_Opolemur_, J. E. Gray, P. Z. S., 1872, p. 853.
The term _Opolemur_, by which this genus is designated, is not altogether
appropriate, and is, indeed, even somewhat misleading. It was applied in
the first instance to the typical species on account of the thickened base
of its tail, which in the type-specimen was a very conspicuous character.
The deposit of fat by which this thickening was caused was not then known
to be merely transitory--a store of food collected at the base of the tail
and on other parts of the body, to supply the needs of the animal during
the arid and foodless season, when it retires into a state of torpidity. It
is now known that {62}other species of this sub-family (as we have seen
above in the case of the Mouse-Lemurs), which are generically distinct from
_Opolemur_, share this peculiarity.
The two species included in this genus are intermediate between the
Mouse-Lemurs and the Dwarf-Lemurs, and are really more nearly related to
the former than to the latter. The skull is flat and depressed as in
_Chirogale_, and the brain-case small and almost vertical behind. The
posterior foramina in the palate are small. In respect to their dentition,
the cusps of the upper molars are blunter and shorter than in the
Mouse-Lemurs, but less so than among the Dwarf-Lemurs; the hind inner cusps
of the anterior and median molars are large, and the ridge from the inner
cusp is less intimately joined to the two outer cusps than in the
Dwarf-Lemurs.