many cases at least, come from tlie under sides of
the stems, being held in place by the superposition of the latter. The
grouping of the leaves in bundles occurs irregularly and rather rarely.

234 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

Possibly these specimens may be the narrower leaves on forms of the pre-
ceding species, but this is hardly probable. It is rare, but more common
than the preceding species.

Laeicopsis brevifolia, sp. nov.

Plate CII, Figs. 5, 6.

Twigs slender, branching freely ; leaves distributed and attached as in
the preceding two species, thin, flat, wide in proportion to their length,
short, acute at the tips ; nerves not seen ; length of leaves 1™ and little
more, width 8°"", crowded on the younger branches, deciduous when old.

Localities: Fishing hut above Dutch Gap Canal; entrance to Trent's
Reach.

This plant is quite rare. The leaves are, in proportion to their length,
much wider than those of the two preceding species. Fig. 5 presents two
lower branches on the right-hand side that are entirely deprived of their
leaves. The leaves of this species look something like those of Heer's
genus Inolepis.

TORREYA Arnott.

Small trees, with leaves linear or lanceolate, in two rows, either oppo-
site or alternate, flat, decurrent at base, without a midrib, but marked
longitudinally on the lower side, on each side of the central line of the
leaf, by a narrow sunken band.

This genus has not furnished to the Potomac flora any considerable
element, since the two species found are quite rare.

TOEEEYA ViRGINICA, sp. nOV.
Plate CIX, Fig. 8.

Stems slender ; leaves subopposite, linear, narrowed gradually to the
base and apex, at the apex prolonged into a short spinous tip, attached by
a short slightly twisted footstalk to the margins of the stems or slightly
within them, slightly decurrent; midnerve not apparent. The leaves have
on each side of their axial line a strong cord-like line running through the
leaf nearly parallel, converging at the base and apex, and seeming to be

DESCRIPTION OF THE SPECIES. 235

imprints made by the two medial depressed lines of the leaf; leaves
rather remote, flat, coriaceons, and persistent.

Locality : 72d mile-post, near Brooke ; only one specimen fonnd.

This plant is qnite different from the species of Cephalotaxopsis and
Nageiopsis found in the Potomac flora. The leaves were leathery and
durable, and marked by two prominent cord-like ridges in the center, which
do not seem to have been nerves.

TOEEEYA FALCATA, sp. nOV.
Plate CXIII, Fig. 4.

Stems of ultimate twigs slender ; leaves coriaceous, distichous, ap-
proximate, spreading, attached by a broad base to the margins of the twigs,
or somewhat within the margins, slightly decurrent, linear, falcate, acute,
prolonged at the summit into a short spinous tip. Marked in the medial
line with two strong parallel lines.

Locality : Hill-side near Potomac Rixn ; rare.

This plant is a good deal like T. parvifoUa, Heer, as given in Flor.
Foss. Arctica, vol. 3, pt. 2, PI. XVII, Figs. 1, 2.

CEPHALOTAXOPSIS, gen. nov.

Trees or shrubs, with fruit probably in the form of drupaceous and
nut-like seed, branching copiously, with branches umbellately arranged or
alternate in the same plane, often opposite from paired terminal buds ;
stems comparatively very stout, rigid, and woody ; leaves distichous, vary-
ing a good deal in size, flat, linear, thick and leathery, persistent, attached
by very short slightly twisted footstalks to the sides of the stems or
slightly within the margins, prolonged at the apex into a short spinous
tip, with a single flat broad midnerve, which on the lower side of the leaf
is bordered on each side like Torreya by a sunken line.

This is a very important genus in the- Potomac flora, on account of
both the number of species and the great number of individuals in some of
the species. The genus is one of the most characteristic types of the Poto-
mac vegetation. It is very near to Cephalotaxus, but does not appear to be

236 THE POTOMAC OR YOUNGER MESOZOIO FLORA.

identical with it. It rather seems to be a composite type, uniting some of
the features of Cephalotaxus, Torreya, and perhaps Taxiis. A common mode
of growth of the branches seems to have been by a terminal bud with oppo-
site buds, one being on each side of the terminal one, all being covered with
scales, which, as in Cephalotaxus, leave sometimes distinct scars at the base of
the shoots of annual growth.

No fruit has been found attached to the leafy twigs of these plants,
hence its nature has not with certainty been determined, but certain nut-
like'fruits have been found in company with the leaves which most prob-
ably belong to this genus.

Cephalotaxopsis magnifolia, sp. nov.

Plate CIV, Figs. 4, 5 ; Plate CV, Figs. 1, 2, 4 ; Plate CVI, Figs. 1, 3 ; Plate CVII, Figs. 1, 2, 4 ; Plate

CVIII, Figs. 1, 3, 4.

A tree or large shrub, with stout limbs, so far as seen, branching spar-
ingly, the branches being in the same plane and remote, opposite or alter-
nate, the ultimate twigs showing sometimes at their bases scars of the bud-
scales ; leaves variable in size, attaining a maximum length of 6"" and a
maximum width of 5"°^ ; subspirally arranged, that is, attached mostly to
the sides of the twigs, but sometimes somewhat within the margins and
slightly on the upper and lower surfaces ; attached by short slightly twisted
footstalks in two rows in the same plane, subopposite or alternate, rather
remote, with the ultimate twigs terminated abruptly by a leaf; the leaves
very thick and leathery, persistent, and very durable, widest near the base
and generally abruptly rounded off there, more rarely tapering gradually
to the base, gradually narrowing towards the apex, where they terminate
in a spinous or mucronate point; the leaves (see PI. CV, Fig. 1) below
and near the shoots of annual growth sometimes unusually small ; midrib
broad, flat, distinct, with a narrow sunken line on each side.

Localities: Fishing hut above Dutch Gap Canal, rare; Fredericks-
burg, very common.

This is one of the most abundant plants at Fredericksburg, where
many well-preserved specimens occurred. The growth of the twigs seems
often to have been made by a terminal bud flanked by two opposite lat-

DESCRIPTION OF THE SPECIES. 237

eral ones, and these seem to have had persistent bud-scales, which have
sometimes left quite distinct scars, as in PI. CV, Fig. 1.

Owing to the leathery character and great durability of the leaves,
they ma}^ often be found as perfectly preserved as if they had been pressed
in a herbarium, even sometimes having a gi'eenish color. They then
show the minutest details of their structure. The spiny tip at the ends of
the leaves seems to be the prolongation of the midrib beyond the leaf
Tliis tip, however, is not generally preserved. The thick character of the
leaves has caused them in drying to wrinkle transversely, as in PI. CVI,
Fig. 1^ The leaves are notably thick and prominent. As shown in PI.
CV, Fig. 2, the ultimate twigs are terminated by a leaf in a manner similar
to cycads. The midrib has two depressed lines running very close to it
that leave in some cases two imprints looking like two parallel nerves, as
in PI. CVIII, Fig. 4, and PI. CIV, Fig 5. These remind one of the two
imprints seen in Torreya. The variation in the size of the leaves does not
surpass that seen in Ceplialotaxus drupacea, which this plant closely resem-
bles. The bud-scales seem to have been persistent for some time.

Cephalotaxopsis eamosa, sp. nov.

Plate CIV, Figs. 2, 3; Plate CVI, Figs. 2, 4; Plate CVII, Fig. 3; Plate CVIII, Fig. 2.

Tree or shrub, with stout branches in whorls or scattered alternately,
and in the same plane ; bud-scales persistent at the bases of the shoots of
annual growth ; leaves comparatively thin, narrow, tapering gradually to
the base and apex, insertion and arrangement of the leaves as in C. magni-
folia ; the leaves have a maximum length of 4"" and a maximum width of
4"™.

Localities : Fredericksburg, common ; road-side near Potomac Run.

This plant is much like G. magnifolia, but it is much more copiously
branched, the leaves are narrower in proportion to their length, have a
thinner texture, and a proportionally narrower midrib. It is rather more
abundant at Fredericksburg than C. magnifolia. It may possibly be a form
of G magnifolia, but the facies is constant and different from that of this
species. The tendency to a whorled grouping of the branches is marked.
A common mode of arrangement is that given in PI. CVII, Fig. 3, PI. CIV,

238 THE P0T0MA.0 OE YOUNGER MESOZOIO FLOEA.

Fig. 2. The branches are now by pressure brought into one plane: In
PI. CVIII, Fig. 2, the right-hand lateral branch has been torn off. In PI.
CVI, Fig. 2, they appear to have been pinnately arranged, a mode not so
common as the umbellate one. In PI. CIV, Fig. 2, all the fragments seem
originally to have belonged to the same branch.

Cephalotaxopsis brevifolia, sp. nov.

Plate CV, Fig. 3 ; Plate CVI, Fig. 5 ; Plate CVII, Fig. 5.

Trees or shrubs, with ultimate branches, so far as seen, alternate and
strictly in one plane ; leaves thick and leathery, attached and arranged as
in the preceding species, narrowly oblong to narrowly elliptical, mostly
narrowed gradually at the base and apex, maximum dimensions 21""" by
3°"", average dimensions 13"" by 2"", short in proportion to the width;
midnerve slender.

Localities: Fishing hut above Dutch Gap Canal; Fredericksburg;
road-side near Potomac Run ; rare.

PL CV, Fig. 3, a specimen from Fredericksburg, gives the largest leaves
seen. Only small fragments of ultimate branches were found. The leaves
in proportion to their size are remarkably thick and leathery.

Cephalotaxopsis microphylla, sp. nov.

Plate CVIII, Fig. 5 ; Plate CIX, Fig. 9.

Tree or shrub, copiously branching, with branches alternate, slender,
all in one plane ; leaves arranged and attached as in the preceding species,
very small, average dimensions 1"" by 7""", leaf-substance thin, in shape
narrowly oblong to narrowly elliptical, tapering gradually to the base and
apex; midnerve slender.

Localities: Fredericksburg; fishing hut above Dutch Gap Canal.

This plant is quite rare, and is the smallest of the genus. The leaves
on the ultimate twigs towards the summit of the branches are very minute,
as on the uppermost branch on the left hand in PI. CIX, Fig. 9, from the
Dutch Gap locality. The midnerve, owing to its slenderness, is generally
not visible.

DESCEIPTION OF THE SPECIES. 239

ATHROTAXOPSIS, gen. nov.

Trees or shrubs, copiously branching, with principal stems or branches
proportionally strong, cylindrical, rigid, sending off thickly placed, long,
slender, cord-like, ultimate twigs, all in the same plane and spreading widely ;
the ultimate twigs leave the penultimate ones under a very acute angle and
show a tendency to a fastigiate grouping; cones mostly broadly oblong,
rarely globular, obtuse and rounded at base and apex, average dimensions
10"" by 14'°'^, attached singly on the summit of short lateral branches and
placed on the lower portions of the leafy stems and branches, the twig with
its cone representing the branching leafy twigs which occur higher up;
scales of the cones woody, thick, wedge-shaped in the basal portions,
expanded at the free ends, and probably shield-shaped, numerous, spirally
placed, attached at a large angle, the middle ones being nearly or quite at
a right angle with the axis, close appressed, opening with age ; seed under
each scale one, elliptical in shape, smooth and bony in texture, average
dimensions 1°"° by 2.6°"° ; leafy branches ending abruptly in an ultimate
twig similar to those sent off pinnately and alternately lower down ; leaves
very thin and scale-like, elliptical, rhombic, or oblong, with varying age
changing their shape, the rhombic forms representing the oldest and most
crowded leaves, slightly keeled on the back, spirally arranged.

As now found, owing to maceration, the leaves are rarely visible or
appear very indistinct. The upper or free surface of the scales of the
cones was in no case seen sufficiently well preserved and so presented as
to show clearly its original chai'acter. This surface seems to have been
expanded something like the similarly placed part in the scales of Sequoia.
The shape of the cone also is a good deal like that of the cone of that
genus, but the leaves and the number of seed under the scales differ. The
scales of Athrotaxopsis are wedge-shaped, thick, and woody. In a number
of cases they were found sufficiently well preserved to permit one to sepa-
rate them from the cone, and to pick out the comparatively large seed,
which were very well preserved. The cones are comparatively quite small
in size, and are found on the lower portions of leafy principal twigs. In
some cases, where the cones are numerous, the branch seems to have borne

240 THE POTOMAC OR YOUNGEE MESOZOIC FLORA.

no leafy twigs, as in the specimens given in PI. CXVI, Figs. 1, 2. The
cones when unripe are compact, Avith close-appressed scales, but with age
the scales diverge.

Heer^ describes his genus Gyparissidium as having an oval strobile,
furnished with numerous scales, which are spirally arranged on the axis,
imbricated, coriaceous, and rounded, loosely spreading at the apex, mucro-
nate, etc.; seed one under each scale and rounded f ; leaves alternate, imbri-
cated, and appressed. Heer bases his conclusions as to the character of the
seed on the imprint of a I'ounded object under a scale similar to those that
he attributes to Cyparissidium (See PL XIX, Fig. 11.)

While Atlirotaxopsis has a number of the characters of Cyparissidmm,
the differences are too important to allow its being united with the latter
genus; the character of the cone is essentially different. Atlirotaxopsis in
many features, both of the foliage and the cones, is strikingly like the liv-
ing genus Athrotaxis, and perhaps may be regarded as an ancestral form of
this genus. The main distinction is in the single seed under each scale. It
has also, in the character of the leaves and branches, points in common with
Echinostrobus and Saporta's genus Pakeocyparis. It is evidently a compre-
hensive type. The great length and slenderness of the ultimate twigs make
it probable that they were pendulous.

Atheotaxopsis geandis, sp. nov.

Plate CXIV, Figs. 1-3; Plate CXVI, Figs. 1-4 ; Plate CXXXV, Fig. 10.

Trees or shrubs, with strong principal branches, bearing cones on the
lower portions, and in the upper portions leafy branchlets alone; stems seen
P"" thick, with a length of 30™ and an expanse of over 25"", the terminal
portions not being preserved. Cones as given in the generic description,
leafy stems copiously branched in an alternate manner, the branches being
crowded and all in the same plane. The ultimate twigs are long, comj^ara-
tively strong, and cord-like, and were probably pendulous, mostly un-
branched, or sometimes dividing dichotomously ; leaves close appressed,
elliptical when young and acute at their tips; rhombic when old, and
crowded, thin, slightly keeled on the summit.

' Flor. Foss. Arctioa, vol. 3, pt. 'i, p. 74.

DESCEIPTION^ OF THE SPECIES. 241

Localities: Fredericksburg; 72d mile-post, near Brooke.

At the latter place the plant is rare, but at the former it is quite com-
mon, being in one layer one of the most common plants. It occurs here
sometimes in very large specimens. The fine form figured in PI. CXIV,
Fig. 1, is a part of a specimen which, although still only a fragment of a
branch, was considerably larger than the part figured. Most of the large
specimens have suffered so much from the action of water before entomb-
ment that they are decorticated and have lost their leaves..

Athrotaxopsis tenuicaulis, sp. nov.

Plate CXIV, Figs. 4, 5 ; Plate CXV, Fig. 4 ; Plate CXVJ, Fig. 6 ; Plate CXVII, Fig. 2.

Small trees or shrubs, with comparatively very slender stems, branch-
ing copiously and mostly at short intervals; branches alternate and in the
same plane, iiltimate branches short, slender, thread-like, with an ultimate
branch terminating the penultimate branches, the ultimate twigs simple or
rarely dichotomous ; leaves arranged spirally, close appressed, keeled
slightly at the tips, elliptical to rhombic in shape, acute.

Localities: Fishing hut above Dutch Gap Canal; Fredericksburg.

At the latter place the plant is rare, while it is not uncommon at the
former. This form is characterized by the narrowness and the shortness of
the ultimate branches. They are usually numerous and closely placed.
The leaves are rarely preserved, and they sometimes show a faint keel at
their tips, as in PI. CXVII, Fig. 2^

Athrotaxopsis expansa, sp. nov.

Plate CXIII, Figs. 5, 6 ; Plate CXV, Fig. 2 ; Plate CXVI, Fig. 5 ; Plate CXVII, Fig. 6 ; Plate CXXXV

Figs. 15, 18, 22 (cones).

Trees or shrubs, the leafy branches being very long and with slender
woody axes, spreading widely, sparingly branched, branches in one plane ;
the ultimate twigs alternate, remote, very long and cord-like, probably
pendulous, unbranched or rarely dichotomous ; leaves quite thick (com-
paratively), keeled, elliptical to subrhombic, acute to obtuse, the lateral
ones often rather obtuse and divergent from the stem, cones, oblong, some-
times from distortion made more or less globular in form, comparatively
MON XV — 16

242 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

large, being 14°"" by 11™"" on an avei'age, scales and other parts as in the
generic description.

Localities: Hill-side near Potomac Run ; entrance to Trent's Reach;
banks of Dutch Gap Canal ; fishing hut above the canal.

This plant is very common in large specimens at the first and last
named localities. At the Potomac Run locality, on the hill-side in the
woods, it is, next to the ferns, the most common plant, but it is not found on
the road-side only a few hundred feet away. The fine specimen, PI. CXV,
Fig. 2, comes from the fishing hut. The lower detached fragments were
once no doubt attached to the same stem with the upper portion. This
figure shows well the characteristic mode of branching of the species and
the wide spread of the twigs. This species shows a mode of preservation
of the twigs common in this but rare in the others. In it the leaves on
the upper face of the older stems have fallen off, exposing the slender
woody axis, whereas on the ultimate youngest twigs all the leaves are pre-
served. The cone, PI. CXVII, Fig. 6, from Potomac Run, is no doubt
globular in form on account of distortion, being compressed in the direc-
tion of its length. These cones are larger than those of A. grandis. Plate
CXXXV, Fig. 15, gives one of the largest size.

AtHEOTAXOPSIS PACHYPHYLLA, sp. UOV.
Plate CXV, Figs. 1, 3; Plate CXVII, Figs. 1, 3-5.

Small trees or shrubs, copiously branching, with branches all in one
plane, comparatively stout, rigid, and mostly long, cylindrical in shape;
ultimate twigs mostly simple ; leaves very thick, prominent, horny in
texture, with strong keel, arranged as in the preceding species, elliptical to
rhombic in shape, very durable, dropping off with increasing age ; cones
not seen.

Localities: In the banks of Dutch Gap Canal; fishing hut above
Dutch Gap Canal.

This plant is one of the most common ones in the banks of Dutch
Gap Canal. It occui-s, however, in a very fragmentary condition. It is
characterized by the thickness of the leaves.

DESCEIPTION OF THE SPECIES. 243

SEQUOIA Torrey.
Sequoia cycadopsls, sp. nov.

Plate CXII, Figs. 9-11; Plate CXIII, Figs. 1-3.

Leafy branches, with keeled stems which were apparently succulent,
branching dichotoniously ; leaves remotely placed, alternate to subopposite,
widest near the base, decurrent, narrowly linear, acute, varying in length
considerably, attaining the maximum dimensions of S.S""" in length and
2"" in width, margins of the leaves apparently thickened from being rolled
slightly, obliquel}^ inserted, the longer leaves straight or slightly curved
upwards, shorter leaves (on younger branches 1) strongly falcate, all thick,
leathery, and rigid, with a midnerve that is prominent on the lower side of
the leaves and forms a sort of keel in the longer leaves, showing a sunken
central line on the upper side of the leaves.

Locality: 72d mile-post, near Brooke.

This plant is very rare. It is in some respects unlike the ordinary
forms of Sequoia, and so strongly resembles Cycadites that for some time I
thought that it should be placed in that genus, but the finding of branching
stems, such as are shown in PI. CXII, Fig. 9, shows that it can not be
Cycadites. Perhaps it should be regarded as a new genus, but as it stands
apparently nearest to Sequoia I have placed it provisionally in that genus.
It seems to be a comprehensive form, combining the characters of Cycadites
with those of some of the species of Podocarpiis, such as P. Meyeriana
Endlicher, and P. elongata E. Meyer. It is also a good deal like Taxites
falcatus Nathorst (see Floran vid Bjuf, PI. XXII, Fig. 11). In the decur-
rent leaves lying strictly in one plane it resembles Sequoia. It is a good
deal like Dawson's Cycadites imjiga (see Cretaceous and Tertiary Flora of
British Columbia, PI. I, Figs. 2, 2^).

Sequoia Reichenbachi (Geinitz) Heer.

Plate CXVIII, Figs. 1, 4; Plate CXIX, Figs. 1-.5; Plate CXX, Figs. 7, 8; Plate CXXII, Fig. 2; Plate

CLXVII, Fig. 5.

Branches elongate, leaves decurrent at base, spreading, linear-lanceo-
late, falcate, incurved, acuminate, widest at base; one-nerved.

244 THE POTOMAC OR YOUNGER MESOZOIO FLORA.

Localities: Fredericksburg; fisliing hut above Dutch Gap Canal;
banks of Dutch Gap Canal.

This plant is quite abundant at the fishing hut in the forms with
narrow leaves, such as are figured in PL CLXVII, Fig. 5. It is also com-
mon in such forms as PI. CXVIII, Fig. 4, etc. It is comparatively rare
at the other localities.

The type of Sequoia illustrated in S. Reichenhachl is much the most
common one in the Potomac flora. It is illustrated in such plants as
S. amhigiia and S. siibulata. Those witli scale-shaped leaves are very rare-

S. BeicheMhacM is the most common conifer at the fishing hut. Nearly
all the specimens have the leaves closely placed on the twigs. The twigs
branch copiously, and by their size indicate that the growth was vigorous
All the leaves are widest at base, strongly falcate and acute, decurrent at
base, with a distinct midrib, the larger leaves being acuminate. PI. CXX,
Fig. 1, shows an unusual mode of insertion of the leaves, they being at
right angles with the stem. This position seems to be assumed by the
older leaves. As a rule the younger leaves are obliquely placed and
strongly curved upwards. The scars left by the leaves after falling off
from the older twigs are obovate, rounded at the top, with a round vascular
scar at the top and a furrow running down from it (see PI. CXIX, Figs. 4,
5). Fig. 4 gives the natural size, and Fig. 5 gives the scars from another
stem enlarged. The forms, PI. CXVIII, Fig. 1, and PI. CXIX, Fig. 1,
show some differences from the Dutch Gap specimens in having the leaves
more remote and obtuse. They look something like Heer's species 8.
Smithiana. The first-named specimen shows that some of the forms
attained very considerable dimensious. In PI. CXVIII, Fig. 4, and PI.
CXIX, Fig. 3, at the points marked («), we have the tips of twigs showing
a growing bud with undeveloped leaves.

Sequoia Reichenbachi (Gein.) Heer, var. longifolia, n. v.

Plate CXVII, Fig. 8.

Stems comparatively very stout, branching freely; leaves rather re-
motely placed, strongly falcate, narrowly linear, widest at base, decurrent, and
united to form a narrow wing, very long and acuminate ; midnerve slender.

DESCEIPTIUN OF THE SPECIES. 245

. Localities: Fredericksburg; fishing hut above Dutch Gap Canal; rare.
This plant differs from the normal S. BeichenbacJii in the very long and
slender leaves.

Sequoia subulata Heer.

Plate CXVII, Fig. 7 ; Plate C'XVIII, Figs. 5, C.

Branches comparatively slender, pinnately arranged in one plane; the
ultimate branches are nearly at right angles with the penultimate stems;
leaves obliquely inserted, widest at base, acuminate, very narrow, some-
times acicular, very long in proportion to their width, usually closely
placed on the ultimate twigs, more remote on the older ones, united at base.

Localities: Fishing hut above Dutch Gap Canal; Fredericksburg;
near Telegi-aph Station.

The plant is rather common at the Dutch Gap locality, but is very
rare elsewhere. PI. CXVII, Fig. 7, gives a portion of an older twig with
unusually remote and very narrow leaves. PI. CXVIII, Fig. 6, has on
the ultimate twigs closely placed leaves that are very long in proportion to
their width.

Sequoia ambigua Heer.

Plate CXVIII, Fig. 2; Plate CXX, Figs. 1-6; Plate CXXVII, Fig. 5; Plate CXXXII, Fig. 3.

Branches elongate, fully leaved througliout, branchlets alternately
grouped; leaves decurrent, short, rather thick, falcate, incurved, acuminate,
one-nerved; strobiles globose in form ; scales peltate, rather flat.

This description which Heer gives^ for his Sequoia ambigua, from the
Kome beds of Greenland, and his figures agree so closely with certain of
the Potomac conifers, that there seems to be no doubt that this plant is found
in the Potomac flora also. It may be added, for the Potomac forms, that
the leaves are widest at base, narrowly oblong to subtriangular.

Localities: Fishing hut above Dutch Gap Canal; river bank a few
yards above the fishing hut ; near Telegraph Station.

The plant is rather common at the first and second localities, and rare
at the third. There are a few points of difference in the Kome and Poto-
mac forms, but no greater than might be expected in the same species when

I Flor. Foss. Arctica, vol. 3, PI. XXI, Figs. 1-11.

246 THE POrOMAC OR YODNGEE MESOZOIG FLORA.

grown so far apart. Tlie leaves of the Potomac plant are apparently not
quite so thick as those from Kome and not so constantly incurved, and
they are usually more closely placed. The cones of the Potomac plant
have the fi-ee surface not so much elongated transversely, and the transverse
depression on their summit is greater.

Sequoia eigida Heer.

Plate CXVril, Fig. 3 ; Plate CXXI, Fig. 2 ; Plate CXXVI, Fig. 2 ; Plate CXXX, Fig. 3.

Leaves coriaceous, rigid, linear, acuminate at apex, patent, straight,
one-nerved, transversely very finely rugulose, not narrowed at base,
adnately long decurrent.

This description of S. rigida, given by Heer,^ agrees very well with
some of the Potomac conifers, the transverse rugosity alone being absent.
This, however, is accidental, and due to the accidents of preservation. The
localities for the Potomac fossils are near Telegraph Station ; hill-side near
Potomac Run. The form PI. CXXI, Fig. 2, is one of the most common
plants near Telegraph Station. Heer sa.js that this species is more common
in the Atane than in the Kome beds. PI CXXX, Fig. 3, is a good deal like
Glijptostrobus Grcenlandiciis, as given by Heer.^ He speaks of the leaves
of S. rifjida as prolonged into a fine point. This feature may be seen on a
number of the specimens of the Potomac fossil. It is not, however, a
character that would in most cases be preserved. It is noteworthy that so
far as seen this species does not occur at Fredericksburg and Dutch Gap.

Sequoia densifolia, sp. nov.

Plate CXXI, Fig. 4.

Stems slender ; leaves narrowly linear, acute and acuminate, strongly
falcate, widest at base, decurrent and adnate, showing a tendency of the
leaves to ci-owding and aggregation into groups, in which the members have
their bases overlapping in some cases, or adnate; midnerve slender but
distinct.

Locality: Fishing hut above Dutch Gap Canal; very rare.

'Flor. Foss. Arctica, vol. 3, p. 80. ^¥\ov. Foss. Arctica, vol. 3, PI. XXII, Fig. 12.

DESCRIPTION OF THE SPECIES. 247

This plant differs from all the other Sequoias in the peculiar crowding
of the leaves at their bases, which seeuis to arise from a grouping in whorls,
the groups being separated by a comparatively considerable interval.

Sequoia gracilis Heer.

Plate CXXVI, Figs. 3, 4.

Heer' describes S. gracilis as Sequoia, with alternate branches, approx-
imate ; leaves scale-shaped, imbricated, subfalcate, decurrent at base, and
without a midnerve.

This description and the figures given in PI. XXII, Figs. 1-10, PI.
XVIII, Fig 1", agree closely with some of the Potomac plants.

Locahties: 72d mile-post, near Brooke, common; bank near Brooke,
rare.

The specimens are found in small bits and fragments of twigs, and
these are among the most abundant fossils at the first-named locality.
Such bits as those given in Fig. 3 are the most common.

Sequoia delicatula, sp. nov.

Plate CXXI, Fig. 3.

Principal twigs slender, penultimate and ultimate ones all in one
plane, minute, short, closely placed, alternate and pinnate in arrangement ;
leaves very small, narrowly linear, acute or acuminate, widest at base, de-
current, and mostly crowded ; midnerve slender but distinct.

Locality: Fishing hut above Dutch Gap Canal ; very rare.

This plant is a good deal like S. suhUata, but the leaves are proportion-
ally wider and not so falcate, while the ultimate branches are placed at
more uniform intervals.

Sequoia, species?

Plate CXX, Fig. 9.

Stem with very broad elliptical to nearly circular leaf-scars, which
are spirally arranged.

Locality: Found very rarely at Fredericksburg.

This may possibly be one of the older twigs of S. Beichenbachi.

' Flor. Foss. Arctica, vol. 3, pt. 2, p. 80.

248 THE POTOMAC OE YOUNGER MESOZOIO FLUEA.

Sequoia, species ?

Plate CXVI, Fig. 7 ; Plate CXXXII, Figs. 2, 5, 6.

Leafy twigs unknown ; cones rather large; scales deciduous with age,
large, wedge-shaped at base, with the free summits shield-shaped, and fur-
nished with an umbo; upper portions marked with several furrows, which
run longitudinally on the scale and resemble those of the scales of Glyp-
tostrobus.

Localities : 72d mile-post, near Brooke, not rare ; Fredericksburg,
very rare.

These scales, found mostly at the 72d mile-post, are not uncommon
there. They have a marked character, which makes it easy to recognize
them. They are always found in a fragmentary state, only a few scales
adhering to the axis and widely diverging, indicating that the scales were
quite deciduous and diverged widely on the ripening of the cones. A
marked feature is the occurrence of deep fuiTows on the upper expanded
ends of the scales, which possibly indicates some affinity with Glyptostrohus.
The shape, too, of the scales resembles that of Splienoleirklium^ so that the
type may be a comprehensive one. Plate CXVI, Fig. 7, from Fredericks-
burg, shows a portion of a cone compressed logitudinally.

Sequoia, species ?

Plate CXXXII, Fig. 10.

Leafy stems unknown ; cones large ; scales wedge-shaped at base
and expanded towards the free ends, surface of the free ends of the scales
not made out; the upper expanded portions of the scales are marked with
longitudinal furrows as in the preceding species, and the scales appear to
have been deciduous.

Locality: Fredericksburg.

Only one cone of this kind was found. It shows the same longitudi-
nal plications or furrows on the upper portions of the scales as the preced-
ing species, but not to such a marked extent, and the cone is considerably
larger than any of those found at the 72d mile-post. It evidently forms a
distinct species.

DESCRIPTION OF THE SPECIES. 249

ARAUCARIA Juss.

Leaves sometimes thickened or coriaceous, four-sided, falcate, incurved,
keeled on the back and sometimes flattened, possessing several nerves,
acute at the apex or mucronate, inserted by a narrowed and twisted base
and decurrent, spirally inserted, or generally distichous on the lateral
branches and branchlets.

The above description by Saporta^ gives the character of the two
types of the leaves of Araucaria. The kind of leaves given in the latter
part of the description is that of certain forms found in the Potomac flora,
and I have placed these provisionally in this genus.

Araucaria podocarpoiues, sp. nov.

Plate LXXXVI, Fig. 4.

Stems comparatively stout; leaves small, oblong, elliptical, subacute,
narrowed to the base and apex, alternate, distichous, inserted by short
slightly twisted footstalks spirally on the stems, placed near the margins
and arranged in two rows in the same plane by the twisting of the foot-
stalks; nerves slender, indistinct, several in number, diverging at their
entrance into the leaf, then parallel to the summit, where they were not
distinctly seen.

Locality: 72d mile-post, near Brooke, where it was found in only one
specimen.

This plant has the appearance oi Podozamites, but the leaves are spi
rally arranged, and the nerves are not converging apparently at the sum-
mit. It is also like Nageiopsis, but the insertion of the leaves is different.
It is very much like Gardner's Podocarpus incerta, from the Eocene of
Bournemouth.^

Araucaria oj!tusifolia, sp. nov.

Plate LXXXV, Fig. 13.

Leaves spirally disposed, arranged in four (?) rows, flat, obtuse, widest
near the base, falcately curved upwards, decurrent and imbricated at base ;
nerves thin, parallel, several in number.

'Pal. Franfaise, V^ggtaux, vol. 3, 1878, pp. 412, 413.
^Brit. Eooeue Flora, vol. 2, PI. XI, Figs. 1-3.

250 THE POTOMAC OR YOUNGER MESOZOIG FLORA.

Locality: Entrance to Trent's Reach; only one specimen found.

This peculiar plant differs from most Araucarias in several features.
On the upper face of the stems scai's appear, as if formed by the removal
of leaves, indicating that they were arranged in four rows. It is possible
that the leaves on the upper and lower faces of the twigs were different
from the lateral ones and smaller. The top of the twig shows what seems
to be a growing bud of undeveloped leaves, and it indicates that the leaves
were really spirally arranged, but by twisting of the bases or footstalks
were brought into the same plane, grouping themselves in four rows. The
nerves were obscure.

Araucaria zamioides, sp. nov.

Plate CXXI, Fig. 1.

Leafy ultimate twigs terminating with a leaflet like those lower on the
twig ; stem slender ; leaves closely placed, alternate, pinnately arranged in
the same plane, flat, thin, slightly falcate, widest near the base and nar-
rowing gradually to the tips, which are acute, attached by a slightly
twisted base ; nerves several, parallel, and ending as in Zamia, partly on
the margins near tlie tips, quite slender and inconspicuous.

Locality : Hill-side near Potomac Run ; very rare.

This plant is a good deal like a cycad of the Pterophyllum type.

TAXODIUM Richard (GLYPTOSTROBUS Endl.)

The fossils of the Potomac flora belonging to Taxoclhim are found in
the group of plants united by Endlicher in the genus Glyptostrobits, which
genus is now by Bentham and Hooker placed with Taxodium. Schenk^
says of Glyptostrobus, that the leaves are attached spirally and are of
various shapes; "they are either upright, short, appressed, oval, acute,
scale-shaped, the tips on the older stems not seldom divergent, or else on
the horizontal twigs arranged distichously, linear acute. On upright stems
these also are directed upwards. Both kinds of leaves have decurrent
bases. * * * Ripened cones, woody, oboval in shape, with scales wedge-

'Zittel's Handljucli der Palaeoutologie, vol. 2, p. 295.

DBSCEIPTION OF THE SPECIES. 251

shaped and widened at the tips, which are imbricated, and have on their
ends a rounded rim marked with from three to seven furrows."

This description agrees Avell with the appearance of a number of leafy
twigs found in the Potomac strata.

Taxodium (Glyptosteobus) ramosum, sp. nov.

Plate CXXIII, Figs. 2, 3; Plate CXXIV, Fig. 2; Plate CXXVII, Fig. 1 ; Plate CXXXII, Fig. 1 ; Plate

CLXVI, Fig. 1.

Stems profusely branching at short intervals ; branches short and
rigid, often showing a tendency to a fastigiate arrrangement ; leaves on the
older twigs proportionally long, narrowly elliptical, mostly appressed,
especially on the upper and lower faces of the twigs, the lateral ones some-
times slightly divergent at the tips and incurved; the leaves on the younger
stems short, na,rrowly elliptical, thick, and close appressed, strongly convex,
and keeled on the back; male aments on the tips of short branches not
seen; nerves single and thread- like.

Locality: 72d mile-post, near Brooke; very common.

This plant is one of the most common conifers at the 72d mile-post.
The ultimate twigs often show at their tips a whorl of short, scale-like,
divergent leaves, that seem to have surrounded the base of the male aments.
These in all cases had fallen off, and hence their character could not be
made out. There is little doubt, however, that some of the numerous
aments of conifers from this locality, described as aments of conifers («),
(b), (c), (d), come from this plant. Some of the forms of this plant are
a good deal like Widdringtonia Beichii, as figured by Velenovsky,^ and
they also resemble the branches of Taxodium {Qlyptostrohiis) expansum, but
differs from both of these in the strong convexity of the leaves on the
young twigs and their short, elliptical shape, as well as in being more
rigid, stouter, and much shorter in the twigs. The chief resemblance is
in the nerves, which in both Widdringtonia and in the Potomac plant
are single in each leaf, slender and thread-like, running along the mid-
dle of the leaves throughout their whole length. The ultimate twigs of
the Potomac plant are sometimes more delicate than in any of the forms

' Die Gymnospermen der bobm. Kreideformatioa, PI. X, et seq.

252 THE POTOMAC OR YOUNGER MESOZOIO FLORA.

figured, but are short and rigid. Some of the ultimate twigs, as those
marked 3* and 3^, on PI. CXXIII, are so short and minute that a good lens
is needed to make out their details, but the leaves are seen to be sharply
defined and very convex. PI. CXXIII, Fig. 3, shows a much-branched
twig with very minute and short ultimate branches. PI. CXXII, Fig. 1,
shows a tendency to fastigiate grouping of the branches.

