Skip to main content

Full text of "A Cretaceous and Lower Tertiary Section in South Central Montana"

See other formats

Early Journal Content on JSTOR, Free to Anyone in the World 

This article is one of nearly 500,000 scholarly works digitized and made freely available to everyone in 
the world by JSTOR. 

Known as the Early Journal Content, this set of works include research articles, news, letters, and other 
writings published in more than 200 of the oldest leading academic journals. The works date from the 
mid-seventeenth to the early twentieth centuries. 

We encourage people to read and share the Early Journal Content openly and to tell others that this 
resource exists. People may post this content online or redistribute in any way for non-commercial 

Read more about Early Journal Content at 
journal-content . 

JSTOR is a digital library of academic journals, books, and primary source objects. JSTOR helps people 
discover, use, and build upon a wide range of content through a powerful research and teaching 
platform, and preserves this content for future generations. JSTOR is part of ITHAKA, a not-for-profit 
organization that also includes Ithaka S+R and Portico. For more information about JSTOR, please 





Vol. XLI. April, 1902. No. 170. 


(Plate XXIX.) 
{Read ApHl 3, 1902.) 

This paper is intended only as a preliminary report of an inter- 
esting geological section — an account of what has been done and a 
suggestion of what is yet to be accomplished. The points of inter- 
est are: (i) The completeness of the Upper Cretaceous which 
overlies the older beds, probably Jurassic and Lower Cretaceous, 
and underlies the Fort Union, which here contains mammalian 
remains, correlating it with the Torrejon of New Mexico; (2) the 
excellent exposures of the strata, giving a good opportunity for 
study; and (3) the occurrence of interesting fossils, especially verte- 
brates, in several different horizons. 

The region here referred to lies east of the Crazy Mountains and 
south of the Big Snowies, in the basin of the Musselshell River, in 
Sweetgrass County. It extends from south of the Musselshell River 
southward twelve or fifteen miles, and eastward from a line passing 
southward from Harlowton on the Musselshell about the same dis- 
tance. This is part of the south limb of a broad anticline, the 
general trend of which is south of east. This anticline is dissected 
longitudinally by the Musselshell. The lowest strata exposed are 
upheaved into a dome-shaped uplift southeast of Harlowton and 
four or five miles south of the river, where strata which are appar- 
ently of Jurassic age are exposed. 

This region is on the western border of the elevated plains coun- 
try, and occupies a position intermediate between the plains and 



the foothills. The strata are, as a rule, not horizontal, but have 
been affected by the disturbances which have elevated the moun- 
tains farther to the west or north. In restricted localities the beds 
are horizontal and in others nearly vertical, and there are all inter- 
mediate grades. The average dip is probably not more than fifteen 
or twenty degrees. 

The relief beautifully expresses the geological character. Through 
the whole section there are alternations of sandstones and shales 
and all grades between the two. Sometimes, as in the Fort Benton 
and Fort Pierre, the shales predominate and attain a considerable 
thickness. Again, as in the Dakota (?), Niobrara, Fox Hills, etc., 
sandstones predominate — at least there is enough indurated sand- 
stone to retard erosion and to produce prominent ridges which can 
be followed for long distances — fifty miles or more. In all the 
formations there is considerable sandstone, and in all there is much 
shale ; but I have seen but very little limestone in the whole section, 
though it sometimes occurs in concretions or in thin layers. 

It does not appear that during the whole period of deposition the 
sea ever attained any great depth. Probably it was deepest at times 
during the Benton epoch, yet even here the great amount of sand 
in the shales indicates near-shore deposition. The erosion features 
will be given in the descriptions of the different formations. 

So far as I am aware this particular region has been described 
only by the writer (see Science , January 3, 1902, p. 31, and Febru- 
ary 14, 1902, p. 272). A little to the west is the area mapped in 
the Little Belt Folio (No. 56) of the U. S. Geol. Survey, and some 
work was done to the eastward on Swimming Woman and Careless 
Creeks by W. Lindgren and George H. Eldrege, in connection 
with the Northern Transcontinental Survey.^ 

Of course there is no single section where all the features here 
described can be seen, and the depressions or ridges into which the 
different strata weather have frequently to be followed for a few 
miles to obtain good exposures. Fortunately this is easily done. 

