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GLOSSARY. 
Ammonite. An extinct and very numerous genus of the order of 
molluscous animals, called Cephalopoda, allied to the modern 
genus Nautilus, which inhabited a chambered shell, curved 
like a coiled snake. Species of it are found in all geological 
periods of the secondary strata ; but they have not yet been 
seen in the tertiary beds. They are named from their resem- 
blance to the horns on the statues of Jupiter Ammon. 
Amorphous. Bodies devoid of regular form. Etym., a, a, with- 
out, and fxopfr], morphe, form. 
Amygdaloid. One of the forms of the Trap-rocks, in which agates 
and simple minerals appear to be scattered like almonds in a 
cake. Etym., apvyBaXa, amygdala, an almond. 
Analcime. A simple mineral of the Zeolite family, of frequent 
occurrence in the trap-rocks. 
Analogue. A body that resembles or corresponds with another 
body. A recent shell of the same species as a fossil-shell, is 
the analogue of the latter. 
Anoplothehe, Anoplotherium. A fossil extinct quadruped be- 
longing to the order Pachydermata, resembling a pig. It has 
received its name because the animal must have been singularly 
wanting in means of defence, from the form of its teeth and the 
absence of claws, hoofs, and horns. Etym., avo7r\og, anoplos, 
unarmed, and dqpiov, therion, a wild beast. 
Antagonist Powers. Two powers in nature, the action of the one 
counteracting that of the other, by which a kind of equilibrium 
or balance is maintained, and the destructive effect prevented 
that would be produced by one operating without a check. 
Antennae. The articulated horns with which the heads of insects are 
invariably furnished. 
Anthracite. A shining substance like black-lead ; a species of 
mineral charcoal. Etym., avdpa.%, anthrax, coal. 
Anthracotherium. A name given to an extinct quadruped, sup- 
posed to belong to the Pachydermata, the bones of which were 
found in lignite and coal of the tertiary strata. Etym., avQpa%, 
anthrax, coal, and Oypiov, therion, wild beast. 
Anthropomorphous. Having a form resembling the human. Etym., 
avdpwKog, anthropos, a man, and [ioptprj, morphe, form. 
Anticlinal Axis. If a range of hills, or a valley, be com- 
posed of strata, which on the two sides dip in opposite directions, 
the imaginary line that lies between them, towards which the 
strata on each side rise, is called the anticlinal axis. In a row 
of houses with steep roofs facing the south, the slates represent 
inclined strata dipping north and south, and the ridge is an east 
