Recognition of a primate in the mammalian assemblage now being recorded from one of the faunal stages of the Sespe, north of the Simi Valley, California, comes with startling abruptness, yet is not wholly unexpected. No fewer than five fragments of jaws, probably representing as many individuals, have been found recently. The sudden appearance of this material in the collections of fossil mammalian remains obtained at Locality 150 Calif. Inst. Tech. Vert. Pale. commands attention when it is stated that excavations at this site have been in progress more or less continuously during the past two years

Stock, Chester

English

Caltech Authors - Main

954 GEOLOGY: C. STOCK PRoC. N. A. S.
AN EOCENE PRIMATE FROM CALIFORNIA
By CHESTER STOCK
BALCH GRADUATE SCHOOL OF THE GEOLOGICAL SCIENCES, CALIFORNIA INSTITUTE OF
TECHNOLOGY
Communicated September 20, 1933
lntroduction.-Recognition of a primate in the mammalian assemblage
now being recorded from one of the faunal stages of the Sespe, north of
the Simi Valley, California, comes with startling abruptness, yet is not
wholly unexpected. No fewer than five fragments of jaws, probably repre-
senting as many individuals, have been found recently. The sudden ap-
pearance of this material in the collections of fossil mammalian remains
obtained at Locality 150 Calif. Inst. Tech. Vert. Pale. commands attention
when it is stated that excavations at this site have been in progress more or
less continuously during the past two years.
Relationship of the new type appears to be particularly close with that
division of the tarsiid lemurs (Anaptomorphidae) which includes the
Eocene genera Omomys, Hemiacodon and Euryacodon. Lending interest
to the discovery is the fact that this form represents the latest primate to
be recorded from the North American Tertiary. Moreover, the occurrence
marks another outpost for a group of mammals whose presence on this
continent during the Eocene has been identified heretofore with intermon-
tane basins of the Cordilleran region.
Chumashius baichi, n. gen. and n. sp.
Type Specimen. Fragmentary left ramus of mandible with P3-M
and alveoli for P2 and C, No. 1391 C. I. T. Vert. Pale., plate 1, figures 1, la.
Paratypes.-An incomplete left mandibular ramus, No. 1392, plate 1,
figures 3, 3a and 3b, and a fragment of palate with M2 and M3, No. 1394,
plate 1, figure 4.
Referred Specimens.-Two incomplete mandibular rami with portions of
the premolar-molar series, No. 1393, plate 1, figures 2 and 2a, and No. 1390.
Locaity.-Sespe Upper Eocene, north of Simi Valley, Ventura County,
California; Locality 150 C. I. T. Vert. Pale.
Generic and Specific Characters.-Dentition 2?, 1, 3, 3. P4 without dis-
tinct metaconid. Paraconid median and distinct in MI, more reduced in
M2, vestigial in M3. M3 reduced in size and with inner and posterior
cusps of heel subdued or absent. Enamel smooth. M2 and M3 with well
developed cingula, except on external sides. Intermediate cuspules small
and faintly indicated. M3 more reduced in transverse diameter than in
Euryacodon. No indication of antero-internal cuspules on M2 and M3
as in Euryacodon. Referred specimens larger than type and paratype and
GEOLOGY: G. STOCK
approximate in size the species Omomys carteri. The species is named for
Mr. Allan C. Balch.
Description.-Although the maxillary fragment bearing the two upper
molars cannot be directly associated with any one of the jaws, the presence
of probably four individuals of this primate at locality 150, as based upon
the lower jaw material, makes it reasonable to assume that all of the speci-
mens pertain to the same type of creature. Moreover, some of the charac-
ters exhibited by the upper teeth are to be correlated with those displayed
by the lower posterior molars. The four lower jaws from locality 150
show some variation in size (compare for example Figs. 1, la and 2, 2a).
Judging from the state of wear of the teeth in these specimens, the difference
in size cannot be accounted for on the basis of age. With exception of the
larger size of M3, relative to the anterior molars, in No. 1393, no important
structural features appear to distinguish this specimen from the type. On
the other hand, the differences in size may reflect a difference in sex. In
this connection it may be mentioned that the canine alveolus in the referred
ramus, No. 1390, suggests the presence of a tooth of comparatively large
size.
In Chumashius the mandibular rami were not fused at the symphysis.
The horizontal ramus, as seen in No. 1391, is straight and sturdy. Two
mental foramina are present, the posterior situated beneath P3. and the
anterior below and slightly in front of the alveolus for P2. The anterior
base of the ascending portion of the ramus is broad but thins rapidly in its
upward course. The anterior portion of the masseteric area is best shown
in the paratype, No. 1392, where it is seen to be quite shallow. The pos-