The Lake Basin, to which reference will frequently be made, is a 
large, depressed area nearly fifty miles long east and west and 
twenty-five miles north and south in the widest portion. The 
former represents the greatest east and west extension. The east- 
ern portion extends northeastward. This portion I have not ex- 

1 Tenth Census of the United States^ Vol. XV, p. 243. 


plored. The basin has no outward drainage, but has several small 
lakes without outlets, into which small streams empty, when there is. 
an excess of precipitation. The basin is bounded on the south by 
the high rocky bluffs of the Fox Hills, and on the north, at least in 
the western portion, by the hard sandstones of the Niobrara and 
the Dakota (?). The name Lake Basin seems doubly appropriate, 
for it not only contains lakes, but it resembles the bed of some 
ancient body of water with bays and inlets, and with capes, pro- 
monotories and peninsulas extending into it from the southward. 
The scene is spread out like a great panorama ; the southern hills 
and northern ridges become hazy in the distance and the farther 
border seems a dim ridge on the eastern horizon. At the foot of 
the Fox Hills bluffs are the Fort Pierre shales and still farther away 
the Fish Creek beds. 

As the principal object of this paper is to show something of the 
characters of the uppermost Cretaceous and Lower Tertiary forma- 
tions in this locality, and to give a little light tending toward the 
clearing up of the problem concerning the boundary between the 
Mesozoic and the Cenozoic ages in the Rocky Mountains, I will 
give only a brief sketch of the formations lower than the Niobrara. 

Jurassic, etc. 

The supposed Jurassic is exposed in a dome-shaped uplift, so that 
the strike of the outcrop is nearly a circle. The beds are sand- 
stones and sandy clays. The latter are largely red in color. This 
is apparently due to the combustion of coal. There are bones of 
large Dinosaurs and of some smaller reptiles, but they have not been 
studied. It is possible that this stratum with the sandstones above 
may belong to the Lower Cretaceous. There are many hundreds 
of feet of hard sandstones and shales between the fossil-bearing 
horizon and the Fort Benton. The upper portion probably belongs 
to the Dakota formation. 

The I^ort Benton Formation. 

These beds and their contained fossils are much like the cor- 
responding ones in other regions. They are principally dark shales 
with bands of sandstone in the lower portion, and in one place I 
found a half dozen specimens of Prionocyclus Meek in brown con, 
cretions in' the shales. Higher were Ammonites, Scaphites, Inoce- 


rami^ small Baculites and other Mollusca, all of Benton types. 
These shales weather into ravines between the sandstones of the 
Dakota below and the Niobrara above. 


In the Niobrara gray sandstones predominate, though there are 
beds of shale. This differs from the usual character of this forma- 
tion in most other regions where it has been observed. It has 
usually been described as being composed principally of limestone 
and marl, though sometimes containing considerable sand. The 
sandstones here are very much like some of those of the Laramie, 
and near the middle portion are seams of coal. In two or three 
places I looked in vain for any well-preserved plant remains in the 
carbonaceous shales and in the sandstones above and below the 
coal, and followed ravines cutting through the prominent sandstone 
ridges without finding any good fossils. However, about twenty 
miles to the southeastward a few plant impressions were found — the 
best of which was apparently a Sequoia — in beds which I take to be 
Niobrara. Undoubtedly, by careful, continued search, a fair col- 
lection could be obtained. 

In one place, where Mud Creek cuts through the formation, the 
beds approach near to a vertical position. I should not estimate 
the thickness to be less than 700 or 800 feet here. It may be 
more. The sandstones form a prominent ridge where they are 
much inclined. These ridges are sometimes wooded, though the 
trees are usually not very large or numerous. 

Fish Creek Beds, 

Above the Niobrara are beds which I believe to belong to the 
Belly River formation, but until they are certainly correlated with 
the latter I give them the above name. 

They are best exposed between Fish Creek and Mud Creek, only 
a few miles from where the latter empties into the Musselshell 
River. Here they are nearly horizontal, while the underlying 
Niobrara dips at a considerable angle to the southward. Farther to 
the east and west I did not notice any unconformity between the 
two formations. In the above-mentioned locality, where they are 
horizontal, they weather into ''bad land '' forms. The material is 
principally rather soft sandy clay, with hard, almost black concre- 


tions and hard sandstone layers. In the latter there are, in some 
places, plant impressions. The softer layers contain fossil wood, 
bivalve mollusks, turtles and bones of Dinosaurs of the genus 
Claosaurus, The bones are generally petrified and occur also in 
the dark concretions which also contain plant remains. Though 
they are, as a rule, excellently preserved, yet sometimes there is 
what seems to be a good portion of a Dinosaur broken into myriads 
of little fragments. The beds are probably either fresh or brackish 

This formation was observed in several places in this region, and 
in all there were bone fragments ; but we found no other equally 
good exposures. About twenty- five miles to the southeast, in the 
Lake Basin north of Columbus, the formation lying immediately 
below the Fort Pierre in one place has a considerable thickness of 
sandstone containing petrified logs, but only one or two small 
fragments of bone were found. Some of the plants of this forma- 
tion are related to Sequoia, The bivalve shells were so fragile as 
to crumble with the soft matrix in which they were imbedded. 

