Contains the following families, those that are not Indian being in italics;—
(1) Anomaluridæ; (2) Sciuridæ; (3) Ischyromyidæ, a fossil genus; (4) Haplodontidæ; (5) Castoridæ.
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 probably help it in climbing trees. There are several other peculiarities, which I need not dwell on here, which have justified its separation from the true squirrels. The flying membrane, which is quite as large as that of the flying squirrels, extends from the elbow to the heel instead of from the wrist, and it is held out by a strong cartilaginous spur starting from the elbow.
Of the Sciuridæ we have many examples in India, which will be noticed further on.
The Ischyromyidæ is founded on a single North American fossil genus (Ischyromys typus), which is nearly allied to the Sciuridæ, but also shows some affinity to the beavers.
The Haplodontidæ is also an American family, founded on one genus, but an existing and not a fossil animal. The Haplodon rufus is a small burrowing rodent, valued by the Indians both for its flesh and its skin, of which from twenty to thirty are sewn together to form a robe; the teeth are rootless, simple, and prismatic, the surface of each being surrounded by a mere border of enamel.
The Castoridæ is the beaver family, which is also unknown in India. Unlike as this animal is externally to the squirrels, its anatomy warrants its position in the Sciuromorpha, otherwise one would feel inclined to include it in the next section.
We see that of the five families, of which this section is composed, only the second has its representatives in India.
This family contains the true squirrels, including the flying ones, and the marmots. The distinctive characteristics of the former are as follows: The gnawing teeth are smooth, compressed. The grinding teeth are 5—5/4—4 or 4—4/4—4; in the former case the first upper premolar is small, and sometimes deciduous; they are tubercular, at least in youth, and rooted. Skull with distinct post-orbital processes; infra-orbital opening small, usually placed in front of the maxillary zygomatic process; palate broad and flat; twelve or thirteen pairs of ribs; tail cylindrical and bushy; feet either pentadactylous or with a tubercle in place of a thumb on the fore-feet. Mostly quite arboreal.