AMPHITHERIUM (Gr. _amphi_, both; _therion_, beast). A genus of Jura.s.sic Mammals.

AMPHITRAGULUS (Gr. _amphi_, both; dim. of _tragos_, goat). An extinct genus related to the living Musk-deer.

AMPLEXUS (Lat. an Ambrace). A genus of Rugose Corals.

AMPYX (Gr. _ampux_, a wreath or wheel). A genus of Trilobites.

ANARTHROPODA (Gr. _a_, without; _arthros_, a joint; _pous_, foot).

That division of _Annulose_ animals in which there are no articulated appendages.

ANCHITHERIUM (Gr. _agchi_, near; _therion_, beast). An extinct genus of Mammals.

ANCYLOCERAS (Gr. _agkulos_, crooked; _ceras_, horn). A genus of _Ammonitidoe_.

ANCYLOTHERIUM (Gr. _agkulos_, crooked; _therion_, beast). An extinct genus of Edentate Mammals.

ANDRIAS (Gr. _andrias_, image of man). An extinct genus of tailed Amphibians.

ANGIOSPERMS (Gr. _angeion_, a vessel; _sperma_, seed). Plants which have their seeds enclosed in a seed-vessel.

ANNELIDA (a Gallicised form of _Annulata_). The Ringed Worms, which form one of the divisions of the _Anarthropoda_.

ANNULARIA (Lat. _annulus_, a ring). A genus of Palaeozoic plants, with leaves in whorls.

ANNULOSA (Lat. _annulus_). The sub-kingdom comprising the _Anarthropoda_ and the _Arthropoda_ or _Articulata_, in all of which the body is more or less evidently composed of a succession of rings.

ANOMODONTIA (Gr. _anomos_, irregular; _odous_, tooth). An extinct order of Reptiles, often called _Dicynodontia_.

ANOMURA (Gr. _anomos_, irregular; _oura_, tail). A tribe of Decapod _Crustacea_, of which the Hermit-crab is the type.

ANOPLOTHERIDae (Gr. _anoplos_, unarmed; _ther_, beast). A family of Tertiary Ungulates.

ANOURA (Gr. _a_, without; _oura_, tail). The order of _Amphibia_ comprising the Frogs and Toads, in which the adult is dest.i.tute of a tail. Often, called _Batrachia_.

ANTENNae (Lat. _antenna_, a yard-arm). The jointed horns or feelers possessed by the majority of the _Articulata_.

ANTENNULES (dim. of _Antennoe_). Applied to the smaller pair of antennae in the _Crustacea_.

ANTHRACOSAURUS (Gr. _anthrax_, coal; _saura_, lizard). A genus of Labyrinthodont Amphibians.

ANTHRAPALaeMON (Gr. _anthrax_, coal; _paloemon_, a prawn--originally a proper name). A genus of long-tailed Crustaceans from the Coal-measures.

ANTLERS. Properly the branches of the horns of the Deer tribe (_Cervidoe_), but generally applied to the entire horns.

APIOCRINIDae (Gr. _apion_, a pear; _krinon_, lily). A family of Crinoids--the "Pear-encrinites."

APTERYX (Gr. _a_, without; _pterux_, a wing). A wingless bird of New Zealand, belong to the order _Cursores_.

AQUEOUS (Lat. _aqua_, water). Formed in or by water.

ARACHNIDA (Gr. _arachne_, a spider). A cla.s.s of the _Articulata_, comprising Spiders, Scorpions, and allied animals.

ARBORESCENT. Branched like a tree.

ARCHaeOCIDARIS (Gr. _archaios_, ancient; Lat. _cidaris_, a diadem).

A Palaeozoic genus of Sea-urchins, related to the existing _Cidaris_.

ARCHaeOCYATHUS (Gr. _archaios_, ancient; _kuathos_, cup). A genus of Palaeozoic fossils allied to the Sponges.

ARCHaeOPTERYX (Gr. _archaios_, ancient; _pterux_, a wing). The singular fossil bird which alone const.i.tutes the order of the _Saururoe_.

ARCTOCYON (Gr. _arctos_, bear; _kuon_, dog). An extinct genus of Carnivora.

ARENACEOUS. Sandy, or composed of grains of sand.

ARENICOLITES (Lat. _arena_, sand; _colo_, I inhabit). A genus founded on burrows supposed to be formed by worms resembling the living Lobworms (_Arenicola_).

ARTICULATA (Lat. _articulus_, a joint). A division of the animal kingdom, comprising Insects, Centipedes, Spiders, and Crustaceans, characterised by the possession of jointed bodies or jointed limbs. The term _Arthropoda_ is now more usually employed.

ARTIODACTYLA (Gr. _artios_, even; _daktulos_, a finger or toe).

A division of the hoofed quadrupeds (_Ungulata_) in which each foot has an even number of toes (two or four).

ASAPHUS (Gr. _Asaphes_, obscure). A genus of Trilobites.

ASCOCERAS (Gr. _askos_, a leather bottle; _keras_, horn). A genus of Tetrabranchiate Cephalopods.

ASIPHONATE. Not possessing a respiratory tube or siphon. (Applied to a division of the _Lamellibranchiate_ Molluscs.)

ASTEROID (Gr. _aster_, a star; and _eidos_, form). Star-shaped, or possessing radiating lobes or rays like a star-fish.

ASTEROIDEA. An order of _Echinodermata_, comprising the Star-fishes, characterised by their rayed form.

ASTEROPHYLLITES (Gr. _aster_, a star; _phullon_, leaf). A genus of Palaeozoic plants, with leaves in whorls.

ASTRaeIDae (Gr. _Astroea_, a proper name). The family of the Star-corals.

ASTYLOSPONGIA (Gr. _a_, without; _stulos_, a column; _spoggos_, a sponge). A genus of Silurian Sponges.

ATHYRIS (Gr. _a_, without; _thura_, door). A genus of Brachiopods.

ATRYPA (Gr. _a_, without; _trupa_, a hole). A genus of Brachiopods.

AVES (Lat. _avis_, a bird). The cla.s.s of the Birds.

AVICULA (Lat. a little bird). The genus of Bivalve Molluscs comprising the Pearl-oysters.

AXOPHYLLUM (Gr. _axon_, a pivot; _phullon_, a leaf). A genus of Rugose Corals.