Lying over these beds is a series of shales and hard laminated 
sandstones. Some fossil leaves were seen in the latter. A series of 
dark shales, perhaps thirty feet thick, was carefully examined. The 
shales were full of carbonaceous plant fragments, and some fairly 
good leaves were found in the thin interbedded layers of sand or 
sandy concretions. I do not know whether these beds should be 
put in this series or in the Fort Pierre. I think it better to consider 
them, until they are more thoroughly explored, as belonging to the 
Fish Creek series. 

Fort Pierre, 

Above the beds just described are the Fort Pierre shales. This 
represents a well-distinguished horizon, so well marked by lithologi- 
cal characters and by characteristic fossils that its position is 
beyond doubt. The description of the Pierre in Colorado, Wyom- 
ing, etc., would answer almost equally well for the formation here. 
Dark, soft shales predominate. There are occasional thin bands of 
sand and many brownish concretions which break into angular 
fragments. These sometimes contain marine fossils and sometimes 
a network of calcite seams. The best preserved invertebrate fossils 
are in these concretions. The shells are those oi Ammonites, Bacu- 
lites, Scaphites, Nautili, and small Gasteropods and Cephalopods, 


Some hard limestone concretions are crowded with these small 

What distinguishes the Pierre here from that in other places is 
the presence of many vertebrate fossils. Several Mosasaurs have 
been found. In the summer of 1900, Mr. Albert Silberling and I 
found portions of two individuals, including a skull. In the sum- 
mer of 1 90 1, the Princeton Expedition in charge of Dr. M. S. Farr 
procured a nearly complete skeleton except the skull. 

But the most interesting fossil remains are those of the Dinosaurs. 
They have been found to be more numerous here than the Mosa- 
saurs. The greater number of them belong to the genus Claosaurus 
and apparently to described species. Two portions of skeletons 
belong to quadrupedal type, probably to the Ceratopsid(E. A Clao- 
saurus skull and the greater part of the skeleton was obtained for 
the Princeton Museum last summer (1901). The digging was easy, 
but the removal of the bones was slow and tedious, as they had to 
be hardened. Nodules had formed around some of them, but 
many were in clear shale. The skeleton was just above a layer of 
yellowish, partly consolidated sandstone two or three inches in 
thickness. There were some thin layers or lenses in the shale, in 
which the remains were imbedded. There was also a minute seam 
of coal not thicker than cardboard. Cones or ends of twigs of 
what appeared to be Sequoia, Ammonites, Scaphites, Baculites and 
other molluscs, and shark's teeth were found in the matrix while 
removing the skeleton. Only the teeth and a few of the shells 
could be preserved, as the fossils in the shale disintegrated on 
exposure to the sun and rain. The deeper into the shale excavation 
was made, the larger the flakes into which it would break. Quite a 
number of other portions of skeletons were found during this and 
the previous year. Often the bones are solid, though lying among 
the grass roots, where the soil is composed of the disintegrated 
shales. Sometimes the nodules surrounding the bones are very hard 
and flinty. 

The finding of Dinosaur remains in these marine beds was un- 
expected, but the sea was evidently shallow. In some places there is 
much gypsum in good-sized crystals, or in minute ones scattered 
through the shales. 

The Pierre beds being soft, have weathered into depressions. 
They are usually covered, except in restricted portions, with a good 
growth of grass^ but are treeless except for a few small willows or 


cottonwoods that occasionally grow along the streams. They make 
grass-clad rolling prairies, with small ravines cutting into the soft 

The transition beds between the Fort Pierre and Fox Hills are 
usually obscured by the material washed down from the bluffs of 
the latter ; but on the ranch of Mr. B. Forsythe, near the head of 
a branch of Big Coulee Creek, they can be nicely seen. The shales 
gradually become more sandy, and contain bands of sandstone 
until the latter predominates and the shales become shaly sand- 
stones or sandy clays. In them I found no trace of fossils. 