Taxodium (Glyptostrobus) Virginicum, sp. nov.

Plate CXXr, Fig. 6.

Branches slender, going off at an acute angle ; leaves verj^ small, with
the average dimensions, 1"" by 4™", narrowly oblong in shape, narrowed
to the base and summit, acute, remotely placed; nerves not seen, but
apparently single.

Locality : Hill-side near Potomac Run ; very rare.

This plant is nearest to Glyptostrobus Groenlandiciis Heer, among de-
scribed fossils, but the leaves are much smaller. It is also somewhat like
Sequoia fastigiata Heer, but the twigs are not fastigiate. The leaves seem to
have been somewhat deciduous, and to have had a mucronate tip.

Taxodium (Glyptostrobus) expansum, sp. nov.

Plate CXXIII, Fig. 1.

Twigs alternate and pinnately arranged, going off" at an angle of 45°,
spreading widely, directed slightly upwards, very long and cylindrical in
form ; leaves thick and convex, narrowly elliptical or narrowly oblong,
proportionally very long and narrow, decurrent, usually close appressed,
the lateral ones with their tips sometimes diverging ; nerves not seen.

Locality : Near Telegraph Station.

This plant is not uncommon -at the locality near Telegraph Station,
and is one of the most abundant conifers at that place. To judge from the
specimen figured, the plant must have been wide-spreading, for this is a
mere fragment of what must have been a large branch, the basal portion
of the ultimate twigs being all that is preserved. The rigid character of
the species is well shown in this specimen. The specimen figured is one of
those with the stoutest ultimate twigs. Many are more delicate and thread-

DESUEIPTION OF THE SPECIES. 253

like. The plant is a good deal like Velenovsky's Sequoia heteropJiijUa, in
those forms with the shortest and most appressed leaves (see Die Gymno-
sperm. der bohmisch. Kreideformation, PL XIII, Figs 6, 8). It is also like
some of the forms of Cyparissklium Hear, but the leaves are longer and
narrower than those of this genus.

Taxodium (Glyptostrobus) fastigiatum. sp. nov.

Plate CXXV, Figs. 1, 3.

Stems branching copiously ; twigs long, cylindrical, branching at long
intervals in a dichotomous manner and very irregularly, the branches as-
suming a fastigiate grouping ; lateral leaves on the older twigs oblong to
ovate, acute, decurrent, diverging slightly, and incurved ; facial leaves close
appressed, elongate-oblong, towards the summit of the stem elliptical to
ovate-acute; leaves on the younger twigs elongate-oblong to narrowly
elliptical, close appressed, or with the lateral ones sometimes slightly diverg-
ing ; midnerve distinct, but slender and thread-like.

Localities : 72d mile-post, near Brooke ; hill-side near Potomac Run.

This plant is rare at the 72d mile-post, but is one of the most common
conifers at the Potomac Run locality. The specimen figured in PI. CXXV,
Fig. 1 , must have been originally very large, for the lower and detached
branch is plainly a part of the upper portion. This plant is, in the form of
the leaves, like Glyptostrobus l^uropceus, and may possibly be an ancestral
form of this species. The leaves and twigs remind one of Biota pendida
Endlicher, one of the varieties of B. orientalis.

Taxodium (Glyptostrobus) denticulatum, sp. nov.

Plate CXXIV, Fig. 1.

Branches comparatively stout and rigid, rather copiously pinnately
and alternately subdivided; leaves thick, convex, very elongate- oblong to
elongate and narrowly elliptical, close appressed, with ends lancet-shaped
and prolonged into an acute spinous tip, midnerve strong and prominent.

Locality : Kankey's.

Only one specimen was found, but as the material accessible was very
limited in amount and unfavorable for the preservation of specimens, no

254 THE POTOMAC OE YOUI^GEE MESOZOIG FLOKA.

idea can be gotten from the apparent rarity of the forms found here of
their real abundance. Dioonites Btichianus, in great abundance, formed
nearly all the specimens obtained here.

Taxodium (Glyptostrobus) Brookense, sp. nov.

Plate CXXII, Fig. 1; Plate CXXIV, Figs. 3-9; Plate CXXXI, Fig. 5; Plate CLXV, Figs. 1-3;
Plate CLXVI, Figs. 4,7; Plate CLXVII, Fig. 3.

The principal stems seen are moderately stout and very rigid, the sec-
ondary ones mostly slender and rigid, the ultimate ones usually very long,
slender, and unbranched, wide-spreading, often very delicate and thread-like,
going off at an angle of about 45°, but from distortion due to pressure fre-
quently appearing fastigiate and irregularly grouped ; leaves on the oldest
stems elongate-linear, acute, close appressed, on the younger stems all
very narrowly oblong, or narrowly elliptical, acute to obtuse, very closely
appressed, not distinctly visible without the help of a lens in many cases,
all spirally arranged ; the facial leaves usually acute, the lateral ones usually
more obtuse and sometimes slightly divergent at the tips and incurved ;
midnerves slender and thread-like.

Locality: 72d mile-post, near Brooke; abundant and in fine specimens.

This beautiful plant is found in abundance in an interrupted and thin
layer of fine clay along with the best preserved of the Angiosperms which
occur at the 72d mile-2)0st, such as Menisper mites, Sassafras, etc. Strange
to say, it is not found at the bank on the railroad near by. It evidently
had twigs that spread widely in one plane, and some of the twigs indicated
an expanse of more than a foot. The shale or clay was very unfavorable
for the extrication of the specimens, and many of them were much broken
up in taking them out.

This was the case with all of the largest imprints. Plate CXXII,
Fig. 1, gives a form with the ultimate twigs of the maximum thickness.
It gives well the original mode of attachment and the expansion of the
branches. In most cases distortion from pressure has crowded the twigs
together and much disguised their true arrangement. This may be seen
in PI. CLXV, Figs. 2, 3, and these figures show also the minuteness of
some of the ultimate twigs. They often look like slender threads, the

DESCEIPTION OF THE SPECIES. 255

facial leaves are often much elongated, the sides forming joarallel lines and
the top being an acute ti-iangle. This elongation of the leaves on the
front aspect, and the presence of the thread-like midnerves, make some of
the twigs to a])pear striated. The male inflorescence shown in PI. CLXVI,
Fig. 7, occurs at the locality near Brooke, associated with T. Brookense in
such a way as to make it probable that it belongs to this ])lant.

The varying forms of the leaves on the younger twigs and the char-
acter of the midnei-ves are well shown in PI. CXXII, Figs. l-\ l*". Tlie
leaves on the upper face of the older twigs are not usually preserved, being
perhaps sooner destroyed on account of their greater exposure. The lat-
eral leaves are usually so closely appressed that in most cases, if seen with-
out the help of a lens, they seem to be consolidated with the stem, and the
ultimate twigs look like cords. On many of the ultimate twigs the lateral
leaves arch slightly away from tlie stems in the center, the tips curving in
and being closely united to it. The lateral leaves are most commonly
rather obtusely rounded at the tips. Tlie facial ones, when much drawn
out, often end in a lancet-shaped point. The thread-like nerves run
throughout the entire length of the leaves without change in their thick-
ness, and this gives them their peculiar cord-like character, which can be
seen only with the help of a lens.

Most of the plant-bearing material at the 72 d mile-post is a confused
mixture of sand and clay, composed of torn up and redeposited matter.
In this occur the various forms .of Sphenolepklium found at this locality
and some of the Augiosperms, but these plants are always in small frao--
ments. No specimens of Taxodium Brookense occur in this material, but
they are found in the layer of clay above mentioned. As all the well-pre-
served and most remarkable Angiosperms of this locality occur in this
layer, and a number of tliem nowhere else, it is proper to describe it more
particularly. This clay layer does not seem to be a deposit of an age dif-
ferent from that of the confused matter, but it is simply a more uniform
material, the result perhaps of pauses in the movement of the agitated
waters in which fine clay in small irregular patches was somewhat uni-
formly laid down. It is only one or two inches thick, and does not con-
tinue unbroken, but is cut out here and there by the confused material, and

256 THE POTOMAC OR YOtTNGEE MESOZOIC FLORA.

runs with an undulating dip beneath the raih-oad track, exposing some five
or six feet of length. The clay is very fine, unmixed with sand, and fairly
well laminated. In this the leaf imprints occur beautifully preserved.
Unfortunately but a few feet in length of this substance was found.

Taxodium Brookense is in many features a good deal like the plant
which Velenovsky calls Widdnngtonia- Beichii, and of which he gives
figures representing an enlarged twig closely resembling some of the forms
of the Potomac fossil, especially in the shape of the leaves and in the
lancet-shaped tips of the facial ones. His description in many points will
apply to the Potomac plant. The older stems, such as the one given in
PI. VIII, Fig-. 6, depart more widely from the Potomac forms.

On the whole the twigs of the Potomac plant are stouter and more
rigid than tliose of W. Relclm. Possibly the Potomac fossil is an ancestral
form of the Bohemian plant. Heer describes a fossil from the Atane beds
of Grreenland similar to the Bohemian fossil, but says its leaves have no
midrib. As stated, it is not easy in all cases in T. Brookense to detect the
midnerve, and Heer may have had specimens in which it was not pre-
served, although originally present. Velenovsky does not show that the
Widdringtonia like cone which he assigns to his plant is certainly con-
nected with it. The shape and the arrangement of the leaves of T.
Brookense are strikingly like what may be seen in the young leaves of
Glyptostrohus pendulus Endlicher.

Taxodium (Glyptostkobus) Brookense, var. angustifolium, sp. nov.

Plate CLXVII, Fig. 1.

Copiously branched, with very slender twigs ; leaves very narrow,
linear, closely appressed, obtuse to subacute; ultimate twigs cord-like,
and going off irregularly^ from the penultimate ones; nerves very slender
and thread-like.

Locality: White House Bluff.

This plant in essentials is the same as the normal T. Brookense, but it
is uniformly more slender, the leaves are narrower and always close
appressed, and it has a more irregular mode of branching, with more

' Die Gymnosperraen der bohmiscli. Kreideformation, PI. VIII, Figs. 4-6, 16 ; PI. X, Figs. 1, 11,
12 ; PI. VIII, Fig. 16.

DESCRIPTION OF THE SPECIES. 257

crowded twigs. It is much the most common conifer at "White House,
where it seems to have been abundant. Owing-, however, to the friable
nature of the clay which contains the imprints and its admixture with sand
the specimens are poorl}^ preserved. The specimen figured was evidently
a very large form originally. When found it extended over five or six
inches of area, but was broken in taking it up.

SPHENOLEPIDIUM, Heer (SPHENOLEPIS Schenk).

Branches and twigs alternate, with spirally placed, short, imbricated
leaves that are decurrent at base, acute or acuminate on the younger
twigs, appressed on the older ones, divergent and somewhat curved in-
wards; cones placed on axillary lateral branchlets which have close
appressed leaves and form a raceme, persistent, rounded, or oblong ; scales
of the cones persistent, leathery, wedge-shaped, with the upper margin
truncate, when mature, divergent.

This description of the genus by Schenk appHes very nearly to a
number of coniferous plants from the Potomac flora, which, with the species
of Taxodium, form very important elements in this flora. These two genera
usually are to be found associated together at the same localities and in
the same layers, and with them we usually find some of the species of
Sequoia. The constant association of the forms of these three genera is no
doubt due to the accidents of preservation, the conditions favoring the
preservation of one promoting likewise that of the others. It is possible
that some of these plants may really belong to that group of Sequoias that
possesses imbricated scale-shaped leaves, such as S. concinna, etc. In the
absence of fructification the question can not be positively decided. Cer-
tainly these plants possess in the forms of the leaves and twigs many
features seen in that section of the Sequoias.

Sphenolepidium paecekamosum, sp. nov.

Plate CXXIX, Fig. 7 ; Plate CXXX, Pig. 8 ; Plate CXXXI, Fig. 2.

Branches long and slender, dividing at long intervals in a dichotomous
manner, giving a few rather stout, long, cylindrical branches, showing a
tendency to fastigiate grouping ; lateral leaves short, acute, with a distinct
MON XV — 17

258 THE POTOMAC OR YOUNGEE MESOZOIC PLOEA.

slender midnerve, subfalcate, narrowly oblong to narrowly elliptical,
decurrent, with the tips slightly divergent and incnrved, those on the
upper and lower surfaces of the stems (facial ones) close appressed, with
no visible midrib, oblong to elliptical, ol}tuse to subacute, remote.

Locahties: Fredericksburg; 72d mile-post, near Brooke.

This plant is not very rare at Fredericksburg, and is very common at
the 72d mile-post, where it occurs in numerous fragments in the confusedly
mixed sand and clay. The peculiar mode of branching reminds one of
Heer's Sequoia concmna from the Atane beds of Greenland, but the leaves,
although of the same general character as those of S. concinna, are more
closely placed and not so long and slender.

Sphenolepidium dentifolium, sp. nov.

Plate CXXVII, Figs. 3, 4 ; Plate CXXVIII, Figs. 2-6 ; Plate CXXIX,Fig.5; Plate CXXX, Figs. 4-6, 10

Stems branching freely, with long, slender, rigid, alternate twigs, that
are obliquely attached; leaves ovate, oblong, or elliptical, tliick, short,
acutely dentate in form, obliquely placed, decurrent, and united at base in
the same plane, with no leaves apparently on the upper and lower faces of
the twigs ; midnerve distinct and often strong.

Locality : Fredericksburg.

This plant is one of the most common conifers at Fredericksburg.
It is much like Sequoia Couttsice, but the thick, short, tooth-shaped leaves
differ from those of this Sequoia. PI. CXXX, Fig. 6, and PI. CXXVII,
Fig. 4, give two twigs which show on their tips two lateral undeveloped
leaf-buds and a terminal partially developed one. The ultimate twigs on
most of the specimens are placed rather remotely and irregularly, showing
a tendency to a fastigiate grouping, but in PI. CXXVIII, Fig 5, they are
closely placed at regular intervals and in a pinnate manner. The plant
reminds one of some forms of Sphenopteris Mantelli.

Sphenolepidium eecuevifolium, sp. nov.

Plate CXXVII, Fig. 2 ; Plate CXXX, Figs. 2, 7.

Branches and branchlets slender and very long, ultimate branches
inserted very obliquely and at irregular intervals, strongly turned upwards;

DESCRIPTION OF THE SPECIES. 259

leaves, so far as seen, inserted only laterally, strongly decurrent, and
adnate or united, thick and leathery, strong-ly recurved, oblong to ovate,
acute or acuminate, much wider at base than elsewhere, cut away on the
upper side; midnerve very strong and rigid.

Localities: Fishing hut above Dutch Gap Canal; hill-side near Poto-
mac Run; near Telegraph Station; rare at each locality.

This well-marked plant is in some respects like some of the species
of Pagiopliyllum (Pachyphyllum). The shape and the great thickness of
the leaves are the main points of resemblance. The fine specimen given
in PI. CXXVII, Fig. 2, shows towards the tips of the ultimate twigs a
recurvation stronger than usual, so that the leaves stand nearly at riglit
angles to the stem. The plant belongs to the type of Sequoia Couttske.

Sphenolepidium pachyphyllum, sp. nov.

Plate CXXXI, Figs. 6, 7.

Branches long, rigid, and slender, sending off at irregular intervals
alternate subordinate twigs ; leaves, so far as seen, strictly distichous, with
no facial ones, crowded, adnate at base or overlapping, much wider at
base than elsewhere, gradually tapering to an acute tip so as to give them
a triangular or ovate form ; acute or acuminate, straight or slightly falcate,
attached nearly at right angles to the stems, very thick and dense in
texture, with an unusually large midnerve.

Locality: Near Telegraph Station.

This strongly marked plant is very rare. It is very much like Pagio-
phyllum Heer {Pachyphyllum Saporta), in the great thickness of the leaves.
It is almost exactly like the form of Sequoia Beichenbachi given by Schenk.'

Sphenolepidium Virginicum, sp. nov.

Plate CXXV, Fig. 4 ; Plate CLXVI, Fig. 6.

Branches comparatively stout, alternate ; facial leaves elliptical and
close appressed, lateral ones ovate, acute, slightly divergent and incurved
at the tips, strongly decurrent, all with distinct midneiwes, on the youngest
twigs they are elliptical and closely appressed ; female strobile terminal on

'Foss. Pfl. der Wernsdorlev Schichteu, PI. 4, Fig. 2.

260 THE POTOMAC OR YOUNGER MBSOZOIC FLORA.

stout short twigs, oblong- in form, with woody or leathery scales wedge-shaped
and truncate on the free surface, strongly divergent when mature; male
aments f narrowly oblong-elongate, persistent, composed of thin, ovate,
imbricated scales, terminal at the ends of short slender lateral twigs.

Locality: 72d mile-post, near Brooke.

This plant is rather common at the above-named locality. In the
character of the cones it is somewhat like Atlirotaxopsis, but unlike that
gentvs the scales opened widely on ripening. The leaves also are unlike
those of Atlirotaxojisis. The male aments given at («) seem to be persist-
ent, for they remain on branches that show the ripened cones. They
show open chaffy scales. The plant is not uncommon at the 72d mile-
post, but very rarely shows cones, and is a good deal like S'pJienolepidkim
Kurrianum Heer (Sphenolepis Kurriana Schenk), but the cones are not
globose.

Sphenolepidium Kurrianum, Heer.

Plate CXXVI, Figs. 1, 5, 6; Plate CXXVIII, Figs. 1, 7 ; Plate CXXIX, Figs. 1, 4, 6, 8; Plate CXXX,
Fig. 11 ; Plate CXXXI, Fig. 4 ; Plate CLXVII, Fig. 2.

Twigs branching copiously, often much crowded, ultimate twigs rather
short and rigid, going off very obliquely and tending to assume a fastigiate
grouping; leaves imbricated, scale-shaped, the facial ones close appressed,
elliptical or oblong, subacute, lateral ones oblong or ovate-acute, often
with the tips spreading and incurved, decurrent, lateral and facial, leaves
keeled on the back, all usually thick and sometimes deciduous; cones not
seen.

Localities : All the Dutch Gap localities, especially at the entrance
to Trent's Reach and the fishing hut above the canal ; Fredericksburg ;
72d mile-post; bank near Brooke; near Telegraph Station.

It is more common at the 72d mile-post than at any other place. It
is very abundant here in the form of small fragments. Some of the spec-
imens show a very copious branching and crowding of the twigs, covering
the shale with an intricate mass of them. Of such a character is the spec-
imen PI. CXXVIII, Fig.- 1 from near Telegraph Station, and PI. CXXVI,
Fig. 1 from the 72d mile-post. This latter is a form with leaves thinner
and more slender than usual. In some of the other specimens, such as PI.

DESCRIPTION OP THE SPECIES. 261

CXXVI, Fig. 6, PI. CXXVIII, Fig. 1, and PL GLXVII, Fig. 2, the leaves
are shorter, more convex, and more closely appressed than in others.
Indeed, there is a considerable degree of variation in the leaves. In such
forms as PI. CLXVII, Fig. 2, the leaves are thick, horny, and exceedingly
durable. They can be detached from the shale in the form of small black
shining scales.

In this and other forms of Splienolepidium the facial leaves often appear
of somewhat different shape from the lateral ones, being more obtuse, prob-
ably from their close appression to the stem. The forms, such as PI.
CXXVIII, Fig. 1, resemble Ettingshausen's Widdringtonites Haidingeri
from the Wealden of Hanover (see Beitrage zur Flor. der Wealdenperiode,
PL XI, Fig. 1).

This plant is the most common conifer at the 72d mile-post, a place
where conifers form the predominant fossils. It is a widely diffused species.

Sphenolepidium Steenbeegianum (Dunk, sp.) Heer.

Plate CXXI, Figs. 8, 10, 11 ; Plate CXXX, Fig. 9.

Branches slender, long, remote, going off very obliquely ; leaves linear,
falcate, acute to acuminate, sometimes acicular, patent, decurrent, much
wider at base, with slender but distinct midnerve, apparently distichous,
and attached only laterally ; cones not seen.

Localities : Hill-side near Potomac Run ; Fredericksburg.

This, the normal form of -S'. Sternbergianum, is comparatively rare,
being much less common than the variety densifoUum. It differs from
Heer s forms only in not showing leaves on the upper surfaces of the twigs,
but this is no doubt due to the removal of these leaves from their more
exposed position.

Sphenolepidium Steenbeegianum, var. densifolium Heer, sp.

Plate CXVIII, Fig. 7; Plate CXXI, Figs. 5, 7, 9; Plate CXXV, Fig. 2; Plate CXXIX, Fig. 3;
Plate CXXX, Fig. 1 ; Plate CXXXI, Figs. 1, 3 ; Plate CXXXII, Fig. 4.

Branches slender, ultimate twigs going off very obliquely so as to
appear dichotomous, tending to a fastigiate arrangement, subdividing irreg-
ularly ; leaves short, lateral ones acute, linear to narrowly ovate, diverg-

262 THE POTOMAC OK YOUNGER MESOZOIC FLOEA.

ing, falcate or subfalcate, comparatively closely placed, strongly decur-
rent; miduerve distinct; facial leaves ovate to elliptical, apparently obtuse
and smaller than the lateral ones, closely appressed, with often no midnerve
visible, sometimes removed by maceration ; cones not seen.

Localities : Near Telegraph Station ; hill-side near Potomac Run ;
7"2d mile-post ; Fredericksburg.

This plant is rare at all the localities except the 72d mile-post, Avhere
it is quite common. Plate CXXXI, Fig. 1, shows a number of undevel-
oped branches and buds. This plant is a good deal like Sequoia fastigiata.
It has the leaves more crowded, straighter, and less diverging than the nor-
mal S. Sternbergianmn, and tlie facial leaves, probably owing to compres-
sion, seem to be blunt and elliptical in form.

GYMNOSPERMOUS FRUITS.

The following fruits of Grymnosperms, not being connected with leafy
twigs, probably in some cases belong to plants described from their leaf
branches under otlier names. In some cases, owing to their imperfect
preservation, it is not possible to place them with certainty in their true
position.

ABIETITES Mantell.

Under this head I group certain cones that have in the main the char-
acter of some forms of Abies.

Abietites macrocakpus, sp. nov. ?

Plate CXXXII, Figs. 7.

Axis thick ; scales long, thin, and closely appressed, imbricated, nu-
merous.

Locality: Fishing hut above Dutch Gap Canal; very rare.

This cone, although very imperfect and wanting the base and the
apex, was evidently very long. Only the bases of the scales are preserved,
aad those on the upper face have been stripped off. It seems to be more
like that of Abies than that of any other conifer. It resembles Cunning-
ham ites Oxycedrus Ettingshausen, from the Cretaceous flora of Nieder-
schona.

DESCRIPTION OV THE SPECIES. 263

Abietites ellipticus, sj). nov. 1

Plate CXXXII, Figs. 8, 9; Plate CXXXIII, Figs. 2-4 ; Plate CLXVIII, Fig. 8.

Cones of medium size, elliptical in outline; scales thin, long, imbri-
cated, and closely appressed ; axis thick.

Locality : Fredericksburg.

This cone is not uncommon at Fredericksburg. It is very much like
that of Ahles. In PI. CXXXII, Fig. 9, the upper surface of the cone has
been accidentally removed so as to expose the axis. This, towards its base,
is very thick. The species seems to be of the same general character as A.
macrocar^nis, but the cones are smaller and much shorter.

Abietites angusticarpus, sp. nov. 1

Plate CXXXIII, Fig. 1.

Cone oblong, very narrow in proportion to its length ; axis propor-
tionally very thick and short ; scales short, comparatively thick at base,
thin towards the summit, imbricated, closely appressed.

Locality : Fredericksburg.

This was found in only one specimen, which, although imperfectly
preserved, is clearly different from the two previously described species.
It was evidently very narrow in proportion to its length, for the base and
summit are not preserved. The scales appear unusually thick at base as if
still inclosing the seed, and they are proportionally very short. They have
been removed from the upper surface of the axis so as to show the scars
of insertion.

ARAUCARITES Sternb. emend.

Under this head I place certain fragments of cones that appear to be
more nearly allied to Araucaria than any other conifer, but whose true
place is doubtful.

Aeaucarites Vieginicus, sp. nov.

Plate CXXXIV, Fig. 7.

Cone obovate, rounded at the summit ; scales large, numerous, thick,
transversely subrhomboidal to nearly round, shield-shaped, umbonate.
Locality : Entrance to Trent's Reach.

264: THE POTOMAC OR YOUNGEE MESOZOIO FLORA.

Only one specimen was found. The cone, whose form is pretty well
preserved, is in shape and in the character of the scales a good deal like
Sequoia. It resembles more than any other cone that of Araiicaria Cretacea
Brongniart, as given by Schimper,^ but it is much smaller.

Araucarites Aquiensis, sp. nov.

Plate CXXXIII, Figs. 8-12.

Scales of the cones varying considerably in size and shape, attaining
the maximum dimensions in length of 5*"" and in width across the top of
3*"°, with the minimum of S.S*"" by 1.5™; scales probably closely appressed
and imbricated, wedge-shaped, and narrowed at base into a sort of foot-
stalk, thickened at the summit, and rounded on the upper margin, with a
depressed transverse furrow, very deciduous, and always found scattered
singly and sparingly in the clay.

Locality: Bank near Brooke.

These scales are not uncommon. No cone was found from which they
could come. In their shape and deciduous character they resemble some
of the forms of Ahies. The scales are like those of Dammara also. Near
their summits they all show on one face a distinct curving imprint, as if
made by the pressure of the terminal edges of the overlapping next lower
scales. I have taken its specific name from Aquia Creek, near which
the locality yielding them occurs.

CARPOLITHUS St.

Under the head of CarpolUlms I place a number of nut-like seed of
conifers which have not been found in connection with leafy branches,
and whose proper place can not be made out with any certainty. No
doubt some of them belong to some of the conifers described with other
names, the characters being taken from leafy branches. These fruits form
an important element in the Potomac flora, and they are the most abun-
dant gymnospermous fruits found.

'Traits dePalgont. V6g., Atlas, PI. LXXVI, Fig. 2.

DESOEIPTION OP THE SPECIES. 265

Carpolithus fasciculatus, sp. nov.

Plate CXXXIV, Fig. 1.

Seed nut-like, with a hard smooth surface, broadly elliptical in shape,
sessile, on a short stout stem, crowded into a fascicle, comparatively large.

Locality: Fredericksburg.

Only one specimen was found. As this fruit has not been found
attached to any leafy twigs, its place can not be fixed. It occurs at Fred-
ericksburg with numerous leafy twigs of Cephalotaxopsis, and as the fruit
of Gephalotaxus has a nut-like bony seed, it is probable that these fossils
belong to some species of the first-named genus. The twig to which the
nut-like seeds are still attached is more like the twigs of Cephalotaxopsis
than any of the other coniferous wood found at the locality.

This fruit and those next to be described have suff'ered a good deal
from maceration; hence, as now presented, they must be more or less
disguised.

Carpolithus teenatus, sp. nov.

Plate CXXXIV, Figs. 2-4, 6, 8.

Seeds oblong, obtuse, smooth, grouped in threes, the individuals more
or less united and sessile, attached to the sides and summits of short stout
stems, which are attached to thick, woody, principal branches; texture of
the nut like seed hard and woody.

Locality: Fredericksburg; rather common.

This is the most abundant Carpolitlms at Fredericksburg. The seeds
have a peculiar character of union at the bases, forming a palmately
three-lobed cluster. Possibly this union, real or apparent, may be due to
the immaturity of the seed if it is real, for they show gradations in separa-
tion which seem to be connected with age, the oldest and largest being
most distinct. Thus in Fig. 6 the lowest group on the right-hand side
shows seed separated nearly to the base, while in some groups, as in the
upper part of Fig. 4, the individuals are united nearly to their summits.
These seed also are probably those of Cephalotaxopsis. They remind one
of Lesquereux's Equisetum glohiilosum. (See Cretaceous and Tertiary
Floras, PI. XL VIII, Fig. 3.)

266 THE POTOMAC OK YOUNGBE MESOZOIO FLOEA.

Caepolithus Virginiensis, sp. nov.

Plate CXXXIV, Figs. 11-14; Plato CXXXV, Figs. 1, 5; Plate CLXVIII, Fig. 7.

Seeds hard, smooth, and nut-like, small, obovate or broadly elliptical,
sometimes globular, often more or less strongly ridged, ridges seen for the
most part three in number, borne singly on short pedicels, arranged
alternately on the principal branches, and tending to assume a fasciculate
grouping.

Localities: Near Telegraph Station; fishing hut above Dutch Gap
Canal.

These fruits are rare at the first-named locality, but are not uncommon
at Dutch Gap. The ridges seen do not seem to show themselves unless
maceration has removed some of the exterior tissue of the seed. The seed
seem originally to have had smooth, firm exteriors. Like the preceding
species of CarpoUihus, they were probably inclosed in some sort of fleshy
matter, possibly having been plum-like. These seeds occur with abundant
impressions of the leaves of Baleropsis, and the pedicels with the principal
stems resemble the woody matter of Baieropsis more than that of any
other plant. It is probable that these are the seeds of some species of that
genus, perhaps of B. pluripartita, the one with which they are most com-
monly associated. The fact that almost exactly similar seed are found
constantly with Baiera Munsteriana makes this all the more probable, since
that plant seems to be nearer to Baieropsis than to the true Baieras. These
latter, according to the figures of Heer and Nathorst, have their leaves
sparingl}^ subdivided into lobes of equal importance, are very narrowly
wedge-shaped, and are grouped on the summits of short shoots. These
features are not found in some of the forms of Baiera Munsteriana. These
seed resemble Lesquereux's Cinchonidium ovale, but these latter are smallei".
They may be compared also with the seed of Heer's^ C^ehanoivskia. They
are strikingly like Lesquereux's Carpites gemmaceus? PI. CLXVIII, Fig. 7.
is peculiar in showing only one strong rib, instead of three.

'Flor. Foss. Arctica, vol. 6, Part I, PI. Vl, Fig. 15.
- Cretaceous and Tertiary Floras, PI. XL, Fig. 19.

DESOEIPTION OF THE SPECIES. 267

Carpolithus agglomeratus, sp. nov.

Plate CXXXIV, Fig. 5.

Seed small, globular in form, smooth, nut-like, crowded together
closely into a species of head, which is sessile, or borne on very short
pedicels, and carried on short lateral branches.

Locality: Fredericksburg.

These seeds are very rare. They probably belong to some s))ecies of
Baieropsis, and, as the most abundant and indeed almost the only species
of this genus occurring at that place is B. expansa, these seed may belong
to it. They are a good deal smaller than those of the preceding species.
Owing to the close crowding and the very short pedicels, some of these
forms appear united at base, as in G. ternatus.

Carpolithus conjugatus, sp. nov.

Plate CXXXIV, Fig. 9.

Fruit apparently composed of a whorl made of three pairs of nut-
like seeds united near their bases and of a single one radiating from a
central point, probably the summit of a pedicel ; the component nut-like
seed are obovate, obtuse, and rounded at the free ends, narrowed to a
sort of neck at the place of union, marked by transverse striae or wrinkles,
which run around the bodies.

Locality: Fredericksburg.

Only one specimen was found. As it is quite possible that this is dis-
torted by pressure, it may be much disguised, at least in the grouping of
the seed-like bodies. I am unable to offer even a conjecture as to the true
place of this group of bodies.

Carpolithus geminatus, sp. nov.

Plate CXXXIV, Fig. 10.

Seed of medium size, elliptical or obovate, smooth, nut-hke, and firm,
in pairs at the summit of a very short pedicel, almost sessile.

Locality: Fishing hut above Dutch Gap Canal.

Only one specimen was found. The left-hand nutlet of the pair has
had its summit removed by accident, and hence does not present the true

268 THE POTOMAC OE YOUNGEE MESOZUIO FLOEA.

shape of the seed. It is under these ckcumstances impossible to say any-
thing positive about the affinity of the fossil. It is, however, in the pair-
ing of the seeds, their shape and position, most like the seeds of Ginhjo.

Caepolithus Bkookensis, sp. nov.

Plate CXX5V, Figs. 2, 4; Plate CXXXVI, Fig. 6; Plate CLXVII, Fig. 6.

Seed elliptical, prolonged above into an acute beak of considerable
length, which is usixally bent to one side, below narrowed into a pedicel
for attachment to the stem; on the upper surface usually three strong
ridges shown, which run longitudinally tlie entire length of the fruit.

Localities: Bank near Brooke; fishing hut above Dutch Gap Canal.

This form of seed is not uncommon at the bank near Brooke, where
they are never found attached, but occur scattered through tlie clay. The
unusual form shown in PL CLXVII, Fig. 6, was found in a single specimen
at the fishing hut above Dutch Gap Canal. It shows no ridges, but a
kernel-like nucleus within the mass of the seed. It may be a different
species. At the bank near Brooke, where these seed are most common, no
plant occurs to which these seeds could probablj^ belong besides Baierop-
sis foHosa and Nageiopsis angustifolia. The former is quite common, and
it is probable that the fossil now in question forms the fruit of it.

Saporta^ calls attention to the fact that the seeds of the older conifers
are usually angled, and says that the young ovule of Salishuria is slightly
compressed, showing two or three angles. This two or three sided struct-
ure, showing more or less pronounced keels or wings, is found, as he says,
in the most primitive conifers. It may then be questioned whether or not
the angled or keeled surface of the ovule of Salishuria is an embryonic
feature. It will be noted also that the young ovule of Salishuria shows a
tendency to form a beak on its free extremity. The possession of a beak
may also be an embryonic feature. If so, it is interesting to note so many
embryonic characters in these seeds, which probably belong to Baierojms,
an old member of the Salishuria family.

These seed show a considerable amount of variation, and possibly
they do not all belong to the same species.

' Pal6ont. Franfaise, 2" ser., vol. 3, p. 139.

DESCRIPTION OF THE SPECIES. 269

Carpolithus latus, sp. nov.

Plate CXXXV, Fig. 3.

Seed of medium size, broadly pear-shaped, with a verj^^ short acute
projection or mucro on the summit as wide as long, narrowed below into
a comparatively very stout pedicel, showing on the upper surface two
strong flat ribs, which are placed on each side of the medial line and run
nearly parallel with the margins.

Locahty : Fishing hut above Dutch Gap Canal.

Only one specimen of this plant was found, and hence its character is
imperfectly shown. It is clearly different from all the other Potomac forms
of Carpolithus. It shows a peculiar flaring out in width in the middle.
It is probably a seed of some Baieropsis.

Caepolithus cuevatus, sp. nov.

Plate CXXXV, Fig. 17.

Seed large, elongate, broader at one end than at the other, curved on
one margin and nearly straight on the other, convex, covered with a thick,
smooth, and shining epidermis.

Locality: Fredericksburg; found in only one specimen.

This curious form casually inspected looks something like the imprint
of a shell. It is in shape and size unlike all the forms of Carpolithus
found in the Potomac beds. It may be a Cycadeospermum.

Carpolithus sessilis, sp. nov.

Plate CXXXVI, Fig. 9.

Seed small, subrhombic to elhptical in form, acute, much narrowed at
each end, upper surface marked with three lines denoting ridges, sessile;
principal stem comparatively stoixt.

Locality : Fishing hut above Dutch Gap Canal.

This and the form next to be described are very rare. They are both
much like the nut-like seed of Cephalotaxus, and probably belong to some
species of Cephalotaxopsis.

270 TEE POTOMAC OE YOUNGER MESOZOIC FLORA.

Carpolithus mucronatus, sp. nov.

Plate CXXXVI, Fig. 15.

Seed of medium size, elliptical, widest towards the summit, ending in
a short rigid tip (mucro), narrowed graduall}^ towards the base into a very
short stout pedicel, by which it is attached to the principal stem, marked
on the upper surface with three strong lines or ridges.

Localities: 72d mile-post ; bank near Brooke ; very rare.

This is probably a seed of Ceplialotaxopsis.

CYCADEOSPERMUM Saporta.

In the genus Cycadeospermmn I place various smooth horny seeds,
which resemble those of cycadaceous plants more than those of conifers,
but which are always found detached and isolated. This fact, and the
additional one that they are usually imperfectly preserved, render the
correct placing of these plants impossible. They ai-e always few in num-
ber, and form a very insignificant element in the Potomac flora.

Cycadeospermum acutum, sp. nov.

Plate CXXXV, Fig. 12.

Seed oval, acute, small, with a smooth, firm surface, obtusely rounded
at base.

Locality : Hill-side near Potomac Run.

This small seed is very rare. It was found only isolated and not in
connection with any leafy twigs. The seed figured by Heer^ as the seed
of Ginkgo sihirica are a good deal like this one.

Cycadeospermum obovatum, sp. nov.

