Apterous

Devoid of wings.

Apteryx

(Gr. a, without; pterux, a wing). A wingless bird of New Zealand, belonging to the order Cursores.

Aquiferous

(Lat. aqua, water ; fero, I carry. Water-bearing: applied to all vessels or canals by which water is distributed through an organism.

Arachnida

(Gr. arachne, a spider). A class of the Articulata, comprising Spiders, Scorpions, and allied animals.

Arborescent

Branched like a tree.

Archaeopteryx

(Gr. archaios, ancient; pterux, wing). The singular fossil bird which alone constitutes the order of the Saururae.

Archencephala

(Gr. archo, I overrule; egkephalos, brain). The name applied by Owen to his fourth and highest group of Mammalia, comprising Man alone.

Arenaceous

Sandy, or composed of grains of sand.

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).

Ascidioida

(Gr. askos, a bottle; eidos, a form). A synonym of Tunicata, a class of Molluscous animals, which have the shape, in many cases, of a two-necked bottle.

Asexual

Applied to modes of reproduction in which the sexes are not concerned.

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 radiing lobes or rays like a star-fish.

Asteroidea

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

Astomatous

(Gr. a, without; stoma, mouth). Not possessing a mouth.

Atlas

(Gr. the god who holds up the earth). The first vertebra of the neck, which articulates with and supports the skull.

Atrium

(Lat. a hall). Applied to the great chamber or " cloaca," into which the intestine opens in the Tunicata.

Aurelia

(Lat. aurum, gold). Applied to the chrysalides of some Lepidoptera, on account of their exhibiting a golden lustre.

Auricle

(Lat. dim. of auris, ear). Applied to one of the cavities of the heart, by which blood is driven into the ventricle.

Autophagi

(Gr. autos, self; phago, I eat). Applied to birds whose young can run about and obtain food for themselves as soon as they escape from the egg.

Aves

(Lat. avis, a bird). The class of the Birds.

Avicularium

(Lat. avicula, dim. of avis, a bird). A singular appendage, often shaped like the head of a bird, found in many of the Polyzoa.