J^ox Hills, 

In this formation the hard sandstones form a prominent ridge 
adjoining the depression made by the Pierre. It is the next promi- 
nent ridge above the Niobrara. I have followed its base for about 
thirty-five or forty miles. In only one place was there any confusion 
or any difficulty in tracing it, and this was caused by some change 
in the geological structure obscuring the Pierre shales. The out- 
crop extends southeast and northwest. It forms the southern rim 
of the Lake Basin. It furnishes many springs which, uniting their 
waters, produce little streams that cut through the rocky ridge and 
flow out upon the Pierre flats. In the Fish Creek region they 
empty into Fish Creek. In the Lake Basin, if the water does not 
soak into the ground, they flow into the land-locked lakes. Where 
the streams form little caiions and ravines through the Fox Hills 
strata, they are fringed with trees and shrubbery. In little valleys 
and amphitheatres there are often springs surrounded by groves, 
which are very picturesque, and in the heat of summer these places 
form a delightful retreat from the almost treeless wastes around. 
The trees, which are principally evergreens, cottonwoods, poplars 
and willows, follow the streams a little way toward the Pierre flats 
and then disappear. 

Though these beds usually appear to be sandstone ridges, yet in 
places where conditions of weathering are favorable they are seen 
to contain much sandy clay, and in places for a short distance 
resemble *'bad land " forms. 

Fossil leaves and reptilian bone fragments were found in consid- 
erable abundance. Dr. Farr brought back some of the fossil leaves, 
but they have not yet been determined. Most of the bones are too 
fragmentary to be of much use. Some teeth were recognized as 


belonging to Claosaurus. The only fossil plant we were able to 
recognize in the field was a species of Salisburia, 

Though this is probably still below the Laramie — at least there 
are thousands of feet of what is apparently Laramie above it — yet 
this is the highest level in which we found Dinosaur x^-m^vsx^ in this 
region. This is interesting, as in other regions the ClaosaurSy with 
one exception, have come from beds which have been supposed to 
be above the Fox Hills. 

It is not certain just wher^ the Fox Hills ends and the Laramie 
begins. It is possible that these bones, or at least some of them, 
are in the lowest Laramie; but as the two formations represent 
differences in conditions of depositions rather than difference in 
age, as distinguished by change or progression of the fauna or flora, 
it is not so essential, except as bearing on the more interesting ques- 
tion of the extinction of a very remarkable class of animals and 
the occupation of their territory by a class that had for millions of 
years held a subordinate position. 

Above the Pierre, in the Fish Creek region, are alternations of 
dark shales and gray sandstones. In places the sandstone is warped, 
twisted or made up of imperfectly concentric layers. Above these 
are brownish laminated and greenish or brownish unlaminated 
sandstones and sandy clays. Provisionally, I place the base of the 
Laramie above these latter beds. They contain fossil leaves and 
bone fragments. 


The lowest beds, which are here taken to be Laramie, are a series 
of alternating various-colored shales and gray unlaminated sand- 
stones. There are several hundreds of feet of these and no fossils 
were found in them. There are in some layers brownish concre- 
tions, some of which are large and composed of sandstone. These 
beds form a depression, but not so low as that of the Pierre shales. 

Over these lies about an equal thickness of similar sandstones and 
gray shales. The former are harder and form a bench or ridge. 
There are several thin seams of coaly matter and the shales hold 
impressions of ferns and other delicate plants different from what 
we observed elsewhere. 

Near or at the top of this series there are at least two layers 
containing non-marine fossils. In one of the fossils are principally 
Gasteropods and in the other bivalves — probably Unio. It 


is said that this layer extends for twenty miles up Fish Creek, 
but I have not tried to trace it, so do not know whether it is con- 
tinuous or not. It is also said that these fossils gave the Mussel- 
shell River its name. Here we quite sure that we are in the 
Laramie, for fresh or brackish water conditions prevail, but it prob- 
ably extends between looo and 2000 feet below. 

Still higher are shales forming a flat or depression, above which 
are conical hills or hog-backs — the remains of dissected ridges cut 
through by ravines and by streams which are fed by springs in the 
Fort Union sandstone above. These hills or ridges are capped with 
brownish, compact, laminated sandstone. No fossils were seen 
except fragments of wood in the shale. 

Above these sandstones dark shales again predominate. I cannot 
tellj at least without more careful study and observation, where the 
Laramie terminates and the Fort Union begins. In fact, it looks 
as if there were in this section almost continuous deposition from 
the Jurassic up. We found here no traces of the volcanic material 
of the Livingston formation, which only thirty or forty miles to the 
southwest is so well developed. It appears that here deposition 
went on quietly and uninterruptedly. There is little doubt that 
part of the strata were deposited synchronously with those of the 
Livingston. Here, so far as we have discovered, as in other places, 
Nature has left no waymarks and laid down no boundary line to 
distinguish between the great "Age of Reptiles ** and the ** Age of 
Mammals.'* There appears to be no sign of the disturbance that 
is supposed to have closed the Mesozoic and brought in a new order 
of things ; yet only a few miles away there was a region of upheaval 
and of intense volcanic activity. The strata in the section under 
consideration have been disturbed, but the Tertiary beds are also 
involved in the upheaval. Perhaps microscopic or chemical exam- 
ination may reveal the presence of fine volcanic material here. 