Plate CXXXV, Fig. 13.

Seed of medium size, obovate in form, narrowed towards the base,
where a trace of the pedicel is seen ; smooth and firm.

Locality : Hill-side near Potomac Run ; rare.

This seed is something like Carpolithus Virginiensis, but it is larger,
and besides is smooth and glossy on the surface.

1 Flor. Foss. Arctica, pt. 2, vol. 4, PI. XI, Figs. 13-20.

DESCRIPTION OF THE SPECIES. 271

Cycadeospeemum spatulatom, sp. nov.

Plate CXXXV, Figs. 11, 21.

Seed of considerable size, smooth and g'lossy on the surface, spatulate
in form, truncate and abruptly rounded off at the base, narrowed towards
the upper end ; the sides nearly straight.

Locality : Hill-side near Potomac Run ; rare.

These seed, found always detached, are covered by a smooth, glossy,
parchment-like epidermis, which peels off from the stone. It is the most
common seed at the Potomac Run locality, but still is not abundant.

Cycadeospermum ellipticdm, sp. nov.

■Plate CXXXV, Fig. 19.

Seed broadly elliptical, nearly orbicular, smooth and firm, covered
with a smooth, shining epidermis, that is very durable.

Localities : Fishing hut above Dutch Gap Canal ; Fredericksburg ;
rare.

This seed must have had a considerable amount of woody matter in
its composition, as it leaves a deep depression in the clay. It is the most
common cycad seed at Dutch Gap.

Cycadeospermdm rotundatum, sp. nov.

Plate CXXXVI, Fig. 12.

Seed small, suborbicular ; surface smooth and firm, with a leatheiy,
durable epidermis.

Locality : Kankey's.

This small seed, found in only one specimen, is in shape similar to the
preceding, but is much smaller.

Cycadeospermum angustum, sp. nov.

Plate CXXXV, Fig. 20.

Seed narrowly elliptical, elongate, smooth, and firm.
Locality : Hill-side near Potomac Run.

This seed, found in only one specimen, is very long in proportion to
its width. It seems to be a distinct species.

272 THE POTOMAC OR YOUNGEE MESOZOIC FLOEA.

Ament of angiospeem ?, sp. 1

Plate CXXXV, Fig. 16.

This may have been the pollen-bearing catkin of some unknown
Angiosperm. As only one specimen was found, and it was very imper-
fectly preserved, nothing definite can be said as to its true place.

Locality : Fishing hut above Dutch Gap Canal.

Fruit capsules, sp. 1

Plate CXXXV, Fig. 14.

This figure shows two capsules of some fruit apparently united at
base and borne on a short pedicel. They are elongate-elliptical in shape,
having at the summit tooth-like projections, as if due to incipient dehis-
cence.

Locality : Occurs in only one species, at the fishing hut above Dutch
Gap Canal

Cone of callitris I sp. ?

Plate CLXIX, Fig. 8.

This fossil, which appears to be nearer Callitris than any other, seems
to be a broadly oblong cone, truncate at the summit. It is attached by a
very stout pedicel to a thick twig, and appears to be split into several
portions, which are narrowly oblong.

Locality: It was found in only one specimen, at the fishing liut above

Dutch Gap Canal.

Seed of pinus !, sp. 1

Plate CLXX, Fig. 4.

The figure represents what seems to be a seed of Pinus. It is of
small size, elliptical in form, and has attached to it a large scale.

Locality : One specimen only found at Covington street, Baltimore.

Pollen sacs ?.

Plate CXXXVI, Fig. 7.

Fig. 7 gives a number of small capsules, natural size, grouped in a
radiate manner, that resemble the pollen sacs of Taxiis. They may belong
to Athrofaxopsis.

Locality: A single specimen found at the 72d mile-post.

DESCRIPTION OF THE SPECIES. 273

WILLIAMSONIA Carr.

WiLLIAMSONIA ViRGINIENSIS, sp. IIOV.
Plate CXXXIir, Figs. 5-7; Plate CLXV, Fig. 5.

Axis stout, with a broad, deep depression at its summit, surrounded by
an elevated ridge which has been left by the fruit. Bracts in at least two
whorls, which alternate with each other, and are situated beneath and
around the scar left by the detachment of the fruit, oblong to narrowly
ovate in shape, apparently originally covered with numerous extremely fine
hair-like appendages, which, however, owing to the accidents of preser-
vation, are now often absent.

Localities : Entrance to Trent's Reach ; fishing hut above Dutch Gap
Canal.

This fossil is rare at the latter locality, and is not uncommon at the
former in the layer with Dioonites Buchiamis, Frenelopsis parceramosa, etc.
Some of the bracts are smooth and show no traces of the hair-like append-
ages. The best preserved specimens, however, show them very distinctly
under a lens, and to the unaided eye they appear as fine strise. The bracts
were evidently thick and fleshy, for in many cases they appear convex on
the surface.

Von Otto^ gives illustrations of large star-shaped bodies, which he
calls Asterosoma radiciforme. These resemble the Potomac fossils now in
question, but they are much larger, and have fewer bracts than W. Vir-
giniensis. Von Otto says of these fossils, that in nearly all four specimens
found there occur near the star-shaped bodies thread-like little cylinders
which wind about and occasionally He upon the star-shaped bodies. This
description would seem to indicate the existence on these bodies oi" thread-
like appendages like those on the Potomac fossils. These Williamsonia-
like fossils of Von Otto come from the upper Quader of the vicinity of
Konigstein in Saxony.

' Additameute zur Flora des Quadergebirges, pt. 2, PI. II, Fig. 4; PI. Ill, Figs. 1, 2.
MON XV IS

274 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

UNDETERMINED PLANTS.

The plants next following- do not possess characters that place them
definitely in any particular group of vegetable forms. I give figures of
them, as thej seem to be worthy of notice, and, so far as can be made out,
they are different from any of the fossils described under other heads in
this memoir.

Macrospores % sp.

Plate CXXXVI, Fig. 1.

At the fishing hut above Dutch Gap Canal we occasionally, but
rarely, find, on certain thin layers of fissile, very fine-grained clay, a num-
ber of minute circular markings confusedly associated together. As seen
under a lens, they are in the form of a circular raised ring, in the center of
which is a minute knob. They occur also in the red clay ball in the banks
of Dutch Gap Canal.

Undetermined plant (a).

Plate CXXXVI, Fig. 13.

This peculiar stem is more like an Ephedra than any other plant
known to me. It has a number of long, slender, woody cylindrical stems,
which radiate from a common point. In several places they seem to be
jointed, but the jointing does not appear to be generally present. In sev-
eral there are scars, as if left by the detaching of twigs. The stems are
decorticated.

Locality: Fredericksburg; only one specimen.

Undetermined plant (&).

Plate CXXXVI, Fig. 14.

This plant is composed of a number of woody cylindrical twigs, that
branch in a dichotomous manner, and pursue an irregular, flexuous course.
In the irregular branching and flexuous character of the twigs it looks
more like a root than an aerial growth.

Locality: Occurs in one specimen at Fredericksburg.

DESCRIPTION OF THE SPECIES. 275

Undetermined plant (c).

Plate CXXXVir, Fi^. 1.

This singular fossil comes from Fredericksburg in only one specimen.
The main stem seems to have been rather succulent. It has attached lat-
erally towards the top a niimber of flat leathery appendages that seem to
have had a slight woody axis or midnerve. The}" remind one of the rib-
bon-like subterranean leaves of Stigmaria. The fossil is apparently a root.

Undetermined plant {cl).

Plate CXXXVII, Figs. 2, 3.

This fossil appears in the form of large main stems, that are strongly
striated and send off irregularly large striated branches. They seem to
have been somewhat succulent in character, and probably were roots.

Locality: The plant occurs rarely at Fredericksburg.

Undetermined plant (e).

Plate CXXXVII, Fig. 4.

This fossil, found in only one specimen at Fredericksburg, is very
imperfect. It shows the curious feature of having a number of stems
radiating from the same zone on a common stem. The bases only of these
are preserved. They appear swollen and even bulbous, and are marked
by transverse striae. They look something like the singular stems found at
Baltimore, and figured on PI. CLIX, Figs. 4, 5.

Undetermined plant (/).

Plate CXXXVII, Fig. 5.

mis is a woody branching stem, found in only one specimen at Fred-
ericksburg. It is without significant character, being decorticated. It may
belong to Atlirotaxopsis.

Undetermined plant ((/).

Plate CLXIX, Figs. 4, 5.

The specimens of this plant show very long and slender cylindrical
stems, witli a comparatively small woody axis, surrounded by a succulent

276 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

cortical layer. The branches, which are like the main stems, go off at long-
intervals from the same zone, apparently in whorls. They go off usually
at right angles from the main stem and then bend upwards at a right angle,
so as to be parallel to the main stem. The branches are often as thick as
the main stem.

Localities: Quite common at Belt and Covington streets, Baltimore.

Undetekmined plant (/i).

Plate CLXIX, Fig. 9.

This fossil is composed of long cylindrical stems, which send off very
obliquely, and apparently in whorls, branches which are similar to the prin-
cipal stems. The stems and branches had a stout woody axis, which was
surrounded by a cortical layer, succulent in nature, and of considerable
thickness. This latter sometimes leaves a wrinkled and puckered margin
to the woody axis, but it is not always preserved. The bases of the
branches seem to be swollen, and they are marked by transverse scars,
which may be due to the fall of bud-scales, or may be simply wrinkles
from shrinking in the cortical layer. The plant may be the stem of Ce]}li-
alotaxopsis or Baieropsis.

Locality: It occurs rarely at Covington street, Baltimore.

Undetekmined plant {i).

Plate CLXXIII, Fig. 11.

This fossil occurs in the form mostly of detached, circular, sheath- like
impressions, having a small circular orifice in the center. The imprints
show a number of moderately strong nerves or ribs, that radiate from the
central orifice and end in spike-like teeth around the margin. Usually a
number of these imprints are found near one another, and sometimes vague
indications of a stem occur, but too much disguised by maceration to give
any idea of the mode of attachment. The imprints look more like sheaths
of some JEquisetum than anything else.

Locality: They are not uncommon at Covington street, Baltimore.

DESCRIPTION OF THE SPEOIES. 277

ANGIOSPERM^E.

The angiosperms of the Potomac flora form an important element in
it. In number of species, however, they are far inferior to the conifers
and ferns, and do not equal these in the extent of their diffusion. The
localities at which angiosperms occur in notable amounts, in the strata
in place, are the 72d mile.-post; bank near Brooke; White House Bluff;
the two localities at Baltimore and at Fredericksburg. The plants at
Fredericksburg are much more archaic in type than those of the other
localities.

It is, then, only from Fredericksburg northwards that we find this mod-
ern element playing an important part in the flora of the beds in place.
All of the localities in this more northern portion of the Potomac area do
not contain any considerable proportion of tliese plants. None occur at
the hill-side near Potomac Run, and only a few fragments are found on the
road-side near by, as well as near Telegraph Station. The two localities
at Baltimore show the Variegated Clay or upper member of the Potomac
in place over, the plant-bearing beds. At Brooke the Eocene caps the fos-
siliferous strata. Only a few imperfect fragments of angiosperms occur in
the strata in place in the immediate vicinity of Dutch Gap Canal ; but at
Deep Bottom, where the Eocene caps the Potomac, angiosperms predom-
inate in the fossils found in the disturbed bowlders of sandy clay and clay
which come from the destruction of beds that once lay upon the sand of
the lower Potomac These are of more recent type, as are those of the
Brooke localities, White House Blufi", and the two Baltimore localities.
But, as has been stated before, these beds can not be separated in age.
The Lower Potomac era seems to have had a flora that was rapidly chang-
ing. In the lower and -middle strata, ferns, cycads, equiseta, and con-
ifers predominated, giving the flora a Jurassic facies, but with these were
mingled a considerable number of angiosperms, mostly of archaic type.
The strata of Dutch Gap Canal and at Fredericksburg give us a good type
of this portion of the formation. Towards the upper part of the formation

278 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

angiosperms abounded and predominated, several haviiag living genera, but
with them many of the plants found lower down in the formation still
existed. The beds at Brooke, White House Bluff, and Baltimore are types
of this portion of the formation

It is a noteworthy fact that many of the fossils that are nearly, allied
to living genera are comprehensive types, showing perhaps ancestral foi'ms
of living types. The same may be said of the conifers that are associated
with these angiosperms, and which show affinities with living genera of con-
ifers. They are not, then, either the conifers or the associated angiosperms,
so recent in type as a hasty inspection might indicate. When in any
series of beds at a given localit}^ the fossils are of the character of those
found at Fredericksburg and at Dutch Gap, we may conclude that the
absence of angiosperms is explainable by the removal by erosion of the
upper strata, which contain them in large numbers.

Another fact that should be noted as probably indicating the really
great antiquity of the most modern-looking angiosperms is the great rarity
of individuals in most of these, and it is the most recent types that show
the fewest individuals. This probably means that the type is of recent
introduction. This feature should, however, be accepted with caution as a
basis for reasoning concerning the scarcity or abundance of forms, since
we know nothing concerning the conditions which favored or opposed the
preservation of given plants. Apparent relative abundance or rarity may
be determined solely by the conditions controlling fossilization. Then, too,
the amount of material obtained from a given locality has, of course, much
influence in fixing the apparent abundance of the plants found only at
that spot. These remarks apply with special force to the Potomac flora,
which shows su.ch a remarkable localization of the plants. It will be,
perhaps, proper to state in this connection that a very larg'e amount
of material was obtained at the entrance to Trent's Reach; fishing hut
above Dutch Gap Canal ; Fredericksburg ; the two Brooke localities ; a
smaller amount, but still large, at White House Bluff, the two Balti-
nore localities, and th^ two Potomac Run localities, and very little from
the others.

DESCEIPTION OF THE SPECIES. 279

CONOSPERMITES Ett.

CONOSPEKMITES ELLIPTICUS, Sp. nOV.
Plate CXXXVIII, Fig. 14.

Leaves very thick and leathery, with entire margins, elliptical in
snape ; nerves three in number, slender but distinct, one medial and two
marginal, the latter parallel to the margins of the leaf, all running from
the base to the apex, and apparently uniting at the apex ; no other nerves
seen.

Locality: Road-side near Potomac Run.

Only one specimen was found. The thick leathery texture of the
'eaves concealed all the nervation except the three main nerves. They
continue without much diminution from base to apex. 14* is a reproduc-
tion of the leaf

ACACIiEPHYLLUM, gen. no v.

Leaves in outline elliptical or spatulate, in texture quite thick, nar-
rowed gradually below into a long petiole ; leaves inserted vei'y obliquely
on comparatively stout stems, arranged spirally ; petiole, on entering the
lamina of the leaf, splitting up into a comparatively stout middle nerve
and two lateral ones, the latter varying in stoutness ; each main nerve
sends off very obliquely subordinate nerves, which anastomose with the
adjacent ones to form long and irregular meshes; ultimate nerves not seen;
the midnerve splits up towards the apex by sending off lateral nerves.
These leaves are more like those of some of the acacias of New Holland
than any other plants. We may compare them with the phyllodes of
Acacia salicina Lind., and A. longifolia Willd.

ACACI^EPHYLLUM LONGIFOLIUM, Sp. nOV.
Plate CXXXVII, Fig. 6; Plate CXXXVIII, Figs. \-i.

Entire leaves not seen, but long elliptical in form, gradually narrowing
below into a long petiole ; midnerve persistent to near the summit of the
leaf, comparatively strong, sending off very obliquely slender secondary

280 THE POTOMAC OE YOUNGER MESOZOIG FLORA.

nerves, and these in turn sending off subordinate ones 'which are very
slender, and anastomose at very long intervals to form very long and large
meshes ; ultimate nervation not seen.

Localities: Fishing hut above Dutch Gap Canal; red clay ball in the
banks of Dutch Cap Canal; very rare.

This leaf differs from the other species of the genus in its large size,
in the great proportional size of tlie midrib, and in the very slender lateral
nerves which are sent off from the basal portion of the leaf, and for some
distance diverge very slightly from the midrib. The lateral primary
nerves hardly surpass in stoutness the secondary ones.

ACACI^PHYLLUM SPATULATUM, sp. nOV.
Plate CXXXVIII, Figs. 4, 6-9.

LeaA'es elliptical or spatulate in shape, mostly of the latter form,
inserted spirally and very obliquely on stout stems by means of long
petioles, into which the leaves gradually narrow, forming wedge-shaped
bases; petiole at the base of the leaf lamina splits up into three nerves of
nearly equal importance, but with the middle slightly predominating ; each
of these sends off ver}^ oblique branches, wliich are quite slender and
anastomose at long intervals, forming very long and large irregularly
shaped meshes ; ultimate nervation not seen.

Localities: Fishing hut above Dutch Gap Canal; the red clay ball in
the banks of Dutch Gap Canal ; rare.

The plant is most common at the first-named locality, but is not
abundant anywhere. The leaves of this plant may be compared with
those of Leucospermum conocarimm R. Brown.

ACACI^PHYLLUM MICROPHYLLUM, Sp. nOV.
Plate CXXXVIII, Fig. 5.

Main stem proportionally very stout; leaves spirally placed and very
obliquely on the stems, small, elliptical in shape, narrowed gradually with
a wedge-shaped base into a petiole of varying length, subacute, nerves as
in the preceding species.

Locality : Fishing hut above Dutch Gap Canal.

DESCEIPTION OF THE SPECIES. 281

Only one specimen was found. On the branch preserved on the left
side of the figure only two leaves are to be seen borne on the summit ;
but this is no doubt due to the fact that the lower leaves have been acci-
dentally removed.

AcACIiEPHYLLUM VAEIABILE, sp. nOV.
Plate CLXX, Fig. 7.

Leaves small, variable in shape, ranging from narrowly elliptical to
subspatulate and broadly elliptical, often inequilatei-al, placed spirally and
very obliquely on the stem, with long petioles; leaf-substance compara-
tively thick and hiding the nerves; nervation as given in the generic
description, but not distinct; primary nerves slender; ultimate nerves not
seen.

Locality: Covington street, Baltimore ; rare.

PROTE^PHYLLUM, gen. nov.

I group under this head a number of leaves with a very archaic type
of nervation that occur in the Potomac flora. In their nervation, and in
many cases in the form of the leaves, they bear a greater resemblance to
species of Protea than any other plants. The main points that characterize
them are the absence of any pronounced difference in the size of the pri-
mary nerves, the great slenderness of these, the lax and irregular reticulation
formed, and the uniformly strong ultimate nerves, which give a reticula-
tion that reminds one of ferns. Indeed, -I was for some time in doubt
whether some of these leaves were really angiosperms and not ferns.
There are two types of these leaves, that differ only in the presence or the
absence of a distinct midrib; when the midrib is present the leaves assume
an elliptical form ; when it is absent, they tend to take an orbicular shape.
We might perliaps divide the genus into two subgenera according to this
distinction, giving one the name rotundatmn. and the other the appellation
elongatum.

The genus may be described as follows : Leaves orbicular or elongate
m form ; in the case of the former, no midrib present ; in the case of the
latter, a thick, vaguely defined, and apparently somewhat succulent midrib

282 THE POTOMAC OR YOUNGER MESOZOIC PLOEA.

exists ; petioles proportionally very thick and apparently succulent ; ner-
vation of the primary order very slender, and with little or no difference in
the strength of the primary nerves ; reticulation of all orders lax, irreg-
ular in shape, and varying in the size of the meshes; ultimate nerves strong,
all of equal strength and fern-like. These leaves form an important por-
tion of the angiosperms that occur with a predominant flora of Jurassic
type, as at Fredericksburg, and they give a very ancient look to the angio-
spermous element of the flora.

Prote^phyllum renifoeme, sp. nov.

Plate CXXXIX, Fig. 3 ; Plate CLVI, Fig. 4 ; Plate CLX, Figs. 1, 2.

Leaves small, reniform, inequilateral ; leaf-substance quite thick ; pet-
iole proportionally very thick and apparently succulent, splitting up on
entering the leaf into a number of nearly equal primary nerves, which,
repeatedly subdividing in a palmate manner and anastomosing, fill the
leaf with a very irregular lax reticulation, the branches being nearly of
equal strength with the primary nerves ; ultimate reticulation not seen.
The smallest reticulation seen is formed by comparatively strong branches,
that generally make large, nearly right angles with their parent nerves.
Tlie branches of the primary nerves go off very obliquely.

Localities : Fredericksburg ; 72d mile-post ; fishing hut above Dutch
Gap Canal ; rare.

The imprint given in PI. CXXXIX, Fig. 3, represents the entire leaf.
On the right-hand low^er side it has been pressed upwards from below so as
to roll over the lower margin of the leaf upon the nerves, making the out-
ermost of them appear to issue from a marginal nerve. This pressure has
probably produced also a distortion of the primarj^ nerves in the left-hand
half of the leaf, crowding them together abnormally. The thick substance
makes it difficult to follow the ultimate nervation. Plate CLX, Fig. 1,
gives a large fragment of a leaf much mutilated and wrinkled transversely.
This specimen, presenting its lower surface uppermost shows the nerves
much more distinctly. It shows that the penultimate meshes seen are sub-
rhombic in shape, being made by nerves meeting mostly under acute
angles, but the ultimate or smallest meshes are irregular, subrotund, or

DESCRIPTION OF THE SPECIES. 283

polygonal in form, quite different from those next above them in size. This
figure does not show any of the original margin of the leaf or of the pet-
iole, although the outline and dimensions of the leaf are evidently retained
nearly unchanged.

This curious leaf, in shape and nervation, reminds one of tlie leaves
called Protorhipis by various authors, under the supposition that they are
the prothalli of ferns. It may well be questioned, however, whether some
of these are not ancient forms of dicotyledons. The nervation of the Poto-
mac plant is something like that of a fern, and is decidedly archaic in type.
The form is similar to that of some Hedem, as H. prhnordialis Saporta, but
in Hedera the midrib and primary nerves are much stronger than the sec-
ondary ones. In the midrib splitting up into numerous primary nerves of
nearly equal size, in the dichotomous forking of the latter, and in the very
thick petiole we have a strong resemblance to some of the Froteacece, as
Protea cordata Thunb. In shape it is a good deal like Begonia hydrocotyli-
folia. It is also similar in shape to Popidus arctica Reer} This species
may be taken as the type of the subgenus Bohmdatum of the forms of Pro-
tecephyllum.

Pp.ote.ephyllum orbiculare, sp. nov.

Plate CXXXIX, Fig. 4.

Leaf small, orbicular in shape, slightly heart-shaped at base; primary
nerves all nearly of equal thickness, diverging slowly, and radiating from
the base of the leaf, sending off obliquely very slender branches, whicli
anastomose to form irregular comparatively large meshes ; ultimate nerves
forming oblong pentagonal or hexagonal meshes.

Locality : ' Fredericksburg ; only one specimen found.

This plant also belongs to the rotundate section of Protecephyllum.
It more than the preceding species resembles Hedera, but the radiate
arrangement of the slender primary nerves does not agree with that genus.
It may also be compared with Protea cordata Thunb. The nervation of
this plant is much like that of Banksites Saportanus, Velenovsky (see Die

' Flor. Foss. Arctica, vol. 7, PI. LXVII, Fig. 2.

284 THE POTOMAC OK YOUNGER MESOZOIG ELOEA.

Flora der bohm. Kreideform., PL I, Fig. 18). Conospcrmites hakecefolius

(Fig. 11 of the same plate) has a nervation similar to that of the Potomac

plant.

Peote.tjphyllum, sp. 1

Plate CXXXIX, Fig. 2. '

This fossil is too fragmentary to justify an attempt to determine its
species. It forms the upper part of an elliptical leaf, most probably has a
midnerve which towards the sunnnit splits up into branches. These are
slender and are sent off obliquely ; they subdivide irregularly into second-
ary branches, which anastomose irregularly to form large lax meshes. It
may be compared with Protea fjlahra Thunb. It belongs to the elongate
section of Protecephyllum.

Locality : Fishing hut above Dutch Gap Canal.

Pkote^phyllum oblongifolium, sp. nov.

Plate CXXXIX, Fig. 5; Plate CXL, Figs. 1, 2.

Leaf rather large, spatulate, oblong or oblong-elliptical, narrowed
very gradually below into the petiole ; sitmmit not seen ; midnerve stout,
and continuing to near the tip of the leaf; secondar}^ nerves very slender,
leaving the midrib at a more or less acute angle, and arching around in an
irregularly flexuous manner to unite with those of the same order next
above, sending off branches obliquely, mainly on the outer side, which
pursue a flexuous course parallel to the margin of the leaf, finally dis-
solving into smaller branches ; the lateral nerves anastomose into large,
irregular meshes, made up of subordinate meshes, the minor branches of the
lateral nerves, which meet under large angles, forming a net-work that is
very irregular; leaf-substance moderately thick; the ultimate reticulation
strong and fern-like.

Locality: Fredericksburg.

Leaves of this character are not uncommon at Fredericksburg. The
nervation is very lax, irregular, and archaic in type. The leaves ai-e
always quite fragmentary, but so many specimens are found giving all
parts of the leaf, that a quite reliable restoration can be indicated. In PI.
CXL, Fig. 2, I give a full-size restoration of the leaf of the largest dimen-

DESCRIPTION OF THE SPECIES. 285

sions. The nervation is something like that of Ficiis protogcea, Ettings-
hausen, from the Cretaceous strata of Niederschona.-^ The irregularity of
the areolation, the slenderness of the primary nerves, and the proportion-
ally very strong ultimate reticulation make the leaf more like some Protects
than any other living forms.

Prote^ephyllum ovatum, sp. nov.

Plate CXLI, Fig. 1.

Leaves of medium size, ovate-acute, with the tip bent^ to one side,
abruptly rounded at base, and subcordate ; midnerve very thick and appar-
ently somewhat succulent ; primary nerves very slender, going ofiP nearly
opposite in pairs, basal pair leaving at a very large angle and curving
strongly around approximately parallel to margin, those higher up leaving
at more and more acute angles, curving gently until near the margin of the
leaf, and then bending strongly upwards, gradually approaching the mar-
gin, sending off slender branches, which anastomose to form large, lax, and
mostly irregular quadrangular primary meshes ; ultimate meshes variable
in size, distinctly defined, and formed chiefly by the meeting of the nerves
under large angles.

Locality : Fredericksburg ; only one specimen found.

This leaf of moderate size is noteworthy for the great thickness of its
midrib, the unusual slenderness of its primary nerves, and the irregularity
of its nervation. This, like the preceding, belongs to the elongate section
of Protecephyllum. The leaf seems to have been somewhat inequilateral.
The nervation has some of the characters of the Gelastrinece, as shown in G.
Scandens.

PROTEiEPHYLLUM ELLIPTICUM, Sp. nOV.
Plato CXLII, Figs. 1,2.

Leaves rather large, oval-elliptical in form, subacute at summit, rap-
idly rounded at base, and then narrowed gradually into the petiole; mid-
nerve very thick, and apparently somewhat succulent; primary lateral
nerves very slender, going off at an oblique angle, arching upwards ap-

1 Kreideflora von Niederschona, PI. II, Fig. 5.

286 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

proximately parallel to the margin for some distance, not meeting one
another ; the primary nerves sending off branches in a dichotomous manner,
and these anastomosing to form large, irregular, lax primary meshes ; the
iiltimate meshes, elongate and mostly quadrangular, rather indistinctly de-
fined, owing to the thick leaf-substance.

Locality : Fredericksburg ; rare.

The nervation of this plant is more like that of Protecephyllum ovahim
than any other in the size and loose texture of the midnerve, the slender
primary nerves, and the irregular lax nervation ; it is proteaceous, but com-
bines with the characters of the Proteacece some of those of the Celastrinece.
Indeed, we may say generally of the leaves of Frotecei)hyllum with a mid-
rib, that they combine features of the nervation of both these genera. This
species may be compared with Persoonia daphnoides. It belongs to the elon-
gate section of Protecephyllum. Fig. 2 is a restoration from several specimens.

Peote.ephyllum tenuinerve, sp. nov.

Plate GL, Fig. 13 ; Plate CLVI, Fig. 2.

Shape of leaf unknown ; leaves apparently of large size and elongate .
leaf-substance thick; midnerve extremely thick, loose-textured, and appar-
ently somewhat succulent ; primary nerves extremely slender, going off at
a more or less acute angle, then arching backwards and splitting up into
branches that are nearly as strong as the primary nerves. These branches
meet obliquely to form oblong or elliptical irregular primary meshes of
large size ; ultimate nervation not visible.

Localities : Fishing hut above Dutch Gap Canal ; road-side near Poto-
mac Run ; rare.

These leaves are remarkable for the striking contrast in the size of the
midnerve and the primary nerves. Tliey really possess no distinct primary
nerves. The nervation is a good deal like that of some Persoonias. The
leaf must have been very large.

Prote.s;phyllum dentatum, sp. nov.

Plate CLVI, Fig. 7 ; Plate CLXXII, Figs. 1, 4 ; Plate CLXXIII, Figs. 12, 14.

Leaves small, orbicular in outline ; leaf substance thin, margins cut into
acute or subacute ovate teeth, which are directed forwards, and are of vary-

DESOEIPTION OP THE SPECIES. 287

ing but always small depth ; no midrib seen ; the base and summit of the
leaves not found ; the nerves very slender and seen with difficulty, they are
several in number, of about the same strength, and appear to diverge from
the base of the leaf with a flexuous course; they unite to form a series
of large, elongate, subrhombic meshes ; slender branches appear to enter
each tooth.

Localities : Belt and Covington streets, Baltimore.

This species is one of the abundant plants at these localities. The leaf-
fragment, PL CLXXII, Fig. 4, is very imperfect, since the margins have all
been removed. The shape of these leaves is more like that of some of tlie
species of Protea, while the nervation resembles that of some of the species
of Persoonia.

ROaERSIA, gen. nov.

Leaves long, narrow, and willow-like, wedge-shaped at base, acute, with
a very strong midnerve and very slender primary nerves ; these go off very
obliquely and diverge very slowly from the midrib, running for a long dis-
tance nearly parallel with the margins of the leaves; they anastomose with
branches sent off from other nerves of like grade higher up to form very
long, irregularly shaped, and lax meshes; ultimate reticulation oblong, sub-
rhombic, of quite uniform dimensions This genus is named for Prof. W.
B. Rogers, who first called attention to the plants of the Potomac formation
and studied its geology.

ROGEESIA LONGIFOLIA, sp. UOV.
Plate CXXXIX, Fig. 6 ; Plate CXLIV, Fig. 2 ; Plate OL, Fig. 1 ; Plate CLIX, Figs. 1, 2.

Leaves narrowly elhptical, gradually narrowed to the base and apex,
with wedge-shaped base, acute, very long in proportion to width ; midrib
comparatively very stout; primary nerves very slender, going off very
obliquely, proceeding upwards for some distance nearly parallel with the
margin, but gradually approaching it ; primary nerves sending off very
obliquely secondary nerves, which anastomose with their neighbors to
form elongate, subrhombic, and irregular meshes, which have their maximum
dimensions turned upwards and slightly outwards ; primary meshes filled

288 THE POTOMAO OE YOUlsGEK MESOZUiO FLORA.

witli pretty sharply defined ultimate meshes, polygonal in shape, and vary-
inff in the number of sides froiu four to six.

Localities : Fishing hut above Dutch Gap Canal ; Fredericksburg ;
Kankey's ; rare.

The shape of these leaves is a good deal like that of Salix. The
midnerve is in size out of all proportion to the primary nerves sent off"
from it. In its primary nerves and in the shape of the leaf the plant is a
good deal like Glossochlamys transmutans Ettingshausen and Gardiner.' The
resemblance in leaf-form and nervation to Persoonia mollis R. Brown is
strong. The affinities of the plants of this genus seem to be with the
Proteacece.

ROGEKSIA ANGUSTIFOLIA, Sp. nOV.
Plato CXLIII, Fig. 2; Plate CXLIX, Figs. 4, 8; Plate CL, Figs. 2-7.

Leaves narrow, small, very elongate-oblong, narrowed gradually to
the base and apex, subacute, sometimes curved ensiform ; midnerve pro-
portionally very strong, with a thick petiole ; lateral or primary nerves
very slender, going off at an acute angle and arching up towards the sum-
mit, forming more or less persistent nerves approximately parallel with the
margin, and having a flexuous course. They send off very obliquely slen-
der lateral nerves, which anastomose with the adjacent ones, and form
irregular, elongate, polygonal meshes, with their longer dimensions directed
upwards. The latter, by splitting up into ultimate nerves, form an irreg-
ular, lax, ultimate net-work.

Locality : Fredericksburg.

This is the most common angiosperm at Fredericksburg, and it is
rather abundant there. It has leaves shaped much like some forms of
Salix, but the nervation is different. The midnerve is remarkable for its
great proportional strength. The nervation is usually so fine that even
the primary nerves are seen with difficulty. The leaf-substance seems to
have been thick and the epidermis firm and durable, so that the leaves are
generally well preserved.

In the shape and nervation of the leavesHhis plant may be compared
with Persoonia mollis R. Brown.

' British Eocene Flora, vol. 1, PI. Ill, Fig. 3.

DESCEIPTION OF THE SPECIES. 289

SASSAFRAS Nees.

The genus Sassafras seems to have been certainly present in the
Potomac flora in forms that differ little from the living species, and in at
least one species the fossil leaves can be matched by the living plants
which abound in the vicinity. The genus, however, is sparingly repre-
sented both in species and individuals. Remarkably few specimens of
undoubted Sassafras were found.

Sassafras parvifolium, sp. nov.

Plate CXXXIX, Fig. 7.

Leaf very small, shape not seen. At the summit there is an obtusely
rounded short lobe, and on each side of this occur two oval subacute lobes
which are imperfectly shown, owing to mutilation.

Locality: Covington street, Baltimore, very rare.

Sassafras cretaceum, Newb., var. heterolobum.

Plate CLII, Fig. 5 ; Plate CLIX, Fig. 8 ; Plate CLXIV, Fig. 5.

Leaves small, but varying somewhat in size, wedge-shaped at base,
expanding rapidly above so as to assume a fan-shape, having at the sum-
mit three lobes, which extend nearly to the same height, but are very shal-
low. The middle one has its margins parallel with the midrib for the
greater portion of its length, but at its summit it is abruptly rounded and
very obtuse, or else narrows to a subacute point; the lateral ones are sep-
arated from this by a rather broad, rounded sinus, and have their tips more
or less divergent, subacute, pretty broad, with the outer margin curving
gently and the inner nearly straight. The petiole seems to have been
strong, and soon after entering the leaf it splits into three nerves, one
medial and two lateral ; lateral nerves going off obliquely at nearly the
same point and running nearly straight into the lateral lobes, each sending
off on the outer side, near the base and at the same height, two strong
branches, that curve upwards ; lateral nerves at higher points and the mid-
nerve throughout, sending on obliquely lateral nerves that are much
smaller than the two lower outer ones. Subordinate nerves and reticula-
MON XV 19

290 THE POTOMAC OE YOUNGER MESO^OIC FLOEA.

tion not seen ; leaves thick, and the lamina of the leaf decurrent for a
short distance on the petiole, forming a narrowing wing.

Locality : 72d mile-post, near Brooke; rare.

This plant seems to be a variety of Sassafras cretaceum Newb., from
the Cretaceous of Dakota, but the nerves are more slender and the terminal
lobes different from the normal species. It is a good deal like S. parvifoliwm,
from Covington street, Baltimore, but is much larger.

Sassafras bilobatum, sp. nov.

Plate CLVI, Fig. V2 ; Plate CLXIV, Fig. 4.

Leaf-substance moderately thick; leaf rather large, elliptical-shaped
at base, cut into a rather long lateral lobe, ovate in shape, which is turned
away from the midrib, having the opposite side of the leaf gently rounded
off; terminal lobe much larger, ovate in shape ; midnerve strong, sending off
on the right-hand side from near the base and into the lateral lobe a strong
nerve, and on the left-hand side from a little higher a smaller one, which
curves upwards, following the margin of the leaf for some distance; the
midnerve above the base at different points sends off minor nerves, which
curve upwards and fork ; ultimate nervation not seen.

Localities: Deep Bottom ; 72d mile-post, near Brooke; very rare.

This plant is strikingly like some leaves of the living species of Sassa-
fras, in which we occasionally find leaves with a single lateral lobe, just
like that in the fossil. Among fossils it is nearest to S. recurvatmn, Lesq.,
from the Cretaceous of the Dakota group. ^ The fine form, PL CLXIV,
Fig. 4, was found at the 72d mile-post. Only one specimen was discovered
here. It is quite possible that if more had been found some of them would
have shown two lateral lobes, for the size of the lowest lateral nerve, on
the left-hand side of the leaf, although inferior to the corresponding one on
the right hand, indicates that the plan of the leaf calls for two lateral lobes.

