Palmlike Plants from the 

Dolores Formation 

(Triassic) 

Southwestern Colorado

GEOLOGICAL SURVEY PROFESSIONAL PAPER 274-H
Palmlike Plants from the 

Dolores Formation 

(Triassic) 

Southwestern Colorado

By ROLAND W. BROWN

A SHORTER CONTRIBUTION TO GENERAL GEOLOGY

GEOLOGICAL SURVEY PROFESSIONAL PAPER 274-H

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1956
UNITED STATES DEPARTMENT OF THE INTERIOR 

Douglas McKay, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

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

Washington 25, D. C.
CONTENTS

Page Page 

Abstract.-_________________________________________ 205 Relationships of Sanmiguelia^-- ______________________ 207

Geologic occurrence of the plants.____________________ 205 Bibliography.___________________-_-___-___-_-----_- 209

Description of the specimens,________________________ 206

ILLUSTRATIONS

Page 

FIGURE 29. Reconstruction of Sanmiguelia lewisi Brown_____________ ______________________________________________ 206

PLATES 32, 33. Triassic plants from southwestern Colorado ___________________________________-------_-- _ -Following 206

in

A SHORTER CONTRIBUTION TO GENERAL GEOLOGY

PALMLIKE PLANTS FROM THE DOLORES FORMATION (TRIASSIC) IN SOUTHWESTERN

COLORADO

By KOLAND W. BROWN

ABSTRACT

Plant remains from the Dolores formation in southwestern 

Colorado include a few small twigs of the conifer Brachyphyllum 

and large, many-ribbed leaves described as those of an angiosperm, tentatively regarded as a primitive palm and named 

Sanmiguelia lewisi. This is the earliest known angiospermous 

flowering plant. Its occurrence in the Middle to Late Triassic, 

however, indicates that evidence for the origin of the angiosperms should be looked for in the earlier Triassic or late 

Paleozoic.

GEOLOGIC OCCURRENCE OF THE PLANTS

In September 1953, G. Edward Lewis, of the U. S. 

Geological Survey, searching for fossil remains in the 

upper part of the San Miguel Kiver valley in southwestern Colorado, found a palmlike leaf impression in 

the red Dolores formation near Placerville. This 

specimen, 38 cm long and 20 cm wide, was fragmentary, 

lacking the apex and base. Therefore, further search 

was made at the same locality early in 1954, but Lewis 

found only a few more fragments, none of which gave 

a clue to the nature of the basal or petiolar portion of 

the leaves. However, in September 1954, Lewis and 

the writer, at an outcrop one-half mile north of the 

original site, succeeded in finding fairly good specimens 

that illustrate the salient features of these leaves, 

some of which were still attached to part of a structureless cast of a stem. Further exploration of the fossilbearing bed along its outcrop for 10 miles on both sides 

of the San Miguel Kiver yielded equally good material 

to the writer in June, 1955.

The principal locality is in SE% sec. 12, T. 43 N., R. 

11 W., in a low cliff of reddish calcareous sandstone, on 

the hillside of the right bank, 420 feet above the San 

Miguel Kiver and 145 feet above the base of the 

Dolores formation, near the old Fall Creek post office, 

about 2% miles southeast of Placerville. Exposed there 

is the following pertinent sequence of strata, omitting 

the overlying 1000 feet of the Jurassic Wanakah and 

Morrison formations, and 250 feet of the Cretaceous 

Dakota sandstone:

364884—56

Partial section at old Fall Creek post office, Colorado

Jurassic

Entrada sandstone. 50 ft. Whitish massive sandstones with

few dark, shaly or limy thin-bedded strata. 

Triassic

Dolores formation. 485 ft. Bright red, calcareous, massive 

and thin-bedded cliff-forming sandstones, few shales, 

and some conglomerates. It yields remains of metoposaurs, phytosaurs, and plants. The lowermost 

whitish conglomeratic sandstone rests on an erosion 

surface of the Cutler formation. 

Permian

Cutler formation. 275 ft. Dark red shales and sandstones, 

with fragmentary plants.