Mr. W. Lindgren made three different measurements of the Lara- 
mie to the eastward of this region (see Ten/k Census of the United 
States, Vol. XV, p. 744). In none of these does he make the 
thickness of the Lower Laramie to be less than 7000 feet. I do not 
think that this, as C. A. White ^ thinks probable, includes the Belly 
River, or anything lower than Fort Pierre. Lindgren's Upper 
Laramie, or Bull Mountain series, is probably Tertiary — apparently 

1 « Correlation Paper, Cretaceous," Bull, 84, U. S, Geol. Survey, p. 174. 


Fort Union. What is supposed to be Laramie in the present sec- 
tion is very thick, probably approximating that of Lindgren's 
measurements. But here, as everywhere else, the boundaries of the 
Laramie are uncertain. Here, however, we have it confined be- 
tween certain limits. We have below a characteristic Fort Pierre 
fauna and above a characteristic Fort Union flora. Just how much 
of that which intervenes is Laramie is not known. I have no 
doubt that here deposition was going on at the same time as that of 
not only the Livingston, but also of the Arapahoe and Denver beds. 
Whether these beds will ultimately be assigned to the Upper Lara- 
mie, or included in a separate formation, depends upon the results 
of future careful investigation. 

Fort Union, 

The dark shales just mentioned continue upward, changing little 
in character ; but brown concretions become numerous, then layers 
containing shells of bivalve Mollusca, then occasional layers of 
sandstone, and above these, often capping the bluffs, heavy gray 
sandstones, usually hard, sometimes laminated and sometimes mas- 
sive. Above this I cannot speak definitely, but think that the Fort 
Union continues much higher. The strata from the top of the bluffs 
south of Fish Creek, which make a bench sloping toward Sweets 
grass Creek in the direction of Melville, perhaps belong to higher 
members of this formation. The strata are not always continuous 
for great distances, but vary locally ; yet a general description can 
be given that will apply fairly well to the beds examined. There 
are dark gray shales that in many places weather to thin, flaky 
particles on the surface. The wind blows away this light material 
and leaves bare depressions without vegetation. The sandstones 
are usually hard, sometimes massive or imperfectly bedded, and in 
some places break into great blocks, which tumble down the steep 
sides of the bluffs. 

In the Fish Creek region these heavy sandstones, which lie above 
the soft shales, form a long line of rugged bluffs extending along 
the south side of the creek from the neighborhood of Porcupine 
Butte eastward for twenty-five or thirty miles ; then it extends 
southeastward, probably forming the divide between the Sweetgrass 
on the southwest and the southern branches of Fish Creek and Big 


Coulee Creek ; but I have not examined all of this territory. 1 ex- 
amined hastily the beds on Sweetgrass Creek east and a little north 
of Big Timber, where I made a collection of fossil leaves. The 
remains of a turtle were also found in the shale. 

The portion of the Fort Union described in this paper apparently 
represents the upper portion of the Crazy Mountain section, as 
given by Weed in the American Geologist oi October, 1896. 

Fossil plants, Unios and Gasteropods, are abundant and may 
occur in any part of the beds favorable for their preservation. Last 
summer (1901) determinable Mammalian remains were found. As 
is well known, the exact position of these beds has been a matter of 
some doubt and difference of opinion. They have usually been 
assigned to the Tertiary, though they have been placed as low as 
the Cretaceous and as high as the Miocene, 

The bones and teeth of Mammals which were found ^ are not 
numerous, but are sufficient to show that the beds are of nearly the 
same age as the Torrejon of New Mexico. They are : 

Mioclcenus acolytus (Cope). 

Anisonchus very near to A. sectorius Cope. 

Euprotogonia puercensis (Cope). 

Pantolambda cavirictis (?). 

Pantolambda (?), a small species. 

Some others are doubtful. 

I felt very certain that these beds were Fort Union, but to settle 
the matter forever and leave no room for a shadow of doubt, a box 
of fossil leaves was sent to Mr. F. H. Knowlton, of the United 
States Geological Survey. Mr. Knowlton examined them at once 
and sent me a list, which I quote : 

Pterospermites cupanioides (Newb.) Knowlton. 

