Introduction.-Since the description [1] of a skull of Amynodontopsis bodei and of a lower jaw referred to this species from the uppermost Eocene, further dental parts have become available for study from localities in the Sespe. These furnish additional characters of value in recognizing the species represented in western Eocene deposits. Now also available is a fragment of skull with cheek-teeth from the Poway Eocene of San Diego County, California. This specimen possesses special significance because it permits a comparison with related forms in America and China. It is likewise of interest because it differs from the amynodonts of the Sespe and is clearly an earlier type

Stock, Chester

English

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PALEONTOLOG Y: C. STOCK
EOCENE AMYNODONTS FROM SOUTHERN CALIFORNIA
BY CHESTER STOCK
BALCH GRADUATE SCHOOL OF THE GEOLOGICAL SCIENCES, CALIFORNIA INSTITUTE OF
TECHNOLOGY
Communicated April 15, 1939
Introduction.-Since the description' of a skull of Amynodontopsis bodei
and of a lower jaw referred to this species from the uppermost Eocene,
further dental parts have become available for study from localities in the
Sespe. These furnish additional characters of value in recognizing the
species represented in western Eocene deposits. Now also available is a
fragment of skull with cheek-teeth from the Poway Eocene of San Diego
County, California. This specimen possesses special significance because
it permits a comparison with related forms in America and China. It is
likewise of interest because it differs from the amynodonts of the Sespe and
is clearly an earlier type.
Amynodon reedi, n. sp.
Type Specimen.-No. 2529, C. I. T. Vert. Pale. Coll., a fragment of the
left side of the skull with P4-M3 inclusive, plate 1.
Locality.-Poway conglomerate and cross-bedded sandstones exposed at
C. I. T. Vert. Pale. Loc. 314, San Diego, California.
Specific Characters.-Smaller than Amynodon advenus, A. antiquus and
A. erectus and resembling A. sinensis in size. P4 is narrow in anteropos-
terior diameter in comparison to its transverse width, more so than in A.
sinensis. Principal axis of metaloph in P4 at right angles to external border
of tooth. I take pleasure in naming this species for Dr. Ralph D. Reed,
penetrating student of California geology.
Description.-This species is distinctly smaller than Amynodontopsis
bodei from the uppermost Eocene Sespe. It is likewise smaller than
Amynodon advenus and related forms from the Uinta. Among American
species nearest resemblance in size to A. reedi is found in a specimen, No.
1936A A. M. N. H. from the Uinta (Uinta B) of Utah. With regard to the
latter it is interesting to record that its occurrence is the earliest among
American amynodonts as at present known. No representatives of the
group have thus far been uncovered in the Bridger Eocene. Presence of
No. 1936A in Uinta B and its resemblance to No. 2529 from the Poway may
be taken as evidence to indicate that the Poway is related in age to this
stage of the Uinta.
Previously recorded mammalian species from the Poway suggest a faunal
stage closely related to but slightly more advanced than the Bridger.
Thus, Yumanius woodringi is a tarsiid primate more advanced than
270 PROC. N. A. S.
PALEONTOLOG Y: C. STOCK
Anaptomorphus. Presence of Metarhinus(?)pater suggests that the Poway
is post-Bridger C and pre-Uinta C. The amynodont here described sug-
gests again an age for the Poway comparable to that indicated by the
titanothere and points more specifically to a time relationship with Uinta
B. Unfortunately, the fauna thus far known from Uinta A is a meager one.
It contains, according to Dr. H. E. Wood, 2nd., an amynodont which he
recognizes as of the species Amynodon advenus (No. 11983 Carnegie Mus.).
Presence of a larger species in the Uinta A horizon makes less certain a
direct correlation between the Poway and the Uinta B on the basis of the
amynodonts. A consideration of the Poway fauna as a whole may empha-
size a time stage comparable to that of the lower Uinta or possibly with one
