e sections,
which are _Sciuromorpha_, or Squirrel-like Rodents, _Myomorpha_ or
Rat-like Rodents, and _Hystricomorpha_, or Porcupine-like Rodents.
It would perhaps render it clear to the reader were I to tabulate
the differences chiefly noticeable in these three sections:--

SECTION I.--SCIUROMORPHA, OR SQUIRREL-LIKE RODENTS.

Molar dentition 4--4/4--4 or 5--5/4--4. In the latter case the
foremost upper molar is small; the fibula is distinct, and never
united, except in some cases where it is attached to the extremity
of the tibia; the zygomatic arch is formed chiefly by the malar, which
is not supported beneath by a continuation of the zygomatic process
of the maxillary; collar-bones perfect; upper lip cleft; the muffle
small and naked; tail cylindrical and hairy (except in _Castoridae_).
Five families.

SECTION II.--MYOMORPHA, OR RAT-LIKE RODENTS.

Molar dentition from 3--3/3--3 to 6--6/6--6, the former being the
usual number; the tibia and fibula are united for at least a third
of their length. The zygomatic arch is slender, and the malar process
rarely extends so far forward as in the preceding section, and is
generally supported below by a continuation of the maxillary
zygomatic process; collar bones are perfect (except in
_Lophiomyidae_); upper lip and muffle as in the last; tail
cylindrical, sometimes hairy, but commonly covered with scales
arranged in rings. Seven families.

SECTION III.--HYSTRICOMORPHA, OR PORCUPINE-LIKE RODENTS.

With one exception (_Ctenodactylus_) have four molars in each upper
and lower jaw; the tibia and fibula are distinct in young and old;
the zygomatic arch is stout, and the malar does not advance far
forward, nor is it supported by the maxillary zygomatic process;
collar-bones perfect in some; the upper lip is rarely cleft; the
muffle clad with fine hair; tail hairy, sub-naked or scaly.

SECTION I.--SCIUROMORPHA.

Contains the following families, those that are not Indian being in
italics;--

(1) _Anomaluridae_; (2) Sciuridae; (3) _Ischyromyidae_, a fossil
genus; (4) _Haplodontidae_; (5) _Castoridae_.

The Anomalures are African animals resembling our flying squirrels,
to which they were at first thought to belong, but were separated
and named by Mr. Waterhouse, the chief peculiarity being the tail,
which is long and well covered with hair, though not bushy as in the
squirrels, and which has, at its basal portion, a double series of
projecting horny scales, which probabl