Populus speciosa Ward. 

Populus amblyrhyncha Ward. 

Ulmus orbicularis ? Ward. 

Vitis xantholithensis Ward. 

Populus daphnozenoides Ward. 

Populus arctica ? Heer. 

Platanus aceroides Gopp. 

Celastrus sp. 

Grewia crenata (Ung.) Heer. 

1 Science, February 14, 1902, pp. 272, 273, 


Viburnum asperum ? Newb. 

Populus cuneata Newb. 

Fopulus sp. 

Platanus nobilis Newb. 

Plaianus basilobata Ward. 

Viburnum sp. 

Paliurus sp. 

Grewiopsis viburnifolia Ward. 

Populus ? n, sp. 

Mr. Knowlton says : '^ The species are all Fort Union beyond a 

Of a few shells which I enclosed, he writes : '* The shells I 
showed to Mr. Stanton, and he says that the two large ones are 
Unio Couesi White ; and the other pretty near to Unio Endlichi 

The Mammals were found in the shale. The collection of fossil 
leaves was made in the sandstone a little higher up, though there 
are concretions and layers of sandstone that contain leaves in the 
same beds as the Mammalian remains. A portion of the collection 
was obtained on Sweetgrass Creek north of east of Big Timber, in 
the locality mentioned above. 

General Observations. 

The problem of greatest interest connected with the study of 
this section is that relating to the transition from Mesozoic to 
Cenozoic times. Of course, if deposition had been continuous, or 
nearly so, and there were no great faunal or floral migrations, there 
could be no distinct boundary between the two. There is a great 
difference between the Cretaceous as a whole and the Tertiary as a 
whole, but where are we to draw the line ? If there was a time of 
widespread or general upheaval throughout the western portion of 
the continent, or of the Rocky Mountain region, this might form 
a convenient division. Upheavals and great volcanic activity cer- 
tainly occurred in restricted localities, but we cannot at present 
prove that such were general or that they did not occur in different 
places and at different times. If we could point to any time when 
the Dinosaurs ceased to be and the higher orders of Mammals took 
their places, then the matter would be easy ; but heretofore most of 
the Cretaceous Dinosaurs^ in fact nearly all of them, have been 


supposed to come from the uppermost portion of the Cretaceous — 
the Laramie — but the other fossils found in these beds have not 
been of a character to settle the doubt concerning the horizon. 
There is no direct proof that the Dinosaurs died out before higher 
forms of Mammals became numerous. Though they have not yet, 
so far as I know, been found in the same beds, yet there seems good 
reason for believing that Dinosaurs were contemporaneous with 
Puerco Mammals. Were it not for the ** Ceratops fauna'* and the 
discovery of a few specimens in the eastern United States and one 
in Kansas, we should say that the Dinosaurs died out at the end of 
the Jurassic. It would seem that if anything had a chance of being 
preserved it would be the large, solid bones of these animals; yet 
there are miles of thickness of strata and thousands of square miles 
of exposure of Lower Cretaceous, Dakota and Colorado beds, and 
nothing, I believe, has been found to tell that these animals still 
lived in this great Cordilleran region, except the type of Claosaurus 
agilis from the Niobrara of Nebraska. This rock must represent 
many millions of years in which Dinosaurs lived, flourished and 
progressed. To our view they disappear in their glory, and after 
ages appear again in glory but transformed ; again they suddenly 
disappear and we see them no more. The morning, midday and 
evening of their splendor is lost to us. Until the discovery of the 
beds described in this paper almost nothing was known of them in 
the Montana formation, at least the beds from which they had been 
collected had not been considered as belonging to that age. The 
point the writer wishes to make is this : It is extremely unsafe to 
say when and where these strange reptiles breathed their last, for 
the presence of fossils is certain evidence of the existence of life, 
but the lack of them is no evidence of its absence. Dinosaurs may 
have continued long in the Eocene, but conditions in the places 
where so many Mammalian remains have been found may not have 
been favorable for them. 

I think we can hardly account for the general absence of Dino- 
saur remains in the Kootenai and Upper Cretaceous, below the 
Laramie, by the beds being in part marine. Much of the strata is 
evidently fresh or brackish water. We should hardly expect to find 
them in the Benton and Fort Pierre shales associated with large ma- 
rine Mollusca, yet as previously stated we do find them in the latter. 
This proves that these animals lived near the sea or where they 
could float into it. Why don't we get them then in the many 


thousands of feet of sandstone which, if marine, must be near-shore 
deposits? It is true that any day we may hear of their being found 
in some of these strata, and we may also hear of their being found 
in Eocene strata, if they have not been found there already. 