terior dental foramen can be discerned on the inner side of the ascending
portion of the ramus (Fig. 3b, p.d.f.). The position of this opening is
closer to the lower border than to the upper anterior border. Fortunately
the angle is preserved in this specimen. A low, subdued crest is present
on the inner surface of the angle. The process extends downward and
backward and is hook-like in shape. The latter character in Chumashius
balchi is totally unlike that in Tarsius and somewhat resembles that in
modem lemurs other than Tarsius as well as in Notharctus.
The present comparisons of the dentition in the Sespe specimens may
be found somewhat limited in scope, in view of the fact that the available
comparative materials of primates include only a cranium and mandible
of Tarsius spectrum borrowed from the U. S. National Museum and the
type specimen of Omomys carteri Leidy kindly loaned to me by the Academy
of Natural Sciences of Philadelphia. However, published descriptions
and illustrations of Eocene primates, particularly those by Wortman,1
Matthew2 and by Gregory3 permit an extension of the observations made
on the forms from the Simi locality.
Although the lower dentition preserved in the materials from the Simi
VOL. 19, 1933 955i
GEOLOGY: C. STOCK
PLATE 1. (Description on opposite page.)
956' PROC. N. A. S.
GEOLOGY: C. STOCK
gives a representation of P3 - M3, three of the four jaws furnish evidence
of value in determining the lower dental formula. In the type specimen,
No. 1391, as well as in No. 1393, two distinct alveoli are to be seen anterior
to P3. These are presumably for the canine and premolar 2. In both jaws
the alveolus for the canine is larger than that for P2. Similar characters
are to be noted in No. 1390. Fortunately, in this specimen more of the
anterior end of the jaw is preserved although the tip is not present. Por-
tions of the alveolar walls of at least two incisors can be discerned. Thus,
in number of lower teeth Chumashius differs from the Eocene genera
Anaptomorphus and Tetonius and resembles Omomys and Hemiacodon.
P3 resembles the comparable tooth in Omomys in shape of base and height
of crown. A rudimentary posterior ledge is present and a metaconid is
absent.
P4 likewise resembles the comparable tooth in Omomys in shape of base
and height of crown. It differs, however, from the fourth premolar in
0. carteri in absence of a distinct imetaconid. In the three specimens from
the Simi where the crown of this tooth is preserved either entirely or in
part, the development of the metaconid is seen to be subject to some varia-
tion. In both the type and No. 1393 a slight bulging of the postero-internal
border of the protoconid is all that denotes the presence of a metaconid.
Greater definition of this cusp is seen in No. 1390, although in this
specimen also the metaconid is not so distinctly formed as in the type of
0. carteri. In tendency to reduce the metaconid the Sespe species appears
to be more advanced than 0. carteri. A narrow ledge extending the full
width transversely forms the posterior base of the tooth. Toward the
outer side the surface of this base as well as that on the lower flank of the
protoconid immediately adjacent are worn, due to occlusion with an upper
tooth. Both P3 and P4 are shorter and wider than the comparable teeth
in 0. carteri.
M1 and M2 are likewise shorter and wider than in the latter species. In
at least one specimen, No. 1390, the basins of the talonids of the anterior
molars appear to be shallower than those of the Bridger species. The
anterior molars show the characteristic widening of the talonid region
seen in Omomys. In Ml (see figure of paratype, plate 1, Fig. 3a) the para-
conid is well developed, and the trigonid region resembles that in the geno-
type of Omomys.
DESCRIPTION OF PLATE 1
Chumashius balchi, n. gen. and n. sp.
Figures 1 and la, type specimen, No. 1391, left ramus with P3-M3 and alveoli for C
and P2, lateral and superior views; figures 2 and 2a, referred specimen, No. 1393, lat-
eral and superior views; figures 3, 3a and 3b, paratype, No. 1392, lateral, superior and
inner views, respectively: figure 4, paratype, No. 1394, maxillary fragment with M2
and M3, occlusal view. All figures X 4.
California Institute of Technology Collection. Sespe Upper Eocene, California.
VOL. 19, 1933 957
In the second lower molar the paraconid is not so well defined as in MT
and is also more reduced. The paraconid is even more reduced or is ves-
tigial in M3. Thus in the lower molars the trigonid region becomes progres-
sively smaller and the greater fore and aft narrowing of this area, as one
proceeds from the first to the last tooth, is particularly striking (Figs.
la, 2a and 3a). A similar progressive reduction of the paraconid in the
molars occurs in Hemiacodon, according to Matthew. In the characters
noted Chumashius balchi differs from Omomys carteri and is more advanced