The Dolores formation, named and described by 

Whitman Cross (1899) from exposures in the valley of 

Dolores River in southwestern Colorado, at first 

included the red beds that are now known as the Cutler 

formation. However, the discovery in 1904 near 

Ouray of an angular unconformity below the fossiliferous horizon in the Dolores caused Cross and his 

associates (Cross, Howe, Ransome, 1905; Cross, 

Ransome, 1905; Cross, Howe, Irving, 1907) to restrict 

the name Dolores to the Triassic strata and to name 

the more reddish underlying beds the Cutler formation, 

provisionally of Permian age. Cross reported that 

R. C. Hills in 1880 and 1882 had announced the discovery of fossils in the Dolores, including reptilian 

teeth, ganoid fishes, mollusks, ana plants. Before 

these could be described, however, they were lost. 

Cross said that in the course of his survey of the area 

more reptilian teeth and a plant, identified by David 

White as Pachyphyllum [an error for Brachyphyllum] 

munsteri, were found. All of these fossils reputedly 

indicated the Triassic age of the Dolores. At the Fall 

Creek post office locality in the Dolores the writer and 

Lewis in 1954 found phytosaurian teeth and the plant 

impressions described in the following pages, including 

the object of unknown identity (pi. 33, fig. 4).

The nonmarine sediments of the Triassic in the "four 

corners" area of the southwestern States are believed

205
206 SHORTER CONTRIBUTIONS TO GENERAL ASSEMBLY

FIGURE 29. Tentative reconstruction of Sanmiguelia lewisi Brown. In life the leaves were probably somewhat stiff, like the lower right hand leaf, rather than 

undulant. No sheaths or crests are shown because discernible evidence for them is lacking. X 1/5

to have accumulated on floodplains and in scattered 

pools and lakes at not many hundreds of feet above sea 

level. Such plants, therefore, as were entombed in the 

sediments, most likely originated in the lowlands of 

the basin of deposition, whereas remains of more distant upland plants did not get into the fossil record. 

Whatever the reason, whether land vegetation was 

sparse on account of climatic conditions, or whether 

the circumstances attending the accumulation of the 

sediments were unfavorable, plant remains in the 

Dolores apparently are relatively scarce.

DESCRIPTION OF THE SPECIMENS

CONIFERS

Brachyphyllum miinsteri Schenk 

Plate 33, figures 1, 3

Brachyphyllum miinsteri Schenk, 1867, Die fossile flora der Grenzschichten des Keupers und Lias Frankens, p. 187, pi. 43, 

figs. 1-12.

The coniferous twigs from the Dolores formation, 

here figured, resemble closely those shown by Schenk 

from the Rhaetic formation at Bamberg, Germany. 

Neither these nor Schenk's specimens, however, quite 

match the usual conception of the features of the genus 

Brachyphyllum with its closely appressed foliage. They 

can be compared with the twigs of some species of 

Palissya, Sequoia, Sphenolepidium, Araucarites, and 

others found in the Triassic and later formations. 

Without cones or other distinguishing features, the 

identification of remains of this kind is fraught with 

much uncertainty. Probably the specimen collected 

by Cross (1899) in the Telluride quadrangle and identified by David White as Pachyphyllum munsteri, was 

a representative of this species—the Pachyphyllum 

being an error for Brachyphyllum. Apparently, that 

specimen is now lost.

Numerous species of conifers have been described 

from the Triassic of the United States, and particularly 

from the southwestern States, notably in and around 

the Petrified Forest National Monument near Hoibrook, Arizona. There is, therefore, nothing especially 

unusual about the presence of such remains in the 

Triassic of southwestern Colorado.

MONOCOTYLEDONS 

SANMIGUELIA Brown, n. gen.

Plants with alternate, simple, large, elliptic, strongly 

pleated, monocotyledonous, palmlike leaves. Stem 

rounded, tapering rapidly toward the apex, but other 

features unknown.

Sanmiguelia lewisi Brown, n. sp. 

Plate 32, figures 1, 2; plate 33, figure 2

Elliptic to ovate entire, firm-textured leaves, attaining a length of 40 cm and width of 25 cm, conspicuously pleated, the strong ribs or veins converging 

toward the apex and the base. Midrib not differentiated. Between the 16 to 20 ribs are closely spaced 

parallel veinlets, as in all palms. The leaves are attached to the stem alternately by broad, thin, clasping, 

or probably sheathing petioles at vertical intervals of 

4 cm, as shown by three leaves preserved in one block 

of sandstone. These permit a tentative reconstruction 

of the plant (fig. 29). However, neither sheaths nor 

crests (hastulas, ligules) are discernible, either because 

none existed or because the preservation around the 

stem is poor. The stem, now only a calcitic cast 

without cell structure, is rounded and in a vertical distance of 10 cm narrows rapidly from a diameter of 4 

cm to a blunt point, thus suggesting that it is the apical 

portion of a low, but mature plant.

