|Fig. 110. - The skeleton of a Catarrhine Monkey (Cercopithecus).
1. The Arctopithecini
, or Marmosets, are small, thickly
furred, long-tailed, habitually quadrupedal. Squirrel-like animals,
which are found only in South America. None of them
are provided with cheek-pouches, nor possess bare and callous
patches of integument over the ischia. The ears are large
and hairy, and the nose is flat and broad as in the Platyrrhini.
The fore-limbs are shorter than the hind-hmbs. The pollex is not
opposable, nor susceptible of extensive abduction
from the other digits, which it resembles in being provided
with a sharp, curved claw. The manus, consequently, is a
mere paw, and the term "hand" is not applicable to it.
The hallux of the foot is very small, and is provided with a
flat nail. The nails of all the other digits of the pes are falcate.
The plantar surface is very long, and the digits are very
short. It follows from these facts that the term "quadrumarnous"
is not applicable, in any sense, to the Marmosets.
The skull is remarkable for the smooth and rounded surface
and relatively large size of the brain-case. Although the
orbits are large, the brow ridges are inconspicuous, and the
occipital region of the skull projects so far backward that the
occipital foramen may lie completely upon the under surface
of the skull, toward the junction of its middle and posterior
thirds; and have its plane almost horizontal, when the face
looks forward. The orbit is almost completely shut off from
the temporal fossa by bone.
The hyoid resembles that of the Lemurs, its body being
narrow and much arched from side to side, while the anterior
cornua are strong.
There are usually nineteen dorso-lumbar vertebra, and the
transverse processes of the atlas are somewhat broad and flattened.
The dental formula is i.
the number of the teeth is the same as in man and the Catarrhini
but in the number of the premolars and molars the Arctopithecini
differ from both the Catarrhini
and the Platyrrhini
having one premolar more than the former and one true
molar fewer than the latter. In Hapale
, the lower incisors
are proclivous; and the canines are approximate to them, and
similarly inclined, as in the Lemurs.
Although the manus is a paw and the pollex is not opposable,
this digit has its proper abductor, adductor,
and short flexors. The existence of a proper opponens
pollex is doubtful, but there is an opponens minimi digiti.
The flexor longus
is completely united with the flexor profundus digitorum,
but the tendon for the pollex comes off on the
radial side instead of on the ulnar side, as it does in some of
the higher Simiadae
. The extensor secundi internodii pollicis
is united with the extensor indicis
, and the extensor minimi
gives off slips to the third, fourth, and fifth digits, so that
there is a complete set of deep extensors. The four dorsal and
three palmar interossei
are not distinctly subdivided, but they
send slips to the extensor tendons.
There are four perenoei. p. longus, p. brevis, p. quarti,
and p. quinti digiti.
The flexor brevis dlgitorum
of the pes has
one division which arises from the calcaneum and goes to the
second digit; the other three heads arise from the tendons of
the flexor perforans.
The flexor accessorius
the whole of the long flexor tendons of the hallux, the flexor
supplying the perforating tendons of the
second and fifth digits; while the flexor hallucis longus
off the corresponding tendons of the third and fourth digits.
in the pes, appear to be represented only by
the pairs of muscles which act as short flexors of the basal
phalanges, and these lie altogether upon the plantar aspect of
the five metatarsal bones. The hallux has no special adductor,
nor is there any transversus pedis.
In fact, the pes is almost
as completely a "paw" as is the manus.
The brain has long and relatively large cerebral hemispheres,
the posterior lobes of which project far beyond the
cerebellum, and thus completely hide it, in the upper view of
the brain. The external surfaces of the hemispheres are almost
smooth, but the Sylvian fissure is well marked, and there
is a trace of that of Rolando. On the inner face of each hemisphere,
the calcarine fissure is deep and gives rise to a wellmarked hippocampus minor
within the posterior cornu of the
lateral ventricle. The corpus callosum
has about a third the
length of the hemispheres. The septum lucidum is very thick,
and the precommissural fibres abundant. The vermis
beyond the lateral lobes of the cerebellum, and the flocculi