Please do not destroy or throw away this publication. If you have no further use 

for it write to the Geological Survey at Washington and ask for a frank to return it 

DEPARTMENT OF THE INTERIOR 

Hubert Work, Secretary 

U. S. GEOLOGICAL SUR.VEY 

Geor~re Otis Smith, Director 

PROFESSIONAL PAPER 147 

SHORTER CONTRIBUTIONS TO 

GENERAL GEOLOGY 

1926 

W. C. MENDENHALL, CHIEF GEOLOGIST 

WASHINGTON 

J GOVERNMENT PRINTING OFFICE 

1927 

,-.-_ _________ ._.....:.____ __ ~ 
DEPARTMENT OF THE INTERIOR· 

Hubert Work, Secretary 

U.S. GEOLOGICAL SURVEY 

George Otis Smith, Direetor 

Professional Paper 147 

SHORTER CONTRIBUTIONS TO 

GENERAL GEOLOGY 

1926 

W. C. MENDENHALL, CHIEF GEOLOGIST 

WASHINGTON 

GOVERNMENT PRINTING OFFICE 

1927 

• 
CONTENTS 

[The letters in pareptheses preceding the titles are those used to designate the papers for advance publication] 

Page 

(A) A comparison of the genera Metaplacenticeras Spath and Placenticeras Meek, by J. B. Reeside, jr. (published Sept. 

14, 1926)---------------------------------------------------------------------------------------------- 1 

(B) The Montana earthquake of June 27, 1925, by J. T. Pardee (published Sept. 20, 1926)--------------------------- 7 

(C) American Tertiary mollusks of the genus Clementia, by W. P. Woodring (published Nov. 22, 1926)---------------- 25 

Index------------------------------------------------------------------------------------------------- 49 

ILLUSTRATIONS 

Page 

PLATES 1-2. Species of Placenticeras and M etaplacenticeras ___________ -------- __ -------------------------------- _ _ _ 4-5 

3. Isoseismallines for Montana earthquake of June 27, 1925------------------------------------------------ 8 

4. Geology of the epicentral area, Montana earthquake of June 27, 1925------------------------------------- 8 

5. A, Damaged schoolhouse at Three Forks, Mont.; B, Wreck of church at Three Forks, Mont_________________ 10 

6. A, Damaged schoolhouse at Manhattan, Mont.; B, Damaged jail at White Sulphur Springs, Mont____________ 10 

7. A, Rock slide near Deer Park, Mont.; B, Lake.at tunnel No.8, near Deer Park, Mont______________________ 10 

8. A, Broken railroad track near Lombard, Mont.; B, Rocks on railroad track near Lombard, Mont_____________ 10 

9. A, B, Fault plane of the slide near Deer Park, Mont____________________________________________________ 10 

10. A, North wall of gorge below Deer Park, Mont.; B, Limestone cliffs and talus slope east of Missouri River at 

Lombard, Mont------------------------------------------------------------------------------- 10 

11. A, Joints in limestone opened by the Montana earthquake; B, Bottom land along Missouri River, Mont______ 10 

12. A, Shattered ground and overturned clods, Roy Gulch, Mont.; B, Crack in road embankment north of Three 

Forks, Mont----------------------------------------------------------------------------------- 10 

13. A, Ground crack near Canyon Ferry, Mont.; B, Twisted chimneys at Logan, Mont_________________________ 10 

14. American Tertiary species of Clementia s. 8------------------------------------------------------------- 44 

15. American Tertiary species of Egesta___________________________________________________________________ 45 

16. American Tertiary and living species of Egesta--------------------------------------------------------- 46 

17. American Tertiary species of Egesta and doubtful species------------------------------------------------ 47 FIGURE 1. Map showing present range and former distribution of C,leme.ntia s. s. and Egesta___________________________ 27 

II 

0 
SHORTER CONTRIBUTIONS -'"fO GENERAL GEOLOGY, 1926 

A COMPARISON OF THE GENERA METAPLACENTICERAS SPATH AND PLACENTICERAS 

MEEK 

By JoHN B. REEsrnE, Jr. 

In a recent examination of a considerable suite of 

specimens from the Western Interior of the United 

States belonging to the Cretaceous ammonite genus 

Placenticeras Meek the writer made comparisons of 

the species from the Interior with those from the 

Cretaceous of the Pacific coast ordinarily designated 

Placenticeras pacificum J. P. Smith, P. californicum 

Anderson, and P. sanctaemonicae Waring. The two 

groups of species differ widely in their characteristics, 

though each is a fairly homogeneous assemblage in 

itself. It was the writer's intention to propose a new 

name for the group of P. 'pacijicum-indeed, one was 

proposed and in type, when the publication by Spath 1 

of the nan1e Metaplacenticeras met the need adequately, 

and that name is of course used here. 'Spath's name 

is based on the citation of Smith's original figure and a 

notation that Metaplacenticeras differs from Placenticeras in its falcoid ribbing and distinct suture line. 

Inasmuch as there has been some divergence of opinion 

as to the scope and probable derivation of the genus 

Placenticeras, based on the study by different writers 

of members of one or the other of the two groups, the 

writer has thought it worth while to record his observations and deductions and to give a fuller account of 

the new genus. 

Smith la investigated the young stages of the species 

pacificum and on the basis of his findings expressed 

the opinion that Placenticeras as represented by it 

was derived through Hoplites from Oosmoceras. He 

found the second, third, and fourth lobes of the adult 

suture to arise from the subdivision of the first lateral 

lobe of the primitive suture shown in the very early 

stages and the first lateral lobe of the adult to arise 

as a marginal lobe dividing the primitive first lateral 

saddle. Douville 2 had already placed the genus in 

~he Hoplitidae on the basis of similarity of the early 

mtures to that of Hoplites, interpreting the first, 

;econd, and third lateral lobes of the adult Placentit Spath, L. F., On new ammonites from the English chalk: Geol. Mag., vol. 63, 

;>. 79, 1926. 

ta Smith, J. P., The development and phylogeny of Placenticeras: California 

i\.cad. Sci. Proc., 3d ser., vol. 1, pp. 181-231, 1900. . 

2 Douvill~, Henri, Classification des c~ratites de la Craie: Soc. g~ol. France Bull, 

ml. 18, p. 288, 1890. 

ceras as direct descendants of the primitive first lateral 

lobe and homologous to the trifid first lateral lobe of 

Hoplites. Hyatt 'J later interpreted the ontogeny of 

Placenticeras meeki Bohm ( =P. whitfieldi Hyatt, P. 

placenta (DeKay) of Meek, the type of the genus) 

as not showing any real relationship with Hoplites. He 

considered the first and second lateral lobes of the 

adult suture as derived from marginal lobes of the 

primitive first lateral saddle and only the third lateral 

lobe of the adult as a lineal descendant of the first 

lateral lobe of the early suture. Pervinquiere 4 

doubted the generic identity of the forms examined 

by Smith and Hyatt because of the very marked 

differences between P. pacificum and P. californicum, 

on the one hand, and P. meeki, P. intercalare, and 

other typical species, on the other, though accepting 

both groups as descended from Hoplites. Sommermeier 5 attempted to reconcile the divergent views by 

interpreting the suture as showing a small lobe dividing the primitive first saddle, two -adventitious 

lobes arising on the siphonal flank of the primitive 

first lateral lobe as forming the first and second 

lateral lobes of the adult, and only the third adult 

lobe as being a direct descendant of the primitive first 

lateral lobe. He considered the primitive second 

lateral lobe to be variable and in P. pacificum to 

exceed the fil,'st lateral in length and become the large 

fourth adult lobe, whereas in P. meeki it Is relatively 

small. The sutures in this view are therefore essentially the same and prove a generic identity. He 

suggests as another possibility that the sixth adult 

lobe is really t1J_e primitive second lateral' lobe and 

that the fourth and fifth adult lobes are adventitious. 

The writer examined the inner whorls .of typical 

individuals of the species pacificum Smith and meeki 

Boehm. He found that he could add nothing to 

Smith's description of the young of the first species 

and agrees with it entirely. For the second species 

a Hyatt, Alpheus, Pseudoceratites of the Cretaceous: u: S. Geol. Survey Mon. 

44, p. 192, 1903. 

4 Pervinquiere, Loon, Etudes de pal~ontologie tunisienne, C~phalopodes des 

terrains secondaires, p. 197, 1907. 

6 Sommermeier, L., Die Fauna des Aptien und Albien im nordlichen Peru, 

Pt. I: Neues Jahrb., Beilageband 30, pp. 319-321, 1910. 

1 
2 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1926 

several interpretations are plausible. Hyatt's figures 6 of isolated early sutures of P. meeki agree with 

those found by the writer at the same stages, and 

Hyatt's interpretation may well be true. However, 

a more complete series such as that figured in Plate 1 

of this paper permits a somewhat different and equally 

plausible explanation. Apparently the first of the 

three large adult lateral lobes is a marginal of the 

primitive first lateral saddle, and the second and third 

are divisions of the primitive first lateral lobe. The 

fourth adult lateral lobe is the second primitive' lateral 

lobe. The writer could detect no sculpture on the 

whorls below 6 or 7 millimeters, though Hyatt found 

faint ribs. At about 10 millimeters obscure rounded 

radial folds ·and sigmoid striae are present. At greater 

diameters only striae were seen. Whatever interpretation of the suture is accepted, it is not very 

strongly suggestive of Hoplites. 

The development of the suture is strikingly different 

from that found in the species paciflcum Smith and 

combined with the persistent difference in sculpture 

is sufficient to put the two series of forms into different 

genera-perhaps even into different families. Smith's 

specimens are strongly ornamented from even the 

very early stages throughout their growth and have 

for a time a very distinct median keel in addition to 

the ventrolateral keels. At certain stages, particularly at about 20 millimeters in diameter, the species 

paciflcum has a suture exceedingly like true Placenticeras in that the lobes and saddles lie nearly on a line 

and the parts of the first lateral lobe have become 

practically independent. At earlier and later stages 

the primitive first lateral lobe still shows its identity 

in the arrangement of the parts of the suture and is 

strongly reminiscent of Hoplites. In Plates 1 and 2 

of this paper adaptations of Smith's figures are given 

for comparison with sutures of Placenticeras meeki. 

Paulcke 7 proposed to place such forms as Placenticeras paciflcum, which have evident relationship to 

Hoplites, and certain species of ·Hoplites that show a 

transition toward Placenticeras in a group with the 

name Hoplitoplacenticeras. For . the forms nearer 

Hoplites he would italicize the first half of the name; 

for those nearer Placenticeras, the second half of the 

name; for'truly intermediate forms he would italicize 

the entire name. The writer believ'es it less complicated to use ~n entirely distinct name where a 

generic distinction is necessary. 

The writer therefore approves and accepts Spath's 

proposal of the name Metaplacenticeras to include the 

forms now called Placenticeras paciflcum J. P. Smith, 

P. californicum Anderson, and p·. sanctaemonicae 

Waring, 8 from the Cenomanian part of the Chico for6 Hyatt, Alpheus, op. cit., pl. 45, figs. 11-14, 1903. 

7 Paulcke, Wilhelm, Die Cephalopoden der oberen Kreide Sudpatagoniens: 

Naturf. Gesell. Freiburg Ber., vol. 15, pp. 178-183, 1907. 

s Waring, C. A., Stratigraphic and faunal relations of the Martinez to the Chico 

and Tejon of southern California: California Acad. Sci. Proc., vol. 7, p. 70, pl. 9, 

figs. 20, 21, 1917. 

mation of California, and probably also some of the 

forms included by Paulcke 9 under the names Hoplites 

plasticus-costatus and H. plasticus-laevis, from · the 

Senonian of Patagonia. The essential characters of 

the genus and its differences from Placenticeras are 

shown in the following tabular comparison based on 

Smith's description of P. paciflcum and the writer's 

study of P. meeki and other material from the Montana group and the Chico formation. 

M etaplacenticeras Spath. 

Genotype M. pacificum J. P. 

Smith. Shell large, discoidal, involute, compressed. 

Whorls stout, rounded to diameter of 4.5 millimeters (2 

whorls); higher than wide 

with channeled venter at 

diameter of 7 millimeters (3 

whorls); very high, compressed, with narrow tricarinate venter to diameter 

of 100 millimeters; large 

adults have compressed 

whorl with venter narrow, 

flat or slightly concave, bordered by finely nodose keels. 

Umbilicus relati~ely wide, onefifth the diameter of the 

shell, with shoulder rounded 

in young and angular with 

steep inner ":all in later 

stages. 

Sculpture of distinct, fairly 

strong numerous ribs in all 

stages above a diameter of 

2 or 3 millimeters. Ribs 

striated and sigmoid in 

form. Umbilical shoulders 

and ventrolateral keels with 

numerous tubercles. 

Suture in adult has four prominent lateral lobes and three 

or four smaller lateral lobes. 

First prominent lateral 

smaller and arises as a marginal in the primitive first 

lateral saddle; next three 

arise by division of the primitive first lateral lobe, which 

in the growth of the individual first loses and then 

regain~ its identity. Even 

in the adult it retains to 

some extent its individuality. The fifth lateral lobe 

of adult is a direct descEmdant of the primitive 

second lobe. 

Placenticeras Meek 

Genotype P. placenta De Kay. 

Shell large, discoidal, involute, compressed. 

Whorls stout, rounded to diameter of 3 millimeters (1% 

whorls); higher than wide 

with flat venter at diameter 

of 4 millimeters (1% whorls); 

very high, compressed, with 

narrow channeled venter 

bordered by sharp continuous or nodose keels or with 

narrow flat venter to diameter of perhaps 200 millimeters; large adults of most 

species have rounded venters. In some species the 

adult whorls are stout, even 

subquadrate (Stantonoceras 

Johnson). 

Umbilicus narrow in typical 

forms, one-seventh the diameter, with rounded shoulder; 

gentle inner slope in the 

young and steep in later 

stages. Stout species have 

relatively wide umbilicus, 

much as in M etaplacenticeras. 

Sculpture weak; faint ribs in 

the very young stages and 

none or only low obscure 

coarse ribs in the later 

stages. Surface with sigmoid striae. Tubercles 

when present not usually 

strong nor numerous. 

Suture in adult has three 

prominent lateral lobes and 

six or seven smaller lateral 

lobes. First prominent lateral develops from a marginal of the primitive first lateral saddle; next two arise 

by division of the primitive 

first lateral lobe, which very 

early loses its identity. The 

fourth lateral lobe is the direct descendant of the primitive second lateral lobe. 

9 Paulcke, Wilhelm, op. cit., pp. 178-183. 

0 
PLATES 1-2 

3 

0 
I 

PLATE 1 

FIGURES 1- 7. Placenticeras meeki Boehm, from a locality near the center of sec. 2, T. 32 N., R. 86 W., Natrona County, Wyo. 

(U. S. Nat. Mus. catalog No. 73133.) 

1. Group of 18 consecutive sutures from a diameter of 1.4 millimeters to a diameter of 4.0 millimeters. 

2. Suture at diameter of 7 millimeters. 

3. Suture at diameter of 10 millimeters. 

4. Suture at diameter of 14 millimeters. 

5. Suture at diameter of 25 millimeters. 

6, 7. Side and front views of the nucleus. 

8-12. Metaplacenticeras pacificum (Smith). Figures adapted from J. P. Smith, California Acad. Sci. Proc., 3d ser., 

vol. 1, pls. 27 and 28. 

4 

8. Nine sutures at diameters of 0.8, 1.16, 1.32, 1.70, 2.2, 2.4, 2.7, 3.0, and 4.1 millimeters for comparison with 

Figure 1. 

9. Mature suture. , 

10. Suture at diameter of 8.5 'llillimeters for comparison with Figur-es 2 and 3. 

11. Suture at diameter of 12.0 millimeters for comparison with Figures 3 and 4. 

12. Suture at diameter of 14.1 millimeters for comparison with Figure 4. 

13. Placenticeras meeki Boehm, mature suture at diameter of 110 millimeters, of a specimen from the Bearpaw shale 

2 miles southwest of McLean's ranch, on Sage Creek, Alberta, Canada; for comparison with Figure 9 and with 

Plate 2, Figures 13 and 16. (U. S. Nat. Mus. catalog No. 73134.) 

() 
U. S. GEOLOGICAL SURVEY PHOFESSIOKAL PAPER 14i PLATE 1 

/ 

I 

I X6 

SPECIES OF l'LA.CENTICERAS AND lHET;\l'LACENTICERAS 
l'ROF I·;s;,;10. A I, 1'.\PE H 111 ] ' L ATE :.l 

0 X IO 

6 

1 

w 

XIO 

7 

X3 

) 

8 X IO 

3 

r,J,o 

5 

14 

\ 

\) 

10 X4 

S I' EC II•:s O F PI.AC E'\TIC I•: t\A A I) li TAI'I.A \. ~ T IC I-:HAS 
' 

PLATE 2 

FIGURES 1- 5. Placenticeras meeki Boehm, from a locality near the center of sec. 2, T. 32 N., R. 86 W., Natrona County, Wyo. 

(U. S. Nat. Mus. catalog No. 73133.) Five cross sections of the whorl at diameters of 3, 4, 7, 10, and 14 milli· 

meters. 

6-10. Metaplacenticeras pacificum (Smith). Figures adapted from J.P. Smith, California Acad. Sci. Proc., 3d ser., vol. 1, 

pl. 28. Five cross sections of the whorl at diameters of 3, 4.5, 7, 12, and 21 millimeters for comparison with 

Figures 1 to 5. 

11-13. Metaplacenticeras pacificum (Smith). Side and peripheral views and suture of a specimen from the Chico formation in Silverado Canyon, Orange County, Calif. (U.S. Nat. Mus. catalog No. 73135.) 

14-16. Metaplacenticeras californicum (Anderson). Side and peripheral views and suture at diameter of 50 millimeters of a 

specimen from the Chico formation in Bowers Canyo!l, in the Santa Susana Mountains, about 4 miles southwest 

of Chatsworth Park, Los Angeles County, Calif. (U. S. Nat. Mus. catalog No. 73136.) 

5 

THE MONTANA EARTHQUAKE OF JUNE 27, 1925 

By J. T. PARDEE 

SUMMARY 

The earthquake of June 27, 1925, in Montana caused considerable damage within an area of 600 square miles or more, 

the center of which is in latitude 46° 5' N. and longitude 111° 

20' W., a short distance southeast of Lombard. It was a 

seismic disturbance of the first order of magnitude, but, owing 

to the hour at which it occur:red and to other fortunate circumstances, no lives were lost and no fires broke out. The shock 

was startling throughout an area extending 7 5 miles or more in 

all directions from the epicenter and was sensible to persons 

within an area of 310,000 square miles. Within the epicentral 

area brick buildings suffered severely, rocks fell from cliffs, 

cracks opened in the ground, and the inhabitants experienced 

the usual symptoms of illness and emotions of alarm. Isoseismals drawn according to the Rossi-Forel scale show a wide 

indentation at the south due to a rapid decline of intensity 

in the volcanic area of Snake River Plain and Yellowstone Park. 

The main shock was preceded by two light foreshocks and 

followed by a great many aftershocks, one of which, occurring 

about three-quarters of an hour later, was almost as severe as 

the main shock. 

The epicenter is in Clarkston Valley, a lowland surrounded· 

by mountains of severely folded Mesozoic and older rocks and 

floored with Tertiary "lake beds" and Recent alluvium. Phys-· 

iographic evidence indicates that Clarkston Valley is a structural 

depression bounded on the east by a fault of post-Miocene age. 

Presumably the origin of the earthquake was on this fault at a 

considerable depth below the surface. It is concluded that 

the region is in a state of moderate seismic activity and is 

likely in the future to be visited by an occasional severe shock. 

INTRODUCTION 

On June 27, 1925, practically all of Montana and 

parts of the neighboring States and Provinces were 

shaken by an earthquake of marked intensity. The 

shock, which was immediately preceded by a light 

foreshock, came at approximately 6.21 p.m., mountain 

time. Newspaper reports published the following days 

indicated that the greatest damage occurred in the 

villages of Three Forks, Logan, and Manhattan and at 

Deer Park, where a large rock slide blocked the Chicago, 

Milwaukee & St. Paul Railway. The area thus indicated lies from 20 to 40 miles northwest of Bozeman 

and about 55 miles east of Butte and an equal distance 

southeast of Helena. The epicenter as subsequently 

determined is a short distance southeast of Lombard, at 

approximately 46° 5' north latitude and 111° 20' west 

longitude. Three Forks contains about 1,200 inhabitants, Manhattan 600, and Logan 300. The remainder 

of the area of high intensity is very thinly inhabited. 

The effects of the earthquake were investigated by 

the writer within the periods of July 10 to 31 and 

A~gust 29 to September 5, 1925. Most of the settlem~nts within a radius of 50 miles of the epicenter were 

visited, and trips were made to a few more distant 

points. The work consisted mainly in observing the 

remaining visible effects upon structures and natural 

objects· and obtaining first-hand records from individual observers. In addition the geologic features of 

the epicen trai area were briefly examined. (See pls. 3 

and 4.) 

For valuable information the writer is indebted to 

the many persons interviewed, and in particular to 

W. T. Lathrop, of the United States Weather Bureau 

at Helena; J. P. Swarts, W. P. Luburg, and H. P. 

Allen, Northern Pacific Railway operators at Lombard; 

and A. D. Burkett, chemist of.the Three Forks Portland Cement Co. at Trident. 

EFFECTS OF THE EARTHQUAKE 

DAMAGE TO BUILDINGS 

The greatest damage caused by the earthquake was 

shown by the school buildings at Manhattan, Logan, 

and Three Forks and a church at Three Forks (pls. 5 

and 6), all of which were built of brick. The church 

is almost a complete wreck. The schoolho~ses, though 

very seriously damaged, W3:rJ not beyond repair. In 

the business sections of Three Forks and Manhattan 

most brick, stone, and cement-block buildings were 

seriously damaged, but none were completely wrecked. 

Some brick and cement houses and virtually all frame 

buildings. escaped serious InJury. Rather serious 

damage was done to brick schoolhouses at Willow 

Creek, Bozeman, Radersburg, and White Sulphur 

Springs, to the courthouse and jail at White Sulphur 

Springs (pl. 6, B), and to cement walls and cement 

block."buildings at Trident. Damages to five schoolhouses in Gallatin County (two at Manhattan and one 

each at Three Forks, Logan, and Willow Creek) were 

estimated by the State architect at approximately 

$62,000. The additional property loss in the towns 

mentioned probably is not large. There was also 

.damage at many other places within a radius of 75 

miles of the epicenter. This damage consisted mostly 

of breaks in chimneys, plaster, and plate-glass windows 

7 
8 SHORTER CONTRIBUTIONS TO GENEJlAL GEOLOGY, 1926 

In addition many persons suffered losses by reason 

of merchandise and household effects being thrown 

about and broken. No estimates of the amounts of 

these losses are available. 

From even a casual inspection it is apparent that all 

well-constructed buildings of whatever type escaped 

with little· damage. Buildings faced or veneered with 

brick laid up without b~ing tied or bonded to the 

inner walls suffered the most. The schoolhouses 

(pls. 5 and 6) are conspicuous examples. In Three 

Forks several walls made of common brick tied in the 

·usual way with a layer of "headers" every fifth or 

sixth row were observed to be practically undamaged, 

though they adjoined veneered or faced walls that had 

failed. Some walls tied as described were wreck,ed, 

but their failure was due to poor mortar, as shown by 

the fact that the fallen bricks were generally separated 

from one another. At White Sulphur Sp~ings part of 

the cornice and veneer on the one-story brick jail was 

sheared from the inner wall, owing to the lack of ties 

or bonding (pl. 6, B). In the same town the peaks of 

the walls forming the gable ends of a two-story brick 

school and the two-story stone courthouse fell. The 

school had previously been condemned as unsafe, but 

the courthouse, though old, was apparently a substantial building. The gable peaks probably fell because they lacked the support of adjoining walls. At 

Radersburg the brick yeneer on the one-story schoolhouse was partly sheared off. 

DAMAGE TO RAILROADS 

At the west portal of tunnel No. 8, near Deer Park, 

on the Chicago, Milwaukee & St. Paul Railway, the 

earthquake caused a rock slide, estimated at 40,000 

cubic yards, that not only blocked the track but 

obstructed the canyon of Sixteenmile Creek, causing 

a lake to form (pl. 7, B). Two weeks was required to 

build a temporary track around the slide, so that the 

railroad could resume traffic over this part of its line. 

Clearing the permanent track wo_uld, it was estimated, 

take several months. A report current in newspapers 

soon after the earthquake that the tunnel at Deer 

Park had been destroyed was erroneous. It had been 

clogged by debris ·at one portal but otherwise was 

undamaged. Between Deer Park and Lombard rocks 

fell on the track at several places, without, however, 

causing serious damage. At Cardinal a water tank of 

an older type, supported by timbers, was thrown 

down. At several places near Lombard the Northern 

Pacific Railway track was broken or obstructed by 

masses of fallen rock (pl. 8). 

DAMAGE BY FIRE 

Fortunately, no fires were caused by the earthquake, but an indirect result of it was a fire the night 

of July 20 which destroyed the main business block in 

Toston. This fire caught from a chimney that had 

been cracked by the earthquake and was not yet repaired. Efforts to put out the fire were hindered by 

a lack of water, due also to the earthquake, which 

had cut off the public supply formerly derived from 

gravel beneath the dry channel of Sixmile Creek. 

INJURY TO PERSONS 

Though many persons experienced narrow escapes 

in the Montana earthquake, none lost their lives, and 

only two were reported to have been injured. This 

fortunate lack of casualties is no doubt due to the fact 

that the shock came at a time when schools, churches, 

and other places of public assembly were vacant. 

The people were mostly on the streets or in their 

homes and away from the larger buildings that collapsed. At Three Forks a woman had a leg broken 

as a result of falling or being thrown down by the 

shock, and near Ennis a man received slight injuries 

when the vibrations sheared the automobile in which 

he.was riding off of the road. A west-bound Chicago, 

Milwaukee & St. Paul Railway passenger train in 

two sections and a Northern Pacific Railway. local 

passenger train were in the epicentral area near 

Lombard when the shock came. The Chicago, Milwaukee & St. Paul train sections had only a few 

minutes before passed the place where the Deer Park 

slide buried the track. They came to a stop while 

huge rocks were falling on the tracks in front of them 

. and behind them, and their escape without a scratch 

seems little short of miraculous. 

EMOTIONS, SENSATIONS, ETC. 

The earthquake was violent enough to alarm the 

inhabitants generally throughout an area having a 

radius of as much as 75 miles from the epicenter. 

In Three Forks and other plaoes near the epicenter 

many persons became wildly excited .or hysterical, 

and the alarm caused by the main shock was renewed 

and increased by several of the closely following aftershocks. Because of earth motion during the heaviest 

parts of the main shock and of the first aftershock 

many persons were unable to walk or go toward a 

door or in any other certain direction. Near Three 

Forks a man who had raised his foot to step over a 

ditch was unable to change this pose for a few seconds; 

then he fell into the ditch. Persons sitting were 

unable to rise out of their chairs. A man who was 

in one of the damaged schoolhouses at Manhattan 

probably owes his life to the fact that he :was unable 

to get to the door for a few seconds, during which 

several heavy masses of brick fell just outside. Many 

persons were partly or completely thrown down and 

in falling caught at the nearest object for support. 

A lady thus thrown in the street at Three Forks found 

herself clasping the knees of a strange man. 

As soon as persons were able to regain their feet or 

make progress despite the earth movements they lost 
N 

T E A 0 A u ·Kemm rer 

0 

117° 116° 115° 113° 1110 110° 109° 
sooo' 

4000' 

3000' 

zooo: 

1000 

PROFESSIONAl~ L'APIO:U 147 l'LATE t 

Sealevet_l_-L ____ ___: _____ -=-=~~~~~~:;.:-=::.....:::.:::.:....::.:..:.::..::=.:::.::..::.._..~.-:==-.:==-=::::J 

Alluvium 

(chiefly stream gravel 

and sand oF Ple/stocene 

and Recent age) 

F7l 

L5J 

Tertiary"lake beds" 

(loosely consolidated claY, 

sand,ondgravel) 

Pre=rertiary rocks 

{chiefly Paleozoic limestones and pre-Cambrian 

arg/1/Jte and quartzite 

w1thsome Mesozoic rochs) 

200/ Stnhe and clip of beds 

'I Strike of vertical beds 

U Upthrow side of fault 

D Downthrow Jide of fault 

GEOLOGY OF THE EPICENTHAL AltEA I•'Oil MONTANA EAHTHQUAKE OJ.+' JUNg 27, 1925 
THE MONTANA. EARTHQUAKE OF JUNE 27, 1925 9 

no time in getting out of doors. In their excitement 

some persons picked up articles of no value. At 

Butte a woman is said to have laid down her baby 

and picked up the cat. Within a large area nearly 

everyone experienced more or less dizziness or nausea, 

and many felt a nervousness difficult to overcome for 

days or weeks afterward. 