PLATE 32

FIGURES 1, 2. Sanmiguelia lewisi Brown. Fig. 1 shows the broad base of the petiole clasping the grayish, granular, rounded stem. 

The latter is a calcitic cast without cellular structure. X %
GEOLOGICAL SURVEY PROFESSIONAL PAPER 274 PLATE 32

TRIASSIC PLANTS FROM SOUTHWESTERN COLORADO
GEOLOGICAL SURVEY PEOFESSIONAL PAPER 274 PLATE 33

TRIASSIC PLANTS FROM SOUTHWESTERN COLORADO
PALMLIKE PLANTS FROM DOLORES FORMATION 207

The generic term Sanmiguelia is feminine and is from 

the name of the river at the type locality. The species 

is named for G. Edward Lewis, vertebrate paleontologist 

of the U. S. Geological Survey and discoverer of the 

first specimens.

RELATIONSHIPS OF SANMIGUELIA

/

Sanmiguelia leurisi is regarded tentatively but credibly as a primitive palm. Superficially its leaves resemble those of species of other monocotyledonous 

genera, such as Carludovica, Curculigo, Cypripedium, 

Joinvillea, Lilium, Potamogeton, Setaria, Smilacina, 

Veratrum, and others. In some of these the plicate or 

accordion-pleated feature of the foliage is almost as 

strongly and comparably developed, and there may be 

no distinct midrib. Consequently, it is regrettable that 

no flowers, fruits, or stems with cell structure, have 

been found with Sanmiguelia to eliminate the foregoing 

genera completely and to establish its identity as a 

palm conclusively.

Besides the suggestive morphologic appearance of 

its leaves, further reason for believing that Sanmiguelia 

represents a palm is derived from consideration of the 

probable ancestral features of primitive palms. The 

late Robert T. Jackson, from observations of the 

juvenile leaves of palm seedlings and with numerous 

lucid illustrations, discussed this phase of the subject 

in part, as follows (Jackson, 1899, p. 124, pi. 23):

Amongst palms many species present interesting features of 

localized stages in development. I have studied the development of seedling palms of thirty-seven species and from published 

figures of von Martius and others know something of the early 

characters of forty-five species distributed through twenty-eight 

genera. Seedlings of all species have simple, early seed-leaves, 

and these are always one of two types. The first and most 

primitive type of seed-leaf is elongate, lanceolate, or oval, terminating more or less acutely, and with a longer or shorter 

rachis, usually long. This type is seen in Latania (pi. 23, fig. 

94), Corypha (pi. 23, fig. 104), Cocos (pi. 23, fig. 102), Phoenix 

(pi. 23, figs. 100, 103, 103a), and many other genera. The second type of nepionic or seed-leaf is similar to the first, except 

that it is distally cleft. It is characteristic of Chrysalidocarpus 

(pi. 23, fig. 95), Kentia (pi. 23, fig. 96), Caryota (pi. 23, fig. 98), 

and many other genera. Very young specimens of genera which 

have distally cleft leaves or exceptional individuals show a transient distal fusion of the apices of the leaf, as in Kentia (pi. 23, 

fig. 96), demonstrating that the cleft type is only a modification 

of the first or entire type. In some types as Stevensonia grandifolia J. Dune. (Phoenicophorum sechellarum H. Wendl.), which 

have distally cleft leaves, the first leaves are entire, the cleft 

character appearing later (third leaf of the specimen in hand).

This is a further demonstration of the primitive nature of the 

entire type * * *. In Latania commersoni J. F. Gmel. (L. 

borbonica Lam.), the seed-leaf is ovate, lanceolate (pi. 23, fig. 

94); during growth the later leaves become relatively broader, 

until, by distal tension, splits take place (pi. 23, fig. 93), and in 

the adult the leaf is a quite broad, fan-leaf type * * *. In the 

growth of a pinnate-leaved palm, when a new leaf first appears, 

the pinnae cling together laterally on their outer margin and to 

the distal leaflet, in such a way that the whole leaf simulates the 

entire type and demonstrates the simple dynamic genesis of this 

type of compound leaf from an ovate leaf like that of the young 

* * *. Also the distal tip of pinnate leaves repeats the form of 

nepionic leaves * * *. Some palms sucker from the base, and 

in such suckers we might expect to find localized stages in development, as is the case. In Raphis flabelliformis L'Herit., a 

fan-leaf palm, suckers from the base have simple leaves like pi. 

