An introduction to the study of mammals living and extinctLydekker, Richard
Science
An introduction to the study of mammals living and extinct
Lydekker, Richard
Mammals
Dentition: _i_ ⁴⁻⁵⁄₃, _c_ ¹⁄₁, _p_ ³⁄₃, _m_ ⁴⁄₄; total 46 or 48. Upper
incisors small, with short broad crowns. Lower incisors moderate, narrow,
proclivous. Canines well developed. Premolars compressed, pointed. Molars
with quadrate tuberculated crowns. Fourth premolar preceded by a small
molariform tooth, which remains in place until the animal is nearly full
grown. Fore feet with two or three of the middle toes of nearly equal
size, and provided with strong, sharp, slightly curved claws; the other
toes rudimentary. Hind feet long and narrow; the hallux rudimentary or
absent; the second and third toes very slender, and united in a common
integument; the fourth very large, with a stout elongated conical claw;
the fifth smaller than the fourth (see Fig. 43). The ungual phalanges of
the large toes of both feet cleft at their extremities (as in _Manis_
among the Edentata, but in no other Marsupials). Head elongated. Muzzle
long, narrow, and pointed. Stomach simple. Cæcum of moderate size.
Pouch complete, opening backwards. Alone among Marsupials they have no
clavicles.
The _Peramelidæ_ form a very distinct family, in some respects
intermediate between the sarcophagous _Dasyuridæ_ and the phytophagous
_Macropodidæ_. In dentition they resemble the former, but they agree
with the latter in the peculiar structure of the hind feet. In the
construction of the fore feet they differ from all other Marsupials.
The Bandicoots, as these Marsupials are popularly termed, are of
fossorial habits, and subsist either on an insectivorous or omnivorous
diet. It has been generally considered that their syndactylous feet
indicate direct affinity with the Diprotodonts, but owing to the
essentially Polyprotodont character of the organisation—which extends
even to their carpal and tarsal bones—Thomas dissents from this view, and
concludes that their syndactylism is an independently acquired character,
and that they are really a direct offshoot from the _Dasyuridæ_. Some
individuals are remarkable for the presence of a longitudinal groove in
the root of the canines, by which feature they approximate to some of the
Mesozoic Polyprotodont forms. They may be divided into three genera.
[Illustration: FIG. 42.—_Perameles gunni._ From Gould.]
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