Măm'mal, n.

n.; pl. MĂM'MALS. [Lat. mammalis, belonging to the breast, from mamma, the breast or pap; Fr. mammal.] (Zoöl.) An animal of the highest class of vertebrates (see ANIMAL KINGDOM), characterized by the female suckling its young.

☞ While far the larger part of mammals are strictly viviparous, one of the grand divisions consists of semi-viviparous species, like the opossum and kangaroo, which produce their young while still in an embryonic condition. The former are placental mammals, and the latter non-placental. The following are the principal subdivisions of mammals:—

I. ARCHONTS. This includes man alone, distinguished from other mammals not only by his spiritual nature, but also structurally in the extreme degree to which the system is made subservient directly to the purposes of the head, the fore limbs being removed from the locomotive series, their position in all other mammals, to the cephalic series, the whole body being thereby made a part of the head-extremity.

II. MEGASTHENES. These have fundamentally a large life-system, and include the larger and more powerful mammals, the mean size of which is lineally about four times that of the microsthenes. The orders are as follows:—1. Quadrumanes. These have the four limbs terminating in more or less perfect hands, as the monkeys. 2. Carnivores. These have the four limbs furnished with strong claws, and feed on flesh, as the lion, dog, bear, seal. 3. Herbivores, or Ungulates. These have the four limbs furnished with hoofs, and have trifurcating teeth, as the elephant, horse, ox, deer, tapir. 4. Mutilates. These have two or four fin-like appendages in place of feet, and are aquatic in life, as the whale, dolphin, and other cetaceans, and the lamantin and dugong.

III. MICROSTHENES. These have fundamentally a small life-system, and include the small mammals. The orders which follow constitute a series in exact parallelism with that of the megasthenes; the cheiropters, or bats, being closely related to the quadrumanes (the two groups following one another in Cuvier's system), and similarly the insectivores being analogues of the carnivores, the rodents of the herbivores, and the edentates of the mutilates. 1. Cheiropters, or Bats. These have pectoral mammæ, and the fore limbs extend to form a wing. 2. Insectivores. These have the body covered with hair, the legs short, the feet furnished with claws, and the teeth partly tuberculated, as the moles, shrews, hedge-hogs. 3. Rodents. These have the body covered with hair, and the legs short, and are furnished with at least two incisor teeth in each jaw, which are rootless and constantly growing, as the mouse, squirrel, porcupine. 4. Edentates, or Brutes. These have the body covered either with hair or with bony scales or plates (in the last, as in some other characteristics, approaching reptiles), are furnished with long claws, and are without incisor teeth, as the sloth, armadillo, ant-eater.

IV. OÖTICOIDS, or semi-oviparous mammals. Of these the larger part are marsupials, or have a pouch for carrying their immature young, as the opossum and kangaroo. A few fail of the pouch, though having the supporting marsupial bones, as the ornithorhynchus, and other monotremes. Dana.