UC-NRLF

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"B E R K E L E Y*\

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UNIVERSITY OF I
CALIFORNIA/

EARTH

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LIBRARY

THE PALEONTOLOGY OF THE

ZORRITOS FORMATION OF THE

NORTH PERUVIAN OIL FIELDS

THE JOHNS HOPKINS UNIVERSITY
STUDIES IN GEOLOGY

No. 3

EDITED BY

EDWARD BENNETT MATHEWS

THE PALEONTOLOGY

OF THE ZORRITOS FORMATION

OF THE NORTH PERUVIAN

OIL FIELDS

BY

EDMUND M. SPIEKER

BALTIMORE
THE JOHNS HOPKINS PRESS

1922

EARTH

SCIENCES

UBRARY

PRESS OF MEYER ft THALHEIMER
BALTIMORE. MD.

ss

i

THE PALEONTOLOGY OF THE ZORRITOS FORMATION
OF THE NORTH PERUVIAN OIL FIELDS

By EDMUND M. SPIEKER
CONTENTS

PACK

Introduction I

Previous work I

Geology of the Zorritos District 3

Analysis of the fauna 12

Systematic Part —

Family Terebridae 35

Conidae 37

Cancellariidae 42

Marginellidae 43

Buccinidae 45

Nassidae . .- 48

Muricidae 51

Doliidae 52

Cypraeidae 55

Cerithiidae 56

Turritellidae 59

Naticidae 87

Turbinidae 91

Nticulidae 93

Arcidae 95

Pectenidae 125

Anomiidae 127

Crassitellitidae 128

Lucinidae 132

Cariidae 134

Veneridae 138

Tellinidae 156

Psammobiidae . 162

THE PALEONTOLOGY OF THE ZORRITOS

FORMATION OF THE NORTH PERUVIAN

OIL FIELDS.*

INTRODUCTION.

This paper presents the results of a detailed study of a
collection of mollusks made by Dr. Joseph T. Singewald, Jr.,
from the Zorritos formation of northern Peru. Much of the
value their evidence offers is due to the careful stratigraphic
work done by Dr. van Hoist, of the Hague, Holland, and
Dr. Singewald, as a result of which the position of the
subsidiary units of the Zorritos formation has been estab-
lished, and a number of misconceptions concerning the
relationships of the units to themselves and to the under-
lying Heath formation have. been corrected.1

PREVIOUS WORK.

The first account of fossils from the neighborhood of
Zorritos was published in 1870 by Edward T. Nelson 2 as a
graduating thesis in the Sheffield Scientific School of Yale
Universitv. This work was based on a collection of fossils

* George Huntington Williams Memorial Publication No. 14.

1 The author wishes to express his indebtedness to Professor
Edward W. Berry under whose direction the work was done,
and to Dr. J. T. Singewald, Jr., of the Johns Hopkins University;
to Messrs. W. H. Dall, T. Wayland Vaughan, W. P. Woodring,
and Miss Julia A. Gardner of the U. S. Geological Survey and
U. S. National Museum ; and to Professor Charles Schuchert of
the Peabody Museum, and Dr. Henry A. Pilsbry of the Philadel-
phia Academy for the loan of material. The figures are the work
of George S. Barkentin.

2 On the Molluscan Fauna of the Later Tertiary of Peru, Trans.
Conn. Acad., vol. 2, pp. 186-206, 1870.

2 STUDIES IN GEOLOGY, No. 3

made by Mr. E. P. Larkin and Professor F. H. Bradley.
The fossils, which were collected in 1867, were labelled "Zor-
ritos, Peru," and comparisons made during the present
study indicate that most of them were probably from the
three members of the Zorritos formation. Nelson men-
tioned 36 species of gastropods and 24 of pelecypods ; of
the gastropods he named 19 species, and of the pelecypods
8 species, mentioning the remainder as indeterminate.

Nelson's work carries very little biologic and no geologic
significance. His comparisons were made with recent forms
only, and as a consequence of his omission of reference to
fossil species his work serves, as he states, (p. 186) simply as
"a catalogue of the genera found in the collection, with
descriptions of part of the species." Although most of his
descriptions are good, the small number of figured speci-
mens made his work difficult to deal with until his collection
was loaned by the Peabody Museum.

Between 1870 and 1899 nothing was published on the
geology and paleontology of the area. In the latter year
Josef Grzybowski,3 then an assistant in the Geological Insti-
tute of Cracow, published the first account of the geology of
the region. With his geologic data Grzybowski included a
study of mollusks collected by him, of which he described
35 species from the Zorritos formation, 14 of gastropods
and 21 of pelecypods. It should be noted that the fossil-
iferous beds designated by Grzybowski as Heath have been
proven to be Zorritos in age ; the fossils "catalogued by Grzy-
bowski as Heath are thus Zorritos. Fuller treatment of
that matter will be offered in the discussion of the stratig-
raphy. The interesting fact that of Grzybowski's 35 species
only two were recognized by him as identical with species
described by Nelson, and that the present work, with the
advantage of Nelson's collection, shows only 6 species to be

3 Die Tertiarablagerungen des nordlichen Peru und ihre Mol-
luskenfauna, Neues Jahrb., Beil. Bd. 12, pp. 610-664, pis. 15-20, 1899.

PALEONTOLOGY ZORRITOS FORMATION 3

common to the two collections, indicates that the two col-
lectors probably worked in different localities.

Grzybowski's account contained the sum total of data
available at the time Van Hoist and Singewald began their
work. The complexity of the regional structure is too
great, and the stratigraphic relationships are consequently
too deceiving to permit the obtaining of accurate results in
the short time spent at geologic observation by Grzybowski,
and it is not surprising to find that his deductions concerning
the Heath and Zorritos formations are frequently erroneous.
According to Singewald * the fossiliferous beds named as
Heath by Grzybowski" are part of the Variegated formation,
the median member of the Zorritos formation, and the
correlation of its few fossils could not be clear with that
misconception as to its stratigraphic position in the way.

GEOLOGY OF THE ZORRITOS DISTRICT.

The coastal region of northern Peru is desert from the
Gulf of Guayaquil southward to the Morrope valley, a dis-
tance of about 200 miles. The coast is fronted as a rule by
barren cliffs which are broken here and there by quebradas,
or narrow valleys, which extend inland ; where sandstone
is the underlying rock the cliffs are prominent, and where
shales occur there are no cliffs. The region behind the
cliffs is of bare hills, which extend in continuous succession
from the coast to the Cordillera d'Amotape, a coast range
about 2000 feet in average height, about 35 miles from
the Pacific Ocean in the latitude of Zorritos, and much
nearer to the coast in the vicinity of Negritos. In the
vicinity of Payta the country inland is more or less even,
consisting of a sandy plateau, but to the north of Cabo
Blanco it is rough, and sharp hills and narrow quebradas
break the surface into' an irregular, inaccessible region.
The rainfall is practically nothing, and the only signs of

4 Singewald, J. T., Jr., personal communication.

4 STUDIES IN GEOLOGY, No. 3

vegetation are those in the larger stream-courses, where
small amounts of water support meager plant growth.

The region from which the fossils described in this paper
were collected is in the vicinity of the town of Zorritos,
extending about ten miles north and south along the
coast, and varying distances inland. It is underlain by a
series of Tertiary sediments which have long excited com-
mercial interest on account of the petroleum they contain,
but which have received scant attention of scientific nature.
Oil wells near Zorritos have been productive since 1880, but
the location of drilling sites has been almost entirely accord-
ing to "wild-cat" methods, and not until recent years has
geologic work of any kind been applied to commercial
purpose.

The first study of the geology of the Zorritos region was
published by Grzybowski 5 in 1899, as the results of obser-
vations made during the course of a trip along the coast
north of Payta. He differentiated five formations, from
highest to lowest as follows :

Age Formation Character

(according to
Grzybowski)

Pliocene Payta .Conglomerates

Upper Miocene Talara Brown shales

Lower Miocene Zorritos Sandstones

Lower Miocene Heath Bituminous shales

Obligocene Ovibio Massive sandstones

The ages assigned by Grzybowski to the formations were
determined through the study of rather small collections
of fossils. The amount of material was too small in most
cases to permit the drawing of valuable conclusions, and in

5 Loc. cit.

PALEONTOLOGY ZORRITOS FORMATION 5

some cases, as will be seen later, his error in the determin-
ation of stratigraphic units led to erroneous results. It is
apparent in some instances that he mixed his faunas, includ-
ing in his collections species undoubtedly not indigenous to
the formations from which he was collecting.

Previous to the work done by van Hoist and Singewald
nothing further was published on the Zorritos region. Their
work, done during the winter of 1919-1920, was of highly
detailed order, covering thoroughly the area indicated above,
and extending well inland. The geologic structure of the
Zorritos country is so highly complex that nothing short
of very painstaking detailed work may be expected to yield
results, and superficial examination is almost certain to lead
to misconceptions, particularly if the worker confines him-
self to the exposures along the coast.

As a result of their investigation van Hoist and Singewald
differentiated the section which is reproduced in figure I.
The units there presented will be discussed in downward
succession.

The Payta and Talara formations do not occur in the
region from which van Hoist and Singewald collected. The
Talara beds appear at the southern end of the area, at Pied-
ras Redondas, consisting there of tan gypsiferous shales
similar in appearance to the sandy phase of the Heath for-
mation. No fossils were collected from these beds. Else-
where in the Zorritos district, ' that is, within a radius of
ten miles along the coast, with Zorritos at the center, the
Talara beds do not appear.

Grzybowski's Zorritos formation is the same as that
outlined by van Hoist and Singewald, with the exception
that he confused the Variegated beds with the Heath, and
did not recognize the upper and lower sandstone members
of the formation. It is perhaps best, in order to make
clear the necessary revision of Grzybowski's sections, to
quote for reference the critical parts of his presentation.

STUDIES IN GEOLOGY, No. 3

Ton.

Connoiba//

conglomerolrs, jand*to oca , local'i^ CaJcarfoos
Pos»i li -Ttrous, locoltu loose or>6 -O-ioble. Color

Gnren clo<(, 'ocoll^ ryd, #-«cf, purplish

shol«, ofttn frpi.ftroos, TYtath«rs a-m/'a/- t0

Ouster

P««»st««)T

Hrortf b«ds of j»bbl«s,wi»*J 8and<^ and argillaceous
int«rbedd«d with Variegated cla</s and loos«, ^r,'

Green clocj. /ocal'(f "d, ^*<f> purplish

Hrar«j b«dd«d iiflht Bellow sandstone w.'t*> sh«l(j inter
calations. Usually ptbbl^ and looo Ilij conjlomeratic.
f'rf^atotlij r«d Or rostij from ir»rt *tain5 .
yerif calcareous and -Posjiliferoas .

Thinner b«ddffd li^ht colored Sands1on«5 with abundant
• nt«rcalation3 of jracj To yellow, sand^ Jhal*5 some of
Which are farbencie«o</4 and contain planT fragments.

dorfe gre«( shales, »vitK corbonat« nodol«»,
dork brown loo$« cla«j fvi'ttj tnuch selcnile

Interbcdded d«rk freij shales, 1/Jht |re^ t0 <je)low,sh
5hal«s, and rh''r> b«<>5 of loose Sand.

, one inch =. £5O'.
Fig. I.— Section of the Tertiary of the Zorritos district.

PALEONTOLOGY ZORRITOS FORMATION 7

At Malpaso, near Caleta Grau, north of Zorritos, he
measured the following section:6

(a) Conglomerate, die zuweilen Rollstiicke iiber Faust-
grosse enthalten und viel versteinertes Holz

fuhren. Sie nehmen die hochsten Punkte des bis
150 m hohen Hiigelzuges ein.

(b) Sandsteine, mittelkornig, graugefarbt, bis 40 m

machtig, die bei Malpaso ganz gut zu beobachten
sind, da sie hier das Meeresniveau erreichen. Sie

sind grabbankig und enthalten senkrecht zu den
Schichtflachen stehende, bis 4 dm lange, meist
rotlich gefarbte, 6'fters verzweigte Cylindriten.

(c) Feinkornige, dunkle, harte Sandsteine mit Zwis-
chenlagen von dunkel graune Schiefern, bis 10 m
machtig.

(d) Rothe Schiefer, bis 12 m machtig; sie sind an man-
chen Orten durch graue oder grunliche Schiefer
vertreten.

(e) Schwarze, glanzende Schieferthone mit Spuren
von Pflanzen, 2 m machtig.

(f) Lignit, blatterig, schwarz, viel Thon enthaltend,
80 cm. bis I m machtig.

(g) Braune Schiefer, bituminos, mit Pflanzenspuren
(h) Austernbank von 80 cm. Machtigkeit.
(i) Bituminose Schiefer mit Gyps.

Beds a to c, inclusive, of this section, belong to the
Upper Zorritos formation, and were considered as Zorritos
by Grzybowski. Beds d to i, however, belong to the Var-
iegated formation ; they were considered as Heath by Grzy-
bowski, who misinterpreted them on account of the
lithologic similarity of the bituminous shales (units e, g,
and i) with those of the Heath formation. The shales of the

6 Loc. cit.

8 STUDIES IN GEOLOGY, No. 3

two formations are identical in appearance either fresh or
weathered, and thus offer every opportunity for confusion;
the shale of the Variegated, however, is always character-
ized by the presence of lignite (unit f) and one or two
oyster beds above and below the lignite, of which the lower
one is fairly persistent, and the other is more or less local
in occurrence. Such beds are not known to occur in the
upper Heath. The identity of the Variegated beds has been
proven beyond doubt through observation of its lower
contact with the underlying Lower Zorritos formation, and
the position of the Lower Zorritos in turn has been deter-
mined through tracing it as an unbroken unit to its contact
with the underlying Heath.

It is thus clear that the beds at Malpaso assigned to the
Heath by Grzybowski are Variegated, and that accordingly
the fossils collected by him from that locality, on the basis
of which he determined the age of his Heath, are not Heath,
but Zorritos in age. The true Heath formation is not known
to bear a molluscan fauna within the. Zorritos region. The
assignment of Lower Miocene as the age 7 of the Heath
formation is not certain; in the present state of knowledge
nothing can be said concerning its age further than the
obvious inference that it is older than the Lower Zorritos
formation.

A collection of fossil plants obtained from the Zorritos
district in 1875 by C. F. Winslow has been described by
Professor Edward W. Berry,8 who considered the beds that
contain them of Burdigalian age. Mention of this conclu-
sion is pertinent at this point on account of the change in its
application resulting from the recognition of the Variegated
beds at Malpaso, from which general locality the plants
were collected. Professor Berry based his stratigraph-

1 Loc. cit, p. 658.

8 Proc. U. S. Nat. Mus., vol.. 55, No. 2270, pp. 279-294, pis. 14-17,
1919.

PALEONTOLOGY ZORRITOS FORMATION 9

ic allocation of the plant horizon on the locality, which was
given by the collector as 20 miles south of Tumbes, and 200
to 300 feet from the ocean. This is undoubtedly the locality
north of Caleta Grau described by Grzybowski, the bed of
lignite there being the only one known in any of the forma-
tions occurring in the neighborhood, and the location other-
wise agreeing with the account given by Mr. Winslo-w. It
should be noted that the evidence of the plants bears upon
the upper Variegated formation instead of the Heath, as
stated by Professor Berry in accordance with Grzybowski's
determination of the beds.

That point clear, discussion of the section as recently
determined may be continued from the point at which it was
left. The Upper Zorritos formation consists at the top of a
yellowish concretionary sandstone, called by van Hoist
and Singewald the "cannonball" sandstone on account of
the characteristic weathering out of the concretions in cliffs.
This peculiarity of the sandstone suggested the name of
Piedras Redondas, at which place it occurs prominently in
the headlands, and at some points it forms cliffs whose
erosion form is recognizable for miles. The "cannonball"
sandstone underlies the Talara beds at Piedras Redondas.
Underlying the "cannonball" is a series of massive beds, in
part heavy conglomerates, and in part sandstones which are
locally calcareous, bearing fossils and often petrified wood.
Yellow is the prevailing color. The Upper Zorritos mol-
luscs later discussed in detail were obtained from these
beds. The base of this series consists of very friable sand-
stones which weather into a yellow sand.

Directly underlying the yellow friable sandstones are the
beds d — i of Grzybowski, which form the upper part of the
Variegated formation. The highest of these are green clays,
locally red, gray, and purplish, the varicolored assemblage of
which suggested the name of the formation. Below these
clays are the carbonaceous Heath-like shales, oyster beds

io STUDIES IN GEOLOGY, No. 3

and lignite mentioned in connection with Grzybowski's
sectiqn. Beneath bed i of his section are heavy pebble beds,
conglomerates, loose, friable sandstones, intercalated with
highly colored clays similar to the uppermost bed of the
formation. These brightly colored clays form the base of
the Variegated formation.

The Lower Zorritos formation, which follows the Var-
iegated in downward succession, consists above of heavy,
massive, in places conglomeratic sandstones, normally light
yellow in color, but frequently stained red or brown by iron.
The lower part of the formation is locally very calcareous
and fossiliferous ; most of the molluscs hereinafter described
from the Lower Zorritos came from these lower horizons.
The basal Lower Zorritos sandstones are thin-bedded, with
abundant intercalations of gray to yellow sandy shales,
some of which are carbonaceous and contain plant fragments.

The Heath formation, the lowest exposed in the district,
consists primarily of gray shales, which weather brown,
with light gray to yellowish gray sandy shales and thin beds
of loose, unconsolidated sands interbedded with dark gray
shales. The uppermost beds are the soft dark gray shales,
with carbonate nodules ; they contain much selenite and
weather to the characteristic reddish brown color, excepting
the vicinity of Sechurita and in Quebrada del Grillo, where
they weather to a pale green. Below the upper shaly beds
the sandy phase appears ; it consists of a thin-bedded alter-
nation of very loose and unconsolidated sands with clays
lighter in color than those mentioned above. At and south
of Quebrada del Grillo the sandy horizon is represented by
a bed of heavy conglomerate. The entire Heath series is
measurable in thousands of feet; its thickness is unknown,
the base not having been seen, but several thousand feet of
it have been observed on the coast south of Zorritos. The
Heath is the mother-rock of the petroleum mined in the
Zorritos 'region, and most of the notable production is
obtained from horizons in its sandy phase. The Zorritos

PALEONTOLOGY ZORRITOS FORMATION II

formation yields oil in places, but the source is undoubtedly
the Heath formation.

Faulting rather than folding characterizes the structure of
the region, most of which. consists of a series of tilted fault-
blocks. There are several lines of major faulting, the
direction of which is a bit more northerly than thai of the
coast line, parallel to which the fault-blocks are usually tilted
inland. In addition there are countless transverse faults
which break the region up into a veritable mosaic. The
general result is, ordinarily, that the Heath formation is
exposed at the base of the major blocks, with either the
Upper Zorritos or the Lower Zorritos at the summit, the
series dipping inland until it is interrupted by the next
longitudinal fault, or crossed by a diagonally transverse
fault. About Boca Pan the whole series is broken up into
very small blocks, and the structure is unusually intricate.

The sections exposed along the coast, where the cliffs
parallel, roughly, the lines of major faulting, give small hint
of the actual structural complexity of the region, and, with
the exception of points at which transverse faults break the
series, the beds appear to dip in continuous succession, undu-
lations bringing the various members to light and carrying
them under again. The impression obtained from Grzy-
bowski, who saw little more than the coastal exposures, is
rather that there is no great complexity. The recent study
has brought out the true nature of the structure as indicated
above. Grzybowski's idea that no great structural difficul-
ties existed was undoubtedly the reason for his failure to
recognize the separate entity of the Variegated beds.

At a point not far north of Caleta Grail the Heath beds
are faulted against the Variegated on the line of one of the
transverse faults. The similarity in lithology of the two
beds might lead a hurried worker to miss the fault; how-
ever, on the ridge north of Caleta Grau the Lower Zorritos
formation is seen to overlie the Heath, and the contact be-
tween the two may be clearly traced to the point at which

12 STUDIES IN GEOLOGY, No. 3

it is cut off by the transverse fault mentioned, and the
Lower Zorritos is juxtaposed to the Variegated. From the
ridge at the point where the three formations meet, the whole
situation is clear.

The principal drainage of the region is determined by the
fault-lines, and the rough physiographic aspect of the terrane
is due to the irregular disposition of the fault-blocks, which
form the hills between the drainage channels.

ANALYSIS OF THE FAUNA.
I — GENERAL CONSIDERATIONS.

An analysis of the collection here studied, made from
either the biologic or the geologic viewpoint, can present
evidence of positive nature almost exclusively. It is almost
certain that enough of the entire Zorritos fauna is as yet
unknown to forbid the drawing of conclusions based on the
absence of any element, and although much can be deduced
from the presence of those forms now known, the satisfy-
ing completeness of a study which includes all inferences,
positive and negative, must be foregone until highly detailed
collecting either furnishes elements yet to be known or
proves that the majority of the species are embodied in the
present study. In the case of the Upper Zorritos formation
it is not certain that a very large fauna exists, although
it is probable that considerable additions may be made
through protracted search for new localities, but both the
Variegated and the Lower Zorritos formation give promise,
through a multitude of indeterminate fragments in the
matrix of the present collection, of a fauna which may
approach in richness some of the famed Antillean and Flor-
idian assemblages of approximately similar age.

One difficulty which must be solved before the study of
these faunas can be completed is the procuring of good
material. This applies in particular to the minute and more
delicate species. The matrix in which most of the specimens

PALEONTOLOGY ZORRITOS FORMATION 13

so far collected occur is far too resistant to permit the
extraction by any known means of specimens at all suscep-
tible to injury through moderate violence; the sands are
firmly cemented by calcium carbonate, and attempts at
removal of matrix by loosening it through chemical destruc-
tion of the cement fail because the shell material is of the
same composition, and is destroyed along with the matrix.
Loose matrix on some of the specimens in the Nelson
collection indicates that there are probably some localities
at which the sands have not been cemented, and with the
discovery of such places a large fauna may be revealed to
the paleontologist.

II — BIOLOGIC ANALYSIS.

The present study has made known 101 species and
varieties of mollusks, of which 44 are gastropods and 57
pelecypods. . Two of the species are indeterminate and 64
are new. 31 occur in the Upper Zorritos formation, 15 in
the Variegated, 43 in the Lower Zorritos, and 20 from
Nelson's collection do not occur in the material collected by
Singewald, and are thus not stratigraphically located beyond
the high probability that they came from the Zorritos for-
mation.

The gastropods are somewhat widely distributed through
the biologic scheme, most of the 18 genera being represented
by one or two species, and only two genera, Conus and
Turrit ella, being represented by more. In the case of the
Cones this is not surprising, since the normal tropical fauna
contains a heavy representation of that genus. The Tur-
ritellas, however, are not ordinarily diversified in the tropics
to the extent found in the Zorritos fauna, and the seventeen
species and varieties here presented seem entirely out of
proportion with the rest of the fauna. Accidents of collecting
might explain the relatively more complete assemblage of
the genus, and thus relieve the disproportionate aspect of the
group, but granted that, the number is still larger than one

14 STUDIES IN GEOLOGY, No. 3

would expect. The recent Peruvian littoral fauna contains
four species of Turritella. Maury 9 lists but three species
out of the 451 discussed by her from Santo Domingo; the
rich Bowden fauna contains but two species; the Chipola
fauna contains six species and varieties ; 10 the Oak Grove
two j11 the Tampa silex beds five species and varieties.12 The
only American tropical fauna which approaches the Zorritos
in mere number of Turritellas is the extremely rich Cal-
loosahatchie assemblage, .which contains 12 species and
varieties. It is worthy of note that of the twelve, seven
are peculiar to the deeper water faunule of the Calloosa-
hatchie River locality, and all occur there; two more are
peculiar to that locality and the Shell Creek, which offers a
facies shallower, though probably still deep, and thus at
least cooler water. It is thus probable that all of these
species are deeper water forms. The other Pliocene faunas
are poor in Turritellas; the Waccamaw contains but one.
The Duplin Miocene, a warm-water fauna, contains about
nine or ten species and varieties, all of which are very much
alike.

In face of comparative data such as these the occurrence
of so varied and extensive a development of the genus in a
fauna, the data on which are by no means complete, is at
least interesting. Analysis of such scattered data on the
habitat of the genus as are available shows that Turritella
seems to prefer comparatively deep water ; however, nothing
definite can be said on that question, since published data
conflict to large extent, and there is thus no certainty. It is
difficult, in the absence of even a little reliable ecologic
information, to say whether or not the abundance of the
Turritellas in the Zorritos fauna means a deep-water origin
of the beds enclosing them. The evidence of the lithology,

'Bull. Amer. Pal., vol. 5, No. 29, pp. 129-130, 1917.

"Ball, W. H., Trans. Wag. Inst, vol. 3, pt. 6, p. 1577, 1903.

11 Ibid., p. 1590.

12 Ibid., p. 1567.

PALEONTOLOGY ZORRITOS FORMATION 15

as well as that of the other species, seems to demand a strictly
littoral zone as the habitat of most of the fauna. Most of the
Upper Zorritos Turritellas, for example, occur at Quebrada
del Toro, in a sandy matrix which does not bespeak deep
water bottom conditions.

It is possible, however, that those horizons which are
notable for the larger, more diversified Turritellas, chiefly of
the Upper Zorritos formation, may represent at least tem-
porary occurrence of deep-water conditions. If that is the
case, the coast must, have had a declivity sharp enough to
permit the carrying of somewhat coarse materials out into
deep water, and the run-off must have been at least locally
strong enough to wash sands and small pebbles some dis-
tance beyond the strand. It is entirely possible that periods
of flood on a steeply sloping coast may have carried the
coarse material found with many of the Upper Zorritos
fossils into comparatively deep water.

The presence of a Triumphis in the collection is of interest
in that the genus, as now recognized, contains but one other
species, and that living, restricted to the West Coast. The
Zorritos species is apparently the first of its direct ancestors
to be known. It is highly probable that a comparative study
of the genus Agasoma Gabb will show a relationship to
Triumphis closer than*that now expressed, with the possi-
bility that Agasoma may have to go into synonymy. In the
latter event the genus will have a broader range, with more
fossil species.

The remaining gastropods are almost uniformly of groups
naturally to be expected in a tropical American Miocene
fauna, and the chief interest they offer lies in their geologic
affinities. One species of Solcnosteira is interesting in that
it is of a type not widely known from the Miocene, but
developed to some degree in the recent fauna of the West
Coast. A single species from Gatun is the only other known
in the Miocene. The ancestors of the recent forms are thus
found in the Panamanian — Peruvian region. Other fossil

1 6 STUDIES IN GEOLOGY, No. 3

species, notably from the Floridian Tertiary, are differently
developed.

Phos latirugatus represents a type which is apparently
little developed anywhere in known faunas; most of the
Photina-e have more rounded, less sharply carinate whorls,
and members of the type here found, with a distinct
shoulder, are not common.

The pelecypods offer somewhat more widely distributed
diversity than do the gastropods, although they, too, are
unbalanced on account of their incompleteness, as a result
of which statistical biologic discussion can enter into few
features with profit. The species are distributed through 20
genera and 13 families. The Taxodonts are an important
element, being represented by 20 species and varieties, of
which 19 are of the genus Area. These 19 species and var-
ieties, distributed through 4 subgenera and sections, are the
most brilliant and prolific, if not the most interesting of the
Zorritos pelecypods. The Lower Zorritos group is charac-
terized by smaller species, and the Upper Zorritos and
Variegated by larger, heavier forms. The closely related
groups have been difficult to separate satisfactorily, and the
author is fully conscious of the fact that others may view
the present treatment with thoughts of revision; however
the grouping here offered is believed to be the most rational
according to the more or less unexpressed limitations of
morphologic differentiation, and the amount of material
available for use in discriminating some of the more trouble-
some species has been sufficient to give the author some
measure of confidence in his decisions.

It is apparent that the .Zorritos region, as well as the
Antilles and Florida, was the scene of the divergence of the
Cunearcas from the true Scapharcas ; the presence of three
species, Area larkinii Nelson, Area pantheonensis n. sp., and
Area zorritensis n. sp., very near the border-line between
the groups, each exhibiting some feature either somewhat
anomalous to the preponderance of other sectional char-

PALEONTOLOGY ZORRITOS FORMATION 17

acters, or indicative of progressive change from one type to
the other, offers further evidence of the transition between
the sections, and adds to the list of illustrations which show
the completeness of the gradation between them.

The presence of the subgenus Noetia is of interest in its
addition to the Miocene occurrence of that group, which is
distinctively American in fossil distribution. Grzybowski
described a species, A. (Noetia) modesta, from Zorritos
which is apparently different from Area cholana, and an-
other unstudied Noetia occurs in a collection of stratigraph-
ically unlocated fossils from Peru which, by inference
from the locality labels, may have come from the Zorritos
formation. The absence of the subgenus Area s. s., an
element normally to be expected in a fauna such as this,
means little as yet.

The one Pecten, P. woodringi, is of the small, tropical
type. Anomia berryi is interesting on account of its size
and weight; the Upper Zorritos and Variegated habitats at
which this species has been found must have been peculiarly
favorable.

One of the striking characteristics of the Lower Zorritos
faunule from Quebrada Zapotal is the abundance of Cras-
satellites berryi n . sp., a distinctive type, undoubtedly repre-
senting a peculiar divergence from the ancestral strain of
C. gibbosus Sowerby, now living on the Peruvian coast.
C. nelsoni (Grzybowski) probably represents the stock
which preceded C. gibbosus in direct genetic line.

The occurrence of dementia dariena Conrad, a member
of a genus with sparse fossil and not much wider recent
distribution, is worthy of note. This species is known so
far only from Panama, Costa Rica and Peru, and its clear
identity makes it a conspicuous element, despite the fact that
it is not known to be abundant. It is unfortunate that the
stratigraphically located specimens of C. dariena in the
present collection are not well preserved, the ones in the

1 8 STUDIES IN GEOLOGY, No. 3

uncertainly located Nelson collection, being in very good
condition, having served best for morphologic study ;, the
poorer material gives hints of some variations both in size
and form which may deserve systematic recognition, but
not enough can be substantiated to make distinctions. The
Dosiniinae of the collection are further characterized by the
occurrence of a large, heavy form, Dosinia grandis Nelson,
very much like D. orbicularis Agassiz, of the European
Miocene.

Perhaps the most interesting single occurrence in the
pelecypod fauna is that of Amiantis incrassata var ovoidalis
Sacco, a variety common in the Tongrien of Europe, and of
a genus very rare in known American faunas. It is hardly
possible, in view of the several variations of A. incrassata
in Europe, that this particular variety reached Peru as a
direct migrant from the central European seas, and the ap-
parent absence of the species in well known faunas occurring
along possible lines of migration and at the same general
time horizon lends strength to that assumption. It seems
far more likely that parallel development may account for
the evolution of characters in the Peruvian form exactly
similar to these of the European incrassata.

The Raetas are always an interesting element, and the
Zorritos fauna, with three well-defined yet closely related
species, presents some unusual developments in that group.
Labiosa (Raeta) gardnerae occurs in great profusion in the
Upper Zorritos sandstone at Quebrada de las Alturas, and
one specimen has been found in the Lower Zorritos. L. ven-
tricosa is a short, inflated shell unlike any known fossil
Raeta, and of very interesting aspect. Some of these small
fossil Raetas show affinity to the section Ra'etina Dall,13 of
recent Indo-Pacific distribution, but they all show evidence
of the posterior lateral tooth, the absence of which is a

Trans., Wag. Inst, vol. 3, pt. 5, p. 882,

PALEONTOLOGY ZORRITOS FORMATION IQ

sectional characteristic of Ractina. They are smaller in size
than the usual Miocene Raetas.

The Corbulas of the section Aloidis present transitions
between other similar forms from Antillean horizons, feat-
ures which are brought out in the systematic discussion of
the, group. This genus, with six species, in two sections,
stands next to the Areas in point of specific diversity.
Corbulct (Cuneocorbula) acutirostra n. sp. is a sharply
defined species with an unusually marked development of
the posterior keel, and is most closely related to two species
from the Oligocene of Germany.

A rapid survey of the faunal list confirms the natural
expectancy of finding a tropical facies, and it is hardly worth
while to use space for detailed discussion of that point.
Almost all of the genera thus far described from the region
are characteristic of the tropical seas, and none is extrane-
ous to such a habitat. It is true that some of the types have
been found in cooler-water faunas, but such have a wider
range, and their presence in this fauna introduces no dis-
cordant element.

The preponderance of ecologic evidence offered by the
fauna, and supported by the type of sediments in which they
were entombed, indicates a shallow water habitat as the
rule. All of the species are of genera now living in the
littoral zone, most of them present in the recent fauna of
that zone on the Peruvian coast, an excellent list of which
has been published by Ball.14 Some of the matrix verges on
the conglomeratic in character, containing pebbles of the
sort one would expect to find in somewhat agitated waters,
and hardly in the quiet of the usual off-shore bottom. Most
of the species, however, occur in sediments distinctly of the
sandy littoral type, and it is fairly certain that the fauna
flourished, for the most part, in that zone.

14 Proc. U. S. Nat. Mus., vol. 37, No. 1704, pp. 147-294, pis. 20-28,
1909.

2o STUDIES IN GEOLOGY, No. 3

In the systematic presentation of this fauna the author has
endeavored to supply accurate references to all forms dis-
cussed. These references are to original descriptions in all
cases excepting those in which subsequent treatment is
better either through superiority of figures or greater com-
pleteness of description. References have been made to all
species with which comparison is pertinent, and although it
may seem to some that too large a number of similar forms
has been quoted in the remarks on some of the species, the
writer has included such as are presented out of first-hand
knowledge of the assistance they render to students of
similar faunas. Paleontologic work as a whole is character-
ized by too great brevity of treatment in matters of detail
and comparison — brevity at the expense of efficiency on the
part of those who find need later to use the work; and it
is certainly for the benefit of such, in greatest measure, that
details are mentioned at all.

Ill — GEOLOGIC ANALYSIS.

The determination of the age of a fauna, and particularly
one from a region somewhat distant from the nearest well
known locality, ordinarily involves a number of uncertain-
ties which make advisable, if not necessary, the obtaining of
complete data before valuable conclusions may be drawn.
This is particularly true of faunas which show affinities suf-
ficiently scattered to cause careful weighing of all evidence,
and since many fossil assemblages are of such character an
attempt at correlating a fraction of a fauna, if advisable,
should be accompanied by some statement as to the degree
of faith to be placed in the results. It may be said in behalf
of the present study that the affinities of the Zorritos fauna,
and particularly that of the Lower Zorritos formation, are so
strongly centralized that the discovery of the numerous
additional species which no doubt exist may confidently be
expected to confirm the present deductions, and under no
circumstances to change the character of the evidence

PALEONTOLOGY ZORRITOS FORMATION 21

beyond the possible introduction of a few exotic or other-
wise interesting relationships.

The treatment of a fractional fauna such as that here con-
sidered is more a matter of judgment than of tabulation
and derivation of percentages. The system of expressing
fauna! relationships through percentages is faulty under the
best circumstances if the specific determinations or the align-
ment of affinities is at all loose, and so much variation is
encountered in both of these matters that the evidence of a
group of species needs to be tempered by a differential
weighing of the strength of individual determinations and
the degree of closeness in relationship shown by separate
forms. Could systematic paleontology be standardized the
student would be freed of the necessity for examining closely
the results obtained by others, but the element centering
about the personal equation is inevitable in its effect on the
character of a study, and the student must take separate
account of determinations if his work is to be balanced. So
much depends on the drawing of specific lines that a work
in which it is necessary to make close distinctions is sure to
reflect more the character of the worker than that of the
fauna in matters which hinge on minute determinations.
And it is obvious that anything verging on predisposition is
dangerous.

Although in the present work the major elements will be
expressed in the form of percentages, their value must be
considered to lie in the preponderance of affinity they reveal
rather than in any intrinsic quality of the figures themselves.
It is obvious that the smaller relationships, such as those
with the recent faunas, can not bear much weight for two
reasons which hinge on the size of the fauna: first, the
incompleteness of the assemblage makes an attempt at
expressing proportions probably false, and second, the per-
centages obtained in dealing with smaller total numbers of
fossils are out of proportion with the ideas the numbers
should actually express. In a group of forty species two

22 STUDIES IN GEOLOGY, No. 3

represent five per cent ; if collecting were sure to have been
strictly representative such figures might bear weight,
but such is rarely the case, and is not recognizable if it does
occur. It is obvious that the determination of affinities in
the case of a small fauna of doubtful or heterogeneous aspect
is attended by danger, and it is fortunate for the results of
the present study that the affinities of the Zorritos fauna are
strong enough to leave no doubt as to its age relative to the
known Antillean faunas, and little or no doubt as to its
position in the standard European time-scale.

The accurate determination of the horizons from which
the fossils were taken offered a first-hand opportunity for the
discernment of differences in the faunal characteristics of
the three members of the Zorritos formation, and in view
of the superficially diiferent appearance of the fossils the
work was begun in anticipation of the discovery of faunal
zones, possibly of distinctly different ages. As will be seen
when the three faunas are taken up in detail, such difference
is by no means marked, and although the Upper Zorritos
may to some degree be differentiated from the Lower Zor-
ritos in age, the difference between the two faunas is probably
more one of facies than of time. The Variegated faunule is
too small to permit the drawing of conclusions further than
to indicate its relationship to the neighboring beds.

Six of the eighty-one species are common to the Upper
Zorritos and the Variegated ; two are common to the Lower
Zorritos and the Variegated ; four are common to the Upper
and Lower Zorritos, and a number of species from the
Lower Zorritos formation have close relatives in the Upper
Zorritos. These figures lead to the observation that in point
of common species the Variegated faunule is more closely
related to the Upper Zorritos than to the Lower Zorritos,
but the incompleteness of the Variegated faunule leaves
too many possibilities open to permit serious consideration
of that. .

There is, however, apparently a difference in facies be-

PALEONTOLOGY ZORRITOS FORMATION 23

tween the faunules of the Upper and Lower Zorritos forma-
tions which may well prove constant in face of further
collecting, and may thus serve as a valuable guide to the
recognition of the units where fossils are found and there is
doubt, owing to structural complexities, as to the identity of
the beds. This difference appears most clearly expressed in
the Areas and the Turritellas, Jrecause of the abundance of
those forms and their marked difference in facies. The
Areas of the Upper Zorritos formation, as has been noted,
are larger, heavier shells than those of the Lower Zorritos,
and a similar difference occurs in the Turritellas. Separate
species of other single genera do not occur in both forma-
tions, as far as the present collection shows.

The difference in the Areas may be an index to a greater
time difference between the Upper and Lower Zorritos forma-
tions than the general affinities now apparent seem' to demand.
The Areas of the Upper Zorritos appear to be of a later type,
some of them closely related to A. idonea Conrad, a species
which is most abundant in the Chesapeake Miocene, in beds
of Tortonien age. Others are close to A. grandis Broderip
and Sowerby, and A. tuberculosa Sowerby, both more
modern types. Cerithium Grillanum n. sp. is very close to
C. russeili Maury, from the Helvetien of Santo Domingo,
and two of the Turritellas, T. nelsoni and its variety ro tun-
data are close to species from the Helvetien of Europe.

These later affinities, despite the fact that they are over-
shadowed in present number by the strictly Burdigalien
affinities, promise a greater possibility of finding more evi-
dence of their kind than there is for the Lower Zorritos
faunule, which in its larger number contains a proportionally
much smaller Helvetien and Tortonien element. Thus,
although it is not possible to say that the Upper Zorritos is
very much younger than the Lower Zorritos, it is advisable
to indicate the definite possibility that future work may
reveal a Helvetien element sufficiently strong to necessitate
considering the fauna of that age. In the present state of

24 STUDIES IN GSOUJGY, No. 3

knowledge it appears to be later Burdigalien in age. Such
a difference between the Upper and Lower Zorritos forma-
tions is not irrational to suppose when we consider that the
Variegated formation, with its continental beds, may contain
a hiatus of considerable magnitude.

As might be expected, the fauna as a whole has its nearest
relatives in the general region between Panama and Florida.
The alternative anticipation would be to look for affinities in
the Tertiary of Chile, Patagonia, and New Zealand, and
although in rare cases such occur, they are not suggestive of
any well-defined connection between the faunas of the two
regions. Grzybowski noted the presence of affinities with
the Navidad and Coquimbo beds of Chile, five of the sixteen
species in his Heath (^Variegated) faunule being identical
with or closely related to Chilean species. These five species
are all in his list from the locality north of Caleta Grau,
near Malpaso, at which he was unquestionably dealing with
the Variegated formation. No such species has appeared
in the Hopkins collection, and very few which show any
affinity to Chilean species. Grzybowski noted no Chilean
element in his Zorritos fauna, which is equivalent indiscrim-
inately to the present Upper and Lower Zorritos. He did,
however, note a Chilean element in his Payta fauna.