23, fig. 94, and only in later growth are the typical fan-leaves of 

the species acquired * * *. Suckers of Chrysalidocarpus 

lutescens repeat the form of the seedling so closely that they are 

practically identical in leaf characters * * *.

To Jackson's discussion of juvenile leaf forms should 

now be added Eames' recent interesting observations 

on the development of leaves in the mature stages of 

palms (1953). In general, the simple seedling leaves 

are succeeded, according to the kind of palm, by pinnate or palmate leaves. Study of histological preparations of leaf primordia indicates that the palmate is 

derived from the pinnate form, the central pinna of the 

palmate being the distal pinna of the pinnate leaf, and 

the rachis of the palmate leaf being shortened or telescoped. The rein or marginal flange that is present 

on erupting leaves of mature plants is seldom seen on 

the leaves of juvenile plants.

Ancestral or reminiscent features have not been as 

definitely recognized in the lineage of the palms as they 

have in such genera as Ginkgo (Brown, 1939, p. 246; 

1943, p. 862, figs, la-lc) and Cercidiphyllum (Brown, 

1939). Until now the fossil record of the palms has 

dated from the Jurassic Lias. Lignier (1895, 1908), 

from collections in Normandy, described and illustrated as Propalmophyllum liasinum, fragmentary portions 

of fan-shaped leaves showing chiefly the apexes of the 

petioles and bases of the fans, with a few ribs. Of 

these Seward (1931, p. 366) saidSome French fossils described by Prof. Lignier as Propalmophyllum bear a striking resemblance to pieces of a palm leaf, though 

they cannot be accepted as proof of the existence of palms in a 

Jurassic flora.

Nevertheless, in a table on page 414 of the same book, 

Seward indicates Palmae as dating from the Jurassic. 

I, myself, see no reason for doubting Lignier's identiPLATE 33

FIGUKES 1, 3. Coniferous twigs of Brachyphyllum munsteri Schenk. X 1

2. Sanmiguelia lewisi Brown, showing the numerous parallel veinlets between the prominent ribs. X %

4. Unknown object, probably an animal trail. X 1

5. Paloreodoxites plicatus (Lesquereux) Knowlton, from the Paleocene Dawson arkose near Ramah, Colo. X 2
208 SHORTER CONTRIBUTIONS TO GENERAL ASSEMBLY

fication of his leaves as palms. True, some fragmentary Jurassic and later fossils, superficially somewhat 

resembling the fragments figured by Lignier, have been 

mistaken for remains of palms; but these are the egg 

capsules of chimaeroid fishes (Brown, 1946).

The first authentic remains of palms found in the 

United States are from the early Upper Cretaceous. 

From then on, both fan and feather palms are not 

uncommon. The fossil wood of palms, known as 

Palmoxylon, is fairly abundant at some localities. 

When thoroughly silicified it is attractive and durable; 

and in Aboriginal American days it was sometimes 

used for making arrow-points and other artifacts. 

Fossil trunks, or portions thereof, that are sometimes 

misidentified as Palmoxylon, are the Mesozoic ferns 

known as Tempskya. The fossil fruits of palms, particularly of Nipa, are known. Others, sometimes 

called Palmocarpon, are somewhat indefinite and 

doubtful.

More particularly pertinent to the discussion of the 

relationships of Sanmiguelia lewisi are leaves of Paloreodoxites plicatus (Lesquereux) Knowlton (pi. 2, fig. 5) 

from Paleocene strata in the Denver basin, Colorado— 

the Denver formation at Golden; and the Dawson 

arkose at Ramah. The small fragment from the Eaton 

formation at Tercio, described by Knowlton (1917, p. 

287, pi. 63, fig. 1), must be regarded as doubtfully 

identified. These elliptic to ovate leaves (approximately 20 cm in length and 7 cm in width, with 12 

ribs) were called Oreodoxites plicatus by Lesquereux 

(1883, p. 122, pi. 18, figs. 1-4). Knowlton (1930, p. 41, 

pi. 11, figs. 1-4) changed the generic name of this 

species to Paloreodoxites because the genus Oreodoxites 

was founded by Goppert on an indefinite Permian seed, 

and because Lesquereux may not have known of 

Goppert's genus but thought he was creating the name 

anew on the basis of similarities he saw between his 

leaves and those of the living Oreodoxa. Actually, as 

there appears to be no close relationship between 

Paloreodoxites and Oreodoxa, Knowlton's name is not 

too happy a substitute.

