In the true bandicoots of the genus _Perameles_ (fig. 5) the fore-feet
have the three middle toes well developed, the third slightly larger
than the second, the fourth somewhat shorter, provided with long,
strong, slightly curved, pointed claws. First and fifth toes very
short and without claws. Hind feet with one or two phalanges, in the
first toe forming a distinct tubercle visible externally; the second
and third toes very slender, of equal length, joined as far as the
terminal phalange, but with distinct claws; the fifth intermediate in
length between these and the largely developed fourth toe. Ears of
moderate or small size, ovate, pointed. Tail rather short, clothed
with short depressed hairs. Fur short and harsh. Pouch opening
backwards. Vertebrae: C. 7, D. 13, L. 6, S. 1, Ca. 17. (see
BANDICOOT.)
[Illustration: FIG. 6.--Skeleton of Hind Foot of _Choeropus
castanotis_.
c, calcanium; a, astralagus; cb, cuboid; n. navicular; c³,
ectocuneiform; II. and III. the conjoined second and third digits; IV.
the large and only functional digit; V. the rudimentary fifth digit.]
The rabbit-bandicoot, _Peragale_ (or _Thylacomys_) represents a genus
in which the cheek-teeth are curved, with longer crowns and shorter
roots than in the last. Hind extremities proportionally longer with
inner toe represented only by a small metatarsal bone. Muzzle much
elongated and narrow. Fur soft and silky. Ears very large, long and
pointed. Tail long, its apical half-clothed on the dorsal surface with
long hairs. Pouch opening forwards. Vertebrae: C. 7, D. 13, L. 6, S.
2, Ca. 23.
The one species, from Western Australia, is the largest member of the
family, being about the size of a rabbit, to which it bears sufficient
superficial resemblance to have acquired the name of "native rabbit"
from the colonists. It burrows in the ground, but in other respects
resembles bandicoots in habits.
In the pig-footed bandicoot (_Choeropus castanotis_) the dentition
generally resembles that of _Perameles_, but the canines are less
developed, and in the upper jaw two-rooted. Limbs very slender;
posterior nearly twice the length of the anterior. Fore feet with the
functional toes reduced to two, the second and third, of equal length,
with closely united metacarpals and short, sharp, slightly curved,
compressed claws. First toe represented by a minute rudiment of a
metacarpal bone; the fourth by a metacarpal and two small phalanges
without a claw, and not reaching the middle of the metacarpal of the
third; fifth entirely absent. Hind foot long and narrow, mainly
composed of the strongly developed fourth toe, terminating in a
conical pointed nail, with a strong pad behind it; the first toe
represented by a rudimentary metatarsal; the remaining toes completely
developed, with claws, but exceedingly slender; the united second and
third reaching a little way beyond the metatarso-phalangeal
articulation of the fourth; the fifth somewhat shorter. Tail not quite
so long as the body, and covered with short hairs. Ears large and
pointed, and folded down when the animal is at rest. Fur soft and
loose. Pouch opening backwards. Vertebrae: C. 7, D. 13, L. 6, S. 1,
Ca. 20.
The only species of this genus is about the size of a small rat, found
in the interior of Australia. Its general habits and food appear to
resemble those of other bandicoots. A separate family, _Notoryctidae_,
is represented by the marsupial mole (_Notoryctes typhlops_), of the
deserts of south Central Australia, a silky, golden-haired, burrowing
creature, with a curious leathery muzzle, and a short, naked stumpy
tail. The limbs are five-toed, with the third and fourth toes of the
front pair armed with enormous digging claws; there are no external
ear-conchs; and the dentition includes four pairs of upper, and three
of lower, incisors, and distinctly tritubercular cheek-teeth. The
small pouch, supported by the usual epipubic bones, opens backwards.
In correlation with its burrowing habits, some of the vertebrae of the
neck and of the loins are respectively welded together. The eyes have
degenerated to a greater extent than those of any other burrowing
mammal, the retina being reduced to a mass of simple cells, and the
cornea and sclerotic ("white") to a pear-shaped fibrous capsule
enclosing a ball of pigment. The reason for this extreme degeneration
is probably to be found in the sandy nature of the soil in which the
creature burrows, a substance which would evidently irritate and
inflame any functional remnant of an eye. The portion of the lachrymal
duct communicating with the cavity of the nose has, on the other hand,
been abnormally developed, apparently for the purpose of cleansing
that chamber from particles of sand which may obtain an entrance while
the animal is burrowing. (See MARSUPIAL MOLE.)
[Illustration: From Gould.