Page:Mammalia (Beddard).djvu/528



The 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.