It is probable that at least during the periods of the Upper
and Lower Zorritos formations connection with the south-
ern coast was cut off. A point of land similar to that about
Point Aguja and Gabo Blanco, which now diverts the colder
Humboldt current seaward, and marks the northern limit of
the Peruvian Province, probably existed farther to the
south during part of Miocene time, giving rise to conditions
similar to those now existing, but with the southern limit
of the purely tropical littoral, corresponding to the present
Panamic Province, farther south. The location of such a
point at the various stages of the Tertiary will be known
when the coastal geology and paleontology have been
studied in greater detail and over the entire area.

PALEONTOLOGY ZORRITOS FORMATION 25

This postulate demands a distribution of marine currents
and temperatures, and thus marine animals, somewhat differ-
ent from that existing today. In a study of the recent
littoral molluscan fauna of the coast of Peru Dall found
that the Magellanian element in the fauna is the most con-
spicuous, despite the fact that many of the species are
common to the Panamic Province, and that accordingly the
fauna seems to be largely of southern origin. Since the
beginning of Tertiary time conditions have probably vacil-
lated somewhat, with the north Peruvian coast as the scene
of change from colder-water, Magellanic faunas to tropical,
Antillean-Panamic faunas as changes in the coast line varied
the point of divergence of the southern, now called the Hum-
boldt current. Temperature conditions seem to be the chief
governing factor in the constituency of a littoral molluscan
fauna.

It is possible that during Variegated time there was a
reversion from the purely tropical conditions of the Lower
Zorritos to conditions under which the colder currents again
had access to the north Peruvian coast, and the Chilean
element noted by Grzybowski may thus be accounted for.
Two things, however, alter the clearness of such a postu-
late : first, the existence of the Chilean forms in the Varie-
gated has not been checked, and second, it is the opinion of
some observers of South American geology that a consider-
able land mass existed during Miocene time to the west of
the present coast and in the general region south of central
Peru; a slight change in the course of ocean currents such
as that called upon to explain the Chilean element in the
Variegated depends on coastal conditions essentially similar
to those now existing, and the presence of a considerable
projecting land mass to the south would have eliminated the
colder water entirely from the Peruvian region. The exis-
tence of such a land mass, however, is far from proven,
and the presence of Chilean types in the Variegated beds
needs to be explained. A shifting of the point of land which

26 STUDIES IN GKOLOGY, No. 3

caused the diversion of the southern current might well
have allowed the Chilean forms access to the north Peruvian
waters during Variegated time.

Ortmann,15 in discussing the possibility of a separation
of South America into two masses according to the "Arch-
hellenis — Archiplata" theory of von Ihering, points out
the dissimilarity of the north Peruvian faunas from those of
Navidad, Chile, and Patagonia in support of the hypo-
thetical central seaway as a barrier to the intermingling of
the regional faunas. It does not seem necessary to pre-
suppose so vast a change as the splitting apart of South
America in order to explain the difference between faunules
which by virtue of their location alone might be expected to
differ. All data so far collected indicate that there is un-
broken structural and geologic continuity along the Andean
axis from Panama to the Straits of Magellan. The exis-
tence of norrh-south lines of tectonic weakness is established
both through the immense Andean uplift and the sunken
blocks which have given rise to the famous deeps off the
west coast, and it is extremely unlikely that a major line of
weakness existed in comparatively recent times at right
angles to these known. The sea separating "Archhellenis"
and "Archiplata" would have had to be deep enough to
prevent the migration of molluscs, and broad enough to
forbid the passage of free-swimming larvae. Evidence of
so great a break in the continental mass of western South
America, which should be discernible if the seaway existed,
apparently is not present, the general geologic situation on
the west coast suggesting complete continuity, with no hint
of a break.16 There may have been, and probably was a
profound embayment of the Amazon basin, but submergence
of the site of the Andes is not evident from observations thus

15 Princet. Exp. Patag., vol. 4, p. 298, 1901 ; also pp. 319-324.

16 See Berry, E. W., Geol. Soc. Am. Bull., vol. 29, pp. 637-648,
1919; Proc. Pan Pacific Sci. Conf. pp. 845-865, 1921.

PALEONTOLOGY ZORRITOS FORMATION » 2fJ

far available, and can not be proven through mere dissimil-
arity of faunas in regions which might have offered differ-
ent habitats for any one of a number of reasons involving
the disposition of coastal land and the distributions of ocean
currents, or which might have been faunally isolated from
one another for similar reasons.

There is evidence, on the other hand, which is difficult of
explanation if a sea-barrier separated two continental masses
according to von Ihering. The upper Cretaceous flora of
Argentina, according to Kurtz 1T is derived from that of
North America. It could hardly have passed the sea-barrier.
The Miocene flora of the Navidad beds, Chile shows close
aflinity to floras of similar age found in Ecuador and Peru,
and extremely close relatives of the Navidad plants are
living today in the upper Amazon country, in Peru and
Bolivia, according to B.erry.18 These facts do not support
but contradict the theory of a central seaway.

The remaining part of this discussion will be concerned
with the age relations of the fauna. A survey of the table
of distribution arid affinities, will show at once the relation-
ships of the separate species, and the discussion to follow
will embody merely the grouping of the evidence, with
remarks on pertinent points and without repetition of faunal
lists.

The fauna as a whole, shows affinities so strongly Bur-
digalian that much discussion is not necessary. The term
Burdigalien is used not to indicate that the age determin-
ation has been made through European comparisons, but
because the European units are more expressive of exact
age relationship, and are standard; the fauna is closest to
Panamanian-Antillean-Floridian assemblages of well-estab-
lished Burdigalien age.

17 Kurtz, F., Rev. Mus. La Plata, vol. 10, pp. 43-60, (1899) 1902.

18 Berry, E. W., personal communication; also Proc. U. S.
Nat. Mus., vol. 55, No. 2270, p. 283, 1919.

28 ' STUDIES IN GEOLOGY, No. 3

The following table will show readily the distribution of
affinities for the total fauna. The percentages represent
those of species either occurring elsewhere or having close
relatives elsewhere at the horizons noted.

Restricted to Burdigalian . . . .' 43%

Occurring in Burdigalian 71%

Restricted to Helvetian 7%

Tortonian and later 11%

Oligocene (chiefly Aquitanian) 10%

Eocene $%

It is thus clear, although these figures are really not the
most efficient medium of expression, that the fauna is un-
mistakably Burdigalian in age. Since 87 of the 101 species
are peculiar to the Zorritos formation it is practically nec-
essary in attempts at expressing analysis to consider close
affinities together with identical occurrences, and inasmuch
as such affinities as have been indicated are close enough to
warrant such action, the two are not separated in discussions
of totals.

This determination confirms Grzybowski's statement of
the age of his collections from the same horizons, and it is
worthy of note that he obtained his results through compar-
ison with European species, almost to the exclusion of
others, at a time when the geology of the Panamanian-
Antillean region was little known. He did not place his
fossils definitely in the Burdigalian, but stated that they
were of Lower Miocene age. A later determination of the
age of the Variegated formation, by Berry,19 depends on
fossil plants for its conclusion, and agrees with Grzybowski's
results in calling the beds Burdigalian. The results of these
observations, diverse in manner of treatment, agree with
satisfying precision.

Twenty-two of the 101 species are either closely related to
or identical with Gatun species; 29 with Santo Domingan

19 Proc. U. S. Nat. Mus., vol. 55, No. 2270, pp. 283-284, 1919.

PALEONTOLOGY ZORRITOS FORMATION 29

species from the Cercado formation, of Burdigalian age, and
8 with Chipolan species. The remaining Burdigalian affin-
ities are scattered as shown by the table.

Thirteen species either occur at Bowden or have close
relatives there. The latest opinion, based on unpublished
studies by Dr. W. P. Woodring, of the United States Nat-
ional Museum, is that the Bowden beds are Helvetian in
age ; however, most of the Bowden forms related to species
from Zorritos are of clearly older affinities, and the Zorritos
fauna contains few species closely related to that more
modern element in the Bowden fauna which indicates its
place in a higher stage.

The species which occur elsewhere may be tabulated as
follows :

Gatun 5

Santo Domingo (Cercado) 3

Santo Domingo (Gabb) 2

Bowden 5

Atlantic Miocene 2

Chipola Marl I

European Oligocene i

The geologic discussion of the fauna will conclude with a
brief consideration of each of the constituent four groups.

Upper Zorritos Fauna: The proportions of the Helvetien
and Burdigalien elements in the Upper Zorritos fauna have
already been discussed in general. Exact tabulation of rela-
tionships will be found in Plates 2, 3, and 4; it will suffice
to say here, statistically, that in the large Burdigalien
element represents about half of the total fauna, with the
Helvetien and Tortonien aggregating somewhat less than
a third. The Helvetien element is so characteristic and
profuse, however, that the numerical expression fails to por-
tray the situation fully. Although present evidence demands
consideration of the fauna as Burdigalian along with the
Variegated and Lower Zorritos, there is no doubt that it

30 STUDIES IN GEOLOGY, No. 3

represents, faunally, a later stage, and that the appearance
in further collecting of a reasonable number of more modern

• species would easily throw the balance toward the Helvetien.

As was noted in the preceding discussion of formational
inter-relationships, the Areas and the Turritellas are the
chief distinctive groups of the Upper ZorritO'S, and although
some of the species range into the Variegated, their complete
difference in the Lower Zorritos affords one point of dis-
tinction between the two formations which may prove of
use in field recognition. Other species, such as Pecten
woodringi, Conus cacuminatus, and Cerithium infrano datum,
of the Upper Zorritos ; Dosinia grandis, Corbula propinqua,
and Macrocallista helenae, of the Variegated ; and a much
larger number from the Lower Zorritos appear to be char-
acteristic, and may serve similar purpose ; however, they

- are as a whole not as prominent as the Areas and Turritellas,
and their range is not yet sufficiently well known to make
them of high value.

Variegated Fauna: The collection from the Variegated
beds, of fifteen species, is too small to permit far-reaching
conclusions, but a few observations may be worth while.
The preponderance of Burdigalian elements, well over half
the total, in the fauna here represented is such as leave small
doubt as to the age of the beds, and although the general
facies is in some ways similar to that of the Upper Zorritos
fauna, the affinities are closer to those of the Lower Zorritos.
That fact .lends strength to the possibility that the whole
formation is of nearly the same age, but it can not mean much
at present ; future work might easily change the conclusions
based on so small a faunule as that now available. There is
small doubt, however that the Variegated will prove to be of
Burdigalien age.

Grzybowski lists 16 species from the Variegated (his
Heath), of which only three occur in the present collection,
with none of the three from the Variegated. The remaining

PALEONTOLOGY ZORRITOS FORMATION 31

13 species appear to have well-defined lower Miocene affin-
ities, and five of them are apparently of Chilean Miocene
types. It is the belief of the writer that the Variegated beds
will be shown to contain many more species in common
with the Upper and Lower Zorritos formations than are
now apparent.

Lower Zorritos Fauna: This fauna presents the most
strongly peculiar aspect of all. In addition to the fact, al-
ready noted, that it shows very strongly centralized affinities,
it has a facies more distinctly peculiar than has either of
the other two faunas. The Gatun-Cercado elements are
certainly predominant, and the age of the fauna is certainly
Burdigalien, at least in the sense of the American strati-
graphers. Over half of the Lower Zorritos species are
closely related to species restricted to* the Burdigalien, and
approximately eighty per cent to species occurring in the
Burdigalien. The affinities of other elements in the fauna
may be seen readily in the tables, plates 2, 3 and 4.

Nelson's Collection: The collection described by Nelson
contains a number of species which do not occur in the
Hopkins collection. Inasmuch as Messrs. Larkin and
Bradley, the collectors, stated that the specimens came from
the direct vicinity of Zorritos, in which locality the Zorritos
and Heath formations are the only ones exposed, and since
the general facies of Nelson's fossils indicates a common
origin, they have been assumed to come from the Zorritos
formation. It is unfortunate that they have not been located
within the limits of that unit, but when considered with the
fauna as a whole they contribute interesting additional evi-
dence of the Burdigalian age of the beds. Approximately
forty per cent of the species have restricted Burdigalian
affinities.

The exact relationships of the species in this group may be
seen in the accompanying table, where they are listed as
"Undifferentiated."

STUDIES IN GEOLOGY, No. 3

CLOSELY RELATED STECIES

Terebra gausapata B. & P. 1
Terebra gausapata B. & P. I

3 tortuosostriatus Toula 1
3 marginatus Sowerby j
3 molis B. & P. 1

to

1

sllaria (Aphera) islacolonis Maury

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LS var. subgradata Sac.
.s var. turritisaima S.

itella mimetes B. & P.
itella subgrundif era Dall 1

j

i

at
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itella ocoyana Conrad
itella ocoyana Conrad J
itella ocoyana Conrad ]

i
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itella concava

itella megalobas

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itella terebrali
itella terebralj

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X X

X

x

TABULAR LIST OP SPECIES
PROM THE ZORRITOS FORMATION

x = occurrence of Zorritos species
0 = occurrence of closely related species

j

1 Terebra "gausapata var. herviderana n. v.
j Terebra tuberosa (Nelson)

1 finnus mil-m-irfl-hja vnr. traza B. & P.

Conua bocapanensis n. sp.
Conus berryi n. sp.
Conus cacuminatus n. sp.

§

1
6
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1 Mare-inella incraaaata Nelson

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£
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1 Nasaa zorritenais (Nelson)

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ea anKU3^lr^ma n. sp.
hium inf ranodatum n. sp.
lium grillanura n. SP.

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tella robuata Grzybowaki
tella robusta var. abrupta n. var.
tella charana n. sp.

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lella bifastir.ata Nelson

tella f iHcincta Grzybowak:

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1 Turritella nelsoni n. sp.
Turritella nelsoni var. rotunda

tella nelsoni var. trulliaf
tella infracarinata Grzybo*

Lena inrracarina-wi var. zt
tella prenuncia n. sp.
Lftlla •oranuncia var. incon

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PALEONTOLOGY ZORRITOS FORMATION

33

CLOSELY RELATID SPECIES

C

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Cardium samba icun Maury I

Dosinia orbicularis Ag. I

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ipharca) zapotalensis n. sp.

i) fissicosta n. sp.

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L) charanenais n. sp.

0 hispaniolana !,Iaury

i) larkinii Nelson

i) imporcata n. sp.

L) obesiformis Qrz.

L) creacena n. ap.

| Area (Anadara) aeptifera Grz.

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1 Area (Anadara) toroensia n. ap.

| Area (Anadara) toroensia var. crassa n.v.

I Area (Anadara) toroensis var. prolata. n.v.

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(Trigoniocardia) affinis (Nelaon)

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34

STUDIES IN GEOLOGY, No. 3

CLOSELY RELATED SPECIES

joaquinensis Anderson 1

Macrocallista conradiana Gabb

P-I

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ZORRITOS SPECIES

dementia dariena Conrad

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propinqua n. ap.
a) hendersonii Ball

(Lirophora) latilirata Conrad

lina zapotalensis n.sp.

lina (Eurytellina) aequicincta n. sp.

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PALEONTOLOGY ZORRITOS FORMATION 35

SYSTEMATIC PALEONTOLOGY

Class GASTROPODA
Superorder STREPTONEURA

Suborder ORTHODONTA

Order CTENOBRANCHIATA

Superfamily TOXOGLOSSA

Family TEREBRIDAE

Genus TEREBRA Adanson

Terebra gausapata var. herviderana n. var.
PLATE I — Fig. i.

Shell small, delicate, sharply sculptured, the apical angle
very small. The fasciole is sharply defined, of medium
width. Spiral sculpture on the main part of the whorl of
about eight unequal bands separated by narrower inter-
spaces. On the fasciole are vestiges of a spiral sculpture
of about three or four fine threads, situated on the upper
half of the fasciole. Longitudinal sculpture of sharp ribs,
17-18 to the whorl, which are not crossed by the spiral
bands. These ribs are cut by the suture on one side of the
fasciole, where they offset, the rib of one whorl abutting
against the interspace on the fasciole of the succeeding
whorl. On the other side of the fasciole they are cut by a
deeper suture. The body whorl is rounded, and is larger
than the preceding whorls. The typical sculpture continues
across the base to the columella. The whorls are convex
between fascicles. The inner aperture is not known. Height
of fragment showing body whorl and two of the spire, 13.5 ;
maximum diameter, 5.25 mm.

This variety differs from T. gausapata Brown and Pils-
bry 20 from Gatun, in being somewhat larger, having 17-18

Proc. Ac. Nat. Sc. Phila., vol. 63, p. 340, pi. 22, figs. 8, 9, 1911.

36 STUDIES IN GEOLOGY, No. 3

spiral ribs instead of 14, and in the less prominent threads
on the band ; otherwise it is identical. It differs from the
variety foevifasciola Maury, from Santo Domingo,21 in its
larger number of longitudinal ribs, and in the presence of
vestigial spirals on the fasciole. The absence of such spirals
is apparently the only point of difference between laevifas-
ciola and gausapata.

Lower Zorritos. Hervideras, Zorritos district.
Terebra tuberosa (Nelson)
PLATE I— Fig. 2.

Myurella tuberosa Nelson, Trans. Conn. Acad., vol. 2, p. 193,
i8;d.

"Shell turreted, slender and acuminate; whorls eight to
ten, depressed or slightly concave, except the body whorl;
sutures indistinct. Cincture broad, elevated, with obtuse
tubercles, not as wide as the spaces between them. Longi-
tudinal ribs distinct. Whorls marked by from four to six
nearly equal transverse ridges, which rise into strong tuber-
cles over the ribs, x x x " — Nelson, 1870.

The spiral sculpture consists of six bands on the main
part of the whorl, separated by narrow interspaces. The an-
teriormost of the spiral bands is usually not prominent, and
is sometimes occluded by encroachment of the fasciole. The
longitudinal sculpture consists of a series of raised ridges,
about 14 on a whorl, which are prominent on the fasciole,
giving it the appearance of a worn cog-wheel. On the main
surface of the whorl the ridges are more subdued, but still
distinct, raising the spiral bands into the tubercles noted by
Nelson. Usually one or more of the longitudinal ribs on
each whorl is bifid at the summit. Lines of growth cross
all parts of the whorl. The base is sculptured with spiral
bands similar to those on the main body of the whorls, the
continuation of the area covered by the fasciole being

21 Bull. Amer. Pal., vol. 5, No. 29, p. 27, pi. 3, fig. 19, 1917.

PALEONTOLOGY ZORRITOS FORMATION 37

marked by a flat-topped keel bearing four of the spiral bands.
The spiral sculpture decreases in strength toward the base,
and the longitudinal ribs converge toward the point of the
columella. The columella is biplicate, the posterior fold
rising sharply at its anterior end. The aperture is narrow,
and the anterior canal reflexed. The apical angle is some-
what wide for the genus. Altitude, 2.6 cm. ; maximum
diameter, 9 mm.

T. tuberosa differs from T. gausapata Brown and Pils-
bry,22 from Gatun, and its varieties laevifasciola Maury,23
from Cercado de Mao, Santo Domingo, and herviderana n.
var., in its wider apical angle, less prominence of the longi-
tudinal ribs on the main body of the whorl, and compara-
tively broader fasciole. T. tuberosa has fewer spiral bands.
T. prote.rta Conrad, most recently described by Maury 24
from Santo> Domingo, though not as close as the gausapata
group, is similar in general conformation. The spiral bands
in protexta are much broader, and the longitudinal ridges
less elevated. The fasciole is more prominent in tuberosa.

Zorritos formation. Zorritos.

Family CONIDAE

Genus CONUS Linnaeus

\

Conus multiliratus var. gaza Johnson and Pilsbry

Conus gaza Johnson and Pilsbry, Proc. Ac. Nat. Sc. Phila.,
vol. 63, p. 342, pi. 23, figs. 2, 3, 1911.

Conus gaza Maury, Bull. Amer. Pal., vol. 5, No. 29, p. 46, pl.K
7, fig. 12, 1917.

Conus multiliratus var. gaza Woodring, Bowden Ms.

"The shell is biconic, diameter over half the length, the
spire is nearly one-third the total length, concavely conic,
attenuate towards the apex. Post-embryonic whorls about

22 Proc. Ac. Nat. Sc. Phila., vol. 63, p. 340, pi. 22, figs. 8, 9, 1911.

23 Bull. Amer. Pal., vol. 5, No. 29, p. 27, pi. 3, fig. 19, 1917.

24 Bull. Amer. Pal., vol. 5, No. 29, p. 28, pi. 4, fig. i,

38 STUDIES IN GEOLOGY, No. 3

9, slightly concave, the lower edge of each angular, project-
ing a little ; the angle tuberculate in the first post-embryonic
whorl, smooth in the rest; sculptured with deeply arcuate,
narrow, low and widely spaced riblets and striae ; no spiral
striae. Last whorl acutely angular at the shoulder, barely
convex below the angle, the outline becoming concave in the
lower part; sculptured with 20-22 strong, smooth spiral
cords, separated by wider intervals which are sharply striated
by growth-lines. Aperture very narrow. Length, 24,
diam. 13.1 mm." — Johnson and Pilsbry, 1911.

Lower Zorritos. Quebrada Zapotal, Zorritos district;
Santo Domingo; Bowden, Jamaica; Gatun, Panama.

Two specimens in the Hopkins collection are referable to
this species. A coating of calcite obscures the finer details
of sculpture, and the presence of the longitudinal striations
on the body whorl characteristic of gaza are not clear, but
other characters agree with sufficient closeness to advise at
least tentative reference to the Antillean variety.

This form occurs at Cercado de MaO', Santo Domingo,
in beds ascertained by Maury 25 to be Burdigalian in age.
It occurs also in the Bowden beds of Jamaica, and at Gatun.
It is closely related to Conns bocapanensis and Conus berryi,
of the Zorritos fauna. A detailed discussion of its relation-
ships to them will be found in the remarks on each.

Conus bocapanensis n. sp.
PLATE I — Fig. 3.

Conus sp. ind. A, Nelson, Trans. Conn. Acad., vol. 2, p. 194,
1870.

Shell small to medium-sized, unequally biconic, the spire
turreted. The spire is fairly high, including about a third
of the entire height, its slopes straight in profile. Whorls
8-9 in number, the first two of the spire smooth and rounded,
the following with a marked keel at the lower third, the

"Bull. Amer. Pal. No. 30, Table at end.

PALEONTOLOGY ZORRITOS FORMATION 39

surface above the keel being concave and below straight.
On the spire the sculpture is of growth-lines, poorly defined,
only. On the body whorl are sixteen or seventeen spiral
bands, separated by narrow interspaces, with growth-lines
in the interspaces. The spiral sculpture is weaker near the
shoulder. The shoulder of the body whorl is sharp, the
surface below being straight. Aperture fairly narrow, of
constant width, the columella slightly reflexed at the base.
Height, 37; diameter, 17 mm.

This species is closely related to a group of small cones
from the Antillean-Carribean region. It is perhaps closest
to C. tortuosostrmtus Toula,26 from Gatun; it differs only
in having simple instead of differentiated spiral sculpture,
and in lacking the beaded keels characteristic of tortuosos-
triatus. It is also similar to Conus multiliratns var. gaza
Johnson and Pilsbry,27 from Gatun, Bowden, and Santo
Domingo and Zorritos, but it is more slender, and has
broad-topped ribs on the body whorl instead of the finer
spirals of gasa. C. imitator Brown and Pilsbry,28 from
Gatun, differs in having 16 ribs on the lower half of the
body whorl instead of 16 over the entire surface, and in
having the profile of the spire concave instead of straight.
The spire of bocapanensis differs in similar way from that
of C. planiliratns Sowerby,29 from Santo Domingo; the
profile is straight in lines instead of concave.

Lower Zorritos. North of Quebrada de Boca Pan.

Conns berryi n. sp.
PLATE I— Fig. 4.

Shell small, biconic, the altitude little more than 1.5 times
the diameter, and the cone of the body whorl about 1.5 times

26Jahrb. k.k. geol. Reichs., Bd. 61, p. 508, pi. 31, fig. 22, 1911.
'" Proc. Ac. Nat. Sc. Phila., vol. 63, p. 342, pi. 23, figs. 2, 3, 1911,
as (Conns gaza).

28 Idem., fig. 4.

29 Man ry, Bull. Amer. Pal., vol. 5, No. 29, p. 45, pi. 7, fig. 10, 1917.

4O STUDIES IN GEOLOGY, No. 3

the length of the spire. Whorls about 9 in number, the sur-
face of each whorl inclined from the suture to a sharp keel,
from which it recurved to the suture. The spire is thus
turreted. The keel is waved, giving the spire a coronate
appearance.- Sculpture of slightly arcuate lines of growth
on the spire ; on the sides of the body whorl are spiral bands
separated by narrow interspaces. The lower bands are very
sharply defined, but they decrease in sharpness of definition
above. Faint lines of growth cross the bands. The aperture
is narrow. Height, 17; diameter, 10.75 Him.

This species is similar to C. marginatus Sowerby 30 from
Antillean Miocene horizons, from which it differs in having
a higher spire, which is coronate, not smoothly keeled. C.
multiliratus var. gaza Johnson and Pilsbry 31 is similar to
both these forms ; it differs from berryi in being more taper-
ing, longer, with a proportionally lower spire, the whorls of
which are not coronately keeled.

Lower Zorritos. Hervideras, Zorritos district.

Conus cacuminatus n. sp.

PLATE I— Fig. 5.
Conus sp. ind. B. Nelson, Trans. Conn. Acad., vol. 2, p. 194, 1870.

Shell large, moderately heavy ; the spire of medium height,
and the body whorl tapering gracefully in a straight-sided
cone. Whorls 9-10 in number; the 2^2 nuclear whorls
smoothly convex, and the remainder concave, with a smooth
keel at the outer edge just above the suture. Sculpture of
lines of growth, arcuate on the whorls of the spire, straight
on the body whorl and lamellose in worn specimens. The
best preserved specimen shows numerous very faint spiral
striae on the whorls, with a faintly impressed spiral line at
the deepest point of the concave whorl-surface. Near the

30 Quart. Jour. Geol. Soc. Lond., vol. 6, p. 44, 1849; Maury,
Bull. Amer. Pal., vol. 5, No. 29, p. 46, pi. 7, fig. II, 1917.
81Proc. Ac. Nat. Sc. Phila, vol. 63, p. 342, pi. 23, figs. 2, 3, 1911.

PALEONTOLOGY ZORRITOS FORMATION 41

base of the body whorl are six to eight spiral cords with nar-
rower interspaces; these are most prominent just inside the
aperture. The shoulder of the body whorl is sharp, and the
sides descend from it, with very little convexity, in straight
lines. The aperture is somewhat wide. Height, 73 ; diam-
eter, 38.5 mm.

A number of specimens of this graceful cone occur in
Nelson's collection, and a cast in the Singewald collection
from the Upper Zorritos formation is questionably identified
with it. It is similar to Conus molts Brown and Pilsbry,32
of the Gatun fauna, differing from that species in having
straighter sides, lacking the prominent spiral striae on the
body wrhorl, and in having a proportionally higher spire.
It is a much smaller form. It differs from C. vnolis var.
bravoi, of the local fauna, as noted in the remarks on that
variety.

Upper Zorritos ( ?). Quebrada de las Alturas.

Conus molis var. bravoi n. var.
PLATE I— Fig. 6.

Conus sp. ind. C. Nelson, Trans. Conn. Acad., vol. 2, p. 194, 1870.

Shell large, solid, heavy. The spire very low, almost flat
except at the apex, where the early whorls rise in a nipple-
like peak. Whorls twelve to fourteen in number, the last
four or five flat to very slightly concave, the remainder flat
to convex. The whorls of the spire are depressed in some
specimens at the suture, the edge of the succeeding whorl
rising above the suture. Sculpture of moderately arcuate
growth-lines on the spire; on the body whorl the growth-
lines are prominent on worn specimens ; there is no evidence
of spiral sculpture on the spire and upper part of the body
whorl; on the lower part of the body whorl are fairly coarse
spiral threads. A distinct, thread-like keel marks the outer
edge of each whorl ; on the body whorl it marks the apex

32Proc. Ac. Nat. Sc. Phila., vol. 63, p. 343, pi. 23, fig. I, 1911.

42 STUDIES IN GEOLOGY, No. 3

of the shoulder, which is subacute and rounded just below
the keel. The surface is straight below. The aperture is
long and narrow. Height, 75 ; diameter, 48 mm.

A number of individuals of this variety occur in both the
Hopkins and Nelson collections. It differs from C. molis
Brown and Pilsbry,33 from Gatun, in being somewhat
smaller, lacking the fine spiral striae, having the whorls of
the spire less concave, and in being convex for a shorter
distance below the shoulder of the body whorl. Conus ca-
cuminatus, of the local fauna, differs in having a straighter
profile and a much more conic spire.

Upper Zorritos. Quebrada Tusillal, and del Toro.

Family CANCELLARIIDAE

Genus CANCELLARIA Lamarck

Subgenus Aphera H. & A. Adams

Cancellaria (Aphera) peruana Nelson

PLATE IV— Fig. 13.

Aphera peruana Nelson, Trans. Conn. Acad., vol. 2, p. 190, pi. 6,
fig. 3, 1870.

"Shell elongated, sub- fusiform ; spire short, pointed,
formed by five or six moderately convex whorls. Body
whorl large, three-fourths the length of the shell, ventricose.
Surface marked by nearly equal longitudinal and transverse
ridges, which form strong raised cancellations, and are so
arranged as to form blunt, obtuse granulations at the point
of contact. Longitudinal lines finer, and much crowded
near the outer lip. Aperture oblong-oval, t narrow, half as
long as the shell. Lips covered with callus, which is con-
tinuous above and below the aperture. Callus of columella
lip strongly reflexed over the shell, much broader above
than below, almost completely covering the umbilicus. Outer

Proc. Ac. Nat. Sc. Phila., vol. 63, p. 343, pi. 23, fig. I, 1917.

PALEONTOLOGY ZQRRITOS FORMATION 43

lip thick, and reflexed above, furnished within with a few
rather strong teeth. Inner lip with two plaits near the
center, the upper one being much the stronger. There is
also a plait at top of the lip, small but quite distinct. Canal
wanting. Aperture prolonged into a short, open sinus.
Length, 17.4 mm.; length of spire, 4.4 mm. ; breadth 10 mm.
This species closely resembles Apherai tesselata Adams, but
is distinguished from that species by its less slender form,
stronger cancellating ridges, by its shorter and more open
aperture, and by the third fold at the top of the columellar
lip." — Nelson, 1870.

As noted by Nelson ,a very close relative of this species is
A. tesseiata Sowerby, which is now living on the west coast
from the Gulf of California to Chile. C. dariena Toula,34
from Gatun, is similar, excepting the lack of the reflexed
inner callus characteristic in peruana, and its coarser sculp-
ture, with -the longitudinal ribs missing near the aperture ;
they are complete in peruana.

Cancellaria (Aphera) islacolonis Maury,35 from the Lower
Miocene of Santo Domingo, is the closest known fossil
relative. It differs in having finer sculpture, and in the
aperture, the outer lip of which is more deeply crenate than
in peruatia.

Zorritos formation. iZorritos.

Superfamily RHACHIGLOSSA
Family MARGINELLIDAE
Genus MARGINEXLA Lamarck
Marginella incrassata Nelson

PLATE I— Fig. 9.

Marginella incrassata Nelson, Trans. Conn. A>cad., vol. 2, p.
197, pl. 6, figs. 5, 6, 1870.

34Jahrb. k.k. geol. Reiche., Bd. 58, p. 703, pl. 28, figs. 2a, b, 1908.
85 Bull. Amer. Pal., vol. 5, No. 29, pp. 65-66, pl. 10, figs. I2a, b,
1917.

44 STUDIES IN GEOLOGY, No. 3

Shell large, conical, ovate, two-thirds as wide as long,
thick. Spire rather short and acuminate. Sutures indis-
tinct. Body whorl regularly conical, very convex, broadest
one- fourth from top, forming a well rounded shoulder, and
tapering rapidly from this point to end of spire. Aperture
linear and narrow. Outer lip with the margin thick and
broad. Columellar lip with four nearly equal, well developed
plaits ; the two upper more widely separated than the lower
ones." — Nelson, 1870. Height, 28; diameter, 18 mm.

This species is very close to M. coniformis Sowerby,36
from Antillean Miocene horizons, differing only in lacking
the slight depression behind the posterior canal which is
characteristic at least of the Bowden specimens of coni-
formis, in being distinctly larger and heavier, with a deeper
posterior canal. The body whorl of incrassata tapers more
sharply on the ventral side. The two are very close, and if
incrassata were not so much larger than coniformis it might
readily be regarded as a variety of that species.

It is also very close to M. aurora Ball,87 from the Chipola
beds of Florida. The posterior canal of incrassata is not as
deep, the spire is somewhat lower, and there are no denticu-
lations on the inner surface of the outer lip as in aurora.
N. mavensis Maury,33 from the Santo Domlngan Miocene,
is similar, differing in having heavier plaits on the pillar,
and in that the body whorl is not as sharply tapered as in
incrassata,

Zorritos formation. Zorritos.

36 Quart. Jour. Geol. Soc. Lond., vol. 6, p. 45, 1850.

"Trans. Wag. Inst, vol. 3, pt. i, p. 51, pi. 6, fig. 4a, 1890.

88 Bull. Amer. Pal., vol. 3, No. 29, p. 71, pi. n, fig. 7, 1917.

PALEONTOLOGY ZORRITOS FORMATION 45

Family BUCCINIDAE

Genus SOLENOSTEIRA Dall

Solenosteira alternata (Nelson)

PLATE I — Figs. 10, ii.

Cuma alternata Nelson, Trans. Conn. Acad., vol. 2, p. 198, pi. 7,
figs. 3, 4, 1870.

Shell of good size, fairly thick, well proportioned. Spire
conic, acuminate, turreted, with about 25/2 smooth embryonic
whorls; the following whorls rather sharply convex, and
sculptured with large longitudinal folds, the intervals wider,
of which there are eight or nine on the body whorl, and
sharply defined, closely spaced spiral threads. The folds
rise into points at the keel of each whorl, and on the
shoulder of the body whorl the points are sharp in hori-
zontal direction. The spiral threads may be separated into
three orders : of the first order there are about 28 on the
body whorl between the suture and the base of the outer
lip, with several more on the basal fasciole; between the
primary threads are varying numbers of secondaries — near
the sutures there are as many as four or five, whereas mesi-
ally one is the rule. Tertiary threads are interstitial between
the secondaries throughout. The differentiation of the three
orders of threads is sharper above and below the keel than
it is mesially. Fine growth-lines cover the entire shell, cross-
ing the spiral sculpture. The body whorl is concave below
the keel, and expanded into a curving ridge about the
umbilicus, which is distinct but shallow, and funnel-shaped.
The anterior canal is open, deep and reflexed., The pillar is
simple, with a thin callus. The aperture is oval in shape,
differentiated from the canal; the throat is lirate, the Hrae
being small and equi-distant. The basal fasciole is strong.
Height,, 52 ; diameter, 33 mm.

This species is a beautifully sculptured, gracefully pro-
portioned shell, perhaps the most pleasing 10 look upon of

46 STUDIES IN GEOLOGY, No. 3

all the Zorritos mollusks. It was referred by Nelson to the
genus Cuma, which has since been placed in synonymy with
Cymia, but it is obviously not of that genus. It is very close
to S. dalli Brown and Pilsbry,39 from Gatun, differing from
that species in having a larger number of more closely spaced
primary threads, with the three orders of threads not as
prominently differentiated as in dalli; the sculpture on the
shoulder of the body whorl is not nearly as strong ; the base
is somewhat more produced, the canal and f asciole being
longer. The recent S. elegans is somewhat similar, but
differs in having heavier spiral threads, with the longitudinal
folds equally strong over the entire length of the whorl ; in
altemata they are stronger at the keel and subdued near the
suture.

Lower Zorritos (Variegated?). South of Quebrada
Pantheon ; Quebrada Zapotal.

Subfamily PHOTINAE

Genus PHOS Montfort

Phos (f) latirugatus n. sp.

PLATE I — Fig. 12.

Shell of medium size, turreted, the spire high, the whorls
inflated. First neanic whorls unknown; the following
whorls fairly evenly convex ; at about the fifth whorl a keel
develops, and with the keel a series of longitudinal folds.
On the later whorls the shoulder set off by the keel becomes
more nearly horizontal, the keel becoming more nearly level
with the suture, and the longitudinal folds grow broader and
farther apart. At the juncture of the longitudinal folds and
the keel nodes exist. Spiral sculpture of two orders of
threads ; between the keel and the base on the body whorl
there are about n or 12 major threads which are more
closely spaced below ; between the major threads are almost

Proc. Ac. Nat. Sc. Phila., vol. 63, p. 348, pi. 24, fig. 14, 1911.

PALEONTOLOGY ZORRITOS FORMATION 47

uniformly three subsidiary threads, of which the middle
one sometimes approaches the strength of a major thread.
Aperture oval; details not known. Height, 26; diameter,
14.5 mm.

The closest relative of this species is P. polygonus var.
percostata Sacco,40 from the Lower Miocene of Europe. It
is not typical of the common Photinae, the pronounced keel
giving the whorls a squarish aspect rather unusual to the
group, and in the absence of detailed knowledge of the
aperture it is not completely certain that it belongs in the
genus; however, there is small doubt, since all visible char-
acters agree very well with those of P. polygonus, which is
one of Cossman's plesio- types of the genus Phos s.s.41 It is
a well-characterized species, and appears to have no close
relatives in the American Tertiary. It differs from P.
polygonus var. percostata Sacco in having broader longi-
tudinal folds and a sharper keel which is more nearly level
with the suture than in percostata. The sculpture of latiru-
gatus is more diverse. In general shape the two are close.

The spiral sculpture commonest to P. latirugatus, that
mentioned in the description, is not similar to that of
polygonus, but some mutants of the Peruvian species show
a coarser sculpture which does agree fairly well with that
of the variety percostata figured by Sacco (loc. cit). These
mutants may prove to deserve recognition as separate vari-
eties of latirugatus, but as far as the material now available
shows they are sufficiently close to the type to make differ-
entiation inadvisable.

Lower Zorritos. Quebrada Zapotal.

40 Piemonte, pte. 30, p. 58, pi. 14, figs. 60, 61, 1904.
^Essais de Pal. Comp., vol. 4, p. 158, 1901.

48 STUDIES IN GEOLOGY, No. 3

Family NASSIDAE
Genus NASSA Lamarck
Nassa zorritensis (Nelson)
II— Figs, i, 2.

Argobuccinum zorritense Nelson, Trans. Conn. Ac. Sc., vol. 2,
p. 196, pi. 7, figs, i, 2, 1870.

Shell large, strongly turreted, spire high, conical; whorls
about seven in number. Whorls convex; the earlier ones
rounded, the later ones having a prominent keel which sets
off a narrow shoulder, becoming stronger and more nearly
level with the suture as the shell grows more mature. Sculp-
ture of spiral cords only on the earlier whorls ; on the later
whorls a series of longitudinal folds begins, growing
stronger and more widely spaced with the growth of the
shell; the folds are drawn out into strong tubercles at the
keel, and on the body whorl the tubercles are much larger
and more widely spaced, with the folds dying out below
them in the broad surface of the shell. The spiral cords are
irregular; on the earlier whorls they are well differentiated,
but on later whorls they often coalesce to form low, flattened,
strap-like ribs. The spiral sculpture lacks prominence on the
body whorl. The sides of the body whorl descend vertically
from the keel, curving smoothly into the convex base. The
aperture is oval-triangular, with a slight posterior mouth
and a short, sharp anterior canal which is sharply reflexed.
The columella is plicate, unworn specimens showing a sharp
upper plait and a thicker one below. Outer lip lirate within,
the lirae extending faintly for some distance. Height, 57;
diameter, 35 mm. (large specimen). Average specimen,
height, 46.5 ; diameter, 26.5 mm.