Most persons who had not already eaten failed· to 

get their suppers that night. Near the epicenter 

many tables with suppers already served were thrown 

to the floor in a general mixup with other household 

articles. At Three Forks and places similarly situat_ed 

dishes were commonly upset, and in general the people 

became too excited or ill to think of eating. Many 

of the inhabitants of Three Forks, Manhattan, and 

other places and even a few as far away as Butte and 

Anaconda remained out of doors part or all of the 

night after the earthquake. At Three Forks and other 

places that suffered conspicuous damage to buildings 

the people wisely did their cooking out of doors for 

several days or until their chimneys could be repaired. 

Fortunately, because it was summer, this caused the 

least amount of inconvenience, and for the same reason 

the houses did not need to be warmed. There is 

record of only one fire resulting from the use of a 

damaged chimney (p. 8). 

Fright or terror was exhibited also by domestic 

animals within the area of startling shock, but few 

details were obtained on this phase of the subject. 

EFFECT UPON MITNES 

Contrary to a rather widespread apprehension, the 

workings of mines were not damaged by the earthquake, and in fact the shock was not generally noticed 

by the miners who were underground at the time. 

.At Barker a group of miners who were at work in a 

stope at a depth of 250 feet did not feel the shock, 

though it was generally noticed in that neighborhood 

by persons at -the surface. So far as learned the 

thousands of miners at Butte who were underground 

at the time were generally unaware that an earthquake had occurred. In view of the fact that mine 

workings are generally constructed so as to withstand 

the jars from blasting, it is not surprising that they 

would resist damage by the less violent vibrations of 

this earthquake. Owing to the common occurrence 

of the jars caused by blasting, miners at work would 

not be likely to notice especially the somewhat 

similar vibrations of seismic origin. Furthermore, as 

these vibrations are less destructive in areas of solid 

rock than in loose materials, they would be" less 

noticeable underground than at the surface. 

ROCK SLIDES 

Rocks and rock masses were shaken down rather 

generally from the steep slopes and cliffs existing 

within a radius of 12 or 15 miles of the epicenter, and a 

few rock falls occurred as far away as 40 miles. 

Deer Parle slide.-The largest mass dislodged by the 

earthquake was that which blocked the valley of 

Sixteenmile Creek at the west portal of tunnel No. 8, 

near Deer Park (pl. 7, A). The size of this slide does 

not mean, however, that the shaking was more ·severe 

in that locality than elsewhere, but that at that point 

an unusually large mass was already sufficiently 

loosened by erosion to be easily shaken down. Tunnel 

No. 8 goes through a narrow limestone spur that 

projects a short distance from the south wall of the 

canyon and causes Sixteenmile Creek to make a north 

bend (pl. 4). At the point of the spur the canyon is 

narrow, and its floor is practically occupied by the 

stream, which is 10 to 12 yards wide. .Above and 

below the spur the canyon widens a few hundred feet. 

The east side of the spur, which faces upstream, is a 

sheer wall of limestone (pl. 7, B), which before the 

slide was 100 to 300 feet high. The north side of the 

canyon opposite the spur is a similar wall, and the 

west or downstream side of the spur is only a little less 

precipitous. Surmounting the walls on both sides of 

the canyon are steep slopes that rise 1,000 feet higher. 

The gorgelike constriction of the valley at this place 

is due to a belt of resistant Paleozoic limestone that 

trends northward across the course of the stream. 

The bend in the gorge is probably an incised meander. 

The limestone dips about 30° W. and therefore inclines 

downstream and at right angles to the axis of the spur. 

.A fault or slip plane that coinci<\es nearly with the 

bedding (pl. 9) touches the top of tunnel No. 8 at or 

near its west portal. Its trace appears about 60 feet 

above the tunnel at the east portal, in the vertical east 

wall of the spur (pl. 7, B) .. · This trace is visible 

farther south and also across the stream on the north 

side of the canyon (pl. 10, A), where it shows the maximum dip. Above and below this fracture are other 

similar slip planes. All of them probably were caused 

by the readjustments between the beds necessitated by 

the folding, and none are to be regarded as major 

structural features. 

The mass of the .spur above the fault plane described fell during the earthquake. Prior to that 

event its supports had been cut away on all sides except the south. The shaking, therefore, easily broke 

it loose along joints and minor fractures and started 

it sliding down the inclined floor on which it lay. 

Scratches made on this plane by the sliding mass go 

across small grooves and ridges made during previous 

fault movements. 

Slides near Lombard.-For a mile or more north -

and south of Lombard, Missouri River is bordered on 

the east side by limestone cliffs and talus slopes several hundred feet high (pl. 10, B), at the foot of which 

the Northern Pacific Railway is built. On the west 

side of the river are lower cliffs beneath which the 

Chicago, Milwaukee & St. Paul Railway passes for 

a short distance. Fortunately, the bedding planes in 
10 SHORTER CONTRJBUTIONS TO GENERAL GEOLOGY, 1926 

the ~liffs east of the river are nearly horbmntal. If 

their dip was toward the river slides probably exceeding that near Deer Park would have occurred. Joint 

planes were opened in these rocks, however (pl. 11, .A.), 

and considerable material was shaken down (pl. 8, B). 

Solid masses weighing as much as 100 tons were detached from the cliffs and rolling down smashed the 

track (pl. 8, .A.). One of these masses estimated to 

weigh 30 tons is. illustrated on Plate 11, B. Along 

Sixteenmile Creek below the Deer Park slide and along 

Missouri River west of Lombard the Chicago, Milwaukee & St. Paul track was similarly obstructed in 

many places. In all tributary canyons or other places 

near by where steep or cliff-like slopes occur much 

material was dislodged and added to the talus accumulations already existing. Observers along Sixteenmile Creek reported that for some time after the rocks 

began to fall the air was filled with a dense and choking dust. At Lombard the cliffs were hidden for several minutes by a cloud of dust, below which the rock 

debris could be seen rolling and sliding down to the 

nver. 

Rock falls in outlying areas.-Beyond the epicentral 

area rock falls of comparatively small extent occurred 

along the bluffs adjacent to Madison River south of 

Three Forks, along Jefferson River above Willow 

Creek, near Accola, and near Canyon Ferry. Most 

of these were masses that were well on the way to 

being let down by the ordinary processes of erosion. 

Dust arising from some rock falls near Willow Creek 

appeared from a distance like smoke and led to the. 

report that the town was on fire. ' 

GROUND CRACKS 

- Newly formed ground cracks were observed in many 

places within a radius of 15 or 20 miles of the epicenter 

and also at one place, Canyon Ferry, about 40 miles 

distant. Apparently all were due to the shaking, and 

none represented a surface slip along the line of a deepseated fault. Those described in the following paragraphs were observed in or near the epicentral area. 

Roy Gulch.-Cracks on both sides of Roy Gulch, a 

short distance southeast of Cardinal, extend for a 

quarter of a mile or more in a ·southeasterly direction 

p~rallel to the gulch and bound an area of alluvium 

that in places has settled 2 feet or more. At the top 

of the slope southwest of the gulch is a series of more 

or less continuous cracks extending also in a southeasterly direction for a mile or more. These cracks 

are branching, and' at one place they occupy a zone 

several feet wide in which the ground is completely 

shattered and broken into clods that have been shuffled 

about and overturned (pl. 12, .A.). The cracks appear 

to extend through the soil and into the underlying 

Tertiary "lake beds," which here consist of moderately hardened layers of clay and sand. 

Garden Gulch.-In the bottom of Garden Gulch, 

about 3 miles south of Cardinal, several cracks were 

observed in alluvium, causing certain areas to settle 

and thus obstruct the flow of water through ditches. 

At another place three cracks having a direction a 

little west of south cut across a ridge of Tertiary 

"lake beds." These cracks are each 100 yards or 

more long and from 1 to 3 or 4 inches wide. The 

ground on the west side of each had settled slightly.-

North of Oardinal.-Near the ranches of Jonas 

Stockburger and Dave Johnson, respectively about 

2 ~iles northeast and 3 miles north of Cardinal, many 

ground cracks were observed that range from 50 to 

200 or 300 feet in length and from 1 to 3 inches in 

width. These occur in a hilly region composed 

chiefly of Paleozoic limestones bearing a rather thin 

soil or surface mantle. Ti1e cracks appear in the 

soil and generally follow along the foot of a hill just 

below the outcrops of bare rock. Whether or not they 

penetrate the rock beneath the soil is not shown. As 

a rule the area on the lower side of each crack has 

settled a little. 

Near Three Forks.-On the highway northeast of 

Three Forks a crack several rods long and several 

inches wide opened in the embankment forming the 

approach to the bridge over Jefferson River. The 

crack had been filled up and was not visible when the 

writer visited the scene, but evidence of it is given by 

a photograph (pl. 12, B). A report published in the 

papers soon after the earthquake stating that a fissure 

had opened extending continuously from Three Forks 

to Manhattan was apparently without foundation. 

Greyson Oreek.-At John Denzer's place, about 15 

miles north of Cardinal, on alluvial land bordering 

GreysoD: Creek, a crack opened more than 100 yards 

long and 6 inches in maximum width. It is parallel 

to the creek, and the bank on that side has settled a 

little. 

Canyon Ferry.-In the field of William Ames, near 

Canyon Ferry, cracks 2 or 3 inches in maximum width 

(pl. 13, .A.) partly surround an area of an acre or less 

that has settled slightly. This block lies in an area 

of alluvium in the valley near the edge of the bench 

lands. It includes a shallow swale that is not crossed 

by a stream, the swale apparently being the result of 

settling at some former time. 

CHANGES IN SPRINGS AND WELLS 

Many springs within a radius of 50 miles from the 

epicenter were increased or diminished by the earthquake. Some were made turbid for a short time. 

Several wells went dry, and others became. muddy. 

The ground-water flow beneath the dry bed of Sixmile Creek, upon which the town of Toston depended 

mainly for its public water supply/ failed shortly after 

1 U.S. Geol. Survey Water-Supply Paper 539, p. 52,1925. 
U. S . C:EOLOW C.\ L Sl' R\' EY l'HOFESSIO~AL PAPgR 11'1 l'LA'l'E 5 

A. DAMAGED SCHOOLHO USE AT TliH..EE FOHK.::>, J\ 10 T. 

lJ. \\HECK OF C II UHC II AT TII.IU<: E FOl'{KS, 1\lO T. 

ole scparalion of lhe fa llen bricks from one artoLhcr Jue Lo failure of morlar 
U. ::;. <:EOLO<:I<'AL SUnVEY I'HOFESSIO'\' AL PAP Ell 141 f>LATE () 

A. DA \lA(;ED SCilOOLHOUSI£ AT \1Al\llATTAl\, \lONT. 

1\olc Sl'JJUraLion of partition \\all~ from oulsidP \\all duf' to laf'k of lie!> 

l\ule shearing- of hrick veneer from hack" all 

• 
U. ::;. Ul!:OLOGlCAL SUlt\"(!;Y 

'l"crriJH>rary tr:u·k in IPI"I l"or<'grouu<i 

o rock falls m-curn•d within !lw tururd. !'holograph b II. P. lien 
U. S. UEOLOUICAL SUH\·F;Y l'llOFESfHOXAL PAPER 147 l'LA'l'E 8 

A. BHO I' EN HAILHOAD THACK NEAU. LOJ\'IHAU.D, MONT. 

NoLc rebound of I hP- hrok••n rail. Photograph by .J.P. Swarls 

11. HOChS ON HAILHOAD THACK 'NEAH. LOMBAHD, \lUNT. 

Plwlog raph by J . 1'. Swarb 
t; . S. (;EOLO<:ICAL Sl"RVEY l' HOFESf'HOXAL I'AI'l·:lt 1~7 PLA'l'E \l 

FAULT Al\ ~ OF Till•: S LIIH: l\ ~. \11 )l EH. J>AI~h , \lUNT. 

l'l1ulograplll; IJy ll. J>. Allnn 
U. S. GEOLOGil'.\L l::iUH\'EY I'HOFES:-;10:\AL l'Al'EH Hi l'LATE 10 

A. 

JJ. Lll\lESTO:'\E CLIFFS <\. . 0 TALUS SLOPE EAST OF \liSSOUIH JU\EH AT LO\lBAHD, MO ''l'. 

Li;;hter-colored streaks on the talu'l slope represent debris shaken down by the ear lhquakc 
C'. S . GEOLOCICAL SUL1VEY 

Boulder dislod;.:ed rrorn a cli fl" by thp Pa rthqu:tk(• allll parll y 

buried hy Lhc l"orco of iL:; fall 
U. 1-i. W ·: OLOGI<'AL ~lJ !t\.'EY P!tOFicSBIO:\"AL PAl'Blt l..JI l'LA'l'B 13 

. 1. SIIATTEHED GHOUND AND OVEHTUHNED CLODS, ROY GULCH, MONT. 

The upLurned duds ,., how ''hilt· IH'<:ath£' of' a de po,;il of lime "e; tlidw" just. ht~lt ea t.lt I he soil 

B. CRACK lN HOAD EMBANKMENT NOll.TH OF TIIIIEE L•'OHt,s, \10 T. 
l'I!Ol•' t•; ::;::;IOXAL PAl'EI{ Ill !'LATE 13 
I 

THE MONTANA EARTHQUAKE OF JUNE 27, 1925 11 

the earthquake. Presumably the water was diverted 

to some other underground channel. Big Spring, 2 

above Toston, was said to have been muddy for two 

'days, and the flow of Mockel Spring,3 south of Radersburg, was considerably increased. Increased flows of 

hot water are reported by the proprietors of White 

Sulphur Springs and Alhambra Springs, at .Clancy. 

In the valley of Jefferson River, near Willow Creek, 

several new springs are said to have broken out, 

though existing springs went dry. According to press 

reports, a spring having a flow estimated on July 20 

at 100 gallons a minute broke out in a field near Lewistown shortly after the earthquake. 

RENEWED FLOW OF OIL AND GAS 

An oil well near Cody, Wyo., that had been unproductive for several years "blew" considerable gas and 

oil for a few days after the earthquake. This well, 

which probably is the one described in published reports 4 as Shoshone Oil Co.'s well No. 1, is situated 

north of Shoshone River, 3 miles east of Cody. It was 

bored in 1909-1912 to a depth of 1,720 feet and found 

gas and small'amounts of oil in several differ~nt layers. 

Its total production, however, probably did not exceed 200 barrels. The well is about 300 feet north of 

the Cody branch of the Chicago, Burlington & Quincy 

Railroad and 300 ·feet east of Cottonwood Creek. 

W. 0. Taylor, of Cody, who witnessed the recurrence 

of activity, reports that the well started flowing about 

noon of the day after the earthquake. By the middle 

of the afternoon the flow had reached such proportions that the fire hazard appeared too great for trains 

to pass. Throughout the afternoon the well threw a 

column of mixed oil and water accompanied by gas 

from 30 to 40 feet in the air. The flow of gas was estimated at about 5,000,000 cubic feet a day, and the 

oil and water together at 1,500 barrels a day, the proportion of oil ranging from 5 to nearly 100 per cent. 

At 7 o'clock the next morning (June 29) the well was 

still spouting 10 or 15 feet in the air and making considerable oil. At 9 o'clock the flow had ceased. As 

a result of the well's activity the ground had become 

oil soaked for 100 feet around it. 

Since the spurt described the well has remained 

quiet, and at t4e time of Mr. Taylor's report (Dec. 19, 

2 Idem, p. 46. 

a Idem, p. 47. 

• Hewett, D. F., The Shoshone River section, Wyo.: U. S. Geol. Survey Bull. 

541, pp.ll0-111, 1914. Hewett, D. F., and Lupton, C. T., Anticlines in the southern 

part of the Big Horn Basin, Wyo.: U.S. Geol. Survey Bull. 656, pp. 187-188,1917. 

1925) oil stood in the casing about 60 feet below the 

top. 

Edwin Binney, jr., of New Haven, Conn., who 

visited the scene about three weeks after the earthquake, observed evidences of the recent activity of 

the .well as described. Mr. Binney saw the same well 

in 1924. At that time it was discharging a small 

amount of gas, and oil was standing in it to the depth 

of at least 100 feet. The writer is indebted to Mr. 

Binney for calling his attention to the behavior of 

this well and suggesting its possible relation to the 

earthquake. 

The well is within the zone in which the earthquake 

intensity ranged from 4 to 5 on the Rossi-Forel scale. 

The Byron, Garland, and Elk Basin oil fields in 

Wyoming, and the Cat Creek and Kevin-Sunburst 

oil fields, in Montana are also in the same zone; the 

Salt Creek and other fields in Wyoming are in zones 

of less intensity. It is not known whether any wells 

in these fields were affected by the earthquake. 

SAND SPOUTS 

At Clarkston, in the alluvial bottom lands along 

Missouri River, a crack opened and sand and water 

spouted up for several hours. Mterward the crack 

closed, and at the time of the writer's visit, two months 

later, nothing could be seen but the deposit of sand 

spread over a square rod or two. . Similar occurrences 

were reported near Townsend and in the horseshoe 

basin west of Menard·, where water and mud are said 

to have spouted up like a geyser. 

INTENSITY OF THE EARTHQUAKE 

The intensities of the earthquake at different places, 

as shown by the following table, were estimated by 

the writer from the visible effects upon buildings and 

natural objects; reports obtained by letter or .interview from persons who experienced the shocks, 

reports made by observers .of the United States 

Weather Bureau, and reports published in the newspapers. Altogether 110 reports were obtained by 

interviews with persons who were within a radius of 

40 or 50 miles of the epicenter. Sixty-five replies 

were received to letters addressed to postmasters or 

others in the outlying parts of the disturbed area, 

and a score or more of reports from scattered points 

were obtained from Weather Bureau observers _and 

selected from the newspapers. 

•' I ~~ I • 
12 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1926 

Intensity and effects of Montana earthquake of June 27, 1925 

[Principal shock at 6.21 p.m.] 

Place a Latitude Longitude Inten- Effects, etc. N. W. sity b 

CardinaL___________________ 46 7 

Stockburger's, 2~ miles north- 46 8 

east of Cardinal. 

Deer Park ___________________ 46 8 

Garden Gulch, 4 miles south- 46 6 

east of Lombard. 

Dave Johnson's, 3 miles north 46 9 

of Cardinal. 

Lombard____________________ 46 8 

Perugin's, 9 miles southeast of 46 15 

Townsend. 

Clarkston___________________ 46 2 

Jacobs's, 10 miles southeast of 46 15 

Townsend. 

Denzer's, 8 miles southeast of 46 17 

Townsend. 

Roy Stillman's, 7 miles south- 46 4 

west of Maudlow. 

Trident_'____________________ 45 57 

Three Forks _________________ 45 56 

Manhattan __________________ 45 42 

Logan _______________________ 45 53 

Toston ______________________ 46 10 

Mackel's, 7 miles south-south- 46 8 

east of Radersburg. 

Valley of Madison River, 8 45 46 

miles south of Three Forks. 

Gallatin Valley, 3 miles south 45 50 

of Manhattan. Maudlow ____________________ 46 8 

Accola__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 45 54 

Menard_____________________ 45 58 

Radersburg __________________ 46 13 

Walbert's, 9 miles north-north- 46 2 

west of Three Forks. 

Doherty's, 6 miles east-south- 46 18 

east of Townsend. 

Thompson's, 6 miles east of 46 19 

Townsend. 

Townsend___________________ 46 20 

Willow Creek ________________ 45 40 

Steingruber's, 4 miles north of 45 53 

Willow Creek. 

Belgrade____________________ 45 2 

Carroll's, 9 miles southeast of 46 2 

Maudlow. 

Helena __ ~------------------- 46 36 

Whitehall_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 45 48 

Jefferson Island _________ -_-__ 45 47 

0 I 

111 22 

111 20 

111 19 

111 20 

111 21 

111 24 

111 22 

111 24 

111 22 

111 23 

111 17 

111. 29 

111 33 

111 20 

111 26 

111 26 

111 36 

111 32 

111 20 

111 10 

111 13 

111 12 

111 39 

111 38 

111 25 

111 25 

111 32 

111 39 

111 39 

111 11 

111 6 

112 0 

112 6 

111 57 

9 

Extensive rock falls from cliffs. Heavy stove moved east. 

Furniture in small house thrown violently about. Cracks in ground. 

Log buildings distorted and made to lean eastward. 

Extensive rock falls and slides. Heavy stove moved northwest. 

Other furniture in small house thrown about,. · Loose clods in plowed field "danced and shuffled about." Stove in 

cabin thrown over eastward. Log cabin sprung out of shape. 

Ground cracks. All loose objects in small frame house thrown about 

violently. 

Extensive ro·ck falls. Telephone poles leaned strongly to the northwest, then righted. Heavy steel safe in Northern Pacific Railway 

depot moved to the southeast. Strong surge on Missouri River. 

Swells formed on railway track. 

Doors of stove jerked off. 

9+ Ground cracks and sand spout. Visible ground waves. 9 Small frame house distorted. Furniture thrown about. 

9+ Doors jerked off of hinges. Furniture, etc., thrown about and 

wrecked. Ground cracks. 

9 All loose articles in small house thrown about. 

9 All chimneys broken or thrown down. Cement walls and foundations 

seriously damaged. 

9 Brick and stone buildings seriously damaged; some partly wrecked. 

9 Several brick and stone buildings seriously damaged; some partly 

wrecked. 

9 Brick schoolhouse partly wrecked. Chimneys generally overthrown. 

9 Many chimneys overthrown. Piano moved eastward. Loose articles on shelves fell eastward. 

8+ Chimneys overthrown. 

8 Rock falls. Chimneys overthrown. Cracks opened in cliffs. Water 

thrown out of troughs. 

8+ Chimneys overthrown. 

8 Some chimneys overthrown. Loose articles fell from shelves. 

8+ Rock falls. 

8+ Chimneys overthrown. 

8+ Chimneys overthrown. Some brick and stone buildings seriously 

damaged. 

8+ Visible ground waves. Water thrown out of trough. 

8+ Heavy tractor thrown south off the timbers on which it had been 

blocked up. Chimneys overthrown. 

8+ Doors on one-story frame house swung violently. Loose articles fell. 

8+ Loose articles thrown from shelves. Doors and lights swung violently. Some chimneys overthrown. 

8+ Brick schoolhouse seriously damaged. Some chimneys overthrown. 

Plate-glass windows broken. Visible earth waves. Goods spilled 

from shelves on north and south sides of room. Few articles on west side clown. 

8 Loose articles thrown about. Rock falls. 

8 Cornice on brick schoolhouse fell. Some chimneys overthrown. 

Brick and stone walls cracked. 

8 Loose articles thrown from shelves. Chimneys broken. 

7 Slight damage to some buildings and a few chimneys wrecked. Loose 

articles fell from shelves in several stores. 

7 Top of a two-story brick wall fell off on west side. Chimneys damaged. 

Some loose articles fell from shelves. Automobiles facing east and 

west in a garage rolled forward and back in unison. 

7 Buildings and other objects swayed alarmingly. 

" Localities in Montana except as indicated otherwise. b The figures indicating intensity are those of the Rossi-Forel scale, which as published in the Bulletin of the Seismological Society of America (vol. 11, p. 218) is as 

follows: 1. Microseismic shock; recorded by a single seismograph or by seismographs of the same model but not by several seismographs of different kinds; the shock felt by as 

experienced observer. · 2. Extremely feeble shock; recorded by several seismographs of different kinds; felt by a small number of persons at rest. 3. Very feeble shock; felt by several persons at rest; strong enough for the direction or duration to be appreciable. 4. Feeble shock; felt by persons in motion; disturbances of movable objects, doors, windows; creaking of ceilings. 5. Shock of moderato intensity; felt generally by everyone; distur~a~ce of furniture, beds( etc,., ringing of s':"inging be.lls. . . . . 6. Fairly strong shock; general awakening o fthosc asleep; general rmgmg of house bells; osmllatwn of chandeliers; stoppmg of pendulum clocks; v1s1ble agitatiOn of trees 

and shrubs; some startled persons leave their dwellings. . . . . ., . 7. Strong shock; overthrow of movable objects; fall of plaster; nngmg of church bells; general pamc, Without damage to bm,dmgs. 

8. Very strong shock; fall of chimneys; cracks in walls of buildings. 9. Extremely strong shock; partial or total destruction of some buildings. . 10. Shock of extreme intensity; great disaster buildings ruined; disturbance of the strata; fissures in the ground; rock falls from moun tams. 
THE MONTANA EARTHQUAKE OF JUNE 2'7, 1925 13 

Intensity and effects of Montana earthquake of June 27, 1925-Continued 

[Principal shock at 6.21 p. m.] 

Place Latitude Longitude Inten- Effects, etc. N. W. sity 

Bozeman ____________________ 45 41 111 3 

White Sulphur Springs ________ 46 33 110 54 

Doggett's, 18 miles northwest 46 43 

of White Sulphur Springs. Fort Logan__________________ 46 42 

House's, 10 miles northeast .of 45 50 

Bozeman. Clyde Park __________________ 45 53 

Wilsall ______________________ 46 0 

Ringling_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 46 16 

Canyon Ferry________________ 46 39 

111 12 

111 11 

110 53 

110 37 

110 39 

110 49 

111 42 

Clancy____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 46 28 111 58 

Norris ______________________ 45 34 111 42 

Harrison _____ . _______________ 45 42 ·111 48 

Livingston ___________________ 45 40 

Eldridge____________________ 45 12 

Ennis _______________________ 45 21 

Virginia City _______________ - 45 18 

Twin Bridges________________ 45 33 

Butte _______________________ 48 0 

Sieben______________________ 45 54 

Wolf Creek __________________ 47 1 

Drummond_____ _ _ _ _ _ _ _ _ _ _ _ _ _ 46 40 

Great Falls __________________ 47 30 

110 34 

111 14 

111 44 

111 56 

112 20 

112 33 

112 8 

112 4 

113 8 

111 17 

Neihart _____________________ 46 15 11_0 43 

Belt ________________________ 47 22 110 56 

Barker ______________________ 47 4 

Monarch ____________________ 47 6 

Cascade_____________________ 47 15 Anaconda ___________________ 46 7 

110 37 

110 50 

110 42 

112 57 

Philipsburg __________________ 46 20 113 18 

Columbus ___________________ 45 38 109 15 

Hutchens's, 32 miles south of 44 51 111 37 

Ennis. Gardiner ____________________ 45 3 110 44 

Missoula ____________________ 46 53 114 0 

Superior _____________________ 37 12 114 59 

RoundUP-------------------- 46 27 108 34 

Fort Benton _________________ 47 50 110 41 

Grangev!lle, Idaho ___________ 45 50 116 8 

Moscow, Idaho ______________ 46 42 117 0 

ShelbY---------------------- 48 30 111 52 

Havre ___________________ · ___ 48 33 

Cody, Wyo __________________ 44 33 

Salmon, Idaho _______________ 45 10 

Mackay, Idaho_ _ _ _ _ _ _ _ _ _ _ _ _ _ 43 56 

Nezperce, Idaho _____________ 46 12 

Pullman, Wash_ _ _ _ _ _ _ _ _ _ _ _ _ _ 46 44 

Malta ______________________ 48 22 

Challis, Idaho _______________ 44 30 

109 40 

109 3 

113 53 

113 37 

116 15 

117 11 

107 52 

114 14 

Dubois, Idaho _______________ 44 10 112 15 

85638°-26--2 

7 A few chimneys overthrown. A few brick buildings seriously damaged. 

Chandeliers swung violently. Heavy steel safe moved a few inches 

south. 

7 A few brick or stone buildings seriously damaged. Several chimneys 

o"verthrown. Water in a trough splashed out on north and south ~d~. . 6+ Chandeliers swung violently. 

7 Building swayed alarmingly. 6+ Buildings swayed. Some chimneys cracked; one _fell. 

7 

6+ 

7 

7+ 

7 

7+ 7+ 

6+ 

6 

6 

6+ 

6+ 6+ 

6 

5+ 5+ 

5 

5+ 

5 

5 

5 

5 

6 

6 

6 

5 

5 

5 

4 

5 

4 

4 

4 

4 

4 

4 

4+ 

3+ 

3 

3 

4 

3 

Plaster cracked. Some chimneys overthrown. 

Some loose objects thrown from shelves. 

Cracks in plaster and chimneys. 

Some chimneys overthrown. Surges on Lake Sewell. Ground cracks. 

Earth banks fell. 

Several chimneys thrown dowri. Flow of hot springs increased. 

Chimneys damaged; some overthrown. School bell rung. 

Cement walls cracked. Chimneys damaged and plaster cracked. 

Visible earth waves. Some chimneys cracked. Loose objects fell. 

Log house shaken strongly. Loose objects moved or rattled. 

Hanging lamps swung. A few loose bricks fell from top of wall. 

Old stone walls and chimneys cracked. A few chimneys . down. 

Plaster cracked. A few bricks sheared from the cornices of some buildings. 

Several chimneys damaged and a few overthrown. 

Some old brick walls and chimnevs cracked or fallen. Chandeliers 

·swung. Vases and similar objects toppled over. Smt.ll house strongly shaken. 

Chandeliers swung. 