situated between the lower Uinta and the upper Bridger.
COMPARATIVE MEASUREMENTS (IN MILLIMETERS)
A. reedi, N. sP. Amynodon, sp. A. sinensis' A. antiquus
NO. 2529 NO. 10047
C. I. T. NO. 1936 A PRIN. U.
TYPE A. M. N. H. TYPE TYPE
POWAY UINTA B CHINA WASHAKIE
Length, anterior end of P4 to
posterior end M3 103.8
Length, anterior end of Ml to
posterior end M3 85.8 86.2 73.5 93
P4, anteroposterior diameter a12 14.8 23.1
P4, transverse diameter 24.7 22.1
Ml, anteroposterior diameter 25.1 28.2 a24.5 36.4
M1, transverse diameter 29.9 a31.5 25
M2, anteroposterior diameter 29.5 29.7 29
M2, transverse diameter 33.7 34.1 28.8
M3, anteroposterior diameter 27.9 32.4 25.1
M3, transverse diameter 31.1 34.2 27.8
1 Measurements after Zdansky.
a, Approximate.
Amynodon sp., possibly advenus Marsh
A single, imperfect tooth, M2, No. 2537 C. I. T. Vert. Pale. Coll., Plate 2,
figures 6, 6a, comes from locality 202 in the Sespe. This site is situated
stratigraphically from 600 to 800 feet below locality 150 in the Sespe de-
posits exposed north of the Simi Valley, Ventura County, California, and
represents an earlier (Upper Eocene) faunal horizon than that known from
locality 150 (Uppermost Eocene).
No. 2537 approximates in size comparable teeth that have been referred
to Amynodon advenus. However, teeth are present in the collections from
locality 150 that are actually smaller than No. 2537. In contrast to one of
these teeth, also an lkI2, from locality 150, No. 2337 exhibits a smooth wall
lining the valley between protoloph and metaloph.
VOL. 25, 1939 271
PALEONTOLOG Y: C. STOCK
PLATE 1
Amynodon reedi, n. sp.
Type specimen, No. 2529 Calif. Inst. Tech. Coll. Vert. Pale., a fragment of skull
with P4-M3, inclusive, lateral and occlusal views, X 1.
Poway Conglomerate, San Diego County, California. Upper Eocene.
PLATE 2 (RIGHT)
Figures 1 to 5a. Amynodontopsis bodei Stock. Figure 1, left canine, No. 2530, lateral
view; figure 2, maxillary fragment with P3 and P4, No. 2532, occlusal view; figure 3,
maxillary fragment with P2 and P3, No. 2531, occlusal view; figures 4, 4a, M2, No.
1089, occlusal and lateral views; figures 5, 5a, M3, No. 2535, occlusal and lateral views;
X 1. Sespe Uppermost Eocene, California.
Figures 6, 6a. Amynodon, sp., possibly advenus Marsh. M2, No. 2537, occlusal
and lateral views; X 1. Sespe Upper Eocene, California.
All specimens in Calif. Inst. Tech. Coll. Vert. Pale.
272 PROC. N. A. S.
PALEONTOLOG Y: C. STOCKVOL. 25, 1939 273
PALEONTOLOG Y: C. STOCK
Length of tooth, No. 2537, measured in millimeters along outer side, is
46.2.
Amynodontopsis bodei Stock
Referred to this genus and species are several parts of the dentition be-
longing to individuals smaller than the type, No. 1087 C. I. T. These
specimens display additional characters not heretofore recorded for the
Sespe amynodonts. The superior canine, No. 2530, shows a sinuous curva-
ture in its longitudinal course as viewed from in front. The crown, which
is broad in front and terminates in a sharp ridge behind, is approximately
one-third the length of the tooth.
Premolars 1 to 3 are shown in specimens No. 2531, 2532, Plate 2, figures
3 and 2. In P2 the crown is almost as wide as it is long. On the occlusal
surface are seen the protoloph and metaloph, which spring from the inner
wall of the ectoloph as narrow bands but become swollen along their inner
halves. The protoloph is distinct from the anterior border of the tooth,
but fuses with the inner border. The metaloph is distinctly smaller than
the protoloph and in the stage of wear shown by No. 2531 is distinct from
the inner and posterior border of the crown. Thus, both the pre- and post-
fossettes are open. The inner wall of the principal cusp of the ectoloph is
directed inward and backward and helps to define the border of the fossette.
The occlusal pattern in P3 may not differ greatly from that in P2. The
metaloph has a more posterior position than in P2; the prefossette may be
open or closed internally. A noteworthy feature is the small longitudinal