The prime question now is, Are the leaves of Paloreodoxites plicatus leaflets of a large compound leaf, as 

Lesquereux seems to have conjectured; simple, mature 

leaves; or simple, seedling leaves? Because none of 

these leaves has been found attached to a rachis or 

stem, their exact nature is open to speculation. The 

leaves could be simple seedling leaves of fan or of 

feather palms, both kinds having been present in the 

Denver basin and adjoining areas during Paleocene 

time. The leaves could be mature leaflets of a pinnate 

palm, or they could be mature leaves of a primitive 

kind of palm, a leftover from early Mesozoic time.

Whatever the answer to the foregoing question, the 

leaves of Sanmiguelia resemble somewhat those of 

Paloreodoxites and some from the Stonesfield slates in 

the Jurassic Oolite at Eyeford, England, called Lilia 

[an error for Lilium] lanceotata Buckman (in Murchison, 

.1845, p. 93, pi. 2, fig. 3). This is Buckman's description—

Leaf ovato-lanceolate, with a slight acuminated point—leafstalk short. An elegant parallel veined endogenous leaf, having 

much the appearance of leaves of the liliaceous tribe of plants.

On the same plate Buckman figured two somewhat 

similar but more fragmentary leaves as Naiadea 

acuminata and Stricklandia acuminata, both of which 

he described as endogenous leaves. Seward (1904, 

p. 121, 122) synonymized "Lilia" and Naiadea with 

Podozamites stonesfieldensis and Stricklandia with Baiera 

phillipsi. As I have not seen these specimens I can 

form an independent opinion of them only from 

Buckman's descriptions and illustrations. Consideration of these almost persuades me that perhaps Seward's 

disposition of the specimens was not altogether appropriate. Particularly, I am doubtful about Buckman's 

pi. 2, fig. 3 of "Lilia". How Buckman, whose other 

illustrations seem to be fairly accurate, could have 

drawn a coarsely ribbed leaf from a specimen that, if 

Seward is correct, should have no ribs but only numerous closely spaced parallel veins, as in typical 

Podozamites, I do not comprehend. His illustration 

looks too much like those of small leaves of Paloreodoxites, Sanmiguelia, or seedling leaves of living palms, 

to be dismissed too lightly as Podozamites. Moreover, 

Seward (1904, p. 152, pi. 11, figs. 5, 6) described and 

figured as Phyllites a poplarlike leaf from the same 

beds. This leaf has the appearance of an authentic 

dicotyledonous leaf, and if it is such, it strongly supports the opinion that primitive palms, or at least 

monocotyledons, also could have existed simultaneously somewhere and perhaps in the same flora. 1 

Furthermore, the fan palms (Propalmophyllum) of 

Lignier were already in existence in Lias time in 

Normandy. The doubtful nature of "Lilia," and the 

impossibility of demonstrating any but a superficial 

resemblance among "Lilia," Paloreodoxites, and the 

specimens here being reported, necessitate a new name 

for the Colorado monocotyledon.

Possibly Sanmiguelia lewisi represents some plant 

other than a palm or similar monocotyledon with 

parallel-veined leaves. For example, Cordaites has 

strap-shaped leaves whose veins are closely spaced but 

the leaves are not plicate or strongly ribbed. Perhaps 

the yuccalike leaves sometimes reported from Triassic

i Under the name Sassendorfites benkerti, Oskar Kuhn, in a report just received 

from Germany, describes and illustrates another dicotyledonous leaf, this from lower 

Jurassic strata at Sassendorf, near Bamberg. (Orion, Jahrg. 10, no. 19-20, Oct. 1955.)
PALMLIKE PLANTS FROM DOLORES FORMATION 209

localities under the name Yuccites are cordaitean 

foliage. Some cycads have leaves comparable in size 

to those of Sanmiguelia but the veins are not ribbed as 

in palms, and, if closely parallel, may fork or anastomose to make a notably reticulate pattern. So far as 

I am aware, no other extinct or living plants, except 

palms and species of the monocotyledons already 

mentioned, have leaves that match or closely resemble 

those of Sanmiguelia lewisi. This species, if not a 

primitive palm, is a palmlike monocotyledon, whose 

simple leaves without midribs are fully developed, not 

seedling leaves, of a mature plant. If this be true, 

these specimens are the oldest known megascopic 

remains of the angiospermous flowering plants.