As shown by this paper, the presence of Claosauridce, and proba- 
bly of CeratopsidcBy is far from showing that the beds in which they 
are found are as late as Laramie — I mean as the Laramie as it is 
understood. It is true that the Fort Pierre, and in some places the 
Fox Hills with it, represents an incursion of the sea, and that con- 
ditions of life were not greatly different during the time of the 
deposition of the Belly River beds from what they were in the 

At present the fossil plants, together with orographic movements 
and their results when they occur, are the only things we can use to 
distinguish these doubtful formations as the Laramie, Livingston, 
Denver, etc. The plants, on account of mixtures of the flora of 
different horizons in collecting, have not been available for use until 
the material has been carefully separated. As Mr. Knowlton has 
been doing this work, his forthcoming monograph on the Flora of 
the Laramie and Allied Formations will be looked for with interest. 

There is not much doubt that the Livingston in Montana repre- 
sents the upper portion of what has been called the Laramie in the 
plains region farther to the east. Both have Laramie strata below ; 
both are overlaid by Fort Union beds. In Colorado it seems that 
the Arapahoe, and probably the Denver, or the greater part of it, 
sustains the same relation to Laramie. Mr. Knowlton says : *' From 
these considerations it appears beyond question that the flora of 
the Livingston formation finds its nearest relationship with the Den- 
ver beds of Colorado,'' ^ If the Livingston and Denver are of the 
same age, as has for some time been suspected, then the Denver 
must be older than the Fort Union, and therefore older than the 
Torrejon. With its apparently Cretaceous Vertebrate fauna, we are 
not warranted at present in placing the Denver much higher than 
the Livingston. It may be in part contemporaneous with the Fort 

The Puerco should be nearly of the same age, as it lies between 
Laramie and Fort Union (Torrejon) strata. 

Below is given a table which is intended to show the probable 

1 Bull, 105, U, S, Geol, Survey, p. 63. 


relations in time of the formations under consideration concerning 
which there is doubt : 

Table Showing Probable Relations of the Laramie and Overlying 
Beds in Different Regions. 



In Wyoming 

Flains of Montana . 

Laramie of King 


Fort Union 

Crazy Mts., Montana 

Denver Ba^in 

Laramie Livingston 

Fort Union 

Laramie Arapahoe Denver 

Puerco River, N. Mex, 

Laramie Puerco 


The names given are the ones by which the different divisions 
have been called. There does not seem to be much doubt that the 
Livingston, Denver, Puerco, etc., are contemporaneous with what 
in other places has been assigned to the upper portion of the Lara- 
mie. Whether all will be included in the Laramie later will de- 
pend on the results of further careful investigation. I have indi- 
cated the doubtful division between the Cretaceous and Tertiary by 
a dotted vertical line passing between the Livingston and Fort 
Union and between the Puerco and Torrejon, or approximately so, 
not claiming that the time division line between the two sets of 
strata would fall exactly in the same place. The horizontal parallel 
lines are intended to represent contemporaneity of deposition. 
Deposition in the Denver Basin was not continuous and the blank 
spaces indicate non-deposition. The broken or dotted lines indi- 
cate probable continuity. 

Remarks on the Fossil Mammals. 

The mammals are represented by about a half dozen species. 
Five of these are represented by teeth. Almost any one of these 


taken alone would strongly incline one to the belief that the form- 
ation containing them is contemporaneous with the Torrejon of 
New Mexico. This is made still stronger by nearly every specimen. 
There are a radius and ulna which are different from any found in 
New Mexico, so that they cannot be assigned to any genus with cer- 
tainty, and there is a premolar much like that of Pantolambda, but 
indicating an animal much smaller than any species of that genus, 
to which, however, I refer it with doubt. The other four are 
•cogeneric if not cospecific with Torrejon forms. 

Mioclanus acolyius (Cope). (Plate XXIX, Figs. 9 and 10.) 

This is represented by a small portion of a mandible with a molar 
tooth which is almost unworn. The anterior cusps are connate at 
base and much higher than the posterior ones. 

Anisonchus Cope. (Plate XXIX, Figs. 3-5.) 

This is also represented by a portion of a mandible. There are 
two teeth, a fourth premolar and a first molar. They are of nearly 
equal length. In size and character the teeth are nearly like A, 
sectorius Cope. It may, however, be another species. 