This large and interesting species has been rather difficult
to place generically, and although its reference here to Nassa
indicates the fact that many comparisons with types have
shown it to belong, probably, to that genus, the author

PALEONTOLOGY ZORRITOS FORMATION 49

leaves open the possibility that a different systematic posi-
tion may be found necessary. The Nassidae are in a bad
state as regards the crystallization in the literature of differ-
ential characteristics, and the revision that is necessary is
naturally without the bounds of this work ; . without such
revision the designation of a new unit to receive this shell
would only add to> the confusion which now awaits the atten-
tion of a reviser.

The most closely allied species known to the writer is
Nassa veneris Fauj., of the ,Burdigalian of the Gironde,
France, and the Mediterranean Tertiary, described by Bell-
ardi,42 and later referred by Cossmann 43 to the genus Dor-
sanum Gray. Reference to the type of Gray's genus shows
that N. veneris probably does not belong to it, and it is ap-
parent that -N. zorritensis and .N. veneris are of a sub-group
yet to be designated, differing from Nassa chiefly in being
strongly keeled, with a distinct shoulder giving a squarish
aspect to the upper parts of the whorls and of the aperture.
Most of the Nassas have a stronger callus than have the two
forms here discussed, and it is probable that that feature will
prove a further point of differentiation.

Variegated Zorritos. South of Quebrada Pantheon.

Genus TRIUMPHIS Gray

Triumphis solida (Nelson)

PLATE II— Fig. 3.
Clavella solida Nelson, Trans. Conn. Acad., vol. 2, p. 199, 1870.

Pyrula roscta Grzybowski, Neues Jahrb., Beil. Bd. 12, p. 648,
pi. 19, fig. 6, 1899.

"Shell oval, ventricose, and heavy; spire moderately ele-
vated and tapering. Whorls five to seven, more or less
depressed above. Sutures distinct. Body whorl large, more

42 Piemonte, pte. 3, p. 58, pi. 4, figs. 3a, b, 1882.

43 Essais de Pal. Comp., vol. 4, p. 219, 1901.

50 STUDIES IN GEOLOGY, No. 3

than two-thirds the length of the shell, regularly convex,
depressed above the shoulder, which is large and strong,
and forms a very distinct ridge, extending more than half
around the shell. The upper whorls are marked by a series
of longitudinal ridges, eight or ten to a whorl, and crossed
by strong, equidistant, revolving lines. The two lower
whorls are destitute of the ridges, but ornamented by revol-
ving lines, which become more or less indistinct on the body
whorl in mature specimens. The base of the body whorl is
marked by much stronger lines. Variable in size. Aperture
oblong-oval ; outer lip thin. Canal long and slightly reflexed.
Umbilical chink bordered by a broad keel. Measurements
as follows: length 43.2; breadth (at shoulder) 30.6; breadth
(below shoulder) 28 mm." — Nelson, 1870.

The aperture is marked by a heavy inner callus, which is
strong posteriorly, and bears the recurved notch characteris-
tic of the genus. Grzybowski's figure (q.v., loc. cit.) shows
this feature better than does the material available for the
present study.

The occurrence of this species, the second of the genus to
be known, in the Miocene of Peru, is of unusual interest.
The specimens in both the Nelson and Hopkins collections
lack the full aperture, and the presence of the heavy, callus
posterior lip characteristic of T. distort® Wood, from Pan-
ama, the type of the genus, is not clear. Grzybowski (loc.
cit.) apparently had a specimen with the full aperture pre-
served, and although his figure is not all one might ask, it
shows that the species is aperturally configured much as is
T. distort®, and is undoubtedly of the genus, Grzybowski,
referring his shell to Pyrula Lamarck, apparently thought
that the basal portion of the columella had been broken off,
and drew dotted lines below to indicate the continuation of
the shell, whereas his shell was really perfect basally; in
reference to his figure it is accordingly necessary to disregard
the lines added by him.

The genus, typically of the West Coast, is thus seen t<3

PALEONTOLOGY ZORRITOS FORMATION 51

have had representatives in the early Miocene which may be
taken to be the ancestors of the living distortd. Triumphis
is certainly very closely related to Gabb's genus Agasoma ; 44
Fischer 45 notes that the two are probably synonymous, and
a close study of the Californian Agasomas may show this to
be the case. It is highly probable that a closer relationship
than that now expressed between Triumphis and Agasoma
exists, and it is the opinion of the writer that they are not
farther apart, actually, than subgenera under the same gen-
eric heading.

Lower Zorritos. Between Quebradas Heath and Charan.

Family MURICIDAE

Genus MUREX Linnaeus

Murex laqueoratus n. sp.

PLATE II— Fig. 4.

Shell small, turreted, fairly stout. Whorls about six in
number, the first two smooth, the remainder delicately sculp-
tured and convex. Sculpture of regular longitudinal folds,
eight to the whorl, which are negligible at the suture, in-
creasing rapidly to full strength at the mid-line of the whorl,
and decreasing again. On the body whorl all except the last
two continue over the base as narrow rounded folds; the
last two die out just below the shoulder. Spiral sculpture of
fine threads, about six to the whorl, with occasional inter-
stitial threads above or below the periphery of the whorls;
there the two central threads are prominent, forming a band
which heightens the prominence of the nodes on the longi-
tudinal ridges. On the body whorl there are twelve pri-
mary threads between the band and the base, with occasional
interstitial threads. Aperture almost circular, smooth within,

"Geol. Surv. Cal. Palaeont., vol. 2, p. 46, 1869.
45 Man. de. Conch., p. 627, 1887.

52 STUDIES IN GEOLOGY, No. 3

with a raised lip and a fan-like flare bordering the outer lip
over which the spiral sculpture continues to the raised
peristome. The canal is very narrow, open and short. Co-
lumella almost straight. Height, 18; diameter, (maximum)
ii mm.

This beautiful little Murex has its nearest fossil relative
in M. missippiensis Conrad,46 from the Vicksburg, Tampa,
and Chipola formations of Florida. It differs in having a
shorter canal, with the inner apertural margin smooth instead
of crenulate, and with the aperture not as nearly circular
as in laqueoratus.

Zorritos formation. Zorritos district.

Suborder STRSPTODONTA
Superfamily TAENIOGLOSSA

Family DOLIIDAE

Genus DOUUM Lamarck

Subgenus MAI^A Valenc.

Dolium (Malea) camura (Guppy)

Malea ringens Conrad Pac. R.R. Repts., vol. 6, p. 72, pi. 5, fig.
22, 1857.

Malea camura Guppy, Quart. Jour. Geol. Soc. I^ond., vol. 22,
p. 287, pi. 17, fig- 9, 1866.

Malea sp. ind. Nelson, Trans. Conn. Acad., vol. 2, p. 196, 1870.

Malea ringens Gabb, (ex parte) Trans. Amer. Philos. Sbc.,
vol. 15, p. 223, 1873.

Malea camura Guppy, Quart. Jour. Geol. Soc. Lond., vol. 32,
p. 525, 1876.

Malea camura Dall, Trans. Wag. Inst, vol. 3, pt. 6, p. 1584,
1903 (checklist).

"Jour. Ac. Nat. Sc. Phila., ser. 2, vol. I, p. 116, pi. 11, fig. 30,
1848.

PALEONTOLOGY ' ZORRITOS FORMATION 53

Malea camura Brown and Pilsbry, Proc. Ac. Nat. Sc. Phila.,
vol. 63, p. .356, 191 1.

? Dolium (Malea) sp., (vielleicht eine neue Art) Toula, Jahrb.
kk etc., vol. 61, p. 500, 1911.

Dolium (Malea) camura Woodring, Bowden Ms.

The specimens from Zorritos are large and heavy, although
not as ponderous as some of the extremely developed An-
tillean specimens. The spire is somewhat high. One large
distorted cast was probably about 78 mm. high when com-
plete. Height, about 60 mm. ; diameter, 42 mm.

Three casts of this species, with enough of the shell remain-
ing to make identification fairly sure, occur in Nelson's col-
lection. They have the somewhat high spire characteristic
of the specimens from Gatun, and thus differ somewhat from
the Santo Domingan forms, which have a lower spire. The
Bowden specimens are much smaller, but in proportion are
identical with those from Peru, the contour of the body
whorl and the apical angle of the spire agreeing entirely.
The Zorritos specimens are in a bad state o<f preservation,
and the characteristic swollen outer lip has been broken off ;
a difference in that part of the shell is the only one which
might alter the determination here offered. Toula has fig-
ured fragments of a Dolium from Gatun which is' probably
of the same species ; it is accordingly placed tentatively in
the synonymy of D. camura.

Zorritos formation. Zorritos district.

Dolium (Malea) sp. indet.

A cast of a large Dolium very close to D. camura Guppy
occurs in the collection from the Variegated beds. It differs
from that species in being more globose, with a much lower
spire. The sculpture apparently agrees. The spire appears
to be almost flat. Height of cast, 66; diameter, 65.5 mm.

This specimen, which occurs in the form of a cast lacks
the lower columella and the early whorls o>f the spire in addi-
tion to most of the shell. It is thus not describable in detail

54 STUDIES IN GEOLOGY, No. 3

but is probably a new species. Fragments of the shell which
remain are similar to that of D. camura Guppy.
Variegated Zorritos. South of Quebrada Pantheon..

Genus PYRULA Lamarck

Pyrula peruviana n. sp.

PLATE II— Figs. 5, 6.

Shell of moderate size, delicate, gracefully rounded. Spire
low, the early whorls standing up above the later ones.
Whorls about five in number, the 2^ earliest being smooth,
and the following ones delicately sculptured with spiral and
longitudinal threads. The spiral threads are of two orders
of strength; the major spirals are strong, and between them
the surface is slightly concave, ornamented by seven evenly
spaced minor threads, of which the median one is somewhat
stronger than the others. Longitudinal threads, of an order
of strength midway between the extremes of the spirals,
cross the spiral threads, appearing under the microscope to
have been laid across them. The longitudinal threads are not
evenly spaced ; they are from .5 to I mm. apart on the median
surface of the body whorl. The body whorl has the shape
characteristic of the genus. Height of figured fragment, 36
mm. ; diameter, 21 mm.

This species is very close to several Miocene species from
the Florida^-Caribbean region. It differs but slightly from
P. eopapyracea Gardner (Ms) from, the Chipola marl of
Florida, having additional minor spiral threads, seven instead
of three between the major spirals, as in eopapyracea. Pyrula
micronematica Brown and Pilsbry,47 from Gatun, is identical
in type of sculpture, differing in having the longitudinal
threads more widely spaced, and in being somewhat larger.
Pyrula carbasea Guppy,48 from the Caroni series of Trinidad,

47 Proc. Ac. Nat. Sc. Phila., vol. 64, p. 507, pi. 22, fig. 8, 1912.
48 Quart. Jour. Geol. Soc. Lond,, vol. 22, p. 580, pi. 26, fig. 7,

1866. (as Ficula carbasea}

PAI,EONTOIX)GY ZORRITOS FORMATION 55

differs in having five minor spiral threads instead of seven,
and in being distinctly larger.

Lower Zorritos. Quebrada Zapotal.

Family CYPRAEIDAE
Genus CYPRAEA Linnaeus
Cypraea angustirima n. sp.

PLATE II— Figs. 7, 8.

Shell large, solid, with a narrow, closely denticulate aper-
ture and a somewhat flattened base. The aperture is prac-
tically straight anteriorly, and is curved posteriorly. The
inner lip is distinctly shorter than the outer lip at the pos-
terior canal, and the outer lip is produced dorsally,
heightening the contrast between the two sides of the canal
as viewed dorsally. The outer lip bears about 19 teeth, of
which the posterior three or four may be produced as slight
corrugations on the basal surface of the outer lip. The teeth
on the inner lip are strong anteriorly, obsolete posteriorly.
The dorsal surface is somewhat irregular; a pronounced
central hump marks the point of greatest convexity ; before
it the surface is evenly convex, and behind it a depressed
area slopes off to the aborted inner lip at the posterior canal ;
on the other side of the canal the outer lip rises prominently.
Length, 44; width, 32; height, 26.5 mm.

This somewhat irregular, strong Cypraea is similar in
many ways to C. wilcoxii Dall,49 from the Chipola beds of
Florida. It differs, however, in being fuller in width and
height, and in its peculiar shorter inner lip. C. henekeni
Sowerby,50 from Santo Domingo and Gatun, is somewhat
similar, but differs in the tuberculate back apparently pecu-
liar to that species, as well as in its distinctly wider, more

49 Trans. Wag. Inst, vol. 3, pt. i, p. 166, pi. 5, figs. I2b, c, 1890.

50 Quart. Jour. Geol. Soc. Lond., vol. 6, p. 45, pi. 9, fig. 3, 1850
(as Cypraea henikeri}.

56 STUDIES IN GEOLOGY, No. 3

irregular aperture. C. henekeni does not have the inner
lip shortened posteriorly.

Only one specimen of this species occurs in the collection.
It is sufficiently distinct to permit its description as a new
species ; however, the depressed dorsal area before the pos-
terior canal notch may require verification through study of
more material, since it is possible that the shell may have
been deformed. Close examination of the specimen shows
this feature to be a possibly natural development, reasonably
correctable with the slight dorsal posterior depression caused
by the appression of the posterior inner lip, and 'it is accord-
ingly noted in the description as a likely natural character of
the shell.

Lower Zorritos. Quebrada Zapotal.

Superfamily CERITHIACEA

Family CERITHIIDAE

Genus CERiTHiUM Bruguiere

Cerithium infranadatum n. sp.

PLATE II — Fig. 9.

Shell large, tapering moderately, nodose, the sutures dis-
tinct, but slightly impressed. Whorls 10-12 in number; the
early whorls decorated with numerous longitudinal ridges
which are slightly arcuate, each with four lateral nodes
caused by spiral sulc'i which cross both ribs and interspaces ;
with the growth of the shell the longitudinal ribs become less
numerous and more widely-spaced ; on about the seventh
whorl they are larger, broader, and not so deeply cut by the
spiral grooves; and • on the last two to four whorls they
center into strong, round, pustular tubercles situated below
the median line of the whorl, and in some specimens near
the base of the whorl. On the specimens examined, which
are badly worn, it is difficult to tell whether or not the spiral
sculpture continues, but lines of growth are evident. Aper-

PALEONTOLOGY ZORRITOS FORMATION 57

ture unknown. Height of fragment bearing 4^ whorls,
58.5 ; maximum diameter, 27 mm.

The sculpture of the lower whorls of C. infranodatum is
similar to that of C. nodulosum Bruguiere,51 the type of
Cerithiuni s.s., a group not known fossil. The sculpture of
the earlier whorls recalls somewhat that of C. grillanum of
the Zorritos fauna. The species is characterized by
the marked difference in sculpture shown by the earlier and
later whorls.

Upper Zorritos. Quebrada del Grillo.

Cerithium grillanum n. sp.
PLATE II— Fig. 10.

Shell small to medium-sized, highly ornate. Whorls prob-
ably eight to ten in total number. Sculpture of transverse
nodes crossed by spiral cords ; on the earlier whorls the nodes
are long and undifferentiated, appearing in worn specimens as
cogs ; on the later whorls of the spire they are differentiated
into two series through the swelling laterally of their upper
and lower parts, and not through mesial sulcatlon ; the upper
of the two series gradually becomes the more prominent
until on the body whorl the lower nodules are almost obsolete,
and three additional rows of nodules, really nodulate spiral
straps, appear on the basal surface. There is some varia-
tion in the differentiation of the nodules ; on some speci-
mens the upper series gains the ascendancy well up on the
shell, whereas in others the rows are subequal until the
penultimate whorl. In specimens which show early differ-
entiation of the two series of nodes the lower series contains
more nodes than the upper. A series of fine spiral cords,
which are weaker on the nodes, covers the whorls. On the
base of the body- whorl there are two or three cords between
the noded straps ; thence upward they are similarly distri-

51Cossman, Ess. Pal. Comp., vol. 7, p. 66, pi. 3, fig. 10, 1906.

58 STUDIES IN GEOLOGY, No. 3

buted over the nodose whorls. Aperture unknown. Height
of specimen bearing 4^ whorls, 32 ; diameter, 16 mm.

A number of worn specimens of this Cerite were collected
from the Upper Zorritos formation, and one from the upper
part of the Variegated beds. A small group from the Varie-
gated at Quebrada de los Angeles may be referable to this
species, but they are in bad condition, and are not identifi-
able. The most closely related species appears to be C. rus-
selli Maury,52 from the upper horizon in Santo Domingo.
C. grillanum differs from russelli in that the larger and
smaller nodes of the sculpture are reversed in position, the
more prominent ones being above; and there is no sub-su-
tural sulcus in grillanum; the prominent nodes swell out
beneath the suture with no interruption.

Upper Zorritos; Variegated. Quebradas del Grillo, del
Toro, de los Angeles, Tijeritas, near Boca Pan.

Genus POTAMTD^S Brongniart
Potamides ormei var. infraliratus n. var.
PLATE II — Fig. n.

Shell large and solid, the whorls closely coiled, the apical
angle moderate. Early whorls unknown : the complete shell
might have ten or twelve whorls. Whorls usually flat, some-
times slightly convex; the sutures ordinarily indistinct.
Cancellate sculpture of quadrate beads formed by the inter-
section of longitudinal and spiral grooves which set off
strap-like ribs ; the longitudinal grooves are arcuate on each
whorl, and are about 30 in number to the whorl ; the spiral
furrows set off three rows of beads, of which the anterior
two are subequal in width and the posterior-most is much
broader. Beneath the beads of the body whorl are seven or
eight strap-like spiral ribs which form the basal sculpture.
The body whorl flares at the aperture, the sculpture opening

83 Bull. Amer. Pal., vol. 5, No. 29, p. 123, pi. 22, figs. 2, 3, 1917.

PALEONTOLOGY ZORRITOS FORMATION 59

out in fan-shape, and the sutural margin ascending to cover
part of the preceding whorl. The aperture is large, pointed
oval in shape, with the outer lip strong and thickened and
the callus heavy. The posterior notch is distinct ; the anter-
ior canal is truncate, sharp. Height of fragment bearing
the lower four whorls, 37 mm. ; maximum diameter at base,
24 mm. ; at 4th whorl, 10 mm. A longer fragment, bearing
5 whorls, but lacking the outer lip of the aperture, is 41
mm. in height, and probably had a maximum diameter of
27 mm.

Several specimens of this Potamides, from both the Upper
Zorritos and the Lower Zorritos formations, are very close
to P. ormei Maury,53 from the Middle Oligocene of Santo
Domingo, and might be united with it in a loose regard for
specific limitations, but the sculpture varies constantly from
that of P. ormei, and the Zorritos specimens are distinctly
larger and heavier. The upper set of quadrate beads on the
whorls of infraliratus is proportionally larger than in ormei,
and there appear to be more spiral ribs on the base. Maury's
figure is not clear, and her description lacks mention of
many important points, but there are apparently about five
lirae beneath the beads on the body whorl of ormei, instead
of seven or eight, and the number of longitudinal grooves
to the whorl seems to be less than in infraliratus. These
differences are very constant in the specimens of the Hop-
kins collection.

Lower and Upper Zorritos. Quebradas del Grille, de loa
Angeles and Heath.

Family TURRITELLIDAE

Genus TURRITELLA Lamarck

Turrit ella altilira Conrad

PLATE II— Fig. 12.

"Idem., p. 126, pi. 22, fig. 8.

60 STUDIES IN GEOLOGY, No. 3

Twritella altilira Conrad, Pac. R.R. Rept., vol. 6, pt. 2, p. 72,
pi. 5, fig- !9, i857-

Not T. altilira Gabb, Jour. Ac. Nat. Sc. Phila., vol. 8, p. 34*.
pi. 44, figs. 9, 9a, 1877 (=T. sapotensis Brown and Pilsbry, loc.
cit, p. 359, PL 27, fig..io).

Not T. altilira Grzybowski, Neues Jahrb., B.B. 12, p. 645, pi. 20,
fig. 7, 1899 (=-T. dicingula Woodring Ms. )

Turritella gabbi Toula, Jahrb. k.k. geol. Reichs., vol. 58, p. 695,
pi. 25, fig. 5, 1908.

Turritella altilira Brown and Pilsbry, Proc. Ac. Nat. Sc.
Phila., vol. 63, p. 358, pi. 27, figs; 2, 3, 1911.

"Subulate, carinated; volutions with 2 distant, elevated,
revolving, crenulated ribs, interstices with revolving lines;
body volution, bicarinated at the angle." — Conrad, 1857.

" — It tapers slowly, and, judging from the broken speci-
mens seen, must attain a length of upwards of 100 mm.,
with a basal diameter of 18 mm., and probably over 25
whorls. Each whorl bears two very high spiral ribs, cren-
ulated at their summits, the lower rib narrow, the upper
wider, usually but not always double at the ridge, or with a
lower cord below the main one. The deep concavity between
the ridges has sculpture of several unequal spiral cords, more
or less crenulated ; and the whole surface, when most perfect,
has a fine spiral striation. The last whorl has a third rib,
sub-peripheral in position, the base below it somewhat con-
vex, marked with some radial striae and lamellae. On the
early whorls the spiral ribs are less prominent and the inter-
stitial beaded cords are rather better developed. "—Brown
and Pilsbry, 1911.

In the Zorritos forms the upper rib is not double, but it
often bears the lower cord noted by Brown and Pilsbry.
The difference in width between the two prominent ribs is
not always marked. The crenulations are partially lost on
the ribs of the body whorl, and the interspace is more
rounded out, more gently concave. On most of the whorls
of the spire there is a fine indentation below the first cord

PALEONTOLOGY ZORRITOS FORMATION 61

under the upper rib which simulates a suture. Synthesis of
three fragments gives the following measurements : Length
(163/2 whorls) 90 mm.; diameter at base, 17 mm.; diameter
at posterior extremity, 3.5 mm.

The species erroneously referred to this name by Gabb
(loc. cit.) has been properly differentiated by Brown and
Pilsbry (loc. cit.) as T. sapotensis. Comparison of Gabb's
figure with the photograph of the same specimen given by
Brown and Pilsbry shows how far some of Gabb's figures
may be trusted. Grzybowski (loc. cit.) referred a specie,;
from Caleta Grau to T. altilira, basing his decision, appar-
ently, on Gabb's work, and quoting him only in synonymy
Grzybowski's figure has the appearance of being less trust-
worthy than that of Gabb, if his specimens agreed at all with
Gabb's figure, and it is doubtful that he had the same form.
It is difficult to place Grzybowski's species ; his figure indi-
cates roughly that it is probably of .the altilira group, but if
even the broad lines are correctly depicted it is neither
altilira nor sapotensis. It is highly probable that it is closest,
possibly equal to T. dicingula Woodring (Ms), from the
Bowden Miocene of Jamaica; the figure corresponds more
nearly to the specimens from Bowden than to any other
seen by the writer.

Turritella guppyi Cossmann (=T. tornata Guppy 54) is
similar, but has a line above the upper rib which is not
present in altilira, and has two rows of granules between
the ribs, whereas altilira has three or more. Brown and
Pilsbry (loc. cit.) have noted that the interstitial sculpture
of guppyi is much less prominent. The specimens of guppyi
from Bowden are more delicate than those of altilira from
Peru.

Turritella dicingula Woodring (Ms) from the Bowden
beds of Jamaica, is also related, but varies more widely than

54 Quart. Jour. Geol. Soc. Lond., vol. 22, p. 580, pi. 26, fig. 12,
1866.

62 STUDIES IN GEOLOGY, No. 3

does guppyi; it is still more delicate, and has a somewhat
greater apical angle. The ribs are subequal, the anterior, if
any, being more prominent in both guppyi and dicingula.
Lower Zorritos. Between Quebradas Heath and Charan.

Turrit ella alturana n. nom.

II— Fig.|3.

*Turritella plana Nelson, Trans. Conn. Acad., vol. 2, p. 188, 1870;
not of McCoy, nor of Brinkhorst, 1861.

Shell large, heavy, solid, the apical angle small and the
spire very high. Whorls, averaging 16 in number, pos-
sibly more, flat-sided, the earlier ones being set off merely
by a deep, sharp, L-shaped depression at the suture, and
the later ones having the semblance of a carina near the
base, the sutural depression being broader. In full grown to
gerontic specimens the body whorl and the penultimate are
rounded-convex, the surface being distorted by rough and
irregular growth-wrinkles. Sculpture of fine subequal
threads, about 17 in the space of 5 mm. on the later whorls
(not 25, as stated by Nelson), separated by still finer inter-
spaces. The threads coalesce occasionally, two or more
combining to form a group set off on either side by deeper
depressions. Broadly sinuate growth-lines are discernible
over the entire shell ; on the last two whorls of old specimens
they are magnified into irregular wrinkles. Length of frag-
ment bearing jy2 lower whorls, 117 mm.; diameter of body
whorl, 29.25 mm. ; of uppermost whorl, 13.5 mm. Estimated
length of complete full-grown specimen bearing 17 whorls,
163 mm.

Well-defined fragments of the anterior portion of this
species occur in a block of gray marl which was found on
the beach near Quebrada Tijeritas, north of Zorritos. Since
all three members of the Zorritos formation are exposed
within reasonable distance of the spot it is not safe to suppose
the origin of the material, and when the fact is considered
that the species is not typical of the American Miocene, but

PALEONTOLOGY ZORRITOS FORMATION 63

rather of the Eocene Turritellas, confirmation of its strati-
graphic position in Peru must be forthcoming before it can
be taken seriously. The type specimen, beautifully pre-
served, and a striking object, occurs in Nelson's collection,
and was undoubtedly taken from a different locality. Inas-
much as the Zorritos formation is the only one exposed
within the area from which the Hopkins, and, presumably,
Nelson's fossils were taken, it is highly probable that 7\
alturana occurs somewhere within the limits of that forma-
tion. T. andersoni Dickerson,55 from the Tejon Eocene of
California, is the most closely related form, and excepting
its marked difference in size might be held by some to be
identical with T. alturana. Its sutural depression is by no
means as prominent as is that of alturana, but otherwise the
figure (magnified three times) given by Dickerson corres-
ponds exactly to the smaller specimens of alturana in the
Zorritos collections.

It is also close to T. infragranulata Gabb,56 from the Cali-
fornia Eocene, but lacks the granules of that species. T.
pachecocnsis Stanton57 is similar, but has a much wider
sutural depression, and bears granules. Two species from
the Alabama Eocene, T. alabamiensis Whitfield 58 and T.
saffordi Gabb,59 are similar, but much smaller and more
delicate.

Horizon unknown. Loose block near mouth of Quebrada
Tijeritas.

Turritella bifastigata Nelson
III— Fig. i.

Turritella bifastigata Nelson, Trans. Conn. Acad., vol. 2, p.
9, 1870.

53 Univ. Cal. Bull. Geol., vol. 9, p. 501, pi. 42, hgs. 9, gb, 1916.
56 U. S. G. S. Ann. Rept. No. 17, p. 1044, pi. 66, fig. 3, 1896.
"Idem., p. 1043, pi. 66, figs. I, 2.
58 Bull. Amer. pal., vol. i, No. 4, p. 109, pi. n, fig. 6.

59 Ibid., p. 109, pi. 11, fig. 7.

64 STUDIES IN GEOLOGY, No. 3

Turritella gothica Grzybowski, Neues Jahrb. f. Min., etc., Beil.
Bd. 12, p. 645, pi. 20, fig. 10, 1899.

"Shell turreted, slender, whorls twelve to sixteen, flat or
slightly concave, except the body whorl, which is regularly
convex; whorls bordered on each side by a strong obtuse
ridge. Intermediate spaces ornamented by fine, raised,
nearly equidistant, revolving lines, about ten in the space
of five millimeters. Sutures small and narrow x x x. Body
whorl somewhat convex, except in young shells; strongly
wrinkled by the lines of growth, which, on well-preserved
specimens, are strong and acute. Base of this whorl marked
by from seven to ten -lines, nearly as strong as the ridges of
the upper whorls. Aperture rounded; outer lip thin and
slightly produced below." — Nelson, 1870.

The ridges or shoulders at the sutural extremities of the
whorl set off the suture very clearly, giving the appearance
of lips. The posterior rib is distinctly stronger, and tends
sometimes to lap over the base of the preceding whorl, giving
the spire a slightly step-like surface. Length of anterior
fragment of middle-sized individual bearing 7 whorls, 61.5
mm. ; diameter of the body whorl, 18 mm. Diameter of the
body whorl of a larger specimen, 20.5 mm. Estimated
length of a full-grown shell, 88 mm.

Grzybowski's figure is that of a form somewhat more
squat than that apparently typical of the species, but the
essential characters of T. bifastigata are plainly enough
evident to make certain the synonymy of his gothica. In the
local fauna, T. alturana is most similar, but differs in being
much larger, stouter, and in lacking the ridges bordering
the sutures. Grzybowski mentioned T. cathedralis Brongni-
art60 from the Lower Miocene of Europe, as similar, but
reference to Sacco's figure will show that the sculpture of
all varieties of cathedralis is far coarser, and that the pos-
terior ridge or lip is far more obtuse.

Sacco, Piemonte, pte. 19, p. 31, pi. 3, figs. 12-24, inc., 1895.

PALEONTOLOGY ZORRITOS FORMATION 65

T. reversa Waring,61 from the Martinez Eocene of Cali-
fornia, is apparently so close that there is possibility of
identity, but the figure of reversa is too poor, and the descrip-
tion too inadequate to allow a decision, and the matter must
be held in abeyance pending comparison of material, with the
possibility in mind that reversa may be a synonym. The
only difference notable is that the shoulder appears stronger
in bifastigata. Waring compares his species with T. hum-
erosa Conrad,62 from the Eocene of Maryland, and if the
similarity exists reversa may be quite different from bifas-
tigata, for humerosa differs materially.

T. concava Hutton,63 from the Miocene of New Zealand, is
very close, but has a wider apical angle, and the posterior
shoulder is not as prominent as in bifastigata. There is a
submedian ridge on the whorls of concava which is certainly
not present in bifastigata.

Upper Zorritos. Quebrada del Toro.

Turritella filicincta Gryzbowski
III— Fig. 2.

Turritella filicincta Gtzybowski, Neues Jahrb. f. Min. etc., B.B.
12, p. 645, pi. 20, fig. 2, 1899.

"Die conischen Windungen sind dicht iiber der Naht mit
scharf nach unten abgeschnittenem Kiel versehen. Die ganze
Oberflache is mit tiberaus feinen Spiralleistchen gezeichnet,
die dicht beieinander liegen. Es stehen deren 26 auf einen
Raum von 5 mm. In dem oberen Teile der Windungen sind
sie ziemlich gleich, in dem unteren dagegen liegt immer ein
starkeres .Leistchen zwischen zwei schwacheren. An der
Basis verlaufen 4 Spiralrippen, die auch mit den feinen
Leistchen bedeckt sind." — Grzybowski, 1899.

61 Proc. Cal. Ac. Sc., 4th ser., vol. 7, p. 88, pi. 12, fig. 15, 1917.

62 Md. Geol. Surv., Eocene, p. 148, pi. 27, figs, i, la, 1901.
83 New Zeal. G. S., Pal. Bull. 3, p. 7, pi. 5, fig. 4,

66 STUDIES IN GEOLOGY, No. 3

In addition to the fine sculpture noted by Grzybowski
there are four raised spiral ribs on each whorl, somewhat
similar to the basal keel, but much more subdued. The
anterior three of these ribs are equally spaced, but the space
between the fourth and the third is smaller than the others.
The alternation of strong and weak threads in the finer
sculpture, noted by Grzybowski, is best seen under the micro-
scope. The subsidiary sculpture covers the keel and ribs,
but opens out somewhat in their surfaces. The shell tapers
slowly; Grzybowski's figure suggests an apical angle larger
than that common to the species. Length of fragment
bearing 5^ whorls, 54.5 mm. ; diameter of body whorl, 17.5
mm. ; diameter of 6th whorl, 9.5 mm.

This species differs from T. bifastigata Nelson, of the
Upper Zorritos fauna, in its development of but one sutural
keel or shoulder, and in its more regular sculpture. In
filicincta the stronger keel is at the posterior margin of the
whorl ; in bifastigata the reverse is true. T. filicincta differs
from its variety varicosta in its greater regularity of sculp-
ture and comparatively more prominent keel. It differs from
T. alturana; of the Zorritos fauna, in the possession of a
keel, and in its diversification of sculpture. T. megalobasis
Dall,64 from the Orthaulax bed at Ballast Point, Florida, is
similar in sculpture and general appearance, but its apical
angle is far larger, and its keel is not as prominent.

Lower Zorritos. Between Quebradas Heath and Charan.

Turritella filicincta var. varicosta n. var.
PLATE III— Fig. 3.

This variety differs from T. filicincta in having a larger
number of primary ribs, irregularly arranged, and in having
a somewhat less prominent keel. One specimen only is in the
collection, and it is somewhat worn, with the subsidiary
sculpture not altogether clear; but it appears to agree with

"Trans. Wag. Inst., vol. 3, pt. 2, p. 310, pi. 17, fig. n, 1892.

PALEONTOLOGY ZORRITOS FORMATION 67

T. nlicincta in that respect. Its general relationships are
similar to those of filicincta.

Upper ZorritoS'. Mouth of Quebrada de las Alturas.

Group of TURRITELLA NELSON i

Twelve of the species and varieties of Turrit ella in the
Zorritos fauna form a natural group whose internal rela-
tionships are sufficiently interesting morphologically and
probably genetically to make it better worth while to con-
sider them together than to leave the discussion of their
differential characteristics to the isolated remarks normally
accompanying each specific description. The group is desig-
nated here the "group of Turrit ella nelsoni" as much because
of the apparent abundance of that form in the fauna as
because of its central or typical position in the group as
here presented. The species and varieties which constitute
the group are :

Turrit ella inca Grz.

inca var. trita n. var.

nelsoni n. nom.
" 'nelsoni var. rotundata (Grz.)

nelsoni var. trullissatia n. var.

infracarinata Grz.

infracarinata var. zorritensis n. var.

prenuncia n. sp.

prenuncia var. inconspicua (Grz.)

robusta Grz.

robusta var. abrupta n. var.
" char ana n. sp.

Progressive development in the group is characterized by
changes along two different lines, one from bicarinate con-
vex forms (inca, trita) to rounded convex forms (rotundata,
inconspicua, zorritensis) and the other from the bicarinate
convex forms (inca) through monocarinate forms with the
supracarinal surface flat, conical (trullissatia, infracarinata,

68

STUDIES IN GEOLOGY,, No. 3

BiCOrinol* forms with Cquol y»r««dj ot>Ov*
poiTenor can no-, wlwrls appear banded

INCA

* *

155

£ X / Sli^Htltf bicori not* forms v»irH 2 promio«nt one*

q^ $;{ ing subsidiary -threads above tfct posW.'cr tarina

IKC A vor.TRlTA

Forms v»'rt> on«- corino, tfcc band oDsol** in odwlt
\ Whorl*; manif fin* int«r*tihal thr«od^, tht aoprocor, n« I

Sorfttrr cenyvx, ni'ln an angular ctravati'tn «^ fnc f>o4t.r,0r
porl •{ rf,, rvh«rl

NELSON I

forms fw.'th rhf cor i no ebeol«1«, ftc wharls
, ihc scoljc^ur* much a* in MEL3o

WEL50NI rar. KOTUNDATA

Smell (•mi w'rt) *>« nrtnic Yvherl*
fltt aflolt whorls round«d,

PREWOKCIA «r. JKCOK5PICUA

(l?ro i''n»s indicate rarielal

praminrnT e*rina, rhe sculp fi'r«
a « fn NC1.SOHI (4 main Mprorari nal tt>r/< ' v
K I fh« oueroeorinal svri'arr ?!«'', end no indfnt.
^ 1 tion «1 *»>» po-jlt-rior part «f rfi* wh»r(

k I TRULLT5SATIA

5 nirf> eon»«. t»an<Hi rvhorlj. with rht seolp- § / Shape «f wKerl as «n yar. Tipji.i3S»»TiA , btrt

as in INFR^CKinrV/HTA ~/ nerrxalli, w.rt> 5promin«o7 *i;pra*«r.'n*l H.rr«a»,

X . ~- - !.»•-- • • ' - - •-

INFRACARINftTA

Torn* »»i.rt> meneean'
nnerls, ivitn rnt italffon at

Styractrinal }<Jfftf'e flat

PRENUr(CIA

showing iiatcr/i&.l
relationships of frwy oP
Titm'je 77* ne2so n i

PALEONTOIXJCY ZORRITOS FORMATION 69

prenuncia) } to forms with one prominent anterior carina and
the main surface of the whorls concave (robusta, charana
abrupta). The morphologic relationships of the members
of the group to one another may be pointed out most
clearly by the use of the accompanying diagram. The
arrangement of the species in the diagram has not
been made with the idea of expressing consistent
genetic relationships, and as a whole it could hardly be
regarded as a phylogenetic table; but it is not impossible
that it may indicate something of the general ancestry of 'the
different species, and if we disregard the direction in which
evolution may have proceeded, portions of the arrangement
seem to express most likely genetic relationships.

The variety trita is distinguishable from T. inca by the
obsolescence of both the posterior carina and the subsidiary
threads above the main carina. In trita the space corres-
ponding to the band in inca bears no prominent threads, and
the band is purely vestigial, the upper carina being faintly
distinguishable. In nelsoni the upper carina is lost, and there
is a varied development of the interstitial threads, with a
tendency in some forms toward rounding of the anterior
carina. Such partially rounded forms verge on the variety
rotundata, and although they represent a partially expressed
transition, a large number of specimens shows that the two
are distinct, that the carina is constantly present in nelsoni,
even though it is less sharp in some forms than in others.
The differential characters of T. nels&ni are the single carina
at the anterior fourth of the whorl-length, the slightly con-
vex supracarinal surface with four- primary and varying
subsidiary threads, and the sutural indentation formed by a
short, sharp bevelling of the posterior part of the whorls and
the longer pre-carinal surface of the succeeding whorls.

Grzybowski's figure of T. inca depicts the earlier whorls
as more rounded than the later ones, which bear the charac-
teristic band. A curious reversal of this characteristic is

70 STUDIES IN GEOLOGY, No. 3

found in nelsoni, the earlier whorls of which are distinctly
banded similarly to inca, with the later whorls rounded.

The neanic whorls of inconspicua are monocarinate in-
stead of bicarinate, as in the young of nelsoni, and the sculp-
tural threads are more widely spaced. The adult whorls of
both are rounded, but the difference in sculpture of incon-
spicua is easily recognizable as constant. The difference be-
tween T. prenuncia and its variety inconspicua parallels that
between T. infracarinata and its variety zorritensis; pre-
nuncia is a carinate, slightly rounded form, with straight-
sided whorls, and inconspicua has the whorls well rounded.
The sculpture of the two is practically the same. The early
neanic whorls of inconspicua are not known, but those parts
of the spire available indicate that it is probably somewhat
like that of form (a) of prenuncia. (see systematic discus-
sion of prenuncia.)

The forms which branch off diagrammatically from
nelsoni in the other direction, towards flat-angular and con-
cave-angular outlines, are of two series, the first of which
(trullissatia, infracarinata \ prenuncia) is closely related to
T. nelsoni, being different chiefly in having the supracarinal
surface flat, and the second of which (robusta, charana,
abrupta) does not show relationships as clear as the fore-
going, but which nevertheless seems to represent a continu-
ation of the general type, the common difference lying in the
concavity of the whorls above the suture.

The variety trullissatia is distinct from T. nelsoni, on one
side, through its flat supracarinal surface, with a generally
sharper carina; on the other side it differs from infracarin-
ata in the sculpture, the interstitial threads being absent, and
five instead of four prominent threads occupying the supra-
carinal surface. The variety trullissatia is further distinct
from nelsoni in the absence of a sutural notch, tendency
towards greater diversification of sculpture, and greater
coarseness of the primary and secondary sculpture. T. in-
fracarinata apparently represents a development of trullis-

PA^ONTOLOGY ZORRITOS FORMATION 71

satia with the strengthening of the chief tertiary thread
behind the carina to secondary rank and the obsolescence of
the subsidiary sculpture. It is like trullissatia in shape, and
different in sculpture. The relationship is sufficiently close
for the consideration of infracarinata as a variety of trullis-
satia, but since the latter is itself a variety of nelsoni, and
infracarinata is too far removed from nelsoni to be consid-
ered as a variety of it on a plane with trullissatia, the rela-
tionship can not be truly expressed through taxonomic
scheme, and it is necessary to retain infracarinata in the
status of a species. The variety trullissatia has the sculp-
ture of nelsoni, but differs in shape ; T. infracarinata has the
shape of trullissatia } but differs in sculpture; infracarinata
is thus different in both characters from nelsoni. The
ground plan of the sculpture is similar for all the forms of
the nelsoni group, and in those forms which do not bear
subsidiary threads the seven or eight primaries remain
rather constantly.

