CHAPTER XVI 
INSECTIVORA——CHIROPTERA 
Order XI. INSECTIVORA. 
Tue Insectivora’ are an order of mammals to which it is (to 
quote Professor Huxley) “exceedingly difficult to give a definition.” 
They are, however, none of them large animals, and most of them 
are nocturnal in habit—two circumstances which may have had 
something to do with their survival from past ages, as may have 
also their modification to so many and diverse modes of life ; 
for everything points to the antiquity of the group. They are, 
for instance, more or less plantigrade. The snout is generally 
long, and is often prolonged into a short proboscis.” There is 
a tendency for the teeth to be of a generalised type, and 
their number is often the typical mammalian forty-four. 
Moreover, trituberculate teeth, which are certainly an ancient 
form of tooth, are common; and indeed the Insectivora of the. 
southern regions of the globe, e.g. Centetidae, Solenodontidae, and 
Chrysochloridae, have the most prevalent trituberculism, a fact 
which is of importance in considering the age of the animal life 
of these regions of the world. The limbs are, as a rule, provided 
with five digits.) The hemispheres of the brain are usually 
smooth, and do not extend over the cerebellum. The palate 
is often fenestrate as in the Marsupials, and as in that group 
the lower jaw is sometimes inflected. But the latter character 
also occurs In the Sea-lions and elsewhere. Clavicles are present, 
as a rule, but not in Potamogale. 
1 See especially Dobson, 4 Monograph of the Insectivora, London, 1886-90. 
2 Even in the Otter-like Potamogale the upper jaw, though broad and flat, 
projects considerably beyond the lower. 