House shook. Hanging lampstswung. 

Chandeliers swung. A few vases, etc., toppled over. Buildfngs 

swayed perceptibly. 

Loose articles moved but did not topple over. Bricks fell from an old 

chimney. 

Hanging lamps swung. Posts, etc., swayed. An old cracked chimney 

thrown down. 

Buildings swayed. 

Posts swayed. Loose articles moved. 

Loose objects moved. A few articles fel1 from shelves. 

Buildings swayed; some loose bricks fel1. Some dishes and vases overturned. Automobiles in garage moved back and forth. Water 

splashed out of pail. A "dead" motor on railway track moved. 

Buildings swayed alarmingly. Some plaster cracked and loose 

bricks shaken from tops of some walls. Courthouse clocks stopped 

at 6.22 p.m. 

Felt by nearly everyone. Some foundations settled and some chimneys toppled. 

Hanging pictures shifted awry. 

Strong shock. Hanging lamps, etc., swung. 

Felt generally. Hanging lamps swung moderately. A few cracks in 

plaster. 

Chandeliers swung. Walls creaked. Felt distinctly for several 

seconds. 

Felt by nearly "everyone indoors and out. Lamps swung. Loose 

objects moved. 

Felt by several persons outdoors. Loose objects moved. Frame 

building creaked. Shocks came at 6.30 and 7.30 p. m. Felt by many persons. Houses creaked and bed "wiggled." 

Hanging lamps swung. Loose objects moved or rattled. Two 

water-pipe connections broken. 

Felt generally. Hanging lamps and pictures swung. Windows 

rattled. 

Felt by nearly everyone. Pendulous objects swung. Doors and 

windows'rattled. 

Felt generally by persons indoors. Hanging lamps, etc., swung. 

Felt by everyone. Loose objects moved or rattled. Lamps swung. 

Noticed by several persons indoors. Chandeliers swung and windows 

rattled. · 

Noticed by several persons indoors. Windows, etc., rattled slightly 

Noticed by several persons indoors. Windows rattled. 

Noticed by several persons indoors. Hanging lamps swung. 

Noticed by nearly everyone indoors. Hanging lamps swung and 

windows rattled. 

Felt by several persons indoors. 
14 SHORTER CONT'RIBUTIONS TO GENERAL GEOLOGY, 1926 

Intensity and effects of Montana earthquake of June 27, 1925-Continued 

[Principal shock at 6.21 p.m.] 

Place Latitude Longitude Inten- Effects, etc. N. W. sity 

Lethbridge, Alberta__________ 49 43 

Macleod, Alberta ____________ 49 44 

Forsyth _____________________ 46 16 

Baker, Oreg _________________ 44 47 

Colfax, Wash ________________ 46 54 

Medicine Hat, Alberta _______ 1 50 0 

Cardston, Alberta ____________ 49 11 

Maple Creek, Saskatchewan___ 49 55 

Swift Current, Saskatchewan__ 50 17 

Glacier Park _________________ 48 26 

Wibaux _____ . ________________ 46 59 

Casper, Wyo ________________ 42 52 

Lewiston, Idaho ___ ---------- 46 23 

St. Anthony, Idaho ___________ 43 58 

We.iser, Idaho _______________ 44 15 

Warm Springs_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 46 11 

Hamilton ___________________ 46 15 

KalispelL _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 48 12 

Dillon ______________________ 45 14 

Lima _______________________ 44 38 

Miles City_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 46 24 

Boise, Idaho __________ .:: ______ 43 37 

Sheridan, Wyo _______________ 44 48 

Thermopolis, Wyo ___________ 43 38 

Southern Cross ______________ 46 12 

Billings ___________ ------- --.-~45 47 

Spokane, Wash ______________ 47 40 

Sand Point, Idaho ___________ 48 17 

Bonners Ferry, Idaho _____ -___ 48 42 

St. Maries, Idaho ____________ 47 19 

Carmangay, Alberta __________ 50 5 

Taber, Alberta _______________ 49 39 

Calgary, Alberta _____________ 51 4 

Moose Jaw, Saskatchewan_____ 50 24 

East End, Saskatchewan______ 49 35 

Assiniboia, Saskatchewan_____ 49 41 

112 52 

113 23 

106 38 

117 52 

117 24 

110 40 

113 20 

109 27 

107 49 

113 12 

104 11 

106 17 

117 1 

111 43 

116 58 

112 47 

114 10 

114 17 

112 38 

112 36 

105 51 

116 12 

106 54 

108 12 

113 15 

108 30 

117 25 

116 32 

116 20 

116 33 

113 6 

112 8 

114 5 

105 32 

108 50 

106 0 

3+ Felt by persons indoors only. Clock in Canadian Pacific Ry. station 

stopped at 6.23 p. m. Shock lasted ·30 seconds. Lights and 

hanging objects in hardware store swayed. Flower pots fell from a window ledge. A piano moved perceptibly. Clocks stopped. A 

second shock about 6.45 p. m. 3+ Felt by many persons, some of whom were outdoors. Hanging 

objects swayed and windows rattled. Shocks came about 6 and 

7p. m. 4 Felt on ground floor. Caused dizziness. Loose objects moved or rattled. 

3 About 5.25 p. m. ( = 6.25, mountain time). Felt by several persons 

indoors only. Chains and saws in hardware store rattled. Time 

of "regulator" clock in jewelry store was slowed down 2 minutes. 

3 Felt by several persons indoors only. Windows rattled. A bench 

and a bed moved perceptibly. 

2 + Felt by several persons indoors only. Hanging lamps swayed slightly. 

Persons sitting in chairs felt a swinging motion. Clock in Canadian 

Pacific Ry. station stopped at 6.23 p. m. 3 Felt by several persons, some of whom were outdoors. Shock com- posed of two tremors. Furniture moved "nervously." Some 

persons became ill. 

2+ Felt by several persons, some of whom were outdoors. 

2 Felt by several persons indoors only. Slight on ground floor. Fairly 

distinct on upper floors. Dishes rattled in an apartment on the 

fourth floor. 

3 Felt by most persons indoors. Hanging lamps swung slightly. 

2+ Felt by a few persons indoors and on upper floors. A rocking sensa- tion like that caused by ocean waves. Windows rattled. 

2 Felt on fifth floor. Loose objects rattled. 

2+ Felt by a few persons indoors only. Loose objects rattled slightly. 

2 Felt by several persons indoors only. 

3 Felt by a few persons indoors. Lamps swung and loose objects 

rattled. 

6 Some brick veneering fell and some walls cracked. 

5+ Some merchandise shaken from store shelves. Some plaster cracked. 

People rushed out. 

3+ Shocks lasting 10 seconds at 6.20 and 7.10 p. m. 6+ Some plaster fell and some dishes broken. People alarmed and ran out. 

5+ At 6.23 p. m. People ran out of doors. 

3+ At 6.26 p. m. Pictures and chandeliers swung. Some persons ran out of doors. A second shock at 7.07 p.m. 

2+ At 6.23 p. m. Slight alarm on upper flpors of hotels. 

3+ Small shock. Felt in several widely scattered localities. Time, 

6.23 p.m. 

3 ± Light shock at 6.35 (6.25?) p. m. 5+ Water in a pool splashed up in the face of a man drinking. A large 

rock loosened and rolled down hill. Trees waved from side to side. 

6 Cracks opened in some old brick buildings. Some old wood-block 

paving buckled. Mild panic. 

2+ Registered on seismograph of Gonzaga University at 5.25 p. m. (6.25, mountain time). Felt in homes and downtown office buildings. 

3 Tremors felt lasting 2 or 3 minutes. 

3 Do. 

3 Do. 

3 Shock lasted 15 to 30 seconds. Rocking motion felt upstairs in a 1 Y2-story house. 

3 Shock lasted 3 or 4 seconds. Lights suddenly swayed. A counter 

in a store swayed forward and back. A house swayed gently. 

2 Felt by persons in high buildings only. Clocks stopped at 6.28 p. m. 2 Felt by several persons. Dishes danced on a table on the fourth 

floor. Elevator, which had stopped at the same floor, was made 

by the shock to move up 2 feet. Four distinct shocks reported. 

2+ Clock in Canadian Pacific Ry. station stopped at 6.23 p. m. 3 Distinct. Shock lasted 8 seconds. 
THE MONTANA EARTHQUAKE OF JUNE 27, 1925 15 

Negative reports were re~eived from the following 

places: 

Latitude Longitude N. W. 

0 I 0 I 

Regina, Saskatchewan ____________________ 50 27 104 35 

High River, Alberta--------------------- 50 35 113 52 Rossland, B. c ___________________________ 49 4 117 37 Cranbrook, B. C _________________________ 49 30 115 46 Culbertson, Mont ________________________ 48 9 104 31 

Plentywood, Mont _______________________ 48 46 104 35 Baker, Mont _________________________ --_ 46 23 104 15 Ekalaka, Mont ______ , ___________________ 45 53 104 33 Sundance, Wyo __________________________ 44 24 104 20 

Newcastle, Wyo __________________________ 43 52 104 10 Lander, W yo ____________________________ 42 50 108 43 Evanston, Wyo __________________________ 41 15 110 57 Kemmerer, W yo _________________________ 41 48 110 32 Green River, Wyo ________________________ 41 32 109 28 Paris, Idaho _____________________________ 42 13 111 24 

Montpelier, Idaho ________________________ 42 18 111 18 Preston, Idaho ___________________________ 42 6 111 39 Twin Falls, Idaho ________________________ 42 34 114 49 Gooding, Idaho ______________________ :.. ___ 42 56 114 43 Rupert, Idaho ___________________________ 42 37 113 41 

Idaho Falls, Idaho ________________________ 43 29 112 4 

American Falls, Idaho ____________________ 42 47 112 53 Shoshone, Idaho _________________________ 42 56 114 24 

Blackfoot, Idaho _________________________ 43 11 112 21 Pocatello, Idaho _________________________ 42 52 112 26 

Hailey, Idaho ____________________________ 43 30 114 18 Silver City, Idaho ________________________ 43 0 116 42 Council, Idaho ___________________________ 44 44 11n 25 Logan, Utah _____________________________ 41 45 111 50 Brigham, Utah ___________________________ 41 30 112 1 

La Grande, Oreg-----------------~------- 45 20 118 7 

Enterprise, Oreg _________________________ 45 25 117 18 Pomeroy, Wash __________________________ 46 28 117 42 

Walla Walla, Wash _______________________ 46 4 118 22 I>ayton, Wash ___________________________ 46 17 117 59 

Rawlins, Wyo ___________________________ 41 47 107 14 

DIRECTION OF THE MOTION 

Positive evidence as to the direction in which the 

vibrations traveled is given by the operator of the 

~hicago, Milwaukee & St. Paul Railway at Jefferson 

Island. He was worlcing on the train dispatcher's 

telepl:JI)ne at the time and heard the operator at Three 

Forks say they were having an earthquake. In a few 

seconds he felt it himself, and still later he heard it 

reported by the operator at Butte. In a straight line 

Three Forks is 20 miles east of Jefferson Island and 

Butte 30 miles to the west. · Near Toston during the 

earthquake an observer in an automobile traveling on 

a road leading southeastward, or toward the epicenter, 

noticed nothing unusual in the beha~ior of his car. 

Another traveling in a northeasterly direction had 

difficulty in keeping his car on the road, presumably 

because he was traveling crosswise to the direction of 

motion. Man.v of the observers reported the direction 

that the earthquake waves seemed to travel, and most 

of these directions, whether leading toward or away 

from the epicenter, when platted on the map, coincide 

nearly with radii. 

22958°-27--2 

NATURE OF.THE MOTION 

Observers near the epicenter describe the earthquake 

motion as a violent bumping and rocking. Elsewhere 

practically all describe it as a rocking motion, which· 

a few qualify with the terms bumping, jerking, or 

twisting. Visible ground waves, much like the swell 

in the wake of a steamboat, were reported by many. 

persons. Similar waves were indica ted by the behavior of buildings, fences, telegraph poles, etc., which 

were observed to lean to one side and then to the other, 

describing arcs of as much as 30°. Standing auto-

. mobiles, including a heavy tractor, were seen to dance 

a comical sort of jig, rising first on one side then on the 

other. At Three Forks a frame house appeared to 

buckle up along the comb of the roof, like a cat humping its back at sight of a dog, and then straighten out 

again without being seriously damaged. At Willow 

Creek an observer was able to see clear under a house 

momentarily as one end lifted clear of the foundation 

and settled back to place. 

At Radersburg, Logan, and other places some chimneys were broken at the roof line and twisted clockwise 

one-eighth to one-quarter of a revolution (pl. 13, B). 

SOUNDS 

Sounds of low pitch were heard by 80 per cent of the 

observers who were within 25 miles of the epicenter, 

and by 65 per cent of those within 80 miles. Beyond 

·that distance only 30 per cent of the observers report 

sounds, but information from this outlying belt is ·too 

scanty to fix the limit of the sound area. The great 

majority of the observers describe the sounds as a low 

rumbling, and several add that it was like a train or 

a heavy truck passing by or crossing a bridge, or like 

thunder. A few describe the sound as a roaring, 

a rushing or swishing like the wind, or like a storm or 

a low growl. 

AREA 

The area throughout which the 'shock was sensible 

to persons, which is the area bounded by isoseismal 2 

(see pl. 3) is about 310,000 square miles. The 

disturbed area is· therefore of about the same order 

of magnitude as that of tect~nic earthquakes of the 

first rank. The intensity of the Montana disturbance 

. was apparently somewhat less than that of the 

California earthquake of 1906, and the damage, owing, 

as already explained, to the lack of populous cities 

near the epicenter, was comparatively insignificant. 

TIME AND DURATION 

·The time at which the main shock occurred is reported variously from 6.15 to 6.35 p. m., but 70 per 

cent of the observers set the time between 6.20 and 
16 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1926 . ' 

6.25 p. m. Of those who were within a radius of 50 

or 60 n1iles from the epicenter 60 per cent reported 

the time as either 6.20 or 6.21 p. m., the weight of 

evidence, all things considered, being much in favor 

of 6.21. Clocks stopped at that time in a drug store 

at Three Forks and in the office of the United States 

Weather Bureau at Helena. Outside the area described, 12 observers out of a total of 24 place the 

time at 6:23 and 4 at 6.25; the remainder are scattering. 

Estimates of duration reported by 66 persons range 

from 5 seconds to 3 minutes, but about three-fourths 

of the estimates lie between 15 seconds and 1 minute, 

and their average is about 30 seconds. No one reported having timed the shock with a watch or other 

instrument, but within the area of startling shock 

the duration was at least 15 or 20 seconds, for in less 

time the observers could hardly have traversed the 

distances or performed the tasks that they claimed 

to have done while the shaking was in progress. 

Apparently in outlying areas where the intensity 

was moderate or feeble the sensible vibrations continued for 30 seconds or more. 

SPEED OF TRANSLATION 

Clocks in Canadian Pacific Railway stations at 

Lethbridge and Medicine Hat, Alberta, and East 

End, Saskatchewan, stopped at 6.23 p.m. A Western 

Union clock at Glasgow, Mont., was reported stopped 

also at that time. The distance of these places 

from the epicenter ranges from 264 miles for Lethbridge to 276 miles for Medicine Hat. If the times 

as given for these places and for the epicenter are 

accepted as correct, then the vibrations were propagated outward an average distance of 270 miles in 

two minutes, or at the rate of 2 U miles a second. 

Owing to the fact, however, that the time observations 

were made to the nearest minute only, there remains 

the possibility of ·an error as great as one minute, 

plus or minus. Therefore, the total time of translation for the distance mentioned may be as short as 

one minute or as long as three minutes, and the speed 

at which the vibrations traveled lies between 4}1 and 

1 ~ miles a second. 

ISOSEISMALS o 

DATA AVAILABLE 

Compared to the size of the disturbed area the 

number of observations available is rather small, 

and therefore the isoseismal lines as drawn (pl. 3) 

doubtless appear more precise and definite than they 

should. Where their position is believed to be 

de~ermined within rather narrow limits they have 

6 "An isoseismalline, or simply an isoseismal, is a line drawn through all places 

at which the intensity of the shock is the same. "-Davison, C., A manual of seismology, p. 4, Cambridge Univ. Press, 1921. 

been drawn as full lines; where the evidence for placmg 

them is less definite, they are represented by dashes. 

Isoseismal 9 is perhaps determined with more certainty than any of the others. It incloses Three 

Forks, Manhattan, Logan, Toston, and other places 

where the earthquake effects were most conspicuous 

and abundant. The central part of this area is thinly 

inhabited and almost devoid of structures that would 

be easily damaged· by earthquake shocks. If the 

effects on similar things are compared, however, the 

intensity seems tor•have been considerably higher in 

this central area than at Three Forks and the other 

places mentioned. . Accordingly, an isoseismal provisionally labeled 10 has been drawn inclosing an area 

of about 80 square miles in Clarkston Valley and the 

adjoining hills on the east and north. Lombard, the 

largest settlement within this isoseismal, contains two 

railroad stations of one-story frame construction with 

brick chimneys and eight or ten small frame houses, 

some of which are merely converted box cars. Clarkston consists of a station, a grain elevator, and two or 

three small houses. Cardinal and Deer Park each have 

two or three small buildings. The remainder of the 

area contains only a few small hQuses of frame or log 

construction. None of these buildings was very seriously damaged, though they plainly show the effects of 

severe shaking. All chimneys were overthrown and 

plaster was broken in the few houses that possessed such 

features. Common~y door, window, or house frames 

were sprung or distorted. Some log cabins and barns 

. were noticeably sprung out of shape or made to lean 

to one side. Some doors were jerked off their hinges. 

Furniture, including stoves and ranges, and other loose 

articles were overturned or thrown about, and in most 

houses practically every dish or other breakable article 

was demolished. The racking a small but substantial 

unplastered frame house at Cardinal suffered is shown 

by torn wall paper and lining. The intensity c9f the 

shock at Roy Gulch is indicated by the cracking and /'. shattenng of moderately firm ground and the overturning of clods (pl. 12, B). At Garden Gulch an 

observer saw the clods in a plowed field shuffled about 

like checkers being shaken on a board. Rock falls in 

this area have been described (pp. 9-10). 

At Three Forks and other places outside the area 

being considered the overthrowing of furniture and 

the breaking of dishes were less general or complete 

and the springing or racking of door and house frames 

was rather exceptional. The crack that appeared in 

the road north of Three Forks opened in an artificial 

embankment not to he compared in resistance to the 

firm ground which was shattered at Roy Gulch. At 

Trident there are cliffs essentially similar to those at 

Lombard, but much less material was shaken down 

from them. 

So far as the evidence goes, therefore, the shock 

appears to ~}ave been much stronger in this central 
THE MONTANA EARTHQUAKE OF .JUNE 27, 1925 17 

area than elsewhere. After comparing effects in the 

field it is difficult to escape the conclusion that had a 

town such as Three Forks, for example, been situated 

here every brick building in it would have been leveled. 

POSITION OF THE EPICENTER 

The longer .axis of the innermost isoseismal trends 

about N. 10° E. and lies a little east of Cardinal, 

crossing the lower parts of Roy and Garden Gulches. 

Its position is not far from a line dividing T. 4 N., 

R. 3 E., into east and west halves. The longer axis 

of the next isoseismal (No. 9) is parallel to that of the 

smaller curve, but it lies about a mile farther west. 

As nearly as can be determined, therefore, the epicenter 

lies either on one of these ~xes or between them a~d 

within a belt extending south 3 or 4 miles from 

Cardinal. 

FORM OF THE ISOSEISMALS 

As drawn isoseismal curves 7, 8, and 9 show a 

tendency to expand toward the west; possibly this is 

an erroneous interpretation, due to the lack of sufficient data or to undue weight having been given to the 

evidence from the more populous areas. Such a result 

has been guarded against as far as possible, however, 

and the expansion is believed to be real. It may 

possibly be due to the westward hade of the fault on 

which the earthquake is supposed to have originated, 

(seep. 22). 

The three outer isoseismals show a striking irregularity at the south, where they are crowded inward 

so as to exclude a wide reentrant from the area of 

sensible shock. St. Anthony, Idaho, near the peak 

of this reentrant, is only 150 miles south of the epicenter, whereas in other directions the shock persisted 

for distances of 300 to 400 miles. This abrupt and 

abnormal decline of intensity begins at the edge of the 

Snake River Plain, a great valley floored with lava. 

Presumably the lava overlies a considerable thickness 

of unconsolidated sediments, al}d thes.e in turn rest 

upon the upturned and eroded edges of older and 

harder rocks like those of the surrounding mountains. 

At the northeast th~ lava of the Snake River Plain 

merges with the lavas of Yellowstone Park, which 

consist of a great thickness of flows, tuffs, and breccias. 

The whole forms a heterogeneous mass that coincides 

suggestively with the zone in which the southward 

progress of the vibrations was arrested. At the west a 

similar indentation is indicated where the disturbed 

area touches the Columbia Pl::tteau, but only isoseismals 2 and 3 are affected. Here the vibrations persisted somewhat beyond the edge of the lava, but 

there was a sudden and marked decline of intensity 

as soon as the main lava area was reached. 

· Columbia Plateau is made up of many lava flows, 

between some of which are beds of gravel or silt, the 

whole forming a mass of similar physical character 

to the rocks of the Snake River Plain and Yellowstone 

Park. It would seem, therefore, that these rather 

loosely aggregated masses were able to break up and 

check the rather feeble vibrations that reached them. 

This explanation, however, becomes less certain when 

the fact is considered that toward the northeast the 

vibrations extended farther than anywhere else, 

though the region they traversed is underlain by 

rocks (Cretaceous sediments) that are not especially 

dense or homogeneous. 

Both the Snake River Plain and the Columbia 

Plateau may be regarded as great structural depres-" 

sions, and it is possible, therefore, that the vibrations 

were cut off or deflected by bordering fault zones, but 

there are many similar though smaller structural 

. features within the disturbed area that do not seem to 

have hindered the tremors at all. 

FORESHOCKS 

Although 80 per cent of the observers report the 

onset of the main shock as rapid or abrupt, without 

any warning, the remainder felt a preliminary quiver 

which, according to several persons, was separated 

from the main shock by a brief pause. Reports of 

this preliminary tremor which may possibly be classed 

as a foreshock, were obtained at places well distributed 

through an area measured by a radius of 125 miles 

from the epicenter. Doubtless the failure of most 

observers to notice it was due to lack of experience. 

Many of the shocks that were rather generally observed after June 27 were probably of no greater 

intensity. 

An interesting foreshock occurred May 31, reports 

of which were obtained from five observers. At 

Lombard this shock, as timed by J. P. Swarts and 

W. P. Luburg, Northern Pacific Railway operators, 

occurred at 7.55 a. m. Loose articles in a small 

frame house (a converted box car) moved or rattled, 

and a doorframe was sprung slightly. At the same 

time another observer, Arthur Jersey, who was walking in the hills 3 miles northwest of Sixteen, felt a 

shock in which the ground seemed to rise suddenly 

and then settle back and quiver a little. At Menard 

the same shock, as reported by Mrs. A. R. Hill, 

made things rattle, and according to W. T. Lathrop, 

two light shocks were felt in the office of the United 

States Weather Bureau (SL"\:th floor) at Helena, and 

in a residence at Kenmore. Lombard is a short 

distance northwest, Menard 12 miles southeast, 

Sixteen 20 mile.s northeast, and Helena about 50 

miles northwest· of the epicenter of the earthquake . 

of June 27. Apparently the shock of May 3,1 emanated from the same center. 

AFTERSHOCKS 

A great many aftershocks were felt at Three Forks, 

Manhattan, and other. places near the epicenter, and 

several of them were perceptible also at more distant 
18 SHORTER CONTRIBUT'IONS TO GENERAL GEOLOGY, 1926 

points. ·The ground is said to have been in an almost 

continuous tremble during the night of June 27 at 

Lombard, Deer Park, and similarly situated places. 

At Trident sensible shocks are estimated to have 

averaged four a day for the first month and two a day 

for the second month after the earthquake. Between 

June 27 and July 6 a record was kept by A. D. Burkett 

of 52 shocks that were strong enough to be felt by 

nearly everyone. The total number of aftershocks 

recorded prior to August 14 is about 75. 

shorter duration. It caused additional roc~ falls.,. 

threw down some more chimneys, and caused many 

brick walls that had been loosened by the first shock 

to topple over. It came on very abruptly, accompanied by a deep rumble or roar, and caused renewed 

and increased alarm among the inhabitants. 

This shock was felt at Miles City, 270 miles east, 

at Macleod, Alberta, 270 miles north, and at Kalispell, 

200 miles northwest of the epicenter. On the south 

the most distant point reporting it is Hutchens, 

on Madison River, 75 miles from the epicenter. There 

the intensity was between 3 and 4. The shock is 

thus indicated to have been sensible throughout an 

area of nearly 200,000 square miles. The available 

records are tabulated below: 

The -strongest aftershock and the first one to be 

generally observed occurred at 7.10 p. m., or about 

three-quarters of an hour after the main shock. It 

was more or less distinct over a large area, most of the 

observers in which describe it as being nearly, if not. 

quite, as strong as the main shock but of somewhat 

Summary of reports of aftershock of the Montana earthquake of June 27, 1925, occurring at 7.10 p.m. mountain time 

Place o Latitude Longitude ·In ten· Remarks N. W. sity 

Townsend___________________ 46 20 

Deer Park ___________________ 46 8 

Dave Johnson's, 3 m;les north 46 9 

of Cardinal. 

Stockburger's, 2% miles north- 46 8 

east of Cardinal. Butte _______________________ 46 0 

Logan ______________________ 45 53 

Manhattan __________________ 45 52 

Three Forks _________________ 45 53 

Trident _____________________ 45 57 

Roy Sti:ilman's, 7 miles south- 46 4 

west of Maudlow. 

Jacobs's, 7 miles southeast of 46 15 

Townsend. 

Clarkston---------------.---- 46 2 

Perugin's,9 miles southeast of 46 15 

Townsend. 

Belgrade____________________ 45 2 

Willow Creek ________________ 45 50 

Walbert's, 9 miles north-north- 46 2 

west of Three Forks. 

Radersburg __________________ 46 13 

Menard_____________________ 45 48 

Maudlow _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 46 8 

3 miles south of Manhattan ___ 45 50 

Mockel's, 7 miles south-south- 46 8 

east of Radersburg. Helena ______________________ 46 36 

Whitehall ____________________ 45 48 

Jefferson Island ______________ 45 47 

Bozeman ____________________ 45 41 

White Sulphur Springs _______ _ Fort Logan _________________ _ 

House's, 10 miles northeast of 

Bozeman: Clyde Park _________________ _ Norris _____________________ _ 

Harrison ___________________ _ 

46 ' 33 

46 42 

45 50 

45 53 

45 34 

45 42 

o In Montana except as otherwise indicated. 

111 32 

111 9 

111 21 

111 20 

112 33 

111 26 

111 20 

111 53 

111 29 

111 17 

111 22 

111 24 

111 22 

111 11 

111 39 

111 38 

111 39 

111 12 

111 10 

111 20 

111 36 

112 0 

112 6 

111 57 

111 3 

110 54 

111 11 

110 53 

110 37 

111 42 

111 48 

8 Clock stopped 7.10 p. m. Duration 30 seconds. Almost as strong as first shock. 

9+ Short but so violent persons could not stand alone. 

9 Shorter than first shock. 

9 + Seemed longer than first shock. 

5± Duration 40 seconds. 

9+ Seemed harder than first shock. Bricks fell at schoolhouse. 

9+ A sudden hard shock. Observer could not keep feet or reach door. 

Most of the fallen brick at schoolhouse came down at this time. 

9+ Abrupt and harder than first shorl{ but shorter. Some persons standing were thrown down. Most of the brick fell from church at this 

time. 

9 + Seemed stronger than first shock. 

9+ Abrupt but shorter than first shock. 

8 ± Shorter than first shock. 

8± Do. 

8 ± Shorter than first shock. In two phases. 

8 ± At 7 .)5 p. m. Many bricks came down. One observer says it was more violent than first shock; another observer who was in a mov- ing automobile on a slippery road did not feel the shock. 

8 ± Shorter than first shock, but trees swayed as if they would snap off. 

House raised clear off foundation on one side and came back to 

place. 

7 ± Shorter than first shock. 

7± Do. 

7± Do.· 

7 ± Shorter than first shock. Did not shake as many goods from shelves as first shock, but more bricks came down. 

8 This shock turned upper part of brick chimney one-eighth revolution 

clockwise and threw dishes from shelves. 

7± 

5 ± Strong vibration of several seconds at 7.07 p. m., but shorter and 

weaker than first shock. 

? Shorter than first shock. 

6± Do. 

6 ± Automobile moved forward and back. Flagpole swayed east and 

west. 

6± 

6 ± Weaker than first shock. 

6 ± Buildings swayed. 

7 ± Seemed harder than first shock. 

? Half as long as first shock. 