FICOPHYLLUM, gen. nov.

Leaves elliptical in outline, subacute, gradually narrowed at base, with
the lamina of the leaf more or less decurrent along the petiole ; midnerve

' Cretaceous aud Tertiary Floras, p. 57 ; Cretaceous Flora, PI. X, Fig. 3.

DESCRIPTION OF THE SPECIES. 291

and petiole extremely thick proportionally : lateral or primary nerves pro-
portionally and in most of the forms absolutely slender, extremely irregular
in arrangement, forming a lax reticulation of very archaic type. Ultimate
reticulation strongly marked and fern -like.

This genus is an important one in the Potomac flora, and has con-
tributed a considerable number of individuals to the vegetation of that
epoch. It is largely developed in association with Jurassic types of plants,
as at Fredericksburg, where it is most abundant, and is almost wanting in
the strata where more modern elements abound, as at Brooke, White
House, and Baltimore. As illustrating the archaic and pecuHar features of
these leaves and those of ProtecepJiyUum, I may state that for some time
no other leaves but these were found at Fredericksburg, and finding them
associated only with plants of Jurassic facies I found it difficult to give
any good characters distinguishing them from ferns. There is a general
and strong resemblance between these plants and some species of Ficus,
and for this reason it seems best to place them in a new genus, indicating
by its name the apparent affinity with that genus. It is quite possible that
these are ancestral forms of Ficus.

FiCOPHYLLUM CEASSINERVE, sp. nOV.

Plate CXLIV, Fig. 3; Plate CXLV, Fig. 3; Plate CXLVI, Fig. 1 ; Plate CXLVII, Fig. 4 ; Plate
CXLVIII, Figs. 1, 2, 4; Plate CLVII, Fig. 4; Plate CLXXIIl, Fig. 10.

Leaves large, of varying size, sometimes attaining very large dimen-
sions, eUiptical in outhne, subacute, with tips often .broadly wedge-shaped,
rounded off" gradually at base, and narrowed slowly into the petiole. Mid-
rib very stout, woody, and strong nearly to the tip of the leaf, rather
vaguely defined, and apparently somewhat succulent ; primary nerves in
proportion to the mid-rib slender, but compared with those of the other
species of the genus thick ; they go off on each side of the midrib, mostly
very obhquely, subopposite or alternate, arch backwards and then strongly
forwards, curving around so as to connect with the next nerves of the same
rank ; they send off on the outer side branches which continue for some
distance curving towards the summit and gradually approaching the
margin ; between the main lateral nerves, which are usually thick and
strongly marked, subordinate lateral ones are commonly shown, as in PL

292 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

CXLIV, Fig. 3, PI. CXLVII, Fig. 4. These unite witli the main lateral
nerves or the larger branches from them, and form very large, irregularly-
shaped, lax meshes. Sometimes the principal net-work in the interspaces
of the main lateral nerves is formed by large branches from these ; the
iinion of the principal lateral nerves, or of their main branches, makes a
row of well-defined arches near the margin of the leaf; the ultimate meshes
are quite uniform in size, mostly subrhombic in form, and not so sharply
defined as in most of the types with archaic forms of nervation from Fred-
ericksburg.

Localities: Fredericksburg, quite common ; Deep Bottom; fishing hut
above Dutch Gap Canal, rare.

This singular plant must have had in some of its leaves a very great
size. This is indicated by such fragments of leaves as are shown in PI.
CXLIV, Fig. 3, and PI. CXLVIT, Fig. 4, both of natural size. The midrib
especially is conspicuous for its great thickness. It, and especially its
extension as the petiole, seem to have been somewhat succulent. This was
much the largest species of leaf found at Fredericksburg. As these archaic-
looking leaves were the first ones found, and as I found it difficult to give
any characters which would distinguish them from ferns, I jiave given the
details of their nervation more fully than I would have done if the presence
of angiosperms had then been fully established in the Potomac flora. Up
to this time these strata have been held by most persons to be Triassic.

The leaf, PI. CXL, Fig. 3, shows what might at first sight seem to be
a petiole, but it is really a portion of the midrib from which the lamina of
the leaf has been stripped, and the basal portion of the lamina, still shown,
is doubled back and contorted. Plate CXLVIII, Figs. 1, 2, shows leaves
of the smallest size.

The nervation of these leaves is a good deal like that of Dawson's
Ficus maxima, Cretaceous and Tertiary Floras of British Columbia.

FiCOPHYLLUM TENUINERVE, Sp. nOV.

Plate CXL, Fig. 3; Plate CXLI, Fig. 2; Plate CXLV, Figs. 1, 4; Plate CXLVII, Fig. 2; Plate
CXLIX, Figs. 1, 3, .5; Plate CLVI, Fig. 1.

Leaves varying in size, sometimes attaining very considerable dimen-
sions, oval in outline, rapidly rounded off towards the base, where it is

DESCRIPTION OF THE SPECIES. * 293

widest, and then gradually narrowed to the petiole, subacute at the tip,
where the margins for some distance down are generally straight ; midrib
comparatively very thick, and apparently somewhat succulent; petiole
somewhat succulent and very thick ; the leaves probably pinnately ar-
ranged ; primary nerves very slender in proportion to the size of the mid-
rib, departing at an angle of about 45°, arching around to connect with
those next above, and sending off branches mostly on the outer side, form-
ing by their union several series of arches between the midrib and the mar-
gin ; between the main primaries subordinate ones spring from the midrib,
sending off branches to vinite with the main primaries ; primary net-work
of nerves formed of the principal branches of the primaries meeting nearly
at a right angle, composed of large, lax, obtuse-angled meshes, four to six
sided; ultimate net-work composed of nerves of uniformly equal strength,
meshes nearly of the same size, obtuse-angled, and generally four-sided.

Localities: Road-side near Potomac Run, very rare; Fredericksburg;
common.

The petiole of this plant is, in proportion to the primary nervation,
even more massive than that of F. crassinerve. The primary nerves are
notably slender, and their branches meet more nearly at a right angle,
while the series of arches running parallel with the margin are more num-
erous than in F. crassinerve. Plate CXLI, Fig. 2, indicates that some oi
the leaves must have attained dimensions rivaling those of F. crassinerve.
This shows well also the straight margins towards the tips of the leaves,
which are caused here to have a triangular outline. On the other hand,
the small leaf, PL OXLIX, Fig. 3, gives a degree of smallness never found
in F. crassinerve. The leaves in Fig. 5 of the same plate occur in such a
position as to suggest they were attached in pairs or pinnately. The upper
leaf, on its left-hand basal margin, has the lamina torn loose and pressed
over on the midrib, while the similarly situated portion of the lower leaf is
crushed back and doubled over upon itself. This figure shows a great
thickness of petiole, but it was evidently somewhat succulent, as it is
wrinkled and slightly puckered. Plate CXLV, Fig. 4, gives a restoration
made out from a large number of specimens which give all parts of the leaf,
so that it may be relied upon as giving a pretty accurate idea of it.

294 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

FlCOPHYLLUM SEREATUM, sp. IIOV.
Plate CXLV, Fig. 2 ; Plato CXLIX, Fig. 9.

Leaves of medium size, strongly serrate-toothed, teeth often irregular
in size, sometimes double, acute, and directed forwards ; shape of the leaf
not fully disclosed, but apparently elliptical ; midnerve proportionally very
strong, lateral or primary nerves very slender, not fully disclosed, but ap-
parently forming by the union of the branches of the primary nerves
irregular large meshes ; ultimate nervation not seen.

Locality : Fredericksburg ; very rare.

With the exception of the toothing this leaf is very much like F. ten-
uinerve. It is somewhat similar to Quercus Johnstrwpi ' Heer, from the
Patoot beds of Greenland, but the Potomac plant is larger and has a dif-
ferent nervation.

FlCOPHYLLUM EUCALYPTOIDES, Sp. nOV.
Plate CLXIV, Figs. 1, 2.

Leaves of medium size, narrowed towards the base and summit, rapidly
rounded towards the base, prolonged at the summit into an acute or mucro-
nate j^oint ; leaf-substance very thick, with a dense glossy epidermis ; mid-
nerve proportionally strong and continuing strong to near the summit ;
lateral or primary nerves extremely slender, closely placed, going off at
nearly equal intervals, subparallel, curving forwards, sending off obliquely
delicate branches, which split up dichotomously and anastomose to form
elongate, subrhombic, irregular meshes, ending near the margin in a fine
nerve, which runs for some distance nearly parallel to the margin.

Locality : 72d mile-post, near Brooke ; very rare.

The leaves seem to have been attached in a pinnate manner. In the
marginal nerve and the slender primaries it resembles JEucalypttis. It is a
good deal like Ficus magnolicefolia Lesq., Cretaceous and Tertiary Floras,
PI. XVII, Figs. 6, 6. ■

FICUS Tournef.

The genus Ficus is represented in the Potomac flora doubtfully by
only two species, and these have, so far as found, very few individuals. If
present, it seems to be newly introduced.

' Flor. Foss. Arctica, vol. 7, PI. LVI, Figs. 7-12.

DBSOEIPTION OF THE SPECIES. 295

Ficus ViEGiNiENSis, sp. nov.

Plate CXLIII, Figs. 1,3; Plate CXLIV, Fig. 1.

Leaves small, elongate-oblong, obtuse, gradually narrowed towards
the base into the petiole, so as to form a long, narrow wing along the
petiole ; midrib distinct to the summit ; lateral nerves slender, but very
sharply defined, making a large angle with the petiole and going off at reg-
ular and equal intervals, opposite or subopposite, arching over in a flex-
uous manner to unite with those next above, forming a sei'ies of well-defined
arches not far from the margin ; branches on the outer side from the arches
form a flexuous nerve, which runs parallel with and near to the margin, and
which, by sending branches to the principal arches, forms a sei'ies of subor-
dinate ones ; branches sent off from the primaries and from the midrib
unite under large angles to make a series of meshes irregular in size and
polygonal in form ; these are filled by the ultimate reticulation, which is.
as are all the nerves, sharply defined.

Locality : Fredericksburg ; rare.

This plant, in shape of leaf and nervation, is like some forms of Sapin-
dus. It is much like Lesquereux's Ficus lauropliylla^^ but the primary
nerves are not so strong and the arches are more pronounced.

Ficus Fredeeicksburgensis, sp. nov.

Plate CXLVIII, Figs. 3, 5.

Leaves of medium size, oblong or elliptical, subacute ; midnerve very
strong ; primary nerves rather strong, leaving the midnerve alternately at
an angle of about 45°, at regular and nearly equal intervals, arching back-
wards and then forwards until near the margin, where they bend abruptly
forwards, forming arches, by union with the primaries next above ; reticula-
tion not seen.

Locality : Fredericksburg ; rare.

The plant is a good deal like Sapindopsis elliptica, but the nervation is
stronger, and the leaves are larger.

' Cretaceous aud Tertiary Floras, PI. I, Figs. 12, 13.

296 THE POTOMAC OR YOUNGEE MESOZOIC FLORA.

SAPINDOPSIS, gen. no v.

Leaves pinnate, both odd pinnate and abruptly pinnate ; terminal leaves
iisuall}^ move or less united at base ; upper pairs of leaves decurrent, form-
ing a wing on the common stem, the wing lessening in width on the pairs
in descending ; leaves mostly opposite in pairs, sometimes subopposite ;
the lowest pairs lack the wing, and are sometimes short-petioled ; leaves
thick, with dense and often glossy epidermis, elliptical or lancet-shaped,
with a strong prominent midrib, which extends with slight diminution to the
tip of the leaf ; lateral nerves going off at a large angle, and uniting more
or less completely near the margin to form a series of arches ; the lateral
or primary nerves, as seen on the lower side of the leaves, strong and prom-
inent, but on the upper side, owing to the thickness of the leaves, generally
indistinct ; the ultimate reticulation is strong, and forms a series of rather
large, irregular, polygonal meshes.

This genus is a very important one in the strata containing the more
recent types of plants, especially as seen at the two Brooke localities and at
White House. It has furnished an immense number of individuals, forming
at these places the predominant fossils. The upper leaves, perhaps owing
to the presence of the wings, seem to have been very persistent. It is
probable that, normally in all cases, the lowest leaflets on the compound
leaf were petioled, but, perhaps owing to this fact, they are by no means so
commonly found attached to the stems as the upper ones. The leaves are
so much like those of Sapindus that perhaps they might with propriety be
placed in that genus. They seem to be at least ancestral forms of Sapindus.
The leaves of some species seem to be very variable within certain limits.

Sapindopsis coedata, sp. nov.

Plate CXLVII, Fig. 1.

Leaf small, oblong with a subcordate base of thick consistency; mid-
nerve and petiole strong, nervation mostly concealed by the thickness of
the leaves ; primaiy nerves as seen very slender, going off at an angle of
about 45°, and half-way to the margin bending suddenly forward to connect
with the next primaries, sending off at the point of sudden bending a branch
which connects with the next lower primary.

DESOEIPTIOE^ OF THE SPECIES. 297

Locality : Fredericksburg ; very rare.

The thick leaf-substance and the dense glossy epidermis obscure the
nerves. The leaf figured seems to be one of the lower petioled ones, and
apparently presents its lower face uppermost.

Sapindopsis elliptica, sp. nov.

Plate CXLVII, Fig. 3.

Leaves elongate, elliptical, narrowed gradually towards the base and
apex ; midnerve strong and prominent ; primary lateral nerves slender but
distinct, going oif at an angle of about 45°, arching backwards slightly and
then forwards, and then at three-fourths of the distance to the margin ab-
ruptly turned forwards to unite with the next primaries to form a series of
arches which run parallel with the margin and near to it ; intervening minor
nerves leave the midnerve, as do the primaries, and unite mostly with the
middle points of the arches ; ultimate reticulation distinct, composed of pro-
portionally large, irregular, polygonal meshes.

Locality : Fredericksburg ; very rare.

The plant is much like Sapindus in the form of the leaf and in the
nervation. It has some of the features of Ficus lauropliylla^ Lesq.

All the nervation of this plant is slender, but very distinct.

Sapindopsis magnifolia, sp. nov.

Plate CLI, Figs. 2, 3 ; Plate CLII, Figs. 2, 3 ; Plate CLIII, Fig. 2 ; Plate CLIV, Figs. 1, 5 ; Plate

CLV, Fig. 6.

Leaves odd-pinnate, leaf-substance thick and leathery, epidermis thick
and glossy ; leaflets comparatively large, lancet-shaped to elongate-ellip-
tical, subacute, upper pair and terminal leaflet sometimes united for some
distance ; uppermost pair of leaflets mostly decurrent on the lower side by
a broad wing, on the upper side cut away nearly or quite to the midrib,
wings diminishing in width on tlie leaflets in descending, lowest pairs of leaf-
lets short-petioled ; leaflets placed opposite or subopposite in pairs ; mid-
nerve very stout, rounded, and prominent, continuing strong to the tip of
the leaflets; primary nerves comparatively slender, conspicuous only on the
under sides of the leaflets ; the primary nerves go off pinnately at about

' Cretaceous aud Tertiary Floras, PI. I, Figs. 12, 13.

298 THE POTOMAC OE YOUNGBE MESOZOIO FLORA.

au angle of 45°, arcli at first slightly forwards, and then bend strongly for-
wards to form arching nerves, which run for some distance approximately
parallel to the margin, gradually approaching it ; these communicate with
one another by one strong nerve each to form large spaces approximately
pentagonal in form, and by a series of minor nerves, which meet at a large
angle, connect with the midrib and primary nerves to form quadrangular or
subrhombic primary meshes ; the ultimate meshes quadrangular or sub-
rhombic and comparatively distinct.

Localities: 72d mile-post ; bank near Brooke ; White House Bluff.

This plant is very common at all these localities. It, with S. variahilis,
makes up the greater part of the fossils at these places. The plant is much
like 8. variabilis, and may possibly be a large variety of it. The leaves,
however, are uniformly thicker in substance than those of that species.
They show a greater tendency to short, broad forms, and the midnerve con-
tinues remarkably strong to tlie tips of the leaves. The chief cause of se^J-
aration is the nervation, which is quite different from that of S. variabilis,
lacking the distinct connecting marginal and arching nerve seen in that
species. Fragments found indicate leaflets larger than any of those figured.
Plate CLIV, Fig. 5, shows an abnormally short thick leaf It may pos-
sibly be the terminal one, for this is sometimes different from those lower
down. Plate CLII, Fig. 3, gives a pair of large leaves which remind one of
Hymencea, but they are the terminal leaflet of the compound leaf, and one
(the right-hand) lateral leaflet ; the other lateral leaflet on the left-hand
side has been accidentally torn away.

Sapindopsis variabilis, sp. nov.

Plate CLI, Fig. 1 ; Plate CLII, Figs. 1, 4 ; Plate CLIII, Fig. 3 ; Plate CLIV, Figs. 2-4 ; Plate CLV,

Figs. 2-5.

Leaves and leaflets small ; leaflets, especially the upper ones, varying
much in size, shape, and mode of arrangement; leaves odd or abruptly
pinnate ; leaflets narrowly elliptical to lancet-shaped ; leaf-substance leath-
ery and thick, epidermis dense and glossy ; leaflets normally opposite or
subopposite, upper leaflets decurrent normally by a narrow wing, but often
losing these features ; the wing diminishes in width on the pairs descending,

DESCRIPTION OF THE SPECIES. 299

Lintil the lowest pairs are short-petioled ; midrib and nerves as seen on
the under side prominent and sharply defined ; midrib stout at base, but
towards the sunmiit rapidly attenuated ; lateral primary nerves going off
])innately at uniform and nearly equal intervals, proportionally very strong,
at first inclining slightly forwards, and then three-fourths of the distance
to the margin bending abruptly forwards at nearly a right angle, to form a
bow-shaped, strong nerve, which connects with the next primary at the
angle made by it, thus forming a series of arches ; this marginal nerve and
the primaries send off nearly at right angles a series of branches which are
proportionally very strong and distinct, forming the primary reticulation.
They unite nearly at right angles, and form four to six sided primary meshes;
the ultimate meshes are of the same general character, but smaller.

Localities: 72d mile-post ; bank near Brooke ; White House Bluff.

This is the most abundant angiosperm at the last-named locality. It
is very common at the two Brooke localities, but is not so abundant there
as S. magnifolia. This plant is very variable, and shows a curious fluctua-
tion between odd and abruptly pinnate leaves and an alternate or opposite
arrangement of the leaflets, as if the habit of the plant was not yet fixed.
Plate CLII, Figs. 1, 4, seems to give the normal mode of arrangement of
the leaves ; i, e , they are odd-pinnate, with the lower leaves in pairs. In
none of the species, however, does the odd or abruptly pinnate mode of
arrangement of the terminal leaves seem to mean anything or to be fixed.

I have given a number of figures of abnormal forms of this plant to
illustrate its variability. PI. CLIV, Fig. 2, shows union of the three
terminal leaves and the decurrence of the two outer or lower ones by
means of a very wide wing. The next lower pair of leaves are narrowly
decurrent and normally paired. Fig. 4 of the same plate shows the
decurrence of the uppermost leaves, but the leaves next below are not
paired, and are unequally winged. The next lower leaf stands alone and
the stem is quite flexuous. Fig. 3 of the same plate shows two terminal
leaves united and decurrent to the next lower one on the left-hand side,
which is single, and uniting with it at base. On the right-hand side the
terminal leaf on that side is decurrent to the paired leaves below, with
which, however, it does not unite. PI. CLV, Fig. 4, shows a terminal

300 THE POTOMAC OE YOUNGER MESOZOIC FLOEA.

decurrent pair, and the following ones lower down, widely separated, and
alternate. PI. CLIII, Fig. 3, shows what seems to be the base of the
common petiole, and it looks as if it were clasping. This figure, however,
has the abnormal character of possessing only three leaves and all of them
terminal, the only case of the kind seen.

Sapindopsis parvifolia, sp. nov.

Plate CLIV, Fig. G.

Leaves and leaflets very small, leaves odd-pinnate; terminal leaflet
much larger than tlie others, united with the right-hand next lower leaflet;
uppermost leaflets subopposite, long-decurrent, united by a narrow wing
with the pair next below; second pair from the top subopposite, slightly
decurrent, not reaching to the next pair ; last or third pair subpetioled ;
midnerves comparatively strong, other nervation not seen ; leaves elliptical
in shape, subacute, with the lamina of the leaf cut away obliquely on the
upper side; leaf-substance thick and leathery.

Localities: 72d mile-post; bank hear Brooke; White House Bluff;
rare.

This may be only a small form of S. variahilis.

Sapindopsis brevifolia, sp. nov.

Plate CLIII, I'ig. 4 ; Plate CLV, Figs. 1, 7; Plate CLXIII, Fig. 3.

Leaves odd-pinnate, terminal leaflet usually the largest ; leaf-substance
thick and leathery, obscuring the nerves ; terminal leaflet oval or elliptical,
sometimes slightly inequilateral, very wide in proportion to length ; lower
paired leaflets elliptical in shape, very short in proportion to the width,
sometimes slightly falcate, subacute or obtuse; upper pair cut away
obliquely on the upper side nearly or quite to the midrib, decurrent on
the lower side, or subpetioled ; midnerve strong, lateral nerves not fully
shown ; the primaries are pinnately arranged, go off at equal intervals, and
arch slightly forward, the lower portions alone being seen.

Localities: 72d mile-post ; bank near Brooke ; rare.

This plant shows some variation, but not enough to cause a separation
into distinct species. In PI. CLXIII, Fig. 3, the terminal leaflets, all that

DESCEIPTION OP THE SPECIES. 301

were seen, are closely ci-owded, so that the lateral ones overlap the terminal
one ; the leaves ai-e elliptical, and the nerves ai-e stronger than in any of
the other specimens. In PI. CLIII, Fig. 4, and PI. CLV, Fig. 7, the
terminal leaflet is distinctly petioled and comparatively remote from the
lower ones, which also are furnished with petioles. This seems to be quite
a distinct species from the preceding.

Sapindopsis tenuinervis, sp. nov.

Plate CLIII, Fig. 1.

Leaves odd-pinnate, summits of the leaflets not seen, but they are appar-
ently of considerable size ; leaflets narrowed gradually at their bases, more
so in the lower ones, which are wedge-shaped at base, and the lowest pair
petioled; uppermost pair of leaflets slightly united to the terminal one,
and this latter larger than the others and less narrowed at base ; uppermost
leaflets cut away obliquely at base on the upper side nearly to the midrib,
decurrent on the lower side, with a narrowing wing to the next pair, but
not uniting with it ; next lower pair very slightly decurrent, and wedge-
shaped at base ; leaflets quite remote, the leaf-substance thick and leathery;
epidermis firm and glossy ; midnerves comparatively slender; lateral primary
nerves slender ; the lowest primary nerves go off" very obliquely and run
approximately parallel with the margin for some distance ; succeeding pri-
maries go off at more obtuse angles until towards the middle of the leaflet
they go off at right angles ; towards the margins of the leaflet they bend
abruptly forwards and connect with the next higher primaries, forming a
series of arches ; intermediate subordinate nerves go off from the midnerve,
and send off branches which anastomose with branches from the primaries,
forming finally an ultimate reticulation mostly subrhonibic in shape ; ner-
vation all quite slender and the reticulation lax.

Localities: 72d mile-post; bank near Brooke ; not uncommon.

This plant seems to be quite a distinct species.

Sapindopsis obtusifolia, sp. nov.

Plate CLVI, Fig. 13 ; Plate CLIX, Figs. 3-6.

Leaf-substance very thick ; leaflets glossy, oblong, i-ounded, and very
obtuse at the tips, often slightl}' inequilateral, that is, the midnerve does

302 THE POTOMAC OR YOUNGEK MESOZOIC FLORA.

not divide the leaves exactly in half; midnerve stout, rigid, and rounded;
lateral primary nerves very slender, not fully disclosed, going off at small
intervals from the midrib at an angle of about 45°, arching slightly forward
to near the margin, and then abruptly bending forwards to connect with the
next primary at rts sudden bend, the connecting nerves forming a marginal
one ; ultimate reticulation not made out.

Localities : Deep Bottom ; 72d mile-post, near Brooke ; not very rare
at the latter place.

SALICIPHYLLUM, gen. nov.

I group under this liead a number of leaves imperfectly preserved and
of doubtful affinity owing to tlie poor preservation of the nerves. In the
nervation, so far as it could be made out, and in the sliape of the leaves,
they appear to be nearer Salix than any other genus. The leaves may be
described as elongate-elliptical in outline, with midnerves strong at base
and much attenuated towards the summit ; lateral nerves slender, the pri-
maries going off very obliquely and curving strongly towards the summit
of the leaf, continuing apjDroximately parallel with the margin, but grad-
ually approaching it.

This genus has furnished a considerable element to the Potomac flora,
the plants being chiefl}^ found in the strata showing the flora with more
recent aspects.

Saliciphyllum longifolium, sp. nov.

Plate CL, Fig. 12.

Leaves small, oblong elliptical, very long in proportion to their wddth,
summit not seen, gradually narrowed towards the base ; midnerve towards
the base very strong, attenuated above ; lateral nerves slender ; primary
nerves going off at an acute angle, inclining forward to near the mai-gin,
then abruptly bent forward to form an arch which is approximately parallel
with the margin, this connecting with the next primary above at the point
where it suddenly bends ; the successive arches make a continuous sinuous
marginal nerve, which is as strong as the primaries connected by it ; inter-
calated subordinate nerves from the midrib send off branches which unite

DESCRIPTION OP THE SPECIES. 303

with those of the primaries, and finally form the ultimate meshes, which are
irregular in form and size, quite large, and mostly subrhombic in form.

Locality: Road-side near Potomac Run; very rare.

The shape and nervation of this leaf remind one strongly of Salix.
It has also a good deal of likeness to Persoonia daplinoides.

Saliciphyllum ellipticum, sp. nov.

Plate CXLVI, Figs. 2, 4; Plate CL, Fig. 8; Plate CLXIII, Fig. 5; Plate CLXVI, Fig. 2.

Leaves elliptical in outline, small, broad in proportion to their length,
narrowed gradually at the base and summit, acute; midnerve strong at
base and attenuated at the summit; primary lateral nerves going off at a
very acute angle, arching strongly forwards; ultimate nervation not seen.

Locahties: Fishing hut above Dutch Gap Canal; Fredericksburg; 72d
mile-post, near Brooke; rare.

Angiosperms are very rare at the fishing hut above Dutch Gap Canal.
This fossil is the most common of those at this place. The leaf-substance
appears to have been quite thick, and so was the epidermis, so that this
latter was quite durable. It was owing to this character of the leaf that
the finer nervation was concealed.

Saliciphyllum parvifolium, sp. nov.

Plate CLXXII, Fig. 5.

Leaf very small, broadly elliptical, acute, narrowed at base and apex ;
petiole proportionally very strong, expanded below with a wing as if due
to stipules or to a clasping mode of attachment ; midnerve very slender,
lateral nerves going off very obliquely and curving upwards, only par-
tially seen ; ultimate reticulation not seen.

Locality: Covington street, Baltimore; found in only one specimen.

CELASTROPHYLLUM (Etting sp.).

Leaves small, elliptical in shape, margins toothed or entire ; midnerves
slender; primary nerves very slender, going off obliquely and pinnatel}^,
curving up towards the apex, connected by comparatively strong nerves.

304 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

which run nearly at right angles with the connected nerves, forming an
irregular, slender, lax reticulation ; ultimate reticulation not seen ; leaf-sub-
stance mostly thin.

Under the head of CclastropliyUum I group a number of small leaves,
which mostly have the nervation too slender and poorly preserved to enable
one to fix the character with any definiteness. The placing of these in a
group based on affinities with the Celastrincce is of course, under such cir-
cumstances, only provisional. On the whole, the general character of
these leaves is nearer to Celastrus than to any other living plant. They
form a considerable element in the Potomac flora, although no species fur-
nishes, so far as found, any great number of individuals.

Celasteophyllum aecinerve, sp. nov.

Plate CXLVI, Fig. 3.

Shape of leaf not seen, probably oval or elliptical ; midnerve compara-
tively strong ; leaf-substance thin ; primary nerves very slender but com-
paratively distinct, going off at an acute angle and curving strongly upwards
towards the tip of the leaf, running for a long distance parallel to one
another, and gradually nearing the margin, bent into a series of bow-
shaped arches, which are connected by a regular series of cross-bars or
nerves, going off nearly at right angles and forming a series of large pen-
tagonal meshes filled by small nearly rectangular meshes ; the ultimate
reticulation formed of mainly pentagonal or hexagonal meshes.

Locality : Fredericksburg ; very rare.

This plant differs in some points of the nervation from the others
grouped under the head of Celastropliyllum, except perhaps C. latifoUum, to
be described later. It is on the whole considerably like Celastrus trigyniis,
and also resembles C. ruher.

Celastrophtllum peoteoides, sp. nov.

Plate CXLVI, Fig. 5.

Leaf small, elongate-elliptical, narrowed gradually to the base into the
petiole; leaf-substance thin; no nerves seen; they must be very slender.
Locality : Fishing hut above Dutch Gap Canal.

DESOEirTION OF THE SPECIES. 305

Only one specimen was found. The leaf is too imperfectly shown to
enable its character to be made out. It may be compared with Celastrus
Senegalensis.

Celastrophyllum acutidens.

Plate CLVI, Fig. 8.

Leaves small, narrowly-elliptical ; leaf-substance comparatively thick ;
mai'gins with acute, shallow, and small teeth, that are curved forwards ;
midnerve proportionally quite strong ; lateral nerves very slender, going
off at an angle of about 45°, curving forwards and forking dichotomously,
very poorly disclosed; reticulation not seen.

Locality: 72d mile-post, near Brooke; very rare.

This plant looks something like a Banksia in its toothing and in the
shape of the leaf.

Celastrophyllum obtusidens, sp. nov.

Plate CLVI, Fig. 5.

Leaves rather large, with a comparatively thick and firm leaf-substance,
apparently elliptical in shape, having on the margins of the leaves shallow,
obtusely-rounded teeth, turned outwards and very closely placed ; mid-
nerve proportionally quite thick ; primary nerves very slender, going off
obliquely and curving forwards, the bases only being seen ; ultimate ner-
vation not visible.

Locality : 72d mile-post, near Brooke ; quite rare.

This plant also resembles Banksia in the peculiar teeth and the very
slender primary nervation. The teeth have been accidentally removed,
except at the summit of the leaf It is close to C. acutidens, and may be a
variety of it.

Celastrophyllum Brookense, sp. nov.

Plate CLVIII, Fig. 8; Plate CLIX, Fig. 7.

Leaves of medium size, varying considerably in dimensions, narrowed

towards the base, so as to give them a wedge-shaped form, swelling rapidly

out in the middle to a broad elliptical shape ; towards the summit narrowed

rapidly and prolonged to a point probably ; midnerve very distinct, lateral

MON XV 20

306 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

primaries going off at equal intervals, very strongly curved upwards ; minor
nerves not seen ; leaf-substance thick.

Locality : 72d mile post ; not very rare.

This plant is a good deal like Euonymus glaber.

Celastrophyllum denticulatum, sp. nov.

Plate CLXIX, Fig. 10; Plate CLXXII, Fig. 7.

Leaf very small, elliptical to ovate in shape, acute ; margins minutely
dentate; midnerve slender, lateral nerves going off obliquely and curving
up, very slender, lower ones more oblique and arching more strongly than
the upper ones ; ultimate nervation not seen.

Locality : Covington street, Baltimore ; very rare.

Celastrophyllum latifolium, sp. nov.

Plate CLXSII, Figs. :5, 6 ; Plaie CLXXIII, Fig. 13.

Leaves very small, broadly elliptical to nearly orbicular, obtuse at
summit, flared out in the middle, narrowed to the base ; leaf-substance very
thin ; midnerve slender, attenuated towards the summit ; lateral nerves very
slender, going off very obliquely, and curving in a circular manner towards
the tip of the leaf, opposite, connected by transverse nerves, that go off
nearly at right angles and make quadrangular subrhombic meshes ; ultimate
reticulation not seen.

Localities : Belt and Covington streets, Baltimore.

These leaves are quite common at the Baltimore localities. In shape
and nervation they are much like the living plant Celastrus nutans. The
leaf given in PI. CLXXIII, Fig. 13, is a good deal like G. arcinerve in the
peculiar nervation, but it is smaller and more delicate.

Celastrophyllum tenuinerve, sp. nov.

Plate CLXXII, Fig. 2.

Leaf very small, probably orbicular in shape, rounded abruptly at base;
midnerve comparatively strong ; primary nerves imperfectly shown, very
slender, going off at rather a large angle, tending outwards and then up-

DESCRIPTION OF THE SrEOlBS. 307

wards, branching apparently in a dichotomous manner ; ultimate reticula-
tion not seen ; leaf-substance very thin.

Locality : Covington street, Baltimore ; very rare.

Celasteophyllum obovatum, sp. nov.

Plate CLXXII, Figs. 9, 10.

Leaf-substance very thin ; leaves small, rounded, and very obtuse at
summit, narrowed gradually to the base, obovate in shape ; midnerve strong
at base, much attenuated towards the summit ; lateral nerves very slender,
going off very obliquely and curving around towards the summit, flexuous
in their course and sending off obliquely branches which connect either
with other brandies or with the primaries, forming large, elongate, subrhom-
bic meshes ; ultimate nervation not seen.

Localities : Belt and Covington streets, Baltimore ; not uncommon.

This leaf is much like that of Euonytmis frigidus. It is also like that
of Celastrus ohovatus, but the nervation is different.

QUERCOPHYLLUM, gen. nov.

Leaves small, wedge-shaped at base ; leaf-substance thick, with strong
ovate teeth directed forwards ; midnerve strong at base, rapidly attenuated
above ; lateral or primary nerves sometimes slender, going off very obliquely
and curving forwards, forking dichotomously ; ultimate nervation not seen.

The leaves placed in this genus, from their affinity with Quercus, are
rare and unimportant, since they play but a very small part in the Potomac
flora. The amount of material found is too small, and the degree of pres-
ervation too poor, to permit their character to be definitely fixed.

QUERCOPHYLLUM GROSSEDENTATUM, Sp. nOV.
Plate CLVI, Fig. 9.

Leaf small, entire shape not shown ; margin furnished with very large
ovate, acute, unequal teeth, that are turned upwards ; midnerve quite strong
towards the base, much attenuated above, and splitting up into the primary
nerves ; primary nerves subopposite, strong at base, forking dichotomously.

Locality : 72d mile post, near Brooke ; found in only one specimen.

308 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

QUERCOPHYLLUM TENUINERVE, Sp. IIOV.
Plate CXLIX, Figs. 6, 7.

Leaves elliptical, narrowed towards the apex and base, wedge-shaped
at base ; margins beginning some distance from the base, serrate-toothed,
with the teeth directed forwards ; midnerve strong towards the base ; pri-
mary nerves very slender, going off at a very acute angle, and arching for-
wards to end in the teeth, sending off obliquely on each side alternate, very
slender, subordinate nerves; ultimate reticulation not seen.

Locality: Fredericksburg; quite rare.

VITIPHYLLUM (Cissites?), gen. nov.

Leaves small, approximately fan-shaped, cut to different depths into
obtuse, flabellately arranged lobes of varying shapes and size ; nerves
mostly radiating from the top of the petiole, the main ones generally three
in number, the middle one being the strongest ; petioles very long and
comparatively stout. The leaves, which I group under this head from their
general resemblance to Vitis, form a very considerable element in the Poto-
mac flora as found in the beds at Baltimore. They are abundant there and
are the most common plants at that locality. They have most affinity with
some of the fossils described by authors under the name Cissites.

VlTIPHYLLUM CEASSIFOLIUM, Sp. noV.
Plate CL, Figs. 9, 10.

Form of leaves not made out, as only segments were seen ; principal
segments of comparatively large size, incised obliquely into oblong-obtuse
lobes, which in turn are notched at the summit to form two or three shal-
low obtuse lobes ; nerves going off obliquely one into each main lobe,
slender and imperfectly shown, only one branch seen in each lobe ; leaf-
substance veiy thick ; ultimate nervation not seen.

Locality: Road-side near Potomac Run; very rare.

The specimens shown in Figs. 9, 10, seem to be fragments of pi'inci-
pal or primary segments of the leaf, probably the middle one.

DESGEIPTION OF THE SPECIES. 309

VlTIPHYLLUM PARVIFOI>IUM, sp. nOV.
Plate CLXXn, Figs. 11, 12.

