Macigno. In Italy this term has been applied to a siliceous sandstone sometimes containing calcareous grains, mica, &c.
Madrepore. A genus of corals, but generally applied to all the corals distinguished by superficial star-shaped cavities. There are several fossil species.
Magnesian Limestone. An extensive series of beds, the geological position of which is immediately above the Coal Measures; so called, because the limestone, the principal member of the series, contains much of the earth magnesia as a constituent part.
Mammiferous. Mammifers. Animals which give suck to their young. To this class all the warm-blooded quadrupeds, and the Cetacea, or whales, belong. Etym., mamma, a breast, fero, to bear.
Mammillary. A surface which is studded over with rounded projections. Etym., mammilla, a little breast or pap.
Mammoth. An extinct species of the elephant (E. primigenius), of which the fossil bones are frequently met with in various countries. The name is of Tartar origin, and is used in Siberia for animals that burrow under ground.
Manati. One of the Cetacea, the sea-cow, or lamantine (Trichechus manatus, Lin.)
Marl. A mixture of clay and lime; usually soft, but sometimes hard, in which case it is called indurated marl.
Marsupial Animals. A tribe of quadrupeds having a sack or pouch under the belly, in which they carry their young. The kangaroo is a well-known example. Etym., marsupium, a purse.