The skull has strong temporal ridges, which form a sagittal crest, and the arch of the zygoma is well grown. The animal has a longer facial part of the skull and a smaller brain-case than the other Dasyures, and the brain has large olfactory or front lobes. The cerebral hemispheres are small, and there are no convolutions. This is essentially a North American animal, and is found from Mexico to the Southern States inclusive. The female brings forth from twelve to sixteen young at a time, and her nest, which is formed of dry grass, is usually at the root of a tree or bush. When first born, the young are said not to be more than a grain in weight, and blind, naked, and shapeless. They find the teats in the mother’s pouch, unless she places them on to them with her mouth, and they cling on so as not to be separated except by violence. In about five days, so rapid is their growth, they have reached the size of a Mouse, and all their parts are developed. They then leave the pouch, and return to suckle and when danger appears. During this time the female shows great attachment to her young; and Mr. Waterhouse, from whose work these descriptions are taken, states that she will suffer any torture rather than permit the pouch to be opened. [Illustration: CRAB-EATING OPOSSUM.] AZARA’S OPOSSUM.[124] This is a smaller animal than the common or Virginian Opossum, but its tail is long in proportion to its body. It is the South American representative of its larger fellow species, and is found over a very wide extent of country. It was noticed by the celebrated naturalist D’Azara in Paraguay; Mr. Darwin found it at Maldonado, La Plata; and specimens have been obtained from the Brazils, Santa Fé de Bogota, and Bolivia. This is because it is not entirely a forest animal, but is found occasionally in the open country. It may be distinguished from the common Opossum by three distinct black marks on its head, by its large tail, one-third of which is covered with fur like that on the body. The rest of this important member is scaly, with small hairs springing from between, the scales being black in the second third, and white at the tip in colour. The habits of this Opossum are nocturnal, and it lies concealed by day in burrows in the ground or in thickets. At night it climbs trees to feed upon fruits and birds’ eggs. It will chase and catch sleeping birds, and suck their blood like a Weasel. THE CRAB-EATING OPOSSUM.[125] A small Opossum, with a long black tail tipped with white, and a dull-coloured fur to its body, lives in Brazil and Guiana, and has a very omnivorous disposition. Preferring swampy situations, it lives mostly on the trees, hunts small birds and insects, and even catches a reptile now and then, but its fondness for the Crustacea of the swamps is proverbial, and hence its name of Crab-eater.