Fig. 120.—Hedgehog.
Photo: Berridge.
The Insectivora are by many of their features recognisable as low types of placental mammals. They have a primitive type of skull, and frequently show a rather marked similarity between the several classes of teeth. The brain is relatively ill-developed, reminding one rather strongly of the Marsupials, and the hemispheres show little if any tendency to develop those wrinkles and fissures which always accompany the higher type of intelligence. Probably the most primitive member of the whole group is the Centetes from Madagascar, shown in Fig. 119. The hedgehog and the shrews are its best-known examples. An interesting point regarding the hedgehog is that, like few other mammals, it has persisted almost unchanged from early tertiary times. It is thus to be regarded as a very antique type, not only in its main features, but in its details.
Fig. 121.—Vampires.
Fig. 122.—Porpoises.
Fig. 123.—Sea Lions.