a in part, but the majority
to the American continent, chiefly South America.

I give the general characteristics of the section as laid down by
Mr. Alston:--

"One premolar above and below (except in _Ctenodactylus_); grinding
teeth rooted or rootless, not tuberculate; frontals with no distinct
post-orbital processes (except in _Chaetomys_); infra-orbital
opening large, sub-triangular, or oval; zygomatic arch
proportionately stout; molar not advancing far forward, (except in
_Ctenodactylinae_ and _Chinchillidae_) and not supported below by
a continuation of the maxillary zygomatic process; incisive foramina
small; foramina in the base of skull proportionally large; an
inter-pterygoid fissure; mandible with its angular portion
springing from the _outer side_ of the bony covering of the lower
incisor, triangular, usually pointed behind; coronoid process small,
and condyle low; clavicles perfect or imperfect; fibula persistent
as a distinct bone throughout life; upper lip rarely cleft; muffle
clad with fine hairs; nostrils pointed above, sigmoid or linear; ears
usually emarginate behind; tail hairy, sub-naked, or scaly."--'P.
Z. S.,' 1876, p. 90.

As I have said before, we have only to do with the _Hystricidae_ or
Porcupines, but many of the others are familiar by name. Of the
_Octodontidae_ the best known is the coypu of the Andes, one of the
largest of the rodents, and the ground-rat or ground-pig of western
and southern Africa. The chinchilla, which is the typical form of
the third family, is known to all, especially ladies, from its
delicate soft fur. The agouti of South America is the representative
of the _Dasyproctidae_. The family _Dinomyidae_ consists of one
animal only, _Dinomys Branickii_; the only known example of which
was obtained in Peru on the Montana de Vitoc. It was found walking
about in a yard at daybreak, and showed so little fear of man that
it suffered itself to be killed by the stroke of a sword. It is a
pity no one was sensible enough to try and take it alive. As yet
nothing is known of its habits. Of the last family, _Caviidae_, the
cavy and the capybara are well known to travellers in South America,
and the common guinea pig is familiar to us all.

FAMILY HYSTRICIDAE--THE PORCUPINES.

In this family the hairs of the body are more or less converted into
spines or quills; the form of the skull is peculiar, being ovate,
often greatly inflated with air cavities in the bones; the facial
por