The variety zorritensis of T. infracarinata differs from
the true species in its rounded whorl-outline. The sculpture
is closely similar. In form and ground-plan of sculpture
zorritensis is similar to nelsoni, and thus represents a con-
necting link between infracarinata and nelsoni; however,
it lacks the diversified sculpture characteristic of nelsoni
and its varieties, and in consistent alignment of affinities it
belongs in a place close to infracarinata, whose relationship
to the other forms has just been reviewed.

The last three members of the group, robusta, var.
abrupla, and charana, differ from their nearest relatives in
contour of the whorls, prominence of the carina, and sculp-
ture; there is thus less in common between these species
and the rest of the group than between other smaller
divisions.

T. robusta differs from its variety abrupta almost solely
in the character of the sculpture, which consists of widely

72 STUDIES IN GEOLOGY, No. 3

spaced threads in robusta, and of closely set cords or ribs in
abrupta. The point of smallest whorl-diameter seems to be
lower on the later whorls of abrupta, with the surface curv-
ing outward to the suture instead of vertically, as in robusta,
but a larger amount of material might show inconstancy in
that feature. Both these forms, however, differ in this
point from char ana, in which the suture is at the apex of a
distinct notch, the posterior surface of the whorl inclining
toward it at an appreciable angle. Charana differs further
from both in the keel, which is somewhat more solid and less
attenuate, although none the less sharp. The sculpture of
charana is similar to that of abrupta, but the threads seem
to be more distantly spaced than in that variety.

All of the species named are in the Hopkins collection
save Turrit ella inca Grzybowski, whose relationships are
discussed here on the basis of Gryzbowski's figure and
description. It is somewhat unsatisfactory to work with
figures as poor as those published by Grzybowski, but in
this case the characteristics of inca seem to be sufficiently
well defined to allow conclusions from the data available.

It is only natural to find that those nearly related species
which are represented by an abundance of material show
puzzling intergradations, and a separation of such into
groups best conforming to the limitations of a species has
not been always as clear a matter as the exactness of descrip-
tory or diagrammatic differentiation might suggest; how-
ever, the writer has endeavored to select as dividing points
those characteristics which promise to serve best to make
future study of the fauna clear, doing so in full apprecia-
tion of specific values as, well as arbitrary matters of distinc-
tion. Thus although intergrading forms may present diffi-
culty, it is believed that the characters emphasized in this
presentation will give an intelligible index to the placing of
those forms which belong in the general group.

PALEONTOLOGY ZORRITOS FORMATION 73

Turrit ella inca Grzybowski

Turritella inca Grzybowski, Neues Jahrb. f. Min., etc., Beil. Bd.
12, p. 644, pi. 20, fig. i, 1899.

"Umgange convex, etwas zweikantig. Die 4 untersten
Spiralleistchen sehr schwach angedeutet, dicht beieinander
liegend, die fiinfte und siebente Rippen sind die starksten;
sie bilden zwei Kanten, die ein flaches, in der Mitte mit
schwachen Leiste versehenes Band umgrenzen. Es folgen
gegen oben noch 5 ziemlich starke, gleiche Spiralleistchen.
Die hohe des der Spitze entbehrenden Bruchstiickes 90
mm, Dicke und der Miinding 22 mm., oben 6 mm. Die
totale Lange mochte bis 115 mm. betragen." — Grzybowski,
1899.

This species does not occur in the Hopkins or Nelson
collections, but it is mentioned here to complete the group
of which it is an end member. Grzybowski has pointed out
its similarity to varieties of T. triplicate* Sacco, from the
Miocene of Italy. It is closer to T. gatunensis Conrad G5
from the Gatun Miocene. The only notable difference be-
tween the two lies in the apparently sharper early whorls of
gatunensis, and a heavier thread above the band, together
with the lack of the thread on the band mentioned and fig-
ured by Grzybowski ; but the figure of inca is poor, and com-
parison of material might reveal specific identity.

Upper Zorritos or Variegated. Pantheon at Zorritos.

Turritella inca var. trita n. var.
PLATE III— Fig. 4.

Shell much as in T. inca, with the following characteristic
differences: The upper carina barely noticeable instead of
prominent; the band almost smooth, bearing one subsidiary
thread near the anterior carina ; above the band are only two

85 Brown and Pilsbry, Proc. Ac. Nat. Sc. Phila., vol. 63, p. 358,
pi. 27, fig. 4, 5, 9, 1911.

74 STUDIES IN GEOLOGY, No. 3

prominent threads, with interstitial threads barely percep-
tible. The chief point of difference lies in the less promin-
ent band. Length of fragment bearing the five anterior
whorls, 67 mm. ; maximum diameter at base, 22.5 mm.

The differentiation of the variety trita from the typical
inca in the absence of abundant material has been a matter of
some deliberation ; but as matters stand the differences shown
by the form here proposed are too clear to permit its entire
identification with Grzybowski's species. T. (Haustator)
triplicatus var. dertosimplex Sacco,66 from the Miocene of
Europe, is closer to trita, apparently, than to the inca figured
by Grzybowski ; the comparison drawn by him places inca
midway between the varieties der to simplex and superneapli-
cata of Sacco's triplicatus, and reference to Sacco's figures
shows some of the characteristics of trita to be susceptible
of similar placing. Observations such as that give rise to
the doubt concerning the identity of inca. Under present
circumstances, however, the best course seems to be to
retain trita as separate, particularly since the strength of the
upper carina, the dividing point, is constant in both the
Italian forms.

Upper Zorritos. Quebrada del Toro.

Turritella nelsoni n. nom.
PLATE III— Figs. 5, 6.

Turritella suturalis Nelson, Trans. Conn. Acad., vol. 2, p. 188,
1870, (ex parte} ; not of Sowerby, nor of Phillips.

Young shell small, delicate. Whorls tightly coiled, the
apical angle moderate. Neanic whorls characterized by prom-
inence of two subcentral threads which set off a band similar
to that characteristic of the adult T. inca, but situated farther
back on the whorl ; in the first two neanic whorls these two
threads are the only ones discernible, but on the third whorl
a faint subsidiary thread appears below the band and near

"Piemonte, pte. 19, p. 27, pi. 2, fig. 33, 1895.

PALEONTOLOGY ZORRITOS FORMATION 75

the suture. On the fourth whorl this subsidiary thread is
stronger, and a distinct intermediary thread develops on the
band, which is gradually growing less prominent ; anterior to
the band another thread develops. On the fifth whorl two
additional threads appear above and below the one before
the band, making three subequal threads between it and the
suture. On the sixth whorl a subsidiary thread appears
between the posterior thread of the band and the one behind,
and on the seventh whorl another subsidiary thread appears
between this posteriormost prominent thread and the suture.
This sculpture continues on the spire, the threads gaining
strength ; on the body whorl the threading seems somewhat
subdued. At about the sixth whorl of the spire the band
has lost prominence, and succeeding whorls are rounded in
outline; the two threads which form the band in the neanic
whorls are so prominent as to give a bicarinate appearance,
but this is lost in later whorls. Some specimens show whorls
with somewhat flattened sides, but most are evenly convex.
Length of young specimen, 17.25 mm.; diameter, 5.5.

Adult shell strong, large. Whorls twelve or more, the
sutures distinct ; shape of whorls convex, a prominent carina
at about the anterior fourth of the whorl-length marking
the point of greatest diameter. Above the carina the surface
is slightly convex, with a distinct indentation just before
the suture ; before the carina the surface is flat to slightly
rounded (in cross-section), turning in somewhat sharply
to meet the suture. Sculpture of four primary cordate
threads behind the carina, the second from the carina fairly
constantly the most prominent, the others subequal ; between
the primary threads are variably placed secondaries, of which
that just above the carina is usually most prominent; and
tertiary threads occur in most specimens, particularly near
the carina. The carina may or may not be marked by a
thread ; sometimes it is set off by two closely set secondary
threads. Before the carina are three to four secondary
threads, between which in the adult whorls tertiary threads

76 STUDIES IN GEOLOGY, No. 3

are sometimes noticeable. In most specimens growth-lines
are evident on all the whorls ; in the lower whorls they are
imbricate, the growth-periods being s°et off. Base rounded,
the carina becoming obsolete near the peristome. Dimen-
sions of fragment of largest specimen: length of 3 whorls,
57 mm.; maximum diameter, 26.5 mm. A fragment bear-
ing 5^2 whorls is 78 mm. long, with a maximum diameter
of 25 mm.

The generally central position of this species in the group
of related forms has suggested giving its name to the group.
The comparatively large amount of material in the Nelson
and Hopkins collections shows somewhat diverse varia-
tion, particularly in sculpture, and it has been difficult to
discern those characters which might rationally be held to
carry specific weight ; however, the salient features men-
tioned in the discussion of the group seem to express specific
relationship, and at all events are certainly constant and
recognizable in the suite of specimens studied. The number
and position of the subsidiary threads is by no means con-
stant for the species as here delimited; the outline of the
whorls and the primary sculpture seem to offer the best
criteria for recognition.

T. nelsoni was described by Nelson (loc. cit.) as T. sutu-
ralis, but, that name being preoccupied, it is necessary to
propose a new one. In the group of specimens labelled
suturalis by Nelson were a half-dozen or more of rotundata
Grzybowski. Nelson's description, though too brief and in-
exact, unaccompanied by a figure, shows that he drew no
distinction between nelsoni and rotundata. Grzybowski
apparently had no true nelsoni in his collection.

The young forms are described separately from the adults
on account of the possibility that they may be of different
species. The writer hesitated some time before deciding that
they should be united, and although all evidence now avail-
able seems to require such procedure, there are important
arguments for their separation. The smaller forms have the

PALEONTOLOGY ZORRITOS FORMATION 77

appearance of adults, and occur in fairly uniform size,
without enough specimens clearly transitional to the large
ones to make their identity certain. In controversy to that is
the fact that the development of the sculpture is identical
for the two — the small forms show exactly what one would
expect to find in the young of nehoni, and it does not seem
rational to separate them.

The small forms are strikingly similar in many ways to
T. plebeia Say,67 of the Miocene of Maryland and neighbor-
ing regions. The neanic whorls of plebeia are subcentrally
bicarinate, apparently banded as in the young of nelsoni.
The sculpture is generally similar but in plebeia the diversi-
fication of the threading appears in earlier whorls than in
nelsoni, and the sharpness of the threads is greater. In addi-
tion, the sutural depression in plebeia is deeper. The adult
forms are very close to T. terebralis var. subgradata Sacco,68
from the Helvetien of Italy, differing chiefly in having less
coarse and more diversely threaded sculpture.

Upper Zorritos. Quebradas del Tore and los Angeles.

Turrit ella nelsoni var. rotundata (Grzybowski)
PLATE III— Fig. 7.

Turritella suturalis Nelson (ex parte) Trans. Conn. Acad., vol. 2,
p. 188, 1870; not of Sowerby, nor of Phillips.

Turritella rotundata Grzybowski, Neues Jahrb. f. Min., etc., Beil.
Bd. 12, p. 643, pi. 20, fig. 6, 1899.

"Die Umgange sind stark convex, gerundet, die Naht tief.
Das Gewinde ist mit Spiralstreifen verziert, von denen die
4 untersten zusam>men 1/3 der Umgangshohe einnehmen,
schwach angedeutet sind, und nahe beieinander liegen. Die
oberen 4-5 werden zu starkeren Spiral-rippen und es schalten
sich zwischen sie noch ganz feine secundare Streifchen ein.
xxx Hohe des Bruchstiickes von 4 unteren Ungangen 65

6T Md. Geol . Surv., Miocene, p. 234, pi . 56, figs. 4-9, incl., 1904.
68 Piemonte, pte. 19, p. 9, pi. i, fig. 26, 1895.

78 STUDIES IN GEOLOGY, No. 3

mm. Breite an der Munching 27 mm., oben 15 mm." —
Grzybowski, 1899.

The variety rotundata differs from the true nelsoni only in
having the whorls evenly rounded, with the carina absent or
very faintly noticeable. The sculpture is exactly similar to
that of nelsoni. The point of greatest whorl-diameter is
at the position of the carina, but the surface is evenly
rounded. Dimensions similar to those of nelsoni.

This variety is closely similar to T. terebralis var. turri-
tissima Sacco,*9 from the Aquitanian and higher horizons
(chiefly Helvetien) of Italy and central Europe, but the
whorls are more convex and the sculpture apparently finer
and more diverse than in turritissima.

Upper Zorritos. Quebrada del Toro.

Turrit ella nelsoni var. trullissatia n. var.
PLATE III— Fig. 8.

Shell large, heavy. Whorls angular, roughly sculptured
with strong, cordate threads. Surface of whorls monangular
in profile, a prominent carina at about the anterior fourth
and the surfaces before and behind the carina plane in
profile. Sculpture of spiral threads clearly differentiate into
four orders of strength ; of these the first is represented by
one, the carinal thread, which is very strong and cordate;
behind the carina are four threads of the second order, which
are also strong; between the second and third of these is a
thread of the third order which occurs constantly in all speci-
mens seen, invariably located nearer to the third secondary
thread behind the carina : other tertiary threads occur be-
tween the first and the second and between the fourth and
the suture, but they are not constant and are always slightly
weaker than the first mentioned. Before the carina is one
secondary thread half-way between it and the suture, with a
tertiary thread on each side of it, and a basal secondary

Idem., fig. 27.

PALEONTOLOGY ZORRITOS FORMATION 79

thread at the suture. These pre-carinal threads are weaker
in some specimens. Threads of the fourth order are very
fine and closely spaced, occurring over the entire length of
the whorl. The main thread is covered with these quaternary
threads. Lines of growth are prominent, particularly on the
later whorls; they incline to the right (shell held upright)
at an angle of about 45° from the suture halfway to the
carina ; thence they curve broadly downward, crossing the
carina at right angles and continuing, with a slight turn
to the left, into the suture. They are slightly sinuate in the
spaces between the secondary and primary threads. Apical
angle moderate. Whorls estimated 17 or more in number for
complete specimen. Base of body whorl, set off from the
lateral surface by the post-sutural secondary thread, sculp-
tured by numerous threads of about the third order of
strength : of these, two equally spaced, are sometimes more
prominent. Length, 130 mm. ; maximum diameter, 24 mm.

The characters which separate the variety trullissatia from
nelsoni are brought out in the discussion of the general
group. It is easily recognizable through its generally rugged,
angular appearance, and although its relationship to nelsoni
is easy to see there is no difficulty in separating the two. It
is somewhat similar to T. mimetes Brown and Pilsbry,70 from
Gatun, with the difference that the precarinal surface of
trullissatia is much larger, and the carina hence much more
protuberant than that of mimetes. The two are not really
very close.

Upper Zorritos. Quebrada de las Alturas.

Turrit ella infracarinata Grzybowski
PLATE III — Figs. 9, 10.

Turritclla infracarinata Grzybowski, Neues Jahrb. f. Min., etc.,
Beil. Bd. 12, p. 643, pi. 20, fig. 5, 1899.

"Umgange dachformig abfallend, in }/4 der Hohe gekielt,

Froc. Ac. Nat. Sc. Phila., vol. 63, p. 357, pi- 27, fig. i, 1911.

8o STUDIES IN GEOLOGY, No. 3

von da gegen die Naht verschmalert. Sie tragen 8 Spiral-
rippen, von denen die dritte von unten, die auctf den Kiel
bildet, am starksten ist. Die anderen verlaufen gleichmassig
in gleichen Zwischenraumen. Zwischen den 3 unteren sind
noch feine lineare Spirastreifchen wahrnehmbar. Lange 95
mm., Breite bei der Miindung 23 mm." — Grzybowski, 1899.

In some specimens there is a fine subsidiary thread in the
first three interspaces above the carina. Ordinarily, how-
ever, these spaces are free of secondary sculpture. Those
forms which show the interstitial threads have but four
heavy threads above the carina instead of the normal five.
Apical angle moderate. Growth-lines similar to those of
T. nelsoni var. trullissatia are visible but not prominent.

Length (fragment of 6y2 whorls) 82 mm.; maximum
diameter, 26.5 mm. ; estimated length of complete speci-
men, 105 mm.

This species is somewhat similar to T*. mimetes Brown and
Pilsbry,71 from Gatun, though not close; it differs in form
much as it does from T. nelsoni var. trullissatia (q.v.), with
additional variance in sculpture. T. subgrundifera Dall,72
from the Chipola beds of Florida, is closer than any other
American form. It differs in being more delicate, with the
keel finer and more attenuate, and in having more definite
subsidiary threads. T. subangulqta var. spirata Brocchi (2),
from the Helvetien and later of Europe, is more closely
related than either of the other two forms mentioned. It
differs chiefly in its more refined, more delicately chiselled
appearance.

Upper Zorritos. Quebrada de las Alturas.

Turritella infracarinata var. zomtensis n. var.

PLATE III— Fig. n.
Shell large, solid ; whorls convex, rounded, about twelve to

"Idem.

"Trans. Wag. Inst, vol. 3, pt.. 2, p. 313, pi. 22, fig 23, 1892.

PALEONTOLOGY ZORRITOS FORMATION 81

fifteen in number. Sculpture of seven subequal spiral
threads, with no distinct subsidiaries. Occasionally an eighth
thread is visible at the extreme base of the whorl, margin-
ating the suture. The anterior three of the seven threads
normally visible are equally spaced ; between the third and
fourth the space is smaller, and the fifth and sixth are very
close together, with the seventh about as far from the sixth
as the fourth is from the fifth. This spacing is common,
but rare forms have the threads more nearly equally spaced,
excepting the fifth and sixth, which are constantly proxi-
mate. Subsidiary threads occur but rarely, and then indis-
tinctly. A hint of an additional posterior thread, very fine,
is present on one specimen. The subcarinal subsidiaries
normally present in infracarinata s.s. are only suggested in
this variety. The form of the whorls is convex, rounded,
with no distinct carina. The point of greatest whorl-diam-
eter is at the position of the carina in the angular infracarin-
ata, but a sharp carina is never present, and the supracarinal
surface is always covex, if only slightly so in some speci-
mens. Length of fragment showing the body whorl and
2]/2 on the spire, 59 mm. ; maximum diameter, 24 mm. Di-
mensions of complete shell probably similar to those of
infracarinata.

Upper Zorritos. Quebrada del Toro.

Turrit clla prenuncia n. sp.
PLATE IV — Figs. 1-3.

Shell small, delicate, the apical angle moderate, whorls
fairly tight-coiled, sutures distinct. There appear to be
two types of early development, each of which attains the
same end result in the fully mature whorls, but which are
sufficiently different in the neanic whorls to deserve notice.
The two types are here described separately, being noted, for
convenience in reference, as (a) and (b).

(a). Protoconch bulbous, consisting of one and a half
turns. Neanic whorls carinate, strongly sculptured by cor-

82 STUDIES IN GEOLOGY, No. 3

date threads, of which there are three on the first whorl, the
anteriormost the strongest, forming the carina. On the
second whorl a fourth faint thread appears above the pos-
teriormost of the three mentioned, and on the third whorl an
intermediate thread appears behind the carinal thread, as
well as a subsidiary thread before the carina. On the fourth
whorl the subsidiary threads have grown equal in strength to
the others. This sculpture of six equal threads continues
over the rest of the shell, with the introduction of faintly
visible intermediate threads between the first and second,
third and fourth, and fourth and fifth strong threads, and
the addition of a faint posterior thread near the suture. The
fifth whorl is rounded in outline, the carina having lost prom-
inence, and succeeding whorls are more rounded, with the
point of maximum diameter at the location of the obsolete
carina.

(b). Neanic whorls strongly carinate, the carina at the
anterior third, accentuated by a coarse thread. The first
three whorls below the protoconch bear two prominent
cordate threads, of which the anterior one, on the carina, is
stronger ; on the fourth whorl a faint thread appears on the
basal surface before the carina ; this is strengthened on the
fifth whorl, where another light thread appears above the
posterior of the two original ones. On the sixth whorl
there occurs in addition a faint intermediary thread between
the original two, which have lost strength, comparatively;
on the seventh whorl the threads mentioned approach
equality in strength, and a faint posterior thread appears.
The characteristic adult sculpture of the species is attained
in the eighth whorl through the interposition of a sub-
sidiary thread between the fourth and fifth of those named
for the preceding whorl. The seventh and eighth whorls
are more evenly sculptured and contoured, the carina being
obsolescent, and all the threads save the 5th and 7th attaining
equality in strength. Length of eight whorls of form (a),
20 mm.; of form (b), n mm.

PALEONTOLOGY ZORRITOS FORMATION 83

Aside from the difference in development of the sculp-
ture, there is the difference in size noted, with slight differ-
ence in proportion. The adult whorls are very constantly
similar in sculpture, bearing five primary threads with two
secondaries, one on each side of the posterior primary. The
species is apparently normally found small in the Lower
Zorritos formation, but somewhat larger forms, stratigraph-
ically not allocated, occur in Nelson's collection. Length of
large fragment bearing 5 whorls, 34 mm. ; maximum diam-
eter, 12 mm.; minimum diameter, 5 mm.

The detailed discrimination between the neanically differ-
ent forms of -this species is offered in consideration of the
normal biologic importance of ontogenetic development as a
key to identity. Were anything to be gained by it, the two
might be considered as separate, but the identity of the
adult whorls detracts from the value of a differentiation, if
only because by far the most collected material shows only
the later whorls of the spire, the more fragile neanic whorls
having usually been broken off. These specimens which
have more of the spire preserved show that there is appar-
ently a predominance of the neanic type (a). The sculpture
of the adult whorls is the same in ground plan as that of the
other members of the nelsoni group, and in number of ribs:
it is entirely similar to that of the much larger T. infrauir-
inata. T. prennncia is undoubtedly the diminutive fore-
runner of infracarinata.

Lower Zorritos. Quebrada Zapotal.

Turritella prenuncia var. inconspicua (Grzybowski)
PLATE IV— Fig. 4.

Turritella inconspicua Grzybowski, Neues Jahrb. f. Min., etc.,
Beil . Bd. 12, p. 644, pi. 20, fig. 4, 1899.

"Umgange gewolbt, mit 7 gleichen Spiralleisten, von
denen die sechste von unten die schwachste ist und wie ein-
geschaltet zwischen die Nachbarleisten erscheint. Hohe

84 STUDIES IN GEOLOGY, No. 3

eines aus 6 Windangen bestehenden Bruchstiickes 37 mm.,
Breite, unten 12 mm., oben, 4 mm." — Grzybowski, 1899.

In addition to the seven subequal threads noted by Grzy-
bowski there is an occasional microscopically visible inter-
stitial thread on some specimens, particularly between the
third and fourth primary threads. Grzybowski emphasized
the weakened sixth rib in his description, but his figure does
not correspond in that it shows that rib to be equally as
prominent as all save the fifth and seventh, and there is
thus question as to the validity of his statement. The speci-
mens here studied agree with his figure, and it is undoubtedly
true that his mention of a weakened sixth rib is an error.

This form is here treated as a variety of prenuncia in order
to preserve the rationality of relationships within the group
of Turritella nelsoni. To make prenuncia the variety of
inconspicua would reverse the order of varietal relationships
in the group, and a desire to avoid inconsistency as well as
to preserve the meaning of names has led to the present
proposition. Thus placed, T. prenuncia and its variety
inconspicua parallel the other two pairs (nefconi-var. rotun-
data : infracarinata-var. zorritensis) which comprise carinate
and rounded forms with similar sculpture.

Zorritos formation. Zorritos.

Turritella robust® Grzybowski
PLATE IV— Fig. 5.

Turritella sp. ind. Nelson, Trans. Conn. Acad., vol. 2, p. 190,
1870.

TurriteVa (Haustatnr) robusta Grzybowski^ Neues Jahrb. f.
Min. Beil. Bd. 12, p. 646, pi. 20, fig. 3, 1899.

" — Whorls broad and very concave; sutures indistinct.
Surface just above each suture marked by a very strong
ridge. Intermediate surface marked by a few distinct con-
centric lines, five to seven on each whorl." — Nelson, 1870.

PALEONTOLOGY ZORRITOS FORMATION 85

Die Umgange sind stark conisch, unten stark gekielt,
zwischen dem Kiel und der flachen Naht concav eingesch-
niirt. Die Oberflache tragt iiber dem Kiel 5, unter demselben
i flache Leiste. Die Hohe der 2 unteren Umgange 45 mm.,
Breite unten 35 mm., oben, 23 mm. ; die totale Lange mag
140 mm. betragen." — Grzybowski, 1899.

The keel is very sharp and attenuate, forming a knife-
like edge, and giving the shell something of the appearance
of an Archimedes spiral. Four of the threads above the
keel are always strong, and the one nearest the keel is some-
times distinctly weaker. In some specimens this thread Is
obsolete, and there is an additional thread above. In the
earlier whorls the suture is always indistinct, and in some
specimens it is not marked on all oi the whorls, but others
show a plane-bottomed projection of the base of the lower
whorls which indicates clearly the position of the suture.
This overhanging base is developed to varying degrees of
strength. Lines of growth are clearly visible. Length about
loo mm. or more; diameter at base, 31 mm.

This species is a striking form of a type which is appar-
ently not known on the Atlantic Coast outside of the Eocene,
but which appears in the Miocene of California. It is very
close to T. ocoyana Conrad,73 from the Lower Miocene of
California, from which it differs chiefly in having a sharper
keel.

Upper Zorritos. Quebrada del Toro.

Turritella robusta var. abrupta n. var.
PLATE IV— Fig. 6.

Shell essentially similar to T. robusta in all characters
save the sculpture, which consists of closely set cordate ribs
instead of separated threads. There are about eight of these
cords above the keel and three below. The anteriormost
precarinal cord borders the suture, which is everywhere in-

73Pao. R.R. Rept, vol. 5, p. 329, pi. 8, figs. 73, 73a, b, 1856.

86 STUDIES IN GEOLOGY, No. 3

distinct, and in the upper whorls scarcely discernible. The
remaining two precarinal cords are close together. Those
behind the carina are equally spaced, the interspaces being
mere convex-sided v-shaped depressions. Lines of growth
are not evident. The line of smallest whorl-diameter is near
the suture in the earlier whorls, but in later whorls it is
nearer the keel, the surface curving outward to the suture.
Height of fragment bearing eight whorls, 75 mm. ; diam-
eter below, 25 mm. ; above, 6 mm.

This variety differs from robusta in its more closely-set
sculpture. In this respect it is closer to T. ocoyana Conrad
(loc. cit.) from the Lower Miocene of California, than is
robiista; however, it differs from ocoyana in having a sharper
keel.

Zorritos formation. Zorritos.

Turritella charana n. sp.
IV — Fig. 7.

Shell of moderate size, the apical angle larger than that of
local related species. Whorls concave, with a pronounced
sharp keel at the anterior fourth. Before the keel the sur-
face descends, at an angle of about 45° "to the long axis of
the spire, to the suture, which marks the line of least whorl-
diameter. Behind the keel the surface is gently concave, its
angle with the long axis decreasing until at the suture it is
almost parallel to it. Sculpture of irregularly spaced spiral
cords or ribs, of which there are three before the keel and
seven behind it. The anteriormost cord borders the suture.
The second cord behind the keel is the strongest, and the
others are subequal in strength, the third above the keel
being possibly the least developed. Height of fragment
bearing 3^ whorls, 29 mm.; diameter below, 17.5 mm.;
above, 7.75 mm.

This species is perhaps closer to T. ocoyana Conrad 74

"Idem., pi. 7, figs. 73, 733, b.

PALEONTOLOGY ZORRITOS FORMATION 87

than is abrupta. It is different, however, in that its sculp-
tural threads are more nearly equal in strength, and
that its keel overhangs the suture more sharply than in
ocoyana,

Lower Zorritos. Ridge between Quebradas Heath and
Charan.

Family NATICIDAE

Genus POLYNICES Montfort

Polynices snbangiilata Nelson

PLATE IV— Fig. 8.

Polynices subangulata Nelson, Trans. Conn. Acad. Sc., vol. 2,
p. 195, pi. 6, figs. 4, 12, 13, 1870.

"Shell varies from obliquely oval to sub-globular, moder-
ately heavy and ventricose ; spire short and pointed ; body
whorl large, nearly seven-eighths of the length of the shell,
convex, slightly produced anteriorly, broadest about one-
fourth from top. From this point the whorl slopes, becom-
ing very much flattened and presenting a marked angular
appearance. Surface marked by distinct but irregular lines
of growth. Sutures quite indistinct, except when the epi-
dermis is slightly worn off. Aperture semi-lunular, half as
wide as long, broadest a little below the middle. Outer lip
sharp and thin. Columellar lip covered by a very thick
callus, which rises into a more or less prominent ridge at the
broadest part of the shell. Umbilicus small ; in most speci-
mens reduced to a mere chink by the callus, which is pro-
longed below." — Nelson, 1870.

The male shells and the young are more evenly rounded
than the mature females, which have the shoulder more
prominent, and in which the body whorl has a subcylindrical
shape. The callus widens above, merging with the inner
wall of the body whorl a short distance behind the peristome
at its inner margin, and meeting the peristome exactly at its

88 STUDIES IN GEOLOGY, No. 3

outer margin. There is a wedge-shaped portion of the
upper lip projecting over the callus. The callus is sharply
emarginated below, at about the anterior third, the outer
margin making a right-angled indentation, and the callus
continuing at about half its upper width ; it extends below
into a folding-over of the lower inner peristome. The um-
bilicus is situated at the right-angled emargination of the
callus. The nuclear whorls are smooth; the later whorls
sculptured by lines of growth. Dimensions : Large mature
shell, Height, 55 ; Diameter, 43.5 mm. Medium-sized shell,
Height, 31.5; Diameter, 28.5 mm. Young shell, Height, 18;
Diameter, 14 mm. Very young shell, Height, 7.5 ; Diameter,
6.5 mm.

This species is very abundant. It is characterized by the
sub-plane sides of the whorls, and the peculiar, wedge-shaped
callus. It differs very slightly from Polinices stanislas-
meunieri Maury,75 from the Middle Miocene of Santo Do-
mingo; the spire of subangulata is lower, and the apical
angle hence wider; the whorls are flattened on the sides,
and not smoothly rounded; and the callus is wedge-shaped,
the margins converging anteriorly, whereas that of stanislas-
meunieri has parallel margins. The chief difference lies in
the different apical angle.

Lower Zorritos; Variegated. Ridge between Quebradas
Heath and Charan, Quebrada Tusillal, south of Ouebrada
Pantheon.

Polynices porcana n. sp.
PLATE IV— Fig. 9.

Shell fairly large, heavy, the spire low and the apical
angle somewhat broad. Whorls about five, well rounded and
smooth excepting perceptible growth- wrinkles ; sutures fairly
distinct, not channelled. The last whorl of the spire is lower

"Bull. Amer. Pal., vol. 5, No. 29, p. 136, pi. 23, figs. 15, 16,
1917-

PALEONTOLOGY ZORRITOS FORMATION 89

than in P. subangulata, and there is no shoulder. A heavy,
bulbous callus surrounds the lower columella, merging into
the peristome at its upper extremity, and terminating below
in a rounded, bulb-like mass. There is no umbilical chink.
Peristome, inner aperture, and base of columella broken away
in all specimens available, but the aperture is undoubtedly
somewhat narrow and oblique. Base rounded. Height, 34 ;
maximum diameter (estimated) 35-37 mm.

This species differs from P. subangulata Nelson in being
lower and in the callus, which is more bulbous, completely
covering the umbilical region. The general conformation of
the upper whorls is practically the same for the two species.
In general shape, and in type of callus, P. porcana is similar
to Natica josephinia Risso, from the Miocene and later of
Europe.76 In shape it is much like N. josephinia s.s., and
the callus is similar to that of the variety antiqua Sacco.77

Lower Zorritos. Between Quebradas Heath and Charafi.

Genus SINUM Bolten

Sinum carolanum n. sp.

PLATE IV— Fig. 10.

Shell depressed, with a smooth nucleus of 3^ whorls, in
all with five or six whorls. The smooth nucleus slopes
abruptly, being separated by something of a depression from
the later rapidly widening whorls, which bear the character-
istic sculpture of spiral threads of three orders of strength,
with finely graven interspaces. Seen under the microscope
the primary threads appear very broad in contrast to the
secondaries, and the tertiaries are just visible in the inter-
spaces as fine ridges. There seems to1 be no definite order
of arrangement of the three types of threads. At some points
they branch and anastomose much as do the corrugations in

76 Sacco, Piemonte, pte. 8, p. 83, pi. 2, figs. 54-60, incl., 1891 . '
"Idem., p. 85, pi. 2, fig. 55.

9o STUDIES IN GEOLOGY, No. 3

a human finger-print. The flat tops of the threads are
crossed at right angles by very fine growth-lines, and in
places growth-wrinkles give them a wavy outline ; under
the microscope some of the wrinkles appear as deep sinuses.
The suture is distinct, the periphery rounded. The aperture
is very broad, and the peristome inclines backward. The
central base, hidden by irremovable matrix, is not known.
Height, 14; maximum diameter, 23.5 mm.

This beautifully sculptured shell is somewhat similar to
S. obliqua Gabb,78 from the Tejon Eocene of California
According to Gabb's figure obliqua has a much higher spire,
but a figure published by Dickerson,79 which does not agree
with Gabb's, is closer to carolanum, although not identical.
Gabb's figure is very likely the faulty one. The sculpture of
obliqua is proportionally coarser than that of carolanum, and
obliqua is much smaller. In general appearance S. carol-
anum is something like S. nolani Maury,80 from the Middle
Miocene of Santo Domingo, but the sculpture is more pro-
nounced in carolanum,, and it is much lower. S. multilineatus
Gabb,81 from Sapote, Costa Rica, is also somewhat similar,
but differs in having a less oblique aperture and in being
higher. S. excentricus Guppy 82 is perhaps closer than any
other. It differs in having the aperture at a lower angle
than in carolanum, and in the ribs, which are rounded in
excentricus, flat-topped in carolanum. Guppy's figure and
description give little hint of the finer characters of the
sculpture. ,

Lower Zorritos. Quebrada Zapotal.

78Geol. Surv. Cal., Pal., vol. i, p. 109, pi. 21, fig. 112, 1864; (as
Naticina obliqua).
T'Proc. Cal. Ac. Sci., ser. 4, vol. 5, pi. 5, figs. 5a, sb, 1915.

80 Bull. Amer. Pal., vol. 5, No. 29, p. 139, pi. 24, fig. i, 1917.

81 Jour. Ac. Nat. Sci. Phila., vol. 8, p. 339, pi. 44, fig. 6, 1881.
"Quart. Jour. Geol. Soc. Lond., vol. 32, p. 519, pi. 29, fig. n,

1876.

PALEONTOLOGY ZORRITOS FORMATION 91

Superfamily RHIPIDOGLOSSA
Family TURBINIDAE
Genus TURBO Linnaeus

Turbo belli n. nom.
PLATE IV — Fig. n.

Callopoma lineatum Nelson, Trans. Conn. Acad., vol. 2, p.
186, pi. 6, fig. 2, 1870; not Turbo lineatus of Da Costa, 1778; nor
of Lea, 1845.

''Shell turreted; spire elevated; whorls six, convex. Up-
per whorls slightly depressed in front, marked by a few
strong, subnodulous ridges, alternating with finer revolving
lines. Body whorl very convex, marked above by two
strong tuberculose ridges, and laterally and below by a few
revolving lines, varying in size, as on the upper whorls.
Whole surface marked by very fine and numerous longi-
tudinal lines, rather broader than the spaces between them."
—Nelson, 1870.

The aperture is round. On the earlier whorls one strong
thread forms a marked keel; on the body whorl the keel is
broadly nodulous, as is the thread beneath it. The growth-
lines noted by Nelson are very regular and distinct. Alti-
tude, 15.5; diameter, 15 mm.

This species is somewhat similar to T. domincensis var.
Ictloi Maury,83 from the Lower Miocene of Santo Domingo,
but the whorls of the spire are more angulated, and stand
out more prominently than in that species, and the sculp-
ture of laloi is broader, the ribs being all fuller. The nodula-
tion of the ribs on the shoulder of laloi is more profuse than
in lineatum. This species is named in honor of Dr. Fred-
erick Keller Bell, of Baltimore, Md.

Zorritos formation. Zorritos.

83 Bull. Amer. Pal., vol. 5, No. 29, p. 154, pi. 24, fig. 15, 1917.

92 STUDIES IN GEOLOGY, No. 3

Turbo belli var. aequifilicatum n. var.
PLATE; IV — Fig. 12.

Shell turreted, the whorls distinct, angulated. Differs
from belli chiefly in sculpture, which consists of evenly
spaced major cords without the regular subsidiary threads.
On the last whorl of the spire one of the cords forms a keel,
behind which the surface is horizontal, bearing one less
prominent cord, and before which the surface is almost
vertical, bearing two prominent cords between the keel and
the suture. The body whorl bears many more ribs — about
ten from the keel to the base of the columella. Just below
the keel on the body whorl is one subsidiary thread, and the
two on either side of the lowest prominent rib are less prom-
inent than the rest. In shape and other characteristics this
variety is similar to the restricted species. The dimensions
are therefore similar.

Lower Zorritos. Quebrada Zapotal.

Genus CALLIOSTOMA Swainson

Calliostoma (Eutrochus) noduliferum Nelson

PLATE I— Figs. 7, 8.

Calliostoma noduliferum Nelson, Trans. Conn. Acad., vol. 2,
p. 187, pi. 16, fig. i, 1870.

Shell of medium size, spire moderately elevated, sutures
distinct. Whorls six in number, convex, evenly rounded
above. Sculpture of finely beaded spiral threads, six to the
whorl, the interspaces about twice as wide ; at the beginning
of the latter half of the body whorl interstitial threads
develop, beginning as very fine simple threads and gradually
becoming beaded, but remaining subsidiary in size. The
base of the body whorl is set off by a fairly sharp peripheral
keel, and is flattened to convex, with about twelve spiral
cords between the keel and the columella. Aperture sub-

PALEONTOLOGY ZORRITOS FORMATION 93

quadrate, the outer lip sharp, the columella covered with
callus. Height, 8; diameter, 10.75 mm-

This species is somewhat similar to two Floridian shells,
C. linulum Dall,84 from the Calloosahatchie Pliocene and
C. palmeri Maury,85 from the Chipola marl. The differences
between these two species are small, hardly of specific value.
C. noduliferum is clearly of the same strain, having the
same typical sculpture of alternating beaded lines, and the
general appearance characteristic of the Floridian species,
but it is much larger, has convex, not flat whorls, and has
two more beaded spirals to the whorl.

Zorritos formation. Zorritos.

Class PELECYPODA

Order PRIONODESMACEA

Superfamily NUCULACEA

Family NUCULJDAE

Genus LKDA Schumacher

Leda peruviana Dall

PLATE V— Fig. i.

Leda acuminata Nelson, Trans. Conn. Acad., vol. 2, p. 205, pi. 7,
fig. 8, 1870 (not von Buch, 1845).

Leda peruviana Dall, Trans. Wag. Inst, vol. 3, pt. 4, p. 579,
1898.

Leda balboae Brown and Pilsbry, Proc. Ac. Nat. Sci. Phila.,
vol. 63, p. 362, pi. 27, fig. 8, 1911.

Shell of medium size, delicate, elongate, inflated. Anterior
margin produced, rounded, the dorsal part straight and the
ventral part rounded; ventral margin arcuate, the lowest
point well before the median line of the beaks. Posterior
margin produced, the marginal angle acute and the posterior

84 Trans. Wag. Inst., vol. 3, pt. 2, p. 404, pi. 8, fig. 7a, 1895.
85 Bull. Amer. Pal., vol. 4, No. 10, p. 32, fig. 4 of pi. 8, 1910.

94 STUDIES IN GEOLOGY, No. 3

dorsal margin about straight. Umbones pointed, fairly
prominent, opisthogyrate, central in position. Surface gen-
erally convex except behind the posterior keel, where a well-
defined area is concave on either side of the juncture of the
valves. The keel is sharp, and broadly curved, the concave
side upward. Sculpture of concentric, sharp and clearly
graven ribs, asymmetric in cross-section, the dorsal side
steeper, about 14 in the space of 5 mm. on the median surface
of a specimen 19.5 mm. long. On the posterior area the
ribs are radial, running nearly parallel to the juncture of the
valves. Teeth normal, fairly strong in the center of each
series, and becoming smaller distally and toward the beaks,
A-shaped, the apices turned toward the beaks. Inner shell
smooth. There is no well-defined lunule. Dimensions of
two specimens: Length, 19.5; alt., n; diam., 8.5 mm.
Length, 25; alt., 15; diam., 14 mm.