than this type. A closer approach to our form appears to be made by
specimens described by Wortman and referred to the species Euryacodon
lepidus.
M3 in the Simi form is distinctly narrower transversely than either M2
or Mi and there is likewise less widening of the talonid region. No inner
cusp is present on the talonid and the inner rim swings backward to form the
posterior rim of the posterior lobe. The posterior rim is worn in No. 1393
and in No. 1391 and there is no clear indication of a hypoconulid. In
No. 1392, however, the faintly scalloped inner rim merges posteriorly with
a worn surface marking the presence of a hypoconulid. Wortman has
pointed out that in the third lower molar of the jaw referred to Euryacodon
lepidus the crown is narrower than in Omomys and differs also from that in
the latter in absence of distinct pointed cusps in the talonid region.
The discrepancy in size between M3 and the anterior molars is not so
evident in the referred specimen, No. 1393, as in the type and paratype of
C. balchi. Unfortunately, the last molar is lacking in the second referred
specimen, No. 1390.
In the second upper molar of the paratype, No. 1394, a well defined cingu-
lum is present on the anterior and posterior sides of the tooth and also where
it is preserved along the inner side. A portion of the cingulum on the inner
side has been broken away, but sufficient of it remains to indicate that an
antero-internal cuspule, such as characterizes Euryacodon, was not present.
The intermediate cuspules are low and not very distinct.
M3 is considerably more reduced in transverse diameter than the com-
parable tooth in Omomys or in Euryacodon. The tooth is broader inter-
nally than that ofE. lepidus. The anterior intermediate cuspule is vestigial.
The enamel surfaces of both upper teeth are smooth.
Relationships.-In two primitive characters, namely, the sutural separa-
tion of the mandibular rami at the symphysis and the hook-like angular
process, Chumashius differs from the modern tarsier. These characters
have been noted by Gregory4 as also distinguishing the earlier species of
Notharctus. In contrast to the primitive features and small size of the Simi
form, Chumashius is more advanced than Tarsius in tendency to reduce the
metaconid in P4, reduction in size of paraconid in the posterior lower molars
with vestigial character of this cusp in M3, and in reduction in size of the
GEOLOGY: C. STOCK958 Psoc. N. A. S.
MATHEMATICS: J. L. WALSH
last upper and lower molars. Chumashius balchi cannot, therefore, be
regarded as occurring in the direct line of development leading upward to
the Recent tarsier.
In lower dental formula Chumashius exhibits a closer relationship to
Omomys and Hemi4codon than to Anaptomorphus and Tetonius. The
character of the lower posterior premolars in Uintanius suffice to remove
this Bridger genus from any close relationship with the Simi form. In addi-
tion to the presence of a comparable number of lower teeth the structural
details of the dentition, in so far as these are known, point also to a kinship
between Chumashius and that division of the Anaptomorphidae including
Omomys and Hemiacodon. The characters of the Simi genus suggest a de-
velopment from those of an antecedent form like Omonys or Hemiacodon.
Possibly Euryacodon is also situated close to the stem form from which
Chumashius has evolved. No previously described tarsiid from the North
American Eocene has been found in association with a fauna as advanced
as that occurring with Chumashius balchi at Locality 150 in the Sespe
deposits of the Simi Valley region, California.6
1 Wortman, J. L., Amer. Jour. Sc., 15-17 (1903-1904).
2 Matthew, W. D., Bull. Amer. Mus. Nat. Hist., 34,445-465 (1915).
3 Gregory, W. K., Mem. Amer. Mus., n. s., 3, pt. 2 (1920).
" Gregory, W. K., Bull. Geol. Soc. Amer., 26, 419-446 (1915).
6 Stock, C., Proc. Nat. A cad. Sci., 18, 518-523 (1932); 19, 434-440, 481-486, 762-
767 (1933).
NOTE ON POLYNOMIAL INTERPOLATION TO ANALYTIC
FUNCTIONS
By J. L. WALSH
DEPARTMENT OF MATHEMATICS, HARVARD UNIVERSITY
Communicated October 10, 1933
Let C be a Jordan curve of the z-plane, and let the function w = +(z)
map the exterior of C onto the exterior of the unit circle IwI = 1 so that the
points at infinity correspond to each other. Let C, denote generically the
curve I (z) = p > 1 exterior to C.
If the function f(z) is single-valued and analytic interior to C, but has a
singularity on Cp, then any sequence of polynomials pn(z) of respective de-
grees n is said to converge to f(z) on C with the greatest geometric degree of
convergence provided for every R < p there existsM dependent on R but not
on n or z such that we have
if(z) - p.(z)j mR' z on C. (1)
VOL. 19, 1933 959


An Eocene primate from California

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An Eocene primate from California

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