Leaves very small, arranged alternately and rather remotely on very
long and proportionally stout petioles, more or less fan-shaped, quite varia-
ble in form and size, cut down to near the base into three main lobes, and
these subdivided again towards the summit into lobes or teeth, which
diverge slightly; primary nerves three, radiating from the summit of the
petiole, the middle one being the strongest, each going into a main lobe ;
the primary nerves send off obliquely branches which go into the subordi-
nate lobes or teeth.

Localities : Belt and Covington streets, Baltimore ; rare.

This is a very peculiar Cissus-Hke leaf, which in some of its forms is
not unlike Synaphcea polymorpha R. Br.

VlTIPHYLLUM MULTIFIDUM, Sp. UOV.
Plate CLXXIII, Figs. 1-9.

Leaves small, varying a good deal in size and shape, broadly fan-
shaped to subrotundate, more or less heart-shaped at base, cut generally
pretty deeply into three principal lobes separated by sinuses that turn
slightly outwards ; these in turn are subdivided variously ; in the larger
leaves they are cut into subordinate lobes that are like the principal ones,
Init are cut less deeply ; the larger lobes terminate in shallow lobes or
teeth that are mostly bluntly rounded off or emarginate ; primary nerves
normally radiating flabellately from near the base of the leaf and going
into the principal lobes, the lowest ones being smallest and increasing
inwards to the central one, which is the largest ; the primaries sending off
obliquely branches on each side which go into the ultimate lobes and teeth;
reticulation not seen ; leaf-substance quite thick ; petiole very long and
proportionally quite stout.

Localities: Belt and Covington streets, Baltimore; very common.

This plant is the most common angiosperm at the two Baltimore local-
ities. Some of the leaves must have attained proportionally a considerable

310 THE POTOMAC OE YOUNGER MESOZOIO FLORA.

size, as indicated by PL CLXXTII, Fig. 2. Tliat shown in Fig. 5 of the
same plate seems in lobing and nervation somewhat different from the
others.

MYRICA L.

The genus Myrica is represented in the Potomac flora by only one
doubtful species, and this is exceedingly rare.

Mykica Brookensis, sp. nov.

Plate CL, Fig. 11 ; Plate CLVI, Fig. 10.

Leaves quite small, elliptical in outline, acute, narrowed to the base,
pinnate, margins beginning a little above the base, serrated with small
acute teeth directed forwards; petiole quite short; midrib rather stout at
base, much and rapidly attenuated above ; primary nerves slender, leaving
the midrib obliquely curving upwards and following the margins for some
distance, connected with one another by nerves that go off nearly at right
angles ; ultimate nerves not seen.

Locality: 72d mile-post, near Brooke ; very rare.

BOMBAX L.

This genus also has one doubtful and veiy sparingly developed
species. The leaf placed in this genus occurs very rarely.

BoMBAX ViEGINIENSIS, Sp. nOV.
Plate CLI, Fig. 4.

Leaf small, oblong, tip not seen, elliptically rounded at base ; mid-
nerve slender ; jjetiole long, slender, and curved to one side, both distinct
and prominent ; leaf-substance thick and leathery ; lateral primary nerves
going off nearly at right angles, forking about midway in the leaf, sending
nerves backwards and forwards, which unite to form pentagonal spaces,
from the angles of which branches go off nearly perpendicularly towards
the margins.

DESCRIPTION OF THE SPECIES. 311

Locality: 72d mile-post, near Brooke ; very rare.
This plant resembles Velenovsky's Bombax argillaceum} It also resem-
bles in some points Sajpindopsis.

POPULOPHYLLUM, gen. nov. •

Leaves rotundate ; petiole thick and apparently somewhat succulent ;
nerves tending to a radiate grouping from the summit of the petiole; mid-
nerve not much surpassing in strength the nerves which go off on each side
of it.

The leaves, which I place in this genus from their resemblance to Pop-
ulus, are too fragmentary to permit their precise determination. They are
always rare, and form no important element of the flora.

PoPULOPHYLLUM RENIFOBME, Sp. UOV.
Plate CLV, Fig. 9 ; Plate CLVI, Fig. 3.

Leaves small, reniform, margins crenate ; petiole thick and apparently
succulent ; midnerve hardly stronger than the lateral nerves ; primary
nerves radiating from the base of the leaf, forking freely, and anastomosing
to form irregular, elongate, subrhombic, or pentagonal meshes ; leaf-sub-
stance rather thick.

Locality : 72d mile-post, near Brooke ; quite rare.

This plant is like Profecephyllum reniforme, but the margins are slightly
crenate, and it has a more pronounced midnerve. It is a good deal like
Populus retusa,^ Heer, from Cape Lyell.

PoPULOPHYLLUM HEDEE^FOEME, sp. nOV.
Plate CLXVI, Fig. 3.

Leaf angular and polygonal in outline, small, entire shape not seen ;
leaf-substance thick and glossy ; petiole thick and long, apparently some-
what succulent ; no midnerve seen ; primary nerves of nearly equal
strength, radiating from the base of the leaf and forking higher up ; ulti-
mate nervation not seen.

Locality: 72d mile-post ; very rare.

' Die Flor. der bohm. Kreideform., pt. 2, PI. IV, Figs. C-9.

*Flor. Fo88. Arctica, vol. 4, pt. 1, Beitrage zur foss. Flor. Spitzbergens, PI. XIV, Figs. 6, 7.

312 THE POTOMAC OE YOUNGEli MESOZOIC FLORA.

This plant is very much like some species of Populus, especially in its
petiole, which indicates a tremulous leaf.

POPULOPHYLLUM CRASSINEEVE, Sp. nOV.
Plate CLVIII, Fig. 4.

Leaf too fragmentary to make out its .shape, but apparently very
large ; midnerve not much surpassing the size of the lowest primary nerves
that go off on each side of it, and which, apparently with the midrib, radi-
ate from the base of the leaf; the lowest lateral primaries and the mid-
nerve in its upper portion send off very obliquely strong subordinate
nerves, which in turn branch, but the further subdivision could not be fol-
lowed ; the minor nervation not seen.

Locality: Deep Bottom ; very rare.

This leaf differs in the pronounced midnerve and the strong nervation
from the other species of the genus. Possibly it may be a different genus,
but in general character it is most like Populus.

ULMIPHYLLUM, gen. nov.

Leaves too irAperfectly shown in most cases for the shape to be made
out; midnerve comparatively strong, and prominent; lateral or primary
nerves opposite or subopposite, strong, and prominent, proceeding straight
and parallel to near the margin.

The leaves placed under this head belong to only a few species and
furnish but few specimens. They have some of the features of Quercus,
but are on the whole nearer to Uhnus.

Ulmiphyllum Brookense, sp. nov.

Plate CLV, Fig. 8; Plate CLXIII, Fig. 7.

Leaves small, oval in shape, subacute ; margins cut into subacute
shallow teeth that are mostly double; midnerve very strong; lateral
primary nerves going off very obliquely, subopposite, directed upwards,
nearly straight and parallel in their course to the margin, the basal pair
being considerably the strongest and most branched; the primary nerves

DESCRIPTION OP THE SPECIES. 313

send off obliquely on both sides branches, the largest on the lower side ;
ultimate branches sent off nearly at right angles from these and from the
midnerve, which meet under a large angle to form the ultimate reticula-
tion ; this composed of irregular, three to five sided, distinctly marked
meshes i from the base of the lowest primaries on the lower side two strong
lateral nerves go off.

Locality: 72d mile-post, near Brooke; rare.

Ulmiphyllum tenuineevk, sp. nov.

Plate CLVIII, Fig. 1.

The leaf is too fragmentary to make out its shape ; midnerve distinct
but small; lateral primary nerves going oft' at equal and regular intervals, ■
opposite, and oblique, proceeding straight and parallel towards the mar-
gin; branches going off at angles varying from 45° to 90° from the pri-
maries meet and sometimes form a pretty continuous intermediate connect-
ing ultimate nerve ; ultimate reticulation slender, and composed of meshes
that vary much in size and shape, being angular and four to six sided.

Locality : 72d mile-post, near Brooke ; very rare.

The arrangement of the primaries in this species . is much like that in
U. crassinerve, but the ultimate nervation is quite different.

Ulmiphyllum crassinerve, sp. nov.

Plate CLVIII, Figs. 6, 7.

Leaf apparently large, form not made out; midnerve moderately
strong but very distinct ; lateral primary nerves comparatively thick and
very distinct, leaving at an angle of 45°, opposite, going straight and
parallel to the margin; the primary nerves send off at right angles branches
that fork, with the branches diverging widely and anastomosing to form a
very irregular net-work that varies much in size and shape ; the meshes
are mostly elongate, with their largest dimensions perpendicular to the
primaries.

Locality: Deep Bottom ; not very rare.

This leaf is much like Quercus of the Q. faginea type.

314 THE POTOMAC OR YOUNGER MBSOZOIC FLORA.

STERCULIA L.

A g'oocl many of the leaves found in the Potomac flora appear to liave
some affinity with SterciiUa, but only one species seems to be near enough
to the genus to justify its being jjlaced in it.

Stekculia elegans, sp. nov.

Plate CLVII, Fig. 2 ; Plate CLVIII, Figs. 2, 3.

Leaves palmately tripartite, the middle lobe largest, subrhombic in
shape and acute ; lateral lobes elliptical, acute, slightly curved upwards,
with the lower margin towards the base more convex than the upper, so as
to give the basal outline of the leaf a subcordate shape; a strong- midnerve
runs through the middle of each lobe, the tln-ee radiating from the base
of the leaf; subordinate nervation not seen.

Locality : Deep Bottom ; not very rare.

These leaves vary a good deal in size. The base of the leaf has the
outline of some Sassafras. PI. CLVII, Fig. 2, is a restoration of the leaf

ARALIA L.

The genus Aralia, like Sterculia, plays a very unimpoi'tant part in the
Potomac flora, having, if present at all, only one veiy doubtful species.

Aralia dubia, sp. nov.

Plate CLVII, Figs. 1, 7.

Leaf-substance thick ; shape of leaf not made out ; leaf divided for
some distance down into oblong-elliptical lobes, which at tip are subacute
and sometimes prolonged into a mucronate point, each lobe having one or
two midnerves, and from these lateral nerves go off obliquely and remotely
that arch strongly up towards the tips of the lobes, following the margin
in their upper course ; ultimate nervation not seen.

Locality: Deep Bottom ; rare.

PI. CLVII, Fig. 1, seems to represent the upper part of a lobe. In
Fig. 7 tlie leaf seems to have been divided into four or five lobes. The
]-ight-hand segment, containing two midnerves, seems to be the central lobe.

DESCEIPTION OF THE SPECIES. 315

probably dividing higher up. The fragment on the left, partly covered by
the main leaf, appears to be a detached lobe, which is wrinkled from press-
ure. The plant on the whole seems to be nearer to Aralia than to any
other genus, but it is too poorly preserved to permit its character to be
definitely fixed.

JUGLANDIPHYLLUM, gen. nov.

I place under this head a leaf that occurs rarely in the Potomac flora.
Its afiinities are doubtful, but it seems to be nearer to Juglans than to any
other genus. The specific description gives the generic desci'iption also.

JUGLANDIPHYLLUM INTEGEIFOLIUM, sp. nOV.
Plate CLVII, Figs. 3, 5, 6.

Leaves of medium size, bases not seen, tips oval in outline, prolonged
into a tooth-like tip that is turned to one side ; leaf-substance thin ; mid-
nerve strong ; primary lateral nerves sti'ong and very distinct, going off at
regular and equal distances alternately, parallel, arching forward to near
the margin, where they are bent abruptly upwards, gradually approaching
the margin, branches going off at a large angle from these and the mid-
nerve and forking, making by their meeting a set of strong meshes, that are
elongate, subrhombic, varying much in shape and size, and standing mostly
at I'ight angles to the main nerves with their longer dimensions ; these
meshes having sharp angles and very distinct; the ultimate reticulation
(Fig. 6^) strong, being made by nerves which meet nearly at a right angle,
the meshes four to six sided and rotundate.

Localities : Deep Bottom, comparatively common ; White House
Bluff; very rare.

This plant has some of the features of Persea, and in some respects it
resembles some forms of Querciis.

MYRICiEPHYLLUM, gen. nov.

This genus includes plants that stand nearer to Myrica than to any
other, yet are not near enough to be placed in that genus. Generic de-
scription same as the specific description given below.

316 THE POTOMAC OE YOUNGEE MESOZOIC i^^LOEA.

Myeic^phyllum dentatum, sp. nov.

Plate CLVI, Fig. 6.

Leaves small, linear-oblong, base and summit not seen ; margins cut
deeply into acute teeth that are turned forwards and often double ; leaf-
substance thick, leaves quite narrow ; midnerve strong ; primary nervation
not seen.

Locality : 72d mile-post, near Brooke ; very rare.

PLATANOPHYLLUM, gen. nov.

In this genus I place leaves that in general resemble Platanus, but
which can not be certainly placed in that genus. The generic description,
as there is only one species, is essentially the same as that of the species.

Platanophyllum crassinerve, sp. nov.

Plate CLVIII, Fig. 5.

Shape of leaf not seen, leaf apparently quite large ; margins not pre-
served on any specimen; midnerve very strong, especially toward the
base ; basal pair of primaries much stronger than those higher, sending off
on the lower side near the base a strong nerve ; the primaries are arched
strongly upwards and send off branches mainly on the lower side ; branches
going off nearly at right angles connect the primaries, and by forking
freely and anastomosing they form subrhombic elongate meshes that stand
with their longer dimensions nearly at right angles with the primaries.

Locality : Deep Bottom ; very rare.

This plant, in the strong lower basal branches sent off from the lower
primaries, resembles Aralkepliyllum, but they are not so strong as in this
genus. It also vQsemblQS Redera platanoides Lesq.

ARALI^PHYLLUM, gen. nov.

Leaves more or less fan-shaped, divided more or less deeply into three
principal lobes, the middle or terminal one subrhombic or elliptical in out-
line, rapidly narrowed to an acute tip, and separated from the lateral lobes
by broad sinuses rounded at the bottom; the lateral lobes divided into two

DESCRIPTION OF THE SPECIES. 317

minor lobes, one being larger than the other; the larger one ovate, some-
times inequilateral, and turned upwards; the outer or snaaller one is ovate,
and turned outwards; the primary nerves three, radiately diverging from
•the same or nearly the same point at the base of the leaf, going to the sum-
mit of each primary lobe; from the two lateral primaries a strong branch
o-oes off a short distance above the base on the lower side and extends to
the summit of the outer smaller lobes ; all the primaries are strong, and send
off on each side branches which curve up and anastomose ; ultimate reticu-
lation not seen.

These leaves are comprehensive in type and unite some of the charac-
ters of Liquidamher, Aralia, and Sassafras. In their primary nervation they
resemble Sassafras recurvatiim,^ Lesq. The lobing is a good deal like that
of S. platanoides, Lesq.^ The mode of nervation resembles that of Liqiiid-
amher integrifolmm, Lesq.

Arali^phyllum obtusilobum, sp. nov.

Plate CLXIII, Figs. 1, 4 ; Plate CLXIV, Fig. 3.

Leaf-substance thick; leaves rather small, broad fan-shaped in outline,
narrowed rapidly at base into the petiole, with a slight decurrence of the
lamina on the petiole ; petiole comparatively very stout, on entering the
leaf split up into three strong primary nerves, which diverge palmately
to go one into each principal lobe; some distance above the point of diverg-
ence a strong branch is sent out on the lower side of each lateral primary
to go into the outermost and smallest lobes; middle lobes broadly elliptical,
separated from the lateral ones by sinuses that are rounded at base, obtuse
or subacute ; lateral principal lobes ovate, or oblong-obtuse, or subacute ;
sometimes inequilateral and curved slightly upwards ; minor lateral lobes
separated from the main ones by wedge-shaped sinuses turned outwards,
broadly ovate, obtuse, or subacute ; branches of small size go off from the
primaries higher in the leaf in an oblique manner, and curve upwards to-
wards the ends of the lobes.

Locality: 72d mile-post, near Brooke; quite rare.

' Cretaceous aud Tertiary Floras, ix 57 ; Cretaceous Flora, PI. X, Fig. 3.
2 Cretaceous aud Tertiary Floras, PI. VII, Fig.l.

318 THE POTOMAC OK YOUNGEE MESOZOTC FLOEA.

PI. CLXIII, Fig. 1, differs iu several points from PI. CLXIV, Fig. 3,
being more like Ar. acutilohum.

Arali^phyllum acutilobum, sp. nov.

Plate CLXIII, Fig. 2.

Leaves small, broad fan-shaped, rounded off rapidly at base ; leaf-sub-
stance thick ; primary nerves comparatively strong and distinct, the middle
one the strongest, three in number, radiating from the base of the leaf;
leaves cut into three principal lobes ; the middle lobe narrowed at the base,
flared out in the middle, and narrowed again towards the tip so as to be
broadly elliptical in outline, considerably larger than the lateral ones, sep-
arated from the latter by a sinus that is directed outwards and widest at the
base ; main lateral lobes turned at lirst outwards and then curved slightly
upwards, inequilateral, with a very convex outer margin furnished with a
short acute tip, almost mucronate ; these main lateral lobes towards the base
of the leaf incised into an ovate, subacute, short lobe that is turned out-
wards and slightly downwards ; the outer primary nerves, near their base,
send off a strong branch on the lower side that goes into the outermost
small lobe or tooth; reticulation not seen.

Locality: 72d mile-post, near Brooke; ver}^ rare.

This plant is a good deal like the preceding species, but seems to be
distinct from it.

Akali^ephyllum magnifolium, sp. nov.

Plate CLIX, Figs. 9, 10.

Leaf very large, but the specimens found are too fragmentary to make
out the shape ; nerves seen, especially the primaries, very strong : the
primaries, three in number, radiating from the same point at the base of the
leaf, the middle one being the strongest ; the lateral or outermost primaries
send off some distance above their base a strong nerve on the lower side ;
the branches sent off by them higher are not so strong; the arrangement
of these principal nerves indicates that the lobing of the leaf is similar to
that of tlie preceding species.

DESGEIPTION OF THE SPECIES. 319

Locality: 72d mile-post, near Brooke; very rare.

In Fig. 9, in 'the right-hand upper portion of the fragment, at («), we
have apparently a portion of the original sinus and margins of the lobes
preserved, as well as a part of the right lateral main lobe. This shows
that the leaf must have been quite large. In Fig. 10, at (a), in the right-
hand basal portion of the leaf, we have apparently a portion of the original
basal margin, indicating that the lower part of the leaves was shaped like
that portion of the preceding species.

Akali^phyllum aceroides, sp. nov.

Plate CLVI, Fig. 11; Plate CLXII, Fig.2.

Leaf large, approximately fan-shaped, cut pretty deeply into three
large lobes, the lateral ones about lialf-way down to the base cut on the
outer margin into a shallow, acute, tooth-hke lobe, similar to those of
Liriodendron ; the middle and largest lobe not preserved, but apparently
shaped hke that of the other species of the genus — that is, it was broadly
elliptical and flared out in the middle, being narrowed to the base and
summit ; separated from the main lateral lobes by a sinus that is turned
slightly outwards and is broadest at the bottom ; the main lateral lobes
above the tooth-like lobe inequilateral, slightly convex on the upper mar-
gin, with the lower one very convex, turned upwards, and ending in a sub-
acute tip ; three principal strong nerves diverge from the base of the leaf,
one going into each piincipal lobe, the middle one being the strongest; the
two outer lateral primaries send off on their lower side, some distance from
and at the same height above their divergence, a strong branch that curves
upwards to enter the lateral tooth-like lobe; the primaries send off at
points higher smaller branches nearly at right angles, which curve upwards
and branch. The lateral primaries send off on the outer side the largest
branches.

Locality: 72d mile-post, near Brooke; very rare.

This splendid leaf differs in some respects from the previously

described species of Aralkephylhm, more especially in the peculiar shape

and smaller size of the subordinate lateral lobe, but it is so close to them

. in essential points that it cannot be separated and placed in a distinct

320 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

genus. This, more than any other species of the genus, shows a markedly
comprehensive character. The general shape of the leaf and the position
of the lobes remind one strongly of Sassafras. It is also a good deal like
some species of Acer. The small outermost lobes are strikingly like those
of Liriodendron. Its generic affinities are with Aralia.

HYMEN^A L.

The genus Hymencea appears to be represented by one well-character-
ized species, which, however, so far as seen, shows very few individuals.
It should, however, be stated that most of the well-preserved species of
angiosperms from the 72d mile-post, near Brooke, such as those of Sassa-
fras, AralkeplujUum, Hymencea, Menispermites, Iledertephyllum, etc., are ob-
tained from the thin layer of well laminated clay before described. As
nearly all these plants are found nowhere but in this layer, and as the
amount of material obtained from it was very small, the apparent rarity of
these fossils may result solely from this fact, and statements concerning the
abundance of the specimens should be made with this qualification.

Hymen^a Virginiensis, sp. nov.

Plate CLXIII, Fig. 6.

Upper pait of the leaves not seen; towards the base they are narrowed
into an elliptical shape ; leaves in pairs at the sirmmit of the petiole ; pet-
iole very strong ; midnerves of the leaves strong and prominent ; lateral
nerves not seen ; leaf-substance thick ; epidermis thick and glossy ; the
right-hand leaf is considerably larger than the left-hand one ; the midnerves
of the leaves do not run through the centers of the leaves, the outer portion
of the lamina being wider.

Locality : 72d mile-post, near Brooke ; rare.

This plaiit is a good deal like Hymencea jprimif/enia': Saporta, as figured
by Yelenovsky, but the leaves are wider at base.

ACERIPHYLLUM, gen. nov.

This genus is formed to contain a species of comprehensive type wdiich
stands nearer to Acer than to any other, but still differs too much to permit

1 rior. der Tjolim. Kreicleform., pt. 2, PL VI, Fig. 4.

DESOEIPTION OF THE SPECIES. 321

its being united with it. The generic character is the same with that of
the species.

ACEEIPHYLLUM AEALIOIDES, Sp. nOV.
Plate CLTCIII, Fig. 8.

Leaves of medium size, in outline fan-shaped, at base subcordate, lam-
ina of the leaf slightly decuri-ent, cut deeply into three lobes, the lateral
ones slightly overlapping the middle one ; the middle lobe the largest and
prolonged considerably beyond the lateral ones, broadly elliptical, much
narrowed at the base, flared out in the middle and rounded off to a sub-
acute end, separated from the lateral ones by a sinus which is widest at bot-
tom and directed outwards ; lateral lobes ovate-subacute, turned upwards
and slightly outwards ; the upper margin of the lateral lobes convex and
directed outward; the outer margin, in its upper portion, nearly straight
and directed towards the summit of the leaf; the primary nerves, three
in number, the middle one considerably the largest, radiating from the
base of the leaf and going one into each lobe ; they send off alternately
and obliquely branches which curve upwards ; the lateral primaries send
off much stronger branches on the lower than on the upper side, and the
basal one on each side, as in Aralicephyllum, much surpasses the others ;
ultimate reticulation not seen.

Locality: 72d mile-post; very rare.

This elegant leaf is a remarkably comprehensive type, combining
features of Acer, Sterculia, Sassafras', and Aralia. It reminds one strongly
of Aralicephyllum, but lacks the subordinate lateral lobes.

MENISPERMITES Lesq.

This genus, like most of the angiosperms of modern type, has but few
specimens in the Potomac beds ; possibly, as before stated, because the
strata that contain them chiefly have yielded very little material.

Menispermites Vieginiensis, sp. nov.

Plate CLXI, Figs. 1, 2.

Leaves large, orbicular in shape, witli margins undulate or obscurely
crenulate ; leaf-substance moderately thick ; nerves (primary) numerous,
MON XV 21

322 THE POTOMAC OR YOUNGEE MESOZOIC PLOEA.

radiating from a point considerably above the base, principal ones turned
upwards, lesser ones turned outwards, and the smallest turned downwards ;
primary nerves send off branches very obliquely, so that they appear
almost dichotomous; the primary reticulation, formed by branches from
these sent off nearly at right angles, is composed of large, irregularly
shaped meshes, mostly four or five sided, made by the meeting of branches
nearly at a right angle ; the ultimate reticulation is similar but smaller.

LocaHty : 72d mile-post, near Brooke ; very rare.

This fine leaf is a good deal like the living Menispermmn Canadense,
but wants the acute summit of that leaf The base of the fossil is not
shown with sufficient distinctness to make it perfectly clear whether the
leaf is peltate or not. It seems to be deeply auriculate, the auricles over-
lapping largely. It occurs in the same stratum with the fine specimens of
TaxocUum, Brookense, AralicephyUum, Aceriphyllmn, Sassafras, etc.

Menispermites tenuinervis, sp. nov.

Plate CLXXII, Fig. 8.

Leaf small, orbicular in shape, subpeltate ; leaf substance very thick ;
nerves very obscure and slender, only three seen, radiating from a point
some distance above the base of the leaf

Locality : Covington street, Baltimore ; very rare.

This plant looks something like a Lemna. The leaf is much smaller
than that of M. Virginiensis.

ARISTOLOCHI^PHYLLUM, gen. nov.

I place in this genus certain fragments which apparently belonged to
a large, rather coarse leaf, which has a strong likeness in its nervation to
Aristolocliia. The fragments are too imperfect to permit the shape of the
leaf to be made out, but it was apparently similar to that of some species
of this genus.

Aristolochi^phyllum crassinerve, sp. nov.

Plate CLX, Figs. 3-6.

Shape of leaf not seen ; the leaves were apparently large and rather
coarse ; leaf-substance thick ; petiole and primary nerves very strong and

DESOEIPTION OF THE SPECIES. 323

woody ; subordinate nerves strong and cord-like, ultimate reticulation
strong, with the nerves prominent and thread-like ; primary nerves go off
from the midnerve at an angle of about 45°, sweeping around to form
bow-shaped curves ; they send off branches nearly at right angles, which
anastomose to form irregularly shaped, strongly defined meshes filled by
an ultimate reticulation which is very distinct and prominent, formed by
nerves meeting nearly at right angles.

Locality: 72d mile-post, near Brooke; rather common.

This plant has a nervation so prominent and well characterized that a
small bit of it may be readily recognized. The fragments are so much
broken that little idea can be gotten from them of the shape of the leaf.
They occur in the redeposited sand and clay. The fragmentary condition
of the fossils is perhaps partly due to the large size of the leaf. That shown
in Fig. 3 seems to be a fragment from the central portion of the leaf. It
may show a part of the midrib. That shown in Fig. 6 seems to come from
the lower left-hand portion of the leaf, apparently being a portion of a
basal auricle which is pressed against what seems to be a part of the peti-
ole. This part of the leaf seems to have been crushed against the petiole
so as to cause the leaf to double over on itself The great size of the petiole
and that of the primary nerve in this figure indicate that the leaf must have
been very large. Fig. 5 seems to represent a fragment of the midrib, or of
a large primary nerve ; Fig. 4 gives a fragment apparently from a basal
auricle, magnified three diameters to show the nervation.

HEDERJEPHYLLUM, gen. nov.

The two species placed in this genus have the general character of
Hedera, but do not agree with it closely enough to unite them with this
genus. They apparently were but slightly developed, if we may judge
from the few specimens found.

The genus may be characterized as containing leaves of rather small
size, rotundate in form, with nerves radiating from the base of the leaf,
the middle one being the strongest; petioles long and moderately strong;
leaf-substance thick.

324 THE POTOMAC OE YOUNGER MESOZOIC FLOEA.

Hedee^phyllum crenulatum, sp. nov.

Plate CLXII, Fig. 3.

Leaf rather small, probably rotundate, with subcordate base, shape
not fully sho\yn; margms undulate to crenate ; leaf-substance thick; petiole
and lower portion of the midrib comparatively strong; midnerve rapidly
diminishing above ; primary nerves radiating from the top of the petiole,
the middle one the strongest ; on each side of the midnerve, at its base, a
strong lateral nerve goes off and proceeds obliquely upwards to near the
margin ; this sends off from its base a strong, much divided branch, which
turns outwards and downwards ; both this and the main lateral nerve from
which it proceeds forked often, the branches flabellately diverging ; reticu-
lation not seen.

Locality : 72d mile-post, near Brooke ; very rare.

This plant is a good deal like some forms of Pojpuhphjllum^ but the
nervation, although different in some details from the species next to be
described, is essentially the same. In this the branches go off much more
obliquely, and the basal outermost branch is proportionally much larger.
The leaf is much like some of those of Redera Helix.

Hedee^phyllum angulatum, sp. nov.

Plate CLXII, Fig. 1.

Leaf-substance thick and glossy; leaf small, with margins straight,
and at intervals bending abruptly, forming right angles or larger angles
with the former direction, the lower margin nearly at right angles with the
petiole and turning slightly downwards ; shape of the lower part of the
leaf polygonal ; terminal lobe incomplete, so that its shape can not be made
out ; on each side of it a broad tooth or lobe like the lateral one of Lirio-
dendron occurs, separated from the terminal one by a broad sinus, so that
the upper margin of the lateral lobe has a direction nearly at right angles
with the midrib ; petiole long, rather slender, but distinct ; primary nerves
radiating from the top of the petiole at the base of the leaf, in type similar to
that of Aralicephyllmn. There are three primaries ; the middle and principal
one proceeds to the tip of the leaf, and the two lateral ones to the lateral

DESCRIPTION OF THE SPECIES. 325

lobes; these latter sending off from near their base on the outer side two
strong branches, and these and the primaries higher up sending off slender
branches nearly at right angles that anastomose ; reticulation not seen.

Locality : 72d mile-post, near Brooke ; only one specimen seen.

This leaf also belongs to a comprehensive type, but does not combine
the features of so many different leaves as the preceding. It unites the
features of AralicepJiyllum, Hedera, and Liriodendron.

EUCALYPTOPHYLLUM, gen. nov.

This genus contains only one species, whose character, owing to the
scantiness of material and the imperfection of the specimens, cannot be
further characterized than as having a near affinity with Eucalyptus.

EuCALYPTOPHYLLUM OBLONGIFOLIUM, sp. nOV.
Plate CLXII, Fig. 4.

Leaves small, oblong, base and summit not seen ; midnerve compara-
tively strong ; lateral nerves very slender, crowded, going off obliquely,
flexuous, a,nd branching copiously ; the ultimate branches form a closely
crowded reticulation, composed of elongate, subrhombic meshes, that sta)id
nearly at right angles with the midrib ; all the nerves are very slender.

Locality: 72d mile-post, near Brooke; very rare.

This leaf is something like Tristania la.urina, R. Brown.

PHYLLITES Brongn.
Phyllites pachyphyllus, sp. nov.

Plate CXLIX, Fig. 2.

Leaf small, apparently spatulate in shape, flared out a little below the
middle, broad, and rounded at the summit, and gradually narrowed towards
the base ; leaf-substance very thick; midnerve quite strong ; nervation not
seen.

Locality: Fredericksburg; only one specimen found.

This leaf shows no characters that can serve to place it in any par-
ticular genus.

326

THE POTOMAC OR YOUNGEK MESOZOIO PLOEA.

GENERAL REMARKS AND CONCLUSIONS.

The following list gives all the different fossil plants found in the
Potomac formation of which figures and descriptions are given in this
work :

LIST OF POTOMAC FOSSIL PLANTS.

CRYPTOGAMS.

EQUISETE^.

Equisetum L.

Page.

1. E. Virginioum, sp. nov 63

2. E.Lyelli Mantell 65

3. E. Marylandioum, sp. nov 65

3a. Equisetum, sp 65

36. Equisetum, sp 66

FiLICES.

Cladolphlebis Brongn., es parte.

4. C. constricta, sp. nov 68

5. C. latifolia, sp. uov 69

6. C. Virginiensis, sp. nov 70

7. C. dentioulata, sp. nov 71

8. C. falcata, sp. nov 72

9. C. parva, sp. nov 73

10. C. acuta, sp. nov 74

11. C. oblongifolia, sp. nov 74

12. C. orenata, sp. nov 75

13. C. species ? , sp. nov 76

14. C. inclinata, sp. nov 76

15. C. distaus, sp. no v 77

16. C. species ?, sp. nov 77

17. C. alata, sp. nov 77

18. C. species ?, sp. nov 78

19. C. rotundata, sp. nov 78

20. C. sphenopteroides, sp. nov 79

21. C. petiolata, sp. nov 80

22. C. inaequiloba, sp. nov 80

23. C. pachyphylla, sp. nov 80

24. C. brevipennis, sp. nov 81

25. C. species ? , sp. nov 81

Pecopteris Biong.

26. P. Virginiensis, sp. nov 82

27. P. strictinervis, sp. nov 84

28. P. ovatodeutata, sp. nov 85

29. P. microdonta, sp. no v 85

30. P. constricta, sp. nov 86

31. P. brevipennis, sp. nov 86

32. P. socialis Heer 87

33. P. augustipennis, sp. nov 87

34. P. Browniana Danker 88

35. P. pachyphylla, sp. nov 88

Sphenoptekis Brong.

Pago.

36. S. thyrsopteroides, sp. nov 89

37. S. acrodentata, sp. nov 90

38. S. latiloba, sp. nov 90

39. S. Mantelli Brongn 91

40. S. spatulata, sp. nov 93

41. S. pachyphylla, sp. nov 93

ASPIDIUM Sw.

42. A. Fredericksburgense, sp. uov 94

43. A., ellipticum, sp. nov 95

44. A. heterophyllum, sp. nov 96

45. A. Virginioum, sp. nov 97

46. A. angustipinnatum, sp. nov 98

47. A. cystopteroides, sp. nov 99

48. A. Oerstedi Heer 99

49. A. oblongifolium, sp. nov 100

50. A. parvifolium, sp. uov 100

51. A. piunatifidum, sp. nov 101

52. A. Dunkeri Schimper, sp , 101

53. A. dentatum, sp. nov lOi

54. A. macrocarpum, sp. nov 103

55. A. microcarpum, sp. nov 103

POLYPODIUM L.

56. P. fadyenioides, sp. nov 104

57. P. dentatum, sp. no v 105

ACROSTICHUM L.

58. A. crassifolium,sp. nov . 105

AcROSTiCHOPTERis gen. nov.

59. A. longipennis, sp. nov 107

60. A. densifolia, sp. nov 107

61. A. parvifolia, sp. nov 108

62. A. parcelobata, sp. nov , . 108

63. A. cyolopteroides, sp. nov 109

ASPLENIUM L.

64. A. dubium, sp. nov 109

Thinnfeldia Ett. ex parte.

65. T. variabilis, sp. nov 110

66. T. granulata, sp. nov Ill

67. T. rotundiloba, sp. nov Ill

LIST OF POTOMAC FOSSIL PLANTS.

327

Stenopteris Saporta.

Page.

68. S. Virginica, sp. nov 112

Angiopteridium Sohimper.

69. A. auriculatum, sp. nov 113

70. A. nervosum, sp. nov 114

71. A. elliptioum, sp. nov 114

72. A. densinerve, sp. nov 115

73. A. pachyphyllum, sp. nov 115

74. A. ovaCum, sp. nov 115

75. A. striotinerve, sp. nov 116

76. A. striotinerve, var.latifolium, sp. nov. 116

77. A. dentatum, sp. nov , 117

AsPLENiOPTERis, gen. nov.

7S. A. pinnatifida, sp. nov 118

79. A. adiantifolia, sp. nov 118

Gleichenia Sw.

80. G.NordenskiolJi, Heer 119

81. Undetermined fern, sp. nov 119

Thyrsopteris Kunze.

82. T. Virginica, sp.nov 120

83. T. brevifolia, sp. nov 121

84. T. dentata, sp. nov 121

85. T. nervosa, sp. nov 122

86. T. rarinervis, sp. nov 123

87. T. brevipennis, sp. nov 124

88. T. alata, sp. nov 124

89. T. divaricata, sp. nov 125

90. T. Meekiana, sp. nov 125

91. T. Meekiana, var.angustiloba, sp.nov.. 126

92. T. orenata, sp. nov 127

93. T. insignis, sp. nov 127

94. T. insignis, var.angustipennis, sp.nov.. 128

95. T. densifolia, sp. nov 129

96. T. crassinervis, sp. nov 130

97. T. decurrens, sp. nov 130

98. T. angustif olia, sp. nov 131

99. T. microphylla, sp. nov 131

100. T. pachyrachis, sp. nov 132

101. T. elliptica, sp. nov 133

102. T. distans, sp. nov 134

103. T. angustiloba, sp. nov 134

104. T. pachyphylla, sp. nov 135

105. T. pecopteroides, sp. nov , 135

106. T. pinnatifida, sp. nov 136

107. T. heteromorpha, sp. nov 136

108. T. varians, sp. nov 137

109. T. rUombifolia, sp. nov 138

110. T. beteroloba, sp. nov 139

111. T.bella, sp. nov 139

112. T. microloba, sp. nov .•^.. .. 140

Thyrsopteris Kunze — Continued.