This form was named Leda acuminata by Nelson (loc.
cit.), but, that name being preoccupied, Dall proposed Leda
peruviana in 1898. It is identical with the subsequently
named Leda balboae Brown and Pilsbry (loc. cit.) from
Gatun. Specimens in Nelson's collection agree perfectly with
the figure of balboae published by Brown and Pilsbry, and
the points noted in their description tally perfectly, excep-
ting the number of teeth, which is given as 18 behind the
beak and 28 before for the Gatun specimens. The Zorritos
forms have constantly 14 teeth behind the beak, and 22
before. Other points, however, agree to> such fineness of
detail that the two can hardly be held to be of different
species.

Zorritos formation. Zorritos.

PALEONTOLOGY ZORRITOS FORMATION 95

Superfamily ARCACEA

Family ARCIDAE

Subfamily ARCINAK

Genus ARCA (Linnaeus) Lamarck

Subgenus NOETIA Gray

Area (Noetia) cholana n. sp.

PLATE V— Figs. 2, 3.

Shell triangular in general outline, moderately inflated.
Anterior margin rounded, merging into the upper margin of
the ligament area ; ventral margin slightly rounded, posterior
margin unknown. Umbones opisthogyrate, situated just for-
ward of the middle, flattened above, the upper surface sloping
forward. Umbonal slope gently rounded anteriorly, the gen-
eral anterior surface being only slightly convex, and the
central surface similar ; posterior keel very sharp and distinct
from the top of the beak to the ventral margin, curving out-
ward ; posterior slope slightly excavated. Ribs, 35 in num-
ber, flat and low, with many fine, wavy, delicate, imbricated
growth-lines which cross both ribs and interspaces. Ribs
about equal in width to interspaces. A fine subsidiary rib is
present in the posterior interspaces, its strength increasing
posteriorly. Area in two parts; the ligamental part, before
the beaks, bearing pronounced transverse striations and
being hollowed out to form part of a cylinder. Just beneath
the beak the transverse striations change suddenly, becoming
very fine and numerous for a distance of about 2.5 mm.
The ligament area terminates directly below the point of
the beak, behind which is a lunule of roughly triangular
shape, the longer upper limb of the triangle being the last
posterior rib; it is crossed transversely by a distinct V-
shaped sulcus, and longitudinally by very fine parallel stria-
tions. The hinge-plate is moderately wide posteriorly, bear-
ing medium-coarse teeth, which merge into the transverse

96 STUDIES IN GEOLOGY, No. 3

striations of the ligament area before the beaks. Length
(left valve) 32; height, 24.5; (semi) diam., 12 mm. Length
(right valve) 35 ; height, 28; (semi) diam., 12.5 mm. Length
ligament area, left valve, n ; right valve, 12 mm.

This species is similar to A. modesta Grzybowski,86 from
Zorritos, but differs in shape, being decidedly lower and
more squat in appearance. Other points of similarity or
difference may exist, but are not notable here on account of
the meagerness of Grzybowski's description and the lack of
detail in his figures. Comparison with his figure reveals a
broad difference in shape. A. cholana is lower and broader
than A. trinitaria Guppy,87 and the posterior keel is not pro-
duced downward as in trinitaria. The beaks of trinitaria are
fuller, higher, rounder viewed posteriorly, and more acute
viewed laterally. The anterior margin of trinitaria is less
produced, and the posterior surface less excavated and less
alate. A. sheldoniana Maury,88 from the upper Oligocene
(Aquitanien) of Trinidad, is similar in shape and ribbing,
but is much smaller. The area seems to be different, but
Maury's description is inadequate, and the plates do not show
sufficient detail for fruitful comparison.

Variegated (near base). Quebrada Tusillal.

Subgenus SCAPHARCA (Gray) Ball

Section CUNEARCA Ball

Area (Cunearca) zorritensis n. sp.

PLATE V— Figs. 4, 5.

Scapharca sp. ind. Nelson, Trans. Conn. Acad., vol. 2, p. 205,
1870.

s'Neues Jahrb, Beil. Bd. 12, p. 635, pi. 28, figs. 4, 4a, 1899.
"Quart. Jour. Geol. Soc. Lond., vol. 22, p. 583, pi. 26, figs 3a,
3b, 1866.

88 Jour. Ac. Nat. Sci. Phila., 2nd ser. vol. 15, p. 43, pi. 8, figs.
10, u, 1912.

PALEONTOLOGY ZORRITOS FORMATION 97

Shell of moderate size, high, trigonal, marginally cuneate
in cross-section. Anterior margin rounded, descending
abruptly into the ventral margin, which continues to descend
almost to the posterior extremity of the shell, whence the
posterior margin rises abruptly in an elliptical curve. Um-
bones erect, submedian in position, slightly prosogyrate,
inflated. Anterior surface smoothly convex, the valves
meeting at an acute angle ; median surface convex ; poster-
ior surface somewhat excavated behind the beaks, with a
very gentle carina descending from the beaks and flattening
towards the posterior marginal angle. At the marginal
juncture of the valves the surfaces are somewhat attenuated,
the form being wedge-like. Sculpture of 25 low, squarish
ribs, marginally nodulose over the entire length of the left
valve, on the right valve slightly nodulose anteriorly, smooth
posteriorly ; upper sculpture of both valves unknown. Inter-
spaces slightly wider than ribs anteriorly, equal mesially
and posteriorly, crossed by fine concentric lines. Area
lanceolate, smooth, bounded by a distinct, fine marginal
furrow. Teeth, visible in cross-section as joined valves are
viewed from above, fine mesially, coarser distally. Inner
shell unknown. Length, 16.25 ; height, 15.5 ; diam., 12.5 mm.
A single complete specimen of A. zorritensis, in Nelson's
collection, was marked by him "species indeterminate," but
inasmuch as all of the characters of the outer shell are visible
save the upper sculpture of the ribs it is deemed advisable to
describe the form. Unfortunately, the exact geologic hori-
zon of Nelson's fossils is not known, and description of them
thus normally carries but little significance ; but in the case of
a clearly defined form such as this it is well to name the
species, trusting to future collecting in the region for its
geologic allocation. It is fairly safe to say that it was taken
from the Zorritos formation, but inasmuch as Nelson's forms
appear to have come indiscriminately from all three units of
that group a more definite assumption is not warranted. It

98 STUDIES IN GEOLOGY, No. 3

is very close in shape to A. alcima Ball 89 from the Caloosa-
hatchie Pliocene, but its area is not wide, as is that of alcima,
the number of ribs is 25 instead of 30, and there is no marked
discrepancy in the two valves either in this respect or in the
matter of size; the anterior-ventral margin descends at a
higher angle in zorritensis, and the nodulation of the ribs
is not as sharp. The beaks of alcima are a bit higher.

A. zorritensis has most of the characteristics of a Cunearca,
but is very near the border line between that section and
Scapharca s.s., if, indeed, such a line may be said to exist.
It has the area, discrepant sculpture, and general shape of a
Citnearca, and although the discrepancy on the valves is no
greater than that of the average Scapharca s.s., it seems
advisable to place it in the section C linear c a. Area filicata
Guppy,90 from the lower Oligocene of Trinidad, is the most
closely related form. It differs in having 30 ribs instead of
23, the ribs being broader than the interspaces, instead of
narrower as in sorritensis, and in being less produced ante-
riorly. The sculpture of the ribs is the same, and the general
shape and size is very little different. In the local fauna A.
pantheonensis, from the Variegated Beds, is very similar,
but differs in being larger, having a wider area, and in its
more pronounced and opposite discrepancy of the valves.

Zorritos formation. Zorritos.

Area (Cunearca) sp. indet.
PLATE V— Figs. 6, 7.

Shell high, inflated. Outline unknown. Umbones high,
erect, not compressed. Umbonal slope rounded in contour
anteriorly and mesially ; a distinct posterior keel curves out-
ward toward the margin, and the surface behind it is
excavated. Ribs, 29 in number, decorated with many non-

89 Trans. Wag. Inst, vol. 3, pt. 4, p. 635, pi. 31, figs. 5, 7, 1898.
90 Quart. Jour. Geol. Soc. Lond., vol. 22, p. 583 pi 26 fig 5
-866.

PALEONTOLOGY ZORRITOS FORMATION 99

concentrically arranged, cog-shaped nodes. On the ventral
parts of the extreme posterior ribs the nodes flatten to insig-
nificance. Area broad, short, transversely striate, bounded
by a distinct furrow. Teeth (few visible) fine, of medium
length.

This form is very close to A. aicima Dall, and the group
of related forms. It is very similar to A. chemnitzioides
Maury,91 from the Oligocene (or later) of Trinidad, but it
has not the concentrically arranged nodulation of that form,
and has a much more pronounced posterior keel. The area
is not as high as that figured by Maury, and is delimited by
a marginal furrow not evident in the figure of chemnitis-
ioidcs; the point of the beak is fuller and more incurved, and
the teeth are apparently not as long. It differs from A.
aicima Dall 92 in having finer, rounder, and less regular
nodulation of the ribs. The posterior keel is curved out-
ward ; that of aicima is nearly straight. Otherwise the char-
acters of the upper part of the left valve agree with those
of aicima. Although the visible characters of this fragment
show that it is probably a new species, naming of it is
deferred until a full description can be made.

Variegated. Quebrada Tusillal.

Section SCAPHARCA s.s.

Area (Scapharca) pantheonemis n. sp.

PLATE V— Figs. 8, 9.

Shell of medium size, inequivalve, the right valve higher,
moderately inflated. Anterior margin slightly rounded, for
the most part at right angles to the hinge, but curving in
slightly to meet the hinge-line. Ventral margin rounded, its
main line parallel to the hinge; posterior margin straight
centrally, curving sharply into the ventral margin and curv-

91 Jour. Ac. Nat. Sc. Phila., ser. 2, vol. 15, p. 44, pi. 7, figs. 13,
14, 15, pi. 8, fig. i, 1912.

92 Trans. Wag. Inst., vol. 3, pt. 4, p. 635,' pi. 31, figs. 5, 7, 1898-

ioo STUDIES IN GEOLOGY, No. 3

ing to meet the hinge at an angle of 135.° Umbones narrow,
erect, very slightly prosogyrate, inflated, 6 mm. distant.
Umbonal slope broadly rounded anteriorly, more acutely
rounded mesially, a gentle keel being followed by a slightly
excavated posterior surface on the left valve ; the right valve
is not excavated posteriorly. Valves meet marginally in an
acute angle ventrally and posteriorly. Ribs, 24 in number
on each valve, square, concentrically noded on left valve
with cog-like corrugations, the posterior ribs being nearly
smooth; on the right valve the ribs are not noded except
anteriorly, but are crossed by numerous fine lines of growth.
The ribs are separated by interspaces about equal in width
mesially and posteriorly, but much wider than the ribs
anteriorly. Area lozenge-shaped, a little longer behind the
beaks than before, plain except for one lozenge-shaped fur-
row two-thirds of the distance from the beak to the hinge,
crossed by numerous very fine longitudinal lines and bounded
by a marginal furrow whose outer wall is slightly elevated.
Length, 30.5; height, (left valve) 28.5, (right valve) 30;
diameter 27; length of hinge, 17.5 mm.

This species is clearly transitional between the true Scap-
harcas and the Cunearcas. It has the shape and discrepant
valves of Cunearca (although the right valve is the
larger instead of the left), and the area is entirely smooth
save for one furrow. It probably represents a stage in the
development of the divergent stock at which the chief
characteristics of the Cunearcas have assumed definite shape,
with the trace of areal furrowing as a disappearing vestig-
ial inheritance of Scapharcan characteristics. It is most
closely allied to A. (Scapharca) cor-cupidonis Maury,93 from
the Miocene (?) of Santo Domingo, agreeing with it entirely
in all characters save the following: the area is equally wide
before and behind the beaks, not discrepant, has but one

93 Bull. Amer. Pal., vol. 5, No. 29, p. 175, pi. 30, figs. 5, 6, 7,
1917-

PALEONTOLOGY ZORRITOS FORMATION 101

groove and a marginal furrow with universally elevated
ridge instead of several furrows and an elevation behind the
beak only; the meeting of the valves, which is perfect and
not discrepant as in cor-cupidonis; pantheonensis is not as
highly inflated, and is somewhat more produced posteriorly.

Area niicata Guppy,94 from the Manzanilla beds of Trin-
idad, is a much smaller form, but is evidently related. It
has, among other features of difference, a larger number of
ribs. Area alcinia Dall/5 from the Caloosahatchie Pliocene
of Florida, represents the next step in the evolution of this
type, with the assumption of the characters of the true
C linear ca. It is true that alcima itself is on the border-line
of the group, but, as Ball (loc. cit.) has pointed out, it has
sufficiently well developed the Cunearca hinge, area, and
discrepant sculpture to place it in that group. A. larkinii
Nelson is similar as pointed out in the description of that
species.

Variegated. Small quebrada south of Quebrada Pantheon.

Area (Scapharca) zapotalensis n. sp.
PLATE V — Fig. 10.

Shell of medium size, moderately inflated, produced pos-
teriorly. Anterior margin rounded. Ventral margin broadly
curved, descending at a low angle ; posterior margin recurves
in a sharp angle, being nearly straight, and forming an
angle of about 130° with the hinge. Umbones erect, inflated,
somewhat broad. General surface convex except posteriorly,
where it is slightly excayated behind the beaks. Valves join
posteriorly to form a wedge-like shape. Sculpture of about
29 ribs, apparently squarely nodular on the left valve and
smoother on the right. Area narrow ; exact characters not
visible. Teeth and inner shell not known. Length, 24.5 ;
height, 21.5; diam., 18; length of hinge, 15 mm.

94 Quart. Jour. Geol. Soc. Lond., vol. 22, p. 583, pi. 26, fig. 5,
1866.
93 Trans. Wag. Inst, vol. 3, pt. 4, p. 635, pi. 31, figs. 5, 7, 1895

io2 STUDIES IN GEOLOGY, No. 3

The Hopkins collection contains one complete specimen
of this form, and although it is coated with calcium carbon-
ate, with the definition of some of its characters thus some-
what lost, its difference from other similar forms makes
clear its identity as a distinct species, and warrants descrip-
tion. It is very close to A. zorritensis, but differs in the
number of ribs and in being much less oblique, the ventral
margin being much more nearly parallel with the hinge. It
is also somewhat similar to A. pantheonensis, of the Varie-
gated fauna, but is less inflated, smaller, and has not so
wide an area.

The group of A. singewaldi, of the Zorritos fauna, A.
proletariaf Br. & Pils. and A. intunmlata Br. & Pils.96 of the
Santo Domingan Oligocene, and A. improcera Conrad,97 of
the Miocene of North Carolina, is similar, differing as a
whole mainly in the greater number of ribs and the narrower
interspaces. Anadara darwini (Mayer), described by
Sacco98 from the Tortonian to the Astian of the Italian
Piedmont, is similar in shape, but is more inflated, and has
broader ribs. A. donacia Dall," from the lower Miocene
of Jamaica, is somewhat similar, but is much smaller, has
comparatively lower beaks, is longer in proportion to height,
has less ribs, and lacks the nodulose rib-sculpture.

Lower Zorritos. Quebrada Zapotal.

Area (Scapharca) fissicosta n. sp.
PLATE V— Fig. .11.

Shell of medium size, inflated, smoothly cpnvex. Ante-
rior margin broadly rounded, somewhat produced ; ventral
margin elliptical, in the main parallel to the hinge-line ; pos-
terior margin slightly curved, meeting hinge at an angle of

"Proc. Ac. Nat. Sc. Phila., vol. 69, p. 188, 1917.

9TFoss. Med. Tort, p. 60, pi. 31, fig. 5, 1845.

"Piemonte, pte. 26, p. 24, pi. 5, figs. 11, 12, 1898.

"Trans. Wag. Inst, vol. 3, pt. 4, p. 649, pi. 33, fig. 13, 1898.

PALEONTOLOGY ZORRITOS FORMATION 103

125.° Umbones prominent, full, incline forward, strongly
prosogyrate, situated at the anterior third of the entire
length. General surface convex; posterior slope slightly
excavated behind a broad keel which descends from the
umbone to the marginal angle. Sculpture of 39 low, flat-
topped ribs, of which the anterior fourteen are longitudinally
sulcate near the margin, and the remainder are smooth.
Interspaces, evenly equal in width to the ribs, show concen-
tric lines which are less prominent to obsolete on the ribs.
Area extremely narrow, nearly three-fourths of its length
being behind the middle of the beaks, separated from the
rest of the sculpture by a raised ridge. Teeth fine, distally
oblique. Inner shell unknown. Length, 29.5 ; height, 23.5 ;
(semi) diam., 10.5; length of hinge, 18.5 mm.

The form which seems most closely related to Area fissi-
costa is A. hypomela Ball,100 from the upper Oligocene of
Ballast Point, Alum Bluff, and the Chipola marl of Florida.
It differs in being much more produced posteriorly, and thus
longer in proportion to height, and in having the ribs chan-
neled over a larger part of the shell. In number and type
of ribs, and in general appearance the two are clearly similar.
In the local fauna A. singewaldi var. do ma is somewhat
similar, but rarely reaches the size of A. fissicosta, and in
addition has nine to ten less ribs.

Lower Zorritos. Quebrada Zapotal.

Area (Scctpharca) singewaldi n. sp.
PLATE V — Figs. 12, 13.

Shell small, inflated, inequilateral, oblique. Anterior
margin rounded, somewhat truncate, meeting hinge-line at
an angle clearly greater than 90,° but not markedly obtuse;
ventral margin evenly elliptical ; posterior margin almost
angular, meeting hinge-line at an angle of about 140,° and
forming a straight line between the hinge and the end of

Idem., p. 637, pi. 33, fig. I.

IO4 STUDIES IN GEOLOGY, No. 3

the posterior keel, at which point it recurves sharply into the
elliptical anterior margin. Umbones prominent, inflated,
their apices twisted anteriorly, situated at the anterior third
of the full length. The upper surface of the beaks slopes
distinctly forward, and is indented by a sulcus which is
distinct on the inner side of the beaks, but which is lost on
the umbonal slope. The umbonal slope is rounded near the
beaks, the surface slightly excavated posteriorly, the keel
tending to be angular, and the anterior surface gently
rounded but full. Ribs 33 on each valve, equal in width to
the interspaces on the central part of the shell and much
wider posteriorly; square in cross-section, those of left valve
prettily noded, the nodes becoming indistinct to absent on the
posterior part of the shell; noding much less distinct, often
absent, on right valve except anteriorly. Near the anterior
ventral margin the ribs of the left valve are longitudinally
sulcate ; those of the right valve are only slightly sulcate ven-
trally on the anterior slope. The area is narrow, of medium
length, with two to three fine wave-shaped furrows and the
margin elevated behind the beaks. The teeth are in a very
straight, even row, and are distally oblique. Dimensions of
2 specimens: Length, 24.5; height, 18; (semi) diam., 8.75;
length of hinge, 17 mm. Length, 25.5 ; height, 19.25 ; (semi)
diam., 10; length of hinge, 18 mm.

This form is very closely related to Area proletariat01 and
A. intumulata Pilsbry & John.,102 from the Oligocene of
Santo Domingo. Comparison with the types of these forms
brought out the following differences, which are here given
in critical detail on account of the extreme similarity in gen-
eral appearance of the forms: in A. proletaria the ventral
margin descends posteriorly, being nowhere parallel to the
hinge, whereas in singewaidi it is in general almost parallel ;
the posterior margin of proletaria meets the hinge at an

lMProc. Ac. Nat. Sc. Phila., vol. 69, p. 188, 1917.
102 Idem., p. 187.

PALEONTOLOGY ZORRITOS FORMATION 105

angle of 120° instead of 140,° as in singewaldi, and the angle
between the posterior and ventral margins is accordingly less
acute; the umbones are similar except that the sulcus in
proletaria is slightly less perceptible, and does not extend
as far from the point of the beaks ; the surface of the valves
is identical for the two forms anterior-mesially, but the pos-
terior keel is slightly less sharp in proletaria, and the sur-
face adjacent to the posterior margin is excavated, the mar-
ginal surface flattening out somewhat, whereas in singewaldi
there is no such flattening, and the valves have a much more
solid appearance. The ribs of proletaria are distinctly
broader than the interspaces, and do not show the marginal
sulcation characteristic of singewaldi; the area of proletaria
is proportionally longer and much more narrow ; the teeth
are similar, but there is no break in the series of singewaldi,
and the hinge of proletaria is somewhat longer. In general
contour the shells are decidedly similar.

Area intumulata is longer than singewaldi; otherwise it
differs much as does proletaria, but has the following points
of similarity not present in that species : some of the ribs of
intumulata are sulcate very nearly as distinctly as those of
singewaldi; the area, though longer, is similar in appear-
ance; the sulcation of the beak is similar; and the teeth are
in a continuous row, though coarser, The nodes on the ribs
of intumulata are not as prominent as those of singewaldi.

A. singeimldi is also strikingly similar in general appear-
ance to A. improcera Conrad,103 and the related forms, A.
improcera var. buccula and A. plicatura Conrad.104 Compar-
ison with specimens of these forms from the Miocene of
North Carolina shows improcera to be less inflated, longer,
with proportionally wider ribs which are plain instead of
nodulate, and with the valves meeting in an angle more acute
than that of singewaldi; plicatura is slightly less inflated, the

l03Foss. Med. Tert, p. 60, pi. 31, figs. 5, 18, 1852.
1M Idem., p. 61, pi. 32, fig. 4.

io6 STUDIES IN GEOLOGY, No. 3

posterior surface is more flattened, and not as full, the
beaks are more dome-like, and the valves are less oblique.
The resemblance to var. buccula is stronger, possibly, than
to the others in shape, degree of inflation, size, shape and
number of ribs, but buccula is more produced anteriorly,
the anterior margin being more fully rounded, and is less
produced posteriorly ; the ribs are little or not at all nodulose,
and the distal teeth are coarser and longer. In some speci-
mens of buccula the beaks are nearly as high as those of
singewaldi, but in such the hinge-line is shorter.

A. singewaldi differs from A. transversa Say105 in being
more inflated, thus more rounded in general appearance,
more produced and flatter anteriorly, with lower, less in-
flated beaks, and smaller area.

Lower Zorritos. Quebrada Zapotal and quebrada north
of Quebrada Boca Pan.

Area (Scapharca} singewaldi var. doma n. var.

Characters agree with those of A. singewaldi except as
follows : This form has 50 ribs instead of 33, with the pos-
terior ribs flatter than those of singewaldi. The nodulation
of the ribs is finer and less distinct. The posterior slope of
the shell is more blunt than that of A. singewaldi, the angle
between the posterior margin and the hinge being nearer to
125° than 140,° and the posterior margin curving back,
lessening the production of the shell posteriorly. The um-
bones are not sulcate. The area is narrower. Length, 19;
height, 17; (semi) diam., 8.5 mm. Length of hinge, 13.75
mm.

Lower Zorritos. Quebrada Zapotal.

Area (Scapharca) vanhols.fi n. sp.

PLATE: V — Fig. 14.

Shell small, thin, only moderately inflated, of slightly
103 Idem., p. 15, pi. i, fig. 2.

PALEONTOLOGY ZORRITOS FORMATION 107

elongated rhomboidal shape, inequilateral. Base elliptical.
Anterior end rounded, the margin sloping posteriorly in an
even curve from the hinge-line, with which it forms approx-
imately a right angle. Posterior margin produced beyond
end of hinge-line, with which it makes an incident angle of
about 133.° Beaks not prominent, situated near anterior
third of length, sulcate near apex, the ribs anastomosing
into the sulcus, and the sulcus dying out entirely on the main
slope of the shell. Umbonal slope widens rapidly from apex
of beaks, curving in even contour anteriorly and forming a
perceptible keel posteriorly. Ribs, 23 in number, not sulcate,
square in shape over the entire length of the shell, with
terior wing and extreme anterior end. Ribs show growth-
interspaces wider than the ribs mesially, vice versa on pos-
lines, which in places tend to form nodes, but no distinct or
regular quadrisection is evident to the naked eye. Micro-
scopic examination reveals an irregular but distinct nodosity.
Cardinal area low and narrow, with elevated margin behind
the beaks, and with two1 wave-like furrows. Teeth small,
fine, vertical. Inner margin fluted. Length, 16; altitude,
10.25 >" semi-diameter, 5 ; length hinge, 12.5 mm.

This small and delicate Area is represented in the collec-
tion by one left valve and a young incomplete right valve. In
general characters it is closely similar to A. cibaoica
Maury 106 from the lower Miocene of Santo Domingo, but it
lacks the marked submedian sinus of cibaoica, has decidedly
less elevated beaks, and is less produced anteriorly. The
umbonal sinus of vanholsti may represent the incipient devel-
opment of a more general and pronounced undulation such
as that of cibaoica. In vanholsti the sinus, though sharp, is
not prominently noticeable, since it is small, confined to the
upper surface of the beak, and does not extend to the lateral
surface of the shell.

106 Bull. Amer. Pal., vol. 5, No. 29, p. 173, pi. 30, figs. 19, 20,
1917.

io8 STUDIES IN GEOLOGY, No. 3

Area (Scapharca) donacia Dall 107 is in some ways more
similar than is cibaoica. In general contour and sculpture
i't offers a strong superficial resemblance, and Woodring108
notes the presence of a similar sulcus on the umbo of the
right valve of forms from the Bowden beds. Comparison
with Woodring's specimens shows the sulcus to be shallower
and longer in donacia than in vanholsti. In the left valve
of donacia the sulcus is absent or very poorly developed:
in vanholsti it is equally prominent in both valves. A further
difference lies in the extent of the indentation, which in
donacia broadens toward the ventral margin, causing a
slight but perceptible emargination of the median ventral
margin ; in vanholsti, as noted above, the sulcus is confined
to the immediate surface of the beaks, and is totally lost
on the main surface of the shell, with no trace of indenta-
tion of the ventral margin. Thus, in donacia the develop-
ment of the submedian sulcus appears to be at a stage mid-
way between that of cibaoica and vanholsti.

The most striking difference between vanholsti and donacia
is in size, vanholsti being decidedly larger. Other distinc-
tive differences are : the ribs of vanholsti are more promin-
ent and sharply chiselled, showing, as well as the interspaces,
the concentric growth-crenulations absent in the ribs of
donacia; the angle between the anterior margin and the
hinge-line, obtuse in donacia, is about 90° in vanholsti; and
the beaks of donacia are much more prominent than those
of vanholsti.

Lower Zorritos (base). Escarpment overlooking Lobitos
well in quebrada north of Quebrada Boca Pan.

"Trans. Wag. Inst., vol. 3, pt. 4, p. 649, pi. 33, fig. 13, 1898.
108 The Mollusca of the Bowden Beds of Jamaica, Mss.

PALEONTOLOGY ZORRITOS FORMATION 109

Area (Scapharca) chamnensis n. sp.
PLATE V— Fig. 15.

Shell very inequilateral, moderately inflated, produced
posteriorly. Anterior margin rounded, meeting hinge-line
at approximately a right angle ; ventral margin slightly
curved, descending posteriorly to a point about 12 mm.
beyond the vertical bisectrix of the beak, whence it curves
upward to form the posterior margin, which is broadly
rounded, and meets the hinge-line at an angle somewhat
greater than 90.° Umbones conical, situated at about the
anterior third of the full length, pointed, with the upper
surface sloping anteriorly; umbonal slope characterized by
distinct but gentle furrow about 3 mm. wide, bounded by an
anterior and a posterior keel, both of which die out distally,
the anterior surface being gently hollowed out, and the
posterior keel flattening out into the alate posterior surface.
Ribs, probably 30 in number (36 visible in specimen), very
narrow in middle of shell, with interspaces 2-3 times as
broad ; broader and flat-topped on posterior part of shell and
more closely spaced anteriorly. Area and teeth not visible.
Length, 33.5; height, 23; (semi) diameter (estimated) 7-8
mm. Locality : West side of hill between Quebradas Heath
and Charon, Zorritos district. Horizon : Lower Zorritos.
Collection : Johns Hopkins University.

This form is represented by a single indifferently pre-
served pseudomorph, all of whose characters are not visible,
but of which the observable features are sufficiently distinct
from the most closely related described forms to warrant the
description of the species. It is most similar to A. gatun-
etmj'Toula,108 from the Gatun beds of Panama, but differs
in that its posterior margin is truncate, not rounded ; there
is no tendency toward bifurcation of the ribs, as in gatun-

Jahrb. k.k. geol. Reichs., Bd. 61, p. 493, pi. 30, fig. 4, 1911.

no STUDIES IN GEOLOGY, No. 3

ensis; it is more equilateral, and has the furrowed umbonal
slope not present in the Panama form. If Toula's total
thickness of 38 mm. is correct, gatunensis is much more
inflated than charanensis, which could not be greater than
16 to 1 8 mm. in total diameter. It is also much like A.
inequilateris Guppy,110 but the ribs lack, apparently, the
nodes of Guppy's figure (forms from the Bowden beds of
Jamaica do not have nodes as prominent) , the beaks are not
as sharply conical in shape, and the furrow in the umbonal
slope of charanensis is not present in inequilateris. A. dari-
ensis Br. & Pils.111 another form from the Gatun beds, has a
more fully curved anterior margin, and the ventral margin
does not descend posteriorly ; its ribs are divided by a groove
and it is not so fully produced posteriorly as is charonensis.
Lower Zorrkos. West side of hill between Quebradas
Heath and Charon.

Area (Scapharca) hispaniolana Maury (?)

Scapharca hispaniolana Maury, Bull. Amer. Pal., vol. 5, No. 29,
p. 176, pi. 30, figs. 9, 10, 1917.

Shell high, short, cuneiform, inflated. Anterior margin
absent in specimen. Ventral margin straight, apparently
nearly parallel to the hinge-line; posterior margin truncate,
forming slightly less than a right angle with the ventral
margin, and an angle of 130° with the hinge-line. Umbones
prominent, narrow, incurved; umbonal slope flattened, with
decided right-angled keel posteriorly. Ribs, 20-22 in num-
ber, square in cross-section, with interspaces equal in width
to a trifle wider than the ribs ; concentric growth-lines more
distinct in interspaces than on the ribs. Ribs nodulose,
giving quadrisulcate appearance to the shell similar to that

""Quart. Jour. Geol. Soc. Lond., vol. 22, pp. 293-294, pi. 28,
fig. 2, 1866.

111 Proc. Acacl. Nat. Sci. Phila., vol. 63, p. 362, pi. 22, fig. 10,
1911.

PALEONTOLOGY ZORRITOS FORMATION in

of A. santarosana Dall. Nodules tend to become absent
near the ventral margin about the umbonal keel, and the
ribs show a shallow longitudinal sulcus for a short distance
above the ventral margin, the sulcus being more prominent
mesially. Area short, narrow, with two furrows. Teeth
small, with comparatively broad interspaces, the hinge-plate
becoming wider posteriorly. Length, 18; height, 20; (semi)
diameter, 10 mm.

Only one imperfect left valve of this form is present in the
Hopkins collection. It offers a difference from Maury's
figured A. hispaniolana in that its ribs are uniformly equal
w idth to the interspaces, whereas the ribs of hispaniolana are
broader than the interspaces and there is further difference
in the ventrally sulcate ribs of this form, Maury's figure
and description giving no hint of such structure, but the
presence of the one imperfect specimen only makes differ-
entiation of the form unwise, and unless further specimens
of the Peruvian form show it to have constant differences it
may well be united with hispaniolana.

The sculpture and general appearance of the shell suggest
strongly A. (Cunearca) alcima Dall,112 but it is clearly a
typical Scapharca, and in addition is much smaller, with 20
instead of 30 ribs. Area chemnitzii Philippi is also similar
in appearance, but it, as well as alcima, is a Cunearca. A.
chemnitzioides Maury,113 from the Oligocene of Trinidad,
is similar, but in addition to being a Cunearca it has a greater
number of ribs, and is posteriorly alate instead of truncate,
as is hispaniolana.

Lower Zorritos. Quebrada Zapotal.

Area (Scapharca?) larkinii Nelson
PLATE V— Figs. 16-18.

Area Larkinii Nelson, Trans. Conn. Acad., vol. 2, p. 204, pi. 7,
figs. 5, 6, 7, 1870, (not Area Larkinii Grzybowski 1899)

112 Trans. Wag. Tnst, vol. 3, pt. 4, p. 635, pi. 31, figs. 5, 7, 1898.

113 Jour. Ac. Nat. Sc. Phila., vol. 15, p. 44, pi. 7, fig. 15, 1912.

H2 STUDIES IN GEOLOGY, No. 3

"Shell thick and heavy. Anterior extremity short and
rounded, posterior more or less produced. Beaks widely
separated, raised and very prominent. Ligament area large,
about half as broad as long. Surface marked by from 30 to
33 radiating ribs, which are rounded and broader than the
spaces between them. Ribs ornamented by rounded tubercles
and crossed by numerous fine lines of growth. Teeth num-
erous, strong, nearly straight, equidistant, except at the
extremities of the hinge line, where they become divergent
and much stronger. The margin of the shell is deeply
scalloped by the extremities of the exterior ribs and grooves.
* * * Anterior muscular scar almost circular; posterior
elongated and narrow." — Nelson, 1870.

Examination of Nelson's specimens shows the anterior
margin to be almost straight, and curved only where it meets
the ventral margin, which is straight and almost parallel
to the hinge-line. The posterior margin is little if at all pro-
duced ; the shell is subequilateral and has a squarish aspect
viewed laterally. The anterior surface is rounded, with a
hint of a keel ; the median surface is flattened, and the pos-
terior slope is flat to slightly excavated, being separated
from the median surface by a prominent keel which drops at
an angle approaching the vertical from the umbone to the
margin, where it meets the apex of the posterior marginal
angle. The area is smooth except for very fine longitudinal
lines, and is set off from the rest of the shell by a deep
marginal furrow followed by a thin smooth band, which
is sometimes indented by a subsidiary furrow. The teeth are
in two series, vertically disposed mesially, and oblique dis-
tally, the anterior distal teeth being shaped. Length, 27.5.

Exact locality and horizon not known. Although no speci-
mens of A. larkinii occur in the Hopkins collection, it is so
striking a form, and offers so many interesting features
inherently as well as through its relationships to other Areas

PALEONTOLOGY ZORRITOS FORMATION 113

in the fauna that some mention of it is pertinent. It is
another of the forms on the border-line between the Cunear-
cas and the true Scapharcas, "being in this respect much like
A. pantheonensis except for the equality of its valves. It has
the smooth area set off by a marked groove, the character-
istic teeth, and the general appearance o>f a Cunearca, but its
valves are nearly equal in size, and the sculpture is not dis-
crepant. A. pantheonensis has the discrepant valves, but
has a distinct furrow on the area.

Its nearest relatives are in the Zorritos fauna. Area pan-
theonensis bears the relationship noted above, but in addi-
tion to those differences it is more oblique in shape, and has
more regularly nodulate sculpture instead of the irregularly
tuberculate ribs of A. larkinii. A. imporcata is very similar
to A. larkinii, being almost indistinguishable from it in
general appearance, but it has consistently less ribs, and the
area is deeply furrowed; that of larkinii is smooth. A.
tuberculosa Sowerby,114 of the recent Peruvian fauna, likened
by Nelson to his A. larkinii is similar only in the tuberculose
character of the ribs, being much more oblique, inequilateral,
and produced than larkinii. The recent peruvian A. grandis
Brod. & Sow.115 is much larger, but is similar in shape.
Both tuberculosa and grandis are clearly true scapharcas.

Area (Scapharca) imporcata n. sp.
PLATE V — Figs. 19, 20.

Area larkinii Grzybowski, Neues Jahrb. f. Min., etc., Beil. Bd.
12, p. 633, 1899, (not of Nelson, 1870).

Shell thick, medium-sized, sub-equilateral, rhomboidal.
Anterior margin straight at juncture with hinge, curving
gently into ventral margin, which is normally straight and
nearly parallel to the hinge. Posterior margin little if at all

ll4Dall, W. H., Proc. U. S. Nat. Mus, vol. 37, p. 154, pi. 27,
fig. 4, 1910.

115 Idem., pi. 25, figs. 9, 10.

ii4 STUDIES IN GEOLOGY, No. 3

produced, straight. Umbones and general shape exactly as
in A. larkinii. Ribs 27 to 28 in number, prominent, rounded
to squarish in cross-section, tuberculate, with interspaces
about equal in width. The tuberculate ornamentation of the
ribs is best developed on the anterior surface, and loses
strength posteriorly, the posterior ribs not being noded. The
strength of the lines of growth near the margin gives the
valves a concentrically wrinkled appearance. The area is
marked by three to six wave-shaped furrows which are often
crossed by longitudinal lines near the hinge. The teeth are
fine and short mesiajly, becoming longer distally. Inner
margin fluted. Length, 35.5 mm. ; alt., 32.5 mm. ; diameter,
32.25 mm.

This species is one of four forms from the Zorritos region
which are so closely related that some emphasis of distinction
is necessary for unambiguous treatment. Of these four, A.
larkinii Nelson, A. imporcata n. sp., A. obesiformis Grzyb.,
and A. crescens n. sp., larkinii differs from all in the area,
and the other three form a series progressing in the order
named from erect, squarish forms (imporcata) through
more produced and more oblique forms (obesiformis) to
extremely produced and very oblique forms (crescens).
Other characteristics of these three species are more or less
constant, and the close relationship of the extremes to the
median form of the series begets the temptation to include
all in one species, but examination of a large number of
specimens shows the progressive difference in shape to be
sufficiently constant in each of the three species as here
proposed to make advisable, in the interest of clearness if
for no other reason, their consideration as separate groups

A. larkinii is exactly similar to A. imporcata in every feat-
ure save the area. The area of larkinii is smooth, excepting
a series of closely set, microscopic longitudinal lines, whereas
that of imporcata is characteristically furrowed. Grzy-
bowski's statement "Die weite Area tragt ausser dachform-
igen Furchen deutliche dichte Querleistchen, besonders stark

PALEONTOLOGY ZORRITOS FORMATION 115

an die Seite des Wirbels, was bei den Abbildimgen Nelsons
unberiicksichtigt 1st" in his description of A. larkinii (loc.
cit.) makes clear the fact that he was dealing with A. im-
porcata, and not the species described by Nelson as larkinii.
Other somewhat similar forms in the Zorritos fauna are A.
toroensis, A. scptifera, and A. nelsoni, all of which differ in
being larger, heavier forms much different in shape and
general contour. Perhaps the most closely similar form out-
side of Peru is A. idonea Conrad116 from the Miocene of
Maryland and neighboring regions. It differs in having
squarer ribs, less erect beaks and ordinarily a smaller area.
Upper Zorritos : Caleta Grau, Quebradas del Toro, del
Grillo.

Area (Scapharca) obesiformis Grzybowski
PLATE VI — Figs, i, 2.

Area obesiformis Grzybowski, Neues Jahrb., Beil. Bd. 12, p. 633,
pi. 28, figs. 3, 3a, 1899.

"Schale queroval mit zugestumpften Vorder — und ver-
langertem Hinterrande. Schlossrand gerade, Area lang,
breit, mit schwach angedeuteter Querstreifung iiber den
dachformigen Furchen. Die hohen Wirbel stehen in 1/3 der
Lange und sind 5 mm. von der Mittellinie entfernt. Ober-
flache mit 30 starken Rippen und scharf markierten Zu-
wachsstreifen. Hohe 30 mm., Lange 37 mm., Dicke (einer
Schale) 18 mm/' — Grzybowski, 1899.

The anterior margin is broadly rounded, meeting the
hinge-line at an angle barely obtuse; the ventral margin
descends slightly posteriorly; the posterior margin is pro-
duced, curving back to meet the hinge at an angle of about
140° — 145.° The umbones vary from nearly erect to decid-
edly inclined anteriorly. The ribs, from 28 to 30 in number.
are tuberculate anteriorly as in A. larkinii; the posterior ribs
are simple and show only distinct growth-lines. The ribs

Mel. Geol. Surv., Miocene, p. 389, pi. To6, figs, i, 2, 1904.

no STUDIES IN GKOLOGY, No. 3

are about equal in width to the interspaces, sometimes nar-
rower. The valves 'are often slightly ^discrepant in height,
the right valve being higher.

