62 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 t> a, a, with- 

 out, and fJLoptyr], 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., a^uvy^aXa, 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. 



ANOPLOTHERE, 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., avoTrXoe, anoplos, 

 unarmed, and Q^PLOV, Iherion, 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., av0pa^, 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., avOpa^ 

 anthrax, coal, and Qripiov, therion, wild beast. 



ANTHROPOMORPHOUS. Having a form resembling the human. Etym., 

 a>0/)W7roe, anthropos, a man, and fiop^r;, 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 



