evergreen tree and shrubby kinds. _Etym._, [Greek: melas], _melas_,
black, and [Greek: stoma], _stoma_, mouth; because the fruit of one
of these species stains the lips.

MESOTYPE. A simple mineral, white, and needle-shaped, one of the
Zeolite family, frequently met with in the Trap-rocks.

METAMORPHIC ROCKS. A stratified division of hypogene rocks, highly
crystalline, such as gneiss and mica-schist, and so named because
they have been _altered_ by plutonic action. _Etym._, [Greek: meta],
_meta_, trans, and [Greek: morphe], _morphe_, form.

MICA. A simple mineral, having a shining silvery surface, and
capable of being split into very thin elastic leaves or scales. It
is often called _talc_ in common life; but mineralogists apply the
term talc to a different mineral. The brilliant scales in granite
are mica. _Etym._, _mico_, to shine.

MICA-SLATE, MICA-SCHIST, MICACEOUS SCHISTUS. One of the metamorphic
or crystalline stratified rocks of the hypogene class, which is
characterized by being composed of a large proportion of mica united
with quartz.

MIOCENE. A division of tertiary strata intervening between the
Eocene and Pliocene formations; so called, because a minority of its
fossil shells are referable to living species. _Etym._, [Greek:
meion], _meion_, less, and [Greek: kainos], _kainos_, recent.

MOLASSE. A provincial name for a soft green sandstone, associated
with marl and conglomerates, belonging to the Miocene Tertiary
Period, extensively developed in the lower country of Switzerland.
_Etym._, French, _molle_, soft.

MOLLUSCA, MOLLUSCOUS ANIMALS. Animals, such as shell-fish, which,
being devoid of bones, have soft bodies. _Etym._, _mollis_, soft.

MONAD. The smallest of visible animalcules, spoken of by Buffon and
his followers as constituting the elementary molecules of organic
beings.

MONITOR. An animal of the saurian or lizard tribe, species of which
are found in both the fossil and recent state.

MONOCOTYLEDONOUS. A grand division of the vegetable kingdom
(including palms, grasses, Lilaceae, &c.), founded on the plant
having only one _cotyledon_, or seed-lobe. _Etym._, [Greek: monos],
_monos_, single.

MORAINE, a Swiss term for the dabris of rocks brought into valleys
by glaciers. See p. 228.

MOSCHUS. A quadruped resembling the chamois or mountain goat, from