This species differs from A. imporcata chiefly in its more
produced posterior margin, more inclined beaks, and conse-
quent more oblique shape. Its valves are sometimes slightly
discrepant in height, but never prominently so, as are those
of Area crescens, and it is further distinguishable from
crescens by its less oblique outline. Grzybowski notes the
similarity between obesiformis and A. cardiiformis Bast.,117
from the Miocene of Europe. That form is less produced,
and has no pronounced posterior keel; the furrows of its
area are more regular and more nearly straight and longitu-
dinal, meeting the marginal furrow at angles, whereas the
furrows in the species under discussion are more irregular,
and either branch into the marginal furrow or meet at the
hinge-line. A. obesiformis is even more closely similar to
A. idonea Conrad118 than is A. imporcata. It differs, how-
ever, in having a much broader area.

Upper Zorritos. Quebrada del Toro.

Area (Scapharca) crescens n, sp.
PLATE VI— Figs. 3, 4.

Shell of medium size, heavy, oblique, the right valve
higher than the left. Anterior margin bluntly rounded,
meeting the hinge at an angle, though obtuse, very nearly
90.° Ventral margin long, slightly bowed, nearly parallel
to the hinge-line in its posterior half; posterior margin
greatly produced, forming an acute angle with the ventral
margin, and, beyond the curved apex of this angle, nearly a
straight line, forming an angle of 150° — 155° with the
hinge-line. Umbones prominent, inflated, prosogyrate, and

11THoernes, M., Abh. k.k. geol. Reichs., Bd. 4, p. 331, pi. 43,
figs- 3, 4, 5, 1870.
118 Md. Geol. Surv., Miocene, p. 389, pi. 106, figs. I, 2, 1904.

PALEONTOLOGY ZORRITOS FORMATION 117

inclined forward. Umbonal slope rounded anteriorly and
mesially, with a distinct posterior keel sloping backward at
a low angle. Ribs 27 to 28 in number, pronounced, rounded,
with tubercles anteriorly, plain posteriorly, tending to become
lost on the nearly flat posterior surface of the valves. Ribs
narrow, the interspaces often wider, but usually about equal.
Area long and broad, with the furrows and striations char-
acteristic of this group. Teeth fine and short, increasing in
size and coarseness distally. Inner margin fluted. Length,
47.5 mm; height of right valve, 37.5 mm.; of left valve,
32.5 mm. ; diameter, 39.75 mm.

This species is distinguishable from A. imporcata and A.
obesiformis, its nearest relatives, chiefly through its shape ;
it is much more produced, long, and oblique. The discrep-
ancy in height of the valves affords a clear distinction from
imporcata, whose valves are equal in height, and from obesi-
formis, in some forms of which there is a slight discrepancy,
but never a marked one. The ribs are narrower and more
widely spaced than in either of the other two forms. The
umbones are usually much more distant.

Upper Zorritos. Mouth of Quebrada del Grille.

Section ANADARA Gray

Area (Anadara) septifera Grzybowski

PLATE VI— Figs. 5, 6.

Area septifera Grzybowski, Neues Jahrb., Beil. Bd. 12, p. 633,
pi. 13, fig. 2, 2a, 1899.

Shell large, heavy, very thick (thickness of 9.5 mm. meas-
ured on broken left valve) , rounded in contour. Anterior mar-
gin broadly rounded and somewhat produced, forming a right
angle at its juncture with the hinge-line; ventral margin
rounded as far as known ; posterior margin broken away in
all specimens. Umbones high, incurved, nearly erect, upper
surface about 18 mm. vertically above the hinge line in the
average specimen. Umbones about 10 mm. distant. Um-

n8 STUDIES IN GEOLOGY, No. 3

bonal slope rounded anteriorly and mesially, the anterior
surface being modelled outward somewhat to meet the
slightly produced anterior margin, and the central surface
evenly round. Posterior slope not entirely known, but
there is apparently a keel similar to that in the forms related
to this. Ribs, 30-32 in number, sub-square in cross-section,
equal in width to the interspaces over entire surface, except-
ing one or two interspaces just forward of the posterior
keel, which are slightly broader, showing growth-lines, with
irregular tendency to form knobs, and with pronounced im-
brication of growth-layers near the ventral margin. Area
large, long and broad, with 6 to 7 simple wave-shaped
furrows which form angles obtuse near the hinge and more
acute toward the beaks. Hinge-plate about 5 mm. or more
wide anteriorly, 1.5 mm. wide mesially, lost posteriorly;
teeth fine below beaks, although coarser than in A. toroensis,
increasing in length and coarseness distally. There is a
growth on of semi-elliptical cross-section, viewed laterally,
on the hinge, which may represent the septum of Grzy-
bowski's figured specimen, but it is too poorly defined to sub-
stantiate the characteristic presence of the feature. Length
estimated at 58-60 mm.; height, 54.5 mm.; (semi) diameter,
28.5 mm.

This species is most closely similar to A. toroensis, of the
Zorritos fauna. It differs from that form in its more closely
proximate, fuller, and more highly incurved beaks, its
heavier hinge-line, with generally coarser teeth, and its
simply and evenly furrowed area: the area of toroensis is
furrowed irregularly in most specimens. The septum noted
by Grzybowski in his description of Area septifera is not
typically present, and although there is in the form here
described a perceptible semi-elliptical thickening of the hinge-
plate beginning about 10 mm. behind the vertical line of the
beak-point, it is such a feature as might be ascribed ordi-
narily to a pathological growth due to the stimulus of some
foreign matter. Grzybowski's septum is figured as V-shaped

PALEONTOLOGY ZORRITOS FORMATION 119

in cross-section; the growth here noted could hardly have
been so shaped even if weathering away were offered as a
cause for its possible reduction; the comparatively clear-cut
condition of all similar parts of the shell suggests strongly
the impossibility of such a change.

A. septifcra belongs in the group of similar forms in the
section Anadara of which A. grandis and A. cctmuloensis are
members. The former of the two is living at present on the
west coast; the other occurs in the Miocene and later of
California. A. septifera differs from A. camuloensis
Osmont 119 in being less quadrate, more rounded, with fuller,
less pointed beaks, the hinge-line proportionally longer, and
the rib-sculpture less regular than in camuloensis.

Upper Zorritos. Quebrada del Grillo.

Area (Anadara) nelsoni n. sp.
PLATE VI— Figs. 7, 8.

Shell thick, stout, of moderate size, rounded in contour.
Anterior margin broadly rounded, meeting hinge-line at an
angle slightly more than 90° ; ventral margin arcuate, pos-
terior margin recurving into a straight line which meets the
hinge at an angle of from 135° to 145°. Umbones dome-like
viewed laterally, high, inflated, prosogyrate. Umbonal slope
smoothly convex anteriorly and mesially, with slight excava-
tion near the anterior margin in some individuals; a poste-
rior keel runs from the marginal angle to the umbone. Pos-
terior surface slightly excavated. Ribs, 30-31 in number,
prominent, square in cross-section, smooth posteriorly and
somewhat irregularly noded anteriorly by concentric chan-
nellings which cross the interspaces but are not as prominent
there. Interspaces deep, narrower than the ribs in unweath-
ered specimens. Area short, bounded by a deep marginal
furrow and an elevated band, and bearing about three wave-

119 Univ. Cal. Bull. Geol., vol. 4, p. 98, pi. 10, figs. 6, 6a, 1904.

120 STUDIES IN GEOLOGY, No. 3

like furrows which are sometimes more or less irregular, and
which are crossed by longitudinal imbricated channels near
the hinge. Teeth in a single series, fine, rather long,
slightly oblique and longer distally. Inner margin fluted.
Length, 40; height, 40.5; (semi) diameter, 18.5; length of
hinge, 30 mm.

This species is very closely related to others in the Zorritos
fauna, and might be termed a mutant or variant of some of
them if the special characters which serve to distinguish it
were less constant or if there were more perceptible inter-
grading. Area toroensis is distinguished from it by its larger
and more irregularly furrowed area, its generally less pro-
nounced marginal furrow and band bounding the area, and
ijts tendency to be angular and to flare ventrally; A. nelsoni
is always smoothly rounded. A. nelsoni is distinct from A.
septifera in its smaller and less furrowed area and its gen-
erally finer teeth. In shape and other characters the two
agree. A. septifera seems to attain a larger size than nelsoni,
and its -ribs are ordinarily coarser, but on the whole the two
are very similar, and are separable chiefly on account of
thfe difference in area. A. nelsoni differs from the other
related Areas of the local fauna proportionally as they differ
from the forms noted; it is somewhat like the A. imporcata
group, but differs more clearly from them than from the
forms mentioned.

Outside of Peru its closest relatives are to be found in the
Caribbean Oligocene and Miocene. Scapharca anguillana
Cooke 12° from the Oligocene of Antigua, is very close, but
has more prominent tuberculation of the ribs, the area bears
eight furrows, the teeth are shorter, and the shell flares
ventrally; that of nelsoni does not. It differs less promin-
ently from. A. chiriquiensis Gabb (2) from the Miocene of

120 Carnegie Inst. Wash., Publ. 291, p. 127, pi. 5, figs. loa, b, 1919.
(2) Maury, Bull. Amer. Pal., vol. 5, No. 29, p. 174, pi. 28, fig.
2, 1917-

PALEONTOLOGY ZORRITOS FORMATION 121

Santo Domingo. Maury's figure shows an anterior sinus in
the left valve ; this does not exist in nelsoni } and the granu-
lation of the ribs is coarser in chiriquiensis. The area of
nelsoni is lower and the teeth are larger. Otherwise the two
are closely similar.

A. nelsoni shows close relationship to two European
forms, Anadara diluvii var. bollenensis (Fantannes)121 and
A. nchteli (Deshayes),122 which Sacco has described from
the Tertiary of Italy. A. diluvii, which ranges from the
Helvetien to the Astien, has apparently about the same num-
ber of ribs, and is in other features entirely similar except
that the beaks of nelsoni are a bit higher, and the area some-
what shorter, with the result that the posterior margin of
nelsoni meets the hinge at an angle greater than in Sacco's
form. A. nchteli, from the Helvetien and Tortonien of the
Piedmont, is also similar, but its ribs are broader in propor-
tion to the interspaces. The area is shorter in nelsoni.
According to figures given by Hoernes 123 the furrows in
nchteli are more numerous, more evenly spaced, and less
sharply V-shaped than in nelsoni. Areas of this type ap-
parently did not appear in Europe until the Helvetien. They
were present in the Caribbean and adjacent regions at least
as early as late Oligocene.

Upper Zorritos. Quebradas del Toro and del Grille.

Area (Anadara) toroensis n. sp.
PLATE VI— Figs. 9, 10; PLATE VII— Fig. i.

Shell large, heavy, inflated. Anterior margin broadly
rounded, forming a right angle with the hinge-line ; ventral
margin gently rounded, its flattest part being usually nearly
parallel to the hinge-line, in some specimens descending
slightly posteriorly. Posterior margin produced and rounded

121 Piemonte, pte. 26, p. 22, pi. 4, fig. 13, 1898.

122 Ibid., p. 23, pi. 5, figs. 2-8.

123 Abh. k.k. geol. Reichs., Bd. 4, p. 331, pi. 43, figs. 3, 4, 5, 1870.

122 STUDIES IN GEOLOGY, No. 3

more acutely than the anterior margin, forming an angle of
142° with the hinge-line. Umbones high, almost uniformly
14 mm. above the hinge, situated at about the anterior third
of the entire length, rounded in outline viewed laterally, with
the upper surface sloping distinctly forward in some mutants,
and symmetrically erect in others. Umbonal slope dome-like
anteriorly, circular in cross-section mesially, and with a
distinct surficial keel running from the posterior side of the
umbone to the posterior margin at an angle of about 45°.
The keel is flared in some forms, forming a distinct shoulder
parallel to the margin. Ribs, 28 in number, (29 on some
left valves) prominent, rounded, with interspaces slightly
more than twice as broad as the ribs (largest ribs i mm.;
interspaces 2.2 mm.) showing growth-lines prominently
near the ventral margin, and noded irregularly, the nodes
being knob-like. Area high and broad, with wave-like im-
bricated furrows increasing in distance of separation from
the hinge-line to the beak and more sinuous above. Teeth
small and short, numbering about 85, set on a thin hinge
plate 36 to 40 mm. long, becoming more widely separated
and coarser distally. Greatest vertical length of anterior
teeth, 2.5 mm. ; of posterior teeth, 2.75 mm. ; of smallest
tooth, i mm. Inner margin regularly and deeply fluted.
Dimensions of two specimens: Length, 50; height, 47.5;
diameter, 24.5 ; Length, 47 ; height, 42 ; diameter, 20 mm.

This form resembles A. septifera, of the local fauna, very
much, and is closely related to it, but the beaks are less prox-
imate and not so far incurved, the area is larger, and the
teeth are finer and more numerous. The septum noted by
Grzybowski 124 in his original description of septifera is not
present in any of a large number of specimens of toroensis.
A. imporcata, also of the local fauna, is similar, but is
smaller, with proportionally lower beaks, smaller area with
less varied furcation, and with decidedly more rectangular

"*Neues Jahrb., Beil. Bd. 12, p. 633, pi. 13, fig. 2, 1899.

PALEONTOLOGY ZORRITOS FORMATION 123

outline. The ribs of A. imporcata are wider than the inter-
spaces; the reverse is true of A. torocnsis. There is consid-
erable variation in outline in this species, and it was con-
sidered advisable at first to divide the group more finely,
giving such differences specific value, but the intergrada-
tion of the characters and their irregular overlapping in
various specimens led to the "lumping" of all forms which
show constancy in the major characters. Two mutants, the
varieties crassa and prolata, show sufficient variance from
the form considered as the type to require at least varietal
distinction.

Area chiriquiensis Gabb,125 from the Miocene of Santo
Domingo and the Oligocene (?) of Chiriqui, is very closely
related. The ribs of toroensis are not as thick as those of
chiriquiensis, and are less coarsely noded; the hinge-line is
normally longer than that of chiriquiensis, and the vertical
distance between the hinge and the ventral margin is smaller.
Otherwise the two tally closely. A. anguillana 12° Cooke,
from the Oligocene of Antigua, is exactly similar in shape,
and differs only in size and in the area, which in toroensis is
not bounded by a marginal elevation, has a larger number
of more irregular grooves, and is longer.

There is striking resemblance between the more rounded
specimens of A. toroensis and A. idonea Conrad 127 from the
Miocene of Maryland, Virginia, and Florida. The only
differences between the two lie in the ribs, which are some-
what tuberculated and more rounded in A. toroensis, and the
area, which is uniformly higher, with a narrower limiting
angle.

Upper Zorritos. Quebradas del Toro, Tijeritas and del
Grillo.

ia''Maury, Bull. Amer. Pal., vol. 5, No. 29, p. 174, pi. 28, fig. 2,
1917.

126 Carnegie Inst. Wash., publ. 291, p. 127, pi. 5, figs, roa, b, 1919

127 Md. Geol. Surv.. Miocene, p. 389, pi. 106, figs, i, 2, 1904.

124 STUDIES IN GKOLOGY, No. 3

Area (Anadara) toroensis var. crassa n. var.
PLATE VII— Fig. 2.

Shell much like type, but thicker and heavier. Anterior
margin slopes posteriorly from the hinge-line, forming with
it an angle of about 85° ; ventral margin descends slightly
posteriorly; posterior margin unknown. Beaks high, the
upper surface about 21 mm. above the hinge, rounded in
outline as viewed laterally, erect. General contour of shell
as in typical A. toroensis. Ribs 22 in number, from anterior
end to posterior keel ; thence unknown — probably 28-30 in
total number; rounded, tending to squarish shape, about
1.6 mm. broad, with equal interspaces. Growth-lines prom-
inent. Area very high, with many waved furrows and
sinuous grooves, the latter prominent near the beaks and the
former near the hinge. Hinge-line narrow, with many fine
teeth. Length, 53; height, 51; (semi) diameter, 28.5;
length of hinge, 41.5 mm.

The differentiation from the typical Area toroensis is
based on variations which would certainly have specific value
if the characters were more constant. As matters stand,
with some heterogeneity within the species of A. toroensis,
the likelihood of very close association between the true
form and this variety is high, and although the obviously
larger area, proportionally broader ribs, and incurving ven-
tral surface of this form offer striking difference, and seem
to demand distinction greater than that implied by the assign-
ment of varietal rank, the probability of close relationship
precludes the use of a specific name until more material
shows the variation to be thoroughly constant.

The variety is very close to A. fichteli Deshayes, figured by
Hoernes 128 from the Miocene of the Vienna basin. The only
difference lies in the area, which in fichteli is furrowed regu-
larly, the furrows being evenly spaced, whereas in crassa

Abh. k.k. geol. Reichs., Bd. 4, p. 331, pi. 43, figs. 3, 4, 5, 1870

PALEONTOLOGY ZORRITOS FORMATION 125

they are irregular and more widely spaced near the beaks.
Upper Zorritos. Quebrada del Toro.

Area (Anadara) toroensis var. prolata n. var.
PLATE VII— Fig. 3.

Shell high, thick, inflated. Characters as in A. toro<ensis.
with the following exceptions: Beaks narrow and pointed,
much higher than in toroensis. Area very high in propor-
tion to length, covered with many fine longitudinal grooves
which grow more distantly separated toward the beak. Either
symmetrical in shape or slightly produced posteriorly; not
distinctly so as is toroensis.

The separation from the typical toroensis presents much
the same sort of problem as that offered by the variety
crassa; the points of difference would have specific value but
for an intergradation. Its differentiation is advisable on
account of the wide variation in shape and general appear-
ance. However, its clear relationship to the parent species
indicates the sub-specific nature of the differences.

Upper Zorritos. Quebrada del Toro.

Superfamily

Family PECTINIDAE

Genus PKCTKN Miiller

Pecten woodringi n. sp.

PLATE VII— Figs. 4, 5.

Pecten sp. indet. Nelson, Trans. Conn. Acad., vol. 2, p. 205,
1870 (ex parte).

Shell small, slightly inequivalve, the left valve more con-
vex, subequilateral. The right valve somewhat flattened,
with about 15 round ribs, arranged in fan shape, a little
wider than the interspaces. Submargins steep, smooth, flat ;
anterior ear with four distinct radiating ribs, crossed by

126 STUDIES IN GEOLOGY, No. 3

sharp concentrically channelled threads which extend across
the part next the submargin in reversed curves, making the
complete threading S-shaped ; byssal notch prominent ; com-
parative length of ear not known. Posterior ear subrec-
tangular, with sculpture of very fine, closely spaced concen-
tric threads and very faint radial ribs. Sculpture on the
disc of very fine growth-lines which cross the ribs and inter-
spaces in smooth circles. Inner shell fluted.

The left valve similar to the right ; anterior ear orna-
mented by about six somewhat widely spaced radiating ribs
which are crossed by fine lines of growth; outline unknown.
Posterior ear unknown excepting a fragment near the sub-
margin, which shows several radiating ribs crossed by very
fine lines of growth. Sculpture on disc of fine growth-lines
which curve upward on the ribs and downward on the inter-
spaces, giving the threading a sinuous aspect. Both valves
have apical angles of 90° or more. The margins form
approximate semicircles. Dimensions : Right valve, length,
37.5; height, 36.25 mm. Left valve, length, 32; height,
30.75 mm.

This species is very close to a group described by Cooke
in 1918 from the Oligocene of Cuba and Anguilla. Though
smaller, P. gardnerae,129 from Anguilla, is perhaps closest
of the three similar forms ; it differs in being more inflated,
smaller, with higher ribs, and in having five ribs instead of
four on the anterior ear of the right valve. P. vcnighani
var. flabellum Cooke 13° (not of Arnold 1906), also from the
Oligocene of Cuba, has similar ribs, but differs in being
smaller and in that the ribs do not extend to the beaks. This
character of the ribs is the chief differential feature between
the variety ftabellum and Pecten vaughani Cooke131 (not
Arnold, 1906), but that species differs from woodringi in

123 Carnegie Inst. Wash., pub. 291, p. 134, pi. 7, figs. 5, 6, 1919.

130 Idem., p. 134, pi. 8, figs. 8, 9, 10.

131 Idem., p. 133, pi. 8, figs. 2, 3, 4.

PALEONTOLOGY ZORRITOS FORMATION 127

having the posterior ear of the right valve smooth, whereas
it is ribbed in woodringi. P. perplexus Cooke,132 from the
Oligocene of Anguilla, is similar in general appearance,
but has spines between the ribs which are apparently absent
in woodringi, and has a larger number of ribs. Pecten cer-
cadica Maury,133 from Cercado de Mao, Santo Domingo, is
somewhat similar, but has faintly instead of prominently
threaded ears, and has proportionally broader ribs.

Upper Zorritos. Quebradas Pantheon, del Toro, de las
Alturas and del Grillo.

Superfamily ANOMIACEAE

Family ANOMIIDAE
Genus ANOMIA (Linnaeus) Miiller

Anomia berryi n. sp.
PLATE VII— Figs. 6, 7.

Shell large, heavy, very convex, fairly regular. Left valve
much inflated. Umbones usually broad, somewhat incurved.
Sculpture of radial ribs, somewhat irregular, between the
major ones of which are from three to five minor ribs which
are seen under a lens to be crossed by fine, wavy growth-
lines, with the formation of something like nodes. The ir-
regular, wavy concentric growth-lines are fine from the
hinge half-way down the shell ; on the ventral half they are
coarse and imbricate. Interior of valves not known. Length,
60 ; height, 46.5 ; diameter left valve, 26 mm.

This species is an unusually large and heavy species. It
differs from most of the species common to the American
Tertiary, but recalls some varieties of the European A.
ephippium, of which the variety rugulosostriata Brocchi,134

132 Idem., figs. 8, 9, 10.

133 Bull. Amer. Pal., vol. 5, No. 29, p. 188, pi. 34, fig- u, IQI
134Sacco, Piemonte, pte. 23, p. 34, pi. 10, figs. 18-24, 1897.

128 STUDIES IN GEOLOGY, No. 3

from the Helvetian to the Astian of Italy, is somewhat sim-
ilar in sculpture, and the variety helvetica Mayer,135 from
the Helvetian to the Astian, is similar in shape. The only
closely related American form is A. gabbi Pilsbry and John-
son,136 from Santo Domingo. It is, however, more delicate,
not as much inflated,, and has more distinct primary radial
ribs, with occasional strong interstitial ribs which are not
present in berryi. A gabbi lacks the imbrication of growth-
lamellae common to the ventral slope of berryi. The two are
very close in type of sculpture.

Upper Zorritos ; Variegated (basal). Quebradas Zapotal
and del Grillo.

Order TELEODESMACEA

Superfamily ASTARTACEA

Family CRASS ATELUTIDAE

Genus CRASSATEUJTES Kriiger

Section SCAMBULA Conrad

Crassatellites (Scambula) nelsoni (Grzybowski)

PLATE VII— Fig. 8.

Crassatella gibbosa Nelson, Trans. Conn. Acad., vol. 2, p. 203,
pi. 7, 'fig. 9, 1870 (ex parte) ; not Sowerby.

Venus nelsoni Grzybowski, Neues Jahrb., Beil. Bd. 12, p. 639, pi.
19, figs. 2, 2a, 1899.

Mature shell heavy, large, subtriangular, inflated; young
shell more inequilateral. Anterior margin rounded; ventral
margin arcuate in mature shell, the curve more shallow in
adolescent specimens. Posterior margin biangular, truncate
in adult, more produced in adolescent shell. Umbones high,
full, distinctly flattened above, the flat surface sloping back-

133 Ibid.; p. 37, pi. 10, fig. 39.

l3*Proc. Ac. Nat. Sc. Phila., vol. 69, p. 193, 1917.

PALEONTOLOGY ZORRITOS FORMATION 1 29

ward; surface of valves evenly convex except posteriorly,
where a marked keel is bounded anteriorly by a broad,
shallow sulcus which grows narrower toward the beaks,
and posteriorly by a similar narrower concavity. In mature
specimens the keel is sulcate, having thus two edges, the sul-
cation flattening posteriorly and being stronger in the right
valve. The inner carinal ridge bounding the sulcus is often
the sharper of the two. Sculpture of concentric growth-
lines ; on the beaks are three to five sharp concentric waves.
Lunule deeply impressed, distinct, oval, bounded by a sharp
line, within which is another less intense line about one-
fifth of the distance toward the juncture of the valves;
escutcheon long and narrow. Hinge normal, the middle
cardinal tooth of the right valve sometimes pronounced.
Muscle scars deep; internal margins of valves smooth;
pallial line deeply incised. Length, 48 ; height, 32 ; diameter,
22.5 mm.

Nelson's collection contains a group of Crassatellites,
labelled C. gibbosa Sowerby, which includes a few frag-
ments of the true gibbosa with a number of well-preserved
and very large specimens of C. nelsoni. A glance suffices to
distinguish nelsoni from the recent gibbosa; the former is
much more inflated, shorter, and the area is more deeply
impressed. The specimens of nelsoni in the Hopkins col-
lection are much smaller than those studied by Nelson, but,
as noted below, there is little doubt as to their identity.
Grzybowski described and figured the adolescent form as
Venus nelsoni. Comparison with his figure shows his form
to be identical with the specimens of C. nelsoni in the Hop-
kins collection, and although he did not figure or describe
the hinge beyond saying that it is "normal," there is small
doubt that his generic determination is at fault, and that his
Venus nelsoni is the Crassatellites here described.

In the present description some distinction is made between
the characters of adolescent and mature forms. This is done
because of the apparent fact that at some localities the

130 STUDIES IN GEOLOGY, No. 3

smaller forms only exist. Careful comparison of growth-
stages in the large and small specimens has led to the con-
clusion that they are of the same species. The younger
forms are more produced posteriorly, and thus lower than
the larger ones, which are subequilateral, but tracing out of
the growth-lines on larger forms corresponding to the
margins of the younger ones reveals a clear identity of
shape.

C. nelsoni is very much like several forms from the Carib-
bean and Floridian Miocene. C. reevei Gabb,137 from Gatun.
is different in being broader posteriorly, having a broader
surface behind the posterior keel, with (apparently) not so
prominent a sulcus behind the keel, and in its sculpture,
which is concentrically waved over the entire surface, where-
as nelsoni has the waved sculpture on the beaks only. C.
(Scambula) densus Dall,138 from the Oak Grove beds of
Florida, is very close, probably the most closely related form
outside of Peru. The only point of difference in the mature
shells of the two species, disregarding size, is a greater pos-
terior attenuation in nelsoni; densus is much more evenly
elliptical in cross-section viewed dorsally. The mature shells
of nelsoni are somewhat larger.

C. (Scambula) melinus var. meridionals Dall 139 is also
very close, but is higher, less inflated, and the ventral margin
does not ascend posteriorly as does that of nelsoni. C.
(Scambula) deformis Heilprin 14° is somewhat similar, but
differs in having pronounced undulatory sculpture, and in
the resilium, which is narrower than in nelsoni t and oval
instead of triangular in shape.

137 Brown and Pilsbry, Proc. Ac. Nat. Sci. Phila., vol. 64, p. 515,
pi. 24, fig. 5, 1912.

38 Trans. Wag. Tnst., vol. 3, pt. 6, p. 1472, pi. 39, figs. 9, 10, 11, 12,
1903.

139 Idem., p. 1473, pi. 37, figs. 6, 13.

140 Dall, Bull. U. S. Nat. Mas. 90, p. 131, pi. 22, figs. 6, 7, 1915.

PALEONTOLOGY ZORRITOS FORMATION 131

Lower Zorritos. Ridge at head of Quebrada Heath.

Crassatellites (Scambula) berryi n. sp.
PLATE VII — Figs. 9, 10.

Shell of medium size, anteriorly inflated, posteriorly atten-
uate. Anterior margin rounded; ventral margin rounded
anteriorly, ascending posteriorly in a reflex curve to the
apex of the first of two marginal angles. The posterior
dorsal margin is about straight, descending to meet the
apex of the second posterior marginal angle. Umbones
high, erect, inflated, prosogyrate, proximate, the tops flat-
tened, with the flat surface sloping backward. Anterior
surface convex. A prominent keel, sharp on and near the
beaks and flattened ventrally, runs from the umbo to the
lower marginal angle ; before the keel there is a sulcus,
narrow and sharp umbonally and shallower ventrally. Be-
hind the posterior half of the keel is a flat to concave surface
which is often bounded posteriorly by a second vestigial
keel. Sculpture of strong concentric undulations, their
dorsal slopes steeper, sharp on the beaks and decreasing in
prominence ventrally but evident over all of the shell, sharper
anteriorly on the median surface. There is additional sculp-
ture of fine growth-lines. The concentric sculpture parallels
the margins. Lunule deeply impressed, distinct, oval ; es-
cutcheon of similar lines but more lanceolate. Hinge nor-
mal. Muscle scars deeply impressed ; internal valve-margins
smooth ; parallel line sharp. Length, 40.5 ; height, 28 ; diam-
eter, 20.5 mm.

This form differs from Crassatellites nelsoni, chiefly in
the possession of strong concentric undulations over most or
all of its surface instead of on the beaks alone. This sculp-
ture tends to become obsolete on the ventral-posterior part
of the shell, but it is clearly marked elsewhere on all speci-
mens, and some show it almost equally strong over the entire
shell. The beaks are not as prominently flattened as in nel-

132 STUDIES IN GEOLOGY, No. 3

soni, and the valves are more highly inflated anteriorly,
tapering off in greater contrast to a thin, produced posterior
ring which is much narrower and longer than that of nelsoni.
No specimens as large as those of nelsoni in the Nelson
collection have been found. C. berryi is very prolific in the
Lower Zorritos formation. Crassatellites reevei Gabb,141
from Gatun, Santo Domingo, and Sapote, Costa Rica, is
somewhat similar, and is perhaps the closest species known
from the Americas. It differs chiefly in lacking the attenu-
ate posterior wing of berryi. In addition the area behind
the keel is flatter and smaller in berryi, the beaks being
higher and the keel more curved.
Lower Zorritos. Quebrada Zapotal.

Superfamily LUCINACEA

Family LUCINIDAE

Genus PHACOIDES Blainville

Subgenus PSEUDOMUVTHA Fischer

Phacoides (Pseudomilthaf) insleyi n. sp.

PLATE VII— Fig. n.

Shell medium-sized, moderately inflated, somewhat pro-
duced ventrally. Anterior dorsal margin broadly curved,
forming a blunt but perceptible angle with the lateral mar-
gin. Ventral margin full and rounded, somewhat produced.
Posterior dorsal margin similar to anterior, but the angle
with the lateral margin is more pronounced and is slightly
nearer the beaks. Umbones sharp, inclined forward, distinct.
General surface convex, excepting a slight concavity before
the beaks. There is no surficial sinus. Sculpture, of fine
concentric growth-lines, known only from small patches of
the epidermis, which is thin, and cleaves off readily, showing

141 Brown and Pilsbry, Proc. Ac. Nat. Sci. Phila., vol. 64, p. 515,
pi. 24, fig. 5, 1912.

PALEONTOLOGY ZORRITOS FORMATION 133

an under surface with concentric sculpture similar to that
of the outer layer and, in addition, very fine radial lines.
Areas imperfectly known, but do not appear prominent.
Inner shell unknown. Length, 27.5 ; height, 27.5 ; diameter.
13.5 mm.

This species is very close to P. glumindus Woodring,142
from the Bowden beds of Jamaica, and examination of
more material may show the advisability of expressing a
relationship closer than that suggested, but such evidence as
is now available indicates sufficiently strongly the possibility
of specific difference to suggest the naming of the form as a
new species. Specimens of P. glumindus have the ventral
margin less deeply arcuate, and the umbones less promin-
ent, with no radial lines on the under surface of the shell.
One fragment of the Zorritos form suggests the possibility
of a ventral margin similar to that of glumindus, but the
type here described seems to predominate, and the other
differences appear constant. The sculpture of glumindus
is coarser and more irregular than that visible on patches of
the epidermis of insleyi .

Two east coast Miocene species are similar. Phacoides
foremani Conrad,143 from the Miocene of Maryland, differs
in having a posterior sulcus and rougher sculpture ; it is
identical in shape. P. anodonta Say,144 also from the Mary-
land Miocene, attains a larger size than that known for
insleyi, but adolescent forms of anodonta are similar excep-
ting their slightly more orbicular shape, ruder sculpture,
and posterior sulcus. The epidermis of anodonta is propor-
tionally thicker, and the radial sculpture beneath it is much
coarser and stronger than in insleyi.

Two species from the Eocene of California appear to be

142 Dissertation, Johns Hopkins Univ.

l"Foss. Med. Tert, p. 71, pi. 40, fig. 4, 1845 (as Lucina fore-
mani} .
144 Md. Geol. Surv., Miocene, p. 337, pi. 90, figs. 3, 4, 1904.

134 STUDIES IN GEOLOGY, No. 3

similar. Lucina oregonensis Dickerson,145 from the Tejon
Eocene, has more regular concentric sculpture, and is pro-
portionally lower. Phacoides m-uirensis Dickerson,146 from
the Martinez Eocene, is closer than oregonensis, but is
thicker marginally, has the ventral margin more broadly
rounded, and has a posterior sulcus.

Knowledge of the interior of the shell and the availability
of a larger amount of material for study may change the
validity of many of these observations, and the author hesi-
tated on account of the lack of such evidence to name a
species so closely related to other forms as new ; but with
these relationships and the possibilities of identity pointed
out, future work will probably be made less intricate by
the separation of the form instead of including it in a
synonymy from which it might necessarily be extricated
later.

Lower Zorritos. Ridge between Ouebradas Heath and
Charan.

Superfamily CARDIACE;A

Family CARDIIDAE

Genus CARDIUM (Linnaeus) Lamarck

Subgenus TRACHYCARDIUM Morch

Cardium (Trachycardium) zorritensis n. sp.

PLATE VII— Fig. 12.

Shell thin, inflated, subequilateral. Anterior margin
rounded, not produced ; ventral margin rounded ; posterior
margin slightly produced. Umbones high, inflated, narrow.
Surface generally convex except on either side of the beaks,
where a slight concavity leads into the poorly defined areas.
Sculpture of 32 smooth A-shaped ribs with V-shaped inter-

145 Univ. Cal. Bull. Geol., vol. 9, p. 484, pi. 37, figs. la, b, 1916.
148 Idem., vol. 8, p. 132, pi. 10, figs, na, b. 1914.

PALEONTOLOGY ZORRITOS FORMATION 135

spaces about equal in width ; in the right valve of worn
specimens the posterior five ribs are roughly bifid for their
entire length, and in the left valve a similar sulcation of the
posterior ribs is evident, but some of the bifurcations are
still more uneven, giving one of the paired ribs the appear-
ance of a secondary interstitial rib. These irregular ribs
represent the bases of spines which are lost on the specimens
available. Area, teeth, and inner shell unknown. Length,
31.25 ; height, 33.5 ; (semi) diameter, 15 mm.

This species is superficially somewhat similar to C. peru-
vianum, but differs in being smaller and in having far fewer
ribs. C. phlyctaena Ball,147 from the Ballast Point beds of
Florida, is similar, but differs in being less depressed an-
teriorly, and in having lower beaks. C. zorriiensis ap-
proaches C. taphrium Dall 148 from the Ballast Point and
Oak Grove beds of Florida, more closely than does C> peru-
vianum; however, taphrium is different in having narrower
interspaces between the ribs. " With the exception of its far
greater number of ribs, C. dominicense Gabb,149 from Santo
Domingo, Costa Rica and Panama, is similar. It has the
bifid posterior ribs, and the general outline is similar, with
the exception that it is a much broader shell.

Lower Zorritos. Quebrada Zapotal.

Cardium (Trachycardium) peruvianuni n. sp.

PLATE VIII— Fig. i.
Cardium sp. ind., Nelson, Trans. Conn. Acad., vol. 2, p. 203, 1870.

Shell large, inflated, evenly rounded. Marginal outline
unknown. Umbones prosogyrate, broad and full dorsally,
tapering rapidly terminally. Surface very convex, evenly
rounded, excepting the usual excavations before and behind

47 Trans. Wag. Inst., vol. 3, pt. 5, p. 1097, pi. 48, fig. 13, 1900.
148 Idem., p. 1098, pi. 40, fig. 9.

149Toula, Jahrb. k.k. geol. Reichs., Bd. 58, p. 720, pi. 27, fig. 4,
pl. 28, fig. 1 8, 1908.

136 STUDIKS IN GEOLOGY, No. 3

the beaks. Sculpture of about 50 sharply defined, square,
strong ribs, with channelled interspaces equally broad;
spines may have existed, but the specimens available are
worn. Area and hinge normal. Inner margins unknown.
Length, 46; height, 46; (semi) diameter, 18.5 mm.

This species is very similar in appearance to< C. domin-
ie ense Gabb,150 from Santo Domingo, Costa Rica, and Pan-
ama, differing in being more nearly round in outline, thus
of broader proportions, with five to ten less ribs which are
distinctly separated by channelled interspaces; in domin-
icense the interspaces are rather merely the sides of the
closely adjacent ribs. In dominie ens e the tops of the ribs
slant anteriorly ; in perumanum they are parallel to the sur-
face of the shell. C. taphrium Dall,151 from the Ballast Point
and Oak Grove beds of Florida, is similar in shape, but has
only 34 instead of 50 ribs.

Zorritos formation. Zorritos.

Subgenus FRAGUM Bolten

Section TRIGONIOCARDIA Dall

Cardium (Trigomocardia) affinis (Nelson)

PLATE VIII— Figs. 2, 3.
Hemicardia affinis Nelson, Trans. Conn. Acad., vol. 2, p 204, 1870.

Shell small, high, inflated, obovate, heart-shaped viewed
from behind. Anterior margin rounded, joining through a
blunt angle with the descending, almost straight ventral
margin. Posterior marginal angle prominent and acute ; the
posterior margin ascends from the lowest point of the shell
almost vertically in a straight line, curving more or less
abruptly into the posterior dorsal margin. Beaks high, erect,

"° Trans. Amer. Philos. Soc., vol. 15, n.s., pp. 250-251, 1873;
also Toula, Jahrb. k.k. geol. Reichs., vol. 58, p. 720, pi. 27, fig. 4,
pi. 28, fig. 18, 1908.

"Trans. Wag. Inst., vol. 3, pt. 5, p. 1098, pi. 40, fig. 9, 1900.

PALEONTOLOGY ZORRITOS FORMATION 137

narrow, and inflated, very slightly if at all prosogyrate, and
somewhat involute. Anterior surface rounded, gently con-
vex excepting a slight excavation just before the beaks;
median surface sharply convex but smoothly rounded, a
distinct rounded carina separating it from the posterior sur-
face, which is flat ventrally, and somewhat excavated
dorsally, though not markedly alate. Sculpture of about
21 ribs, broad and flat-topped anteriorly and narrower pos-
teriorly, with narrow, sharply channelled interspaces. Both
ribs and interspaces are crossed by microscopic lines of
growth which are stronger in the interspaces than on the
ribs. The ribs are more rounded near the beaks than ven-
trally, where they are distinctly flat-topped. The inner
surface of the shell is smooth except marginally, where there
is fluting. The raised elements of the fluting are slightly
sulcate centrally. Hinge not known. Length, 10.5 ; height,
14; diameter, 10 mm.

Nelson's description of this species is inadequate, and he
gives no figure. The description here offered was made on
examination of his specimens together with an incomplete
right valve in the Hopkins collection. Nelson's specimens
are much worn, and have lost almost all of the epidermis ; in
this condition they appear different from the better pre-
served right valve, the under layers showing much narrower
ribs, but a small fragment of the original sculpture adher-
ing to one of Nelson's specimens enables their identification
with that in the Hopkins collection. All notes concerning
the sculpture are made from the latter form.

The most closely similar of several forms obviously related
to C. affinis is C. sambaicum Maury,152 from the Dominican
Republic. It is more nearly equilateral, being longer than
affinis, and is more broadly rounded in outline ventrally.
According to Maury the ribs of sambaiciim show definite
signs of having been universally noded ; those of affinis are

Bull

Amer. Pal., vol. 5, No. 29, p. 212, pi. 36, fig. 7, 1917.

138 STUDIES IN GEOLOGY, No. 3

not noded, but both forms show the prominent yet fine con-
centric lines in the interspaces. The ribs of affinis are a
trifle broader mesially. C. castum Guppy,153 from Manzan-
illa, Trinidad, is somewhat similar, but is more rounded in
shape, and not as high ; in addition it has nodulose ribs which
are not as broad as those of affinis, and are of greater num-
ber. Both forms show the cross-lining of the interspaces.
Another Trinidadian species, C. carolinae Maury,154 from
beds of Chipolan age, is similar in general outline, but has
the rib-nodulation common in Trigoniocardia, and absent
in affinis. Other features are entirely similar. C. reniformis
Koenen,155 from the lower Oligocene of north Germany, is
similar, being very close in shape, but it has more ribs, the
upper surfaces of which slope anteriorly — those of affinis are
flat-topped — but the fine cross-striation of the rib-surfaces is
similar.