7 + Seemed about as hard as first shock but shorter. Kitchen cabinet 

flew open and dishes spmed. Seemed harder than first shock to one observer. 
· THE MONTANA EARTHQUAKE OF JUNE 27, 1925 19 

Summary of reports of aftershock of the Montana earthquake of June 27, 1925, occurring at 7.10 p. m. mountain time-Continued 

Place Latitude Longitude In ten- Remarks N. w. sity 

- 0 I 0 I 

Twin Bridges ________________ 45 33 112 20 5 Seemed lighter than first shock. Fence swayed strongly. Butte _______________________ 46 0 112 33 5±· 40 seconds. 

Drummond __________________ 46 40 113 8 4± -Great Falls __________________ 47 30 111 17 4± Some movement of dishes, but none fell. Neihart _____________________ 46 56 110 43 3-4 Scarcely felt by persons out of doors. Belt ________________________ 47 22 111 56 4± Part of a dry stone wall fell. Anaconda ___________________ 46 7 112 51 5± About like first shock. .Philipsburg __________________ 46 20 114 18 5± Fence swayed back and forth. Seemed harder than first shock to one observer. 

Hutchens's, on Madison River_ 44 51 111 37 3-4 Felt distinctly. ,Superior ____________________ 47 12 114 59 2± Weaker and shorter than first shock. 

Macleod, Alberta ____________ 49 44 113 23 2 About 7 p. m. Miles City ____________ ..: _____ 46 24 105 51 2± At 7.07 p.m. Lamps swung. Ka1ispel1 ____________________ 48 12 114 17 2± At 7.10 p.m.; 10 seconds. Missoula ____________________ 46 53 114 0 ------ At 7.06 p.m. Hardin _____________________ 45 49 107 37 ------ At 7.07 p.m. Billings _____________________ 45 47 108 30 3± At 7.07 p.m.; 20 seconds. 

Lethbridge, Alberta __________ 49 43 112 52 2 About 6.45 p. m. Pine Grove __________________ 46 49 109 4 ------ At 7.05 p.m. Stronger than first shock. Big Timber_ ___ .: _____________ 45 50 109 53 ------ At 7.00 p.m. .B usteed _____________________ 45 53 109 22 ------ At 7.10 p.m. Findon _____________________ 46 37 110 22 ------ Do. 

Hebgen Dam ________________ 44 51 111 20 ------ At 7.05 p.m. Hobson _____________________ 47 0 109 50 ------ At 7.10 p.m. Duration, 10 seconds. Fla.twillow __________________ 46 50 108 24 ------ At 7.15 p.m. {)vando _____________________ 47 2· 113 7 ------ At 7.00 p.m. .Stevensville _________________ 46 31 114 7 ------ At 7.05 p.m. 

As nearly as can be determined the epicenter of the 

shoe~ at 7.10 p. m. is a short distance south of the 

Additional aftershocks up to August 13 were recorded as follows, including the 52 shocks reported 

epicenter of the main shock. · by A. D. Burkett at Trident: 

Aftershocks from June 27 to August 13 

Time Places reporfing 

Indicated 

size of area disturbed 

(square miles) 

June 27, 8.35 p. m _______________ Stevensville, Helena, Anaconda, Billings (8.37), Big Timber (8.40) ___________ _ .June 27, between 9.20 and 9.41 Conway, Philipsburg, Helena, Anaconda (violent) __________________________ · __ 50, 000 

17, 000 

p.m. 

June 27, between 10.25 and 10.30 

p.m. . 

June 27, between 10.39 and 10.40 

p.m. 

June 28, between 1.55 and 2.00 a. m_ 

June 28,2.20 a. m ______________ _ .June 28,3.00 a. m ______________ _ 

June 28, between 3.30and 3.33a. ttL 

June 28,4.42 a. m ______________ _ June 28, 5.14 a. m __________ :_ ___ _ ..June 28, 6.05 a. m ______________ _ June 28,8.39 a. m ______________ _ 

.June 28, 11.00 a. m_ ------------- .June 28, between 3.30 and 3.38 

Anaconda, Helena, Philipsburg, Trident (heavy) __________________________ _ 17, 000 

Livingston (set light bulbs swaying), Trident (heavy), Helena _______________ _ 7,500 

Trident (heavy), Philipsburg_____________________________________________ 17, 000 

~~i~~~t~~~~~~!========================================================= Conway, Hebgen ========== dam _____________________ -.-- ____________________________________ _ 

Trident (heavy)------------------------------------------------------------------- Helena (distinct, 2 or 3 seconds) __________________________________________ ---------- Trident (moderate) _______________________________________________________________ _ Trident ________________________________________________________________ ---------- Trident ________________________________________________________________ ----------

Helena (light), Manhattan (heavy), Trident, Bozeman, Livingston___________ 7, 500 

p.m. June 28, 10.30 p. m_ _ _ __ _ _ _ _ __ _ _ _ Helena _______________________________ -_- _________ - ___ -- ___ ------------- ______ -- __ 

.June i~~: 29, ~g: 2.02 ~g:~g a. ~: m :;:~ _______________ = = == = = == == == = -Trident ~~~~d~~----~ (very ~ = == noticeable ~= = = = = = = == in == quarry; == = = == rock == === falls) = == == ______________________________ == = = == == == == == == = === = = = = == == = ---------- = == = = == == = .June 29, between 2.25 and 2.30 Trident (shook town from one end to the other), Helena (sharp; 7 seconds), 50, 000 a. m. Great Falls (several seconds; dishes and pictures moved), Billings, Philipsburg. June 29, 4.10 a. m_ _ _ _ _ _ __ _ _ _ _ _ _ _ Trident (small) ____ ------------------------ ___________________________________ - ---

June 29, 4.30 a. m_ -------------- Helena---------------------------------------------------------------------------

June 29, 8.00 a. m_ _ _ __ _ _ _ _ _ _ _ _ _ _ Lombard ________ -----------------_------_- ___ --- ____ -- __ ----------- ____ -- ____ ---- June 29, 10.00 a. m_ _ _ _ _ _ _ _ _ _ _ _ _ _ Lombard ____________ --- _____________ ------------_- __ ------------------_ -- ____ ---- June 29, 10.49 a. m_ _ _ _ _ _ _ _ _ _ _ _ _ _ Trid~nt (moderate) _____________________________ -- ____ -- __ ----------- _________ ·_-- _-

June 29, 5.39 p. m _______________ Trident (heavy)------------------------------------------------------------------ June 29, 10.16 p. m_ __ __ __ ___ _ _ _ _ Trident _____________________________ ----------------------------------- ---------- June 29, 10.30 p. m_ ______ ____ __ _ Bozeman ____________________________ ----------------------------------- ----------

June 29, between 11.30 and 11.35 Helena, Livingston, Philipsburg, Trident (very noticeable in kiln room), Boze- 30, 000 

p.m. man. 
' 

20 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1926 

Aftershocks from June 27 to August 13-Continued 

Time Places reporting 

Indicated 

size of area disturbed 

(square miles)· 

June 30, 2.44 a. m _______________ Trident (one shock) _______________________________________________________________ _ June 30,2.48 a. m _______________ Trident _________________________________________________________________________ _ 

iS~ f.gt.~t~~p:~-~-~~== = = = :::::: _ ~~i~~~~i;;;~: :::::::::::::: :=:: :::: =: =::::: :: :=: =: ==::::: :::==:== =: ::: :::::::::: 

July 1, 7.45 a. m _________________ Trident (light, but nearly steady for 15 minutes) _____________________________________ _ July 2, 2.25 a. m _________________ Trident _________________________________________________________________________ _ 

July 2, 2.50 a. m _________________ Trident (long and steady, but not very severe) ______________________________________ _ July 2, 3.15 a. m _________________ Trident _________________________________________________________________________ _ 

July 2, 3.48 a. m _________________ Trident (long and steady, but not very severe) ______________________________________ _ July 2, 8.15 a. m____ _ ___ _ _____ __ _ Trident _________________________________________________________________________ _ July 2, 8.24 p. m _____________________ do __________________________________________________________________________ _ 

July 3, 1.25 a. m _________________ j Trident (light; 3 minutes) _________________________________________________________ _ July 3, 2.30 a. m _________________ Trident (one sharp shock) _________________________________________________________ _ July 3, 8.27 a. m___ _ _ _ _ _ _ _ _ _ __ __ _ Trident (intermittent shocks) ______________________________________________________ _ July 3, 10.00 p. m _______________ Trident (six shocks). _____________________________________________________ ---------- July 3, 11.00 p. m _______________ Trident (weak shocks lasting nearly an hour) ________________________________________ _ July 4, 2.25 a. m _________________ Trident (single distinct shock for% minute) _________________________________________ _ 

July 4, 4.00 a. m _________________ 

1 

Trident (six light, distinct shocks) _________________________________________ ----------

July 4, 9.04 p. m ________________ Trident (one shock)------------------------------------------------------ _________ _ July 4, 10.20 p. m _______________ Trident (six light shocks, one stronger shock) _______________________________ ---------- July 4, 10.30 p. m _______________ Trident (one sharp shock, noticeable in packing house) ________________________________ _ July 5, 2.10 a. m___ _ _ _ _ ____ __ _ _ _ _ Trident (sharp shock) _____________________________________________________________ _ 

July 5, 2.17 a. m _________________ Trident (one light shock)------------------------------------------------- _________ _ July 5, 2.21 a. m ______________________ do _________________________________________________________________ ---------- July 5, 2.40 a. m _________________ Trident (three light shocks) ________________________________________________________ _ 

July 5, 4.47 a. m _________________ Trident (intermittent bumping shocks lasting 3 minutes) _____________________ ---------- July 5, 6.16 a. m___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Trident (heavy and apparently of deep-seated origin, rounding waves, lasting _________ _ 

2 minutes). July 5, 10.26 p. m _______________ Trident (very noticeable in transformer building) ____________________________ ----------

~~!~ i: H~ :: :::==:::: ::::::::::: -~~~i~~5~~~~y~ ::: :=: :::::::::::::::::::: :=::: ::::::: =:: := =: :::::= :::::: = ::::::::: 

July 6, 10.15 a. m _____________________ do ____________________________________ · _____________________________ ----------

July 6, 11.46 p. m _______________ Trident (very noticeable in packing house) ___ . ______________________________ ----------

1~~~ July 10, ~8; 6.00 1~o8°a~~~~== a. m ____________ = = = = = = = = = :_ = 

________ = = _ ~e!~ct~== do _________________________________________________________________ = = = = = = = = == = = = = == = = = = = = = = = = = = == = = == = = = = == = = = = = = == == == == ====== == = = ---------- = = == === = = 

July 10, between 7.42 and 7.48 a.m. Anaconda (30 seconds; in two parts with a pause between), Deer Lodge, Boze- 50, 000 

man, Missoula (intensity 2-3), Great Falls (3 seconds; intensity 3-4), Billings 

(intensity 2), Three Forks (loose bricks fell; intensity 6), Manhattan (intensity 6), Trident (stiff shock; 30 seconds);.,. Helena (10 seconds), Cardinal (intensity 6-7), Logan, Livingston, Willow vreek, Butte. 

July 10, 2.00 p. m ______________ _ Helena (very slight) ____________________________________ . __________________________ _ 

July 20, between 10.05 and 10.07 Missoula, Great Falls (slight) ______________________________________________________ _ 

a.m. July 22, 4.53 p. m_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Lombard (light) __________________________________________________ :_ _______________ _ July 24, 2.55 p. m_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Trident (light) ___________________________________________________________________ _ 

Aug. 12,8.10 p. m _______________ Trident (strong; 5 seconds; ground waves) __________________________________ ----------

Aug. 13, 1.30 a. m _______________ Trident (strong)------------------------------------------------------------------- Aug. 13, 3.30 a. m ________ ------- _____ do ________________________________________________ ------------ ______________ _ Aug. 29, 8.00 a. m_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Lombard __________________________________________ ------ ________________________ _ 

Aug. 29, 10.00 a. m ______________ Cardinal (upset bottles, etc.; rocks fell; three light shocks the following night), 1, 000 

Menard (strong), Lombard (very severe), Trident, Logan. 

Sept. 3, 2.00 a. m _________ · _______ Menard (caused a bottle to tip over).------------------------------------------------

Shocks reported from Helena by the Associated 

Press occurred September 19 at 3.45 a. m. (sharp, 

short), September 30 at 2.30 a. m. (cause<,i snow 

slides from roofs), and early in the day of October 6 

(short, sharp). These also are doubtless to be classified as aftershocks of the earthquake of June 27, but 

reports of them from ulaces nearer the epicenter are 

lacking. 

PHYSIOGRAPHY AND GEOLOGY OF EPICENTRAL AREA 

SURFACE FEATURES 

The area within isoseismal 10 includes a lowland 

along Missouri River at Clarkston and parts of the 

hills that adjoin it on the east and north (pl. 4). The 

lowland, which will be referred to herein as Clarkston 

Valley, is a depression about 10 miles long and 5 or 6 

miles across at the middle and widest part. It is 

bordered on the east by the moderately steep Horseshoe Hills, 1,000 to 3,000 feet high, which are in fact 

the extreme northern part. of the Belt Mountains. 

At the north and south are broad spurs extending west 

from the Horseshoe Hills, .and at the west is an 

unnamed range of hills of somewhat less elevation. 

Together the hills and ridges described form a surrounding wall that is broken at three places only, 

each opening being a narrow stream-cut valley or 

gorge. At the northeast is the gorge of Sixteenmile 

Creek, in which the Deer Park slide occurred. At 
•THE MONT AN A EARTHQUAKE OF JUNE 27, 1925 21 

the south, at Trident, is a ·narrow, steep-sided valley 

that admits Missouri River, and at the north, beginning at Lombard, is a deep, narrow, and crooked 

gorge, known as Horseshoe Bend, through which the 

river escapes. 

Clarkston Valley consists of a strip of level bottom 

land along the river and a larger area of rather low 

terraces or bench lands. The terraces, which are 

generally known throughout this region as "benches," 

are remnants of stream-cut plains that were developed 

at higher levels and at an earlier period than the plain 

that now forms the valley bottom. They are due to 

the downcutting of streams, and it follows that most 

of them surmount the divides between stream courses 

that lead from the mountains to the river. Their 

fronts or edges are steep descending slopes or scarps, 

and thejr tops are smooth plains that rise gradually 

toward the mountains. In the gorges at Trident and 

Lombard and here and there along the west side of 

Clarkston Valley are small benches 40 or 50 feet higher 

than the bottom lands. 

On the east side of the valley t.he benches occupy 

the greater part of an area about 3 miles wide that 

adjoins the mountains and extends the full length of 

the valley. Here the fronts or scarps of the benches 

are mostly 100 to 150 feet high, and their tops 

slope upward toward the mountain with a gradient 

of about 300 feet to a mile. Near the mountains 

this slope is increased slightly, but not enough to 

mask the point at which a definite and rather abrupt 

change to the steeper slope of the mountain takes 

place (pl. 4) . 

STRATIGRAPHY 

Rocks ranging in age from pre-Cambrian to late 

Mesozoic (Cretaceous) form the surrounding mountains and hills and, within Clarkston Valley, probably 

constitute a bedrock floor beneath the Tertiary and 

later deposits. As shown by Peale, 6 the spur that incloses the valley at the south is composed chiefly of 

Paleozoic limestones with some sandstone and other 

beds of Paleozoic and Algonkian age. The same 

rocks continue northward, forming the hills east and 

west of the valley and the spur that bounds it on the 

north. North of Clarkston, near the middle of the 

valley, a hill of the Paleozoic limestones projects 

through the Tertiary beds like an island in a lake, and 

there is a similar occurrence farther northeast on the 

north side of Garden Gulch. North of Lombard 

sandstone, shale, and limestone of Cretaceous age are 

folded in with the Paleozoic rocks. Excellent sections 

of the rocks mentioned are exposed in the gorges· of 

Missouri River and Sixteenmile Creek, and strati6 Peale, A. C., U.S. Geol. Survey Geol. Atlas, Three Forks folio. (No. 24), 1896. 

graphic details of them are given by Campbell 7 and 

Haynes. 8 

Beds of moderately hardened clay and weakly 

cemented sand and gravel, commonly known as 

Tertiary "lake beds," compose the "benches" and 

probably occur also beneath the alluvium of the valley 

bottom. They lie upon the upturned and eroded 

edges of the older rocks described and are in turn 

partly covered and concealed from view by gravel of 

Pleistocene and Recent age. They are correlated 

with the Oligocene and Miocene beds occurring a 

, short distance to the north in Townsend Valley 9 and 

in the valleys of southwestern Montana generally. 

STRUCTURE 

The older rocks mentioned are involved in rather· 

close folds that vary in trend from north to northeast 

and cause the beds in most places to be steeply 

inclined. The section at Trident shows an anticline 

t}fat is overturned eastward and faulted. 10 In the 

neighborhood of Deer Park several faults of apparently small extent that trend northwestward are 

mapped by the geologists of the Anaconda Copper 

Mining Co.U Their age and displacement are not 

known. In the hills west of Missouri River is· an 

overthrust fault, called the Lombard overthrust/2 

that extends from a point north of Three Forks northeastward for 13 miles or more. Its trace crosses 

Horseshoe Bend about a mile west of Lombard. There 

the fault dips about 40° W. and has brought Belt 

(Algonkian) rocks eastward over rocks of Cretaceous 

age. Beds that are stratigraphically 6,800 feet apart 

are in contact, and the maximum displacement is 

estimated at about 2 miles. The fault is younger 

than Lower Cretaceous (Kootenai) strata exposed 

near Lombard and probably older than the lower 

Oligocene beds described by Douglass.13 

The only visible structural feature of the Tertiary 

beds is a persistent eastward dip of 10° to 20°. Owing 

to the fact that these beds break down rather easily 

under weathering, good exposures are few and are 

generally confined to very steep slopes or newly cut 

ravines. Hence it is possible that some minor folds 

or faults were overlooked,- but there seems no doubt 

as to the prevailing eastward dip. At only one place 

north of Garden Gulch and within 100 feet of the area 

of older rocks were the Tertiary beds observed as 

7 Campbell, M. R., Guidebook of the western United States, Part A, The North· 

ern Pacific Route: U. S. Geol. Survey Bull. 611, pp. 116-118, 1!H5. 

s Haynes, W. P., The Lombard overthrust: Jour. Geology, vol. 24, pp. 269-2901 

1916. 

D Pardee, J. T.;u. S. Geol. Survey Water-Supply Paper 539, pp.17-34, 1925. 

10 Campbell, M. R., op. cit., p. 117, fig. 26. 

11 Unpublished map. 

12 Haynes, W. P ., op. cit. 

1a Douglass, Earl, Fossil Mammalia of the White River beds of Montana: Am. 

Philos. Soc. Trans., new ser., vol. 20, pp. 238-279, 1902. 
22 SHORTER CONTRJBUT10NS TO GENERAL GEOLOGY, 1926 

dipping westward. The boundary between the Tertiary and older rocks at the east edge of the valley is 

rather generally concealed by alluvium and deep surface mantle, but it holds a rather straight course and 

is not extensively deflected where it crosses gulches 

or ridges. .Apparently, therefore, this boundary is 

the trace of a steeply pit~hing surface toward which 

the Tertiary beds are inclined. Such a relation is 

difficult to explain except as a result of faulting by 

which the Tertiary beds were relatively downthrown. 

This idea is supported by certain features of the 

valley itself. Clarkston Valley is a wide depression 

in deformed and eroded pre-Tertiary rocks. Its rim 

or surrounding wall is broken only by three narrow 

stream gorges. Such a basin could be formed in only 

two ways-by erosion or by structural movements. If 

due to erosion, it must have been an area of rocks 

that were softer and more easily e:roded than the 

rocks in which the gorges were cut, which is evidently 

not true. Therefore there seems no alternative but 

to regard the valley as a relatively depressed or 

down-faulted area. The features of the Tertiary beds 

indicate that down faulting occurred along the east 

side of the valley during Miocene or later time, the 

pitch of the fault being toward the west. 

Similar features are shown in Townsend Valley, a 

short distance to the north. There also the Tertiary 

beds rest in a basin depressed in the older rocks and 

show a persistent dip toward the east side of the 

valley. At the point where Sixmile Creek (which is 

about 4 miles north of Sixteenmile Creek) leaves the 

mountains the eastward-dipping Tertiary beds abut 

against the older rocks/4 the relation being interpreted as due to a fault with the downthrow on the 

side next to the valley. 

CAUSES OF THE EARTHQUAKE AND LOCATION OF 

THE FOCUS 

The size of the disturbed area, the gradual decline 

of intensity away from the epicenter, and other features of the Montana earthquake indicate that it was 

the result of fault movements rather than of volcanic 

action. So far as observed in the neighborhood of the 

epicenter no new fault displacement is manifest at the 

surface. This may be explained by the fact that there 

is a thick superficial cover of rather soft sediments 

(Tertiary "lake beds"), in which a slip originating in 

the rocks below might be distributed and lost. 

Of the faults previously mapped in this region the 

Lombard overthrust (p. 21) is too far from the epicenter to be considered. The faults mapped by geologists of the Anaconda Co. as crossing Sixteenmile 

Creek near Deer Park are not far from the epicenter, 

but their strike differs considerably from the course of 

the longer axis of the isoseismal curves. They cut 

Paleozoic rocks, and whether they are older or newer 

14 Pardee, J. T., U.S. Geol. SurveY Water-SupplY Paper 539, p. 32, 1925. 

than the Tertiary beds is not known. The writer did 

not identify them, but owing to their location and trend· 

he is inclined to believe that they do not contain the 

focus of the earthquake. 

In the absence of positive evidence to the contrary 

it must be admitted that the earthquake may have 

orl.ginated along some fracture that has not yet been 

discovered or even suspected. All necessary conditions, however, are met by the assumption that the 

slip occurred in depth on the fault postulated as extending along the east side of Clarkston Valley. This 

fault is Miocene or younger and is probably still active. 

The difference between the longer and shorter diameters of the inner isoseismal curves is from 6 to 10 

miles, which presumably is of the same order of magnitude as the length of the focus or the distance along 

which slipping occurred. The extent of the area in . 

which the shock was strong or destructive presumably . 

indicates that the focus was moderately deep, perhaps 

several miles. 

PROBABILITY OF FUTURE EARTHQUAKES 

On the theory that the earthquake of June 27 with 

its succeeding aftershocks accomplished the relief of 

stresses that for some time had been accumulating a 

period of quiet may be expected so far as .movement 

on the particular fault that caused the disturbance is 

concerned. The neighboring region, however, probably contains many other faults that are carrying unrelieved strains and may therefore become active at 

any time. Several of the mountain ranges of this 

region-Madison Range, for example-present high, 

steep fronts which suggest that they have been newly 

elevated and perhaps are still growing and therefore 

to be regarded as accumulating strains that will 

eventually result in earthquakes. Southwestern Montana is part of the Cordilleran region, which as a 

whole is a region in which rather severe earthquakes 

have occurred now and then in the past and are 

reaSonably to be expected in the future, 

In Montana prior to 1925 no destructive earthquakes 

have been recorded, but earlier than 50 or 60 years ago 

settlements here were so few and far between that 

strong shocks might have passed unnoticed. According to some of the pioneer residents a moderate earthquake was experienced in the Gallatin Valley in 1883 

that threw dishes off shelves and awakened sleepers. 

In 1805 sounds that were probably of earthquake 

origin were noticed near the present site of Great Falls 

by members of the Lewis and Clark expedition. In 

his journal of June 18-20, 1805, Captain Clark 15 

records that the men of the expedition first told him 

of hearing the sound for which he supposed they had 

mistaken distant thunder. On June 19, however, 

while walking on the plain above the falls he himself 

16 Original journals of the Lewis and Clark expedition, edited by Reuben Gold 

Thwaites, vol. 2, p. 176, Dodd, Mead & Co., 1904. 
THE MONTANA EARTHQUAKE OF JUNE 27, 1925 23 

heard the noise distinctly and paused, listening for 

two hours, during which time it was twice repeated. 

He describes it as an "unaccountable rumbling" and 

also as resembling distant artillery fire. It seemed to 

come from the west, was heard at irregular intervals, 

and consisted of a single discharge or of several discharges in quick succession. This description tallies 

closely with that of sounds called brontides/6 which 

are regarded by authorities as partly at least of seismic 

origin-possibly the final representatives of a series of 

aftershocks. · 

It is probable, from the facts above set forth, to .. 

gether with the evidence of the recent earthquake, 

that the general region here considered is in a_ condition of moderate seismic activity and is likely to be 

visited by an occasional severe shock. It behooves the 

inhabitants, therefore, to take at least a few simple 

precautions toward the prevention of future damage. 

18 Davison, Charles, A manual of seismology, pp. 63-65, Cambridge Univ. Press, 

1921. 

For example, the prevailing custom of laying up veneer 

or face brick without ties or bonding to fasten it to the 

back wall should be outlawed. The use of poor or 

insufficient mortar is of course to be condemned under 

any condition. Apparently a rich Portland cement 

mortar will make brick walls proof against shocks as 

severe as the recent one, and chimneys may be prevented from falling by a few braces of strap iron. 

Many of the towns are built on deposits of unconsolidated stream gravel, on w~ch a shock is likely to be 

more destructive than on solid rock. This condition 

can be overcome, however, by making the foundations 

deeper and heavier than ordinarily is needed. It is 

evident that the wrecked schools at Three Forks and 

elsewhere could hav~ been made earthquake proof 

when they were built, at a fraction of the cost it has 

taken to repair them. Apart from this there appears 

a more weighty consideration. When will the next 

earthquake come~ When schools are in session or 

congregations assembled~ 

AMERICAN TERTIARY MOLLUSKS OF THE GENUS CLEMENTIA 

By W. P. WooDRING 

INTRODUCTION 

Aside from its value as an aid in determining the 

age of Tertiary beds, the chief interest of the genus 

Clementia lies in the anomalous features of its present 

and forn1er distribution. An attempt is made in this 

paper to trace its geologic history, to point out its 

paleobiologic significance, and to describe all the 

known American Tertiary species. 

The fossils from Colombia used in preparing this 

report were collected during explorations made under 

the direction of Dr. 0. B. Hopkins, chief geologist of 

the Imperial Oil Co. (Ltd.), who kindly donated them 

to the United States N ationall\1useum. Dr. T. Wayland Vaughan, of the Scripps Institution of Oceanography, furnished information relating to specimens collected by him in .Mexico. Dr. Bruce L. Clark, of the 

University of California; Dr. G. Dallas Hanna, of the 

California Academy of Sciences;. Dr. H. A. Pilsbry, of 

the Philadelphia Academy of Natural Sciences; and 

Dr. W. D. Matthew, of the American Museum of Natl,lral fiistory, generously loaned type specimens and 

other material. Doctor Clark and Doctor Hanna also 

gave information concerning the Tertiary species from 

California. Mr. Ralph B. Stewart, of the University 

of California, read the manuscript, and I have taken 

advantage of his suggestions. ·I am also indebted 

to Mr. L. R. Cox, of the British Museum, for information relating to the fossil species from Per~a, Zanzibar, 

and Burma, and to Dr. Axel A. Olsson, of the International Petroleum Co., for data concerning undescribed Tertiary species from Peru. 

THE GENUS CLEMENTIA 

CHARACTERISTIC FEATURES 

Clementia is a clamlike bivalve mollusk of the 

family Veneridae, which embraces a large number 

of fossil and living mollusks, including the hardshelled clam (Venus mercenaria) and others used for 

food. The most elaborately sculptured and most brilliantly colored shells of this family are found in the 

tropical seas. The hinge and pallial sinus of this 

genus are its most characteristic features, as in other 

genera of the Veneridae. Although these features are 

rarely seen on fossil specimens, Clementia has a 

characteristic sculpture consisting of Inoceramus-like 

waves-a feature that suggBsted the name of one of 

the American species. Mactra (Harvella), which may 

be confused with Clementia on the basis of sculpture, 

belongs to the family Mactridae and has an entirely 

different hinge. Even if the hinge can not be seen, 

Harvella can easily be recognized, as its shell is 

almost equilateral, whereas almost all species of Clementia are very inequilateral. Harvella also has a 

sharp-crested ridge extending from the urn bo to the 

posterior ventral edge of the shell. This ridge may 

not be visible on internal molds, but the shallow furrow 

that lies in front of it can be seen. No species of 

Clementia has either ridge or furrow. The mactroid 

genera Pteropsis and Labiosa (Raeta), which have 

Clementia-like sculpture, can readily be distinguished 

by their shape and other features. · 

The shell of most species of Clementia is thin and 

fragile. Many fossil specimens are crushed and distorted, and generally they are preserved as internal 

molds to which parts of the shell may cling. The 

thin shell and closely interlocking hinge partly account 

for the scarcity of detached valves that show the 

hinge. Most of the fossils are internal molds of both 

valves in attached position. 

PRESENT DISTRIBUTION 

The living species of Clementia listed on page 26 have 

been described. There is no modern revision of the 

genus, and some of the names in the list, which is 

probably incomplete, may be duplicates. 

