OLDUVAI GORGE 199
depression for the superior sagittal sinus (which one
would expect to find near bregma). Internally, a groove
for a meningeal vessel could be for the anterior branch
of the middle meningeal of L side. In sum, this piece
may be a composite. In particular, the posterior frag-
ment of this smaller parietal, which is separated from
the rest by a strip of plaster, shows no continuity with
the anterior part. Furthermore, it may not be associ-
ated with the counterpart parietal.
Mandible and Lower Dentition. Judging from
completeness of L internal alveolar crest (it swings
completely around behind M2), and from apparent
absence (on underside) of crypt for M3, no M3 was
going to develop. This specimen was thus adult in
terms of tooth eruption.
Symphyseal region fairly intact. In profile, symph-
ysis vertical; from above, it appears as fairly gently
curved around front. Originally, tooth rows may have
been fairly divergent. Postincisal plane was probably
long, quite gently sloping. Relative to size of specimen,
bone of corpora quite thick b/l. Preserved L mental
foramen moderate in size; lies below and just behind
P1 root. Anterior root of ramus (on L) takes origin be-
low a broad septum between M1 and 2. Seen from
side, ramus would have masked most of M2. Anterior
edge of rising ramus is quite well separated internally
from buccal side of M2 (thus there is a reasonably de-
veloped mandibular gutter). Behind internal alveolar
crest surrounding back of M2 is an irregular hole of
uncertain origin. On L, alveolar resorption buccally
from P2 to M2.
Is and Cs unusual, especially in being still very
tall crowned (even though Is very worn). For their
height, Is quite narrow m/d. 11s narrower than 12s;
none excessively flared. Lingual surfaces on all Is
smooth, gently concave; lack lingual tubercles. I
roots thick b/l. Crushing gives erroneous impression
that Cs, especially on the L, are not fully erupted.
Both C roots stout; better-preserved LC root very
long. Both C roots closed off (hence no longer
erupting). Cs have slight buccal cingulids, and rela-
tively stout but not very tall distal margocristids.
Margocristids accentuated by creases on their mesial
sides. C crowns slightly exodaenodont; shorter lin-
gual surfaces are gently concave, not terminating in
distinct tubercles. In profile, mesial and distal edges
of Cs are rather vertical; mesial edge from apex is
short, gently sloping; distal edge is steeper, much
longer.
Pls slightly bulbous buccally; apex of proto-
conid slightly internally placed. On Pls there is a
slight swelling somewhat below and appressed to
protoconid; swelling fainter on L than R. Thick
cristid originates from swelling, runs down and dis-
tally around modest talonid basin, then courses up
side of protoconid. On the R (but not the L), small
thickening of enamel lies mesially at base of proto-
conid. On both Pls, a very shallow concavity lies on
mesiolingual side of crown. In outline, Pls some-
what teardrop shaped, tapering mesially and broad-
ening distally. P2 metaconid and protoconid well
developed and subequal in size; lie quite mesially on
crown and opposite each other. Mesial juncture of
metaconid and protoconid marked by a small fovea.
Tooth narrows somewhat behind protoconid and
metaconid. Thick cristid arcs distally from one cusp
apex to the other; encircles a deep but not very open
talonid basin. Buccal side of protoconid slightly
swollen; lingual side of metaconid more vertical.
Premolar roots broken inferiorly; were very long.
Ml hypoconulid and protoconid largest cusps;
remaining three cusps smaller and subequal in size.
Apices of hypoconulids lie in midline of crown.
Apices of protoconid and hypoconid slightly inter-
nally placed; those of metaconids and entoconids
more peripheral. Internal aspect of hypoconid ex-
tends lingually across midline of crown. Evidence of
small, wedge-shaped trigonid basin (or perhaps
paracristid; tooth heavily worn) intruding between
protoconid and metaconid. As seen on the L,
hypoconulid swells out distal margin of crown. Dis-
tal ends of Mls are not smoothly rounded; there is a
buccal "notch" between hypoconid and hypoconulid.
In outline, as judged from the L, M1 generally
ovoid. Preserved M2 long, relatively narrow; buccal
cusps slightly more internally placed than lingual
cusps (which are not quite peripheral). Talonid basin
long, deep, and trough-like. M2 metaconid and pro-
toconid similar in size, lie opposite one another; a
small mesial ledge intrudes between their bases.
Moderate metastylid closely appressed to metaconid.
Two small conulids lie distally at base of inner side
of metaconid. Entoconid small; lies slightly distal to
larger hypoconid. Very large hypoconulid twinned,
centrally placed. Smaller twinned part situated quite
far lingually (but not as far as entoconid). Larger
twinned section of hypoconulid extends from just
lingual to midline to a bit farther buccally. M1
mesial and distal roots not very divergent; even less