INSECTA (Lat. _inseco_, I cut into). The cla.s.s of articulate animals commonly known as Insects.

INSECTIVORA (Lat. _insectum_, an insect; _voro_, I devour). An order of Mammals.

INSECTIVOROUS. Living upon Insects.

INSESSORES (Lat. _insedeo_, I sit upon). The order of the Perching Birds, often called _Pa.s.seres_.

INTERAMBULACRA. The rows of plates in an _Echinoid_ which are not perforated for the emission of the "tube-feet."

INTERMMAXILLae or PRaeMAXILLae. The two bones which are situated between the two superior maxillae in _Vertebrata_. In man, and some monkeys, the praemaxillae anchylose with the maxillae, so as to be irrecognisable in the adult.

INVERTEBRATA (Lat. _in_, without; _vertebra_, a bone of the back).

Animals without a spinal column or backbone.

ISOPODA. (Gr. _isos_, equal; _podes_, feet). An order of _Crustacea_ in which the feet are like one another and equal.

KAINOZOIC (Gr. _kainos_, recent; _zoe_, life). The Tertiary period in Geology comprising those formations in which the organic remains approximate more or less closely to the existing fauna and flora.

LABYRINTHODONTIA (Gr. _laburinthos_, a labyrinth; _odous_, tooth).

An extinct order of _Amphibia_, so called from the complex microscopic structure of the teeth.

LACERTILIA (Lat. _lacerta_, a lizard). An order of _Reptilia_ comprising the Lizards and Slow-worms.

LAMELLIBRANCHIATA (Lat. _lamella_, a plate; Gr. _bragchia_, gill).

The cla.s.s of _Mollusca_ comprising the ordinary bivalves, characterised by the possession of lamellar gills.

LEPIDODENDRON (Gr. _lepis_, a scale; _dendron_, a tree). A genus of extinct plants, so named from the scale-like scars upon the stem left by the falling off of the leaves.

LEPIDOPTERA (Gr. _lepis_, a scale; _pteron_, a wing). An order of Insects, comprising b.u.t.terflies and Moths, characterised by possessing four wings which are usually covered with minute scales.

LEPIDOSIREN (Gr. _lepis_, a scale; _seiren_, a siren--the generic name of the Mud-eel or _Siren lacertina_). A genus of Dipnoous fishes, comprising the "Mud-fishes."

LEPIDOSTROBUS (Gr. _lepis_, a scale; _strobilos_, a fir-cone).

A genus founded on the cones of _Lepidodendron_.

LEPTaeNA (Gr. _leptos_. slender). A genus of Brachiopods.

LINGULA (Lat. _lingula_, a little tongue). A genus of Brachiopods.

LYCOPODIACEae (Gr. _lupos_, a wolf; _pous_, foot). The group of Cryptogamic plants generally known as "Club-mosses."

MACHaeRACANTHUS (Gr. _machaira_, a sabre; _acantha_, thorn or spine).

An extinct genus of Fishes.

MACHAIRODUS (Gr. _machaira_, a sabre; _odous_, tooth). An extinct genus of Carnivora.

MACROTHERIUM (Gr. _makros_, long; _therion_. beast). An extinct genus of Edentata.

MACRURA (Gr. _makros_, long; _oura_, tail). A tribe of Decapod _Crustaceans_ with long tails (e.g., the Lobster, Shrimp, &c.)

MAMMALIA (Lat. _mamma_, the breast). The cla.s.s of Vertebrate animals which suckle their young.

MANDIBLE (Lat. _mandibulum_, a jaw). The upper pair of jaws in Insects; also applied to one of the pairs of jaws in _Crustacea_ and Spiders, to the beak of Cephalopods, the lower jaw of Vertebrates, &c.

MANTLE. The external integument of most of the Mollusca, which is largely developed, and forms a cloak in which the viscera are protected. Technically called the "pallium."

Ma.n.u.s (Lat. the hand). The hand of the higher Vertebrates.

MARSIPOBRANCHII (Gr. _marsipos_, a pouch; _bragchia_, gill).

The order of Fishes comprising the Hag-fishes and Lampreys, with pouch-like gills.

MARSUPIALIA (Lat. _marsupium_, a pouch). An order of Mammals in which the females mostly have an abdominal pouch in which the young are carried.

MASTODON (Gr. _mastos_, nipple; _odous_, tooth). An extinct genus of Elephantine Mammals.

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 Tria.s.sic 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 Sh.e.l.l-fish proper, the _Polyzoa_, the _Tunicata_, and the Lamp-sh.e.l.ls; 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 cla.s.s 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.