folds which give added complexity to the forward side of the metaloph and
to the inner wall of the prefossette. In P4 the protoloph is well developed.
A relatively thin, curved crest connects the rudimentary metaloph with
protoloph, thus closing a prefossette internally.
Among upper molars collected at locality 150 in the Sespe are several
similar in size to the molars in the type of A. bodei. At least two teeth,
Nos. 1089, 2535, Plate 2, figures 4 and 5, are distinctly smaller. If these
teeth are correctly assigned to A. bodei, they demonstrate the existence of
appreciable variation in size among individuals of this amynodont.
M2, No. 1089, Plate 2, figure 4, exhibits at least two wrinkles of the
enamel lining the inner side of the ectoloph near the head of the median
valley separating protoloph and metaloph. Similar modification of the
enamel surface may be seen on the anterior side of the metaloph in M3,
Plate 2, figure 5. In this respect these teeth of the Sespe species differ
from those of other Eocene amynodonts and are presumably more special-
ized. M3, No. 2535, in contrast to the comparable tooth in Amynodon
reedi, possesses a higher crown.
274 PROC. N. A. S.
PHYSIOLOGY: A. KROGH
MEASUREMENTS (IN MILLIMETERS) OF TEETH OF Amynodontopsis bodei
Superior canine, No. 2530, anteroposterior diameter at base of crown 19.4; width 15. 1
P2, No. 2531, anteroposterior diameter on outer side 15.2; width 15.1
P3, No. 2531, anteroposterior diameter on outer side 16.6; width 20.7
P3, No. 2532, anteroposterior diameter on outer side 16.4; width 21.1
P4, No. 2532, anteroposterior diameter on outer side 20 ; width 26.2
M2, No. 1089, anteroposterior diameter on outer side 42.8; width 31.4
M3, No. 2535, anteroposterior diameter on outer side 38. 1; width 36.5
1 Stock, C., Proc. Nat. Acad. Sci., 19, 762-767 (1933); 22, 263-265 (1936).
THE ACTIVE UPTAKE OF IONS INTO CELLS AND ORGANISMS
By AUGUST KROGH
LABORATORY OF ZO6PHYSIOLOGY, UNIVERSrTY OF COPENHAGEN
Read before the Academy, April 24, 1939
It is well known that the ionic composition of the protoplasm in animal
cells differs significantly from that of the surrounding lymph or blood,
potassium and phosphate being generally preponderant in the former and
sodium and chloride in the latter. Since there is practically always osmotic
equilibrium the ions within the cells must be largely free and in aqueous
solution. Generally the actual concentrations are not well known, and only
in the case of certain eggs has it been possible to show that certain ions
are absorbed and concentrated from quite dilute outside solutions.
In the large plant cells studied by Osterhout, Collanderl and others,
active absorption of ions into the cell sap has been repeatedly observed
and mechanisms, especially for the active absorption of potassium ions,
have been suggested.
In plant roots Lundeg&rdhl has demonstrated an active transport of
anions from very dilute external solutions into the much more concentrated
sap rising in the stems. He finds that both monovalent and divalent anions
can be so absorbed, but that the absorption requires a large expenditure of
energy, provided probably by catabolism of carbohydrate. The CO2 pro-
duced seems to act as part of the absorption machinery and the whole
process is intimately bound up with the growth of the roots.
In a number of freshwater animals we have in my laboratory studied
much more specialized mechanisms for absorbing and concentrating cer-
tain ions. These mechanisms come into play when the salt content of the
body fluid has been depleted, e.g., by prolonged treatment with distilled wa-
ter, and their biological significance is the maintenance of a more or less
constant concentration in the body fluids round about a hundred times
higher than that of the surrounding fresh water. In all the cases more
VOL. 25, 1939 275


Eocene Amynodonts from Southern California

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Eocene Amynodonts from Southern California

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