The present range of the subgenera Clementia s. s. and 

Egestaisdiagranunaticallyshownin Figure 1. The living speciss of Clementia s. s. are strung out in the western 

Pacific from Japanese waters southward to Tasmania. 

Species also are recorded froxn the Indian Ocean, the Red 

Sea, and South Africa. Most of these living Clexnentias 

are concentrated in the region froxn the Philippine 

Islands southward to Australia and in the Indian 

Ocean-that is, they are found in the tropical waters 

of the western Pacific and Indian Oceans and also in 

the cooler waters of southern Australia. Though the 

range of Clementia s. s. is probably continuous froxn Tasmania and Australia northward to Japan and westward along the border of the Indian Ocean, it is 

25 
26 SHOR.TER CONTRIBUTIONS TO GENERAL GEOLOGY, 1926 

plotted in Figure 1 only at localities for which records 

could be found. There seem to be only two living 

species of Egesta, one in the waters off Japan and 

Chosen and the other in the Gulf of California. 

Living species of Clementia 

Species Type locality 

Clementia (Clementia) hyalina (Philip- pi) a _ ________ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Philippine Islands (?). 

Clementia (Clementia) similis Sowerby b __ ____________ ----------- ____ Philippine Islands. 

Clementia (Clementia) granulifera 

Sowerby c _______ ---------------- Do. 

Clementia (Clementia) papyracea (Gray) a ______________________ :_ __ Australia. 

Clementia . (Clementia) strangei Des- hayes e___________________________ Do. 

Clementia (Clementia) moretonensis Deshayes '- __ _ _ __ _ __ __ ____ ___ _ _ __ Do. 

Clementia (Clementia) tasmanica Pet- terd a_____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Tasmania. 

Clementia (Clementia) vitrea (Chem- nitz) h ____ • _______________________ Indian Ocean. 

Clementia (Clementia) crassiplica (Lamarck) i ______________________ Indian Ocean(?). 

Clementia (Clementia) annandalei 

Preston i _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Indian Ocean. 

Clementia (Clementia) cumingii Des- hayes "_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Red Sea. 

Clementia (Clementia) mcclellandi 

Tomlin z_ ____ _ _ _ _ _ ____ _ _ ___ ___ __ _ South Africa: 

Clementia (Egesta) vatheliti Mabillem__ Japan. 

Clementia (Egesta) solida Dall n _ _ _ _ _ _ Gulf of California. 

o Philippi, R. A., Abbildungen und Beschreibungen neuer oder wenig gekann ten Conchylien, vol. 3, p. 83, Venus, pl. 10 (XXII, 5), fig. 6, 1851. b Sowerby, G. B., Thesaurus Conchyliorum, pt, 13, pp. 70D-701, pl. 151, fig. 156, 1852. . c Idem, p. 701, pl. 151, fig. 154. d Gray, J. E., A list and description of some species of shells not taken notice of 

by Lamarck: Ann. Philosophy, new ser., vol, 9, p. 137, 1825. Wood, W., Supple- ment to the Index Testaceologicus, p. 5, pl. 2, fig. 8, 1828. . • Deshayes, G. P., Descriptions of two new species of Clementia in the collection 

of Hugh Coming, Esq.: Zool. Soc. London Proc., pt. 21, p. 17, 1853. I Idem, p, 18. o Petterd, W. F., Description of new Tasmanian shells: Jour. Conchology, vol. 

4, p. 145, 1884. h Chemnitz, J. H., Neues systematisches Conchylien-Cabinet, vol. 11, p. 219, 

pl. 200, figs. 1959-1960, 1795. i Lamarck, M. le Chevalier de, Histoire naturelle des animaux sans vertebres, 

vol. 5, p. 471, 1818. Lamy1 Edouard, Rflvision des Mactridae vivants du Musflum 

d'histoire naturelle de Pans: Jour. Conchyliologie, vol. 63, pp. 273, 363, pl. 7, fig. 8, 

1917. i Preston, H. B., Mollusca from the Chilka Lake on the east coast of India: Indian 

Mus. Rec., vol. 10, p. 306, figs. 14, 14 a, b, 1914. k Desha yes, G. P ., DP.scriptions of new shells from the collections of Hugh Cuming, 

Esq.: Zoo!. Soc. London Proc., pt. 22, p. 346, 1854. l Tomlin, J. R. le B., Six new marine shells from South Africa: Jour. Conchology, vol. 16, p, 215, pl. 8, fig. 6, 1921. m Mabille, Jules, Testarum novarum diagonoses: Soc. philomathique Pans 

Bull., 9th ser., vol. 3, pp. 57-58, 1901. Jukes-Browne, A. J., On a new species of 

Clementia: Annals and Mag. Nat. Hist., 8th ser., vol. 12, pp. 61-62, pl. 1, figs. 3-4, 

1913. n Dall, W. H., Synopsis of the family Veneridae and of the North American Recent 

species: U. S. Nat. Mus. Proc., vol. 26, pp. 401-402, pl. 14, fig. 4, 1902. 

Jukes-Browne 1 described as Clementia obliqua a shell 

that was supposed to have bee.n collected at Mayaguez, 

t Jukes-Browne, A. J., On a new species of Clementia: Annals and Mag. Nat. 

Hist., 8th ser., vol. 12. pp. 58-62, pl. 1, figs. 1-2, 1913. 

Porto Rico. Dall 2 showed that this shell not only is 

not a Clementia but must have been collected on the 

Pacific coast of North America, for it is the species 

described by Carpenter 8 in 1865 as Clementia~ subdiaphana, now referred to the genus Marcia. JukesBrowne 4 admitted the error as to locality, but still 

considered Marcia subdiaphana a species of Clementia. 

GEOLOGIC HISTORY 

The localities where Tertiary species of Clementia s. s. 

and Egesta have been found are shown diagrammatically 

in Figure 1. So far as known Tertiary species of 

Egesta are confined to the United States and Mexico. 

Clementia s. s. was more widely distributed particularly 

in America and the Orient. In America a suite of' 

Eocene, Oligocene, and Miocene species has been 

collected at several localities extending from· Brazil 

and Trinidad to Costa ~ica along the Atlantic and 

Caribbean coasts, and from Peru to Costa Rica along 

the Pacific coast. The middle Miocene (Helvetian) 

marls 6f St. Florian (or Grosse Florian) in the Gratz 

Basin, province of Styria, Austria, carry the only European Tertiary species, Clementia (Clementia) ungeri 

(Rolle) .

5 Furthermore, this is the only locality in 

Europe where this species has been found. According 

to Rolle's figures of the exterior and right hinge, 

Clementia (Clementia) ungeri closely resembles the small 

living oriental species. Fuchs s described as '' Venus 

(Clementia) cf. ungeri Rolle" molds that were collected 

from middle MiQcene be.ds cropping out in the Siwah 

oasis, in the Libyan Desert. In contrast to these 

isolated finds in Europe and north Africa, Clementia s. s. 

has been recorded at the localities in the Orient and east 

Africa listed on page 28. The names used in the list are 

those given by the writers cited, most of whom regard 

these Tertiary Clemen tias as representing living species. 

1 Dall, W. H., Note on Clementia obliqua Jukes-Browne: Nautilus, vol. 27, pp. 

103-104, 1914. 

a Carpenter, P. ·P., Diagnoses specierum et varietatum novarum Moluscorum. 

prope Sinum Pugetianum a Kennerlio Doctore, nuper decesso, collectorum: Acad. 

Nat. Sci. Philadelphia Proc.,vol. 17, p. 56, 1865. 

• Jukes-Browne, .A. J., Note on Clementia subdiaphana Carpenter: Annals and 

Mag. Nat. Hist., 8th ser., vol. 13, pp. 338-339, 1914. · 

6 Rolle, Friedrich, Die terti!lren und diluvialen Ablagerungen in der Gegend 

zwischen Gratz, Kiiflach, Schwanberg und Ehrenhausen in Steiermark: K.-k. geol. 

Reichsanstalt Jahrb., vol. 7, p. 572, 1856; Ubcr einige neue oder wenig gekannte 

Mollusken-Arten aus Terti!ir-Ablagerungen: K. Akad. Wiss. Wien Sitzungsber .• 

Math.-Naturwiss. Classe, vol. 44, pt. 1, pp. 215-217, pl. 2, figs. 1, 1a, 2, 2a, 1862. 

8 Fuchs, Theodor, Beitrlige zur Kenntnis der Miocaenfauna Aegyptens und der 

Libyschen Wiiste, in Zittel, K. A., Beitr!ige zur Geologie und Palaeontologie der 

Libyschen Wilste und der angrenzenden Gebiete von Aegypten, pt. 2: Palaeontographica, vol. 30, pt. 1,p. 39 (p. 21), pl. 6, fig. 9, 1883. 
t6o-· ---1eo.- 160-~ -- 140• tozo• too• 8/J. so· 40-.- 'Zd d" 2J:f ~- so• eo..-- too• tzo• 140" 100" 160 ·~ I I I I ~ ........ Kti IJ ..... _ I I i'J)• I :z")l£f) I I I ':·~ I I 

:~ !. 

·~ ' dr~ .. 

·ll Jl· 

ROPIC OP' CANCI!:.R 

·~ 

-:~~:.': :.~ ... 

~ 

ANTARCTIC CIRCLE. 

·. 

.. TROPIC I OF' CAPRICORN 

~:.~:·.~ •.. 

) 

·' 

' 

··' ·:·· ····~·/· ... , .. 

.~o· ,Jo. ,Jo· ,4o. .zo• .oo· ~a ' ~oa ~· · ioa o• -let .«,. ~· eO· ~ .~o· 140° ,Joa :!::a .J...JI 

FIGURE 1.-Map showing present range and former distribution of Clementia s. s. and Egesta. Present range: Clementia fs. s., lined areas; Egesta, solid black.areas. Tertiary localities: Clementia s. s., crosses; 

-Egesta, circles 

> 

~ tz:j 

b:j 

1-1 

0 

> 

z 

b5 

1-1 

~ 

> 

~ 

~ 0 

t"" 

t"' 

q 

U1 

@ 

0 

l'!lj 

~ 

~ tz:j 

Q 

tz:j 

z 

0 

U1 

0 

t"' 

tz:j 

~ tz:j 

z 

~ 

~ 

~ 

'I 
28 SHORTER. CONTRIBUTIONS TO GENERAL GEOLOGY, 1926 

Oriental and east African Tertiary species of Clementia s. s. 

Species Locality Age 

Clementia sp. o _____ -------------------- Persia _______ ------------ Fars series (late Miocene or 

Clementia nonscripta Sowerby),b 

Pliocene). 

(J.de C. Province of Sind, west- Gaj group ern India. (Miocene). 

Clementia hyderabadensis and Haime.) • 

(d' Archiac ____ .do___________________ Do. 

Clementia nonscripta (J .de C. 

Sowerby),d 

Clementia nonscripta (J.deC. 

Sowerby).• Clement!a papyracea (Gray)! _________ _ 

Clementia papyracea (Gray) u __ -.-------

Clementia papyracea (Gray) h _________ _ 

Clementia nonscripta (J. de C. Sowerby) '[C. papyracea (Gray)]; ______ _ 

Clementia nonscripta (J. de C. Sowerby) var.? k 

Clementia papyracea (Gray) I [C. hya- lina (Philippi)] m 

Clementia nonscripta (J. de C. Sowerby)." . Clementia speciosa Yokoyama •-------- Clementia nonscripta (J. de C. Sowerby),P 

Burma__________________ Miocene. 

Nias Island, off south- west coast of Sumatra. 

Java. ____ --------------- Adenara Island, east of 

Flores. 

Timor ____ -------------- Celebes._--------------_ 

Aru Islands,· south of 

New Guinea. 

Miocene(?). 

Miocene. 

Late Tertiary. 

Pliocene. 

Late Tertiary. 

Do. 

Luzon, P. !. ____________ Miocene. 

Formosa.--------------- Tertiary. 

Japan ___________________ Pliocene. 

Zanzibar, east Africa____ Miocene. 

o Pilgrim, G. E., The geology of parts of the Persian provinces of Fars, Kirman, 

and Laristan: India Geol. Survey Mem., vol. 48, pt. 2, p. 89, 1924. In 1908 Pilgrim listed "Clementia n. sp. aff. cumingii Desh., Clementia n. sp. aff. non scripta d' A. 

& H., and Clementfa n. sp." from the Fars series (India Geol. Survey Mem., vol. 

34, pt. 4, p. 46, 1908). b Sowerby, J. de C., in Grant, C. W., Memoir to illustrate a geological map of 

Cutch: Geol. Soc. London Trans., 2d ser., vol. 5, p. 327, pl. 25, fig. 8, 1840. D' Archiac, 

le Vicomte, and Haime, Jules, Description des animaux fossiles du groupe Nummulitique de l'Inde, p. 246, pl. 17, figs. 7, 7a, Paris, 1853. Fedden, J., On the distribution of the fossils described by Messrs. D' Archiac and Haime in the different 

Tertiary and Infra-Tertiary groups of Sind: Geol. Survey India Mem., vol. 17, 

p. 202, 1880. • D'Archiac, le Vicomte, and Haime, Jules, op. cit., p. 247, pl. 17, figs. 8, Sa. Fedden, J., op. cit. 

d Cox, L. R., Some late Kainozoic Pelecypods from the Aru Islands: Geol. Mag., vol. 61, No. 716, p. 63, 1924. • Woodward, Henry, Further notes on a collection of fossil shells, etc., from 

Sumatra, pt. 2: Geol. Mag., decade 2, vol. 6, p. 442, pl. 11, fig. 3, 1879. Reprint, 

Mijnwezen in Nederlandsch Oost-Indie Jaarboek, year 9, p. 224, pl. 3, fig. 3, 1880. 1 Martin, K., Die Terti!irschichten auf Java, pp. 99-100, pl. 17, figs. 6, 6a, Leiden, 

1879-80; Die altmiociine Fauna des West-Progogebirges auf Java, pt. B: Geol. Reichs-~us. Leiden .samml., new ser., vol. ~. No. 7t p. 273, 1917. u Martm, K:z. op. mt. (1879-80), p. 100; op. c1t. (1917J, p. 273. h Boettger, v., Liste die tertHiren und jiingeren Versteinerungen, in Verbeek, 

R. D. M., Geologische verkenningstochten in bet oostelijke gedeelte van den 

Nederlandsch Oost-Indischen Archipel: Mijnwezen in Nederlandsch Oost-Indie 

Jaarboek, year 37, p. 669, 1908. • Dollfus, G. F., Pal~ontologie du voyage l}.l'tle C~lebes de M. E. C. Abendanon, 

in Abendanon, E. C., Geologische en geographische Doorkruisingen van MiddenCelebes, vol. 3, p. 994, pl. 1, figs. 817, 818, 818a, Leiden, 1917. (French ed., pp. 1012-

1013, pl. 1, figs .. 817, 818, 818a, Leiden, 1918.) i Martin, K., Bemerkungen iiber sogenannt oligoc!ine und andere Versteinerungen von Celebes: Geol. Reichs-Mus. Leiden Samml., new ser., vol. 2, No. 7, p. 301, 1917. Dollfus considered these deposits of Oligocene age, but according to Martin they are Miocene or later. k Cox, L. R., Some late Kainozoic Pelecypoda from the Aru Islands: Geol. Mag., 

vol. 61, No. 716, p. 62, fig. 4, 1924. 1 Martin, K., Uber Tertiaere Fossilien von den Philippinen: Geol. Reichs-Mus. 

Leiden Samml., vol. 5, pp. 57, 59, 1896. English translation, Concerning Tertiary fossils in the Philippines, in Becker, G. F., Report on the geology of the Philippine Islands: U. S. Geol. Survey Twenty-first Ann. Rept., pt. 3, pp. 618, 619, 1901. 

Smith, W. D., Contributions to the stratigraphy and fossil invertebrate fauna of 

the Philippine Islands: Philippine Jour. Sci., vol. 8, sec. A, p. 272, pl. 7, fig. 5, pl. 

8, fig. 3, 1913. m Dickerson, R. E., A fauna of the Vigo group; its bearing on the evolution of 

marine molluscan faunas: Philippine Jour. Sci., vol. 18, p. 12, 1921. Reprint under 

title, Notes on a fauna of the Vigo group and its bearing on the evolution of marine 

molluscan faunas: California Acad. Sci. Proc., 4th ser., vol. 11, p. 15, 1921. 

" Cox, L. R., Some late Kainozoic Pelecypoda from the Aru Islands: Geol. Mag., vol. 61, No. 716, p. 63, 1924. • Yokoyama, l\.1., Tertiary Mollusra from Deinichi in Totomi: Tokyo Imp. 

Univ. Coli. Sci. Jour., vol. 45, art. 2, p. 15, pl. 2, figs. 14-15, 1923 (I have not seen this report); Mollusca from the Tertiary basin of Chichibu: Tokyo Imp. Univ. 

Faculty Sci. Jour., sec. 2. vol. 1, pt. 3, p. 119, pl. 14, fig. 7, 1925; Molluscan fossils 

from the Tertiary of Mino: Idem, pt. 7, p. 222, 1926. . P Cox, L. R., op. cit. and written communication. 

Clementia s~ s. and Egesta, like many other groups of 

mollusks, had an extensive distribution in the Tertiary seas, but are now restricted to the Pacific and 

Indian Oeeans. It is difficillt to trace the history of 

this expansion and subsequent restriction. Characteristic sp·ecies of Clementia s. s. appear in the deposits 

of the middle Eocene Caribbean Sea and also in those 

of the eastern Pacific, where, according to Olsson,7 the 

genus is represented in the middle Eocene deposits 

of Peru. The ancestry of these American Clementias 

7 Olsson, A. A., written communication. 

is unknown. Jukes-Browne 8 suggested that Ve.nus 

ovalis Sowerby, a species from the Upper Greensand 

(Albian, upper part of Lower Cretaceous) of England, 

is an ancestral Clementia and proposed for it the name 

Flaventia as a subgenus of Clementia. This species 

is so different from the American Eocene Clementias 

that there is no reason to believe it is an ancestral 

Clementia. Its sculpture is different; its lunule is 

bounded by a groove; its right posterior cardinal consists of two distinct parts of unequal length; according to Woods's figures, 9 its left anterior cardinal is 

bifid; and its pallial sinus is not so deep. Clementia 

deshayesi, an Eocene species from the Paris Basin 

described by Cossmann 10 more closely resembles 

Clementia, as it has a thin shell and concentric waves, 

and at least the right valve has a Clementia-like hinge. 

But its truncate posterior end, well-defined escutcheon, 

and lunule bordered by a groove show that it is not 

like the living species of Clementia s. s. or like the 

American Tertiary species. It probably represents a 

divergence from an unknown ancestral stock, similar 

to the later divergence of Egesta in American \Vaters. 

The American Clementia (Clementia) dariena vetula, 

C. (C.) dariena rabelli, and C. (C.) dariena dariena seem 

to represent a continuous genetic stock developed in 

American seas. One of the routes by which Clementia 

s. s. migrated from the eastern Pacific into the Caribbean Sea, or in the opposite direction, is indicated by 

the discovery of 0. (C.) dariena dariena in beds 

cropping out at Santa Maria de Dota, in central 

Costa Rica near the east edge of the pr-ovince of San 

,Jose. This subspecies has also been collected on the 

Pacific coast of Costa Rica near Punta Arena~ and 

on the Atlantic side of Costa Rica in the valley of Rio 

Revantazon. The deposits extending across Costa 

Rica, which seem to be of lower Miocene age, were 

laid down in a channel that connected the Pacific 

Ocean and Caribbean Sea, as several writers have 

pointed out.U At most places these beds are concealed by later lava and tuff, but they crop out at 

:-;everallocalities. 

If it is assumed that the American Tertiary species 

belong to the same genetic stoek as the living oriental 

species, Olementias. s. probably migrated from the eastern Pacific to the oriental region by way of the north 

border of the Pacific, perhaps during Eocene time, 

when climatic zones were not so marked as now. 

s Jukes-Browne, A. J., On the genera of Veneridae represented in the Cretaceous 

and older Tertiary deposits: Malacol. Soc. London Proc., vol. 8, pp. 167-169, pl. 

13, fig. 10, 1909. 

g Woods, Henry, A monograph of the Cretaceous Lamellibranchia of England, 

vol. 2, pt. 5, pp. 191-192, pl. 29, figs. 19-26, Palaeontographical Soc., 1908. 

10 Cossmann, M., Catalogue des coquilles fossiles de l'Eocene des environs de 

Paris: Soc. roy. malacol. Belgique Annales, vol. 21 (4th ser., vol. 1), pp. 127-128, 

pl. 7, figs. 1-2, 1886. 

11 Gabb, W. M., On the geology of the Republic of Costa Rica (manuscript in 

library of U.S. Geological Survey), pp. 45-46. Alfaro, Anastasio, Comprobaciones 

geol6gicas: Bol. de Fomento, year 1, pp. 123-124, 1911. Romanes, James, Geology of 

a part of Costa Rica: Geol. Soc. London Quart. Jour., vol. 68, p. 137, 1912. Olsson, 

A. A., The Miocene or northern Costa Rica: Bull. Am. Paleontology, vol. 9, pp. 

205-206, 1922. 
AMERICAN TERTIARY MOLLUSKS OF THE GENUS CLEMENTIA 29 

This supposition is not confirmed by fossil occurrences, 

ror no Tertiary species are known in the north Pacific, 

md in the Orient the earliest species that are definitely 

dated are of Miocene age. For some unknown 

reason after Miocene time this subgenus disappeared 

ln. the Caribbean Sea and in the eastern Pacific. 

Clementia (Clementia) ungeri, which is recorded from 

Miocene beds in Egypt and Austria, probably repre-

;ents a temporary Miocene invasion of oriental 

nollusks into the Mediterranean Sea. This invasion 

.s attested by other genera, such as Cancellaria 

:scalptia), Cancellaria (Ventrilia), Mitra (Thala), 

~tossichia, group of Turritella terebralis/2 and Placuna. 

Dr. A. Morley_ Davies, of the Imperial College of 

:;cience and Technology, who has recently discussed 

:orne of the evidence for tbis invasion/·~ kindly called 

tttention to these oriental genera that are found in 

\1editerranean Miocene deposits but not in earlier 

ieposits in the Mediterranean region. There is a 

>Ossibility that some of these genera represent a 

nigration in the opposite direction, but it is more 

>robable that they are autochthonous in oriental seas. 

Egesta apparently represents a divergence from the 

lmerican stock of Clementias. It first appeared in 

he Gulf of Mexico in Miocene time and in California 

~pparently at almost the same time. Its route of 

nigration across America is not known. It has 

Lot been found in the Caribbean region, and appar-

:ntly the route lay farther north, perhaps in the 

sthmus of Tehuantepec. During late Miocene time 

~ migrated out of the Gulf of Mexico as far north as 

he Chesapeake embayment and New Jersey. For 

orne lmknown reason it then disappeared in Atlantic 

raters, but it remained in the eastern Pacific, where it 

; now found in the Gulf of California. Inasmuch as 

n Egesta that is similar to the fossils of the southastern United States is now found in Japanese .waters, 

b is assumed to represent a migration around the 

orth border of the Pacific during late Tertiary time, 

hough again no fossil records substantitate this. suposition. This group of Egestas is unrepresented in 

lw Tertiary deposits of California, and it is also not 

~presented at the present time in the eastern Pacific. 

" second phylum of Egesta, typified by Clementia 

Egesta) pertenuis, is found only as Miocene and 

•Iiocene fossils in California. A third phylum seems 

) be represented by C. (E.) conradiana, a Miocene 

pecies from California, and C. (E.) solida, now living 

1 the Gulf of California. 

PALEOBIOLpGIC SIGNIFICANCE 

There seem to be no records 9f the conditions under 

·hich Egesta lives. Dredging records of Clementia s. s. 

u Guillaume, L., Essai sur la classification des Turritelles, ainsi que sur leur 

·olution et leurs migrations, deimis la d~but. des temps tertiaires: Soc. g~ol. France 

llll., 4th ser., vol. 24, pp. 3()()-302, 1924. 

1a Wayland, E. J ., and Davies, A.M., The Miocene of Ceylon: Geol. Soc. London 

1art. Jour., vol. 79, pp. 588-589, 591, 1923. 

that could be gathered from published accounts are as 

follows: 

Dredging records of Clementia s. s. 

Species Depth Character of Locality (fath- bottom oms) 

Clementia (Clementia) gran- Manila 

ulifera Sowerby. a Islands. Bay, Philippine 4-6 Sandy mud. 

Clementia (Clementia) papy- Torres Strait, south of New 3-11 racea (Gray).b Guinea. 

Clementia (Clementia) tas- Off Long Bay and Brown's 7 

manica Petterd.c River, Tasmania. 

Clementia (Clementia) an- Lake Chilka and other local- 1-2 Mud. 

nandalei Preston.a ities, India. 

a Sowerby, G. B., Thesaurus conchyliorum, pt. 13, p. 701, 1852. b Smith, E. A., Report on the Lamellibranchiata: Challenger Rept., Zoology, vol 

13, pt. 35, p. 154, 1885. c Petterd, W. F., Description of new Tasmanian shells: Jour. Conchology, vol. 4, 

p. 145, 1884. d Preston, H. B., Mollusca from the Chilka Lake on the east coast of India: Indian 

Mus. Rec., vol. 10, p. 306, 1914. (Lake Chilka is a lagoon of salt water connected 

with the sea.) 

Through the kindness of Dr. Paul Bartsch, curator 

of the division of mollusks of the United States N ationa! Museum, the following records are given of unstudied specimens of Clementia s. s. collected by the 

United States Bureau of Fisheries steamer Albatross in 

the seas adjoining the Philippine Islands. 

Dredging records of Clementia s. s. collected by U. 8. Bureau of Fisheries steamer Albatrobs in Philippine waters 

Sta- Locality Number of Depth Character 

tion specimens (fath- .of bottom oms) 

5164 Off Tawi Tawi Island, Sulu Archipelago. 

1 right valve 18 Green mud. 

5593 Sibuko Bay, Borneo.------------------ 1 right valve 38 Fine sand. 

5358 Off Sandakan Light, Borneo ___________ 3 rig h t 39 Mud. 

valves, 1 

left valve. 

5235 Nagubat Island, east coast of Min- 1 right, 1left 44 Soft mud. 

danao, Philippine Islands. valve. 

5311 China Sea, off Pratas Island ___________ lleft valve __ 88 Coarse sand 

and shells . ... 

None of these records show whether living or dead 

shells were collected. Probably all the shells were 

dead, but it is not likely that these paper-thin shells 

were carried far by waves or currents. According to 

these records Clementia s. s. lives in protected shallow 

water at depths of 1 to 11 fathoms, or in quiet deeper 

water in exposed localities at depths of 18 to 88 

fathoms. In both the shallow and the deeper water it 

is generally found on a bottom of mud or fine sand. 

This habitat is in harmony with the thin texture of 

the shell. No observations have been made on living 

shells, but the deep pallial sinus and the statement 

by Desha yes 14 to the effect that Clementia s. s. has long 

united siphons show that it burrows in the mud or 

fine sand. 

Clementia s. s. lives in sea water of normal salinity and 

also in water of low salinity. According to Stoliczka,111 

two unnamed species were collected in brackish water 

u Deshayes, G. P., Catalogue of the Conchifera or bivalve shells in the collection 

of the British Museum, pt. 1, p. 197, 1853. This statement seems to be the basis fo:: 

the accounts in the manuals. 

u Stoliczka, F., Cretaceous fauna of southern India, vol. 3, Pelecypod&. Geol. 

Survey India Mem., Palaeontographica Indica, 6th ser., pts. 1-4, p._158, 1871. 
30 SHORTER CONTRIBUTION~ TO GENERAL GEOLOGY, 1926 

near Calcutta, and Preston 16 recorded 0. (C.) annandalei 

from Port Canning, in the Gangetic delta. 

No field studies have been made with the object of 

gathering data on the manner in which the American 

fossil species of Clementia s. s. lived and ·died, but their 

occurrence confirms the assumption that they lived 

under essentially the same conditions as the present 

living species, with the exception that there is no 

evidence to show that the fossil species tolerated 

water of low salinity. In the whole Caribbean 

region Clementia is found in beds of mud, which 

may be calcareous, and in fine sand, but not in 

coarse sand or gravel nor in reef limestones. This 

bottom control explains its absence in many parts 

of the Carribbean region. The Eocene beds in 

Colombia carrying Clementia are n;md deposits, but 

no specimens have been collected from widespread 

Eocene reef limestones of the Caribbean region. In 

Porto Rico Clementia is found in the mud beds at the 

base of the Tertiary deposits, which are of middle 

Oligocene age, and not in the overlying limestones. 

Elsewhere in the Caribbean region deposits of middle Oligocene age are reef limestones, in which 

Clementia has never been found. The mud beds in 

the Gatun formation of the Panam~ Canal Zone carry 

more specimens than any other Tertiary deposit in 

the Caribbean region. Along .the Caribbean coast of 

Costa Rica Clementia is not found in the coralliferous 

limestones of the Gatun formation nor in the strand 

sandstones or conglomerates, nor in the coastalswamp muds, but only in the mud or fine sand that 

was deposited between the reefs and the strand. 