Lower Zorritos (base). Quebrada north of Boca Pan.

Superfamily VENERACEA
Family VENERIDAE
Subfamily DOSINIINAE
Genus DOSINIA Scopoli
Section DOSINIDIA Dall
Dosinia (Dosinidia) grandis Nelson

PLATE VIII— Fig. 4.

Dosinia grandis Nelson, Trans. Conn. Acad., vol. 2, p. 201, 1870.

"Shell large, solid, subequilateral ; length and breadth

nearly equal, broadest just above middle line. Beaks ele-

** Quart. Jour. Geol. Soc. Lond., vol. 22, p. 582, pi. 26, fig. 4,
1866.

154 Jour. Ac. Nat. Sci. Phila., 2nd. ser., vol. 15, p. 54, pi. 9, figs.
5, 6, 1912.

LWAbh. geol. Spez. Preuss. Bd. 10, Hft. 5, p. 1154, p. 77, figs-
9, 10, ii, 1893.

PALEONTOLOGY ZORRITOS FORMATION 139

vated, nearly central, curved inward and forward. Lunule
heart-shaped, very deeply impressed, two-thirds as wide as
long, marked by striations which become finer as they pass
into it. Anterior end short. Anterior and posterior ends
nearly equally rounded. Ligament large ; scar long, striated
longitudinally. Surface covered by a thick epidermis, and
marked by broad, flat concentric ribs, which become larger
and smoother over the middle of the shell, but not wholly
obsolete. With the epidermis removed the shell still shows
the striations, especially about the beaks. Hinge line nearly
straight, very broad. The median tooth (cardinal) of the
right valve is large and pointed ; the posterior cardinal deeply
bifid. Lateral tooth large, nearly as long as the posterior
cardinal, and parallel with it. In the left valve the median
cardinal is bifid throughout the upper half of its length.
Hinge area forming a very obtuse angle with the ligament
area. Muscular scars and pallial impression not observed.
A young and a full-grown specimen give the following meas-
urements: Young, length, 46; breadth (height) 47; height
(diameter) 22.6 mm. Mature, length, 95.6; breadth
(height) 95.2; height (diameter), 47.2 mm." — Nelson, 1870.

Nelson's description covers the characteristic features of
the species very well. It should be noted, however, that with
the epidermis removed the sculpture of the shell is quite
different ; there remains but small trace of the heavy concen-
tric waves which are a prominent feature of the unweathered
specimens, and the surface is crossed by fine concentric
growth-lines, some of which are heavier than others, and is
smooth with the exception of occasional shallow concentric
sulcae which are the only reminder of the pronounced undu-
latory sculpture of the epidermis.

This large and characteristic species is represented in the
Hopkins collection by two individuals, the ventral margins
of which have been broken off, and the epidermis of which
has been eroded away with the exception of small patches,
but which are unmistakably identifiable with the abundant

140 STUDIES IN GEOLOGY, No. 3

material in the Nelson collection. It is apparently, not closely
similar to any known American species. Dosinia orbicularis
-Agassiz,156 of the Miocene of Italy, France, and Austria,
agrees in every character save that the beaks are far more
anterior.

Variegated. South of Quebrada Boca Pan.

Dosinia (Dosinidia) delicatissima Brown and Pilsbry

Dosinia (Artemis) cf acetabulum Conr. Toula, Jahrb. k.k. geol.
Reichs., Bd. 58, p. 727, p. 27, figs. 8, 8a, 1908.

Dosinia delicatissima Brown and Pilsbry, Proc. Acad. Nat. Sc.
Phila., vol. 64, p. 516, pi. 26, fig. i, 1912.

Shell of moderate size, lentiform, slightly inflated, thin
and very delicate. Entire margin subcircular in outline.
Umbones not prominent, inclined slightly forward, pointed.
Surface convex, lentiform. Sculpture of many concentrically
arranged flat ribs, with very narrow interspaces which are
finely and delicately graven on the flat surface. Lunule
heart-shaped, deeply impressed, striated by fine lines which
are the continuation of the concentric sculpture. Escutcheon
absent or very slightly marked. Hinge moderately strong,
normal. Muscle scars and pallial.line feeble. Dimensions
of two specimens: Length, 51.5; height, 49.5; (semi) diam-
eter, 12 mm. Length, 65; height, 62; diameter, 31 mm.

This delicate and beautifully sculptured shell is common
in the Lower Zorritos. The thickness of the Peruvian shells
varies somewhat, some being proportionally even thinner
than those cited by Brown and Pilsbry from Gatun, but the
chief characters agree perfectly.

Toula's figured specimen agrees entirely with the speci-
mens from Peru, with the possible exception that his form
does not appear to have so deeply impressed a lunule ; how-
ever, faulty reproduction in his figure might account for that.

^Hoernes, M., Abh. k.k. geol. Reichs. Bd. 4, p. 142, pi. 16, fig. I,
1862; Sacco, Piemonte, parte 28, p. 48, pi. 11, fig. 10, 1900.

PALEONTOLOGY ZORRITOS FORMATION 141

His figured hinge agrees absolutely with that of the Peruvian
specimens. It is obvious that Toula's form is not D. aceta-
buluni Conrad ; as noted by Brown and Pilsbry, there is
decided difference in sculpture, and acetabulum is a heavier
shell. Toula's comparison with D. orbicularis Agassiz,157
from the Oligocene to Pliocene of Italy, France, and Austria,
is apt as far as the surface sculpture and general shape are
concerned, but the European form is much thicker and
heavier, has deeply impressed muscle scars, is posteriorly
truncate, and the beaks are far more forward in position.
D. (Dosinidia) liogona Ball,158 "from the Oak Grove beds of
Florida, is similar. As noted by Brown and Pilsbry (loc.
cit.), the sculpture of delicatissima does not rise in sharp
lamellae toward the end of the shell, as in liogona; otherwise
the likeness is marked. The hinge does not agree with that
of liogona in that the anterior cardinal is not as strong, and
is of different shape. The entire hinge of delicatissima is
not as broad and heavy as that of liogona.

Lower Zorritos. Head of Quebrada Zapotal.

Genus CLEMENTIA Gray

dementia dariena (Conrad)

PLATE VIII— Fig. 5.

Meretrix dariena Conrad, Pac. R. R. Rept, vol. 5, p. 328, pi.. 6,
%• 55, 1856, (not op. cit. vol. 6, p. 72, 1857).

Harvella sp. ind. Nelson, Trans. Conn. Acad., vol. 2, p. 201, 1870.

dementia dariena Gabb, Jour. Acad. Nat. Sci. Phila., vol. 8, p.
344, pi. 44, figs. 16, i6a, 1881.

Clementia dariena Ball, Trans. Wag. Inst., vol. 3, pt. 6, p. 1235,
1903.

157 Hoernes, M., Abh. kk. geol. Reichs. Bd. 4, p. 142, p. 16, tig. I,
1870; Sacco, Piemonte, pte. 28, p. 48, pi. n, fig. 10, 1900.

158 Trans. Wag. Inst., vol. 3, pt. 6, p. 1230, p. 53, figs. 4, 7; pi.
54, figs. 11, 1903.

142 STUDIES IN GEOLOGY, No. 3

Clementia dariena Toula, Jahrb. k.k. geol. Reichs., Bd. 61, p. 725,
pi. 27, figs. 9, 10, 1908.

Clementia dariena Brown and Pilsbry, Proc. Acadv Nat. Sci. Phila.,
vol. 63, p. 371, pi. 28, fig. i, 1911.

Shell large, inflated, ventricose, oblique. Anterior straight
for a short distance before the beaks, then broadly rounded,
descending abruptly into the ventral margin, which curves
broadly in sub-circular form into the posterior margin.
Umbones somewhat high, prosogyrate, not strongly invo-
lute, proximate, widely conical. Surface somewhat exca-
vated before the beaks and slightly produced, very convex
mesially, becoming more flattened ventrally. Sculpture of
inoceriform concentric undulations, prominent from the
beaks about half-way down the shell; thence ventrally the
surface is nearly smooth. About 17 undulations are promi-
nent in the average valve. Upon these undulations are
superimposed fine concentric lines of growth which continue
on the smoother part of the shell, where they are irregular
in strength. The sculpture of the right and left valves from
Zorritos is identical. There is no lunule, but a deep
escutcheon provided housing for the cylindrico-ellipsiodal
ligament. The escutcheon, whose upper margins are sharp,
projecting, and rather broadly lanceolate in outline, is
marked on its inner surface by very fine longitudinal lines ;
a somewhat prominent furrow separates the main surface
of the escutcheon from the overhanging lip, which is
wide posteriorly, decreasing to nothing at the beaks. Hinge
as follows : "Nach vorn stehen zwei Zahne, der zweite
bogig gekriimmt ; hinter einer dreieckigen tiefen Grube
folgt dann ein lamellarer Doppelzahn, der bis an den Rand
des Schloszfeldes hinabreicht."— Toula, 1908. Length, 75
(approx.) ; height, 86; diameter, 48.5 mm.

This form is of particular interest on account of its
limited known occurrence ; thus far it has been reported
from only Panama and Costa Rica, and it is apparently
absent in the' Tertiary of Bowden and the Dominican Re-

PALEONTOLOGY ZORRITOS FORMATION 143

public, as well as from similar horizons in the United
States. Its appearance in the north Peruvian Tertiary offers
further evidence of the close relationship between the fauna
of those beds and the Panamanian Miocene fauna.

The undulations on the form figured by Toula appear
to continue farther down on the valve than in either Brown
and Pilsbry's figured form or those from Peru. There is
thus probably some variation in this respect. The specimen
figured by Brown and Pilsbry shows fairly regularly spacea
stronger concentric threads on the ventral part of the shell;
in this matter, too, there is some variation, since most of
the Peruvian shells are evenly sculptured ventrally, and in
those which show heavier threads they are not regularly
placed. The undulatory sculpture of C. dariena is entirely
similar to that almost peculiar to the Inocerami, and detached
umbonal fragments have on that account a very misleading-
appearance.

Clementia inoceriformis Wagner,159 which is found in
the Miocene of Maryland, is similar, but is generally more
delicate and less strongly sculptured.

Lower and Upper Zorritos. South of Quebrada de las
Alturas.

Subfamily MERETRICINAE

Genus TRANSENNELLA Dall.

Trans ennella herviderana n. sp.

PLATE IX— Figs, i, 2.

Shell large and heavy for the genus, inflated. Anterior
dorsal margin concave ; posterior dorsal margin nearly
straight; ventral margin elliptical. Marginal extremities not
known. Umbones full, high, prosogyrate, inclined forward.
Surface convex excepting the lunular excavation. Sculpture

159 Md. Geol. Surv., Miocene, p. 315, pi. 82, figs, i, 2, 1904.

144 STUDIES IN GEOLOGY, No. 3

of concentric growth-lines, which are of irregularly spaced
folds simulating concentric ribs. Lunule ovate, denned by
a slightly impressed line; there is no escutcheon. Hinge
normal, the cardinals well developed and distinct in the
right valve; in the left valve the anterior lateral tooth is
highly developed, taking the shape of a flattened dowel-pin,
the flat sides horizontal, the posterior edge straight, and
the anterior edge curved, the tooth thus having the shape of
a half-D, viewed dorsally. This tooth is received into the
usual socket in the right valve. Inner shell unknown.
Length (estimated) 25-27; height, 20.5; (semi) diameter
8 mm.

This species is much larger than any of the fossils of
the genus listed from the Americas. It has an interesting
development of the strong anterior lateral tooth character-
istic of the genus, and may be recognized very readily by
that feature as well as by its size. The hinge of the right
valve is that characteristic of the common Transennellas,
excepting possibly the strong development of the socket
which receives the peculiar anterior lateral tooth of the
opposite valve. None of the members of the genus from
the Floridian, Antillean, or Atlantic Miocene are closely
similar. It is unfortunate that both of the two specimens
in the Hopkins collection lack the anterior and posterior
extremities, and a comparison of the outline is thus subject
to revision; however, the visible portions indicate that it is
probably less triangular than the known fossil species. It is
considerably more inflated and larger than any Miocene
species thus far described.

The most closely similar species is T. joaquinensis Ander-
son and Martin,160 from the lower Miocene of Kern River,
California, which differs in being smaller and more delicate,
with the left anterior lateral tooth elongated diagonally

lfl°Proc. Cal. Acad. Sci., 4th sen, vol. 4, p. 60, pi. 3, figs. 6a, b,
c, 1914.

PALEONTOLOGY ZORRITOS FORMATION 145

instead of transversely. The outline and general shape
appear to be close. T. herviderana differs from such forms
as T. carolineiisis Dall 1G1 from the Miocene of North
Carolina, chiefly in being larger and heavier, with the
characteristic anterior lateral tooth. It is not very close.

Toula 162 lists a form from the Gatun as Callista (?)
(Dione) sp. which may be a Transennella somewhat similar
to T. herinderana, though even larger. It is described from
a cast with fragments of the shell remaining, and since the
hinge is not preserved a generic determination is not possi-
ble, but the contour of the shell is evidently similar.

Lower Zorritos. Hervideras.

Genus MACROCALUSTA Meek

Macro callista helenae n. sp.

PLATE IX— Figs. 3, 4.

Shell medium-sized, thin, somewhat delicate, produced
posteriorly. Anterior margin rounded, very little produced;
ventral margin broadly elliptical; posterior dorsal margin
almost straight, the posterior marginal angle acute. Surface
uniformly convex, excepting the impressed areas, with a
long keel extending from the beak to the posterior marginal
angle. Umbones strongly prosogyrate, situated very near
the anterior end, proximate. Sculpture of concentric lamel-
lae, the sharp edges directed upward, about 4 in the space
of 5 mm. on the posterior slope near the margin. Areas
rather deeply impressed; the escutcheon is lanceolate,
bounded by a distinct ridge, and the lunule is small, of
elongated heart-shape. Hinge with a prominent bifid right
anterior cardinal tooth. Inner shell not known. Length,
32; height, 26.5; diameter, 15.5 mm.

This species is very close to Macrocallista conradiana

161 Trans. Wag. Inst., vol. 3, pt. 6, p. 1242, pi. 55, fig. 4, 1903.
ir'2Jahrb. k.k. geol. Reichs. Bd. 58, p. 726, pi. 28, fig. 9, 1908.

146 STUDIES IN GEOLOGY, No. 3

Gabb, from the California Eocene, but has more inclined
and more anterior beaks, with finer sculpture, and is normal-
ly a larger species.163
Variegated. Quebrada Tusillal.

Subfamily

Genus AMIANTIS Carpenter

Amwntis incrassata var. ovoidalis Sacco

PLATE IX— Fig. 5.

Amiantis incrassata var. ovoidalis Sacco, Piemonte, parte 28, p.
21, pi. 4, fig. 33, 1900.

"Testa affmis var. Suessi, sed postice productior, oblon-
gior, subovata." — Sacco, 1900.

The shell is medium-sized, ovate, strong, inflated. Anterior
margin bluntly angulate at its extremity ; ventral margin
broadly arcuate ; curve of posterior angle rather broad.
Umbones strongly prosogyrate, the points twisted back
about 1.5 mm. from the hinge, inclined forward, full,
rounded above, somewhat distant. Surface evenly convex,
the valves joining ventrally at an angle somewhat more
acute than that of most specimens of A. incrassata s.s.
Sculpture of concentric growth-lines. Escutcheon long,
narrow, deeply impressed, the ligament occupying the im-
pressed cavity which is almost closed over above by the
overhanging dorsal margin ; the walls of the impressed area
continue anteriorly to form the inner surfaces of the beaks,
between which the slit continues. Lunule indistinct on the
specimen studied, but probably similar to that of incrassata f
i.e., large, bounded by a somewhat faintly impressed line.
Hinge normal to the genus. Inner shell smooth ; there is no
evidence of radial ribs on the inner disk. Length, 44 ; height,
41.5; diameter, 30.5 mm.

163 Pal. Cal., p. 169, pi. 32, fig. 282, 1864; Dickerspn, Proc. Cal. Ac.
Sc., 4th ser., vol. 5, p. 82, pi. 3, figs, i, a, b, c, 1915.

PALEONTOLOGY ZORRITOS FORMATION 147

One specimen of this interesting genus, in the Nelson
collection, undetermined by him, is apparently identical with
the European Amiantis incrassata var. ovoidalis Sacco, and
is accordingly referred to that variety. Comparison with
specimens of A. incrassata from the Eocene of France
shows clearly that the Peruvian form is of the same species,
and according to such varietal differences as have been
worked out it appears identical with var. ovoidalis Sacco,
from the Tongrian of the Italian Piedmont. The species as
a whole is common in the Eogene of Europe.

To the author's knowledge only two species of Amiantis
are known from the North American Tertiary, A. callosa
Conrad,164 from the Pleistocene and Recent of southern
and Lower California, and A. dalli^ from the upper San
Pablo Miocene of California, but both are dissimilar to
incrassata.

The exact horizon of the Peruvian specimen is not known,
but it is highly probable that it came from one of the three
members of the Zorritos formation.

Genus PITARIA Roemer
Subgenus HYSTEROCONCHA Fischer

Section LAMEXUCONCHA Dall

Pitaria (Lamelliconcha) planivieta (Guppy)

PLATE X— Fig. 6.

Cytherea (Callista) planivieta Guppy, Quart. Jour. Geol. Soc.
Lond., vol. 22, p. 292, pi. 18, fig. 3, 1866.

Callista planivieta (Guppy) Gabb, Trans. Am. Phil. Soc., n. s.
vol. 15, p. 250, 1873.

Cytherea planivieta Guppy, Geol. Mag., dec. 2, vol. i, p. 442 (check
list) 1874.

164 Jour. Ac. Nat. Sci. Phila., vol. 7, p. 252, 1837.

165 Univ. Cal., Bull. Geol., vol. 8, p. 465, pi. 50, fig. 2, pi. 53,

figs. 1-4, 1915.

148 STUDIES IN GEOLOGY, No. 3

Cytherea planivieta Guppy, Quart. Jour. Geol. Soc. Lond., vol.
32, p. 531, 1876.

Cytherea planivieta Grzybowski, Neues Jahrb., Beil. Bd. 12, p.
639, pi. 19, fig. 3, 1899.

Pitaria (Lamelliconcha) planivieta Dall, Trans. Wag. Inst, vol.
3, pt. 6, p. 1268, 1903.

Pitaria planivieta Maury, Bull. Amer. Pal., vol. 5, No. 29, p. 217,
pi. 37, fig. 3, 1917-

Pitaria (Lamelliconcha) planivieta Woodring, Mollusca Bowden
Beds, Jamaica, Ms.

With the slight exception, as noted by Grzybowski, that
the concentric rugae are a bit more crowded, there is no
essential difference between the forms from Peru and those
from the lower Miocene of the Antilles. The concentric
sculpture of the Peruvian form is slightly different, the
rugae giving the appearance of being less regularly placed,
but a distinction on the basis of that feature would be
valueless. The hinge of the Peruvian specimens is some-
what broader and heavier than that of planivieta from the
Bowden beds, but the elements are the same. One specimen
from Peru attains dimensions somewhat greater than those
usual in the Antillean planivieta. The forms in the Hopkins
collection were found in the Lower Zorritos formation.
Grzybowski's forms were taken from beds which he called
Heath, but which are known to be part of the Variegated
formation. The species thus has a known range in Peru
from the Lower Zorritos to the upper Variegated.

Pitaria- aequicincta, from the uppermost Upper Zorritos,
undoubtedly represents a further development of the plani-
vieta strain. It is so close to planivieta that some delibera-
tion preceded its separation, but its sculpture is sufficiently
different to make advisable its consideration as another
species. In addition to the difference in sculpture the lack
of a well defined lunule in aequicincta marks another point
of departure, and makes the entity of the species more
eminent. In general contour the two are identical. Length

PALEONTOLOGY ZORRITOS FORMATION 149

of large specimen, 48.5; height, 42; (semi) diameter, 14
mm. Smaller specimen, length, 30.5; height, 25.5; (semi)
diameter, about 8 mm.

Lower Zorritos, Variegated. Quebrada Zapotal.

Pitaria (Lamclliconcha) com var. aequicincta n. var.
PLATE IX— Figs. 6, 7.

Shell thin, large, somewhat compressed. Anterior margin
broadly rounded; ventral margin elliptical, its juncture with
the posterior margin in the form of an apically rounded
acute angle. Surface generally convex, but the shell is not
highly inflated. Sculpture of fine, nearly even concentric
ribs, which are slightly steeper on their dorsal slopes, and
which appear very finely and sharply graven. There is no
radial striation. The cardinal areas are poorly defined. Inner
shell unknown except that the anterior muscle scar is but
slightly impressed, the posterior not at all, and that the
inner valve-margins are smooth. Length (large specimen)
49.5; height 38; (semi) diameter 10 mm. Length (smaller
specimen) 31.5; height ?; (semi) diameter 6 mm.

Two casts, one with perfectly preserved portions of the
shell remaining, represent this variety in the Zorritos col-
lection. In outline and type of sculpture it agrees well with
Pitaria cora Brown and Pilsbry,166 from Gatun, but cora
is a fuller shell, being much more inflated, and having the
muscle scars and pallial line much more deeply impressed.

The Zorritos variety appears further to attain a larger
size. As noted by Brown and Pilsbry (loc. cit.), Pitaria
hillii D'all,167 from the Gatun formation, is a longer, lower
form. In sculpture, however, it is entirely similar, and its
relationship to both cora and the variety aequicincta is close.
P. cercadica Maury,168 from the lower horizon in -the

l68Proc. Ac. Nat. Sc. Phila., vol. 63, p. 370, pi. 28, fig. 3, 1911.
187 Trans. Wag. Inst, vol. 3, pt. 6, p. 1268, pi. 54, fig. 7, 1903.
168 Bull. Amer. Pal., vol. 5, No. 29, p. 216, pi. 37, fig. 10, 1917.

150 STUDIES IN GEOLOGY, No. 3

Dominican Republic is a similar, though smaller, form. In
sculpture and general outline it shows little difference, but
it appears to be more rounded posteriorly than aequicincta,
and the lunule is certainly more clearly defined. P. labreama
Maury,169 from the upper Oligocene ( ?) of Trinidad, ap-
pears similar according to the figure, but differs in size,
being smaller, and in sculpture, the ribs being more widely
separated than in aequicincta.
Upper Zorritos. Quebrada de las Alturas.

Subfamily
Genus CHIONE Megerle von Miihlfeld

Section CHIONE s.s.
Chione (Chione) variabilis Nelson

PLATE IX— Figs. 8, 9.
Chione variabilis Nelson, Trans. Conn. Acad., vol. 2, p. 202, 1870.

Shell large, fairly thick, heavy, slightly oblique. Anterior
dorsal margin ascending somewhat from end of lunule;
anterior margin broadly rounded, ventral margin similarly
curved. Posterior margin slightly angulate. Umbones
inflated, prosogyrate, proximate. Surface excavated before
umbones, elsewhere smoothly convex, and in the region of
the beaks almost globose in some specimens. Concentric
sculpture of closely spaced ridges, the under surface of
which is noded, each node being sulcate in the center of
the disc. Radial sculpture of closely spaced ribs, somewhat
obscure in all specimens available, but some worn specimens
show a pairing of the ribs on the disc, with one less prominent
rib between the pairs. In much worn specimens all traces of
most of the concentric lamellae are gone, but some, more
distantly separated, remain, giving the appearance of a
different sculpture. There is a distinct lunule, somewhat

Jour. Ac. Nat. Sc. Phila., vol. 15, p. 57, pi. 9, figs. 14, 15, 1912.

PALEONTOLOGY ZORRITOS FORMATION 151

impressed, and longitudinally striate; it is heart-shaped,
and fairly broad, with the median line (juncture of the
valves) raised. In young specimens the elevation of the
margins in the lunule is more prominent. The escutcheon
is narrow, lanceolate, and V-shaped in cross-section; it is
deep and finely striate longitudinally. Hinge not known.
Length, 31; height, 28.5; diameter, 14 mm. (young speci-
men) ; estimated dimensions of full-grown specimen, length,
65 ; height, 56 ; diameter, 28 mm.

All of Nelson's specimens of the species are considerably
worn, most of them amounting to little more than casts
with the inner layer of shell remaining, and those of the
Hopkins collection, which are better preserved, are identi-
fied as the same species after comparison of the sculpture
with fragments of that remaining on some of Nelson's
specimens. Chione variabilis is not far removed from
C. angelana, of the Upper Zorritos, having similar sculpture
and agreeing in other general features except the shape and
the area. C. angelana is more elongate both anteriorly and
posteriorly, and its lunule is much more deeply impressed,
more perfectly heart-shaped, and not raised at the juncture
of the valves. The anterior dorsal margin ascends more
abruptly in angelana.

C. walli Guppy,170 from Manzanilla, Trinidad, has similar
concentric sculpture, and the presence of the paired radial
ribs on the disc emphasized by Guppy in his description of
walli serves further to mark the similarity. Guppy's figure
shows walli to be more produced posteriorly and apparently
not as highly inflated as variabilis; this difference, together
with the fact that variabilis is much larger, and has slightly
more closely set concentric lamellae, separates the two
species.

Upper Zorritos. Quebradas del Grillo and del Toro.

Quart. Jour. Geol. Soc. Lond., vol. 22, p. 581, pi. 26, fig. 16, 1866.

152 STUDIES IN GEOLOGY, No. 3

Chione (Chione) angelana n. sp.

PLATE IX — Figs. 10, n.
Chione sp. indet. B. Nelson, Trans. Conn. Acad., vol. 2, p. 203, 1870.

Shell large, plump, somewhat elongate. Similar to Chione
variabilis except for following features: Anterior dorsal
margin ascends sharply, making a sharp U-shaped depres-
sion in the outline before the beaks. Ventral margin broadly
elliptical. Posterior margin almost angular; valves produced
both anteriorly and posteriorly. Beaks more inclined
forward and much more strongly prosogyrate than in
variabilis. Lunule deeper, more sharply set off, more per-
fectly heart-shaped. Length, 55 ; height, 44.5 ; diameter,
34 mm.

The forms which are grouped under the specific limita-
tions here outlined are sufficiently constant in their differ-
ences from Chione variabilis to make necessary their recog-
nition as a separate species. Both C. angelana and C. vari-
abilis are apparently fairly abundant in the Upper Zorritos
formation ; lumps of fossiliferous marl from several local-
ities show fragments of the characteristic sculpture in some
profusion. Nelson mentioned C. angelana as an indetermi-
nate species, but his specimens, poor though they are, offer
sufficient evidence to permit their classification and description.
C. angelana differs from C. walli Guppy (loc. cit.) in being
larger, more produced anteriorly, flatter basally, and with a
more deeply impressed lunule. Otherwise the two are closely
similar.

Upper Zorritos. Quebradas de las Alturas, de los An-
geles and del Toro.

Chione (Chione) propinqua n. sp.
PLATE IX— Fig. 12.

Shell of medium size, subtrigonal, inflated. Anterior
margin rounded, ventral margin arcuate. Posterior margin

ZORRITOS FORMATION 153

forms a distinct angle with the ventral margin, and is almost
straight. Umbones prosogyrate, anterior in position. Gen-
eral surface markedly convex ; a pronounced posterior
carina separates the narrow posterior surface of the shell
from the rest. Concentric sculpture of the prominent lamel-
lae typical of the group, distinctly spaced, crenulate on the
under surface. Radial sculpture of ribs which show a some-
what indistinct yet recognizable pairing on the disc; there
are less prominent ribs between the pairs. Lunule not clear-
ly visible on specimens studied, but it appears to be im-
pressed and configured much as in C. walli Guppy, C. wood-
wardi Guppy, and related species. The escutcheon is long,
somewhat broad. Inner margin finely crenulate. Length,
24; height, 21.5; (semi) diameter, 8.5 mm.

The difference between this species and C. walli Guppy,171
from the Oligocene ( ?) of Trinidad, is small. The Trini-
dad form has a greater number of more closely spaced
concentric lamellae, and the pairing of the radial costae is
apparently more prominent. Otherwise differences are small
and not constant. C. woodwardi Guppy 172 is also similar,
but lacks the pairing of the ribs, which are obviously stouter.
In shape the forms are similar. Maury has described 173
as Chione cf. walli a form which she states to show the
pairing of the ribs characteristic of walli, but her figure
indicates rather the absence of the feature, and there is
small doubt that the specimen figured is C. woodwardi.

C. spenceri Cooke,174 from the Oligocene of Antigua, is
of the same general type, but differs in having weaker
radial ribs, particularly distally, and, apparently, in lacking
the paired ribs.

171 Quart. Jour. Geol. Soc. Lond., vol. 22, p. 581, pi. 26, fig. 16, 1866.

172 Idem., p. 292, pi. 18, fig. i; Maury, Bull. Amer. Pal., vol. 5,
No. 29, p. 218, pi. 37, fig. 6, 1917.

173 Bull. Amer. Pal., vol. 5, No. 29, p. 218, pi. 37, fig. 7, 1917.

174 Carnegie Inst. Wash., Publ. 291, p. 150, pi. 15, figs. la, b, 1919.

154 STUDIES IN GEOLOGY, No. 3

It is interesting to note that all of the Chiones s.s. known
from the Zorritos formation have the double ribs which
are a characteristic feature of Chione walli Guppy, a com-
mon point which serves to emphasize their relationship not
only to one another, but to the Chiones of the Trinidad
beds of slightly earlier age. A number of unstudied forms
from probably younger horizons in Ecuador show this
feature clearly.

Lower Zorritos. Quebrada Zapotal.

Section LIROPHORA Conrad
Chione (Lirophora) hendersonii Dall

Venus paphia Guppy, Quart. Jour. Geol. Soc. Lond., vol. 22, p.
292, 1866; (not of Linnaeus, 1758).

Chione paphia Gabb, Trans. Amer. Phil. Soc. n. s., vol. 15, p. 249,
1873-

Venus paphia Guppy, Geol. Mag., dec. 2, vol. i, p. 442, (check
list) ex parte, 1874; (not of Linnaeus).

Venus paphia Guppy, Quart. Jour. Geol. Soc. Lond., vol. 32, p.
530, 1876; (not of Linnaeus).

Chione (Lirophora) hendersonii Dall, Trans. Wag. Inst., vol. 3,
pt. 6, pp.» 1295-1296, pi. 55, fig. 22, 1903.

Chione (Lirophora) hendersonii Maury, Bull. Amer. Pal., vol. 5,
No. 29, p. 219, pi. 37, fig. 8, 1917.

Chione (Lirophora) hendersonii Woodring, Ms.

This species is common in the Bowden beds of Jamaica,
and occurs also in the lower Miocene of the Dominican
Republic. In its Antillean occurrences it is somewhat
variable in form, ranging from more convex forms with
higher beaks, more incurved anterior margin, steeper
posterior slope, and wider cardinal areas to those with these
characters at the opposite extreme. To quote Woodring
(Ms) "the species is characterized by its rather numerous
ribs and the relatively wide posterior area over which the
ribs are lower and sharper. The form mentioned in the

PALEONTOLOGY ZORRITOS FORMATION 155

original description, C. ballista Ball,175 from the Tampa
silex beds, has less numerous, occasionally ventrally striated
ribs that are attenuated above to the dorsal margin. The
Oak Grove C. glyptocyma Ball 17° resembles the less convex
race, but it has a less excavated anterior margin, ribs that
are ventrally striated and the point of reduction of the ribs
is nearer the escutcheon. The recent C. paphia (Lin-
naeus)177 has a similar appearance, but reaches a larger size
and has a more arcuate base and more closely appressed
ribs."

The Zorritos forms of C. hendersonii are distinctly larger
than those of the Antilles, and have the lunule constantly
somewhat less impressed, but they agree well enough with
the Bowden specimens to be regarded as the same species.
Unfortunately, they are not sufficiently well preserved to
determine the closeness in agreement of the posterior change
in the lirae, but all indications available point toward a
similarity in this respect as well as in others. Length, 34;
height 32; diameter, 16 mm. One large specimen, im-
perfect, is 40 mm. long.

Lower Zorritos. Quebrada Heath.

Chione (Lirophora) latilirata (Conrad)

Venus paphia Lamarck, An. Sans Vert., vol. 5, p. 608, No. 2, 1818;
(not Linnaeus, 1767) .

Venus alveata Say, Am. Conch., vol. 7, pi. 63, 1833; (n°t Con-
rad, 1831).

Venus latilirata Conrad, Proc. Ac. Nat. Sc. Phila., vol. I, p. 28,
1841; Fos. Med. Tert, p. 88, pi. 38, fig. 3, 1845.

Venus varicosa Sowerby, Thes. Conch., vol. 2, p. 725, pi. 155,
fig. 67, 1853; Ball, Bull. U.S. Nat. Mus., No. 37, p. 54, 1869.

75 Trans. Wag. Inst, vol. 3, pt. 6, p. 1295, pi. 55, fig. 23, 1903.
178 Idem., p . 1296, pi . 55, fig. 21 .

177Syst. Nat. ed. 12, p. 1129, 1767-; Reeve, Conch. Icon., vol. 14,
Venus, pi. 19, fig. 89, 1863; (as Venus paphia).

156 STUDIES IN GEOLOGY, No. 3

Venus latilirata Tuomey and Holmes, Pleioc. Fos. S. C., p. 85,
pi. 21, fig. 12, 1857; Emmons, Geol. Rept. N. C., p. 293, fig. 219,
1857; Dall, Trans. Wag. Inst, vol. 3, p. 1198, pi. 42, fig. 3, 1900.

Circumphalus (Lirophora) latilirata Conrad, Proc. Ac. Nat. Sc.
Phila., for 1863, p. 575, 1864.

Circumphalus (Lirophora) athleta (Conrad) Idem., pp. 575, 586,
1864.

Chione (Lirophora) latilirata Dall, Trans. Wag. Inst., vol. 3, pt.
6, p. 1298, pi. 42, fig. 3, 1903-

Chione (Lirophora) latilirata Glenn, Md. Geol. Surv., Miocene,
p. 309, pi. 77, figs. 3, 4, 5, 6, 1904.

Chione (Lirophora) latilirata Gardner and Aldrich, (check list)
Proc. Ac. Nat. Sc. Phila., vol. 71, p. 19, 1919.

Two specimens from the Lower Zorritos agree so closely
with typical specimens of C. latilirata from the Maryland
and Carolina Miocene that it is inadvisable to express a
difference. The only constant variation noticeable is that
the Peruvian forms are somewhat more inflated than the
North American, and that consequently the lirae of the
Peruvian specimens are more arcuate ventrally. The speci-
mens studied are both broken posteriorly, and it is con-
sequently impossible to compare the posterior marginal
angles, but indications are that with the exception of a
slightly greater obtuseness due to the deeper curve of the
ventral lira they probably agree. Length, (est.) 26; height,
22.25; (semi) diam. 10.5 mm. ,

Lower Zorritos. Quebrada Zapotal.

Superfamily

Family TELLINIDAE

Genus TELUNA (Linnaeus) Lamarck

Tcllina zapotalensis n. sp.

PLATE X— Figs, i, 2.

Tellina sp. ind. A. Nelson, Trans. Conn. Acad., vol. 2, p. 201,
1870.

PALEONTOLOGY ZORRITOS FORMATION 157

Shell large for the genus, thin, fragile, subequilateral.
Margins not preserved in specimens studied, but casts show
them to be probably evenly rounded, the ventral margin
moderately arcuate. Umbones pointed, not prominent,
terminal. A barely perceptible posterior keel, followed
behind by a shallow sulcus, breaks the otherwise evenly
rounded surface, which is only slightly convex; in some
specimens the central surface is almost flat. Sculpture of
fine concentric growth-lines. Escutcheon long and narrow;
lunule poorly marked or absent. Hinge strong for the genus,
the anterior cardinal of the left valve being prominent and
clearly bifid, and the socket behind it large and well marked ;
otherwise the hinge is normal. Inner shell unknown.
Length, 67; height, 42; (semi) diameter, 9.5 mm.

This species is very similar to a number from the Miocene
of Panama, Dominican Republic, and Europe. It is close to
T. aequiterminata Brown and Pilsbry,178 from Gatun, but
its ventral margin is rounded instead of straight, as in
aequiterminata. Further points of difference or similarity
can not be determined on account of the incompleteness of
the Gatun form. It is similar in shape to T. maoica
Maury,179 from the lower Miocene on the Dominican Re-
public, but is less inflated, the , sculpture is less prominent,
and the posterior fold is not so well marked. T. dbaoica
Maury 18° is also similar, but is likewise more inflated, and
the hinge is weaker.

The hinge, which is distinctive, is closely similar to none
described from the Americas, but is practically the same
as that of two European species which appear in the Tor-
tonian — T. strigosa, Gmelin 181 and T. planata Linnaeus.132

178Proc. Ac. Nat. Sc. Phila., vol. 64, p. 517, pi. 26, fig. 5, 1912.

179 Bull. Amer. Pal., vol. 5, No. 29, p. 223, pi. 38, fig. 5, 1917.

180 Idem., p. 223, pi. 38, fig. 10.

mHoernes, M., Abh. k.k. geol. Reichs., Bd. 4, p. 83, pi. 8,
figs. 8a, b, c, 1870.
182 Idem., p. 84, pi. 8, figs. ;a, b, c.

158 STUDIES IN GEOLOGY, No. 3

The shape of these European species is distinctively differ-
ent, but the hinge is closely similar to that of T. sapota-
lensis. , ,

Lower Zorritos. Head of Quebrada Zapotal.

Section EURYTEXUNA

Tellina (Eurytellina) aequicincta n. sp.

PLATE X— Fig. 3.

Tellina (Eurytellina) sp. Dall, Trans. Wag. Inst, vol. 3, pt. 5,
p. 1024, 1900.

Tellina (Eurytellina) sp. ind. Woodring, The Mollusca of the Bow-
den Beds of Jamaica, Ms.

Shell medium-sized, moderately thick for size, long, of
elegant appearance. Anterior margin rounded, produced ;
ventral margin long and nearly straight. Posterior margin
biangular. Umbones pointed, terminal. Surface flattened
but convex ; a posterior sulcus from the beak to the anterior-
most marginal angle is the only sharply curved part of the
shell. Sculpture of concentric flat-topped ribs with finely
graven interspaces, about 8 in 5 mm. near the margin, and
growing finer toward the beaks. The sculpture is sharply
curved at both ends of the shell, and is parallel to the
margin, in straight lines over most of its length. Escutcheon
long and narrow. Hinge and inner shell not known. Length,
38; height, 22; (semi) diameter, 4 mm.

The beautiful sculpture of T. aequicincta gives it clear
distinction from the other Tellinas in the collection, none
of which approach it in delicacy of external finish. The
Bowden form mentioned by Dall and Woodring as noted
in the synonymy appears to be sufficiently close to justify
uniting it with aequicincta, at least until further material
from the Bowden beds is available for comparison. Frag-
ments of the Bowden form show the same characteristic
sculpture, with the slight difference that the concentric lines
are a bit more closely spaced in the Bowden specimens,

PALEONTOLOGY ZORRITOS FORMATION 159

and casts show the same shape. The difference, should
there prove to be .such, can hardly be greater than varietal
in value.

T. aequicincta is very similar to T. cyneglossula Harris 183
from the Claiborne Eocene, being only larger and less
arcuate ventrally,with finer concentric striae near the mar-
gins. Comparison of the hinge is not possible. Were the
sculpture of T. aequiterminata Brown and Pilsbry,184 from
the Gatun beds, known, a resemblance to that form might
be found, the two being closely similar in shape. T. aequi-
cincta is very close to T. nitida Poli,185 from the Pliocene
of Italy, the only apparent difference being in the ellipsoidal
bases of the concentric curves in the sculpture of nitida,
those of aequicincta being straight, and in the consequently
sharper upward curve of the sculptural lines posteriorly in
aequicincta. T. nitida is regarded by Sacco as an atavistic
development of the Miocene T. bipartida Basterot. The dif-
ferences pointed out between the other Tellinas here
described and T. cibaoica and maoica of Maury will make
clear the further distinctness of T. aequicincta from those
forms. The sculpture offers the chief point of variance.