Page.

113. T. microloba var. alata, sp. nov 140

114. T. nana, sp. nov 141

115. T. ineequipinnata, sp. nov 142

116. T. heterophylla, sp. nov 142

117. T. obtusiloba, sp. nov 143

118. T. sphenopteroides, sp. nov 143

119. T. squarrosa, sp. nov 143

120. T. rbombiloba, sp. no v 144

121. T. retusa, sp. nov 144

1216. Undetermined fern 145

OSMUNDA L.

122. O. spbenopteroides, sp. nov 145

123. O. Dicksonioides, sp.nov 146

124. O. Dicksonioides, var. latipenms, sp.nov 147

Sagenopteris Pr.

125. S. latifolia, sp. nov 148

126. S. elliptica, sp. nov 149

127. S. Virginiensis, sp. nov 150

ScLEROPTERis Saporta.

128. S. elliptica, sp. nov 151

129. S. elliptica, var. longifolia, sp. nov 152

130. S. Virginica, sp. nov 152

131. S. dentata, sp. nov 153.

Ctenopteris Brongn.

132. C. insignis, sp. nov 156

133. C. Virginiensis, sp. nov 157

134. C. minor, sp. nov 157

135. C. integrifolia, sp. nov 158

136. C. angustifolia, sp. nov 159

137. C. longifolia, sp.nov 1,59

Zamiopsis, gen. nov.

138. Z. pinnatifida, sp. nov 161

139. Z. insignis, sp. nov 162

140. Z. longipennis, sp. nov 164

141. Z. laciniata, sp.nov 164

142. Z. petiolata, sp. nov 166

PHANEROGAMS.
■ GYMNOSPERM^.
ZAMIEiE.

Anomozamites Schimper.

143. A. angustifolius, sp. nov .

144. A. Virginicus, sp. nov . . .

167
168

328

THE POTOMAC OR YOUNGER MESOZOIC FLORA.

Anomozamites (subgenus Platypteki-
GiUiM) Scliimper.

145. P. densinerve, sp. nov . . .

146. P. Bogersianuni, sp. nov

Zamites Brongn., emend.

147. Z. tenuinervis, sp. nov

148. Z. crassinervis, sp. nov ..

149. Z. distantinervis, sp. nov

150. Z. ovalis, sp. uov

151. Z. subfalcatua, sp. nov —
151a. Z. species ?

Page.
1C9
171

171
172
172
173
173
173

NAGEiOPSl.'i, gen. nov. — Continued.

170. N. decrescens, sp. nov

171. N. ovata, sp. nov

172. N. obtusifolia, sp. nov

173. N. iuaequilateralis, sp. nov.

174. N. acuminata, sp. nov

175. N. heterophylla, sp. nov . . .

176. N. microphylla, sp. nov

177. N. angustifolia, sp. nov

178. N. subfalcata, sp. nov

Page.
199
199
200
200
201
201
201
202
203

Encephalaktopsis, gen. nov.

152. E. nervosa, sp. nov

Ctenophyllum Sohimper.

153. C. latifolium, ap. nov

Glossozamites Sohimper.

154. G. distans, sp. nov

Ctenis (Lind. & Hut.) Zigno emend.

155. C. imbricata, sp. nov

PoDOZAMiTES Fr. Braun., emend.

156. P. subfalcatus, sp. nov. ...

157. P. distantinervis, sp. nov .

158. P. pedicellatus, sp. nov . . .

159. P. grandifolius, sp. nov . .

160. P. acutifolius, sp. nov

179
179
180
180
181

DioONiTES Bornem.

161. D. Buchianus Sohimper

162. D. Buohianus, var. obtusifolius, Sohim-

per, sp

163. D. Buchianus, var. angustifolius, Sohim-

per, sp

Tysonia, gen. nov.

164. T. Marylandica, sp. nov

184
184

CONIFERS.
Nageiopsis, gen. nov.

165. N. longifolia, sp. nov 195

166. N. zamioides, sp. nov 196

167. N. reourvata, sp. nov 197

168. N. crassioaulis, sp. nov 198

169. N. latifolia, sp. nov 198

Phyi.locladopsis, gen. nov.

179. P. heterophylla, sp. nov

Feildeniopsis, gen. nov.

180. F. crassinervis, sp. nov

Baieropsis, gen. nov.

181. B. expansa, sp. nov 207

182. B. pluripartita, sp. nov 208

183. B. pluripartita, var. minor, sp. nov 208

184. B. foliosa, sp. uov 209

185. B. deutioulata, sp. nov 210

186. B. deutioulata,var. angustifolia, sp.no V. 210

187. B. longifolia, sp. nov 210

188. B. adiautifolia, sp. nov 211

189. B. adiautifolia, var. minor, sp. nov 212

190. B. macrophylla, sp. nov 212

Baiera F. Braun, emend.

191. B. foliosa, sp. nov 213

Frenelopsis Sohenk.

j 192, F. ramosissinia, sp. nov
182 1 193. F. paroeramosa, sp. nov

Brachyphtllum Brongn. ex parte,
Sohimper.

194. B. crassioaule, sp. uov

195. B. parceramosum, sp. nov.

196. B. species ? (cone)

197. B. species ? (cone)

198. B. species ? (cone)

215
218

221
223
223
224
224

Leptostrobus Heer.

199. L. longifolius, sp. no v 228

200. L. foliosus, sp. nov 230

201. L. ? multiflorus, sp. nov 230

202. L. ? seed (a) species? 231

203. L.? seed (6) species? 231

204. L, ? seed (c) species? 232

LIST OF POTOMAC FOSSIL PLANTS.

329

Laricopsis, gen. uov.

Page.

205. L. longifolia, sp. uov 233

206. L. angustifolia, sp. nov 233

207. L. brevifolia, sp. nov 234

TORREYA Aruott.

208. T. Virgiuica, sp. uov 234

209. T. falcata, sp. nov 235

Cephalotaxopsis, gen. nov.

210. C. magnifolia, sp. uov 236

211. C. ramosa, sp. nov 237

212. C. brevifolia, sp. nov 238

213. C. microphylla, sp. nov 238

Athrotaxopsis, gen. nov.

214. A. grandis, sp. nov 240

215. A. tenuicaulis, sp. nov 241

216. A. espansa, sp. nov 241

217. A. paohyphylla, sp. nov 242

Sequoia Torrey.

218. S. cycadopsis, sp. nov 243

219. S. EeicbenbacM (Geinitz, sp.) Heer. .. 243

220. S. Keicheubachi, var. longifolia, Heer,

sp 244

221. S. subulata Heer 245

222. S. ambigua Heer 245

223. S. rigida Heer 246

224. S. densifolia, sp. nov 246

22.=S. S. gracilis Heer 247

226. S. delicatula, sp. nov 247

227. S. species? 247

228. S. species? 248

229. S. species? 248

Araucaria Juss.

230. A. podocarpoides, sp. nov 249

231. A. obtusifolia, sp. nov 249

232. A. zamioides, sp. nov 250

Taxopium Eiob. (Glyptostrobus Endl.)

233. T. ramosum, sp. nov 251

234. T. Virgiuicum, sp. nov 252

235. T. expansum, sp. nov 252

236. T. fastigiatum, sp. uov 253

237. T. denticnlatum, sp. nov 253

238. T. Brookense, sp. nov 254

239. T. Brookense, var. angustifolium, sp.

nov , 256

Sphenolepidium Heer (Sphenolepsis
Scbenk).

240. S. parceramosum, sp. uov 257

241. S. dentifolium, sp. nov 258

SphenolEpidium Heer (Sphenolepsis
Schenk) — Continued.

Page.

242. S. recur vifolium, sp. nov 258

243. S. pacbypbyllum, sp. nov 259

244. S. virginieum. sp. nov 259

24,5. S. Kurrianum (Dunk.) Heer 260

246. S. Sternbergianum (Dunk, sp.) Heer. .. 261

247. S. Sternbergianum, var. densifolinm,

Heer, sp 261

Abietites.

248. A. macrocarpus, sp. nov 262

249. A. elliptieus, sp. nov 263

250. A. augusticarpus, sp. nov 263

Araucarites Sternb., emend.

251. A. Virginious, sp, nov 263

252. A. Aquiensis, sp. uov 264

Carpolithus Sternb.

253. C. fasciculatus, sp. nov 265

254. C. ternatus, sp. nov 265

255. C. Virginiensis, sp. nov 266

256. C. agglomeratus, sp. nov 267

257. C. coujugatus, sp. nov 267

258. C. geminatus, sp. nov 267

259. C. Brookeusis, sp. nov 268

260. C. latus, sp. nov 269

261. C. curvatus, sp. nov 269

262. C. sessilis, sp. nov 269

263. C. mucronatus, sp. nov 270

Cycadeospermum Saporta.

264. C. acutum, sp. nov 270

265. C. obovatum, sp. nov 270

266. C. spatulatum, sp. uov 271

267. C. ellipticum, sp. nov 271

268. C. rotuudatum, sp. nov 271

269. C. angustum, sp. uov 271

Aments of conifers, etc., species unde-
termined.

270. Male (?) anient (a), species ? 225

271. Male anient (i), species ? 225

272. Male anient (c), species ? 226

273. Male ament {d), species ? 22(1

274. Male ament fe), species? 226

275. Male ament (/) , species ? 227

276. Ament of angiosperni, species? 272

277. Fruit capsules, species? 272

278. Cone of Callitris ? , sp. uov 272

279. Seed of Pinus ? , sp. nov 272

280. Pollen sacs ?, species ? 272

330

THE POTOMAC OE YOUNGER MESOZOIG FLORA.

WlLLIAMSONIA Can.

Page.

281. Williamsouia Virginiensis, sp. nov 273

Undetermined plants.

281a. Macrospores sp 274

282. Undetermined plant (a) 274

283. Undetermined plant (6) 274

284. Undetermined plant (c) 275

285. Undetermined plant (rf) 275

286. Undetermined plant (c) 275

287. Undetermined plant (/) 275

288. Undetermined plant (i;).., 275

289. Undetermined plant (/i) 276

290. Undetermined plant (0 276

ANGIOSPERM^.

CONOSPEKMITES Ett.

291. C. ellipticus, sp. nov 279

ACACLEPHYLLUM, gen. nov.

292. A. lougifolinm, sp. nov 279

293. A. spatulatum, sp. nov 280

294. A. microphyllum, sp. nov 280

295. A. variabile, sp. nov 281

PROTEiEPHYLLUM, gen. nov.

296. P. reniforme, sp. nov 282

297. P. orbiculare, sp. nov 283

298. P.species? 284

299. P. oblongifolium, sp. nov 284

300. P. ovatum, sp. nov 285

301. P. ellipticum, sp. nov 285

302. P. tenninerve, sp. nov 2-6

303. P. dentatum, sp. nov 286

EOGisRSiA, gen. nov.

304. E. longifolia, sp. nov 287

305. E. angustifolia, sp. nov 288

Sassaeras Nees.

306. S.parvifolinm, sp. nov 289

307. S. cretaceumNewb.jSp.var.heterolobum 289

308. S.bilobatum, sp. nov 290

FicoPHYLLUM, gen. nov.

309. F. crassinerve, sj). nov 291

310. F. tenninerve, sp. nov 292

311. F. serratum, sp. nov 294

312. F. eucalyptoides, sp. nov 294

Ficus Tournef.

313. F. Virginiensis, sp. nov 295

314. F. Fredericksburgensis, sp. nov 295

Sapindopsis, gen. nov.

Page.

315. S. cordata, sp. nov 296

316. S. elliptica, sp. nov 297

317. S. magnifolia, sp. nov 297

318. S. variabilis, sp. nov 298

319. S. parvifolia, sp. nov 300

320. S. brevifolia, sp.nov 300

321. S. teuuincrvis, sp. nov 301

322. S. obtusifolia, sp. nov 301

Saliciphyllum, gen. nov.

323. S. longifolium, sp. nov 302

324. S. ellipticum, sp. nov 303

325. S. parvifolium, sp. nov 303

Celastrophyllum Ett.

326. C. arcinerve, sp. nov 304

327. C. proteoides, sp. nov 304

328. C, acutidens, sp. nov 305

329. C. obtusidens, sp. nov 305

330. C. Brookeuse, sp. nov 305

331. C.denticulatum, sp. nov 306

332. C. latifoUum, sp. nov 306

333. C. tenninerve, sp.nov 306

334. C. obovatum, sp. nov 307

QuEKCOPHYLLUM, gen. nov.

335. Q. grossedentatum, sp. nov 307

336. Q. tenninerve, sp. nov 308

ViTiPHYLLUM (Cissites), gen. nov.

337. V. crassifolium, sp. nov 308

338. V. parvifolium, sp. nov 309

339. V. mnltifidum, sp. nov 309

Myrica L.

340. M. Brookensis, sp. nov 310

Bombax L.

341. B. Virginiensis, sp. nov 310

POPULOPHYLLUM, gen. nov.

342. P. reniforme, sp. nov 311

343. P. hederteforme, sp. nov 3H

344. P. crassinerve, sp. nov 312

Ulmiphyllum, gen. nov.

345. U. Brookense, sp. nov 312

346. U. tenninerve, sp. nov 313

347. U. crassinerve, sp. nov 313

GENERAL EBMARKS AND CONCLUSIONS.

331

Sterculia L.

Page.

348. S. elegans, sp. nov 314

Aralia L.

349. A. dubia, sp. nov 314

JUGLANDIPHYLLUM, geu. nOV.

350. J. integrifolium, sp. nov 315

Mykic^phyllum, gen. nov.

351. M. dentatum, sp. nov 316

Platanophyllum, gen. nov.

352. P. orassinerve, sp. nov 316

Arali^phyllum, gen. nov.

353. A. obtusilobnm, sp. nov 317

354. A. acutilobum, sp. nov 318

355. A. magnifolium, sp. nov 318

356. A. aceroidea, sp. nov 319

HY'MEN/EA L.

Page.

357. H. Virginiensis, sp. nov 320

ACERIPHYLLUM, gen. uov.

358. A. aralioides, sp. nov 321

Menispermites Lesq.

359. M. Virginiensis, sp. nov ,

3c 0. M. teuiiinervis, sp. nov

Aristolochi/ephyllum, gen. nov.

361. A. orassinerve, sp. nov

HedeR/Ephyllum, gen. nov.

362. H. crenulatnm, sp. nov

321
322

322

324
324

363. H. angulatuin, sp. nov

Eucalyptophyllum, gen. nov.

364. E. oblongifolium, sp. nov 325

Phyllites, Brongu.

365. P. paohypby Ilus, sp. nov 325

Of these plants a considerable number may be omitted in any compari-
son with other floras, since they do not present any features that can aid
in identification. When, however, these have been omitted, there still re-
main many that are well characterized, and that are largely represented
and widely diffused. These may be taken as characteristic of the flora,
and they should have more weight than any others in determining the age
of the strata which contain them.

Before the examination of the geological relations of the Potomac
flora is undertaken it will be well to define in what sense the names of cer-
tain geological formations, to which frequent reference must be made, will
be taken in this memoir. The two formations which are capable of mis-
conception are the Wealden and Neocomian. By some the Wealden forma-
tion is regarded as an independent group forming the uppermost member
of the Jurassic. Others regard it as a series of beds contemporaneous with
a portion of the lower Neocomiaii, formed in estuaries and marshes at the
time when a portion of tlie typical lower Neocomian, which is marine, was
being deposited in the sea. The latter view is the one assumed in this
memoir.

In this work the Neocomian period is taken as including the Urgonian
and Aptian of D'Orbigny, the former being, when present, the middle

332 THE POTOMAC OR YOUNGER MBSOZOIC FLORA.

member and the latter the upper member of the formation. When, then,
reference is made to Neocomian plants, fossils of the Wealden, Urgonian,
and Aptian groups are included and not distinguished.

In the regions containing Potomac areas the older flora which comes
next to that of the Potomac beds is that described by me in Contributions
to the Knowledge of the older Mesozoic of Virginia (Mon. U. S. Geol.
Survey No. 6). This is Rh?etic in age.

In Virginia, and as far north as the Potomac beds have been traced
and identified, if we except the doubtful location of the trunks of Tysonia
Marylanclka, no plants of any value in determining age have been found
in any Mesozoic strata above the lower Potomac.

But in New Jersey a large number of well-preserved fossil plants have
been collected from the sands and clays that form the lowest member of the
Cretaceous of that State, and which are so largely worked at some localities
for the manufacture of fire-brick and pottery. These plants form the flora
which comes next above that of the lower Potomac beds, and possesses im-
portance in determining geological relations.

The New Jersey fossils are being studied and described by Dr. New-
berry. Until his conclusions are published we must wait for a final deter-
mination of their age. It may, however, be stated here that these fossils
have been generally taken to be of nearly the age of those from the Dakota
group of the United States, or of the Cenomanian of Europe.

The geological relations of the plant-bearing beds of New Jersey and
the upper Potomac, or mottled clay group of Maryland, have not been
determined, but, as has been stated before, these two groups will probably
prove to be of the same age. The two floras then with which that of the
lower Potomac may be compared as next preceding and following it, in the
areas where it is found, are the Rhsetic plants of Virginia and North Caro-
lina, and the probably upper Cretaceous New Jersey flora. The compari-
son with these is important, as showing on the one hand survivors from the
older flora, and on the other hand precursors for the younger.

By the kindness of Dr. Newberry I have been enabled to see a large
number of drawings of the New Jersey plants. They show that the flora
of this formation is totally different from that of the lower Potomac. The

GEOLOGICAL AFFINITIES OF THE POTOMAC PLANTS. 333

difference is much greater than one would expect in the fossils of two for-
mations so near each other in geological age.

All of the numerous remarkable types so characteristic of the Potomac
strata are wanting in the New Jersey Cretaceous. But besides this, in the
New Jersey beds angiosperms constitute much the greater part of the plants.
In the Potomac formation the ferns, cycads, and conifers form much the
greater element in the flora. One is induced to think that in producing
such an entire change in the vegetation some other cause besides the mere
lapse of time must have acted. The alteration is mainly caused by the
very general extinction of the Jurassic types which still survived in the
Potomac flora, and of the warmth-loving plants which existed in it. The
question might be asked, Was this change hastened by the coming on of a
cold period in this region in the interval between the lower Potomac and
the New Jersey Cretaceous 1

GEOLOGICAL AFFINITIES OF THE POTOMAC PLANTS.

In the description of the different species of Potomac plants attention
was called in each case to the known fossils that are identical with or most
nearly allied to the plant being described. It will perhaps be useful to re-
peat in this place these statements, in part at least, and to add such details as
may suggest themselves, in order that we may get a connected view of the
geological relations of the flora. For this purpose I will take up in succes-
sion the different groups of plants, and try to give what may be deduced
from their character.

It might cause error to attempt to determine the age of the flora by
giving percentages of the elements common to the Potomac and known
floras. In many cases particular species are represented by few individu-
als, and these are not well characterized. In other cases, much fewer in
number perhaps, the species may be represented by numerous individuals
which are well characterized and widely diffused. Species of the kind last
mentioned, although much inferior in numbers to the kind first named, ought
to have more weight than these in fixing the character and determining the
age of a flora. Then, again, some species may be merely survivors of an
older flora, or newly introduced precursors or prototypes of forms that
attain their typical character later. These are not of so much value in

334 THE POTOMAC OR YOUNGER MESOZOIG FLORA,

fixing age as species attaining their maximum development in the age in
question.

One of the most noteworthy features of the Potomac flora is the over-
whehning predominance of new species and the proportionally very large
number of peculiar types. It is true that, owing to the absence of the flow-
ers and fruit, we may in many cases fail to place with accuracy the forms
in still living groups ; but still, in a very large number of cases, enough is
shown in the foliage to indicate that it diff"ers in type from that of the plants
of other formations, and in a considerable number of instances the charac-
ter is so remarkable and well defined as not to require any other evidence
to prove the uniqueness of the plants possessing it.

We might explain the remarkable abundance of new forms in the Po-
tomac by assuming, for the region and period possessing this flora, unusual
topographical or climatal features, but this is rendered improbable by the
fact that the flora of the formation possesses a number of species known
from other parts of the world. When we consider the distance that sepa-
rates the countries in which these common species grew their similarity is
surprising.

It is more probable that the peculiarity of the Potomac flora is to be
explained by the fact that it belongs to a period whose land plants have not
been found elsewhere, or if found are poorly represented. As will be seen
later, this conclusion tallies with the deductions to be drawn from an exami-
nation of the individual elements composing the flora. If, as we are led to
think from a study of the plants composing this flora, its ag'e is Neocomian,
then we should expect to find in any large collection of its fossils a great
proportion of new forms ; for the Neocomian, taken the world over, is pre-
dominantly marine, and its land flora is one of the least known.

Taking up now the different groups composing the Potomac flora, we
find the JEquiseta first in order.

EQUISETA.

In passing from the flora of the Rhsetic beds of North Carolina and
Virginia to that of the Potomac, we find a very marked change in the
Equisetaceoe. There is in the Potomac no trace of Schimneura, a group
meagerly represented in the Rhsetic flora in foliage at least.

GEOLOGICAL AFFINITIES OP THE POTOMAC PLANTS. 335

The Equiseta have undergone a significant change, assuming decidedly
more recent features. The Rhsetic equiseta, although few in species, seem
to have attained a very large size and to have lived in vast numbers in cer-
tain conditions of the marshes, hardly any other fossils being found with
them. They were also apparently unbranched. In the Potomac era the
species were small in size, copiously branched, like some living kinds, and
they seemingly no longer, as in the Rhsetic, lived in such immense colonies.
It can hardly be doubted that the mode of occurrence of the specimens of
IS. Virginiciim, at the fishing hut above Dutch Gap Canal, fairly represents
its distribution in life. It seems to have grown sparingly, scattered here
and there in the midst of a vegetation consisting mainly of ferns, cycads,
and conifers, with now and then an angiosperm. At Baltimore i?. Mary-
landicum grew rather abundantly with similar elements, but with a pre-
dominant angiospermous flora. These two, from their comparative abun-
dance, appear to be the most characteristic equiseta of the era. E. Lyelli
is almost wholly confined to Fredericksburg, and from its rarity there
seems to be a survivor from Jurassic times. This is indicated also by its
comparatively large size. While the general character and distribution of
the Potomac equiseta indicate an age decidedly younger than the Rhfetic
and even the Jurassic, the same result would be deduced from an examina-
tion of the two more characteristic species.

Equisetum Virginicum is so near to E. Burchardti Dunk., that it is not
entirely clear that it should be made a distinct species. At least it may be
regarded as a representative of E. Burchardti in America. E. Marylandi-
cum belongs to the same type of small equiseta as E. Virginicum and E.
Burchardti, which, in its copious branching and small size, stands near to
the living species of the genus.

So far, then, as the meager evidence of the Equiseta goes, we would
infer that the age of the Potomac beds is Wealden (i. e., older Neocomian)
or younger.

FEENS.

The evidence of the ferns, if we look to the species alone, is not clear
and positive for any conclusion. A typical Mesozoic or pre-Cretaceous
flora consists almost wholly of four elements. These are ferns, cycads,

336 THE POTOMAC OE YOUNGER MESOZOIO FLORA.

conifers, and eqniseta. In such a flora genei'ally the ferns and conifers
stand first in the number of kinds and of individuals, tlie cycads usually
coming next, and the equiseta last. Were it not for the considerable
angiosperm element in the Potomac flora it would be typical Mesozoic, and
this would be largely due to the great variety and the universal difi"usion
of the ferns. While the number of different kinds of ferns is proportionally
very large, the number of individuals of each kind is, comparatively
speaking, very small. There is also a curious mingling of older and more
recent types, and a i-emarkable localization of many of the species. The
species identified with those of other floras seem to be mainly a few world-
wide and long-lived forms. Many of the older types seem to be survivors
from the Jurassic. The flora of the Cenomanian is quite well known from
a number of widely separated regions. The fact that nearly all of the
ferns of the Potomac are absent from the different Cenomanian floras is
strong evidence that the Potomac flora is older than Cenomanian.

Let us now rapidly examine the evidence to be deduced from the dif-
ferent groups of ferns. Gladophlehis : The ferns placed in the genus Cla-
dophlebis do not, it is true, show fructification, but the plan of their foliage
and nervation is a well-marked one, which is, the world over, very charac-
teristic of Jurassic floras. The great number of species of this type found
in the Potomac flora is certainly significant. In no flora which does not
have strong Jurassic affinities could such a large proportion of the ferns be
of this type. It would seem that the conditions prevailing in Jurassic
times favored the development of this particular kind of foliage, and we
may assume that in the Potomac era these conditions had not wholly passed
away.

The presence of such a large element, having the facies of Cladophkbis,
is entitled to more weight in fixing the geological relations of a flora than
the establishing of the identity or near relationship of a few species in
two widely separated floras. But we are not without confirmatory evi-
dence derived from this source. The species of this genus in the Potomac
flora are probably all new, but some of them differ so little from some of
those occurring in the Rhsetic and Jurassic floras, that they may faii'ly be
taken as survivors and representatives of the older species. For example,

GEOLOGICAL AFFINITIES OF THE POTOMAC PLANTS- 337

C. constricta is very near to Alethopteris cycadina Scheak, from the Weal-
den. C. Virginiensis is perhaps not to be distinguished from Brongniart's
Pecopteris Whithiensis of the Oohte of England, and is very near to Acros-
tichides linncecefoliiis, from the Rhgetic of Virginia. C. deuticulata is much
like Neuropteris ligata, Lindley and Hutton, from the Oolite of England.
Cfalcata is very similar to a large number of Jurassic ferns grouped by
some under the general name JVhithiensis, being in its smaller forms espe-
cially like C. nehbensis Nathorst, from the Rha^tic of Sweden. C. imrva is
very close to C. pseudowMthiensis, from the Ehajtic of Virginia. It is hardly
worth while, however, to trace further the resemblance of the species of
Potomac Cladophlebids to those of other floras.

Pecopteris: The genus Pecopteris, taken simply as a type of foliage
and nervation, has but little value in fixing age, for this group does not
seem to be characteristic of any particular geological period. The genus
is but little developed in the Potomac, and its comparative rarity may
perhaps be taken as evidence, such as it is, of the comparatively recent
age of the beds. But in this genus we are enabled to detect two species
as common to the Potomac and known floras, while several are very close
to previously described plants. The identification of the Potomac frag-
ments with Heer's P. Socialis, from the Atane beds or Middle Cretaceous
of Greenland, does not have much Aveight, as the Potomac fossils are quite
rare and imperfect. The case is diff"erent with P. Broivnianu. This is an
important and characteristic plant in the Wealden of Europe. It is wide-
spread in the Potomac beds, and is largely represented by identical or
nearly allied forms, such as Pecopteris strictinervis and P. constricta, giving,
indeed, a type form. Besides these we have P. Virginiensis, much like P.
denticulata Brong., an Oolitic fossil.

Splienopteris : The genus Sphenopteris, like Pecopteris, taken simply as
a type of foliage and nervation, does not characterize any particular era.
But in the Wealden everywhere there is one particular type of Sphenopteris
which is highly characteristic of that formation. This is the so-called
species Splienopteris Mantelli. The adjective so-called is used because in
my opinion too many probably different plants have been united under
this name, as has been done in the case of Pecopteris Whithiensis. As
MON XV 22

338 THE POTOMAC OR YOUNGER MESOZOIG FLORA.

matters now stand, Splicnopteris MantcUi is the name of a particular
type of foliage and nervation very conuiion in Wealden ferns rather than
the name of a single species. But however this niay he, the evidence
given by the presence of this type of fern is not affected. The existence
in a flora of a large element in the ferns which has the type of S. ManteUi
may be taken as indicating affinities with the Wealden flora.

Now in the Potomac flora not only is S. ManteUi present in beds
which show plants of the most recent facies existing in the formation, but
there is a very important group of ferns which, although placed in the
genus Thyrsopteris, have nearly the nervation and foliage typified in 8.
ManteUi. The g-reat development in the Potomac of ferns of the general
type of (S. ManteUi gives strong evidence of Wealden or somewhat later
age. A somewhat later age than Wealden is indicated, perhaps, as most of
the species are somewhat modified, so as to depart more or less from the
typical S. ManteUi, and to assume the facies of Thyrsopteris. The other
species of Sphenopteris give little help in fixing the age of the Potomac
strata.

Asp)idi'um: The genus Aspiditmiysr o\x\di seem to be, when largely devel-
oped in a flora, a decidedly recent element. The finding of as many as
fourteen species of true Aspidium in the Potomac flora, and the compara-
tively large number of individuals shown by some of these, would, if taken
alone, indicate a very recent age for this flora. There is nothing in the
foliation or in the fi-uctification to make us think that these plants could not
be still living. Aspidium Oerstedi is determined as present, but the identi-
fication is doubtful, as the amount of material found is too small to permit
any sure conclusion. With the exception of A. Dunkeri Schimper, the other
species are peculiar to tlie Potomac formation. Pecopteris Dimkeri Schim-
per, of the Wealden of Europe, seems to be quite characteristic of that for-
mation. It is pretty certainly an Aspidium, as shown by the Potomac
forms. It is a plant of considerable importance in establishing the exist-
ence of Wealden elements in the Potomac flora.

Polypodiiim and AcrosticJmm : These two living genera are probably
sparingly represented in the Potomac flora. Of course, as far as their evi-
dence goes in this flora, they establish relations with living plants rather than

GEOLOGICAL AFFINITIES OF THE POTOMAC PLANTS. 339

with the older pre-Cretaceous floras. But then- presence is not certainly
established, and, if present, their species are too. few and feebly developed
to indicate anything more than a recent introduction.

AcrosticJiopteris seems to be an extinct genus, peculiar to the Potomac
formation. It can then give but little aid in fixing geological age. The
fact, however, that it is extinct probably denotes a comparatively great age
for the formation to which it is confined.

Asplenium: This genus also, if present, is probably to be considered
as a recent element, but newly introduced.

TJiinnfekUa : This genus shows three species; one of them, Thinnfeldia
variabilis, being quite common at the 72d mile-post, near Brooke. The genus
is an old one, characterizing the Rhsetic, and Infra-Lias. The continuance
of this type into the Potomac formation makes an important addition to the
older elements of the flora. The species, although not capable of identifi-
cation with any of those of the older floras, must be regarded as survivors.

Stenopteris: This genus is doubtfully present. It is too rare and too
imperfectly preserved to be of use if present. It is one of the still linger-
ing Jurassic types, now almost extinct.

Angiopteridium : This is a more valuable genus in throwing light on
the age of the flora containing it. The absence of fructification in the
Potomac plants, however, renders it impossible to say positively whether
or not these forms are really Angiopteridium ; but it is at least clear that
large ferns with this type of foliage are more characteristic of the older
Mesozoic formations than of the later ones. While the number of indi-
viduals of any particular species is very small, yet the number of species
is surprisingly large, and the genus adds much to the archaic facies of the
flora. This is one of the groups which does not appear to go up into the
Cenomanian flora, and hence, like CladopMebis, it must be regarded as a
still surviving older element.

Gleichenia: This genus, which, as Heer has shown, is so largely rep-
resented in the older Cretaceous of the northern part of the American con-
tinent, shows a surprising deficiency in forms in the Potomac flora.

Aspleniopteris : This is an extinct form peculiar to the Potomac beds,
and for that reason it can give us little help in determining the age of the

310 THE POTOMAC OR YOUNGEE MESOZOIO FLORA.

Potomac by a comparison of its plants with known floras. Its extinction
indicates a considerable antiquity for the Potomac strata.

Thyrsopteris : What was said of CladopJilebis may in the main be
repeated for this genus. It is true that, as no fructification has been found
on these ferns, they may be incorrectly placed in the genus Tliyrsopteris. ,
Still, the very great development in the Potomac flora of ferns with a
foliage and nervation so characteristic of the later Jurassic and Lower Cre-
taceous can not be without significance. This type of fern is much the
most common in the Potomac strata. The species, most of them w^ell char-
acterized, number forty. They are distributed over the whole of the Poto-
mac area, and a number of them are among the most common ferns at the
localities yielding them. This group, more than any other, tends to give a
]\Iesozoic facies to the Potomac flora. They have almost oi- quite passed
away in the interval between the time of the deposition of the lower Poto-
mac and that of the oldest Cretaceous of New Jersey. Their absence in
the flora of the latter group greatly adds to the comparatively recent
aspect of this latter.

A number of these Thyrsopterids have the same type of foliage as the
Wealden ferns, Splmiopteris Mantelli Brongn.; S. Gapperti Dunker; 8. cor-
dal Schenk ; 8. plurinervia Heer ; and 8. Gomesiana Heer, as well as the
Urgonian plants Asplenium JDicksonianum Heer; A. Nauckhoffiamim Heer,
and various Dkhsonias, such as JD. Jolmstrupi Heer. It is a significant fact
that this type of foliage, so common towards the close of the Jurassic and
in the oldest Cretaceous, is the most abundant single type in the Potomac
strata also. Such a general prevalence of a type is more significant of
geological relationship than the identification of a few species common to
two formations. It is not worth while to examine in detail the affinities of
the difi'erent species. Most of them are new and unique. One or two
have some resemblance to Oolitic species, while a greater number may
be grouped as belonging to the two Wealden types 8. Mantelli and 8
Gcejjpjerti.

Osmunda: The plants placed in the genus Osmunda, although not
numerous in species, are very common at the Potomac Run locality.
They quite possibly differ somewhat from true Osmundas, the genus not

GEOLOGICAL AFFmiTlBS OF THE POTOMAC PLANTS. 341

Ijeing fully differentiated. If so, this genus can not be used in determining
the age of the strata. It would simply indicate for them a very consider-
able antiquity.

Sagenopteris : This is a well-marked genus, not easily mistaken for any
other, and hence it is valuable in determining age. It has such a wide range
in time, however, that it will not enable us to fix within narrow limits the
iiorizon of the beds containing it. It appears to extend from the Rhsetic
into the lower Cretaceous or Neocomian, surviving in the Neocomian of
Westphalia.

Sderopteris : This genus is well characterized, so that it is readily
detected. It has a considerable number of species in the Potomac beds,
although none of them are anywhere common. This group of plants
o-ives to the Potomac flora one of its most important Jurassic elements, for
this type is eminently characteristic of the later Jurassic. It must be
regarded as a survivor in the Potomac, coming down from an older flora.

Ctenopteris : This genus has, so far as the question of age is concerned,
very nearly the same significance as Sderopteris, being Jurassic. But the
Ctenopterids of the Potomac appear .to be modified descendants of the
forms found in the older floras. They do not necessarily imply an age as
gi-eat as even that of the Oolite, and it should be noted that some of them
much resemble Heer's genus Ctenidium, found in the "Wealden of Portugal.
There is nothing in the general character of these Potomac plants that
would make it improbable that they occur in the older Neocomian.

Zamiopsis : This is a remarkable type, peculiar, so far as known, to
the Potomac. It can not help us in determining the question of age.
This genus appears in some points to be allied with Ctenopteris, for it has
the same curious union of the characters of ferns and cycads.

CYCADS.

The comparatively large number of cycads in the Potomac strata
does much to separate the flora of this formation from that of the Ceno-
manian, and to increase in it the resemblance to the typical Mesozoic or
Jurassic flora. They indicate that in the Potomac tropical conditions still
prevailed to a considerable extent. Cycads are rare after the Neocomian

342 THE POTOMAC OE YOUNGEE MESOZOIC FLORA.

in the fossil floras of countries now possessing a cool temperate climate.
We are, then, from a consideration of the family as a whole, entitled to
hold that the Potomac flora can not be later than Neocomian in age. The
character and the degree of development of the particular genera and
species point unmistakably to the Neocomian as the age of this formation.
Anomozamites : This is an old type, belonging to the Rha^tic and older
Jurassic. Anomommites proper is but shghtly developed in the flora, and
at the same time, not being clearly established by the few and imperfect
specimens found, may be passed by. The case is difi'erent, however, with
the subgenus Platypterujimi. This is a well-chai-acterized form, and the
comparatively large number of fairly well preserved specimens found at
Fredericksburg give it considerable weight. The genus seems to be most
characteristic of the Rhsetic and older Jurassic, but it almost certainly
survives until the middle Cretaceous in Heer's Nilssonia Johnstnipi, from
the Atane beds of Grreenland. There is, then, nothing strange in finding
this genus in Neocomian strata.

Zamites: This is eminently a later Jurassic genus, but the Potomac
specimens are too imperfect and uncertain to be used.

Enceplialartopsis : This genus, from its nearness to the living Enceplia-
larfos, is a recent element in the flora. From its great rarity, however, it
is not entitled to much weight, and must be regarded as a newly introduced
form.