Bottom control excludes Clementia from the middle 

Miocene Bowden formation of Jamaica, which carries 

a fauna of species that lived on a gravelly or sandy 

bottom at depths ranging from the intertidal zone to 

about 200 fathoms. In Venezuela and Brazil specimens are found in limestones or in less calcareous mud 

beds. It is strange that no Clementias have been discovered in the Miocene mud deposits of the Dominican 

Republic and the Republic of Haiti, although hundreds 

of species of mollusks and thousands of shells have been 

collected from these beds. They carry many large, 

heavy shells, and the water in which they were deposited may have been too much agitated. This 

explanation is not entirely satisfactory, for it is unreasonable to believe that the water was nowhere in this 

area quiet enough to permit these mollusks to live. 

These burrowing shells apparently lived and died 

and were buried at or close to the place where they 

now are found-that is, their occurrence is autochton, 

to use the nomenclature introduced by EhrenbergP 

16 Preston, H. B., Mollusca from the Chilka Lake, on the east coast of India: 

Indian Mus. Rec., vol. 10, p. 306, 1914. 

17 Ehrenberg, Kurt, Uber das Vorkommen von Fossilrestim: Naturwissenschaften, 

year 12, No. 29, pp. 593-596, 1924. 

They are almost invariably found with both valves in 

attached position, indicating that they remained buried 

in the mud or fine sand in which they burrowed while 

they were alive. If they had lain unburied for some 

time on the sea bottom the valves would now gape or 

would be separated, depending on whether they were 

buried before or after the ligament decayed. If these 

thin shells had been ·washed about they would soon 

have been broken up. Unfortunately there are no 

confirmatory data with regard to the orientation of 

the shells in the deposits from which they have been 

collected. 

The heavier shells of Egesta are in harmony with 

their occurrence in sands and sandstones, though they 

are also found in marls. Some of the sandstones in 

California that carry Egesta are coarse, but generally 

specimens are not found in pebbly sandstones or conglomerates. These mollusks burrowed in sand or mud. 

Their shells may at times have been carried by waves 

and currents some distance from the place where they 

lived and died, for detached valves are found at some 

localities. 

The distribution of these two subgenera-Olementia 

and Egesta-also affords evidence of temperature control. Figure 1 shows that the American Tertiary 

species of Clementia s. s. were confined to tropical seas. 

On the Atlantic side the genus never got farther north 

than the Caribbean Sea. On the Pacific side fossil 

species have been found in northern Peru, Ecuador, 

Panama, and Costa Rica. The occurrence of Clementia s. s. in the Tertiary seas of the Orient is in 

harmony with its distribution in American Tertiary 

seas, and the Miocene Mediterranean Sea, in which 

the deposits of the Gratz Basin and Libyan Desert 

were laid down, was warmer than the present Mediterranean Sea. At the present time this subgenus is 

found in both tropical and warm temperate seas. In 

the waters of the Miocene Gulf of Mexico and on the 

Atlantic and Pacific coasts of the United States 

Clementia s. s. was replaced by Egesta. According to 

present interpretations, Egesta tolerated a considerable 

temperature range, for it is found in a variety of faunas 

ranging from the subtropical fauna of the Chipola formation of Florida to the warm-temperate faunas of 

the Calvert and Choptank formations of Maryland 

but not in cool temperate or boreal faunas. At the 

present time Egesta is found in the Gulf of California 

but not in the cooler waters of the California coast. 

Temperature control may account for its absence in the 

Pliocene deposits of California except in the warmwater facies of the Purisima formation. 

AMERICAN TERTIARY SPECIES 

The American Tertiary species of Clementia s. s. and 

Egesta, their age, and the localities where they have 

been found are as follows: 
AMERICAN TERTIARY MOLLUSKS OF THE GENUS CLEMENTIA 31 

Clementia (Clement?:a) dariena vetula Woodring, n. subsp., middle Eocene, Colombia. 

Clementia (Clementia) dariena rabelli Maury, middle Oligocene, 

Porto Rico. 

Clementia (Clementia) darien(!, dariena (Conrad), lower and middle Miocene, Panama (Atlantic and Pacific sides), Costa 

Rica (Atlantic and Pacific sides and interior), Colombia, 

Venezuela, Trinidad, Brazil, Ecuador, and Peru.· 

Clementia (Egesta) grayi Dall, lower and middle Miocene, 

Florida, and lower Miocene, Mexico. 

Clementia (Egesta) inoceriformis (Wagner), middle Miocene, . 

Maryland, and upper Miocene, New Jersey. 

Clementia (Egesta) conrg,diana, (F. M. Anderson), lq.wer and 

middle Miocene, California. 

Clementia (Egesta) martini (Clark), upper Miocene, California. 

Clementia (Egesta) pertenuis (Gabb), lower Miocene to lower 

Pliocene, California. 

The following table shows at a glance the compara1 tive age of these species: 

Age and distribution of American Tertiary species of Clementia 

Atlantic coast of United Pacific coast of Central 

Time divisions Borders of Gulf of Mexico Caribbean region America and northern Pacific coast of United States States South America 

Upper 

Q) 

~ Middle Q) 

C) 

0 Clementia (Egesta) ~ Lower pertenuis, Purisima f~rmation, Calif or- ma. 

Clementia (Egesta) Clementia (Egesta) 

inoceriformis, martini, San Pablo 

Kirkwood forma- formation (upper 

tion (Shiloh marl part) and Santa 

Upper member), New Margarita formaJersey. tion, California. 

Clementia (Egesta) 

pertenuis, C. (E.) 

conradiana, Santa 

Margarita formation, California. 

Clementia (Egesta) Clementia ( Egesta) Q) inoceriformis, Cal- pertenuis, Topanga !=: 

<J.) vert, Choptank, formation and Tur- C) and St. Marys ritella ocoyana zone, 0 

~- Middle formations, Mary- (ClemenCalifornia. 

land. Clementia (Egesta) Clementia (Clemen- Clementia Clementia (Ej.esta) grayi, Shoal River tia) dariena dari- ita) dariena dari- conradiana, urriformation, Florida. ena, Gatun forma- ena, Zorritos for- tella ocoyana zone, tion, Panama; Cos- mation, Peru; California. 

ta Rica; Colombia. Panama. 

Clementia (Egesta) Clementia (Clemen- Clementia (Clemen- Clementia (Egesta) 

grayi, Chipola and tia) dariena dari- tia) dariena dari- pertenuis, c. (E.) 

Oak Grove forma- en a, Culebra for- ena, E c u ad or ; conradiana, Vaque- Lower tions, F 1 or ida; mation (upper Panama; Costa ros formation (TurTux pan formation, part), Panama; Rica. ritella inezanazone), 

Mexico. Costa Rica; Co- California. 

lombia; Venezuela; 

Trinidad; Brazil. ---

Upper Clementia (Clementia) sp. b, Peru. 

Q) 

!=: Clemflntia (Clemen- Q) tia)dariena rabelli, C) 

0 

bO Middle San Sebastian shale :..::l and Juana Diaz 0 shale, Porto Rico. 

Lower 

Upper Clementia (Clementia) sp. b, Peru. 

<J.) 

!=: Clementia (Clemen- Clementia (Clemen- Q) 

C) tia) dariena vetula, tia) sp. b, Peru. 0 Middle ~ Colombia. Clementia (Clementia) sp. a, Peru. 

Lower 
32 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1926 

Clementia? taeniosa Guppy/8 an upper Miocene 

species from Trinidad, is a Mactra (Harvella). The 

type of this species is in the collections of the United 

States National Museum (catalog No. 107106). It 

may possibly be the species recently riamed Mactra 

(Harvella) sancti-blasi by Maury, 19 though it is la:rger 

than Maury's type and has fuller umbos. Dosinia 

mercenaroides Aldrich, a species from the middle 

Eocene Gosport sand of Alabama, described by Harris 20 as a Clementia, has none of the features of Clementia s. s. or Egesta. The discovery of characteristic 

Eocene Clep1entias in Colombia and Peru disposes 

of the idea, advocated by Harris, that this species 

is a transitional form leading up to Clementia. · 

Key to the American Tertiary species of Clementia 

Shell thin, upper posterior slope not concave, posterior end not 

truncate, pallial sinus relatively wide_ Subgenus Clementia s. s. 

Anterior end extended, length of adult shell not exceeding 

45 millimeters _________________ C. (C.) darienavetula. 

Anterior end not extended: 

Length of adult shell not exceeding 50 millimeters 

C. (C.) dariena rabelli. 

Length of adult shell not exceeding SO. millimeters 

C. (C.) dariena dariena. 

Shell thin or relatively thick, upper posterior slope generally 

concave, posterior end generally truncate, pallial sinus very narrow ________________________________ Subgenus Egesta. 

Upper posterior slope concave, posterior end truncate: 

Shell very inequilateraL ______________ C. (E.) grayi. 

Shell moderately inequilateraL _ C. (E.) inoceriformis. 

Upper posterior slope not concave, posterior end not 

truncate: 

Lunular area deeply depressed ___ C. ( E.) conradiana. 

Lunular area not deeply depressed: 

Shell moderately inequilateraL __ C. (E.) martini. 

Shell slightly inequilateraL ____ C. (E.) perten_uis. 

DESCRIPTION OF SPECiES 

Family VENERIDAE 

Subfap1ily DOSINIINAE 

Genus CLEMENTIA Gray 

Subgenus CLEMENTIA s. s. 

Gray, Synopsis of the contents of the British Museum, cd. 44, 

p. 7 5, 1842 (genus without species); Zool. Soc. London Proc., 

pt. 15, p. 184, 1847. 

Type (by original designation, 1847): Venus papyracea Gray, 

Ann. Philosophy, new ser., vol. 9, p. 137, 1825. Wood, Supplement to the Index Testaceologicus, p. 5, pl. 2, fig. 8, 1828. 

Recent, Australia. 

Shell generally small, thin and fragile, ovate, 

inequilateral. Lunule recognizable only by absence 

or suppression of sculpture. Sculpture consisting 

of coarse concentric waves and fine concentric threads, 

both of which are strongest in the umbonal region 

and may be replaced on the ventral part of the shell 

by growth line~. Under the umbo and extending a 

1a Guppy, R. J. L., U.S. Nat. Mus. Proc., vol. 19, p. 327, pl. 30, fig. 8, 1896. Dall, 

W. H., Wagner Free Inst. Sci. Trans., vol. 3, pt. 6, p. 1235, 1903. Maury, C. J. 

Bull. Am. Paleontology, vol. 10, p. 295, 1925. 

19 Maury, C. J., Bull. Am. Paleontology, vol. 10, pp. 266-267, pl. 32, fig. 2, 1925. 

zo Harris, G. D., Bull. Am. Paleontology, vol. 6, p. 151, pl. 47, figs.'-8-11, 1919. 

short distance parallel to the posterior cardinal lies a 

narrow shallow resilium groove. Hinge of right 

valve consisting of an anterior cardinal, a slightly 

heavier middle cardinal, and a long slender bifid 

' posterior cardinal; hinge of left valve consisting of 

an anterior cardinal, a· long, heavy middle cardinal, 

and a long, very slender posterior cardinal. On 

both valves a deep niche, formed by the hinge plate 

and the margin of the shell, lies in front of the anterior 

cardinal. Pallial sinus deep, ascending, wide, tapering to an asymn1etrically U-shaped apex. 

The name Clementia was first used by Gray in 1840 

in the forty-second edition of a booklet entitled 

"Synopsis of the contents of the British ~1useum." 

As no copies of any editions of this booklet are available, the following account is based on Iredale's quotations.20a This name as used in 1840 is absolutely 

nude 20b and therefore has no standing. But in the 

forty-fourth edition, issued in 1842, the following is 

added to the name Clementia: "The Tapes and 

Venerupes have oblong shells with very compressed 

teeth, and the Clementia are like the latter but are 

very thin and have a cavity in the n1argin before and 

behind the teeth." 200 On account of this brief sentence the name Clementia as used in 1842 must be accepted as recognizable, or it must be considered a 

doubtful name (nomen dubium). The statement 

that the shell is thin and that it has a "cavity" lying 

in front of and behind the hinge justifies the contention, here advocated, that the genus is recognizable on 

the basis of the 1842 publication, though no species 

are mentioned. It is assumed that the "cavity behind the teeth" refers to the space between the hinge 

plate and the nymph, though this "cavity" ~s not so 

pronounced as the "cavity" in front of the hinge, 

which is a striking feature. Venus papyracea still 

remains the genotype by original designation, for a· 

species was first assigned to the genus in the article in 

the Proceedings of the Zoological Society of London, 

184 7, and in this article Gray definitely states that he 

is designating types. If the name Clementia as used 

in 1842 is considered a doubtful name, its use in 1847 

is automatically invalidated. On the assumption that 

Venus papyracea arid Venus inoceriformis, the type of 

Egesta, are congeneric, all Clementia-like mollusks would 

then take the generic name Egesta-a name that was 

published in 1845 and that everyone has overlookedand the species similar to Venus papyracea would take 

some other name, which apparently would have to be 

a new name, as a subgenus of Egesta. The burden of 

proof rests on anyone who would advocate such a 

change in currrent nomenclature. 

The very thin fragile shell, slender hinge, and wide 

--pallial sinus are characteristic of Clementia s. s. The 

2oa Iredale, Tom, A collation of the molluscan parts of the synopses of the contents 

of the British Museum, 1838-1845: Malacol. Soc. London Proc., vol. 10, pp. 294-309, 

1913. 

2ob Idem, p. 298. 

20c Idem, p. 304. 
AMERICAN TERTIARY MOLLUSKS OF THE GENUS CLEMENTIA 33 

hinge plate is narrow and the hinge is spread out, 

so that the left middle cardinal is almost parallel 

to the edge of the nyrnph. 

There are slight differences between the American 

species here described and the living species from the 

western Pacific, including the genotype, C. papyracea,· 

and refined work may eventually eliminate the American species from Clementia s. s. The American fossils 

are larger than C. papyracea and other living species 

from the western Pacific, and they have a slightly 

heavier shell. Size alone may have no significance. 

C. mcclellandi Tomlin, a living species from South 

Africa, is fully as large as the .American fossil C. dariena. 

All the American fossils have a recognizable escutcheon 

limited by a low ridge extending from the umbo almost 

or quite to the edge of the shell, where as on C. papyracea the ridge disappears almost under the umbo. 

The resilium groove of the American species is wider, 

probably on account of the heavier shell. Though 

the hinge of none of the American fossils is. fully 

known, enough of it is known to show that it is heavier 

than in C. papyracea, probably too heavy to be compensated alone by their heavier shell. Moreover, the 

hinge of the American fossils is compressed into a 

shorter space. Their pallial sinus is not quite so wide 

as in C. papyracea. On the basis of a comparison with 

C. papyracea the separation of the Ame:tican fossils as 

a section of Clementia s. s. is justifiable, but such action must await a study ·of all the living and fossil 

species, for which material is not now available. 

EOCENE SPECIES 

Clementia (Clementia) dariena vetula Woodring, n. subsp. 

... Plate 14, Figures 1-4 

Shell relatively small, moderately inequilateral, 

anterior end extended. Lunular area shallow, sculptured only with growth lines. Escutcheon narrow, 

limited by a ridge extending from the umbo almost or 

quite to the margin of the shell. Sculpture consisting 

of coarse concentric waves and fine low concentric 

threads of irregular width. Interior inaccessible 

except a broken right hinge, which shows a heavy 

middle cardinal and a long slender deeply bifid posterior cardinal. 

Holotype, young shell: :tength 24 millimeters, 

height 22 millimeters, diameter (both valves) 12 

millimeters. Para type: Length 33 millimeters, estimated height 28 millimeters, diameter (both valves) 

19.8 millimeters. Another para type: Estimated length 

42 millimeters, height 32.5 millimeters, diameter (right 

valve) 10 millimeters. 

The holotype has a definitely limited lunule, which 

seems to be due to a calcareous crust that at one place 

extends across the boundary of the lunular area. 

Neither para type has a definite lunule. The ridge 

bounding the escutcheon is prominent. The paratype 

that shows the broken hinge also shows the deep, 

narrow groove at the upper edge of the ligament area 

and the long resilium groove lying back of the tip of 

the umbo parallel to. the posterior cardinal. 

This Eocene subspecies is represented by three specimens. Only one young shell, which is taken as the 

holotype, is perfect. It is remarkably similar to small 

specimens of the Miocene C. dariena dariena. The 

holotype and one of the paratypes show that the shell 

is more equilateral than in most specimens of dariena 

dariena (compare figs. 4 and 7,pl.14), but some specimens of dariena dariena are almost as equilateral as 

vetula. The concentric waves extend to the base of 

the largest specimen ~f vetula, whereas on adult 

shells of dariena dariena they disappear on the lower 

third or less of the shell. This distinction may have 

no significance, as the largest shell of vetula, which is 

only half as large as the largest specimen of dariena 

dariena, may not be full grown. The difference in 

shape and apparent difference in size are the most 

significant distinctions, but they seem to be of only 

· subspecific value .. 

The beds carrying vetula are undoubtedly of Eocene 

age and probably middle Eocene, although they may 

be as yOlmg as upper Eocene. The same collection 

contains a Volutospina very similar to V. petrosa 

tuomeyi (Conrad), from the Wilcox group of Alabama, 

and also similar to heavily callused specimens of V. 

peruviana Woods,21 from the middle Eocene Parinas 

sandstone of Peru; a Olavilithes resembling 0. pacificus 

Woods, 22 an Eocene species from Peru; an Operculina 

resembling 0. willcoxi (IIeilprin), an upper Eocene 

species from Florida; and speCies of Oliva, Neverita, 

Lunatia, Glycymeris, "Scapharca," Callocardia, and 

Pitar similar to species from the Claiborne group of the 

Gulf States. In addition to these fossils the collection 

contains remarkably large cashew nuts described by 

Berry 23 as Anacardium eocenicum. The possibility of 

mixing an Oligocene or Miocene Clementia with these 

Eocene fossils is eliminated, for the specimens of 

Clementia have precisely the same appearance as the 

Eocene shells and contain the same matrix, and no 

Oligocene or Miocene beds crop .out in the region 

where they were collected. 

Type locality: Middle Eocene, station 160 on traverse from Arroyo Macamajon to Ovejas, southeast of 

Pijaguay, Department of Bolivar, Colombia, R. L. 

Beckelhymer, collector; station 1/968; three specimens (holotype and two paratypes), all of which are 

figured. 

Type material: Holotype (young shell, both valves 

in attached position), U. S. Nat. Mus. catalog No. 

3_54036; _two paratypes, U.S. Nat. Mus. catalog No. 

354037. 

21 Woods, Henry, in Bosworth, T. 0., and others, Geology of the Tertiary and 

Quaternary periods in the northwest part of Peru, pp. 101-104, pl. 15, figs. 3-5, 

London, 1922. 

22 Idem, pp. 99-100, pl. 13, fig. 10; pl. 14, figs. 1-2. 

23 Berry, E. "\V., New Tertic species of Anacardium and Vantanea from Colombia: 

Pan-Am. Geologist, vol. 42, pp. 259-262, pl. 18, l!i24. 
34 SHORTER CONTRIBUTIONS TO GENERAL GEO~GY, 1926 

OLIGOCENE SPECIES 

Clementia (Clementia) dariena rabelli Maury 

Plate 14, Figure 5 

Clementia rabelli Maury, New York Acad. Sci. Scientific Survey 

Porto Rico and Virgin Islands, vol. 3, pt. 1, pp. 37-38, 

pl. 6, figs. 2-3, 1920. 

Maury, Bull. Am. Paleontology, vol. 10, p. 294, pl. 37, fig. 

2, 1925. 

Clementia dariena [not Conrad] Hubbard, New York Acad. Sci. 

Scientific Survey Porto Rico and Virgin Islands, vol. 3, 

pt. 2, pp. 118-120, pl. 19, figs. 10-11, 1921. 

Shell medium sized, very inequilateral. · Escutcheon 

narrow, limited by a low ridge extending from the 

umbo almost to the margin ~f the shell. Sculpture 

consisting of coarse concentric waves and fine concentric threads, which may not be visible on internal 

molds. Near the base of adult shells the concentric. 

waves disappear and are replaced by growth lines. 

Hinge and pallial sinus not known. · 

Holotype: Length 43 millimeters, height 38 millimeters, diameter (left valve) 6 millimeters. Paratype, distorted specimen: Length 43 millimeters, 

height 36 millimeters, diameter (both valves) 24.5 

millimeters. 

Clementia dariena rabelli is even more similar to 0. 

dariena dariena than 0. dariena vetula, but it is smaller 

than dariena dariena, though a little larger than vetula. 

According to Hubba,rd, who tabulated the dimensions 

of a number of specimens of rabelli and dariena dariena, 

average full-grown shells of rabelli are about two-thirds 

as large as full-grown specimens of dariena dariena. 

The holotype of rabelli is less elongate and less inflated 

than specimens of dariena dariena of the same size, 

but the shape of both species is variable. According 

to Maury (1925), rabelli is more inequilateral than 

dariena dariena, but most specimens of dariena dariena 

are very ineq uila teral. 

Clementia dariena rabelli is the only Clementia so far 

discovered in the West Indies proper and also is the 

only known American Oligocene Clementia. It is 

found in the middle Oligocene San Sebastian shale (also 

called Rio Collazo shale), at the base of the Tertiary 

system in northwestern Porto Rico, and in beds of 

the same age, known.as the Juana Diaz shale, on the 

south side of the island. 

All the American Tertiary ~pecies of Olementia s. s. 

and most of the living species have essentially the 

same sculpture. This feature should be borne in 

mind in considering the remarkable similarity of 0. 

dariena vetula (middle Eocene), 0. dariena rabelli 

(middle Oligocene), and 0. dariena dariena (lower and 

middle Miocene). So far as shape and sculpture are 

concerned, these three subspecies represent a genetic 

stock or gens, as clearly as phylogeny can be demonstrated by the morphology of fossils. The increase 

in size of progressively younger specimens is the most 

striking feature of this series. If specimens were 

available from deposits of intermediate age it would be 

very difficult, if not impossible, to represent the different stages of this series by the usual methods of 

Linnean nomenclature. Inasmuch as the principal 

difference between rabelli and dariena is one of size~ 

it seems desirable to consider rabelli a subspecies of 

dariena. 

Type locality: Middle Oligocene (San Sebastian 

shale), Rio Collazo near San Sebastian, Porto Rico. 

Other localities: Middle Oligocene (San Sebastian 

shale), other localities on Rio Collazo near San Sebastian, Porto Rico (Maury, Hubbard). Middle Oligocene (Juana Diaz shale), Juana Diaz, Porto Rico 

(Hubbard). 

Type material: Holotype (left valve), Am. Mus. 

Nat. Hist., Div. Geology and Invertebrate Paleontology, catalog No. 22509. Para type (distorted specimen, both valves in attached position), Am.' Mus. 

Nat. Hist., Div. Geology and Invertebrate Paleontology, catalog No. 22508. 

MIOCENE SPECIES 

Clementia (Clementia) dariena dariena (Conrad) 

Plate 14, Figures 6-11 

Meretrix dariena Conrad, U. S. Pacific R. R. Expl., vol. 5 

(33 Cong. 2d sess., H. Ex. Doc. 91), pt. 2, appendix, p. 

328, pl. 6, fig. 55, 1855. (Reprint, Dall, U. S. Geol. 

Survey Prof. Paper 59, p. 170, 1909.) 

Clementia dariena (Conrad). Gabb, Acad. Nat. Sci. Philadelphia Jour., 2d ser., vol. 8, p. 344, pl. 44, figs. 16, 16a, 

1881. 

Dall, Wagner Free lnst. Sci. Trans., vol. 3, pt. 6, p. 1235, 

1903. 

Tou1a, K.-k. geol. Reichsanstalt Jahrb., vol. 58, pp. 725-· 

726, 757, pl.· 27, figs. 9-10, 1909. 

Brown and Pilsbry, Acad. Nat. Sci. Philadelphia Proc., 

vol. 63, p. 371, pl. 28, fig. 1, 1911. 

Olsson, Bull. Am. Paleontology, vol. 9, pp. 404-405, pl. 

34, fig. 4, 1922. 

Spieker, Johns Hopkins Univ. Studies in Geology, No. 3, 

pp. 141-143, pl. 8, fig. 5, 1922. 

Maury, Bull. Am. Paleontology, vol. 10, pp. 293-294, pl. 

37, figs. 1, 3, 5-7, 1925. 

Harris, in Waring, Johns Hopkins Univ., Studies in Geology, No. 7, p. 110, pl. 20, fig. 8, 1926. 

Not Cytherea? (Meretrix) dariena? Conrad, U. S. Pacific 

R. R. Expl., vol. 6 (33d Cong., 2d sess., S. Ex. Doc. 78), 

pt. 2, p. 72, pl. 5, fig. 21, 1856 [probably= Macrocallista 

maculata (Linne)]. (Reprint, Dall, U. S. Geol. Survey 

Prof. Paper 59, p. 1 'f8, 1909.) 

Harvella? sp. undet., Nelson, Connecticut Acad. Arts Sci. 

Trans., vol. 2, p. 201, 1870. 

Clementia dariena [part] (Conrad) Hubbard, New York Acad. 

Sci. Scientific Survey Porto Rico and Virgin Islands, 

vol. 3, pt. 2, pp. 118-120, pl. 19, fig. 12 (not pl. 19, 

figs. 1D-11=Clementia dariena rabelli Maury), 1921. 

Clementia sp. cf. C. dariena (Conrad). Woods, in- Bosworth 

and others, Geology of the Tertiary and Quaternary 

periods in the northwest part of Peru, p. 113, pl. 20, 

figs. 4a, 4b, London, 1922 .. 

?Clementia brasiliana Maury, Brasil Servicio geol. mineral. 

Mon., vol. 4, pp. 422-423, pl. 24, fig. 3, 1925. 

Shell moderately large, very inequilateral. Lunular area moderately depressed. Escutcheon narrow, 
AMERICAN TERTIARY MOLLUSKS OF THE GENUS CLEMENTIA 35 

limited by a low ridge extending from the umbo almost 

to the margin of the shell. Sculpture consisting of· 

coarse concentric waves and fine concentric threads. 

On the ventral third or less of adult shells the concentric waves disappear and the threads merge into 

growth lines. Pallial sinus deep, moderately wide, 

ascending. 

Neotype: Length 61 millimeters, height 48.6 millimeters, diameter (both valves) 30.2 millimeters. 

Topotype: Length 78 millimeters, height 65 millimeters, diameter (both valves) 27 millimeters. 

Most specimens of this subspecies are elongate and 

very inequilateral, for the umbo lies close to the anterior end. Some shells have a more extended. anterior 

end. These less inequilateral shells, which are most 

abundant in lower Miocene deposits, resemble vetula. 

Two small inequilateral shells are figured for comparison with vetula. Most of the specimens of C. 

dariena darieria in the collections· of the United States 

National Museum are wholly or in part internal 

molds, and none show the hinge. Toula figured a 

right hinge, which consists of a slender anterior 

cardinal, a heavier middle cardinal (apparently 

broken), and a long, deeply bifid posterior cardinal. 

The pallial sinus is visible on several internal molds. 

C. dariena dariena was widely distributed along the 

south and west edge of the Carribean Sea during 

lower and middle Miocene time and also in the eastern 

Pacific. from Peru to Costa Rica. It has already been 

recorded from Brazil, Trinidad, Panama, Costa Rica, 

and Peru, and records are here given for Venezuela, 

Colombia, and Ecuador. Middle Miocene deposits 

carry th~ largest shells. Virtually all the specimens 

from lower Miocene beds are relatively small and 

grade almost imperceptibly into 0. dariena rabelli. 

The type of C. dariena dariena is apparently lost, as 

it is not in the United States National Museum among 

the types of the fossils described by Conrad in the 

reports of the Pacific Railroad explorations. The type 

specimen was collected by W. P. Blake, geologist of· 

the surveying party lmder the command of' Lieut. 

R. S. Williamson. Blake proceeded to San Francisco 

by way of the Isthmus of Panama and collected the type 

specimen and other fossils in a cut along the railroad 

"at Gatun, or Monkey Hill?" 25 Although the precise locality is a little uncertain it is of no great importance, as the Gatun formation, of middle Miocene 

age, is the only formation cropping out in this region. 

The specimen· shown in Figure 10, Plate 14, is to be 

regarded as the neotype, at least until the original 

type is found. By this time topotypes are in many 

museums, for in the Canal Zone C. dariena dariena is 

very abundant in the lower part of the Gatun formation. 

The only specimens from the Culebra formation of 

the Panama Canal Zone were collected from beds 

ta Blake, W. P., U.S. Pacific R. R. Expl., vol. 5 (33d Cong., 2d sess., H. Ex. Doc. 

91), pt. 2, p.·1, 1855. 

lying in the upper part 59 and 66 feet below the base 

of the En1perador limestone, according to MacDonald's section (stations 6019d and 6019b).26 These 

specimens are very small and may not represent C. 

dariena dariena. The upper part of the Culebra 

formation seems to be Miocene (Aquitanian). 