Botanists and paleobotanists have long been looking 

for evidence concerning the time, place, and manner of

origin of the angiospermous plants. Adequate summaries of the speculations on this matter may be found 

in Arnold (1947, p. 333-365) and Axelrod (1952), with 

pertinent bibliographies. Sanmiguelia lewisi does not 

seem to provide answers to some of the fundamental 

questions involved in this speculation: Did the monocotyledons come from the dicotyledons or the dicotyledons from the monocotyledons or did both descend 

from a common ancestor? Did woody monocotyledons derive from herbaceous ancestors? Did the 

angiosperms originate in upland areas, according to 

Axelrod's thesis? As representatives of the angiosperms existed in the early Jurassic it is not altogether 

surprising now to find their ancestors in the Triassic. 

Perhaps their ultimate origin must be sought in the 

Paleozoic.

BIBLIOGRAPHY

Arnold, C. A., 1947, An introduction to paleobotany: New York, 

McGraw-Hill Co.

Axelrod, D. I., 1952, A theory of angiosperm evolution: Evolution, v. 6, p. 29-60.

Brown, Roland W., 1939, Fossil plants from the Colgate member 

of the Fox Hills sandstone and adjacent strata: U. S. Geol. 

Survey Prof. Paper 189, p. 239-275, pis. 48-63.

———— 1939, Fossil leaves, fruits, and seeds of Cercidiphyllum: 

Jour. Paleontology, v. 13, p. 485-499.

———— 1943, Some prehistoric trees of the United States: Jour. 

Forestry, v. 41, p. 861-868, fig. 1.

1946, Fossil egg capsules of chimaeroid fishes: Jour.

Paleontology, v. 20, p. 261-266, pis. 38, 39. 

Buckman, James, 1845, in R. I. Murchison, Outline of the

geology of the neighborhood of Cheltenham, p. 93-109,

pis. 1-13. 

Cross, Whitman, Howe. Ernest, and Irving, J. D., 1907, Ouray

quadrangle, Colorado: U. S. Geol. Survey, Geol. Atlas of

the U. S., Folio 153. 

Cross, Whitman, Howe, Ernest, and Ransome, F. L., 1905,

Silverton quadrangle, Colorado: U. S. Geol. Survey, Geol.

Atlas of the U. S., Folio 120.

Cross, Whitman, and Purington, C. W., 1899, Telluride quadrangle, Colorado: U. S. Geol. Survey, Geol. Atlas of the

U. S., Folio 57. 

Cross, Whitman, and Ransome, F. L., 1905, Rico quadrangle,

Colorado: U. S. Geol. Survey Atlas of the U. S., Folio 130.

Eames, Arthur, J., 1953, Neglected morphology of the palm 

leaf: Phytomorphology, v. 3, no. 3, p. 172-189.

Hills, R. C., 1880, Note on the occurrence of fossils in the Triassic 

and Jurassic beds near San Miguel in Colorado: Am. Jour. 

Sci., v. 19, p. 490.

——— 1882, Jura-Trias of southwestern Colorado: Am. Jour.

Sci., v. 23, p. 243. 

Jackson, R. T., 1899, Localized stages in development in plants

and animals, Mem. Boston Soc. Nat. Hist., v. 5, no. 4,

p. 89-153, pis. 16-25. 

Knowltoh, F. H., 1917, Fossil floras of the Vermejo and Raton

formations of Colorado and New Mexico: U. S. Geol.

Survey Prof. Paper 101, p. 223-455.

———— 1930, The flora of the Denver and associated formations 

of Colorado: U. S. Geol. Survey Prof. Paper 155.

Lesquereux, Leo, 1883, The Cretaceous and Tertiary floras: 

U. S. Geol. Survey Terr. Rept., v. 8.

Lignier, Octave, 1895, Vegetaux fossiles de Normandie—II, Contributions a la flore liasique de Sainte-Honorine-la-Guillaume 

(Orne.): Mem. Soc. Linn. Normandie, v. 18, p. 121-152, 

figs. 1-6.

———— Idem, 1908, V. Nouvelles recherches sur le Propalmophyllum liasinum Lignier: Idem., v. 23, p. 1-14, pi. 1.

Seward, A. C., 1904, Catalogue of the Mesozoic plants in the 

Department of geology British Museum (Natural History). 

The Jurassic flora—II, Liassic and oolitic floras of England.

———— 1931, Plant life through the ages: New York, The 

Macmillan Co.

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