Ctemplnjllum : This is an old type. As it is exceedingly rare and
differs a good deal from the most common Rhsetic form, it must be regarded
as a survivor.

Ctenis: The same may be said of this as of GtenopliyUimi. It is a
considerably modified survivor from the Rhsetic and Jurassic floras.

Podozamites: This has no value in fixing definitely the age of a flora,
for, as the name has been used, it rc'inges throughout the J\Iesozoic. In
addition to this, the Potomac yields only detached and sparingly dispersed
leaves.

Dioonites: This genus, known from the Neocomian (Urgonian) of the
Wernsdorf strata, is entitled to great weight in fixing the age of the Poto-
mac. It is well characterized, widely distributed, and very abundant in

GEOLOGICAL AFFINITIES OP THE POTOMAC PLANTS 343

the Potomac, being one of the most characteristic plants in it. It is sur-
prising to find such a close resemblance between the most common forms
of the Potomac plant and the Wernsdorf fossil. This species is more impor-
tant than a large number of vaguely defined plants.

Tysonia: The trunks of Tysonia have their nearest relations in later
Jurassic and Wealden forms, and hence may well exist in a Neocomian
flora.

CONIFERS.

The conifers form much the most important and aljundant element in
the Potomac flora. In development they surpass all other groups. The
proportion of conifers in the flora, taken alone, is a feature that strongly
indicates that it is Neocomian in age, for it seems that in this period the
conifers, in proportion to the other elements of the flora, are more abundant
than they are at any other time. The Neocomian age of these plants is
indicated also by the near affinity of many of the types to present forms, and
by the existence in it of very important and well-characterized genera that
distinguish the Neocomian strata of various parts of the world. At the same
time, however, there are in this flora a number of unique types, that indicate
that the Potomac was a period of rapid development for the conifers, in
which many genera became extinct. The existence of these and a number
of groups which might be regarded as prototypes or ancestral forms of
living genera shows that, notwithstanding the existence in it of a number
of angiosperms, this is a very old flora.

Nageiopsis: This remarkable genus is greatly developed in the Poto-
mac and highly characteristic of it. It is so much like the Nageia section of
Fodocarpus living in the East Indies, Java, and Japan, that it is difficult to
resist the idea that there is a genetic connection between them ; Nageia
being a survivor and descendant of Nageiopsis. This is confirmed by the
remarkable isolation and limited development of Nageia. It is interesting
to note the fact that so many of the characteristic coniferous types of the
Potomac flora have their nearest living representatives in certain genera of
very limited development and restricted distribution confined to the eastern
coast of Asia and to Australia. Among these may be mentioned, in addi-
tion to Nageiopsis, Athrotaxopsis, now represented by Athrotaxis in Tas-

344 THE POTOMAC OK YOUNGER MESOZOIG FLOKA.

mania ; Frenchpsis, represented by Frencla in New Holland ; Ceplialotax-
opis by CepheMotaxm, in China and Japan ; and Baieropsis, by Ginkgo in
Japan. The same is true of a number of the ferns, cycads, and protea-
like angiosperms.

While Nageiopsis has not been recognized outside of the Potomac for-
mation, yet some of the species are much like fossils previously known
and described under other names. There are a number of species of
Podosamites that resemble some of the forms of Nageiopsis, which it is not
worth while to mention. Zamites Gcepperti Schenk, however, from the
Wernsdorf beds, is so much like Nageiopsis longifolia that it is difficult to
think that it is a different plant, while N. latifolia seems to belong to the
same broad-leaved coniferous type as the Podozamitcs Reinii of Geyler.

Feikleniopsis : This is a decidedly recent element, being near Heer's
Miocene Feildenia.

Phyllodadojms : This might be placed with Nageiopsis, etc., among the
types which are represented most nearly among living plants by restricted
genera in the Chino-Australian region, as it finds its nearest kin in Phyllo-
cladus of New Zealand, Borneo, and Tasmania. But both Feildeniopsis
and Pliylhcladopsis are too rare in the Potomac flora to have much impor-
tance. So far as they go, they indicate a more recent age for the formation.

Baieropsis : This is a very important genus in the Potomac, but
owing to the fact that it is a peculiar type, confined to the flora of that foi'-
motion, it can be of little help in determining age. This is one of the most
widely diffused and characteristic types found in the formation. The fan-
shaped and split-leaved Giugkos form a group eminently characteristic of
the later Jurassic and Wealden. Possibly Baieropsis is a descendant of
Ginkgophijllum., and if so, its presence is quite compatible with the Neoco-
mian age of the flora which contains it.

Baiera: This is most characteristic of the Jurassic, but it is too spar-
ingly present to have any importance.

FreneIo2)sis : This genus has all the characters that would give a fossil
plant weight in a flora. It is well characterized, well distributed, and very
abundant at some localities. Frenelopsis parceramosa is very near to the
Neocomian F. Holieneggeri, and the genus is confined to the Wealden and

GEOLOGICAL AFFINITIES OP THE POTOMAC PLANTS. 345

Urgonian groups. Frenelopsis ramosissima is so much like Frenela that a
genetic connection can hardly be denied, and this latter would seem to be
a younger form than F. parceramosa.

Bracliypliyllum : The Potomac forms of BrachyphjUum are most like
Heer's BrachyphyUum obesmn from the Wealden of Portugal.

Leptostrohus : This is Jurassic, aiul lends additional weight to the older
elements of the flora.

Laricopsis : This must be regarded as a recent element, but it differs
from Larix enough to render it doubtful whether it could be regarded as
indicating any particular post- Jurassic time.

Torreya: This belongs to the more recent forms, but it is too slightly
developed in the flora to have much weight.

CepJialotaxopsis : This is a very important and highly characteristic
plant. It is unmistakable in character, widely diffused, and represented by
several species, some of which seem to have been abundant. It is so much
like Cephalotaxus that possibly it should not be separated from it. It adds
much weight to the more recent elements of the flora.

Atlirotaxopsis : This is very near the living genus Athrotaxis, and the
same may be said of its significance that was said of CepJialotaxopsis.

Sequoia: This is the most important genus of conifers in the Potomac
formation, on account of both its large development and the number of
species that it shows common to the Potomac and to the lower Cretaceous
floras of other parts of the world. Thus we find in the Potomac and in
the Urgonian strata of Kome, Greenland, the species S. ReichenbacJii, S.
ambigua, S. rigida, S. gracilis; and, in addition, the species S. suhulafa is
found in both the Potomac and the Atane, or middle Cretaceous, beds of
Greenland. Considering the number of species, this is proportionally a
large number of common ones. Sequoia gives more previously known
species than any other genus of plants.

Araucaria: This genus begins in the Jurassic and comes down to the
present time, so that the Potomac species, being peculiar to it, can not
indicate any particular post-Jurassic era.

Taxodium {Glgptostrohus): The Glyptostrobus type of Taxodlmn is
most characteristic of the middle and upper Cretaceous ; and the Potomac

346 THE POTOMAC OE YOUNGBE MESOZOIO FLOEA.

species, although new, have most affinity with species from formations of
those ages.

Sphcnolqndium : This is one of the most important coniferous genera
in the Potomac. It gives two characteristic genera of the Wealden abun-
dant in the Potomac, viz, iS*. Kurrianum and S. Sternherfjiarmm. The Large
development of this type adds mucli to the weight of evidence for the
Neocomian age of the Potomac.

Abietites: The type of cones placed in AhletUes is too poorly preserved
and too rare to have much value; but, so far as their evidence goes, it
indicates an age more recent than the lower Cretaceous.

AVe may pass over the various forms of fruits and inflorescence, and of
course the undetermined plants, as too poorly characterized to throw light
on the question of age, and take up the angiosperms.

ANGIOSPEEMS.

The angiosperms, in the number of kinds and in the degree of devolop-
ment of some of the species, are pretty well represented. Hitherto it has
proved so uniformly true that, with the single exception of Heer's Populus
primceva from Kome, angiosperms are totally absent from all Neocomian
floras, that Saporta is inclined to think that this Populus was erroneously
ascribed to Kome. Any considerable nnmber of angiosperms in a flora
would, perhaps by most if not all paleobotanists, be taken by itself as almost,
if not quite, proving the post-Neocomian age of the flora which contains them.

Now, for the first time, we have presented in a flora which possesses
an overwhelmingly large proportion of Jurassic or typical Mesozoic
elements a very considerable number of angiosperms. The presence of
these plants, taken by itself, should not induce any one to assume that the
Potomac flora is post-Neocomian. It simply confirms the assumption
made by more than one writer, that the apparently sudden advent of this
type of plants in predominating numbers in the Cenomanian is not to be
taken as indicating their true mode of appearance. Perhaps all paleobot-
anists will admit that angiosperms really made their appearance gradually,
and that their first advent must be looked for far back in the Mesozoic, in
the midst of a flora essentially Jurassic or Mesozoic in type.

GEOLOGICAL AFFINITIES OF THE POTOMAC PLANTS. 347

The character of the Potomac angiosperms shows that the first advent
of this class must be looked for still fmiher back in time, but the Potomac
flora gives us the first appearance of this high type in any notable amounts,
and shows that these plants, at least as early as the oldest Cretaceous, were
present in considerable numbers, thus pushing back by at least one epoch
the date of their considerable development. It should be noted that we do
not find in them, although many of them are quite archaic in type, any
forms establishing a transition between angiosperms and the ferns or gym-
nosperms.

The examination of most of the genera in this group will give us but
little help in making out the precise age of the Potomac flora. Most of
them are too poorly characterized or too remote from living genera to
make a comparative sti\Aj worth much. The fact, however, that a number
of the most pecuhar forms seem to be generalized types, indicates a very
considerable antiquity for the flora.

As, however, all or very nearly all of the species of these angiosperms
passed away before the advent of the flora of the New Jersey Cretaceous,
we are entitled to conclude even from this group that the Potomac flora is
older than the Cenomanian. Such genera as AcacicBj)hyllimi, Protecephyllum,
and Rogersia seem to be very archaic. The same may be said, perhaps,
of GelastrophyUum, and certainly of FicophyJhim. Poimlopliyllum, Querco-
phyUuin, UlmiphyUum, Saliciphyllum, Juglandiphylhim, and Eiicalyptopliyllwm,
etc., are too imperfectly characterized to be of use.

Such genera as Sassafras, Vitiphyllum, Sapindopsis, Myrica, SteraiUa,
Hymencea, and Menispermites are found in the Cenomanian or have closely
allied forms in it. Vitipliyllum is very near Cissites, and Sapindopsis is very
close to Sapindus, both being genera occurring in the Cenomanian. All
these, however, are represented in that formation by species difiFerent from
those of the Potomac.

The remarkable leaves shown in Aralicephyllum, AceripJiyllmn, and He-
deraphyUum, as illustrated in H angiUatum, seem to be comprehensive types,
and hence are probably old forms

Taken as a whole, then, and compared with the Cenomanian flora
of the Dakota and New Jersey Cretaceous strata, the angiosperms of

348 THE rOTOMAC OK YOUNGER MESOZOIO FLORA.

the Potomac decidedly point to the Neocomian as the age of the Potomac
beds.

From this brief review of the flora, we see that there is in it a very
l-AYge and important element that belongs to the Jurassic or typical Meso-
zoic flora; a less important, but still large element, that has near relations in
Cenomanian and even living forms; while the largest, most fully developed,
and characteristic element is most nearly allied to forms distinguishing the
Neocomian.

All the important species common to the Potomac and the floras of
known formations are found in the Neocomian, including under this name
both the Wealden and Urgonian.

If any additional evidence were needed of the Neocomian age of the
Potomac, it may be found in the peculiar union of old and new types,
whose evidence, if we consider them by themselves, is contradictory.

Schenk, in Die Foss. Pflanz. der Werns. Schichten, page 29, in speak-
ing of the character of the Neocomian flora of the Wernsdorf beds, well
says that the flora of the older Cretaceous occupies in the development of
the plant kingdom a position similar to that of the Trias, for the forms
characteristic of two great periods of development meet in it ; that is, the
survivors of the past period (Mesozoic) and the new forms of the approach-
ing one (Tertiary).

This being true, we should expect to find in any large collection of
Neocomian plants a gi-eat mingling of types. We would find the survivors
of the old floras and the newly arrived precursors of the more recent ones
mingled with a number that attain their development in and are peculiar
to the Neocomian. This is exactly what we find to be true of the Potomac
flora. That so many of these plants are new is perhaps to be explained,
in part at least, by the fact already mentioned, that the flora of this epoch
is very poorly represented and comparatively but little known. It is not
possible to say positively to what precise epoch of the Neocomian the
Potomac belongs. Its flora ranges from the Wealden through the Urgo-
nian, and probably includes some Cenomanian forms.

TABLES.

350

THE POTOMAC OR YOUKGER MESOZOIC FLOEA.

Table l.—List of specks of the Potomac formation^ with the- localities at which thetf ivere collected.

Equisetiim Yirgiuicum, ii. sp

EijuisetuQi Lyelli Maut

Equisetum IiiarylandicTim, n. sp

Clatlophlebis constiicta, n. sp

Cladophlebis laMtblia, n. sp

Ciadoplilebis Yirgiuiensis, n. sp

Cladoplilebis denticulata, n. sp

Cladopblebis falcata, n. sp

Cladopblebis parva, n. sp

Cladopblebis acuta, n. sp

Cladopblebis oblongifolia, n. sp

Cladopblebis creoata, n. sp

Cladopblebis, species

Cladopblebis inclinata, n. sp

Cladopblebis distans, n. sp

Cladopblebis, species

Cladopblebis alata, n. sp

Cladopblebis rotundata, n.sp

Cladopblebis, species

Cladopblebis spbenopteroides, n. sp . .

Cladopblebis potiolata, n. sp

Cladopblebis ina^qniloba, n. sp

Cladopblebis brevipcDiiis, n. sp

Cladopblebis, species

Cladopblebis pacbypbylla, n. sp

Pecopteris Yirginiensis, n. sp

Pecopteris stnctinervis, n. sp

Pecopteris oTatodentata, n. sp

Pecopteris microdonta, n. sp

Pecopteris constricta, n.sp

Pecopteris brevipennis, n.sp

Pecopteris socialis Heer

Pecopteris angustipeunis, n. sp

Pecopteris Browniana Dunk

Pecopteris pachypbylla, n. sp

Spbenopteris thyrsopteroides, ii. sp . . .

Splienopteris acrodentata, n. sp

Spbenopteris latiloba, n. sp

Spbenopteris Mantolli Brongn

Spbenopteris spatulata. n.sp

Spbenopteris pacbyphylla, n. sp

Aspidium Frederickeburgense, n. sp.
Aapidium cllipticum. n. sp

a

jj

W

k

rt

a

i

%

U

t

Ph

C4

+^

2

■k ^

H

^

B

r"

^ '-' — = - -

^

■7

■=

ph aH^i:,>;^|A4Si:-B

TABLES. 351

Tablk I. — List of species of the Potomac formation, tcifh theloealities at which they were collected — Cont'd.

a

a
1

Names of the species.

(2 c

5 H

ft

J

1

1

&
1

1

1

s

1

p.

1

:4
g

1

•^
^

o
'■

Ho
H

1

1

1

3

m

3

1

1

il

1

a
3

1

1

06

97

98 .

09

99
1(10
100
101
101
102

46

Aspidium angustipiDnatum, n. sp

Aspidiam cystopteroides, ii. sp

. 1

I .-

1
1

. 1

1

1
1
1

1

1
1

Aspidium dentatum, n. sp

103

1
1
1

103

104

105

105

107

107

108

108

109

109

110

111

111

112

113

114

114

115 .

115 .

115 .

116 .
116

117 .
119 .
119 .

50

1
1

1

■il)

(in

Acrostichopteris densifolia, n. sp

L ..

61

. 1

K")

L .-
1 ..

1

1

1
1

1

f:t

fil

L -.

1

;;

1
1

fiS

1
1
1
1
1
1
1
1
1

1

70

Angiopteridium nervosuiu, n. sp

n

71

7')

70
77
78
79
80
81
82
S3

A. strictinerve, var. latifolium, n. sp

..

TJndeteriiiined fern, n. sp

1
1

1

1

1

118 .

120 .

121 .

121 .

122 .

123 .
124

124 .

125 .
125 1.

1 .
1 .

1
1

1

R'l

Rt

8(>

Thyrsopteiis rariuervis, n. sp

. 1

R7

1 1

RS

1

89
90

1 1

.J]

1
1

Thyraopteris Meekiana, n. sp

352 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

Table I. — List of species of the Potomac formation , ivith the localities at tvMch they ivere collected — Cont'd.

.0

a

1
1

Names of the speciea.

-3

i tlil

126

1 1

E » h (§ t=
1 .. 1

1
a

- 1

1
1

V.

5-

.a
p.

ti)

W

f

1
1

1 s 1

i

91

o- fl b n

128 .

95

- 1

130

97
98

Th^-rso^teris decarrens n s ^

130 .. .. 1

131 .. 1 ..

1

1
L 1

^. , ^ . ' J

132

133 .. .. 1

134

134 .. 1 ..

135 .

1 .. 1 1 .

1

Tbyrsopteria elliptica, u. sp

135

136

136

137

138

139

110

Tbyrsopteris heteroloba, n.sp

139 '.. 1 ..

140

140 '

141 !

142

142

1 -- 1

Tbyrsopteria injequipinuata, ii.sp

Thyrsopturis obtusilobii, 11. sp

143 .. .. 1

143

143

1

Tbyrsopteris rbombiloba, n. sp

144 . .

122

145 .. .. 1
146

134

147

*

148 .. ..

1

149 .. ..

Scleropteria elliptica, n. sp

151

152

1

129

130

152 .- .. 1

131

132

158 .... .

... 1 1

136

! Ctenopteris minor, n. sp

1 Ctenopteris longifolia, n. sp

157

137

159

TABLES.

353

Table I. — List of species of tlie Potomac formation, with the localities at ivhich they were collected — Cont'd.

i

s

s
1

Names of the species.

Page.

Deep Bottom.
Trent's Eeacb.
Dutch G-ap Canal.

Fishins hut. etc.

1 Sailor's Taveru.

.- 1 Fredericksburg.

1 Eoad.sidenearPotomacEun.
! Hill-.side nnar Potomac Run.

72d mile-post.
1 Bank near Brooke.
1 Kanke.v's.

1

1 1

s

1 - «

a
1

5

138
139

■ ■ innatifida

Zamio^sis insignia us ^

164

142
143

1 ..

.. 1

Platy pterigium densinerve, n. sp

169

171

171 . .. 1

146
147

11

.. 1

J

173 .. .. 1

Podozamites subfalcatus, n. sp

158

160

181 1

182 .. 1 1

184 .. .- 1

185 ..11

1 .. .. 1 ..

11

.. 1 ..

.. 1
1 1

1

1 ..

162

1

1 1

164
165
166
167

1

195 1 .. 1

196 .. .. 1

197 1

198 1

198

1 .. 1

1 X

1 ... 1

.. 1

Kageiopsia recurvata, n. sp

1 1

1 -- 1 1 .-

1 .... 1

170

172
173

Na^eio^sis ohtusifolia^n s

Na°eio^5is ina3 uilateralis'n s

. .. 1

N " • ^ • ■ ''• t ' ^

1 1

175
176
177
178
179

Na°eio^ i het ro h Ua n 3

201

201

202

203

204

1 1

° . ^''.^ ■ "^ ^ -ii ' ^

111

e^ops^s ^^^"P ^^.^'^ ^P

1 .. 1 1 ..
1

1 1 ..

.. 1

1 ..

Na^V^^i' a ot o ^ ^ p

Ph^n^^d^^ i h*^t r ' b Ua n 3

1

F Udeni^ "f ^ "^ "^ i"^ "ri^ n s ''

181-

e opsscraasner s, p

207 .. 1 1

208 .. 1 1

208 ..11

209 1

aieropsis expansa n. sp

.-

^^^.ft" ^ ■' ^

::::i.:..L.!

184

Baieropsis folioaa, n. sp

.. 1 ..

1

I....I..

354 THE POTOMAC OR YOUNGER MESOZOIG FLORA.

Table I. — List of upecien of the Potomac formation, with the localities at which thcij were collected— Cont'd.

a

a
1

Names of the species.

to

1

a

1

1

I

I

1

1

1
■■
1

o
.a

3
P

1

1
1

1

s

]a
1

1
1

1
1

1

1

1
1
1

1

1

1
1
1

1
1

1
1

1

1

B

i
■3

a c
1

i

3 -

1

1
o

p.

s

1

(2

1 1

a
1

1

2

210
210
210
211
212
212
213
215
218
221
223
223
224
224
228
230
230
231
231
232
233
233
234
234
235
236
237
238
238
240
241
241
242
243
243
244
245
245
246
246
247
247
247
248
248
249
249

18G

1
1
1

1

187
188
189
190
191
192
193

1
1

1

1

- 1

I 1

1

1
■"

196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221

223
224

B • h h U ies ' (cone)

Leptostrobus longifolius, n. sp

- 1

1

1
1
1
1
1
1

. 1

1

1 .

. 1

-•
1
1
1

. 1

1

1
1

. 1

226

227

1
1

1

228

. 1

99q

230
231

. 1

Araucaria obtusifolia, n.ap

....

TABLES. 355

Table I.— List of species of the Potomac formation, with the localities at which they were collected — Cont'd.

1

a

a
a

1

Names of the species.

Page.

Deep Bottom.
Trent's Reach.
Dutch Gap Canal.

II

i d ti) 1^ fS

3' s d b

III 1 1

^ EC £ S p

. p

1 i 1

S M M

i i
1 1

0 H

3

1

1 ii

- si

d

a

1
S

i: a S

1
§
0

232

233

231

235

236

237

238

239

240

2il

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

251

1

„ \

.. 1

Taxodium fasti "-latum n^

253 I

Taxodium deuticulatum, n. sp -

1

254

T. Brookense, Tar. angustifolium, n. sp

■"se

1

Spbenolepidium dentifolium, n. sp

Sphenolepidlum recurvlfolium, n. sp

258

1 1

1

.. 1

" ""1 "

260 ..11

11..

.. 1

Spbenolepidium Sternbergianum (Dunk.) Heer .
S. Sternbergianum, var. densifolium Heer, n. sp. .

.- - I .... X

261

2B2

263

263

.. .. 1 .... I

1

.. 1

jj. ^n ' ^

Abietites angnsticarpus, n. sp

Araucarites Virginicus, n. sp

263 1

Car oil thus fasciculatns n^s

265

Car'^olithns ternatus n s "

265

^ ^. . '^ . ^^

266

1

.. 1

Car^olithus aT-rtomeratus n s

C r^olithu coD-u-'atus n's ^

267

" ^ ^ ''•"t n ^

267

268

269

269

1

Carpolithus Brookensis, n. sp

cV lithuscurvatus n s

C^ ^"lithus sessilis n s ^

269 .... ..

270

270

c'"^^''rth mucronatus^n s

1

arpoi ^""^^^^^^^^^^'^ ^'^

yea eo„pe^^^^^ obo-ratum n^s

270

971

1

Cycadeospermum apatulatum, n. sp

271

271

f^'^d ^ 1 d t '

. 1

yea eospeim ^^^ ^ ^^^^^^ ^^ ^ ^

271

yea eospermum a s ^^^ p

A^^t of Conifer (t)' species'

a"™! of Conifer (c) species'

1

""^ ° ' . , 1

men o °'^\^^ • spec es ^

272

272

272

1

^ ^ ■ ,^

Cone of Callitris !, species ?

1

...|....

..!..

' Cherry Hill Station.

356 THE POTOMAC OR YOUNGER MESOZOIC FLORA.

Table J.— List of species of the Potomac formation, with the localities at which they were collected — Cont'd.

a

0

E
1

Names of the species.

Page.

Deep Bottom.
Trent's Reach.
Dutch Gap Canal.

1 i

j«i i i

5 cc fi w S

1 72d mile-post.

Bank near Brooke.
1 Kankey's.

d -^
n P.
3 g

O H

S
S

0 a

1 t.i

V Is
1

a

a

o

272

272 .

273 ..1 ..

274 .. .. 1
274 ..

Macrospores ?, sp

274 ..

275 . .. .
275

. 1

■'Rt

1

275 ..

. .. 1

275

275 ..

276 ..

■'qn

276 ..

9q-|

279 .

•>^'>

Acacieephyllum longifolium, n. sp

279 1

280 .- .. 1

280

281 ..

•>m

?q4-

1 .. -.

OPt

■'Pfi

282 ..

1

vm

253

. .- 1 ....

WR

284

284 ..

?w

ProtCEephyllum oblongifolium, n. sp

Protejepliyllum ovatum,n. sp

. 1

finn

285 .-

1

'tOI

285 .

1

30?,

ProteEephyllum tenuinerve, n. sp

286

286

sna

287

288 .-

in'i

1

snn

289 ..

■

1(17

289

3flR

soq

291 1

292 -.

1 .. 1 ..
1 1

310

311

294 ..

1

31',

294

313

295

314

295

297

31fi

296

317

297

1 1 ..
11..
1 1 ..

1
1
1

318

298

311

300

3-'n

3'^1

301 .. .

1 1

3'>S

301 1

3?3

302

324

Saliciphyllum ellipticum, n. sp

303

1 .. 1

1

TABLES.

357

Table I. — List of species of the Potomac formation, with the localities at tvhich they were collected — Cont'd.

M
a

a
I
1

Names of tbo species.

11

%'S'S' s s

1 kS M tS

^ i

1 a 'i
g 1 M

? ft
11

4
s

1
'i s ^

^ it

i

.a
1

w 3 p

o

.. .. 1

304 .. .. ..

1

1

1

Celastropbyllum tenuinerve, d. 9p

306

307 ..

Quercophyllum grossedentatum.n. sp

307

308

308 -.

1 ...

1

v-f h\^ -f r ' ^

1

Vitiphyllum parvifolium, n. Rp

309

309

310

310 ..

1

1

Popnlophyllum reniforme, n. sp

311 ..

1

311 -.

1

^ ilo^h^-U • , ' ^

312 1

Ulmi if llura Biookense na ^

312

313 .... ..

313 1 .. ..

1 ...

1

314 1 .. ..

349

314 1

1

M "ricT! h Hnm dentalum n a ' '

316 ..

Platano'^h'^Uum cras-inerve n^s

316 1

A ]• h -U bt -I b ' ^

1

Arali!e^h^lum aoutilobum n s ^

318

1

A r ^h^U -f r ' ^

318

319

320

1

...I....

1

361

Ariato^ochiT h Hum cnstinervo

322

1

362

Hea r b -11^ "^ 1 t ^

324

1

HederT^b\lnm an<^ulatutu n *> ^

324

1

Eucalyptopbyllutn oblongifolium, n. sp

365

325

. 1

358

THE POTOMAC OR YOUNGER MESOZOIC FLORA.

Table II. — List of species of plants of the Potomac formation identical

Species.

Si

FOBMATIOKS IN WHICH THE SPECIES COMPAKED OOCUB.

Triassic.

Jurassic.

Creta-
ceous.

lib ae tic.

Ehai-
tic or
Lias.

Lias.

Oolite.

Coral-
lian.

Kira-

raerid-
gian.

Wealden.

1

s
i

1
o

1

>

1

.2

2

i

a

la

1

i
«

g
2

■a

pH

a

.a

1

§. I
a J
tti y

1

pi

1

t3

b.

■3

3
1

1

.a
.S

a

II
1

|§
•So

a
1
1
1

3
1

Equiaetnm Virginicum, n. sp

63
65
68

2

i

1

Cladophlebis latifolia, n. sp

Cladopbiebia Yirginiensis, n. sp

^ ■

5

69

1 .

1 .

1 .
1 .

6

70

71

1
1

7

1 .

72

1

1

1 -
1 .
1 .

1

. I

73

74

1 .

1

1
1

Cladophlebis oblongitblia, n. sp

11

74
75

1

1

1 .

1

77
77
79
81
80
82

1

ClaJopblebis sphenopteroides, n. sp

Cladopblebis brevipennis, n. sp

Cladophlebis pachyphylla, n. sp

I ....

1

1
1

27

84
85
87
88

1
1

"^ . " i ^„' ^

p

31

Pecopteris Browniana Bunk

1

TABLES.

with or allied to species descriied from other localities and formations.

359

FORMATIONS IN WHICH THE SPECIES COMFAKED OCCUR.

Species with ■which, compared.

1

1

Cretaceous.

i

H
1

i

hi;

Neocomian.

Urgonian.

Ganlt.

Cenoma-
nian.

Da-
kota.

Senonian.

Lara-
mie.

Is

i

o

1

(1

1
1

-1

o

S

to

■|

s

<(

1

& .
a"

u

i
1

5

1
i

1

1
0

>>

1
(5

1
3

i
f

t

1

1

s

g

■s

1

1

1
Hi

EquisetumBurchardti(Dnuk.) Schimp.

1

2
4

5
6

7
8

9

10

11
12

14
17
20
23
25
26

27
30
32
34

1

Pecopteria haihurnensis L. &H

Acrostichides liunieaefolius Bunb

Acrostichides rhombifolius Font

1

Neuropteris recentior (L'hill.) L. & H..

Asplenium WhitbicBse (Bigt.) Heer. ..

Cladophlebis pseudowhitbiensis Font. .

1

1

Cyathea Tchibatchewi Schenk

1

■

1

1

Identical

360 THE POTOMAC OE YOUNGER MESOZOIO FLOUA.

Table II. — List of species of plants of the Fotomao formation identical

Species.

Si

FORMATIONS IN WHICH THE SPECIES COMPARED OCCUR.

Triassic.

Jurassic.

Greta-
ceons.

Ehajtic.

Eha;.
tic or
Lias.

Lias.

Oolite.

Coral-
lian.

Kim-

merid-
gian.

Wealden.

e

1
I

1

1

6

■a
>

s"

0

2

a ■'
1 1

3 o

I

1

1

1 ^.

i
m
P4
o ■?

g i

i 1 1
1 1 1

S

M

a

■a
w -

'.3

o"
_s

t.
1

*

t2

.a

1

a
t

England, including rurbeck
hads. Isles of Wight and
Portland.

North Germany.

?Eussia (Klin).

. .

89

91
94
96
98
99
101
102
104
109

11..

Aspidium Frederickshargense, n. sp

Aspidium heterophyllum, n. sp

Aspidium anguatipinnatum, n. sp

1 ..

1 ..

Polypodium fadyenioides, n. sp

1 ..

110
113

1

Angiopteridinm auriculatnm, n. sp

Angiopteridium nervosum, n. sp

Angiopteridiura ellipticura, n. sp

1

114

1

1 ..

1

1
1

114
115
116

119
119
120

1

1

Angiopteridinm strictinerve, n. sp

Gleichenia Nordenskiiildi (?) Heer

1

Tbyrsopteris Virginica, n. sp

121

Thyrsopteris dentata, n, sp

121
122
123

1 ...

1 ....

TABLES.

with or allied to species described from other localities and formations — Continued.

361

FORMATIONS IN WHICH THE SPECIES COMPARED OCCUR.

Speciea with -whicli compared,

Cretaceous.

Neocomiau.

TJrgonian

Gault.

Cenoma-

Da-
kota.

Senonian.

Lara- <
mie. c

St

i
1

1

1

£
1

1

1

t

§

4

4i

o.S

1
'cu

CO

1

i

i

to

a

1

s

1

•a

s

%.

1;

.a -2

° t
1 1

& 1

a

d

■|

1
-I

Spheuopteris "Williamsonis Ergt

1

1

1
1

Aspidium Oerstedi Heer....

1

Identical

Tliyrsopteris Murrayana ("Brgt.) Heer .

1

Aspleiiium argutnlum Heer .".

1

Tffiniopteris vittata Ergt

AngiopteridiumMcClenaDdi(0. &M.)
Schimp.

Tseniopteria steDODeuva Sclienk

Tasniopteris teuuinprvis Braiins

Angiopteridium ense (Oldb.) Schimp..

Macrotseniopteris ovata Schimp

Oleandridium tenniuerve (Brauns)
Schimp.

71

74

75

1
1

?

Aspleniuiu Bicksoniaoum Heer

1^

fi'>

Adiantites Nympharam Heer .

81

SphPDopteris hymenophylloides Brgt..

84-

Thyrsopteris prisca (Eichw.) Heer

Rfi

1

AspleDium Dickaouianura Heer

Thyrsopteris elongata Geyl

362

THE POTOMAC OR YOUNGEE MESOZOIO FLORA.

Table II. — List of species of plants of the Potomac formation identical

Species.

FOKMATIONS IN WHICH THE SPECIES COMPAKED OCCUR.

Triaasic.

Juraaaic.

Creta-
ceoua.

Khastio.

Rbaj.
tic or
Liaa.

Liaa.

Oolite.

Coral- B^:

Wealden.

si

_ ^s
1, M

a^

1: Ih
"ilia

a „••= * -2
W 2i S

a

a
1

1

o
1

1

a c
1 1

3

f

M

.a

e
•s

M
'■3

S

II

i

.a

1
O •?

S ir

i

a

ft

1 I

!a

s

a
1

a.

1

1

P
t

a

93
95
116
125
126

■ ■ ■„ ■

127
129
142
148
149

Thyrsopteris densifolia, n. ap

Thyrsopteria beterophylla, n. ap

I

1 ..

1

1 ]

Sa„en pte ^_ ' ^ ^^

1 ..

128
130
134
141
145

151
152
158
164
169

1 ..

c er p 3 p , p

.. 1 .

1

Ctenopteria integrifolia, n. sp

Zamiopaia laciniata, n. ap

Platypteriginm denainerve, n. sp

Ctenopliylliini latifolinm, n. sp

1

1

1

i

153
154
155

175
176
176

1

Ctenis imbricata, n. ap

156

179

160

181

182
185

193

195
198
207
218
221

1

1

1

1

1 .-

.. 1

1 1

Dioonltes Bncbiamia Scbimp

Dioonites Bucbianus Scbimp., var. an-
guatifolina Font.

161
163

164

1 ..

1

1 . ..
1 .. ..

jTysomaMarya

165
169
181
193
194

Na„eop , „ , p

Baieropsis expansa, n. .sp

Frenelopsia parceramoaa, n. sp

Braobypbyllnm crassicaule, n. sp

. 1

TABLES.

witli or allied to species described from other localities and formations — Continued.

363

FOKJUTIONS IN WHICH THE SPECIES COMPARED OCCUR.

Cretaceong.

1
\

. Species -with -whicli compared.

Neooomian.

Urgonian.

Gaxat.

Cenoma-

Da-
kota.

SenOBian.

Lara-
mie. |.

.a
•§1

S'S

w (1

3

g

-a
. ft

1

3"
i

1

1

g

1

<1

ei

-S
to

n .
o.g

o

1
1

£

a

CO

1

a

1

£

3

g

H

'3

1
S

1
1

to

i

1

As leniumJohnstru i Heer

93
95

. Sphenopteris Gcepperti Dunk

. Pachypteria lanceolata (Phill.) Brgt...

. Macrotfeniopteria magnifolia (Rogers)
Schimp.

1

. Pterophyllum Biaunsii Schetik

. Pteropbyllum princeps 0. & M

. Ctenophyllum grandi folium Font

. Gloasozamites Zitteli (Scheiik) Schimp .

1

1
1

1

Tin

^ Podozamites lanceolatus {L. & H.)
Brgt.

ino

1

1

ifii

. Identical (Pterophyllum abietinum
Giipp. and Dioonites abietinus Miquel.

Ifit

1R4

1

1(1 '■i

inn

1

1

IRI

1

. FrenelopsisHolieneggeri (Ett.) Sclienk

i<):t

194

. Brachyphy Hum Moreauanum Ergt

364 THE POTOMAC OR YOUNGEE MESOZOIC FLORA.

Table II. — List of species of xilants of tlte Potomac formation identical

Species.

S

&

FORMATIONS IN WHICH THE SPECIES COMPjUlED OCCUR.

Triassic.

Jnrassic.

Creta-

EhsBtic.

Eha;-
ticor
Lias.

Lias.

Oooliie.

Coral-
lian.

Kim-
merid-
gian.

Wealdon.

M

i

a
O

>

2

1
fa

3 1

a

6

pi
5

M

.a

a
«
.3

1

a

B

o 1

0 i

i 1 \

1

1 ^

il

5

a
p.

Ha

IS

1
i

1
«

1
1

1

•5

il

M

2

up
■§0

ii
Is

195 1 liracbypliylluiu parceramosum, D. sp ...

223
223
224
232
235
243

1

1
1

Brachypbyllum, species ? (cone)

]

Sequoia Keicbenbacbi (Gein.) Heer

243
245
245
246
247
247
249
251
252
252
254
257
259
259
260
261

261

262
263
266

.n„

Taxodium Virginicnm, n. sp

235

•

'40

Spbenolepidium parceramosnm, n. sp. -.