According to Maury's figure, Clementia brasiliana 

(pl. 14, fig. 11), based on .specimens collected from 

lower 11iocene beds in Brazil, seems to represent 

small specimens of C. dariena dariena. The specimens 

from Brazil are like small, slightly elongate shells of 

C. dariena dariena from Venezuela and other localities. 

Suites of specimens from the type locality of dariena 

dariena show that the shape of this species is too variable to introduce another name for small, slightly 

elongate Clementias from the lower Miocene beds of 

tropical America. At the anterior end of the shell the 

concentric waves of C. brasiliana are represented as 

erect frills, as in Chione (Lir9phora), but this feature 

may have been exaggerated by the artist. 

Type locality: Middle Miocene (Gatun formation), 

near Gatun, Panama Canal Zone. 

Other localities: Lower Miocene (upper part of 

Culebra formation), west side of Gaillard Cut near 

Las Cascadas, bed 12c ·of section, Panama Canal 

Zone; D. F. MacDonald and T. W. Vaughan, collectors; station 6019d; one small specimen; identification 

doubtful. Lower Miocene (upper part of Culebra 

formation), ·same locality as 6019d, bed 11 of section; 

D. F. MacDonald and T. W. Vaughan, collectors; 

station 6019b; one small specimen; identification 

doubtful. Lower Miocene, V amos-a-Vamos (now under water), Panama Canal Zone; R. T. Hill, collector; 

station 2682; one specimen. Lower Miocene, Sapote 

(or Zapote), Rio Revantazon, Costa Rica (Gabb). 

Lower Miocene, near San Andres, Department of 

,Bolivar, Colombia; H. S. Gale and E. S. Bleeker, collectors; station 1/151; one small specimen. Lower 

Miocene, ''Dam site" series, northwest of Agua Clara, 

Falcon, Venezuela; Ralph Arnold, collector; station 

8071; one small specimen. Lower Miocene, Rio Coro, 

near coal mu;_e at Isiro, 6 miles south of Coro, Falcon, 

Venezuela; Ralph Arnold, collector; station 6308; one 

small specimen. Lower Miocene, Guaico-Tamana 

road, Trinidad; two small specimens (Maury). Lower 

Miocene, Manzanilla, Trinidad; two small specimens 

(Maury). Lower 11iocene (Esta<_tao formation), agricultural station on railroad from Braganca to Belem, 

155 kilometers west of Braganca, Para, Brazil (Maury). 

Lower (?) Miocene, pit at well location of Standard 

Oil Co. of California near Bajada and Amen, Santa 

Elena Peninsula, Ecuador; H. S. Gale, collector; 

station 1/453; one small crushed specimen; identification doubtful. Lower Miocene, Santiago de Veraguas, 

Panama; 0. H. Hershey, collector; one specimen. 

26 MacDonald, D. F., The sedimentary formations of the Panama Canal Zone, 

with special reference to the stratigraphic relations of the fossiliferous beds: U. 8, 

Nat. Mus. Bull. 103, pp. 537-538, 1919. 
36 SHOR.'TER CONTRIBUTIONS TO GENERAL GEOLOGY, 1926 

Lower Miocene, crest of divide along'~road to Aguadulce, about 5 miles northeast of Santiago de Veraguas, Panama; W. P. Woodring, collector; station 8465; 

one specimen. Lower Miocene, half a mile above 

Sulphur Spring, northwest of San Felix, Chiriqui 

Province, Panama; D. F. MacDonald, collector; station 6534; one broken specimen; identification doubtful·. Lower Miocene, near San Felix, Chiriqui Province, 

Panama; Henri Pit tier, collector; station 6262; one 

small specimen. Lower Miocene, Rio Papayal, first 

main fossil bed above Pecten shale, Chiriqui Province, 

Panama; J. T. Duce, collector; station 1/690; one small 

crushed specimen; identification doubtful. Lower 

Miocene, Rio Gualaca, 500 meters north of mouth, 

Chiriqui Province, Panama; J. T. D'uce, collector; station 1/691; three small broken specimens; identification doubtful. Lower Miocene, Oonus bed, road to 

Gualaca, Chiriqui Province, Panama; J. T. Duce, collector; station 1/715; one small crushed specimen; 

identification doubtful. Lower Miocene, Carballo Cliff, 

east of Punta Arenas, Costa Rica; J.D. Sears, collector; 

station 8330; one broken specimen; identification 

doubtful. 27 Lower Miocene, Caldera, near Corballo 

tunnel, Costa Rica; A. Alfaro, collector; station 5468; 

one specimen. Lower Miocene, Santa Maria de Dota, 

Quebrada Rivas, Costa Rica; J. F. Tristan, collector; 

station 7274; one specimen. Middle Miocene (Gatun 

formation), cut on relocated line of Panama Railroad, 

1 Yz to 2 miles west of Camp Cotton toward Monte 

Lirio, Panama Canal Zone; D. F. MacDonald and 

T. W. Vaughan, collectors; station 6030; 17 specimens 

(topotypes), one of which (neotype) is figured. Middle Miocene (Gatun formation), lowest bed in cut on 

relocated line ·of Panama Railroad, one-quarter to 

one-half mile from Camp Cotton toward Monte Lirio, 

Panama Canal Zone; D. F. MacDonald and T. W. 

Vaughan, collectors; station 6029a; three specimens 

(topotypes). Middle Miocene (Gatun formation), 

basal part of section, half a mile from Camp Cotton 

toward Gatun, Panama Canal Zone; D. F. MacDonald and T. W. Vaughan, collectors; station 6031; 

two broken specimens ( topotypes). Middle Miocene 

(Gatun formation) lower part of lowest bed in cut on 

relocated line of Panama Railroad about 3,500 feet 

south of Gatun railroad station, Panama Canal Zone; 

D. F. MacDonald and T. W. Vaughan, collectors; station 

6033a; two specimens ( topotypes). Middle Miocene 

(Gatun formation), same locality as preceding collection but from upper part of lowest bed; station 

6033b; two specimens ( topotypes). Middle Miocene 

(Gatun formation), same locality as preceding collection; D. F. MacDonald, collector; station 6004; 

one broken specimen ( topotype). Middle . Miocene 

(Gatun formation), cuts on railroad southeast of 

Gatun; A. A. Olsson, collector; station 8381; four 

21 Romanes collected C. dariena at the Carballo Cliff (Romanes, J., Geology of 

a part of Costa Rica: Geol. Soc. London Quart. Jour., vol. iS, p. 125, 1912). 

specimens (topotypes). Middle Miocene (Gatun formation), first high cut on left side of railroad going 

from Gatun toward Panama, Panama Canal Zone; 

W. P. Woodring, collector; station 1/997; two specimens (topotypes). Middle Miocene (Gatun formation), Quebrancha Hills overlooking Gatun Lake, 1~ 

miles northeast of Gatun, Panama Canal Zone; D. F. 

MacDonald, collector; station 5845; three specimens. 

Middle Miocene (Gatun formation), near spillway of 

Gatun Dam, Panama Canal Zone; D. F. MacDonald, 

collector; station 5846; eight specimens, two of which 

are figured. Middle Miocene (Gatlin formation), 

cuts west of Gatun Dam, Panama Canal Zone; A. A. 

Olsson, collector; station 8365; one unusually well 

preserved, small specimen. Middle Miocene (Gatun 

formation), west of Gatun Lake, Panama Canal Zone; 

A. A. Olsson, collector; station 8360; one broken 

specimen. Middle Miocene (Gatun formation), 

N ancys Cay, Bocas del Toro Province, Panama (Olsson). Middle Miocene (Gatun formation), upper 

Hone Creek and its tributary Sousi Creek, Costa 

Rica (Olsson). Middle Miocene· (Gatun formation), 

Banana River, Costa Rica; D. F. MacDonald, collector; station 5882Z; one specimen. Middle Miocene, 

edge of town of Balsanco, Cerro de San Antonio area, 

Department of Magdalena, Colombia; H. S. Gale, collector; station 1/927; one broken specimen; identification doubtful. Middle Miocene, near Tubara, Department of Atlantico, Colombia; F. A. Sutton and 

P. Squibb, collectors; station 1 /987; two specimens, 

one of which is figured. Middle Miocene, Tubara, 

Department of Atlantico, Colombia; A. Iddings, collector; station 1/988; one specimen, figured. · Middle 

Miocene, Villa Nueva, Department of Bolivar, Colombia; 0. B. Hopkins, collector; station 1/101; 

four ·specimens. Middle Miocene (Zorritos formation), near Zorritos, Peru (Nelson, Woods, and Spieker). Middle 0) Miocene, Quebrada Las' Ajontas, a 

mile above confluence with Rio Cristobal, Chiriqui 

Province, Panama; E. R. Smith, collector; station 

7961; one specimen. · 

Type material: N eo type (both valves in attached 

position), U. S. Nat. Mus. No. 354038. 

Subgenus EGESTA Conrad · 

Conrad, Fossils of the Tertiary formations of the United States, 

p. 70, 1845. (Reprint, Dall, under title "Conrad's fossils 

of the medial Tertiary of the United States," p. 70, 1893.) 

Type (by monotypy): Venus inoceriformis Wagner, Acad. Nat. 

Sci. Philadelphia Jour., vol. 8, pp. 51-52, pl. 1, fig. 1, 1839. 

Middle Miocene, Maryland. 

Shell relatively large, thin or heavy, inequilateral, 

upper posterior slope generally flattened or slightly 

concave, producing a truncate posterior end. Lunular area moderately or deeply depress·ed, otherwise 

poorly defined. Escutcheon poorly defined. Sculpture Olementia-like, consisting of coarse concentric 

waves and fine concentric threadsJ both of which may 
AMERICAN TERTIARY MOLLUSKS· OF THE GENUS CLEMENTIA 37 

be replaced on the ventral part of the shell by growth 

lines. Resilium groove long, wide, and deep. Hinge 

of right valve consisting of a slender anterior cardinal, 

a heavier middle cardinal, and a slender, deeply bifid 

posterior. cardinal; hinge of left valve consisting of a 

slender anterior cardinal, a heavy middle cardinal, 

and a very thin posterior cardinal. Pallial sinus 

narrow, deep, ascending, slightly tapering to an asymmetrically U-shaped apex. 

Conrad casually gave the name Egesta, as a subgenus of Venus, to Venus inoceriformis and promptly 

forgot it~ Apparently the name has been overlooked 

It is here proposed to use Egesta as a subgeneric name 

embracing several American fossils and two living 

species-Clementia solida Dall, from the Gulf of California, and Clementia vatheliti Mabille, from waters off 

Japan and Chosen. 

The larger and heavier shell, flattened or concave 

upper posterior slope, accompanying truncation of 

the posterior end, longer and deeper resilium groove, 

heavier hinge, and narrower pallial sinus separate 

Egesta from Clementia s. s. A comparison of Clementia 

papyracea with Clementia solida (pl. 16, figs. 7, 8), 

which seems to be the culminating species of the subgenus. Egesta, shows pronounced differences, but when 

other species are considered the separation of the 

subgenera is not so satisfactory. Egesta has a heavier 

hinge, a natural result of the heavier shell, and it is 

compressed into a relatively shorter space, so that 

the right posterior cardinal is not so far from the right 

middle cardinal and is less recumbent, and the left 

middle and posterior cardinals are less recumbent. 

According to tbe meager evidence available the 

American fossil species referred to Clementia s. s. have 

precisely the same kind of heavy compressed hinge. 

The pallial sinus of the American species of Egesta, 

both living and fossil, is very narrow, much narrower 

than in Clementia s. s., but Clementia vatheliti, which 

is here referred to Egesta, has a pallial sinus of intermediate width. The resilium groove of this species 

is not so wide as· in the American species of Egesta. 

The niche in front of the anterior cardinal of living 

species of Clementia s. s. is almost eliminated in Egesta 

and in the American fossil Clementia s. s. on account 

of the greater thickness of the shell and hinge plate 

and the greater depression of the lunular area. The 

lunular area of Clementia (Egesta) solid~ is deeply 

depressed, its margin being thus brought almost 

parallel to the anterior cardinal, but this feature is 

not so pronounced in other species except the fossil 

0. (E.) conradiana. 

The characteristic features of Egesta are less pronounced in the Miocene species 0. (E.) grayi and 0. 

(E.) inoceriformis. Their shells are. not so heavy, the 

upper posterior slope is not so concave, the posterior 

truncation is not so pronounced, thelunular area is not 

so deeply qepressed, and the pallial sinus is not quite 

so narrow. The living Japanese species 0. (E.) vatheliti 

i_s more similar in these features to these two American 

Tertiary species than to C. (E.) solida. Dall 29 pointed 

out the similarity of C. (E.) grayi and C. (E.) vatheliti. 

On the basis of its narrow pallial sinus Venus pertenuis, 

a fossil species from California, is an Egesta, but its 

upper posterior slope is not flattened. Venus conradiana and Venus martini are considered Egestas, 

but their pallial sinus is not known. 

MIOCENE SPECmS 

Clementia (Egesta). grayi DalJ 

Plate 15, Figure 4 

Clementia grayi Dall, Wagner Free Inst. Sci. Trans., vol. 3, 

t pt. 5, p. 1193, pl. 37, fig. 12, 1900; pt. 6, p. 1236, 1903. 

Gardner, U. S. Geol. Survey Prof. Paper 142, p. 154, pl. 24, 

fig. 6, 1926. 

Clementia cf. dariena Conrad. Dickerson and Kew, California 

Acad. Sci. Proc., 4th ser., vol. 7, table opposite p. 128, 

1917. 

Shell moderately large, thin or moderately heavy, 

very inequilateral. Upper posterior slope flattened 

or slightly concave, posterior end truncate. Lunular 

area moderately depressed. Sculpture consisting of 

coarse concentric waves and fine concentric threads ' both of which are confined to about the umbonal 

third of adult shells and are replaced by irregular 

growth lines on the remainder of the shell. Hinge 

of right valve consisting of a slender anterior cardinal, 

a heavier middle cardinal, and a long, slender bifid 

posterior cardinal; hinge of left valve consisting of a 

slender anterior cardinal, a heavy middle cardinal, 

and a long, thin posterior cardinal; pallial sinus deep, 

narrow, ascending, slightly tapering to an acute apex. 

Holotype: Length 63 millimeters, height 54 millimeters, diameter (left valve) 19 millimeters. 

The holotype is an almost perfect left valve, 

though the hinge is defective. It is the only fully 

a~ult specimen discovered except two broken internal 

mold~. The shell of the holotype is relatively thick, 

so thick that the concentric waves are not visible on 

the interior. It is the only shell that is so thick. 

The concentric waves are visible on the interior of a 

piece of shell collected at the same locality, but this 

thinner shell is smaller than the holotype. All the 

young shells are thin. The hinge of the right valve 

is known only from a small shell fragment collected 

at station 3856. 

\c. (E.) grayi is a characteristic Egesta and is similar to 

the living species C. (E).vatheliti. Itisfoundin western 

Florida in the Chipola (lower Miocene), Oak Grove 

(lower Miocene), and Shoal River (middle Miocene) 

formations, and also in Mexico in the Tuxpan forma~ 

tion (lower Miocene). All the specimens from the 

Chipola formation are internal molds, except one 

29 Dall, W. H., Wagner Free Inst. Sci. Trans., vol. 3, pt. 6, p. 1236, 1903. 
38 SHORTER· CONTRIBUTIONS TO GENERAL GEOLOGY, 1926 

specimen collected at station 7151. The flattened 

upper posterior slope is very obscure on most of these 

molds and generally can not be seen at all on young 

specimens. The type locality of grayi is the only 

lo({ality where it has been found in the Oak Grove 

sand. At one locality in the Shoal River formation 

(station 3856) it is very abundant, but none of the 

shells are full ·grown. The largest specimens from 

the Tuxpan formation of the Tampico embayment of 

Mexico are very similar to specimens from Florida, 

but it is more difficult to identify small specimens. 

Type locality: Lower Miocene (Oak Grove sand), 

Yellow River, half a mile east of Oak Grove, Okaloosa 

County, Fla.; F. Burns, collector; station 2646; one 

specimen (holotype) and fragments of another specimen. 

Other localities: Lower Miocene ( Chipola formation), north bank of Tenmile Creek, at _wagon bridge 

on road from Forestville to Marianna, Calhoun 

County, Fla.; C. W. Cooke and W. C. Mansfield, collectors; station 7151; one specimen. Lower Miocene 

(Chipola formation), Sopchoppy, Wakulla County, Fla.; 

G. C. Matson, collector; station 7468; seven specimens. Lower Miocene ( Chipola formation), Bruce 

Creek just above Waldon Bridge, about 5 miles 

west of Red bay, Walton County, Fla.; W. C. Mansfield and W. M. Gomillion, collectors; station 1/979; 

two specimens. Lower Miodene ( Chipola formation), 

near Rocky Landing, Choctawhatchee River, Washington County, Fla.; W. C. Mansfield and W. M. 

Gomillion, collectors; station 1/968; one specimen. 

Lower Miocene ( Chipola formation), The Woodyard, 

·three-fourths mile above Shell Landing, Holmes 

Creek, Washington County, Fla.; lower bed; J. A. 

Gardner, collector; station 1/609; one specimen. 

Lower Miocene ( Chipola formation), Whites Creek, 

half a mile below bridge on road from Eucheeanna to 

Knox Hill, Walton County, Fla.; J. A. Gardner, collector; station 1/611; two specimens. Lower Miocene 

(Tuxpan formation), San Fernando, Tamaulipas, 

Mexico; W. F. Cummins, collector; station 4568; 

one broken internal mold. Lower Miocene (Tuxpan formation), 1 kilometer west of Temapache, 

Vera Cruz, Mexico; T. H. Kernan, collector; one 

specimen. Lower Miocene (Tuxpan formation), 

Huasteca Railroad, cut 10 kilometers from east terminus of railroad, District of Ozuluama, Vera Cruz, 

Mexico; T. W. Vaughan, collector; eight specimens. 

Middle Miocene (Shoal River formation), 5 to 6 miles 

west of Mossyhead, Walton County, Fla.; G. W. 

Nichols, collector; station 3856; 22 specimens. Middle 

Miocene (Shoal River formation), Folk's Creek, about 

4 miles south of Argyle, Walton County, Fla.; T. W. 

Vaughan, collector; station 5192; one small specimen; 

identification doubtful. Middle Miocene (Shoal River 

formation), Shoal River, 1 Yz miles below Shell Bluff, 

Walton County, Fla.; T. W. Vaughan, collector; station 5193; one small specimen; identification doubtful. 

Same locality as preceding collection; station 5194; 

one specimen. Middle Miocene (Shoal River formation), Shoal River half a mile below Shell Bluff, Walton 

County, Fla.; T. W. Vaughan, collector; station 5079; 

one specimen. 

Type material: Holotype (left valve), U. S. Nat. 

Mus. catalog No. 107381. 

Clementia (Egesta) inocerlformis (Wagner) 

Plate 15, Figures 5, 6 

Venus inoceriformis Wagner, Acad. Nat. Sci. Philadelphia Jour., 

vol. 8, pp. 51-52, pl. 1, fig. 1, 1839. 

Conrad, Fossils of the Tertiary formations of the United 

States, p. 70, pl. 40, fig. 1, 1845. (Reprint, Dall, under 

title "Conrad's fossils of the medial Tertiary of the 

United States," p. 70, pl. 40, fig. 1, 1893.) 

Clementia inoceriformis (Wagner). Conrad, Acad. Nat. Sci. 

· Philadelphia Proc., vol. 14, p. 575, 1863. 

Dall, Wagner Free Inst. Sci. Trans., vol. 3, pt. 6, pp. 1235-

1236, 1903. 

Glenn, Maryland Geol. Survey, Miocene, pp. 315-316, pl. 

82, figs. 1-2, 1904. 

Clementia inoceramiformis (Wagner). Meek, Smithsonian 

Misc. Coil., vol. 7, No. 183, p. 10, 1864 (error for inoceriformis). 

Shell medium sized, relatively thin, moderately 

inequilateral, anterior end extended. Upper posterior 

slope flattened, posterior end truncate. Lunular area 

deeply depressed. Sculpture con~isting of coarse concentric waves and fine concentric threads; the waves 

are most pronounced on the dorsal half of the shell 

and may be absent on the ventral half. Hinge of 

right valve consisting of a slender anterior cardinal, 

a heavier middle cardinal, and a very slender bifid 

posterior cardinal; hinge of left valve consisting of a 

slender anterior cardinal, a heavy middle cardinal,' 

and a very thin, long posterior cardinal. Pallial sinus 

deep, narrow, ascending. 

Holotype: Length 7 5 millimeters, height 64 millimeters, diameter (left valve) 17 millimeters. 

This species is the only Olementia-like mollusk 

found on the Atlantic coast of the United States north 

of Florida. Though it is recorded from the middle 

Miocene Calvert, Choptank, and St. Marys formations 

of Maryland, only a few specimens have been collected. 

An internal mold collected from the Calvert formation 

1 Y2 miles above Plum Point, on Chesapeake Bay 

(station 2457), closely resembles grayi, but the mold 

may be distorted. Two small hinges glued to the 

interior of the holotype are labeled "Shiloh, N. J." 

They probably represent small specimens of inoceriformis. If this locality label is trustworthy, these 

specimens represent the northernmost locality at which 

Egesta has been collected on the Atlantic coast. The 

internal mold from Gay Head, Mass., mentioned by 

Dall 30 as possibly representing this species seems to be 

some other veneroid mollusk, probably Macrocallista. 

ao Dall, W. H., Wagner Free Inst. Sci. Trans., vol. 3, pt. 6, p. 1236, 1903. 
AMERICAN TERTIARY MOLLUSKS OF THE GENUS CLEMENTIA 39 

0. (E.) inoceriformis is similar to grayi but is larger 

and less inequilateral, and the flattening of its upper 

posterior slope is ·not so pronounced. The concentric 

waves of inocerifOI'mis extend farther down on the 

shell. 

Type locality: Middle Miocene (St. Marys formation), Porto bello, St. Marys River, St. Marys County, 

Md. 

Other localities: Middle Miocene (Calvert formation), clay bed below Plum Point marl member, 1U 

n1iles above Plum Point, Calvert County, Md.; G. D. 

Harris, collector; station 2457; one specimen. Middle 

Miocene (Calvert formation), Hollin Cliff and Wye 

Mills, Calvert County, Md. (Glenn). Middle Miocene 

( Choptank formation), west shore of Chop tank River, 

about one-fourth to one-half mile below Barker's 

Landing and about 5 miles southeast of Easton, 

Talbot County, Md.; F. Burns and G. D. Harris, 

collectors; station 2350a/ ·one specimen, piece of left 

valve showing hinge. Middle Miocene (Chop tank 

formation), Governor Run and Sand Hill, Calvert 

County, Md. (Glenn). Middle Miocene (St. Marys 

formation), Cove Point, Chesapeake Bay, Calvert 

County, Md.; Maryland Geol. Survey; three broken 

specimens. Upper Miocene (Shiloh marl member of 

Kirkwood formation), Shiloh, Cumberland County, 

N.J.; two specimens .. 

Type material: Holotype (left valve), Philadelphia 

Acad. Nat. Sci. catalog No. 4303. 

Clementia (Egesta) conradiana (F. M. Anderson) 

Plate 15, Figures 1, 2; Plate 17, Figures 4, 5 

Venus (Chione) conradiana F. M. Anderson, California Acad. 

Sci. Proc., 3d ser., Geology, vol. 2, pp. 195-196, pl. 14 

fig. 35, 1905. 

Shell large, moderately elongate, very inequilateral, 

anterior end not extended, lunular area deeply depressed. Sculpture consisting of coarse concentric 

waves and fine concentric threads. Near the base of 

the shell the concentric waves and threads merge 

into growth lines. Pallial sinus not known. 

Hqlotype (measurements based on Anderson's 

figure):. Approximate length 90 millimeters, height 78 

milli1neters. Figured specimen from Santa Margarita 

formation: Length 74 millimeters, height 65 millimeters, diameter (both valves) 35 millimeters. 

This species is not represented in the collections of 

the United States National Museum. The unfluted 

inner margin, described by Anderson, shows that it is 

neither a Venus nor a Chione. When this account was 

first written it was supposed that the. holotype was 

destroyed in the San Francisco fire of 1906, but later 

information shows that it stood the ordeal. Doctor 

Hanna kindly sent the photographs reproduced as 

Figures 4. and 5 on Plate· 17 and also a cast of the 

hinge. This material unexpectedly shows that, unlike 

the other fossil species from California, this species has 

a deeply depressed lunular area, though it has no 

definite lunule. It therefore seems to be similar to 

the living 0. (E.) solida, but it is more inequilateral, 

and its upper slope is not concave. Plate 17 was 

added after this paper was· in proof. 

A specimen in the colle~tions of the California 

Academy of Sciences (pl. .15, fig. 1) seems to represent 

Venus conradiana, as it is very inequilateral, but it 

was collected from the upper Miocene Santa Margarita formation. 

According to Clark81 and other writers, the Vaqueros 

formation of reports issued by the United States 

Geological Survey on the oil fields of central California embraces two faunal zones-a lower zone 

carrying Turritella inezana, which corresponds to 

Merriam's Turritella hoffmanni ( = T. inezana) zone 32 

and to Smith's Vaqueros fauna, 38 and an upper zone 

carryjng Turritella ocoyana, which corresponds to 

Merriam's Turritella ocoyana zone and to Smith's 

"Temblor" fauna. Clark restricted the name Va-

. queros (Vaqueros "group," as used by Clark) to the 

lower zone, and for the upper zone used the name 

"Temblor group," a name first proposed by F. M. 

Anderson 84 in the form "Temblor beds." In a 

recent publication on the geology of Ventura and 

Los Angeles Counties Kew85 adopted the restriction 

of the name Vaqueros formation to the lower Miocene 

deposits carrying Turritella inezana and proposed the 

name Topanga formation for the middle Miocene 

beds carrying Turritella ocoyana. tn the following 

list of localities and elsewhere in this report the beds 

in central California carrying Turritella ocoyana, 

which apparently are the equivalent of the Topanga 

formation, are referred to as the Turritella ocoyana 

zone. 

Smith 86 recorded 0. (E.) conradiana from both the 

lower Miocene Vaqueros fauna and the middle 

Miocene "Temblor" fauna. 

Type locality: Middle Miocene ( Turritella ocoyana 

zone), 3 miles east of La Panza Springs, San Luis 

Obispo County, Calif.87 

Other localities: Lower Miocene (Vaqueros fauna), 

California (Smith). Upper Miocene (Santa Margarita formation), bed of small creek about 2 miles 

north of Santa Margarita, about 100 yards south of 

31 Clark, Bruce, The marine Tertiary of the west coast of the United States; its 

sequence, paleogeography, and the problems of correlation: Jour. Geology, vol. 29, 

pp. 595-600, 1921. 

u Merriam, J. C., A note on the fauna of the lower Miocene of California: Cali· 

fornia Univ. Dept. Geology Bull., vol. 3, pp. 377-381, 1904. 

83 Smith, J. P., Geologic range of Miocene invertebrate fossils of California: Oali· 

fornia Acad. Sci. Proc., 4th ser., vol. 3, pp. 164-165, 1912. 

34 Anderson, F. M., A stratigraphic study in the Mount Diablo Range of Cali· 

fornia: California Acad. Sci. Proc., 3d ser., Geology, vol. 2, p, 170, 1905; A further 

stratigraphic study in the Mount Diablo Range of California: California Acad. 

Sci. Proc., 4th ser., vol. 3, pp. 18-20, 38-39, 1908. 

86 Kew, W. S. W., Geology and oil resources of a part of Los Angeles and Ventura 

Counties, Calif.: U. S. Geol. Survey Bull. 753, pp. 4o-51, 1924. 

se Smith, J. P., Geologic range of Miocene invertebrate fossils of California: Cali· 

tOrnia Acad. Sci. Proc., 4th ser., vol. 3, p. 178, 1912. 

87 Kew (U. S. Geol. Survey Bull. 753, p. 51, 1924) listed " Venus cf. V. conradianus 

Anderson" from the middle Miocene Topanga formation of southern California. 
40 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1926 

Mr. Meyer's house, San Luis Obispo County, Calif.; 

F. M. Anderson, collector; California Acad. Sci. station 7 4; one specimen, figured; identification doubtful. 

Type material: Holotype (left valve), California 

Acad. Sci. catalog No. 2152. 

Clementia (Egesta) martini (Clark) 

Plate 15, Figure 3 

Venus martini Clark, California Univ. Dept. Geology Bull., 

vol. 8, pp. 470-471, pl. 54, fig. 1, 1915. 

Shell moderately large, elongate, moderately inequilateral. Sculpture · consisting of coarse concentric 

waves and fine conceU:tric threads. The waves 

extend to the base of the shell, but near the base they 

are more closely spaced. Hinge of left valve similar 

to left hinge of pertenuis. Pallial smus not known. 

