MEGALONYX (Gr. megas, great; onux, nail).  An extinct genus of Edentate Mammals.

MEGALOSAURUS (Gr. megas, great; saura, lizard).  A genus of Deinosaurian Reptiles.

MEGATHERIUM (Gr. megas, great; therion, beast).  An extinct genus of Edentata.

MESOZOIC (Gr. mesos, middle; and zoe, life).  The Secondary period in Geology.

MICROLESTES (Gr. mikros, little; lestes, thief).  An extinct genus of Triassic Mammals.

MILLEPORA (Lat. mille, one thousand; porus, a pore).  A genus of “Tabulate Corals.”

MIOCENE (Gr. meion, less; kainol, new).  The Middle Tertiary period.

MOLARS (Lat. mola, a mill).  The “grinders” in man, or the teeth in diphyodont Mammals which are not preceded by milk-teeth.

MOLLUSCA (Lat. mollis, soft).  The sub-kingdom which includes the Shell-fish proper, the Polyzoa, the Tunicata, and the Lamp-shells; so called from the generally soft nature of their bodies.

MOLLUSCOIDA (Mollusca; Gr. eidos, form).  The lower division of the Mollusca, comprising the Polyzoa, Tunicata, and Brachiopoda.

MONOGRAPTUS (Gr. monos, single; grapho, I write).  A genus of Graptolites.

MYLODON (Gr. mulos, a mill; odous, tooth).  An extinct genus of Edentate Mammals.

MYRIAPODA or MYRIOPODA (Gr. murios, ten thousand; podes, feet).  A class of Arthropoda comprising the Centipedes and their allies, characterised by their numerous feet.

NATATORES (Lat. nare, to swim).  The order of the Swimming Birds.

NATATORY (Lat. nare, to swim).  Formed for swimming.

NAUTILOID.  Resembling the shell of the Nautilus in shape.

NERVURES (Lat. nervus, a sinew).  The ribs which support the membranous wings of insects.

NEUROPTERA (Gr. neuron, a nerve; pteron, a wing).  An order of Insects characterised by four membranous wings with numerous reticulated nervures (e.g., Dragon-flies).

NEUROPTERIS (Gr. neuron, a nerve; pteris, a fern).  An extinct genus of Ferns.

NOTHOSAURUS (Gr. nothos, spurious; saura, lizard).  A genus of Plesiosaurian Reptiles.

NOTOCHORD (Gr. notos, back; chorde, string).  A cellular rod which is developed in the embryo of Vertebrates immediately beneath the spinal cord, and which is usually replaced in the adult by the vertebral column.  Often it is spoken of as the “chorda dorsalis.”

NUDIBRANCHIATA (Lat. nudus, naked; and Gr. bragchia, gill).  An order of the Gasteropoda in which the gills are naked.

NUMMULINA (Lat. nummus, a coin).  A genus of Foraminifera, comprising the coin-shaped “Nummulites.”