Spbenolepidinm pachyphyllum, n. sp . - .

Spbenolepidium Yirginicum, n. sp

Spbenolepidinm Kurriannm Heer

Spbenolepidinm Sternbergiannra
(Dnnls.) Heer.

Spbenolepidinm Sternbergianum
(Dnnlt.) Heer, Tar. densifolinm, n. var

243

1 ..
1 ..

1 ..

245

246

251

f'i'i

Carpolitbns agglomeratns, n. sp

1

256

267

1 ....

TABLES.

365

ivith or allied to species described from other localities and formations — Cootiuued.

FORMATIONS IN WHICH THE SPECIES COMPARED OCCUR.

Gretaceoua.

Speciea "witli "wbich compared.

i

\

1

3

Neocoiuian.

Urgouian.

Gault.

Conoma-

Da-
kota.

Senoniau.

Lara-

1 .

1

O

1

I

1
-a

1
5

s
1.

■it

a

§
-1

CO

p. .

1
1

£

a"

•o
la

§

to

s

a-

■g

3 1
' 1

Hi

11:

is.

; .a '-

1

a"

i
s

s

d
a

1 =

CD r
1 .

a

a

ci

S
1

197
204
209
218

1

1 .
1 .

1

1

1

1
1
1
1

1

1 .

1

. 1

1

1

219
221
222
223
225

1
1
1

1

1

1

1 Podocarpus incerta Ett. & Gard

. "Widdringtonitee Keicbii (Ett.) Heer. , .

1

233
234
235
238
240
243
244
245

1

1

1

1 .

,

1

1
1

1

q 6 bachi (Gem) Heer...

1

p oepc

1

.

Id n ■ al

1

1

1

1

1 .

1

-

- Sequoia fastigiata (Sternb.) Heer

248
251

1

. Eaiera Muiisteriana (Presl.) Heer

. Baiera Miinsteriana (Presl.) Heer

2.%

366

THE POTOMAC OE YOUNGER MBSOZOIO FLORA.

Table II.— List of species of plants of the Potomac formation identical

Species,

F4

FORMATIONS IN WHICH TllE BrBCIBS COMl'AKED OCCUlt.

Triassic.

Jurasfiicr

Creta-
ceous.

Khffitic.

Ehaj-
tic or
Lias.

Lias.

Oolite.

Coral. Sd.
'"">■ gian.

Wealden.

1

i

>

1

a

1

p^

.a

§
'3

1

t
3

r:!
It

i

1 »
- 'g

S "

ti 'Si

1 1 1
1

India (Jabalpur group, etc.).

Japan.

France (Verdun, St. Mihiel.).

1
1

Franco (Morestel, Armaille,
etc.).

Eugland, including Purbeck
beds, Isles of Wight and
Portland.

North Germany.
1 ?Eus8ia(Klin).

264
270
281
297

Cycadeospermum aentum, n. ap

270
225
273
283

1

Williatnsonia Virgmiensis, n. sp

Protea;phyllum orhiculare, n. sp

Protea;phyllum oblongifolinm, n. sp

299
304

307

308
309
311
312
313
315
341
352
353

284
287

289

290
291
292
294
295
297
310
316
317

Sassafras cretacea Netrb., Tar. bete-
roloba, n. var.

Ficophyllnm serratum, n. .sp

Ficophyllum eucalyptoides, n. sp

FicusVir^n^^^ ^^^^ p ^

apm ops

Platanophyllura crassinerve, n. sp

Araliajphyllum obtusilobum, n. sp

AraliiEphyllum acutilobum, n. sp

Aralisephyllum majnifolium, n. sp

354

318

355

318

356

319

Hymeniea Virginiensis, n. sp

357

320

TABLES.

wiWi. or allied to species desmied from other localities and formaiiona — Continued.

367

FOKMATIONS IN WHICH THE SPECIES COMPARED OCCUR.

Species with which compared.

Cretaceous.

1

0

1

8.

a
'T
fa

Neocomian.

UrgoniaB.

Gault.

Cenoma-

Da-
kota.

Senonian.

Lara-
mie.

11

i

s

i

to

1
1

3"

1

§
§

i

1

g
c5

1
t

'i|

to

1

s

1

2.9

1

la

I"
1

1

a

■3

1
I?

go

5

^

o

1

.■s
p

S

1
1

264

Brachyphylliim Moreauamim Brgt

■'7n

1

1

1

297

Conospermites hakeseibliua Ett

Ficas protogBEa Ett (nee Heer)

Grloasochlainys tranaimitans Ett. &
G-ard.

1

299

1

301

1

1

308

1

1

311

1
1
1

1

1

1
1

1
1

1
1

1
1

I

1

Liquidambar integrifoliuui Lx

1

Liquidambar integrifolium Lx

1

1

368

THE POTOMAC OR YOUNGEE MESOZOIC ELOEA.

Table III. — Localities other than those of the Potomac formntion at which Po'omac species or their allies
hare heen found, arranged primarilij in the ascending order of their geologic age.

Geological formations.

Potomac species (systematic nnre
left; page on Avhich described on

bers on the
the rigbt).

Species witb Tvbicb compared.

I.— Ehffitio of Virginia and

6. Cladopblebis Virginieusis

70

Acrosticbides linna;a;foliu8 Bunb.

North Carolina.

Acrosticbides rbombifolius Font.

73

C. pseudowbitbieusis Font.
S. rboifolia Presl.

125. Sagenoptcris lalifolia

148

145. Platypterigium densinerve - .

100

Macrota-'uioptoris maguifolia (Rogers)
Scbimp.

153. Cteuopbyllum latifolium

175

C. grandifolium Font.

n.— Eb.-Etic of Germany

160. Podozamitcs acutifolius

181

. 72

P. Emmousii Kewb.
Pecopteris Wbitbiensis Brongn.
T. rbomboidalis Ett.

(Franconia, etc., Seinstedt).

65. Thinnfeldia variabilis

110

Pecopteris AVbitbiensis Brongu.
TicDioptcris stenoucura Scbcnk.

70. Angiopteridium nerv^osum

Ill

Taiuiopteris teuuiuerve Brauns.

75. .Angiopteridium strictiucrve .

lie

Oleandridium tenuinerve (Brauns)
Scbimp.

125. S.igenopteris latltolia

148

S. rboifolia Presl.

126. Sagenopteris elliptica

149

Do.

145. Platypterigium densinerve . . .

169

Pteropbyllum Braunsii Scbenk.

... 260

Baiera Miinsteiiana (Presl.) Heer.
T^nioptoi-is vittata Brongn.

III.— ELa;tic of Sweden

70. Angiopteridium nervosum . . .

114

125. Sagenopteris latifolia

148

S. rboifolia Presl.

145. Platypterigium densinerve . . .

169

Pteropbyllum Braunsii Scbenk.

1.^5. Ctenis imbricata

176

C. fallax Natb.

218. Sequoia cycadopsis

243

Taxites falcatus Natb.

IV.- Jurassic of Cbina

255. C.arpolitbus Virginieusis

160. Podozamites acutifolius

206

181

Baiera Munsteriana (Presl.) Heer.
P. lanceolatus (L. »fc H.) Brongn.
P. Emmonsu Newb.

8. Cladopblebis falcata

72

Pecopteris Wbitbiensis Brougn.

74

Do.

69. Angiopteridium anriculatum

113

Pecopteris salicilulia 0. & M.

114

A.McClellandi (0. & M.) SoUimp.
A. ense (Oldb.) Scbimii.

71. Angiopteridium ellipticum

114

74. Angiopteridium ovatum

115

Macrotmniopteris ovata Scbimp.

145. Platypterigium densinerve ...

169

Pteropbyllum princeps, 0. & M.

VI. Ooliteoflndia

160. Podozamites acutifolius

181

72

P. lanceolatus (L. & H.) Brongn.

Pecopteris Indica 0. & M.
P. lanceolata (L. & H.) Brongn.
Pecopteris liberata Heer.
S. Pomelii Sap.

VII.— Oolite of Cape Bohe-

160. Podozamites acutifolius

181

. 68

man, Spitzbergen.

130. Scleropteris Virginica

152

vm.— Oolite of Eastern Si-

160. Podozamites acutifolius

181

P. lanceolatus (L. & H.) Brongn.
Asplenium spectabile Heer; A.Wbitbienso
(Brongn.) Heer.

beria.

20. Cladopblebis .spbenopteroides.

79

Tbyrsopteris prisca Eicbw.

53. Aspidiura dcutatum

102

Tbyrsopteris Murrayana (Brongn,) Heer.

64. Asplenium dubium

109

A.argutulum Heer.

120

Adiantites Nympbarum Heer.
T. prisca (Eicbw.) Heer.

83. Tbyrsopteris nervosa

122

116. Tbyrsopteris beterophylla

143

T. Maakiana Heer.

160. Podozamites acutifolius

181

P. lanceolatus L. & H.) Brongn.

194. Bracbj-phyllum crassicanle . . .

221

B. insigne Heer.

204. Leptostrobus ? species (c) hcoU

232

Samaropsis rotundata Heer.

255. Carpolithns Virginieusis

266

Czekanowstia rigida Heer.
Czekanowsliia setacea Heer.

TABLES.

369

Table III. — Localities other than tliose of the Potomac formation at which Potomac epedes or their allies
have been found, etc. — Continued.

Geological formations.

Potomac species (systematic numbers on the
left; page on which described on the right).

Species with which compared.

Vlll.—Oolite of Eastern Si-
beria— C on tinned.
IX.— Oolite of Kussia

X.— Oolite of Italy

XI.— 0 o 1 i t e of Yorkshii
England.

XII. — Corallian of France . . .

XIII. — Corallian of Solenho-
fen, Bavaria.

XIV.— Kirameridgian of

XV.— Wealden of Germany .

256. Carpolithus agglomeratns 267

264. Cycadeospermum acutnm 270

8. Cladophlebis falcata 72

12. Cladophlebis crenata 75

134. Ctenopteris integrifolia 158

8. Chidophlebis falcata 72

5. Cladophlebis latifolia 69

6. Cladophlebis Virginiensis 70

7. Cladophlebis denticnlata 71

9. Cladophlebis parv.a 73

11. Cladophlebis oblongifolia 74

25. Cladophlebis pachyphylla 80

26. Pecopteris Virginiensis 82

36. Sphenopteris thyrsopteroides 89

53. Aspidium dentatutn 102

70. Angiopteridium nervosum 114

83. Thyrsopteris brevifolia 121

84. Thyrsopteris dentata 121

126. Sagenopteris eUiptica 149

128. Scleropteris elHptica 151

155. Ctenis imbricata 176

160. Portozamites acutifolius 181

130. Scleropteris Virginica 152

194. Brachyphyllum craasicaule 221

270. Ament of Conifer (a), species? 225

195. Brachyphyllum parceramosum 223

196. Brachyphyllum, species? (cone) 223

197. Brachyphyllum, species? (cone) 224

141. Zamiopsis laciniata 164

195. BrachyphyUam parceramosum 223

196. Brachyphyllum, species? (cone) 223

197. Brachyphyllura, species? (cone) 224

1. Equisetum Virginicum 63

4. Cladophlebis constricta 68

8. Cladophlebis falcata 72

10. Cladophlebis acuta 74

23. Cladophlebis brevipennis 81

27. Pecopteris strictinervis 84

30. Pecopteris constricta 86

34. Pecopteris Browniana Dunk 88

39. Sphenopteris Mantelli Erongn 91

52. Aspidium Uunkeri (Schimp.) Font 101

64. Asplenium dubium 109

86. Thyrsopteris rarinervifl 123

95. Thyrsopteris densifolia 129

161. Dioonites Buchianus Schimp 182

— 2i

Baiera Miinsteriana (Presl.) Heer.
Ginkgo Sibirica Heer.
Asplenium spectabile Heer.
Cyathea Tchihatchewi Schenk.
Dichopteris Viaianica Zigno.
Pecopteris Whitbiensis Brongn. ; P. inaig-
nis L. »fe H. ; Neuropteris recentior (Phill.)
L.&H.
Pecopteris Haiburnensis L. & H.
Neuropteris undulata L. &. H.
Pecopteris Whitbiensis Erongn.
Pecopteris tenuis Schouw.
Neuropteris ligata L. & H.
Pecopteris dentata L. & H.
Pecopteris Whitbiensis Brongn.
Pecopteris William sonis Brongn.
P. denticulata Brongn.
S. Williamsonis Brongn.
S. donticailata Brongn.
Thyrsopteris Murrajana (Brongn.) Heer.
Tajniopteris vittata Brongn.
Sphenopteris dissocialis Pbill.
Sphenopteris hymenophylloides Brongn.
Sphenopteris affiuis Phill.
Glossopteris Phillipsii Brongn.
Pachypteris lauceolata (Phill.) Brongn.
C. falcata L. &. H.
P. lanceolata (L. & H.) Brongn,
S. PomeliiSap.
B. Moreauanum Brongn.
Brachyphyllum Moreauanum Brongn.
B. gracile Brongn.

Do.

Do.
Stenopteris desmomera Sap.
B. gracile Brongn.

Do.

Do.
E. Burchardti (Dunk.) Schimp.
Alethopteris cycadina Schenk.
Pecopteris Whitbiensis Brongn.
Neuropteris Albertsii Dunk.
Alethopteris Albertsii Schenk.
Pecopteris Murchisoni Dunk.
P. Browniana Dunk.
P. Browniana Dunk.
Identical.
Do.
Do.
Neuropteris Albertsii Dunk.
Sphenopteris Lmgifolia Dunk.
Sphenopteris Gcepperti Dunk.
Identical.

370

THE POTOMAC OR YOUNGER MESOZOIO FLORA.

Table III.

-LocaUUes other than those of the Potomac formation at which Potomac species or their allies
have been found, etc. — Continued.

Geological formations.

Potomac species (aystematic numfeera on the
left; page on wbicb described on the right).

Species with which compared.

XV.— Wealden of Germany-
Continued.

XVI.— Wealden of England.

XVII.-Wealden ? (Neoco-
mian?) of Klin, Russia.

XVIII.— Jur.iasic? (Weal-
den? Neocomian?) of Ja-
pan.

XIX.— Neocomian (Koota-
nie) of Brit. NW. T.

XX.— Neocomian of Portu-
gal.

XXI.— Neocomian of West-
phalia.

XXII. — Neocomian? of
France.

XXin.— Urgonian of Green-
land.

XXIV.— Urgonian of Aus-
trian Silesia.

163. D. Buchiauua angustifolius Font 185

244. Spbenolepidium Virginicum 259

245. Spbenolepidium Kurrianum Heer 260

246. Spbenolepidium Sternbergianum 261

(Dunk.) Heer.

2. Equisetum Lyelli Mant 65

39. Spbenopteris Maiitelli Brongn 91

164. Tysonia Marylaudica 193

8. Cladopblebis falcata 72

11. Cladopblebis oblongifolia 74

17. Cladopblebis alata 77

86. Tbyrsopteris rarinervia 123

160. Podozamites acutifolius 181

169. Nageiopsis latifolia 198

234. Tasodiuni Virginicum 252

39. Spbenopteris Mantelli Brongn 91

52. Aspidium Dankeri (Schimp.) Font 101

244. Spbenolepidium Virginicum 259

246. Spbenolepidium Kurrianum Heer 260

246. Spbenolepidium Sternbergianum 261
(Dunk.) Heer.

246. Spbenolepidium Sternbergianum 261

(Dnnk.)Heer.
251. Araucaritea Virginicua 263

4. Cladopblebis constricta 68

12. Cladopblebis crenata 75

56. Polypodium fadyenioides 104

78. Gleicbenia Nordenskiiildi ? Heer 119

79. Undetermined fern 119

82. Tbyrsopteris Virginica 120

86. Tbyrsopteris rarinervis 123

93. Tbyrsopteris insignis 127

193. Frenelopsis parceramosa 218

209. Torreya falcata 235

219. Sequoia Eeicbenbachi (Gein.) Heer... 243

222. Sequoia ambigua Heer 245

223. Sequoia rigida Heer 246

225. Sequoia gracilis Heer 247

234. Taxodium Virginicum 252

247. Spbenolepidium Sternbergianum var. 261

densifolium Heer.

154. Glossozamites distans 176

156. Podozamites subfalcatus 179

161. Dioonites BncliiaiiTia Schimp 182

165. Nageiopsis lor gifolia 198

181, Baieropsis expansa 207

193. Frenelopsis parceramosa 218

Identical (^ Pterophyllum abietinum Gopp.

and D. abietinus Miquel).
S. Kurrianum Heer.
Identical,
Do.

Do.
Do.

Bennettites.

Mantellia.

Pecopteris Whitbiensis Brongn.

Do.
Pecopteris exiliforrais Geyl.
T. elongata Geyl.
P. lanceolatus (L. & H.) Brongn.
Podozamites Reinii Geyl.
Glyptostrobus GronLindicus Heer.

Identical.

Do.
S. Kurrianum Heer.
Identical.

Do.

Do.

Arancaria cretacea Brongn.

Pecopteris borealis Brongn.
Pecopteris borealis Brongn.
Nathorstia angnstifolia Heer.
Identical.

Asplenium Dicksonianum Heer.
Dickfonia Johnatrupi Heer.
Asplenium Dicksonianum Heer.
Asplenium JTobnstrupi Heer.

F. Hobeneggeri (Ett.) Schenk.
T. parvifolia Heer.
Identical.

Do.

Do.

Do.
T. (Glyptostrobus) Gronlandicum Heer.
Sequoia fastigiata (Sternb.) Heer.

G. Zittoli (Schenk) Schimp.
Zamites ovatns (L. &H.) Morr.
Z. af&nis Schenk.

Z. nervosua Schenk.

Identical.

Zamites Gcepperti Schenk ?

Baiera cretosa Schenk.

F. Hobeneggeri (Ett.) Schenk.

TABLES.

371

Table III. — Localities other than those of the Potomac formation at ^vhich Potomac species or their allies
have l)een found, etc. — Contiuaed.

Geological iormationa.

Potomac species (systematic numbers on the
left ; page on which described on the right).

Species with which compared.

XXIV.— Urgonian of Ang-
trian Silesia — Continued.

XXV.— Gault of Spitzber-
gen.

XXVI— CeE
Born holm.

XXVII.— C e
Greenland.

XXVIII.— Cenomauian of
Bohemia and Moravia.

XXIX.— Gene
Saxony.

XXX.— Dakota Group,
United States.

219. Sequoia Keichenbaclil (Gein.) Heer... 243

243. Sphenolepidium pachyphyllum 259

93. Thyrsopteris insignis 127

219. Sequoia Eeichenbachi (Gein.) Heer... 243

223. Sequoia rigida Heer 246

247. Sphenolepidium Stembergianum , var. 261
densifoliuni Heer.

6. Cladophlebia Virginiensis 70

7. Cladophlebis denticulata 71

10.' Cladophlebiaacuta 74

14. CladopblebisinclinaU 77

26. Pecopteris Virginiensis 82

32. Pecopteris socialis Heer 87

42. Aspidium Fredericksburgense 94

44. Aspidium heterophyllum 96

46. Aspidium angustipinnatum 98

48. Aspidium OerstediHeerV 99

69. Angiopteridiura auriculatum 113

145. Platypterigium densinerve 169

219. Sequoia Reichenbacbi (Gein.) Heer ... 243

221. Sequoia subulal a Heer 245

222. Sequoia ambigua Heer 245

223. Sequoia rigida Heer 246

226. Sequoia delicatula 247

247. Sphenolepidium Stembergianum, var. 261

densifolium Heer.

353. Arali;Bphyllum obtnsilobum 317

354. Aralisepbyllum acutilobum 318

355. Aralisephyllura magnifoUum 318

356. Araliaiphyllum aceroides 319

219- Sequoia Reichenbacbi (Gein.) Heer ... 243
238. Taxodium Erookense 254

247. Sphenolepidium Stembergianum, var. 261

densifolium Heer.
297. ProteEephyllum orbiculare 283

341. Bombax Virginiensis 310

357. Hymensea Virginiensis 320

161. Dioonites Buchianus Scbimp 182

219. Sequoia Eeichenbachi (Gein.) Heer... 243

248. Abietites macrocarpus 262

281. Williamsonia Virginiensis 273

299. Protejephyllum oblongifolium 284

78. Gleichenia Nordenskioldi ? Heer 119

219. Sequoia Reichenbacbi (Gein.) Heer... 243
247. Sphenolepidium Stembergianum, var. 261
densifolium Heer.

307. Sassafras cretacea heteroloba 2S9

308. Sassafras bilobata 290

312. Ficophyllum eacalyptoides 294

313. Ficus Virginiensis 295

315. Sapindopsis elliptica 297

Identical.

Sequoia Reichenbacbi (Gein.) Heer.

Asplenium Johnstrupi Heer.

Identical.

Do.
Sequoia fastigiata (Sternb.) Heer.

Pecopteris tenuis Schouw.

Pecoptera denticulata Heer.

Pteris Albertsii Heer.

Pteris Albertsii Heer.

Pteris frigida Heer.

Identical.

A. Oerstedi Heer.

A. Oerstedi Heer.

A. Jenseni Heer.

IdenlicaL

Pteris longipennis Heer.

Nilssonia Johnstrupi Heer.

Identical.

Do.

Do.

Do.
S. subulata Heer.
Sequoia fastigiata (Sternb.) Heer.

Sassafras recurvatum Lx.

Identical.

"Widdringtonia Reichii Efct.

Sequoia fastigiata (Sternb.) Heer.

Banksites Saportanus Velen.
Conospermites baketefolius Ett.
B. argillaceum Velen.
H. primigenia Sap.
Identical.

Do.
Cunninghamites oxycedrus Presl.
Asterosoma radiciforme Otto.
Ficus protoga?a Ett. (nee Heer).
Identical ? .
Identical.
Sequoia fastigiata (Sternb.) Heer.

S. cretacea Newb.
S. recurvata Ls.
Ficus magnoliiEfolia Lx.
F. laurophylla Lx.
Ficus laurophylla Lx.

372

THE POTOMAC OR YOUNGER MESOZOIO FLORA.

Table III.

-Localities other than those of the Potomac formation at which Potomac species or their allies
have been found, etc. — Continued.

Geological formations.

Potomac species (systematic numbers on the
left; page on which described on the right).

XXX.— Dakota Group,
TJnited States— Continued.

XXXI — Senonian ol' Patoot,
Greenland.

XXXn.— Senonian of
British America.

SXXni.— Senonian of Qued-

linburg.
XXXIV.— Senonian (Goaau)

of Tyrol.

XXXV.— Senonian of West-
phalia.

XXXVI.— S e n 0 n i a n of
Aachen.

XXXVII.— Laramie group . .

XXXVin.— Eocene of Eng-
land.

Species with which compared.

352. Platanophyllnm orassinerve 316

353. Araliiephyllum obtusilobum 317

354. Aralia"piiyllum acutilobum 318

355. Araliasphyllum magnifolium 318

356. Aialiwphyllum aceroides 319

221. Sequoia subulata Heer 245

223. Sequoia rigida Heer 246

226. Sequoia delicatula 247

240. Sphonolepidium parceramo.sum 257

247. Sphenolepidium Sternbergianum, var. 261

denaifolium Heer.
311. Ficophyllum senatum 294

218, Sequoia cycadopais 243

219. Sequoia Eeichenbachi (Gein.) Heer... 243

309. i^cophyllum crassinerve 291

219. Sequoia Eeichenbachi (Gein.) Heer.-. 243

219 Do 243

223. Sequoia rigida Heer 246

233. Taxodium ramosnm 251

235. Taxodium expansum 252

219. Sequoia Eeichenbachi (Gein.) Heer ... 243

244. Sphenolepidinm Virginicum 259

245. Sphenolepidium Kurrianum Heer 260

246. Sphenolepidium Sternbergianum 261

(Dunk ) Heer
219. Sequoia Reichenbachi (Gein.) Heer ..- 243

219.

.Do.

230. Araucaria podocarpoides 249

304. Eogersia lougifolia 287

Hcdera platanoidea Lx.

Sassafras recurvatum Lx.
Liquidambar integrifolium Lx.

)
Identical.

Do.
S. subulata Heer.
Sequoia coucinna Heer.
Sequoia fastigiata (Sternb.) Heer.

Quercus -Johnatrupi Heer.

Cycadites tjnjiga Daw.

Identical.

Ficus maxima Daw.

Identical.

Do.

Do.

Widdringtonites Keichii (Ett.) Heer.
Sequoia heterophylla.
Identical.

Sphenolepidium Kurrianum Heer.
Identical.
Do.

Podocarpus incerta Ett. & Gard.
Glossochlamyfl transmutans Ett. &. Gard.

INDEX.

Abietites Mantell 262

iiiacrocarpu3 262

ellipticua 263

AngQsticarpus 263

Acacisepbj'lliitu 279-2S1

lougifolium 279

apatulatum 280

microphyllura '. 2S0

variabile 281

Aceripbyllum 320,321

aralioides 321

Acrosticiiopteris 106-109

longipennis 1 07

densifolia 107

parvifolia 108

parcelobata 108

cyclopteroides 109

Acrosticbum L 105, 106

crassifolium 105

Anient of angiosperm? 272

Aments of conifer sp. 1 225-227

Angioptendium Scbimper 113-117

auricub-tum 113

nervosum 114

ellipticum 114

densinerve 115

pacbypbyllum 115

ovatuiu 115

strictiner ve 116

Tar.latifoliaoi 116

dentatum 117

Angiosperm JE 277-325

Anomozamites Scbimper 167-171

angust ifolius 167

Virginicus 168

subgenus Platypterigium Scbimper 168-171

AraliaL 314

dnbia 314

Aralijepbyllum 316-320

obtusilobum 317

acutilobum 318

magnifoUum 3!8

aceroidea 319

Page.

Araucaria Jnss 249, 250

podocarpoides 249

obtusifolia 249

zamioides 250

Araucarites Sternb. emend 263

Virginicus 263

A quiensis 264

Aristolocbiaepbyllum 322,323

crassinerve 322

AspidiumSwartz 93-104

Fredericksburgense 94

ellipticum 95

beteropbyllum 96

Virginicum 97

angustipinnatum 98

cystopteroides 99

Oerstedi 99

oblongifolium 100

parvifolium 100

pinnatiUdum 101

Dunkeri 101

dentatum 102

macrocarpum 1C3

microcarpum 103

Aspicniopteris 117-119

pinnatifida 118

adiantifolia 118

AspleniumL 109,110

dubium 109

Albrotaxopsis 239-242

grandis 24 0

tenuicauli3 241

expansa 241

pacbypbylla 242

B.

Baiera F. Braun emend 212

foliosa 213

Baieropsis 205-212

expansa 207

pluripartita 208

var. minor 208

foliosa 209

denticulata 21o

Tar. anguslifolia 210

373

374

INDEX.

Page.

Baieropsis longifoUa ,.,.. 210

adiantifoUa 211

var. minor 212

macropbylla 212

Bombax 310

Virginiensis 310

Bracbypliyllam (BrongDiart) Schimper 220-225

crassicaiile 221

parceramosmn 223

sp. ? 223,224

Brooke stiition (plant locality) described 19, 20

C.

Callitris, cone of? 272

Carpolitlins St 264-270

fascicnlatus 265

tematus 265

Tirginiensis 26G

agglomeratns 267

conjagatns 267

geminatus , 267

Erookensia 268

latns 269

cnrratus _ 269

sessilis 269

mucronatns 270

Celastrophyllum (Etting ? sp) S03-307

arcinerre 304

proteoides 304

acutidens 305

obtnsidens 305

Erookense 305

denticulatum 306

latifoliiim 306

tenninerve 306

obovatiim 307

Cepbalotaxopsis 235-238

magnifolia 236

ramosa 2?7

brevifolia 238

Cepbalotaxopsis micropbylla 238

Cladopblebis Brongn 67-81

constricta 68

latifolia 69

Tirginiensis 70

denticnlata 71

falcata 72

parva 73

acata 74

oblongifolia 74

crenata 75

sp.? 76

inclinata 76

distans 77

sp.1 77

alata 77

sp.? 78

rotrmdata 78

sphenopteroides 79

petiolata 80

itiseqniloba 80

pachyphylla 80

sp.? 81

brevipennis 81

Conifers 193-262

Conospemiites Ett 279

ellipticns 279

Page.

Cryptogams 63-166

Ctenis (L.and H.) Zigno emend 177,178

imbricata 177

Ctenopbyllum Scbimper 174r-176

latifolium 175

Ctenopteris Brongn 153-159

insignis 156

Tirginiensis 157

minor 157

integrifolia _ 158

angustifolia 159

longifolia 159

Cycadeosperranm Saporta 270,271

acutum 270

obovatiim 270

spatulatiini 271

ellipticum 271

rotundatnm 371

angustnm 271

D.

Deep Bottom (plant locality) described 10,11

Dioonites Bomemann 181-186

Bucbianns Scbimper 182

■vor. obtnsifolius 184

var. angnstifolins 185

Dntch Gap Canal (plant locality) described 12-14

E.

Encepbalartopsis 174

nervosa 174

Eqniseteic 63-66

EquisetTim L 63-66

Virginicum 63

Lyelli Mantell 65

Ehizoraeof 65,66

Marylandicu <u 65

Eucalyptopbyllnm 325

oblongifolium 325

F.

Eieldeniopsis 204, 205

crassinerris 205

Eicopbyllum 290-294

crassinerre 291

tenninerve 292

serratnm 294

encalyptoides 294

FicuaToumef 294,295

Tirginiensis 295

Fredericksbnrgensis 295

Filices 66-166

Frederickabnrg (plant locality) described 15,16

Erenelopsis Scbenk 213-220

ramosissima 215

parceramosa 218

"ruit capsules sp. ? 272

G.

Gleicbenia Swartz 119

Nordenskioldi ? Heer 119

Glossozamites Scbimper 176

distans 1'^^

Gymnospermffi 166-277

Gymnospermous fmits 262-273

INDEX.

375

Hedercephyllum .

crenulatuiu ..

angulatam . .
Hymenica L

Yirginiensis.

Page.
233-225

JuglamUpljyllum .
inlegrifolium .

Kankey's (plant locality) described .

Laricopsis

longifolia

aBgustifolia .

brevifolia . ..
Leptostrobus Hei

longifoliua .-

folii

! luultiflorus .

M.

Macrospores ? sp

McGee, "W J, proposed Potomac as tbe name of a
goological group

traced Potomac formation to bead of Chesapeake

Eay

Meek, F. B., fossil plants found at Baltimore by

Hcnispermites Lesq

Yirginiensis

tenuinervis

Myrica L -

Brookensia

MyricajpbyUum

deutatum

P.

Pecopteris Brongn ^l"^*

Virginiensia

strictinervia °*

ovatodentata ^^

microdonta

constricta ''"

brevipennia

socialia - °J

angustipennia ^'

Browniana ^^

pacbypbylla

Phanerogama

Phyllitea Brongn '''f'

pacbyphyllus ■ ^^^

Pbyllocladopaia ^J'*

beterophylla ■

Plant localitiea deacribed W-33

Platanopbyllnm ^J^

crassinerTO

Platypterigiam

densiuerve

171
Kogersianura

Podozamites Fr. Braun emend 178-181

subfalcatus

distautinervis

pedicellatua

'^ ,.,,•„= 180

granditolms ^^^

acn tifolius

Pollen sacs?

Polypodium L

fadyenoidea

dentatum

PopulophyUum

reniforme

bederaiforme

N.

194-203

166-325

168-171

Nageiopsis

longifolia y

zamioides

recurvata

crasaicanlia

latifolia

decreacena -

ovata ■

obtnsifolia ■ ^""

inaiquilateralis

• i 201

acuminata

beteropbylla ""■'■

micropbylla ;■

angustifolia "^■'

subfalcata -"^

Newberry, J. S., actnowledgements to 4,33

0.

Osmunda L

spbenopteroides

Dicksonioidea ■

var. latipeunia .

272
104, 105

104

105
311, 312

311

crassinerve

Potomac fossil plants, list of 326-331

Potomac proposed by W J McGee as name of a geo-
logical group 1' 3*

Potomac Eun (plant locality) described 17, 18

231-287

Proteiopbyllum -
rtniforme - .-
orbicalare...

282
283

oblongifoliu

ovatum

ellipticum. .
tenuinerve .
dentatum . .

ercopbyllum

grossedentatnm .
tenuinerve

E.

Eogera, WiUiam B., cited on geological relationa, 1, 4, 6, 33, 34,

35, 49, o2

287,288

Eogersia \^^

l™g'f°"=' ; 288

angustifolia

376

INDEX.

SagenopteriQ Pr 148

latifolia 14S

elliptica U9

Virgiuieusis 150

SaliciphyUum 302,303

loDgifolium 302

ellipticum 303

parvifolium 303

Sapindopsis 296-302

cordata 296

olliptica 207

magnifolia 297

Tariabilis 293

parvifolia 300

brevifolia 300

teDuiuei'vis 301

obtusifolia 301

Sassafras ^^ees 289,290

parvifolium 289

oretaceum ^e wb. , var. heterolobuni 289

bilobatum 290

Scleropteris Saporta 150-153

elliptica : 151

var. longifolia 152

Tirginica 152

dentata - 153

Seed of Pinu3 ? sp. ? 272

Sequoia Torrey 243-248

cycadopsia 243

EeicbeDbaclii (Geinitz) Heer 243

var. lougifolia 244

sublata 245

ambigua Heer 245

rigida Heer 246

densifolia 24G

gracilis Heer 247

delicatulata 247

sp.? --.. 247,248

Sphenolepidium Heer (Sphc-nolepis Sclienk) 257-262

parceramosum 257

dentifolium 258

recurvifolium 258

pacbyphyllnm 259

Virginicum 250

Kurrianum Heer 260

Sternbergianum (Dunli. sp.) Heer 261

var. densifolium Heer 26]

Sphenoptoris Brongn 89-93

tbyrsopteroides 89

acrodentata 90

latiloba 90

Mantelli 91

spatulata 93

pactiypbylla 93

Stenopteris Saporta 112

Yirginica - 112

SterculiaL 314

elegans 314

T.

Tasodium Kichard ( G lyptoatrobaa Endl. ) 250-257

ramosum 251

Virginicum 252

espausum 252

fastigiatum - 253

Tiixodium denticulatum 1 253

Brookeuse 254

var. augustifoUum 250

Taylor, E. C, cited on fossil plants at Fredericksburg 4

Telegraph Station (plant locality) described 22

Tbiuufeldia Ett 110-112

variabilis 110

gramilata ill

rotuudiloba Ill

Tbrysopteris Kuuze 119-144

Yirginica 120

brevifolia 121

dentata 121

nervosa 122

rarinervis 123

brevipennis 124

alata 124

divaricata 125

Meekiana 125

var. angTistlloba 126

crenata 127

insignis 127

var. angustiiteunis 128

densifolia 129

crasainervia 130

decurrens 130

angustifolia 131

microphylla 131

pacbyracbis 132

elliptica 133

distans 134

anguatiloba 134

pacby pbylla 135

pecopteroides 135

piuuatifida 136

beteromorpba ■. 136

varians 137

rhombifolia 138

beteroloba 139

bella 139

microloba 140

var. alata 140

nana 141

inaicpiipinnata 142

betcrophylla 142

obtusiloba 143

spbeuopteroides 143

squarrosa 143

rbombiloba 144

retnsa 144

Torreya Aruott --- 234,235

Virginica ,234

falcata 235

Trent's Keach (plant locality) described 11, 12

Tyson, P., fossil cycads found by 5,30,31

Tysonia.--. 186-193

Marylandica 1 93

IT.

Uhler, P. K., discovered fossil plants 5, 6, 15, 33

acknowledgments to 33

irimipbyllum 312,313

Brookense 312

tenuinerve 313

crassinerve 313

INDEX.

377

Pa ire.

Undetermined fern 119

TJndfitermined fi-rn in circinate vernation 145

Undeteriuiued plauta 274-276

V.

Vitiphyllum (Cissites ?J 308-310

crassifolium 308

parvilolium 3(i9

multifidum 309

W.

Ward, Lester F., made the tables comparing Potomac

plants and other fossil floras SXII

coUi'cti'd fossil plants at Baltimore 29

acliiiowledjiments to 33

White House Bluff (plant locality) described 22,23

Pajr

Williamaonia Carr -2

Yirginieusis 2

Z.

ZamiesB 166-1

Zamiopsis I6u-l

pinnatifida j

insiy:cis i

loDffipenuia ]

laciniala \

petiolata ]

Zamites Broujin 171-1

teuuiiiervis i

crassinervis ]

distant inervis ]

ovalis 1

subfalcatus i