Holotype: Length 63 millimeters, approximate 

height 50 millimeters, diameter (both valves) 32 

millimeters. 

This species also is not represented in the collections 

of the United States National Museum. The holo-. 

type is somewhat distorted, and no undistorted large ' 

specimens are available. A small undistorted topotype is suspiciously similar to 0. (E.) pertenuis, 

Additional material may show that martini and 

pertenuis represent the same species. Two topotypes show broken left hinges that, so far as can be 

seen, are essentially similar to left hinges of pertenuis. 

As 0. (E.) martini now stands, it is very similar to 

elongate specimens of pertenuis _but apparently is 

more elongate and more inequilateral, though less 

inequilateral than conradiana. 

According to Clark 0. (E.) martini is found in the 

upper part of the San Pablo formation of Contra Costa 

County,· Calif., and also in the Santa Margarita 

formation of the region north of Coalinga in beds 

carrying 0. (E.) pertenui8. 

'Type locality: Upper Miocene (upper part of San 

Pablo formation), center of north edge of NW. ~ 

sec. 28, T. 1 S., R. 1 E., Mount Diablo ,quadrangle, 

Contra Costa County, Calif.; Univ. California station 

741. 

Other localities: Upper Miocene (upper part of San 

Pablo formation), other localities in Contra Costa 

County, Calif. (Clark). Upper Miocene (Santa 

Margarita formation), north of Coalinga, Fr~sno 

County, Calif. (Clark). 

Type material: Holotype (both valves in attached 

position), Univ. California Pal. Coil. catalog No. 11570. 

MIOCENE AND PLIOCENE SPECIES 

Clementia (Egesta) pertenuis (Gabb) 

Plate 16, Figures 1-6 

Venus kennerlyi Reeve? Gabb, California Geol. Survey, 

Paleontology, vol. 2, p. 22, pl. 5, fig. 37, 1866.38 

as The ti.tle-page of t1lis publication gives the date 1869, but according to the foot· 

note on page xiv of the preface, section 1, part 1 (pp. 1-38), was published in 1866. 

I am indebted to Mr. Ralph B. Stewart for pointing out this discrepancy in dates. 

A copy of section 1, part 1, in the library of the Geological Survey bears the date 1866. 

Venus pertenuis Gabb, California Geol. Survey, Paleontology, 

vol. 2, pp. 22, 55-56, pl. 5, fig. 37, 1866. 

Arnold, U. S. Geol: Survey Bull. 396, p. 17, pl. 8, fig. 3, 

1909. 

Arnold and R. Anderson, U: S. Geol. Survey Bull. 398, 

pp. 85, 86, pl. 30, fig. 3, 1910. 

Venus (Chione) pertenuis Gabb. F. M. Anderson, California 

Acad. Sci. Proc., 3d ser., Geology, vol. 2, p. 195, 1905. 

Shell relatively thin, reaching a large size; shape 

variable, slightly or decidedly elongate, slightly 

inequilateral, anterior end extended. Lunular area. 

moderately depressed. Sculpture consisting of co.arse 

concentric waves and fine concentric threads. Near 

the ventral margin the waves are lower and more 

closely spaced, or they may disappear. Hinge of 

right valve consisting of ~ slender anterior cardinal, 

a heavier middle cardinal, and a long, slender, deeply 

bifid posterior cardinal; hinge of left valve consistingof a heavy anterior cardinal, a slightly heavier middle 

cardinal, and a long, thin posterior cardinal. Pallial 

sinus deep, very narro"N, ascending. 

Holotype: Length 58 millimeters, height 52 millimeters, diameter (both valves) 24 millimeters. Topotype: Approximate length 62 millimeters, height 52 

millimeters; diameter (both valves) 25.5 millimeters. 

Figured specimen from Santa Margarita formation: 

Length 79 millimeters, height 63 millimeters, diameter 

(both valves) 38 millimeters. Specimen figured by 

Arnold: Length 91 millimeters, height 75 millimeters, 

diameter (both valves) 44.6 millimeters. 

The very narrow pallial sinus of this species indicates. 

that it is an Egesta, although the upper posterior 

slope is not flattened, and therefore the p<;)sterior end 

is not truncate. Figure, 2 on Plate 16 shows part of 

the pallial sinus impressed on the internal mold of a. 

topotype and showing where the shell is broken. 

The hinge (pl. 16, figs. 5, 6) is visible on shells from 

.Kern River, where, in contrast to other localities, 

the shells are beautifully preserved. The right 

posterior cardinal of the specimen shown in Figure 5 

was broken after the description was written. So' far 

as the hinge is concerned 0. (E.) pertenuis closely resembles grayi and inocerijormis, but its left anterior 

cardinal is a little heavier, and its left middle cardinal 

is not quite so heavy. 

The specimens shown on Plate 16, figures 2, 3, may 

be regarded as topotypes, as they were collected from 

the Turritella ocoyana zone in the general region of 

the type locality. Figure 3 represents a slightly 

elongate shell that closely resembles the holotype (pl. 

16, fig. 1). Figure 2, which represents a more elongate 

shell collected at the same locality, shows that the 

shape is variable. Most specimens from the Santa 

Margarita formation are elongate. (See pl. 16, fig. 4.) 

Arnold figured a large elongate specimen from the 

Turritella ocoyana zone of the Coalinga district. The 

shell is also variable in thickness, but in virtually all 

specimens it is so thin that the concentric waves are 

impressed on internttl molds. 
4-MERICAN TERTIARY MOLLUSKS OF THE GENUS CLEMENTIA 41 

According to Smith, 39 Venus pertenuis is found in the 

Vaqueros," Temblor," Santa Margarita, and Purieima 

faunas of California-that is, its range is lower Miocene to lower Pliocene. Apparently all the specimens 

in the collections of the United States National Museum are from the middle Miocene Turritella ocoyana 

zone and the upper Miocene Santa Margarita formation. 

In the Santa Cruz folio 4? the Purisima formation 

is c9nsidered upper Miocene and Pliocene, but it is 

now generally regarded as· of lower Pliocene age. 

Type locality: ''From the Miocene, at Griswold's 

on road to New Idria, Monterey· County" [San Benito 

County, Calif.] .. 

Other localities: Lower Miocene (Vaqueros fauna), 

California (Smith) .

41 Middle Miocene ( Turritella 

ocoyana zone), Griswold's, by Vallecitos Valley, San 

Benito County, Calif.; ll. W. Turner, collector; 

station 213; one specimen (topotype). Middle Miocene ( Turritella ocoyana zone), Griswold ville,' Fresno 

County (apparently error for San Benito County), 

Calif.; H. W. Turner, collector; station 422; one 

specimen (topotype). Middle Miocene ( Turritella 

ocoyana zone), Vallecitos Valley, San Benito County, 

Calif.; H. W. Turner, collector; station 424; four 

specimens (topotypes), two of which are figured. 

Middle Miocene ( Turritella ocoyana zone), south side 

of the Vallecitos, 3,72 miles due west of Ashurst place 

and about 1Pi miles south of Dixon Spring, SW. Pi 

sec. 9, T. 17 S., R. 11 E., San Benito County, Calif.; 

Robert Anderson, collector; station 5~15; two specimens (topotypes). Middle Miocene (Turritella ocoyana zone), Turritella-bearing bed on east flank of high 

hill northeast of Oil City, SE. Pi NE. Pi sec. 16, 

T. 19 S., R. 15 E., Fresno County, Calif.; Ralph 

Arnold and J. H. Pierce, collectors; station 4631; 

four specimens, one of which was figured by Arnold. 

Middle Miocene ( Turritella ocoyana zone), Turritellabearing bed about 11 miles north-northeast of Coalinga 

just below Big Blue serpentinous member in ridge in 

sec. 10, T. 19 S., R. 15 E., Fresno County, Calif.; 

Ralph Arnold, collector; station 4633; one specimen. 

Middle Miocene ( Turritella ocoyana zone), reef beds 

one-fourth mile south-southeast of Barton's cabin, 

in NW. ;!4 sec. 23, T. 25 S., R. 18 E., Devils Den district, Kern County, Calif.; Ralph Arnold, collector; 

station 4861; one specimen; identification doubtful. 

Middle Miocene ( Turritella ocoyana zone), reef bed 

1,72 to 3 miles west of Painted Rock ranch, Carrizo 

Plain district, San Luis Obispo County, Calif.; Ralph 

Arnold,_ collector; station 5161; one specimen; identification doubtful. Middle Miocene ( Turritella ocoyana 

au Smith, J.P., Geologic range of Miocene invertebrate fossils of California: California Acad. Sci. Proc., 4th ser., vol. 3, p. 174, 1912. 

49 Branner, J. C., Newsom, J. F., and Arnold, Ralph, U. S. Geol. Survey Gcol. 

Atlas, Santa Cruz folio (No. 163), pp. 5-6, 1909. 

11 Kew (U. S. Geol. Survey Bull. 753, p. 46, 1924) listed " Venus cf. V. pertenuis 

Gabb" from the Vaqueros formation of southern California (station 8137). This 

collection is not in the United States National Museum at the present time. 

zone), bluff on south bank of Kern River, 500 feet 

east of Barker's old ranch house, one-half mile north 

of Ant Hill, Kern County, Calif.; Robert Anderson, 

collector; station 6088; one specimen, figured. Middle 

Miocene ( Turritella ocoyana zone), south bank of 

Kern River, along abandoned irrigation ditch about 

300 yards east of old buildings at Barker's ranch, 

Kern County, Calif.; R. W. Pack and J.D. Northrop, 

collectors; station 6613; one specimen. Middle Miocene ( Turritella ocoyana zone), north bank of Kern 

River, bl~s above irrigation ditch about 1~4 miles 

northeast of Rio Bravo ranch, Kern County, Calif.; 

R. W. Pack and A. T. Schwennesen, collectors; 

stat_ion 6623 ;·one specimen, figured. Middle Miocene 

( Turritella ocoyana zone), about a mile southeast of 

Rio Bravo ranch, gullies ·draining southwestward 

from crest of 1,100-foot ridge due south of junction of 

Kern River and Cottonwood Creek, Kern County, 

Calif.; A. T. Schwennesen, collector; station 6611; 

one specimen. Middle Miocene ( Turritella ocoyana 

zone), small arroyo tributary to Adobe Canyon, W . .72 

sec. 36, T. 27 S., R. 28 E., Kern .County, Calif.; 

R. W. Pack and A. T. Schwennesen, collectors; 

station 6627; six specimens. Middle Miocene (Turritella ocoyana zone), southwest slope of. Pyramid 

Mountain, hard sandstone reefs just north of old road 

.running east an'd west between Kern River and Poso 

Creek, Kern County, Calif.; J. D. Northrop and R. W. 

Pack, collectors; station ~638; one specimen. Middle 

Miocene (Topanga formation), Aliso Canyon, creek 

bed one-half to three-quarters mile southwest of A. 

Joughlin's place, Los Angeles County, Calif.; W. q. W. 

Kew and C. M. Wagner, collectors; station 8127 

(Kew).42 Middle Miocene (Topanga formation), trail 

eading solJ,theastward from road over Santa Monica 

!Mountains up Sierra Canyon, Los Angeles County, 

Calif.; W. S. W. Kew and C. M. Wagner, collectors; 

station 8135 (Kew) .

42 Upper Miocene (Santa Margarita formation), Big Blue Hills, north bank of 

Domengine Creek, NE. Pi sec·. 33, T. 18 S., R. 15 E., 

Fresno County, Calif.; Robert Anderson and R. W. 

Pack, collectors; station 5833; four specimens, one of 

which is figured. Upper Miocene (Santa Margarita 

formation) t Big Blue Hills, 2Pi miles northwest of 

Domengine place; SW. ~4 sec. 18, T. 18 S., R. 15 E., 

Fresno County, Calif.; Robert Anderson and R. W. 

Pack, collectors; station 5827; three specimens; 

identification doubtful. Upper Miocene (Santa Margarita formation), Big Blue Hills, 2,72 miles northwest 

of Domengine place, about 1,000 feet northwest of 

station 5827, Fresno County, Calif.; Robert Anderson 

and 0. P. Jenkins, collectors; station 5828; one specimen. Upper Miocene ($anta Margarita formation), 

Coalinga district, just above big oyster bed one-fourth 

mile northwest of Perliss well, Fresno County, Calif.; 

12 These collections are not in the United States National Museum at the present 

time. 
42 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1926 

Ralph Arnold, collector; station 4848; two specimens. 

Upper Miocene (Santa Margarita formation), Tejon 

Hills, !{ern County, Calif. (Nomland 48). Lower 

Pliocene (lower part of Purisima formation), Santa 

Cruz quadrangle, Calif. (Branner, Newsom, and 

Arnold 44 ). 

Type material: Holotype (both valves in attached 

position), Univ. California Pal. Coll. catalog No. 12000. 

Doubtful species 

The following descriptions, which were added after 

this account was in proof, may represent Clementia, · 

but the species can not no~ be certainly identified. 

Astarte dubia D'Orbigny · 

Plate 17, Figures 1, 2 

Astarte dubia D'Orbigny, Voyage dans 1' Amerique meridionale, 

Paleontologie, vol. 3, pt. 4, p. 105, 1842; vol. 8, pl. 6, 

figs. 12, 13, 1847. 

According to D'Orbigny's figures, which are here 

reproduced, this species may be a Clementia. The 

dimensions given are as follows: Length 38 millimeters; height, 33 millimeters; diameter, 20 millimeters. The following is a free translation of D'Orbigny's statement concerning this species: 

I will not consider the age or locality of this species. I 

found it in a collection at Chuquisaca, and I was told that it 

came from Peru. It belongs, I think, to the Cretaceous terrains of these regions. · 

Though Chiquisaca is probably in the interior of 

Peru, it should be noted that D'Orbigny states that 

he found this specimen in a collection at Chuquisaca, 

not from Chuquisaca. It may possibly have been 

collected from the Tertiary beds in the coa~tal region 

of northwestern Peru, though, according to the 

figures, it is not the same as either of two undescribed 

Eocene and Oligocene species from Peru, specimens 

of which Doctor Olsson kindly sent me. 

43 Nomland, J. 0., Fauna of the Santa Margarita beds in the North Coalinga 

region, Calif.: California Univ. Dept. Geology Bull., vol. 10, p. 302, 1917. 

44 Branner, J. C., Newsom, J. F., and Arnold, Ralph, U.S. Geol. Survey Geol. 

Atlas, Santa Cruz folio (No. 163) p. 6, 1909. 

Venus brioniana Trask 

Plate 17, Figure 3 

Venus brioniana Trask, California Univ. Dept. Geology Bull., 

vol. 13, p. 151, pl. 5, fig. 1, 1922. 

Mr. Ralph B. Stewart called my attention to this 

species, which otherwise would have been overlooked. 

The holotype is an internal mold of a right valve, with 

part of the shell attached, impressed on coarse detrital 

rock. It has a length of, about 87.7 millimeters and a 

height of about 88.5 millimeters. So far as can be 

seen, this specimen is virtually undistorted. It has 

a trigonal shape and is only slightly inequilateral. 

The sculpture consists of Olementia-like waves that 

become obscure on the lower half of the shell. It can 

not be seen whether the shell has a lunule, and all the 

internal features are inaccessible. 

This specimen is less inequilateral and has a greater 

relative height than any large specimens of Clementia 

(Egesta) pertenuis examined, though it is quite similar 

on an enlarged scale to slightly elongate shells of this 

species, such as the topotype shown in Plate 16, 

Figure 3. Although this species is probably an 

Egesta, its disposition must await additional material. 

It has a much greater relative height than the holotype 

of Clementia (Egesta) martini, which, however,. is 

crushed, so that comparisons based on that specimen 

are unreliable. According to Trask, both Clementia 

(Egesta) martini and Venus brioniana are found in the 

Briones sandstone. They may represent the same 

species, and both may be the same as 0. (E.) pertenuis. There is no doubt that the outline of pertenuis 

is variable. As it is found in the Santa Margarita 

formation it would not be surprising to find it in beds 

lying between the Santa Margarita formation and the 

Turritella ocoyana zone. In Trask's photograph the 

shell is not correctly oriented and therefore appears 

too ineq uila teral. 

Type locality: Upper Miocene (Briones sandstone), 

Concord quadrangle, Calif.; Univ. California station 

177. . 

Type material: Holotype (right valve), Univ. California Pal. Coll. catalog No. 12377. 
( 

PLATES 14-17 

43 
PLATE 14 

[All figures natural size except as otherwise indicated] 

Page 

FIGURES 1, 2. Clementia (Clementia) dariena vetula Woodring, n. subsp. Holotype. Middle Eocene, southeast of Pijaguay, 

Colombia, station 1/986. U.S. Nat. Mus. catalog No. 354036 ___ ---------------------------------- 33 

3, 4. Clementia (Clementia) dariena vetula Woodring, n. subsp. Paratypes. Same ·locality. U. S. Nat. Mus. 

catalog No. 354031--------------------------------------------------------------------------- 33 

5. Clementia (Clementia) dar1:ena rabelli Maury. Holotype. Middle Oligocene (San Sebastian shale), near San 

Sebastian, Porto Rico. Am. Mus. Nat. Hist. Div. Geol. and Invertebrate Pal. catalog No. 22509 __ ____ 34 

6, 7. Clementia (Clementia) dariena dariena (Conrad). Middle Miocene (Gatun formation), Spillway, Gatun 

• Dam, Panama Canal Zone, station 5846. U.S. Nat. Mus. catalog No. 354039----------------------- 34 

8. Clementia (Clementia) dariena dariena (Conrad). Middle Miocene, Tubara, Colombia, station 1/988. Slightly 

elongate specimen. U.S. Nat. Mus. catalog No. 354040 __ -----------------------------.. ---------- 34 

9. Clementia (Clementia) dariena dariena (Conrad). Middle Miocene, near Tubara, Colombia, station 1/987. 

Elongate, slightly distorted specimen. U.S. Nat. Mus. catalog No. 354041__________________________ 34 

1Q. Clementia (Clementia) dariena dariena (Conrad). Neotype. Middle Miocene (Gatun formation), east of 

Gatun, Panama Canal Zone, station 6030. U.S. Nat. Mus. catalog No. 354038---------------------- 34 

11. Clementia (Clementia) dariena dariena (Conrad)? Holotype of Clementia brasiliana Maury. Lower Miocene 

(Estagao formation), agricultural station near Braganca, Brazil. After Maury, Brasil Servicio geol. 

mineral. Mon., vol. 4, pl. 24, fig. 3, 1925_ -------------------------------------------------------- 34 

44 
U . S. (:BOLO<:ICAr_, SUHYEY l'H<H'Jo}SSIOXAL P .\l'E lc 117. l'LATI•; ll 

1 / 

3 

... 2 

5 

4 

8 

6 

11 

7 

9 10 

A \I EHICA TEH.TIAH. r SPECIES (W CLK\IEI'\TlA S. S. 
U . S . GEOLOGICAL SURVEY l'HOFEI~SIOKAL l'Al'EH Hi. l'LATE 15 

) 

1 

2 

3 

4 \ 

.. 

5 

6 

A "\fERICAN TEH.TlARY SPECIES OF ECEST A 
PLATE 15 

[All figures natural size] 

FIGURE 1. Clementia (Egesta) conradiana (F. M. Anderson)? Upper Miocene (Santa Margarita formation), near Santa 

Margarita, Calif., California Acad." Sci. station 74. California Acad. Sci. catalog No. 2212 _______________ _ 

2. Clementia (Egesta) conradiana (F. M. Anderson). Holotype. Middle Miocene (Turritella ocoyana zone), La 

Panza Springs, Calif. After F. M. Anderson, California Acad. Sci. Proc., 3d ser., Geology, vol. 2, pl. 14, 

fig. 3 5' 1 905- 0

- - - - - - - - - - - - - - - - - - - - --- - - - - - - - - - -- - - -- - - -- - - ---- - - - - - - - - -- - ---- - - - - -- - - - -- - - - - - - - - -

3. Clementia (Egesta) martini (Clark). Holotype. Upper Miocene (San Pablo formation), Contra Costa County, 

Calif., Univ. California station 741. Univ. California Pal. CoiL catalog No. 11570 ______________________ _ 

4. Clementia (Egesta) grayi Dall. Holotype. Lower Miocene (Oak Grove sand), Oak Grove, Fla., station 2646. 

U.S. Nat. Mus. catalog No. 10738L_ --------------------------------------------------------------

5, 6. Clementia (Egesta) inoceriformis (Wagner). Holotype. .Middle Miocene (St. Mary~ formation), Portobello, 

Md. Philadelphia Acad. Nat. Sci. catalog No. 4303. The anterior and posterior cardinals are broken. 

The hinges glued on the interior are labeled "Shiloh, N.J." __ -----------------------------------------

45 

• 

Page 

r 

39 

40 

37 

38 
PLATE 16 

[All figures natural size] 

Page 

.FIGURE 1. Clementia (Egesta) pertenuis (Gabb). Holotype. Middle Miocene (T.urritella ocoyana zone), Vallecitos, Calif. 

Univ. California Pal. Coll. catalog No. 12000--------------------------------------------------------- 40 

2, 3. Clementia (Egesta) pertenuis (Gabb). Topotypes. Middle Miocene (Turritella ocoyana zone), Vallecitos, Calif., 

station 424. U.S. Nat. Mus. catalog No. 354042---------------------------------------------------- 40 

4. Clementia (Egesta) pertenuis (Gabb). Upper Miocene (Santa Margarita formation), north of Coalinga, Calif., 

station 5833. U.S. Nat. Mus. catalog No. 354045_~- ---------.. ----------------------------------.,.-- 40 

5. Clementia (Egesta) pertenuis (Gabb). Hinge of right valve. Middle Miocene (Turritella ocoyana zone), Kern 

River, Calif., station 6623. U. S. Nat. Mus. catalog No. 354044. The lower part of the posterior cardinal 

is broken--------------------------------------------------------------------------------------- 40 

6. Clementia (Egestci). pertenuis (Gabb). Hinge of ·left valve. Middle Miocene (Turritella ocoyana zone), Kern 

River, Calif., station 6068. U.S. Nat. Mus. catalog No. 354043_ -------·------------------------------ 40 

7, 8. Clementia (Egesta) salida Dall. Holotype. Recent, Topolobampo, Gulf of California. U. S. Nat. Mus. 

catalog No. 126352. The posterior cardinal is broken. 

46 
l'JWl'E~:-;10:\ .\L 1' .\l'E it l 17 . 1'1 ,, \TI~ JG 

1 2 3 

5 

6 -1 

7 8 

AI\1ERICA r TERTIAHY A D LT\ll\G SPECIES OF ECEST\ 
l ' I<OFI·::-;:-; Io'\ .\I . J' .\1'1·: 1( 11 7. 1'1 .. \Tl: 17 

1 

3 

• 

4 

2 

A'\JEilLC".N 'J'EitTHHY SPEC IE'\ OJ<' IWE.;T\ .\'\D J)OlJIITI•'UL Sl'I CIE ) 
PLATE 17 

[All figu~es natural size] 

Page 

FIGURES 1, 2. Astarte dubia D'Orbigny. Locality and age unknown. After D'Orbigny, A., Voyage dans !'Amerique 

meridionale, vol. 8, pl. 6, figs. 12, 13, 1847________________________________________________________ 42 

3. Venus brioniana Trask. Holotype. Upper Miocene (Briones sandstone), Concord quadrangle, Calif.; 

Univ. California station177. Univ. California Pal. Coli. catalog No. 12377__________________________ 42 

4, 5. Clementia (Egesta) conradiana (F. M. Anderson). Holotype. Middle Miocene (Turritella ocoyana zone), 

La Panza Sorings, Calif. California Acad. Sci. catalog No. 2152------------------------------------ 39 

47 
INDEX 

Page 

Acknowledgments for aid--------------------------------------------------- 7, 25 

Astarte dubia D'OrbignY------------------------------------------------- 42, pl.17 

Canyon Ferry, Mont., ground crack near, plate showing.------------------- io 

Clementia, American Tertiary species oL----------------------------------- 30-32 

description oL. ------. _ ---. _ --. ______ ------------------ _________________ 32-33 

distribution oL --------------------- _________________ ---- _______________ 25-26 

features of _______ --- __ -------------------- ____ ---- ___ -------------_______ 25 

geologic history of __ ---------------------------- __ ---------------- _______ 26-29 

paleobiologic significance._------- ______ ---- _____________ ---------------- 29-30 

(Clementia) dariena dariena (Conrad)----------------------------- 34-36, pl.14 

darienarabelli MaurY--------------------------------------------- 34, pl. 14 

vetula Woodring, n. subSP----------------------------------- 33, pl.14 

(Egesta) conradiana (F. M. Anderson)------------------------ 39-40, pls.15,17 

grayi DalL.-------------------------------------------------- 37-38, pl.15 

inoceriformis Wagner------------------------------------------ 38-39, pl.15 

martini Clark·---------------------------------------------------- 40, pl.15 

pertenuis (Gab b)---------------------------------------------- 40-42, pl.16 

Deer Park, Mont., lake formed by earthquake, plate showing________________ 10 

rock slide near, plates showing__________________________________________ 10 

wall of gorge below, plate showing_______________________________________ 10 

Egesta Conrad._---------------------------------------------------------- __ 36-37 

Limestone, joints in, opened by the Montana earthquake, plate showing______ 10 

Logan, Mont., twisted chimneys at, plate showing__________________________ 10 

Lombard, Mont., limestone cliffs and talus slope at, plate showing__________ 10 

railroad track near, broken by earthquake, plate showing________________ 10 

rocks thrown down on, plate showing________________________________ 10 

Manhattan, Mont., schoolhouse damaged by earthquake at, plate showing.. 10 

Metaplacenticeras Spath, comparison of, with Placenticeras Meek__________ 1-5 

californicum (Anderson)------------------------------------------------ 1, pl. 2 

pacificum (J.P. Smith) _______ : _______________________________________ 2, pis. 1, 2 

Missouri River, Mont., bottomland along, plate showing____________________ 10 

Montana, probability of future earthquakes in--------------------------~--- 22-23 

Montana earthquake of June 27, 1925, aftershocks at specific places __________ 17-20 

area affected by------_-------------- ____ --------------------------------- 15 

cause.s of. _______ --- ___ --------------------------------------------------- 22 

damage by fire after_---------------_------------------------------------ 8 

to buildings by----------------- __ ----------------------------------- 7-8 

to railroads by ________________________ ------------------------------- 8 

48 

Page 

Montana earthquake of June Zl, 1925, direction of the motion oL___________ 15 

emotions, sensations, etc ____________ ·---- ___ ------·--------------------__ 8-9 

epicenter, position oL __ -------------------------------------- _ ----- __ _ __ 17 

epicentral area, geology oL---------------------------------------- _______ 21-22 

geology of, plate showing·------------------------------------------- 8 

physiography oL ----------------------------------------------- _____ 20-21 

flow of oil and gas renewed·--------------------------------------------- 11 

focus of, location oL _ ---------------------~------------ _______ ----~--- ___ 22 

foreshocks of. __________ .-----------------_-- __ ----- ___ -- ______ ----_______ 17 

ground cracks made bY-------------------------------------------------~ 10 

injury to persons by ______ -------------------------------------- ____ ----- 8 

intensity of, at specific places •.• ----------------------------------------- 11-14 

isoseismals of. ______ --- __ --------------------------------- ______ --------- 16-17 

plate showing •. ---------------------------------------------.------_ 8 

mines not affected by----------------------- __ --------------------------- 9 nature of the motion oL ____ --- ___ -- ___ ---- ___ ---- __ --- _ -- _ _ _ _ __ _ _ ___ __ _ _ 15 

places near by where shock was not felt__________________________________ 15 

rock slides caused bY---------------------------------------------------- 9-10 

sand spouts caused by--------------------------------------------------- 11 

sounds produced by----------------------------------------------------- 15 

springs and wells, changes in •. ------------------------------------------ 10-22 

speed of translation oL __ ------------ _ ------------------- ____ _ _ _ _ _ _ __ __ __ 16 

summary on ______________ --------------- _____________ ---________________ 7 

time and duration of. •••• ------------------------------------'------------ 15-16 

Pardee, J. T., The Montana earthquake of June 27, 1925--------------------- 7-23 

Placenticeras Meek, comparison of, with Metaplacenticeras________________ 1-5 

Placenticeras meeki Boehm.--------------------------------------------- 2, pls.l, 2 

Reeside, John B., jr., A comparison of the genera Metaplacenticeras Spath and 

Placenticeras Meek •• _____ --------- ______ .--- __ ---------------___ 1-5 

Roy Gulch, Mont., ground shattered by earthquake at, plate showing_______ 10 

Three Forks, Mont., buildings damaged by earthquake at, plate showing.__ 10 

crack in road embankment north of, plate showing.--------------------- 10 

Venus brioniana Trask-------------------------------------------------~- 42, pl.l7 

White Sulphur Springs, Mont., jail damaged by earthquake, plate showing._ 10 

Woodring, W. P .. American Tertiary mollusks of the genus Clementia ______ 25-47 

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