Lower to Upper Zorritos. Quebradas Heath, Zapotal,
de las Alturas.

Section ANGULUS

Tellina (Angulus) pressa Dall
PLATE X— Fig. 4.

Tellina sp. indt. B. Nelson, Trans. Conn. Acad., vol. 2, p. 201,
1870.

Tellina (Angulus) pressa Dall, Trans. Wag. Inst, vol. 3, pt. 4, p.
1026, pi. 47, fig. 5, 1900.

Tellina (Angulus) pressa Woodring, Bowden Ms.

183 Bull. Amer. Pal., vol. 6, p. 161, pi. 49, figs. 15, 16, 1919.

184 Proc. Ac. Nat. Sc. Phila., vol. 64, p. 517, pi. 26, fig. 5, 1912.

185 Sacco, Piemonte, pte. 29, p. no, pi. 23, figs, na, b, 12, 1901.

160 STUDIES IN GKOLOGY, No. 3

"Shell thin, compressed, inequilateral; beaks low, hardly
interrupting the dorsal profile, but sharp and almost
pustular, ligament rather long, hinge delicate but normal;
surface polished, with rather distant, fine, concentric im-
pressed lines; the posterior dorsal slope with sparse, sharp,
little elevated concentric lamellae: near the beaks the shell
is smooth; interior with a faint anterior elevated ray which
separates the adductor scar from the anterior part of the
long, high pallial sinus, which is wholly confluent below;
the interior more or less obscurely radially striate. Lon.
12.5 ; alt. 7.5 ; diam. 2 mm. A thin and delicate species with
no observable flexure or ridge on the posterior end, and
whose especial characteristic is the high dorsal profile,
behind the beaks." — Dall, 1900.

The Peruvian forms, though delicate and thin, are some-
what heavier than the usual specimen from Bowden, the
chief evidence of greater weight being found in the pro-
portionally stronger hinge armature, in which the elements
are exactly similar, but the development of the individual
teeth- is somewhat greater, and the armature of the inner
dorsal valve-margins consists of a heavier plate than in the
Bowden specimens. Otherwise the forms are identical, and
Ball's description covers every point worth noting. The
anterior margin is produced, rounded; the ventral margin,
flat to very slightly emarginate, ascends somewhat; the
characteristic posterior marginal angle is prominent; the
posterior dorsal margin is high in profile, and curved, as
noted by Ball. The concentric sculpture follows the mar-
ginal outline, and is hence flat to slightly flexed upward
mesially. A complete shell from Zorrito<s has the following
dimensions: length, 15.5; height, 8.5; diam., 3 mm.

A single complete specimen, mentioned by Nelson as inde-
terminate, and a perfect left valve which appears in some
Zorritos material not exactly allocated, are referable to this
species. Slight differences, as noted above, exist between
the Peruvian and Antillean specimens, but careful com-

ZORRITOS FORMATION l6l

parison of material shows the specific characters of the two"
groups to be identical, and the small variation in the hinge
of the Zorritos specimens may be waived as of no systematic
importance. The occurrence of this beautiful and interesting
little shell in Peru extends its known range to cover the
area between Florida and Zorritos, and it may not im-
profitably be sought in the large collections from Gatun
now awaiting study at the United Sates National Museum,
as well as in beds of similar age in Ecuador and Colombia.
It differs from T. singewaldi, in being smaller, longer in
proportion to height, and in having the median concentric
sculpture and ventral margin straight instead of arcuate.

Tellina (Angulus?) singewaldi n. sp.
Pr,ATE X— Fig. 5.

Shell medium-sized, subequilateral, very fragile, com-
pressed. Anterior margin rounded, somewhat produced;
ventral margin slightly elliptical; posterior margin rounded,
shorter than the anterior. Umbones pointed, not prominent.
Surface generally flattened ; a posterior keel is bounded on
either side by shallow sulci. Sculpture of fine growth-lines,
concentric, subangular at the posterior keel, evenly curved
elsewhere. Escutcheon small. Hinge not known. Pallial
sinus deep, extending nearly to anterior muscle scar. Pos-
terior muscle scar long and narrow. Length, 34 ; height, 23 ;
(semi) diameter, 2.5 mm.

This species may be distinguished from T. zapotalensis,
of the local fauna, by its smaller size, greater fragility,
sharper posterior keel, and proportionally more pronounced
sculpture. In shape it is more nearly like T. maoica
Maury,186 from the lower Miocene of Santo Domingo, than
is zapotalensis, but is not nearly as much inflated, the sculp-
ture is more angulate at the posterior keel, and the posterior

Bull. Amer. Pal., vol. 5, No. 29, p. 223, pi. 38, fig. 5, 1917.

162 STUDIES IN GEOLOGY, No. 3

sulcus is more prominent. It is also like 7". cibaoica Maury
(loc. cit), but is less inflated, shorter, has a more prominent
posterior sulcus, and the posterior margin is more blunt.
T. aequiterminata Brown and Pilsbry,187 from Gatun, is also
similar, but differs much as it does from T. zapotalensis.
T. singewaldi and T. zapotalensis, being closely related,
have naturally the same general affinities. T. singewaldi is
perhaps nearest to T. papyria Conrad,188 of the Claiborne
Eocene. Comparison with specimens of papyria from Lisbon
and Claiborne shows an agreement which is imperfect only
in the longer form of papyria.
Lower Zorritos. Quebrata Zapotal.

Family PSAMMOBIIDAE

Genus TAGELUS Gray
Tagelus gibbus (Spengler)

Solen gibbus Spgl., Skrift. Nat. Selsk., vol. 3, p. 304, 1794.

Solen guineensis Chemn., Conch. Cab., vol. n, p. 102, pi. 198, fig.
1937, 1795; Dilwyn, Descr. Cat., vol. i, p. 62, 1817; Wood, Gen.
Conch., p. 129, 1835.

Solen declivis Turton, Conch. Diet, p. 164, fig. 80, 1819.

Psammobia declivis Turton, Dithyra Brit., p. 91, 1822.

Solen caribaeus Lam. An. sans. Vert., vol. 5, p. 454, 1818.

Siliquaria notata Schum. Essai, p. 129, pi. 7, figs. 2-3, 1817.

Solecurtus caribaeus, Blainv., Diet. Sc. Nat., vol. 29, p. 240, 1825;
Conrad, Am. Mar. Conch., p. 22, pi. 4, fig. 3, 1831 ; Gould, Inv.
Mass., p. 30, 1841; Mighels, Bost. Journ. Nat. Hist., vol. 4, p. 312,
1845; Sowerby, Conch. Icon., Solecurtus, fig. 2ia, b, 1874.

Solen adamsonii Bosc., Hist. Nat. Coq., vol. 3, p. 12, 1802.

Cultellus caribaeus Conrad, Am. Jour. Sc., 2nd ser. vol. i, p. 404,
1846; not of Med. Tert, pi. 43, fig. i, 1845.

Siliquaria gibba H. & A. Adams, Gen. Rec. Moll., vol. 2, p. 347,
not p. 93, figs. 5, sa, 1856.

L87Proc. Ac. Nat. Sc. Phila., vol. 64, p. 517, pi. 26, fig. 5, 1912.
188 Harris, Bull. Amer. Pal., vol. 6, No. 31, p. 159, pi. 49, figs. 7-11,
1919.

PALEONTOLOGY ZORRITOS FORMATION 163

Siliquaria caribea Holmes, Post-Pleic. Fos. S.C., p. 54, pi. 8, fig.
14, 1858.

Siliquaria carolinensis Conrad (ex parte) Proc. Ac. Nat. Sc. Phil.
for 1862, p. 571, 1863.

Solecurtus sp. ind. Nelson, Trans. Conn. Acad., vol. 2, p. 200,
1870.

Solecurtus angulatus Sow. Conch. Icon. Solecurtus, p. 8, fig. 23,
1874-

Solecurtus centralis Sow. Conch. Icon., fig. 18, 1874, (not Say).

Tagelus gibbus Dall, Proc. Bost. Soc. Nat. Hist., vol. 13, p. 251,
1870; Trans. Wag. Inst., vol. 3, pt. 5, p. 983, 1900.

Two posterior fragments on complete casts of this form
occur in Nelson's collection. Comparison with typical speci-
mens of T. gibbus shows no difference in any detail. Known
occurrences of T. gibbus point to its first occurrence in the
Yorktown Miocene, and its occurrence in Peru in strata of
greater age is of interest. Although the lack of exact
locality labels for Nelson's forms lessens the assurance with
which they might be taken to come from the Zorritos
formation, the absence in the vicinity of Zorritos of beds
younger than the Zorritos formation makes rather strong
the probability that they were collected from those beds.

Superfamily
Family SOLENIDAE
Genus SOLECURTUS (Blainville)

Subgenus PHARELLA Gray

Solecurtus (Pharella) planifolliculus n. sp.

PLATE X— Fig. 7.

Shell small, long, thin and very fragile. Anterior and
posterior margins subequally rounded; dorsal margin nearly
straight on either side of the beaks, forming an angle of
about 1 60° ; ventral margin nearly straight, apparently
slightly emarginate. Beaks very nearly central in position.

164 STUDIES IN GEOLOGY, No. 3

Surface gently and evenly convex. Shell almost entirely
smooth, but with microscopic sculpture of very fine con-
centric growth-lines. There is an impressed area on the
cast before the beak; no escutcheon is evident. Inner shell
not known. Length, 32.5; height, 12; (semi) diameter
approx. 2 mm.

Fragmental impressions in matrix from the Lower Zor-
ritos give evidence of the abundance of this species, but its
extreme fragility almost precludes its extraction from the
hard rock in which it occurs. It is unfortunate that only
one specimen could be laid bare in sufficient entirety to
justify attention ; however, enough may be observed of
that one to note its important external characters, and such
observation shows it to be almost certainly new.

It is very much like Solen dombeyi Lamarck,189 described
by Philippi from Coquimbo, Chile, but is much smaller and
apparently more delicate. Fragments noted in matrix indi-
cate that S. plamifolliculus probably grew to no greater size
than that of the specimen described.

Solen tenuis Philippi,190 from Chile, is represented by
its author as a cast with two pieces of the shell adhering,
and although it is a form of apparently the same size and
delicacy of S. planifolliculus, the shape indicated by Philip-
pi's cast differs in being arcuate ventrally whereas plani-
folliculus is ventrally straight or very slightly sinuate.

Lower Zorritos. Head of Quebrada Zapotal.

Los. Fos. Terc. y Cuart. de Chile, p. 163, pi. 34, fig. 5, 1887.
Idem., fig. 7.

PALEONTOLOGY ZORRITOS FORMATION 165

Superfamily MACTRACEA
Family MACTRIDAE
Subfamily MACTRINAE
Genus MULINIA Gray

Mulinia zorritensis (Nelson)
PLATE X— Figs. 8, 9.

Mactra zorritensis Nelson, Trans. Conn. Acad., vol. 2, p. 201,
1870.
Mactra sp. ind., Nelson, ibid., p. 201, 1870.

Shell small, very delicate, inflated, triangular. Anterior
margin nearly straight dorsally, curving into the ventral
margin, which is elliptical ; posterior margin nearly straight,
meeting the ventral margin in a sharp angle. Umbones sub-
central in position, apically small, inflated, prosogyrate,
about 1.25 mm. distant in a shell 22 mm. long by 19.5 mm.
high. Anterior surface evenly convex; medium surface
longitudinally flat and vertically convex. A sharp posterior
carir.a is distinct from the top of the beak to the posterior
marginal angle; behind it the surface is flat ventrally and
slightly excavated near the beaks. Sculpture of fine con-
centric lines ; in some shells irregular differentiation of
growth-stages gives a somewhat rough appearance, and
others are more nearly smooth. Dorsal areas distinct, de-
limited by sharp lines which form a lanceolate posterior area
and an olive-shaped anterior area; surface of areas finely
striate longitudinally. Hinge normal, very delicate. Di-
mensions of 2 specimens: Length, 19.5; height, 16; diame-
ter, ii mm. Length, 22; height, 19.5; diameter, 9.5 mm.

Nelson differentiated the Mulinias in his collection,
naming a portion Mactra zorritensis, and leaving the others,
which show all characters very well, as indeterminate. He
says concerning his "indeterminate" species, "This species
may be told from the preceding '(M. zorritensis)' which
it much resembles, in being broader, having less prominent
umbos, and being less convex ; posterior margin not so angu-

166 STUDIES IN GEOLOGY, No. 3

lated." These characters are exactly as noted, but in the
group he set aside as M. zorritensis as well as the other are
specimens which show an even gradation from the longer,
posteriorly more pointed, less inflated forms typical of his
"species indeterminate'' to the shorter, generally rounder
forms he called sorritensis, and a close study of all char-
acters shows the relationship to be sufficiently close to
warrant their grouping into a single species. The species
is simply variable, as is the case in many other natural
specific groups in the genus.

M. zorritensis shows remarkable similarity throughout to
M. lateralis Say,191 from the Miocene to Recent of the
Atlantic States. Such differences as occur are functional of
the greater thinness and fragility of zorritensis, whose hinge
armature is more delicate, the lateral laminae in the right
valve being far less stout than in lateralis; the cardinal
teeth, however, are entirely similar. Although every char-
acter of zorritensis has its analogue in lateralis, even the
somewhat wide variations of the northern species being
paralleled by similar mutations in zorritensis, the complete
difference in weight gives rise to a contrast which deserves
systematic recognition.

Zorritos formation. Zorritos.

Subfamily PTEROPSIDINAE
Genus LABIOSA (Schmidt) Moller

Subgenus RAETA Gray
Labiosa (Raeta) gabbi Pilsbry and Johnson

Raeta canaliculata Gabb, Trans. Amer. Philos. Soc., vol. 15, p. 248,
1873; (not Say, 1821).

Labiosa (Raeta) gabbi Pilsbry and Johnson, Proc. Ac. Nat. Sc.
Phila., vol. 69, p. 202, 1917.

"The shell is oval-triangular, the beaks nearer the anterior

191 Md. Geol. Surv., Pliocene and Pleistocene, p. 194, pi. 55, figs.
1-4, 1906.

PALEONTOLOGY ZORRITOS FORMATION 167

end ; sculptured with small concentric ribs which are weaker
in the middle, where there is a slightly depressed, quite
inconspicuous wedge-shaped area radiating from the beaks.
Posterior end rounded, somewhat compressed, the contour
in dorsal view being somewhat wedge-shaped. Hinge not
exposed. Length, 28; alt. 23; diam. 13.8 mm." — Pilsbry
and Johnson, 1917.

The shell is small, delicate, moderately inflated, long,
somewhat low. Anterior dorsal margin nearly straight, some-
what produced; extreme anterior margin rounded; ventral
margin almost straight, ascending slightly. Posterior mar-
ginal angle blunt, pronounced ; the shell is produced
posteriorly. Umbones pointed, prosogyrate, moderately
inflated, erect, situated just forward of the middle. Surface
generally convex, flatter posteriorly, where the shell is some-
what attenuate, and very slightly excavated behind the beaks.
Sculpture of prominent, sharp concentric undulations, about
4 in the space of 5 mm. on the center of the disc of Zorri-
tos specimens. Inner shell unknown. Length, 36; height,
27; diameter, 16.5 mm.

This species is somewhat similar to Raeta (Raetina)
indica Dall,192 but differs in being less produced and more
blunt posteriorly, and chiefly in having the posterior lateral
tooth, the lack of which is a sectional characteristic of
Raetina. It differs from L. gardncrae, in having the wedge-
shaped area on the disk, which is not present in gardnerae,
and in that the ventral margin does not ascend posteriorly
with nearly the sharpness common to gardnerae, with the
result that the sculpture of gabbi is biangulate in outline,
the ribs being flat ventrally and turned up on either side,
whereas that of gardnerae is monangulate, as in canaliculata
Say. The posterior marginal angle of gardnerae is much
sharper.

The Zorritos specimens compare very well with Pilsbry

192 Trans. Wag. Inst, vol. 3, pt. 4, p. 882, li

i68 STUDIKS IN GEOLOGY, No. 3

and Johnson's types from the Dominican Republic, with the
exception that the ribs of the Peruvian form are not as
much weakened centrally as in the Domingan gabbi. These
differences are barely perceptible, and can not be held to
have systematic value.

Upper Zorritos. Quebrada de las Alturas.

Labiosa (Raeta) gardnerae n. sp.
PLATE X — Fig. 10.

Shell small, anteriorly inflated, very thin, subtrigonal in
outline. Anterior margin broadly rounded; ventral margin
elliptical, ascending rather sharply to the posterior marginal
angle, which is less than a right angle ; posterior-dorsal
margin nearly straight. Umbones small, inflated, pointed,
incline slightly backward, prosogyrate. Anterior surface
highly convex, with a suggestion of a carina. Posterior
surface attenuate, flattened, with a slight broad concavity
halfway between the beaks and the marginal angle. Sculp-
ture of concentric plications, externally sharp at the top
and with concave slopes, about equal in declivity dorsally
and ventrally ; interspaces comparatively broad, U-shaped.
Hinge not known. Length, 28.5; height, 23.5; (semi) diam.
about 8 mm.

This species is similar in general appearance to L. canal-
iculata Say,193 from the Miocene and later of the Atlantic
Coast. It differs, however, in being much smaller, with more
erect beaks and proportionally more as well as finer con-
centric undulations. It differs from the recent Raeta (Rae-
tina) Indica Dall 194 in being less produced posteriorly, and
in the sharper ascent or its ventral margin. It is much
smaller than the species characteristic of the subgenus Raeta
s.s., and in point of size it corresponds more nearly to the
section Ractina Dall ; but the ventral margin ascends sharply,

193 Jour. Ac. Nat. Sci. Phila., vol. 2, p. 310, 1821; (as Lutraria
canaliculata} .
194 Trans. Wag. Inst., vol. 3, pt. 4, p. 882, 1898.

PALEONTOLOGY ZORRITOS FORMATION 169

restricted subgenus. Raetina lacks the prominent posterior
lateral.

L. gardnerae differs from L. gabbi Pilsbry and Johnson,
in having finer concentric undulations, in being less pro-
duced and more acutely angulate posteriorly, and in lacking
the flat base characteristic of that species.

Upper Zorritos. Quebrada de las Alturas.

Labiosa (Raeta) ventricosa n. sp.
PLATE X — Fig. ii.

Shell high, short, ventricose, highly inflated. Anterior
margin rounded, descending abruptly to a broad angulation,
from which the posterior ventral margin ascends rather
abruptly to the posterior marginal angle, which is approxi-
mately a right angle. Posterior dorsal margin straight.
Umbones pointed, situated just before the median line,
constricted, erect, distinctly episthogyrate. Anterior surface
convex. A submedian keel, sharp on the beaks, and broader
below, extends from the beaks to the broad ventral marginal
angle. The posterior surface is attenuate, as is characteristic
of the genus. Sculpture of strong, sharp concentric plica-
tions. Hinge and interior unknown. Length, 39; height, 42;
diameter, 28 mm.

This interesting Raeta is closer to L. canaliculata Say195
from the Miocene and later of North Carolina and sur-
rounding regions, than are the other two from the Zorritos,
but differs from canaliculata in having more erect beaks,
and in being shorter and much more ventricose.

The specimens studied occur in a lot of unsorted material
from Zorritos in Nelson's collection, and although an exact
locality label is lacking, their presence with specimens of
both gabbi and gardnerae in the same peculiar matrix makes
it likely that they came from the Upper Zorritos formation.

193 Jour. Ac. Nat. Sc. Phila., vol. 2, p. 310, 1821; (as Lutraria
canaliculata) .

170 STUDIES IN GEOLOGY, No. 3

Super family MYACEA

Family CORBULIDAE

Genus CORBUI,A (Bruguiere) Lamarck

Section ALOIDIS Megerle

The Corbula lietis GROUP

The two species of Corbula, section Aloidis, here described
from the Zorritos district, Corbula bradleyi Nelson, and
Corbula prenuncia n. sp., are members of a natural group
whose relationships are interesting in that they show a trans-
ition from somewhat acutely triangular, many-ribbed forms
to squarer, more coarsely ribbed forms. This series, with
the change in the characters named, is as follows :

Corbula vieta Guppy 1 f , ,. .,

_ , . , most and finest ribs

Corbula heterogenia I most triangular J

least inflated beaks

Corbula bradleyi Nelson less triangular fewer and coarser ribs

Corbula vieta Maury still less triangular still fewer and coarser

(not Guppy)197 ribs

Corbula prenuncia Spie- most nearly square coarsest and fewest ribs,

ker most inflated beaks

136 These two are held distinct by Ball and are combined by Wood-
ring under the name of C. heterogenea Dall. Brief examination of
the Bowden material shows the two forms separated by Dall to
exist, and the matter rests on the specific validity of the characters
on which DaM made the distinction, namely, narrower, less elevated,
less prominent beaks, and the posterior part of the shell more pro-
duced in Dall's heterogenea than in his vieta.

97 This form is one from the Santo Domingan Miocene, described
by Maury (Bull. Amer. Pal., vol. 5, No. 29, p. 231, pi. 39, fig. 13,
1917) as Corbula vieta Guppy, but to which species the shell figured
obviously does not belong, it being much squarer than the true
vieta, and having about half as many, much coarser ribs. Since
it is not possible to correct Maury's synonymy here, the form
described by her may be referred to as Maury's C. vieta. The
Santo Domingan form is probably a new species.

PALEONTOLOGY ZORRITOS FORMATION 171

The only discrepancy in the transition lies in the unusual
size of C. bradleyi, which is 20 mm. long and 18.5 mm. high;
the largest of the other species is 10 mm. in length. Pro-
portionally considered, however, the external characters of
the species grade into one another, with sufficient difference
between each and its neighbor in the series to require system-
atic distinction.

Corbula (Aloidis) bradleyi Nelson

PLATE X— Figs. 13, 14.
Corbula bradleyi Nelson, Trans. Conn. Acad., vol. 2, p. 200, 1870.

"Shell very ventricose; wedge-shaped, umbones large,
convex, incurved over the hinge area. Anterior margin
rounded ; lunule very deeply impressed ; ligament area twice
the length of the lunule; strongly angulated with the poste-
rior margin. Hinge tooth large, recurved ; fossette triangular
and deeply impressed. Surface of shell marked by strong,
convex, concentric lines, separated by narrow but well
marked spaces, about five of the lines in five millimetres.
The triangular shape is very characteristic, as is also the
angulation of the posterior margin ; beak very prominent."
—Nelson, 1870.

The posterior surface is marked by two carinas about 5
mm. apart at the hinge, between which the surface is flat
to somewhat excavated. The strong lirae curve across this
surface, diminishing in size as they converge across the im-
pressed area which Nelson has incorrectly described as an
escutcheon. The liration tends to be irregular ventrally.
Length, 20; height, 18.5 mm.

Unfortunately, Nelson's collection affords but one right
valve of Corbula bradleyi, and it does not occur in the Hop-
kins collection. Relationships which might hinge on char-
acters of the left valve are accordingly impossible of note.
However, the characters offered by the specimen available
show that, other things being equal, C. bradleyi has a defin-
ite place among the Miocene members of the section Aloidis.

172 STUDIES IN GEOLOGY, No. 3

It is a species noted for its unusual size, and will undoubt-
edly prove to be one of the characteristic fossils of the
Zorritos group.

Discussion of its affinities is hardly necessary after the
indications offered in the brief consideration of the Corbu-
la vieta group. It is of a type characteristic of Antillean
Miocene horizons, and its presence in the Zorritos offers
further evidence oi the close relationship between the mollus-
can faunas of the two regions during Lower Miocene time.

Corbula (Aloidis)' prenuncia n. sp.
PLATE X— Fig. 12.

Shell small, inflated, triangular. General form pyramidal ;
anterior margin short, rounded ; ventral margin elliptical;
posterior margin biangular, very little produced. Umbone of
right valve high, prominent, strongly incurved, inflated.
General surface smoothly round ; rostrum keels well marked,
but posterior portion not markedly gibbous. Sculpture of
heavy, proportionally coarse, concentric lirae, about 18-20
on the right valve. Inner shell and left valve unknown.
Length, 5.5 ; height, 5.5 mm.

This species, although somewhat imperfectly known, offers
sufficient evidence of a distinctive character. It is related to
the forms mentioned in the presentation as a whole of the
Corbula vieta group. It is close to Corbula bradleyi Nelson,
and was thought at first to be the young of that species, but
a comparative study of the, young of other species in the
section Aloidis shows that it is distinct as noted in the dis-
cussion of relationships.

Lower Zorritos. North of Quebrada Boca Pan.

Section CUNEOCORBULA Cossman

Corbula (Cuneocorbula) fabiformis n. sp.

PLATE X— Fig. 15.

Shell of average size, ovate, somewhat produced. Ante-
rior margin rounded, ventral margin elliptical ; posterior

PALEONTOLOGY ZORRITOS FORMATION 173

margin short and biangulate. Umbones anterior, not prom-
inent. Sculpture of fine concentric lines. Surface ovately
convex, the rostral portion flat, with the rostral keel obso-
lescent, and the intercarinal surface concave. Cardinal angle
not acute. Posterior and pointed, although somewhat bluntly
so. Lunule and escutcheon absent. Pallia! line impressed.
Teeth unknown. Length, 9.5; height, 6; (semi) diameter,
2.5 mm. (right valve) ; diameter of entire shell, 4.5 mm.

This species is similar in general outline to C. propinqua,
of the Variegated fauna, but differs as noted in the discus-
sion of that form.. It is most closely related to C. caimitica
Maury,198 of the Santo Domingan Lower Miocene, which
differs in being slightly shorter, with more nearly central
beaks ; it is not as much produced posteriorly ; the first pos-
terior carina is sharper, and turns upward in the left valve,
whereas that of fabiformis is nearly straight. Maury gives
no description worth noting, and her figures are insufficient
owing to high lights ; but such features as are notable show
the two forms to be probably of different species, though
very close. It is similar in general outline to C. sphenia
Dall,199 from the Chipola of Florida, but the sculpture of
sphenia is much coarser. C. kaghriana Dall,200 from the
Orthaulax zone of Ballast Point, Florida, is also similar,
but differs in being shorter and in having coarser sculpture,
the interspaces between the ribs being wider. Corbula
hatcheri Ortmann,201 from the Lower Miocene of Patagonia,
is very similar, but is shorter, and its ventral margin ascends
more abruptly to the posterior marginal angle. The ventral
surface of hatcheri is very similar to that of fabiformis.

Lower Zorritos. Quebrada north of Boca Pan.

198 Bull. Amer. Pal., vol. 5, No. 29, p. 233, pi. 39, figs. 18, 19, 1917.
109 Trans. Wag. Inst, vol. 3, pt. 4, p. 847, pi. 36, fig. 10, 1898.
200 U. S. Nat. Mus. Bull. 90, p. 155, pi. 21, figs. 4, 5, 1915.
^Princet. Exp. Patag., vol. 4, p. 151, pi. 30, figs. 4a, b, c, 1901.

174 STUDIES IN GEOLOGY, No. 3

la (Cuneocorbula) pro pin qua n. sp.
PLATE X— Fig. 16.

Shell ovate, somewhat produced, of good size for the
section. Anterior margin somewhat produced, rounded;
ventral margin elliptical, ascending posteriorly; posterior
( dorsal) margin nearly straight. Shell pointed posteriorly.
Umbones inconspicuous, anterior in position. General sur-
face convex except posteriorly, where a narrow concave
area exists between the characteristic keel. The ventral
surface of the left valve is squared off. The extreme pos-
terior portion of the left valve (and possibly the right —
specimens broken) is drawn out to form a horizontal chisel-
like point inside the end of the rostral keel. Sculpture of
fairly regular, fine concentric ribs which are slightly more
prominent and more irregular on the right valve. On the
chisel-like point the sculpture is of fine longitudinal lines.
No lunule, and small trace, if any, of an escutcheon is visible
on the material examined. Length, 15; height, 9; diameter,
5.5 mm.

This species is similar in many characteristics to C. fabi-
formis. It differs primarily in being much larger and in
having the posterior end more pointed. The flattened pos-
terior point is not present in fabiformis. It is also similar to
C. kaghriana Dall,202 from the Orthaulax bed at Ballast
Point, Florida, but is longer, more pointed, and has finer
sculpture. Otherwise the resemblance is close.

Variegated. Quebrada Tusillal.

Corbula (Cuneocorbula) bravoana n. sp.
PLATE X— Fig. 17.

Shell of good size, distinctly triangular, less rounded than
the usual Cuneocorbulas. Anterior margin straight dorsally,
somewhat abruptly curved below. Ventral margin nearly
straight, ascending slightly throughout its length; posterior

U. S. Nat. Mus. Bull. 90, p. 155, pi. 21, figs. 4, 5, 1915.

PALEONTOLOGY ZORRITOS FORMATION 175

dorsal margin straight in left valve, biangular in right. Um-
bones anterior, not prominent, sharp, slightly prosogyrate.
Anterior surface rounded. Surface bounded by anterior
margin, first posterior carina, and ventral margin forms a
triangle, subcylindrical in contour. First posterior carina
prominent, bevelled in both valves, curved upward ventrally
and leading into the umbo in a straight line in the left valve,
curving over slightly in the right valve on account of its
convexity. Second posterior carina not prominent ; clearer
in right valve than in left. Intercarinal space concave in
both valves, larger in right. Sculpture of raised concentric
ridges, whose sharper slope is above, about 1 1 in the space of
5 mm. on the right valve and 16 in the same space on the
left. The sculpture is of constant strength over the entire
shell. Neither lunule nor escutcheon is apparent. Interior
of shell unknown. The shell is of greatest diameter at the
prominent carinae. Length, 11.5; height, 7.5; diameter,
4 5 mm.

This species is one of a series of closely related Cuneocor-
bulas in the Zorritos, being clearly similar to C. fabiformis,
C. propinqua, and, to a lesser degree, to C. acutirostra. One
specimen only occurs in the collection. The characteristic
sculpture and bevelled carina of C. bravoana are undoubtedly
features of a species distinct from those named, despite the
fact that other external characters are close enough to cause
some hesitation in pronouncing it different. It differs from
C. fabiformis in sculpture, as suggested above, in having
more prominent concentric rugae, which are less curved
mesially than in fabiformis; the bevelled carina is lacking in
fabiformis, and the general shape of bravoana is nearer to
the strictly triangular. C. propinqua is nearer generally.
However, the lack of the bevelled carina, the finer and more
irregular sculpture, the broader ventral surface, and the
more sharply ascending ventral margin of propinqua mark it
as distinct. C. bravoana does not have the chisel-like point
of propinqua.

176 STUDIES IN GEOLOGY, No. 3

Comparison with these species to which the other Cuneo-
corbulas of the Zorritos have been likened will show similar-
ities, but none is as clear as the relationships named above.
C. sphcnia Ball 203 from the Chipola of Florida, is close, but
is less clearly triangular in shape, lacks the bevelled carina,
and has slightly coarser sculpture. In sphenia the carina
curves downward as it approaches the ventral margin ; in
bravoana it curves upward. It is also similar superficially to
C. caimitica Maury 204 of the Lower Miocene of Santo Do-
mingo. The sculpture does not curve ventrally in bravoana
as it does in caimitica; the bevelled carina is again a point
of difference, and the anterior margin of caimitica is more
completely rounded. This species departs a bit more widely
from those European forms to which C. acutirostra is com-
pared. It is named in honor of Dr. Jose Bravo, chief of the
Cuerpo de Ingenieros de Peru.

Lower Zorritos. Between Quebradas Heath and Charon.

Corbula (Cuneocorbula) acutirostra n. sp.
PLATE X— Figs. 18, 19.

Shell of medium size, rostrally truncate, triangular. An-
terior margin rounded ; ventral margin elliptical ; posterior
margin sharply angulate. Beaks not prominent, anterior in
position, proximate, somewhat flattened above. Anterior
surface rounded; mesial surface flat longitudinally and
curved vertically. Posterior surface concave, separated from
the rest of the shell by a very sharp carina which is bowed,
its concave side upward. Sculpture of fine and regularly
graven concentric lines which limit somewhat broader ribs.
On the concave surface behind the sharp carina the lines are
broader and stronger, recurving toward the hinge, and the
elevated ribs are thin and cusp-like. There is a second faint
carina near the postero-dorsal margin. The valves are

"3 Trans. Wag. Inst, vol. 3, pt. 4, p. 847, pi. 36, fig. 10, 1898.

2(14 Bull. Amer. Pal., vol. 5, No. 29, p. 233, pi. 39, figs. 18, 19, 1917.

PALEONTOLOGY ZORRITOS FORMATION 177

nearly equal, the right being the more inflated, and are
equally sculptured. There is neither lunule nor escutcheon.
Inner shell unknown. Length, 17.5; height, 10; diameter,
7 mm.

This species is characterized by its very sharp carina, and
the distinctly sculptured intercarinal area. In this set of
features it is unlike any fossil Cuneo'corbula from the Wes-
tern Hemisphere known to the writer. Two European forms
have the very acute carina, and one is very close. In exter-
nal characters it is similar to C. revoluta Brocchi,205 and C.
basteroti Hoernes,206 from the lower Oligocene of Germany.
C. revoluta is the closer of the two, being indistinguishable
but for the sculpture of the intercarinal area, more deeply
channelled in acutirostra, the general sculpture, apparently
coarser in revoluta, and possibly in the ventral margin, which
is obscured by irremovable matrix in the available specimens
of acutirostra. C. basteroti is likewise coarser in sculpture,
and differs further .in being shorter, with the beaks sub-
central in position.

Comparisons with American species offer less satisfaction
because of greater differences, and the selection of related
species carries less meaning. C. caimitica Maury,207 from
the Lower Miocene of Santo Domingo, is somewhat similar,
but is much shorter, lacks the very sharp carina, has coarser
sculpture, and has the prominent carina straight in its upper
part, whereas that of acutirostra curves over into the beak.

Upper Zorritos. South of Quebrada de las Alturas ; Que-
brada del Grillo.

-05Abh. k.k. geol. Reichs., Bd. 4, p. 38, pi. 3, fig. 9, 1870.

200 Ibid., p. 39, pi. 3, fig. 10.

207 Bull. Amer. Pal., vol. 5, No. 29, p. 233, pi. 39, figs. 18, 19, 1917.

i;8 STUDIES IN GEOLOGY, No. 3

PLATE I.

Fig. i. Terebra gausapata var. herviderana Spieker, x2.

2. Terebra tuberosa (Nelson), x2.

3. Conus bocapanensis Spieker, x2.

4. Conus berryi Spieker, x2.

5. Conus cacuminatus Spieker.

6. Conus molis var. bravoi Spieker.

7,8. Calliostoma (Eutrochus) noduliferum Nelson, x2.

9. Marginella incrassata Nelson.

10, ii. Solenosteira alternata (Nelson).

T2. Phos (?) latirugatus Spieker.

STUDIES IN GEOLOGY III

PLATE I

180 STUDIES IN GEOLOGY, No. 3

II.

Figs. 1,2. Nassa zorritensis (Nelson).

3. Triumphis solida (Nelson) .

4. Murex laquoratus Spieker.
5,6. Pyrula peruviana Spieker.
7,8. Cypraea angustirima Spieker.

9. Cerithium infranodatum Spieker.

10. Cerithium grillanum Spieker.

11. Potamides ormei var. infraliratus Spieker.

12. Turritella altilira Conrad.

13. Turritella alturana Spieker.

STUDIES IN GEOLOGY III

PLATE II

13

182 STUDIES IN GEOLOGY, No. 3

PLATE III.

Fig. i. Turritella bifastigata Nelson.

2. Turritella felicincta Grzybowski.

3. Turritella filicincta var. varicosta Spieker.

4. Turritella inca var. trita Spieker.
5,6. Turritella nelsoni Spieker.

7. Turritella nelsoni var. rotundata Grzybowski.

8. Turritella nelsoni var. trullissatia Spieker.

9. 10. Turritella infracarinata Grzybowski.

ii. Turritella infracarinata var. zorritensis Spieker.

STUDIES IN GEOLOGY III

PLATE III

184 STUDIES IN GEOLOGY, No. 3

PLATE IV.

Figs, i, 2, 3. Turritella prenuncia Spieker.

1. x3.

2. X5.
3- X2.

4. Turritella prenuncia var. inconspicua Grzybowski, x2.

5. Turritella robusta Grzybowski .

6. Turritella robusta var. abrupta Spieker.

7. Turritella charana Spieker.

8. Polynices subangulata Nelson.

9. Polynices porcana Spieker.

10. Sinum carolannm Spieker, x5.

11. Turbo belli Spieker, x2.

12. Turbo belli var. aequifilicatus Spieker.

13. Cancellaria (Aphera) peruana Nelson, x2.

STUDIES IN GEOLOGY III

PLATE IV

i86 STUDIES IN GEOLOGY, No. 3

PLATE V.

Fig. i._ Leda peruviana Dall.

2,3. Area (Noetia) cholana Spieker.

4, 5. Area (Cunearca) zorritensis Spieker, x2.

6,7. Area (Cunearca) sp. indet.

8,9. Area (Scapharca) pantheonensis Spieker.

10. Area (Scapharca) zapotalensis Spieker.

11. Area (Scapharca) fissicosta Spieker.

12. 13. Area (Scapharca) singewaldi Spieker.

14. Area (Scapharca) vanholsti Spieker.

15. Area (Scapharca) charonensis Spieker.
1.6, 17, 18. Area (Scapharca) larkinii Nelson.

19,20. Area (Scapharca) imporcata Spieker.

STUDIES IN GEOLOGY III

PLATE V

1 88 STUDIES IN GEOLOGY, No. 3

PLATE VI.

Figs. 1,2. Area (Scapharca) obesiformis Grzybowski

3,4. Area (Scapharca) crescens Spieker.

5,6. Area (Anadara) septifera Grzybowski.

7,8. Area (Anadara) nelsoni Spieker.

9, 10. Area (Anadara) toroensis Spieker.

STUDIES IN GEOLOGY III

PLATE VI

10

190 STUDIES IN GEOLOGY, No. 3

VII.

Fig i. Area (Anadara) toroensis Spieker.

2. Area (Anadara) toroensis var. crassa Spieker.

3. Area (Anadara) toroensis var. prolata Spieker.
4,5. Pecten woodringi Spieker.

6, 7. Anomia berryi Spieker.

8. Crassatellites (Scambula) nelsoni (Grzybowski)

9, 10. Crassatellites (Scambula) berryi Spieker.

ii. Phacoides (Pseudomiltha) insleyi Spieker.

12. Cardium (Trachycardinm) zorritensis Spieker.

STUDIES IN GEOLOGY 111

PLATE VII

i92 STUDIES IN GEOLOGY, No. 3

PLATE VIII. . ;•

Fig. i. Cardium (Trachycardium) peruvianum Spieker.

2,3. Cardium (Trigoniocardia) affinis (Nelson).

3- X2.

4- Dosinia (Dosinidia) grandis Nelson.
5. Clementia dariena (Conrad).

STUDIES IN GEOLOGY III

PLATE VIII

194 STUDIES IN GKOLOGY, No. 3

PLATE IX.

Figs. 1,2. Transennella herviderana Spieker.

3,4. Macrocallista helenae Spieker.

5. Amiantis incrassata var. ovoidalis Sacco.

6,7. Pitaria (Lamelliconcha) cora var. aeqnicincta Spieker,

8,9. Chione (Chione) variabilis Nelson.

10,11. Chione (Chione) angelana Spieker.

12. Chione (Chione) propinqua Spieker.

STUDIES IN GEOLOGY III

PLATE IX

11

196 STUDIES IN GEOLOGY, No. 3

PLATE X.

Figs. 1,2. Tellina zapotalensis Spieker.

3. Tellina (Eurytellina) aequicincta Spieker.

4. Tellina (Angulus) pressa Ball, side view x5.

5. Tellina (Angulus) singewaldi Spieker.

6. Pitaria (Lamelliconcha) planivieta (Guppy).

7. Solecurtus (Pharella) planifolliculus Spieker.
8,9. Mulina zorritensis (Nelson).

10. Labiosa (Raeta) gardnerae Spieker.

11. Labiosa (Raeta) ventricosa Spieker.

12. Corbula (Aloidis) prenuncia Spieker, x3.

13. 14. Corbula (Aloidis) bradleyi Nelson.

15. Corbula (Cuneocorbula) fabiformis Spieker, x3

16. Corbula (Cuneocorbula) propinqua Spieker.

17. Corbula (Cuneocorbula) bravoana Spieker.

18. 19. Corbula (Cuneocorbula) acutirostra Spieker.

STUDIES IN GEOLOGY III

PLATE X

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