Euproiogonia puercensis (Cope). (Plate XXIX, Figs, d-'^,) 

Represented by a third premolar and a second molar of the right 
side and a third molar of the left. The molars differ somewhat 
from the type. Matthew has carefully studied the many specimens 
in the American Museum collection and finds a wide range of varia- 
tion in the teeth, but no constant characters that will serve to sepa- 
rate the various forms which Cope has named. Of the many speci- 
mens no two appear to be exactly alike. I have compared the 
present specimens with those in the above collection and find that 
they do not differ so much from some of the American Museum 
specimens, as the latter vary among themselves. What comes near- 
est to being a distinguishing character is the smallness of the hypo- 
cone as compared with the protocone, but this is at least nearly 
paralleled by some of the above-named specimens. 

Pantolambda (?) (Plate XXIX, Figs, i, 2, 14.) 

There are the greater portions of a radius and ulna, and two 
phalanges which are different from anything described from the 


Torrejon. They more resemble in some respects the corresponding 
bones of Coryphodon, 

The ulna is much larger than the radius, is broad antero-poste- 
riorly but narrow transversely. The upper portion of the olecranon 
is broken off, but a cross section above the glenoid cavity is trian- 
gular with the anterior edge thin. The sigmoid cavity is convex 
transversely. The outer portion is much less convex longitudinally 
than the inner ; it extends lower and its upper portion makes an 
oblique emargination on the outer side of the olecranon. There are 
two fairly large surfaces for articulation with the radius. The upper 
outer surface of the bone has a quite deep longitudinal furrow which 
dies out near the middle of the shaft. The inner surface is longi- 
tudinally concave from the olecranon to the enlargement near the 
distal end of the bone, where there is considerable swelling and 
roughening. The distal articular surface is elliptical, slightly con- 
cave palmo-dorsally and convex transversely. This surface is very 
slightly oblique to the long axis of the bone. 

The radius is subcylindrical above. The head is partly broken, 
but the surface for articulation with the humerus is shallow and 
appears to have been nearly circular. There is a longitudinal 
roughening on the ulnar side, to correspond with similar rugosities 
on the radial side of the ulna. Below these is a rugosity on the 
antero-inner side of the radius and on the opposite side. The bone 
has the appearance of being twisted on itself. The form of the 
bone suggests freedom of motion of the limb other than a fore-and- 
aft movement. 

A proximal and medial phalanx apparently do not differ greatly 
from those figured in Osborn*s paper on '* Evolution of the Ambly- 


Length of ulna from upper portion of glenoid cavity . 1970 

Antero-posterior diameter at middle of shaft . .0310 

Transverse diameter at middle of shaft . . .0143 

Transverse diameter of shaft of ulna at middle . .0195 

Pantolambda cavirictis Cope (?). 

Fragments of upper jaw, with teeth from which enamel has been 
removed. The size is nearly the same as the corresponding teeth 

^ Bull. Amer, Mus, Nat, Hist., Vol. X, p. 187. 



of P, cavirictis, and there is nothing to distinguish it from that 

Paniolambda (?) sp. (Plate XXIX, Figs. 11-13.) 

An upper premolar, much smaller than P^ of P. bathmodon or P. 
cavirictis^ but it is possible that it may be a P ^ of nearly as large a 
form. It is very doubtful, however, whether it belongs to Panto- 
lambda at all. The protocone is more conical, the outer slope on 
the median line of the tooth is steeper and the inner less so. The 
outer surface near the base of the crown is more concave. 

A canine found with the above is not like that of the known 
species of Pantolambda, but can hardly be distinguished from that 
of modern Carnivores. It probably belongs to some Creodont. 

Princeton University, May 24, 1902. 

Explanation of Plate XXIX. 

Figs, i and 2. Ulna and radius possibly belonging to some species of Panto- 
lambda, % natural size. 

Figs. 3-5. Anisonchus sectorius (?) 

Last lower premolar and first lower molar with portion of mandible. Outer 
and inner view of mandible and upper view of teeth. X 2. 

Figs. 6-8. Euprotogonia puercensis, 

6. Right upper second molar, x 2. 

7. Left upper third molar. X 2. 

8. Right third upper premolar, x 2. 
Figs. 9, 10. Mioclcsnus acolytus. 

A lower molar with portion of a mandible. X 2. 
Figs. 11-15. Pantolambda Q"), Upper premolar, x 2. 

13. Canine tooth found with 11. 

14. Phalanx found near i and 2. x Vi- 

15. Scale of Lepidosteus found with mammals. X 2. 

Proceedings Amer.Phil.S oc. Vol XLL No 170. 

Fvlierson del. 

Fort Union Mammals.